烧碱蒸发节能技术改造
|
摘要
烧碱是一种重要的基本化工原料，在国民经济各个领域用途都极为广泛，在工农业生产及人民生活中占有十分重要的地位。我国烧碱生产主要采用隔膜法制碱工艺和离子膜法制碱工艺，截止到2005年底，国内烧碱生产能力已达到1574.6万t／a，其中，隔膜法烧碱生产能力为836.4万t／a，占整个烧碱生产能力的53.1％。遵义碱厂烧碱生产能力为10万t／a，其中，隔膜法烧碱生产能力为6万t／a左右。
在隔膜法烧碱生产工艺中，蒸发是烧碱生产系统的重要环节，是一个耗能较多的工序，蒸发料液所需的加热蒸汽折成等价热值，其数值约占烧碱综合能耗的25％～35％，仅次于电解工序。因此，采用先进、适用节能工艺技术对烧碱蒸发工序进行技术改造，将直接影响整个烧碱生产系统的用能水平和生产企业的经济效益。
遵义碱厂原蒸发系统采用三效五体生产工艺蒸发隔膜碱料液，技改前(2000年)蒸发生产能力3.5万t／a左右。2001年电解系统技术改造后，隔膜法烧碱产能达5.6万t／a左右，蒸发系统由于生产场地等制约因素未进行相应改造。因此，在基本保持原蒸发系统工艺及设备的基础上，通过节能技术改造，使原蒸发系统满足烧碱扩能和降低消耗的要求，就成为本次技术改造的目标。
经过认真的分析和考察，本文提出了遵义碱厂原蒸发系统主要存在的问题：
●料液进效温度过低，浓度波动较大；
●蒸发过程中料液结盐严重；
●蒸发设备配置不合理；
●末效真空装置存在缺陷，真空度过低。
●成品碱冷却装置存在缺陷，烧碱合格率偏低。
电解碱液蒸发过程的控制因素是一个热量传递过程。本文从传热基本方程式Q=KA△t着手，重点对传热系数K和传热温差△t的影响因素进行了细致的分析和比较，结合生产实际确定了真空系统、采盐系统及生产工艺等重点影响因素，为节能技改方案提供了理论基础。
针对原蒸发系统存在的问题，本文提出了如下技术改造措施：
●利用废弃加热室作预热器改造料液预热工艺，提高料液进效温度；强化电解槽操作管理，控制电解碱液浓度在120～135g／L。
●改双加热室蒸发器为单加热室蒸发器，提高蒸发室高度，增加加热室换热面积。
●改顺向采盐工艺为逆向采盐工艺，增置母液分盐器，减少母液含盐量。
●采用空塔冷凝器组合真空装置抽吸末效二次蒸汽，改进真空管道及除沫器，提高末效真空度。
●利用废弃加热室作冷却器增置一套成品碱冷却装置，降低成品碱温度，提高盐的结晶析盐率。
●改手工控制进料、过料为油压控制，优化操作工艺。
技改措施投入运行后，蒸发生产系统运行稳定，主要工艺技术指标控制稳定并明显提高；技改前后，蒸发生产能力从35070t／a提高到57383t／a，蒸汽平均消耗从5.37t／t100％NaOH降到4.19t／t100％NaOH，成品碱合格率从75％提高到95～100％。本次技术改造成功地达到预期目标，大大节约了能耗，提高了企业经济效率。
Caustic soda, an important basic raw material for chemical industry, is widely used in all areas of the national economy, and it occupies a very important position especially in industrial and agricultural production and people's lives . Alkali production of caustic soda used in our country is mainly divided into diaphragm process alkali and ion-exchange membrane process alkali. By the end of 2005, the capacity of caustic soda production had reached 15746000 t/a, in which the capacity of diaphragm caustic soda production is 8364000 t/a , accounting for the production of caustic soda 53.2%. The capacity of caustic soda is 100000 t/a in Zunyi Alkali Factory, in which the capacity of diaphragm caustic soda production is about 60000 t/a.
