THE QUESTION OF INTEGRATED USE OF ASH AND SLAG WASTES ON THE FAR EAST OF THE RUSSIAN FEDERATION (CASE OF CHP-2, )

A. TASKIN*, V. PETUKHOV*, A. YUDAKOV** and O. DANILOV*

* Far Eastern Federal University (FEFU), 10 Ajax Bay, Russky Island, Vladivostok, 690922, ** Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, pr. 100 years of Vladivostok, Vladivostok, 690022, Russia

SUMMARY: The possibility of complex combined use of the ash and slag waste in various industries, basing of the assessment of the chemical composition, is presented in this work (on the example of CHP-2, Vladivostok city, Primorsky region). Existing modern technical and technological solutions for the processing of ash and slag wastes are analyzed. An optimal author's version of complex, large-tonnage, ecologically safe and economically effective processing of these wastes, including obtaining valuable metal concentrates, is proposed. The feasibility studies of the efficiency of creating commodity products according to the proposed processing scheme are presented.

1. INTRODUCTION

The current world level of consumption and use of natural raw materials in various technological areas is characterized, firstly, by significant volumes (up to 30 billion tons of minerals are extracted annually), and secondly, by insignificant use of their resource potential, as a whole (orientation toward Mono-product, or an extremely limited group of prime products). As a result, the amount of various man-caused waste in the world has avalanche-like increase, the anthropogenic load on the surrounding environment is increasing, local and global ecological risks are forming, and this creates hazards for the normal functioning of natural ecosystems. One of the global consumers of energy resources, solid fossil fuels, is thermal power that burns hundreds of millions of tons of solid fuel annually. As a result, large-tonnage waste is formed - ash and fuel slags. Depending on the type of fuel and the conditions of its combustion, the ash content in the initial fuel can fluctuate very significantly: for coal from 5 to 30%, for brown coals - from 10 to 35%. Today the world has accumulated 11.5 billion tons of ash and slag wastes. In percentage terms, the distribution of waste by country is as follows: the USA - 23.5% (2.7 billion tons), Russia - 13% (1.5 billion tons), other countries - 63.5% (7.3 billion tons). All ash and slag wastes in the Russian Federation are accumulated at specialized landfills,

Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy

Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017 and their capacities are almost completely depleted (two thirds of the currently functioning coal- fired power plants have fully filled ash dumps). At the same time, obtaining additional land allocation is either problematic or impossible. In these conditions, serious problems in the ecology of Russia should be expected. So, if we consider the anticipated growth of coal generation by 2030, with an increase of 1.5 times compared to the existing one, we can expect an additional 35-36 mln.t. of ash and slag wastes annually. As a result, their volume may reach 1.7 billion tons by 2020, and 2.0 billion tons by 2030. The solution of the global ecological problem of uncontrolled growth of ash and slag wastes, considering both world and Russian experience, is possible through their processing, through progressive technological solutions with obtaining a wide range of marketable products (various building materials, concentrates of precious and rare metals, etc.). At the same time, the energy intensity of the technological conversion of waste should be less, or comparable with the processing of natural raw materials and have a positive technical and economic efficiency. At present, the USA, Germany, China and several other countries are leaders in the processing of ash and slag wastes. Abroad, the level of effective processing of the waste and its using in industry ranges from 70 to 100%. At the same time, the need for processing is fixed at the legislative level and violators are subject to significant penal sanctions from the state. As for technological level of use of ash and slag wastes in the Russian Federation, a disappointing conclusion can be done. Starting from 2007, in open sources, the statistical data on the volumes of ash and slag formation and utilization of the largest thermal energy companies is not given. The level of utilization of ash and slag waste (ASW), according to Russian experts in this area is extremely small - from 4 to 13%. It should be emphasized that during burning of only 1 ton of fossil coal, more than 2 kg of valuable metals such as Zn, Co, U, Ge, Be, Pb, Ni can be contained in the ash received during the coal combustion. Therefore, considering the aforesaid, it can be concluded that the subject of the presented research work in terms of the integrated use of ash and slag wastes is an important scientific and practical task.

2. INVESTIGATION OF THE POSSIBILITY OF COMPLEX PROCESSING OF ASH AND SLAG WASTES OF THE FAR EAST OF THE RUSSIAN FEDERATION (USING THE EXAMPLE OF CHP-2, VLADIVOSTOK)

As a research object, ash and slag wastes from the main thermal power stations and boiler houses of (57 lithogeochemical samples) were selected:

1) CHP-2 (Vladivostok city); 2) CHP (Artyom town); 3) Boiler room ( town); 4) Boiler room ( town); 5) GRES1 ( town); 6) Primorskaya GRES ( town). Studies related to the issue of integrated processing and utilization of ash and slag wastes of

1 The term GRES refers to a condenser type electricity-only thermal power station introduced in the Soviet Union which still exist in Russia and other former

Soviet republics. The Russian abbreviation stands for state-owned district power plant (often abbreviated in English as SDPP). Over time the abbreviation has lost its literal meaning, and the term refers to a high-power (thousands of megawatt) thermal power station of condenser type. Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017

Primorsky Krai were started by the scientific team in the 1990s on the basis of the Far Eastern State Technical University. During the work, data on the chemical composition of fossil coals of various grades of the main Far Eastern coal deposits was obtained (Table 1).

