A biomass entrained-flow gasification system and gasification process with waste heat recovery

Abstract

The present invention provides a biomass fluidized bed gasification system and a gasification process with waste heat recovery. The gasification system includes a feeding unit, a gasification unit, a waste heat recovery unit, a dechlorination device, a ash removal and water washing unit and a CO conversion device. The feeding unit includes a pulverizing and conveying device; the gasification unit includes an fluidized bed gasifier, which is provided with a gasification nozzle and is connected to the output end of the pulverizing and conveying device; the waste heat recovery unit includes a radiation waste pot and a convection waste pot, the input end of the radiation waste pot is connected to the fluidized bed gasifier, and the output end is connected to the convection waste pot; the dechlorination device is arranged at the output end of the convection waste pot; the ash removal and water washing unit is connected to the output end of the dechlorination device, and includes a fly ash filter and a water washing tower; the CO conversion device is connected to the output end of the water washing tower. The gasification system in the present invention can solve the problems of high energy consumption, poor economy, low gasification efficiency, low operation reliability, and difficulty in achieving long-term operation in the prior art, and the gasification process is simple and reliable.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass energy conversion, and in particular relates to a biomass fluidized bed gasification system and a gasification process with waste heat recovery. Background Art

[0002] With the continuous growth of global energy demand and the increasingly severe environmental problems, the efficient and clean conversion and utilization of biomass as a renewable energy source has attracted widespread attention. In particular, with the surge in demand for green fuels such as green methanol and sustainable aviation kerosene in recent years, the industry's demand for biomass gasification technology has also gradually increased; entrained-bed gasification technology has been widely used in the coal chemical industry due to its advantages such as high carbon conversion rate and high cold gas efficiency. However, in the field of biomass gasification, this technology still faces many challenges.

[0003] Biomass such as straw has disadvantages such as low bulk density, high moisture content and low grindability, making it difficult to adapt to the requirements of fluidized bed dry powder gasification technology for raw material particle size, moisture content, and transport fluidity. The chlorine content in straw biomass is also very high. If the traditional fluidized bed gasification technology with quenching process is directly adopted, a large amount of chlorine-containing wastewater that is difficult to utilize will be generated, and the cost of wastewater treatment is extremely high. In addition, the high concentration of hydrogen chloride in the synthesis gas makes it difficult to select materials for the synthesis gas quenching chamber, water scrubber and pipeline in the system, posing a challenge to the equipment selection and stability of the gasification system.

[0004] Patent CN102559272B provides a microwave plasma biomass fluidized flow gasifier and process. Although this technology is theoretically feasible due to the use of microwave and plasma technology, the actual operation energy consumption is extremely high and the technical and economic efficiency is very poor. In addition, the fluidized flow gasification technology used in this patent does not take into account the adverse effects of high content of chlorine and potassium elements in biomass on the gasification system, and it is difficult to adapt to the special needs of biomass fluidized flow gasification. Patent CN204529764U provides a small test device for preparing synthesis gas by biomass fluidized flow gasification, but does not take into account some difficulties and pain points of biomass fluidized flow gasification in actual industrial projects. Its application in the field of biomass gasification is still in the experimental stage, lacks large-scale industrial application cases, and is difficult to apply to actual engineering projects. Patent CN113025384A provides a system and method for preparing synthesis gas, which uses hydrothermal carbonization technology to pretreat biomass. The hydrothermal carbonization technology has high energy consumption, and hydrothermal carbonization also produces a large amount of waste liquid that is difficult to handle, and the technical and economic efficiency is very poor.

[0005] Internationally, there are many successful cases of entrained-flow gasification technology in the field of coal chemical industry, such as the dry powder gasification technology of Air Products and Chemicals in the United States, the GSP gasification technology of Siemens in Germany, the Colin gasification technology of Colin in Germany, and the Prenflo gasification technology of ThyssenKrupp Uhde. In China, there are also technologies such as aerospace furnace and single-nozzle cold-wall pulverized coal pressurized gasification (SE Oriental furnace) being developed and applied. The main application market of coal entrained-flow gasification technology is in China. At present, large-scale coal chemical projects in China basically use entrained-flow gasification technology to produce synthesis gas. However, the entrained-flow gasification technology used for biomass at home and abroad is still very immature and is in the research and development and testing stage, and has not yet been commercialized on a large scale.

[0006] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies in the prior art. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a biomass fluidized bed gasification system and gasification process with waste heat recovery, so as to solve the problems of high energy consumption, poor economy and low gasification efficiency of the prior art biomass fluidized bed gasification process.

[0008] In order to achieve the above-mentioned object and other related objects, the present invention provides a biomass entrained flow gasification system with waste heat recovery, the gasification system comprising:

[0009] A feeding unit, the feeding unit comprising a powder making and conveying device, the powder making and conveying device is used to make biomass into biomass powder and convey the biomass powder for feeding;

[0010] A gasification unit, wherein the gasification unit comprises an entrained flow gasifier, the entrained flow gasifier is provided with a gasification nozzle, the output end of the powder making and conveying device is connected to the gasification nozzle, and the biomass powder enters the entrained flow gasifier through the gasification nozzle;

[0011] A waste heat recovery unit, the waste heat recovery unit includes a radiation waste boiler and a convection waste boiler, the input end of the radiation waste boiler is connected to the fluidized flow gasifier, and the output end of the radiation waste boiler is connected to the convection waste boiler. The high-temperature synthesis gas and ash generated in the fluidized flow gasifier enter the radiation waste boiler and the convection waste boiler in turn and exchange heat with water, and the steam produced as a by-product of the radiation waste boiler and the convection waste boiler enters the steam pipeline network for utilization.

