JPH0672001B2 - Hydrogen rich gas manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for producing a hydrogen rich gas by combining a high temperature steam reforming step and a CO shift reaction step.

LP is one of the processes for producing hydrogen-rich gas.
A method is known in which hydrocarbons such as G and naphtha are steam reformed in an external heat type high temperature reactor, and the obtained reformed gas is treated in a CO shift reactor. In this method, the ratio of the feed hydrocarbons and steam supplied to the external heat type high temperature reactor, that is, the high temperature steam reforming reactor, is specifically defined as "moles of supplied steam / number of carbon atoms of supplied hydrocarbons". By reducing the generated steam ratio, it is possible to reduce the heat load on the high temperature steam reforming reactor, and thus to improve the efficiency of the entire hydrogen-rich gas production process.
However, when the above steam ratio is reduced, the amount of steam that remains in the reformed gas inevitably decreases, so the amount of hydrogen in the hydrogen-rich gas obtained by treating the reformed gas with the CO shift reactor is There is a disadvantage that the steam ratio is considerably reduced as compared with the case where the steam ratio is not reduced.

The heat load on the high temperature steam reforming reactor can be reduced by raising the preheating temperature of the feedstock hydrocarbons supplied to the reactor and raising the inlet temperature of the reactor.
However, since the direct preheating of the feedstock hydrocarbon to raise its temperature results in promoting olefin formation and carbon precipitation in the high temperature steam reforming reactor, the conventional technique is the upstream of the high temperature steam reforming reactor. It is proposed that a low temperature steam reforming reactor be installed on the side to reform the raw material hydrocarbons into methane gas in advance. According to this method, the feedstock hydrocarbons are reformed in the low-temperature steam reforming reactor into CH ₄ , H ₂ , CO, and CO ₂ methane rich gas, so this is supplied to the high-temperature steam reforming reactor. In this case, the inlet temperature of the high temperature steam reforming reactor can be raised by preheating to a considerably high temperature without fear of olefin formation or carbon deposition.

The present invention lowers the steam ratio in the reactor by increasing the inlet temperature of the high temperature steam reforming reactor, which is different from the concept of the prior art of reducing the heat load of the reactor. In order to reduce the heat load and reduce the steam yield by reducing the steam ratio, steam or water was added to the reformed gas from the high temperature steam reforming reactor.
We propose a new method for producing hydrogen-rich gas, which is prevented by using CO shift reaction.

That is, in the method of the present invention, the feedstock hydrocarbon is supplied to the high temperature steam reforming reaction zone to generate a reformed gas, and this reformed gas is supplied to the CO shift reaction zone to increase the hydrogen concentration in the gas. In the method for producing hydrogen-rich gas, the steam reforming reaction is allowed to proceed at a steam ratio of less than 3.0 (steam ratio = mol of supplied steam / number of carbon atoms of supplied hydrocarbon),
It is characterized in that steam or water is added to the reformed gas obtained by this reaction and is supplied to the CO shift reaction zone.

Hereinafter, the method of the present invention will be described in more detail with reference to the accompanying drawings. Raw material hydrocarbons such as LPG and naphtha flowing in the line 1 are, if necessary, subjected to hydrodesulfurization treatment and then, together with steam flowing in the line 2. , High temperature steam reforming reactor 3
Is supplied to. This steam reforming reactor 3 has a temperature of 750 to 850.
℃, pressure 10 ~ 30kg / cm ² G is maintained, space velocity 20
The mixture of feed hydrocarbon and steam passing at 00-6000 Hr ^-1 , steam ratio <3.0 is steam reformed by contacting the reforming catalyst. As the reforming catalyst in this case,
Due to the fact that the reaction conditions are maintained at a high temperature and low steam ratio, troubles such as carbon precipitation occur with ordinary catalysts, so a special catalyst or ruthenium-based catalyst with an additive that suppresses carbon precipitation is generally used. It is customary to do so. However, a low-temperature steam reforming reactor (not shown) is installed on the upstream side of the high-temperature steam reforming reactor 3 and 1.0
Nickel-based catalysts can be used in high temperature steam reforming reactors by reforming to methane rich gas with a steam ratio of ~ 2.0. In a mode in which a low-temperature steam reforming reactor is attached, some steam is supplied to the methane gas from the reactor and the steam is supplied to the high-temperature steam reforming reactor. The ratio of the amount of the raw material hydrocarbons supplied to the reactor and the total amount of the steam supplied to both the low temperature reactor and the high temperature reactor, that is, the total steam ratio is maintained at less than 3.0 in the present invention.

