JPS606986B2 - City gas production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for producing city gas using a cyclic gasification plant that reforms light hydrocarbons with steam and converts the resulting reformed gas into CO.

CO conversion catalysts include expensive catalysts that exhibit high activity even at low temperatures (e.g., COMOX catalysts) and inexpensive catalysts that have low activity at low temperatures but exhibit sufficient high activity at high temperatures of 30,000 or higher (e.g., Fe-based catalysts). ).

Therefore, when converting gas of about 290q○ or less to CO, first perform CO conversion using the former (hereinafter represented by a COMOX catalyst), and then use the generated reaction heat to elevate the latter (hereinafter represented by a Fe-based catalyst). Warm up,
Continuing CO conversion in a highly active state is advantageous from both economical and thermal efficiency standpoints. However, COMOX-based catalysts require presulfidation, whereas Fe-based catalysts are inhibited in their activity by encapsulation by sulfur, so one CO
It was impossible to use both in a metamorphosis device. Therefore, in the past, the entire amount of expensive C was used as a catalyst.
using an OMOX-based catalyst.' }Total amount of Fe as catalyst
The first stage, which is filled with NCOMOX type catalyst, performs Cq transformation of gas heated to about 300q0 or more using NCOMOX type catalyst.
Methods such as configuring a CO converter with a column and a second column filled with an Fe-based catalyst have been used, but none of these methods are economically satisfactory in terms of catalyst costs, heating costs, construction costs, etc. hard. Therefore, as a result of various studies, the inventor of the present invention discovered that COM
An OX catalyst and a Fe catalyst are separated and filled in a single CO conversion device, and the latter is kept under pressure to protect it from being poisoned by a sulfiding agent such as Ni2S during pre-sulfurization of the former. It has been found that the problems of the prior art can be overcome by this method. The present invention was completed based on such knowledge. The present invention will be described in detail below with reference to embodiments shown in the drawings.

In the cyclic gasification plant shown in Figure 1,
During steady operation, gas or liquid fuel from the line 3 is first mixed with oxygen-containing gas such as air from the line 5 and combusted, and then this combustion exhaust gas heats the checker bricks in the heating chamber 7, Furthermore, from line 9 to reforming reactor 1
1 and heats the internal reforming catalyst to the temperature required for the reforming reaction, line 15, scarlet heat recovery boiler I7,
It is discharged into the atmosphere via line 19 and stack 31.

Next, the supply of fuel from line 3 and air or other oxygen-containing gas from line 5 is stopped, and water or steam from line 5 is supplied to preheater 7 to be heated to near the reforming reaction temperature. is further fed to the reforming reactor 11 from line 9. Vertical hydrocarbons such as naphtha, LPG, and natural gas are supplied to the reforming reactor 1 1 from a line 13.
Steam reforming is carried out in the presence of a known reforming reaction catalyst such as a Ni○-Mg○ type catalyst. The reforming reaction conditions are usually a pressure of 100
0 to 200 m water column, liquid space velocity 0.8 to 1.22 above/
/hr, and the outlet temperature is about 650 to 900oC. Although the composition ratio of the generated reformed gas differs depending on the type of raw material vertical hydrocarbon, the main components are CH4, CO2, CO, etc., and the CO content is usually about 12 to 20%. When the temperature of the subheater 7 and the reforming reaction device 11 decreases by continuing the reforming reaction, heating with the combustion exhaust gas is repeated in the same manner as described above. By providing a plurality of sets of the subheater 7 and the reforming reaction device 11, the heating process and the gas production process can be appropriately switched to continuously produce the gas. The waste purchased gas from the reforming reactor 11 enters the scarlet heat recovery boiler 17 via line 15, and after being lowered in temperature, it passes through line 19 and is converted to C along with steam from line 21.
Enter the O transformation device 23. Output gas from the CO converter 23 whose CO content is below a predetermined value (usually about 8% or below) passes through a line 25 and enters the scarlet heat recovery boiler 27.
After the heat is recovered, it is taken out of the system through line 29.
FIG. 2 schematically shows a graph showing the arrangement of the COMOX catalyst and the Fe catalyst in the CO shift converter 23 and the catalyst temperature in each layer.

The first half 23a of the CO shift device is filled with a COMOX-based catalyst that has high activity even at low temperatures, and the second half 23b, which is separated from the unfilled middle section 35, is filled with a Fe-based catalyst that has good activity at high temperatures. Filled with catalyst.