[0012] A dechlorination device, which is arranged at the output end of the convection waste boiler, and the synthesis gas and fly ash after cooling by the convection waste boiler enter the dechlorination device, and the dechlorination device is used to remove hydrogen chloride gas in the synthesis gas;

[0013] A ash removal and water washing unit, the ash removal and water washing unit is connected to the output end of the dechlorination device, the ash removal and water washing unit comprises a fly ash filter and a water washing tower, the synthesis gas and fly ash after dechlorination by the dechlorination device enter the fly ash filter and the water washing tower in sequence, the fly ash filter is used to remove most of the fly ash, and the water washing tower is used to further wash a small part of the fly ash that has not been removed, and remove the residual hydrogen chloride gas in the synthesis gas at the same time;

[0014] A CO conversion device is connected to the output end of the water scrubber, and the synthesis gas after being washed by the water scrubber enters the CO conversion device to undergo a conversion reaction.

[0015] Preferably, the gasification system further comprises a drying and roasting device, the output end of which is connected to the powder making and conveying device, and the drying and roasting device is used to dry, dehydrate and roast the biomass raw materials.

[0016] Preferably, the gasification unit further comprises an air separation device, and the air separation device is used to produce oxygen. The oxygen produced by the air separation device is connected to the gasification nozzle, and the oxygen enters the entrained flow gasification furnace through the gasification nozzle.

[0017] Preferably, a quenching device is further provided between the radiation waste boiler and the convection waste boiler, the quenching device is connected to the output end of the radiation waste boiler, and the quenching device is used to quench and cool the high-temperature synthesis gas and fly ash flowing out of the output end of the radiation waste boiler.

[0018] Preferably, the quenching device is connected to the water scrubber via a quenching gas compressor, a small portion of the synthesis gas is extracted from the outlet of the water scrubber and pressurized by the quenching gas compressor before entering the quenching device, thereby quenching and cooling the high-temperature synthesis gas and fly ash flowing out of the output end of the radiation waste boiler.

[0019] Preferably, the waste heat recovery unit also includes a low-pressure waste boiler, which is arranged between the fly ash filter and the water washing tower. The synthesis gas exchanges heat with the water in the low-pressure waste boiler and is further cooled. The by-product steam in the low-pressure waste boiler enters the steam pipeline network for utilization.

[0020] Preferably, a slag discharge device is provided at the bottom of the radiation waste boiler, and most of the ash in the radiation waste boiler enters the slag discharge device for slag removal under the action of gravity.

[0021] Preferably, the gasification system further comprises a slag water treatment device, which is respectively connected to the slag discharge device and the water washing tower, and the black water discharged from the slag discharge device and the water washing tower enters the slag water treatment device for treatment.

[0022] The present invention also provides a biomass entrained flow gasification process with waste heat recovery, wherein the biomass is gasified using the above-mentioned biomass entrained flow gasification system with waste heat recovery, and the gasification process comprises the following steps:

[0023] S1, adding the dried, dehydrated and roasted biomass into the powder-making and conveying device to prepare biomass powder, and the biomass powder and oxygen enter the entrained flow gasifier through the gasification nozzle to undergo a gasification reaction to generate high-temperature and high-pressure synthesis gas and ash, the gasification reaction temperature is 1200-1500° C., and the gasification reaction pressure is 2MPa-8MPa;

[0024] S2, the high-temperature and high-pressure synthesis gas and ash generated in step S1 first enter the radiation waste boiler to exchange heat with water to complete the initial cooling, and the steam generated by the radiation waste boiler enters the steam network for utilization;

[0025] S3, the syngas and fly ash after the initial cooling enter the quenching device for the second cooling;

[0026] S4, the synthesis gas and fly ash after the second quenching and cooling enter the convection waste boiler to exchange heat with water to complete the third cooling, and the steam produced as a by-product of the convection waste boiler enters the steam network for utilization;

[0027] S5, the synthesis gas and fly ash after the third cooling enter the dechlorination device and a dechlorinating agent is used to remove hydrogen chloride gas in the synthesis gas;

[0028] S6, the dechlorinated synthesis gas and fly ash enter the fly ash filter to remove most of the fly ash, and then enter the low-pressure waste boiler to exchange heat with water and cool the synthesis gas for the fourth time, and the steam produced as a by-product of the low-pressure waste boiler enters the steam network for utilization;

[0029] S7. After the fourth cooling, the synthesis gas and a small amount of fly ash enter the water washing tower for washing to remove the fly ash and the residual hydrogen chloride gas in the synthesis gas. Most of the synthesis gas after washing enters the downstream CO conversion device for conversion reaction. The small amount of synthesis gas after washing in the water washing tower is pressurized by the quenching gas compressor and then enters the quenching device to quench the temperature of the synthesis gas.

[0030] Preferably, the gasification process also includes a slag water treatment step, specifically, most of the ash in the radiation waste boiler in step S2 enters the slag discharge device under the action of gravity to remove the slag, discharge the coarse slag, and transport the black water to the slag water treatment device; at the same time, the black water discharged from the washing tower in step S7 is also transported to the slag water treatment device, and the slag water treatment device treats the black water.

[0031] As described above, the biomass entrained flow gasification system and gasification process with waste heat recovery of the present invention have the following beneficial effects:

[0032] The present invention adopts a drying and baking device to pretreat the biomass. The calorific value of the biomass after drying and baking is improved, the moisture content is greatly reduced, the grindability is greatly improved, and the energy consumption of powder making and conveying device for powder making is significantly reduced. The particle size and powder fluidity of the prepared biomass powder fully meet the requirements of fluidized bed gasification pressurized dense phase conveying, which solves the problems of small processing capacity, high energy consumption and poor powder conveying fluidity of traditional biomass direct powder making, and at the same time can improve the adaptability of fluidized bed gasification technology to different types of biomass raw materials; radiation waste boiler and convection waste boiler are used to recover the sensible heat of the high-temperature synthesis gas generated by the fluidized bed gasification furnace, the system has high cold gas efficiency, and the by-product steam is used in the system to improve the economy of the entire system.

