Chemistry: fischer-tropsch processes; or purification or recover – Group ib metal containing catalyst utilized for the...
Reexamination Certificate
1999-12-07
2001-04-17
Richter, Johann (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
Group ib metal containing catalyst utilized for the...
C518S702000, C518S703000, C518S704000
Reexamination Certificate
active
06218439
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing methanol, particularly, to a method of manufacturing methanol in which carbon dioxide is utilized for increasing the methanol yield.
Japanese Patent Disclosure (Kokai) No. 1-180841 discloses a method of manufacturing methanol (CH
3
OH) from hydrocarbons such as natural gas by the processes described below:
(Synthetic Gas-Forming Process)
In the first step, a synthetic gas containing as main components hydrogen (H
2
), carbon monoxide (CO) and carbon dioxide (CO
2
) is formed in a reformer by the reaction between a natural gaseous hydrocarbon or a gaseous hydrocarbon evaporated from a liquid hydrocarbon and steam at a predetermined temperature in the presence of a nickel-based catalyst.
Steam is added to the hydrocarbon from a moistening device arranged upstream of the reformer, followed by supplying a superheated steam prepared in a boiler or the like to the hydrocarbon so as to introduce a gaseous mixture containing hydrocarbon and steam into the reformer.
Since the steam reforming reaction noted above is an endothermic, reaction accompanied by a large amount of reaction heat, the reformer is heated from the outside in the process of forming the synthetic gas.
(Crude Methanol Synthetic Process)
A crude methanol is synthesized by the reaction among the synthetic gas, carbon monoxide and hydrogen or among the synthetic gas, carbon dioxide and hydrogen at a predetermined pressure and temperature in the presence of a methanol synthesizing catalyst to synthesize a crude methanol.
(Distilling Process)
The liquid crude methanol recovered in the methanol synthesizing process is distilled in a single or a plurality of distillation columns so as to separate the crude methanol into a waste liquid material and a refined methanol, said waste liquid material containing organic compounds having melting points lower than that of methanol (hereinafter referred to as “low boiling point organic compound”), organic acids and organic compounds having boiling points higher than that of methanol (hereinafter referred to as “high boiling point organic compound”).
Methanol is manufactured via the processes described above.
In recent years, it is of high importance to suppress the amount of carbon dioxide discharged from a plant as a measure against warming of the earth.
In a plant for manufacturing methanol from hydrocarbon such as natural gas, the heat required for the endothermic reaction between carbon monoxide and hydrogen is supplied to the reformer by heating the reaction tube loaded with a steam reforming catalyst with a combustion gas. Also, a boiler for steam generation is used for replenishing a required amount of a high pressure steam consumed in the plant. Naturally, a large amount of carbon dioxide is contained in the combustion waste gas of the reformer and the boiler for the steam generation. It follows that the plant tends to be rendered disadvantageous in economy where a tax and regulation for the carbon dioxide discharge are started in future.
On the other hand, in the method of manufacturing methanol from natural gas, the hydrogen concentration in the synthetic gas formed by the steam reforming reaction is about 1.5 times as high as that required for synthesizing methanol by the reaction of hydrogen with carbon monoxide and carbon dioxide contained in the synthetic gas. Therefore, in the process of synthesizing methanol, the unreacted gas separated from the synthesized methanol is recycled to the synthesizing reactor in order to improve the reaction efficiency within the synthesizing reactor, and the unreacted gas is partly released to the outside of the system to release the excess hydrogen. Also, the recycling amount of the unreacted gas is set at a value which permits moderating the heat generation rate during reaction in the catalyst layer loaded in the synthesizing reactor.
Under the circumstances, the idea of supplying carbon dioxide to a fluid passageway through which a synthetic gas formed in a reformer is supplied to the methanol synthesizing reactor is shown in
FIG. 5
of “INCREASED PRODUCTION FROM EXISTING METHANOL PLANTS BY A. English, I. A. Forbes, M. N. Islam, J. D. Korchank PRESENTED TO: WORLD METHANOL CONFERENCE Dec. 2-4, 1991 HYATT REGENCY HOTEL VANCOUVER, BC, CANADA, pp. 1-12”.
However, if a synthetic gas containing a large amount of carbon dioxide is supplied to the reactor in the crude methanol synthesizing step, the activity of the methanol synthesizing catalyst loaded in the reactor tends to be lowered.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a methanol manufacturing method capable of effectively utilizing an excess hydrogen in the mixed gas formed in the reformer to increase the methanol yield without bringing about reduction in the activity of the methanol synthesizing catalyst in the methanol synthesizing step, capable of effectively utilizing carbon dioxide so as to decrease the discharged amount of carbon dioxide, and also capable of decreasing the amount of steam supplied from outside into the reformer.
Another object is to provide a methanol manufacturing method capable of effectively utilizing the unreacted gas in the methanol synthesizing step so as to increase the methanol yield, and also capable of effectively utilizing carbon dioxide so as to decrease the discharged amount of carbon dioxide.
According to a first aspect of the present invention, there is provided a method of manufacturing methanol, comprising the steps of:
supplying a raw material gas containing hydrocarbon as a main component and steam into a reformer, the raw material gas being supplied into the reformer through a moistening device, to carry out reaction between the hydrocarbon and steam to form a synthetic gas containing as main components hydrogen, carbon monoxide, and carbon dioxide;
performing reaction of the synthetic gas in the presence of a methanol synthesizing catalyst to synthesize a crude methanol; and
distilling a liquid crude methanol recovered in the synthesizing process to separate the crude methanol into a waste liquid material and a refined methanol, the waste liquid material containing low boiling point organic compounds and high boiling point organic compounds,
wherein carbon dioxide is supplied to at least one fluid passageway selected from the group consisting of a fluid passageway positioned upstream of the moistening device and another fluid passageway interposed between the moistening device and the reformer.
In the methanol manufacturing method of the present invention, it is possible for the moistening device to include a first stage moistening device and a second stage moistening device arranged downstream of the first stage moistening device and upstream of the reformer such that hydrocarbon and carbon dioxide are supplied to a fluid passageway positioned upstream of the first stage moistening device, and the waste liquid material recovered in the distilling process is supplied to a circulating water passageway of the first stage moistening device.
It is also possible to supply an additional carbon dioxide to at least one fluid passageway selected from the group consisting of a fluid passageway interposed between the first and second moistening devices and another fluid passageway interposed between the second stage moistening device and the reformer.
In the methanol manufacturing method of the present invention, it is desirable to use carbon dioxide recovered from at least one combustion gas selected from the group consisting of the combustion gas for heating the reformer and the combustion gas for heating a boiler for steam generation.
In the methanol manufacturing method of the present invention, it is desirable to use in the step of synthesizing the crude methanol a reaction apparatus comprising a reactor and a triple pipe consisting of an outer pipe, an intermediate pipe and an inner pipe that are concentrically arranged. The reactor is vertically partitioned by two partition plates into three chambers consisting of a syn
Imai Tetsuya
Kobayashi Kazuto
Nagai Hideaki
Osora Hiroyuki
Seiki Yoshio
Cooper & Dunham LLP
Mitsubishi Heavy Industries Ltd.
Parsa J.
Richter Johann
White John P.
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