准东煤气化过程中钠、硫、氮的迁移规律研究

发布时间：2018-05-16 11:17

本文选题：准东煤 + 流化床　；参考：《中国科学院大学(中国科学院工程热物理研究所)》2017年硕士论文

【摘要】：目前煤炭仍是我国主要的能源来源,面对日益突出的环境问题,洁净煤技术受到普遍重视,其中流化床气化技术因气化强度大、气化条件温和等优点受到广泛关注,但煤气化过程中硫、氮污染物的迁移规律尚不清晰。准东煤储量大、活性好,是很好的化工、动力用煤,但准东煤中钠含量高,在燃烧、气化过程中容易引发结渣、积灰、腐蚀等问题,因此研究准东煤气化过程中钠、硫、氮的迁移规律,对于准东煤的开发应用及缓解我国能源资源紧张、环境恶化的局面具有重要意义。本文利用热重-质谱联用技术及建立的小型立式炉试验台,结合化学热力学计算软件,在接近流化床气化反应条件下研究了准东煤气化反应特性;探索了温度、O2/C等因素对准东煤气化过程中钠、硫、氮的迁移特性的影响;构建了试验研究与模拟计算间的关联。利用热重-质谱联用技术,对准东煤和神木煤在燃烧及CO2气化过程中硫、氮气体的迁移规律进行了研究。结果表明:准东煤和神木煤在燃烧过程中释放的含硫气体主要为COS和SO2,含氮气体主要为HCN、NO、NO2和NH3;CO2气化时硫主要以H2S、COS和SO2的形态释放到气相中,氮几乎全部以HCN形态释放;燃烧和CO2气化条件下硫、氮的转化机理不同。利用小型立式炉试验台考察了准东煤流化床空气气化特性。结果表明:试验过程中反应器内温度、压力平稳,未发生严重结渣现象;随气化温度升高,煤气中CO、H2体积百分比增大,煤气热值、煤气产率、碳转化率和冷煤气效率均增大;随O2/C增大,煤气中H2、CO体积百分比减小,CO2和N2体积百分比增大,煤气热值减小,碳转化率和煤气产率均增大,.而冷煤气效率呈现先增大后减小的趋势;与神木煤相比,准东煤气化活性高于神木煤。利用小型立式炉试验台进行了准东煤流化床空气气化试验,考察了准东煤气化过程中钠、硫、氮的迁移特性。结果表明:准东煤气化后的底渣、飞灰颗粒未发生明显的熔融粘结;飞灰中钠主要以NaCl、NaAlSi2O6和NaAlSiCO4的形态存在,底渣中钠主要以NaAlSi2O6和NaAlSiO4的形态存在,高气化温度和高O2/C条件下的底渣、飞灰中有更多的NaAlSiO4;钠的固留率随气化温度升高呈先减小后增大的趋势,随O2/C增大呈先略有减小后逐渐增大的趋势;准东煤原煤及气化底渣、飞灰中硫大部分以硫酸盐的形态存在;气化过程中有65%～75%的硫以H2S、COS和CS2形式释放到气相中;准东煤原煤中氮以季氮、吡咯和吡啶的形态存在,气化后底渣、飞灰中氮的形态发生了变化。气化过程中有60%～75%的氮析出至气相中,其中绝大部分转化为N2,少量氮转化为HCN和NH3;煤气中HCN含量大于NH3含量,而随着温度升高、O2/C增大,氮转化为NH3的比例增大。利用FactSage6.1软件对准东煤气化过程进行化学热力学平衡计算,讨论了气化温度和O2/C对准东煤中钠、硫、氮等元素的迁移和转化特性的影响。结果表明:温度和O2/C能显著影响钠、硫、氮的形态;与试验研究结果相结合可知,增强炉内混合、诱导生成高熔点含钠化合物并避免使用二氧化硅作为床料有助于预防高钠煤流化床气化结渣。
[Abstract]:At present, coal is still the main source of energy in China. In the face of increasingly prominent environmental problems, clean coal technology has been widely paid attention to. The fluidized bed gasification technology has received extensive attention due to the advantages of large gasification intensity and mild gasification conditions. However, the migration law of sulfur and nitrogen pollutants in the process of coal gasification is not clear. It is a good chemical and power coal, but the content of sodium in the coal is high. In the process of combustion and gasification, it is easy to cause the problems of slag, ash accumulation and corrosion. Therefore, it is of great significance to study the development and application of the coal and alleviate the situation of energy resources shortage and environmental deterioration in China. The effects of temperature, O2/C and other factors on the migration characteristics of sodium, sulfur and nitrogen in the process of coal gasification were investigated, and the effects of temperature and O2/C on the migration characteristics of sodium, sulfur and nitrogen in the process of coal gasification were investigated. Using the thermogravimetric - mass spectrometry (TG MS) technique, the transfer of sulfur and nitrogen gas in the combustion and CO2 gasification process is studied by TG mass spectrometry. The results show that the sulfur gases released in the combustion process are mainly COS and SO2, and the nitrogen containing gases are mainly HCN, NO, NO2 and NH3; CO2 is gasified when gasification. Sulfur is released mainly in the form of H2S, COS and SO2 into the gas phase, and almost all nitrogen is released in the