JPH10311502A - Coal gasifying device and operation method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability and the economical efficiency of a heat transfer pipe of a heat recovery type boiler to recover heat from coarse produced gas generated at a coal gasifying furnace by the heat transfer pipe of the heat recovery boiler is formed of a Cr radical alloy steel. SOLUTION: In a coal gasifying device, the surface on the coarse produced gas side of a heat transfer pipe 4 of a heat recovery boiler 1 is formed of a Cr radical alloy steel containing at least 8 wt.% or more (preferably 12 wt. % or more) Cr and steam occupying 20 50 Vol.% of coarse produced gas is fed to the coarse produced gas inlet 2 side of the heat recovery boiler 1. This constitution forms an oxidation film of Cr having corrosion resistance against H2 S on the surface of the heat transfer pipe 4 of the heat recovery boiler 1, containing Cr, through oxidation of steam during the starting of operation of the heat recovery boiler 1, prevents the occurrence of corrosion by using a low-cost material, and improves reliability and the economical efficiency of the heat recovery boiler heat transfer pipe 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coal gasifier having improved reliability and economy of a heat recovery boiler heat transfer tube and a method of operating the same.

[0002]

2. Description of the Related Art Attention has been focused on integrated coal gasification combined cycle, which is cleaner and more efficient than conventional coal-fired power plants. FIG. 6 is a flowchart showing the configuration of a general integrated coal gasification combined cycle device. As shown in this figure, coal 14 and oxidant 1
5 is introduced into a coal gasifier 16, the generated crude gas is led to the heat recovery boiler 1, heat is recovered, then the dust is removed by the dust remover 17, the desulfurization is performed by the desulfurizer 18, and the clean product gas is removed. The generator is driven by being guided to the turbine 19 and burned. At the same time, the exhaust gas of the gas turbine 19 is guided to the exhaust heat recovery boiler 20 to recover the exhaust heat. The steam obtained by the heat recovery boiler 1 and the steam obtained by the exhaust heat recovery boiler 20 are combined with a steam turbine 2
Lead to 1 and drive the generator. As described above, the integrated coal gasification combined cycle has two heat cycles of the gas turbine 19 and the steam turbine 21, and can obtain higher efficiency than the coal-fired power of the conventional steam turbine cycle alone. In the integrated coal gasification combined cycle, there are a water cooling wall, a heat recovery boiler 1 and an exhaust heat recovery boiler 20 of a coal gasifier 16 not shown as a steam source.
In particular, the heat recovery boiler 1 that recovers heat from the crude product gas is an important device that controls the efficiency of the integrated coal gasification combined cycle, and a heat transfer tube 4 having a huge heat transfer area is disposed inside the heat recovery boiler 1.

[0003]

Generally, carbon steel or low alloy steel is used for the heat transfer tube of the heat recovery boiler because the metal temperature is 500 ° C. or less. However, in the case of the integrated coal gasification combined cycle, the crude product gas is a reducing gas rich in H ₂ and CO, and contains up to several thousand ppm of highly corrosive H ₂ S. Therefore, to operate the heat recovery boiler 1 for a long time, H ₂
Consideration of corrosion by S is necessary. Therefore, as countermeasures, (1) using low-sulfur coal, and (2) performing a material or a surface treatment having excellent corrosion resistance by H ₂ S can be mentioned. Among these measures, (1) is not preferable from the viewpoint of effective utilization of resources because the brand of usable coal is limited. Next, (2) is an alloy containing Cr or Co having excellent corrosion resistance,
For example, a Co-based alloy typified by stellite, a method using a double tube using 50Cr50Ni as an outer tube and carbon steel or a low alloy steel as an inner tube, a method of spraying stellite or 50Cr50Ni onto a carbon steel or a low alloy steel, and SCC resistance Although there is a method using Incoloy 800H, which is an Fe-based superalloy, which is excellent in quality, they are expensive materials, and there is a problem in terms of cost when used in large quantities. Also, 18-8 austenitic stainless steels represented by SUS321H and SUS347H may cause SCC when the apparatus is stopped, and cannot be used for heat transfer tubes of heat recovery boilers. An object of the present invention is to improve the reliability and economy of a heat recovery boiler heat transfer tube that recovers heat from a crude product gas generated in a coal gasifier.