[0033] The present invention adopts dry powder fluidized bed gasification technology, and most of the chlorine in the biomass raw material is transferred to fly ash and slag after fluidized bed gasification, and a small amount of chlorine enters the synthesis gas. By adding a dechlorination device downstream of the convection waste boiler, the hydrogen chloride gas content in the synthesis gas is greatly reduced (about tens of ppm), and the chloride ion content in the wastewater is also significantly reduced accordingly. The fly ash filter and the water washing tower and other equipment can be made of conventional materials, which effectively solves the chlorine corrosion problem caused by the gasification of high-chlorine biomass; due to the high K content in straw biomass, when the synthesis gas passes through the convection waste boiler, the convection waste boiler is prone to ash accumulation, the heat transfer resistance is increased, and the heat transfer efficiency is affected. A synthesis gas quenching device is added at the outlet of the radiation waste boiler, and a small amount of synthesis gas is extracted at the outlet of the water washing tower and pressurized by the quenching gas compressor to quench the high-temperature synthesis gas and ash at the outlet of the radiation waste boiler, so that the liquid fly ash entrained in the synthesis gas loses viscosity after solidification, and will not contaminate the convection waste boiler. At the same time, by optimizing the structural layout and flow field distribution of the convection waste boiler, the ash accumulation risk of the convection waste boiler is significantly reduced.

[0034] The biomass fluidized bed gasification process of the present invention is simple and reliable. Through innovative raw material pretreatment, the waste boiler process is used to recover the high-temperature sensible heat of the synthesis gas, and the fly ash filter is used to separate the fly ash in the synthesis gas, the wastewater discharge is reduced, the wastewater treatment cost is low, and the energy consumption of the fluidized bed gasification process is reduced; the waste boiler process is used to recover the high-temperature sensible heat of the synthesis gas to generate steam, and the gasification system has high cold gas efficiency, which improves the economy and environmental friendliness of the entire system, effectively solves the pain points and difficulties of the biomass fluidized bed gasification technology, and realizes the safe, stable and reliable operation of the biomass fluidized bed gasification device, which is of great significance to the clean and efficient utilization of biomass. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Shown is a schematic diagram of the process structure of a biomass fluidized flow gasification system with waste heat recovery according to the present invention.

[0036] Description of Figure Numbers

[0037] 100 Drying and baking device

[0038] 201 Flour milling and conveying device

[0039] 202 Air separation unit

[0040] 301 Gasification Nozzle

[0041] 302 Entrained Flow Gasifier

[0042] 401 Radiation Waste Pot

[0043] 402 Chilling Device

[0044] 4021 Chilled Air Compressor

[0045] 403 Convection waste pot

[0046] 404 Low pressure waste boiler

[0047] 501 Fly Ash Filter

[0048] 502 Water washing tower

[0049] 600 CO conversion device

[0050] 701 Slag discharge device

[0051] 702 Slag water treatment device

[0052] 800 Dechlorination unit DETAILED DESCRIPTION

[0053] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0054] Before further describing the specific embodiments of the present invention, it should be understood that the protection scope of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments, rather than to limit the protection scope of the present invention. The test methods in the following examples without specifying specific conditions are generally carried out under conventional conditions or under conditions recommended by the manufacturers.

[0055] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the grasp of the prior art by those skilled in the art and the record of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention can also be used to realize the present invention.

[0056] See also Figure 1 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0057] The present invention provides a biomass entrained flow gasification system with waste heat recovery, the gasification system comprises a feeding unit, a gasification unit, a waste heat recovery unit, a dechlorination device 800, a ash removal and water washing unit and a CO conversion device 600;

[0058] Among them, the feeding unit includes a powder making and conveying device 201, which is used to make biomass into biomass powder and convey it into the fluidized flow gasifier; the gasification unit includes an fluidized flow gasifier 302, and the fluidized flow gasifier 302 is provided with a gasification nozzle 301, the output end of the powder making and conveying device 201 is connected to the gasification nozzle 301, and the biomass powder enters the fluidized flow gasifier 302 through the gasification nozzle 301; the waste heat recovery unit includes a radiation waste boiler 401 and a convection waste boiler 403, the input end of the radiation waste boiler 401 is connected to the fluidized flow gasifier 302, and the output end of the radiation waste boiler 401 is connected to the convection waste boiler 403, the high-temperature synthesis gas and ash generated in the fluidized flow gasifier 302 enter the radiation waste boiler 401 and the convection waste boiler 403 in turn and exchange heat with water, and the steam generated by the radiation waste boiler 401 and the convection waste boiler 403 enters The dechlorination device 800 is arranged at the output end of the convection waste boiler 403, and the synthesis gas and fly ash after being cooled by the convection waste boiler 403 enter the dechlorination device 800, and the dechlorination device 800 is used to remove the hydrogen chloride gas in the synthesis gas; the ash removal water washing unit is connected to the output end of the dechlorination device 800, and the ash removal water washing unit includes a fly ash filter 501 and a water washing tower 502. The synthesis gas and fly ash after dechlorination by the dechlorination device 800 enter the fly ash filter 501 and the water washing tower 502 in turn, the fly ash filter 501 is used to remove most of the fly ash, and the water washing tower 502 is used to further wash a small part of the fly ash that has not been removed, and at the same time remove the residual hydrogen chloride gas in the synthesis gas; the CO conversion device 600 is connected to the output end of the water washing tower 502, and the synthesis gas after being washed by the water washing tower 502 enters the CO conversion device 600 for conversion reaction.

