A Life Cycle Analysis of Deploying Coking Technology to Utilize Low-Rank Coal in China

sustainability

Article A Life Cycle Analysis of Deploying Coking Technology to Utilize Low-Rank Coal in China

Yan Li 1, Guoshun Wang 1, Zhaohao Li 2, Jiahai Yuan 3 , Dan Gao 2,* and Heng Zhang 2

1 School of Business, Central South University, Changsha 410083, China; [email protected] (Y.L.); [email protected] (G.W.) 2 School of Energy, Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China; [email protected] (Z.L.); [email protected] (H.Z.) 3 School of Economics and Management, North China Electric Power University, Beijing 102206, China; [email protected] * Correspondence: [email protected]

Received: 12 May 2020; Accepted: 10 June 2020; Published: 15 June 2020

Abstract: At present, the excess capacity in China’s coke industry can be deployed to utilize some low-rank coal, replacing coking coal with potential economic gains, energy efficiency, and environmental benefits. This study presents a life cycle analysis to model these potential benefits by comparing a metallurgical coke technical pathway with technical pathways of gasification coke integrated with different chemical productions. The results show that producing gasification coke is a feasible technical pathway for the transformation and development of the coke industry. However, its economic feasibility depends on the price of cokes and coals. The gasification coke production has higher energy consumption and CO2 emissions because of its lower coke yield. Generally speaking, using gasification coke to produce F-T oils has higher economic benefits than producing methanol, but has lower energy efficiency and higher carbon emissions.

Keywords: coal coking; life cycle analysis; gasiﬁcation coke; metallurgical coke; low-rank coal

1. Introduction Since the beginning of the new century, the rapid development of China’s urbanization and industrialization has driven the rapid development of the coke industry and the rapid expansion of its domestic coke capacity. China’s coke production totaled 438 million tons in 2018, accounting for over 60% of the world’s total coke production, and China is the world’s largest coke country [1]. From the statistics of coke consumption structure by industry, coke consumption in the steel industry accounts for about 85% of the country’s total coke consumption [1]. However, the steel industry has faced supply-side structural reforms recently in China, which have forced coke companies to reduce capacity under tremendous pressure. On the other hand, there are fewer coking coal resources for producing coke. China has more proven reserves of low-rank coal, with reserves of about 875.73 billion tons, accounting for 59% of proven reserves [2]. Utilizing excess coke capacity, replacing some high-quality coking coal with low-rank coal with large reserves and low cost, and producing gasiﬁcation coke for the chemical industry will be conducive to the sustainable development of the coke industry [3]. Life cycle analysis (LCA) is an environmental impact assessment analysis tool that is used to evaluate the activity, process, and product. Using LCA, one can study the environmental impact and corresponding energy use throughout the life cycle (LC) of the research object [4]. At present, LCA has been widely used in chemical catalysts [5,6], biofuels [7–9], solar energy [10,11], wind energy [12,13], power generation [14,15], and the coal chemical industry [16–18]. Among them, using LCA in the coal chemical industry can analyze the coal-based synthetic natural gas (SNG) life cycle (LC) [19,20],

Sustainability 2020, 12, 4884; doi:10.3390/su12124884 www.mdpi.com/journal/sustainability Sustainability 2020, 12, x 2 of 17

Sustainability 2020, 12, 4884 2 of 17 in the coal chemical industry can analyze the coal-based synthetic natural gas (SNG) life cycle (LC) [19,20], coal-to-methanol alternative fuel [21–23], and coal to olefins [24,25]. Ou et al. studied fuel consumptioncoal-to-methanol and alternative CO2 emission fuel throughout [21–23], and the coal LC to process olefins [with24,25 a]. focus Ou et on al. the studied carbon fuel emissions consumption [26]. Ouand et CO al.2 emission used the throughout LCA method the to LC evaluate process traditional with a focus gasoline on the fuels, carbon coal emissions-based methanol [26]. Ou etnew al. vehicleused the fuels, LCA electric method-powered to evaluate vehicles, traditional and gasoline biofuels, fuels, and found coal-based that methanolfuel consumption new vehicle and fuels, CO2 emissionelectric-powered of biofuels vehicles, were andsignificantly biofuels, lower and found than thatother fuel fuels consumption or energy [ and27]. COQin2 emissionet al. used of software biofuels towere study significantly CO2 traces lower throughout than other the LC fuels process or energy [28]. Li [27 et]. al. Qin studied et al. the used production software process to study of SNG CO2 andtraces power throughout cogeneration the LC [29 process]. In the [28 research,]. Li et al. the studied fuel consumption the production and processCO2 emission of SNG were and the power key problems.cogeneration Studies [29]. of In s theome research, research the pathways fuel consumption of synthetic and natural CO2 emissiongas found were that thesynthetic key problems. natural gasStudies can of reduce some research fuel consumption pathways of and synthetic CO2 emission. natural gas Based found on that the synthetic above literature natural, gas however, can reduce no studiesfuel consumption specifically and investigated CO2 emission. coal liquefaction Based on the LCA above to supply literature, vehicle however, power. no studies specifically investigatedThis paper coal uses liquefaction LCA to study LCA tothe supply impact vehicle and economic power. potential of coal coking transformation technologies.This paper Some uses research LCA to coal study coking the impact pathways and economicare studied potential in detail of for coal their coking economic transformation benefits, energytechnologies. consumption Some research, and CO2 coal emissions. coking In pathways Section 2, are the studied modeling in detail detail fors and their equations economic of LCA benefits, are introduced.energy consumption, In Section and 3, COthe2 economy,emissions. energy, In Section and2, theenvironment modeling detailsal performance and equations of some of LCA typical are researchintroduced. pathways In Section of 3coal, the coking economy, are energy, compared. and environmental In Section 4, some performance findings of with some perspective typical researchs are concludedpathways of. coal coking are compared. In Section4, some findings with perspectives are concluded.

