外文翻譯--利用分隔壁和分隔柱改進二甲醚凈化過程的能量效率（英文）

1、1500?To whom correspondence should be addressed. E-mail: mynlee@yu.ac.krKorean J. Chem. Eng., 29(11), 1500-1507 (2012) DOI: 10.1007/s11814-012-0048-6INVITED REVIEW PAPEREnergy efficiency improvement of dimethyl ether pur

2、ification process by utilizing dividing wall columnsLe Quang Minh, Nguyen Van Duc Long, and Moonyong Lee?School of Chemical Engineering, Yeungnam University, Gyeongsan 712-749, Korea (Received 6 December 2011 ? accepted

3、5 April 2012)Abstract?The alternative fuel, dimethyl ether (DME), which can be synthesized from natural gas, coal or biomass syngas, has been traditionally used as a diesel substitute or additive. DME purification proces

4、ses with a conventional distillation sequence consume a large amount of energy. We used dividing wall columns (DWCs) to improve the energy efficiency and reduce the capital cost of the DME purification process. Various p

5、ossible DWC arrangements were ex- plored to find the potential benefits derived from thermally coupled distillations. The results show that utilizing DWCs can significantly reduce both the energy consumption and investme

6、nt cost of the DME purification process. The lower energy consumption also results in the reduction of the CO2 emission.Key words: Distillation, Dimethyl Ether, DME, Dividing Wall Column, DWC, Thermally Coupled Distillat

7、ion ColumnINTRODUCTIONTo reduce the environmental problems caused by the direct com- bustion of fossil fuels and the diminishing energy supply, there is an urgent need to investigate alternative fuels and energy systems

8、[1]. Dimethyl ether (DME), which can be synthesized from natural gas, coal or biomass syngas, has been traditionally used as a diesel substitute or additive [2,3]. It does not attack the stratospheric ozone and allows fo

9、r the better emission control of NOx, CO, SOx, non- methane hydrocarbons and particulates such as soot [4]. DME rep- resents a potential alternative to liquefied petroleum gas, liquefied natural gas and diesel. DME can a

10、lso be an ideal fuel in the form of a hydrogen carrier, due to its high H/C ratio, high energy density, ease of storage, and ease of transportation [5]. Traditionally, DME has been produced in a two-step process (the con

11、ventional route) where syngas (typically generated from the steam reforming of methane) is first converted to methanol, followed by its dehydration to DME [6]. Natural gas is not the only resource that can be used to gen

12、erate syngas; coal and biomass can also be used. Hence, DME production is not limited to one feedstock. Also, new processes are being commercialized to produce DME in a single step via auto-thermal reactors and slurry ph

13、ase reactors. In compar- ison with the two-step method, the single-step procedure is attract- ing more attention because of its economic value and theoretical significance. The research at present into the single-step pr

14、ocedure for producing DME from syngas is focused on the best catalyst to use, as well as the process conditions and synergy effect of the reac- tions. In the single-step procedure, the effluent stream from the reac- tors

15、 contains DME, methanol, water, carbon dioxide and other gases [7-9], and a separation unit to purify DME is necessary and crucial to the overall economics of the production process. The contribu- tions made so far focus

16、ing on the separation of the mixture are stilllimited, particularly in terms of the distillation technology. Moreover, the huge energy consumption required for the purification of DME from the effluent mixture needs to b

17、e reduced. Therefore, the main target for process engineers has been to develop a new process utiliz- ing the energy sources efficiently and improving the energy efficiency significantly in every particular unit of the D

18、ME purification pro- cesses. Distillation, as a workhorse of chemical process industries, is an energy-intensive process and, therefore, it is the first to be addressed to improve the energy efficiency over the short- an

19、d long-term. Fur- thermore, since the huge amount of energy consumed in the distilla- tion process has a big impact on greenhouse gas emissions, saving energy in this area has become an important issue from an envi- ronm

20、ental standpoint [10,11]. To reduce the total annualized cost (TAC), which includes the operating and capital costs, the use of complex distillation arrangements should be considered, such as heatFig. 1. Schematic diagra

21、m of fully thermally coupled distillation configuration.1502 L. Q. Minh et al.November, 2012uct. The bottom stream from T103 is mixed with the aqueous feed stream, which contains MeOH and water, from the upstream sepa- r

22、ator and then fed to the MeOH recovery column (T104) to remove the water. The purified MeOH from the top of T104 is recycled tothe reactors for producing DME continuously. Based on the feed composition and product specif

23、ications of the conventional distillation sequence, a simulation was performed to quantify the energy consumption as well as the total annualized cost (TAC). Table 2 includes the reboiler and condenser duties for each co

24、lumn. To minimize the refrigeration costs, all of the columns were designed to operate at relatively high pressures of approximately 30 bars. The column hydraulics and flooding conditions were consid- ered to estimate th

25、e capital cost. To determine its maximum flooding level, the rating mode was simulated based on the internal specifica- tions of the column such as the type of trays, column diameter, tray spacing, and number of passes.

26、The hydraulic parameters used in this study are also listed in Table2. All of the columns were designed with a load of near 80% to prevent their flooding [25]. Guthrie’s modular method [26] was applied to estimate the ca

27、pital cost. The capital cost for conventional distillation is the total cost of the col- umn and auxiliary equipment, such as the reboiler and condenser,Fig. 3. Simplified flow sheet illustrating DME purification process

28、.Fig. 4. Various configurations of complex column network used to purify DME. All of the gray columns are newly replaced DWCs.Table 2. Column hydraulics, energy performance of the conven- tional column sequenceT100 T101

29、T102 T103 T104Number of trays 40 30 30 30 30Tray type Sieve Sieve Sieve Sieve SieveColumn diameter (m) 3.8 2.5 1.2 2.6 2.7Number of flow paths 1 1 1 1 1Tray spacing (mm) 609.6 609.6 609.6 609.6 609.6Max flooding (%) 79.2