Production system for biomass carbonization and gasification and urea synthesis

Abstract

The utility model belongs to the field of chemical production, and relates to a production system combining biomass carbonization and gasification with urea synthesis, which comprises a biomass carbonization unit, a charcoal gasification unit, a water gas shift reaction unit, an ammonia synthesis unit and a urea synthesis unit which are sequentially connected in series, the biomass carbonization unit comprises a biomass carbonization furnace; the biochar gasification unit comprises a biochar gasification furnace; the water gas shift reaction unit comprises a shift reactor and is used for converting carbon monoxide and water vapor in the combustible gas 2 into hydrogen and carbon dioxide through reaction; the ammonia gas synthesis unit comprises an ammonia gas synthesis tower; and the urea synthesis unit comprises a urea synthesis tower. According to the technical scheme, in a urea synthesis unit process, the problems that equipment is blocked by tar, the urea synthesis efficiency is influenced by deposition on the surface of a catalyst and the like are effectively avoided, and the production efficiency and the yield are improved.

Description

Technical Field

[0001] This utility model belongs to the field of chemical production technology and relates to a production system that combines biomass carbonization and gasification with urea synthesis. Background Technology

[0002] The traditional method of synthesizing urea involves converting biomass or coal into syngas through biomass gasification or coal gasification, then using the syngas to undergo a chemical reaction to synthesize ammonia, and finally using the ammonia to synthesize urea, a fertilizer raw material.

[0003] However, the gas produced by direct biomass gasification has a complex composition, mainly containing hydrogen, carbon monoxide, carbon dioxide, and alkanes (such as methane), as well as impurities such as tar, sulfur compounds, nitrogen compounds, and dust. If this combustible gas is used directly for urea synthesis, the following key challenges exist: the impact of tar and impurities. Tar produced during the gasification process easily deposits on the surface of pipelines or catalysts, leading to catalyst poisoning, affecting ammonia synthesis, inhibiting urea synthesis, and reducing product yield.

[0004] Therefore, carbon dioxide and hydrogen need to be purified during the urea synthesis process, but the purification process is currently difficult and the cost is relatively high.

[0005] Therefore, in order to further save energy and reduce consumption, improve product quality, and further reduce process difficulty and cost, it is very necessary to provide a new urea synthesis production system. Utility Model Content

[0006] The purpose of this application is to provide a production system for carbonizing and gasifying biomass and synthesizing urea, the production system comprising a biomass carbonization unit, a biochar gasification unit, a water-gas shift reaction unit, an ammonia synthesis unit and a urea synthesis unit connected in series.

[0007] The biomass carbonization unit includes a biomass carbonization furnace, which includes a biomass inlet, a biochar outlet, and a combustible gas outlet, used to convert biomass into biochar and combustible gas.

[0008] The biochar gasification unit includes a biochar gasifier, which has a biochar inlet and a combustible gas 2 outlet for converting biochar into combustible gas 2. The biochar inlet is connected to the biochar outlet, and the combustible gas 2 includes carbon monoxide.

[0009] A water-gas shift reaction unit includes a shift reactor, which is used to react and convert carbon monoxide and water vapor in the combustible gas 2 into hydrogen and carbon dioxide; the shift reactor includes a combustible gas 2 inlet, a water vapor inlet, a hydrogen outlet and a carbon dioxide outlet, and the combustible gas 2 inlet is connected to the combustible gas 2 outlet.

[0010] The ammonia synthesis unit includes an ammonia synthesis tower, which includes a hydrogen inlet and an ammonia outlet, with the hydrogen inlet connected to the hydrogen outlet.

[0011] The urea synthesis unit includes a urea synthesis tower, which has an ammonia inlet and a carbon dioxide inlet. The ammonia inlet is connected to the ammonia outlet, and the carbon dioxide inlet is connected to the carbon dioxide outlet.

[0012] Preferably, the production system further includes a separation unit connected to the water-gas conversion reaction unit for separating hydrogen and carbon dioxide; the production system further includes a hydrogen storage unit and a carbon dioxide storage unit for storing the hydrogen and carbon dioxide separated by the separation unit, and includes a hydrogen storage tank and a carbon dioxide storage tank, respectively.

[0013] Preferably, the production system further includes an ammonia storage unit, which includes an ammonia storage tank connected to the ammonia synthesis tower for storing ammonia synthesized by the ammonia synthesis tower.

