JPH07116455B2 - Desulfurization method in gasification furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for desulfurizing gas produced by gasifying coal.

[Conventional technology]

In recent years, the use of coal as an energy source has advanced rapidly,
A method of burning coal as a fuel as it is or a technique of using coal as a pollution-free fluid fuel by gasifying and liquefying coal is also expanding. Among them, in Japan, as a technology development for gasifying coal, development of a high-calorie gasification process for obtaining a raw material gas or a fuel gas and a low-calorie gasification process for the purpose of power generation are mainly advanced.

Recently, development of a process in which coal is slag gasified in a spouted bed using oxygen or air and steam and this ash is discharged as slag is under development.

In this slag gasification process, the temperature inside the furnace is 1,500 ° C.
Since the ash in the coal is melted and discharged from the furnace bottom by the above, the gasification reaction rate of the carbon in the coal is very fast, and the carbon utilization rate is close to 100%. In the case of slag gasification, the gas produced is rich in carbon monoxide and hydrogen in order to gasify coal at high temperature and high pressure. Considering the combination with gasification power generation, it is important to process the produced crude gas in a high temperature state. When coal is gasified, sulfur in the coal is mainly H ₂ S, so desulfurization at high temperature is a major issue.

A first example of the conventional gasification power generation flow is shown in FIG. The produced gas at the outlet of the gasification furnace 1 contains dust and sulfur compounds such as H ₂ S and COS as harmful components. Gasification furnace 1
The high-temperature gas exiting from the above first enters the high-temperature dust remover 8 to remove dust, and then enters the desulfurization tower 9. In the desulfurization tower 9, harmful components such as H ₂ S are removed at high temperature, and the purified gas is combustor.
It is supplied to the gas turbine 11 via 10. If such a method is adopted, the gas temperature entering the gas turbine 11 is high, so that the power generation efficiency of the gas turbine 11 is increased. As the desulfurizing agent, a desulfurizing agent such as limestone, dolomite, zinc oxide and iron oxide is usually used, and as the form of the desulfurizing tower 9, a fixed bed, a fluidized bed or a spouted bed is generally used. A spouted bed using a fine powder desulfurizing agent is desirable to improve the utilization rate of

Next, a second example is shown in FIG. In the slag gasification furnace 1, since the temperature of the produced gas is 1,500 ° C. or higher, the heat transfer tube 12 is arranged in the empty column part in the gasification furnace 1 to recover the heat of the high temperature gas. The high temperature gas discharged from the gasification furnace 1 further enters the heat exchanger 14 to recover heat, and the cyclone 15 removes scattered particles. The produced gas from which the dust has been removed enters the desulfurization tower 9 where the sulfur compounds in the H ₂ S tower are removed, and the purified gas is sent to the combustor 10 and supplied to the gas turbine 11. 16 is an exhaust gas pipe.

[Problems to be solved by the invention]

However, as shown in FIGS. 5 and 10, the gasifier 1
In addition to the above, the desulfurization tower 9 is necessary in the conventional process, and it is necessary to simplify the process and reduce the apparatus cost.

However, in the example shown in FIG.
Even if the desulfurizing agent is supplied to the reactor, the reaction conditions necessary for desulfurization are not satisfied, and the desulfurizing agent is entrained in the gas flow, so that the reaction rate of the desulfurizing agent is not so good. It is also another sulfur compound
Since COS does not react with the desulfurizing agent, in order to improve the desulfurization rate on the gas side, it is absolutely necessary to react and remove COS.

Further, according to the example of FIG. 10, a complicated gasification furnace is provided in which a heat transfer tube 12 is arranged in the empty column portion of the gasification furnace 1 for cooling the high temperature gas, and a high temperature desulfurization tower other than the gasification furnace. 9 is required. Therefore, entrain desulfurization in which fine powder of limestone is blown into the gasification tower is considered, but there are the following problems.

(1) In the entrain desulfurization of fine limestone, when a sulfide is formed on the surface of the desulfurizing agent, the desulfurization reaction is rate-determined by diffusion in the solid phase, and the reaction rate of the desulfurizing agent decreases.

(2) In the entrain type reactor, the desulfurizing agent, which is a fine powder of limestone, undergoes a desulfurization reaction in the state of being entrained in the produced gas, so that the gas film membrane resistance is large, and the desulfurization is required unless the contact efficiency between the desulfurizing agent and the gas is improved. The rate is low.

