JPH10237464A - Method for starting up coal gasifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit the always stable start-up of a coal gasifier while preventing dew point corrosion by a waste combustion gas during start-up by using charr as a fuel for starting up a coal gasifier. SOLUTION: Air 57 is sucked in and is separated into oxygen 18 and nitrogen in a rectifying tower 1, and the both are respectively transferred to an oxygen compressor 21 and a nitrogen compressor 23. After the pilot burner inside a coal gasifier 5 is ignited, the charr loaded on a charr feed hopper 11 is transferred to a charr burner by entrainment on nitrogen 20 through a pipe and is burnt with oxygen transferred to the burner. After the temperatures of the respective sections of the plant are raised to ones at which the moisture generated during coal gasification is not condensed, the coal 4 in a coal feed hopper 3 is fed into the gasifier 5 to start gasification. The charr burner is extinguished. The charr 12 produced by the gasification of coal is collected in a deduster 9 and stored as a start-up fuel in the hopper 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plant that uses a coal gasifier to gasify coal and use the gasified fuel gas for chemical raw materials, gas fuel, power generation, and the like.
In particular, it relates to a method for starting a coal gasifier.

[0002]

2. Description of the Related Art As a fuel for starting a coal gasifier in a coal gasification plant, a liquid fuel such as light oil or heavy oil which is easy to supply and easy to handle is used. However, these fuels contain hydrogen and sulfur, and H ₂ O and SOx are generated in the combustion exhaust gas, and moisture in the combustion exhaust gas is condensed during the temperature raising and pressure increasing operations at the time of startup. Therefore, it is necessary to avoid clogging and corrosion (dew point corrosion) of the downstream equipment. Regarding the starting method of coal gasifier,
As shown in Japanese Patent Publication No. 5-59954 and Japanese Patent Publication No. 7-76346, a start-up burner is installed in a coal gasifier and the following procedure is performed using a start-up fuel.

First, the inside of the system is purged using low-pressure nitrogen 28, 29, 31 or the like. After the purge is completed, the fuel 24 such as light oil is burned by a mixed gas of oxygen 26 and nitrogen 28 by the starting burner 6, and the combustion exhaust gas is used to burn the coal gasifier 5,
The temperature of the heat recovery boiler 7 and the piping are raised. When a liquid fuel such as light oil is used, the dew point of the flue gas at normal pressure is about 6
Since the outlet temperature of the heat recovery boiler 7 is low and the combustion exhaust gas is lower than the dew point in the initial stage of the temperature rise, the dust removal device 9 downstream of the heat recovery boiler 7 has a bypass line 10 to prevent clogging. When the inlet temperature of the dust removing device 9 reaches about 150 ° C. for a while, the valve is switched to allow the combustion exhaust gas to pass. In addition, the dust removal device 9, the char supply hopper 11, and the piping around it are subjected to indirect heating 50 by steam from an auxiliary boiler or the like, thereby preventing drainage after switching the combustion exhaust gas. At this stage, the temperature raising operation ends. Next, the load on the start-up burner 6 is increased to increase the amount of combustion exhaust gas, and a pressure increasing operation is performed. However, since the dew point of the combustion exhaust gas rises due to the pressure increase (26 ata, about 140 ° C.), the pressure increase speed is adjusted so that the outlet temperature of the heat recovery boiler 7 does not become lower than the dew point. And after the boost operation is completed,
The starting burner 6 is extinguished, and the coal 4 is charged into the coal gasifier 5 by the gas flow transport using the nitrogen 31 via the coal supply hopper 3, and gasification is started by the oxygen 29. The generated gas containing the char (referred to as a mixture of about 50% of carbon and ash) generated by gasification enters the dedusting device 9, where the char 12 is separated, and the dedusted generated gas is Then, it is refined and used as fuel for power generation.
The char 12 collected by the dust removing device 9 is recycled to the coal gasification furnace 5 through the char supply hopper 11 by air flow conveyance with nitrogen 41.

[0004] That is, in these starting methods, first, in the early stage of temperature rise, in order to prevent clogging due to drainage, a dust removal device 9 downstream of the heat recovery boiler 7 is bypassed by a bypass line 10. During the heating of the coal gasification furnace 5, the heat recovery boiler 7, and the generated gas piping, indirect heating 50 is performed on the dust removing device 9, the char supply hopper 11, and the piping around it by steam from an auxiliary boiler, etc. There is a problem that drainage after switching must be prevented. In addition, in the pressurization process, the dew point of the combustion exhaust gas increases, so that in order to prevent dew point corrosion due to drainage, the pressurization speed must be adjusted and sufficient temperature control must be performed. There is a problem that a complicated driving operation is required. Further, if one of these starting operations is mistaken, there is a possibility that the dust removing device 9 may be clogged and each device may be corroded.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a stable coal gasification system by preventing dew point corrosion caused by combustion exhaust gas at the time of starting a coal gasification furnace in a starting operation of a coal gasification plant. To provide a coal gasification plant that enables furnace start-up operations;
It is an object of the present invention to provide an economical coal gasification plant which is excellent in operability at start-up, operability at start-up and environmental preservation, and does not require a start-up burner.