[0014] Preferably, the production system further includes a combustible gas 1 combustion unit, which includes a combustible gas 1 combustion furnace for burning combustible gas 1 to generate high-temperature flue gas. The combustible gas 1 combustion furnace includes a combustible gas 1 inlet, an oxygen-containing gas inlet, and a high-temperature flue gas outlet. The outer wall of the biomass carbonization furnace includes a jacket, which includes the flue gas inlet and the flue gas outlet for allowing high-temperature flue gas to enter and exit. The combustible gas 1 inlet is connected to the combustible gas 1 outlet, and the flue gas inlet on the jacket is connected to the high-temperature flue gas outlet of the combustible gas 1 combustion furnace.

[0015] Preferably, the production system further includes a biomass preheating unit; the biomass preheating unit includes a biomass preheating furnace, which is provided with a flue gas inlet, a biomass inlet, a biomass outlet and a flue gas outlet;

[0016] The biomass inlet is used to add biomass raw materials; the biomass raw material outlet is used to output preheated biomass; the biomass raw material outlet is connected to the biomass inlet of the biomass carbonization unit; the flue gas inlet on the biomass preheating furnace is connected to the flue gas outlet of the biomass carbonization furnace.

[0017] Preferably, the production system further includes a combustible gas 2 heat energy recovery unit connected to the biochar gasification unit, used to exchange the heat energy of the combustible gas 2 generated by the biochar gasification unit with the cooling water, thereby turning the cooling water into preheated water.

[0018] The combustible gas heat recovery unit includes a gas-liquid heat exchanger, which includes a combustible gas inlet 2, a combustible gas outlet 2, a cooling water inlet 2, and a preheated water outlet 2; the combustible gas inlet 2 is connected to the combustible gas outlet 2 in the biochar gasification unit.

[0019] Preferably, the production system further includes a boiler unit connected to the biochar gasification unit for heating preheated water into steam; the boiler unit includes a combustion furnace or an electric heating furnace; the combustion furnace or electric heating furnace includes a preheated water inlet and a steam outlet; the preheated water inlet is connected to the preheated water outlet of the combustible gas 2 heat energy recovery unit; the biochar gasification furnace includes a steam inlet, and the steam outlet is connected to the steam inlet of the biochar gasification furnace.

[0020] Preferably, the production system further includes a combustible gas 2 purification unit, which is connected to the combustible gas 2 outlet of the biochar gasification unit, and the combustible gas 2 purification unit includes a combustible gas 2 purification device.

[0021] Compared with the prior art, the production system of this utility model mainly achieves the following technical effects in the urea synthesis process:

[0022] 1) Avoiding tar clogging of equipment: Existing biomass gasification technology produces combustible gas 2 with high tar and other impurity content, which causes a series of problems for urea synthesis: tar and impurities affect the process. Tar produced during gasification easily deposits on the pipe surface, severely impacting production efficiency and yield. Complex purification processes are required to obtain suitable gaseous feedstock for urea synthesis, which not only increases production costs but also affects efficiency. This invention's production system connects biomass carbonization, biochar gasification, and urea synthesis units in series. First, biomass is carbonized and pyrolyzed, converting most of its volatiles into combustible gas 1. The vast majority of tar is released during biomass carbonization along with combustible gas 1, resulting in biochar with low volatile content. Then, the biochar is gasified to obtain combustible gas 2, with significantly reduced tar and other impurity content. This segmented gasification process of biomass carbonization and biochar gasification allows for the separate collection and utilization of combustible gas 1 and combustible gas 2. The combustible gas has a low content of tar and other impurities, making it suitable for urea synthesis and effectively solving the above problems.

[0023] 2) High energy efficiency and low emissions: Existing technologies typically use fossil fuel combustion for the thermal energy of carbonization, gasification, and the high-temperature steam required for gasification. This not only increases energy consumption but also fails to meet the requirements of energy conservation and emission reduction. This technical solution provides thermal energy for the biomass carbonization, biomass preheating, and biomass gasification steam preheating processes through the further combustion of combustible gas 1 produced by biomass carbonization. This achieves efficient utilization of biomass, reduces the consumption of traditional fossil fuels, and realizes energy conservation and emission reduction.

[0024] 3) Broad prospects for industrial application: The production system of this utility model is applicable to the resource utilization of biomass (agricultural and forestry waste), and can be combined with the transformation of existing fertilizer plants to promote the green upgrading of the biomass energy-chemical industry chain, with significant economic and environmental benefits. Attached Figure Description

[0025] Figure 1 A schematic diagram of a production system that combines biomass carbonization and gasification with urea synthesis.

[0026] Figure 2 This is a schematic diagram of the structure of a biomass carbonization furnace.

[0027] Figure 3 This is a schematic diagram of a biochar gasification furnace.