[0059] Specifically, biomass powder and oxygen enter the fluidized flow gasifier 302 through the gasification nozzle 301, and undergo a gasification reaction under high temperature and high pressure to generate CO and H as the main components. 2 The synthesis gas of the fluidized bed gasifier 302 outlet is first cooled by the radiation waste boiler 401, and most of the ash enters the slag discharge device under the action of gravity. The synthesis gas and the entrained fly ash are cooled by the quenching device 402 and then enter the convection waste boiler 403 for further cooling. The synthesis gas cooled by the convection waste boiler 403 enters the dechlorination device 800 to remove the hydrogen chloride gas in the synthesis gas by the dechlorination agent. The dechlorinated synthesis gas and fly ash enter the fly ash filter 501 to remove most of the fly ash, and then enter the water washing tower 502 to further wash the small part of the fly ash that has not been removed, and at the same time remove the residual hydrogen chloride gas in the synthesis gas. The synthesis gas washed by the water washing tower 502 is divided into two parts. A small part is pressurized by the compressor to quench the high-temperature synthesis gas and ash at the outlet of the radiation waste boiler 401, and most of the synthesis gas enters the downstream CO conversion device 600 for conversion.

[0060] In a specific embodiment of the present invention, the radiation waste boiler 401 and the convection waste boiler 403 recover the sensible heat of the high-temperature synthesis gas generated by the fluidized flow gasifier 302, the system has a high cold gas efficiency, and the by-product steam can also be used in the system, thereby improving the economy of the entire gasification system; the chlorine in the biomass raw material is mostly transferred to the fly ash and slag after being gasified in the fluidized flow gasifier 302, and a small amount of chlorine enters the synthesis gas. By adding a dechlorination device 800 downstream of the convection waste boiler 403, the hydrogen chloride gas content in the synthesis gas is greatly reduced, and correspondingly the chloride ion content in the wastewater is also significantly reduced; and then the fly ash filter 501 and the water washing tower 502 and the pipeline equipment can be made of conventional materials, which effectively solves the chlorine corrosion problem caused by the gasification of high-chlorine biomass.

[0061] Furthermore, the radiation waste boiler 401 and the convection waste boiler 403 can be of water tube or fire tube structure as required; the radiation waste boiler is in the high temperature section and produces high pressure steam, and the radiation waste boiler 401 is preferably of water tube structure; while the convection waste boiler 403 is in the medium temperature section and produces medium pressure steam. At the same time, to prevent the heated surface from being dusted, the convection waste boiler 403 is preferably of vertical fire tube structure. Both the radiation waste boiler 401 and the convection waste boiler 403 transfer the heat of the synthesis gas to water through the heating surface, thereby generating saturated or superheated medium pressure or high pressure steam.

[0062] As an example, the gasification system further includes a drying and roasting device 100 , the output end of which is connected to the powder making and conveying device 201 , and the drying and roasting device 100 is used to dry, dehydrate and roast the biomass raw materials.

[0063] Specifically, the drying and baking device 100 is used to pre-treat the biomass. After drying and baking, the calorific value of the biomass is increased, the moisture content is greatly reduced, and the grindability is greatly improved, so that the energy consumption of powder making is significantly reduced. The particle size and conveying fluidity of the biomass powder obtained by the powder making and conveying device 201 fully meet the requirements of the fluidized bed gasification pressurized dense phase conveying, and solve the problems of low processing capacity, high energy consumption, and poor conveying fluidity of the traditional direct biomass powder making. In a specific embodiment of the present invention, 90% of the particle size of the biomass powder is less than 1 mm, and preferably, 90% of the particle size of the biomass powder is less than 500 μm; the main factors affecting the conveying fluidity of the biomass powder are the particle size and distribution of the biomass powder, as well as the moisture content of the biomass powder. The moisture content of the biomass powder obtained after pre-treatment by the drying and baking device 100 is almost 0, and its particle size and conveying fluidity fully meet the requirements of the fluidized bed gasification pressurized dense phase conveying.

[0064] Furthermore, by adjusting the key parameters of the drying and baking device 100 (baking temperature and residence time, etc.), different types of biomass can be reliably and low-energy produced into biomass powder that meets the requirements of fluidized bed gasification pressurized dense phase transportation after drying and baking, thereby improving the adaptability of gasification technology to different types of raw materials; in a specific embodiment of the present invention, the drying temperature is 100-150°C, and the drying time is 10-30 minutes; the specific baking conditions are a baking time of 15-120 minutes, preferably 30-60 minutes; and a baking temperature of 200-350°C, preferably 200-300°C.

[0065] Furthermore, a pilot-scale pressurized transportation test was carried out on the biomass powder in the specific embodiment of the present invention. The test results showed that the transportation was stable and controllable, and there was no pipeline blockage or powder bin bridging phenomenon.

[0066] As an example, the gasification unit further includes an air separation device 202 , which is used to produce oxygen. The oxygen produced by the air separation device 202 is connected to the gasification nozzle 301 , and the oxygen enters the entrained flow gasification furnace 302 through the gasification nozzle 301 .

[0067] Specifically, the air separation device 202 separates nitrogen from the air, and the remaining oxygen is used as a gasifying agent and enters the fluidized flow gasifier 302 through the gasification nozzle 301. In a specific embodiment, oxygen and biomass powder simultaneously enter the fluidized flow gasifier 302 through the gasification nozzle 301. The specific structure of the air separation device 202 is not limited here.

[0068] As an example, a quenching device 402 is also provided between the radiation waste boiler 401 and the convection waste boiler 403 . The quenching device 402 is connected to the output end of the radiation waste boiler 401 . The quenching device 402 is used to quench and cool the high-temperature synthesis gas and fly ash flowing out of the output end of the radiation waste boiler 401 .

