JPH10182535A - Method for producing dimethyl ether - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The cooling and cooling of dimethyl ether in the dimethyl ether production process using the vaporization cooling of liquefied natural gas.
Provided is a method for producing dimethyl ether, which can carry out separation and can reduce operating costs such as electric power required for a dimethyl ether production step. SOLUTION: The gaseous reaction mixture 5 containing gaseous dimethyl ether generated by the reaction between hydrogen gas and carbon monoxide gas is cooled, and liquefied natural gas 10 is used as cold heat used for separating liquid dimethyl ether 8. The cold heat obtained when vaporizing is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing dimethyl ether.

[0002]

2. Description of the Related Art In a commercial synthesis method of dimethyl ether (DME), a method is used in which methanol is used as a raw material and one molecule of water is dehydrated from two molecules of methanol. However, dimethyl ether is directly converted from hydrogen and carbon monoxide. A technique for synthesizing a color has recently been developed (Japanese Unexamined Patent Publication No.
No. 181453).

A method for synthesizing dimethyl ether using hydrogen and carbon monoxide as raw materials includes many reaction steps. That is, the synthesis of methanol from hydrogen and carbon monoxide, the synthesis of dimethyl ether by a dehydration reaction from the synthesized methanol, and the reaction of water and carbon monoxide by-produced in the synthesis reaction of dimethyl ether to produce hydrogen and carbon dioxide. Three types of reaction processes for producing carbon proceed simultaneously. The reaction formulas are as follows.

CO + 2H ₂ → CH ₃ OH 2CH ₃ OH → CH ₃ OCH ₃ (dimethyl ether) +
H ₂ O H ₂ O + CO → H ₂ + CO ₂ When looking at each of the above reaction steps, dimethyl ether is synthesized from carbon monoxide and hydrogen as represented by the following reaction formula. 3CO + 3H ₂ → CH ₃ OCH ₃ (dimethyl ether)
+ CO ₂

The typical reaction temperature in the above synthesis reaction is about 150 to 400 ° C., and the reaction pressure is about 10 to 10
0 kg / cm ² , preferably 15-80 kg / cm ² ,
Particularly preferably, it is 20 to 70 kg / cm ² . However, the conversion of the starting materials in this synthesis method is not actually 100%, and since unreacted carbon monoxide and hydrogen are present in the reaction mixture, these unreacted gases are separated from the product. , And is recycled to the reactor as raw material gas. That is, a dimethyl ether separator is provided downstream of the dimethyl ether synthesis reactor because it is necessary to separate generated dimethyl ether and unreacted gas.

In a dimethyl ether separator, dimethyl ether (reaction product) is separated from hydrogen and carbon monoxide (unreacted gas) by utilizing a difference in boiling points. That is, the temperature in the dimethyl ether separator is set to -30 ° C to-
After cooling to 40 ° C., dimethyl ether is liquefied from the reaction mixture gas and separated from hydrogen gas and carbon monoxide gas. As a cooling means of the dimethyl ether separator, a method of cooling a refrigerant by a device such as a refrigerator or the like and cooling the components in the dimethyl ether separator by circulating the refrigerant has been adopted. However, the cost of electric power and the like for operating the refrigerator is large, and has greatly increased the cost of the dimethyl ether production method.
For this reason, the efficiency of dimethyl ether production depends on the cost of the refrigerator (Japanese Unexamined Patent Publication No. 3-528).
No. 35).

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing dimethyl ether using a raw material gas containing hydrogen and carbon monoxide as main raw materials. Another object of the present invention is to provide a means for reducing the energy cost when cooling the dimethyl ether separator.

