JP3988008B2 - Coal gasification system and method of operating the system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent condensation of the water content in a gas when a carrier gas is mixed with a powder fuel and to stably effect carrying of the powder fuel. SOLUTION: This system has a coal gasification furnace 8 for forming a combustible gas by reacting pulverized coal with a gasifying agent, and the pulverized coal obtained by grinding coal is supplied to this coal gasification furnace 8. Further, char 13 is generated upon forming a combustible gas and this char 13 is recovered by a cyclone 17 and a filter 18 and recycled to the coal gasification furnace 8. In such a coal gasification system, part of the combustible gas after recovering the char is withdrawn and heated by a heat exchanger 44. Then, with the use of the combustible gas after heating as the carrier gas, the pulverized coal and the char are supplied to the coal gasification furnace 8.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coal gasification system, and more particularly to a coal gasification system in which a combustible gas is produced by reacting coal with a gasifying agent and purified gas is produced by desulfurizing the combustible gas.
[0002]
[Prior art]
Generally, a coal gasification system is configured to generate flammable gas by reacting pulverized coal with a gasifying agent in a coal gasification furnace, and desulfurizing the combustible gas with a desulfurizer to obtain purified gas. ing. The pulverized coal is conveyed by the conveying gas and supplied to the coal gasification furnace. In the coal gasifier, char is generated when combustible gas is generated, and the char is discharged from the coal gasifier together with the combustible gas. And by passing this combustible gas through a cyclone and a filter, char is recovered from the combustible gas, and the recovered char is also transported by the transport gas and supplied to the coal gasifier.
[0003]
By the way, in the said coal gasification system, nitrogen gas isolate | separated from air in the rectification tower is used as conveyance gas for conveying pulverized fuels, such as pulverized coal and char. In order to use this nitrogen gas as a carrier gas, it is necessary to increase the pressure, and if the auxiliary power for that purpose is increased, there is a disadvantage that the plant efficiency decreases. Moreover, since nitrogen gas is an inert gas, when such an inert gas is mixed in a combustible gas, there also existed a fault that the emitted-heat amount of the refined gas after desulfurization will fall.
[0004]
Therefore, a method of using a combustible gas instead of nitrogen gas as a carrier gas has been proposed. This method is a method in which a part of combustible gas generated in a coal gasification furnace is branched and further pressurized to convey pulverized fuel. In this case, since the location where the combustible gas is branched is the outlet of the water washing tower, the differential pressure with the coal gasification furnace is small, and the auxiliary power required for the pressure increase can be reduced as compared with the case where nitrogen gas is used. Further, since the inert gas is not mixed, the calorific value of the purified gas after desulfurization does not decrease.
[0005]
Furthermore, a method of using CO2 rich gas separated in the desulfurization apparatus as a gas for conveying pulverized fuel has also been proposed (for example, JP-A-63-12690).
[0006]
[Problems to be solved by the invention]
However, if the flammable gas or the CO2 rich gas is used as it is as the carrier gas as described above, the moisture in the gas is condensed when the carrier gas is mixed with the pulverized fuel. There is a problem that the transfer pipe is blocked by being fixed to the inner surface of the sheet.
[0007]
An object of the present invention is to provide a coal gasification system capable of preventing the condensation of moisture in the gas when the carrier gas is mixed with the pulverized fuel and stably carrying the pulverized fuel, and a method of operating the system. Is to provide.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a coal gasification furnace that generates flammable gas by reacting pulverized coal with a gasifying agent, and pulverized coal supply means for supplying pulverized coal to the coal gasification furnace. And char supply means for recovering char generated when combustible gas is generated in the coal gasification furnace and supplying the char to the coal gasification furnace; and desulfurization means for obtaining purified gas by desulfurizing the combustible gas after char recovery. In the coal gasification system provided, a cooling means for taking out a part of the combustible gas after the char recovery , cooling the taken out combustible gas, and a pressure increasing means for increasing the pressure of the combustible gas cooled by the cooling means, And a heating means for heating the combustible gas boosted by the boosting means, and the pulverized coal supply means uses the flammable gas heated by the heating means as a carrier gas to convert the pulverized coal into the coal gasification furnace. To supply said Catcher over supply means is characterized by supplying to the coal gasifier char with combustible gas heated by said heating means as a carrier gas.
[0009]
According to the said structure, the temperature of the combustible gas heated with the heating means has risen, and even if it mixes with pulverized fuels, such as pulverized coal and char, the water | moisture content in gas will not condense. Therefore, the pulverized fuel can be stably conveyed without the pulverized fuel adhering to the inner surface of the conveying pipe and closing the conveying pipe.
