JP5489264B2 - Settling separator for gasified combustible gas content - Google Patents

Description

The present invention relates to a gasification furnace in which a substance containing organic matter such as biomass such as coal, pitch, oil coke, waste oil, organic sewage sludge and waste wood, waste plastic, general household waste, and textile waste is used as a combustible gas. The present invention relates to an apparatus for sedimentation separation of solid and liquid contents contained in generated flammable gas (referred to as “gasified flammable gas” in the present invention). In addition, the present invention relates to the property that gasified combustible gas generated from a gasification furnace can be mixed with by-product gas generated in the steel industry.

  In recent years, the need for depletion of petroleum resources and reduction of carbon dioxide emissions has been increasing as attention has been focused on resource problems and environmental problems. For this reason, biomass utilization and waste recycling are being promoted as alternative energy for fossil fuels. Alternative technologies for fossil fuel include processing natural fiber and starch into ethanol, processing waste wood and waste plastic into solid fuel (RPF), converting waste plastic into hydrocarbon oil, waste wood, sewage Methods such as converting organic sludge and waste plastics into flammable gases and using them in steelmaking facilities such as blast furnaces and coke ovens are being used.

  Among these methods, organic materials such as coal, pitch, oil coke, waste wood, organic waste sludge, waste plastic, general household waste, organic industrial waste such as clothing waste and reinforced plastic, construction waste containing wood, etc. The method (gasification technique) for converting a substance containing flammable gas has an advantage that various organic substances can be used, and there is no problem even if a mixture thereof is used. Further, the gasified combustible gas recovered by the gasification technology contains a large amount of hydrogen, carbon monoxide, methane, and, in some cases, other combustible hydrocarbons. Since this gasified combustible gas has a combustion heat of 6 to 15 GJ per cubic meter, it can be used as fuel for boilers and heating furnaces. Moreover, when recovering gasified flammable gas centering on hydrogen and carbon monoxide, it can also be used in the process of producing chemical raw materials such as ammonia and methanol. This gasification technology is also applied to coal, pitch and oil coke gasification.

  In gasification processing using waste or biomass, the raw material may not be stably received depending on the situation, so that it is often impossible to operate a boiler or a heating furnace using this as a single fuel. For this reason, gasified combustible gas is often used by being mixed with fuel such as natural gas or heavy oil. For example, there is an example in which a by-product combustible gas and a gasified combustible gas are mixed and used as a fuel gas in an ironworks having a blast furnace and a coke oven. Further, there is an example in which a gasified combustible gas is mixed with a gas for chemical raw material and a gas obtained by gasifying naphtha or the like.

  Thus, it becomes possible to substitute fossil fuel by using the gasification combustible gas collect | recovered with the gasification technique. However, various mixtures exist in the gasified combustible gas obtained by such a method. This reduces the cleanliness of the gas. The raw materials such as biomass and waste plastic contain ash. Ash is an inorganic substance such as silicon oxide, aluminum oxide, or sodium oxide. In general, coal and biomass contain 10 to 30% by mass of ash, and waste plastics contain 3 to 5% by mass of ash. A certain ratio of this ash is separated into bottom ash and slag in the furnace and is discharged out of the gasification furnace, but part of it is mixed in the gas as dust. Moreover, when biomass and waste plastics are gasified, substances (soot and tar) that are not completely gasified may remain. For example, under conditions where the temperature is higher than 1000 ° C and oxygen is sufficiently supplied, most of the gas will be hydrogen and carbon monoxide, and there will be almost no non-gasified material, but gasification that will leave methane and ethane. When a gas having a high calorific value per unit volume is obtained by the method, soot and tar are generated. This is contained in the gas processing apparatus together with the gas.

  Many of these dusts, soot, and tars have a size of 1 micrometer or less to several tens of micrometers. These cause problems of adhering in the gas processing apparatus, and when they finally arrive at a burner such as a boiler together with gas, they adhere to the inside of the burner or the flow meter and cause clogging. Therefore, the gasified combustible gas discharged from the gasification furnace is purified by the dust removing device and the tar recovery device, and then becomes a gas for fuel and chemical raw material.

  As a method of purifying gasified combustible gas, for example, as described in Patent Document 1, a method of removing mist and dust using a wet fiber filter, or as described in Patent Document 2 In addition, there is a method in which the coolant is refined and sprayed on the exhaust gas to raise the exhaust gas, and at this time, particles with fine dust are captured by gravity. By these methods, dust, soot, and tar in gasified combustible gas are removed to prevent clogging or failure of the gas processing device, and environmental problems and equipment problems are prevented in the combustion process. It was done to prevent a failure.

