Preparation method and device of green fuel

Abstract

The invention provides a preparation method and device of green fuel, and the preparation method of the green fuel comprises the following steps: 1) carrying out gasification treatment on biomass to obtain a gas mixture; 2) washing the gas mixture to obtain crude synthesis gas and black water; (3) sequentially carrying out water-gas conversion treatment and purification treatment on the crude synthesis gas to obtain purified synthesis gas; 4) performing grey water treatment on the black water to obtain salt-containing wastewater and grey water; the preparation method of the green fuel comprises the following steps of (1) preparing salt-containing wastewater, (2) purifying the salt-containing wastewater, (3) pre-treating the salt-containing wastewater, and carrying out electrolytic treatment to obtain electrolytic wastewater and hydrogen, and (4) mixing the purified synthesis gas with the hydrogen, and carrying out a synthesis reaction to obtain the green fuel. The preparation method of the green fuel can reduce the discharge amount of the high-salt-content wastewater and reduce the consumption of water resources.

Description

Technical Field

[0001] This invention belongs to the field of synthetic technology, and in particular relates to a method and apparatus for preparing green fuel. Background Technology

[0002] Biomass gasification technology converts solid biomass into syngas, primarily composed of CO and H2, through high-temperature thermochemical reactions, and is a crucial step in the production of green fuels (such as green methanol, renewable natural gas, and sustainable aviation fuel). However, biomass gasification generates large amounts of highly saline wastewater (containing ammonia, formate, sulfate, chloride, carbonate, and cyanide compounds), which is costly and energy-intensive to treat. Meanwhile, traditional water electrolysis for hydrogen production (such as alkaline water electrolysis and proton exchange membrane electrolysis) relies on high-purity water as a raw material, leading to significant water resource consumption.

[0003] Therefore, reducing the discharge of high-salinity wastewater and reducing water consumption have become urgent technical problems to be solved at this stage. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing green fuel that can reduce the discharge of high-salinity wastewater and reduce water consumption.

[0005] The present invention also provides a green fuel preparation apparatus that can reduce the discharge of high-salinity wastewater and reduce water resource consumption.

[0006] In a first aspect, the present invention provides a method for preparing green fuel, comprising the following steps:

[0007] 1) Gasification of biomass yields a gas mixture;

[0008] 2) The gas mixture is washed to obtain crude syngas and black water;

[0009] 3) The crude syngas is subjected to water-gas shift treatment and purification treatment in sequence to obtain purified syngas;

[0010] 4) The black water is treated with ash water to obtain saline wastewater and ash water;

[0011] 5) After pretreatment of the saline wastewater, it is then subjected to electrolytic treatment to obtain electrolytic wastewater and hydrogen gas;

[0012] 6) The purified synthesis gas is mixed with the hydrogen gas and then a synthesis reaction is carried out to obtain the green fuel.

[0013] In the preparation method described above, the electrical energy for the electrolytic treatment is derived from wind and / or solar power generation;

[0014] And / or, the biomass is obtained by grinding raw biomass into powder;

[0015] And / or, the gasification process employs fluidized bed gasification.

[0016] In the preparation method described above, the washing water used in the washing process comes from the water-gas conversion process.

[0017] In the preparation method described above, the pretreatment includes stripping treatment and ion removal treatment.

[0018] The preparation method described above further includes: returning the ash water for washing the gas mixture.

[0019] In the preparation method described above, the water used for the ash water treatment comes from the water-gas conversion process and / or supplemental demineralized water.

[0020] The preparation method described above further includes a process of post-treatment of the electrolytic wastewater.

[0021] In a second aspect, the present invention provides an apparatus for performing the preparation method described above, comprising a gasification unit, a washing unit, a conversion unit, a purification unit, an ash water treatment unit, a pretreatment unit, a water electrolysis unit, and a synthesis unit;

[0022] The gas outlet of the gasification unit is connected to the gas inlet of the washing unit; the gas outlet of the washing unit is connected to the gas inlet of the conversion unit; the liquid outlet of the washing unit is connected to the first liquid inlet of the ash water treatment unit; the gas outlet of the conversion unit is connected to the gas inlet of the purification unit; the gas outlet of the purification unit is connected to the first gas inlet of the synthesis unit; the first liquid outlet of the ash water treatment unit is connected to the liquid inlet of the pretreatment unit; the liquid outlet of the pretreatment unit is connected to the liquid inlet of the water electrolysis unit; and the hydrogen outlet of the water electrolysis unit is connected to the hydrogen inlet of the synthesis unit.

