牛粪热解挥发分催化重整提质过程中氨气协同去除效果研究

Catalytic Reforming of Volatiles from Sorption-enhanced Pyrolysis of Cattle Manure for Synergistic Gas Upgrading and Ammonia Removal

摘要:

针对牛粪在单级热转化过程中热解气品质不佳及氨气(NH3)释放问题,本文研究了二氧化碳(CO2)吸收强化热解衔接挥发分催化重整的两级热转化工艺对牛粪热解气提质协同NH3去除效果。实验结果表明:牛粪热解时NH3的释放温度区间为275~450℃,加入氧化钙吸收剂可提高热解挥发分产量,H2产量由2.4mmol/g增至4.1mmol/g,CO产量由0.8mmol/g显著增至5.3mmol/g,NH3释放强度同步增强,在750℃时达到0.0866mmol/g。在650℃下,当CaO与牛粪的添加比例从0增至3∶1时,H2产量由1.7mmol/g增至4.0mmol/g,成为热解气中最主要组分,CO产量由1.5mmol/g增至2.7mmol/g,但同时使得NH3释放强度从0.0314mmol/g最高增至0.1229mmol/g。进一步经六方氮化硼负载的金属镍催化剂(Ni/h–BN)在700℃下对热解挥发分重整后,热解气总产量从7.5mmol/g增加至10.0mmol/g,H2与CO总浓度达到70% ,同时NH3分解率可达14.7% ,实现了催化重整过程中对NH3的协同去除。本文为牛粪高效清洁热转化过程中NH3的协同控制提供了研究基础。

Abstract:

Aiming to address the issues of inferior gas quality and ammonia (NH3) emission during the conventional pyrolysis of cattle manure, the effect of a two-stage thermochemical conversion process was investigated, integrating CO2 sorption-enhanced pyrolysis with subsequent catalytic reforming of the derived volatiles, on the upgrading of cattle manure pyrolysis gas with a simultaneous NH3 removal. The results showed that NH3 was mainly released in a temperature range of 275 ~ 450℃. CaO addition significantly improved the yield of pyrolysis volatiles, but simultaneously promoted the emission intensity of NH3 from 0. 031 4 mmol/ g for the pure manure to the highest value of 0. 122 9 mmol/ g depending on the CaO dosage. Elevating the pyrolysis temperature from 550℃to 750℃markedly increased H2 and CO yields, while simultaneously enhancing NH3 emission. At 650℃, raising the CaO-to-manure ratio from 0 to 3∶1 boosted H2 to 4.0mmol/g and CO to 2.7mmol/g, but at the cost of nearly a 4-fold increase in NH3 emission intensity. After the catalytic reforming of pyrolysis volatiles over the metallic nickel catalyst supported by hexagonal boron nitride (Ni/h–BN) at 700℃, the yield of the upgraded pyrolysis gas was increased from 7.5mmol/g to 10.0mmol/g, with the total concentration of H2 and CO reaching 70% . Meanwhile, the NH3 decomposition rate reached the highest value of 14.7% , demonstrating a synergistic effect on pyrolysis gas upgrading and NH3 removal. The research result can lay a research foundation for the control of NH3 emission for the clean thermochemical conversion of cattle manure.