JP 2007-21476 A Japanese Patent Laid-Open No. 3-72913

  As described above, the prior art for purifying gasified combustible gas by gasifying waste containing organic substances has been performed. Most of the dust, soot and tar (hereinafter referred to as mist soot) in the gasified combustible gas, generally 90 to 98% by the above-described techniques such as the fiber filter and the spraying of the refined coolant. However, it was difficult to further reduce the content by these methods. As a result, in the prior art, the problem of equipment stoppage due to dirt caused by mist and dust inside the gas treatment equipment could be avoided, but environmental problems and equipment failures should not occur in the combustion process of gasified combustible gas. It wasn't always good.

  For example, in the removal technique using a fiber filter, the gap between the fiber filters is usually 0.1 to several mm, and fine mist dust in the gas slips through the filter, making complete removal difficult. In particular, it was difficult to capture particles of several micrometers or less. As a countermeasure, it is conceivable to narrow the fiber filter gap so that mist dust does not pass through. However, this countermeasure has a problem that the gas pressure loss in the fiber filter increases. As a result, more fiber filters are required, and there is a problem that the gas purification device becomes large and the gas pumping power increases. Further, the filter having such a structure is likely to be clogged, so that there is a problem that the filter needs to be frequently cleaned. As a result, there was a problem that the operating rate of the gasifier decreased.

  On the other hand, the coolant spraying technique is suitable for removing solid dust, but it is not a technique that can completely remove mist dust containing oil such as tar. In other words, in this structure of the mist / dust removal device, the fine mist of the cooling liquid with a trapping function removes dust using the reverse flow that flows in the wake, but since the principle of gravity separation is used, the separation efficiency is increased. Requires a high flow rate. Therefore, there is a problem that particles having a terminal velocity smaller than the gas flow velocity cannot be separated. Moreover, it has been difficult to remove tar particles and soot having poor wettability with water. Therefore, mist dust cannot be completely removed even by the coolant spraying technique.

  As described above, in the prior art, mist dust cannot be removed with high efficiency and the gasifier can be operated normally, but gasified combustible gas is used in a boiler or a heating furnace. However, it was not possible to achieve a gas cleanliness level that would not hinder the gas utilization device. As a result, in the prior art, even if the mist dust removal is incomplete or can be removed at a high removal rate, it is necessary to frequently stop the device for cleaning the device. Therefore, a new technique for solving the above problems has been demanded.

The present invention was made in order to solve the problems that occur when cleaning gasified combustible gas including mist soot made of dust, soot, oil, etc. generated from a gasification furnace. As described in (1) to (4) .

(1) The shape of the settling device is a polygonal column or cylinder, the main body is separated into an upper tank and a lower tank, the upper tank is open at the bottom, and the lower tank is open at the top. This is a sedimentation separator having a structure. The projected shape of the device on the ground is such that the upper tub fits inside the lower tub. The collected water is stored at the bottom of the lower tank, and the upper tank is blocked from outside air by the collected water. The upper tank moves up and down to change the volume, and has a structure that always maintains an appropriate residence time against fluctuations in the amount of gasified combustible gas.

(2) The structure according to (1) , wherein the flow direction of the gasification combustible gas outlet pipe is 90 degrees or more with respect to the flow direction of the gasification combustible gas from the gas inlet pipe to the sedimentation separator. It is a sedimentation apparatus for gasified combustible gas-containing materials.

(3) A structure using a sedimentation separator having a cylindrical or polygonal column shape, wherein the product of the height and the maximum width of the apparatus is 100 times or more the area of the gas inlet pipe (1) Or it is a sedimentation-separation apparatus of the gasification combustible gas containing material as described in (2) .

(4) with extracting a mixture of collecting water and mist dust from the bottom of the precipitator, to any one of (3) from a structure of extracting the collected water from the site within 1m from the surface (1) It is a sedimentation separation apparatus of the gasification combustible gas content of description.

  ADVANTAGE OF THE INVENTION According to this invention, the mist dust in gasified combustible gas can be removed with high efficiency, and gasified combustible gas can be utilized effectively as gas for fuel gas or a chemical raw material.

Is a diagram showing an apparatus configuration example of a gasification process equipment for carrying out the sedimentation method gasification combustible gas inclusions. It is sectional drawing which shows an example of the sedimentation-separation apparatus used with the gasification processing equipment of FIG. It is sectional drawing which shows the other example (reference example) of a sedimentation separator. It is sectional drawing which simplifies and shows the sedimentation-separation apparatus of FIG.