[0023] As described above, the pretreatment unit includes a stripping unit and an ion removal unit;

[0024] The first liquid outlet of the ash water treatment unit is connected to the liquid inlet of the stripping unit; the liquid outlet of the stripping unit is connected to the liquid inlet of the ion removal unit, and the liquid outlet of the ion removal unit is connected to the liquid inlet of the water electrolysis unit.

[0025] The apparatus described above further includes a biomass milling unit; the biomass outlet of the biomass milling unit is connected to the biomass inlet of the gasification unit.

[0026] The green fuel preparation method provided by this invention simplifies the process and reduces wastewater treatment steps by directly using pretreated saline wastewater for hydrogen production via water electrolysis. Furthermore, the concentration of saline wastewater through water electrolysis significantly reduces the overall wastewater volume and energy consumption for wastewater treatment. Replacing high-purity water with pretreated saline wastewater as the feedstock for hydrogen production via water electrolysis greatly reduces water resource consumption. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a green fuel preparation apparatus provided by the present invention;

[0029] Figure 2 A schematic diagram of another green fuel preparation apparatus provided by the present invention;

[0030] Figure 3 This is a schematic diagram of the green fuel preparation apparatus for Comparative Example 1.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1: Gasification unit; 2: Washing unit; 3: Conversion unit; 4: Purification unit; 5: Ash water treatment unit; 6: Pretreatment unit; 7: Water electrolysis unit; 8: Synthesis unit; 9: Biomass milling unit; 61: Stripping unit; 62: Ion removal unit. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] Against the backdrop of the global energy structure accelerating its transformation towards a low-carbon and sustainable direction, green fuel products, such as green methanol, renewable natural gas, and sustainable aviation fuel, have become a research and application hotspot in the energy field due to their significant advantages such as being clean and renewable. They are of great significance for alleviating the energy crisis and addressing climate change.

[0035] Biomass gasification technology, as a highly promising green energy conversion pathway, can efficiently convert solid biomass into combustible gases, primarily CO and H2, through high temperatures, partial oxidation, and a series of complex chemical reactions. This syngas not only has a high calorific value but is also widely available and renewable, providing a rich raw material base for the production of green fuel products. However, the biomass gasification process is not without its flaws. While producing syngas, it also generates a large amount of gasification wastewater. This wastewater is typically high-salinity wastewater with a complex and diverse composition, containing numerous harmful substances such as ammonia, formate, sulfates, chlorides, carbonates, and cyanide compounds. If this wastewater is discharged directly without proper treatment, it will inevitably cause serious pollution to the surrounding soil, water bodies, and other ecological environments, threatening ecological balance and human health.

[0036] Furthermore, the hydrogen-to-carbon ratio in the syngas produced by biomass gasification often fails to directly meet the stringent requirements of downstream green fuel product synthesis. To address this issue, precise adjustment of the syngas's hydrogen-to-carbon ratio is typically achieved through methods such as hydrogen conversion and supplementation with green hydrogen. Among these methods, the water electrolysis hydrogen production unit, a crucial step in obtaining green hydrogen, utilizes different water electrolysis technologies to electrolyze water into H2 and O2. However, this process consumes a significant amount of high-purity water, which increases the pressure on water resources and production costs. Therefore, reducing the discharge of high-salinity wastewater and minimizing water consumption have become pressing technical challenges that need to be addressed.

[0037] The inventors of this application have discovered through research that if high-salinity wastewater is pretreated and then electrolyzed, and the hydrogen obtained from the electrolysis is used to synthesize green fuels, the discharge of high-salinity wastewater and the consumption of water resources can be greatly reduced.

[0038] Based on this, in a first aspect, the present invention provides a method for preparing green fuel, comprising the following steps:

[0039] 1) Gasification of biomass yields a gas mixture;

[0040] 2) The gas mixture is washed to obtain crude syngas and black water;

[0041] 3) The crude syngas is subjected to water-gas shift treatment and purification treatment in sequence to obtain purified syngas;

[0042] 4) Black water is treated with grey water to obtain saline wastewater and grey water;

[0043] 5) After pretreatment of saline wastewater, electrolysis is performed to obtain electrolyzed wastewater and hydrogen.

[0044] 6) The purified syngas is mixed with hydrogen and then a synthesis reaction is carried out to obtain green fuel.

