Impact of Gas Control Policy on the Gas Accidents in Coal Mine

processes

Article Impact of Gas Control Policy on the Gas Accidents in Coal Mine

Wei Ke and Kai Wang * School of Emergency Management and Safety Engineering, China University of Mining & Technology (Beijing), Beijing 100083, China; [email protected] * Correspondence: [email protected]

Received: 8 October 2020; Accepted: 2 November 2020; Published: 4 November 2020

Abstract: Coal mine gas accidents pose a serious threat to the safety of coal mines in China. To prevent such accidents, the Chinese government and relevant agencies have issued a number of related control policies, though the effect of these policies on gas accidents is still lacking. In this study, the relevant data of coal mine gas accidents in China from 2003 to 2018 are sorted and analyzed. The analysis results show that the number of coal mine accidents and deaths has decreased significantly. However, gas accidents account for the highest proportion of deaths and pose the largest threat, compared with other types of accidents. Subsequently, the developmental stages of China’s gas control policies are summarized; they are the independent development stage, the promotion stage and the consolidation stage. A method of calculating the intervention degree of the gas control policies is proposed. The results show that the policy intervention degree is the highest, and the number of accidents is the fastest in the stage of promotion. It is concluded that gas control policies have obvious inhibitory effects on the occurrence of gas accidents, and these policies are fundamental in preventing coal mine gas accidents.

Keywords: coal mine; gas accident; control policy; delphi method; intervention degree

1. Introduction Coal plays an important role in the supply of energy worldwide for producing heat, electricity and other valuable industrial materials over the past few centuries. To date, coal still represents approximately 27.6% of the total primary energy supply in the world [1] According to statistics, in 2018, the total coal consumption in the world was 3.772 billion tons of oil equivalent. Among them, the United States used 317 million tons, and India used 452 million tons. China ranked ﬁrst in all countries with 1.907 billion tons of coal consumption (BP, 2019). China is currently the world’s largest consumer of coal, as well as the largest emitter of energy-related carbon dioxide (CO2). Nearly 80% of China’s annual energy-related CO2 emissions are from the combustion of coal and coal-derived products [2,3]. With the rapid development of China’s economy, China has become a major energy producer and consumer in the world. However, the discrepancy between its economic and environmental states has become increasingly prominent [4,5]. China’s resource conditions, which are relatively rich coal, poor oil, less gas and uranium, lead to coal being China’s main energy source, which will not change in the short term [6–8]. According to a BP report, coal accounted for 58% of China’s primary energy consumption in 2018 [9], and it is an irreplaceable and stable main energy source in the short term. China’s coal resource endowments and long-term high demands have led to an increase in mining intensity and a decrease in the amount of shallow resources [10]. Most mines are gradually entering a state of deep resource exploitation [11]. Deep resource exploitation in kilometer-deep wells has gradually become a new normal for resource exploitation, and the mining depth has extended at a speed of 10~25 m per year [12].

Processes 2020, 8, 1405; doi:10.3390/pr8111405 www.mdpi.com/journal/processes Processes 2020, 8, 1405 2 of 20

Coal mine gas accidents are mainly coal and gas outbursts and gas explosions. A gas outburst accident refers to an accident caused by a geological disaster as a result of the formation of a coal seam under the action of ground stress and the gravitational force released by the gas, which causes the weak coal seam to break through the line of resistance and instantly release a large amount of gas and coal. The main reason for this is mining caused by stress concentration, when the load exceeds the strength limit of coal and rock, resulting in shear damage [13]. If the concentration of gas in the air reaches an explosive concentration, an explosion can occur in the presence of an open flame. A gas explosion will produce a high-temperature, high-pressure shock wave and release toxic gas. With continuous increases in mining depth, the geological conditions of resources become more complex. The geostress level increases and the geotemperature rises, which makes it more difficult to exploit resources and worsens the working environment. The gas pressure in coal seams also increases. The intensity and frequency of coal mine gas accidents obviously increase with increasing depth, and the coal mine safety situation deteriorates further [14]. To achieve favorable levels of accident prevention and control, the statistics of 362 major coal mine accidents in China between 2000 and 2016 were collected and a human factor analysis and classification system for China’s mines (HFACS-CM) was established [15]. Based on these statistical methods, 106 coal dust explosion accidents that occurred in China between the years of 1949 and 2007 were investigated, so as to review the overall situation and provide quantitative information on coal dust explosions [16]. Fatal gas accidents in Chinese coal mines were quantitatively analyzed using data from 2006 to 2010 [17] and a cause classification framework based on the 24Model for accident causation [18] A method to assess the risk value of unsafe behavior was presented, based on the analysis of fatal injuries in underground coal mines [19]. The frequency of major gas explosion accidents between the years 1980 and 2010 was reviewed [20] and the safety fractal analysis method was described and used to guide investigators in exploring the elements [21]. By illuminating unsafe behaviors and their distribution characteristics in a systematic fashion, the mine safety professionals was provided with valuable information to reduce the number of gas explosions [22]. In previous studies, the data statistics, data analysis and other means have been used to analyze the occurrence of various types of accidents and provide pertinent suggestions. More and more studies have focused on the investigation of the policy influencing security. The evidence on the impact of EU policies on global food security was reviewed, focusing on several EU policy areas [23]. A one-sector integrated assessment framework was combined with a series of well-proposed energy security metrics to extensively explore the unidirectional consistency between climate policy and energy security from a national perspective [24]. The innovative concept of food security policy was described, presenting a theoretical microeconomic model of food security [25]. An analysis on institutionalization, standardization and normalization concepts was performed to clarify the management focus and objective use of institutionalization, standardization and normalization of safety production [26]. These studies have analyzed the relevant policies in various fields of safety production, but there are still some deficiencies in the research on gas control policies. In the present study, the correlations between gas accidents and relevant control policies are analyzed comprehensively. The main contents of this work are arranged as follows. The background and analysis method are introduced in Sections2 and3, respectively. The results of the gas accident analysis are in Section4, and the influence of policy on gas accidents is in Section5. The last section presents the main conclusions.

2. Background According to the Coal Mine Accident Analysis Reports from the State Administration of Coal Mine Safety (SACMS) over the years [27–34], the number of accidents and death toll were obtained. As shown in Figure1, the number of accidents decreased from 4143 to 224 for coal mines in China from 2003 to 2018, and the associated deaths decreased from 6434 to 333 during the same period. A number of 25,588 coal mine accidents have occurred since the year 2003, resulting in 42,439 deaths. Among these accidents, there were 1843 major accidents and 8252 deaths, accounting for 7.20% of the total accidents Processes 2020, 8, 1405 3 of 20

Processes 2020, 8, x FOR PEER REVIEW 3 of 21 and 19.44% of the total deaths, respectively; 336 tremendous accidents and 5219 deaths, accounting for 1.31%accounting of the total for accidents 1.31% of andthe total 12.30% accidents of the totaland 12.30% deaths, of respectively; the total deaths, and 55respectively; extraordinarily and 55 serious accidentsextraordinarily and 3282 serious deaths, accidents accounting and for3282 0.21% deaths, of acco theunting total accidents for 0.21% andof the 7.73% total accidents of the total and number 7.73% of deaths,of the respectively. total number of deaths, respectively.

8000 8000 Number of accidents Death toll 7000 6434 7000 60275938 6000 6000 4746 5000 5000 3786 4143 4000 4000 3215 3641 2631 3306 2433 3000 Death toll Death 3000 2945 1973 2421 1384 2000 Number of accidents of Number 1086 2000 1954 946 1616 598 526 1000 1403 383 333 1201 1000 779 0 608 520 352 249 226 224 0 -1000 4 7 2 5 8 05 10 13 2003 200 20 2006 200 2008 2009 20 2011 201 20 2014 201 2016 2017 201

FigureFigure 1. Changes 1. Changes in in the the number number ofof coalcoal mine acci accidentsdents and and deaths deaths in China in China from from 2003 2003to 2018. to 2018.