(3) Since the pressure of the gasification furnace is high at 20 to 30 atm,
When the gas transportation method is adopted, it is difficult to control the supply amount of fine limestone.

As mentioned above, when the coal slag gasification process is applied to power generation, the sulfur compounds in the produced gas are efficiently removed at high temperature to increase the power generation efficiency of the gas turbine, while at the same time simplifying the process and reducing the equipment cost. This is a problem to be solved.

An object of the present invention is to provide a desulfurization method in a gasification furnace capable of efficiently and economically removing sulfur compounds in a produced gas at a high temperature in a coal slag gasification process.

[Means for solving problems]

In order to solve the above problems, the present invention is a desulfurization method in a gasification furnace in which coal fine powder is carried by slag gasification by carrying air stream with oxygen or air, wherein the coal fine powder and oxygen or air are lower parts of the gasification furnace. And the fine powder desulfurizing agent and water vapor are simultaneously supplied to the empty tower section of the upper part of the gasification furnace, and the fine powder desulfurizing agent is tangential to the peripheral surface of the gasification furnace. Alternatively, the gas is supplied downward from the horizontal direction of the gasification furnace.

[Action]

According to the above configuration of the present invention, by simultaneously supplying the fine powder desulfurizing agent and steam to the empty column portion of the coal slag gasification furnace, the optimum reaction temperature is maintained and at the same time H ₂ S and COS are removed.

The desulfurizing agent in the form of fine powder is supplied tangentially to the peripheral surface of the gasification furnace, whereby the desulfurized particles swirl and come into countercurrent contact with the gas. Alternatively, the finely divided desulfurizing agent is brought into countercurrent contact with the gas by being supplied downward with respect to the horizontal direction of the gasification furnace. This improves solid-gas contact efficiency and improves the utilization rate of the fine powder desulfurizing agent.

〔Example〕

 Next, an embodiment according to the present invention will be described with reference to the drawings.

First Embodiment A first embodiment of the present invention is shown in FIG. The process consists of a gasifier 1 for slag gasifying coal and its associated equipment. The pulverized coal to be gasified is supplied from the coal supply pipe 4 to the lower slag portion of the gasification furnace 1, and at the same time, oxygen or air as a gasifying agent is supplied from the O ₂ supply pipe 5. There, the coal is gasified to generate product gas and H ₂ S and COS which are harmful components. Also, the ash in the coal is melted and discharged as slag from the slag extraction pipe 6 to the outside of the system.

On the other hand, a desulfurizing agent supply pipe 2 for removing H ₂ S and COS, which are sulfur compounds, is provided in the empty column section in the upper part of the gasification furnace 1, and a desulfurizing agent of fine powder such as CaO, ZnO, dolomite, FeO, etc. To supply. The nozzle supply direction of the desulfurizing agent is tangential to the peripheral surface of the gasification furnace 1 as shown by the arrow in FIG. 2, and the desulfurizing particles come into countercurrent contact with the gas by the swirling motion.
Thereby, the solid-gas contact efficiency is improved, and the utilization rate of the desulfurizing agent is significantly improved. The reaction formula when CaO is used as the desulfurizing agent is as follows.

CaO + H ₂ S → CaS + H ₂ O Further, a steam supply pipe 3 is provided in the empty column portion of the gasification furnace 1 at a position almost similar to the desulfurizing agent supply pipe 2, and steam which is steam is also supplied at the same time. This steam controls the empty space in the optimum temperature range for the desulfurization reaction, and at the same time, plays an important role of decomposing COS, which is a sulfur compound that does not react with the desulfurization agent, into H ₂ S. This reaction formula is as follows.

COS + H ₂ O → H ₂ S + CO _{2 By the} above method, the sulfur compounds in the product gas are almost completely removed, and the purified gas remains at high temperature through the product gas outlet pipe 7 and the gas turbine 11 (see FIG. 5). ) Can be sent to.

Fig. 3 shows the relationship between the reaction temperature and the reaction rate of the CaO desulfurizing agent. C
The reaction rate of aO reaches its maximum when the reaction temperature is around 930 ° C, and the reaction rate tends to decrease regardless of whether the temperature is raised or lowered.

Figure 4 shows the relationship between reaction temperature and COS decomposition rate. From COS
The reaction rate to H ₂ S is shown, and it can be seen that the decomposition rate of COS becomes constant at 820 ° C. or higher, and it decomposes to H ₂ S of 99% or more.

