JPH03277695A - Purification of fuel gas - Google Patents

Abstract

PURPOSE:To purify a fuel gas containing CO, H, dienes, olefins and O- and S-compounds without causing carbonaceous deposition by subjecting the fuel gas to hydrogenation and CO conversion, followed by heat recovery and removal of both steam and S-compounds. CONSTITUTION:Steam is added to a fuel gas containing CO, H, dienes, olefins and O- and S-compounds. The mixture is preheated at 100-250 deg.C by heat recovered from steam and/or a process gas, and hydrogenation is carried out for hydrogenating the dienes, olefins and O-compounds. Then, CO conversion is carried out by converting the CO in the hydrogenated fuel gas into CO2 and H. After recovery of heat of the fuel gas thus treated, the gas is further cooled to removed steam. Then, removal of the S-compounds gives a purified fuel gas.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for purifying fuel gas such as coke oven gas in which carbon monoxide, hydrogen, dienes, olefins, oxygen, sulfur compounds, etc. coexist.

Prior Art> In order to react carbon monoxide and water vapor to produce carbon dioxide and hydrogen, an iron-chromium catalyst is used to react with 250 to 4
There is high-temperature modification in which modification occurs at 00° C. When modifying a raw material gas containing a large amount of sulfur compounds, a sulfurized cobalt-molybdenum catalyst may be used.

If there is no sulfur compound, use a copper-zinc catalyst to
There is a method of low-temperature metamorphosis at 0 to 250°C.

These techniques are used to reduce carbon monoxide in fuel gas and synthesis gas.

However, it has been found that when these conventional techniques are applied to gas such as coke oven gas in which dienes, olefins, oxygen, and sulfur compounds coexist, the following disadvantages occur.

<Problem to be solved by the invention> When water vapor was added to coke oven gas in which dienes, olefins, oxygen, and sulfur compounds coexisted, a carbon monoxide conversion reaction test was conducted, and it was found that the activity of the catalyst significantly deteriorated. (It was found that stable performance could not be maintained.

This is thought to be due to the fact that when coke oven gas is preheated to a temperature at which the carbon monoxide shift catalyst can be used, carbonaceous substances are generated, perhaps due to polymerization and decomposition reactions of the contained components, and adhere to the catalyst, causing activity deterioration. .

This problem may be solved by lowering the preheating temperature, but low-temperature shift catalysts lose their activity due to sulfur compounds, so they can only be used for gas after desulfurization and purification.

The present invention provides a fuel gas that can remove carbon monoxide and sulfur compounds without causing troubles due to carbonaceous precipitation when refining fuel gas containing carbon monoxide, hydrogen, dienes, olefins, oxygen, and sulfur compounds. The purpose is to provide a purification method for

Means for Solving the Problem> A fuel gas having the composition shown in Table 1 is passed through a reaction tube filled with balls made of alumina or calcium silicate, and a
After operating for 200 hours with a temperature distribution of 300°C, the fuel gas was stopped, nitrogen gas was flowed, and the tank was cooled and opened to observe the adhesion of carbon to the packed bed. Discoloration was observed from around 200°C. At around 250° C., it was black, and it was clear that carbonaceous substances were attached.

We believe that the cause of carbonaceous precipitation is polymerization and decomposition caused by the coexistence of dienes and olefins with oxygen, so we hydrogenate dienes, olefins, and oxygen at as low a temperature as possible to convert them into saturated hydrocarbons and water. We investigated a method that enables preheating to the carbon monoxide metamorphosis reaction temperature by making it thermally stable.

However, when hydrogenating a gas with the composition shown in Table 1, the temperature rises by 120°C due to the heat of reaction, so the temperature after hydrogenation is reduced to 20°C.
In order to keep it below 0°C, the inlet temperature must be kept below 80°C.

When hydrogenating a gas having the composition shown in Table 1 at 80° C. using a Pd catalyst, it was found that the reaction was inhibited, probably due to strong adsorption of carbon monoxide or sulfur compounds.
It has also been found that the reaction proceeds smoothly when the temperature is 100°C or higher, preferably 120 to 200°C.