FromFrom 2003 2003 to 2018,to 2018, the the total total number number of coal coal mine mine accidents accidents in China in China exhibited exhibited a downward a downward trend. trend. The descentThe descent was verywas surprising,very surprising, which which corresponded corresponded to decreases to decreases of 94.59% of 94.59% and 94.82%, and 94.82%, respectively. The curverespectively. of the The fatality curve rate of the also fatality fell rapidly. rate also Asfell shown rapidly. in As Figure shown2 ,in it Figure decreased 2, it decreased from 3.724 from in 2003 and3.724 0.093 in in 2003 2018. and There 0.093 in are 2018. two There reasons are two for reasons the rapid for the decline rapid ofdecline the curveof the curve illustrated illustrated in Figure in 2. On theFigure one 2. hand, On thewith one the hand, improvement with the improvement of the mechanization of the mechanization and intelligence and intelligence of coal mining, of coal more and moremining, workers more and were more gradually workers replacedwere gradually by automated replaced by machinery automated and machinery equipment, and equipment, and the number of workersand the innumber the work of workers place was in the reduced. work place On the was other reduced. hand, On relevant the other agencies hand, relevant issued aagencies series of gas controlissued policies, a series which of gas control played policies, a key guiding which played role in a key coal guiding mine safetyrole in coal production. mine safety Overall, production. the safety Overall,Processes the2020 safety, 8, x FOR production PEER REVIEW of coal mines in China is improving. 4 of 21 production of coal mines in China is improving.

4.0 Fatality rate(Deaths per million tons coal prodution) 3.5

3.0

2.5

illion tons coal production) illion 2.0

1.5

1.0

0.5

0.0 Fatality Rate(Deaths per m Rate(Deaths Fatality 03 04 05 06 08 09 10 11 12 14 15 16 17 0 0 0 2 20 20 20 2007 2 20 20 20 20 2013 2 20 20 20 2018 Figure 2. Changes in the fatality rates in coal mines from 2003 to 2018. Figure 2. Changes in the fatality rates in coal mines from 2003 to 2018.

In terms of gas accidents, from 2003 to 2018, there were 2984 gas accidents in China, with 12,807 deaths (Table 1), accounting for 11.66% and 30.18% of the total number of coal mine accidents, respectively. The specific data analysis is presented in Section 4.

Table 1. Statistics of gas accidents from 2003 to 2018.

Tremendous and Above Gas Accidents Major Gas Accidents Gas Accidents Year Number of Number of Quantity Proportion Deaths Proportion Deaths Deaths Accidents Accidents 2003 584 14.10% 2118 32.92% 173 785 33 766 2004 492 13.51% 1900 31.52% 134 596 32 867 2005 414 12.52% 2171 36.56% 115 505 41 1331 2006 327 11.10% 1319 27.79% 126 591 26 490 2007 272 11.24% 1084 28.63% 83 413 22 460 2008 182 9.31% 778 24.20% 63 290 18 352 2009 157 9.72% 755 28.70% 57 260 11 374 2010 145 10.33% 623 25.61% 57 299 11 220 2011 119 9.91% 533 27.01% 43 233 12 207 2012 72 9.24% 350 25.29% 29 144 7 159 2013 59 9.70% 348 32.04% 20 119 10 192 2014 47 9.04% 266 28.12% 18 74 10 162 2015 45 12.78% 171 28.60% 20 94 3 42 2016 26 10.44% 226 42.97% 12 54 8 161 2017 25 11.06% 103 26.89% 13 54 3 32 2018 18 8.04% 62 18.62% 8 36 1 13

3. Methodology Many researchers have analyzed industrial accidents, based on the frequency of accidents occurring in fixed intervals, and have used various sources of accident data to study security in mining [35–38]. Accident statistics and analysis is the basis of objective management of safety work. Without the correct conclusion of accident statistics and analysis, objective management cannot be

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In terms of gas accidents, from 2003 to 2018, there were 2984 gas accidents in China, with 12,807 deaths (Table1), accounting for 11.66% and 30.18% of the total number of coal mine accidents, respectively. The speciﬁc data analysis is presented in Section4.

Table 1. Statistics of gas accidents from 2003 to 2018.

Tremendous and Gas Accidents Major Gas Accidents Above Gas Accidents Year Number of Number of Quantity Proportion Deaths Proportion Deaths Deaths Accidents Accidents 2003 584 14.10% 2118 32.92% 173 785 33 766 2004 492 13.51% 1900 31.52% 134 596 32 867 2005 414 12.52% 2171 36.56% 115 505 41 1331 2006 327 11.10% 1319 27.79% 126 591 26 490 2007 272 11.24% 1084 28.63% 83 413 22 460 2008 182 9.31% 778 24.20% 63 290 18 352 2009 157 9.72% 755 28.70% 57 260 11 374 2010 145 10.33% 623 25.61% 57 299 11 220 2011 119 9.91% 533 27.01% 43 233 12 207 2012 72 9.24% 350 25.29% 29 144 7 159 2013 59 9.70% 348 32.04% 20 119 10 192 2014 47 9.04% 266 28.12% 18 74 10 162 2015 45 12.78% 171 28.60% 20 94 3 42 2016 26 10.44% 226 42.97% 12 54 8 161 2017 25 11.06% 103 26.89% 13 54 3 32 2018 18 8.04% 62 18.62% 8 36 1 13

3. Methodology Many researchers have analyzed industrial accidents, based on the frequency of accidents occurring in ﬁxed intervals, and have used various sources of accident data to study security in mining [35–38]. Accident statistics and analysis is the basis of objective management of safety work. Without the correct conclusion of accident statistics and analysis, objective management cannot be carried out. In order to reduce casualties, we should focus on reducing repetitive accidents and preventing major accidents. Statistical analysis of accidents can help us to understand the development trend of accidents, quantify the severity of accidents and excavate the root causes of accidents, which plays an important and positive role in preventing accidents. In this paper, a similar method is used to study the occurrence law of coal mine gas accidents. To quantitatively analyze the impact of policies, many scholars use the Delphi method to rank the importance of policies and assign relevant weighted scores [39–42]. The advantage of the Delphi method is that the opinions are anonymous, so it is more likely to express unpopular opinions, all of which have the same weight, avoiding the problem of domination by important people. At the same time, experts do not have to gather in a certain place at a certain time, which is more convenient and widely representative. This paper uses this method to rank the importance of gas prevention policies, provide the corresponding weight of the degree of inﬂuence and analyze the relationships between gas accidents and relevant prevention policies. Processes 2020, 8, x FOR PEER REVIEW 5 of 21 carried out. In order to reduce casualties, we should focus on reducing repetitive accidents and preventing major accidents. Statistical analysis of accidents can help us to understand the development trend of accidents, quantify the severity of accidents and excavate the root causes of accidents, which plays an important and positive role in preventing accidents. In this paper, a similar method is used to study the occurrence law of coal mine gas accidents. To quantitatively analyze the impact of policies, many scholars use the Delphi method to rank the importance of policies and assign relevant weighted scores [39–42]. The advantage of the Delphi method is that the opinions are anonymous, so it is more likely to express unpopular opinions, all of which have the same weight, avoiding the problem of domination by important people. At the same time, experts do not have to gather in a certain place at a certain time, which is more convenient and widely representative. This paper uses this method to rank the importance of gas prevention policies, provide the corresponding weight of the degree of influence and analyze the relationships between gasProcesses accidents2020, 8, and 1405 relevant prevention policies. 5 of 20

4. Results 4. Results To analyze the occurrence law of gas accidents more comprehensively, the time of occurrence, To analyze the occurrence law of gas accidents more comprehensively, the time of occurrence, accident grade, region, accident type, mine ownership, number of mines and their relationships with accident grade, region, accident type, mine ownership, number of mines and their relationships with China’s economic development are studied in this section. China’s economic development are studied in this section.

4.1.4.1. Distribution Distribution of of Accident Accident Intervals Intervals FromFrom 2003 to 2018,2018, throughthrough a a series series of of e ﬀeffectivective controle control measures, measures, the the number number of gasof gas accidents accidents and anddeaths deaths in China in China showed showed a decreasing a decreasing trend yeartrend by year year by (Figure year3 ).(Figure From 20033). From to 2018, 2003 the to number 2018, the of numberaccidents of decreased accidents fromdecreased 584 to from 18, a decrease584 to 18, of a 96.92%, decrease and of the 96.92%, number and of deathsthe number decreased of deaths from decreased2118 to 62, from with 2118 a decrease to 62, with of 97.07%. a decrease A control of 97.07%. eﬀect A is obvious.control effect is obvious.

1000 2400 2118 2171 Number of gas accidents Death toll 1900 800 1800

1319 600 584 1084 1200 492 778 755 414 623

400 533 600 Deathtoll 327 350 348 266 272 171 226

Number of gas accidents gas Number of 103 62 200 182 0 157 145 119 72 59 47 45 26 25 18 0 -600 4 6 8 3 5 7 0 0 007 0 009 11 1 014 1 016 1 018 2003 20 2005 20 2 20 2 2010 20 2012 20 2 20 2 20 2 FigureFigure 3. 3. ChangesChanges in in incidents incidents of of and and deaths deaths from from coal coal mine mine gas gas accidents accidents in in China China from from 2003 2003 to to 2018. 2018.

