JPS60225621A - Desulfurization of high temperature gas - Google Patents

Abstract

PURPOSE:To enhance the reactivity with H2S to lower a powdering ratio and to enable regeneration, by using a particulate substance by hydrating crushed particles of an alumina cement clinker through the contact with water. CONSTITUTION:Formed H2S gas is guided to a desulfurization tower 12 from a duct 15 and absorbed by a desulfurization agent, which is obtained by hydrating an alumina cement clinker, in said tower 12. The desulfurization agent comes to CaS by absorbing H2S and enters an oxidizing tower 13 to be oxidized by air from a supply pipe 16 to be converted to CaSO3. Subsequently, the desulfurization agent enters a reducing tower 14 and reduced to CaO by CO and H2 gases to be returned to the desulfurization tower 12 through a conveyor pipe 23. At this time, a new desulfurization agent can be replenished from a replenishing pipe 24 in an amount corresponding to a damaged amount. The outlet gas from the reducing tower contains SO2 and sent to a byproduct preparation apparatus from a duct 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a desulfurization method for removing hydrogen sulfide in a reducing hot gas using hydrated alumina cement clinker particles.

[Background of the invention]

Coal gasification has attracted attention in recent years as an energy alternative to oil, and its development is being promoted.It is expected to be used not only as a city gas fuel but also in fields such as electric power and the chemical industry.

As coal is gasified, most of the sulfur content in the coal becomes hydrogen sulfide (H2S), which is present in the generated gas. Therefore, in the process of using gasified coal, it is necessary to desulfurize it before use, as a measure to protect the environment.

Conventional gas desulfurization methods include wet desulfurization methods, in which H28-containing gas is washed and desulfurized with an alkaline aqueous solution or organic solvent.
It has been put into practical use in various fields such as the chemical industry. However, in the wet desulfurization method, the desulfurization temperature is as low as room temperature to 120°C, so the high-temperature gas from the coal gasifier must be cooled to 120°C or lower.

On the other hand, if the high-temperature gas desulfurization method, which desulfurizes at a temperature of 400°C or higher, can be applied to processes that utilize high-temperature purified gas, such as fuel gas for combined cycle power generation, CO shift reaction raw material gas, etc., the gas cooling and reheating step can be omitted. This can greatly improve the thermal efficiency of high-temperature gas and equipment costs. Therefore, recently, dry desulfurization methods targeting high-temperature gases have been viewed as promising.

As absorbents (desulfurizing agents), there is an increasing trend towards methods that take into account the treatment of waste desulfurizing agents and regenerate and use them.

The use of iron-based and calcium-based solid desulfurization agents is being considered for the dry desulfurization method. The former type of iron-based desulfurization agent is difficult to use because sintering of the desulfurization agent occurs at high temperatures.
The reaction temperature with S is 350°C to 460°C. This slows down the reaction rate and makes it impossible to obtain sufficient absorption and regeneration performance. Furthermore, since the reaction temperature is lower than that of the coal gasification furnace, a cooling device must be installed in front of the desulfurization equipment, resulting in a decrease in thermal efficiency due to sensible heat loss of the produced gas, and the system is also complicated. It has some drawbacks.

On the other hand, as the latter calcium-based desulfurization agent, naturally occurring calcium-containing minerals such as limestone and dolomite are used. The absorption performance of this calcium-based desulfurization agent is 870℃.
There is a drawback that the temperature is high in the vicinity, and the absorption performance decreases both below and above that temperature range. Since the regeneration reaction absorbs H, 8 and becomes calcium sulfide (Ca8), it is carried out by oxidizing calcium sulfate (CaS04) VC with air or the like, and then reducing it with a reducing gas such as carbon monoxide (CO). Since the reduction reaction temperature here requires a high temperature of 1000° C. or higher, deterioration of the activity of the desulfurizing agent due to sintering becomes a problem. What is especially fatal is that calcium-containing minerals are subject to extremely high wear due to a decrease in physical and mechanical strength when decarboxylation, absorption, and regeneration reactions are repeated at high temperatures, and when reactions are conducted in fluidized beds. It has the drawback that it is large in size, causes problems in post-processing due to powdering and scattering, and furthermore, the necessary desulfurization performance cannot be obtained due to powdering and scattering, and the supply amount must be increased.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned drawbacks, and provides a desulfurization method that has sufficiently high reactivity with H2S in reducing high-temperature gas, has a low powdering rate, and can be repeatedly regenerated. It is about providing.