[0004]

The object of the present invention is to provide a coal gasifier having a coal gasifier for gasifying coal to obtain a crude product gas and a heat recovery boiler for recovering heat from the crude product gas. The rough product gas side surface of the heat transfer tube of the boiler is achieved by being a Cr-based alloy steel containing at least 8 Wt% of Cr. The object is to provide a coal gasifier having a coal gasifier for gasifying coal to obtain a crude product gas and a heat recovery boiler for recovering heat from the crude product gas. The surface is at least Cr
Is a Cr-based alloy steel containing 8 Wt%, which is achieved by providing a steam supply means for supplying steam to the crude product gas inlet side of the heat recovery boiler. The object is to provide a coal gasifier having a coal gasifier for gasifying coal to obtain a crude product gas and a heat recovery boiler for recovering heat from the crude product gas. The surface is a Cr-based alloy steel containing at least 8 Wt% of Cr. The steam supply means for supplying steam to the crude product gas inlet side of the heat recovery boiler, and the oxygen concentration and the sulfur concentration in the crude product gas in the heat recovery boiler are determined. This is achieved by providing the oxygen concentration and sulfur concentration measurement means to be measured, and the steam supply amount control means for controlling the supply amount of steam based on the oxygen concentration and the sulfur concentration measured by the oxygen concentration and sulfur concentration measurement means. The object is to provide a coal gasifier having a coal gasifier for gasifying coal to obtain a crude product gas and a heat recovery boiler for recovering heat from the crude product gas. The surface is formed of a Cr-based alloy steel containing at least 8 Wt% of Cr, and at the start of operation of the heat recovery boiler, 20-50 Vo of the crude gas is supplied to the crude gas inlet side of the heat recovery boiler.
Achieved by supplying steam which accounts for 1%.
According to the above configuration, a Cr oxide film having corrosion resistance to H ₂ S is formed on the surface of the heat recovery boiler heat transfer tube containing Cr.
It is formed by steam oxidation at the start of operation of the heat recovery boiler. Corrosion can be prevented using inexpensive materials, and the reliability and economy of the heat recovery boiler heat transfer tubes can be improved. In order to form an oxide film of Cr having corrosion resistance, it is necessary to contain 8 Wt% of Cr on the surface of the heat transfer tube, and it is desirable to contain 12 Wt% or more. 20V water vapor concentration in crude product gas
If the content is less than 8% by weight, the formation of an oxide film is insufficient even if the content of Cr is 8% by weight or more. And the power generation efficiency decreases. Also, even if the sulfur content of the raw coal used fluctuates or the ratio of the raw coal to the oxidizer fluctuates and the operating conditions of the coal gasifier change, the oxygen and sulfur concentrations in the crude gas are measured. By adjusting the supply amount of water vapor in this way, it is possible to control the heat transfer tube to a region where the Cr oxide film is stably present.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing the configuration of the heat recovery boiler according to the embodiment of the present invention. As shown in this figure, the product gas led from the crude product gas inlet 2 of the heat recovery boiler 1 is recovered by the heat transfer tube 4 disposed inside, and discharged from the crude product gas outlet 3. The flow rate of the steam is adjusted by a steam flow rate control valve 9, guided to a steam nozzle 11 by a steam pipe 10, and jetted into the crude product gas near the crude product gas inlet 2. Further, an oxygen concentration measuring device 5 for measuring the oxygen concentration in the crude product gas and a sulfur concentration measuring device 6 for measuring the sulfur concentration are arranged in the heat recovery boiler 1, and a signal from these measuring devices is transmitted via an AD converter 7. To the computer 8 for control. Then, the steam flow control valve 9 is operated by an operation signal from the computer 8. In this figure, the oxygen concentration measuring device 5 and the sulfur concentration measuring device 6 are installed at three places of the upper part, the middle part and the lower part of the heat recovery boiler 1, but the position and the number are not limited. May be changed as appropriate according to the size of the heat transfer tube 4 and the position of the heat transfer tube 4.