[0045] The green fuel preparation method provided by this invention involves pretreating saline wastewater, followed by electrolysis, and then using the hydrogen obtained from the electrolysis to synthesize green fuel. This method can significantly reduce the discharge of high-salinity wastewater and reduce water resource consumption.

[0046] Specifically, in step 1), biomass is first gasified to obtain a gas mixture. Biomass is a widely available and renewable resource, including agricultural waste, forestry residues, and municipal solid waste. By gasifying it to obtain crude syngas, these biomass resources, which might otherwise be considered waste, are effectively utilized and transformed into valuable energy products. This greatly improves the utilization rate of resources, helps reduce dependence on fossil fuels, alleviates the energy crisis, and achieves the goals of sustainable development and recycling.

[0047] In step 2), the gas mixture is washed to remove ash and slag, yielding crude syngas and black water.

[0048] In step 3), the crude syngas undergoes a water-gas conversion process, which converts water and some carbon monoxide in the crude syngas into hydrogen and carbon dioxide. Then, it is purified to remove sulfides from the crude syngas. The purified syngas obtained mainly contains hydrogen, carbon monoxide, and carbon dioxide.

[0049] In step 4), the black water undergoes greywater treatment. For example, the black water is evaporated in an evaporative hot water tower and / or flashed in a vacuum flash tank and / or filtered by a filtration system to obtain saline wastewater and greywater, as well as some ash residue. The ash residue is discharged. The saline wastewater mainly includes at least one of ammonia, formate, sulfate, chloride, carbonate, and cyanide compounds. Typically, the salt concentration in saline wastewater is high, and it can also be called high-salinity wastewater.

[0050] In step 5), the saline wastewater is pretreated to remove ammonia nitrogen and calcium and magnesium ions. The pretreated saline wastewater is then electrolyzed to generate hydrogen and oxygen, yielding electrolyzed wastewater. This electrolysis process concentrates the saline wastewater, reducing the amount of wastewater that can be treated subsequently and thus lowering the energy consumption for wastewater treatment.

[0051] Traditional hydrogen production via water electrolysis relies on high-purity water, leading to water waste. This invention utilizes pretreated saline wastewater as a feedstock for electrolysis, significantly reducing water consumption. Furthermore, directly using high-salinity wastewater can cause corrosion of electrolysis equipment, such as electrode corrosion or membrane fouling. Pretreatment of the saline wastewater reduces damage to the electrolysis equipment and ensures the stability of the electrolysis process.

[0052] In step 6), the hydrogen produced by electrolysis is mixed with purified syngas to carry out a synthesis reaction, producing green fuels such as methanol, methane, and sustainable aviation fuel SAF.

[0053] Therefore, this invention simplifies the treatment process and reduces wastewater treatment steps by directly using pretreated saline wastewater for hydrogen production via water electrolysis. Each treated wastewater contains 1000 Nm³ of hydrogen. 3 The crude syngas from CO and H2 can reduce wastewater treatment volume by 0.1~0.2t. Furthermore, by producing hydrogen through water electrolysis, the saline wastewater is concentrated, significantly reducing the overall wastewater volume and energy consumption of the entire process. Replacing high-purity water with pretreated saline wastewater as the feedstock for hydrogen production through water electrolysis reduces the energy consumption by 1000 Nm³ per unit volume. 3 H2 reduces the consumption of high-purity water by about 1 ton, greatly reducing water resource consumption.

[0054] In some embodiments of the present invention, the electrical energy generated by the electrolysis process is derived from wind and / or solar power generation.

[0055] The hydrogen production method using water electrolysis in this invention is a very clean method that produces no harmful pollutants, only hydrogen and oxygen, making it a relatively environmentally friendly approach. Furthermore, wind and / or solar energy, as the power source for water electrolysis, are inexhaustible and renewable energy sources that do not produce greenhouse gases or pollutants during use, helping to reduce dependence on traditional fossil fuels and carbon emissions. Combining wind and / or solar energy with water electrolysis enables comprehensive energy utilization and optimized allocation, improving energy efficiency.

[0056] In some embodiments, biomass is obtained by grinding raw biomass into powder.

[0057] Optionally, the powder processing may include processes such as impurity removal, heating and carbonization, drying and dehydration, cutting, baking, and grinding.

[0058] In some embodiments, the gasification process employs fluidized bed gasification, which can fully gasify biomass to obtain a gas mixture.

[0059] In some embodiments of the present invention, the washing water used in the washing process comes from the water-gas conversion process.

