Ways to save energy in the distillation process

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Guangdong Chemical Industry WWW．gdchem．com Issue 11, 2007, Volume 34, Total Issue 175: Energy-saving Approaches in Distillation Processes Bian * Mian, Zhu Yinhui, Li Hui (1. Hebei Provincial Product Quality Supervision and Inspection Institute, Shijiazhuang 050051, Hebei)； 2. Hebei Vocational College of Industry, Shijiazhuang, Hebei 050091) Distillation is an important unit operation in processes such as chemical engineering, petrochemicals, and pharmaceuticals. It is a type of unit process with high energy consumption, accounting for approximately 60% of the energy used in chemical production. Ways to save energy include multi-effect distillation, heat pump distillation, heat coupling distillation technologies, internally heat-integrated distillation columns, and new high-efficiency separation techniques. Multi-effect distillation consists of N distillation columns operating in parallel, and the heating steam required for the reboiler can be reduced to about 1/N of the heating steam needed in single-effect distillation ； Heat pump distillation can reduce energy consumption by about 20% ； Thermocoupled distillation can save about 30% compared to distillation using two conventional columns ； Internal heat-integrated distillation towers can save 30–60% in energy consumption. These technologies have successfully completed pilot testing, achieving energy savings of 30–60%. distillation ； Energy Saving: The Energy Saving Approach in Rectification Process Bian Ximian, Zhu Yinhui, Li Hui (1. Hebei Province Product Quality Surveillance Examination Institute, Shijiazhuang 050051) ； 2. Hebei Institute of Vocation&Technology, Shijiazhuang 050091, China) Abstract: Rectification is a key unit operation in the chemical industry, petrochemical industry, pharmaceutical industry, and so on; it is a process with high energy consumption, accounting for 60% of the total energy used in the production process. Energy-saving approaches include multi-effect rectification, heat-pump rectification, hot-couple rectification, internal heat integrated distillation towers, new high-efficiency separation technologies, and others. Multi-effect rectification involves N parallel rectification columns, and the heating steam required by the reboiler can be reduced to 1/N compared to traditional single-effect rectification, resulting in a 20% reduction in energy consumption. Heat-pump rectification can lead to a 30% reduction in energy use compared to conventional columns. Internal heat integrated distillation towers enable a 30–60% reduction in energy consumption. These technologies have proven successful in pilot tests, with energy savings of 30–60%. Keywords: rectification ； Energy conservation: The distillation process is one of the most important unit operations in the chemical industry; it is also a type of unit operation that consumes a large amount of energy. Research on energy saving in distillation processes has seen significant progress in terms of tower design over the past decade or so. The main ways to save energy in the distillation process include: improving the separation efficiency of the tower, reducing energy consumption, and increasing the product recovery rate ； Multi-effect distillation technology, heat pump technology, heat coupling distillation technology, new tower types, and high-efficiency packing are employed. 1. Multiple-effect distillation: The general process of multiple-effect distillation is shown in Figure 1. Multi-effect distillation consists of N distillation columns operating in parallel; as shown in Figure 1, the operating pressure decreases from column to column from left to right. The vapor from the top of the tower with higher pressure at the front serves as a heating medium for the bottom reboiler of the tower with lower pressure at the back, where it condenses. If the heat loads of the condensers and reboilers in adjacent towers are balanced, then only the reboiler of the first tower requires heating steam, while the condenser of the last tower needs a cooling medium. After employing N-effect distillation, the heating steam required for the reboiler can be reduced to about I/N of the heating steam needed for single-effect distillation. Practice has shown that the heat required for two-effect distillation is less compared to that of single-effect distillation. 【Date of receipt】July 6, 2007 【Author’s profile】Bian * Mian 0965-1), female, from Dingzhou, Hebei Province; engineer, working in product quality inspection and certification. VIP Information: http://www.cqvip.com. Issue 11, 2007; Volume 34, Total Issue 175. Guangdong Chemical Industry: www.gdchem.com. It is possible to reduce costs by 30–40%. Yu Haoran. Chemical Separation Engineering. Beijing: Sinopec Press, 1999. Pages 271–281. Feng Xiao, Li Qinling. Principles and Technologies for Energy Saving in Chemical Processes. Beijing: Chemical Industry Press, 1998. Pages 34–36. Agrawal R, Fidkowsk Z F. Are thermally coupled distillation columns always thermo-dynamically more efficient for ternary distillations? 1st Eng Chem Res, 1998, 37(8), 3444–3454. Schutz M, Stewart D. Reduce costs using dividing-wall columns. Chem Eng Proc, 2002, 98(5): 64–71. 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