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Fossil Fuels
The industrial waste as part of coal-water slurry fuels Galina Nyashina, Nikita Shlegel, Ksenia Yu. Vershinina, and Pavel A. Strizhak Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b02826 • Publication Date (Web): 17 Oct 2018 Downloaded from http://pubs.acs.org on October 23, 2018
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Energy & Fuels
The industrial waste as part of coal-water slurry fuels Galina S. Nyashina, Nikita E. Shlegel, Ksenia Yu. Vershinina, Pavel A. Strizhak* National Research Tomsk Polytechnic University 30, Lenin Avenue, Tomsk, 634050, Russia E-mail:
[email protected]. Website: http://hmtslab.tpu.ru.
Abstract Industrialized regions of the world are actively polluting the environment. In this research, we consider one of the developed industrial regions, Siberia (Russia), as an example. The paper presents typical volumes of annually stored waste, in particular, waste of oil production and refinery (76,800 tons), liquid and watered waste of the municipal sector (167,875 tons), and food waste (5,906 tons). The parameters of ignition and combustion of such wastes have been studied in the compositions of coal-water slurry fuels with petrochemicals. The experimental results have demonstrated that most of the wastes in the industrial region under study have high potential (according to environmental, economic and energy criteria) as additives to fuels. In particular, a comprehensive comparative analysis has shown that the ignition delay time for fuel slurries with waste can be reduced by 10–60%; the minimum ignition temperature, by 10–45 °C; and concentrations of NOx and SO2 emissions, by 5–50%. The combustion heat of composite fuels can be increased by 5–20% when using admixtures from industrial waste.
Keywords: fuel slurry; industrial waste; disposal; incineration; anthropogenic emissions.
1. Introduction Industrial waste incineration provides the highest energy potential, which is widely used in many countries.1–3 Combustion of waste can significantly reduce their accumulated volume, annual growth rates, land area occupied, and greenhouse gas emissions, as well as generate
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electricity and heat. At present, more than 800 waste incineration plants are in operation in almost 40 countries around the world. They recycle approximately 11% of wastes and produce approximately 429 TWh of energy.4 For example, according to Psomopoulos5 in the United States, on average, burning 1 ton of household waste results in the electricity production of 600 kWh, which reduces consumption of coal by 0.25 tons or oil – by 1 bar.5 When treating waste as an energy resource, it is important to consider the composition its various types. Municipal solid waste from residential, industrial and commercial sources is the most common type of waste disposed of for energy production.6 However, construction waste, agricultural and forestry waste, and hazardous chemical waste can also be suitable for energy generation, depending on their specific composition and energy content. Based on the above, it is proposed to consider the wastes of a particular industrial region and the possibility of their recycling for producing additional thermal and electric energy by burning as part of composite liquid fuels. We have opted for the average size (315,000 km2) region of Russia with developed raw material industries. The industrial potential of the region is represented by more than 3,600 enterprises. Main industries are oil and gas, chemical and petrochemical, food, nuclear, power, engineering, and timber industry. In the structure of industrial production the share of the chemical and petrochemical industry is 5.1%. The availability of relatively cheap raw materials and geographical proximity to China create conditions for possible sustainable growth of the industry. Currently, 11.5% of the Russian volume of synthetic resins, including almost 16.5% of polyethylene, 36.3% of polypropylene, and a quarter of the total production of methanol in Russia, is produced here. The region is also characterized by a developed forest and wood processing industries. About 60% of the territory is covered by forests. Developed industry and infrastructure led to the accumulation of large amounts of waste of various types (including domestic). The problems of their disposal are currently not fully solved. Direct combustion of such wastes is often technologically difficult and economically costly, since their ignition is difficult; the fuel burns unstable and has a large
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Energy & Fuels
underburning. It is important to develop the basis for a more large-scale and environmentally friendly way for utilization of the multiple wastes of enterprises and industries. In recent years, the processes of co-combustion of coal and biomass (wood, agricultural waste, e.g., straw, sunflower husk, etc.) have been widely studied and tested.7–11 Co-incineration of plant waste with fossil fuels, such as coal, has several advantages. First, emissions of greenhouse gas, sulfur and nitrogen oxides are significantly reduced.9–10 Second, a large number of combustible agricultural and wood wastes of a group of industries (forestry, agriculture, construction, and food industry11) are disposed. Third, the cost of adapting an existing coal-fired power plant to co-combustion is significantly lower than the cost of building new systems.12 In the study of the possibility of using plant waste and coal, much attention is paid to the preparation, ignition, and combustion; the composition of combustion products and ash deposition is studied in detail.13–15 In addition to the analysis of co-combustion of coal and biomass, some of the known studies (in particular,16–21) consider the possibility of using various kinds of household and industrial waste in the composition of coal water slurry (CWS). Coals of different metamorphic grade22 and coal flotation waste (filter cakes)23,24 may be used as main components for the preparation of slurry fuels. A dispersed medium16,25 may be water of different quality (contaminated or pure). Oil sludge17, waste automobile and industrial oils26, water-oil emulsions23, fuel oil27, kerosene28, alcohols29, and solvents22 may serve as additives (usually with a concentration of 5–20%). Such additives are introduced to improve the parameters of ignition and combustion of slurry and to increase its combustion heat. Jianzhong et al.16 presented the results of experimental studies of combustion of CWS, in which water was replaced with liquid waste of the petrochemical industry. These results proved that compared to conventional CWS, slurries based on liquid waste are characterized by low viscosity, faster ignition, increased flame temperature, as well as a reduced concentration of NOx and SO2 emissions.
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Zhao et al.17 investigated of the combustibility of CWS with the admixture of sewage sludge and revealed a significant impact of additives on the level of harmful emissions into the atmosphere, compared with CWS. It was found that by increasing the concentration of sewage sludge (from 0 to 40%), the amount of NOx in gas combustion products is increased from 156 to 289 mg/Nm3, while the SO2 concentration decreased in the range from 138 to 18 mg/Nm3. The effect of sewage sludge on the rheological characteristics and stability of CWS was studied in the paper18. The size and morphology of the particles of the obtained slurry were analyzed. Experimental results showed that the admixture of sewage sludge can improve the efficiency of grinding and the stability of fuel. A similar study was conducted by Wang et al.19, Wang et al.20, which developed a new approach to sewage sludge recycling without pre-drying within the composition of coal-sludge-slurry and petroleum coke-sludge-slurry. Liu et al.21 developed the technology of co-combustion in the fluidized bed of oil sludge and CWS. The combustion characteristics, as well as the volume of gaseous emissions of contaminants were determined. The range of SO2 emissions varies from 120 to 220 mg/Nm3, with an average SO2 value of 177.5 mg/Nm3, which meets the environmental requirements in China (
