JP2009040816A - Purification method of coal gasification gas and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purification method of a coal gasification gas, which can surely remove tar components contained in a gas obtained by low-temperature gasification of coal while simplifying processes and reducing costs, thereby contributing to achievement of low-temperature coal gasification, and to provide an apparatus therefor. <P>SOLUTION: A gasified gas is cooled by a heat exchanger 2 thereby to recover heat; the gasified gas after cooled is directly cooled by a direct cooler 3 by water-spraying; the directly cooled gasified gas is indirectly cooled by a first indirect cooler 4 to condense a heavy tar component, a light tar component and steam; the directly cooled gasified gas at normal pressure is treated by a mist-remover 5 to remove a misty tar component; the gasified gas treated by the mist-remover 5 is pressurized in a booster 6 to lower the saturated vapor concentration of the tar component in the gasified gas; and the gasified gas with its temperature raised by pressurization is indirectly cooled by a second indirect cooler 7 to condense, atomize and remove a heavy tar component and a light tar component. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and apparatus for purifying coal gasification gas.

  Generally, in the gasification process of coal, gasification by a partial oxidation process using oxygen or air is known. However, the conventional partial oxidation process gasifies coal at a high temperature of 1300 ° C. or higher by partial oxidation heat. In addition, since the tar content contained in the generated gasification gas is very small, there was almost no problem with respect to the removal of the tar content. However, in this case, since the gasification process is performed at a high temperature and a high pressure, there is a disadvantage that the cost of the gasification furnace is increased.

  Therefore, the present inventors have developed a method for reducing the cost of a gasification furnace by performing gasification process at a low pressure by gasifying coal with steam at a low temperature of 700 ° C. to 900 ° C. The tar content contained in the generated gasification gas has a problem that it is very high compared to gasification at a high temperature. When using gasified gas as a raw material for chemical synthesis, tar content in gasified gas may be caused by blockage of piping due to condensation, equipment trouble, poisoning with synthetic catalyst, etc. in downstream equipment and chemical synthesis processes. To cause problems, the tar content must be removed from the gasification gas.

  By the way, in biomass and waste gasification processes where gasification is performed at a low temperature compared to gasification of coal at high temperature, the tar content contained in the gasification gas is converted into gasification gas at high temperature of coal. Since it shows a higher amount than the tar content, applying a method for removing impurities such as tar contained in gasification gas such as biomass to gasification gas at low temperature of coal is also being studied. .

For example, Patent Document 1 shows a general technical level of a gasification gas refining method for removing trace components such as tar contained in a waste gasification gas.
JP 2007-45857 A

  However, in the case of a method for removing impurities such as tar contained in a gasification gas such as biomass, as described in Patent Document 1, the cleaning oil is sprayed in the tower and the gas and the cleaning oil are brought into contact with each other. This requires a light oil scrubber that dissolves the light oil contained in the gas in the cleaning oil, a distillation tower that distills and separates the light oil from the cleaning oil recovered by the light oil scrubber, and the process is complicated and It is also disadvantageous in terms of cost.

  For this reason, when examining the process of gasifying coal at a low temperature, the method for removing impurities such as tar contained in gasified gas such as biomass as described in Patent Document 1 is applied as it is. It is difficult, and it can be said that there is much room for improvement.

  In view of such circumstances, the present invention can reliably remove the tar content contained in the gasification gas at low temperature of coal while simplifying the process and reducing the cost, thereby contributing to the realization of coal low temperature gasification. It is an object of the present invention to provide a method and apparatus for purifying coal gasification gas.

