Бурение грунтовых зондов, установка энергетических колодцев

Approximately 3.3 million metric tons per year, or about 9% of the estimated world methanol production, is based on the gasification of coal or heavy residues.

Methanol is an important intermediate and, as can be seen from Figure 7-3, approximately two-thirds of the production goes into the manufacture of formalde­hyde and MTBE (methyl tertiary-butyl ether). The demand for methanol has varied substantially from year to year, creating some dramatic price swings when supply has failed to keep up with demand. At the time of this writing, the future of MTBE as a component in reformulated gasoline is still uncertain, and this has its effects on the market.

During the 1990s the typical size of world-scale natural gas-based plants increased from 2000 to about 3000 mt/d. Current designs go up to 5000 t/d, and three plants of this size are in the design stage (Gohna 1997). Most plants based on gasifi­cation technologies are somewhat smaller. The largest, in the Leuna refinery in Germany, has a nameplate capacity of 2060 mt/d.

Synthesis Gas Specification

Methanol synthesis takes place by the reaction of hydrogen with carbon oxides according to the following reactions:

CO + 2 H2 => CH3OH -91 MJ/kmol (7-3)

and

C02 + З H2 => CH3OH + H20 -50 MJ/kmol (7-4)

Modern low-pressure methanol synthesis takes place today at a pressure between 50 and 100 bar over a copper catalyst. An ideal synthesis gas specification is

For the methanol synthesis it is important to recognize that the above specification for the stoichiometric ratio (SR = (H2 — C()2)/(CO + C()2)) and carbon dioxide content represent an optimized synthesis gas. This is not the quality produced by the majority of plants using steam reforming of natural gas, as shown in Table 7-2.

The data in Table 7-2 show that the conventional steam reforming process operates with a considerable hydrogen surplus (SR = 2.7) and high C02 content. Combined reforming using a steam reformer with an oxygen-blown secondary reformer is able to supply an optimized stoichiometric ratio, but it still has a high C02 content. Since the conversion rate of C02 is considerably less than that of CO,

it is preferable to keep the C02 content low if reasonably possible; however, a small amount of C02 is required to ensure a high CO conversion. The optimum C02 content lies between 2.5 and 3.5 mol%.

Supp (1990) provides a detailed explanation for these optima in his book How to Produce Methanol from Coal, so these aspects of methanol synthesis will only be touched upon here. Furthermore, he has described the manufacture of methanol from coal in considerable depth, and those interested in the topic are referred to his work. As a practical example, we will therefore review the process of making methanol from petroleum residues.

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