METHANOL PLANT DME CONVERSION

DME is an acronym for Di-Methyl Ether Chemical formula: (CH3OCH3)

Chemistry 101

Other Names: Wood ether

Prozone

Dimethyloxide

Methyl ether

Chemistry 101

* Chlorinated Fluorocarbons

DME is a colorless, gaseous,

simple ether that was originally

developed as a replacement

for CFC’s* in an effort to

decrease greenhouse gasses.

DME is Non-toxic and

Biodegradable.

Chemistry 101

•DME can be

made from

Methanol, Coal,

LPG, Natural

Gas, or Biomass.

Chemistry 101

Aerosol Spray Propellants

Excellent CFC Free Solvent

and Raw Material for

Chemical Products

FUTURE USES OF DME

DME is a

Next-Generation

Clean Fuel that

can be used as a

substitute for

Gasoline and Diesel Fuels

DME is adaptable

for use in

Thermal Electrical

Power Generation

Plants,

Cogeneration

Plants and

Stationary Fuel Cell Technology.

DME and The Environment

DME and The Environment

Extremely Low toxicity

Zero Soot Emissions

Zero SO2 Emissions

DME is Non Ozone Depleting and is

not a Greenhouse Gas

Lower NOx

than Diesel

DMEProduction

DME ProductionDME production begins by using natural gas, coal or other raw materials to produce a synthesis gas made up of carbon monoxide and hydrogen. DME is produced from this synthesis gas in one of two ways: “methanol dehydration" (indirect synthesis) or "direct synthesis."

• Methanol dehydration is a process of producing DME from a dehydration reaction, with methanol produced from the synthesis gas.

• Direct synthesis produces DME directly from synthesis gas. The two main varieties are the "fixed bed reactor process" (Haldor Topsoe A/S of Denmark) and the "slurry bed reactor process" (JFE, Air Products and Chemicals, Inc. of the U.S.).

DME Production• Conventional DME production involves a methanol

dehydration reaction but over the last several years there

have been attempts to develop the technology to

synthesize DME directly from synthesis gas (hydrogen,

carbon monoxide) in order to produce it at low cost and in

sufficient quantities to be used as fuel.

• DME synthesis is very similar to methanol synthesis, but

simpler than methanol synthesis considering lower

reaction heat and lower synthesis pressure.

• Direct synthesis of DME requires a temperature of 210-

290°C and pressure of 3-10 MPa; a mixed function

catalyst can be used to achieve methanol synthesis and

dehydration.

DME Production

INDIRECT SYNTHESIS

•Methanol dehydration: a process of

producing DME from a dehydration

reaction of methanol produced from

synthesis gas.

•Methanol dehydration heats and

evaporates liquid methanol so that it is

converted to DME in a dehydration

reactor. The energy consumed in DME

refining is high at about 20% of the

calorific value of the DME product.

DIRECT SYNTHESIS

•Direct synthesis produces DME directly

from synthesis gas. The two main

varieties are the "fixed bed reactor

process" and the "slurry bed reactor

process“.

•DME synthesis generates large

quantities of reaction heat (exothermic),

and how to remove this heat is one of

the major engineering hurdles faced.

Because the methanol synthesis

equilibrium limitation can be avoided in

the direct DME synthesis reaction a

higher conversion rate can be achieved

Conversion of

Methanol Plant to

DME Production

Methanol Plant Conversion to DME

Conversion of the Methanol Plant for DME production would be accomplished most effectively based on the methanol dehydration or “indirect synthesis” process, utilizing the existing desulfurization, reforming, synthesis and distillation processing train.

• High reaction conversion ratio; DME appx. 99%, overall appx. 95%

• The process for methanol and indirect DME production consists of established, mature commercial technology resulting in proven reliability.

• The production duality of fischer-Tropsch type reactors may be utilized in reducing the capitol expense of additional equipment.

• Current commercial availability of catalyst.

Approach Advantages...

Indirect DME Synthesis from Methanol

Sulfur Removal

ReformingMethanol Synthesis

DME Synthesis

DME Distillation

FeedstockDME

Product

DME Production

Existing Plant

Additional Equipment

Legend:

Methanol to DME Indirect Synthesis

Process Flow Diagram

Feed methanol is fed to a DME reactor after vaporization. The synthesis pressure is 1.0 - 2.0 MPaG. The inlet temperature is 220 - 250 °C and the outlet is 300 - 350 °C. Methanol one pass conversion to DME is 70 – 85 % in the reactor. Produced DME with by-product water and unconverted methanol is fed to a DME column after heat recovery and cooling. In the DME column 99.9 DME is separated from the top as a product. Water and methanol are discharged from the bottom and fed to a methanol column for methanol recovery and reprocessing.

Conclusions

Dimethyl ether (DME) is considered a clean energy source and

since it generates no sulfur oxide, less NOx and zero soot during

combustion, its environmental impact is very low.

Owing to its non-toxicity and easy liquefaction properties, DME is

easy to handle and therefore can be used as a domestic-sector fuel

(substitute for LPG), transportation fuel (diesel vehicles, fuel cell

vehicles), power plant fuel (thermal plants, cogeneration plants,

stationary fuel cells), and as a raw material for chemical products.

Currently DME is produced by dehydrating methanol and direct

synthesis plants are now beginning production. Approximately ten

thousand tons per year are produced in Japan, and 150 thousand

tons per year worldwide. Currently, it is primarily used as a spray

propellant. However, given the above-described superior properties,

once DME becomes widely available in large volumes at a

reasonable price, DME could be used as a fuel in a wide variety of

fields.

Conclusions, continued

Methanol production has slowed in North America where the natural

gas required for methanol production is very expensive.

Because of the lower demand for methanol, most, if not all, marginal

methanol production has moved to areas where large supplies of

natural gas are available at a relatively low cost, such as the Persian

Gulf, Trinidad, India or South America.

New plants will likely be built in those areas where natural gas is

abundant and relatively inexpensive as compared to the price in

North America. Accordingly, Methanol Plants are being relocated

and/or converted to DME or GTL production.

Conclusions, continued

The Cheyenne Methanol Plant produces high grade methanol utilizing the

following process steps:

Feedstock Desulfurization and Saturation

Synthesis Gas Production and Heat Recovery

Synthesis Gas Compression

Crude Methanol Synthesis Loop (Fisher -Tropsche)

Distillation

The methanol conversion process used in this plant is comprised of essentially the

same distinct steps as those found in the DME and GTL processes, i.e. (a) syngas

synthesis and compression, (b) product (methanol) synthesis, and (c) product

upgrading. The plant also utilizes a Multi-Tubular Reactor (i.e. a vessel having a

plurality of catalyst-filled tubes affixed therein), and accordingly, is ideal for utilization

as a subsystem for methanol production utilized in the indirect synthesis of DME.

Additionally, since the plant is equipped with a Multi-Tubular FT reactor, other DME

and GTL direct synthesis processes are possible with minor catalyst and subsystem

revisions.

References

Journal of Chemical and Engineering Data, Kenneth N. Marsh, Editor,1992

Large Scale DME Production, Ishinada, Akiera, Mitsubishi Gas Chemical,1997

Modifications of a Methanol Plant for Converting Natural Gas to Liquid Hydrocarbons (U.S. Patent), Peter, Tim; Loring, David; Noda, Leigh,1996

Japan DME Forum, Ohno, Yatoro, 2005

Koenig, Mark D., Environmental Scientist