4.2. Analysis by Grade 4.2. Analysis by Grade According to the number of casualties and direct economic losses caused by production safety According to the number of casualties and direct economic losses caused by production safety accidents, accidents are generally classiﬁed into the following grades: accidents, accidents are generally classified into the following grades: 1. An extraordinarily serious accident refers to an accident that causes more than 30 deaths, more than 100 serious injuries (including acute industrial poisoning, the same as below) or direct economic losses of more than 100 million yuan; 2. A tremendous accident refers to an accident that causes the deaths of more than 10 people and fewer than 30 people, serious injuries of more than 50 people and fewer than 100 people or direct economic losses of more than 50 million yuan and less than 100 million yuan; 3. A major accident refers to an accident that causes the deaths of more than 3 persons and fewer than 10 persons, serious injuries of more than 10 persons and fewer than 50 persons or direct economic losses of more than 10 million yuan and less than 50 million yuan. 4. A general accident refers to an accident that causes the deaths of fewer than 3 persons, serious injuries of fewer than 10 persons or direct economic losses of less than 10 million yuan.

From 2003 to 2018, there were 971 major gas accidents that caused 4547 deaths in China, accounting for 52.69% of the total major coal mine accidents and 55.10% of the total deaths, respectively. There were Processes 2020, 8, x FOR PEER REVIEW 6 of 21

1. An extraordinarily serious accident refers to an accident that causes more than 30 deaths, more than 100 serious injuries (including acute industrial poisoning, the same as below) or direct economic losses of more than 100 million yuan; 2. A tremendous accident refers to an accident that causes the deaths of more than 10 people and fewer than 30 people, serious injuries of more than 50 people and fewer than 100 people or direct economic losses of more than 50 million yuan and less than 100 million yuan; 3. A major accident refers to an accident that causes the deaths of more than 3 persons and fewer than 10 persons, serious injuries of more than 10 persons and fewer than 50 persons or direct economic losses of more than 10 million yuan and less than 50 million yuan. 4. A general accident refers to an accident that causes the deaths of fewer than 3 persons, serious injuries of fewer than 10 persons or direct economic losses of less than 10 million yuan.

ProcessesFrom2020 ,20038, 1405 to 2018, there were 971 major gas accidents that caused 4547 deaths in China,6 of 20 accounting for 52.69% of the total major coal mine accidents and 55.10% of the total deaths, respectively. There were 248 tremendous and above gas accidents that caused 5828 deaths, accounting248 tremendous for 63.42% and above and gas68.56% accidents of the that total caused trem 5828endous deaths, or more accounting severe for accidents, 63.42% and respectively 68.56% of (Figuresthe total 4 tremendous and 5). Gas or accidents more severe account accidents, for more respectively than 50% (Figures of all major4 and5 or). Gasmore accidents severe accidents account for in coalmore mines. than 50%Thus, of gas all majoraccidents or more are consider severe accidentsed as the in first coal killer mines. of coal Thus, mines. gas accidents are considered as the ﬁrst killer of coal mines.

300 1000 Number of major accidents Death toll 785 800 250

596 591 600 200 505 173 413 400 290 299 150 260 134 233 126 144 200 115 119 Death toll 74 94 100 54 54 36 83 0

Number major accidentsof 63 57 57 50 43 -200 29 20 18 20 12 13 8 0 -400 3 4 9 0 5 6 06 07 08 13 14 00 0 0 0 00 01 0 0 01 01 2 200 2005 2 2 2 2 2 2011 2012 2 2 2 2 2017 2018 Processes 2020, 8, x FOR PEER REVIEW 7 of 21 FigureFigure 4. 4. ChangesChanges in in the the number number of of major major gas gas accidents accidents and and deaths. deaths. 80 1500 1331 Number of tremendous accidents and above Death toll 70

867 1000 60 766

50 490 460 500 352 374

accidents and above accidents 41 220 40 207 159 192 162 161 42 32 33 32 13 0 Death toll 30 26 22 20 18 -500 12 11 11 10 10 10 7 8

Number of tremendous Number of 3 3 1 0 -1000 5 8 3 6 003 00 006 007 00 010 011 01 014 015 01 018 2 2004 2 2 2 2 2009 2 2 2012 2 2 2 2 2017 2 FigureFigure 5. 5. ChangesChanges in in the the number number of of tremen tremendousdous gas gas accidents accidents and and deaths. deaths.

AsAs seen seen from from Figure Figure 44,, thethe numbernumber ofof majormajor gasgas accidentsaccidents andand deathsdeaths decreaseddecreased fromfrom 173173 andand 785,785, respectively, respectively, in in 2003 2003 to to8 and 8 and 36, respectively, 36, respectively, in 2018, in 2018,which which corresponded corresponded to decreases to decreases of 95.37% of and95.37% 95.41%, and respectively. 95.41%, respectively. As seen from As seen Figure from 5, Figurethe number5, the of number tremendous of tremendous and above and gas above accidents gas andaccidents deaths and decreased deaths decreased from 33 and from 766, 33 respectively, and 766, respectively, in 2003 to in 1 2003 and to13, 1 respectively, and 13, respectively, in 2018, inwhich 2018, corresponded to decreases of 96.97% and 98.30%, respectively. Thus, in the past 15 years, the occurrence of gas accidents has been significantly curbed.

4.3. Analysis by Region From 2008 to 2013, the provinces with the most gas accidents were Hunan and Guizhou, with more than 45 cases each, followed by Yunnan and Sichuan, with 38 and 26 gas accidents, respectively, and Chongqing, Shanxi and Henan, with more than 10 gas accidents each (Figure 6).

100 400 Number of accidents Death toll 350 80 293 300 254 253 266 250 201 60 174 200 48 47 121 150

40 38 100 Deathtoll

Number accidents of 26 50 20 19 0 15 14 -50

0 -100 Hunan Guizhou Yunnan Sichuan Chongqing Shanxi Henan

Figure 6. Statistics of gas accidents in different provinces from 2008 to 2013.

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80 1500 1331 Number of tremendous accidents and above Death toll 70

867 1000 60 766

50 490 460 500 352 374

accidents and above accidents 41 220 40 207 159 192 162 161 42 32 33 32 13 0 Death toll 30 26 22 20 18 -500 12 11 11 10 10 10 7 8

Number of tremendous Number of 3 3 1 0 -1000 5 8 3 6 003 00 006 007 00 010 011 01 014 015 01 018 2 2004 2 2 2 2 2009 2 2 2012 2 2 2 2 2017 2 Figure 5. Changes in the number of tremendous gas accidents and deaths.

As seen from Figure 4, the number of major gas accidents and deaths decreased from 173 and 785, respectively, in 2003 to 8 and 36, respectively, in 2018, which corresponded to decreases of 95.37% andProcesses 95.41%,2020, 8 respectively., 1405 As seen from Figure 5, the number of tremendous and above gas accidents7 of 20 and deaths decreased from 33 and 766, respectively, in 2003 to 1 and 13, respectively, in 2018, which correspondedwhich corresponded to decreases to decreases of 96.97% of 96.97% and 98.30%, and 98.30%, respectively. respectively. Thus, Thus,in the in past the past15 years, 15 years, the occurrencethe occurrence of gas of gasaccidents accidents has hasbeen been significantly signiﬁcantly curbed. curbed.

4.3. Analysis Analysis by by Region Region From 20082008 toto 2013,2013, the the provinces provinces with with the the most most gas gas accidents accidents were were Hunan Hunan and Guizhou,and Guizhou, with morewith morethan 45than cases 45 cases each, each, followed followed by Yunnanby Yunnan and and Sichuan, Sichuan, with with 38 38 and and 26 26 gasgas accidents, respectively, respectively, and Chongqing, Shanxi and Henan, with more than 10 gas accidents each (Figure6 6).).

100 400 Number of accidents Death toll 350 80 293 300 254 253 266 250 201 60 174 200 48 47 121 150

40 38 100 Deathtoll

Number accidents of 26 50 20 19 0 15 14 -50

0 -100 Hunan Guizhou Yunnan Sichuan Chongqing Shanxi Henan

FigureFigure 6. 6. StatisticsStatistics of of gas gas accidents accidents in in di differentﬀerent provinces from 2008 to 2013.

