JPH03290494A - Device for preparing city gas - Google Patents

Abstract

PURPOSE:To provide a low pressure continuous partial combustion city gas- preparing device permitting to elongate the service life of a low temperature reformation catalyst and preventing the lowering of the reformation rate by disposing a desulfurization device on the upstream of a raw material. CONSTITUTION:In a low pressure continuous partial combustion style city gas- preparing device 1 having a low temperature reformation device and operated under a low pressure of <=1kg/cm<2>, a desulfurization device 4 is disposed between a vaporizer 2 and a reformation oven 3 and a high temperature reformation device 5 and a low temperature reformation device 6 are also disposed on the downstream of the reformation oven 3. Since the desulfurization device is disposed on the upstream side of the reformation oven, a desulfurization catalyst is highly simply exchanged with a new catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a low-pressure continuous partial combustion city gas production facility having a low-temperature shift converter.

[Prior art] Low-pressure continuous partial combustion city gas production equipment is widely used at city gas supply stations in Japan, and uses LPG (liquefied petroleum gas) or naphtha as raw materials, and processes steam reforming reactions and partial combustion of the raw materials. By combustion, gases containing components such as hydrogen, carbon oxide, and -carbon oxide are produced.

Furthermore, since carbon monoxide in this component is toxic, its content is reduced in the supply gas.

This reduction in carbon oxides is achieved by spreading carbon monoxide and water into carbon dioxide and hydrogen by means of a CO-modified widening medium. Conventionally, this metamorphosis reaction was carried out at a relatively high temperature (300 to 350°C) using an iron-based catalyst.

However, this method has a low transformation rate, and in order to reduce the concentration of carbon monoxide in the supplied gas more than before, low-temperature transformation using a copper-based catalyst has begun to be carried out.

[Problems to be solved by the invention] However, unlike conventional high-temperature shift catalysts, this low-temperature shift catalyst is extremely sensitive to sulfur (S) and adsorbs sulfur well, so it cannot be activated even with a small amount of sulfur. drop down. Therefore, compared to conventional high-temperature transformation catalysts, the catalyst has a very short lifespan and must be replaced frequently. This requires a lot of effort and may even impede gas production.

Here, the relationship between the sulfur content and the activity of the low-temperature shift catalyst will be explained.

As an example, if the sulfur content in the raw material is 10 ppm, the raw material L
The calorie of PG is 11,800 Kcal/kg, and the calorie of reformed gas (manufacturing gas) is 1,700 Kcal/N.
+n3, the gasification efficiency is 90% (ratio of the total heat value of the produced gas to the total heat value of the raw material), the molecular weight of sulfur is 32, the molecular weight of hydrogen sulfide is 34, and the sulfur content is all converted to hydrogen sulfide in the reforming furnace.

If the raw material is 1 kr/h, the total calorific value of the manufactured gas is I
11800 Xo, 9 = 10620 cal/h.

Production gas amount is 10620/1700=6.25 Nm
The amount of 3/h violet is l xlooooxO,001/100 x34/32=
0.01 g/h Therefore, the hydrogen sulfide content per 113 Nl of produced gas is 0.01/6.25 = 0.002 g
/Nl113.

In low-temperature metamorphism reactions, a metamorphism rate of 80% or more is usually required (less than this is not very meaningful). Also, according to actual results, this transformation rate is achieved when 0.44% of hydrogen sulfide is adsorbed on the catalyst. Therefore, the time required to reach this amount of adsorption is calculated assuming that all of the adsorption is achieved.

The filling amount of the shift catalyst is 2100 kg, and the amount of produced gas is 3300 Nm3/h. These are 1, values for a very common device.

2100x0.44/loo =9.24kg9.24
x1000/ (3300x0.002 > =140
Assuming 0 hours and 15 hours of operation per day, 1400/15 = 9
Therefore, the low-temperature shift catalyst must be replaced every 93 days. Although the shift catalyst itself has sufficient activity for two to three years, it must be replaced within such a short period of time.

