JPH01272693A - Method for desulfurizing coat gas and apparatus therefor - Google Patents

Abstract

PURPOSE:To readily recover an unreacted desulfurizing agent, simultaneously reduce amounts of the desulfurizing agent and waste desulfurizing agent and facilitate solidification treatment of slag, by dividing powder contained in desulfurized coal gas, successively collecting and separating powder starting from a group having a large grain diameter. CONSTITUTION:A powdery desulfurizing agent (e.g., CaO) is fed to treat coal gas produced in a jetting stream bed coal gasification oven and powder contained in the resultant desulfurized coal gas is divided into groups in at least 3 stages for each grain diameter and then successively collected and separated starting from the powder of the group having a large grain diameter for each group. For example, in the case of collection and separation in the 3 stages, coal char is collected in a dust collector in the first stage and almost all of the unreacted desulfurizing agent and part of the desulfurization product (e.g., CaS) are collected in the second stage. The desulfurization product and a trace amount of the unreacted desulfurizing agent are collected in the third stage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for desulfurizing coal gas, and more particularly to a desulfurization method and apparatus suitable for effective use of a desulfurizing agent.

[Conventional technology]

Coal gasification power generation plants are being developed in various places that gasify coal to produce coal gas rich in H2 and CO, and after desulfurizing this coal gas, use it as fuel for boilers and gas turbines to generate electricity. . In particular, coal gasification equipment for combined cycle power plants that combine gas turbines and steam turbines is being developed as part of next-generation high-efficiency power plants. In this coal gasification device for a combined power generation plant, the temperature of the generated coal gas is kept as high as possible, and the sulfur compounds (H, S, etc.) in the gas are kept as high as possible.

Desulfurization of C05) is desirable and is an existing technology.

Instead of using liquid absorbent at room temperature.

Research is being conducted on methods for dry desulfurization at high temperatures.

As a method of dry desulfurization at high temperatures, a patent application was filed in 1983.
There is an air bed desulfurization method proposed in No. 282957, in which a fine desulfurization agent is directly sprayed into the generated coal gas to desulfurize while entraining the desulfurization agent in one coal gas flow. In this gas bed desulfurization method, the desulfurization reaction is carried out in a high-speed air stream, so in order to increase the reaction rate as much as possible, a finely powdered desulfurization agent with a large specific surface area is used. In addition, compared to other fixed bed, fluidized bed, and moving bed methods, this method can easily accommodate load fluctuations in the gasifier, and it is also possible to use dolomite-based limestone-based or iron oxide-based fine powder as the desulfurization agent. By incorporating these sulfurized fine powders into the coal ash slag to improve the fluidity of the molten slab and trapping the desulfurization products in the slag, a safe and non-polluting coal gasification device can be created. It can be done.

[Problem that the invention seeks to solve]

However, in order to obtain a high desulfurization rate in the above method, it is necessary to add more than three times the theoretical reaction amount of desulfurization agent to the sulfur compounds in the generated coal gas. There are many things.

This results in an increase in the dust collection load on the wake line and an increase in the amount of dust in the coal gas supplied to the gas turbine.

Furthermore, the containment performance during assimilation and containment of the waste desulfurization agent in the slag after desulfurization has been caused to deteriorate.

At the same time, an excessive amount of desulfurization agent was used, making it not an economical desulfurization method.

An object of the present invention is to provide a coal gas desulfurization method and apparatus that can reduce the amount of desulfurization agent input without reducing desulfurization performance.

[Means to solve the problem]

The above-mentioned problem is to supply a powdered desulfurization agent to the coal gas generated in a spouted bed coal gasifier to desulfurize it, and to collect and separate the powder contained in the desulfurized coal gas. This is achieved by a coal gas desulfurization method in which the particle size of the powder is divided into at least three ranges, and the powder is collected and separated in each step in order from the largest particle size range.

The present invention also includes: A spouted-bed coal gasifier that achieves the above-mentioned problems, a desulfurizing agent supply path connected to the gasifier and supplying a desulfurizing agent, and a coal gas flow path connected to the gasifier;
A device is installed in the coal gas flow path to collect and collect powder in the coal gas.
In a coal gas desulfurization apparatus comprising a separating dust collector, the dust collector comprises at least three dust collectors each having a different particle size range of the powder to be collected, The present invention also provides a coal gas desulfurization apparatus in which the dust collectors having larger particle sizes are disposed closer to the gasifier and are connected in series to carry out the desulfurization method.

[Operation] The coal gas generated in the spouted bed coal gasifier flows into the dust collector together with the coal char generated from the coal (pulverized coal) and the charged pulverized desulfurizing agent.

