JPH0832894B2 - Spouted bed coal gasifier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a spouted bed coal gasifier, and in particular, it is used for removing sulfur compounds in gas produced by gasifying coal in a spouted bed coal gasification furnace. To a spouted bed coal gasifier effective for treating the treated desulfurization agent.

[Conventional technology]

In recent years, the use of coal as an energy source has been rapidly progressing, and in addition to a method of using coal as a fuel as it is, a technique of using coal as a pollution-free fluid fuel by gasifying and liquefying coal is also expanding. Among these, in Japan, as a technological 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 power generation is mainly advanced. Among them, for the purpose of power generation, in order to improve the gasification efficiency, it is considered that the process of gasifying coal in the spouted bed using oxygen or air and steam and discharging ash as slag is very effective. Has been.

In this spouted bed gasification process, the temperature inside the furnace was set to 1500 ° C.
By doing so, the ash in the coal is melted and discharged from the bottom of the furnace, so the reaction rate of carbon gasification in the coal is very fast and the carbon utilization rate is close to 100%. In the case of spouted bed gasification, it is necessary to raise the temperature of the gasification furnace to discharge the ash in the coal as slag, and considering the combination with gasification power generation, this generated crude gas is kept in a high temperature state. It is important to improve the power generation efficiency by purifying the gas and introducing it to the gas turbine.

When coal is gasified, sulfur in the coal is mainly H ₂ S, and if it is put into a gas turbine as it is, it causes corrosion of turbine blades. Therefore, desulfurization at a high temperature is a major issue.

A conventional gasification power generation flow is shown in FIG. In the spouted bed gasifier 1, the temperature of the generated gas is 1500 ° C. or higher.
The high-temperature gas discharged from the spouted bed gasification furnace 1 enters the heat exchanger 11 to recover heat, and the cyclone 7 removes scattered particles.
The produced gas from which dust has been removed enters the desulfurization tower 17, where
The sulfur compound such as H ₂ S is removed, and the obtained purified gas is sent to the combustor 18, used for power generation by the gas turbine 19, and then discharged through the exhaust gas pipe 20.

If such a method is adopted, since the temperature of the gas entering the gas turbine 19 is high, the power generation efficiency in the gas turbine 19 is high. As the desulfurizing agent, usually, a desulfurizing agent such as limestone, dolomite, zinc oxide and iron oxide is used, and a fixed bed, a fluidized bed or a fusulized bed is generally used as the type of the desulfurizing tower. It is said that a spouted bed using a fine-powder desulfurizing agent is desirable for improving the utilization rate. However, it is essential to efficiently carry out the pollution-free treatment of the reacted desulfurizing agent regardless of whether the fine powder desulfurizing agent or the granular desulfurizing agent is used.

The gasification desulfurization process using granular limestone is based on Esso, Sq.
Various development studies have been carried out at uires, Westinghouse, etc., but none of them have established the process up to the treatment of reacted limestone. In addition,
In Japanese Patent No. 4188, a method is proposed in which a waste desulfurizing agent, such as CaS or FeS, is supplied to the slag forming section and the waste desulfurizing agent is discarded.

[Problems that the invention seeks to achieve]

The desulfurizing agent used to remove the sulfur compounds in the produced gas needs to be treated to be pollution-free.However, this desulfurizing agent becomes a sulfide in a reducing atmosphere, so it must be treated in any form and then discarded. I have to.

When the used desulfurizing agent is supplied to the slagging section of the gasification furnace to solidify the slag, the decomposition rate of the used desulfurizing agent may vary depending on the type of gas used to supply the used desulfurizing agent to the slag forming section. There are different problems.

The object of the present invention is to eliminate the problems of the above-mentioned conventional techniques, and to eliminate the pollution by efficiently dissolving the desulfurizing agent used for removing the sulfur compounds in the produced gas from the gasification furnace into slag. An object of the present invention is to provide a blown-bed coal gasification apparatus that can be gasified.

[Means for solving problems]

The above-mentioned purpose is a reactive desulfurization agent (waste desulfurization agent) generated when desulfurization treatment is performed on the generated gas from the gasification furnace.
Is achieved by providing a line for recycling the reducing gas to the slagging section of the gasification furnace.