In order to prevent this, it may be possible to place a desulfurization catalyst upstream of the low-temperature shift catalyst (that is, on the upstream fence in the shift converter) to desulfurize the produced gas before shift conversion.

However, this method has fundamental drawbacks. That is, it takes a lot of effort to replace the desulfurization catalyst. In order to replace the catalyst in the shift converter, the shift converter must be shut down and cooled down. Furthermore, after replacement, the temperature must be raised to operate the transformer. For this reason, it takes a very long time to replace the desulfurization catalyst. It is also conceivable to install two desulfurizers in the system and operate them in a switching manner, but in this case, there are problems with temperature rise during switching, equipment costs, etc.

Therefore, in this industry, there has been a long-awaited facility for producing city gas that does not have the above-mentioned drawbacks.

[Means for Solving the Problems] In view of the above-mentioned current situation, the present inventor has completed the present invention equipment as a result of intensive research. In a partial combustion city gas production facility, a desulfurization device is installed in the upstream line of the raw material reforming furnace.

Here, low-pressure continuous partial combustion city gas production equipment is defined as 1.
Among those that produce city gas at less than kg/dG, the heat required for the reforming reaction (endothermic reaction) is provided by burning part of the raw material, and the reforming reaction and combustion reaction are performed simultaneously in the same furnace. It is characterized by what happens within.

Raw materials are those that undergo a reforming reaction, and are mainly LPG (
Hydrocarbons such as liquefied petroleum gas and naphtha.

A reforming furnace is a reactor that decomposes raw materials with steam, and if the raw materials contain sulfur, they become hydrogen sulfide.

The upstream line of the reformer may be any line up to the inlet of the reformer. That is, it may be located between the raw material tank and the reforming furnace. If it has a raw material paper riser, it may be upstream or downstream of it. Therefore, desulfurization can be carried out in a liquid state or in a gaseous state.

The desulfurization device is a container filled with a desulfurization catalyst, through which the sulfur in the raw material is adsorbed and removed. Desulfurization catalyst is Jll! in liquid state. Whether it is in the form of sulfur or in the gaseous state, ordinary ones may be used, and there is no need to use any special ones.

In short, conventionally, the sulfur content in the raw material was low (1
0 to 80 ppm), which was not a problem because high-temperature shift catalysts are relatively resistant to sulfur, but the use of low-temperature shift converters has been considered to eliminate sulfur poisoning, which has been a focus of close attention. It is for the purpose of Desulfurization before the reforming furnace eliminates various drawbacks, and except for this point, ordinary city gas production equipment can be used.

Usually, most of the sulfur is removed after passing through a desulfurization catalyst (a certain amount), so for the process after the desulfurizer,
The effect of sulfur can be ignored. Therefore, in the present invention, there is no effect of sulfur on the shift catalyst, which is the drawback mentioned above.

[Example] FIG. 1 is a schematic flow sheet showing an example of the equipment 1 of the present invention. A desulfurizer 4 is provided in the raw material line between the vaporizer 2 and the reforming furnace 3. A high temperature shift converter 5 and a low temperature shift converter 6 are provided downstream of the reforming furnace 3. Other than this, it is exactly the same as normal low-pressure continuous partial combustion manufacturing equipment.

[Effects of the Invention] Since the present invention is configured as described above, it has the following advantages.

■ Since a desulfurizer is installed, the life of the low-temperature shift catalyst is extended and the decline in shift conversion rate can be reduced.

■ The life of the reforming catalyst and high-temperature shift converter catalyst will also be longer than before.

■ Since the desulfurizer is installed upstream of the reforming furnace, it is very easy to replace the desulfurization catalyst.

[Brief explanation of drawings]

FIG. 1 is a schematic flow sheet showing an example of the city gas production equipment of the present invention. 1...Town gas production equipment of the present invention 2...Paper riser 3...Reforming furnace 4...Desulfurizer 5...High temperature shift converter 6...Low temperature shift converter

Claims (1)

[Claims] 1. A low-pressure continuous partial combustion city gas production facility equipped with a low-temperature shift converter, characterized in that a desulfurization device is installed in the upstream line of a raw material reforming furnace.