JP2006188574A - Method for gasifying and reforming waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for gasifying and reforming waste, capable of decreasing a content of carbon fine particles in a reformed gas. <P>SOLUTION: This method for gasifying and reforming the waste comprises gasifying the waste so as to form a gas, reforming the formed gas, removing dust from the gas by quenching the gas after reformed in a quenching and washing apparatus so as to obtain the reformed gas, and using the reformed gas in another process, wherein fluctuation of a dew point of the formed gas is monitored and steam and/or water is added to at least one of processes comprising a process 1 for gasifying the waste, a process 2 for reforming the gas, and a process 3 for sending the reformed gas to the quenching and washing apparatus, so that the dew point is made to be higher than a temperature of the gas after quenched. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a waste gasification reforming method in which wastes such as municipal waste and industrial waste are gasified and the resulting product gas is recovered as fuel gas.

  Municipal waste and industrial waste are incinerated at the waste disposal site to reduce the volume, and solid matter such as incineration residue that is finally discharged is landfilled at the landfill site. Among these solids, fly ash generated when incinerated or melted contains heavy metals such as zinc and lead, so fly ash is stabilized by cement solidification, chemical treatment, etc. Landfilled after being processed.

When waste is burned, harmful substances such as sulfur oxides, sulfides, hydrogen chloride, heavy metal compounds, and dioxins are generated in addition to pyrolytic gases and combustible components (mainly carbon).
Conventionally, various methods for removing these harmful substances from the combustion gas and reducing these harmful substances contained in the combustion gas have been proposed.

  In Patent Document 1, in an exhaust gas treatment method in which dust is separated by a bag filter after exhaust gas generated by burning waste or the like is cooled, moisture content in the cooled exhaust gas, sulfur oxide or By controlling the cooling temperature of the exhaust gas based on the concentration of at least one of hydrogen chloride, the clogging of the bag filter is prevented, and the removal rate of harmful substances in the exhaust gas, particularly dioxin, is increased. A cooling method is described.

  Patent Document 2 discloses a gas generated from an incinerator for light radioactive waste containing water vapor, acidic pollutants, solid particles and radioactive heavy metals in order to reduce the residual concentration of pollutants in the cleaned gas. A method of cleaning in a process that includes a gas cooling process and a gas filtration process, where the gas is cooled below its dew point in the cooling / condensing unit before the solid particles are filtered or collected from the gas. Capturing radioactive heavy metals in the condensate at the same time as acidic pollutants and soluble particles contained in the gas; treating the condensate to precipitate the radioactive heavy metals and recovering the aqueous solution separated from the precipitate; Absolute salt for collecting salt and water by sending to crystallizer; and heating the gas from the cooling / condensing device to recover the solid particles before returning the purified gas to the atmosphere. fill Feeding the over the water from the crystallizer purification method of incinerating gas to recirculate in the plant is described.

  In Patent Document 3, a small amount of gas is discharged together with dust collection ash from the ash outlet of a dust collector that treats high-temperature exhaust gas, and the gas is cooled to below the dew point together with the dust collection ash, thereby condensing the dust collection ash. A method for humidifying dust collection ash is described which prevents dust ash from scattering and adhering to a transporter by humidification.

  In Patent Document 4, a chimney composed of an ascending cylinder and a descending cylinder is used to first raise the combustion gas in the ascending cylinder, and then guide the liquid to the descending cylinder so that the liquid is finely divided into the descending combustion gas. The combustion gas is sprayed in the form of a mist to quench the combustion gas, and the combustion gas that has reached the saturation point is brought into contact with the atomized fine droplets to further cool and condense the water vapor in the combustion gas to atomize and further condense. Also described is a method for condensing and purifying combustion gas, which forms condensed droplets that take in pollutants (nitrogen oxides, sulfur oxides, carbon dioxide gas), attaches them to the inner wall of the downcomer cylinder, and allows them to flow down for removal. Has been.

  However, in any of the above methods, incineration ash is generated by the incineration process, and in order to dispose of it, a landfill disposal site is required. In recent years, it has become very difficult to secure such a disposal site. . In addition, even when stabilized, there is a risk that heavy metals eluted from landfilled fly ash will cause environmental pollution in the ultra-long term, and it is necessary to take measures to prevent environmental pollution. is there.

