JPH0678541B2 - Reducing gas composition adjustment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a reducing gas, which is adopted as a gas for producing ammonia, a gas for a fuel cell, a simulated gas for coal, for example, The present invention relates to an improvement in a method for adjusting the component ratio of hydrogen and carbon monoxide in gas.

[Conventional technology]

The above-mentioned reducing gas is a mixed gas containing hydrogen and carbon monoxide as main components and also carbon dioxide gas, steam, etc., and this gas is a hydrocarbon-based fluid such as natural gas, off gas from a refinery, or naphtha. The raw materials are light hydrocarbons such as, aromatic hydrocarbons such as benzene, and heavy oil such as asphalt.

As a method for generating the reducing gas, conventionally, there is a method utilizing a partial oxidation method, and in this method, the heat of reaction required for decomposing the raw material is a combustion generated by burning a part of the raw material with oxygen. The heat is used to gasify the raw material. And this partial oxidation reaction is an exothermic reaction,
The main reaction is represented by CmHn + m / 2O ₂ → mCO + n / 2H ₂ , and the following reactions also occur.

CmHn + mH ₂ O → mCO + (m + n / 2) H ₂ CO + H ₂ O → CO ₂ + H ₂ Therefore, in this conventional method, it is not necessary to apply heat from the outside to maintain the reaction temperature.
Further, since no catalyst is used, there are few restrictions on impurities in the raw material, and the raw material can be selected over a wide range.
Further, the reaction furnace may be a cylindrical hollow cylinder which is only lined with refractory bricks, which makes the structure of the gas generating furnace extremely simple.

However, in this case, the temperature in the gas generating furnace is a high temperature of 1300 to 1600 ° C. due to the combustion of the fuel, and the problem of damage to the refractory due to melting of the furnace wall or long-term use is likely to occur. .

Further, in the above ammonia producing gas, fuel cell gas, or simulated gas, it is necessary to be able to efficiently produce a gas consisting of a component ratio of hydrogen gas and carbon monoxide gas suitable for each application, Furthermore, in recent years, the demand for carbon monoxide gas as a chemical raw material gas has increased, and a method for efficiently producing a CO-rich gas having a high ratio of the carbon monoxide gas has been demanded.

Therefore, conventionally, as a method of solving these problems, a method of enlarging the furnace body to lower the furnace wall temperature, by adding steam to the fuel to lower the combustion temperature in the furnace, A method of controlling the ingredients has been adopted.

[Problems to be solved by the invention]

However, although the above-mentioned conventional method could solve the problem of melting of the furnace wall and damage of the refractory due to long-term use to some extent, the following drawbacks remain.

It is not suitable for producing CO-rich gas with a high ratio of carbon monoxide, which is a useful component in combustion gas.

That is, the conventional method of adding steam to the fuel is suitable for the production of H ₂ rich gas with a high proportion of hydrogen gas, but as a method of producing CO rich gas, it produces a large amount of carbon as described below. There is a limit, and it may occur that the component ratio cannot be adjusted sufficiently.

 A large amount of carbon is generated.

Normally, carbon is generated in an amount of about several wt% with respect to the fuel, but in the above-mentioned conventional method, since the excessive amount of steam is added to the fuel, the combustion temperature in the furnace can be lowered, but on the other hand, There is a risk that a larger amount of carbon will be generated, and it is very difficult to control the composition adjustment. As a result, the amount of carbon monoxide produced, which is a useful component in the combustion gas, is reduced by the amount of the increased amount of carbon. In addition, carbon has been conventionally removed in a post process for effective use of fuel and environmental measures.
There is also a problem that the burden of the removal process increases as the amount of carbon increases.

The present invention has been made in order to solve the above problems, it is possible to improve the combustion efficiency while lowering the temperature in the furnace and reduce the amount of carbon generation, and increase the CO component in the combustion gas to increase the CO rich gas. It is an object of the present invention to provide a method for adjusting a combustion gas component, which enables easy and reliable production.

[Means for solving problems]

The present invention is a reducing gas generation method for producing a mixed gas containing at least hydrogen and carbon monoxide by incompletely burning a hydrocarbon fuel, in which hydrogen is added by adding carbon dioxide and steam to the fuel. The feature is that the composition ratio of the gas and the carbon monoxide gas is adjusted.

Here, in the method of the present invention, the ratio and amount of steam and carbon dioxide gas to be added to the fuel are the optimum ratio and amount according to the required properties of the product gas and the type and amount of the raw material used. Yes, this must be obtained in advance by experiments or the like. Further, it is advantageous in terms of cost to separate and purify the carbon dioxide gas to be added to the fuel from the combustion gas from the gas generating furnace.

[Action]

In the reducing gas component adjusting method according to the present invention, since carbon dioxide gas and steam are added to the fuel, the carbon generation amount can be suppressed, and the component ratio of carbon monoxide gas in the combustion gas can be increased. it can. That is, in the case of adding only steam as in the conventional method, the amount of carbon generated may increase, but the present invention reduces steam, and since carbon dioxide gas is added by that amount, while lowering the combustion temperature. Combustion efficiency can be improved, and carbon in fuel is more completely converted to CO or CO ₂ as compared with the case where steam is added in excess, which makes it possible to suppress the amount of carbon generated and to reduce the amount of useful components in combustion gas. It was possible to increase the amount of carbon monoxide gas produced and to produce CO-rich gas.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show a combustion gas generator according to an embodiment of the present invention, and this embodiment is an example applied to a simulated gas generator for coal gas using benzene as a raw material.

First, a manufacturing process of the above simulated gas will be described. In FIG. 3, 1 is a gas generation furnace for producing a mixed gas whose main components are hydrogen and carbon monoxide, 20 is an exhaust heat boiler for utilizing the exhaust heat of this mixed gas, and 21 is the above exhaust heat boiler. It is a scrubber that removes water from the mixed gas that has been heat-exchanged and cooled. 22 is a dehumidifying drum, 23 is a dust collector for removing dust,
24 is a compressor for supplying pressure to the above-mentioned mixed gas from which dust has been removed, and then supplying it to the next step, 26 is separating carbon dioxide gas from the pressurized mixed gas, and sending this as a product to the post-treatment step
It is a CO ₂ absorber, which uses amine compounds such as MEA. 27 is a stripper for purifying the separated carbon dioxide gas.

Next, first and second schematic structures of the gas generating furnace 1 will be described.
In the figure, the gas generating furnace 1 is constructed by connecting a gas discharge part 2 and a fuel inflow part 4 to the upper and lower ends of a body part 3 by flanges, respectively.

The gas discharge part 2 is a substantially disc-shaped material lined with an amorphous refractory 2a, and a gas discharge flow path 5 is provided at the center thereof, and the flow path 5 is connected to the exhaust heat boiler 20. Has been done. The body 3 is of a cylindrical shape lined with a heat insulating material 6 such as refractory brick, and a furnace body support 10 placed on a support stand (not shown) is formed on the lower portion of the outer wall of the body 3. . A pilot burner 11 for igniting a combustion burner, which will be described later, is attached to the lower end of the body portion 3. In addition, 8 is a flange for attaching the thermocouple for temperature measurement.

Further, the fuel inflow portion 4 is a substantially annular one lined with an indefinite refractory 4a, and a burner 15 is arranged at the center thereof. This burner 15 has a burner body 15a inserted at the center of a refractory burner tile 14.
5a is composed of an inner pipe 12 for blowing the fuel into the furnace 7 and an outer pipe 13 arranged so as to surround the inner pipe 12 for blowing oxygen as a combustion improver into the furnace 7.

A fuel supply pipe 29 for supplying benzene as a fuel is connected to the inner pipe 12, and the CO 2 is supplied to the supply pipe 29.
The CO ₂ supply pipe 28 from the ₂ stripper is connected. Further, a steam supply pipe 30 is connected in the middle of the CO ₂ supply pipe 28, so that a mixed fuel obtained by adding CO ₂ and steam to the raw material is blown into the furnace 7.

Next, a mixed gas manufacturing process according to this embodiment will be described.

The fuel composed of benzene is blown into the furnace 7 through the inner pipe 12 and, at the same time, is mixed with oxygen as a combustion improver inserted from the outer pipe 13 and a part thereof is burned. Then, the mixed fuel is accelerated in the oxidation reaction by the heat given from the combustion gas to generate a mixed gas whose main components are hydrogen and carbon monoxide.

This reaction is as follows.

CmHn ＋ m / 2O ₂ → mCO ＋ n / 2H ₂ CmHn ＋ mH ₂ O → mCO + (m + n / 2) H ₂ CO + H ₂ O → CO ₂ + H ₂
The gas is discharged from the gas discharge flow path 5, heat is taken by the exhaust heat boiler 20, and water is removed by the scrubber 21. Then, the mixed gas from which the moisture has been removed has the dust removed by the dust collector 23 and is pressurized by the compressor 24, and then the CO ₂ absorber 2
Sent to 6. Carbon dioxide gas is separated from the mixed gas in the CO ₂ absorber 26, and the mixed gas is supplied to the subsequent process as a product.
Then, the separated carbon dioxide gas is separated into CO ₂ stripper 27
, Where it is further purified.

In the present embodiment, the carbon dioxide gas purified by the CO ₂ stripper 27 is passed through the CO ₂ supply pipe 28 and the steam supply pipe 3
It is added to the fuel in the fuel supply pipe 29 together with steam from 0. In the conventional method of adding only steam, an excessive amount of steam was added in order to reduce the combustion temperature, and as a result, the combustion temperature could be lowered, but there was a problem that the amount of carbon generated increased. On the other hand, in the present embodiment, not only steam but also carbon dioxide gas is added to the fuel, so the steam addition amount is reduced by an amount corresponding to the addition amount of carbon dioxide gas. The combustion temperature in the furnace can be lowered without adding excessive steam, and the combustion efficiency can be improved, the carbon in the raw material can be more completely converted into CO ₂ and CO, and as a result, the generation of carbon can be suppressed. it can. Further, according to the reduction of the carbon generation amount, the burden of carbon removal in the post process can be reduced.

Further, in the present embodiment, the amount of carbon monoxide generated was suppressed, the oxidation reaction from the raw material to carbon monoxide was promoted, and the amount of carbon monoxide gas that was a useful component in the combustion gas was increased. And CO rich gas can be produced. Further, in this case, the component ratio of hydrogen gas and carbon monoxide gas in the combustion gas can be easily adjusted by adjusting the addition amount of carbon dioxide gas and the addition ratio of steam.

Furthermore, in the present embodiment, as the carbon dioxide gas for addition, the carbon dioxide gas generated in the present process is separated and purified so that a separate carbon dioxide gas supply device is not required, resulting in an increase in cost. Can be suppressed.

Table 1 shows the composition of the generated gas in the present examples (C to E) and the conventional example (A, B) without carbon dioxide gas injection.

As is clear from the table, in the case of this example in which carbon dioxide gas was added to the fuel, the combustion temperature was higher than that in the conventional method in which steam was excessively added, but no conventional addition was made. Burning case Compared to the temperature (about 1600 ° C), it drops significantly to about 1500 ° C.

Further, in the present example, since carbon dioxide was added, the conventional C Conversion was 95.5 to 97.7%, while 98.2 to 97.7%.
99.1%, the raw material (benzene) is more completely CO and CO
_It has been converted to ₂ , reducing the amount of carbon generated. Furthermore, with the reduction of the carbon generation amount, the generation amount of carbon monoxide increases, and the H ₂ / OC ratio is as small as 0.33 to 0.36 as compared with 0.5 to 0.6 in the conventional method, that is, You can see that it is rich in CO.

〔The invention's effect〕

As described above, according to the reducing gas component adjusting method of the present invention, the carbon dioxide gas and the steam are added to the fuel. Therefore, the amount of carbon generated is as much as there is no need to add excess steam. Is suppressed, and there is an effect that a CO-rich gas having a high carbon monoxide gas component ratio can be produced.

[Brief description of drawings]

1 to 3 are views for explaining a reducing gas generator according to an embodiment of the present invention, FIG. 1 is a sectional side view of a gas generating furnace, and FIG. 2 is II of FIG. -II sectional view,
FIG. 3 is a diagram showing the gas production process of the above embodiment. In the figure, 1 is a gas generating furnace.

Claims (2)

[Claims] 1. A reducing gas generating method for producing a mixed gas containing at least hydrogen and carbon monoxide by incompletely burning a hydrocarbon fuel in a gas generating furnace,
A method for adjusting the component ratio of the hydrogen and carbon monoxide, comprising adding carbon dioxide gas and steam to the fuel and supplying the same into the gas generating furnace. . 2. The reducing gas component adjusting method according to claim 1, wherein the carbon dioxide gas is separated and purified from the mixed gas and recycled.