As seen from the above chart, gas accidents occurred frequently in Hunan and Guizhou. The reason for this is that the coal occurrence conditions and geological structure conditions in Hunan and Guizhou are complex, the gas content is high and the technical content of mines is low; the accidents mainly occurred in township coal mines. From 2008 to 2013, the fatality rate of accidents in the Henan province was relatively high, which was mainly due to the high frequency of major and above accidents. Eight of the accidents were extraordinarily serious gas accidents, accounting for 57.1% of all accidents, and the highest death toll in a single case was 19. The main reasons for these results were the deep mining of coal seams in the Henan province, high gas content in this area, confusion in management and illegal operations. From 2013 to 2017, the number of gas accidents and deaths in all provinces decreased signiﬁcantly (Figure7). In terms of the number of accidents, there were more than 10 gas accidents in each of 8 provinces. Most of the accidents were in Guizhou and Hunan, which had 27 accidents each, while Chongqing had 17 accidents, Sichuan and Shanxi had 15 accidents each and Yunnan, Heilongjiang and Hubei had more than 10 accidents each. In terms of the number of deaths, only one province, Guizhou, had more than 100 deaths. There were 7 provinces with 50–100 deaths each: Chongqing, Jilin, Hunan, Heilongjiang, Sichuan, Shanxi and Yunnan. According to the statistics, the coal mine safety situation in most provinces is continuing to improve, and the number of accidents and deaths has decreased signiﬁcantly. Processes 2020, 8, x FOR PEER REVIEW 8 of 21

As seen from the above chart, gas accidents occurred frequently in Hunan and Guizhou. The reason for this is that the coal occurrence conditions and geological structure conditions in Hunan and Guizhou are complex, the gas content is high and the technical content of mines is low; the accidents mainly occurred in township coal mines. From 2008 to 2013, the fatality rate of accidents in the Henan province was relatively high, which was mainly due to the high frequency of major and above accidents. Eight of the accidents were extraordinarily serious gas accidents, accounting for 57.1% of all accidents, and the highest death toll in a single case was 19. The main reasons for these results were the deep mining of coal seams in the Henan province, high gas content in this area, confusion in management and illegal operations. From 2013 to 2017, the number of gas accidents and deaths in all provinces decreased significantly (Figure 7). In terms of the number of accidents, there were more than 10 gas accidents in each of 8 provinces. Most of the accidents were in Guizhou and Hunan, which had 27 accidents each, while Chongqing had 17 accidents, Sichuan and Shanxi had 15 accidents each and Yunnan, Heilongjiang and Hubei had more than 10 accidents each. In terms of the number of deaths, only one province, Guizhou, had more than 100 deaths. There were 7 provinces with 50–100 deaths each: Chongqing, Jilin, Hunan, Heilongjiang, Sichuan, Shanxi and Yunnan. According to the statistics, the coal mine safety situation in most provinces is continuing to improve, and the number of accidents Processes 2020, 8, 1405 8 of 20 and deaths has decreased significantly.

70 250 Number of accidents Death toll 60 189 200

50 150

92 98 98 40 78 80 100 68 66 30 36 50 27 27 Death toll

Number of accidents of Number 20 17 0 15 15 14 11 11 10 9 -50

0 -100 u n g n i n g i n - ho na in ua nx na an be ili - iz gq ch ha un gji Hu J Gu Hu on Si S Y on Ch eil H

FigureFigure 7. 7. StatisticsStatistics of of gas gas accidents accidents in in di differentﬀerent provinces provinces from from 2013 2013 to to 2017. 2017.

We can see that in Guizhou, Hunan, Sichuan and other areas with more complex geological We can see that in Guizhou, Hunan, Sichuan and other areas with more complex geological structures, the possibility of gas disasters will increase. This prediction is mainly based on the fact structures, the possibility of gas disasters will increase. This prediction is mainly based on the fact that gas disasters, especially coal and gas outburst accidents, are usually related to the geological that gas disasters, especially coal and gas outburst accidents, are usually related to the geological structure of the coalfield. A closer proximity to the geological structure belt corresponds to an increase structure of the coalfield. A closer proximity to the geological structure belt corresponds to an in abnormal gas occurrences and higher levels of concentrated tectonic stress. Geological structure not increase in abnormal gas occurrences and higher levels of concentrated tectonic stress. Geological only controls the formation of gas occurrence areas, but also affects gas enrichment and migration, structure not only controls the formation of gas occurrence areas, but also affects gas enrichment and which is also the main cause of coal and gas outbursts. migration, which is also the main cause of coal and gas outbursts. 4.4. Analysis by Accident Type Gas accidents are mainly caused by gas explosions, coal and gas outbursts and gas asphyxia. Due to limited data collection, this section only analyzes data from 2008 to 2018. From 2008 to 2018, a total of 341 major gas accidents occurred; 149 gas explosion accidents occurred with 757 deaths, accounting for 43.70% and 45.33% of the total number of major gas accidents and deaths, respectively, and 122 coal and gas outburst accidents occurred with 617 deaths, accounting for 35.78% and 36.95% of the total number of major gas accidents and deaths, respectively. There were 64 gas asphyxia and poisoning accidents and 264 deaths, accounting for 18.77% and 15.81% of the total number of major gas accidents and deaths, respectively (Figure8). From 2008 to 2018, 52 gas explosion accidents occurred with 1181 deaths, accounting for 55.91% and 62.29% of the total number of tremendous and more severe gas accidents, respectively, and 34 coal and gas outburst accidents occurred with 605 deaths, accounting for 35.56% and 31.91% of the total number of tremendous and more severe gas accidents, respectively. Three gas asphyxia and poisoning accidents occurred with 51 deaths, accounting for 3.23% and 2.69% of the total number of tremendous and more severe gas accidents, respectively (Figure9). According to the above data, of all types of disasters, gas explosion accidents were predominant; the number of occurrences was the highest with gas explosion accidents, followed by coal and gas outburst accidents. From 2008 to 2018, the frequencies of the various types of gas accidents fluctuated by year, but there was a significant overall trend showing a decline (Figures 10 and 11). Processes 2020, 8, x FOR PEER REVIEW 9 of 21

4.4. Analysis by Accident Type Gas accidents are mainly caused by gas explosions, coal and gas outbursts and gas asphyxia. Due to limited data collection, this section only analyzes data from 2008 to 2018. From 2008 to 2018, a total of 341 major gas accidents occurred; 149 gas explosion accidents occurred with 757 deaths, accountingProcesses 2020 ,for 8, x 43.70%FOR PEER and REVIEW 45.33% of the total number of major gas accidents and deaths, respectively,9 of 21 and 122 coal and gas outburst accidents occurred with 617 deaths, accounting for 35.78% and 36.95% of4.4. the Analysis total number by Accident of major Type gas accidents and deaths, respectively. There were 64 gas asphyxia and poisoningGas accidents accidents are and mainly 264 deaths, caused accounting by gas explosions, for 18.77% coal and and 15.81% gas ofoutbursts the total and number gas asphyxia. of major gasDue accidents to limited and data deaths, collection, respectively this section (Figure only 8). anal yzes data from 2008 to 2018. From 2008 to 2018, a total of 341 major gas accidents occurred; 149 gas explosion accidents occurred with 757 deaths, accounting for 43.70% and 45.33% Explosion of the total number of major gas accidents and deaths, respectively, and 122 coal and gas outburst Outburst accidents occurred with 617 deaths, accounting for 35.78% and 36.95% of the total number of major gas Others(gas accidents combustion and deaths, and respectively. gas-induced There asphyxia) were 64 gas asphyxia and Processespoisoning2020, 8, 1405 accidents and 264 deaths, accounting for 18.77% and 15.81% of the total number of major9 of 20 gas accidents122 (35.88%) and deaths, respectively (Figure 8). 617 (37.24%)

Explosion 69 (20.29%) Outburst Others(gas combustion and gas-induced asphyxia) 283 (17.08%)

122 (35.88%) 617 (37.24%)

149 (43.82%) 757 (45.68%) 69 (20.29%) Death toll Number of accidents 283 (17.08%) Figure 8. Proportion of various types of accidents in major gas accidents from 2008 to 2018.