[0008]

According to the present invention, a gaseous reaction mixture containing gaseous dimethyl ether formed by the reaction of hydrogen gas and carbon monoxide gas is cooled to separate liquid dimethyl ether. This can be solved by a method for producing dimethyl ether, characterized in that cold heat used for vaporizing liquefied natural gas is used as the cold heat used to perform the process. Further, the present invention provides
The present invention also relates to a method of using a hydrogen gas and / or a carbon monoxide gas prepared by reforming a gas obtained by vaporizing the liquefied natural gas as a raw material for producing dimethyl ether.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method of the present invention will be specifically described with reference to FIG. The liquefied natural gas 10 is sent from the liquefied natural gas tank 9 to the liquefied natural gas vaporizer 11. The liquefied natural gas vaporizer 11 vaporizes the liquefied natural gas 10 using the refrigerant 12. Natural gas 10a vaporized
Can be sent to any process that utilizes it,
When the vaporized natural gas 10a is used in a method for synthesizing dimethyl ether, it is sent to a gas reformer 2. Gas reformer 2 contains natural gas 10
In addition to a, a natural gas reforming agent 1 composed of oxygen, water vapor, and / or carbon dioxide is supplied. The gas reformer 2 generates hydrogen gas and carbon monoxide gas from these source gases.

The raw material gas 3 containing hydrogen gas and carbon monoxide gas as main components thus obtained is sent to a dimethyl ether synthesis reactor 4, where crude dimethyl ether is produced. The generated gas 5 contains unreacted gas and by-products in addition to dimethyl ether. The crude dimethyl ether gas 5 containing these impurities is sent to a dimethyl ether separator 6, where it is cooled and separated into a liquid phase and a gas phase. The liquefied dimethyl ether 8 containing carbon dioxide and the like obtained as a liquid phase is separated into liquefied dimethyl ether and carbon dioxide by the following carbon dioxide separator (not shown). In addition,
The gas phase containing hydrogen gas and carbon monoxide gas, which are low-boiling components, is used as unreacted gas 7 in a dimethyl ether synthesis reactor 4.
It can also be recycled.

On the other hand, the refrigerant 1 used when the liquefied natural gas 10 is vaporized in the liquefied natural gas vaporizer 11 is used.
2 is sent from the cold storage heat tank 13 to the liquefied natural gas vaporizer 11, where the liquefied natural gas is deprived of the heat of vaporization by the liquefied natural gas, and is itself cooled. Return to the cold storage tank 13. The refrigerant 14a cooled in the cold storage tank 13 by utilizing the cold heat of the cooling refrigerant 12a is sent to a temperature controller 15 which is optionally installed, and has a temperature suitable for the dimethyl ether separation step if necessary. And then sent to the dimethyl ether separator 6. In the dimethyl ether separator 6, the crude dimethyl ether gas 5 is cooled by the cold heat of the refrigerant 14a, the dimethyl ether is liquefied, and gas-liquid separation is performed. The refrigerant 14a uses cold heat in the dimethyl ether separator 6, that is, the refrigerant 14a itself is heated, and is returned to the cold storage heat tank 13 again as the heated refrigerant 14. Refrigerant 1
2 is heated in the cool storage heat tank 13 using the heat of the heated refrigerant 14 and sent to the liquefied natural gas vaporizer 11.

As described above, the cold generated when the liquefied natural gas 10 is vaporized via the refrigerants 12 and 12a and the refrigerants 14 and 14a is used for cooling and separating the liquid dimethyl ether from the crude dimethyl ether gas 5. You. Liquefied natural gas, when used, must be vaporized, generating a large amount of cold. In many conventional cases, seawater is used as a heat source for vaporization, and the cooled seawater has been discarded, so that this cold heat has not been effectively used. However, according to the method of the present invention, the operating cost of the dimethyl ether synthesis step can be reduced by utilizing the cold heat obtained from the liquefied natural gas that has been dumped so far in the dimethyl ether separation step.