In a gasifier, convert biomass, such as coal, pitch, oil coke, waste oil, biomass such as organic sewage sludge and waste wood, waste plastic, general household waste, textile waste, into gasified combustible gas To do. Gasification furnace types include shaft type, rotary kiln type, fluidized bed type, etc. Basically, a method of obtaining gasified flammable gas by dry distillation of organic matter or reaction with water vapor, oxygen, etc. It is. The gasified combustible gas includes combustible carbon monoxide, hydrogen, methane, and the like. For example, as shown in FIG. 1, the gasification processing facility includes a raw material supply device 1, a gasification furnace 2, a gas reforming chamber 3, a gas cooling device 4, a primary dust collector 5, a hydrogen chloride / sulfur compound removing device 6, It comprises a sedimentation separator 7 and the like. For example, in a shaft type gasification furnace, oxygen or air is blown from the bottom of the furnace, the raw material is partially burned in the furnace to generate heat, and the generated heat is heat exchanged with the raw material to perform a pyrolysis reaction. The organic matter is gasified by controlling the gasification reaction. The gasified combustible gas to be recovered ranges from 6 MJ / Nm ³ (low calorie example) to 15 MJ / Nm ³ (high calorie example). The combustible gas in the low calorie gasified combustible gas is mainly composed of carbon monoxide and hydrogen, and the combustible gas in the high calorie gasified combustible gas is carbon monoxide, hydrogen, and Mainly hydrocarbon gas such as methane.

  An organic material as a raw material is supplied to the gasification furnace 2 by the raw material supply apparatus 1, and is gasified by using water vapor and oxygen in the gasification furnace 2. In the case where there is a large amount of tar in the gasified combustible gas immediately after the completion of the gasification reaction, the tar is converted into carbon monoxide, hydrogen, methane, etc. in the gas reforming chamber 3. Since the gasified combustible gas after reforming has a high temperature of 700 to 1100 ° C., the gas cooling device 4 cools it by spraying water. Specific examples thereof include a scrubber, a jet scrubber, a venturi scrubber, and a wet wall. The gasified combustible gas includes dust and soot in which inorganic substances contained in the organic material as a raw material are scattered. Moreover, when methane, ethane, etc. are contained in gasification combustible gas, tar vapor | steam contains. This tar vapor becomes a liquid during gas cooling. Therefore, gasification combustible gas contains dust, soot, and tar. Hereinafter, a gas mixture composed of dust, soot, and tar is referred to as mist dust. Mist dust mainly has a particle diameter of 1 to 20 micrometers, is mainly carbonaceous, and has an apparent specific gravity of about 0.7 to 1.2 kg / L.

  The gas temperature in the gas cooling device 4 is 600 to 1100 ° C. at the inlet and 50 to 80 ° C. at the outlet. Here, the water vapor partial pressure is 95% or more of the saturated water vapor partial pressure. When the mist dust content is high, a part of the mist dust is removed by the primary dust collector 5 thereafter. The type of the primary dust collector 5 may be any type, for example, a method in which water is sprayed and absorbed by a cyclone or a scrubber. Further, when hydrogen chloride or sulfur oxide is mixed in the gasified combustible gas, the hydrogen chloride / sulfur compound removing device 6 may remove it.

  The gasified combustible gas obtained by the above method is sent to the sedimentation separator 7. The gasified combustible gas at this time may have a mist dust concentration of 30 to 1000 mg / cubic meter. If it is less than 30 mg / cubic meter, it is not necessary to carry out the method of the present invention. If it exceeds 1000 mg / cubic meter, a large amount of sediment is accumulated inside the sedimentation separator 7, cleaning frequency becomes high, and continuous operation is possible. It may disappear. Further, it is preferable that the mist dust concentration is 500 mg / cubic meter or less, and this 500 mg / cubic meter or less can eliminate sediment by the water circulation of the settling separation device 7 of the type having collected water at the bottom, which will be described later. This is a more desirable concentration because of the amount.