The present invention relates to a coal gasification gas purification method for obtaining a synthesis gas by purifying a gasification gas obtained by gasifying coal in a gasification furnace at a low temperature of 700 ° C. to 900 ° C.
The gasified gas is cooled by a heat exchanger to recover the heat, and the cooled gasified gas is directly cooled by a direct cooler using water spray spray so that the temperature is lowered to 30 ° C. to 90 ° C. The indirect cooling of the gasified gas is performed by indirect cooling using a first indirect cooler to condense the heavy tar, light tar and water vapor, and the indirect cooling is performed at normal pressure. The gas is treated with a mist remover to remove the mist-like tar, and the gasified gas treated with the mist remover is pressurized to about 1 MPa to 5 MPa with a booster to saturate the tar in the gasification gas. Reduce the vapor concentration and condense the heavy and light tar content by indirectly cooling the gasified gas whose pressure has been increased and the temperature has been increased with a second indirect cooler to lower the temperature to 30 ° C. or lower. With mist and removal Those relating to the coal gasification gas purification how.

  In the coal gasification gas refining method, it is desirable to adsorb and remove the vaporized light tar by introducing the gasification gas indirectly cooled by the second indirect cooler into the adsorber.

  In this case, the gasified gas indirectly cooled by the second indirect cooler may be introduced into the auxiliary mist remover to remove the misted tar, and then guided to the adsorber.

  In the coal gasification gas refining method, the combustible substance is concentrated by treating the waste water containing the tar content generated in the tar content removal process with a waste water treatment device, and the concentrated combustible material is gasified. It is also effective to put the gasification furnace as a raw material or heat source.

On the other hand, the present invention is a coal gasification gas refining apparatus for purifying gasification gas obtained by gasifying coal in a gasification furnace at a low temperature of 700 ° C. to 900 ° C. to obtain synthesis gas.
A heat exchanger that cools and recovers heat of the gasification gas;
A direct cooler that directly cools the gasified gas after cooling with the heat exchanger so that the temperature is lowered to 30 ° C. to 90 ° C. by water spraying;
A first indirect cooler that condenses a heavy tar, a light tar, and water vapor by indirectly cooling the gasified gas directly cooled by the direct cooler so that the temperature is lowered to 30 ° C. or less;
A mist remover that removes a mist-like tar from a normal pressure gasification gas indirectly cooled by the first indirect cooler;
A booster that lowers the saturated vapor concentration of tar in the gasification gas by pressurizing the gasification gas treated with the mist remover to about 1 MPa to 5 MPa;
Second indirect cooling that condenses and mists heavy tars and light tars and removes them by indirectly cooling the gasified gas that has been boosted by the booster and the temperature is lowered to 30 ° C. or less. The present invention relates to a coal gasification gas refining apparatus characterized by comprising:

  The coal gasification gas refining apparatus includes an adsorber that introduces the gasified gas indirectly cooled by the second indirect cooler and adsorbs and removes light tar components vaporized in the gasified gas. It is desirable.

  In this case, after the gasified gas indirectly cooled by the second indirect cooler is introduced and the misted tar content in the gasified gas is removed, the auxiliary mist remover for guiding the gasified gas to the adsorber You may make it provide.

  Further, in the coal gasification gas refining method, the combustible substance is concentrated by treating the waste water containing the tar content generated in the equipment for removing the tar content, and the concentrated combustible substance is gasified. It is also effective to provide a wastewater treatment device that is charged into the gasification furnace as a raw material or heat source.

