Impact of Sawmill Waste on SO2 Emissions from Co-firing with Lignite

ABSTRACT

Results of experimental studies of joint pyrolysis processes of a fairly typical and widely used in Russia and Poland 3B grade lignite and wood (sawdust of pine wood) are provided. The results were performed in order to substantiate the previously formulated hypothesis about the mechanism of suppression of sulfur oxides in the combustion products of such mixed fuels. Conclusions on the mechanism of SOx suppression were made after comparing the analysis results of the elemental composition of the initial lignite, wood, and ash remaining after the total completion of the studied mixtures pyrolysis processes, as well as X-ray phase analysis of the ash composition. It was found that the proportion of calcium and aluminum sulfates is higher in the solid pyrolysis products of mixtures of crushed coal and wood compared to the ash of homogeneous coal. Practical significance of the performed studies is that the obtained results of the experiments allow to justify the possibility of using wood as a part of mixed fuels based on 3B grade lignite as an additive that significantly reduces the yield of sulfur oxides during combustion of such fuels in the furnaces of steam and hot water boilers. It has been experimentally established that during high-temperature decomposition of two-component fuels based on 3B lignite in a mixture with fine wood biomass, the effect of reduction of sulfur oxide concentration in gaseous pyrolysis products of such mixtures is obtained due to the formation of calcium and aluminum sulfates in the ash of mixed fuels as a result of chemical reactions between gaseous and solid pyrolysis products of lignite and wood with participation of water vapor.

GRAPHICAL ABSTRACT

KEYWORDS:

• Lignite
• wood
• pyrolysis
• elemental composition
• X-ray phase analysis
• solid combustion products
• calcium and aluminum sulfates

Acknowledgments

The research was supported by Tomsk Polytechnic University Competitiveness Enhancement Program.

Highlights

• The mechanism of the binding of sulfur oxides in the pyrolysis products of pulverized coal and dispersed wood has been substantiated

• Experimental studies were carried out in the temperature range from 400°C to 800°C

• An analysis of the elemental and X-ray phase composition of the initial components, mixed fuels, and ash residue is presented

• A significant increase in the content of calcium and aluminum sulfates in the ash of fuel mixtures has been established

Additional information

Funding

The study was carried out with financial support of RFBR, project No. 18-29-24099\18.