KR20140084466A

KR20140084466A - Coal gasification device and method for coal gasification

Info

Publication number: KR20140084466A
Application number: KR1020120153592A
Authority: KR
Inventors: 고대권
Original assignee: 주식회사 포스코; 재단법인 포항산업과학연구원
Priority date: 2012-12-26
Filing date: 2012-12-26
Publication date: 2014-07-07
Also published as: KR101480503B1

Abstract

Provided is a coal gasification device wherein cheap and low-rank powdered coal can be used in a small-sized coal gasifier that is capable of producing a small amount of gas; stable operation is available with relatively less manpower; and tar generation can be minimized. For such, the present invention comprises: a coal supply unit; a gasification unit that gasifies coal supplied from the coal supply unit; and a gas washing unit that washes gas generated in the gasification unit. The gasification unit has an entrained flow bed reactor that is arranged in a lower portion; and a fluidized bed reactor that is arranged on the entrained flow bed reactor.

Description

TECHNICAL FIELD [0001] The present invention relates to a coal gasification apparatus and a coal gasification method,

The present invention relates to a coal gasification apparatus. More particularly, the present invention relates to a small-sized coal gasification apparatus and a coal gasification method which are capable of producing a small amount of gas using low-grade coal.

Generally, most of the coal gasifier used in the industrial field is a high-temperature and high-pressure gasifier used for IGCC (Integrated Gasification and Conveyed Cycle) or chemical production, and the coal is used at a large capacity of 1,000 tons / day or more. These large facilities have high equipment costs and are not used for the production of small quantities of gas.

For production of a small amount of gas, a fixed bed gasifier is widely used as a coal gasifier which produces a small amount of syngas to be used in a steelmaking or drying process.

Although the compact fixed bed gasifier is advantageous in terms of facility cost, it has various drawbacks as follows.

In the fixed-bed gasifier, a large amount of tar is generated. In addition, complicated cleaning equipment is required to treat tar, and if it is not properly treated, strong odor due to tar may be generated.

In addition, there is a problem in that a thermometer can not be installed for measuring the temperature of the reaction zone because the coal is continuously lowered in the internal reaction zone of the high-temperature gasifier. Conventionally, a method of periodically determining the height of the material layer and the height of the reaction region from the surface color of the probe after inserting and removing the probe into the gasifier was used.

However, the conventional structure described above causes a problem that a large number of personnel must participate for operating the gasifier.

Further, when excessive oxygen is supplied to the coal layer and partial melting of the ash occurs, it may become difficult to coagulate after cooling and difficult to discharge the ash. In the prior art, it is necessary to perform the operation of manually kneading the aggregate through the bedding for the purpose of discharging the ash. Therefore, there is a problem that labor and time are excessively consumed.

In addition, in the conventional fixed bed coal gasifier, massive high-calorific coal is required to be used, so that a large amount of raw material costs are required, and the pulverized coal generated during the handling of coal can not be used. Thus, there is a problem that economical efficiency is low.

Accordingly, there is provided a coal gasification apparatus and a coal gasification method which are capable of using low-cost low-grade coal in a small coal gasifier capable of producing a small amount of gas.

The present invention also provides a coal gasification apparatus and a coal gasification method that enable stable operation with less manpower.

The present invention also provides a coal gasification apparatus and a coal gasification method capable of minimizing occurrence of tar to reduce environmental pollution.

This coal gasification apparatus includes a coal supply section, a gasification section for gasifying the coal supplied from the coal supply section, and a gas cleaning section for purifying the gas generated in the gasification section, wherein the gasification section includes a classification layer reactor , And a fluidized bed reactor disposed above the fractionation bed reactor.

The fluidized bed reactor may have an inverted trapezoidal shape in which the diameter decreases as the diameter decreases.

The coal supply unit may include a crusher for crushing coal, a drier for drying crushed coal, and a crusher for crushing dried coal.

The coal supply unit may further include a separator for introducing coal having a relatively large particle size into the fluidized bed reactor and coal having a relatively small particle size into a fractionation bed reactor.

