【作者】 黄叶飞；

【导师】 董红敏；

【作者基本信息】 中国农业科学院 ， 环境工程， 2009， 硕士

【摘要】 针对集约化畜牧场粪便产生量大、现有处理方式单一,不仅不能充分利用粪便的肥料和能源特性,还对环境造成一定的污染等问题,在充分分析国内外生物质气化研究基础上,本文选择在秸秆类生物质中技术相对成熟的流化床气化技术,对畜禽粪便的气化进行探索性研究。首先对畜禽粪便(猪粪、鸡粪、牛粪)和玉米秸进行了空气灼烧试验,探讨畜禽粪便的可气化性,在此基础上,进一步选择气化性能较好的牛粪进行流化床的气化试验,重点考查温度对气化效果、灰特性的影响及气化过程中碳氮元素的活动规律。主要结论如下:干燥的牛粪低位热值和秸秆类似,且牛粪的元素分析结果和秸秆基本相近,牛粪在干燥条件下适合进行气化等热化学转化。但粪便与玉米秸比较,玉米秸灰产量(小于10%)显著小于畜禽粪便灰产量(猪粪20%以上,鸡粪、牛粪30%),畜禽粪便氮(约25g/kg)和磷(约3g/kg)的挥发量多于玉米秸(氮约15g/kg,磷很少),而钾(约10g/kg)和钠(很少)的挥发量显著小于玉米秸(钾约25g/kg,钠约65g/kg)。因此,粪便热利用特别要注意灰分对气化的影响,及其氮的污染问题,而玉米秸特别要注意钾钠碱金属的问题。气化温度对气化效果有重要影响。随着气化温度(600-900℃)的升高,可燃气体产量不断地上升,从3.5m3/kg增大到4.4m3/kg;气体热值在750℃达到最大为3600kJ/m3;碳转化率和气体热值变化规律相似,在750℃达到最大为42.1%;气化效率先增大后减小,在800℃达到最大为46.1%。在本试验条件下,当量比在0.4-0.5、温度控制在750-800℃,牛粪气化效果较好,牛粪燃气热值为3600kJ/m3左右,产气率为3.8-4.0m3/kg,气化效率为45-50%,且不会造成含氮气体污染。气化温度对牛粪气化固体产物元素含量及活动规律的影响试验表明,随着气化温度不断上升(600-900℃),飞灰中重金属的浓度均不断上升,其中Cu浓度在900℃为274ug/g、Zn浓度在750℃时为537ug/g、Cr浓度在900℃时为269ug/g、Ni浓度在800℃时为166ug/g,超过了GB8173-87的限值。对底渣的元素分析发现,底渣K2O+Na2O含量较高,达18.6%,计算碱性氧化物指数AI为0.91,表明其有严重的结渣性;底渣中重金属Cu、Zn的浓度超过了GB8173-87的限值。飞灰和底渣需进一步处理才能安全利用。温度对气化产生的可燃气体中碳元素含量无明显影响,约为39-40%;随着气化温度不断上升(600-900℃),原料碳元素在固体中的含量从600℃的52.1%下降到800℃的14.3%,在液体中的碳含量从600℃的1.32%下降到900℃的0.39%。原料氮元素在气体(NH3+NOX)中的比例从10.9%下降到2.7%;固体中氮元素含量从600℃的51.1%下降到800℃的13.1%,液体中氮元素含量变化不明显。更多还原

【Abstract】 Large amount of animal manure from concentrated animal feeding operations (CAFOs) has posed tremendous challenges to environment since there are limited technology choices for manure treatment. Anyway animal manure is not always deleterious, it would be valuable if the contained biomass is appropriately treated and used. Manure biomass gasification is a state-of-the-art technology for animal manure treatment and utilization, but there is a lacking knowledge in literatures, therefore this study was designed to look at the effects of temperature on the gasification of animal manure in fluidized bed via several experiments, firstly the gasification feasibility of animal manure (including swine manure, poultry manure and cattle manure) and corn stalk were investigated, and animal manure with the best gasification performance were selected for the subsequent trials, then selected animal manure was gasified in fluidized bed, and the effects of temperature on the gasification, ash characteristics, and carbon and nitrogen contents. The results shown that cattle manure has the best gasification performance and the detailed outcomes of effects of temperature on the gasification of cattle manure in fluid bed are as follows:The low calorific value and the elements contents of dried cattle manure are similar to corn stalk, so cattle manure was best in terms of gasification. Ash yield of corn stalk (less than 10%) was far less than that of both animal manure ash (pig manure>20%; poultry and cattle manure=30%). The amount of volatile nitrogen (about 25g/kg) and phosphorus (about 3g/kg) of animal manure were higher than the counterparts of corn stalks (nitrogen about 15g/kg, few phosphorus), but the amount of volatile potassium (about 10g/kg) and sodium (rarely) of manure were much less than the counterparts of corn stalks (potassium about 25g/kg, sodium about 65g/kg). Therefore, ash and nitrogen pollution problem in animal manure gasification and high K and Na alkali metal in corn stalks gasification should considered.Temperature was an important factor in animal manure gasification, gas yield increased from 3.5m3/kg to 4.4m3/kg with gasification temperature from 600℃to 900℃) and gas calorific value (GCV) peaked at around 750℃with the value of 3600 kJ/m3 . The carbon conversion shown the same pattern as GVC, with maximum of 42.1% at 750℃. The maximum value of gasification efficiency (46.1%) appeared at 800℃. Equivalence ratio (ER) of 0.4-0.5 in combination with temperature in between 750-800℃were optimized for cattle manure, under such condition the gas heat value about 3600kJ/m3, gas production rate of 3.8-4.0m3/kg, and gasification efficiency of 45-50% were obtained, and no nitrogen pollution was incurred.Temperature had effects on solid matter production and elements contents. the concentration of heavy metals in fly ash increased with gasification temperature in between 600℃to 900℃, the content of Cu was 274ug/g at 900℃, the content of Zn was 537ug/g at 750℃, the content of Cr was 269ug/g at 900℃, the content of Ni was 166ug/g at 800℃, exceeding the limit values of GB8173-87. The K2O+Na2O content in slag was 18.6%, the index of alkaline oxides (AI) was 0.91, which indicated that the contents of Cu and Zn in slag were higher than GB8173-87 limits. Both fly ash and bottom char should be further processed.Temperature had no evident effects on carbon contents of combustible gas produced from manure gasification, carbon contents in solid products were 52.1% and 14.3% at temperature of 600℃and 800℃, respectively, which indicated a declining trend with temperature increase. And carbon contents in the liquid products were 1.32% at 600℃and 0.39% at 900℃, it decreased with temperature. Nitrogen contents shown differents shapes, its contents in gas product decline from 10.9% to 2.7% when temperature increased from 600℃to 800℃, and nitrogen contents in solid product declined from 51.1% at 600℃to 13.1% at 800℃.更多还原