A biomass-to-green methanol system

Abstract

The present invention discloses a biomass green methanol system, which mainly includes boiler power generation, air separation unit, gasification unit, conversion unit, desulfurization and decarbonization unit, compression unit, synthesis unit and distillation unit. The biomass feed of the gasification unit adopts pneumatic dense phase transportation, and the conveying gas selects CO2 of the desulfurization and decarbonization unit, and controls the biomass crushing particle size, conveying density, and the temperature and pressure of the conveying gas to ensure the stability of biomass transportation. The gasifier adopts waste boiler technology, and can produce saturated steam by-product by recovering the sensible heat of high-temperature synthesis gas, and use the purge gas of the synthesis unit to overheat it and generate electricity as system electricity. If the power is insufficient, the purge gas of the synthesis unit can be supplemented by the superheated steam produced by the gas boiler. Using biomass as an energy source instead of traditional fossil fuels can significantly reduce dependence on fossil fuels, reduce carbon emissions, improve energy utilization efficiency, and thereby meet green electricity requirements, providing a basis for green methanol certification.

Description

Technical Field

[0001] The invention relates to the technical field of biomass energy conversion, and in particular to a biomass-to-green methanol system. Background Art

[0002] In recent years, green shipping has become the transformation goal of the global shipping industry. Using green methanol as fuel for ships will become a major trend in the future. Using biomass to make methanol is an important source of green methanol, and the transportation and gasification of biomass are key difficulties. At the same time, this project is also a coupling project of green electricity and biomass chemical industry.

[0003] At present, in the field of biomass energy conversion, gasification technology, as a key unit for converting biomass into synthesis gas, has received widespread attention. Existing biomass gasification technologies mainly include fixed bed, fluidized bed and fluidized bed. However, each gasification technology has its own shortcomings. The shortcomings of fixed bed gasification technology are as follows: 1) The bulk density of biomass materials is low, and special additives need to be added to briquette them before entering the furnace. 2) The gasification efficiency is low and the heat transfer is uneven, so that a large amount of tar and solid material particles are mixed in the synthesis gas, which increases the complexity and investment cost of subsequent treatment. 3) The synthesis gas contains a large amount of tar and solid material particles, which not only brings trouble to the synthesis gas washing unit, but also the tar is easy to condense at low temperature, blocking the pipe mouth, valves, instruments, etc., making it difficult for the gasification equipment to operate stably for a long time. 4) The volatile content of biomass is extremely high (more than 60%), making it difficult to control the furnace temperature of the fixed bed. The disadvantages of fluidized bed gasification technology are as follows: 1) In order to ensure the full reaction of the materials, the stability of the bed must be ensured. Some fluidized bed technologies require heating media such as sand, which makes it difficult to operate and easy to wear the equipment, resulting in unstable production and high cost of use. 2) The fluidized bed can only be operated at normal pressure or slightly positive pressure, and the production capacity is small. 3) The synthesis gas contains a large amount of tar and solid material particles, which not only brings trouble to the synthesis gas washing unit, but the tar is also easy to condense at low temperatures, blocking the pipes, valves, instruments, etc., making it difficult for the gasification equipment to operate stably for a long time. 4) The structure of the fluidized bed gasifier is too complicated and the investment is huge. Summary of the invention

[0004] The present application provides a biomass-to-green methanol system, which solves the technical problems in the prior art such as the difficulty in transporting biomass, high chlorine, high potassium and sodium, and power shortage in remote areas.

[0005] In view of the problem of biomass gasification, the solution of this patent is as follows:

[0006] 1. Gasification technology In the process of biomass transportation, because biomass contains a lot of fiber materials and the powder has general fluidity, the transportation density is low. This patent uses carbon dioxide discharged from the desulfurization and decarbonization system as the transportation gas, which can reduce the ineffective use of N2.

[0007] 2. If solid slag discharge is used, the synthesis gas will contain a large amount of tar and solid material particles, which will bring great difficulties to the water treatment system. Therefore, liquid slag discharge is used this time. When the temperature in the combustion chamber is higher than the melting point of the biomass ash, tar and other organic matter react with oxygen to produce CO, H2, and CO2, thereby eliminating the problem of difficult water treatment.