From 2008 to 2018, 52 gas explosion accidents occurred with 1181 deaths, accounting for 55.91% and 62.29%149 (43.82%) of the total number of tremendous and757 more (45.68%) severe gas accidents, respectively, and 34 coal and gas outburst accidents occurred with 605 deaths, accounting for 35.56% and 31.91% of the Death toll total numberNumber of tremendous of accidents and more severe gas accidents, respectively. Three gas asphyxia and poisoning accidents occurred with 51 deaths, accounting for 3.23% and 2.69% of the total number of FigureFigure 8. Proportion 8. Proportion of of various various types types ofof accidentsaccidents in in major major gas gas accidents accidents from from 2008 2008 to 2018. to 2018. tremendous and more severe gas accidents, respectively (Figure 9). From 2008 to 2018, 52 gas explosion accidents occurred with 1181 deaths, accounting for 55.91% and 62.29% of the total number Explosion of tremendous and more severe gas accidents, respectively, and 34 Outburst coal and gas outburst accidents occurred with 605 deaths, accounting for 35.56% and 31.91% of the Others(gas combustion and gas-induced asphyxia) total number of tremendous and more severe gas accidents, respectively. Three gas asphyxia and poisoning accidents occurred with 51 deaths, accounting for 3.23% and 2.69% of the total number of tremendous and122 more (35.88%) severe gas accidents, respectively (Figure 9). 605 (32.76%)

Explosion Outburst 69 (20.29%)

Others(gas combustion and gas-induced asphyxia)

122 (35.88%) 61 (3.3%) Processes 2020, 8, x FOR PEER REVIEW 605 (32.76%) 10 of 21 149 (43.82%) 1181 (63.94%) According to the above data, of all types of disasters, gas explosion accidents were predominant; Number of accidents Death toll the number of occurrences was the highest69 (20.29%)with gas explosion accidents, followed by coal and gas outburstFigureFigure 9. accidents.Proportion 9. Proportion From of variousof 2008 various to types2018, types ofthe of accidents accidentsfrequencie in stremendous tremendousof the various an andd typesabove above ofgas gas gasaccidents accidents accidents from fluctuated from2008 2008 byto 2018.year,to 2018. but there was a significant overall trend showing a decline (Figures 10 and 11). 61 (3.3%)

14950 (43.82%) 1181 (63.94%) 150 Number of major accidents(Explosion) Number of accidents Number of major accidents(Outburst) Death toll Number of major accidents(others) Figure 9. Proportion40 of various types of accidents Death in tremendous toll(Explosion) and above gas accidents100 from 2008 to 2018. Death toll(Outburst) Death toll(Others)

30 50

20 0 toll Death

Number of major accidents major of Number 10 -50

0 -100 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Figure 10. Variations of the diﬀerent types of accidents in major gas accidents from 2008 to 2018. Figure 10. Variations of the different types of accidents in major gas accidents from 2008 to 2018.

20 Number of tremendous accidents(Explosion) Number of tremendous accidents(Outburst) 18 300 Number of tremendous accidents(others) Death toll(Explosion) 16 Death toll(Outburst) 200 Death toll(Others) 14 100 12

10 0

8 -100 Death toll

6 -200 4 Number of tremendous accidents of tremendous Number -300 2

0 -400 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Figure 11. Variations of the different types of accidents in tremendous and more severe gas accidents from 2008 to 2018.

4.5. Analysis by Coal Mine Ownership According to the ownership system, coal mines in China can be classified into national strategic mines (NSM), provincial national mines (PNM) and township mines (TM). Due to limited data

Processes 2020, 8, x FOR PEER REVIEW 10 of 21

According to the above data, of all types of disasters, gas explosion accidents were predominant; the number of occurrences was the highest with gas explosion accidents, followed by coal and gas outburst accidents. From 2008 to 2018, the frequencies of the various types of gas accidents fluctuated by year, but there was a significant overall trend showing a decline (Figures 10 and 11).

50 150 Number of major accidents(Explosion) Number of major accidents(Outburst) Number of major accidents(others) 40 Death toll(Explosion) 100 Death toll(Outburst) Death toll(Others)

30 50

20 0 toll Death

Number of major accidents major of Number 10 -50

0 -100 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

ProcessesFigure2020, 8, 10. 1405 Variations of the different types of accidents in major gas accidents from 2008 to 2018. 10 of 20

10 0

8 -100 Death toll

6 -200 4 Number of tremendous accidents of tremendous Number -300 2

Processes 2020, 8, x FOR0 PEER REVIEW -400 11 of 21 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 collection,Figure this 11. Variationssection only of the analyzes diﬀerent typesdata offrom accidents 2013 into tremendous2018. From and 2013 more to severe 2018, gas 153 accidents major gas Figure 11. Variations of the different types of accidents in tremendous and more severe gas accidents accidentsfrom occurred 2008 to 2018. in China with 1387 deaths. The number of accidents in TM was the largest, with 107 accidentsfrom 2008 and to 2018. 982 deaths, accounting for 69.3% and 70.8% of the total accidents and total deaths, respectively.4.5. Analysis In by addition, Coal Mine there Ownership were 36 accidents and 324 deaths in NSM, accounting for 25.53% and 4.5. Analysis by Coal Mine Ownership 23.36%According of the total to accidents the ownership and total system, deaths, coal respectively. mines in China There can were be classiﬁed 10 accidents into and national 81 deaths strategic in PNM,minesAccording accounting (NSM), provincialto for the 6.54% ownership nationaland 5.84% system, mines of the coal (PNM) total mines accidents and in China township and can total be mines deaths, classified (TM). respectively into Due national to limited(Figure strategic 12). data collection,minesThe (NSM), number this sectionprovincial of gas only accidents national analyzes and datamines deaths from (PNM) in 2013 TM and to were 2018. township obviously From 2013 mines higher to 2018,(TM). than 153 Due those major to in gaslimited NSM accidents anddata PNM.occurred The in main China reason with is 1387 that deaths. with increases The number in co ofal accidentsseam mining in TM depths, was the gas largest, disasters with become 107 accidents more serious.and 982 Compared deaths, accounting with the national for 69.3% mines, and 70.8% which of ha theve totalrelatively accidents good and safety total technical deaths, task respectively. forces, TMIn addition,are obviously there wereweak 36 in accidents technology, and manageme 324 deathsnt in and NSM, equipment, accounting which for 25.53% leads and to 23.36%a higher of probabilitythe total accidents of an accident. and total deaths, respectively. There were 10 accidents and 81 deaths in PNM, accounting for 6.54% and 5.84% of the total accidents and total deaths, respectively (Figure 12).

50 500 Number of accidents(National Strategic Mines) Number of accidents(Provincial National Mines) 400 Number of accidents(Township Mines) 40 Death toll(National Strategic Mines) 300 Death toll(Provicial National Mines) Death toll(Township Mines) 200 30 100

20 Death toll -100

-200 10 Number of major gas accidents Number

-300

0 -400 2013 2014 2015 2016 2017 2018

Figure 12. Changes in gas accidents in coal mines with diﬀerent ownerships from 2012 to 2018. Figure 12. Changes in gas accidents in coal mines with different ownerships from 2012 to 2018.

4.6. Analysis by Mine Quantity Due to limited data collection, this section only analyzes data from 2012 to 2018. Figure 13 shows the changing trend of the number of coal mines and the number of coal mine gas accidents from 2012 to 2018. With continuous adjustments and optimization processes in the industrial structure of China’s coal industry, efforts in eliminating the backward production capacity and resolving the excess production capacity have achieved tangible results. The merging and reorganization of enterprises and the integration of technological innovations have been carried out in an orderly manner, resulting in a gradual decline in the number of coal mines in China. Large-scale modern coal mines have gradually become the main sources of coal production. Industrial concentration has increased, backward production capacity has gradually been eliminated and the ratio of high-quality production capacity has been improved. In particular, the shutdown and elimination of a number of small coal mines that had serious disasters, a lack of safe production conditions, outdated technology and equipment, poor gas prevention and control abilities and frequent accidents played an important role in reducing coal mine accidents in China.

Processes 2020, 8, 1405 11 of 20

The number of gas accidents and deaths in TM were obviously higher than those in NSM and PNM. The main reason is that with increases in coal seam mining depths, gas disasters become more serious. Compared with the national mines, which have relatively good safety technical task forces, TM are obviously weak in technology, management and equipment, which leads to a higher probability of an accident.

4.6. Analysis by Mine Quantity Due to limited data collection, this section only analyzes data from 2012 to 2018. Figure 13 shows the changing trend of the number of coal mines and the number of coal mine gas accidents from 2012 to 2018. With continuous adjustments and optimization processes in the industrial structure of China’s coal industry, eﬀorts in eliminating the backward production capacity and resolving the excess production capacity have achieved tangible results. The merging and reorganization of enterprises and the integration of technological innovations have been carried out in an orderly manner, resulting in a gradual decline in the number of coal mines in China. Large-scale modern coal mines have gradually become the main sources of coal production. Industrial concentration has increased, backward production capacity has gradually been eliminated and the ratio of high-quality production capacity has been improved. In particular, the shutdown and elimination of a number of small coal mines that had serious disasters, a lack of safe production conditions, outdated technology Processesand equipment, 2020, 8, x FOR poor PEER gas REVIEW prevention and control abilities and frequent accidents played an important12 of 21 role in reducing coal mine accidents in China.