Evaporation of caustic soda is a key piont in the technological process of diaphragm caustic soda. The process needs much energy. The evaporation which is from heating vapor into liquid evaporation materials equals to calorific value, the energy consumption of caustic soda occupies about 25% ~ 35% which is next to electrolysis process. Therefore, the use of advanced application of energy-saving technology in caustic soda evaporation process , has a direct impact on production of caustic soda production and the economic efficiency of enterprises.
" Three effect and five compartment" process was adopted in the. original diaphragm caustic soda evaporation system of Zunyi Alkali Factory. At that time , the production capacity was 35000 t/a before the technological transformation(2000 year). The capacity of electrolysis system in 2001 was 56000 t/a after innovation. The evaporation system was constrainted by limited space and other factors for the corresponding transformations of the the diaphragm caustic soda production. So reforming the original evaporation system on the basis of technology and equipment, through energy-saving technology, which allows expansion of caustic soda evaporation system to meet the requirements and lowers consumption, has become the target of this technological transformation. After careful analysis and examination, the original evaporation system of Zunyi Alkali Factory has the main problem as follows :
feed into effective low temperature, concentration fluctuations;
feed salt evaporation process seriously;
evaporation equipment disposition unreasonable;
errors in the end effect vacuum devices, vacuum was too low.
errors in the cooling devices, pass rate of caustic soda was too low.
Heat transfer process is a controlling factor in the evaporation of caustic soda. From basic heat transfer equation Q= KAΔt , focusing on the heat transfer coefficient K and the heat transfer range of temperature At factors . According to careful analysis and comparison, we determined key factors such as the vacuum system, salt-extracting system and other key systems , and provided a theoretical basis for energy saving program.
Aiming at the original evaporation system, we put forward technological transformation as follows :
use the heating chamber for scraped preheating feeding preheater transformation process into improving feeding efficiency . Enhance cell operation and management control the concentration of alkali electrolysis in 120~135g/L.
change the doubl evaporator heating chamber into single evaporator heating chamber to rise evaporator heating chamber to increase heat transfer area.
change salt-extracting process to reverse process adding the original liquor additional sub-salt devices, reducing the salinity of orginal liquor.
the use of air-tower combination of vacuum condenser device end absorb the second steam , improving vacuum tube road to rise vacuum. Use waste heating chamber for a set of additional product base cooling device to lower the temperature and raise the crystallization rate of salt.
After modification measures putting into operation, evaporation system performanced stabbly and controlling of the main indicators of technology improved markedly. After technological transformation, evaporation capacity increased from 35,070 t/a to 57,383 t/a. The summary of typical average steam consumption dropped from 5. 37 t/t 100% NaOH to 4. 19 t/t 100% NaOH. Finished passing rate rised from 75% to 95～100%. The technological transformation has successfully achieved the expected goal of a significant reduction in energy consumption, and increase the economic efficiency of enterprises.