[0028] Figure 4 This is a schematic diagram of the shift reactor structure of the water-gas shift reaction unit.

[0029] Figure 5 This is a schematic diagram of the ammonia synthesis tower.

[0030] Figure 6 a is a schematic diagram of the structure of the first tower of the urea synthesis tower.

[0031] Figure 6 b is a schematic diagram of the structure of the second tower of the urea synthesis tower.

[0032] Figure 7 This is a schematic diagram of the structure of a combustible gas combustion furnace.

[0033] Figure 8 This is a schematic diagram of the structure of a biomass preheating furnace.

[0034] Figure 9 This is a schematic diagram of a combustible gas heat energy recovery device.

[0035] Figure 10 This is a schematic diagram of the combustion furnace of the boiler unit.

[0036] Figure 11 This is a schematic diagram of the purification equipment for combustible gas 2. Detailed Implementation

[0037] The technical solution of this utility model will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present utility model and should not be construed as specific limitations thereof.

[0038] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, and elements, as well as their relative dimensions, may be exaggerated. Throughout, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0039] Biomass carbonization refers to the process by which biomass is slowly decomposed under limited oxygen supply or complete oxygen deficiency conditions to remove volatiles and produce solid carbon products. In addition to solid carbon products, combustible gases (such as carbon monoxide, hydrogen and small molecule alkanes) and biomass tar are also produced.

[0040] Biomass gasification refers to the process under certain thermodynamic conditions in which biomass polymers undergo pyrolysis, oxidation, and reduction reforming reactions with the help of water vapor, oxygen, or a combination of water vapor and oxygen, ultimately transforming into combustible gases such as carbon monoxide, hydrogen, and small-molecule hydrocarbons, as well as biomass tar.

[0041] Biochar gasification refers to the process by which biochar is ultimately converted into combustible gases such as carbon monoxide, hydrogen, and small molecule hydrocarbons under certain thermodynamic conditions with the help of water vapor, oxygen, or a combination of water vapor and oxygen.

[0042] The urea synthesis process uses ammonia and carbon dioxide as raw materials to synthesize urea under high pressure and high temperature.

[0043] Since biomass tar is a volatile component of biomass, if biomass is directly converted into combustible gas through biomass gasification and the combustible gas is used in the urea synthesis process, the high tar content and impurities will affect the urea synthesis process. The resulting tar is prone to deposit on the surface of the pipeline, which seriously affects production efficiency and yield.

[0044] Therefore, in order to address the impact of biomass tar on the production efficiency and yield of urea synthesis, embodiments of this application provide a combined production system that utilizes biomass to convert into combustible gas for urea synthesis, such as... Figure 1 As shown, it includes a biomass carbonization unit, a biochar gasification unit, a water-gas shift reaction unit, an ammonia synthesis unit, and a urea synthesis unit connected in series.

[0045] The biomass carbonization unit includes a biomass carbonization furnace, which includes a biomass inlet, a biochar outlet, and a combustible gas outlet, used to convert biomass into biochar and combustible gas.

[0046] The biochar gasification unit includes a biochar gasifier, which has a biochar inlet and a combustible gas 2 outlet for converting biochar into combustible gas 2. The biochar inlet is connected to the biochar outlet, and the combustible gas 2 includes carbon monoxide.

[0047] A water-gas shift reaction unit includes a shift reactor, which is used to react and convert carbon monoxide and water vapor in the combustible gas 2 into hydrogen and carbon dioxide; the shift reactor includes a combustible gas 2 inlet, a water vapor inlet, a hydrogen outlet and a carbon dioxide outlet, and the combustible gas 2 inlet is connected to the combustible gas 2 outlet.

[0048] The ammonia synthesis unit includes an ammonia synthesis tower, which includes a hydrogen inlet, a nitrogen inlet, and an ammonia outlet, wherein the hydrogen inlet is connected to the hydrogen outlet.

[0049] The urea synthesis unit includes a urea synthesis tower, which has an ammonia inlet and a carbon dioxide inlet. The ammonia inlet is connected to the ammonia outlet, and the carbon dioxide inlet is connected to the carbon dioxide outlet.

[0050] This invention's production system connects a biomass carbonization unit, a biochar gasification unit, and a urea synthesis unit in series. First, biomass is carbonized and converted into biochar. During this process, the biomass undergoes pyrolysis, converting most of its volatile components into combustible gas 1. The vast majority of tar is released along with combustible gas 1 during biomass carbonization, resulting in biochar with low volatile content. The biochar is then gasified to obtain combustible gas 2, which contains significantly reduced tar and other impurities. This segmented gasification process, involving biomass carbonization and biochar gasification, allows for the separate collection and utilization of combustible gas 1 and combustible gas 2. Combustible gas 2, with its low tar and other impurity content, is ideal for urea synthesis, significantly reducing the purification costs of the gas used in urea synthesis.