[0008] 3. High chlorine. The chloride ion content in biomass is generally 0.5-1%. Temperature changes have a significant impact on the corrosion resistance of equipment and pipelines. Generally speaking, as the temperature rises, the activity of chloride ions will increase, and the corrosion effect on equipment and pipelines will also increase accordingly. In addition, the organizational structure of equipment materials will also change at high temperatures, reducing corrosion resistance. Therefore, the gasification pressure is 3.0MPa, and the black water temperature in the gasifier quenching chamber, scrubber and other equipment is guaranteed to be less than 185℃, and key equipment such as the gasifier, scrubber, and lock bucket are designed with special materials, which can reduce corrosion to a certain extent.

[0009] 4. High potassium and sodium. The potassium and sodium content in biomass is greater than 10%. Potassium and sodium corrosion can be avoided from the following perspectives. First, the gasifier combustion chamber adopts a water-cooled wall structure to prevent potassium and sodium from replacing the rubbing in the refractory bricks, causing erosion of the refractory bricks and shortening their lifespan. Secondly, the gasifier adopts a semi-waste boiler design. When designing the radiation waste boiler, it is ensured that the waste boiler section is a high-temperature unit above 700°C, which can maximize the recovery of the heat of the high-temperature synthesis gas and avoid the problem of waste boiler sticking ash and slag blockage caused by the low-temperature precipitation of potassium and sodium alkali metals.

[0010] 5. The factory is built in a remote area with no electricity available. The system is equipped with boiler and steam turbine units. The steam produced by the gas chemical unit is superheated through the exhaust gas of the synthesis unit and then sent to the steam turbine to generate electricity for the system. This can achieve heat source recovery and energy recovery.

[0011] 6. The bulk density of biomass powder is low. Through experimental exploration, processing biomass into characteristic forms before crushing can increase the bulk density of biomass and reduce the storage space of raw materials.

[0012] The present application provides a biomass-to-green methanol system, comprising:

[0013] The air separation unit transports the gasification medium to the gasification unit for biomass powder gasification and combustion;

[0014] Biomass processing unit, which processes biomass into a specific form;

[0015] A powder preparation unit that crushes the biomass into particles;

[0016] In the powder conveying unit, biomass is transported into the combustion chamber by pneumatic dense phase;

[0017] Adjust pipeline parameters, gas parameters and biomass parameters, calculate the pressure drop caused by the resistance of the fluid passing through the particle fixed bed, and control the pressure drop within the threshold;

[0018] A gasification unit, wherein the combustion chamber of the gasification unit is provided with a water-cooled wall, and the gasification unit is designed as a semi-waste boiler, wherein the waste boiler is provided in a high-temperature unit;

[0019] The biomass processing unit, the powder preparation unit, the powder conveying unit, and the gasification unit are connected in sequence, and the air separation unit is connected to the gasification unit.

[0020] In some embodiments, the oxygen purity in the air separation unit is 99.6%; the rod particle specifications processed by the biomass processing unit are length ≤100mm, equivalent diameter ≤60mm; the biomass crushing particle size requirements are: crushing particle size ≤106um, mass fraction 25-45%; crushing particle size ≤250um, mass fraction 55-80%; crushing particle size ≤700um, mass fraction 90-98%; crushing particle size ≤2500um, mass fraction 100%; dense phase conveying density is 200-600kg / m 3 ; The conveying gas temperature is 70~150℃, the conveying pressure difference is 1.5~3.0MPa, and the gas type is carbon dioxide.

[0021] In some embodiments, the synthesis gas produced by the gasification unit sequentially enters a conversion unit, a desulfurization and decarbonization unit, a compression unit, a synthesis unit, and a distillation unit to produce green methanol.

[0022] In some embodiments, the system further comprises:

[0023] An energy storage cabinet, which is connected to each unit to supply power to each unit;

[0024] The boiler and power generation unit includes a boiler and a steam turbine. The gasification unit and the synthesis unit are respectively connected to the boiler pipeline, the boiler is connected to the steam turbine, and the steam turbine is connected to the energy storage cabinet.

[0025] In some embodiments, the high-temperature synthesis gas from the gasification unit enters the waste boiler of the gasifier through the slag port, and uses its own sensible heat to produce high-pressure saturated steam as a by-product. The saturated steam is superheated in the boiler and then enters the turbine to generate electricity. The saturated steam produced as a by-product of the synthesis unit is used by the distillation unit, and the released purge gas is sent to the boiler as a heat source to superheat the saturated steam and use the turbine to generate electricity.

[0026] In some embodiments, the boiler is a gas boiler with a built-in superheater, the fuel is the exhaust gas from the synthesis unit, the steam turbine is connected to the gas boiler by a pipeline, and the superheated steam obtained by combustion is sent to the steam turbine for power generation.