[0010]
The heating means may be configured such that when the combustible gas heated by the heating means is mixed with the pulverized coal by the pulverized coal supply means, or the combustible gas heated by the heating means is supplied to the char by the char supply means. When mixed, the combustible gas is heated so that the temperature of the combustible gas after mixing is equal to or higher than the dew point.
[0011]
When the combustible gas is mixed with pulverized coal or char, if the temperature after the mixing is controlled to be higher than the dew point, it is possible to prevent the moisture in the gas from condensing.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an example in which the coal gasification system of the present invention is applied, and shows the overall configuration of a combined coal gasification combined power generation system. As shown in FIG. 1, coal 1 is pulverized by a pulverizer 2 to become pulverized coal, introduced into a hot air generating furnace 3, and dried by high-temperature heated gas generated in the hot air generating furnace 3. The dried pulverized coal 1 is once stored in the hopper 4, then pressurized by the lock hopper system 5, further transported by the transport gas 7, and supplied to the coal gasifier 8. Further, the air 10 is sent to the rectifying column 12 through the heat exchanger 11, and is separated into nitrogen and oxygen by the rectifying column 12. The separated oxygen is pressurized by the compressor 14 and sent to the coal gasifier 8 as a gasifying agent.
[0013]
In the gasification section of the coal gasification furnace 8, the pulverized coal 1 is gasified by the oxygen, and at the same time, the slag 15 flows down from the bottom of the gasification furnace. The product gas generated in the coal gasification furnace 8 is cooled by the syngas cooler 16 and then introduced into the cyclone 17 and the filter 18 where the char 13 is recovered. The recovered char 13 is pressurized by the hoppers 19 to 21, and further sent to the coal gasification furnace 8 by the transfer gas 7 for recycling.
[0014]
On the other hand, the product gas that has passed through the cyclone 17 and the filter 18 is cooled by the water washing tower 24 and then introduced into the absorption tower 26. The product gas is desulfurized in the absorption tower 26, and sulfur compounds such as hydrogen sulfide and carbonyl sulfide are removed to become purified gas 29.
[0015]
The purified gas 29 is introduced into the gas turbine 31. In the gas turbine 31, the purified gas 29 is burned and rotated, and the generator 32 is driven to rotate by the rotational force. The combustion exhaust gas after driving the gas turbine 31 is sent to the waste heat recovery boiler 33, and is discharged from the chimney 34 to the atmosphere after the waste heat recovery.
[0016]
In the syngas cooler 16 and the waste heat recovery boiler 33, steam is generated by heat exchange, but the generated steam 35 from the syngas cooler 16 and the generated steam 36 from the waste heat recovery boiler 33 are sent to the steam turbine 37, and the steam turbine 37 Rotate. This steam turbine 37 also drives the generator 32 to rotate.
[0017]
In this embodiment, a recycle gas (a part of the combustible gas) take-out line 41 is connected to the combustible gas line 40 at the outlet of the water washing tower 24, and a heat exchanger 42 and a compressor 43 are connected to the take-out line 41. A heat exchanger 44 is provided along the gas flow. The recycle gas taken out to the take-out line 41 is once cooled by the heat exchanger 42, then pressurized by the compressor 43, and further heated by the heat exchanger 44. The heated recycle gas is used as pulverized coal and char transport gas 7.
[0018]
In the figure, 22 and 25 are heat exchangers, 23 is a tank, 27 is a regenerator, 28 is a regeneration waste gas processing section, and 30 is a fuel cutoff valve.
[0019]
FIG. 2 shows the details around the heat exchanger 44. In the extraction line 41, a bypass line 45 is provided in parallel with the heat exchanger 44, and a flow rate adjustment valve 46 is attached in the middle of the bypass line 45. A temperature detector 47, a flow rate detector 48, and a flow rate adjustment valve 49 are provided on the downstream side of the heat exchanger 44 in the take-out line 41.
[0020]
A high-temperature fluid flows through the heat exchanger 44, and the recycle gas is heated by exchanging heat with the high-temperature fluid in the heat exchanger 44. The temperature of the recycled gas after heating is always detected by the temperature detector 47, and the opening degree of the flow rate adjusting valve 44 is controlled based on the detection result. That is, when the temperature of the recycled gas after heating is low, the opening degree of the flow control valve 46 is controlled in the closing direction, and most of the recycled gas is heated through the heat exchanger 44. In addition, when the temperature of the recycled gas after heating is high, the opening degree of the flow rate control valve 46 is controlled in the opening direction, and a part of the recycled gas passes through the bypass line 45 and is heated by the heat exchanger 44. Is suppressed. This makes it possible to control the temperature of the recycled gas to a predetermined temperature.