FIG. 2 is a flowchart showing the configuration of a heat recovery boiler according to another embodiment of the present invention. In this figure, the steam flow control valve 9, the steam pipe 10, and the steam nozzle 11 are installed at three places, that is, the upper, middle, and lower parts of the heat recovery boiler 1. Mixing can be prevented. In this figure, the steam nozzle 1
Although the position 1 is fixed, when the number of heat transfer tubes 4 is large, the number of steam nozzles 11 may be increased as appropriate, or may be movable. As the oxygen concentration measuring device 5, in the case of a coal gasifier, since the coal is partially burned in the coal gasifier 16, the oxygen concentration in the crude product gas is extremely low, and the solid electrolyte zirconia having high sensitivity and excellent response is provided. (ZrO ₂ )
Is desirable as a sensor. On the other hand, as the sulfur concentration measuring device 6, calcium sulfide (CaS), which is a solid electrolyte exhibiting ionic conductivity in a wide range, is desirable as a sensor. In the actual control during the operation of the heat recovery boiler 1, when the signals from these measuring devices change and deviate from the set values, steam is injected from the steam nozzle 11 into the heat recovery boiler 1 to cause the oxygen concentration measuring device 5 And the signal from the sulfur concentration measuring device 6 is set to the set value.

FIG. 3 is a typical Fe-SO equilibrium diagram. This figure is an equilibrium diagram of the Fe—SO system at 500 ° C. In the region A where the Cr oxide is stably present with respect to the oxygen concentration and the sulfur concentration, the coal gas having a large sulfur concentration and a small oxygen concentration is shown. Due to a change in the operating conditions of the gasification furnace 16, there is a possibility that the furnace shifts to a region B where Cr sulfide is stably present. In this case, there is a possibility that the Cr oxide film of the heat transfer tube 4 is sulfided and loses corrosion resistance to H ₂ S. In this state, steam can be added to the crude product gas to reduce the sulfur concentration (sulfur partial pressure in this figure) and increase the oxygen concentration (oxygen partial pressure in this figure) to return to the region A again. .

FIG. 4 is a longitudinal sectional view showing the configuration of the heat transfer tube according to the embodiment of the present invention. As shown in this figure, the heat transfer tube 4 has a double tube structure composed of an outer tube 12 and an inner tube 13. The outer tube 12 is made of a Cr-based alloy steel STB containing 8 Wt% or more of Cr.
A27 (9Cr2Mo), SA213T91 (9Cr1
Mo, Nb, V) 9Cr-based, 12CrMoV 12
18Cr-based such as Cr-based and SUS430 can be used, and carbon steel can be used for the inner tube 13. A single material of only the outer tube 12 containing 8 Wt% or more of Cr having a structure other than the double tube structure may be used, or a material subjected to Cr diffusion treatment (chromized), a material containing 8 Wt% or more of Cr by thermal spraying or overlaying may be used. May be coated on the surface of the inner tube 13. In short, any structure may be used as long as the surface of the heat transfer tube 4 on the crude product gas side contains 8 Wt% or more of Cr.

FIG. 5 is a table showing the relationship between the Cr content and the corrosion amount according to the embodiment of the present invention. The abscissa in this figure indicates the Cr content (Wt%), and the ordinate indicates the amount of corrosion in a crude gas atmosphere and the amount of corrosion of carbon steel not containing Cr is 100. The black square indicates the H ₂ S concentration in the gas atmosphere of 1,000.
0 ppm and a water vapor concentration of 20 vol% are shown, and black diamonds represent a case where the H ₂ S concentration in the gas atmosphere is 1,000 ppm and the water vapor concentration is 10 vol%. As is clear from this figure, in all cases, the corrosion amount decreases as the Cr content increases. In particular, when the Cr content is 8 Wt% or more and the water vapor concentration is 20 vol%, the corrosion hardly increases. This is because the material having a high Cr content has a water vapor concentration of 2
This is because a Cr-rich oxide film having a protective ability against H ₂ S corrosion is formed on the surface of the material at 0 vol%. The conclusion drawn from this figure is that the Cr content in the material is at least 8 Wt%, preferably 12 Wt% or more, and when the water vapor concentration is less than 20 vol%, the Cr oxide film is formed even if the Cr content is 8 Wt%. Is insufficiently formed.