And a boiler installed between the gasification unit and the gas cleaner for recovering waste heat from the high temperature gas produced by the gasification unit.

The gasifier may further include a blower for supplying air into the gasifier, and the gasifier may use air as the oxidizer.

The gasification unit may further include a thermometer installed on an inner wall surface of the fluidized bed reactor or the fractionation bed reactor to detect the reaction temperature.

The gas cleaning unit may include a dust collector that removes particulate matter by having a metallic filter or a filter bag for high temperature, and a scrubber connected to a downstream end of the dust collector to remove sulfide gas.

In this coal gasification method, coal having a relatively large grain size among the supplied coal is charged into a fluidized bed reactor to undergo a fluidized bed reaction, and coal having a relatively small particle size is introduced into a fractionation bed reactor to form a fractionation layer reaction and a fluidized bed reaction And then gasifying the gas.

The coal gasification method may further include recovering waste heat from the high-temperature gas produced through the gasification step.

The gasification step may use air as the oxidizing agent.

The coal supplying step may include crushing the coal, drying the crushed coal, crushing the dried coal, and sorting the crushed coal.

As described above, according to the present embodiment, there is provided a tapered fluidized bed which is operated at a low pressure and uses air as an oxidizer and operates at a low temperature (about 1200 degrees) so as not to melt the ash, By using one gasifier, the following effects are obtained.

It is possible to use coal with a large amount of water and a low calorific value and a low price, thereby improving the economical efficiency of the plant operation.

In addition, since the tar is not generated, the structure of the cleaning equipment for treating the tar can be simplified, so that the facility cost can be lowered and the environmental pollution caused by the tar can be prevented.

Further, by lowering the operating temperature of the lower classification layer reactor, the ash is not melted and the gasification efficiency can be increased.

In addition, by adopting a trapezoidal fluidized bed reactor, it is possible to use coal having various particle sizes and to increase the carbon conversion rate.

1 is a schematic view showing a configuration of a coal gasification apparatus according to the present embodiment.
2 is a schematic flowchart showing the coal gasification process according to the present embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Wherever possible, the same or similar parts are denoted using the same reference numerals in the drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

All terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

FIG. 1 shows the construction of the coal gasification system according to the present embodiment, and FIG. 2 schematically shows a coal gasification process.

As shown, the coal gasification system of the present embodiment includes a coal supply unit 10, a gasification unit 20 for gasifying the coal supplied from the coal supply unit 10, a gas purification unit 20 for purifying the gas generated from the gasification unit 20, And a gas cleaning section 40 for controlling the flow of gas.

The coal supply unit 10 of the present embodiment can use low-cost coal which contains a large amount of water and is low in calorific value and low in price. The coal may be supplied through the process of crushing coal through the coal supply unit, drying the crushed coal, and pulverizing the dried coal.

The coal supply unit 10 includes a crusher 12 for crushing coal so that low-grade coal can be produced as pulverized coal and supplied to the gasification unit 20, a drier 14 for drying crushed coal, And a crusher 16 for crushing the crusher.

Low-grade coal is cheaper per unit calorific value than high-grade coal, and its supply is smooth, resulting in a great economic effect. Conventional gasification apparatuses use expensive fine coal because of the massive amount of coal, so that the cost of raw material is high and the pulverized coal generated during the handling of coal is used up. However, in this embodiment, the cost is low due to the use of low grade coal. And all of the coal including pulverized coal can be used for gasification through the pulverizer.

The coal finally discharged through the crusher 16 is supplied to the gasification unit 20. And is produced as a gas through a gasification process in the gasification section (20).

In this embodiment, the gasification section 20 comprises an entrained bed type 22 disposed at the bottom and a fluidized bed type 24 disposed at the top of the fractionation bed reactor.

In this way, the gasifier 20 is provided with the fractionation layer reactor 22 at the bottom, and the fluidized bed reactor 24 at the top thereof, thereby achieving various operational effects as compared with the conventional small fixed bed gasifier.