  According to the coal gasification gas refining method and apparatus of the present invention, the tar content contained in the gasification gas at low temperature of coal can be reliably removed while simplifying the process and reducing the cost. The outstanding effect that it can contribute to realization of can be produced.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an example of an embodiment for carrying out the present invention.
A gasification furnace 1 that is supplied with coal and water vapor as a gasification raw material and gasifies coal at a low temperature of 700 ° C. to 900 ° C. to generate gasification gas;
A heat exchanger 2 that cools and recovers heat of the gasification gas generated in the gasification furnace 1;
A direct cooler 3 that directly cools the gasified gas after cooling in the heat exchanger 2 by water spraying so that the temperature is lowered to 30 ° C. to 90 ° C .;
A first indirect cooler 4 that indirectly cools the gasified gas directly cooled by the direct cooler 3 to reduce the temperature to 30 ° C. or less and condenses a heavy tar, a light tar, and water vapor;
A mist remover 5 for removing a mist-like tar from the atmospheric gasification gas indirectly cooled by the first indirect cooler 4;
A booster 6 that lowers the saturated vapor concentration of tar in the gasification gas by pressurizing the gasification gas treated in the mist remover 5 to about 1 MPa to 5 MPa;
A second indirect that condenses and mists heavy tars and light tars and removes them by indirectly cooling the gasified gas boosted by the booster 6 so that the temperature is lowered to 30 ° C. or less. A cooler 7;
An adsorber 8 in which the gasified gas indirectly cooled by the second indirect cooler 7 is introduced and adsorbs and removes light tar components vaporized in the gasified gas;
Treating the waste water containing tar generated in the direct cooler 3, the first indirect cooler 4, the mist remover 5, the booster 6 and the second indirect cooler 7 as equipment for removing the tar. And a wastewater treatment device 9 for concentrating the combustible material (tar content, char) and supplying the concentrated combustible material to the gasification furnace 1 as a gasification raw material or heat source.

In the gasification gas from which the tar content is adsorbed and removed in the adsorber 8, sulfur content such as H ₂ S, COS, and CS ₂ is present at a concentration of several tens of ppm or less. Therefore, the sulfur content is removed from the gasification gas. A desulfurizer 10 using a wet desulfurization process or a dry desulfurization process is provided. As the wet desulfurization process, there are a Takahax process using ammonia as an absorbent, a Fumax process, a Diamox process, a Karl Still process, and a Stretford process using sodium carbonate. Furthermore, when desulfurization performance at a level of several ppb is required, a precision desulfurizer 13 such as an activated carbon packed tower filled with activated carbon subjected to chemical treatment is provided as necessary, and the gasifier gas is provided in the precision desulfurizer 13. And a small amount of sulfur may be adsorbed and removed.

  When there are a large amount of nitrogen and chlorine due to the properties of the gasification raw material, a deammonizer 11 and a desalinator 12 for absorbing and removing nitrogen and chlorine that have not been removed by the direct cooler 3 are used as necessary. Should be provided.

  The direct cooler 3 may be a packed tower, a Moretana tower, a cyclones scrubber, a charged scrubber, a venturi scrubber, a jet scrubber, or a stored water scrubber.

  The mist remover 5 may be an electric dust collector, a bag filter, a spray tower or a packed tower, a moretana tower, a cyclone scrubber, a charged scrubber, a venturi scrubber, a jet scrubber, or a stored water scrubber.

  Furthermore, as the adsorber 8, an activated carbon packed tower or a solvent washing tower can be used.

  Next, the operation of the illustrated example will be described.

  First, in the gasification furnace 1, coal is gasified at a low temperature of 700 ° C to 900 ° C. Gasification raw materials are preferably those that are easily gasified at low temperatures, and among coal, lignite, petrocoke, and black liquor that are relatively easy to gasify are listed. Steam is used as the gasifying agent, and steam gasification is performed. The amount of tar contained in the gasification gas generated with the gasification of these raw materials is larger than that of high-temperature gasification of coal and slightly smaller than that of biomass or the like.

  The gasification gas leaving the gasification furnace 1 is 700 ° C. to 900 ° C., and exchanges heat with steam in the heat exchanger 2 until the outlet gas temperature reaches 300 ° C. to 600 ° C. Is recovered as steam.

