JPS62260889A - Method of desulfurization in gasifying oven - Google Patents

Abstract

PURPOSE:To efficiently and economically desulfurize a coal gas at high temp., by feeding pulverized coal together with a powdery desulfurizing agent and moisture into a gasifying oven in which slag gasification of the coal with oxygen or air is conducted. CONSTITUTION:Gasification of coal is conducted by feeding pulverized coal through a supply pipe 4 into the slag zone arranged in the lower portion of a gasifying oven 1 in which slag gasification of the coal is conducted and feeding a gasifying agent, i.e., oxygen or air through an oxygen supply pipe, thereby obtaining a product gas contg. H2S and COS. The coal ash is molten and discharged through an extraction pipe 6 as a slag. Next, a pulverized desulfurizing agent such as CaO, ZnO, dolomite, FeO, etc., is fed through a supply pipe 2 arranged at the upper cavity portion of the gasifying oven 1, and moisture, i.e. steam, through a supply pipe 3, in the tangential direction against the circumference of the gasifying oven 1, thereby removing H2S and COS from the product gas. The purified gas thus obtd. is fed in a high-temp. state without cooling through an outlet pipe 7 into a gas turbine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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 progressed rapidly.
Techniques to burn coal directly as fuel, or to gasify and liquefy coal to use it as non-polluting fluid fuel, are also expanding. Under these circumstances, in Japan, the development of technologies for gasifying coal is mainly progressing in the development of high-calorie gasification processes for obtaining raw material gas or fuel gas, and low-calorie gasification processes for the purpose of power generation.

Recently, progress has been made in the development of a process in which coal is gasified into slag in a spouted bed using oxygen or air and steam, and the ash is discharged as slag.

In this slag gasification process, the temperature inside the furnace is set to 1.50
By heating the temperature above 0℃, the ash in the coal is melted and discharged from the bottom of the furnace, so the gasification reaction rate of the carbon in the coal is extremely fast, and the carbon utilization rate is close to 100%.
For slag gasification.

Because coal is gasified at high temperature and pressure, the gas produced is rich in carbon monoxide and hydrogen. When considering the combination with gasification power generation, it is important to treat the generated crude gas while it is still in a high temperature state.When coal is gasified, the sulfur in the coal is mainly H, 5. , desulfurization at high temperatures becomes a major challenge.

A first example of a conventional gasification power generation flow is shown in FIG. The generated gas at the outlet of the gasifier 1 contains dust, H2S and C.
Contains O8 sulfur compounds as harmful components. The high-temperature gas leaving the gasifier 1 first enters a high-temperature dust remover 8 to remove dust, and then enters a desulfurizer 9. H in the desulfurization tower 9,
Harmful components such as S are removed at high temperature, and the purified gas is supplied to the gas turbine 11 via the comparator 1o.

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 becomes high. Desulfurization agents such as limestone, dolomite, zinc oxide, and iron oxide are usually used as the desulfurization agent, and the type of desulfurization tower 9 is generally a fixed bed, a fluidized bed, or a spouted bed. A fluidized bed or a spouted bed is generally used, but a spouted bed using a finely powdered desulfurizing agent is preferable in order to improve the utilization rate of the desulfurizing agent.

Next, a second example is shown in FIG. In the slag gasification furnace 1, since the temperature of the produced gas is 1500° C. or higher, a heat exchanger tube 12 is disposed in the empty column inside the furnace 1 to recover heat from the high-temperature gas. The high temperature gas leaving the gasifier 1 further enters a heat exchanger 14 for heat recovery, and a cyclone 15 removes scattered particles. The generated gas from which dust has been removed enters the desulfurization tower 9 to remove sulfur compounds from the H2S tower, and the purified gas is sent to the comparator 1o and supplied to the gas turbine 11. 16 is an exhaust gas pipe.

[Problem that the invention seeks to solve]

However, as shown in FIGS. 5 and 10, the conventional process requires a desulfurization tower 9 outside the gasifier 1, and it is necessary to simplify the process and reduce the equipment cost.

However, in the example shown in FIG.
Even if a fine powder desulfurization agent is supplied to the reactor, the reaction conditions necessary for desulfurization cannot be achieved, and since the desulfurization agent is entrained in the gas flow, the reaction rate of the desulfurization agent is not very good. Furthermore, since CO8, which is another sulfur compound, does not react with the desulfurizing agent, it is necessary to react and remove CO8 in order to improve the desulfurization rate on the gas side.