Thus, in recent years, as a waste treatment method that replaces the above-described incineration treatment, heat treatment of waste in a reducing heat treatment furnace has been performed. As an example of such a processing method, a gasification and melting process based on a gasification reforming method has attracted attention, and various proposals have been made (see Patent Documents 5 to 9).
The gasification and melting process using such a gasification reforming method involves converting waste into a gas containing pyrolysis gas and a melt by heat treating the waste in a waste gasification and melting furnace. In the obtained gas, there is an advantage that harmful gas components such as dioxin are small. And since the combustible gas is contained in the pyrolysis gas which generate | occur | produces from a waste, this can be effectively utilized as a fuel for electric power generation, an industrial fuel, a chemical industry raw material, etc. Moreover, since harmful substances such as heavy metals contained in the waste are fixed in the molten slag, the heavy metals are not easily eluted.

In Patent Document 10, in a cooling apparatus for a waste gasification and melting treatment furnace, in order to eliminate various troubles due to deposits in piping, a cylinder disposed in a flue and a high temperature opened on an inner wall are disclosed. It is equipped with a gas inlet, a scraper, and a pipe for sending the fallen deposits to the recovery chamber. Further, it flows down along the inner wall of the cylinder wall, and a coolant supply nozzle is used as a wetting wall. A cooling device for high-temperature gas is described in which an adhesive substance is smoothly collected by providing a nozzle for cooling liquid forming a film.
However, in the conventional method, the fine carbon particles generated in the combustion gas quenching process cannot be efficiently removed.

Japanese Patent Laid-Open No. 11-248124 Japanese National Patent Publication No. 9-510295 JP 58-139776 A JP-A-5-31321 JP 2004-195400 A Special table 2003-511545 gazette JP 2003-1041 A JP 2003-3177 A JP 2002-363777 A JP 2002-267147 A

  An object of the present invention is to provide a method for reducing the content of carbon fine particles in a reformed gas in a waste gasification reforming method.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that carbon fine particles can be reduced by making the dew point of the reformed gas higher than the gas temperature after rapid cooling, thereby completing the present invention. I let you.
That is, the present invention is as described below.

(1) Gasification of waste, reforming of the generated gas, and use of the reformed gas obtained by quenching the reformed gas with washing water in a rapid cooling apparatus for other processes A gasification and reforming method, wherein a dew point variation of the generated gas is monitored and the gasification step, the gas reforming step and the modification step are performed so that the dew point becomes higher than the gas temperature after the quenching. A waste gasification and reforming method, wherein water vapor and / or water is added in at least one of the steps of sending the purified gas to a rapid cleaning apparatus.
(2) The method for gasifying and reforming waste according to (1) above, wherein water vapor and / or water is added so that the dew point is from 60 ° C. to 90 ° C.
(3) The waste gasification reforming method according to the above (1) or (2), wherein the rapid cleaning apparatus is a wet wall type rapid cleaning apparatus with an inner wall temperature of 100 ° C. or less.
(4) The waste gasification and reforming method according to any one of (1) to (3) above, wherein 5% or more of the carbon fine particles in the generated gas are removed in the rapid cooling apparatus.

(5) Wastes as described in (1) to (4) above, wherein a part or all of the cooling water used in the rapid cooling apparatus is cooled by heat exchange and used again as cooling water for the rapid cleaning apparatus. Gasification reforming method.
(6) The waste gasification reforming method according to any one of (1) to (5) above, wherein the pH of the cooling water used in the rapid cleaning apparatus is adjusted to 2 or more and 5 or less.
(7) The waste gas as described in (1) to (6) above, wherein the cooling water used in the quench cleaning apparatus is used for cleaning zinc metal or zinc compound recovered in the gasification reforming furnace. Reforming method.

  According to the present invention, carbon fine particles in the reformed gas obtained by melting and gasifying municipal waste and industrial waste can be effectively removed, so that the apparatus in the gas purification process may be blocked. In addition, the carbon fine particles are removed even when used as a fuel gas, so that the apparatus is not adversely affected.

The method of the present invention is applied in a gasification reforming process by a gasification reforming method (thermoselect method). First, an example of a gasification reforming process will be described with reference to FIG.
The gasification reforming method shown in FIG. 1 includes the following processes.
1. 1. Press and degas channel (1) Waste compression, (2) Drying and pyrolysis 2. High temperature reactor / homogenization furnace (3) Gasification, melting, (4) Slag homogenization, (5) Gas reforming Gas purification (6) Gas quenching (quenching, acid cleaning, acid cleaning), (7) Gas purification (alkali cleaning, desulfurization, dehumidification)
4). Water treatment (8) Water treatment (precipitation, desalination, etc.)

