Basic Theory And Economic Research Of Co-combustion With Biomass Pellets And Coal

Human beings are faced with scarcity of fossil fuels and serious pollutions，whichposes a great challenge for persistent development of our economy and society. Among lotsof scenario，biomass pellets，which are known as low Sulfur，low Nitrogen， neutralemission and similar characteristics with coal，attract more and more attention In recentyears. Co-combustion technology uses biomass pellets to replace part of coal burning in theboilers. The grind ability， co-combustion characteristics and economy issues areinvestigated in this article.Firstly the grind ability of husk pellets，straw pellets and sawdust pellets were testedon a MJ-2ball mill.7hours after the pellets crushed in the mill，the husk pellets shows thebiggest particle size changes while the straw pellets are the most difficult to break intosmall sizes. The ball mill is not suitable to grind biomass pellets and HGI index is notproper to assess the grind ability of biomass pellets.Secondly，co-combustion characteristics with different blending ratios，differentparticle sizes and different coal were investigated on a STA409C Thermal GravimetricAnalyzer（TGA）. Then Fuzzy Evaluation is used to comment the ignition，the combustionand slagging of different co-combustion groups. Blending biomass into coal decreases theignition temperature，and increases the combustion characteristics. The DTG curves shows2peaks when the blending ratio is under20%, and3peaks appear when the mass ration ofbiomass increases to50%. The comprehensive combustion index becomes bigger withsmaller particle size. When blending with different coal, biomass/lignite has the highestintention of slagging. The Fuzzy Evaluation results shows husk/bituminous coal with massratio of2：8perform best in the3co-firing groups of husk and the same results withsawdust.Lastly the economy of co-combustion is researched on a300MW pulverized coalboiler. The cost of1kwh power generated with co-combustion technology is0.067￥higherthan pure coal combustion, which leads to a0.03￥/kwh drop of the power station profit.The power generation cost is sensitive to the coal price and the transport distance ofbiomass pellets.