JPH10204452A - Coal gasification plant and its startup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the coal gasifier that inhibits the moisture in the produced gas from condensing in the waste heat-recovering boiler during the start-up to improve the operation stability by arranging a pipe so that its one end is connected to the other steam source and the other is connected to the cycling means. SOLUTION: In the coal gasifier equipped with the waste heat recovering unit in which the produced gas from the coal gasification furnace is heat- exchanged with the boiler feed water that flows through heat exchanger tubes 3 and with the circulating means for circulating the boiler feed water through the heat exchanger tubes 3 in the waste heat-recovering means, a pipe is arranged to connect its one end to the other steam source and the other to the circulating means. In a preferred embodiment, the fourth pipe is set to connect to the other steam source that can be heated over the dew point of the produced gas and link the other end to the first pipe or the steam drum 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coal gasification apparatus and a method for starting a coal gasification apparatus, in which water in a generated gas is prevented from condensing in a waste heat recovery boiler at startup.

[0002]

2. Description of the Related Art FIG. 3 is a flow sheet showing the structure of a conventional coal gasifier. As shown in this figure, a waste heat recovery boiler 2 is connected to a generated gas line 1 for introducing a high-temperature generated gas from a gasification furnace (not shown), and a heat transfer tube 3 is disposed inside the waste heat recovery boiler 2. The boiler feedwater flowing through the wastewater recovers waste heat from the high-temperature generated gas, and the generated gas is measured by the thermometer 5 by the generated gas line 4 and then guided to the cyclone 6 to collect unreacted char, ash and other dust. You. The dust collected by the cyclone 6 is stored in the cyclone hopper 8 via the hopper connection pipe 7 and discharged from the discharge valve 9. A boiler water supply line 11 is connected to the steam drum 10, and the boiler water is supplied by a liquid level controller 12 and a boiler water supply control valve 13 so that the liquid level is constant. Boiler feedwater is guided from a circulation line 14 connected to the steam drum 10 to a circulation pump 15 and supplied to the heat transfer tube 3. The boiler feedwater evaporates in the heat transfer tube 3, is guided to the steam drum 10 by the evaporator tube 16, performs gas-liquid separation, and is supplied from the generated steam line 17 to the other. The steam led from another steam source by the steam supply line 18 heats the generated gas line 4 connecting the waste heat recovery boiler 2 and the cyclone 6 and the hopper connection pipe 7 by the steam trace 19 and is discharged as drain from the steam trap 20. You.

Next, the start-up of the coal gasifier will be described.
Before the temperature rise of the gasification furnace is started, the generated gas line 4 and the hopper connection pipe 7 are heated by the steam trace 19 with the steam led from another steam source by the steam supply line 18, the circulation pump 15 is started, and the heat transfer pipe 3 is started. Boiler feedwater is supplied and circulated. In this state, the gasification furnace and the production gas line 1 and the production gas line 4 are started to be heated and pressurized. When coal is supplied to the gasification furnace, the gasification furnace must be heated to the coal ignition temperature. In addition, the metal temperature of each device and pipe must reach the dew point of the generated gas so that the moisture in the product gas will not condense and adhere to the pipe inner wall even if the coal fines scatter downstream. It is particularly important to prevent the clogging of the hopper connecting pipe 7 with much dust. The temperature of the boiler feedwater circulating at the time when the coal is ignited and the generated gas flows into the waste heat recovery boiler 2 satisfying the conditions for supplying the coal to the gasification furnace is about room temperature. Is lower than the dew point of the produced gas, the moisture in the produced gas condenses on the surface of the heat transfer tube 3 and scatters downstream. The generated gas line 4 and the vapor trace 19 of the hopper connecting pipe 7 are for preventing the temperature of the generated gas from decreasing, and there is no consideration for evaporating a large amount of condensed water and no heat transfer area.