[0060] The process condensate generated during the water-gas conversion process is used to wash the crude syngas, enabling the recycling of water resources and reducing dependence on external water resources. This not only saves water but also meets the green concept of sustainable development.

[0061] In some embodiments of the present invention, the pretreatment includes stripping treatment and ion removal treatment.

[0062] This invention removes ammonia nitrogen from high-salinity wastewater through stripping treatment (such as steam stripping) and removes calcium and magnesium ions from high-salinity wastewater through ion removal treatment, thereby reducing the risk of corrosion of electrolysis equipment by wastewater.

[0063] Calcium and magnesium ions can be removed by methods such as lime-soda ash method, phosphate precipitation method, ion exchange method, and membrane separation method to prevent scaling in electrolysis equipment.

[0064] In some embodiments of the invention, the method further includes returning the ash water for washing the gas mixture.

[0065] This invention uses the ash water obtained from ash water treatment to wash gas mixtures, forming an internal water recycling system. This reduces the system's dependence on external water resources and can significantly improve water resource utilization efficiency.

[0066] In some embodiments of the present invention, the water used for ash water treatment comes from the water-gas conversion process and / or supplemental demineralized water.

[0067] This invention uses the process condensate and / or supplemental demineralized water from the water-gas conversion process as the water source for the ash water treatment system. Since the process condensate and / or supplemental demineralized water from the water-gas conversion process are both soft water, the risk of scaling of the electrolysis equipment during subsequent electrolysis can be avoided, ensuring the efficient operation of the electrolysis process and extending the service life of the electrodes.

[0068] In some embodiments of the present invention, the process of post-treatment of electrolytic wastewater is also included.

[0069] The wastewater remaining after electrolysis treatment undergoes post-treatment, such as using biochemical treatment to remove organic matter, followed by further concentration and processing through evaporation crystallization or membrane separation technology to ultimately form solid salt residue and reclaimed water. The reclaimed water can be returned to the system for reuse or used in other aspects of production and daily life, thus broadening the scope of its application.

[0070] Secondly, the present invention provides an apparatus for performing the above-described preparation method, such as... Figure 1As shown, the system includes a gasification unit 1, a washing unit 2, a conversion unit 3, a purification unit 4, a greywater treatment unit 5, a pretreatment unit 6, a water electrolysis unit 7, and a synthesis unit 8. The gas outlet of the gasification unit 1 is connected to the gas inlet of the washing unit 2; the gas outlet of the washing unit 2 is connected to the gas inlet of the conversion unit 3; the liquid outlet of the washing unit 2 is connected to the first liquid inlet of the greywater treatment unit 5; the gas outlet of the conversion unit 3 is connected to the gas inlet of the purification unit 4; the gas outlet of the purification unit 4 is connected to the first gas inlet of the synthesis unit 8; the first liquid outlet of the greywater treatment unit 5 is connected to the liquid inlet of the pretreatment unit 6; the liquid outlet of the pretreatment unit 6 is connected to the liquid inlet of the water electrolysis unit 7; and the hydrogen outlet of the water electrolysis unit 7 is connected to the hydrogen inlet of the synthesis unit 8.

[0071] In this invention, biomass is gasified in gasification unit 1 to obtain a gas mixture. The gas mixture is output from the gasification unit 1 gas outlet and enters the washing unit 2 through the washing unit 2 gas inlet for washing treatment to remove ash and slag from the gas mixture, resulting in crude syngas and black water. The crude syngas is output from the washing unit 2 gas outlet and enters the shift unit 3 through the shift unit 3 gas inlet for water-gas shift treatment, causing water and some carbon monoxide in the crude syngas to generate hydrogen and carbon dioxide. The resulting shifted gas is output from the shift unit 3 gas outlet and enters the purification unit 4 through the purification unit 4 gas inlet for purification treatment to remove sulfides from the crude syngas. The resulting purified syngas mainly includes hydrogen, carbon monoxide, and carbon dioxide. The purified syngas is output from the purification unit 4 gas outlet and enters the synthesis unit 8 through the first gas inlet of the synthesis unit 8.