Table 1. Chemical composition of ash and slag from coals of the Far Eastern deposits deposit SiО , % Аl О , % Fе О , % СаО, % МgО, % К О, % Nа О, % /coal type 2 2 3 2 3 2 2 Raichikhinsckoe, B2 (Б2) 37 25 19 15 1,7 0,6 0,1 Pavlovskoye 49,5 23 8 14,5 2 0,6 1 Suchanskiy, Т (T) 60,5 23 5 4,5 2 3,5 1 Cheremkhovskoye, D (Д) 47 30 12 6 3 2 2 Azeyskoye, B3 (Б3) 61,5 22,2 10,4 4,2 1,5 0,2 0,2 Kharanorskoye,B1 (Б1) 51 17,5 11,5 14,5 2 1,5 1 Urgalskoye, G (Г) 66 24 4 2 0,5 2 0,5 Neryungrinskoye, СС (CC) 52,5 36,5 4,5 3,5 1 0,5 0,5 N-Arkagalinskoye, (D) Д 54,5 23 13 5,5 1 1,5 1 V-Arkagalinskoye, (D) Д 62,5 19 9 7 0,5 1 1

In addition, the influence of physical, chemical and granulometric properties of ash and slag wastes of the Far Eastern power industry on the possibility of their use to produce a wide range of high-quality building materials was investigated. Developments are brought to the stage of industrial introduction. The quality of the received building materials is confirmed by their testing and compliance with the requirements of ISO, DIN and GOST.

In this study, the preparation of samples for analysis was as follows:

1. Quartering (homogenization of samples) to form representative samples of waste. 2. Grinding of samples in a grinder to 100 microns class of fineness.

In analytical studies, inductively coupled plasma spectrometry (Agilent 7700 spectrometer) was used to determine the chemical composition of samples, and atomic-absorption spectrophotometry on the Shimadzu 6800 atomic-absorption spectrophotometer was used to determine silver and platinum group elements (Pt, Pd).

3. RESULTS AND DISCUSSION

As a result of the research it was established that the ash and slag wastes of the Russian Federation Far East are an alternative raw material resource to produce building materials (in terms of their physical, chemical and granulometric properties). The technology was brought to the stage of manufacturing application, it tested on the experimental production line. Finished products made with using of ash and slag wastes are shown in Fig. 1-3. Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017

Figure 1. Construction materials from ash and slag wastes from Vladivostok CHP-2 (ash mass content 20% - 80%)

Figure 2. Cement-ash bricks made with using of ash and slag wastes from Vladivostok CHP-2 (ash mass content 70%, M-75-120)

Figure 3. Ceramic brick made with using of ash and slag wastes from Vladivostok CHP-2 (ash mass content 80%, M-120-150)

Analytical studies of ash and slag samples showed the presence of a group of rare and Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017 refractory metals with the following content (g / t): 1) vanadium - 55.3; 2) chrome - 140.72; 3) nickel - 60.74; 4) rubidium - 103.6; 5) zirconium - 205.6; 6) barium - 597.4; 7) cerium - 57.4. The results correlate well with the average contents of valuable metals, given in the literature, for example, for nickel. Regarding precious metals in the ash and slag wastes analyzed, the atomic-adsorption analysis showed the following contents (Table 2).

Table 2. Content of platinum group metals and silver in ash and slag wastes of Vladivostok CHP-2, g / t № Sample Ag Pt Pd

1 CHP-2 (sample 1) heavy non-magnetic fraction 0,50 0,015 <0,001 2 CHP -2 (sample 2) heavy non-magnetic fraction 0,50 0,015 <0,001 3 CHP -2 (sample 1) light non-magnetic fraction 0,50 0,008 <0,001

4 CHP -2 (sample 2) light non-magnetic fraction 0,50 0,006 <0,001

It can be stated that there is silver (0.5 g / t) and platinum (0.015 g / t) and there is no palladium in ash and slag waste. Keeping in mind the found particularities of the chemical composition of ash and slag wastes, the authors proposed a way of their processing, which includes three stages.

I. Waste is classified into fractions, from which iron oxides and unburned fossil coal are removed. Obtained commercial products: iron concentrate, fuel with high caloric content. II. Valuable metals’ concentrates are extracted from wastes III. Different construction materials and products are produces from wastes. IV. Calculation of the main technical and economic indicators of the technological process of the extraction of valuable metal concentrate, including precious metals, shows the competitiveness of ash and slag processing technology:

1) internal rate of return (IRR) - 54.8%; 2) the payback period of capital investments is 3.3 / 3.8 years (static / discounted); 3) profitability of production - 42%.

4. CONCLUSIONS

As a result of the work:

1) high contents of industrially important refractory and rare metals in ash and slag wastes of Vladivostok CHP-2 were established; 2) a group of noble metals - silver and platinum – was found in ash and slag wastes of Vladivostok CHP-2; 3) a complex, large-tonnage, environmentally safe and cost-effective scheme for the processing of ash and slag wastes was proposed, including the scheme for obtaining precious metal concentrates. Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017

Thus, it can reasonably be concluded that the ash and slag wastes of the can reasonably be considered as technogenic raw materials with a large chemical and technological potential and wide prospects for use.

AKNOWLEDGEMENTS

The work was carried out with the financial support of the Ministry of Education and Science of the Russian Federation, within the framework of the state task in the field of scientific activity No. 10.3706.2017/4.6.

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