| China has great reserves on the resources of low-rank coal such as lignite, long flame coal and non-caking coal,and the reserves of lignite as high as13percent of our country’s total coal resources. The lignite has high oxygen content(15%-30%)、high moisture content(20%-60%)、quick chemical reaction、 high heat stability、easy katamorphism in the air and low calorific value after katamorphism, and the effective utilization of lignite is becoming a hot spot in the field of coal chemical industry. With the promotion of mechanical mining technology, the production of lump coal is only as high as15%-20%,and the demanding of lump coal is scarce,the proportion of pulverized coal is becoming more and more high.In order to solve the contradiction between supply and demand,it is more and more critical to make full use of the pulverized coal.By removing the moisture and oxygen within lignite, the calorific value、using range and efficiency of it can be increased. The lignite upgrading technology is refers to enhancing the quality of lignite by physical and chemical method,which including drying and dehydrating upgrading technology、molding technology and pyrolysis technology three categories. The products of lignite pyrolysis including semicoke、tar and pyrolysis gas,which has wide application and higher value.The most of raw materials in low-temperature carbonization chamber is lunp coal, as to the utilization of low rank coal,there was no corresponding low-temperature carbonization furnace,so it is critical to reseach and develop a kind of low-temperature carbonization furnace for the low-rank pulverized coal.The main conclusions of this paper is as follows:1.Under the same terminal carbonization temperature,the yield of pyrolysis gas is incrasing along with the increase of heating rate,however the increase rate is becoming slower,at the same time,the percentage content of H2、CH4、CO2and CO in pyrolysis gas is decreasing gradually,and the percentage content of C2H4and C2H6almost unchanged. The heating rate under the terminal temperature less than450℃has little influence on the yield of pyrolysis gas,while under the terminal temperature higher than450℃the yield is higher along with the higher heating rate,which arrives at the heaviest yield under the20℃/min heating rate. The optimum conditions are as follows:atmosphere of H2, terminal temperature of650℃、heating rate at20℃/min, homoiothermy time of30min,particle size of1-2mm, and carrier flow of720ml/min.2.When undering the same heating rate,the higher terminal temperature,the greater yield of pyrolysis gas; The final percentage content of H2and CH4in pyrolysis gas is increasing gradually along with the increasing of terminal temperature,while the content of CO2is gradually reach a highest value and then decreased, the content of CO is gradually decreased, the content of C2H4and C2H6is gradually reach a highest value and then decreased,which the content of C2H4is higher than the content of C2H6.3.Under the same condition of20℃/min and600℃, the final percentage content of H2and CH4in pyrolysis gas is is gradually reach a highest value and then decreased,which the greatest value is under the homoiothermy time of90min;the content of CO2and CO is gradually increased along with the increasing of homoiothermy time; the content of O2and N2is gradually decreased;the content of C2H4and C2H6is gradually increased.4. Under the same condition of20℃/min、600℃and30min,the order of pyrolysis gas under different atmosphere is:H2>CO>CH4>CO2>N2; Comparing with other atmosphere,the content of CH4under the atmosphere of H2and CO is higher, the content of CO under the atmosphere of CO2is higher, the content of H2under the atmosphere of CH4is higher, the content of CO2under the atmosphere of N2is higher.5. Under the same condition of20℃/min、H2atmophere、600℃and30min, the yield of pyrolysis gas reach highest at particle size of1-2mm,and the content of CH4and C2H6reach the highest value under this size, the content of H2and CO change slightly with the change of particle size; the content of CO2is gradually decreased with the increased of particle size.6. Under the same condition of60min,the yield of pyrolysis is gradually increasing along with the increasing of entering temperature.The content of H2in pyrolyis gas is increasing below450℃,stay still between450℃and550℃,and then increasing swiftly more than550℃; the content of CO change slightly with the change of entering temperature; the content of CH4increast gradually to it’s highest value at500℃, and then more than this temperature there is less change.7. The adsorption-desorption isotherms of lignite briquette are typical type Ⅱ adsorption isotherm. With carbonization temperature increasing, specific surface area of semi-coke reduces gradually, but the average pore diameter and pore volume increase and then decrease. There are four forms carbon exists in coal surface in different terminate temperature, such as C-C and C-H, C-O, C=O and COO-, in which aromatic unit and alkyl (C-C and C-H)account for the largest proportion. The C-C and C-H content with temperature increasing have a significant increasing trend, but the trend of C-O、C=O and COO-is just opposite. There are four forms of oxygen on the surface of coal, but during carbonization process, the main form of oxygen is aromatic hydrocarbons (C-O, C-H). This is because a stable structure can be formed between lone electron pair of oxygen in phenolic hydroxyl and aromatic by a conjugated way.8. With carbonization temperature increasing, the intensity of002diffraction peak of semi-coke in XRD enhanced gradually, which shape tended to be sharp. The intensity of100diffraction peak enhanced slightly. Arrangement of its aromatic sheets in space is clearer and neater, and the order has a significant growth, which aromatic microcrystalline structure size increases slightly.The changing rule of semi-coke’s SEM surface morphology observation is coincided basically with the BET test results.9. From the Raman spectral characteristics of lignite briquette at different terminate temperature we can see that, the G peak width (FWHM) about60cm-1, which is higher than nanomaterials and pyrolytic graphite (15～23cm-1) h. Peak area ratio of ID/IG with temperature increasing can increase, which shows that aromatic carbon layer will tend to be more orderly.10. The swirling style、opposite spraying style and circuited flame path style low-temperature combustion chamber were simulated and optimized respectively,and getting the optimized structure of combustion chamber.Experiments were carried out under the same working condition as the simulating,and the simulation results were consistent with the experiment with a error fluctuation of50-70℃。The simulation and optimization of low-temperature combustion chamber has a significant role for the design of carbonization chamber.At the same time,the heat transfer property of this low-temperature carbonization chamber was simulated,and the vertified experiment was carried out, and the simulation results were consistent with the experiment.The simulation of heat transfer can provide a safe supporting for low-temperature’s structure improvement. |
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