Study of Causticizing Kinetics and Design of Pressurized Reactor

苛化动力学研究及加压反应釜设计

• 批准号: 8917595
• 负责人: Gopal Krishnagopalan
• 金额: $ 13.65万
• 依托单位: Auburn University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-03-01 至 1993-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8917595&HistoricalAwards=false
• 关键词: Study; Causticizing; Kinetics; Design; Pressurized

Wood contains mainly cellulose, hemicellulose, lignin and small quantities of extractives. The primary purpose of chemical pulping is to remove the lignin which binds the fibers in the wood and liberate the cellulosic fibers. Kraft pulping is the major chemical pulping process used by the pulp and paper industry for the liberation of cellulosic fibers from the structural matrix of wood. The kraft process uses sodium hydroxide and sodium sulfide as effective chemicals for pulping. The chemicals along with wood chips are charged into a pressure vessel (digester), and the contents are brought to the reaction temperature at a preset rate. After the digestion the chips are disintegrated by being "blown" into a tank and then sent for further processing. The pulp resulting from digestion and disintegration of the wood chips is washed thoroughly in a counter current system of washers to produce spent liquor or "black liquor". This black liquor is sent through a recovery cycle which involves concentration of black liquor to 60-70% solids by evaporation and burning of the concentrated black liquor in a furnace. In the furnace the organic materials are completely burned to generate steam, the sodium-sulfur compounds are reduced to sodium sulfide, and the remainder of the inorganic components are converted to sodium carbonate. The inorganic compounds are withdrawn as smelt from the furnace, dissolved, and then sent to a causticizing section to regenerate sodium hydroxide by treating with lime. The clarified liquor from the causticizing section, containing mainly sodium hydroxide, sodium sulfide and small quantities of unconverted sodium carbonate, is called "white liquor" and is recycled back as the cooking liquor to the digester. One of the major reasons for the success of the kraft pulping process is the established, efficient chemical recovery process whereby more than 95% of the chemicals used in the cooking process can be recovered. Uniformity of composition of the regenerated cooking liquor is a key factor in the production of uniform quality pulp and therefore in the economy of operation of the entire process. The purpose of this research project is to study the causticizing process and develop a reliable kinetic model for the system, with the ultimate goal to improve the chemical recovery operation in the kraft pulping process. A semi-batch reactor already designed and fabricated, capable of operating at higher pressures and equipped to monitor the composition of the main reaction products continuously will be used. A novel in-situ and on-line sampling and analysis system will be used to measure the feed green liquor concentration. Experimental equilibrium data will be supplemented by theoretical calculations. A tubular flow reactor equipped with analyzers to test the green liquor and reaction products will be designed. Such a reactor will also allow necessary adjustment for lime addition and result in uniform white liquor feed to the digester which in turn will allow stable digester operation, improved pulp quality and higher productivity.

木材主要含有纤维素，半纤维素，木质素和少量提取物。 化学制浆的主要目的是去除结合木材中纤维并释放纤维素纤维的木质素。 牛皮制浆是制浆和造纸工业用来从木材结构基质中解放出纤维素纤维的主要化学制浆过程。 KRAFT工艺使用氢氧化钠和硫化钠作为制浆的有效化学物质。 将化学物质与木屑一起充电到压力容器（消化酯），并以预设速率将含量带入反应温度。 消化后，将芯片“吹入”储罐中，然后发送进一步处理，从而分解了芯片。 木屑消化和瓦解产生的果肉在当前的垫圈系统中彻底洗涤，以生产含水的酒或“黑酒”。 这种黑酒是通过恢复周期发送的，涉及黑酒浓度通过在炉子中蒸发和燃烧浓缩的黑酒，将黑酒浓缩至60-70％的固体。 在炉中，有机材料被完全燃烧以产生蒸汽，将钠硫化合物还原为硫化钠，其余的无机成分将转换为碳酸钠。 无机化合物被从炉子中渗出，溶解，然后通过用石灰处理来再生成氢氧化钠。 固定片段中澄清的酒，主要含有氢氧化钠，硫化钠和少量未经透明的碳酸钠，被称为“白酒”，并作为烹饪酒回收到消化池。 牛皮纸制浆过程成功的主要原因之一是建立，有效的化学回收过程，可以回收烹饪过程中使用的95％以上的化学物质。 再生烹饪酒组成的统一性是生产均匀质量纸浆的关键因素，因此在整个过程的运营经济中。 该研究项目的目的是研究苛性过程并为系统开发可靠的动力学模型，其最终目标是改善牛皮纸制浆过程中的化学回收操作。 将使用已经设计和制造的半批量反应器，能够在较高的压力下运行，并配备了不断监视主反应产品组成的配备。 一种新型的现场和在线抽样和分析系统将用于测量饲料绿酒的浓度。 实验平衡数据将通过理论计算补充。 将设计配备分析仪的管状流动反应器，以测试绿酒和反应产品。 这样的反应堆还将为添加石灰加入必要的调整，并导致对消化池的均匀白酒饲料，从而允许稳定的消化酯运行，提高纸浆质量和更高的生产率。