  The gasified gas exiting the heat exchanger 2 is cooled by spraying water directly in the cooler 3, and the condensed tar content is removed from the gasified gas. A spray cooler is used as the direct cooler 3, and the flow rate of water to be sprayed is adjusted by the gasification gas temperature at the inlet so that the outlet gasification gas temperature is 30 ° C. to 90 ° C. That is, in the direct cooler 3, the gasified gas is cooled to reduce the saturated vapor concentration of tar, and the condensed and mist tar is removed from the gasified gas by collision with spray spray water. It has become. In addition, in order to efficiently remove the misted tar content, an optimal water droplet to be sprayed is used. The droplet diameter of the spray water can be controlled by the type of spray nozzle for spraying and the supply pressure of the spray water. The smaller the spray water droplet size, the greater the contact area and contact efficiency with the tar mist, which is desirable.However, if the spray water droplet size is too small, the sprayed water droplet size is increased by the gasification gas to be treated. The diameter having a terminal velocity equal to or higher than the actual flow velocity in the spray tower is set as a lower limit, and the value is made as small as possible.

  The gasified gas leaving the direct cooler 3 is cooled in the first indirect cooler 4 so as to be 30 ° C. or less. The first indirect cooler 4 reduces the saturated vapor concentration of the tar content in the gasification gas by lowering the temperature as much as possible, and condenses / mists the heavy tar content, light tar content and water vapor as much as possible. To remove. It is more effective if the cooling medium is deeply cooled using seawater or brine. In order to avoid clogging of the gasification gas line due to the tar content condensed inside the first indirect cooler 4, heat exchange on the tar condensing surface is performed periodically or intermittently when the pressure loss exceeds a specified value. Spray hot water or water on the surface and wash away the accumulated tar.

  The gasified gas exiting the first indirect cooler 4 is vented to the mist remover 5 for the purpose of removing the mist tar. When an electric dust collector is used as the mist remover 5, the tar removal rate increases as the applied voltage increases. However, when the applied voltage increases, a spark occurs between the discharge line and the current collecting surface, and the mist removal rate decreases. . Therefore, the operation is performed at the maximum applied voltage at which the operation can be stably performed in a range where no spark is generated according to the composition of the gasification gas to be ventilated and the gas flow rate. Moreover, since the current collection efficiency decreases as the amount of tar deposited on the current collecting surface increases, warm water or water is periodically sprayed on the current collecting surface, and the accumulated tar content is washed away.

  The gasified gas leaving the mist remover 5 is boosted to 1 MPa to 5 MPa by a booster 6. The booster 6 uses a compressor or a pump, and uses either a turbo type or a positive displacement type. In the case where the tar component condensed and misted in the first indirect cooler 4 and the mist remover 5 is removed and the tar component is removed up to the saturated vapor concentration, condensation of the tar component does not occur in the compressor. However, if the first indirect cooler 4 has not completely removed the mist that has been mist-represented by the light tar content, the condensed tar content in the booster 6 will stay in the booster 6 and cause trouble. In addition, a mechanism for discharging the tar content condensed in the booster 6 is provided.

The gasified gas exiting the booster 6 is 100 ° C. to 200 ° C., and is cooled to 30 ° C. or less in the second indirect cooler 7. In this state, the gasification gas is in a pressurized state, and the saturated vapor concentration at 30 ° C. or less is several hundred mg / Nm ^{3 in} benzene. For aromatics having two or more rings having higher vapor pressure than benzene and high molecular weight tars, the concentration can be reduced to several hundred mg / Nm ³ or less.

  The gasified gas exiting the second indirect cooler 7 is passed through the adsorber 8, and the tar content contained in the gasified gas is removed by adsorption. When an activated carbon packed tower is used as an example of the adsorber 8, the tar adsorption performance of activated carbon improves as the temperature decreases. However, the higher the water vapor concentration is, the more specifically, the higher the relative humidity exceeds 50%, the lower the adsorption performance. Therefore, the operating temperature of the activated carbon is set to 25 ° C. to 200 ° C., and the optimum operating temperature is maintained while keeping in mind that the relative humidity in the gasification gas is maintained at 50% or less. In addition, if the heavy mist that has been misted in the mist remover 5 such as an electrostatic precipitator upstream of the adsorber 8 cannot be completely removed, it is necessary to adsorb and remove it in the activated carbon packed tower. Since the quality tar adsorption performance shifts to the higher temperature side, the optimum temperature is maintained in the range of 100 ° C. to 200 ° C. in consideration of the performance of light tar adsorption and the amount to be adsorbed and removed. Furthermore, the activated carbon that has adsorbed the tar content is subjected to regeneration treatment to repeatedly adsorb and remove the tar content.