In any case, in the method of the present invention, since the high temperature steam reforming reaction is carried out under the condition of the steam ratio <3.0, the reformed gas taken out from the high temperature steam reforming reactor 3 to the line 4 is not reacted. The remaining amount of steam is small, and even if this reformed gas is supplied to the CO shift reactor as it is, the desired reaction cannot be advantageously progressed. CO shift reaction: CO + H ₂ O
In terms of equilibrium, CO ₂ + H ₂ is more advantageous for H ₂ generation as the amount of H ₂ O in the raw material system is larger. Therefore, in the present invention, steam or water is added to the reformed gas in the line 4 and supplied to the CO shift reactor 5. The amount of steam or water to be replenished here can be arbitrarily selected within a range in which the H ₂ O / CO molar ratio of the reformed gas supplied to the CO shift reactor can be maintained at 1 or more. The amount is preferably such that the ratio is maintained at 2-7. The CO shift reaction of the present invention is conducted in the usual manner using an adiabatic reactor filled with a high temperature CO shift catalyst such as iron and chromium,
300-350 ℃, Pressure 10-30kg / cm ² G, Space Velocity 2000-6000
It can be carried out under the conditions of Hr ^-1 and also under the condition of temperature of 200 to 250 ° C. by using an external cooling type reactor filled with a catalyst such as a low temperature active copper or zinc catalyst. Considering that the CO shift reaction is an exothermic reaction, it is equilibrium advantageous to employ an external cooling type reactor.

From the CO shift reactor 5, hydrogen-rich gas, which is the target product of the present invention, is taken out in a line 6. This hydrogen-rich gas can be subjected to carbon dioxide removal treatment if necessary,
For this, any of MEA treatment, hot potassium carbonate treatment, and PAS treatment can be adopted. However, the hydrogen-rich gas obtained by the method of the present invention has a relatively large amount of residual methane and also has a small amount of steam, so the amount of heat retained by the high-temperature reforming reactor outlet gas is small, and therefore, such as MEA and hot potassium carbonate, regeneration It is preferable to use the PAS treatment rather than the carbon dioxide removing method that requires a large amount of heat.

Although the method of the present invention has been described above, according to this method, the high temperature steam reforming reaction of the raw material hydrocarbons is carried out under the condition of the steam ratio <3.0, so that it is necessary for the high temperature steam reforming reactor. it is possible to reduce the thermal load, reduction of H ₂ yield in CO shift reaction due to adopt a low steam ratio, the reformed gas from the high-temperature steam reforming reactor, to supply the steam or water This can prevent this. Moreover, the steam and the like added to the reformed gas can be covered by the steam produced as a by-product in the heating furnace for the high temperature steam reforming reactor. Therefore, according to the present invention,
Compared with the conventional method, the heat load required to produce a unit amount of hydrogen can be significantly reduced.

Next, the effects of the present invention will be specifically described by showing Comparative Examples and Examples.

Comparative Example 1 The operating conditions of a high temperature steam reforming reactor (refformer) filled with a ruthenium-based catalyst were set to a pressure of 15 kg / cm ² G and an inlet temperature of 45.
The outlet temperature is 0 ° C, the outlet temperature is 830 ° C, the steam ratio is changed to supply the raw material butane and steam to generate the reformed gas, and the reformed gas is then heated to the inlet temperature of 350 ° C filled with the iron-chromium-based catalyst. The hydrogen-rich gas was supplied to the adiabatic CO shift reactor. The results are shown in Table 1.

Example 1 The same experiment as in Comparative Example 1 was performed except that H ₂ O was additionally supplied to the reformed gas from the refformer, and the results shown in Table 2 were obtained. The values in parentheses in column 8 of Table 2 are
It is a relative value when the heat load of 18.71 MCAL / KMOL in column 7 of the table is 100.

Comparative Example 2 Instead of the adiabatic CO shift reactor having an inlet temperature of 350 ° C., a temperature of 2
Comparative Example 1 except using an isothermal CO shift reactor at 50 ° C
The same experiment was performed and the results shown in Table 3 were obtained. Third
The numerical values in parentheses in column 7 of the table have the same meaning as the numerical values in parentheses in column 8 of table 2.

Example 2 The same experiment as in Comparative Example 2 was carried out except that H ₂ O was additionally supplied to the reformed gas from the reformer, and the results shown in Table 4 were obtained. In Table 4, column 8 (), Table 2 is column 8 ()
Is synonymous with

[Brief description of drawings]

 The drawing shows an example of a flow sheet of the method of the present invention. 1; feedstock hydrocarbon feed line 2; steam feed line 3; high temperature steam reforming reactor 4; reformed gas line 5; CO shift reactor 6; hydrogen-rich gas line

Claims (1)

[Claims] 1. A method for producing a hydrogen-rich gas in which a raw material hydrocarbon is supplied to a high temperature steam reforming zone to generate a reformed gas, and the reformed gas is supplied to a CO shift reaction zone to increase the hydrogen concentration in the gas. In the method, the steam reforming reaction is allowed to proceed at a steam ratio of less than 3.0 (which means the number of moles of steam per carbon atom of the raw material hydrocarbon), and steam or water is added to the obtained reformed gas. Is supplied to the CO shift reaction zone.