[0051] The biomass carbonization unit includes a biomass carbonization furnace, whose function is to carbonize biomass to produce biochar and combustible gas. For example... Figure 2As shown, the biomass carbonization furnace includes a biomass inlet, a biochar outlet, a combustible gas outlet, and a jacket structure disposed on the surface of the biomass carbonization furnace. The jacket structure includes a flue gas inlet and a flue gas outlet. The biomass inlet is used to add biomass raw materials, the biochar outlet is used to output the biochar produced by carbonizing the biomass in the biomass carbonization furnace, and the combustible gas outlet is used to output the combustible gas 1 produced by heating the biomass.

[0052] Biomass carbonization furnaces produce biochar and combustible gas by heating biomass under limited oxygen supply or complete oxygen deficiency conditions (e.g., by heating biomass through the combustion of flammable fuels or by introducing high-temperature flue gas). The biomass is heated to 450-950℃ (exemplary temperatures include 450℃, 550℃, 650℃, 750℃, 850℃, 950℃, etc.).

[0053] The biochar gasification unit includes a biochar gasifier, whose function is to gasify biochar to produce combustible gas 2. For example... Figure 3 As shown, the biochar gasifier includes a biochar inlet and a combustible gas 2 outlet; the biochar inlet is connected to the biochar outlet of the biomass carbonization unit and is used to input biochar, and the combustible gas 2 generated by biochar gasification is transported to the combustible gas 2 heat energy recovery unit through the combustible gas 2 outlet.

[0054] In an optional embodiment, in order to achieve biochar gasification, a steam inlet is added to introduce high-temperature steam into the biochar gasifier to participate in the biochar gasification reaction, converting the biochar into a combustible gas containing carbon monoxide, hydrogen, and alkanes.

[0055] In a preferred embodiment, the biochar gasifier further includes an ash discharge outlet through which the ash produced by biochar gasification is discharged.

[0056] In some embodiments, the biochar gasification unit uses high-temperature steam as a gasifying agent to gasify biochar into combustible gas 2 at a high temperature of 450-950°C (exemplarily including 450°C, 550°C, 650°C, 750°C, 850°C, 950°C, etc.).

[0057] In a preferred embodiment, the biochar gasifier includes an oxygen-containing gas inlet for introducing a limited or small amount of oxygen into the biochar gasifier to assist in the gasification of the biochar into a combustible gas containing carbon monoxide. In a more preferred embodiment, water vapor and oxygen are mixed and introduced into the biochar gasification unit to produce a combustible gas containing carbon monoxide, hydrogen, and alkanes.

[0058] The water-gas shift reaction unit includes a shift reactor, which is used to introduce combustible gas 2 and react the carbon monoxide and water vapor of the combustible gas 2 to convert them into hydrogen and carbon dioxide. The shift reactor may be a solid-bed reactor, containing a catalyst (e.g., an Fe-Cr based catalyst). The solid-bed reactor also includes a heater to provide high-temperature reaction conditions, typically 300-400°C. Thus, as... Figure 4 As shown, the shift reactor includes at least a combustible gas inlet 2, a steam inlet, and a hydrogen and carbon dioxide mixture outlet (hereinafter defined as combustible gas 3). The combustible gas inlet 2 is connected to the combustible gas outlet 2 of the biochar gasification unit.

[0059] In some embodiments, such as Figure 1 As shown, the production system also includes a combustible gas 3 storage unit for storing combustible gas 3.

[0060] The ammonia synthesis unit includes an ammonia synthesis tower, which synthesizes ammonia from hydrogen and nitrogen. The ammonia synthesis is carried out at a pressure of 15.2–30.4 MPa and a temperature of 400–520°C. Figure 5 As shown, the ammonia synthesis tower includes a hydrogen inlet and a nitrogen inlet, or the hydrogen inlet may simultaneously allow nitrogen to be mixed with hydrogen for a mixed input (referred to as the hydrogen-nitrogen mixed gas inlet in the figure). The hydrogen inlet is connected to the hydrogen outlet of the water-gas shift reaction unit. The ammonia synthesis tower also includes an ammonia outlet, which allows ammonia to be output, or allows ammonia mixed with unreacted nitrogen and hydrogen for a mixed output (referred to as the hydrogen-ammonia-nitrogen outlet in the figure).