[Summary of the invention]

That is, the present invention aims to remove H and S from high-temperature gas.
As a result of various searches for a desulfurizing agent that is renewable and has excellent durability, the present invention is characterized by the use of a desulfurizing agent made from alumina cement clinker.

The desulfurization agent used in the present invention is made by crushing alumina cement clinker, which is generally produced in the form of a lump of commercially available fine powder alumina cement in a mixing process, so that it can be applied to various reaction formats such as a fixed bed and a moving bed. After adjusting the particle size, the particles are immersed in water to hydrate the inside of the particles before use.

The alumina cement clinker contains C as a chemical component.
a 036~44% -AI 20g 40~5
5%, Fe2O31 = 15%, 8 Contains A024-111, quickly combines with water, and forms 2CaO#Aj, o, -
8) (, o, Cab-A12o, *10H,0, etc. are produced. In other words, the large clinker of the hydrate means that the porosity is large due to dehydration. Here, hydrated alumina The desulfurization performance of cement clinker is greatly affected by its degree of hydration, and an index of the degree of hydration is necessary to obtain sufficient desulfurization performance.As an example of evaluating the degree of hydration, As a result of measuring the specific surface area from the correlation with the porosity (porosity), it was found that 5 rrf/
It has been found that it is desirable that it be at least 12 rrf/l/, preferably at least 12 rrf/l/.

The particle size of the desulfurizing agent in the present invention is adjusted by crushing alumina cement clinker to a particle size suitable for various reaction types. Thereafter, the particles are immersed in water to cause a sufficient hydration reaction to occur inside the particles. Alumina cement clinker is originally a mixture of the above chemical components, heated, cooled and solidified from a semi-molten state, and because it lacks glassy porosity, it has relatively coarse linker particles as in the present invention. The hydration reaction from the surface of the particle to the inside progresses only gradually, and it takes a long time to reach the center of the particle. In order to make this hydration reaction proceed in a short time, it can be shortened to about 1/1 O-1/3 by conducting it at a temperature slightly higher than room temperature. The desulfurizing agent obtained in this way is
It has superior strength and is easy to manufacture.

N28 absorption as a desulfurization agent It is based on the formula.

C a O+H 2B−+C a 8+H 20 −
”・(1) C contained in alumina cement clinker
FIG. 1 shows the reaction rate of aO and H,8 in terms of molar ratio. The desulfurization performance shown in this figure was measured by the following procedure. That is, by thermobalance, C a 0 as a chemical component
3 8 fo * AI! O B 5 3%
, F e 2 0 Blts (both weight tIb
) After crushing alumina cement clinker in the form of a block with a screen mill, the particle size becomes 0. 5-0. 8
The relationship between the 1-hour absorption of H2S and the reaction temperature was measured and shown using a desulfurizing agent with a specific surface area of about 40 mm, hydrated by the above method, and having a specific surface area of 2 Ofll''/II. The absorbed gas composition was H2SO.
2%, CO3.

Other N2 gas (both have a volume of 1), the total amount is 1. ONj
/min atmospheric gas.

FIG. 1 shows a comparison of the H2S absorption performance of the desulfurization agent 1 according to the present invention and the CaO desulfurization agent 2 obtained by decarboxylating limestone (CaCO3) produced in Ikura, Okayama Prefecture. In the figure, desulfurization agent 1 of the present invention has better absorption performance than limestone desulfurization agent 2 at a temperature of 700 to 1200°C, preferably 850 to 120°C.
It can be seen that sufficient performance can be obtained at 0°C. Therefore,
For example, when coal is gasified at high temperature, the temperature of the generated gas is 1ooo.
It is a desulfurization agent that has an excellent absorption effect even for desulfurization at temperatures around ℃.

On the other hand, in order to regenerate and use the desulfurization agent, CaS generated by equation (1) must be returned to CaO. Therefore, an oxidation step and a reduction step using the following reactions are required.

Ca8+202-+Ca804 +++++++HHHH
++(2)C a S 0 4 +C O-+ C a
O + 8 0 2 + C O g ・” (By carrying out the reaction of formula 31 (2) and (3),
The relationship between the regeneration rate and regeneration temperature when regenerating the desulfurization agent is
Shown in the figure. First, according to the thermobalance experiment, the oxidation process was
0□5chi. Calcium sulfide was oxidized for 2-3 hours with a mixed gas of balance N2. Next item, coaLss remaining Q
N217) Mixed gas, '([J: QIO ~ 60 minutes reduction to regenerate the desulfurization agent. In both steps, the gas flow rate was the same as above H,
The S absorption conditions were the same, and the sulfurized desulfurization agent used at that time was also used. The regeneration rate was evaluated by converting the weight change due to oxidation and reduction into 8 minutes in the desulfurizing agent.