[0027] In some embodiments, the boiler is a biomass boiler, which uses biomass to burn in the boiler to produce saturated steam, which is then superheated and used as a steam turbine to generate electricity.

[0028] In some embodiments, the step of adjusting pipeline parameters, gas parameters, and biomass parameters to calculate the pressure drop caused by resistance when the fluid passes through the particle fixed bed includes:

[0029] Calculate the settling velocity of biomass particles in a stationary gas,

[0030]

[0031] Where g is the acceleration due to gravity, d is the particle size of the crushed biomass, and ρ p is the dense phase transport density, ρ g is the gas density, μ is the gas viscosity;

[0032] Calculate the biomass transport rate, where ρ b is the natural packing density of particles, d is the biomass particle size;

[0033] Calculate pressure drop

[0034] Where L is the length of the pipe, M s is the biomass mass, D is the inner diameter of the pipe, M g is the transport gas mass, ρ s is the biomass transport density.

[0035] In some embodiments, the medium and low pressure steam produced as a by-product of the conversion unit is used as a heat source for the desorption gas of the desulfurization and decarbonization unit. When hydrogen is added to the system, the load of the conversion unit is reduced and the carbon-hydrogen ratio is adjusted to meet the requirements of the synthesis stage.

[0036] In some embodiments, the carbon dioxide removed by the desulfurization and decarbonization unit is pressurized by a compressor and transported to a gasification unit, and used as a transport gas to transport biomass powder to a gasifier; the sulfur removed by the desulfurization and decarbonization unit is transported to a sulfur recovery device.

[0037] In some embodiments, the biomass processing unit subjects the biomass to torrefaction.

[0038] The beneficial effects of this application are as follows:

[0039] By adjusting the biomass crushing particle size, dense phase conveying density, conveying air flow velocity, and adjusting the appropriate conveying pressure difference, the stable conveying of biomass is finally ensured; CO2 is selected as the biomass conveying gas to reduce the ineffective use of N2, which can change the equilibrium direction of the combustion reaction and move toward the direction of generating carbon monoxide, thereby increasing the effective gas content and improving the cold gas efficiency. The biomass gasifier adopts a waste pot structure to recover the sensible heat of the high-temperature synthesis gas and produce high-quality saturated or superheated steam as a byproduct, thereby improving the gasification thermal efficiency of biomass.

[0040] After the biomass enters the gasifier, the oxygen coming from the central oxygen channel is initially atomized and diffused, and then the oxygen coming from the annular oxygen channel is atomized for the second time, which enhances the mixing effect of biomass and oxygen and makes the biomass evenly distributed in the combustion chamber. At the same time, it receives the radiation heat from the flame, the inner wall of the furnace, high-temperature gas, solid matter, etc., as well as the heat from the reflux stream and the return stream (mainly composed of CO, H2, etc.), so that the biomass powder is heated evenly. The biomass evaporates instantly, and the biomass powder undergoes thermal cracking and releases volatiles. The cracking products, volatiles and other flammable components burn quickly and completely under high temperature and high oxygen concentration, releasing a large amount of heat.

[0041] The gasifier uses liquid slag discharge to ensure that the synthesis gas is free of tar. By controlling the amount of oxygen, the temperature of the combustion chamber is ensured to be 50-100°C higher than the ash melting point, so that the ash enters the waste boiler unit in liquid form. Boiler water is sprayed at the inlet of the waste boiler unit to rapidly solidify the ash into a glassy state to avoid scaling on the waste boiler pipe.

[0042] The gasification unit uses its own sensible heat to produce high-pressure saturated steam as a byproduct. The exhaust gas from the synthesis unit is sent to the boiler as a heat source to superheat the saturated steam, and then enters the steam turbine to generate electricity. The heat and energy of the gasification unit and the synthesis unit are rationally utilized to achieve energy conservation and emission reduction. The exhaust gas from the synthesis unit is composed of H2: 65-75%, CO: 4-10%, CO2: 5-15%, CH4: 4-10%. It is sent to the boiler as a heat source and burned with air. The heat generated superheats the high-pressure saturated steam produced by the gasification unit to a certain temperature and is sent to the steam turbine to generate electricity. The system relies on steam turbine power generation to meet the electricity consumption of each unit, thereby reducing operating costs.