[0069] Specifically, in view of the high K content in straw biomass, when the synthesis gas passes through the convection waste boiler 403, the convection waste boiler 403 is prone to ash accumulation, the heat transfer resistance is increased, and the heat transfer efficiency is affected. A quenching device 402 is arranged between the radiation waste boiler 401 and the convection waste boiler 403. The quenching device 402 quenches the high-temperature synthesis gas and ash at the outlet of the radiation waste boiler 401, so that the liquid fly ash entrained in the synthesis gas loses its viscosity after solidification and will not contaminate the convection waste boiler 403. At the same time, by optimizing the structural layout and flow field distribution of the convection waste boiler, the risk of ash accumulation in the convection waste boiler 403 is significantly reduced.

[0070] As an example, the quenching device 402 is connected to the water washing tower 502 through the quenching gas compressor 4021. A small amount of synthesis gas is extracted from the outlet of the water washing tower 502 and pressurized by the quenching gas compressor 4021 before entering the quenching device 402, thereby quenching and cooling the high-temperature synthesis gas and fly ash flowing out of the output end of the radiation waste boiler 401.

[0071] As an example, the waste heat recovery unit also includes a low-pressure waste boiler 404, which is arranged between the fly ash filter 501 and the water washing tower 502. The synthesis gas exchanges heat with the water in the low-pressure waste boiler 404 and is further cooled. The by-product steam in the low-pressure waste boiler 404 enters the steam pipeline network for utilization.

[0072] Specifically, the dechlorinated synthesis gas and fly ash enter the fly ash filter 501 to remove most of the fly ash, and the synthesis gas after removing most of the fly ash is further cooled by the low-pressure waste boiler 404 and enters the water washing tower 502 to further wash the small amount of fly ash that has not been removed, and at the same time remove the residual hydrogen chloride gas in the synthesis gas; wherein, the low-pressure waste boiler 404 cools the synthesis gas and produces low-pressure steam as a by-product, and the radiation waste boiler 401 and the convection waste boiler 404 produce saturated or superheated medium-pressure or high-pressure steam as a by-product.

[0073] As an example, a slag discharge device 701 is provided at the bottom of the radiation waste boiler 401. Most of the ash in the radiation waste boiler 401 enters the slag discharge device 701 under the action of gravity, and the coarse slag is discharged, and the black water is transported to the slag water treatment device 702 for treatment.

[0074] As an example, the gasification system also includes a slag water treatment device 702, which is connected to the slag discharge device 701 and the water washing tower 502 respectively. The black water discharged from the slag discharge device 701 and the water washing tower 502 enters the slag water treatment device 702 for treatment.

[0075] Specifically, the black water discharged from the water washing tower 502 and the black water discharged from the slag discharge device 701 enter the slag water treatment device 702 for treatment. After the slag water treatment, most of the water is clarified as gray water for recycling, and filter cakes are produced at the same time, and a small amount of gray water is used for wastewater treatment.

[0076] In order to better understand the biomass entrained flow gasification system with waste heat recovery in the present invention, the present invention also provides a biomass entrained flow gasification process with waste heat recovery, which specifically includes the following steps:

[0077] S1. Add the dried, dehydrated and roasted biomass into the powder-making and conveying device 201 to make biomass powder. The biomass powder and oxygen enter the entrained flow gasifier 302 through the gasification nozzle 301 to undergo a gasification reaction, thereby generating high-temperature and high-pressure synthesis gas and ash. The temperature of the gasification reaction is 1200-1500° C., and the pressure of the gasification reaction is 2MPa-8MPa.

[0078] S2. The high-temperature and high-pressure synthesis gas and ash generated in step S1 first enter the radiation waste boiler 401 to exchange heat with water to complete the initial cooling, and the by-product steam of the radiation waste boiler 401 enters the steam network for utilization;

[0079] S3, the syngas and fly ash after the initial cooling enter the quenching device 402 for the second cooling;

[0080] S4, the synthesis gas and fly ash after the second quenching and cooling enter the convection waste boiler 403 to exchange heat with water, completing the third cooling, and the by-product steam of the convection waste boiler 403 enters the steam network through the pipeline for utilization;

[0081] S5, the synthesis gas and fly ash after the third cooling enter the dechlorination device 800, and the dechlorination agent is used to remove the hydrogen chloride gas in the synthesis gas; preferably, the dechlorination agent is baking soda or calcium hydroxide or a commercial dechlorination agent;

[0082] S6, the dechlorinated synthesis gas and fly ash enter the fly ash filter 501 to remove most of the fly ash, and then enter the low-pressure waste boiler 404 to exchange heat with water and cool the synthesis gas for the fourth time, and the steam produced as a byproduct of the low-pressure waste boiler 404 enters the steam network for utilization;

[0083] S7. The synthesis gas and a small amount of fly ash after the fourth cooling enter the water washing tower 502 for washing to remove the fly ash and the residual hydrogen chloride gas in the synthesis gas. Most of the synthesis gas after washing enters the downstream CO conversion device 600 to undergo conversion reaction. The small amount of synthesis gas after washing in the water washing tower 502 is pressurized by the quenching gas compressor 4021 and then enters the quenching device 402 to quench the synthesis gas.