[0061] As an optional embodiment, the ammonia synthesis tower consists of a high-pressure resistant head, an outer cylinder, and high-temperature resistant internal components housed within the cylinder. The internal components are surrounded by an insulation layer. During operation, the cold gas entering the tower flows through the annular gap between the inner and outer cylinders, thus preventing the outer cylinder from overheating. The internal components include two main parts: a catalyst basket and a heat exchanger. The basket contains an iron catalyst, where the ammonia synthesis reaction takes place. The function of the heat exchanger is to heat the gas entering the ammonia synthesis tower to the reaction temperature while simultaneously cooling the gas after the reaction. The heat exchanger can be selected from tubular, spiral plate, or corrugated plate types.

[0062] In some embodiments, the production system further includes an ammonia purification unit for purifying a mixture of ammonia, nitrogen, and hydrogen output from the ammonia synthesis tower to obtain ammonia. Furthermore, it includes an ammonia storage unit, such as liquid ammonia or an ammonia storage tank, for storing the purified ammonia.

[0063] The urea synthesis unit includes a urea synthesis tower. The urea synthesis tower converts ammonia into urea, completing a two-step reaction: first, carbon dioxide and ammonia are reacted at 180-200℃ and 14-25 MPa to synthesize ammonium carbamate; second, ammonium carbamate decomposes into water and urea at 120-140℃ and 2-5 MPa.

[0064] The urea synthesis tower includes an ammonia inlet and a carbon dioxide inlet, wherein the ammonia inlet is connected to an ammonia storage tank, and the carbon dioxide inlet is connected to a carbon dioxide storage tank. In some embodiments, urea preparation can be completed in a single tower, achieving a two-step reaction.

[0065] As one embodiment, the urea synthesis tower is a single tower, divided into a high-pressure synthesis zone (180-200℃, 14-25MPa) and a low-pressure decomposition zone (120-140℃, 2-5MPa), separated by an internal structure (such as trays or packing). Optionally, the urea production tower can be a tower reactor, consisting of two parts: an upper reactor and a lower separator. The reactor has a multi-layered plate structure for heating and mixing reactants, while the separator separates urea from unreacted ammonia. The tower reactor operates by pumping carbon dioxide and ammonia into the reactor via a compressor, where they react with a catalyst under high temperature and pressure to produce urea. The reaction products are then separated by the separator.

[0066] As another example, urea preparation can also be completed in a double-tower configuration, such as... Figure 6 As shown in diagram a, the first tower is a synthesis tower used to synthesize ammonium carbamate; as... Figure 6 As shown in b, the second tower is a decomposition tower used to decompose ammonium carbamate to produce urea. The temperature is controlled by external heating. In a more preferred embodiment, the first tower is set above the second tower. The ammonium carbamate coming out from the bottom of the first tower enters from the top of the second tower and decomposes into the urea produced, which comes out from the bottom of the second tower.

[0067] In some embodiments, the production system further includes a separation unit connected to the water-gas shift reaction unit for separating hydrogen and carbon dioxide from the combustible gas 3. As one embodiment, the separation unit includes a separator on which an adsorbent is loaded. This adsorbent selectively adsorbs either carbon dioxide or hydrogen through adsorption, allowing either gas to pass through, thereby achieving separation of the two gases. As another embodiment, the separation unit includes a separator that absorbs carbon dioxide using a low-temperature methanol washing process, achieving separation of hydrogen and carbon dioxide.

[0068] In some embodiments, the production system further includes a hydrogen storage unit and a carbon dioxide storage unit, each comprising a hydrogen storage tank and a carbon dioxide storage tank, for storing hydrogen and carbon dioxide separated by the separation unit, respectively.

[0069] In some embodiments, the production system further includes an air separation unit for separating nitrogen and oxygen. It also includes a nitrogen storage unit and an oxygen storage unit for storing nitrogen and oxygen, respectively. The nitrogen stored in the nitrogen storage unit is fed into an ammonia synthesis tower for ammonia synthesis. The nitrogen storage unit and the oxygen storage unit are storage tanks.

[0070] In some embodiments, the production system further includes a combustible gas combustion unit, which includes a combustible gas combustion furnace for burning the combustible gas to generate high-temperature flue gas. This high-temperature flue gas is used to heat biomass in a biomass carbonization unit, thereby achieving the recovery and utilization of the combustible gas. Figure 7 As shown, the combustible gas combustion furnace 1 includes a combustible gas inlet 1, a combustion-supporting gas inlet 1, and a high-temperature flue gas outlet 1. The high-temperature flue gas generated by the combustible gas combustion unit 1 is output through the high-temperature flue gas outlet 1 and enters the biomass carbonization unit through the flue gas inlet 1.