The temperatures in Figure 2 are for oxidation. For both reaction temperatures of reduction, the range of 7 was 700-1200°C. This range is H! There is no problem with the same temperature as 8 absorption temperature, but the preferred range is 85
The temperature was 0 to 1200°C.

The regeneration rate at each temperature in the figure is the desulfurization agent l according to the present invention.
Both of the desulfurization agent and the limestone desulfurization agent 2 are at the same level around 1 loO'c, but the desulfurization rate of the desulfurization agent of the present invention is high at lower temperatures than that, and has characteristics that are effective even at relatively low temperatures.

From practical knowledge, the reducing gas of the desulfurization agent is CO., which is produced by gasification of coal. N2 etc. can be used as is.

When the desulfurization agent according to the present invention is repeatedly used in desulfurization and regeneration cycles, wear of the desulfurization agent due to the cycle becomes a problem, and the desulfurization agent has excellent mechanical strength and thermal strength associated with handling. This is required. Therefore,
Approximately 40 years of the desulfurizing agent and limestone desulfurizing agent of the present invention were prepared, and the wear amount was measured and compared using this as a starting sample.

The amount of wear was measured in the order of grain size from 0.5 to 1.0 at a temperature of 85%.
A sample was baked at 0°C for 2 hours, and the sample was filled into a stainless steel cylinder with a diameter of 1 inch and a length of 300 mm, sealed, fixed at the longitudinal center of the cylinder, and attached to the shaft. The sample was rotated at a rotation speed of 25 r, p, m, which enabled sufficient vertical movement within the cylinder, and the sample was taken out over time to measure the amount of wear loss.

The amount of abrasion loss was determined by classifying with a 0.25 mm sieve, taking the amount under the sieve as the amount of abrasion loss, and calculating the weight ratio to the starting sample. Since the sample is hygroscopic, it was weighed after gravimetrically drying at the same temperature.

Figure 3 shows the change in wear loss over time. Desulfurizing agent of the present invention l
On the other hand, the limestone desulfurization agent 2 has a large absolute amount of wear, and in particular, the amount of wear loss increases over time. In other words, it is necessary to consider that the initial rapid increase in wear is due to the influence of adhering powder due to particle size adjustment, etc., and it is not reasonable to think that it is the original desulfurization agent wear. Rather, the subsequent wear rate is important, and as a result of comparing the amount of wear loss per unit time for both desulfurization agents, it was found that the limestone desulfurization agent causes seven times more wear than the desulfurization agent according to the present invention. Ta. Therefore, it can be seen that this decrease in strength is the reason why limestone desulfurization agents are not suitable for desulfurization systems that repeatedly perform desulfurization and regeneration.

The desulfurization agent according to the present invention has a simple manufacturing method and excellent strength, so it has the effect of reducing the amount of wear and tear of the desulfurization agent that causes problems during desulfurization, regeneration cycles, and handling, and is suitable for practical use. It is.

Hereinafter, an embodiment in which the present invention is used for desulfurization of coal gasification gas will be described with reference to the flowchart of FIG. 4.

The desulfurization apparatus includes a desulfurization tower 12, an oxidation tower 13 for regeneration, and a reduction tower 14. Here, in order to obtain effective reactivity of the desulfurizing agent in both towers, a structure was adopted in which a fluidized bed was formed. The configuration and operation of the embodiment will be described in detail below.

Coal gasification produces reducing gas at high temperatures of 900-1600°C, so 8 minutes in the coal and H3 in the generated gas are
reacts to produce a compound of H2S.

The generated H,8 gas is present in the coal gasification gas at an amount of several thousand p·p@m, although it varies depending on the type of coal, and is led to the desulfurization tower 12 from the duct 15 connected to the gasifier outlet. In the desulfurization tower 12, a desulfurization agent 11 made by hydrating the alumina cement clinker of the present invention forms a fluidized bed with a particle size of 05 to 3 mm and a linear velocity of 0.5 to 2 Om/s. ing. Here, the desulfurization reaction is carried out at a temperature of 700 to 1200°C, preferably 850-120°C by the reaction of formula 11.
H2S is absorbed by the desulfurizing agent 11 in the temperature range of 00°C.

The gas discharged from the desulfurization tower 12 is purified and discharged from a duct 18 connected to the desulfurization tower outlet.