[0043] The relationship between purge gas consumption and power generation is as follows:

[0044] Biomass consumption is 171t / h, gasifier waste boiler produces 140t / h of steam, 140t / h of steam is superheated to 230℃ and consumes 9800Nm of offgas 3 , the steam turbine generates 49000KW·h of electricity.

[0045] Under normal circumstances, the steam produced by the gasifier waste boiler is superheated and used to generate electricity for the system to use. However, when the steam production of the gasifier waste boiler is reduced due to problems such as scaling, in order to ensure the power generation of the steam turbine, it is necessary to increase the biomass material of the gasification unit and increase the amount of vented gas entering the boiler without affecting the output of green methanol, so as to ensure the stability of the superheated steam at the turbine inlet and keep the power generation of the steam turbine unchanged.

[0046] The relationship between biomass and steam volume is as follows:

[0047] Biomass consumption is 2570Kg, and the exhaust gas can be 2600Nm 3 The boiler can produce 10t / h of superheated steam at 230℃. At the same time, the biomass consumption is 171t / h. The waste boiler of the gasifier produces 130t / h of steam. 130t / h of steam superheated at 230℃ consumes 9100Nm of relaxation gas. 3 , the steam turbine generates 49000KW·h of electricity.

[0048] When the steam output of the gasifier waste boiler remains basically unchanged and the power consumption of the plant continues to increase, the amount of purge gas entering the boiler can be increased by increasing the biomass entering the gasifier to increase the amount of superheated steam entering the turbine.

[0049] The relationship between biomass and steam volume is as follows:

[0050] Biomass consumption is 2570Kg, and the exhaust gas can be 2600Nm 3 The boiler produces 10t / h of superheated steam at 230℃. At the same time, the biomass consumption is 171t / h. The gasifier waste boiler produces 140t / h of steam. 140t / h of steam superheated at 230℃ consumes 9800Nm of relaxation gas. 3 , the steam turbine generates 52500KW·h of electricity.

[0051] Therefore, the change in the amount of biomass, while ensuring the stability of green methanol production, depends on the change in the steam production of the gasifier waste boiler and the change in the total electricity consumption of the plant.

[0052] The gasifier waste boiler can also be designed to produce by-product superheated steam that is directly fed into the steam turbine for power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0054] Figure 1 A schematic structural diagram of a biomass-to-green methanol system provided in this application. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0056] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0057] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0058] The embodiment of the present application provides a biomass-to-green methanol system, which solves the technical problems in the prior art of difficult biomass transportation and remote plant construction sites without electricity.

[0059] The biomass mentioned in the technical solution includes but is not limited to wheat straw, corn stalks, garbage, cow dung, wood and other materials.

[0060] The analysis data represented by corn stalks is shown in the following table

[0061] The following table shows the analysis data of corn straw in Inner Mongolia

[0062]

[0063] As can be seen from the table above, the entrained-bed gasification of biomass represented by corn stalks also has the following advantages:

[0064] 1. High volatile matter, the volatile matter in biomass can reach 74%-84%, which is conducive to gasification reaction;

[0065] 2. High reactivity. Biomass has high reactivity. Generally, the reactivity of biomass at 1000℃ can reach 100%;

[0066] 3. Low ash melting point, high silica. The ash content of straw is generally 5-10%, and the ash melting point is generally 1250℃; the ash content of forest wood is generally less than 1%, and the ash melting point is generally around 1400℃. The silica content is greater than 60%, which is conducive to liquid slag discharge and the formation of glass.

[0067] The technical solution in the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows:

[0068] like Figure 1 As shown, the present application provides a biomass-to-green methanol system, comprising:

[0069] The air separation unit transports the gasification medium to the gasification unit for biomass powder gasification and combustion;

[0070] A biomass processing unit processes the biomass into a specific form. In this embodiment, the biomass processing unit processes the biomass into rods and pellets;

[0071] A powder preparation unit that crushes the biomass into particles;

[0072] In the powder conveying unit, biomass is transported into the combustion chamber by pneumatic dense phase;

[0073] Adjust pipeline parameters, gas parameters and biomass parameters, calculate the pressure drop caused by the resistance of the fluid passing through the particle fixed bed, and control the pressure drop within the threshold;

[0074] If N2 is used as the carrier gas, the biomass transport density remains unchanged. Because N2 has a low density and a small mass flow rate at the same temperature and pressure, when transporting biomass of the same particle size, the minimum biomass transport speed is reduced by 20% and the transport pressure difference is reduced by 15%, which is within a controllable range and is beneficial to the transport system.

