JPS61245819A - Method for purifying high temperature reductive gas - Google Patents

Abstract

PURPOSE:To stabilize the concns. of CO and H2, by absorbing a S-compound with an absorbent based on metal oxide and regenerating said absorbent by O2-gas and subsequently reducing the absorbent until the concn. of reducing gas before absorption becomes same to that after absorption and repeating this operation. CONSTITUTION:Gas 1 based on H2 and CO from a gasifying process receives dust removal treatment and is flowed to an absorbing regeneration tower 6 packed with an absorbent 9 comprising oxide of a metal such as Fe, Zn, Mo, Mn, Cu or W to remove a S-compound. O2-containing gas 2 is passed through an absorbing regeneration tower 7 to regenerate the absorbent and SO2-gas 5 is obtained. Further, part of the gas from the gasifying process is flowed to an absorbing tower 8 to reduce the absorbent until the concns. of H2 and CO in the purified gas 3 become constant and the treated gas is returned to the gas 1 of the gasifying process through a valve 24. These processes are successively changed over to stabilize the concns. of H2 and CO and the purified gas is continuously supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for purifying high-temperature reducing gases, such as the product gas of a coal gasification process. This invention relates to a method for purifying high-temperature reducing gas that most rationally removes hydrogen.

(Conventional technology) In recent years, diversification of fuels (or raw materials) has been called for due to the depletion of petroleum sources and soaring prices. , vacuum residual oil, etc.) is being developed. A typical example is the method of gasifying coal or heavy oil to be used as shipping, fuel, or synthetic raw material.

However, this gasification product gas contains hydrogen sulfide of several hundred to several thousand ppo, depending on the raw material coal or heavy oil, and this is used to prevent pollution, or to prevent corrosion of downstream equipment and poisoning of catalysts. .

It is necessary to remove it.

There are wet and dry methods for this removal, but the wet method requires cooling the process gas, which is disadvantageous in terms of thermoeconomics, and coexisting components (tar, naphthalene, hydrogen, NH,
The process becomes complicated because pretreatment and wastewater treatment equipment are required to remove contaminants such as HON, HON, 008 dust, etc., or to prevent contamination and deterioration of the absorption liquid.

On the other hand, the dry method is thermoeconomically advantageous and has a simple process configuration, so it has become a common practice to adsorb and remove sulfides at high temperatures using an adsorbent containing metal oxides as the main component. Adsorbents include Fa, Zn, Mo, Mn, and C.
Metal oxides such as u, W are used, and 2505450
The adsorption reaction in the case of Fa is said to proceed as shown in equations (11 to (3)).

Fe2O, + H2 → 2FaO+ H2O...Song (1)
Fe203 + Go →2FaO+ Co2---
--(2) FsO+ H2S 4 F@S + H2O
(3) Next, the adsorbent after the adsorption reaction is regenerated into metal oxide with oxygen-containing gas as shown in equation (4), and by repeating this adsorption and regeneration reaction, the sulfur compound in the high-temperature reducing gas is converted to sulfur dioxide gas. It will be collected and removed as such.

4Fe8 + 702-+ 2Fe20. +4H2
(4) The adsorbent used in this process is the above-mentioned metal oxide alone or supported on a heat-resistant porous material, and in the case of a moving bed method, it is formed into a spherical or cylindrical shape. In the case of fixed bed systems, honeycomb-shaped materials have traditionally been used.

In the adsorption reaction, Fe2O3 is sequentially converted to KF via FeOt-.
ag, the reaction from Fe2O3 to FeO is rate-determined by a chemical reaction, the reaction from FaO to Fe8 is rate-determined by diffusion within the reaction product layer, and the reaction rate from KF・0 to FeS is F6□03 It is said that the reaction rate from FeO to FeO is about 40 times slower in the operating temperature range. In addition, the spherical adsorbent used in the moving bed system has a particle size of about 5 to 10 mm in practical use from the viewpoint of preventing dust clogging.

11) From the difference in reaction rate between equation (2) and equation (31), (11(
In formula 21, the adsorption proceeds to the inside of the absorbent, whereas in formula (3), only about one layer of the surface layer of the absorbent is used, and adsorption breakthrough is reached, so the regeneration layer 1iK must be transferred. Gas purified by removing sulfur compounds from reducing gas such as coal gasification gas is used as an energy source, so Go, H2
It is preferable to use a process that produces a stable concentration;
[1] The reaction of formula 12) must be suppressed as much as possible. In the moving bed method, the adsorption process and regeneration process are repeated continuously, so the above technical problems are met! This problem is easy to overcome because in the fixed bed method, the adsorption process and regeneration layer a are repeated intermittently.

In switching between the adsorption layer and the regeneration layer, CO in the purified gas.

Since the temperature drops to 828 degrees at the start of the adsorption reaction, it is not practically preferred as a method for purifying high-temperature reducing gases.