The particle size of coal char varies somewhat depending on the coal gasification conditions, but in general, the average particle size is about 15 to 20 μm and 50 to 6 μm.
Contains 0% by weight of carbon.

In addition, the desulfurizing agent to be charged is a fine powder of 300 mesh anda with an average particle size of 8 to 9 μm, and at the stage of flowing into the dust collector, the desulfurizing agent has completed the desulfurization reaction (for example,
If it is aO, it is a mixture of CaS) and a substance undergoing a desulfurization reaction.

Since the dust collector with a larger particle size to collect is placed closer to the gasifier, the first stage dust collector 5 is placed closest to the gasifier. In the vessel.

Coal char in the largest particle size group is collected. The desulfurizing agent has a smaller particle size than the coal char, and passes through the first stage dust collector without being collected.

The coal gas that has passed through the first stage dust collector is collected in the second stage J1i.
Almost all of the desulfurization agent that has flowed into lpPl and for which the desulfurization reaction has not been completed and a portion of the desulfurization products are collected.

The coal gas that has passed through the second-stage dust collector flows into the third-stage dust collector, where the powder remaining in the coal gas is collected.

The powder collected by the third-stage precipitator is mostly desulfurization products (eg, Ca S ), and contains a very small amount of unreacted desulfurization agent.

The desulfurization reaction progresses while H and S in the coal gas react with the powdered desulfurization agent (e.g. C&0) to produce desulfurization products (e.g. Ca5), but this reaction occurs outside the powdered desulfurization agent. (
Since the desulfurization agent progresses from the surface toward the inside (center side), the larger the particle size of the desulfurization agent, the more unreacted desulfurization agent it contains.

Conversely, the smaller the particle size, the faster the reaction is completed and a desulfurization product is produced. For this reason, most of the powder in the second size group collected by the second stage dust collector contains unreacted desulfurization agent for which the desulfurization reaction has not completely completed, and The powder of the size group collected by the stage dust collector becomes a desulfurization product that has completed the desulfurization reaction.

〔Example〕

H2s when using powdered desulfurization agent, e.g. CaO,
As shown in FIG. 3, the reaction with cos starts from the surface of the CaO particles and gradually progresses to the center of the C&O particles. For this reason, in C&O with a small particle size, the desulfurization reaction progresses to the center relatively quickly, whereas in the case of a large particle size, even if the reaction has finished in the outer shell, there is still unreacted C&O in the center.
&○ remains. Further, as mentioned above, the average particle size of the coal char is about 15 to 20 μm, and the average particle size of the desulfurizing agent to be added is 8 to 9 μm. Furthermore, the specific gravity of C a S, which is a desulfurization product, is 2.5, and the specific gravity of Ca O is 3.5.
Less than 3.

As the desulfurizing agent, in addition to Cl0 (quicklime), limestone, dolomite, and fine powders such as zinc oxide and iron oxide can also be used. The desulfurization reaction of a desulfurization agent made of limestone or CaO is expressed by the following equation.

CaC0,+H1SnCaS+CO2+H20-(1)
CaO+H, 54CaS+H20...(2) CaO
"CO5-4CaS" COt...
(3) Figure 2 is an example showing the frequency distribution of particle sizes for each type of powder and their totals when one coal gas flows into the dust collector together with powder.

The present invention relates to coal char in the produced coal gas.

We analyzed the unreacted desulfurization agent (the desulfurization agent that has not completed the desulfurization reaction, the same applies hereinafter) and the reacted desulfurization agent, focusing on the differences in particle size and specific gravity, as well as the form of the reaction progress of the desulfurization agent, as described above. The coal gas is separated from the coal gas and each is recycled to the most suitable location.

An embodiment in which the present invention is applied to a spouted bed coal gasifier will be described with reference to FIG. The illustrated coal gasifier includes a spouted bed coal gasifier 1, a coal gas passage 10 connected to the top of the gasifier, and a front-stage dust collector connected to the coal gas passage 10. a first cyclone 2, a heat recovery heat exchanger 3 connected to the first cyclone 2, and a second cyclone 4, which is a second stage dust collector connected to the heat exchanger 3.

The main equipment includes a Haku filter 5 which is a third stage dust collector connected to the second cyclone 4.