2. Mathematic Mathematic M Modelingodeling Section 22 presents a a mathematic mathematic modeling modeling coal coal-coking-related-coking-related pathways pathways LCA. LCA. In this In this paper, paper, the lowthe- low-rankrank coal coal used used was was the thelong long flame flame coal, coal, which which came came from from the the Shenfu Shenfu coalfield coalfield in in Yulin Yulin City, City, Shaanxi Province. Long Long fla flameme coal coal is is the the bituminous bituminous coal coal with with the the lowest lowest degree degree of of metamorphism, and its main characteristics are high volatilityvolatility (volatile(volatile onon drydry ash-freeash-free volatilevolatile VVdafdaf > 37%) and no cohesion or weak cohesion (caking index G < 5). In In Figure Figure 11,, thethe processesprocesses fromfrom coalcoal toto thethe finalfinal products related toto thethe coal-coking-relatedcoal-coking-related pathways pathways are are shown. shown. Four Four parts parts make make up up Figure Figure1. 1. Tables Tables1 1and and2 list 2 the list coal-coking-related the coal-coking-related research research pathways pathways and the input and andthe outputinput and of typical output metallurgical of typical metallurgicalcoking and gasification coking and coking gasific processes.ation coking processes.

Coal Product Coal mining transportation Production distribution

Coking Metallurgical Railway Coking Truck Steelmaking coal Coke raw materials

Gasification Railway Coking Truck Low coke rank coal Chemical Methanol Tanker raw materials Methanol synthesis truck

Fischer-Tropsch Gasoline & Tanker Transportation synthesis diesel truck fuel

Figure 1. FourFour coal coal-coking-related-coking-related research pathways pathways..

TableTable 1. CoalCoal-coking-related-coking-related research pathways.

AbbreviationAbbreviation Mining Mining Transportation Transportation Production Production Distribution Distribution Coking coal RailwayRailway TruckTruck long long delivery MCMC Coking coal mining CoalCoal coking coking mining transportationtransportation toto Steelmaking Steelmaking CokingCoking coal coal and and Railway Truck long delivery GC Low-rank coal Railway Coal coking Truck long delivery GC Low-rank coal transportation Coal coking to chemical mining transportation to chemical mining Coking coal and Tanker Truck long Coking coal and Railway CoalCoal coking coking and and GC-M Low-rank coal Railway Tankerdelivery Truck to long GC-M Low-rank coal transportation methanolmethanol synthesis mining transportation deliverychemical to chemical mining synthesis Coking coal and Tanker Truck long Coking coal and Railway Coal coking and Tanker Truck long GC-O Low-rank coal Railway Coal coking and delivery to fuel GC-O Low-rank coal transportation F-T synthesis delivery to fuel mining transportation F-T synthesis station mining station Sustainability 2020, 12, 4884 3 of 17

Table 2. Input and output of typical metallurgical coking and gasiﬁcation coking processes.

Type Metallurgical Coking Gasiﬁcation Coking 58% coking coal + 42% low-rank Coal as ﬁre 100% coking coal coal Coke yield 75% 67% Tar yield 3.15% 4.07% Crude benzene yield 0.95% 1.24% Coke oven gas production 340 m3/t 451 m3/t

In order to ensure the fairness of comparison, this paper assumed that the raw coal transportation distance was 50 km and the product transportation distance was 500 km. Therefore, the technical pathway MC in Table1 can be expressed as: after being mined and washed, the coking coal was transported 50 km by railway to the coking plant and used for production of metallurgical coke and other by-products, then finally transported 500 km to the steel plant in a large truck. Other pathways can also be expressed as such. Metallurgical and gasification coke production can share the same coke oven, and the production processes are basically similar. The main differences are the characteristics of the incoming coal and various products. Related data of typical metallurgical and chemical gasification coke productions are listed in Table2[ 3,30]. It can be seen that, compared with metallurgical coke production, the coke production of gasification coke is reduced, but the tar, crude benzene, and coke oven gas production are increased. In particular, it is important to note that the final products of some technical pathways involved in this paper were chemical raw materials, not energy products, so estimating the energy consumption and CO2 emission of products at the end use was not easy. Therefore, the whole life cycle described in this paper was uniformly defined as four stages that ended in the product; that is, the final use of the product was not considered.