[0021]
As described above, in this embodiment, since the recycle gas is controlled to be at a predetermined temperature, even when the recycle gas is mixed with pulverized coal, char or other pulverized fuel, the moisture in the recycle gas remains. Without condensing, blockage of the pulverized coal and char transport piping can be prevented.
[0022]
Next, the relationship between the temperature of the recycle gas and the dew point when the recycle gas and pulverized fuel are mixed will be described. FIG. 3 shows the relationship between the temperature of the recycled gas, that is, the carrier gas, and the temperature after mixing. When the conventional method, that is, the carrier gas is mixed with the pulverized fuel as it is without being heated, depending on the temperature of the pulverized fuel, the temperature after the pulverized fuel and the carrier gas are mixed (hereinafter, the temperature after mixing) Is below the dew point of the carrier gas, and the moisture in the carrier gas is condensed.
[0023]
However, if the carrier gas is heated as in the present embodiment, the temperature after mixing becomes the dew point or higher, and the moisture in the carrier gas does not condense. Therefore, it is necessary to heat the carrier gas so that the temperature after mixing is equal to or higher than the dew point.
[0024]
According to the present embodiment, since the pulverized fuel can be transported by the recycle gas, the auxiliary power can be reduced. Further, since it is possible to minimize the mixing of an inert gas such as nitrogen gas into the purified gas, the output of the gas turbine can be improved without reducing the amount of heat generated by the purified gas.
[0025]
【The invention's effect】
As described above, according to the present invention, since the combustible gas is heated and then mixed with powdered fuel such as pulverized coal or char, moisture in the combustible gas is not condensed, and the powder It is possible to prevent the piping for conveying the body fuel from being blocked. As a result, the pulverized fuel can be stably conveyed.
[0026]
Further, it becomes possible to transport the pulverized fuel with the recycle gas, and the efficiency of the plant can be improved.
[Brief description of the drawings]
FIG. 1 is an example of an application of a coal gasification system of the present invention, and is an overall configuration diagram of a coal gasification combined power generation system.
FIG. 2 is a system diagram around a heat exchanger which is a main part of the present invention.
FIG. 3 is a diagram showing a relationship between a conveying gas temperature and a temperature after mixing.
[Explanation of symbols]
7 Gas for transportation 8 Coal gasifier 13 Char 16 Syngas cooler 17 Cyclone 18 Filter 24 Water washing tower 26 Absorption tower 29 Purified gas 31 Gas turbine 32 Generator 40 Combustible gas line 41 Extraction line 44 Heat exchanger 45 Bypass line 46 Flow control valve 47 Temperature detector 48 Flow detector 49 Flow control valve

Claims (3)

A coal gasification furnace that generates flammable gas by reacting pulverized coal with a gasifying agent, pulverized coal supply means for supplying pulverized coal to the coal gasification furnace, and combustible gas generation in the coal gasification furnace In a coal gasification system comprising a char supply means for recovering char generated at times and supplying it to a coal gasification furnace, and a desulfurization means for desulfurizing combustible gas after char recovery to obtain purified gas, after the char recovery A part of the combustible gas is taken out , a cooling means for cooling the taken out combustible gas, a boosting means for boosting the combustible gas cooled by the cooling means, and a combustible gas pressurized by the boosting means are heated. Heating means is provided, the pulverized coal supply means supplies the pulverized coal to the coal gasification furnace using the combustible gas heated by the heating means as a carrier gas , and the char supply means includes the heating means. Heated in Coal gasification system and supplying the char to the coal gasifier with the combustible gas as carrier gas. 2. The coal gasification system according to claim 1, wherein the heating unit includes a combustible gas heated by the heating unit when the combustible gas heated by the heating unit is mixed with the pulverized coal by the pulverized coal supply unit. when the sex gas was mixed with the char in the char supply device, coal gasification system, wherein the temperature of the combustible gas after mixing heats the combustible gas so that the above dew point. A coal gasification furnace that reacts pulverized coal with a gasifying agent to generate combustible gas, pulverized coal supply means for supplying pulverized coal to the coal gasification furnace, and combustible gas generation in the coal gasification furnace In a coal gasification system comprising a char supply means for recovering char generated at times and supplying it to a coal gasification furnace, and a desulfurization means for desulfurizing combustible gas after char recovery to obtain purified gas, after the char recovery A portion of the combustible gas is taken out, cooled and then pressurized, and further heated to be used as the pulverized coal supply means, the pulverized coal of the char supply means, and the char transport gas. How to operate the gasification system.

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