[Action]

Since the reactive desulfurizing agent is transported by air by a reducing gas, SO
It is not decomposed into ₂ , and the reactive desulfurization agent enters the slag flowing out of the slagification section and does not scatter to the slagification section, so it should react with oxygen as a gasifying agent supplied to the slagification section. It becomes solid-solved in slag and can be disposed of as a pollution-free substance.

By the way, when the reactive desulfurizing agent, which is a sulfide, is oxidatively decomposed, CaS + 3 / 2O ₂ → CaO + SO ₂ FeS + 3 / 2O ₂ → FeO + SO ₂ , and the sulfide cannot be dissolved in the slag.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a spouted bed coal gasification apparatus of the present invention, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG.
The drawing is a sectional view taken along the line aa 'in FIG.

In a spouted bed coal gasification furnace (hereinafter referred to as a gasification furnace) 1, a desulfurizing agent supply pipe 2 is disposed in the empty tower section A above a reduced diameter portion where the diameter of the furnace is reduced in the vicinity of its middle stage. A slag forming portion B is installed below the reduced diameter portion. A slag tap hole 21 is provided in the slag forming portion B, and the slag tap hole 21
Below is a cooling section in which the cooling water 16 accumulates.

The slag forming section B located above the slag tuff hole 21.
A gasifying agent supply pipe 3 is provided inside, and a coal supplying pipe 4 is provided below the gasifying agent supply pipe 3.

A line for extracting generated gas 6 from the gasification furnace 1 is provided with a first cyclone 7, a second cyclone 8 and a dust remover, respectively.
12 are installed in sequence. The char supply pipe 9 from the first cyclone 7 is connected to the gasification furnace 1 and
The supply port in is disposed at a position corresponding to the supply port of the gasifying agent supply pipe 8. The purified gas pipe 14 from the deduster 12 is branched, the control valve 13 and the compressor 22 are arranged in the middle of the branched pipe, and the reactive desulfurizing agent supply pipe 10 from the second cyclone 8 is connected to this branched pipe. Has been done.
Therefore, the purified gas from the deduster 12 introduces the reactive desulfurizing agent collected by the second cyclone 8 into the slagging section B of the gasification furnace 1.

As shown in FIGS. 2 and 3, the reactive desulfurization agent supply pipe 10 is located on the lower side of the furnace in the slagging section than any of the gasifying agent supply pipe 3, coal supply pipe 4 and char supply pipe 9. It is arranged almost tangential to the inner wall of the furnace.

Next, the operation and effect of the spouted bed coal gasification device configured as described above will be described.

Fine coal to be gasified is supplied from the coal supply pipe 4 to the gasification furnace 1
Oxygen or air as a gasifying agent is supplied to the lower slagging section B, and at the same time, is supplied from the gasifying agent supply pipe 3 to the slagging section B. Here, the amount of oxygen in the gasifying agent is adjusted so that the amount of coal particles is smaller than the theoretical combustion oxygen amount.

In the gasification furnace 1, coal is gasified into H ₂ and CO
The generating the H ₂ S is a harmful component and product gas whose main.
Also, the ash in the coal is melted to form the slag 15 and the slag extraction pipe 5
Is discharged from the system.

On the other hand, the empty column portion A of the gasification furnace 1 contains a sulfur compound.
In order to remove H ₂ S, a desulfurizing agent supply pipe 2 supplies a fine desulfurizing agent such as limestone, ZnO, and dolomite 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) The produced gas desulfurized in the gasification furnace 1 passes through the produced gas extraction pipe 6 and enters the first cyclone 7, where unreacted char is mainly separated. The unreacted char is recycled to the gasification furnace 1 through the char supply pipe 9. The produced gas that has exited from the second cyclone 7 further enters into the second cyclone 8 and the fine powder desulfurizing agent that has mainly reacted is separated. The produced gas leaving the second cyclone 8 enters the heat exchanger 11 and is cooled, then the dust is completely removed by the dust remover 12, and the purified gas pipe 14 sends it to a gas turbine (not shown).

On the other hand, the reactive desulfurizing agent collected by the second cyclone 8 is
It is recycled from the reactive desulfurizing agent supply pipe 10 to the slag forming section B. A purified gas containing H ₂ and CO as main components is used as the transport gas for the reacted desulfurizing agent, and the amount thereof is adjusted by the control valve 13 and sent to the slag forming section B5 by the compressor 22.

