Temperature of wood and straw pellets at carbon burning out

• Дата: 2017
• Автор: Zhovmir, M.
• Формат: Стаття
• Мова: Українська
• Опубліковано: Institute of Renewable Energy National Academy of Sciences of Ukraine 2017
• Теми: solid biofuels; pellets; carbon; burning out; particle overheating
• Онлайн доступ: https://ve.org.ua/index.php/journal/article/view/46
• Назва журналу: Vidnovluvana energetika

Main technological problems at solid biofuels burning areash sintering and submicron solid particles emission, especiallyat straw and straw pellets combustion.A significant content of potassium compounds in the cerealstraw causes low temperatures of ash sintering and melting. Atstraw burning in ash residue at temperatures above 800oC reactionswith the formation of secondary oxides and silicates occurs,which can form a fusible compound blocking movement andburning out of fuel.Low melting salts of solid biofuels ash at temperatures over900oC start to rapidly evaporate and condense with lowering ofthe flue gases temperature, which causes a significant content ofsubmicronic solid particles, creating environmental problems ofbiofuels usage.According to literary data at solid biofuels burning it wasobserved the overheating of blazing particles above muffle temperature.Overheating of blazing fractions of wood and strawpellets and its dependence on process conditions are not coveredin literature. Obviously, the overheating of blazing particles canlead to the intensification of the mentioned negative processes evenat furnace temperatures lower than that for ash sintering and itsatomization.In this paper experimentally investigated a change in temperatureof individual parts of the wood, wood and straw pelletsduring their thermolysis with volatile burning and subsequentoxidation of formed cokeash residue with free air access in amuffle furnace discovered the impact of high ash content on aparticles overheat. Research conducted by the method of an individualparticle burning in a muffle furnace preheated to400...800oC, at that the temperature inside of cylindrical particlesof wood, straw and wood pellets were measured by means of thinthermocouples.The maximum temperature of cokeash particle is achieved onit's axis just before completion of carbon burnout. Dependence ofthe maximum temperature of cokeash particle from furnace temperaturehas a complex saddle character with a local minimum at the furnacetemperature 500...550oC.It has been found that with an increase in fuel ash content theoverheating of burning particle increases: for willow particlewith ash content 0.9% it was up to 450oC; for willow pellets withash content 1.4% it was up to 530oC; for pine pellets with ashcontent 0.4% it was up 350 оС, and for straw pellets with ashcontent 9% it was up to 470оС.For investigated muffle temperature range the maximaloverheating for the cokeash residue of straw pellets were higherby 130… 60 degrees in comparison to that for wood pellets.