  On the other hand, as a device for removing the tar content, waste water containing tar content generated in the direct cooler 3, the first indirect cooler 4, the mist remover 5, the booster 6, and the second indirect cooler 7, The flammable substance (tar content, char) is concentrated by being collected and processed in the waste water treatment device 9, and the concentrated flammable substance is charged into the gasification furnace 1 as a gasification raw material or a heat source.

  The gasified gas exiting the adsorber 8 has its sulfur content removed by the desulfurizer 10, and if the content of the gasification raw material contains a large amount of nitrogen and chlorine, the gasified gas exiting the desulfurizer 10 is required. In response to the removal of nitrogen and chlorine which are guided to the deammonizer 11 and the demineralizer 12 and not directly removed by the direct cooler 3, and further, desulfurization performance at several ppb level is required. The gasification gas is ventilated through the precision desulfurizer 13, and a small amount of sulfur is adsorbed and removed.

  Note that a part of the gasification gas is supplied to the gasification furnace 1 as necessary.

  As a result, in the process of gasifying coal at low temperature, the cleaning oil is sprayed in the tower and the cleaning oil is brought into contact with the cleaning oil as in the method of removing impurities such as tar contained in the gasification gas such as biomass. Gas oil scrubber that dissolves the light oil contained in the gas into the washing oil, and a distillation tower that distills and separates the light oil from the washing oil recovered by the light oil scrubber, etc. The tar content contained in the gasified gas can be reliably removed, the process is not complicated, and the cost is advantageous.

  In this way, while simplifying the process and reducing the cost, the tar content contained in the gasification gas at low temperature of coal can be surely removed, which can contribute to the realization of low temperature gasification of coal.

  FIG. 2 shows another example of the embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components, and the basic configuration is the same as that shown in FIG. However, as shown in FIG. 2, the feature of the illustrated example is that the gasified gas indirectly cooled by the second indirect cooler 7 is introduced and the misted tar content in the gasified gas is introduced. After removing the gas, an auxiliary mist removing device 14 for introducing the gasified gas to the adsorber 8 is provided.

The gasified gas exiting the second indirect cooler 7 is in a pressurized state, and the saturated vapor concentration is reduced to several hundred mg / Nm ³ or less, and the tar content above the saturated vapor concentration is misted. Therefore, when gasified gas is passed through the auxiliary mist remover 14, the mist tar is efficiently removed by the auxiliary mist remover 14.

  When an electrostatic precipitator is used as an example of the auxiliary mist remover 14, the tar removal rate increases as the applied voltage increases. However, when the applied voltage increases, sparks are generated between the discharge line and the current collecting surface, resulting in a mist removal rate. Decreases. Therefore, it is desirable to operate at the maximum applied voltage that allows stable operation in a range where no spark is generated in accordance with the composition of the gasification gas to be ventilated and the gas flow rate. Moreover, since the current collection efficiency decreases as the amount of tar deposited on the current collecting surface increases, it is only necessary to periodically spray hot water or water on the current collecting surface and wash away the accumulated tar content.

  Thus, even when configured as in the example shown in FIG. 2, as in the case of the example shown in FIG. 1, the tar content contained in the gasification gas at low temperature of coal can be reduced while simplifying the process and reducing the cost. It can be removed reliably and can contribute to the realization of coal low-temperature gasification.

  In addition, the coal gasification gas refining method and apparatus of the present invention are not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention.