[0072] After washing and removing ash from the crude syngas in washing unit 2, black water is obtained. This black water exits from the liquid outlet of washing unit 2 and enters ash water treatment unit 5 via the first liquid inlet for further treatment, resulting in saline wastewater, ash water, and some ash residue. The ash residue is then discharged. The saline wastewater mainly contains at least one of ammonia, formate, sulfate, chloride, carbonate, and cyanide compounds. Typically, the salt concentration in saline wastewater is high, and it can also be called high-salinity wastewater. The saline wastewater exits from the first liquid outlet of ash water treatment unit 5 and enters pretreatment unit 6 via the liquid inlet for pretreatment to remove ammonia nitrogen and calcium and magnesium ions. The pretreated saline wastewater exits from the liquid outlet of pretreatment unit 6 and enters electrolysis unit 7 via the liquid inlet for electrolysis, producing hydrogen and oxygen, and yielding electrolyzed wastewater. Hydrogen gas is output from the hydrogen outlet of water electrolysis unit 7 and enters synthesis unit 8, such as methanol synthesis reactor or Fischer-Tropsch synthesis reactor, through the hydrogen inlet of synthesis unit 8. It is mixed with purified synthesis gas to carry out synthesis reaction and generate green fuels, such as methanol, methane, and sustainable aviation fuel SAF.

[0073] The green fuel preparation apparatus of this invention can be used to perform the aforementioned green fuel preparation method. By pretreating saline wastewater and directly using it for water electrolysis to produce hydrogen, the process is simplified and wastewater treatment steps are reduced. Furthermore, by concentrating the saline wastewater through water electrolysis, the amount of wastewater generated in the entire process is significantly reduced, thus lowering the energy consumption for wastewater treatment. Replacing high-purity water with pretreated saline wastewater as the feedstock for water electrolysis to produce hydrogen significantly reduces water resource consumption.

[0074] In some embodiments of the present invention, such as Figure 2 As shown, the pretreatment unit 6 includes a stripping unit 61 and an ion removal unit 62; the first liquid outlet of the ash water treatment unit 5 is connected to the liquid inlet of the stripping unit 61; the liquid outlet of the stripping unit 61 is connected to the liquid inlet of the ion removal unit 62, and the liquid outlet of the ion removal unit 62 is connected to the liquid inlet of the water electrolysis unit 7.

[0075] Specifically, in this invention, the pretreatment unit 6 includes a stripping unit 61 and an ion removal unit 62. The saline wastewater is output from the first liquid outlet of the ash water treatment unit 5 and enters the stripping unit 61 through the liquid inlet to remove ammonia nitrogen. The stripped saline wastewater is then output from the liquid outlet of the stripping unit 61 and enters the ion removal unit 62 through the liquid inlet to remove calcium and magnesium ions. The ion-removed saline wastewater is then output from the liquid outlet of the ion removal unit 62 and enters the electrolysis unit 7 through the liquid inlet to obtain hydrogen and oxygen.

[0076] The stripping unit 61 in this invention can remove ammonia nitrogen from saline wastewater, and the ion removal unit 62 can remove calcium and magnesium ions from saline wastewater, thereby reducing the risk of corrosion of the electrolysis equipment by the wastewater.

[0077] In some embodiments of the present invention, the above-mentioned device further includes a biomass milling unit 9; the biomass outlet of the biomass milling unit 9 is connected to the biomass inlet of the gasification unit 1.

[0078] In this invention, the raw biomass is processed into biomass in the biomass milling unit 9 to obtain biomass. The biomass is output from the biomass outlet of the biomass milling unit 9 and then gasified in the gasification unit 1 through the biomass inlet to obtain a gas mixture.

[0079] This invention obtains biomass by processing raw biomass into powder in biomass milling unit 9, which can make full use of biomass, reduce dependence on fossil fuels, alleviate the energy crisis, and achieve the goals of sustainable development and recycling.

[0080] In this invention, the first liquid outlet of the conversion unit 3 is connected to the first liquid inlet of the washing unit 2; the second liquid outlet of the conversion unit 3 is connected to the second liquid inlet of the ash water treatment unit 5; and the second liquid outlet of the ash water treatment unit 5 is connected to the second liquid inlet of the washing unit 2. This allows the water used for washing to come from the water-gas conversion process, the water used for ash water treatment to come from the water-gas conversion process, and the ash water to be returned for washing the crude syngas. This enables the recycling of water resources, reduces the system's dependence on external water resources, and significantly improves water resource utilization efficiency.

[0081] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0082] Example 1

[0083] The apparatus in this embodiment is a green fuel preparation apparatus, such as... Figure 2 As shown, it includes a gasification unit 1 (gasifier); a washing unit 2 (washing tower); a conversion unit 3 (isothermal tube reactor); a purification unit 4 (desulfurization tower); an ash water treatment unit 5 (evaporation hot water tower); a stripping unit 61 (stripping tower); an ion removal unit 62 (precipitator); an electrolysis water unit 7 (electrolyte); a synthesis unit 8 (methanol synthesis reactor); and a biomass pulverizing unit 9 (pulverizer).