By such a method, the reactive desulfurizing agent that has become a sulfide is transported by a reducing gas (purified gas containing H ₂ and CO as main components) and enters the gasification furnace 1, so that it is decomposed into SO ₂ gas. Without being supplied to the gasification furnace 1. In the slagging section B of the gasification furnace 1, the supply port of the reactive desulfurization agent supply pipe 10 is installed below the supply ports of the gasifying agent supply pipe 3, the coal supply pipe 4 and the char supply pipe 9. Therefore, oxygen as a gasifying agent supplied to the slag-forming section B immediately reacts with coal and char. Therefore, the reactive desulfurizing agent supplied to the slag forming section B enters the slag 15 without reacting with oxygen to decompose into SO ₂ gas.

In this case, as shown in FIG. 3, the reactive desulfurization agent is introduced tangentially to the outflow slag 15 flowing down along the inner wall of the furnace, so that it smoothly enters the outflow slag 15,
It is solid-soluted in the slag without being scattered from the outflow slag 15 to the space part of the slag forming part B. The outflowing slag 15 containing the reactive desulfurizing agent is sulphated into the cooling water 16 in the lower part of the gasification furnace 1 through the slag stub hole 21 and is discharged from the slag extraction pipe 5 to the outside of the system. Therefore, the reactive desulfurization agent can be discarded as a non-polluting substance.

FIG. 4 is a schematic configuration diagram showing another embodiment of the spouted bed coal gasification apparatus according to the present invention. In the spouted bed coal gasifier shown in FIG. 4, an oxidation tower 23 is installed in the middle of the reactive desulfurizing agent supply pipe 10 for returning the reactive desulfurizing agent from the second cyclone 8 to the slagging section B of the gasification furnace 1. The other structure is substantially the same as that of the embodiment shown in FIG.

In the spouted bed coal gasifier shown in FIG. 4, the reactive desulfurizing agent collected in the second cyclone 8 is converted into a sulfuric acid compound in the oxidation tower 23 and recycled to the slag formation section B. When the reactive desulfurizing agent is CaS or FeS, it is converted into a sulfuric acid compound by the following reaction formula.

CaS + 2O ₂ → CaSO ₄ (5) FeS + 2O ₂ → FeSO ₄ (6) Such a sulfuric acid compound has a melting point of 500 compared to sulfides.
~ 800 ° C lower. Therefore, the sulfuric acid compound has the effect of lowering the melting point of ash by dissolving in the outflow slag,
Smooth outflow of slag. Therefore, this example is particularly effective when using coal having a high melting point of ash.

FIG. 5 is a schematic configuration diagram showing still another embodiment of the spouted bed coal gasification apparatus according to the present invention. In FIG. 5, the desulfurizing agent supply pipe 2 for the empty column portion A of the gasification furnace 1 is omitted, and the dedusting tower 12 is provided on the production gas line from the gasification furnace 1 on the downstream side of the first cyclone 7. Upstream of the desulfurization tower
24 are installed.

In the spouted bed coal gasifier shown in FIG. 5, the desulfurization tower 24 is supplied with the granular desulfurization agent, and H ₂ S in the produced gas is removed by the desulfurization reaction by the granular desulfurization agent. The desulfurizing agent reacted here is transported by air flow in the reaction desulfurizing agent supply pipe 10 by a part of the purified gas from the dedusting tower 12 and recycled to the slag forming section B. In this embodiment, since the desulfurization tower 23 is installed outside the gasification furnace, the temperature of the desulfurization tower 23 can be easily changed and a desulfurizing agent suitable for the reaction temperature can be selected.

FIG. 6 shows an O ₂ concentration distribution in the column height direction in the slag forming furnace B having an inner diameter of 200φ under the condition of coal / O ₂ ratio: 0.54. O ₂ concentration is O ₂ supply part (supply port of gasifying agent supply pipe 3)
Is the highest in the tower and gradually decreases in the tower height direction. However, the O ₂ concentration is zero below the coal supply part (supply port of the coal supply pipe 4), and even if a reactive desulfurizing agent is supplied to this part, it is in a reducing atmosphere and will not be decomposed into SO ₂ gas. .

