Study On Molding And Combustion Characteristics Of Straw Particles

Nowadays,global energy consumption is fast and energy reserves are gradually decreasing.Therefore,developing renewable energy is the top priority of energy development strategy of all countries in the world.Biomass energy is known as the"fourth largest"energy,with large reserves,low cost,renewable,pollution-free,in line with the current international"carbon neutral"purpose.Therefore,it is urgent to vigorously develop biomass energy.This thesis studied the cotton straw molding conditions,in order to enhance the physical strength and thermal stability of molding particles,so add waste-low density polyethylene plastic（PE）,coal gangue（CG）as auxiliary materials,and obtain the best process conditions of composite particle molding,calculation of molding particles combustion characteristics and required activation energy,The effects of different combustion conditions on residual K metal ions in ash and ash melting slagging were investigated.（1）The single factor method was used to study the molding particles prepared under different process parameters（raw material particle size,biomass moisture content,molding temperature,molding pressure and molding time）,and the molding density,radial pressure resistance,hydrophobicity and energy density were used as the quality evaluation criteria for the biomass molding particles.Using four factors and three levels L₉（3⁴）orthogonal experimental design,determine the best forming conditions:raw material particle size 0～0.5mm,water content 5%,forming temperature 160℃,forming pressure 7 KN,forming time 60 s.The best addition amount of plastic mulch and coal gangue is 12.5%PE+12.5%CG.（2）The fuel combustion characteristics of cotton straw particles and powder,plastic mulch and coal gangue separately added and mixed together were compared,and the ignition temperature,burnout temperature,comprehensive combustion index,flammability index and kinetic activation energy were analyzed.The results show that the dynamic model is mainly embodied in the three-order model in the volatile combustion stage and the 0.5 order model in the fixed carbon combustion stage.The apparent activation energy of the Coats-Redfern model（C-R model）is compared with that of the Flynn-Wall-Ozawa（FWO）model-free and Starink model-free methods.The C-R model and Starink method can be used to approximate the activation energy at the volatile combustion stage.Therefore,the particle with compound binder has good combustion characteristics and can be used as fuel.（3）Studied the law of metal ion residue represented by K in the combustion process of biomass molding fuel,explored the influence of different combustion time and temperature on metal ion residue of K,and explored the influence of adding inorganic mineral（Ca O）on metal ion residue of biomass molding particles.Instantaneous sampling was used to measure the combustion effect of 12.5%PE+12.5%CG particles at600～1000℃for 5 min,10 min,20 min,30 min and 1 h.The results showed that the higher the temperature,the longer the combustion time,the higher the precipitation rate of K metal ions.With the increase of combustion time,ash is more likely to melt and slagging.When the amount of Ca is within a certain range（5～10%）,the precipitation of K can be promoted.When the content of Ca is too high,the precipitation of K tends to be balanced,possibly because too much Ca O will inhibit the precipitation of K.At high temperature,the addition of Ca O is more conducive to the precipitation of KCl and improves the overall slagging resistance of the fuel.