(Problems to be Solved by the Invention) The present invention has been made in order to overcome the drawbacks of these conventional fixed bed systems. This provides a means for stably supplying Go and H2 concentrations in N gas to downstream equipment.

(Next means for solving the problem) The present invention uses an adsorbent mainly composed of metal oxides to remove sulfur compounds contained in high-temperature reducing gas obtained by gasifying coal, heavy oil, etc. In the adsorption removal method,
A step of regenerating the adsorbent that has adsorbed the sulfur compound with an oxygen-containing gas.

Next, a process S of reducing the reducing gas concentration of the purified target before and after the adsorbent, which has been regenerated and returned to the metal oxide, becomes the same;
A high-temperature reduction characterized in that the concentration of the reducing gas in the purified gas is stabilized by continuously repeating the step of aerating the high-temperature reducing gas and adsorbing and removing the sulfur compound with the adsorbent. This paper relates to a method for purifying sexual gases.

The method of the present invention will be explained in detail below with reference to FIG. 1 showing an embodiment. The gasified gas 1, which is mainly composed of H2 and COD and which has been partially combusted and gasified in the gasifier, is subjected to dust removal and guided to a step of removing sulfur compounds. The gasified gas 1 after this dust removal varies depending on the type of coal and gasification conditions, but it ranges from several tens to several thousand ppm 0H28, 00B, NH,, DON.
The gas temperature is 250 to 500°C due to heat recovery by a steam heater or the like at the outlet of the gasifier, and the pressure is normal pressure to 25 ata, although it varies depending on the type of gasifier.

In the present invention, the gasified gas 1tsye*Zn after dust removal,
The sulfur compounds in the gasification gas 1 are converted into sulfides by venting through the flow path switching pulp 10 to the 41 absorption regeneration tower 6 filled with an absorbent 9 made of metal oxides containing 4% of Mo, Mn, Cu, and W. Removed by adsorption. The absorbent 9 is granular,
It can be of any shape such as cylindrical, honeycomb, or plate-like.

A porous heat-resistant base material such as titania, silica, or zeolite is used to support the above-mentioned metal oxide.

The reaction formula when Fe2O3 is used as an absorbent component is the above-mentioned (
11 (21 (3) shows that the gasification gas 1
Trace amounts of ION and coS coexisting in the ion are also partially removed by the reaction shown in the following equation.

HGN + H20→NH, + C0 003+HO→C02+H2S Reaction temperature is 250S450℃, SU value (gas flow rate Nm'
, /h/absorbent capacity m3) is 1,000 to 20.00
At about 0.07 hr, more than 90% of H2S in the gas is removed, and purified gas 3 is obtained through the flow path switching pulp 25. At this time, the flow path switching valves 13.16.19.22 are closed.

On the other hand, the 42 absorption and regeneration tower 7 is filled with the same absorbent 9 as the 41 absorption and regeneration tower 6, and oxygen-containing gas is passed through the flow path switching pulp 17 to the absorbent that has reached breakthrough by adsorption of sulfur compounds. 2 is aerated to regenerate the absorbent by a roasting reaction as shown in the following equation, and at the same time, a rich S02 gas 5 is obtained via the flow path switching pulp 20. At this time, flow path switching valve 1
1, 14, 23, and 26 are closed.

4Fa8 + 70-+ 2Fe20s+4802 The above reaction is exothermic and occurs rapidly at the same time as the oxygen-containing gas 29 is vented. It is preferable to control the m degree by uniformly supplying the element at a low concentration throughout. This playback temperature is 250S6
Concentrated SO2 dissipated from absorbent 9, carried out at 00 °C
The gas 5 is used as a raw material for producing sulfuric acid, or is led to a process where it is recovered as elemental sulfur or solid sulfur compounds.

In addition, the A3 absorption and regeneration tower is filled with the same absorbent 9 as the 41 absorption and regeneration tower 6゜A2 absorption and regeneration tower 7, which is converted into a metal oxide state through regeneration treatment and gasified after removal of dust into the 9 absorbent 9. A part of the gas 1 is vented through the flow path switching pulp 15 to mainly perform a +11 +21 type reduction reaction.

This reduction reaction is the same as the reduction reaction performed in the A1 absorption regeneration tower 6, but the A2. Pre-reduction reaction until CO concentration becomes constant, flow path switching pulp 2
4 and is returned to the gasified gas 1 after dust removal. At this time, the flow path switching valve 12, 18°21.27 is closed.

At the stage of such preliminary reduction reaction, the H2S adsorption reaction of equation (3) also occurs simultaneously, but the mangoku of equation (1) + 21 is
) Since the reaction is faster than the reaction of the formula (2), after the preliminary reduction reaction is completed, the ventilation of the gasified gas 1 after removal is stopped and the reaction is waited for the start of the adsorption reaction in the next step.