Fortunately, it has been found that in the case of a Pd catalyst, carbonaceous substances do not precipitate even at temperatures of 200° C. or higher within the catalyst layer.

Furthermore, even if water vapor is added, dienes, olefins,
It has also been found that hydrogenation of oxygen can be carried out.

By utilizing these facts, it is possible to raise the temperature by reaction and heat recovery to the temperature required for the metamorphosis reaction of carbon monoxide without carbonaceous precipitation.

That is, in order to achieve the above object, according to the first aspect of the present invention, the carbon monoxide in the fuel gas containing carbon monoxide, hydrogen, dienes, olefins, oxygen and sulfur compounds is removed by adding water vapor. In the method of purifying fuel gas by desulfurizing and removing the sulfur compounds by a carbon monoxide conversion reaction, water vapor is added to the fuel gas, heat from the water vapor and/or process gas is recovered, and the fuel gas is purified by removing the sulfur compounds by desulfurization. gas from 100
After preheating to 250°C, there is a hydrogenation step in which dienes, olefins, and oxygen remaining in the fuel gas are hydrogenated, and carbon monoxide remaining in the fuel gas from the hydrogenation step is converted into carbon dioxide and hydrogen. a low-temperature carbon monoxide transformation step for converting; a step of recovering the heat of the fuel gas from the low-temperature carbon monoxide transformation step and further cooling it to remove water vapor from the fuel gas; Provided is a method for purifying fuel gas, the method comprising the step of removing sulfur compounds.

Further, according to the second aspect of the present invention, the carbon monoxide in the fuel gas containing carbon monoxide, hydrogen, dienes, olefins, oxygen, and sulfur compounds is subjected to a carbon monoxide modification reaction by adding steam. In the method of purifying fuel gas by desulfurizing and removing the sulfur compounds, the fuel gas is preheated to 100 to 250°C using steam and/or heat recovered from the process gas, and then the remaining sulfur compounds remain in the fuel gas. a hydrogenation process for hydrogenating dienes, olefins, and oxygen; steam is added to the fuel gas from the hydrogenation process, and the fuel gas is heated to 250 to 350
a carbon monoxide conversion process that converts carbon monoxide remaining in the fuel gas into carbon dioxide and hydrogen after preheating to ℃;
Recovering the heat of the fuel gas from the carbon monoxide transformation step,
There is provided a method for purifying fuel gas, which comprises the steps of: further cooling to remove water vapor from the fuel gas; and removing sulfur compounds remaining in the fuel gas from which the water vapor has been removed.

The hydrogenation step is preferably carried out using a Pd catalyst in an adiabatic reactor.

The present invention will be explained in more detail below.

FIG. 1 is a reaction system diagram showing an example of the first aspect of the present invention. In the first embodiment, the fuel gas l to be treated is hydrogenated reactor 2 → carbon monoxide shift reactor 3 → desulfurization reactor 11
are processed in this order.

The fuel gas to be treated may be any gas containing carbon monoxide, hydrogen, dienes, olefins, oxygen, and sulfur compounds (for example, coke oven gas is a typical example). .

After water vapor 6 is first added and mixed to the fuel gas 1 to be treated, the fuel gas 1 is preheated to 100 to 250°C, preferably 120 to 200°C, in a raw material preheater 5. This preheating is performed using steam at the start-up raw material preheater 1 only at the start of operation.
3, but during normal operation, it can be performed using only the heat recovered from the process gas, which will be described later. Therefore, compared to preheating with combustion gas in a heating furnace, there is no local exposure to high temperatures, so there is less risk of decomposition and polymerization, and the carbon on the low-temperature hydrogenation catalyst layer of the low-temperature hydrogenation reactor 2 is not exposed to high temperatures locally. Precipitation can be prevented.

Next, this gas is led to the low temperature hydrogenation reactor 2, and dienes,
Olefins and oxygen are hydrogenated and the gas heated to 200 to 300° C. is used in a carbon monoxide conversion reactor 3 to convert carbon monoxide into carbon dioxide and hydrogen. A portion of the sulfur compounds are converted to hydrogen sulfide by hydrolysis or hydrogenation over a carbon monoxide conversion catalyst.