[0071] In some embodiments, the production system further includes a biomass preheating unit. The function of the biomass preheating unit is to utilize the residual heat energy of the waste flue gas after heat exchange in the biomass carbonization furnace to preheat and dry the biomass, thereby achieving efficient utilization of heat energy.

[0072] like Figure 8 As shown, the biomass preheating unit includes a biomass preheating furnace, which is equipped with a flue gas inlet, a biomass inlet, a biomass outlet, and a flue gas outlet. The biomass inlet is used to add biomass raw materials; the biomass raw material outlet is used to output preheated biomass raw materials; the biomass raw material outlet is connected to the biomass inlet in the biomass carbonization unit; and the flue gas inlet of the biomass preheating furnace is connected to the flue gas outlet of the biomass carbonization furnace. This preheating furnace is a gas-solid heat exchange device. This utility model does not provide a more detailed limitation on the structure of the biomass preheating furnace; those skilled in the art can adjust it according to actual needs.

[0073] In a preferred embodiment, the production system further includes a flue gas environmental protection unit, which is connected to the flue gas outlet of the biomass preheating unit and is used to treat the flue gas in an environmentally friendly manner.

[0074] In a preferred embodiment, a combustible gas 2 heat energy recovery unit is provided between the biochar gasification unit and the ammonia synthesis unit. The function of this unit is to exchange heat energy between the high-temperature combustible gas 2 and cooling water, turning the cooling water into preheated water, recovering the heat energy from the combustible gas 2, and cooling the combustible gas 2. The combustible gas 2 heat energy recovery unit includes a combustible gas heat energy recovery device, such as a gas-liquid heat exchanger. As a specific implementation, such as... Figure 9 As shown, the combustible gas heat recovery device is a gas-liquid heat exchanger, including a combustible gas 2 inlet, a combustible gas 2 outlet, a cooling water inlet, and a preheated water outlet. The combustible gas 2 inlet is connected to the combustible gas 2 outlet in the biochar gasification unit, and the combustible gas 2 outlet is connected to the combustible gas 2 purification unit. The cooling water inlet and the preheated water outlet are used for entering cooling water and outputting preheated water.

[0075] This application does not provide more detailed limitations on the specific structure of the combustible gas 2 heat energy recovery unit. Those skilled in the art can make adjustments based on existing technology according to actual needs.

[0076] In a preferred embodiment, the production system further includes a boiler unit. The purpose of the boiler unit is to receive preheated water from the combustible gas heat recovery unit, heat the preheated water into steam, and send it into the biochar gasification unit.

[0077] The boiler unit includes a combustion furnace or an electric heating furnace, which is connected to a combustible gas heat recovery unit and a biochar gasification unit.

[0078] In a more preferred embodiment, the boiler unit includes a combustion furnace. For example... Figure 10 As shown, the combustion furnace includes a fuel inlet, an oxygen-containing gas inlet (e.g., an air inlet), a preheated water inlet, a flue gas outlet, and a steam outlet. The fuel inlet of the combustion furnace is used to input fuel (e.g., ammonia tail gas output from the biomass or urea synthesis unit), and the preheated water inlet of the combustion furnace is connected to the preheated water outlet of the combustible gas 2 heat recovery unit.

[0079] The preheated water in the boiler unit is heated into steam (exemplarily including 100°C to 950°C, such as 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 950°C, etc.).

[0080] The combustion furnace or electric heating furnace used to heat water and convert it into steam in this invention can be existing equipment in the prior art, and will not be described in detail here.

[0081] In a more preferred embodiment, the boiler unit can be connected to the water-gas shift reaction unit simultaneously to send the generated steam into the water-gas shift reaction unit. The steam temperature required by the water-gas shift reaction unit can be conventionally selected or adjusted in the boiler unit according to the reaction requirements.

[0082] In some embodiments, the production system further includes a combustible gas 2 purification unit disposed between the combustible gas 2 outlet of the biochar gasification unit and the combustible gas 2 inlet of the urea synthesis unit. The combustible gas 2 purification unit includes a combustible gas 2 purification device for removing tar, sulfur-containing compounds, nitrogen-containing compounds and other impurities.