The desulfurization agent 11 in the desulfurization tower 12 absorbs H,8 and produces the above (
According to the reaction formula 1), it becomes Ca8, and in this state it overflows from the connecting pipe 21 and enters the oxidation tower 13. The desulfurizing agent transferred to the oxidizing tower 13 is supplied with air (or a gas containing 0□3 or more in inert gas) as an oxidizing agent from the lower part of the oxidizing tower to oxidize the sulfurizing desulfurizing agent from the supply pipe 16. and is oxidized by the reaction of formula (2) above. The oxidation temperature here is a temperature of 700 to 1200°C, preferably 850°C.
In this oxidation step, the sulfurized desulfurization agent is oxidized to CaSO4 in a temperature range of ~1200<0>C.

Next, the oxidized desulfurization agent passes through the connecting pipe 22 to the reduction tower 1.
Enter 4. This reduction tower requires CO, H, and gas as reducing agents. Coal gasifier gas conveniently generates these gases, but since the gas as it is contains H and 8, the desulfurization tower 12 is a clean gas after desulfurization.
Part of the gas is branched from the outlet duct 18 and guided to the duct 17, where it is used as a reducing gas for the desulfurization agent which has become Ca804.

The reduction reaction is carried out by equation (3), with Ca80. is Ca before desulfurization
Return to 0K. The reaction temperature here is 850 to 1200°C,
Preferably it is 1000-1200°C.

One cycle of desulfurization and regeneration has been completed in the steps up to this point, and the regenerated desulfurization agent 11 is supplied to the desulfurization tower 12 through the conveyance pipe 23. A replenishment pipe 24 is attached to this conveyance pipe 23 to supply new desulfurization agent in proportion to the amount of desulfurization agent wasted due to the desulfurization and regeneration cycle.

On the other hand, the outlet gas from the reduction tower 14 is SO□ gas having a concentration of several percent depending on the amount of H2S absorbed into the desulfurizing agent and the degree of oxidation thereof, according to the reaction formula (3). This SO2 gas flows through and is supplied to the by-product manufacturing apparatus (20).

Although the description has been given using an example of a reaction mode using a fluidized bed method, the desulfurization agent according to the present invention is not necessarily limited to a fluidized bed method. Furthermore, it is natural that the desulfurization apparatus may be constructed in such a way that the reaction is carried out in a gasifier in order to obtain an effective reaction temperature.

As described above, according to the present invention, it is effective in desulfurizing reducing high temperature gas, there is no need to lower the gas temperature for desulfurization, and heat loss can be reduced. Furthermore, compared to conventional limestone desulfurization agents, the desulfurization agent of the present invention has excellent desulfurization and regeneration performance. Moreover, since it has high strength, it is possible to significantly reduce the amount of wear due to wear, and it is possible to provide an economical desulfurization method.

[Brief explanation of drawings]

Figure 1 is a comparison diagram of desulfurization performance showing the relationship between CaO reaction rate (mole ratio) and reaction temperature. Figure 2 is a comparison diagram of regeneration performance showing the relationship between regeneration rate and regeneration temperature. The figure is a comparison diagram of wear strength showing the amount of wear loss over time, and FIG. 4 is a flowchart showing an example of the desulfurization method according to the present invention. 11...Desulfurization agent, 12...Desulfurization tower, 1
3... Oxidation tower, 14... Reduction tower. Fig. 1 400 6 (X) 800/QQO12001400 blade ε 1 5th man - n Tsukuda: ('C) Fig. 2 upper residence, 5 articles (degree ('C)) Fig. 3 Saki lvi (h) Fig. 4

Claims (1)

[Claims] 1. A high-temperature gas characterized in that hydrogen sulfide in a high-temperature reducing gas is removed by using a granular material made of crushed particles of alumina cement clinker brought into contact with water and hydrated. desulfurization method. 2. A method for desulfurizing high-temperature gas according to claim 1, wherein the high-temperature gas containing hydrogen sulfide is a coal gasification-reducing gas. 3. In claim 1, the desulfurization temperature is 700
A method for desulfurizing high-temperature gas, characterized in that the temperature is in the range of 1200°C to 1200°C. 4. A method for desulfurizing high-temperature gas according to claim 1, characterized in that the sulfurized hydrated alumina cement clinker is used as an absorbent for hydrogen sulfide in the high-temperature gas, and the sulfurized hydrated alumina cement clinker is recycled and used repeatedly. . 5. In claim 4, a high temperature method characterized in that sulfurized alumina cement clinker is oxidized to calcium sulfate with an oxygen-containing gas, and then regenerated with a reducing gas containing carbon oxide. Gas desulfurization method. 6. The method for desulfurizing high-temperature gas according to claim 5, characterized in that the reducing gas containing carbon oxide is coal gasification gas after being desulfurized.