  In the sedimentation / separation device 7, mist dust in the gasified combustible gas is removed to obtain cleanliness that can be used as fuel. The sedimentation separator 7 is basically a gravity type sedimentation tank. A gasified combustible gas having a water vapor partial pressure of 95% or more of the saturated water vapor partial pressure is introduced into the sedimentation separator 7, and the pressure is increased by 2 kPa or more above the outlet of the gas cooling device 4 and gasified. Reduce flammable gas temperature by 5 ° C or more. By this operation, water vapor in the gasified combustible gas is aggregated to form water mist. When the water mist and mist dust come into contact with each other, the particle diameter of the mist dust increases and the sedimentation speed increases. As a result, mist dust can be separated efficiently even with a simple gravity settling device. In particular, if the pressure difference between the outlet of the gas cooling device 4 and the sedimentation separation device 8 is 3 kPa or more and the gasification combustible gas temperature difference is 15 ° C. or more, the amount of water mist generated increases, Since the particle diameter tends to be 20 micrometers or more, the mist dust separation efficiency is further improved. However, the pressure inside the sedimentation separator 7 is preferably 15 kPa or less. This is because, when the pressure is increased, dissolution of hydrogen chloride in water is promoted and corrosion of the iron plate of the apparatus is prevented from being promoted.

  As the sedimentation separator 7 having such a function, one having a structure in which collected water is stretched at the bottom inside the tank is preferable. The internal temperature of such a sedimentation separator 7 is preferably 10 to 60 ° C. This is because if the temperature exceeds 60 ° C., the collected water tends to evaporate, and the accompanying updraft affects the drop of mist dust. In addition, when the temperature is lower than 10 ° C., the viscosity of the aggregate of the mist dust after collection becomes high, and it becomes difficult to collect the mist dust deposited on the bottom of the collected water.

  The structure of the sedimentation / separation device 7 may basically be a structure in which the volume can be increased and the mist dust inside the sedimentation aggregates and settles, but the minimum flow rate of the gasified combustible gas in the sedimentation / separation device 7 is set. Sedimentation can be promoted by setting it to 0.1 m or less per second. Moreover, the time for the mist dust to settle is ensured by setting the gasification gas residence time inside the sedimentation separator 7 to 300 seconds or more. Here, the residence time is a value obtained by dividing the internal volume of the sedimentation separator 7 by the gasification combustible gas inflow rate (cubic meter / second). Furthermore, it is better that the volume of the sedimentation separator 7 can be changed. By appropriately changing the volume of the sedimentation separator 7, the mixing of the gasified combustible gas inside the apparatus is improved. As a result, the gasified combustible gas passes through a portion near the shortest distance inside the apparatus in a short time. By preventing (short pass), the settling rate of mist dust is improved. Furthermore, when the sedimentation separator 7 is a polygonal column or a cylinder, and the product of the average height and the maximum width of the sedimentation separator is 100 times the area of the gas inlet pipe, The gasified combustible gas introduced into the sedimentation separator 7 spreads well, the gasified combustible gas is dispersed, the flow rate is reduced, the heat transfer of the gas is improved, and the temperature of the gasified combustible gas is decreased. Has the effect of speeding up the generation of water mist.

  An example of the structure of the sedimentation separator 7 having this function is shown in FIG. The sedimentation separator 7 has a polygonal column or cylindrical shape, and the main body is separated into an upper tank 11 and a lower tank 12, and the upper tank 11 has an open bottom surface, and the lower tank 12 has an open top surface. It is a structure that has been. Both the upper tank 11 and the lower tank 12 are steel polygonal columns or cylindrical containers, and the projected shape onto the ground is such that the upper tank 11 fits inside the lower tank 12. The collected water 14 is stored at the bottom 13 of the lower tank 12, and the upper tank 11 is blocked from the outside air by the collected water 14. The upper tank 11 has a structure in which the volume is changed by moving up and down, and an appropriate residence time is always maintained against fluctuations in the amount of gasified combustible gas.

  In order to ensure a sufficient residence time for the settling and separation, the maximum gas passage height is preferably between 1/4 and 2 times the diameter of the settling device body. If the gas passage height is too high, separation within the residence time may be insufficient. If the gas passage height is too low, drift in the sedimentation separator 7 is likely to occur, and there is a possibility that the water surface will be disturbed due to a local increase in flow velocity due to the drift and the trapped matter will be scattered again. Under such conditions, the discharge gas flow rate of the gas inlet pipe 15 into the sedimentation separator 7 is in the range of 1 to 30 m / s, and the distance between the gas inlet 16 and the gas outlet 17 of the sedimentation separator 7 is. Is greater than 1/4 times the maximum value of the gas discharge flow rate per second in the gas inlet pipe 15, the gas distribution of the gas is improved. Furthermore, the flow direction of the gas outlet combustible gas 18 from the gas inlet pipe 15 to the sedimentation separator 7 through the gas inlet pipe 15 is 90 degrees or more (180 in the example of FIG. 2). In this case, the residence time of the gasified combustible gas in the sedimentation separator 7 can be sufficiently secured.