[0075] If the biomass conveying quality increases by 20%, the biomass conveying density increases by 20%. Keeping other parameters unchanged, the minimum biomass conveying speed increases by 30%, and the conveying pressure difference increases by 35%. Exceeding the maximum allowable pressure difference range will cause the conveying pipeline to be blocked. The conveying pressure difference can be reduced by increasing the amount of conveying gas.

[0076] If the average particle size of biomass particles increases by 20%, other conditions remain unchanged, the minimum biomass conveying speed decreases by 5%, and the conveying pressure difference increases by 2%, so that the pressure drop is within a controllable range.

[0077] If the diameter of the biomass conveying pipe increases by 20% and other conditions remain unchanged, the minimum biomass conveying speed increases by 6% and the conveying pressure difference decreases by 2%, making the pressure drop within a controllable range.

[0078] A gasification unit, wherein a combustion chamber of the gasification unit is provided with a water-cooled wall, and the gasification unit is designed with a waste boiler, and the waste boiler is arranged in a high-temperature unit;

[0079] The biomass processing unit, the powder preparation unit, the powder conveying unit, and the gasification unit are connected in sequence, and the air separation unit is connected to the gasification unit.

[0080] The biomass processing unit can choose whether to bake the biomass. Baking generally refers to the baking process of biomass under low temperature and inert atmosphere, and the temperature is generally 200-400℃. Baking can change the elemental composition and microstructure of biomass, making biomass easier to crush and saving crushing power consumption. The removal of moisture during the baking process is due to the removal of free water, bound water and the cleavage of hydroxyl groups in the side chains of hemicellulose and cellulose. The release of CH4 is mainly due to the shedding of -CH3 functional groups in lignin and -CH2- of hemicellulose, cellulose and lignin. The release of CO2 gas is due to the decarbonylation and decarboxylation of glucuronic acid units in hemicellulose. The release of CO gas is mainly due to the cleavage of ether bonds (COC) in phenylpropane units in lignin and the cleavage of xylan units (C=O) in hemicellulose. The release of nitrogen-containing gas is mainly due to the decomposition of N in biomass raw materials into volatiles through deamination, dehydration and decarboxylation, including light gases such as NH3, HCN, and NO. The gas mixture released by baking can be used as fuel. The following table shows the analysis data before and after baking (baking conditions are N2 atmosphere, 280℃ temperature for 20min) of Shanxi corn stalks:

[0081]

[0082] It can be seen from the data in the above table that compared with biomass raw materials, the oxygen content of biomass after baking treatment is reduced, the carbon content is increased, the fixed carbon content is increased, and the volatile matter is reduced. The calorific value of biomass is increased, the hydrophobicity and grindability are improved, and the H / C and O / C are reduced. These changes are more conducive to the gasification of biomass.

[0083] For the biomass raw materials before and after baking used for gasification, the designed consumption and effective gas composition are shown in the following table:

[0084]

[0085] From the data in the table, we can see that gasification after biomass baking can reduce oxygen consumption and increase effective gas components. The load of the biomass transportation section is reduced, and the power consumption of the biomass crushing section is reduced. Therefore, in the biomass processing unit, it is possible to choose whether to bake the biomass.

[0086] In order to reduce transportation costs, the biomass powder processing unit processes the biomass into pellets at each collection point. The pellet specifications are ≤100mm in length and ≤60mm in equivalent diameter. In this process, the biomass density increases from 200kg / m 3 becomes 700kg / m 3 .

[0087] Biomass is stored in the raw material bin, and the biomass particles are weighed from the raw material bin by the weighing feeder and then enter the crusher. The dusty gas in the raw material bin is discharged into the atmosphere by the exhaust fan after passing through the filter to remove dust. The compressed gas pipeline for backblowing is equipped on the raw material bin filter. The biomass from the raw material bin is crushed into powder in the crusher and transported by CO2 gas. Under normal conditions, the biomass crushed particle size is ≤106um, and the mass fraction is 25-45%; the crushed particle size is ≤250um, and the mass fraction is 55-80%; the crushed particle size is ≤700um, and the mass fraction is 90-98%; the crushed particle size is ≤2500um, and the mass fraction is 100%. The crushed biomass passes through the powder filter and enters the powder storage bin.