[0084] Specifically, biomass powder is made from dried, dehydrated and baked biomass, and the biomass powder and oxygen are gasified in an entrained flow gasifier 302 to generate synthesis gas. The entire gasification process is simple and reliable. The waste boiler process is used to recover the high-temperature sensible heat of the synthesis gas, and the fly ash filter 501 is used to separate the fly ash in the synthesis gas, so that the waste water discharge is small and the waste water treatment cost is low. The waste boiler process is used to recover the high-temperature sensible heat of the synthesis gas to generate steam, and the gasification system has high cold gas efficiency. The biomass entrained flow gasification method with waste heat recovery in the specific embodiment of the present invention can be used for biomass to produce green methanol or sustainable aviation fuel, etc., which is of great significance to the clean and efficient utilization of biomass.

[0085] As an example, the gasification method also includes a slag water treatment step, specifically, in step S2, most of the ash in the radiation waste boiler 401 enters the slag discharge device 701 under the action of gravity to remove the slag, discharge the coarse slag, and transport the black water to the slag water treatment device 702; at the same time, the black water discharged from the washing tower 502 in step S7 is also transported to the slag water treatment device 702, and the slag water treatment device 702 treats the black water.

[0086] Specifically, the black water discharged from the water washing tower 502 and the black water discharged from the slag discharge device 701 both enter the slag water treatment device 702 for treatment. After the slag water treatment, most of the clarified gray water is recycled, and filter cakes are produced at the same time. A small part of the gray water is used for wastewater treatment, which reduces the wastewater discharge and reduces the wastewater treatment cost.

[0087] In order to better understand the biomass fluidized bed gasification system with waste heat recovery and the gasification process of the present invention, the biomass fluidized bed gasification system with waste heat recovery and the gasification process of the present invention are described below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0088] Example 1

[0089] See also Figure 1 , this embodiment provides a biomass entrained flow gasification system with waste heat recovery, the gasification system includes a feeding unit, a drying and baking device 100, a gasification unit, a waste heat recovery unit, a dechlorination device 800, a ash removal and washing unit and a CO conversion device 600;

[0090] The feeding unit includes a powder-making and conveying device 201, which is used to make biomass into biomass powder and convey the biomass powder;

[0091] The output end of the drying and roasting device 100 is connected to the powder making and conveying device 201, and the drying and roasting device 100 is used to dry, dehydrate and roast the biomass raw materials;

[0092] The gasification unit includes an entrained flow gasifier 302, on which a gasification nozzle 301 is provided, and the output end of the powder making and conveying device 201 is connected to the gasification nozzle 301, and the biomass powder enters the entrained flow gasifier 302 through the gasification nozzle 301; and further includes an air separation device 202, which is used to produce oxygen, and the oxygen produced by the air separation device 202 is connected to the gasification nozzle 301, and the oxygen enters the entrained flow gasifier 302 through the gasification nozzle 301;

[0093] The waste heat recovery unit includes a radiation waste boiler 401 and a convection waste boiler 403. The input end of the radiation waste boiler 401 is connected to the fluidized flow gasifier 302, and the output end of the radiation waste boiler 401 is connected to the convection waste boiler 403. The high-temperature synthesis gas and ash generated in the fluidized flow gasifier 302 enter the radiation waste boiler 401 and the convection waste boiler 404 in turn to exchange heat with water. The steam produced by the radiation waste boiler 401 and the convection waste boiler 403 enters the steam network for utilization; a quenching device 402 is also provided between the radiation waste boiler 401 and the convection waste boiler 403. The quenching device 402 is connected to the output end of the radiation waste boiler 401, and the quenching device 402 is used to quench and cool the high-temperature synthesis gas and fly ash flowing out of the output end of the radiation waste boiler 401; the quenching device 402 is connected to the output end of the radiation waste boiler 401 by a quenching gas compressor 4021 It is connected to the water scrubber 502. A small amount of synthesis gas is extracted from the outlet of the water scrubber 502 and then pressurized by the quenching gas compressor 4021 before entering the quenching device 402, thereby quenching and cooling the high-temperature synthesis gas and fly ash flowing out of the output end of the radiation waste boiler 401; the waste heat recovery unit also includes a low-pressure waste boiler 404, which is arranged between the fly ash filter 501 and the water scrubber 502. The synthesis gas exchanges heat with the water in the low-pressure waste boiler 404 and further cools down the temperature. The by-product steam in the low-pressure waste boiler 404 enters the low-pressure steam pipeline network; a slag discharge device 701 is arranged at the bottom of the radiation waste boiler 401. Most of the ash in the radiation waste boiler 401 enters the slag discharge device 701 under the action of gravity, and the coarse slag is discharged, and the black water is transported to the slag water treatment device 702 for treatment;

[0094] The dechlorination device 800 is arranged at the output end of the convection waste boiler 403. The synthesis gas and fly ash after being cooled in the convection waste boiler 403 enter the dechlorination device 800. The dechlorination device 800 is used to remove hydrogen chloride gas in the synthesis gas.

[0095] The ash removal and water washing unit is connected to the output end of the dechlorination device 800. The ash removal and water washing unit includes a fly ash filter 501 and a water washing tower 502. The synthesis gas and fly ash after dechlorination by the dechlorination device 800 enter the fly ash filter 501 and the water washing tower 502 in sequence. The fly ash filter 501 is used to remove most of the fly ash, and the water washing tower 502 is used to further wash a small part of the fly ash that has not been removed, and remove the residual hydrogen chloride gas in the synthesis gas at the same time;

[0096] The CO conversion device 600 is connected to the output end of the water scrubber 502, and the synthesis gas after being washed by the water scrubber 502 enters the CO conversion device 600 to undergo a conversion reaction.

