Preparation Of Pyrolytic Biochar From Reed And Its Application In The Tempering And Mechanical Dewatering Of Municipal Sludge

Municipal sludge is a solid waste produced in the process of urban sewage treatment,with high organic content,high moisture content,and difficulty in dewatering.If urban sludge is improperly disposed of,it will not only cause secondary pollution,has a negative impact on the ecological environment and human health,but also cause a waste of resources rich in calorific value sludge.Reeds are plants that improve the water environment in the lake area.Every year after the reeds wilt,they will cause secondary pollution to the water if they are not disposed of in time.In view of the difficulty in dewatering of urban sludge and the waste of reed resources,this thesis uses the pyrolysis method to prepare reed pyrolysis biochar,and modifies the reed biochar.It is used in urban sludge conditioning and mechanical dewatering,which not only improves The dewatering performance of the sludge is improved,and a sludge filter cake with good calorific value is also obtained,which creates conditions for the resource utilization of urban sludge.The pyrolysis method is used to prepare reed pyrolysis biochar and its influencing factors are discussed.The results showed that:the yield of reed pyrolysis biochar decreased with the increase of pyrolysis temperature,and decreased with the increase of pyrolysis time;the volatile content(V_ad)of reed pyrolysis biochar increased with the pyrolysis temperature Increase and decrease with the increase of pyrolysis time,while the change trend of ash content(A_ad)and fixed carbon content(C_ad)is opposite;;During the pyrolysis reaction,the accumulation of C elements increases,the H and O elements gradually decrease,and the N element content does not change much;the pyrolysis of reed can increase its energy density,and the calorific value of reed increases from 15.51MJ·kg^-1 before pyrolysis to heat.The decomposed（reed biochar）21.21～26.03 MJ·kg^-1is conducive to the safe disposal and energy utilization of reeds.The effect of reed pyrolysis biochar on municipal sludge conditioning and mechanical（vacuum filtration）dehydration effect was studied using the experimental method of vacuum filtration and dehydration:the preparation conditions of reed were pyrolysis temperature 300℃and pyrolysis time 0.5h.Reed pyrolysis biochar has a good effect on urban sludge conditioning and mechanical dehydration.When its dosage is 4 g（100ml sludge,with 97%moisture content）and the particle size is 75～180μm,the reed heat Biochar has the best effect on urban sludge conditioning and mechanical（vacuum filtration）dehydration.The moisture content,dehydration time,and sludge specific resistance SRF of the municipal sludge filter cake were reduced from 84.70%,180s,4.6×10¹²m·kg^-1before quenching and tempering to 66.86%,45s,4.2×10¹² m·kg^-1 after quenching and tempering.The calorific value of the municipal sludge filter cake has increased from 10.31 MJ·kg^-1 before quenching and tempering to 14.59 MJ·kg^-1after quenching and tempering,creating conditions for the direct energy utilization of municipal sludge.A high-efficiency sludge conditioner RB-Ⅲ was prepared by using reed pyrolysis biochar to load metal ions A⁺.The reed pyrolysis biochar was pretreated with 1mol·L^-1hydrochloric acid and then loaded with 3mol·L^-1 metal ion A⁺solution.RB-Ⅲ and RB-Ⅲ have significant effects on conditioning and mechanical dewatering of municipal sludge.When the dosage of RB-Ⅲ is 0.9g（100ml sludge,98%moisture content）,after conditioning and mechanical（vacuum filtration）dehydration of municipal sludge,the moisture content,sludge specific resistance（SRF）,and dehydration of the sludge cake Time and supernatant turbidity decreased from 83.25%,1620s,61.25×10¹² m·kg^-1,1620s,1950NTU before conditioning to 70.21%,1.10×10¹²m·kg^-1,45s,9.8NTU,after RB-Ⅲ The calorific value of the municipal sludge cake after quenching and dewatering has been increased from 9.38 MJ·kg^-1 before quenching to13.61 MJ·kg^-1.Through the experimental method of mechanical filter press dehydration,when other filter press conditions are the same,the water content of the filter cake decreases with the increase of the dosage of RB-Ⅲ.When the dosage of RB-Ⅲ is 3g（100ml sludge,the water content is 95%）,the water content of the filter cake decreases with the increase of pressure.At 1.6MPa,the water content of the filter cake is reduced from the current 76.38%to 32.63%.The calorific value of the sludge filter cake has been increased from 9.65 MJ·kg^-1 before quenching and tempering to 16.72 MJ·kg^-1after quenching and tempering.It can be directly burned for power generation,and at the same time realizes the efficient resource utilization of reeds and urban sludge.