Study On Tar Residue Solidification-dry Distillation Pyrolysis Process

Viscous solid tar sludge was produced in the process of gasification and coking of coal,which contains various harmful polycyclic aromatic hydrocarbons and polymer resin substances such as naphthalene,fluoranthene,phenanthrene,anthracene and fluorane.The Environmental Protection Administration had specified that the coking plant will produce.The tar sludge belonged to the hazardous solid waste HM-11.The pollutants contained of tar sludge had serious harm to human health and increased the risk of disease.If the tar sludge was not treated and directly discharged into the ecosystem which will cause serious environmental pollution.And the tar sludge contained a large amount of tar.If a reasonable processing scheme can be found,the coal tar in the tar sludge is extracted,the economic value of the tar sludge can be fully reflected.In this study,tar sludge was used as the research object,and the curing mechanism of tar sludge was studied by scanning electron microscopy,X-ray diffraction and X-ray fluorescence spectroscopy.The added composite molding additive generates a new substance by hydration reaction to fill the tar pores and physical adsorption of the organic matter by the additive,thereby enhancing the strength of the tar sludge solidified block.The effects of the amount of moulding agent,the mass ratio of aggregate to tar sludge and curing age on the strength of tar sludge cured block were investigated.The results showed that,the optimum technological conditions for tar sludge solidification were as follows:the amount of additive was 15%,the ratio of agent to residue was 1:2,and the solidification age was 7 days.Under the optimum process conditions,the compressive strength of the tar sludge solidified block can reach 2 MPa after 7 days,the drop strength can reach 94%,and the thermal stability was 98%,the solidified block of tar sludge after solidification can fully meet the requirements of"Pollutant Control Standard in Agricultural Sludge".Through retorting test,it can be concluded that the residual oil rate of tailings of tar sludge solidified block decreases with the decrease of heating rate,and decreases with the increase of retorting final temperature and holding time.When the heating rate was 10?/min,the retorting temperature was 500?and the holding time is 30 min,the residual oil rate of tailings was less than0.3%,which meeted the national emission standards.Afterwards,the kinetics of the tar sludge wax cracking reaction was studied using Coats-Redfern method.The kinetic analysis showed that the pyrolysis reaction of tar sludge solidified block can be analyzed by first-order chemical reaction kinetics combined with Arrhenius's law at 10?/min.The fitting value?R?is over 0.99392.The activation energy of tar sludge solidified block is142.74 kJ·mol^-1,and the pre-exponential factor is 2.10×10⁶ s^-1.The properties of tar,retort gas and dry distillation sludge obtained from the pilot plant of low temperature pyrolysis were analyzed.The results showed that,the density of dry distillate was 0.9724 g·cm^-3 at 20?,and sulfur content was0.57%in tar,which belonged to sulfur-containing crude oil.The content of heavy components in dry distillate was relatively high,resins and asphaltenes were as high as 10.71%and 20.78%,respectively.The hydrocarbon content of dry distillation gas was 31.5%.The gases which accounted for a large proportion of the gases are methane,ethane,ethylene,propylene and so on.These gases were light and had high calorific value.They can be used as fuel to provide thermal energy for the pyrolysis process of solidified blocks and reduce the total energy consumption of the process.The residual oil content of the tailings after dry distillation is 0.18%,the pH value was 7.7,and the other pollutants were within the control range,which will not cause harm to the environment,and the main components of the tailings and the main components of the inorganic aggregated additives.Similarly,the tailings after dry distillation of the tar solidification block can be used as an additive aggregate,and returned to the solidification-dry distillation treatment system to realize the recycling of the inorganic additive aggregate.