form of HCN. The transformation mechanism of sulfur and nitrogen is different under the condition of combustion and CO2 gasification. The characteristics of the air gasification in the fluidized bed are investigated by a small vertical furnace test bench. The results show that the temperature and pressure in the reactor are stable during the test process, and no serious junctions occur. With the increase of gasification temperature, the volume percentage of CO and H2 in gas increases, gas calorific value, gas yield, carbon conversion rate and cold gas efficiency increase. As O2/C increases, H2, CO volume percentage decreases, CO2 and N2 volume percentage increases, gas calorific value decreases, carbon conversion rate and gas yield increase, while cold gas efficiency presents first. Compared with Shenmu coal, the coal gasification activity is higher than Shenmu coal. A small vertical furnace test bed was used to carry out the air gasification test on the coal bed of the coal, and the migration characteristics of sodium, sulfur and nitrogen in the coal gasification process were investigated. The results showed that the fly ash particles did not have obvious melting bond after the coal gasification. The sodium in fly ash is mainly in the form of NaCl, NaAlSi2O6 and NaAlSiCO4. The sodium in the slag mainly exists in the form of NaAlSi2O6 and NaAlSiO4, the high gasification temperature and the bottom slag under the high O2/C condition, there are more NaAlSiO4 in the fly ash. The retention rate of sodium decreases with the increase of gasification temperature and then increases, then decreases with the increase of O2/C. The gradually increasing trend; most of the sulfur in the fly ash is in the form of sulphate; 65% to 75% of the sulfur is released to the gas phase in the form of H2S, COS and CS2 during the gasification process; the nitrogen in the coal raw coal exists in the form of quaternary nitrogen, pyrrole and pyridine, and the formation of nitrogen in the fly ash, and the form of nitrogen in fly ash. In the process, 60% ~ 75% of nitrogen is precipitated into the gas phase, most of which are converted into N2, a small amount of nitrogen is converted to HCN and NH3, and the content of HCN in gas is greater than that of NH3. With the increase of temperature, O2/C increases, and the ratio of nitrogen to NH3 is increased. The chemical thermodynamic equilibrium calculation of the coal gasification process is carried out with FactSage6.1 software, and gasification is discussed. The effects of temperature and O2/C on the transfer and transformation characteristics of sodium, sulfur and nitrogen in the coal are affected. The results show that temperature and O2/C can significantly affect the form of sodium, sulfur and nitrogen. It is known that it is helpful to prevent the high sodium coal from mixing in the furnace, inducing the high melting point sodium compound and avoiding the use of silica as the bed material. Fluidized-bed gasification and slagging.

【学位授予单位】：中国科学院大学(中国科学院工程热物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ541

【参考文献】