[0097] Example 2

[0098] This embodiment provides a biomass entrained flow gasification process with waste heat recovery, wherein the biomass entrained flow gasification system in Embodiment 1 is used to gasify the biomass. In this embodiment, the biomass refers to agricultural straw materials (such as corn straw, rice straw, wheat straw or cotton straw, etc.), and the gasification process specifically includes the following steps:

[0099] S1. Add the biomass that has been dried, dehydrated and baked (dried at 120°C for 20 minutes for dehydration and baked at 300°C for 60 minutes) into the powder-making and conveying device 201 to make biomass powder. The biomass powder and oxygen enter the entrained flow gasifier 302 through the gasification nozzle 301 to undergo gasification reaction at 1200°C and 2Mpa to generate high-temperature and high-pressure synthesis gas and ash.

[0100] S2, the high-temperature and high-pressure synthesis gas and ash generated in step S1 first enter the radiation waste boiler 401 to exchange heat with water to complete the initial cooling, and the by-product steam in the radiation waste boiler 401 enters the steam network for utilization; most of the ash in the radiation waste boiler 401 enters the slag discharge device 701 under the action of gravity, the coarse slag is discharged, and the black water is transported to the slag water treatment device 702 for treatment;

[0101] S3, the synthesis gas and fly ash after the initial cooling enter the quenching device 402 for the second quenching cooling;

[0102] S4, the synthesis gas and fly ash after the second quenching and cooling enter the convection waste boiler 403 to exchange heat with water, completing the third cooling, and the by-product steam in the convection waste boiler 403 enters the steam network for utilization;

[0103] S5, the synthesis gas and fly ash after the third cooling enter the dechlorination device 800, and baking soda is used as a dechlorination agent to remove hydrogen chloride gas in the synthesis gas;

[0104] S6, the dechlorinated synthesis gas and fly ash enter the fly ash filter 501 to remove most of the fly ash, and then enter the low-pressure waste boiler 404 to exchange heat with water and cool the synthesis gas for the fourth time, and the by-product steam in the low-pressure waste boiler 404 enters the low-pressure steam network;

[0105] S7. The synthesis gas and a small amount of fly ash after the fourth cooling enter the water washing tower 502 for washing, and the fly ash and residual hydrogen chloride gas in the synthesis gas are removed. Most of the synthesis gas after washing enters the downstream CO conversion device 600 to undergo conversion reaction. The small amount of synthesis gas after washing in the water washing tower 502 is pressurized by the quenching gas compressor 4021 and then enters the quenching device 402 to quench the synthesis gas and fly ash; the black water discharged from the washing in the water washing tower 502 is also sent to the slag water treatment device 702, and the slag water treatment device 702 treats the black water.

[0106] In summary, the present invention adopts a drying and baking device to pretreat biomass. The calorific value of the biomass after drying and baking is improved, the moisture content is greatly reduced, the grindability is greatly improved, and the energy consumption of powder making and conveying device for powder making is significantly reduced. The particle size and powder fluidity of the prepared biomass powder fully meet the requirements of pressurized dense phase conveying of fluidized bed gasification, which solves the problems of small processing capacity, high energy consumption and poor powder conveying fluidity of traditional biomass direct powder making, and at the same time can improve the adaptability of fluidized bed gasification technology to different types of biomass raw materials; radiation waste boiler and convection waste boiler are used to recover the sensible heat of the high-temperature synthesis gas generated by the fluidized bed gasification furnace, the system has high cold gas efficiency, and the by-product steam enters the system for utilization, thereby improving the economy of the entire system. The present invention adopts dry powder fluidized bed gasification technology, and most of the chlorine in the biomass raw material is transferred to fly ash and slag after fluidized bed gasification, and a small amount of chlorine enters the synthesis gas. By adding a dechlorination device downstream of the convection waste boiler, the hydrogen chloride gas content in the synthesis gas is greatly reduced (about tens of ppm), and the chloride ion content in the wastewater is also significantly reduced accordingly. The fly ash filter and the water washing tower and other equipment can be made of conventional materials, which effectively solves the chlorine corrosion problem caused by the gasification of high-chlorine biomass; due to the high K content in straw biomass, when the synthesis gas passes through the convection waste boiler, the convection waste boiler is prone to ash accumulation, the heat transfer resistance is increased, and the heat transfer efficiency is affected. A synthesis gas quenching device is added at the outlet of the radiation waste boiler, and a small amount of synthesis gas is extracted at the outlet of the water washing tower and pressurized by the quenching gas compressor to quench the high-temperature synthesis gas and ash at the outlet of the radiation waste boiler, so that the liquid fly ash entrained in the synthesis gas loses viscosity after solidification, and will not contaminate the convection waste boiler. At the same time, by optimizing the structural layout and flow field distribution of the convection waste boiler, the ash accumulation risk of the convection waste boiler is significantly reduced. The biomass entrained flow gasification process of the present invention is simple and reliable. Through innovative raw material pretreatment, the waste boiler process is used to recover the high-temperature sensible heat of the synthesis gas, and the fly ash filter is used to separate the fly ash in the synthesis gas, the wastewater discharge is reduced, the wastewater treatment cost is low, and the energy consumption of the entrained flow gasification process is reduced; the waste boiler process is used to recover the high-temperature sensible heat of the synthesis gas to produce steam, and the cold gas efficiency of the gasification system is high, which improves the economy and environmental friendliness of the entire system, effectively solves the pain points and difficulties of the biomass entrained flow gasification technology, and realizes the safe, stable and reliable operation of the biomass entrained flow gasification device, which is of great significance to the clean and efficient utilization of biomass. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0107] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A biomass entrained flow gasification system with waste heat recovery, characterized in that: The gasification system comprises: A feeding unit, the feeding unit comprising a powder-making and conveying device, the powder-making and conveying device is used to make biomass into biomass powder and convey it for feeding; and also comprising a drying and roasting device, the output end of the drying and roasting device is connected to the powder-making and conveying device, the drying and roasting device is used to dry, dehydrate and roast the biomass raw material; A gasification unit, wherein the gasification unit comprises an entrained flow gasifier, the entrained flow gasifier is provided with a gasification nozzle, the output end of the powder making and conveying device is connected to the gasification nozzle, and the biomass powder enters the entrained flow gasifier through the gasification nozzle; A waste heat recovery unit, the waste heat recovery unit comprises a radiation waste boiler and a convection waste boiler, the input end of the radiation waste boiler is connected to the entrained flow gasifier, the output end of the radiation waste boiler is connected to the convection waste boiler, the high-temperature synthesis gas and ash generated in the entrained flow gasifier enter the radiation waste boiler and the convection waste boiler in turn and exchange heat with water, and the steam produced as a by-product of the radiation waste boiler and the convection waste boiler enters the steam network for utilization; A dechlorination device, which is arranged at the output end of the convection waste boiler, and the synthesis gas and fly ash after being cooled by the convection waste boiler enter the dechlorination device, and the dechlorination device is used to remove hydrogen chloride gas in the synthesis gas; A ash removal and water washing unit, the ash removal and water washing unit is connected to the output end of the dechlorination device, the ash removal and water washing unit comprises a fly ash filter and a water washing tower, the synthesis gas and fly ash after dechlorination by the dechlorination device enter the fly ash filter and the water washing tower in sequence, the fly ash filter is used to remove most of the fly ash, and the water washing tower is used to further wash a small part of the fly ash that has not been removed, and remove the residual hydrogen chloride gas in the synthesis gas at the same time; A quenching device is also provided between the radiation waste boiler and the convection waste boiler, the quenching device is connected to the output end of the radiation waste boiler, and the quenching device is used to quench and cool the high-temperature synthesis gas and fly ash flowing out of the output end of the radiation waste boiler; the quenching device is connected to the water scrubber through a quenching gas compressor, a small portion of the synthesis gas extracted from the outlet of the water scrubber is pressurized by the quenching gas compressor and then enters the quenching device, thereby quenching and cooling the high-temperature synthesis gas and fly ash flowing out of the output end of the radiation waste boiler; A CO conversion device is connected to the output end of the water scrubber, and the synthesis gas after being washed by the water scrubber enters the CO conversion device to undergo a conversion reaction.