Hydrogenation reactor 2 was filled with Pd catalyst and heated to 100 to 250°C.
, preferably at 120 to 200°C to hydrogenate dienes, olefins, and oxygen by reacting the preheated gas to 200°C.
Even if the temperature exceeds ~250°C, no carbon deposition occurs on the catalyst.

The gas after the transformation exchanges heat with the fuel gas l to be treated in the raw material preheater 5, is cooled in the cooler 7, and after separating and removing condensed water 9 in the gas-liquid separator 8, sulfur is removed in the desulfurization reactor 11. Compounds are removed to obtain purified gas lO. The desulfurization reactor 11 is not particularly limited, and a dry type or a wet type can be used.
For example, it may be filled with an iron oxide desulfurization agent.

As described above, the content of carbon monoxide and sulfur compounds in fuel gas such as coke oven gas in which dienes, olefins, and oxygen coexist can be reduced, and gas purification can be performed without carbonaceous precipitation on the catalyst.

Next, a second aspect of the present invention will be explained.

FIG. 2 is a reaction system diagram showing one example. The fuel gas 1 to be treated is treated in the following order: hydrogenation reactor 2 → carbon monoxide shift reactor 4 → desulfurization reactor 1.

Note that explanations similar to those in the first aspect will be omitted.

The fuel gas l to be treated is first heated in the raw material preheater 5 to
It is preheated to 250°C, preferably 12o-200°C.

This preheating is performed in the raw material preheater 13 using steam only at the start of operation, but during normal operation it can be performed only using the heat recovered from the process gas.

Next, this gas is led to the hydrogenation reactor 2, where dienes, olefins, and oxygen are hydrogenated, and steam 6 is added to the gas that has reached 200 to 300°C, and the heat exchanger 12 converts the gas into a process gas, which will be described later. The temperature is raised to 250 to 350° C. by heat exchange, and carbon monoxide is converted into carbon dioxide and hydrogen in a carbon monoxide shift reactor 4.

A portion of the sulfur compounds are converted to hydrogen sulfide by hydrolysis or hydrogenation over a carbon monoxide conversion catalyst.

The gas after the shift exchanges heat with the gas output from the hydrogenation reactor 2 in the heat exchanger 12, further exchanges heat with the fuel gas l to be treated in the raw material preheater 5, is cooled in the cooler 7, and then passes through the gas-liquid separator. After condensed water 9 is separated and removed in step 8, sulfur compounds are removed in a desulfurization reactor 11 to obtain purified gas lO. The desulfurization reactor 11 is not particularly limited, and a dry type or wet type can be used, and for example, one filled with an iron oxide desulfurization agent may be used.

As described above, the content of carbon monoxide and sulfur compounds in fuel gas such as coke oven gas in which dienes, olefins, and oxygen coexist can be reduced, and gas purification can be performed without carbonaceous precipitation on the catalyst.

<Example> The present invention will be specifically explained below based on Examples.

(Example) A fuel gas of 300 Nm"/Hr having the gas composition shown in Table 1 and water vapor 6 (70 kg/Hr l l O ℃) were
According to the diagram, preheat the raw material to 150°C in the raw material preheater 5, and
-Al2O and the catalyst were fed into a hydrogenation reactor 2 filled with 30OL. Hydrogenation of dienes, olefins, and oxygen proceeded, and the temperature of the outlet gas reached 240°C.

Next, a low temperature carbon monoxide shift catalyst (Fe-Cr type) 60
When the gas was fed into the low-temperature carbon monoxide shift reactor 3 filled with 0 L, the shift reaction proceeded and the temperature of the outlet gas reached 310°C.

This gas is heat recovered and cooled by a raw material preheater 5 and a cooler 7,
The condensed water 9 is removed by the gas-liquid separator 8, and the iron oxide desulfurization agent 2 is removed.
Hydrogen sulfide was removed in a desulfurization reactor 11 filled with m' to obtain purified gas 10 having the composition shown in Table 2.