在隔膜法烧碱生产工艺中，蒸发是烧碱生产系统的重要环节，是一个耗能较多的工序，蒸发料液所需的加热蒸汽折成等价热值，其数值约占烧碱综合能耗的25％～35％，仅次于电解工序。因此，采用先进、适用节能工艺技术对烧碱蒸发工序进行技术改造，将直接影响整个烧碱生产系统的用能水平和生产企业的经济效益。
遵义碱厂原蒸发系统采用三效五体生产工艺蒸发隔膜碱料液，技改前(2000年)蒸发生产能力3.5万t／a左右。2001年电解系统技术改造后，隔膜法烧碱产能达5.6万t／a左右，蒸发系统由于生产场地等制约因素未进行相应改造。因此，在基本保持原蒸发系统工艺及设备的基础上，通过节能技术改造，使原蒸发系统满足烧碱扩能和降低消耗的要求，就成为本次技术改造的目标。
经过认真的分析和考察，本文提出了遵义碱厂原蒸发系统主要存在的问题：
●料液进效温度过低，浓度波动较大；
●蒸发过程中料液结盐严重；
●蒸发设备配置不合理；
●末效真空装置存在缺陷，真空度过低。
●成品碱冷却装置存在缺陷，烧碱合格率偏低。
电解碱液蒸发过程的控制因素是一个热量传递过程。本文从传热基本方程式Q=KA△t着手，重点对传热系数K和传热温差△t的影响因素进行了细致的分析和比较，结合生产实际确定了真空系统、采盐系统及生产工艺等重点影响因素，为节能技改方案提供了理论基础。
针对原蒸发系统存在的问题，本文提出了如下技术改造措施：
●利用废弃加热室作预热器改造料液预热工艺，提高料液进效温度；强化电解槽操作管理，控制电解碱液浓度在120～135g／L。
●改双加热室蒸发器为单加热室蒸发器，提高蒸发室高度，增加加热室换热面积。
●改顺向采盐工艺为逆向采盐工艺，增置母液分盐器，减少母液含盐量。
●采用空塔冷凝器组合真空装置抽吸末效二次蒸汽，改进真空管道及除沫器，提高末效真空度。
●利用废弃加热室作冷却器增置一套成品碱冷却装置，降低成品碱温度，提高盐的结晶析盐率。
●改手工控制进料、过料为油压控制，优化操作工艺。
技改措施投入运行后，蒸发生产系统运行稳定，主要工艺技术指标控制稳定并明显提高；技改前后，蒸发生产能力从35070t／a提高到57383t／a，蒸汽平均消耗从5.37t／t100％NaOH降到4.19t／t100％NaOH，成品碱合格率从75％提高到95～100％。本次技术改造成功地达到预期目标，大大节约了能耗，提高了企业经济效率。
Caustic soda, an important basic raw material for chemical industry, is widely used in all areas of the national economy, and it occupies a very important position especially in industrial and agricultural production and people's lives . Alkali production of caustic soda used in our country is mainly divided into diaphragm process alkali and ion-exchange membrane process alkali. By the end of 2005, the capacity of caustic soda production had reached 15746000 t/a, in which the capacity of diaphragm caustic soda production is 8364000 t/a , accounting for the production of caustic soda 53.2%. The capacity of caustic soda is 100000 t/a in Zunyi Alkali Factory, in which the capacity of diaphragm caustic soda production is about 60000 t/a.
Evaporation of caustic soda is a key piont in the technological process of diaphragm caustic soda. The process needs much energy. The evaporation which is from heating vapor into liquid evaporation materials equals to calorific value, the energy consumption of caustic soda occupies about 25% ~ 35% which is next to electrolysis process. Therefore, the use of advanced application of energy-saving technology in caustic soda evaporation process , has a direct impact on production of caustic soda production and the economic efficiency of enterprises.
" Three effect and five compartment" process was adopted in the. original diaphragm caustic soda evaporation system of Zunyi Alkali Factory. At that time , the production capacity was 35000 t/a before the technological transformation(2000 year). The capacity of electrolysis system in 2001 was 56000 t/a after innovation. The evaporation system was constrainted by limited space and other factors for the corresponding transformations of the the diaphragm caustic soda production. So reforming the original evaporation system on the basis of technology and equipment, through energy-saving technology, which allows expansion of caustic soda evaporation system to meet the requirements and lowers consumption, has become the target of this technological transformation. After careful analysis and examination, the original evaporation system of Zunyi Alkali Factory has the main problem as follows :
feed into effective low temperature, concentration fluctuations;
feed salt evaporation process seriously;
evaporation equipment disposition unreasonable;
errors in the end effect vacuum devices, vacuum was too low.
errors in the cooling devices, pass rate of caustic soda was too low.
Heat transfer process is a controlling factor in the evaporation of caustic soda. From basic heat transfer equation Q= KAΔt , focusing on the heat transfer coefficient K and the heat transfer range of temperature At factors . According to careful analysis and comparison, we determined key factors such as the vacuum system, salt-extracting system and other key systems , and provided a theoretical basis for energy saving program.