The basic configuration of this method will be described along the flow as follows.
Wastes such as municipal waste and industrial waste accumulated in the pits are compressed by a press machine, heated and distilled by indirect heating in a dry pyrolysis process, and sent to a high temperature reactor. A lance is arranged at the lower part of the high temperature reactor, and high concentration oxygen is introduced into the furnace by this lance, and this oxygen gas gasifies carbon in the dry distillation product to produce carbon monoxide and carbon dioxide. Further, since high-temperature steam is present, a water gas reaction occurs between carbon and steam, and hydrogen and carbon monoxide are generated. Further, organic compounds (such as hydrocarbons) also react with water vapor to produce hydrogen and carbon monoxide. As a result of the above reaction, crude synthesis gas is recovered from the top of the high temperature reactor.

  On the other hand, the melt produced in the lower part of the high temperature reactor flows out from the high temperature reactor to the homogenization furnace. This melt contains carbon, trace amounts of heavy metals, etc., and oxygen gas is supplied from a burner in the homogenization furnace, and the carbon is gasified with sufficient oxygen or water vapor to produce hydrogen, carbon monoxide, carbon dioxide. Is generated. In the homogenization furnace, the metal melt has a large specific gravity and therefore accumulates in the lower part of the slag. The melt flows down to the granulation system and is cooled and solidified, and the metal / slag mixture is separated into metal and slag by magnetic separation.

  The crude syngas generated from the high temperature reactor is rapidly cooled from about 1200 ° C. to about 70 ° C. by injecting acidic water with a quenching washing apparatus to prevent resynthesis of dioxins. At this time, the gas is washed with acidic water, and heavy metal components such as Pb and chlorine contained in the crude synthesis gas are dissolved during the washing.

  The acid-cleaned synthesis gas is further acid-washed if necessary, and then alkali-washed, and the remaining acidic gas such as hydrogen chloride gas is neutralized and removed. Next, hydrogen sulfide in the gas is converted to sulfur by a desulfurization washing apparatus and recovered as a sulfur cake. Next, the synthesis gas is used as a refined fuel gas after moisture is removed in a low temperature dehumidification process.

FIG. 2 shows the details of the waste gasification reforming method of the present invention.
Wastes such as wood chips and waste plastics are subjected to compression, drying and pyrolysis treatment, and then processed in a gasification and melting process.
The gas which has been gasified and melted and the generated gas is then reformed in a gas reforming step.

  The gas generated in the gasification and melting step 1 is reformed in the gas reforming step 2, and the high-temperature reformed gas is quenched and washed with cooling water in the quench cleaning step 3 to remove water-soluble components and carbon fine particles, Next, the gas is purified in the gas purification step 4 and recovered as fuel gas. On the other hand, the cooling water and the cleaning liquid are heated by exchanging heat with the high-temperature reformed gas, and then a part thereof is sent to the water treatment process, and the remainder is the cold water supplied from the cooling tower 6 in the heat exchanger 5. After being cooled by exchanging heat with, it is sent again to the rapid cooling step as cooling water and cleaning liquid. The cold water heat-exchanged with the cooling water in the heat exchanger 5 becomes warm water, and is returned to the cooling tower 6 and cooled again.

  The present invention is characterized in that water vapor or water is added in at least one of a gasification step, a gas reforming step, and a step of sending the reformed gas to a rapid cooling apparatus. The addition of water vapor and water is as described below.

That is, when the reformed gas is rapidly cooled by a boiler without recovering heat to recover the fuel gas, carbon particles are generated by a reaction such as 2CO → CO ₂ + C in the cooling process.
If the carbon fine particles are contained in the reformed gas, the carbon fine particles may be adversely affected when the fuel gas obtained as a product is used in the gas purification process, which is a subsequent process. Needs to be removed from the reformed gas, but since the carbon fine particles are fine, it is not easy to remove them.

However, if the dew point of the generated gas is higher than the temperature of the gas after quenching (that is, the gas coming out of the quenching cleaning device), the surface of the carbon fine particles contained in the reformed gas after quenching is wetted and trapped. It becomes easy to be done.
For this reason, in the present invention, steam and / or water is added in order to monitor the dew point variation of the generated gas so that the dew point of the reformed gas becomes higher than the gas temperature after the rapid cooling.