Therefore, when the waste gas is converted into CO in the first half 23a, it generates reaction heat, which is then used to feed Fe in the second half 23b.
The system catalyst is heated to exhibit sufficient activity.
In this case, the temperature distribution of the catalyst layer in the CO shift converter 23 is as follows:
This is shown as line A at the bottom of FIG. Therefore, even if the gas temperature from the reforming reactor 11 is relatively low, about 180 to 290q○, the single CQ shift converter 2
3, CO metamorphosis can be carried out to a sufficiently satisfactory degree. C
Pre-sulfurization of the OMOX catalyst can be carried out by feeding the ratio S etc. supplied from the line 37 into the front half 23a through the dispersion mechanism 39 and circulating it if necessary. In order to prevent this, pressure-holding gas is supplied from the line 41 to the rear half 23b.

As the pressure-holding gas, it is possible to use combustion exhaust gas that does not harm the Fe-based catalyst, such as combustion exhaust gas that does not substantially contain nitrogen, nitrogen, or oxygen. The ratio of the COMOX catalyst to the Fe catalyst may vary depending on the amount, temperature and composition of the reformed gas, the degree of CO transformation, the outside air temperature, etc., but is usually 1:
The ratio is within the range of about 2 to 1:3.

According to the method of the present invention, the following remarkable effects are achieved.

{i} Compared to the case where a full COMOX catalyst is used as the CO shift catalyst, the cost of the catalyst can be significantly reduced.

For example, when a COMOX catalyst and a Fe catalyst are used together, the price difference between the two can be reduced by about 3 to 3.5 million yen/t. 'o- Compared to the case where a full Fe-based catalyst is used as the CQ shift catalyst, the inlet temperature of the reformed gas to the CO shift converter can be lowered by about 70 to 10,000 times, so the heat loss is greatly reduced. do.

Furthermore, since the outlet temperature can be lowered, it is also possible to reduce costs by relaxing design standards for the shift converter. Compared to the case of using a CO shift apparatus consisting of a first column filled with a COMOX catalyst and a second column filled with an Fe catalyst, the construction cost is significantly reduced.

Furthermore, no heat or quantity loss occurs in the piping between the first column and the second column. Example 1 A tube with an inner diameter of 25 squares was filled with 50 cm of COMOX catalyst and 150 cm of Fe-based catalyst, and the inlet temperature was 2.
5000, day 20/CO=3.5 (molar ratio), SV Ko8
When a CO-containing gas is supplied into the pipe and subjected to CQ transformation under the conditions of 00/d/hr, the results shown in Table 1 are obtained.

Note that the outlet temperature after CO modification is 380 to 40,000. Table 1 Note that when only Fe-based catalyst is used as a catalyst, the first
As shown in the table, almost the same metamorphism rates were obtained.

[Brief explanation of drawings]

FIG. 1 is a flowchart for explaining one embodiment of the present invention, and FIG. 2 schematically shows the arrangement of two types of catalysts in the CO shift converter and the catalyst temperatures in various calendars. This is a drawing shown. 1...Water or steam supply line, 3...
・Fuel supply line, 5...Oxygen-containing gas supply line such as air, 7...Preheater, 11...Durable reactor, 13...Light hydrocarbon supply line, 1
7...Scarlet heat recovery boiler, 21...Steam supply line, 23...CO transformation device, 23
a... The first half of the CO metamorphosis device, 23b...
...Second half of CO shift converter, 27...Exhaust heat recovery boiler, 31...Stack, 35...OC
Intermediate part of O transformation device, 37... supply line such as Hibu, 39... dispersion mechanism such as QS, 41...
・Gas supply line for maintenance EE. Figure 1 Figure 2

Claims (1)

[Claims] 1 Equipped with a preheater, a reforming reaction device, and a CO shift device, it reforms light hydrogen with steam and converts the obtained reformed gas into CO.
In the method of producing city gas using a cyclic gasification plant that converts CO, CO exhibits catalytic activity at low temperatures.
A shift catalyst and a CO shift catalyst that exhibits catalytic activity at high temperatures are sequentially separated and filled in the gas flow direction within a single CO shift device, and the latter is heated by the CO shift reaction heat generated in the former. A method for producing city gas characterized by: