硫酸盐黑液高温水蒸气气化与直接苛化实验研究
文献类型：学位论文
| ; | |
| 作者 | 袁洪友 |
| 学位类别 | 硕士 |
| 答辩日期 | 2009-05-31 |
| 授予单位 | 中国科学院广州能源研究所 |
| 授予地点 | 广州能源研究所 |
| 导师 | 阴秀丽 |
| 关键词 | 黑液 热解 气化 回收锅炉 直接苛化 |
| 其他题名 | Kraft Black Liquor High Temperature Steam Gasification with Direct Causticization using Titanium Dioxide and Titanates |
| 中文摘要 | Black liquor is the residue from the cooking of wood, straw or other fibrous plants in the alkali pulping process. Recovery of the chemicals used, as well as of the energy contained in the organics, is important for the economics of the paper mill. Nowadays, Tomlinson recovery boilers are used to generate heat from the organic compounds and to recover the cooking chemicals contained in the black liquors, but there are some safety problems and the energy efficiency is relatively low. Gasification of black liquor is a promising alternative for recovery systems in the pulping process. Two gasification processes have been commercialized: a low temperature process operating at about 600℃, and a high temperature process operating at 950-1000℃. Low temperature processes have problems achieving good conversion while avoiding ash agglomeration; high temperature processes suffer material problems caused by extremely corrosive conditions. It is of interest to combine direct causticization of black liquor by TiO2 with gasification. Firstly, a high temperature needed for both gasification and direct causticization can be realized in a single reactor. Secondly, direct causticization with TiO2 produces high melting point products which minimize the smelt formation problem associated with high temperature gasification processes. Thirdly, the sodium penta-titanate formed in the gasifier is leached with water, forming solid sodium tri-titanate and sodium hydroxide, The sodium tri-titanate is separated and recycled to the gasifier. Illuminated by the black liquor gasification with steam at low temperature, one would naturally consider gasification with steam at relatively high temperature, fortunately, using TiO2 this process maybe feasible without smelt formation. The steam gasification research began with the pyrolysis experimental study. The swelling of kraft black liquor was tested at 400-800℃ under nitrogen atmosphere with a visualized single droplet reactor. The main permanent pyrolysis gas components of three kraft liquors were investigated at temperatures up to 850℃. The measurements of H2S release during pyrolysis were realized by iodometry, the total sulfur release was evaluated through char analysis. Steam and CO2 gasification of black liquor at low temperature were conducted with tube furnace. The effect of temperature, atmosphere and reaction time on carbon conversion, sulfate reduction and sulfur release were investigated. Nearly all sulfur release to gas phase except for sulfur in sulfate. Sulfate can be reducted by carbon at solid state. the gasification rates of organic carbon by steam at these low temperature(600 and 650℃) are very slow, though we already know this according literature before, compare with fluidized bed, mass transfer limitation may worsen this problem. For improving of gas-solid contact, a small bench scale fluidized bed was constructed, with an external heater and a steam blowing system. The feedstock of quartz sand, sawdust can be easily fluidized in the small FB. Regretfully, the liquid feedstock of black liquor never successfully realized fluidization. Unlike MTCI low temperature process, the material sprayed into the bed cannot be quickly dried and pyrolyzed, poorly design may account for the failure. When switch to solid feedstock of black liquor mixed with titanium dioxide, fluidization condition cannot be gained all the same, but after 30 min of steam gasification at 800℃, the agglomeration of feedstock in the middle of the bed was found but without any organic carbon remaind. Given the presence of titanium dioxide, the reason for agglomeration was not clear then. Puzzled by the serious problem of agglomeration, and Encouraged by the good carbon conversion at high temperature, we conducted experimental of kraft black liquor high temperature steam gasification with direct caustisization using tube furnace or called fixed bed which can be easily operated. Fortunately, mass transfer limitation doesn’t show too much negative effect on the carbon conversion at relatively high temperature. When choosing pure anatase titanium dioxide as the direct causticization agent, agglomeration of bed material never appeared. All reactions concerned gained high conversion at high temperature, including organic carbon gasification, decarbonization, penta-titanate hydrolyzing. Recycling titanates show similar effects with fresh titanium dioxide, no agglomeration was found either. Anyhow, we reckon the high temperature steam gasification using titanates a promising alternative to conventional recovery process. Method of decreasing organic sulfur emission and improving sulfate reduction need further research. |
| 语种 | 中文 |
| 公开日期 | 2011-07-14 ; 2011-07-15 |
| 页码 | 103 |
| 源URL | [http://ir.giec.ac.cn/handle/344007/5860]  |
| 专题 | 中国科学院广州能源研究所 |
| 推荐引用方式 GB/T 7714 | 袁洪友. 硫酸盐黑液高温水蒸气气化与直接苛化实验研究, Kraft Black Liquor High Temperature Steam Gasification with Direct Causticization using Titanium Dioxide and Titanates[D]. 广州能源研究所. 中国科学院广州能源研究所. 2009. |
入库方式： OAI收割
来源：广州能源研究所
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