(Example 2) Fuel gas with the gas composition shown in Table 1 300 Nm”/llr
was preheated to 150° C. in a raw material preheater 5 according to FIG. 2, and fed into a hydrogenation reactor 2 filled with 30 OL of Pd-Aρ20□ catalyst. Hydrogenation of dienes, olefins, and oxygen proceeded, and the temperature of the outlet gas reached 270°C. Steam 6 is added to this gas (70 kg/Hr 110°C), preheated to 280°C in a heat exchanger 12, and sent to a carbon monoxide shift reactor 4 filled with 600 L of carbon monoxide shift catalyst (Fe-Cr type). When the gas enters, the metamorphosis reaction proceeds and the exit gas becomes 3
The temperature reached 50℃.

This gas is heat recovered and cooled, condensed water 9 is removed by a gas-liquid separator 8, and a desulfurization reactor 1 is filled with 2 m'' of iron oxide desulfurization agent.
1 to obtain purified gas lO having the composition shown in Table 2.

Table 1 Fuel gas composition table Purified gas composition <Effects of the invention> Since the present invention is configured as described above, according to the present invention, carbon monoxide, hydrogen, dienes, olefins, oxygen and sulfur compounds When refining fuel gas containing carbon monoxide and sulfur compounds, purified gas can be obtained by removing carbon monoxide and sulfur compounds without causing trouble due to precipitation of return substances.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are reaction diagrams showing one example of the first and second aspects of the present invention, respectively. Explanation of symbols 1... Fuel gas, 2... Low temperature hydrogenation reactor, 3... Low temperature carbon monoxide shift reactor, 4... Carbon monoxide shift reactor, 5... Raw material preheater , 6... Steam, 7... Cooler, 8... Gas-liquid separator, 9... Condensed water, 10... Purified gas, 11... Desulfurization reactor, 12... Heat Exchanger, 13...Start-up raw material preheater FIG, 1 FIG, 2

Claims (3)

[Claims] (1) The carbon monoxide in the fuel gas containing carbon monoxide, hydrogen, dienes, olefins, oxygen, and sulfur compounds is removed by a carbon monoxide conversion reaction by adding steam, and the sulfur compounds are desulfurized and removed. A method for purifying fuel gas by adding steam to the fuel gas and recovering heat from the steam and/or process gas to refine the fuel gas to
After preheating to 250°C, a hydrogenation step of hydrogenating dienes, olefins, and oxygen remaining in the fuel gas, and converting carbon monoxide remaining in the fuel gas from the hydrogenation step into carbon dioxide and hydrogen. converting a carbon monoxide transformation process, recovering the heat of the fuel gas from the carbon monoxide transformation process,
A method for purifying fuel gas, comprising the steps of: further cooling to remove water vapor from the fuel gas; and removing sulfur compounds remaining in the fuel gas from which the water vapor has been removed. (2) The carbon monoxide in the fuel gas containing carbon monoxide, hydrogen, dienes, olefins, oxygen, and sulfur compounds is removed by a carbon monoxide conversion reaction by adding steam, and the sulfur compounds are desulfurized and removed. In this method, the fuel gas is preheated to 100 to 250°C using heat recovered from steam and/or process gas, and then dienes, olefins, and oxygen remaining in the fuel gas are replaced with hydrogen. A hydrogenation step in which water vapor is added to the fuel gas from the hydrogenation step, and the fuel gas is converted into 2 with the heat recovered from the process gas.
A carbon monoxide conversion step in which carbon monoxide remaining in the fuel gas is converted into carbon dioxide and hydrogen after preheating to 50 to 350°C; heat of the fuel gas from the carbon monoxide conversion step is recovered;
A method for purifying fuel gas, comprising the steps of: further cooling to remove water vapor from the fuel gas; and removing sulfur compounds remaining in the fuel gas from which the water vapor has been removed. (3) The fuel gas purification method according to claim 1 or 2, wherein the hydrogenation step uses an adiabatic reactor filled with a Pd catalyst.