[0006]

Means for Solving the Problems In order to solve the above problems, the first invention is characterized by a method of starting a coal gasifier using char as a starting fuel.

In this case, since hydrogen and moisture are not contained in the char, H ₂ O is not generated in the combustion exhaust gas due to the combustion of the char, and the condensation of the water does not occur. As a result, in the early stage of the temperature rise, there is no need to bypass the dust removal device downstream of the heat recovery boiler in order to prevent clogging due to drainage, and the dust removal device, the char supply hopper and the piping around it are indirectly heated. No need. Further, in the step of increasing the pressure, there is no need to adjust the rate of increase in pressure and to perform sufficient temperature control in order to prevent dew point corrosion due to drainage. Furthermore, since no combustible sulfur is generated in the char, there is no sulfur dioxide in the flue gas, so there is no problem of sulfuric acid corrosion due to the flue gas at startup, and no desulfurization equipment for flue gas generated at startup is required. It is.

The second invention is characterized by a method for starting a coal gasifier using char generated in a coal gasifier plant as a starting fuel.

In this case, it is not necessary to add a new facility for generating char.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for starting a coal gasifier according to the present invention will be described below. As shown in FIG. 1, the coal gasification plant includes a rectification tower 1 and a coal supply hopper 3
, A coal gasifier 5, a heat recovery boiler 7, and a dust removal device 9
And a char supply hopper 11. That is, the rectification tower 1 is connected to the air compressor 13 and the air conveyance pipe 15 on the upstream side, and the oxygen conveyance pipe 17 and the nitrogen conveyance pipe 19 are respectively connected to the oxygen compression pipe 17 and the oxygen conveyance pipe 19 downstream from the rectification tower 1. And a compressor 21 and a nitrogen compressor 23.
Here, the air transfer pipe 15, the oxygen transfer pipe 17, and the nitrogen transfer pipe 19 are each provided with a heat exchanger 25 on the way. Then, the oxygen compressor 21 and the nitrogen compressor 23
Are connected to the coal gasification furnace 5 by an oxygen transfer pipe 29 and a nitrogen transfer pipe 31 each provided with a valve 27. Further, a char gasification oxygen pipe 33 having a valve 34 branched from the oxygen transport pipe 29 is connected to the coal gasification furnace 5.

The coal supply hopper 3 is provided with a nitrogen transport pipe 31.
And is connected to a nitrogen transport pipe 35 having a valve 37. The coal feed hopper 3 is connected to a nitrogen transfer pipe 31 on the downstream side of the valve 27 by a coal transfer pipe 39 having a valve 40. In addition, a coal transportation pipe 38 is connected to the coal supply hopper 3 from an external facility.

The coal gasifier 5 is connected via a valve 43 to a char transfer nitrogen pipe 41 branched from the nitrogen transfer pipe 31. Further, the coal gasification furnace 5 is connected to the heat recovery boiler 7 via a generated gas transfer pipe 45. The slag discharge pipe 46 is connected to the bottom of the coal gasifier 5.

[0013] The heat recovery boiler 7 includes a pipe 4 for conveying generated gas.
7 and connected to a dust removal device 9. Dust removal device 9
Is the char supply hopper 1 through the char transfer pipe 49.
1 is connected. Further, the dust removing device 9 is connected to equipment outside the system via a generated gas transfer pipe 51. The char supply hopper 11 is connected to the char transfer nitrogen pipe 41 via a char transfer pipe 55 having a valve 53.

Next, the operation will be described in detail. In the coal gasification plant, a coal gasification operation is performed through a temperature raising operation and a pressure raising operation of the coal gasification furnace 5. The air 57
After being introduced into the air compressor 13, the air conveying pipe 1
5, the heat is received from a heat exchanger 25 provided on the way, and guided to the rectification column 1. In the rectification column 1, the air 57 is separated, and the oxygen 18 and the nitrogen 20 generated by the separation are separated into
They are conveyed to an oxygen compressor 21 and a nitrogen compressor 23 through an oxygen transport pipe 17 and a nitrogen transport pipe 19, respectively. Here, the oxygen transfer pipe 17 and the nitrogen transfer pipe 19 give heat to the air 57 by passing through the heat exchanger 25 provided on the way. And oxygen 1
8 and nitrogen 20 are supplied to an oxygen compressor 21 and a nitrogen compressor 23
To oxygen transfer pipe 29 and nitrogen transfer pipe 3 respectively
1 to a coal gasifier 5.