[0083] The combustible gas purification unit includes purification equipment for the combustible gas 2, which can be a liquid spray device, a liquid bubble scrubbing device, a Venturi scrubbing device, or a solid-phase adsorption device, etc. In a preferred embodiment, the purification equipment of the combustible gas 2 purification unit is a spray device, which washes the combustible gas 2 to remove impurities such as sulfur oxides, nitrogen oxides, and tar to obtain combustible gas 2 that includes at least carbon monoxide and hydrogen (and may further include carbon dioxide). Figure 11 As shown, the spraying equipment includes a combustible gas inlet 2, a combustible gas outlet 2, a washing water inlet 2, and a washing water outlet 2. The combustible gas inlet 2 is used to connect to the combustible gas outlet 2 in the combustible gas heat energy recovery unit, and the combustible gas outlet 2 is connected to the water-gas conversion reaction unit.

[0084] This application does not limit the specific structure of the spraying equipment; those skilled in the art can make adjustments according to actual needs.

[0085] In a preferred embodiment, such as Figure 1 As shown, the production system also includes a combustible gas 2 storage unit for storing the purified combustible gas 2, which may be a storage tank.

[0086] In some embodiments, the purpose of the flue gas environmental protection treatment unit is to treat waste flue gas. This application does not specifically limit the flue gas environmental protection treatment unit, and those skilled in the art can adjust it according to actual needs.

[0087] In this embodiment, some connecting pipeline units or equipment are also required for transmitting various combustible gases, oxygen, water, water vapor and flue gas, such as gas pipelines, pressure gauges, flow valves, switching valves, thermometers, etc., and some solid transmission units are also required for transporting biomass to the system and transferring biomass and biochar between different units, as well as equipment for collecting ash residue converted from biomass. These are designs made by those skilled in the art based on actual needs and are not specifically limited here.

[0088] It should be noted that the "connection" in the embodiments of the present invention can be a direct connection or an indirect connection. The indirect connection can be between two different units including some intermediate processing units, connecting pipelines, etc. The intermediate processing units and connecting pipelines can be storage units, purification units, cooling pipelines, heating pipelines, etc.

[0089] Based on the above production system, the production process for urea synthesis using biomass converted into combustible gas specifically includes the following steps:

[0090] (1) Biomass carbonization: Biomass is heated at 450-950℃ (exemplary temperatures include 450℃, 550℃, 650℃, 750℃, 850℃, 950℃, etc.) to obtain solid residue (biochar) and combustible gas 1, preferably at 500-700℃ (e.g., 500℃, 550℃, 600℃, 650℃, 700℃, etc.). The biochar after reaction is transferred to a biochar gasifier through a biochar outlet.

[0091] (2) Biochar gasification: Biochar is gasified at a temperature of 450-950℃ (examples include 450℃, 550℃, 650℃, 750℃, 850℃, 900℃, etc.) and steam at 100-950℃ (examples include 100℃, 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, etc.) is introduced to convert it into combustible gas 2 and biochar ash (including residual char, i.e., the char remaining in the biochar ash).

[0092] (3) Heat recovery of combustible gas 2: The high-temperature combustible gas 2 prepared in step 2 is processed by the combustible gas 2 heat recovery unit to turn the cooling water into preheated water through heat exchange.

[0093] (4) Steam preparation: The preheated water generated in step 3 is heated by the boiler unit to prepare steam at 100-950℃ (exemplary values ​​include 100℃, 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, etc.), and the steam is transferred to the biochar gasification step in step 2.

[0094] (5) Purification of combustible gas 2: After indirect heat exchange between combustible gas 2 and water, impurities such as tar are removed in the combustible gas 2 purification unit by adsorption or spraying to obtain combustible gas 2 with carbon monoxide and hydrogen as the main components, and it is stored in the combustible gas 2 storage unit.

[0095] (6) Ammonia synthesis: Combustible gas 2 is output from the combustible gas 2 storage unit, and carbon monoxide and water vapor in combustible gas 2 are reacted and converted into carbon dioxide and hydrogen through the conversion unit to obtain a mixture of hydrogen and carbon dioxide (combustible gas 3). After separation by the separation unit, hydrogen and carbon dioxide are obtained respectively. Hydrogen and nitrogen are further synthesized into ammonia through the ammonia synthesis tower. The ammonia synthesis is carried out at a pressure of 15.2-30.4 MPa and a temperature of 400-520℃.

[0096] (7) Urea synthesis: Urea is obtained by reacting carbon dioxide and ammonia as the main components. The synthesis of urea is divided into two steps: First, carbon dioxide and ammonia are synthesized into ammonium carbamate at 180-200℃ and 14-25MPa; Second, ammonium carbamate is decomposed into water and urea at 120-140℃ and 2-5MPa.

[0097] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application without departing from the principles and spirit of this utility model.