2.1. Economic Benefit Analysis Introducing the net benefit per product (Bp, with the unit Yuan/ton, or USD/ton) as an index for economic analysis: tb tc Bp = P− . (1) mp Here, tb and tc represent the total annual economic benefit and total annual economic cost of whole technical pathway, respectively; mp represents the annual amount of product. tb and tc can be calculated as follows: X tb = mppp, (2) p X X tc = (pc + tpc)mc + Cpro + Cdispmp. (3) c p

Here, mc represents the annual amount of raw coal, pp represents the price of the product; pc and tpc represent the coal price and railway transportation price per ton of coal, respectively; Cdisp is the entire cost per ton of the product in the distribution process; Cpro represents the total annual cost in the process of production, calculated as

Cpro = TCCpro ε + AOMCpro, (4) · with 1 ε = , (5) 1 (1 + i)n − AOMCpro = VOMCpro + FOMCpro = (αV + αF)TCCpro ε. (6) · Sustainability 2020, 12, 4884 4 of 17

Here, TCCpro represents the entire capital cost; ε represents the capital recovery factor; AOMCpro represents the annual operation and maintenance cost, composed of the annual variable operation and maintenance cost (VOMCpro) and the annual ﬁxed operation and maintenance cost, which can be obtained by multiplying the annual TCCpro by empirical coeﬃcients αV and αF, respectively. Cdisp can be calculated as Cpro, and bypassed here. tpc, according to the announcement of the China railway transportation company, can be calculated as follows:

tpc = tpa + tpb Lc. (7) ·

Here, tpa and tpb both represent transportation prices; Lc represents the transportation distance of raw coal. Table3 shows the key parameters for the economic analysis.

Table 3. Key parameters for the economic analysis.

Parameter Value Unit Source Price of coking coal 670 Yuan/ton Ref. [31] Price of low-rank coal (Long flame coal) 240 Yuan/ton Ref. [31] Price of metallurgical coke 850 Yuan/ton Ref. [30] Price of gasification coke 730 Yuan/ton Ref. [30] Price of tar 1800 Yuan/ton Ref. [30] Price of crude benzene 4000 Yuan/ton Ref. [30] Price of coke oven gas 0.5 Yuan/Nm3 Ref. [30] Average price of methanol 2080 Yuan/ton Ref. [32] Average diesel price 7500 Yuan/ton Ref. [33] Average gasoline price 8500 Yuan/ton Ref. [33] Industrial electricity price 0.4744 Yuan/kWh Ref. [34] Railway transport price a (coal) 16.3 Yuan/ton Ref. [35] Railway transport price b (coal) 0.098 Yuan/ton/km Ref. [35] One-off total capital cost of coal coking 224 Yuan/(ton/year) Ref. [36] One-off total capital cost of 5500 Yuan/(ton/year) Ref. [37] methanol synthesis One-off total capital cost of F-T synthesis 15,800 Yuan/(ton/year) Ref. [38] Exchange rate between Yuan and US dollar 7.05 Yuan/USD Ref. [39]

2.2. Life Cycle Energy Consumption Analysis The energy consumption (Ep, with the unit MJ/ton) of a given technology pathway in the life cycle energy analysis is introduced in this paper as follows:

tec Ep = P . (8) mp

Here, tec is the total amount of input primary energy, and the calculation equation is written as follows: tec = ecmin + ectra + ecpro + ecdis. (9) Sustainability 2020, 12, 4884 5 of 17

Here, ecmin, ectra, ecpro, and ecdis represent the energy consumptions of the four processes of coal mining, coal transportation, production, and distribution, respectively. Due to the energy consumption calculation of each process being very similar, we take the calculation of ecpro as an example:

ecpro = PEecpro + SEecpro + MCecpro, (10)

with i X SEecpro SEecpro = (i = electricity, diesel, etc.), (11) η i i Xh j i MCecpro = MC mec + mrec + EFBecpro + EFBRecpro (j = steel, cement, etc.) (12) pro · j j j

i where PEecpro and SEecpro are the direct primary energy and direct secondary energy consumptions per unit of product in the technical pathway, respectively; ηi is the energy transformation eﬃciency during j the secondary energy production; MCpro is the material consumption in the technical pathways; mecj and mrecj represent the energy consumption per unit of material in the production process and the aforementioned material recycling process, respectively; similarly, EFBecpro and EFBRecpro represent the energy consumption per unit of product in the course of the equipment/factory construction and recycling, respectively. The main parameters of the economic beneﬁt analysis in this paper are listed in Table4.

Table 4. Main parameters in life cycle energy analysis.

Item Value Unit Reference Average power consumption of coal mining 25.8 kWh/ton Ref. [40] and washing Average energy consumption in the process 30.5 kgce/ton Ref. [40] of coal mining and washing Average energy consumption in the process 890 kgce/ton Ref. [40] of steel production Average energy consumption in the process 135 kgce/ton Ref. [40] of cement production Average energy consumption for 4.11 gce/ton/km Ref. [41] railway transportation Average loss ratio of power transmission 6.21% - Ref. [42] and distribution Average coal consumption of coal-ﬁred 308 gce/kWh Ref. [42] power generation industry Electricity consumption for coke production 43 kWh/ton Ref. [37] Energy consumption of methanol synthesis 1.4 GJ/ton Ref. [21] Energy eﬃciency of F-T synthesis 42% - Ref. [38]