Next, in order to start the temperature raising operation, the oxygen 18 flowing through the oxygen transport pipe 29 and the nitrogen transport pipe 31
And the inside of the system is purged with nitrogen 20 or the like. After purging is completed, the coal gasification furnace 5 is ignited using a pilot burner (not shown) provided in the coal gasification furnace 5 or the like, and then the char 12 deposited on the char supply hopper 11 is charged.
Is sent to the char transfer nitrogen pipe 41 through the char transfer pipe 55, and transferred to a char burner (not shown) by the nitrogen 20 generated in the rectification column 1. The char 12 transported to the char burner is burned by the oxygen 18 generated in the rectification column 1 being transported to the char burner through the char gasification oxygen pipe 33. The adjustment of the amount of the char 12 is adjusted by a valve (rotary valve) 53 below the char supply hopper 11, and the amount of the oxygen 18 is adjusted so that the concentration of the residual oxygen in the combustion exhaust gas becomes several percent or less with the char amount. It is adjusted by the control valve 34. In addition, the coal gasifier 5
The temperature of the inside is also controlled by the control valve 43 so that the ash in the char is melted and the amount of nitrogen 20 can be discharged from the bottom of the coal gasifier 5 as slag. The temperature of the coal gasifier 5, the heat recovery boiler 7, the dust removal device 9, the surrounding generated gas pipe 47, and the like are raised by the combustion exhaust gas of the char 12. Then, the pressure raising operation is performed simultaneously with the temperature raising operation. Fly ash contained in the combustion exhaust gas is removed by the dust removal device 9 and stored in the char supply hopper 11. When the pressure in the coal gasifier 5 reaches a specified pressure and the temperature in the system rises to a temperature at which moisture generated during coal gasification does not condense, the operation proceeds to the operation of charging the coal 4. The capacity of the char supply hopper 11 is set to a capacity capable of storing the char 12 at least for the time required for the temperature raising and pressure raising operations.

Next, after completion of the above-mentioned temperature raising and pressure raising operations,
The coal 4 deposited on the coal supply hopper 3 is supplied to the coal gasification furnace 5 via the coal transfer pipe 39 and the nitrogen transfer pipe 31 to start gasification. At this time, the supply of the char 12, the oxygen 18 and the nitrogen 20 for the char burner is temporarily stopped. The char 12 generated by the gasification of the coal 4 is collected by the dust removal device 9 and is supplied to the char supply hopper 11.
Is stored in When the storage amount reaches the specified amount, the char 12 is transported again to the coal gasifier 5 together with the nitrogen 20 through the nitrogen pipe 41 for char transport, and gasified by the oxygen 18. The amount of oxygen at this time is smaller than the amount of oxygen at the time of starting the coal gasifier 5, and is adjusted to an amount necessary for improving gasification efficiency. At the time of recharging the char 12 into the coal gasifier 5, char combustion ash generated at the time of start-up is included. .

Next, before the supply of the coal 4 to the coal gasifier 5 is terminated, the supply of the char 12 to the coal gasifier 5 is stopped, and the amount required for the next start of the coal gasifier 5 is reduced. The char 12 is stored in the char supply hopper 11 until this time. Then, after the storage is completed, the charging of the coal 4 and the oxygen 18 into the coal gasifier 5 is stopped. Thereafter, the pressure in the system and the cooling operation are performed while purging with nitrogen 20.

As another embodiment, the same effect can be obtained even if the hopper of the char 12 necessary for starting the coal gasifier 5 is installed separately from the char supply hopper 11. A similar effect can be obtained by burning the char 12 at the time of startup in an incinerator other than the coal gasifier 5.

[0019]

According to the present invention, in the start-up operation of the coal gasification plant, since the flue gas at the start of the coal gasification furnace contains neither moisture nor sulfur, the flue gas does not cause dew point corrosion. The start-up operation of the coal gasifier can always be stabilized and the start-up time can be further reduced.

Since the flue gas at the start of the coal gasifier does not contain sulfur dioxide in the flue gas and is excellent in environmental preservation, a flue gas desulfurization device for the start is unnecessary.

Since a starting burner is not installed in the coal gasifier and utilities such as a starting fuel such as light oil and a heating medium for starting steam and the like are not required, a simple and economical system is provided. It can be.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing an embodiment of a method for starting a coal gasifier according to the present invention.

FIG. 2 is a process explanatory view showing a conventional method of starting a coal gasification furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectification tower 3 Coal supply hopper 4 Coal 5 Coal gasifier 7 Heat recovery boiler 9 Dust removal device 11 Char supply hopper 12 Char 13 Air compressor 18 Oxygen 20 Nitrogen 21 Oxygen compressor 23 Nitrogen compressor 25 Heat exchanger

Claims (5)

[Claims] 1. A method for starting a coal gasifier that starts by burning a starting fuel, wherein a char is used as the starting fuel. 2. The method for starting a coal gasifier according to claim 1, wherein the char is generated in a plant of the coal gasifier. 3. A method for starting a coal gasifier according to claim 1 or 2, wherein the char is burned with oxygen to generate a combustion gas, and the combustion gas is used in a plant system of the coal gasifier. A method for starting a coal gasifier, comprising charging coal into the coal gasifier after raising the temperature and pressure. 4. The method for starting a coal gasifier according to any one of claims 1 to 3, wherein oxygen and nitrogen are char combustion media. 5. A coal gasifier which is started by burning a starting fuel, wherein a char is used as a starting fuel for the coal gasifier.