The gasification furnace 1 has a slag generation section 18. Gasification section 6. A desulfurizing agent input section 7 is provided at the top, and a pulverized coal supply line 8 and a gas and other agent supply line 9 are provided in the gasification section 6.
A desulfurizing agent supply path 12 is connected to the desulfurizing agent input section 7. Further, a coal char recycling line 11 that communicates the bottom of the first cyclone 2 and the gasification section 6 is provided.
．． A recovered desulfurizing agent recycling line 13 that connects the bottom of the second cyclone 4 and the desulfurizing agent input section 7. A reactive desulfurization agent line 14 is provided that communicates the bottom of the bag filter 5 with the gasification section 6. The first cyclone 2, the second cyclone 4, and the bag filter 5 form a dust collector, and the dust collector, the gasifier 1, the desulfurizing agent supply path 12, and the coal gas flow path 1o form a desulfurization device. is formed.

Pulverized coal, which is a raw material, is supplied to the gasification section 6 of the coal gasifier 1 through a pulverized coal supply line 8, and a gasifying agent, which is a gas containing oxygen (oxygen or air), is gasified through a gas and other agent supply line 9. The coal gas is supplied to the gasification section 6, where it undergoes a partial oxidation reaction to form a high-temperature gasification section, and a coal gas rich in H2 and CO is produced. This coal gas contains H, S, and CO8 as a result of the conversion of the sulfur content in the coal.The ash content in the coal is melted in the gasification section 6 and flows down to the slag generation section 18, forming a slag. The slag 17 is discharged from the generation section 18 to the outside of the system. On the other hand, the coal gas produced.

It ascends through the gasification furnace 1 and reaches the desulfurization agent input section 7, where powdered desulfurization agent is supplied through the desulfurization agent supply path 12, and the sulfide in the coal gas and the desulfurization agent undergo a contact reaction. .

The coal gas into which powdered desulfurization agent has been added in the desulfurization agent input section 7 is
The coal char generated from the coal and the desulfurization agent enter the first cyclone 2 through the coal gas flow path 10. usually,
The temperature of the coal gas at the outlet of the gasifier 1 is 800~
The temperature is 1000°C.

In the first cyclone 2, coal char with a large particle size is separated from the coal gas, and is returned to the gasification section 6 of the coal gasification furnace 1 via the coal char recycling line t1 by the carrier gas 16, where it is gasified. Helps improve efficiency.

The coal gas from which the coal char has been separated passes through the heat recovery heat exchanger 3 while entrained with the desulfurizing agent, and is cooled to below about 500°C, reducing its volume by 1 and entering the second cyclone 4. The volume is reduced and the cyclone diameter can be made smaller.

The second cyclone 4 is a high-performance multi-cyclone (a structure in which multiple cyclones with small inner cylinder diameters are combined in parallel to efficiently collect fine particles) in order to collect desulfurizing agents with a particle size of 10 μm or less ) has been adopted. In this second cyclone 4, powder mainly containing unreacted desulfurization agent and partially containing desulfurization products is collected, and the collected powder is
The desulfurizing agent is recycled by the carrier gas 6 to the desulfurizing agent input section 7 via the recovered desulfurizing agent recycling line 13, and unreacted CaO is used again as a desulfurizing agent. Fine powder contained in the coal gas that has passed through the second cyclone for four minutes is collected by a bag filter 5 connected to the second cyclone. The coal gas that has passed through the bag filter 5 is sent to a consumer as purified gas.

Most of the powder collected by the bag filter 5 is the desulfurizing agent (CaS) that has completed the desulfurization reaction, and some unreacted desulfurizing agent (CaO) is also included, but the amount is extremely small. These are blown into the molten coal ash slag 17 flowing through the reactive desulfurization agent line to the slag generation section 18 by the carrier gas 16, and then cooled and solidified into the slab. The powder collected in the second cyclone 4, which is a high-performance multi-cyclone, and the A)f filter 5, which is a third-stage dust collector, is mainly collected in the second cyclone 4 by unreacted desulfurizing agent CaO, and third-stage dust collectors. What mainly becomes Ca S in the filter 5 is H,
Since the desulfurization reaction between S and spherical C&O proceeds from the outside of CaO, the larger the particle size, the more unreacted CaO it contains.
The sooner the situation becomes <CaS, and the more
Due to the difference in specific gravity between S and CaO, -CaS
This is because most of the dust that passes through the second-stage high-performance cyclone becomes CaS, making it difficult to collect.

Figure 2 shows the particle size range of powder collected by each dust collector. In the first cyclone 2, powder having a particle size of approximately 10 μm or more is collected, and most of this is coal char. The powder collected in the second cyclone 4 is powder whose main component is CaO, which is an unreacted desulfurizing agent. The powder collected by the second cyclone 4, in which a large proportion of the reactive CaO remains, is re-injected into the desulfurizing agent input section 7 of the gasifier 1 as described above. At that time, the powders collide with each other and are pulverized into fine particles, resulting in H2S.