22000 80

20000 72 Number of coal mines Number of gas accidents 18000 59 60

16000 47 14000 45 14000 40 12000 12000 11000 10800 26 25 10000 9000 18 20 8000 7000

Number of coal mines 6000 5800 0 Number of gas accidents 4000

2000 -20

0 2012 2013 2014 2015 2016 2017 2018

Figure 13. Changes in the number of gas accidents and coal mines. Figure 13. Changes in the number of gas accidents and coal mines. 4.7. Analysis by Economic Development 4.7. AnalysisCoal, which by Economic is China’s Development main source of energy, has always occupied a large proportion of the primaryCoal, energy which production is China’s andmain consumption source of energy, structure. has Coalalways production occupied anda la consumptionrge proportion not of only the primarymeet the energy needs ofproduction human life and and consumption production, butstructur alsoe. promote Coal production the development and consumption of the coal not industry. only meetWith the needs development of human of life the and economy production, and changes but also in promote industrial the structure, development coal productionof the coal industry. will also Withchange. the There development is a close of relationship the economy between and changes economic in development industrial structure, and coal coal production, production which will aﬀ alsoects change.the safety There of coal is mines.a close relationship between economic development and coal production, which affectsAs the seen safety from of Figure coal mines. 14, with an increase in GDP, the number of coal mine gas accidents decreased yearAs by seen year. from The growthFigure rate14, with of the an GDP increase and thein GDP, declining the ratenumber of the of numbercoal mine of coalgas accidents mine gas decreasedaccidents areyear drawn by year. on The the samegrowth map rate in of Figure the GDP 15. and the declining rate of the number of coal mine gas accidents are drawn on the same map in Figure 15.

250 700 584 GDP 600 492 Number of gas accidents 500 200 414 400 327 272 300 182 157 145 200 150 119 72 59 47 45 100 26 25 18 0

100 90 -100 82.1 74 GDP (trillionyuan) -200 64.1 68.6

59.3 Number of gas accidents 53.9 48.8 -300 50 41.2 31.9 34.9 -400 27 18.7 21.9 13.7 16.2 -500 0 -600 03 04 05 07 08 09 11 12 13 16 17 0 0 0 0 0 20 2 2 2006 20 20 2 2010 20 20 2 2014 2015 20 2 2018

Figure 14. Changes in the number of gas accidents and GDP.

Processes 2020, 8, x FOR PEER REVIEW 12 of 21

22000 80

20000 72 Number of coal mines Number of gas accidents 18000 59 60

16000 47 14000 45 14000 40 12000 12000 11000 10800 26 25 10000 9000 18 20 8000 7000

Number of coal mines 6000 5800 0 Number of gas accidents 4000

2000 -20

0 2012 2013 2014 2015 2016 2017 2018

Figure 13. Changes in the number of gas accidents and coal mines.

4.7. Analysis by Economic Development Coal, which is China’s main source of energy, has always occupied a large proportion of the primary energy production and consumption structure. Coal production and consumption not only meet the needs of human life and production, but also promote the development of the coal industry. With the development of the economy and changes in industrial structure, coal production will also change. There is a close relationship between economic development and coal production, which affects the safety of coal mines. As seen from Figure 14, with an increase in GDP, the number of coal mine gas accidents decreased year by year. The growth rate of the GDP and the declining rate of the number of coal mine Processes 2020, 8, 1405 12 of 20 gas accidents are drawn on the same map in Figure 15.

250 700 584 GDP 600 492 Number of gas accidents 500 200 414 400 327 272 300 182 157 145 200 150 119 72 59 47 45 100 26 25 18 0

100 90 -100 82.1 74 GDP (trillionyuan) -200 64.1 68.6

59.3 Number of gas accidents 53.9 48.8 -300 50 41.2 31.9 34.9 -400 27 18.7 21.9 13.7 16.2 -500 0 -600 03 04 05 07 08 09 11 12 13 16 17 20 20 20 2006 20 20 20 2010 20 20 20 2014 2015 20 20 2018 Processes 2020, 8, x FOR PEER REVIEW 13 of 21 Figure 14. Changes in the number of gas accidents and GDP. Figure 14. Changes in the number of gas accidents and GDP. 15 45 GDP growth rate Gas accident reduction rate 40

12 35

30 9 25

20 6 15 GDP growth rate (%) GDP growth 10 3 Gas Accident reduction rate (%) rate Gas reduction Accident 5

0 0 4 004 005 006 007 008 009 010 011 012 013 01 015 016 018 2 2 2 2 2 2 2 2 2 2 2 2 2 2017 2 Figure 15. Changes in the growth rate of the GDP and the decline in the number of gas accidents. Figure 15. Changes in the growth rate of the GDP and the decline in the number of gas accidents. As seen from the chart, during 2003~2007, the GDP and economic growth increased each year, As seen from the chart, during 2003~2007, the GDP and economic growth increased each year, and the number of coal mine gas accidents decreased, but the decline ratio fluctuated little. and the number of coal mine gas accidents decreased, but the decline ratio fluctuated little. From 2008 to 2018, the overall growth rate of the GDP slowed, but the decline rate of the number From 2008 to 2018, the overall growth rate of the GDP slowed, but the decline rate of the number of coal mine gas accidents fluctuated greatly. For example, from 2007 to 2008, the number of gas of coal mine gas accidents fluctuated greatly. For example, from 2007 to 2008, the number of gas accidents decreased from 16.8% to 33.1%. This result shows that the number of gas disasters in 2008 accidents decreased from 16.8% to 33.1%. This result shows that the number of gas disasters in 2008 was significantly curbed and decreased significantly. However, from 2008 to 2010, the decline rate of the was significantly curbed and decreased significantly. However, from 2008 to 2010, the decline rate of number of gas accidents elicited a large drop, from 33.1% to 7.6%, indicating that the number declined the number of gas accidents elicited a large drop, from 33.1% to 7.6%, indicating that the number during this period and that the rate of decline slowed. Nevertheless, these trends are not obvious. declined during this period and that the rate of decline slowed. Nevertheless, these trends are not obvious.

5. Discussion From the above analysis results, great progress has been made in the safety production and gas prevention of coal mines in China. TM accidents are the most prominent. The main types of TM accidents are gas explosions and coal and gas outbursts. The causes of these accidents include geological conditions, technology, equipment, management and other aspects. In this paper, the impact of national policies related to coal mine gas accidents on the occurrence of accidents is discussed.

5.1. Analysis of Gas Control Policies Research on gas control policies has a certain cross-disciplinary nature, and the definitions of related concepts need to be improved eventually. Therefore, this paper only gives a definition for the scope of discussion: principles, plans, laws, regulations, standards, norms, resolutions, decisions and notifications related to gas prevention and control formulated by the state or departments and the inspection and control of safety in production. Important speeches made by leaders of relevant parties and state and departments are referred to as coal mine gas control policies and policies in a broad sense.