Aiming at the original evaporation system, we put forward technological transformation as follows :
use the heating chamber for scraped preheating feeding preheater transformation process into improving feeding efficiency . Enhance cell operation and management control the concentration of alkali electrolysis in 120~135g/L.
change the doubl evaporator heating chamber into single evaporator heating chamber to rise evaporator heating chamber to increase heat transfer area.
change salt-extracting process to reverse process adding the original liquor additional sub-salt devices, reducing the salinity of orginal liquor.
the use of air-tower combination of vacuum condenser device end absorb the second steam , improving vacuum tube road to rise vacuum. Use waste heating chamber for a set of additional product base cooling device to lower the temperature and raise the crystallization rate of salt.
After modification measures putting into operation, evaporation system performanced stabbly and controlling of the main indicators of technology improved markedly. After technological transformation, evaporation capacity increased from 35,070 t/a to 57,383 t/a. The summary of typical average steam consumption dropped from 5. 37 t/t 100% NaOH to 4. 19 t/t 100% NaOH. Finished passing rate rised from 75% to 95～100%. The technological transformation has successfully achieved the expected goal of a significant reduction in energy consumption, and increase the economic efficiency of enterprises.
引文
[1] 叶蕴琨．高纯烧碱生产路线、技术经济对比及国内高纯烧碱发展方向[J]．氯碱工业，1981，(3～4)：116～117．
[2] 方乐平，刘晋阳，等．氯碱生产技术[M]．江苏：江苏省氯碱工业协会发行，1985，5．
[3] 蒋维钧，余立新．化工原理(化工分离过程)[M]．北京：清华大学出版社，2005，10．
[4] 岳德隆，沃联邦，等．化学工程手册(蒸发及结晶)[M]．北京：化学工业出版社，1998，6．
[5] 李可可，等．最新氯碱产品生产新工艺与过程优化控制及安全事故防范产品检测技术应用手册[M]．北京：化学工业出版社，2006，5．
[6] 王世常．关于隔膜烧碱蒸发的几个问题[J]．氯碱工业，1981，(3～4)：91～94．
[7] 程殿彬．国内烧碱成本比国外高的原因及缩小差距应采取的措施[C]．//氯碱工业编辑部．程殿彬氯碱生产技术论文精品选集．天津：全国氯碱工业信息站，2003，5：1～10．
[8] 张武平，秦玉尧．连体热机-热泵用于烧碱蒸发工艺的探讨[J]_氯碱工业，2002，11：24～26．