Desulfurization reaction progresses through contact with CO8, resulting in CaS. The desulfurizing agent large enough to pass through the second cyclone 4 is C a S that has almost completed the desulfurization reaction.

As described above, according to this embodiment, by appropriately separating unreacted desulfurizing agent and reinjecting it into the gasifier, it is possible to reduce the amount of desulfurizing agent without reducing the desulfurization rate. Fourth
In the figure, fine powder limestone with an average particle size of 10 μm is
．． 4%, 824%, and residual H2 in a reducing atmosphere at 1100°C.

The results of a desulfurization reaction performed with a contact time of 3 seconds are shown. Case 1
This is the case where the new desulfurization agent was added in an amount three times the amount of sulfur in terms of molar ratio, and a desulfurization rate of about 70% was obtained. Case 2 is a case where 50% of the desulfurization agent used in Case 1 is used in addition to the same amount of new desulfurization agent as in Case 1, and the desulfurization rate is improved by about 15%. This shows that the desulfurization performance can be improved by reusing the desulfurization agent for desulfurization. In case 3, the amount of new desulfurization agent is doubled in terms of molar ratio to the amount of sulfur in the target gas, and half of the amount of desulfurization agent used in case 1 is added and used again. In this case, a desulfurization rate equivalent to that in case] was obtained. In case 3, compared to case 1, it was possible to reduce the amount of new desulfurization agent to 2/3 and maintain the same desulfurization rate.

FIG. 5 shows another embodiment of the present invention. In this embodiment, the first cyclone and second cyclone of the above embodiment are integrated to form a cyclone 4 installed downstream of the heat recovery heat exchanger 3. Coal char and unreacted desulfurization agent are collected at the same time, and both the collected coal char and unreacted desulfurization agent are passed through the recovered coal desulfurization agent recycling line by a carrier gas 1G, and then transferred to the gasifier 1. The gas is refluxed to the gasification section. Compared to the case where coal char and unreacted desulfurization agent are separated, collected, and refluxed, the effect of reducing the desulfurization agent is smaller, but it is possible to reuse the unreacted desulfurization agent, reducing equipment costs. Is possible. In this embodiment, the reflux light of the collected powder must be at the coal input section in order to gasify the coal char, and the pulverized coal supply line 8 is suitable.

[Results of the invention]

According to the present invention, the powder entrained in the generated coal gas is divided into groups of different sizes and collected in order from the largest group, making it possible to reuse unreacted desulfurization agent. This has the effect of reducing the usage range of the desulfurization agent, reducing the amount of waste desulfurization agent (desulfurization product) to be treated, and facilitating treatment by slag assimilation.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a spouted bed coal gasifier to which the embodiment of this description is applied, and FIG. 2 shows the particle size frequency distribution of each type of powder entrained in the generated coal gas, This is a graph showing the particle size range collected by each dust collector, Figure 3 is an explanatory diagram showing the progress state of the desulfurization reaction, and Figure 4 is a graph showing the effect of reusing the desulfurization agent. FIG. 5 is a system diagram showing another embodiment to which the present invention is applied, and FIG. 6 is a system diagram showing an example of the prior art. 1... Entrained bed coal gasifier, 2... Dust collector (first cyclone), 4... Dust collector (second cyclone), 5...
... Dust collector (bag filter), 10... Coal gas flow path. 12...Desulfurizing agent supply route agent Patent attorney Tatsu Unuma No. 1 - Uen 1
)

Claims (1)

[Claims] 1. Supplying a powdered desulfurizing agent to the coal gas generated in the spouted bed coal gasifier to desulfurize it, and collecting and separating the powder contained in the desulfurized coal gas. In a coal gas desulfurization method, the particle size of the powder is divided into at least three ranges, and the powder is collected and collected at each stage in order from the largest particle size range.
A method for desulfurizing coal gas characterized by separating it. 2. A spouted bed coal gasification furnace, a desulfurization agent supply path connected to the gasification furnace and supplying a desulfurization agent, a coal gas flow path connected to the gasification furnace, and a desulfurization agent supply path connected to the gasification furnace and provided in the coal gas flow path. In the coal gas desulfurization equipment, the dust collector includes at least three collectors each having a different particle size range of the powder to be collected. 1. A coal gas desulfurization device comprising a dust collector, the dust collector having a larger particle size of collected powder being disposed closer to the gasification furnace and connected to each other in series.