[0004]

As described above, when the moisture in the product gas condensed in the heat transfer tube 3 of the waste heat recovery boiler 2 scatters to the downstream cyclone 6 and the hopper connection tube 7, the generated gas flow stops. Dust adheres and blocks at the place, and the generated gas stops flowing, making it impossible to operate the coal gasifier. An object of the present invention is to prevent water in a generated gas from being condensed in a waste heat recovery boiler when a coal gasifier is started.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a waste heat recovery means for exchanging heat between a gas produced from a coal gasifier and boiler feed water flowing through a heat transfer tube to obtain steam, and a waste heat recovering means for supplying boiler water. In a coal gasifier having a circulation means for circulating a heat transfer tube of a recovery means, this is achieved by providing a pipe connected to another steam source on one side and connected to the circulation means on the other side. The above objects are achieved by heat exchange between generated gas from a coal gasifier and boiler feedwater flowing through a heat transfer tube to obtain steam, and steam obtained by a heat transfer tube of a waste heat recovery boiler having a boiler feedwater and holding steam. A steam drum for gas-liquid separation of
The first connecting the heat transfer tube of the waste heat recovery boiler and the steam drum
, A cyclone for removing dust generated from the waste heat recovery boiler, a cyclone hopper for storing dust collected by the cyclone, a second pipe for connecting the waste heat recovery boiler and the cyclone, a cyclone and a cyclone hopper And a third pipe connecting
This is achieved by providing one of the boiler feed water to another steam source having a temperature capable of heating the dew point of the generated gas or higher and the other to a first pipe or a fourth pipe connected to a steam drum. It is desirable to provide a steam trace that branches off from the fourth pipe and heats the second and third pipes. The above object is achieved by a waste heat recovery means for exchanging heat between a gas produced from a coal gasifier and boiler feedwater flowing through a heat transfer pipe to obtain steam, and a heat transfer pipe of the waste heat recovery means by performing boiler feedwater and gas-liquid separation. In a coal gasifier having a circulating means for circulating between means, when starting the coal gasifier, the steam from another steam source is guided to the circulating means so that the metal temperature of the heat transfer tube is equal to or higher than the dew point of the generated gas. This is achieved by heating the boiler feedwater. According to the above configuration, the boiler feedwater circulating so that the heat transfer tube metal temperature of the waste heat recovery means is equal to or higher than the dew point of the generated gas when the coal gasifier is started up, and the moisture in the generated gas in the waste heat recovery boiler is heated. Can be prevented from condensing. Also, by providing steam traces in the pipe for guiding the generated gas from the waste heat recovery means to the cyclone and in the pipe for discharging dust from the cyclone to the cyclone hopper, the risk of water in the generated gas condensing in the pipe is reduced.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flow sheet showing a configuration of a coal gasifier according to an embodiment of the present invention. The basic configuration shown in this figure is the same as that of FIG. 3 except that a mixer 21 is arranged in the evaporating pipe 16, a steam supply line 18 is connected, a temperature control valve 23 is arranged in the steam supply line 18, and circulation is performed. Line 14
Temperature controller 2 which detects the temperature of the air and operates the temperature control valve 23
2 and the steam trace 19 is excluded.
In the present embodiment, the circulating means is constituted by the circulating line 14, the circulating pump 15, the evaporating pipe 16, and the steam drum 10, but the circulating means also includes natural circulation circulating without the circulating pump 15. Note that the steam supply line 18 may be connected to the steam drum 10 in the loop of the circulation means. Next, the operation of the present embodiment will be described. Before supplying coal to the gasification furnace, the circulation pump 15 is started to circulate the boiler feedwater, and the steam is introduced into the mixer 21 by setting the temperature of the temperature controller 22 higher than normal temperature. As the boiler feedwater temperature rises, the set temperature of the temperature controller 22 is increased, and finally set to 150 ° C. If the set temperature of the temperature controller 22 is set to 150 ° C. from the beginning of the introduction of the steam, the deviation from the detected value at about room temperature is large, and the temperature control valve 23 may be fully opened.
However, it is not preferable to introduce a large amount of vapor in a liquid phase state, since a water hammer occurs. When the indication of the temperature controller 22 becomes 150 ° C., coal is supplied to the gasifier and the generated gas is introduced into the waste heat recovery boiler 2. When the temperature of the generated gas rises and heats the heat transfer tube 3 of the waste heat recovery boiler 2 and the temperature of the boiler feed water becomes higher than 150 ° C., the temperature controller 22 outputs an operation signal to close the temperature control valve 23 because it is in the automatic control mode. And a temperature control valve 2 as the boiler feedwater temperature rises
3 is fully closed, and the introduction of steam is stopped. Since the dew point of the generated gas is about 130 ° C, the temperature of the boiler feedwater is 150 ° C.
When the metal temperature of the heat transfer tube 3 exceeds about 150 ° C., moisture in the generated gas does not condense on the surface of the heat transfer tube 3.