2.3. Life Cycle CO2 Emissions Analysis

In this section, CO2 emissions per product (CEp, with the unit ton/ton) of the given technology pathway in the life cycle environmental analysis is introduced as follows:

tce ECp = P . (13) mp Sustainability 2020, 12, 4884 6 of 17

Here, tce represents the total amount of CO2 emissions. Its calculation method is similar to tec, which is composed of the same aforementioned four parts, and it can be calculated as follows:

tce = cemin + cetra + cepro + cedis. (14)

For example, cepro can be calculated as follows:

cepro = PEcepro + SEcepro + MCcepro, (15)

with X h i i SEcepro = SEW (dce + ice ) (i = electricity, diesel, etc.), (16) pro · i i j

Xh j i MCcepro = MC mce + mrce + Ccepro + CRcepro (j = steel, cement, etc.), (17) pro · j j j where, PEcepro and SEcepro are the direct CO2 emissions per unit of product of the primary energy and the indirect CO2 emissions from the secondary energy in the technical pathway, respectively. dcei and icei represent the direct and indirect CO2 emissions in its energy production; MCcepro represents the indirect CO2 emissions per unit of product from material (such as steel, cement) consumption in the technical pathways; mcej and mrcej represent the CO2 emissions per unit of material in the process of material production and recycling, respectively; Ccepro and CRcepro represent the CO2 emissions due to equipment/factory construction and the recovery process. The main parameters that are applied to compute direct CO2 emissions are listed in Table5.

Table 5. Main parameters used to calculate direct CO2 emissions.

Parameter Value Unit Source Average CO emissions from coal mining 2 64 kg/ton Ref. [21] and washing

Average CO2 emissions from electric industry 627 g/kWh Ref. [21]

Average CO2 emissions from coal combustion 2.71 ton/tce Ref. [38]

Average CO2 emissions from diesel production 0.51 kg/L Ref. [43]

Average CO2 emissions from diesel combustion 2.57 kg/L Ref. [43]

CO2 emissions from metallurgical coke production 0.15 ton/ton Ref. [44]

CO2 emissions from methanol synthesis 3 ton/ton Ref. [21]

CO2 emissions from F-T synthesis 4.79 ton/ton Ref. [38]

3. Results and Discussion The life cycle analyses of diﬀerent technical pathways of coal coking are introduced and analyzed. The four technical pathways are divided into two categories: the product of both MC and GC is coke, and GC-M and GC-O are extensions of the gasiﬁcation coke product chain.

3.1. Economic Benefit Analysis Figure2 shows the economic costs and benefits of the four technical pathways. In Figure2, positive values are benefits, mainly from sales of the main products (coke, methanol, or oil products) and by-products (tar, benzene, coke oven gas, etc.); negative values are costs, which include mainly four parts: raw coal purchase cost, raw coal transportation cost, production cost, and product transportation cost; the red diamonds and values represent the net benefits. In Figures2–4, the unit selected is the Yuan, and the exchange rate between the Yuan and the US dollar is shown in Table3. Therefore, only the Yuan is used in Figures2–4. Comparing the metallurgical coke and gasification coke pathways Sustainability 2020, 12, 4884 7 of 17 according to Figure2, the coke yield of the gasification coke pathway was lower than that of the metallurgical coke pathway, according to the perspective of benefit comparison analysis. This was because the gasification coke pathway had a lower coke yield and price than the metallurgical coke pathway, but its by-product benefits were significantly higher than the metallurgical coke pathway, because of its higher by-product yield (seen in Table2). From the cost comparison of these two pathways, gasification coke was significantly lower than metallurgical coke because gasification coke production used some low-cost and low-rank coal. From the perspective of net benefit comparison, the gasification coke pathway was higher than the metallurgical coke pathway, which showed that the use of coke production capacity and the addition of low-rank coal to produce gasification coke had a Sustainabilitycertain economic 2020,, 12,,value. xx 7 of 17

2500

1500 476 536 135 341 500

-500

-1500

-2500 MC GC GC-M GC-O Cost/benefit Cost/benefit (Yuan/ton coke) Cost/benefit Cost/benefit (Yuan/ton coke) Coke MeOH F-T By-product Coal Transportation Production Distribution Net Benefit

Figure 2. Economic analyses of four coke coke-derived-derived technical pathways.

Figure 3. Sensitivity analyses of two coke price changes. Sustainability 2020, 12, 4884 8 of 17 Sustainability 2020, 12, x 8 of 17

FigureFigure 4.4. Sensitivity analyses of two coal price changes.changes.

WeWe comparedcompared twotwo coke coke pathways pathways with with two two gasification gasification coke-derived coke-derived technical technical pathways pathways (GC-M (GC- andM and GC-O). GC- TheO). The yield yield of the of main the main products products of the latterof the two latter pathways two pathway was significantlys was significantly higher than higher that ofthan the that two of coke the pathways.two coke pathway This wass. because This was the because price of the the price product of the after product derived after chemical derived processing chemical wasprocessing much higher was much than higher the price than of the coke. price After of derivedcoke. After chemical derived processing, chemical processing, however, the however, production the costproduction of the latter cost twoof the pathways latter two was pathway much highers was thanmuch the higher two cokethan pathways.the two coke From pathway the perspectives. From the of netperspective benefit, forof net the benefit unit of, cokefor the production unit of coke the production net benefit ofthe the net latter benefit two of technical the latter pathways two technical was higherpathway thans was that higher of the than two cokethat of pathways, the two coke indicating pathw thatays, itindicating was of economic that it was value of economic to carry out value deep to processingcarry out deep of chemical processing products of chemical based products on gasification based coke.on gasification coke.