Processes 2020, 8, 1405 13 of 20

5.1. Analysis of Gas Control Policies Research on gas control policies has a certain cross-disciplinary nature, and the definitions of related concepts need to be improved eventually. Therefore, this paper only gives a definition for the scope of discussion: principles, plans, laws, regulations, standards, norms, resolutions, decisions and notifications related to gas prevention and control formulated by the state or departments and the inspection and control of safety in production. Important speeches made by leaders of relevant parties and state and departments are referred to as coal mine gas control policies and policies in a

Processesbroad sense. 2020, 8, x FOR PEER REVIEW 14 of 21 5.1.1. Stage of Gas Control Policy 5.1.1. Stage of Gas Control Policy Coal mine gas prevention and control work is the top priority of coal mine safety production. Coal mine gas prevention and control work is the top priority of coal mine safety production. The Chinese government has attached great importance to this work and has issued a series of The Chinese government has attached great importance to this work and has issued a series of policies and measures to promote coal mine gas prevention and control. Generally, there is a time lag policies and measures to promote coal mine gas prevention and control. Generally, there is a time lag between the promulgation of a policy and its eﬀect on the prevention and control of gas accidents. between the promulgation of a policy and its effect on the prevention and control of gas accidents. Therefore, this paper collects and collates the relevant policies of gas prevention and control from Therefore, this paper collects and collates the relevant policies of gas prevention and control from 2000 to 2018. In Figure 16, the developmental stages of gas control policies and the number of annual 2000 to 2018. In Figure 16, the developmental stages of gas control policies and the number of annual promulgation policies are given. promulgation policies are given. 20 19 Number of policies 18 Before 2005 2005 2006~2015 2016~Present 17 Independent Milepost Promotion and development Consolidation and 16 implementation of promotion 15 enterprises 14 14 13 12 11 11 11 10 9 9 8 7 6 6 6 Number of policies of Number 6 5 5 5 5 4 4 4 4 4 4 3 2 2 2 2 1 1 0

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Figure 16. Development stage and quantity distribution of gas control policies. Figure 16. Development stage and quantity distribution of gas control policies. In the past 20 years, the policy system of gas prevention and control has been continuously improved,In the and past the 20 developmentyears, the policy process system has beenof gas divided prevention into the and following control periodshas been or continuously stages: improved, and the development process has been divided into the following periods or stages: 1. Before 2005, the work on gas prevention and control mainly relied on the independent development of coal mine enterprises. At the national level, there is a lack of systematic and normative policy guidance. Most of the policies related to gas prevention and control are contained in comprehensive policies, and there is a lack of targeted policies for gas prevention and control; 2. In 2005, China’s coal mine gas prevention and control mechanism was formally formed, which is an important milestone in promoting the work. After the establishment of the Inter-ministerial Coordination Leading Group for Coal Mine Gas Prevention, a series of targeted policies for gas prevention, such as Opinions on the Implementation of Coal Mine Gas Control and Utilization, have been issued, and the related organizations and functions of gas prevention and control have been further improved; 3. The period from 2006 to 2015 was the promotion and development stage for gas prevention and control. At the national level, we should vigorously promote the rapid development of gas prevention and control, establish and improve the gas prevention and control system, organize major technical tackles, achieve breakthroughs, publish gas control and utilization policies intensively, further expand the policy coverage, continuously refine policy contents and further improve operability and pertinence;

Processes 2020, 8, 1405 14 of 20

1. Before 2005, the work on gas prevention and control mainly relied on the independent development of coal mine enterprises. At the national level, there is a lack of systematic and normative policy guidance. Most of the policies related to gas prevention and control are contained in comprehensive policies, and there is a lack of targeted policies for gas prevention and control; 2. In 2005, China’s coal mine gas prevention and control mechanism was formally formed, which is an important milestone in promoting the work. After the establishment of the Inter-ministerial Coordination Leading Group for Coal Mine Gas Prevention, a series of targeted policies for gas prevention, such as Opinions on the Implementation of Coal Mine Gas Control and Utilization, have been issued, and the related organizations and functions of gas prevention and control have been further improved; 3. The period from 2006 to 2015 was the promotion and development stage for gas prevention and control. At the national level, we should vigorously promote the rapid development of gas prevention and control, establish and improve the gas prevention and control system, organize major technical tackles, achieve breakthroughs, publish gas control and utilization policies intensively, further expand the policy coverage, continuously reﬁne policy contents and further improve operability and pertinence; 4. The period including and following 2016 was the consolidation and promotion stage for gas prevention and control. In 2016, the state started a structural reform on the coal industry’s supply side and issued a series of industry policies. At this stage, the gas prevention and control system had been improved, the technology had been further improved and serious gas accidents had been eﬀectively controlled.

5.1.2. Effectiveness of Gas Control Policy From 2003 to 2018, remarkable achievements were made in the prevention and control of coal mine gas in China. The total number of gas accidents and deaths dropped dramatically. Gas accidents were effectively curbed, and major and more severe gas accidents were essentially eliminated. The important source of these positive results is the promulgation of a series of gas control policies and measures by the Chinese government and relevant departments. By sorting out a series of gas control policies and related accident data in the past 15 years, the preliminary assumption of the intervention degree of gas control policies is proposed, and the relationships between occurrence trends and policy interventions on the degree of gas accidents in China are analyzed. At present, there are many studies that have conducted quantitative assessments of economic security policies in China and in other countries, and the scope of these studies has gradually extended to include assessments of climate protection policies and safety production policies, but there are few quantitative studies on gas control policies. To deeply analyze the correlation between gas prevention and control policies and gas accident control, the idea of the degree of policy intervention is proposed. By ranking the degrees of the importance and influence of policies and considering the number and degree of the influence of policies, a quantitative evaluation of policy intervention degree is made.

5.1.3. Policy Data Sources To conduct a more comprehensive analysis of the role of policies in accident prevention and control, this paper collects and collates relevant policies issued since 2000, mainly from the oﬃcial websites and databases of the National Development and Reform Commission, the Ministry of Finance, the Ministry of Emergency Management, the National Coal Mine Safety Supervision Bureau and other ministries, as well as the compilation of relevant important documents and yearbooks. Processes 2020, 8, 1405 15 of 20

5.1.4. Analysis of Policy Intervention Degree

Policy Classification As shown in Figure 17, the policies are sorted on the basis of time. According to the different publishing institutions and forms of the policies, while considering the different influences of different policies, the gas control policies were divided into five categories: laws and regulations, leaders’ speeches and instructions, targeted inspection and remediation actions, treatment of the personsProcesses 2020 responsible, 8, x FOR PEER for accidentsREVIEW and accident notifications. 16 of 21

Categories

· Handling of the person Speeches and instructions Law and Special inspection and Accident responsible for the from the heads of relevant regulation rehabilitation action notification accident departments

Gas control policy

Development states

Figure 17. ClassificationClassification and development stage of gas control policy. Ranking and Quantitative Assignment Ranking and Quantitative Assignment This paper qualitatively ranks the degrees of influence of the above five types of gas control This paper qualitatively ranks the degrees of influence of the above five types of gas control policies. The order of influence from large to small is as follows: P1 is laws and regulations, P2 is policies. The order of influence from large to small is as follows: P1 is laws and regulations, P2 is leaders’ speeches and instructions, P3 is the handling of accident liabilities, P4 is special inspection and leaders’ speeches and instructions, P3 is the handling of accident liabilities, P4 is special inspection remediation actions and P5 is accident notifications. The weights of 5, 4, 3, 2 and 1 were given to these and remediation actions and P5 is accident notifications. The weights of 5, 4, 3, 2 and 1 were given to five kinds of policies, respectively. these five kinds of policies, respectively. Considering the timeliness of policies, to determine the objective effectiveness cycles of different Considering the timeliness of policies, to determine the objective effectiveness cycles of different policies and analyze the cumulative effects of policies, it was assumed that the objective effectiveness of policies and analyze the cumulative effects of policies, it was assumed that the objective effectiveness policies was obvious and stable in the years of their effectiveness cycles, but weak in the years beyond of policies was obvious and stable in the years of their effectiveness cycles, but weak in the years their effectiveness cycles. The policy effectiveness cycles were roughly divided into three levels: the beyond their effectiveness cycles. The policy effectiveness cycles were roughly divided into three period of effectiveness of P1 was 5 years, those of both P2 and P4 were 3 years and those of both P3 and levels: the period of effectiveness of P1 was 5 years, those of both P2 and P4 were 3 years and those P5 were 1 year. By synthesizing factors such as the number of policies and the weight of the degree of of both P3 and P5 were 1 year. By synthesizing factors such as the number of policies and the weight influence, we can obtain the degree of policy intervention. The concrete calculation model is as follows: of the degree of influence, we can obtain the degree of policy intervention. The concrete calculation model is as follows: Ai = Pi Vi (1) × Ai = Pi × Vi (1) where Ai is the policy intervention degree, Pi is the number of policies and Vi represents the weight of thewhere degree Ai is of the influence. policy intervention degree, Pi is the number of policies and Vi represents the weight of theThe degree annual of influence. and cumulative policy intervention degree were calculated by the above formula, and theThe results annual are and shown cumulative in Figure policy 18. intervention degree were calculated by the above formula, and the results are shown in Figure 18.