Further, the gasified natural gas produced for obtaining the above-mentioned cold heat in the method of the present invention can be used in any step unrelated to the method of the present invention. It can also be used as a gas. That is, in the method of the present invention, the raw gas can be prepared by inserting the vaporized natural gas into the gas reformer 2, and in that case, it is preferable to use the above-mentioned vaporized natural gas. In the method of the present invention, the material supplied to the gas reformer 2 is not particularly limited. For example, a raw material such as a hydrogen gas or a carbon monoxide gas is obtained by reforming a coal gasification gas or a natural gas. Gases can be prepared (see, for example, US Pat. No. 4,430,096). Further, by appropriately controlling the reforming conditions, a mixed gas containing hydrogen gas and carbon monoxide gas having a composition suitable for the method of the present invention can be generated.

In the method of the present invention, a conventional dimethyl ether synthesis method can be used as it is, except that the above-mentioned cold heat is used. Accordingly, for example, the dimethyl ether synthesis reactor 4 used in the method of the present invention is not particularly limited. For example, a single-stage liquid phase reactor into which a slurry in which a solid catalyst is suspended in an inert medium oil is inserted. It is preferably used. These liquid phase reactors are described, for example, in European Patent Publication No. 0324475,
No. 9833, JP-A-3-52835, JP-B-7-57739 and JP-A-6-25031. Known reaction conditions, cooling / separation conditions, and the like of the method of the present invention can be used as they are.

FIG. 1 shows an embodiment in which two kinds of refrigerants 12 and 14 are used via a cold storage heat tank 13.
It is also possible to carry out the method of the present invention using only one kind of refrigerant without providing 3. Also, a cold storage heat tank 13 is provided,
The method of the present invention can also be performed using one type of refrigerant. In the method of the present invention, as the refrigerants 12 and 12a used for vaporizing liquefied natural gas and the refrigerants 14 and 14a used for liquefying dimethyl ether, refrigerants conventionally used for vaporizing liquefied natural gas and liquefying dimethyl ether are used as they are. be able to.

The regenerative heat storage tank 13 is preferably provided because it can perform a buffer function for preventing the temperature of the refrigerant from suddenly changing even when the amount of vaporized liquefied natural gas changes. In addition, the temperature controller 15 which can be optionally provided between the cold storage heat tank 13 and the dimethyl ether separator 6 can maintain the temperature in the dimethyl ether separator 6 at −30 ° C. to −40 ° C. The device is not particularly limited as long as it can adjust the temperature of the refrigerant. Further, in some cases, the temperature controller is connected to the cold storage heat tank 13.
Provided between the liquefied natural gas vaporizer 11 and the liquefied natural gas vaporizer 11, the temperature of the refrigerant 12 sent to the liquefied natural gas vaporizer 11 can be adjusted as appropriate.

[0017]

According to the method of the present invention, the liquefied natural gas, which has not been effectively used in the past, is utilized by utilizing the cold heat of vaporization.
Since cooling and separation of dimethyl ether can be performed in the dimethyl ether production process, operating costs such as electric power required for the dimethyl ether production process can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Natural gas reforming agent; 2 ... Gas reformer; 3 ... Raw material gas; 4 ... Dimethyl ether synthesis reactor; 5 ... Crude dimethyl ether gas; 6 ...
Dimethyl ether separator; 7 ... unreacted gas;
Liquefied dimethyl ether; 9 Liquefied natural gas tank; 10 Liquefied natural gas; 10a Liquefied natural gas; 11 Liquefied natural gas vaporizer;
Refrigerant: 12a: cooled refrigerant; 13: regenerator;
14 ... heated refrigerant; 14a ... cooled refrigerant;
··air conditioner

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masatsugu Mizuguchi 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (2)

[Claims] 1. A method for cooling a gaseous reaction mixture containing gaseous dimethyl ether formed by a reaction between hydrogen gas and carbon monoxide gas, and vaporizing liquefied natural gas as cold heat used to separate liquid dimethyl ether. A method for producing dimethyl ether, characterized by using cold heat obtained at that time. 2. The method according to claim 1, wherein hydrogen gas and / or carbon monoxide gas prepared by reforming a gas obtained by vaporizing the liquefied natural gas is used as a raw material for producing dimethyl ether. Method.