Effects Of Mineral Components And Modified Molecular Sieves On Catalytic Pyrolysis Characteristics Of Industrial Sludge

Industrial sludge is a kind of solid waste with serious toxicity and pollution,meanwhile it also has certain resource utilization potential.On the basis of harmless and reduction treatment,further resource utilization has become a new approach of industrial sludge disposal.In this thesis,the pyrolysis mechanism and catalytic pyrolysis characteristics of industrial sludge from a chemical plant were studied with TG-FTIR and Py-GC/MS method,so as to provide a feasible scheme for the disposal and resource utilization of industrial sludge.Firstly,the basic pyrolysis characteristics of industrial sludge were studied.The pyrolysis of industrial sludge can be divided into three stages:moisture removal,devolatilization and mineral decomposition.The maximum thermal weight loss happened in the third stage,and the thermal weight loss rate was also the highest due to the high ash content of the sludge.The fitting calculation results of pyrolysis kinetic parameters showed that the activation energy was highest in the third stage,and the higher heating rate would enhance the reaction hysteresis.The main components of the volatile product of industrial sludge were acids,sulfur-containing,nitrogen-containing and oxygen-containing compounds,and the hydrocarbon content was relatively low.Higher pyrolysis temperature and suitable residence time promoted the reduction of oxygen-containing compounds and the increase of hydrocarbon.The optimum reaction temperature and residence time in this work were800℃and 10s,respectively.Then,the catalytic effect of specific minerals in the sludge on the pyrolysis characteristics was studied with acid-refining pretreatment and specific minerals addition（Ca O,Fe₂O₃,Si O₂）.The results showed that acid-refining pretreatment and mineral addition brought satisfied catalytic effect.The initial temperature of the pyrolysis reaction decreased and the pyrolysis activation energy reduced.Catalytic pyrolysis also promoted the generation of small molecular gases,such as CO₂,CO and CH₄.The oxygenate compounds in pyrolytic product of acid-refined sludge and specific mineral added sludge were effectively removed.Meanwhile the content of hydrocarbon increased and acid components decreased.All these have improved the quality of pyrolytic product.The catalytic effect of Ca O was better than Si O₂ with the significant increase of aromatic and aliphatic hydrocarbons.Fe₂O₃ showed the preferable effect in oxygenate compounds remove.Finally,HZSM-5 molecular sieve was selected and impregnated with Zn,Ni and Fe to study the light aromatics production in rapid catalytic pyrolysis of industrial sludge.The results showed that under the condition of 25 of Si/Al ratio and 1:2 of IS:HZSM-5 ratio,the content of oxygenate compounds in catalytic pyrolysis products of industrial sludge decreased to the lowest and the total amount of light aromatics increased to the highest value.With metal impregnation modification,the amount of acid on strong acid site was greatly reduced,and this induced further shape selective catalytic reaction.Compared with unmodified HZSM-5,metal modification promoted the increase of the total amount of aromatic hydrocarbons and the proportion of light aromatic hydrocarbons.The yield of toluene and xylene increased to 33.45%and29.47%respectively with Zn modification,and benzene increased to 22.68%with Ni modification.Zn modified HZSM-5 led to the highest yield of light aromatics,up to84.96%.