Furthermore, according to the example shown in FIG. 10, the gasification furnace becomes a complex gasification furnace in which heat transfer tubes 12 are arranged in the empty tower part of the gasification furnace 1 to cool the high-temperature gas, and a high-temperature desulfurization tower 9 is installed in addition to the gasification furnace. 1 force is required. For this reason, entrain desulfurization in which finely divided limestone is injected into the cavity is considered, but it has the following problems.

(1) In entrain desulfurization of fine limestone, when sulfides are formed on the surface of the desulfurization agent, solid-phase diffusion becomes rate-limiting for the desulfurization reaction, and the reaction rate of the desulfurization agent decreases.

(2) In an entrain type reactor, the desulfurization reaction proceeds while the desulfurization agent, pulverized limestone, is entrained in the produced gas, resulting in a large gas film resistance, and the desulfurization rate will decrease unless the contact efficiency between the desulfurization agent and the gas is improved. becomes lower.

(3) Since the pressure of the gasifier is usually as high as 20 to 3 Qatm, it is difficult to control the supply amount of pulverized limestone when a gas transportation method is adopted.

As mentioned above, when the coal slag gasification process is applied to power generation, sulfur compounds in the generated gas are efficiently removed at high temperatures, increasing the power generation efficiency of the gas turbine, and at the same time simplifying the process as much as possible to reduce equipment costs. The problem to be solved is to do so.

An object of the present invention is to provide a desulfurization method that can efficiently and economically remove sulfur compounds from produced gas at high temperatures in a coal slag gasification process.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a gasifier in which fine coal powder is gasified into slag gas by air conveying it with oxygen or air, and a fine powder desulfurizing agent and water are simultaneously supplied to the empty column at the upper part of the gasifier. It is characterized by:

[Effect]

According to the configuration of the present invention, by simultaneously supplying the fine powder desulfurizing agent and moisture to the empty column of the coal slag gasification furnace, the optimum reaction temperature is maintained, and at the same time H, S and CoS
can be removed at the same time, improving air contact and improving the utilization rate of the desulfurizing agent.

〔Example〕

Next, nine embodiments of the present invention will be described based on the drawings.

Star 1 Loss of Storm ■ The first embodiment of the present invention is shown in No. 11ii. The process consists of a gasification furnace 1 for gasifying coal slag and equipment attached thereto. Pulverized coal to be gasified is supplied from a coal supply pipe 4 to the slag section at the lower part of the gasifier 1, and at the same time, oxygen or air as a gasifying agent is supplied from a 0□ supply pipe 5. There, the coal is turned into silica and generates gas and harmful components H2S and CO8. Further, 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 is installed in the upper column of the gasification furnace 1 to remove sulfur compounds such as H, S, and CO8, and a desulfurizing agent supply pipe 2 is provided to remove sulfur compounds such as H, S, and CO8.

Supply ZnO, dolomite, FeO, etc. The direction in which the desulfurizing agent is supplied to the nozzle is tangential to the surface of the gasifier 1, as indicated by the arrow in FIG. 2, and the desulfurizing particles come into countercurrent contact with the gas due to the swirling movement. This improves the solid-gas contact efficiency and greatly improves the utilization rate of the desulfurizing agent.

The reaction formula when CaO is used as a desulfurizing agent is as follows.

Ca O+H, S4Ca O+H, 0 In addition, a steam supply pipe 3 is provided in the empty column part 1 of the gasifier at a position substantially similar to the desulfurization agent supply pipe 2.

Steam is also supplied at the same time. This steam plays an important role in controlling the temperature of the empty column within the optimal temperature range for the desulfurization reaction, and at the same time converting CO8, a sulfur compound that does not react with the desulfurization agent, into H and S. The reaction formula is as follows.・CO8+H2O4H,S+H,0 By the above method, the sulfur compounds in the generated gas are almost completely removed, and the purified gas is sent from the generated gas outlet pipe 7 to the gas turbine 11 (see Figure 5) while remaining at high temperature. Can be sent.

FIG. 3 shows the relationship between the reaction temperature of the CaO desulfurization agent.

The reaction rate of Ca 2 O reaches its maximum at a reaction temperature of around 930° C., and therefore, regardless of whether the temperature is raised or lowered, the reaction rate tends to decrease. - Figure 4 shows the reaction rate of COS to H and S, which shows the relationship between the decomposition rate for CO8 and the reaction temperature. ・If the temperature is 820°C or higher, the decomposition rate of CoS becomes constant and is 99% or more. It is found that it decomposes into H2S.

