Pyrolysis Of Coal And Coal Hydroliquefaction Residue In A Dual Loop Reaction System

China is still one of the few countries in the world that uses coal and coal-related resources as its main energy structure.The model of coal as the main energy consumption has caused tremendous pressure on China's national economic development and environmental protection.It is of great practical significance to develop high-efficiency and environmentally friendly modern coal chemical industry.Coal rapid pyrolysis and coal hydroliquefaction process as a coal-to-liquids process provide a powerful solution to the problem of ensuring China's energy supply and safety and alleviating the shortage of China's petroleum resources.However,the existing rapid pyrolysis oil production process of coal still faces bottlenecks such as poor utili-zation of small particle size coal,poor quality of tar caused by oil-containing pyrolysis gas entrained dust,and for coal hydroliquefaction process the reprocessing of the coal hydrolique-faction residue(CHR)produced as byproduct becomes a problem.In this paper,a new dual loop solid fuel pyrolysis oil production process based on solid heat carrier technology is pro-posed,and a Dual Loop Reraction System(DLRS)is designed and constructed to solve the problem in coal pyrolysis process and in the meanwhile to explore an efficient and continuous utilization route for coal hydroliquefaction residue.In DLRS,the particles grading cyclone(PGC)that achieves efficient and rapid segregation for mixing particles serves as a bridge among the other reaction units,thus forming two independent circulation loops in an orderly manner.The pyrolysis,filtration and combustion in the pyrolysis process are spatially com-pletely independent,which provides independently controllable,preferred process parameters for the thermochemical conversion of solid fuels.Based on DLRS,pyrolysis experiments of coal and coal hydroliquefaction residue were carried out.The specific research contents are as follows:(1)Configuration characteristics of main units in DLRS were evaluated and debugging tests in cold state were carried out.The particles grading cyclone based on the difference of tenninal velocity of binary particles provides possibility of efficient and rapid segregation for mixing particles.The particle venturi for rising,venturi feeder and venturi scrubber in DLRS could achieve the circulation of solid heat carrier particles,the rapid feeding of raw material particles,and the rapid cooling of flue gas.Those units with venturi effect could provide a relatively independent and mutually inert reaction zone in DLRS by ensuring good sealing per-formance of solid heat carriers conveying pipeline.The radial-moving particulate filter with concentric double louver structure preferentially discharges the fine particles accumulated in the inner flow channel which provides a relatively wide and flexible operation space for the pyrolysis under the fluidized bed operation mode.Filtration tests shows that the radial-moving particle filter has the advantages of low operating pressure drop and high filtration efficiency.(2)Based on DLRS,the pyrolysis of Shenmu coal(SM)and Yuyang coal(YY)was carried out with quartz sand as bed material.The effects of different reaction conditions(pyrolysis temperature,fluidization gas velocity,overflow ratio,filter temperature)on pyrolysis products were studied.The results showed that,the pyrolysis tar yields of two coals increased first and then decreased with pyrolysis temperature increasing and reached the extreme values at the pyrolysis temperature of 515 ?,and the yields were 3.5%and 11.9%,respectively,which were 89.7%and 108.2%of the corresponding Fischer Assay value.The difference in pyrolysis heat-ing rate is more favorable for the influence of YY coal with higher volatile content.Increasing the fluidized gas velocity is beneficial to the production of the pyrolysis oil.Higher bed over-flow ratio is unfavorable to complete pyrolysis especially at high fluidized gas velocities.In-creasing the operating temperature of the filter is unfavorable to obtain the pyrolysis oil.Pyrol-ysis oil analysis shows that the dust content in pyrolysis oil was as low as 0.2%and indicates that moving bed filter showed a good filtration performance.Pyrolysis oil extraction analysis shows that the HS of both coal pyrolysis oil decreased with pyrolysis temperature increasing.The light component HS decreased as fluidizing gas velocity and filter temperature increase.GC/MS analysis of pyrolysis oil showed that the content of condensed aromatic hydrocarbons in the two coal pyrolysis oils was the highest and almost the same and light aromatic hydrocar-bons and aliphatic hydrocarbons in SM coal pyrolysis oil were higher than those in YY coal pyrolysis oil.In contrast,the phenols and heterocyclics in the SM coal pyrolysis oil were smaller than those in the YY coal pyrolysis oil.(3)Based on DLRS,the pyrolysis of CHR was carried out with quartz sand as bed material to pursue an efficient and environmentally friendly process for the utilization of CHR.Investi-gation on the way to reduce the caking property of CHR and its continuous feeding was done and the effects of different reaction conditions(pyrolysis temperature,fluidization gas velocity,overflow ratio,filter temperature)on pyrolysis products were studied.The results showed that,the physical property analysis shows that CHR contains high molecular weight organic matter such as aromatic hydrocarbons,which leads to its easily softening characteristics and high cak-ing property.The caking property tended to be weaken after blending a certain amount of inert additives.The debonding effect of quartz sand is the best under the same blending volume ratio.When the blending volume ratio is higher than 3 and above,the caking of CHR is almost elim-inated.Fast and continuous feeding could be achieved by adding quartz sand and using a screw feeder combined with a venturi feeder followed by a double-layer cooling tube.The result from DLRS showed that,the pyrolysis oil yield increased with the pyrolysis temperature increasing and then tended to be flat,when at pyrolysis temperature of around 550?,the yield of pyrolysis oil can reach 20%which was significantly higher than that obtained from the Fischer Assay test.When the fluidized gas velocity ratio U/Umf is increased from 1.2 to 2.8,the pyrolysis oil yield is increased from 20%to 23%,that increasing the fluidized gas velocity is beneficial to the production of the pyrolysis oil;The residue particles size was too small to be easily entrained from the pyrolyzer which is unfavorable to obtain the pyrolysis oil.Increasing the operating temperature of the filter is unfavorable to obtain the pyrolysis oil.Pyrolysis oil analysis shows that the dust content in pyrolysis oil is as low as 0.2%?0.5%,though at higher fluidized velocity.Pyrolysis oil analysis showed that,almost all the HS and a small part of A and PA in the CHR were transferred into the tar during the pyrolysis.The increase of pyrolysis temperature was favorable to the conversion of A to HS,while filter temperature increase lowed the quality of the oil.The GC/MS of the HS component of pyrolysis oil and the infrared analysis of the py-rolysis oil show that there is no obvious change of the HS after the pyrolysis.