1 is an overall schematic configuration diagram showing an example of an embodiment for carrying out the present invention. It is a whole schematic block diagram which shows the other example of embodiment which implements this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gasification furnace 2 Heat exchanger 3 Direct cooler 4 First indirect cooler 5 Mist remover 6 Booster 7 Second indirect cooler 8 Adsorber 9 Waste water treatment device 10 Desulfurizer 11 Deammonizer 12 Desalter 13 Precision desulfurizer 14 Auxiliary mist remover

Claims (8)

In a coal gasification gas purification method for obtaining a synthesis gas by purifying a gasification gas obtained by gasifying coal in a gasification furnace at a low temperature of 700 ° C. to 900 ° C.,
The gasified gas is cooled by a heat exchanger to recover the heat, and the cooled gasified gas is directly cooled by a direct cooler using water spray spray so that the temperature is lowered to 30 ° C. to 90 ° C. The indirect cooling of the gasified gas is performed by indirect cooling using a first indirect cooler to condense the heavy tar, light tar and water vapor, and the indirect cooling is performed at normal pressure. The gas is treated with a mist remover to remove the mist-like tar, and the gasified gas treated with the mist remover is pressurized to about 1 MPa to 5 MPa with a booster to saturate the tar in the gasification gas. Reduce the vapor concentration and condense the heavy and light tar content by indirectly cooling the gasified gas whose pressure has been increased and the temperature has been increased with a second indirect cooler to lower the temperature to 30 ° C. or lower. With mist and removal Coal gasification gas purification method that.   The coal gasification gas refining method according to claim 1, wherein the vaporized light tar is adsorbed and removed by introducing the gasified gas indirectly cooled by the second indirect cooler into the adsorber.   3. The coal gasification according to claim 2, wherein the gasified gas indirectly cooled by the second indirect cooler is introduced into an auxiliary mist remover to remove the misted tar and then led to the adsorber. Gas purification method.   By treating wastewater containing tar generated in the tar removal process with a waste water treatment device, the combustible material is concentrated, and the concentrated combustible material is fed into a gasification furnace as a gasification raw material or heat source. The coal gasification gas refining method according to any one of claims 1 to 3. In a coal gasification gas purification apparatus for purifying gasification gas obtained by gasifying coal in a gasification furnace at a low temperature of 700 ° C. to 900 ° C. to obtain synthesis gas,
A heat exchanger that cools and recovers heat of the gasification gas;
A direct cooler that directly cools the gasified gas after cooling with the heat exchanger so that the temperature is lowered to 30 ° C. to 90 ° C. by water spraying;
A first indirect cooler that condenses a heavy tar, a light tar, and water vapor by indirectly cooling the gasified gas directly cooled by the direct cooler so that the temperature is lowered to 30 ° C. or less;
A mist remover that removes a mist-like tar from a normal pressure gasification gas indirectly cooled by the first indirect cooler;
A booster that lowers the saturated vapor concentration of tar in the gasification gas by pressurizing the gasification gas treated with the mist remover to about 1 MPa to 5 MPa;
Second indirect cooling that condenses and mists heavy tars and light tars and removes them by indirectly cooling the gasified gas that has been boosted by the booster and the temperature is lowered to 30 ° C. or less. A coal gasification gas refining device characterized by comprising:   The coal gasification gas according to claim 5, further comprising an adsorber that adsorbs and removes a light tar component vaporized in the gasification gas, into which the gasification gas indirectly cooled by the second indirect cooler is introduced. Purification equipment.   A gasified gas indirectly cooled by the second indirect cooler is introduced, and an auxiliary mist remover is provided for guiding the gasified gas to the adsorber after removing the misted tar content in the gasified gas. The coal gasification gas refiner | purifier of Claim 6.   Waste water treatment for concentrating combustible substances by treating waste water containing tar contents generated in the equipment for removing tar contents, and charging the concentrated combustible substances into a gasification furnace as a gasification raw material or heat source The coal gasification gas refinement | purification apparatus as described in any one of Claims 5-7 provided with the vessel.

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