[0088] Biomass flows from the powder storage bin to the biomass lock hopper by gravity. When the biomass lock hopper reaches the required high material level, it is isolated from all low-pressure equipment, and then pressurized until the pressure is the same as that of the biomass feed tank. At this time, the pressure balance valve between the two tanks is opened. The biomass lock hopper is pressurized with carbon dioxide, and carbon dioxide enters directly through the ventilation cone at the bottom of the tank and the flute in the middle of the tank. Biomass flows from the biomass lock hopper to the biomass feed tank by gravity. After all the biomass in the biomass lock hopper enters the biomass feed tank, the cut-off valve at the bottom of the biomass lock hopper and the pressure balance valve between the two tanks are closed to isolate it from the high-pressure system. Then, the biomass lock hopper unloads the pressure in the biomass lock hopper to the biomass storage tank filter through the cut-off valve. The operating pressure of the biomass lock hopper is 5.0~0.02MPa(G) (the gasifier pressure is 3.0MPaG), the conveying pressure difference is 1.5~3.0MPa, and the operating temperature is 80℃.

[0089] The biomass lock hopper achieves the purpose of transporting biomass from a low-pressure system to a high-pressure system through the above-mentioned cyclic process of discharging-pressurizing-unloading-pressure relief.

[0090] Oxygen from the air separation unit outside the limit area passes through the oxygen main pipe and enters the gasifier through the flow control valve and the cut-off valve. The oxygen flow measurement needs to be compensated for temperature and pressure. Part of the oxygen enters the gasifier through the outer ring channel of the process burner, and part of the oxygen enters the gasifier through the central channel. During the startup phase, the oxygen is discharged to the atmosphere through the oxygen venting silencer to establish the oxygen flow.

[0091] In the combustion chamber of the gasifier, under certain temperature and pressure, the carbon in the biomass undergoes complex redox reactions with oxygen, water, etc., and a series of side reactions occur, generating crude synthesis gas mainly composed of CO and H2. The incombustible ash in the biomass and some carbon particles that have not reacted completely form ash slag. Therefore, the main components of the crude synthesis gas at the outlet of the combustion chamber of the gasifier include CO, H2, CO2, CH4, H2S and water vapor. A water-cooled wall is set inside the pressure-resistant steel shell of the gasifier.

[0092] There is a descending flame directly below the process burner of the gasifier and forms a high temperature zone. The process burner is radiated by the high temperature zone. The decrease in metal strength at high temperature and the scouring of high-speed flowing biomass often cause wear and thermal stress damage to the process burner. In order to protect the process burner, a water jacket is provided at the end of the process burner, and the burner is cooled by the circulation of the process burner cooling water in the water jacket. The burner cooling water comes from the boiler water of the steam drum.

[0093] The crude synthesis gas leaves the combustion chamber of the gasifier together with the molten liquid ash and flows downward into the radiation waste boiler. The radiation waste boiler produces high-pressure saturated steam as a by-product. The crude synthesis gas is cooled by the radiation waste boiler and then enters the quenching chamber of the gasifier. In the quenching chamber, the crude synthesis gas is cooled by the quenching water bath delivered by the quenching water pump. Most of the ash with larger particles contained in the crude synthesis gas sinks to the bottom of the quenching chamber after cooling, and then enters the lock bucket and is regularly discharged into the slag pool. This part of slag is called coarse slag. The crude synthesis gas coming out of the quenching chamber of the gasifier passes through the venturi scrubber and enters the scrubber tower. The synthesis gas first enters the water at the bottom of the scrubber tower to wash away some of the fine slag. The synthesis gas, which basically does not contain solid particles, flows upward along the scrubber tower and directly contacts the circulating ash water entering from the middle of the tower and the condensate from outside the boundary area added to the upper part of the tower in a countercurrent manner to wash the remaining solid particles. The dust content in the synthesis gas leaving the scrubber tower is less than 1mg / Nm 3 A cyclone plate demister is installed on the top of the scrubber to remove the water mist entrained in the synthesis gas when it leaves the scrubber. The clean synthesis gas enters the conversion unit after leaving the scrubber.