3.2.3.2. Sensitive StudyStudy of Economic Analysis TheThe resultsresults of of the the economic economic analysis analysis largely largely depended depend onedthe on pricesthe price of thes of products. the product For thes. For above the fourabove technical four technical pathways, pathway the pricess, the ofprices cokes of and coke raws and coals raw were coal importants were important parameters parameters affecting affecting the net benefitthe net ofbenefit each technicalof each technical pathway. pathway. IfIf the the price price of of raw raw coal coal and and other other conditions conditions remain remain the same, the the same, selection the selection of the optimal of the technical optimal pathwaytechnical forpathway different for metallurgicaldifferent metallurgical and gaseous and cokegaseous prices coke is shownprices is in shown Figure 3in. Figure If the price3. If the of gasificationprice of gasification coke is less coke than is 900less Yuanthan /900ton (127.66Yuan/ton USD (12/ton),7.66 andUSD/ theton) price, and of the metallurgical price of metallurgical coke is less thancoke 1200is less Yuan than/ ton1200 (170.21 Yuan/ton USD (170.21/ton), theUSD/ productionton), the production of gasification of gasification coke coupled coke with coupled a chemical with a processchemical such process as F-T such will as have F-T thewill largest have the net benefit.largest net If the benefit price. ofIf the metallurgical price of metallurgical coke is higher coke than is 1200higher Yuan than/ton 1200 (170.21 Yuan USD/ton/ ton),(170.21 and, USD/ consequently,ton), and, consequently 300 Yuan/ton, (42.55300 Yuan USD/ton/ton) (42.55 higher USD/ thanton) the higher price ofthan gasification the price of coke, gasifi thecation production coke, the of production metallurgical of metallurgical coke will have coke a large will nethave benefit. a large Ifnet the benefit price. ofIf the gasification price of gasification coke is higher coke than is higher 900 Yuan than/ ton900 (127.66Yuan/ton USD (127.66/ton), USD/ andton) not, lower and not than lower the than price the of metallurgicalprice of metallurgical coke by morecoke by than more 300 than Yuan 300/ton Yuan (42.55/ton USD (42.55/ton), USD/ the productionton), the production of gasification of gasification coke will havecoke awill higher have net a higher benefit. net benefit. IfIf thethe priceprice ofof cokecoke andand otherother conditionsconditions remainremain unchanged,unchanged, onlyonly thethe pricesprices ofof cokingcoking coalcoal andand low-ranklow-rank coal coal change, change, without without considering considering the two the chemical two chemical coke deep coke processing deep processing technical pathwaystechnical (GC-M,pathway GC-O,s (GC-M, whose GC-O, coal whose purchase coal purchase costs were cost thes were same the as GCsame pathways). as GC pathway Thes) net. The benefit net benefit of the cokeof the pathway coke pathway is shown is shown in Figure in Figure4. It can 4. beIt can seen be from seen Figure from Figure4 that the4 that net the benefit net benefit of the twoof the coke two pathwayscoke pathway has as significanthas a significant impact impact on the on prices the price of raws of coals, raw andcoal whens, and the when coal the price coal reaches price reaches a certain a certain level, the net benefits of both pathways will be negative. By fitting the red dashed line in Figure 4 an inequality can be obtained, which is shown as Equation (18): Sustainability 2020, 12, 4884 9 of 17 level, the net benefits of both pathways will be negative. By fitting the red dashed line in Figure4 an inequalitySustainability can2020, be 12, obtained,x which is shown as Equation (18): 9 of 17

BGC > BMC (pcc > 1.34 plrc 113). (18) > ∀ ∀( > 1.34×× − − 113). (18) For EquationEquation (18), the unit is YuanYuan/ton./ton. According to the exchange rate between the Yuan and the US dollar shown shown in in Table Table 33,, the equation for for unit unit USD/ USDton/ton can can be be obtained. obtained. That That is, is,if the if the price price of of coking coal pcc is higher than(1(1.34.34 × plrc − 113)), the gasiﬁcation coke pathway has more economic coking coal is higher than × − , the gasification coke pathway has more economic advantages. If the contrary, the coking coalcoal technicaltechnical pathwaypathway hashas moremore economiceconomic advantages.advantages.