As described above, the use of the present invention makes it possible to remove sulfur compounds efficiently at high temperatures. Further, in the empty column part, by supplying steam, the unreacted char can be gasified at the same time.

As described above, in the present example, by supplying pulverized desulfurizing agent and steam, which is steam, to the superficial part of the coal slag gasification furnace in a tangential direction with respect to the furnace, the reaction temperature is maintained at an optimum H level. simultaneously removing ₂ S and COS, moreover with good solid-gas contact is obtained so as to improve the utilization ratio of the desulfurizing agent.

Conventionally, various processes for high-temperature desulfurization in a fluidized bed or fixed bed at 400 to 900 ° C have been carried out, but an entrain system is also used to supply a desulfurizing agent to a gasification furnace to simultaneously gasify and desulfurize slag gas. There is no other way.

Second Embodiment Next, a second embodiment is shown in FIGS. 6 to 9. This second
In the embodiment, the particle size of the finely powdered limestone to be supplied is set to 30 μm or less, the diffusion resistance in the solid phase is made as small as possible, and the nozzle of the finely powdered limestone to be supplied to the empty column of the gasification furnace is set downward from the horizontal direction. By reducing the film resistance between gas and particles, the desulfurization rate is improved, and by supplying fine limestone as water slurry, it is possible to easily control the supply amount of fine limestone.

The reason for doing the above is as follows.

The particle size of fine limestone supplied to the gasification furnace empty column is 30 μm.
Below, the desulfurization reaction on the particle side is rate-controlled in the solid phase, and the theoretical reaction rate is 95% or more. By the way, it is said that the reaction thickness of sulfide is usually 10 μm.
If the thickness is 30 μm, the theoretical reaction rate is [1- (1/3) ³ ] × 100 = 96.3%. That is, even if a sulfide that forms a resistance to the reaction is formed on the surface of the desulfurizing agent, since the particle size is small, the reaction proceeds almost to the center of the particle and the reaction rate increases.

Further, by pointing the nozzle of the fine powder limestone supplied to the gasification furnace downward, the limestone moves downward due to inertial force. On the other hand, since the produced gas goes from the bottom to the top of the gasification furnace, it makes countercurrent contact with limestone, so that the relative velocity with the particles increases. This reduces the gas film resistance and increases the H ₂ S reaction rate on the gas side.

By supplying water slurries as the method for supplying the fine limestone, the supplying method is easy and the cost is low because the slurry pump can be used. Further, when supplied by water slurry, water is rapidly evaporated in the gasification furnace and particles are scattered to be in a turbulent state, so that the contact efficiency is improved and the reaction rate is increased. Further, the high-temperature product gas is cooled by the latent heat of vaporization of water, and it is not necessary to install a heat transfer tube in the furnace, so that the structure of the gasification furnace is simplified.

The details of the second embodiment described above are shown in FIG. The process consists of a gasifier 1 for slag gasifying coal and its associated equipment. The pulverized coal to be gasified is supplied from the coal supply pipe 4 to the slag gasification section B in the lower part of the gasification furnace 1, and at the same time oxygen or air as a gasifying agent is supplied from the oxygen supply pipe 5. There, the coal is gasified to generate product gas and H ₂ S which is a harmful component. The ash in the coal is melted and discharged as slag from the slag discharge pipe 6 to the outside of the system.

On the other hand, in the empty column part A of the gasification furnace 1, H ₂ which is a sulfur compound is
In order to remove S, a desulfurizing agent supply pipe 2 is provided to supply a fine desulfurizing agent such as limestone, ZnO, dolomite and iron oxide. These desulfurization reactions are as shown below.

CaCO ₃ + H ₂ S → CaS + H ₂ O + CO ₂ (1) CaO + H ₂ S → Cas + H ₂ O ... (2) ZnO + H ₂ S → ZnS + H ₂ O ... (3) FeO + H ₂ S → FeS + H ₂ O ... (4) Empty tower section The particle size of the desulfurizing agent supplied to A is 30 μm or less,
Also, the direction of the supply nozzle is downward from the horizontal,
Further, in this embodiment, the desulfurizing agent is supplied by water slurry.

FIG. 7 shows the experimental results of limestone particle size and particle-side desulfurization rate using a small-scale experimental apparatus. When the particle size of limestone is smaller than 30 μm, the desulfurization reaction on the particle side is rate-controlled in the solid phase, and the desulfurization rate is 90% or more. However, when the particle size is increased due to this, a sulfide that forms a reaction resistance is formed on the surface of the desulfurization agent, and as a result, the desulfurization rate is reduced. Therefore, it is important that the particle size is 30 μm or less.