[0094] The syngas is heat exchanged with the high-temperature shift gas from the shift furnace in the heat exchanger and then enters the shift furnace. After the gas undergoes a shift reaction in the shift furnace, CO reaches an appropriate ratio, and medium-pressure saturated steam is produced as a by-product in the shift furnace. The shift gas leaving the shift furnace is cooled in the heat exchanger and then enters the low-pressure steam waste heat boiler, where low-pressure saturated steam is produced as a by-product. The shift gas enters the boiler water heater for heat exchange and then enters the organic sulfur hydrolysis tank. Under the action of the catalyst in the organic sulfur hydrolysis tank, the gas converts the organic sulfur in the gas into hydrogen sulfide. After entering the desalted water heater, it enters the shift gas cooler. After cooling in the shift gas cooler, the temperature reaches about 40°C. After entering the shift gas separator to separate the water in the gas, the gas is sent to the desulfurization and decarbonization unit. The desulfurization and decarbonization unit can choose low-temperature methanol washing or MDEA method, and the appropriate method can be selected according to the specific conditions of the project. The removed carbon dioxide is pressurized by the compressor and sent to the biomass powder conveying unit to stably convey the powder to the gasifier.

[0095] The synthesis gas from the purification unit enters the synthesis gas compressor. After being compressed, the synthesis gas is cooled and separated from the water, mixed with the circulating gas from the synthesis loop, and then enters the circulating compressor. After being compressed, it is sent to the synthesis system. The synthesis gas compressor and the circulating gas compressor share a shaft. The synthesis gas entering the synthesis unit is heated by heat exchange with the outlet reaction gas of the methanol synthesis tower through the gas-to-gas heat exchanger and then enters the methanol synthesis tower. The outlet reaction gas is preheated by the waste heat boiler to produce medium-pressure steam, and then cooled to 40°C by the water cooler. The cooled gas enters the methanol separator for gas-liquid separation. The separated gas is sent to the compressor circulation unit for pressure increase and then returned to the methanol synthesis system. The by-product steam is sent to the methanol distillation unit for use. The use of internally generated steam reduces dependence on external energy, thereby indirectly reducing the emission of greenhouse gases and other pollutants. The separated liquid crude methanol is sent to the distillation unit after flash evaporation under reduced pressure in the intermediate tank. The flash gas is used as fuel to go to the gas boiler to superheat the high-pressure saturated steam produced by the gasification unit. The heat and energy of the gasification unit and synthesis unit are used rationally to achieve energy saving.

[0096] The crude methanol sent from methanol synthesis enters the pre-distillation tower, where the light components are separated. The gas evaporated from the top of the tower condenses methanol, water and part of the light components through the pre-tower condenser, and the condensate enters the pre-tower reflux tank. The non-condensable gas enters the light component cooler for further cooling. The non-condensable gas leaving the light component cooler goes to the boiler room as fuel gas, and the condensate returns to the pre-distillation tower as reflux liquid. The methanol liquid coming out of the bottom of the pre-distillation tower is pressurized by the methanol feed pump and sent to the pressurized distillation tower. The methanol vapor evaporated from the top of the tower enters the condenser reboiler. The condensation heat of the methanol vapor is used as the heat source of the atmospheric distillation tower. The refined methanol liquid leaving the condenser reboiler enters the reflux tank of the pressurized tower. A part of the refined methanol is pressurized by the pressurized tower reflux pump and sent to the pressurized distillation tower. The rest is cooled to 40°C by the refined methanol cooler and sent to the refined methanol intermediate tank. The methanol liquid coming out of the bottom of the pressure distillation tower is sent to the lower part of the atmospheric distillation tower. The methanol vapor evaporated is condensed by the atmospheric tower condenser and enters the atmospheric tower reflux tank. It is then pressurized by the atmospheric tower reflux pump. A part of the refined methanol is pumped into the atmospheric tower reflux, and the rest is sent to the refined methanol intermediate tank. The product of the refined methanol intermediate tank is sent to the methanol warehouse after passing the test.

[0097] Corn stalks are used as raw materials. A preliminary cost and economic calculation of the above process is carried out. See the table below for details.

[0098]

[0099]

[0100] As can be seen from the table, the cost of green methanol produced from biomass is 1,503 yuan / ton, and the comprehensive energy consumption per unit product of green methanol produced from biomass is 1,232 kgce / t. The energy limit level 1 indicator implemented in the energy consumption limit per unit product of methanol, ethylene glycol and dimethyl ether (GB29436-2023) is 1,380 kgce / t, and the comprehensive energy consumption of methanol produced from biomass is better than the level 1 indicator.

