Process Description dme

PROCESS DESCRIPTION Process simulation is done by using Aspen HYSYS simulation software version 8.6.The advantage of this software is its capability to create process plant. The purpose of creating conceptual design is to have comparison for calculations on the material and the energy balances. HYSYS use the concept of the fluid package to contain all necessary information for performing flash and physical property calculations. This approach allows you to define all information inside a single entity. The key advantages to this approach are the all associated information is defined in a single location. It also allow for easy creation and modification of the information. The fluid packages can be restored as a completely defined entity for use in any simulation. Moreover, the multiple fluid packages can be used in the same simulation.

For the HYSYS, the non-random two liquid equation (NRTL) fluid packages is used. This fluid package is used due to the existance of two and three phase azeotropic mixture in the reaction and the existance of the polar component that is methanol. All the chemical components involve in the process are set in the components library. The components set consist of pure components. For the reaction setting, the reactor was set as the kinetic and the yield was obtained yield from the literature. The major equipment used the same as the process flow diagram which contains a plug flow reactor and two distillation column. A PFD of the process is shown in shown in Figure 1. The essential operations in the process are the preheating of the raw material (nearly pure methanol), reacting methanol to form DME, product separation, contaminant separation, and methanol separation and recycle. Crude methanol, containing about 2 mol % impurities, is fed as a liquid in Stream 1, pumped up to 16.21 atm and heated to 250 oC and combined with Stream 16, a methanol recycle stream. After that, stream 17 sent to packed bed reactor, R-101, to form DME. The reaction is slightly exothermic and the reaction products are heated to approximately 370°C before leaving the reactor. Then stream 6 was cooled to 50 oC using cooler E-102. After that,

methanol conversion of about 80% is achieved in the reactor. The mixture in stream 8 was separated using 2 different distillation columns. Pure DME can be obtain from stream 9. Stream 11 which contain methanol was recycle back to the reactor. In the temperature range of normal operation, there are no significant side reactions, and the equilibrium conversion for pure DME product exceeds 97%. Therefore, the reactor is kinetically controlled in the temperature range of normal operation.

Figure 1: process flow diagram using HYSYS v8.6

WORKBOOK

Table 1: material stream workbook

Table 2: composition stream workbook

Table 3: energy stream workbook.