Microwave-assisted Pyrolysis Of Industrial Solid Waste And Study On The Gases And Condensates

With the rapid development of industry,the production of industrial solid waste is increasing year by year.The problem to be solved urgently is the solid wastes disposal in recent years.Many researchers have favored the emerging microwave assisted pyrolysis technology,which can dispose industrial solid wastes harmlessly and efficiently.However,microwave pyrolysis technology needs improvement and amplification to achieve large-scale application.This paper investigated an auger pyrolyser under microwave using textile dyeing sludge(TDS)and furfural residual(FR)as feedstocks.The effects of different temperature,auger speeds and catalysts on the pyrolysis products were investigated.The gases and condensates were analyzed by GC,FTIR and GC-MS methods.The migration and transformation mechanism of nitrogen in textile dyeing sludge during microwave pyrolysis was summarized.Finally,according to the experimental data,mass balance,energy balance and electricity consumption of two kinds of materials during microwave pyrolysis process were carried out.The results show that:(1)The condensate of textile dyeing sludge reached the maximum yield at 650 ?,12.86wt%.The yield of furfural residue condensate reached the maximum at 550 ?,21.49wt%.The main components of pyrolysis gas are CO2,CO,CH4 and H2.The pyrolysis gas yield of textile dyeing sludge and furfural residual increased with the increase of pyrolysis temperature.The highest yield was obtained at 750 ?,14.00wt%and 40.73wt%respectively.Moreover,the H2 content reached the maximum value,33.77vol%and 28.09vol%respectively.(2)The addition of CaO catalyst can decrease the yield of condensate and pyrolysis gas,and the content of CO2 in thermal gas is also reduced greatly,and the content of H2 is increased.Adding Fe to textile dyeing sludge increased the yield of non-condensable gas by 5.7wt%compared with that without catalyst,and optimized the composition of gas due to H2 content.Adding kaolin and K2CO3 to furfural residual can reduce the yield of condensate and increase the yield of pyrolysis gas.Especially the addition of K2CO3 can promote the pyrolysis,obtain the lowest condensate yield(8.14wt%)and the highest pyrolysis gas yield(51.51 wt%).(3)The pyrolysis oil of textile dyeing sludge contains aromatic compounds,oxygenated compounds,aliphatic compounds and some compounds containing N,P and S atoms.The content of aromatic compounds in pyrolysis oil is the highest,most of which are nitrogen containing aromatic heterocyclic compounds,such as pyridine and their derivatives,which content is about 30%-50%.The influence of temperature on the composition of pyrolysis oil is that the high concentration of oxygen compounds at low temperature,while aromatic compounds occupy the dominant position at high temperature.And the bio-oil obtained after the pyrolysis of furfural residue contains:(1)phenolic compounds,such as phenol,(2)furan compounds,such as 2-furan methanol,etc(3)esters,such as 4-carbonyl valerate,etc(4)ketones,such as 1-(acetyl)2-acetone,etc.(4)HCN and NH3 are the two typical nitrogen-containing gases released during the pyrolysis process.NH3 mainly comes from the decomposition of inorganic salts and protein at low temperature.The maximum yield is 0.65%(650 ?),while HCN mainly comes from the cracking of nitrile and heterocyclic-N compounds at high temperature.The maximum yield is 12.30%(850 ?).During the microwave assisted pyrolysis,the nitrogen recovery of textile dyeing sludge was 72-91%,and at least 1/3 remained in solid phase of TDS.(5)The results of energy balance show that the energy recovery rate of the three-phase products of FR is higher than that of TDS.Under the same experimental conditions(650 ?,1 rpm),the energy recovery rates of gas,liquid and solid phase products of FR were 45.69%,0.95%and 15.7%respectively.While those of TDS were 17%,0.59%and 7.64%respectively.The energy recovery of gas during furfural residual pyrolysis is higher than that of textile dyeing sludge.At the range of 450-750 ? and 1-9 rpm,the electricity consumption of TDS is 0.64-5.26 kWh/kg dry material.When it comes to FR,at the range of 450-750 ? and 1 rpm,the electricity consumption is 1.26-5.13 kWh/kg dry material.Higher auger speed and lower temperatures led to lower electricity consumption.