3.3. Life Cycle Energy Analysis TheThe life life cycle cycle energy energy consumptions consumption ofs di ofﬀerent different technical technical pathways pathway in twos categories in two categories were analyzed were andanalyzed compared. and compared. Figure5 shows Figure the 5 shows full life the cycle full energy life cycle consumptions energy consumption of two cokes of technical two coke pathways. technical Accordingpathways. toAccording Figure5, to of Figure the four 5, stages,of the four the production stages, the phaseproduction accounted phase for accounted the vast majorityfor the vast of themajority total energyof the total consumption energy consumption in the life cyclein the (about life cycle 90%). (about The 90%). energy The consumption energy consumption for raw coal for mining,raw coal washing, mining, and washing product, and transportation product transportation was relatively was small, relatively and the energy small, consumption and the energy for rawconsumption coal transportation for raw coal can transportation be ignored. The can energy be ignored. consumption The energy of the con cokingsumption pathway of the was coking about 25%pathway higher was than about that 25%of the higher metallurgical than that coke of pathway, the metallurgical which was coke mainly pathway because, which the cokewas yieldmainly of thebecause gasiﬁcation the coke coke yield was of lowerthe gasification than that ofcoke the was metallurgical lower than coke. that of the metallurgical coke.

coke) 10 onsumption (GJ/ton onsumption

Energy c Energy 0 MC GC Mining Transportation Production Distribution

Figure 5. Comparison of energy consumptions between the MC and GC pathways.pathways.

Figure6 6 shows shows thethe lifelife cyclecycle energyenergy consumptions consumptions ofof twotwo gasificationgasification cokecoke coupledcoupled chemicalchemical process technical pathwayspathways (GC-M(GC-M and GC-O).GC-O). To showshow thethe energyenergy consumptionconsumption of thethe productionproduction process more clearly, FigureFigure6 6 divides divides the the production production process process into into two two parts: parts: thethe gasification gasification coke coke production process and the chemical production process. In Figure 66,, ofof thethe fivefive stages,stages, thethe energyenergy consumption of the gasificationgasification coke production phase accounted for about 56% of the totaltotal energy consumption, the chemical process energy consumption accounted for more than 37%, and the other process energy consumptionconsumption waswas relativelyrelatively small.small. Sustainability 2020, 12, 4884 10 of 17 Sustainability 2020, 12, x 10 of 17 Sustainability 2020, 12, x 10 of 17

180180 160160 140140 120120 100

100uct) uct) 8080 prod prod 6060 4040 2020

Energy consumption (GJ/ton consumption Energy 0

Energy consumption (GJ/ton consumption Energy 0 GC-MGC-M GC-OGC-O MiningMining TransportationTransportation Production-GCProduction-GC Production-M/OProduction-M/O DistributionDistribution

Figure 6. ComparisonComparison of energy energy consumptions between the GC GC-M-M and GC-OGC-O pathways.pathways. Figure 6. Comparison of energy consumptions between the GC-M and GC-O pathways.

In terms of energy consumption of per ton of product, GC GC-O-O was much higher than GC GC-M.-M. Since In terms of energy consumption of per ton of product, GC-O was much higher than GC-M. Since both methanol and F F-T-T oil can be used as energy products, the energy consumption per unit of heat both methanol and F-T oil can be used as energy products, the energy consumption per unit of heat value of of both both fuels fuels could could be be compared. compared. Figure Figure 7 shows7 shows the the comparison comparison of energy of energy consumptions consumptions and value of both fuels could be compared. Figure 7 shows the comparison of energy consumptions and efficienciesand eﬃciencies between between the GC the-M GC-M and GC and-O GC-O pathways pathways.. According According to Figure to Figure7, the full7, the life full cycle life energy cycle efficiencies between the GC-M and GC-O pathways. According to Figure 7, the full life cycle energy efficiencyenergy eﬃ ofciency the GC of- theM technical GC-M technical pathway pathway was about was 31%, about and 31%, that and of thatthe GC of the-O pathway GC-O pathway was about was efficiency of the GC-M technical pathway was about 31%, and that of the GC-O pathway was about 21%.about 21%. 21%.

100%100%

80%80%

60%60%

40%40%

20%20%

0%0% GC-MGC-M GC-OGC-O Energy consumption/efficiency Energy Energy consumption/efficiency Energy MiningMining TransportationTransportation Production-GCProduction-GC Production-M/OProduction-M/O DistributionDistribution ProductProduct

Figure 7. Comparison of energy consumptions and efficiencies between the GC-M and GC-O FigureFigure 7. 7.CompariComparisonson of of energy consumptions consumptions and and eﬃ efficienciesciencies between between the GC-M the GC and-M GC-O and pathways. GC-O pathways. pathways.

3.4. Life Cycle CO2 Emissions Analysis 3.4. Life Cycle CO2 Emissions Analysis Sustainability 2020, 12, 4884 11 of 17

3.4.Sustainability Life Cycle 2020 CO, 122, xEmissions Analysis 11 of 17 Figure8 shows the life cycle CO emissions of the two coke technical pathways. According to Figure 8 shows the life cycle CO22 emissions of the two coke technical pathways. According to Figure8 8,, thethe COCO2 emissionemission of the the metallurgical metallurgical coke pathway over the life cycle was about 0.37 ton/ton ton/ton coke, and the CO emission of the gasiﬁcation coke pathway was about 17% higher than that of the coke, and the CO2 emission of the gasification coke pathway was about 17% higher than that of the metallurgical coke coke pathway. pathway Of. Of the fourthe fourstages, stages, the production the production stage emitted stage theemitted most CO the2 , accountingmost CO2, for about 60% of the total emissions; followed by the CO emissions from the raw coal mining and accounting for about 60% of the total emissions; followed2 by the CO2 emissions from the raw coal washingmining and stage, washing which stage, accounted which for accounted less than 30%for less of the than total 30% CO of2 emissions; the total CO and2 emissions; regarding and the productregarding transportation, the product transportation, because of the amountbecause of of CO the2 emittedamount byof dieselCO2 emitted combustion, by diesel the COcombustion,2 emitted duringthe CO2 the emitted product during transportation the product accounted transportation for about accounted 10% of for the about total emissions. 10% of the total emissions.