The volatile matter and carbon in the coal sprayed as the fine particles in the lower classification layer reactor 22 react with each other to be gasified, and the granular material having a large particle size is discharged to the lower portion of the reactor. The material having a very small particle size is finally discharged to the upper portion through the upper fluidized bed reactor 24 and is collected by the gas cleaning unit 40, which is a refining facility.

In order to environmentally treat the ash contained in coal, it is preferable to discharge it in the form of molten slag in the case of a large-capacity gasifier. However, in the gasifier 20 of the present embodiment, By minimizing the heat loss to a minimum, the operation efficiency can be maximized. A material containing a small amount of carbon components is discharged from the bottom fractionation bed reactor 22 and can be recycled as cement, for example, into a cement kiln. If it is desired to discharge the ash into the molten slag state even if the efficiency of the gasifier is somewhat lowered, it is possible to operate the reactor so that the temperature inside the reactor is maintained at about 100 ° C or higher than the ash melting temperature.

In the present embodiment, the coal supply unit 10 further includes a separator 18 for separating and supplying coal having a large grain size and coal having a small grain size. The coal supplied by the coal supplying unit 10 is subjected to a screening process by the sorting unit 18 and the coal having a large particle size is charged into the upper fluidized bed reactor 24 and the coal having a small particle size is charged into the lower classification bed reactor 22 do.

That is, in the present embodiment, the upper portion of the fluidized bed reactor 24 is filled with coal particles having a larger particle size than the lower portion.

Thus, coal particles having a large particle size are gasified by pyrolysis during a longer residence time while passing through a fluidized bed reactor, and some carbon is also gasified. The coal particles having a small particle size are transported to the upper part of the fractionation bed reactor and passed through the fluidized bed reactor. In this gasification process, the coal with a large particle size undergoes a fluidized bed reaction process, and the coal with a small particle size undergoes a classification bed reaction process and a fluidized bed reaction process.

The residual carbon contained in the coal of large particles put into the fluidized bed is discharged to the upper part and collected in the refining facility. In order to increase the carbon utilization efficiency, a cyclone may be additionally installed at the downstream end of the upper fluidized bed reactor (24) to collect particles having a high carbon content and re-feed the same to the lower reactor.

Here, the upper fluidized bed reactor 24 has an inverted trapezoidal shape in which the diameter decreases as the diameter decreases.

By forming the upper fluidized bed reactor 24 in a trapezoidal shape, it is possible to use coal having various particle sizes, and particles having a reduced particle size or reduced density as the reaction progresses are also allowed to stay in the upper part of the fluidized bed as long as possible, The conversion rate of carbon can be increased.

The gasification unit 20 further includes a thermometer (not shown) installed on the inner wall surface of the fluidized bed reactor 24 or the fractionation bed reactor 22 to detect the reaction temperature.

Conventionally, in the case of a high-temperature gasifier, a thermometer can not be installed for measuring the temperature of the reaction zone because the coal continuously falls downward in the internal reaction zone. We used the method to determine the height of the ash layer and the height of the reaction zone from the surface color of the probe after periodically inserting the probe into the gasifier.

As described above, the gasification apparatus of this embodiment is provided with the fluidized bed reactor 24 and the fractionation bed reactor 22 so that the internal reaction temperature can be monitored by installing a thermometer at the same position as the inner wall surface of the reactor outside the reactor. Accordingly, the apparatus can easily control the operation conditions of the reactor by controlling the coal and the air flow rate by sensing the measured temperature.

Further, the apparatus further includes a blower 26 for supplying air into the inside of the apparatus, so that air is used as an oxidant in the gasification process. In the conventional large-scale commercial gasifier, oxygen is used as an oxidizing agent and an expensive air separation unit (ASU) is used for oxygen production. In the case of the present embodiment, by supplying air through the blower 26 to the oxidizing agent, the ASU can be omitted and the production facility can be simplified.