In FIG. 8, a method of supplying the desulfurizing agent, in a downward and horizontal N ₂
The results when transported by gas are shown. When placed in the horizontal direction, the desulfurization agent particles are immediately entrained in the gas flow and rise in the reaction tube, so that the desulfurization rate on the gas side is low. On the other hand, when the nozzle is directed downward, the desulfurizing agent moves downward due to inertial force. Since the produced gas is directed from the bottom to the top of the gasification furnace, it makes countercurrent contact with the desulfurizing agent, so that the relative velocity with the particles becomes large. As a result, the gas membrane resistance is reduced, the H ₂ S desulfurization rate on the gas side is improved, and at 900 ° C,
% Or more is obtained.

Fig. 9 shows the experimental results when limestone was transported with 30% water slurry and N ₂ gas. When supplied by water slurry, water rapidly evaporates in the gasification furnace, particles are scattered due to the so-called popcorn phenomenon and a turbulent state occurs, so contact efficiency improves and desulfurization rate increases compared to N ₂ gas transportation. . On the other hand, compared to N ₂ gas transportation, water slurry is easier to use because it can use a slurry pump, the cost is lower, and the supply rate is easier to control.

Further, in the gasification furnace empty column section A, the high-temperature generated gas is cooled by the latent heat of vaporization of water, and the outlet generated gas temperature can be suppressed by controlling the supply amount of water slurry. When this method is adopted, it is not necessary to install a heat transfer tube (see Fig. 10) in the empty column of the gasification furnace, so the structure of the gasification furnace is simple and the construction cost can be reduced.

As described above, by using this embodiment, the sulfur compound can be efficiently removed. Besides limestone, ZnO, dolomite, iron oxide, etc. have the same effect as a fine-powder desulfurizing agent.In addition, when supplied by water slurry, it is possible to simultaneously gasify unreacted char by vaporized steam. Become.

Conventionally, various processes for high-temperature desulfurization in a fluidized bed or fixed bed at 400 to 900 ° C have been carried out.However, the method of entraining and supplying a desulfurizing agent to a gasification furnace to simultaneously gasify and desulfurize slag gas is I can't find anything else.

〔The invention's effect〕

As described above, according to the present invention, in the slag gasification process of coal, it is possible to provide a desulfurization method in a gasification furnace capable of efficiently and economically removing a sulfur compound in a produced gas at a high temperature. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a first embodiment showing the apparatus configuration for carrying out the desulfurization method of the present invention, and FIG. 2 is an AA ′ of FIG.
Sectional view, Fig. 3 is a characteristic diagram showing the reaction rate of CaO, and Fig. 4 is C
FIG. 5 is a characteristic diagram showing the decomposition rate of the OS, FIG. 5 is a block diagram showing a conventional apparatus configuration, FIG. 6 is a schematic diagram showing the second embodiment of the present invention, and FIG. 7 is a graph showing the limestone particle size and the desulfurization rate. FIG. 8 is a characteristic diagram showing the relationship, FIG. 8 and FIG. 9 are characteristic diagrams showing the relationship between the reaction temperature and the desulfurization rate, and FIG. 10 is a block diagram showing another example of the conventional gasification power generation process. 1 ... Gasification furnace, 2 ... Desulfurizing agent supply pipe, 3 ... Steam supply pipe, 4 ... Lime supply pipe, 5 ... O ₂ supply pipe, 6 ... Slag extraction pipe, 7 ... Product gas Outlet pipe.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01D 53/52 53/77

Claims (3)

[Claims] 1. A desulfurization method in a gasification furnace in which a coal fine powder is carried by a stream of oxygen or air for slag gasification, wherein the coal fine powder and oxygen or air are supplied to a lower portion of the gasification furnace and at the same time, The desulfurizing agent and water vapor are simultaneously supplied to the empty tower section of the upper part of the gasification furnace, and the desulfurizing agent of the fine powder is tangential to the peripheral surface of the gasification furnace or in the horizontal direction of the gasification furnace. The method for desulfurization in a gasification furnace is characterized in that the gas is supplied downwardly to the gasification furnace. 2. The desulfurization method in a gasification furnace according to claim 1, wherein the desulfurizing agent for fine powder is fine limestone having a particle size of 30 [μm] or less. 3. A desulfurization method in a gasification furnace according to claim 1 or 2, wherein the fine limestone is supplied as water slurry.