Effect Of Pyrolysis Atmosphere And Cooling Mode On The Structure And Mechanical Strength Of Char

Oxygen-enriched distillation,which is to use oxygen-enriched?or pure oxygen?combustion heating method,with gas modulation and temperature control measures,instead of the current air combustion process to prevent the burning waste gas into the distillation gas and reduce nitrogen content in the gas.As a result,the tar yield can be increased,the gas calorific value can be promoted and make the gas more suitable for chemical products or comprehensive utilization.The work can give a strong support to hydrogen making,co-production of metallurgy and coal chemistry,and has a good application prospect.According to the oxygen-enriched distillation technology proposed by our research group.In this experiment,the samples were pyrolyzed in three reductive atmospheres?H₂?CH₄?CO?and two oxidizing atmospheres?H₂O?CO₂?respectively.The char were collected after the pyrolysis of high temperature char in nitrogen atmosphere was carried out by means of nitrogen with furnace cooling and blistering cooling.The structure and mechanical strength of the samples under the above conditions were analyzed and compared.The microstructure and pore structure of the samples were analyzed by XRD,Raman and BET.The mechanical strength of the samples was tested by the Hardler grindability index tester and the coke good drum strength tester.Compared with the test results,The relationship between changes in atmosphere,microstructure and mechanical strength was established by comparing the test results.It is found that when the pyrolytic atmosphere is 40%H₂?40%CH₄?40%CO,with the increase of the pyrolysis temperature,the specific surface area of the sample increases first and then decreases,and reaches its maximum at 650?.The specific surface area is104m²/g,121m²/g,and 122m²/g respectively.Compared with 100%N₂ atmosphere,the addition of the three atmospheres will reduce the porosity of the semi-coke and decrease the specific surface area.The specific surface area of the CH₄ atmosphere will decrease by 21%,followed by CO,the specific surface area decrease by 8.3%.And the specific surface area under the H₂ atmosphere will decrease by 7.5%.The corresponding grindability index was 16%,3.6%and 1.8%lower than the sample in nitrogen atmosphere.The results show that the microcrystalline structure of the sample is also affected by the atmosphere and some changes have taken place,The total degree of ordering increases with the addition of gases.The crushing resistance is affected by the specific surface area and the ordering degree,the specific surface area is reduced due to the addition of three reducing atmospheres at the early stage of the pyrolysis,and the crushing resistance of the sample is higher than that of the sample under the nitrogen atmosphere,At the late pyrolysis stage,because the atmosphere reduced the internal aromatic rings of semi-coke,the ordering degree of microcrystalline arrangement was reduced,which leads to the deterioration of the crushing resistance.In the experimental temperature,the H₂O atmosphere has a certain promoting effect on the development of the semi-coke pore structure,The specific surface area is larger than the samples of CO₂ and N₂ atmosphere,CO₂ will reduce the ordering degree of samples,while H₂O can increase the ordering degree of samples.Different cooling modes have a great influence on the structure and strength of semi-coke samples.The specific surface area of water foam coke quenching samples is larger,the graphitization degree is lower and the grindability is better,but the anti-crushing performance is poor.Under nitrogen atmosphere,the sample cooling with the furnace has small specific surface area,higher graphitization degree,lower grindability index and good crushing resistance.