2. The biomass entrained-flow gasification system with waste heat recovery according to claim 1, characterized in that: The gasification unit further comprises an air separation device, which is used to produce oxygen. The oxygen produced by the air separation device is connected to the gasification nozzle, and the oxygen enters the entrained flow gasification furnace through the gasification nozzle.

3. The biomass entrained flow gasification system with waste heat recovery according to claim 1, characterized in that: The waste heat recovery unit also includes a low-pressure waste boiler, which is arranged between the fly ash filter and the water washing tower. The synthesis gas exchanges heat with the water in the low-pressure waste boiler and is further cooled. The by-product steam in the low-pressure waste boiler enters the steam pipeline network for utilization.

4. The biomass entrained-flow gasification system with waste heat recovery according to claim 1, characterized in that: A slag discharge device is provided at the bottom of the radiation waste boiler, and most of the ash in the radiation waste boiler enters the slag discharge device for slag removal under the action of gravity.

5. The biomass entrained-flow gasification system with waste heat recovery according to claim 4, characterized in that: The gasification system further comprises a slag water treatment device, which is connected to the slag discharge device and the water washing tower respectively. The black water discharged from the slag discharge device and the water washing tower enters the slag water treatment device for treatment.

6. A biomass entrained flow gasification process with waste heat recovery, wherein the biomass is gasified using the biomass entrained flow gasification system with waste heat recovery as claimed in any one of claims 1 to 5, characterized in that: The gasification process comprises the following steps: S1, adding the dried, dehydrated and roasted biomass into the powder-making and conveying device to produce biomass powder, and the biomass powder and oxygen enter the entrained flow gasifier through the gasification nozzle to undergo a gasification reaction, thereby generating high-temperature and high-pressure synthesis gas and ash; S2, the high-temperature and high-pressure synthesis gas and ash generated in step S1 first enter the radiation waste boiler to exchange heat with water to complete the initial cooling, and the steam produced as a by-product of the radiation waste boiler enters the steam network for utilization; S3, the syngas and fly ash after the initial cooling enter the quenching device for the second cooling; S4, the synthesis gas and fly ash after the second quenching and cooling enter the convection waste boiler to exchange heat with water to complete the third cooling, and the steam produced as a by-product of the convection waste boiler enters the steam network for utilization; S5, the synthesis gas and fly ash after the third cooling enter the dechlorination device and a dechlorinating agent is used to remove hydrogen chloride gas in the synthesis gas; S6, the dechlorinated synthesis gas and fly ash enter the fly ash filter to remove most of the fly ash, and then enter the low-pressure waste boiler to exchange heat with water and cool the synthesis gas for the fourth time, and the steam produced as a by-product of the low-pressure waste boiler also enters the steam network for utilization; S7. After the fourth cooling, the synthesis gas and a small amount of fly ash enter the water washing tower for washing to remove the fly ash and the residual hydrogen chloride gas in the synthesis gas. Most of the synthesis gas after washing enters the downstream CO conversion device for conversion reaction, and a small amount of synthesis gas is pressurized by the quenching gas compressor and then enters the quenching device to quench the temperature of the synthesis gas.

7. The biomass entrained flow gasification process with waste heat recovery according to claim 6, characterized in that: The gasification process also includes a slag water treatment step, specifically, most of the ash in the radiation waste boiler in step S2 enters the slag discharge device under the action of gravity to remove the slag, discharge the coarse slag, and transport the black water to the slag water treatment device; at the same time, the black water discharged from the washing tower in step S7 is also transported to the slag water treatment device, and the slag water treatment device treats the black water.

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