By using the present invention in the above-mentioned method, it becomes possible to efficiently remove sulfur compounds at high temperatures. Furthermore, by supplying steam to the empty column, unreacted char can be simultaneously gasified.

In this way, this embodiment maintains the optimum reaction temperature and at the same time maintains the H,
This method simultaneously removes S and CO8, improves solid-gas contact, and improves the utilization rate of the desulfurizing agent.

Various high-temperature desulfurization processes have been carried out in the fluidized bed or fixed bed at 400 to 900°C. There is no other way to do this. -Σ''j11 However, a second embodiment is shown in FIGS. 6 to 9.

In this second embodiment, (1) the particle size of the finely divided limestone to be supplied is 30
µm or less, to minimize the diffusion resistance in the solid phase, and by directing the nozzle of the pulverized limestone supplied to the gasifier tower downwards from the horizontal to reduce the film resistance between gas and particles, the desulfurization rate is improved. In addition, by supplying pulverized limestone as a water slurry, the amount of pulverized limestone supplied can be easily controlled.

The reason for doing the above is as follows.

The particle size of the pulverized limestone supplied to the gasifier tower is set to 30 μm.
If the reaction rate is below, the rate of the desulfurization reaction on the particle side will be determined by the reaction within the solid phase, and the theoretical reaction rate will be 95% or more. By the way,
Usually, the reaction thickness of sulfide is said to be 10 μm, and if the particle size is 30 μm, the theoretical reaction rate is [1-(1/3)3]X100=97.3%.

That is, even if sulfide, which acts as 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 particles, resulting in a high 1 reaction rate.

Furthermore, by directing the nozzle of the pulverized limestone supplied to the gasifier downward, the limestone moves downward due to inertial force. On the other hand, since the generated gas flows from the bottom to the top of the gasifier, it comes into countercurrent contact with the limestone, so the relative velocity with the particles increases. This reduces the gas film resistance and increases the H, S reaction rate on the gas side.

By using a water slurry to supply limestone, the supply method is easy and the cost is low because a slurry pump can be used.

Furthermore, when water is supplied as a water slurry, water rapidly evaporates in the gasifier, particles are scattered, and a turbulent flow is created, which improves the contact efficiency and increases the reaction rate. Furthermore, the high-temperature generated gas is cooled by the latent heat of vaporization of water, and there is no need to install heat transfer tubes in the furnace, so the structure of the gasifier becomes simple.

Details of the second embodiment described above are shown in FIG. This process consists of a gasifier 1 for converting coal into slag gas and its attached equipment. Supplying pulverized coal to be gasified to the slag gasification section B at the lower part of the coal supply pipe 4 gasifier 1,
At the same time, oxygen or air as a gasifying agent is supplied to the oxygen supply pipe 5.
Supplied from.

There, the coal is gasified to produce gas and the harmful component H.
, S is generated. Further, the ash in the coal is melted and discharged as slag to the outside of the system through the slag discharge pipe 6.

On the other hand, in the empty column A of the gasifier 1, H, which is a sulfur compound, is
, S, a desulfurizing agent supply pipe 2 is provided, and a fine powder desulfurizing agent 1 such as limestone, ZnO, dolomite, iron oxide, etc. is supplied. These desulfurization reactions are as shown below.

CaC0,+H,S→CaS+H,O+CO,"'(1
)Ca○1H,S −+CaS+H20′ −(
2) ZnO+H2S -*ZnS+H,O-(3)F
eO+H,S −+FeS+H,O−(4) Sky tower part A
In this embodiment, the particle size of the desulfurizing agent supplied to the tube is 30 μm or less, the direction of the supply nozzle is downward from horizontal, and the desulfurizing agent is supplied as a water slurry.

FIG. 7 shows the experimental results of the limestone particle size and the desulfurization rate on the particle side using a small experimental device. In a range where the limestone particle size is smaller than →30 μm, the desulfurization reaction on the particle side is rate-determined by the reaction within the solid phase, and a desulfurization rate of 90% or more is obtained. However, as the particle size increases, sulfides that act as reaction resistance are formed on the surface of the desulfurizing agent, and the desulfurization rate decreases.