[0101] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0102] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A biomass-to-green methanol system, characterized in that: include: The air separation unit transports the gasification medium to the gasification unit for biomass powder gasification and combustion; Biomass processing unit, which processes biomass into a specific form; A powder preparation unit that crushes the biomass into particles; In the powder conveying unit, biomass is transported into the combustion chamber by pneumatic dense phase; Adjust pipeline parameters, gas parameters and biomass parameters, calculate the pressure drop caused by the resistance of the fluid passing through the particle fixed bed, and control the pressure drop within the threshold; A gasification unit, wherein a combustion chamber of the gasification unit is provided with a water-cooled wall, and the gasification unit is designed with a waste boiler, and the waste boiler is arranged in a high-temperature unit; The biomass processing unit, the powder preparation unit, the powder conveying unit, and the gasification unit are connected in sequence, and the air separation unit is connected to the gasification unit.

2. A biomass-to-green methanol system as claimed in claim 1, characterized in that: The oxygen purity in the air separation unit is 99.6%; the rod particle specifications processed by the biomass processing unit are length ≤100mm, equivalent diameter ≤60mm; the biomass crushing particle size requirements are: crushing particle size ≤106um, mass fraction 25-45%; crushing particle size ≤250um, mass fraction 55-80%; crushing particle size ≤700um, mass fraction 90-98%; crushing particle size ≤2500um, mass fraction 100%; dense phase conveying density is 200-600kg / m 3 ; The conveying gas temperature is 70-150°C, the conveying pressure difference is 1.5-3.0MPa, and the gas type is carbon dioxide.

3. A biomass-to-green methanol system as claimed in claim 1, characterized in that: The synthesis gas produced by the gasification unit sequentially enters the conversion unit, the desulfurization and decarbonization unit, the compression unit, the synthesis unit and the distillation unit to produce green methanol.

4. A biomass-to-green methanol system as claimed in claim 3, characterized in that: Also includes: An energy storage cabinet, which is connected to each unit to supply power to each unit; The boiler and power generation unit includes a boiler and a steam turbine. The gasification unit and the synthesis unit are respectively connected to the boiler pipeline, the boiler is connected to the steam turbine, and the steam turbine is connected to the energy storage cabinet.

5. A biomass-to-green methanol system as claimed in claim 4, characterized in that: The high-temperature synthesis gas from the gasification unit enters the waste boiler of the gasifier through the slag port, and uses its own sensible heat to produce high-pressure saturated steam as a by-product. The saturated steam is superheated in the boiler and then enters the turbine to generate electricity. The saturated steam produced as a by-product of the synthesis unit is used by the distillation unit, and the released purge gas is sent to the boiler as a heat source to superheat the saturated steam and use the turbine to generate electricity.

6. A biomass-to-green methanol system as claimed in claim 5, characterized in that: The boiler is a gas boiler with a built-in superheater. The fuel is the exhaust gas from the synthesis unit. The steam turbine is connected to the gas boiler through a pipeline. The superheated steam obtained by combustion is sent to the steam turbine for power generation.

7. A biomass-to-green methanol system as claimed in claim 4, characterized in that: The boiler adopts a biomass boiler, which uses biomass to burn in the boiler to produce saturated steam, which is then superheated and used as a steam turbine to generate electricity.

8. A biomass-to-green methanol system as claimed in claim 1, characterized in that: The adjustment of pipeline parameters, gas parameters and biomass parameters to simplify the calculation of the pressure drop caused by the resistance of the fluid passing through the particle fixed bed includes: Calculate the settling velocity of biomass particles in a stationary gas, Where g is the acceleration due to gravity, d is the particle size of the crushed biomass, and ρ p is the dense phase transport density, ρ g is the gas density, μ is the gas viscosity; Calculate the biomass transport rate, where ρ b is the natural packing density of particles, d is the biomass particle size; Calculate pressure drop Where L is the length of the pipe, M s is the biomass mass, D is the inner diameter of the pipe, M g is the transport gas mass, ρ s is the biomass transport density.

9. A biomass-to-green methanol system as claimed in claim 3, characterized in that: The medium and low pressure steam produced as a byproduct of the conversion unit is used as a heat source for the desorption gas of the desulfurization and decarbonization unit. When hydrogen is added to the system, the load of the conversion unit is reduced and the carbon-hydrogen ratio is adjusted to meet the requirements of the synthesis section.

10. A biomass-to-green methanol system as claimed in claim 3, characterized in that: The carbon dioxide removed by the desulfurization and decarbonization unit is pressurized by a compressor and transported to the gasification unit, and used as a transport gas to transport the biomass powder to the gasifier; the sulfur removed by the desulfurization and decarbonization unit is transported to a sulfur recovery device.

11. A biomass-to-green methanol system as claimed in claim 1, characterized in that: The biomass processing unit torrefies the biomass.

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