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1、Methanol Distillation System: Process Analysis and Column Design Sun J insheng , Tian Yu f eng , Xu Shimin , Ding Hui , Wang Tao , Li Xingang , Zheng Yanmei(1 Shool of Chemical Engineering and Technology, Tianjin University, Tianjin 300072;2 National Engineering Research Center for Distillation Tech
2、nology, Tianjin 300072) AbstractBase on industrial research and experience, the process of methanol distillation is analyzed, and above all, a new concept of high pressure flowsheet and low pressure flowsheet is defined. The new configuration helps to handle problems encountered in many factories in
3、 China. The inter influence between process and column internal pattern is also pointed out. Recommendation of new column internal designs is given. Finally, industrial examples tell the how the new concept works and the possibility of combining process to give more opens to solve engineering proble
4、ms.Keywords methanol distillation, two - effect distillation, high pressure flowsheet and low pressure flowsheet, flowsheet analysis, simulation with hydraulic, column internal designA very important material in organic chemical industry, methanol is widely involved in the manufacture of plastic mat
5、erial, synthetic fiber and rubber, dyestuff, covering material, spice, medical field, pesticide and etc. Also, it is not only a fine solvent for many organic compounds but a sound substitute for gasoline in many countries as green energy. With the quick development of the national economy, the deman
6、d (actual or potential) of methanol has sharply increased, which accelerates the development of the methanol industry and increment of the methanol output. Presently, methanol distillation technology has been developed to be large - scale, low energy consuming and more environmental. The main patent
7、 dealers in this industry of the world have the equipments designed for 5 000 7 500 t/dEz.But China (mainland) has hardly no running units with capability over 200kt/a of high quality (such as O - M -232E US). Recently, National Engineering Research Center for Distillation Technology at Tianjin Univ
8、ersity(NERCDT) has done much on technical and market research, including the simulation of all the familiar flowsheets on industrial and lab data, especially studying the 2 - effect heat exchange between the 2 methanol refining columns. As a summary of our work, the high pressure process and the low
9、 pressure process for 3 + 1 -column process was put forward.1 PROCESS DESCRIPTIONMethanol can be synthesized from many materials, for instance, natural gas, gas oil, fuel oil, coal, etc. Except for the difference in catalysts, reaction mechanics and the concentration of methanol in raw product, the
10、subsequent distillation process and equipments are similar, falling into three main assortments: 2 - column process, 3 -column process and 3+1 -column process. A 2 -column process is composed of light ends column and methanol refining column or main column which is found in factories under 100 kt/a,
11、 offering simple process, equipments and low investment. 3 -column process is built up by light ends column, pressured methanol refining column (PMRC) and atmospheric methanol refining column (AMRC), forming a 2 -effects distillation with the mixture of the distillates from the 2 methanol refining c
12、olumns the methanol product. The characteristic of this process is the 2 -effect distillation pattern between PMRC and AMRC, meaning heat exchange between the top of PMRC and the bottom of AMRC. This pattern saves the energy (by 30% 40)and the recycle rate of cooling water. If a methanol recovery co
13、lumn, or stripper, or water column involves after the low pressure methanol refining column to improve the quality of the wastewater, the process will turn into 3+1-column process.1.1 Light Ends ColumnNo matter in 2 - column process, 3 -column process or 3+1-column process, the Light End Column (LEC
14、) plays the same Role. Some of the light component in raw methanol fatal to the product are removed in this column, such as methyl formate (MFOR), dimethyl ether (DME), C1 C6, as well as acetone and methyl ethyl ketone (MEK). Some publications define MFOR,DME and C1 C6 as the alcoholic -soluble impu
15、rities, while DME and MEK the aquatic- soluble impurities. The standard of the division can be found in Table 1.Industrial investigation shows that the basic measures of the removal operation include large reflux ratio and process water inlet or both taken. The principles respectively employ the dif
16、ference of boiling point or relative volatility and solubility of the components.As a routine method, large reflux ratio; say 0. 70. 9 ( reflux to column feed), requires high condenser temperature to remove light impurities of high boiling point, for example acetone. Obviously, this method is accompanied by high energy consumption .Because the above method can not reduce the loss of methanol, process water is added to the column to change the concentration of me