Furthermore, if the amount of gas to be treated in the pre-reduction reaction step is made smaller than the amount of gas to be treated in the adsorption reaction step within a range that allows variation in the concentration of H2 and Co in the purified gas 3, As shown in FIG. It is also conceivable that the gas at the outlet of the absorption regeneration tower 8 is allowed to flow into the purified gas line 3 via the dotted line. The effect of causing the adsorption reaction of sulfur compounds even after the completion of the pre-reduction reaction process at any pressure must be sufficiently prepared to the extent that it does not pose a practical problem. H2 contained in gas 3. co
Enables operation with constant mtxt. Therefore, when the purified gas 3 in the subsequent process is used as gas turbine fuel or synthesis gas fuel, it is possible to stabilize the H2 and Go concentrations and continuously supply it.

In this way, these sNi adsorption reactions, regeneration reactions, and pre-reduction reactions are continuously repeated in each absorption and regeneration tower to reduce H2, Co, etc. in the purified gas, which can be used as a fuel source. It becomes possible to stabilize the gas concentration.

The table below summarizes the opening and closing status of the flow path switching valves installed before and after each absorption regeneration tower.

The flow path switching valves 10, 11, 12, 25゜26.27 are for changing the flow path to obtain the purified gas 3 from the gasified gas 1 after removal, and are used before and after the absorption regeneration tower performing the adsorption reaction. The valve opens.

Otherwise it is closed. In addition, the flow path switching pulp 13,
14, 15, 22, 23, and 24 are for flow path switching to introduce a part of the gasified gas 1 after dust removal in order to pre-reduce the regenerated absorbent and return it to the gasified gas after the pre-reduction. The valves before and after the absorption and regeneration tower performing the preliminary reduction reaction are open, and the rest are closed. Further, the flow path switching pulps 16, 17, 18, 19, 20゜21 are used to switch the flow paths for obtaining SO and rich gas by ventilating and circulating the oxygen-containing gas 2 necessary for the regeneration reaction. The valves before and after the absorption and regeneration tower are open, and the rest are closed.

(Effects) As described above, according to the method of the present invention, fuels such as H2 and Co in the high-temperature reducing gas to be purified can be stabilized and supplied to the next process without temporarily reducing them. This is a purification method for removing sulfur compounds.

(Example) By repeatedly impregnating a commercially available anatase-type titanium oxide carrier with a particle size of 5s+s with an aqueous ferric nitrate solution and drying (110°C x 1ohr), 102.76.01% by weight,
A desulfurizing agent containing F.20.24.0% by weight was prepared, and after firing at 450°C for 5 hours, CO, H2, Co2 in the desulfurizing agent outlet gas during absorption reaction under the test conditions shown in Table 1. ．．
Changes in H2fJ concentration over time were determined.

The results are shown in FIG.

Table 1 Absorption reaction test conditions As can be seen from Figure 2, at the beginning of the adsorption reaction, the H2 and Go fi degrees at the absorbent outlet were low, the adsorption time gradually increased until about 10 minutes, and after 10 minutes, the concentration became stable. ing. This indicates that a reaction in which H2 and Go are adsorbed by the absorbent occurs at the start of the adsorption reaction.If the adsorption reaction is performed immediately after the regeneration reaction is completed, under the test conditions of this example, approximately Go for 10 minutes, purified gas with low H2 concentration will be generated. Also, H2S's lust breakthrough time is 20 ~
30 minutes, and the effect of providing a preliminary reduction step between the regeneration step and the adsorption step as in the present invention is significant. It should be noted that the reason why the CO concentration is steady at 20% in Figure 142 is presumed to be due to the simultaneous occurrence of the following reactions.

00 + HO-+ Co2+ 82

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining an example of the method of the present invention, and FIG. 2 is a diagram showing the results of an example of the present invention. 1...Gasified gas after removal 2...Oxygen-containing gas 3...Purified gas 4...Circulation line 5...SO2 gas 6...Mu1 Absorption and regeneration tower 7...・Hire 2 absorption regeneration tower 8...Ii5 absorption regeneration tower 9...To absorbent 10 27...Flow path switching valve agent 1) Meifu agent Ryo Hagiwara - Figure 1

Claims (1)

[Claims] In a method of adsorbing and removing sulfur compounds contained in high-temperature reducing gases with an absorbent mainly composed of metal oxides,
A step of regenerating the absorbent that has adsorbed the sulfur compound with an oxygen-containing gas, and then reducing the regenerated absorbent with a high-temperature reducing gas until the concentration of the reducing gas to be purified before and after the absorbent becomes the same. , and then continuously repeating the steps of aerating the high-temperature reducing gas and adsorbing and removing the sulfur compound with the absorbent, thereby stabilizing the reducing gas concentration in the purified gas. Gas purification method.