FIG. 7 shows the results of examining the S solid solution ratio of the desulfurizing agent in the reaction tube of the external heat type heater by raising the temperature to the slagging temperature, supplying the coal ash and the reactive desulfurizing agent, and changing the atmosphere gas. It is a graph. In the oxidizing atmosphere containing O ₂ , the S solution rate becomes zero because the reactive desulfurization agent decomposes into SO ₂ , but in the N ₂ gas in the neutral atmosphere, the S solution rate is 55%, and the reducing atmosphere of CO + N ₂ gas Then, it can be seen that the S solution rate still rises to 90%. Therefore, when the waste desulfurizing agent (reactive desulfurizing agent) is solid-solved in the slag, it is important to maintain the atmosphere gas as a reducing gas gas.

In this way, the sulfide, which is a waste desulfurizing agent, can be efficiently solid-solved in the slag. There is no restriction on the sulfide as the waste desulfurizing agent supplied to the slag forming section B, but sulfides such as limestone, dolomite, ZnO and iron oxide are particularly effective.

〔The invention's effect〕

As described above, according to the present invention, the reactive desulfurization agent (waste desulfurization agent) generated by desulfurizing the generated gas from the gasification furnace with the desulfurization agent is air-transported by the reducing gas, and is slag of the gasification furnace. Since it is supplied to the solidification section, the reactive desulfurization agent enters the outflow slag and is discharged out of the system as solidified slag without being decomposed into SO ₂ . Therefore, the reactive desulfurizing agent can be treated to be pollution-free.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a spouted bed coal gasifier according to the present invention, and FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a sectional view taken along the line aa ′ in FIG. 2, FIG. 4 is a schematic configuration diagram showing another embodiment of the spouted bed coal gasification apparatus according to the present invention, and FIG. 5 is the present invention. FIG. 6 is a schematic configuration diagram showing still another embodiment of the spouted bed coal gasification apparatus according to the present invention, FIG. 6 is a graph showing the O ₂ concentration distribution in the gasification furnace, and FIG. Fig. 8 is a graph showing the S solution solubilization rate according to Fig. 8, and Fig. 8 is a schematic configuration diagram showing a conventional spouted bed coal gasifier. 1 ... Gasification furnace, 2 ... Desulfurization agent supply pipe, 3 ... Gasification agent supply pipe, 4 ... Coal supply pipe, 6 ... Generated gas extraction pipe, 7
...... First cyclone, 8 ...... Second cyclone, 9 ...... Char supply pipe, 10 ...... Reactive desulfurizing agent supply pipe, 12 ...... Dust removal tower,
14 …… Purified gas pipe, 15 …… Outflow slag, 16 …… Cooling water,
17 ... Desulfurization tower, 18 ... Combustor, 19 ... Gas turbine, 20 ... Slag tap hole, 23 ... Oxidation tower, 24 ... Desulfurization tower, A ... Empty tower section, B ... Slag formation section.

Claims (5)

[Claims] 1. A spouted bed coal gas in which coal particles are gasified with oxygen or an oxygen-containing gas that is less than the theoretical combustion oxygen amount, the generated gas is discharged, and the ash in the coal is extracted from the slagging section on the lower side of the gasifier. In the gasification device, a desulfurizing agent supply means for supplying a desulfurizing agent for removing a sulfur compound in the generated gas into the generated gas, and a waste desulfurizing agent used in the desulfurization treatment in the desulfurizing agent supplying means by a reducing gas A desulfurization layer coal gasification apparatus, comprising: a waste desulfurizing agent transportation means for carrying out air current transportation to the slagification section. 2. The spouted bed coal gasifier according to claim 1, wherein the reducing gas is a part of a purified gas obtained by purifying a produced gas. 3. The supply port of the waste desulfurization agent in the slagging section is located below the coal supply port and the gasifying agent supply port in the slagification section. Spouted bed coal gasifier according to the range (1). 4. The supply port of the waste desulfurization agent in the slagging section is provided substantially tangential to the inner wall surface of the gasification furnace. Spouted bed coal gasifier. 5. The waste desulfurizing agent transporting means is provided with an oxidizing device for converting the waste desulfurizing agent into a sulfuric acid compound by oxygen in the middle thereof. The spouted bed coal gasifier according to any one of 4).