[9] 何旭光，张定明，代灵，等．提高蒸发强度降低蒸汽消耗量[J]．氯碱工业，2001，12：18～20．
[10] 马红钦，朱慧铭，谭欣，等．聚四氟乙烯在烧碱蒸发器防、除垢中应用的研究[J]．氯碱工业，2002，6：21～24．
[11] 刘明言，李修伦，林瑞泰，等．三相循环流化床强化传热与防、除垢技术在烧碱蒸发器中的应用前景[J]．氯碱工业，2002，11：21～23．
[12] 宋星星．化学法传热强化技术在烧碱蒸发过程的应用前景[J]．中国氯碱，2002，8：15～16．
[13] 裘益发．空心环网板及缩放管强化传热技术在烧碱蒸发器中的应用[J]．中国氯碱，2002，9：36．
[14] 刘自珍．科技进步是氯碱工业发展的基础[J]．氯碱工业，2002，11：1～5．
[15] 石敏，王红东．优化蒸发工艺降低蒸汽消耗[J]．氯碱工业，2006，3：28～30．
[16] 王超武，吴学玉，王本明，等．降低蒸发系统中结盐的措施[J]．氯碱工业，2003，10：24～25．
[17] 陈孝彦，郑平友，刘芙蓉，等．关于冷却系统中NaCI结晶影响因素的几点思考[J]．氯碱工业，2003，12：28～30．
[18] 赵仲照．烧碱蒸发改造设计要点[c]．//抚顺市应用技术研究所．氯碱工业设计计算法手册．辽宁：抚顺市应用技术研究所，1995：74～76．
[19] 张乃慧，林自扬．从Q=KSΔt公式入手提高烧碱蒸发生产能力[J]．氯碱工业，2002，3：29～31．
[20] 项金海．提高预热温度 降低蒸发汽耗[J]．氯碱工业，1995，6：27～30．
[21] 方度，蒋兰荪，吴正德．氯碱工艺学[M]．北京：化学工业出版社，1990，5．
[22] 时钧，汪家鼎，等．化学工程手册(上卷第9篇蒸发)[M]．第二版．北京：化学工业出版社，1996．
[2] 方乐平，刘晋阳，等．氯碱生产技术[M]．江苏：江苏省氯碱工业协会发行，1985，5．
[3] 蒋维钧，余立新．化工原理(化工分离过程)[M]．北京：清华大学出版社，2005，10．
[4] 岳德隆，沃联邦，等．化学工程手册(蒸发及结晶)[M]．北京：化学工业出版社，1998，6．
[5] 李可可，等．最新氯碱产品生产新工艺与过程优化控制及安全事故防范产品检测技术应用手册[M]．北京：化学工业出版社，2006，5．
[6] 王世常．关于隔膜烧碱蒸发的几个问题[J]．氯碱工业，1981，(3～4)：91～94．
[7] 程殿彬．国内烧碱成本比国外高的原因及缩小差距应采取的措施[C]．//氯碱工业编辑部．程殿彬氯碱生产技术论文精品选集．天津：全国氯碱工业信息站，2003，5：1～10．
[8] 张武平，秦玉尧．连体热机-热泵用于烧碱蒸发工艺的探讨[J]_氯碱工业，2002，11：24～26．
[9] 何旭光，张定明，代灵，等．提高蒸发强度降低蒸汽消耗量[J]．氯碱工业，2001，12：18～20．
[10] 马红钦，朱慧铭，谭欣，等．聚四氟乙烯在烧碱蒸发器防、除垢中应用的研究[J]．氯碱工业，2002，6：21～24．
[11] 刘明言，李修伦，林瑞泰，等．三相循环流化床强化传热与防、除垢技术在烧碱蒸发器中的应用前景[J]．氯碱工业，2002，11：21～23．
[12] 宋星星．化学法传热强化技术在烧碱蒸发过程的应用前景[J]．中国氯碱，2002，8：15～16．
[13] 裘益发．空心环网板及缩放管强化传热技术在烧碱蒸发器中的应用[J]．中国氯碱，2002，9：36．
[14] 刘自珍．科技进步是氯碱工业发展的基础[J]．氯碱工业，2002，11：1～5．
[15] 石敏，王红东．优化蒸发工艺降低蒸汽消耗[J]．氯碱工业，2006，3：28～30．
[16] 王超武，吴学玉，王本明，等．降低蒸发系统中结盐的措施[J]．氯碱工业，2003，10：24～25．
[17] 陈孝彦，郑平友，刘芙蓉，等．关于冷却系统中NaCI结晶影响因素的几点思考[J]．氯碱工业，2003，12：28～30．
[18] 赵仲照．烧碱蒸发改造设计要点[c]．//抚顺市应用技术研究所．氯碱工业设计计算法手册．辽宁：抚顺市应用技术研究所，1995：74～76．
[19] 张乃慧，林自扬．从Q=KSΔt公式入手提高烧碱蒸发生产能力[J]．氯碱工业，2002，3：29～31．
[20] 项金海．提高预热温度 降低蒸发汽耗[J]．氯碱工业，1995，6：27～30．
[21] 方度，蒋兰荪，吴正德．氯碱工艺学[M]．北京：化学工业出版社，1990，5．
[22] 时钧，汪家鼎，等．化学工程手册(上卷第9篇蒸发)[M]．第二版．北京：化学工业出版社，1996．