Next, a method of forming a Cr oxide film on the surface of the heat transfer tube 4 on the side of the crude gas will be described. The formation of the Cr oxide film is performed by steam oxidation at the start of operation after the construction of the heat recovery boiler. Since the Cr oxide film is formed in a relatively short time, steam may be injected for several tens of hours. However, when the operation of the heat recovery boiler is stopped, the generated Cr oxide film may be peeled off, so that it is desirable to inject steam for several tens of hours each time the heat recovery boiler is started. The concentration of water vapor to be injected is preferably as high as 20 vol% or more from the viewpoint of formation of a Cr oxide film. However, if the concentration is excessive, when the dust removal device and the desulfurization device downstream of the generated gas are wet, all the injected water vapor condenses and becomes water. As a result, the amount of generated gas decreases, and the drainage from the dedusting device and the desulfurization device increases, thereby increasing the burden of water treatment and reducing the power generation efficiency of the integrated coal gasification combined cycle power plant. .

[0011]

According to the present invention, a Cr oxide film having corrosion resistance to H ₂ S is formed on the surface of a heat recovery boiler heat transfer tube containing Cr by steam oxidation at the start of operation of the heat recovery boiler. The effect of preventing corrosion by using inexpensive materials and improving the reliability and economy of the heat recovery boiler heat transfer tubes can be obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a configuration of a heat recovery boiler according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a configuration of a heat recovery boiler according to another embodiment of the present invention.

FIG. 3 is a typical Fe—SO equilibrium diagram.

FIG. 4 is a longitudinal sectional view showing a heat transfer tube configuration according to the embodiment of the present invention.

FIG. 5 is a table showing a relationship between a Cr content and a corrosion amount according to the embodiment of the present invention.

FIG. 6 is a flowchart showing a configuration of a general integrated coal gasification combined cycle device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat recovery boiler 2 Crude gas inlet 3 Crude gas outlet 4 Heat transfer tube 5 Oxygen concentration measuring device 6 Sulfur concentration measuring device 7 A / D converter 8 Computer 9 Steam flow control valve 10 Steam piping 11 Steam nozzle 12 Outer tube 13 Inner tube 14 Coal 15 Oxidizer 16 Coal Gasifier 17 Dust Removal Device 18 Desulfurization Device 19 Gas Turbine 20 Waste Heat Recovery Boiler 21 Steam Turbine 22 Condenser

Claims (4)

[Claims] 1. A coal gasification apparatus comprising: a coal gasifier for gasifying coal to obtain a crude product gas; and a heat recovery boiler for recovering heat from the crude product gas, wherein the heat transfer tube of the heat recovery boiler A coal gasifier comprising a crude gas side surface made of a Cr-based alloy steel containing at least 8 Wt% of Cr. 2. A coal gasifier comprising: a coal gasifier for gasifying coal to obtain a crude product gas; and a heat recovery boiler for recovering heat from the crude product gas, wherein the heat transfer tube of the heat recovery boiler is provided. A coal gasification apparatus characterized in that a surface of the crude gas side is a Cr-based alloy steel containing at least 8 Wt% of Cr, and steam supply means for supplying steam to the crude gas inlet side of the heat recovery boiler is provided. . 3. A coal gasifier having a coal gasifier for gasifying coal to obtain a crude product gas and a heat recovery boiler for recovering heat from the crude product gas, wherein the heat transfer tube of the heat recovery boiler The crude product gas side surface is a Cr-based alloy steel containing at least 8 Wt% of Cr, a steam supply means for supplying steam to the crude product gas inlet side of the heat recovery boiler, and the crude product gas in the heat recovery boiler. Oxygen concentration and sulfur concentration measurement means for measuring the oxygen concentration and sulfur concentration in, and steam supply amount control means for controlling the supply amount of the steam by the oxygen concentration and sulfur concentration measured by the oxygen concentration and sulfur concentration measurement means, A coal gasifier comprising: 4. A coal gasifier having a coal gasifier for gasifying coal to obtain a crude product gas and a heat recovery boiler for recovering heat from the crude product gas, wherein the heat transfer tube of the heat recovery boiler The crude product gas side surface is formed of a Cr-based alloy steel containing at least 8 Wt% of Cr, and at the start of operation of the heat recovery boiler, 20 to 50 Vol of the crude product gas is supplied to the crude product gas inlet side of the heat recovery boiler.
% Of steam, the method comprising operating a coal gasifier.