  In the collected water, a mixture of fine solid particles and tar sludge in which mist dust aggregates accumulates. The collected water containing oil sludge is extracted from the bottom of the sedimentation separator. In addition, light oil, soot, etc. float on the upper surface of the collected water surface.If the water surface is filled with oil, adsorption of highly hydrophilic substances is hindered, and re-scattering due to volatilization of the oil may occur. In order to keep the amount of oil above a certain level, it is necessary to remove the oil from the upper surface of the water together with the collected water. For this purpose, the collected water is extracted at a site within 1 m from the water surface.

FIG. 3 shows another example (reference example) of a sedimentation separator. In this example, the upper tank 11 and the lower tank 12 are connected by an expansion / contraction part 19 having a bellows structure, and the expansion / contraction part 19 expands and contracts to change the internal volume of the sedimentation separator 7.

  The gasified combustible gas purified by the method described above has a mist dust concentration of 20 mg / cubic meter or less, and has a purity that can be used in an industrial furnace such as a boiler or a heating furnace. In particular, the method of the present invention is effective when mixed with by-product gases recovered at steelworks such as coke oven gas, blast furnace gas, and converter gas. Since these by-product gases contain a lot of water vapor, the gas temperature decreases when using these by-product gases mixed with gasified combustible gas with high concentration of mist dust. In this mixed gas, water mist is generated, and the phenomenon that the residual mist dust and the water mist come into contact with each other in the gas pipe and the particles having a large particle size precipitate is likely to occur. Therefore, it is very effective to mix and use the gasified combustible gas purified by the method for sedimentation and separation of the gasified combustible gas-containing material of the present invention and the by-product gas of the ironworks.

  The sedimentation separation test of the gasified combustible gas-containing material was performed by the sedimentation separator shown in FIG. FIG. 4 shows the sedimentation separation device of FIG. 2 in a simplified manner. In this embodiment, the inner tank D of the upper tank 11 of the sedimentation separation device 7 is 9 m, the internal height H is 4.5 m, the gas inlet 16 and the gas outlet. The distance L of 17 is 7 m, and the angle formed by the flow direction of the gas outlet pipe 18 with respect to the inflow direction of the gasified combustible gas from the gas inlet pipe 15 is 180 degrees. The inlet gas flow velocity at the gas inlet 16 was 12 m / s, and the internal pressure of the upper tank 11 was 3 kPa.

The test results are shown in Table 1. As shown in Table 1, the inlet gas having a mist dust concentration of 100 mg / Nm ³ was able to be reduced to a mist dust concentration of 20 mg / Nm ³ at the outlet gas.

DESCRIPTION OF SYMBOLS 1 Raw material supply apparatus 2 Gasification furnace 3 Gas reforming chamber 4 Gas cooling apparatus 5 Primary dust collector 6 Hydrogen chloride and sulfur compound removal apparatus 7 Sedimentation separation apparatus 11 Upper tank 12 Lower tank 13 Bottom part of lower tank 14 Collected water 15 Gas inlet Piping 16 Gas inlet 17 Gas outlet 18 Gas outlet piping 19 Extendable part

Claims (4)

  The shape of the settling device is a polygonal column or cylinder, the main body is separated into an upper tank and a lower tank, the upper tank is open at the bottom, and the lower tank is open at the top. It is a sedimentation / separation device for gasified combustible gas content having a structure in which the upper tank is housed in the lower tank in a projected shape on the ground, and the collected water is stored at the bottom of the lower tank. An apparatus for settling and separating a gasified combustible gas-containing material, wherein the upper tank has a structure that is blocked from outside air by collected water, and the volume of the upper tank changes by moving up and down. Against the inflow direction of the gasification combustible gas from the gas inlet pipe into the precipitator, according to claim 1, the flow direction of the outlet pipe of the gasification combustible gas, characterized in that at least 90 degrees Settling device for gasified combustible gas content. A precipitator cylindrical or polygonal pillar shape, according to claim 1 the product of the height and the maximum width of the device is characterized in that it is a precipitator is at least 100 times the area of the gas inlet pipe or 2. A sedimentation / separation device for gasified combustible gas-containing material according to 2 . The apparatus for settling and separating a gasified combustible gas-containing material according to any one of claims 1 to 3, wherein the collected water is extracted at a portion within 1 m from the bottom of the apparatus and the water surface.

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