Water vapor and / or water may be added in any one of the steps of gasification, gas reforming, and the step of sending the reformed gas to the rapid cleaning apparatus. May be added.
Steam and water may be added from a burner or lance installed in the gasification reforming furnace, or may be installed by installing a separate pipe. The charging place may be a gasification reforming furnace or a pipe installed between the gasification reforming furnace and the cooling device, but it is preferable to charge in the gas reforming process. Either water or steam has an effect of capturing carbon particles, but it is more preferable to charge steam because the thermal efficiency of the gasification reforming furnace is improved.
It is also possible to increase the fuel gas recovery rate by collecting the captured carbon particles and returning them to the furnace.

It is preferable that the dew point of the generated gas is 60 ° C. or higher and 90 ° C. or lower by adding water vapor or water. This is because cooling water is necessary for cooling, and a normal cooling tower can only cool to about 30 ° C, and if it is less than 60 ° C and the dew point is too low, a chiller is required. Because it disappears. In addition, when the dew point exceeds 90 ° C., the steam is cooled, so that a lot of heat of condensation is generated, the equipment of the cooling tower becomes excessive, and it is not economical.
FIG. 3 shows the relationship between the carbon fine particle amount of the reformed gas and the dew point. When the vertical axis is the relative carbon fine particle amount (the generated carbon fine particle amount with respect to the charged carbon amount), the full scale is about 5%.
As shown in FIG. 3, when the temperature is less than 60 ° C., the amount of carbon fine particles in the reformed gas also increases rapidly. Therefore, it is not only necessary to make the removal equipment excessive, but also the gasification efficiency is lowered, resulting in economic efficiency. Getting worse.

  The gas temperature after rapid cooling is determined by the sensible heat of the sensible heat of the introduced gas, the sensible heat of the charged cooling water, the sensible heat of the cooled gas, the condensation heat of the condensed water, and the sensible heat of the water after cooling. Moreover, the temperature of the gas after cooling cannot be made lower than the temperature of the cooling water to be charged.

As a method of rapidly cooling the gas, a method of spraying water and cooling the gas with latent heat of vaporization that evaporates the water is generally used. In the present invention, it is preferable to use a saturation type cooling device. The saturation type cooling device cools the gas by applying a large amount of water to the gas and increasing the sensible heat of the water, that is, the applied water temperature. In this case, since the cooling is performed at a temperature lower than the dew point, moisture in the gas is condensed. By applying a large amount of water, the temperature of the wall surface of the cooling tower can be made lower than 100 ° C., the surface can be kept moist, and the selection of the material becomes easy. Preferably, the gas is cooled to 70 ° C. or lower. Further, since it is not necessary to evaporate, the cooling volume can be small, and therefore it is possible to rapidly cool.
On the other hand, in the case of the evaporative cooling device, the temperature decrease rate becomes extremely small as the gas temperature decreases.

Further, according to the saturation type cooling device, since it is not necessary to evaporate the applied water, it is not necessary to make small water particles, and it is not necessary to reduce the diameter of the nozzle. Further, when there is a precipitate or the like, the precipitate is dissolved inside the cooling tower, so that it can be used stably for a long time. However, water treatment is required in the saturation type cooling device.
The rapid cleaning apparatus can have two or more stages of a rapid cooling unit and a cleaning unit. That is, in order to increase the rapid cooling effect in the first stage, a large amount of cooling water (cleaning water) is applied so that the cooling effect is greater than the cleaning effect, and the second and subsequent stages are used as cleaning parts for increasing the cleaning effect. it can.

  In the present invention, in the rapid cooling apparatus, it is particularly preferable that the wet wall is formed by cooling water (cleaning water) and the inner wall temperature is maintained at 100 ° C. or lower. For example, when a large amount of cooling water is applied from the wall surface of the rapid cleaning apparatus toward the opposite wall surface, most of the cleaning water falls in the pipe, and part of it flows down along the wall surface to form a wet wall. The droplets trapped by the particles in the entire cooling device are less likely to evaporate, and even if trapped on the wall surface, if the surface is wet and falls, it does not accumulate on that part. Furthermore, if a temperature of 100 ° C. or lower is ensured, the range of selection is widened in terms of material, and the facility can be used for a long time.

  In the rapid cleaning apparatus, 5% or more, more preferably 20% or more of the carbon fine particles are preferably removed. This avoids blockage of the carbon fine particles by the gas purification apparatus, and facilitates removal of the carbon fine particles in the gas purification step.

  It is preferable that a part or all of the cooling water used in the rapid cooling apparatus is cooled by heat exchange and reused as cooling water for the rapid cooling apparatus again. Cooling with new water without reusing increases the amount of water that needs to be treated, and deteriorates the economics of the water treatment device.