Also, it is necessary to operate at a pressure higher than 30 bar which is required in the subsequent reactor for generation of power generation and chemical products at the end of a large-capacity commercial gasifier, but when the gas pressure required by the use gas of the production gas is low, By maintaining the pressure of the gasifier at 1 bar or less, the productivity can be lowered, but the manufacturing cost of the reactor can be lowered.

The gasification apparatus of the present embodiment further includes a boiler 40 installed between the gasification unit 20 and the gas cleaning unit 40 to recover waste heat from the high temperature gas produced by the gasification unit 20. [

Therefore, the high-temperature gas produced through the gasification process is subjected to a cleaning process after recovering heat through a waste heat recovery process.

The discharged synthetic gas passing through the gasification unit 20 has no tar component and mainly contains particulate pollutants and hydrogen sulfide gas, so that the waste heat can be recovered through the waste heat recovery boiler 40. The waste heat recovery boiler 40 can be used in various processes by producing a large amount of steam using the high temperature characteristics of the discharged syngas.

The gas cleaning unit 40 includes a dust collector 42 for removing particulate matter having a metallic filter or a high temperature filter cloth and a scrubber 44 connected to a downstream end of the dust collector to remove sulfide gas.

Conventionally, a large amount of tar is generated in the conventional fixed bed gasifier, complex cleaning equipment is required to treat tar, and if it is not properly treated, strong odor due to tar may be generated.

As described above, in the gasification unit 20 of the present embodiment, since the internal temperature is sufficiently high and no tar is generated, only the dust collector 42 and the scrubber 44 are provided with the generated syngas purification facility, And operating costs.

Also, by keeping the syngas temperature at 350 ° C or lower through the waste heat recovery boiler 40, particulate matter can be removed using a dust collector 42 equipped with a high-temperature filter cloth, which is relatively inexpensive. The syngas is finally removed through the scrubber 44.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

10: coal supply part 12: crusher
14: dryer 16: crusher
18: selector 20: gasifier
22: fractionation bed reactor 24: fluidized bed reactor
26: Blower 30: Boiler
40: Gas washing section 42: Dust collector
44: Scrubber

Claims

A coal gasification unit for gasifying the coal supplied from the coal supply unit; and a gas cleaning unit for purifying the gas generated in the gasification unit,
Wherein the gasification section comprises a fractionation bed reactor disposed below and a fluidized bed reactor disposed above the fractionation bed reactor.

The method according to claim 1,
Wherein the coal supply unit includes a crusher for crushing coal, a drier for drying the crushed coal, and a crusher for crushing the dried coal.

3. The method of claim 2,
Wherein the gas cleaning unit includes a dust collector for removing particulate matter having a filter cloth, and a scrubber connected to a downstream end of the dust collector to remove sulfide gas.

3. The method of claim 2,
Wherein the coal supply unit further comprises a separator for introducing coal having a relatively large particle size into the fluidized bed reactor and coal having a relatively small particle size into a fractionation bed reactor.

5. The method according to any one of claims 1 to 4,
Wherein the fluidized bed reactor has an inverted trapezoidal shape whose diameter decreases as it goes downward.

6. The method of claim 5,
And a boiler installed between the gasification unit and the gas cleaner for recovering waste heat from the high temperature gas produced by the gasification unit.

The method according to claim 6,
The gasification unit may further include a blower for supplying air into the fractionation bed reactor, wherein air is used as an oxidant.

A coal supply step;
The coal having a relatively large particle size among the supplied coal is charged into a fluidized bed reactor to undergo a fluidized bed reaction and a coal having a relatively small particle size is charged into a fractionation bed reactor to be gasified through a fractionation bed reaction and a fluidized bed reaction;
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9. The method of claim 8,
Wherein the coal gasification method further comprises the step of recovering waste heat from the high temperature gas produced through the gasification step.

10. The method according to claim 8 or 9,
Wherein the gasification step uses air as the oxidizing agent.

11. The method of claim 10,
Wherein the coal supplying step comprises the steps of crushing the coal, drying the crushed coal, crushing the dried coal, and selecting the pulverized coal.