Key Factors Of Papermaking Sludge Pyrolysis And Design Of Pyrolysis Furnace Preliminary

Chinese paper industry is developing rapidly,the number of enterprises is decreasing after integration,and the domestic regional layout is more reasonable.Papermaking industry will produce a lot of sewage,and produce a lot of sludge in the process of papermaking wastewater treatment.How to properly,effectively and scientifically treat and dispose papermaking sludge has become an urgent environmental problem in papermaking industry.At present,the sludge disposal methods in China include landfill method,incineration method,land use and building materials utilization.With the increasingly stringent national regulations on solid waste emissions,the shortcomings of traditional sludge disposal methods have gradually emerged.Sludge pyrolysis technology has many advantages,such as the ability to solidify heavy metals,no dioxins,and high calorific value of the product,so it is favored by researchers at home and abroad.In this paper,the key factors affecting the pyrolysis of papermaking sludge were discussed by thermal drying method and pyrolysis experiment method,and the flammability of pyrolysis gas was studied.On the basis of the above,the papermaking sludge pyrolysis furnace was preliminarily designed.The results show that :A blast drying oven was used to dry paper sludge at a constant temperature of 200°C,and the results showed that: With the increase of drying time,the color of sludge changed from dark to light,and the surface gradually hardened and became dense.The gap between the overall particles of sludge became smaller,and the water content decreased significantly.Under the same drying conditions(temperature,time,etc.),the sludge stacking thickness and particle size have a significant impact on the sludge drying effect.The sludge particles were dried at the stacking thicknesses of 5,10 and 15 cm(particle sizes of 1,2 and 3 cm),and the stacking thickness of 5 cm had the best drying effect.The moisture content of sludge particles with 2 cm particle size decreased the fastest.With the increase of stacking thickness,the difference of moisture content among sludge particles with three sizes became smaller and smaller.The pyrolysis process of papermaking sludge was studied by thermogravimetric experiment.According to TG and DTG curves,the pyrolysis process can be divided into four stages : 21～170°C is the first stage,mainly due to the evaporation of water in papermaking sludge and weight loss.170～550°C is the second stage,which shows that the organic matter(cellulose,hemicellulose and small part of lignin)in papermaking sludge is weightlessness due to thermal instability.550 ～ 780°C is the third stage,this stage is the secondary decomposition of pyrolysis products coke and tar and weight loss.The fourth stage after780°C is mainly the decomposition of calcium carbonate and other minerals in paper sludge.During the sludge pyrolysis process,the pyrolysis char yield decreased with the increase of the pyrolysis temperature and the prolongation of the pyrolysis time.When the pyrolysis temperature reaches 500°C,the yield of pyrolysis char is no longer significantly reduced,indicating that the decomposition of thermally unstable organic matter in the sludge has been basically completed.500°C became a turning point in the decline of sludge pyrolysis char yield.The combustion performance of papermaking sludge pyrolysis gas was studied by self-assembly test device.It was found that the moisture content of papermaking sludge was the key factor affecting the combustion performance of pyrolysis gas.The higher the moisture content of papermaking sludge,the greater the water vapor content of sludge pyrolysis gas,and the longer the time required for the pyrolysis gas to be released to stable burning.This provides a basis for the pyrolysis furnace to reuse the pyrolysis gas as a heat source.According to the key influencing factors of papermaking sludge pyrolysis and the flammability of pyrolysis gas.The 1t/h continuous sludge pyrolysis furnace is initially designed,and its structure includes three parts.The first part is sludge drying section,the second part is sludge pyrolysis section,the third part is pyrolysis gas recycling section.From the material and energy balance calculation results,it can be seen that the minimum energy required to dispose of papermaking sludge with a moisture content of 50% at a low temperature of 300°C is 938051.42 k J,the resulting pyrolysis carbon energy is 4128639.5 k J,and the pyrolysis gas is 1745425.2 k J.The reusing the pyrolysis gas can significantly reduce the cost of sludge pyrolysis,and at the same time achieve zero discharge of sludge pyrolysis pollutants.