  In gasification reforming, not only carbon fine particles but also heavy metal gases having a low boiling point exist. The heavy metal precipitates as particles during cooling, and can be absorbed and removed by acidic water. In this case, if the pH is high, the removal rate decreases, and if the pH is too low, there will be a problem with the material of the cooling device and the material of the pH meter for long-term use. Considering the above, it is preferable to adjust the pH of the cooling water used in the rapid cleaning apparatus to 2 or more and 5 or less.

  In addition, the waste contains chlorine, which is normally contained in the generated gas as hydrogen chloride gas when the waste is gasified. This hydrogen chloride is added to the cooling water. When dissolved, the cooling water becomes an aqueous hydrochloric acid solution. Since this hydrochloric acid aqueous solution can absorb and remove gaseous zinc metal or zinc compounds recovered in the gasification reforming furnace, the cooling water used in the rapid cleaning apparatus is recovered from the zinc recovered in the gasification reforming furnace. It is preferable to use it for washing metal or zinc compounds.

  It is economical and preferable to use hot water generated in the system as a supply source of water and water vapor to be added to the gas. As such hot water, (1) hot water for engine cooling generated by gas engine power generation, (2) waste water after using waste heat boiler steam from gas engine power generation in the plant system, (3) After supplying the steam recovered by the waste heat boiler to other facilities for use of residual heat, hot water that has returned can be used.

[Comparative Example 1]
Using a mixture of wood chips and waste plastic as a raw material, a gas mainly composed of hydrogen and carbon monoxide was recovered from a gasification reforming furnace without blowing water vapor. The gas reforming temperature was 1200 ° C. The dew point of the generated gas was 59 ° C. Although the reformed gas was cooled to about 80 ° C. by applying washing water with a quenching washing device, the pressure was lost in the cooling device, and operation was not possible for a long time.

[Example 1]
Using a mixture of wood chips and waste plastic as a raw material, low pressure steam was added at 0.22 t-steam / t-raw material, and a gas mainly composed of hydrogen and carbon monoxide was recovered. The gas reforming temperature was 1200 ° C. The dew point of the generated gas was 76 ° C. The reforming gas was cooled to about 70 ° C. by applying washing water in the quenching washing apparatus, and the operation was possible for a long time without increasing the pressure loss with the cooling apparatus.

  When the method of the present invention is used, since the content of carbon fine particles in the reformed gas obtained by gasifying and reforming municipal waste and industrial waste is low, it is effectively used as a high-quality fuel gas. can do.

It is a figure which shows the outline | summary of the waste processing by a gasification reforming system. It is a figure for demonstrating the gasification-reforming method of the waste of this invention. It is a figure which shows the relationship between carbon fine particle content in reformed gas, and a dew point.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gasification process 2 Gas reforming process 3 Rapid cooling washing process 4 Gas purification process 5 Heat exchanger 6 Cooling tower

Claims (7)

  The waste gas is reformed, and the generated gas is reformed. The reformed gas obtained by quenching the reformed gas with washing water in the quenching washing device is used for other processes. The method of gasification, the gasification step, the gas reforming step, and the reforming were performed so that the dew point fluctuation of the generated gas was monitored and the dew point became higher than the gas temperature after the rapid cooling. A method for gasifying and reforming waste, comprising adding steam and / or water in at least one of the steps of sending gas to a rapid cleaning apparatus.   The method for gasifying and reforming waste according to claim 1, wherein water vapor and / or water is added so that the dew point is 60 ° C or higher and 90 ° C or lower.   The waste gasification reforming method according to claim 1 or 2, wherein the quench cleaning device is a wet cleaning method using an inner wall temperature of 100 ° C or less.   The waste gasification and reforming method according to any one of claims 1 to 3, wherein 5% or more of the carbon fine particles in the generated gas are removed in the quench cleaning apparatus.   The waste water according to any one of claims 1 to 4, wherein a part or all of the cooling water used in the rapid cooling apparatus is cooled by heat exchange and used again as cooling water for the rapid cleaning apparatus. Gasification reforming method.   The waste gasification reforming method according to any one of claims 1 to 5, wherein the pH of the cooling water used in the rapid cleaning apparatus is adjusted to 2 or more and 5 or less.   The waste water gasification according to any one of claims 1 to 6, wherein the cooling water used in the quenching washing apparatus is used for washing zinc metal or zinc compound recovered in the gasification reforming furnace. Modification method.

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