Abstract:

Production of hydrogen-rich syngas from sludge steam gasification based on calcium-based sorbents is an efficient and environmental friendly sludge treatment method. In this paper, a series of calcium-based sorbents were prepared by sol-gel method, using Al₂O₃ as support and Co as catalytic active ingredient. The CO₂ capture capacity and cyclic stability of calcium-based sorbents in multiple carbonation and decarbonization cycles were measured by thermogravimetric analyzer, and sludge steam gasfication experiments were carried out on a fixed bed reactor. The results show that Al₂O₃ and CaO in calcium-based sorbents supported with Al₂O₃ form mayenite (Ca₁₂A_l4O₃₃). The calcium-based sorbents have great pore structure and CO₂ adsorption capacity. The carbonation conversion of sorbents with 10% Co content was stable at about 70% in 30 cycles. Increase of gasification temperature and the addition of Co in calcium-based sorbents promote tar cracking and methane reforming, and significantly increases H₂ yield and syngas concentration and cold gas efficiency of sludge gasification. Compared to pure CaO, H₂ yield increases by 102% and H₂ concentration reaches 85% in syngas when sorbents with 15% Co content is applied at 650℃.

Key words: sewage sludge, hydrogen production, calcium looping process, modification, cobalt

摘要：

基于钙基吸附剂的污泥蒸汽气化制取富氢合成气是一种高效环保的污泥处理方式。本文采用溶胶-凝胶法制备了Co改性、Al₂O₃为载体的钙基吸附剂。借助热重分析仪测定不同钙基吸附剂在多个碳酸化和煅烧循环中的CO₂吸附能力和循环稳定性，并在固定床上进行污泥蒸汽气化实验。结果显示：煅烧过程中，以Al₂O₃为载体的钙基吸附剂中的Al₂O₃与CaO生成七铝酸十二钙(Ca₁₂Al₁₄O₃₃)，并表现出优异的孔隙结构的和CO₂吸附能力，其中，Co质量分数为10%的吸附剂在30次循环（700℃碳酸化35min，850℃煅烧5min）中碳酸化率稳定在70%左右；提高气化温度及Co的添加量可促进焦油裂解和甲烷重整反应，显著提高了合成气中H₂的浓度和产量及污泥气化的冷煤气效率，有利于富氢气体的制取；在650℃下，相比于纯CaO，添加Co质量分数为15%的吸附剂时，H₂产量提高了102%，H₂体积分数提高到85%。

关键词: 污泥, 制氢, 钙循环, 改性, 钴