Claims

1. A production system for carbonizing and gasifying biomass and combining it with urea synthesis, characterized in that, The production system includes a biomass carbonization unit, a biochar gasification unit, a water-gas shift reaction unit, an ammonia synthesis unit, and a urea synthesis unit connected in series. The biomass carbonization unit includes a biomass carbonization furnace, which includes a biomass inlet, a biochar outlet, and a combustible gas outlet, used to convert biomass into biochar and combustible gas. The biochar gasification unit includes a biochar gasifier, which has a biochar inlet and a combustible gas 2 outlet for converting biochar into combustible gas 2. The biochar inlet is connected to the biochar outlet, and the combustible gas 2 includes carbon monoxide. A water-gas shift reaction unit includes a shift reactor, which is used to react and convert carbon monoxide and water vapor in the combustible gas 2 into hydrogen and carbon dioxide; the shift reactor includes a combustible gas 2 inlet, a water vapor inlet, a hydrogen outlet and a carbon dioxide outlet, and the combustible gas 2 inlet is connected to the combustible gas 2 outlet. The ammonia synthesis unit includes an ammonia synthesis tower, which includes a hydrogen inlet and an ammonia outlet, with the hydrogen inlet connected to the hydrogen outlet. The urea synthesis unit includes a urea synthesis tower, which has an ammonia inlet and a carbon dioxide inlet. The ammonia inlet is connected to the ammonia outlet, and the carbon dioxide inlet is connected to the carbon dioxide outlet.

2. The production system according to claim 1, characterized in that, The production system also includes a separation unit connected to the water-gas conversion reaction unit for separating hydrogen and carbon dioxide; the production system also includes a hydrogen storage unit and a carbon dioxide storage unit for storing the hydrogen and carbon dioxide separated by the separation unit, respectively, and the hydrogen storage unit and carbon dioxide storage unit include a hydrogen storage tank and a carbon dioxide storage tank, respectively.

3. The production system according to claim 2, characterized in that, The production system also includes an ammonia storage unit, which includes an ammonia storage tank connected to an ammonia synthesis tower for storing ammonia synthesized by the ammonia synthesis tower.

4. The production system according to claim 1, characterized in that, The production system further includes a combustible gas 1 combustion unit, which includes a combustible gas 1 combustion furnace for burning combustible gas 1 to generate high-temperature flue gas. The combustible gas 1 combustion furnace includes a combustible gas 1 inlet, an oxygen-containing gas inlet, and a high-temperature flue gas outlet. The outer wall of the biomass carbonization furnace includes a jacket, which includes the flue gas inlet and the flue gas outlet for the inlet and outlet of high-temperature flue gas. The combustible gas 1 inlet is connected to the combustible gas 1 outlet, and the flue gas inlet on the jacket is connected to the high-temperature flue gas outlet of the combustible gas 1 combustion furnace.

5. The production system according to claim 4, characterized in that, The production system also includes a biomass preheating unit; The biomass preheating unit includes a biomass preheating furnace, which is provided with a flue gas inlet, a biomass inlet, a biomass outlet, and a flue gas outlet. The biomass inlet is used to add biomass raw materials; Biomass feedstock exports are used for exporting preheated biomass; The biomass feedstock outlet is connected to the biomass inlet of the biomass carbonization unit; the flue gas inlet on the biomass preheater is connected to the flue gas outlet of the biomass carbonization furnace.

6. The production system according to claim 1, characterized in that, The production system also includes a combustible gas 2 heat energy recovery unit connected to the biochar gasification unit, which is used to exchange the heat energy of the combustible gas 2 generated by the biochar gasification unit with the cooling water, thereby turning the cooling water into preheated water. The combustible gas heat recovery unit includes a gas-liquid heat exchanger, which includes a combustible gas inlet 2, a combustible gas outlet 2, a cooling water inlet, and a preheated water outlet. The combustible gas inlet 2 is connected to the combustible gas outlet 2 in the biochar gasification unit.

7. The production system according to claim 1, characterized in that, The production system also includes a boiler unit connected to the biochar gasification unit, which is used to heat preheated water into steam. The boiler unit includes a combustion furnace or an electric heating furnace; the combustion furnace or electric heating furnace includes a preheated water inlet and a steam outlet; the preheated water inlet is connected to the preheated water outlet of the combustible gas 2 heat energy recovery unit; the biochar gasification furnace includes a steam inlet, and the steam outlet is connected to the steam inlet of the biochar gasification furnace.

8. The production system according to claim 1 or 2, characterized in that, The production system also includes a combustible gas 2 purification unit, which is connected to the combustible gas 2 outlet of the biochar gasification unit. The combustible gas 2 purification unit includes a combustible gas 2 purification device.

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