0.5

0.4

0.3

0.2

0.1

CO2 emissions (ton/ton coke) (ton/tonemissions CO2 0 MC GC Mining Transportation Production Distribution

Figure 8.8. Comparison of CO2 emissions between the MC and GC pathways pathways..

Figure9 9 shows shows thethe lifelife cycle cycle COCO22 emissions of two gasificationgasification coke coupled chemical technical pathwayspathways (GC-M(GC-M and GC-O).GC-O). According toto FigureFigure9 9,, the the CO CO22 emissions of GC-MGC-M and GC-OGC-O over the entire life cycle werewere about 3.68 tonton/ton/ton methanolmethanol and 6.97 tonton/ton/ton F-TF-T oil,oil, respectively.respectively. Of the fivefive stages, the subsequent chemical productionproduction stagestage ofof gasificationgasification cokecoke emittedemitted thethe mostmost COCO22, followed by the gasificationgasification coke production stage, and the raw coal mining and washing stage, and the other two stages emittedemitted less.less. Sustainability 2020, 12, 4884 12 of 17 Sustainability 2020, 12, x 12 of 17

8 6 4 2

product) 0 GC-M GC-O

CO2 emissions (ton/tonemissions CO2 Mining Transportation Production-GC Production-M/O Distribution

Figure 9. Comparison of CO2 emissionsemissions between between the GC GC-M-M and GC GC-O-O pathways pathways..

3.5. Comparative A Analysisnalysis of Different Different Coal Transportation ModesModes andand DistancesDistances In China,China, inin additionaddition to to railway railway transportation, transportation, coal coal can can generally generally be transportedbe transported by truck.by truck. In this In section, we analyze and compare the economic benefits, energy consumption, and CO emissions of this section, we analyze and compare the economic benefits, energy consumption, and CO2 2 emissions diof ff differenterent coal coal transportation transportation vehicles vehicles and di ff anderent different transportation transportation distances. distances. Since the two Since gasification the two coke-derivedgasification coke technical-derived pathways technical (GC-M pathways and GC-O) (GC-M are and both GC continuations-O) are both of continuation the gasifications of coke the technicalgasification pathway, coke technical this section pathway compares, this and section analyzes compares only the and two analyzes coking technologyonly the two pathways. coking Thetechnology comparative pathway technicals. The pathwaycomparative is shown technical in Table pathway6, where is shown MC and in GCTable technical 6, where pathways MC and useGC 50-kmtechnical railway pathways transportation, use 50-km 50 railway T represents transportation, 50-km truck 50 transportation, T represents 50 and-km 100 truck R represents transportation, 100-km railwayand 100 transportation.R represents 100-km railway transportation.

Table 6. Coal-coking-related research pathways. Table 6. Coal-coking-related research pathways.

AbbreviationAbbreviation Mining Mining Transportation Transportation Production Production Distribution Distribution 5050 km railway Coal TruckTruck long long delivery MCMC CokingCoking coal coal mining mining Coal coking transportationtransportation coking toto Steelmaking Steelmaking 50 km truck Truck long delivery MC-50T Coking coal mining 50 km truck CoalCoal coking Truck long delivery MC-50T Coking coal mining transportation to Steelmaking transportation coking to Steelmaking 100 km railway Truck long delivery MC-100R Coking coal mining 100 km railway CoalCoal coking Truck long delivery MC-100R Coking coal mining transportation to Steelmaking transportation coking to Steelmaking Coking coal and Coking coal and 50 km railway Truck long delivery GC Low-rank coal 50 km railway CoalCoal coking Truck long delivery GC Low-rank coal transportation to chemical mining transportation coking to chemical mining Coking coal and 50 km Truck Truck long delivery GC-50T CokingLow-rank coal and coal Coal coking transportation50 km Truck Coal Truckto long chemical delivery GC-50T Low-rankmining coal transportation coking to chemical Cokingmining coal and 100 km railway Truck long delivery GC-100R CokingLow-rank coal and coal Coal coking 100transportation km railway Coal Truckto long chemical delivery GC-100R Low-rankmining coal transportation coking to chemical mining As can be seen from Figure 10, different coal transportation methods had basically no effect on economicAs can benefits. be seen Afterfrom Figure the transportation 10, different distancecoal transportation was increased methods from had 50 km basically to 100 no km, effect the neton economic incomebenefits. decreased After the somewhat, transportation to roughly distance RMB was 30 increased/ton. The gasificationfrom 50 km coke to 100 pathway km, the had net a greatereconomic impact income than decreased the metallurgical somewhat, coke to roughly pathway. RMB 30/ton. The gasification coke pathway had a greater impact than the metallurgical coke pathway. Sustainability 2020, 12, 4884 13 of 17 Sustainability 2020, 12, x 13 of 17

1500

1000 341 344 310 500 135 137 106

-500

-1000

Cost/benefit Cost/benefit (Yuan/ton coke) -1500 MC MC-50T MC-100R GC GC-50T GC-100R

Coke MeOH F-T By-product Coal Transportation Production Distribution Net Benefit

Sustainability 20Figure20, 12, 10. x Economic comparison of different diﬀerent coal transportation modesmodes and distances.distances. 14 of 17

It can be seen from Figure 11 that didifferentﬀerent coal coal transportation transportation methods and transportation distances had little effect eﬀect on the total energy consumption of the whole life cycle, because the energy consumption of the coal transportatio transportationn part accounted for a small proportion. From a numerical numerical point of view, the energy consumptionconsumption ofof trucktruck distributiondistribution waswas aboutabout threethree timestimes thatthat ofof trucktruck mining.mining.

