PRODUCTION

There are 18 methanol production plants in the United States with a total annual capacity of over 2.6 billion gallons per year. Worldwide, over 90 methanol plants have the capacity to produce over 11 billion gallons of methanol annually. The global methanol industry generates $12 billion in economic activity each year, while creating nearly 100,000 jobs.

The typical feedstock used in the production of methanol is natural gas. Methanol also can be made from renewable resources such as wood, municipal solid wastes and sewage. The production of methanol also offers an important market for the use of flared natural gas.

In a typical plant, methanol production is carried out in two steps. The first step is to convert the feedstock natural gas into a synthesis gas stream consisting of CO, CO2, H2O and hydrogen. This is usually accomplished by the catalytic reforming of feed gas and steam. Partial oxidation is another possible route. The second step is the catalytic synthesis of methanol from the synthesis gas. Each of these steps can be carried out in a number of ways and various technologies offer a spectrum of possibilities which may be most suitable for any desired application.

Conventional steam reforming is the simplest and most widely practiced route to synthesis gas production:

2 CH4 + 3 H2O _ CO + CO2 + 7 H2 (Synthesis Gas)

CO + CO2 + 7 H2 _ 2 CH3OH + 2 H2 + H2O

This process results in a considerable hydrogen surplus, as can be seen.

If an external source of CO2 is available, the excess hydrogen can be consumed and converted to additional methanol. The most favorable gasification processes are those in which the surplus hydrogen is “burnt” to water, during which steam reforming is accomplished by partial oxidation:

CH4 + _ O2 _ CO + 2 H2 _ CH3OH

CH4 + O2 _ CO2 + 2 H2

The carbon dioxide and hydrogen produced in the last equation would then react with an additional hydrogen from the top set of reactions to produce additional methanol. This gives the highest efficiency, but may be at additional capital cost.

Unlike the reforming process, the synthesis of methanol is highly exothermic, taking place over a catalyst bed at moderate temperatures. Most plant designs make use of this extra energy to generate electricity needed in the process.