DME production from natural gas
Di-methyl-ether (DME) is mainly used as a propellant and can also be used as a substitute for diesel
fuel in diesel engines with the advantage of high efficiency and low exhaust emissions (no
particulates, no Sulphur, and low NOx). It is an alternative to liquefied petroleum gas (LPG).
DME is usually produced directly from natural gas. It involves three main steps: 1) converting
natural gas into synthesis gas (mainly CO2, CO and H2), 2) methanol synthesis and 3) DME production
and separation. You are required to simulate this process.
Converting natural gas into synthesis gas
In this step, methane is first reacted with steam to produce syn-gas in a conversion reactor R-ref at
temperature TR-ref and pressure PR-ref. This steam reforming is an isothermal process, so appropriate
heating or cooling is needed.
๐ถ๐ถ๐ถ๐ถ4 + 2๐ถ๐ถ2๐๐ โ ๐ถ๐ถ๐๐2 + 4๐ถ๐ถ2 (R1)
๐ถ๐ถ๐ถ๐ถ4 + ๐ถ๐ถ2๐๐ โ ๐ถ๐ถ๐๐ + 3๐ถ๐ถ2 (R2)
The conversion rate for each reaction is given in your individual design specification. The gas product
from R-ref is fed into a component splitter (CS-100) where CO and H2 at the molar ratio of 1:2 leave
the splitter from the top as Stream CS100-top while the rest of the product leaves from the bottom
as Stream CS100-bottom.
Methanol synthesis
Stream CS100-top is cooled down to TR3 (the temperature of 1st methanol synthesis reactor) before
the below equilibrium reaction takes place in the reactor.
๐ถ๐ถ๐๐ + 2๐ถ๐ถ2 = ๐ถ๐ถ๐ถ๐ถ3๐๐๐ถ๐ถ (R3)
This reaction can be found in HYSYS equilibrium reaction library. The gas stream from this reactor
goes to a component splitter where methanol is separated as Stream Methanol 1 and sent to DME
production section while the unreacted gas is recycled back to the reactor.
Stream CS100-bottom is cooled down to TR4 before it enters a CSTR reactor where CO2 is converted
into CH3OH at the temperature of TR4.
๐ถ๐ถ๐๐2 + 3๐ถ๐ถ2 = ๐ถ๐ถ๐ถ๐ถ3๐๐๐ถ๐ถ + ๐ถ๐ถ2๐๐ (R4)
You are required to use a kinetic model to simulate this reaction. The forward reaction rate constant
kF and backward reaction rate constant kB are given below:
๐๐๐น๐น = 1.04 ร 1022๐๐๏ฟฝ
โ170000
๐
๐
๐
๐
๏ฟฝ
Sample Solution
Dimethyl Ether (DME) is a safe and cost-effective alternative fuel made from natural gas. DME has qualities that are extremely comparable to LPG. DME is a clean and easy-to-handle fuel that may be utilized in a variety of applications, including power generation, transportation, home heating and cooking, and so on. A novel method for producing DME directly from synthesis gas has been devised. The project to build a 5 ton per day DME production pilot plant (5TPD) was completed successfully in FY2001, and the project to build a 100 ton per day DME production demonstration plant (100TPD) began in FY2002. The Ministry of Economy, Trade, and Industry is supporting and funding these projects (METI). JFE Direct DME Synthesis will pave the path for more cost-effective DME mass production.