Next, another embodiment will be described. FIG. 2 is a flow sheet showing a configuration of another embodiment of the present invention. As shown in this figure, in addition to the configuration of FIG. 1, a steam trace 19 is formed on the generated gas line 4 for guiding the generated gas from the waste heat recovery boiler 2 to the cyclone 6 and the hopper connecting pipe 7 for discharging dust from the cyclone 6 to the cyclone hopper 8. Is provided. As compared with the embodiment shown in FIG.
In addition, a decrease in metal temperature due to heat radiation from the hopper connecting pipe 7 is small, and the possibility that water in the generated gas is condensed is reduced.

As described above, according to the present embodiment,
The generation of water droplets due to the condensation of water in the generated gas can be prevented by the waste heat recovery boiler when the coal gasifier is started. Conventionally, the heating time until coal can be supplied to the coal gasifier is governed by the condition that the temperature around the cyclone is equal to or higher than the dew point of the generated gas, and it takes two days. However, in this embodiment, the temperature of the coal gasifier may be raised until the coal can be ignited, and the temperature rise is completed in one day and the heating time can be reduced to half.

[0009]

According to the present invention, waste heat recovery is achieved by heating the circulating boiler feed water such that the metal temperature of the heat transfer tube of the waste heat recovery means is equal to or higher than the dew point of the generated gas when the coal gasifier is started. The effect of preventing condensation of moisture in the product gas by the means is obtained.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a configuration of a coal gasifier according to an embodiment of the present invention.

FIG. 2 is a flow sheet showing a configuration of another embodiment of the present invention.

FIG. 3 is a flow sheet showing a configuration of a conventional coal gasifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Generated gas line 2 Waste heat recovery boiler 3 Heat transfer tube 4 Generated gas line 5 Thermometer 6 Cyclone 7 Hopper connection pipe 8 Cyclone hopper 9 Discharge valve 10 Steam drum 11 Boiler water supply line 12 Liquid level controller 13 Boiler water supply control valve 14 Circulation Line 15 Circulation pump 16 Evaporation tube 17 Generated steam line 18 Steam supply line 19 Steam trace 20 Steam trap 21 Mixer 22 Temperature controller 23 Temperature control valve

Claims (4)

[Claims] 1. A waste heat recovery means for exchanging heat between a gas produced from a coal gasifier and boiler feedwater flowing through a heat transfer tube to obtain steam, and a heat transfer tube of the waste heat recovery means for supplying the boiler water and supplying steam. A coal gasifier having a circulating means for circulating, wherein one of the pipes is connected to another steam source and the other is connected to the circulating means. 2. A waste heat recovery boiler that obtains steam by exchanging heat between a gas generated from a coal gasifier and boiler feedwater flowing through a heat transfer tube, and a heat transfer tube of the waste heat recovery boiler that holds the boiler feedwater. A steam drum for performing gas-liquid separation of the obtained steam, a first pipe connecting the heat transfer tube of the waste heat recovery boiler and the steam drum, and a cyclone for removing generated gas from the waste heat recovery boiler; Coal gasification comprising a cyclone hopper for storing dust collected by the cyclone, a second pipe connecting the waste heat recovery boiler and the cyclone, and a third pipe connecting the cyclone and the cyclone hopper. In the apparatus, one is connected to another steam source having a temperature capable of heating the boiler feedwater to a temperature equal to or higher than the dew point of the generated gas, and the other is provided with a fourth pipe connected to the first pipe or the steam drum. Coal gasifier, characterized in that the. 3. The coal gasifier according to claim 2, further comprising a steam trace branching from the fourth pipe and heating the second pipe and the third pipe. 4. A waste heat recovery means for exchanging heat between generated gas from a coal gasifier and boiler feed water flowing through a heat transfer tube to obtain steam, and a heat transfer tube of the waste heat recovery means for feeding the boiler feed water and A circulating means for circulating between the gas-liquid separating means, wherein when starting the coal gasifying apparatus, steam from another steam source is guided to the circulating means, and the metal temperature of the heat transfer tube is set to the product gas. Boiler feed water is heated to a dew point or higher.