Therefore, it is important that the particle size is 30 μm or less.

Figure 8 shows the desulfurization agent supply method horizontally and downwardly.
The results are shown when transporting with two gases. When the desulfurization agent particles are introduced horizontally, the desulfurization agent particles are immediately accompanied by the gas flow and rise inside the reaction tube, so 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 inertia. Since the generated gas flows from the bottom to the top of the gasifier, it comes into countercurrent contact with the desulfurizing agent, increasing its relative velocity with the particles. This reduces the gas film resistance and improves the H2S desulfurization rate on the gas side.
At ℃, more than 90% is obtained.

FIG. 9 shows the experimental results when limestone was transported with a 30% water slurry and N2 gas. When water is supplied as a water slurry, water evaporates rapidly in the gasifier, particles are scattered due to so-called popcorn reduction, and a turbulent flow state is created, which improves the contact efficiency and increases the desulfurization rate compared to N2 gas transport. on the other hand,
As for the supply method, compared to N2 gas transportation, using a water slurry is easier because a slurry i pump can be used, the cost is lower, and the supply amount can be easily controlled.

Furthermore, in the gasifier cavity A, the high-temperature produced gas is cooled by the latent heat of vaporization of water, and if the zero-tube method is adopted, which can suppress the temperature of the produced gas at the exit by controlling the amount of water slurry supplied, Since there is no need to install heat transfer tubes (see FIG. 10) in the tower section, the structure of the gasifier becomes simple and construction costs can be reduced.

As described above, by using this example, it becomes possible to efficiently remove sulfur compounds. In addition to limestone, other fine powder desulfurization agents such as ZrO, dolomite, and iron oxide have similar effects.Furthermore, when supplied as a water slurry, it is possible to simultaneously gasify unreacted char using evaporated steam.

Conventional flow at 400-900℃! Various high-temperature desulfurization processes have been implemented in the PIJ layer or fixed bed, but the
- There is no other method that uses the rain method and supplies a desulfurizing agent to the gasifier to perform gasification and desulfurization at the same time as slag gasification.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an efficient and economical desulfurization method capable of removing sulfur compounds in the produced gas at high temperature in a lime slag gasification process.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a first embodiment showing the configuration of an apparatus for carrying out the desulfurization method of the present invention, and FIG. 2 is an A-A in FIG. 1.
' Cross-sectional view, Figure 3 is a characteristic diagram showing the reaction rate of CaO, Figure 4 is a characteristic diagram showing the reaction rate of CaO.
The figure is a characteristic diagram showing the decomposition rate of CO8, and FIG. 5 is a block diagram showing the configuration of a conventional device. Figure 6 is a schematic diagram showing the second embodiment of the present invention, Figure 7 is a characteristic diagram showing the relationship between limestone particle size and desulfurization rate, and Figures 8 and 9 are diagrams showing the relationship between reaction temperature and desulfurization rate. The characteristic diagram shown in FIG. 10 is a block diagram showing another example of the conventional gasification power generation process. 1... Gasifier. 2...Desulfurizing agent supply pipe. 3... Steam supply pipe, 4... Lime supply pipe, 5... 0□ supply pipe, 6... Slag extraction pipe, 7... Produced gas outlet pipe.

Claims (7)

[Claims] (1) A gasifier that converts coal fines into slag gas by transporting them in a pneumatic flow using oxygen or air, characterized in that a fine powder desulfurizing agent and moisture are simultaneously supplied to an empty tower section in the upper part of the gasifier. desulfurization method. (2) In the desulfurization method according to claim 1,
A desulfurization method in a gasifier characterized in that water is supplied as steam. (3) In the desulfurization method according to claim 1,
A method for desulfurization in a gasifier, characterized in that when CaO is used as the desulfurization agent, the temperature in the empty column is maintained at 780 to 1000°C by the above method. (4) A desulfurization method in a gasification furnace according to claim 1 or 2, wherein the desulfurization agent is supplied in a tangential direction to the circumferential surface of the gasification furnace. (5) A desulfurization method in a gasifier according to claim 1, 3, or 4, wherein the desulfurization agent is pulverized limestone of 30 [μm] or less. (6) In the desulfurization method according to claim 5,
A desulfurization method in a gasifier characterized by oriented the supply pipe of pulverized limestone downward rather than horizontally. (7) A desulfurization method according to claim 4 or 5, characterized in that pulverized limestone is supplied as a water slurry.