ProcessesProcesses 20202020, ,88, ,x 1405FOR PEER REVIEW 1716 of of 21 20

500

450 The current year Accumulate 400

350

300

250

200

150 Policy intervention degree 100

0 5 0 5 04 09 14 003 008 013 2 20 200 2006 2007 2 20 201 2011 2012 2 20 201 2016

Figure 18. Histogram of the intervention degree of China’s gas control policy from 2003 to 2016. Figure 18. Histogram of the intervention degree of China’s gas control policy from 2003 to 2016. Figure 18 shows the histogram of the intervention degree of China’s gas control policy from 2003 to 2016.Figure From 18 shows 2003 to the 2004, histogram the degree of the of policyintervention intervention degree in of that China’s year gas was control relatively policy low, from with 2003 little tofluctuation. 2016. From The 2003 degree to 2004, of the policy degree intervention of policy increased intervention significantly in that year from was 2005 relatively to 2007, low, and with the degree little fluctuation.of policy intervention The degree in of that policy year intervention was greater thanincreased in other significantly years, which from directly 2005 to led 2007, to a relativelyand the degreehigh degree of policy of cumulativeintervention policy in that intervention year was gr fromeater 2006 than to in 2008. other After years, 2007, which the directly degree ofled policy to a relativelyintervention high that degree year of remained cumulative relatively policy stable. interven Thistion shows from that 2006 before to 2008. 2005, After the 2007, frequent the occurrencedegree of policyof coal intervention mine gas accidents that year and remained the large relatively number ofstable. deaths This aroused shows the that vigilance before of2005, relevant the frequent agencies, occurrenceand prompt of measures coal mine were gas taken accidents to issue and a seriesthe large of targeted number control of deaths policies, aroused which the played vigilance a positive of relevantrole in the agencies, prevention and andprompt control measures of coal minewere gastaken accidents. to issue a series of targeted control policies, which played a positive role in the prevention and control of coal mine gas accidents. 5.2. Analysis of the Relation between Gas Accidents and Policy Intervention Degree 5.2. Analysis of the Relation between Gas Accidents and Policy Intervention Degree The implementation of a policy has a timeliness effect on the prevention and control of gas accidents.The implementation Therefore, the trendof a policy charts has of the a numbertimeliness of deathseffect on and the accidents prevention in China and werecontrol compared of gas accidents.with the trendTherefore, charts the of trend the cumulative charts of the intervention number of deaths degree and of gas accidents prevention in China and were control compared policies, withas shown the trend in Figure charts 19 of. the cumulative intervention degree of gas prevention and control policies, as shownFrom in Figure the graph, 19. we can see that the corresponding relationship between coal mine gas accidents and the intervention degree of gas prevention and control policies in China has a certain regularity, and the following analysis additionally considers the evolution processes of the policies. From 2003 to 2005, targeted policies for gas control and utilization were issued sequentially, and due to the periodic cumulative effect of policy effectiveness, the intervention degree of gas prevention and control policies increased rapidly. The number of deaths and accidents was negatively correlated with the degree of policy intervention, indicating that at this stage, the gas prevention and control policies were gradually improved and strengthened. The degree of policy intervention has played an active role in ensuring the safe production of coal mines.

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1000 800 Cumulative policy intervention degree Number of gas accidents 600 800

400

600 200

400 0 Average degree

-200 accidents gas of Number

200 Cumulative policy intervention degree intervention policy Cumulative -400 0

2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Figure 19. Trend comparison of gas accidents and the policy intervention degree from 2003 to 2016. Figure 19. Trend comparison of gas accidents and the policy intervention degree from 2003 to 2016. After many extraordinarily serious gas accidents in 2004 and 2005, from 2006 to 2011, the state attachedFrom great the graph, importance we can to see the that safety the ofcorresponding coal production, relationship especially between to the controlcoal mine of gas disasters,accidents and activelythe intervention explored degree the comprehensive of gas prevention utilization and control of gas inpolicies promoting in China sustainable has a certain development regularity, of theand coalthe following industry. Theanalysis competent additionally authorities considers for gasthe preventionevolution processes and control of the work policies. have been stable, and policiesFrom 2003 for to gas 2005, control targeted and utilizationpolicies for have gas control been issued and utilization intensively. were More issued than sequentially, 40 policies have and beendue to issued. the periodic The coverage cumulative of theeffect policies of policy has effectiveness, been further the expanded, intervention involving degree economic of gas prevention policies suchand control as finance, polic taxation,ies increased price, rapidly. technology The number and equipment. of deaths and The accidents contents was of the negatively policies havecorrelated been continuouslywith the degree refined, of policy and intervention, the operability indicating and pertinence that at ofthis the stage, policies the have gas prevention been further and improved. control Thepolicies intervention were gradually degree improved has reached and thestrengthened. highest level The since degree 2003. of policy At the intervention same time, has the played number an ofactive deaths role and in ensuring accidents the has safe declined production rapidly, of coal and mines. the eff orts for gas disaster control have achieved remarkableAfter many results. extraordinarily serious gas accidents in 2004 and 2005, from 2006 to 2011, the state attachedFrom great 2012 importance to 2016, the to policy the safety system of coal of gas production, control and especially utilization to the was control gradually of gas formed disasters, and continuouslyand actively explored improved. the Thecomprehensive intervention utilization degree of of gas gas control in promoting policies remainedsustainable stable, development effectively of guaranteeingthe coal industry. the e Thefforts com forpetent gas prevention authorities and for control gas prevention continued and despite control major work changes have inbeen industrial stable, structure.and policies The for number gas control of gas and accidents utilization continued have tobeen decline issued steadily, intensively. and the More number than of 40 deaths policies showed have abeen declining issued. trend, The coverage but stopped of the declining policies in has 2016. been Up further to 20 gas expanded, accidents involving and 215 deathseconomic occurred policies in coalsuch mines,as finance, accounting taxation, for price, 60.6% technology and 74.4% and of the equipment. total number The ofcontents coal mine of the accidents policies and have deaths, been respectively.continuously Gasrefined, accidents and the are operability still the focus and ofpertinence preventing of the and policies curbing have serious been and further extraordinarily improved. seriousThe intervention accidents. degree has reached the highest level since 2003. At the same time, the number of deaths and accidents has declined rapidly, and the efforts for gas disaster control have achieved 6.remarkable Conclusions results. From 2012 to 2016, the policy system of gas control and utilization was gradually formed and After years of management, the level of safety production in China’s coal industry has been continuously improved. The intervention degree of gas control policies remained stable, effectively significantly improved, especially the occurrence of gas accidents, which has been significantly curbed. guaranteeing the efforts for gas prevention and control continued despite major changes in industrial However, the total number of coal mine accidents in China is still large, and the fatality rate is still structure. The number of gas accidents continued to decline steadily, and the number of deaths far greater than those of developed countries. Gas accidents are still the first killer of coal mines. showed a declining trend, but stopped declining in 2016. Up to 20 gas accidents and 215 deaths Through this study, the main conclusions are as follows: occurred in coal mines, accounting for 60.6% and 74.4% of the total number of coal mine accidents and deaths, respectively. Gas accidents are still the focus of preventing and curbing serious and extraordinarily serious accidents.

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1. Among all types of accidents in coal mines, gas accidents pose the greatest threat to safety in production, accounting for 11.66% of accidents and 30.18% of deaths. 2. Among the gas accidents, gas explosion and coal and gas outburst accidents are the most serious. Complex areas, in terms of geological structure, have the highest frequency of occurrence, and the township coal mines are the main mines in the ownership system. 3. The development of China’s coal mine gas control policy has gone through three stages: the independent development stage of enterprises before 2005, the promotion stage from 2006 to 2015 and the consolidation and promotion stage from 2016 to present, with 2005 being a milestone in the development of gas control policy. 4. With continuous improvements in the gas control policy system, gas accidents have been greatly curbed. Gas control policies are an important aspect in guaranteeing coal mine safety in production and are the main drivers of gas prevention and control work. 5. Gas control policies are active and eﬀective in the prevention and control of coal mine gas accidents, indicating that the comprehensive implementation of safety policies is an important measure to ensure the safety of production activities, having important guidance for high-risk industries, production activities with frequent accidents and areas with signiﬁcantly unsound policies.

Author Contributions: Conceptualization, W.K.; Methodology, W.K.; Validation, K.W.; Formal Analysis, W.K. and K.W.; Investigation, W.K.; Resources, K.W.; Writing—Original Draft Preparation, W.K.; Writing—Review & Editing, K.W.; Visualization, W.K.; Supervision, K.W.; Project Administration, W.K. All authors have read and agreed to the published version of the manuscript. Funding: The authors gratefully acknowledge the financial support provided by the Major Consulting Project of the Chinese Academy of Engineering (No. 2017-ZD-03) and the National Science Foundation of China (No. 51904311). Comments by all anonymous reviewers are highly appreciated. Conflicts of Interest: The authors declare no conflict of interest.

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