气化温度和当量比对玉米秸秆气化多联产产物特性的影响

Effects of gasification temperature and equivalent ratio on the properties of products from maize stover gasification polygeneration

中国秸秆资源丰富,通过生物质气化技术对秸秆进行能源化高值利用,对中国实现“碳中和”和“碳达峰”有重要意义。该文选取玉米秸秆为原料,采用自制的小型固定床气化炉装置,开展玉米秸秆气化多联产试验,研究了当量比和气化温度对玉米秸秆气化性能的影响,并且对气化产生的气体、固体和液体产物的特性进行了分析。结果表明,随着气化温度的升高和当量比的增加,可燃气的质量产率逐渐增加,而生物质炭的质量产率逐渐下降。较高的气化温度和较低的当量比有利于提升可燃气的热值,当气化温度为900ºC,当量比为0.05时,可燃气中可燃气体组分含量最高,H2、CO、CH_(4)和CnHm含量分别为22.00%、25.91%、13.59%和1.12%(以体积分数计,下同),最高热值为11.26 MJ/Nm3。随着气化温度的升高和当量比的增加,生物质炭中的C元素、H元素、挥发分含量大幅下降,而灰分含量大幅上升。随着气化温度的升高,液体产物中酚类、醇类、酸类和醛类物质含量下降,而芳烃类和酯类物质含量大幅增加;随着当量比的增加,液体产物中芳烃类和酚类物质含量下降,酯类物质含量大幅增加。基于小试规模的玉米秸秆气化多联产试验研究,可为大规模的玉米秸秆气化项目设计和投产提供参考依据。

Lignocellulosic biomass is a clean and renewable energy source due to its abundance, wide distribution, and CO2neutrality. Biomass gasification can convert straw biomass into three different products, namely bio-gas, bio-char, and tar which can be used in different industry fields. The bio-gas can be burned in a boiler or engine for the supply of heat and electricity. The bio-char can be used as a precursor for the production of briquette fuel for heat supply or the activated carbon used in the purification of sewage. Therefore, the comprehensive utilization of straw biomass through biomass gasification technology is of great importance to achieve the goal of “carbon neutrality” and “emission peak” in China. In this work, maize stover(MS) was gasified in a small-scale fixed-bed gasification reactor. The effect of gasification temperature and equivalent ratio on the properties of gasified gaseous, liquid, and solid products were tested. Results showed that with the increase of the gasification temperature from 700℃ to 900℃ and equivalent ratio from 0.05 to 0.30, the yield of producer gas gradually increased from 48.49% and 59% to 59% and 74.91%, respectively, while the yield of bio-char gradually decreased from 25.30% and 19.89% to 19.89% and 5.28%, respectively. In addition, the lower heating value(LHV) of the producer gas was improved at higher GT and lower ER. The maximum LHV of producer gas was 11.26 MJ/Nm^(3) with the component distribution of H2(22.00%), CO(25.91%), CH4(13.59%), and CnHm(1.12%) which was obtained at gasification temperature of 900℃ and equivalent ratio of 0.05. Furthermore, the contents of C, H, and volatiles remarkably decreased with the increase of gasification temperature and equivalent ratio, while the content of ash remarkably increased. The bio-char gradually transformed into ash at higher gasification temperatures and ER due to the severer combustion reaction between the combustible compound in maize stover and the oxygen in the atmosphere. At last, the component in the gasified liquid product was mainly composed of phenols, alcohols, acids, aldehydes, and aromatics. With the increase in gasification temperature, the contents of phenols, alcohols, acids, and aldehydes in the liquid product decreased from 39.29%, 14.82%, 4.8%, and 9.60% to 5.26%, 3.4%, 0, and 0%, respectively, while that of aromatics and esters increased from 0.32% and 20.45% to 50.5% and 30.2%, respectively. With the increase of the equivalent ratio, the contents of aromatics and phenols in the gasified liquid product decreased, while that of others increased. This work revealed the evolution pattern of basic properties of gasified gaseous, solid, and liquid products at varying gasification temperatures and equivalent ratios which could provide basic data for the design and application of large-scale maize stover gasification.