10 coke) 5

0 Energy consumption (GJ/ton consumption Energy

Mining Transportation Production Distribution

Figure 11. EnergyEnergy consumption consumption comparison comparison of of different diﬀerent coal transportation modesmodes and distances.distances.

It can can be be seen seen from from Figure Figure 12 that 12 the that eﬀ ect the of effect transportation of transportation distance on distance CO2 emissions on CO2throughout emissions throughoutthe life cycle the was life very cycle small, was very because small, the because CO2 emissions the CO2 ofemissions the coal of railway the coal transportation railway transportation part were partvery were small. very For the small. same For 50-km the same transportation 50-km transportation distance, the COdistance,2 emissions the CO of2truck emissions transportation of truck weretransportation more than were four more times than those four of railwaytimes those transportation. of railway transportation.

0.5

0.4

0.3

0.2

0.1

0 CO2 emissions (ton/ton coke) (ton/tonemissions CO2

Mining Transportation Production Distribution

Figure 12. CO2 emission comparison of different coal transportation modes and distances. Sustainability 2020, 12, x 14 of 17

It can be seen from Figure 11 that different coal transportation methods and transportation distances had little effect on the total energy consumption of the whole life cycle, because the energy consumption of the coal transportation part accounted for a small proportion. From a numerical point of view, the energy consumption of truck distribution was about three times that of truck mining.

10 coke) 5

0 Energy consumption (GJ/ton consumption Energy

Mining Transportation Production Distribution

Figure 11. Energy consumption comparison of different coal transportation modes and distances.

It can be seen from Figure 12 that the effect of transportation distance on CO2 emissions throughout the life cycle was very small, because the CO2 emissions of the coal railway transportation Sustainabilitypart were 2020very, 12 small., 4884 For the same 50-km transportation distance, the CO2 emissions of 14 truck of 17 transportation were more than four times those of railway transportation.

0.5

0.4

0.3

0.2

0.1

0 CO2 emissions (ton/ton coke) (ton/tonemissions CO2

Mining Transportation Production Distribution

Figure 12. CO2 emissionemission comparison comparison of of different diﬀerent coal transportation mode modess and distances.distances.

4. Conclusions In conclusion, life cycle analyses of coal coking technical pathways were studied, focusing on analyzing the economic benefits, energy consumptions, and CO2 emissions. The gasification coke and its derived technical pathways were based on excess coke production capacity and the use of low-rank coal. The gasification coke technical pathway was compared with that of metallurgical coke, and the technical pathways of gasification coke integrated with chemical productions were also discussed. The main conclusions include:

(1) According to the economic benefit analysis, utilizing excess coke production capacity, replacing some high-quality coking coal with low-cost and low-rank coal, producing gasification coke, and using it in chemical production will have additional economic benefits. (2) The economic benefits of each technical pathway depend on the prices of cokes and coals, and this paper gives specific optimized price conditions. (3) Compared with metallurgical coke, gasification coke production would increase the energy consumption and CO2 emissions, because of the lower coke yield. (4) Generally speaking, using gasification coke to produce F-T oils has higher economic benefits than using it to produce methanol, but has low energy efficiency and high carbon emissions. (5) Different coal transportation modes (railway transportation or truck transportation) and transportation distances have little effect on economic benefits, energy consumption, and CO2 emissions throughout the life cycle.

In the actual coke production process, coal tar, coke oven gas, and other by-products have good deep chemical processing potential. For example, CO, H2, and other coke oven gas can be used to produce chemical products. Modern coking enterprises also have such integrated system production cases. Production of gasification coke can produce more by-products, such as tar and coke oven gas, which has more potential for economic benefits. In order to analyze the feasibility, advantages, and disadvantages of gasification coke production in this paper, no research was conducted on the deep chemical processing of these by-products. Sustainability 2020, 12, 4884 15 of 17

Author Contributions: Conceptualization, G.W. and J.Y.; Data curation, Y.L. and D.G.; Formal analysis, Y.L.; Funding acquisition, Y.L. and G.W.; Investigation, Y.L., G.W. and D.G.; Methodology, Y.L. and G.W.; Software, Z.L. and H.Z.; Supervision, G.W.; Validation, Z.L., J.Y. and H.Z.; Visualization, Z.L. and H.Z.; Writing—original draft, Y.L., Z.L. and D.G.; Writing—review & editing, G.W. and J.Y. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by by National Key R&D Program of China (2016YFB0600401). Conflicts of Interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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