[0084] Specifically, the biomass outlet of biomass milling unit 9 is connected to the biomass inlet of gasification unit 1; the gas outlet of gasification unit 1 is connected to the gas inlet of washing unit 2; the gas outlet of washing unit 2 is connected to the gas inlet of conversion unit 3; the liquid outlet of washing unit 2 is connected to the liquid inlet of ash water treatment unit 5; the gas outlet of conversion unit 3 is connected to the gas inlet of purification unit 4; the gas outlet of purification unit 4 is connected to the first gas inlet of synthesis unit 8; the first liquid outlet of ash water treatment unit 5 is connected to the liquid inlet of stripping unit 61; the liquid outlet of stripping unit 61 is connected to the liquid inlet of ion removal unit 62, and the liquid outlet of ion removal unit 62 is connected to the liquid inlet of water electrolysis unit 7; the hydrogen outlet of water electrolysis unit 7 is connected to the hydrogen inlet of synthesis unit 8; the first liquid outlet of conversion unit 3 is connected to the first liquid inlet of washing unit 2; the second liquid outlet of conversion unit 3 is connected to the second liquid inlet of ash water treatment unit 5; and the second liquid outlet of ash water treatment unit 5 is connected to the second liquid inlet of washing unit 2.

[0085] Specifically, the raw biomass is milled in biomass milling unit 9 to obtain biomass. The biomass is then gasified in gasification unit 1 to obtain a gas mixture. The gas mixture is output from the gas outlet of gasification unit 1 and then washed in washing unit 2 through the gas inlet of washing unit 2 to remove ash and slag, resulting in crude syngas and black water. The crude syngas is output from the gas outlet of washing unit 2 and then enters shift unit 3 through the gas inlet of shift unit 3 for water-gas shift processing. The resulting shifted gas is output from the gas outlet of shift unit 3 and then enters purification unit 4 through the gas inlet of purification unit 4 for purification, resulting in purified syngas. The purified syngas is output from the gas outlet of purification unit 4 and then enters synthesis unit 8 through the first gas inlet of synthesis unit 8.

[0086] Black water exits from the liquid outlet of washing unit 2 and enters ash water treatment unit 5 through the first liquid inlet for ash water treatment, resulting in saline wastewater, ash water, and some ash residue. The saline wastewater exits from the first liquid outlet of ash water treatment unit 5 and enters stripping unit 61 through the liquid inlet for stripping treatment to remove ammonia nitrogen. The stripped saline wastewater exits from the liquid outlet of stripping unit 61 and enters ion removal unit 62 through the liquid inlet for calcium and magnesium ion removal. The ion-removed saline wastewater exits from the liquid outlet of ion removal unit 62 and enters electrolysis unit 7 through the liquid inlet for electrolysis treatment, resulting in hydrogen, oxygen, and electrolytic wastewater. The hydrogen exits from the hydrogen outlet of electrolysis unit 7 and enters synthesis unit 8 through the hydrogen inlet of synthesis unit 8, where it is combined with purified synthesis gas to produce methanol.

[0087] Comparative Example 1

[0088] The apparatus and method for preparing the green fuel in Comparative Example 1 are basically the same as those in Example 1, such as... Figure 3 As shown, the difference is that the stripping unit 61 and the ion removal unit 62 are not included, that is, the pretreatment unit 6 is not included. The saline wastewater is not stripped or ion removed, that is, the saline wastewater is not pretreated. Instead, the saline wastewater is directly post-treated by electrolysis using high-purity water.

[0089] Compared to Comparative Example 1, Example 1 contained 1000 Nm per treatment. 3 The crude syngas from CO and H2 can reduce the amount of saline wastewater treated by 0.12 t, for every 1000 Nm³ of CO and H2 produced. 3 H2 reduces the consumption of high-purity water by 1 t.

[0090] Therefore, compared with the comparative example, the green fuel preparation method provided by this invention simplifies the process and reduces wastewater treatment steps by directly using pretreated saline wastewater for hydrogen production via water electrolysis. Furthermore, by concentrating the saline wastewater through water electrolysis, the amount of wastewater generated in the entire process is significantly reduced, thus lowering the energy consumption for wastewater treatment. Replacing high-purity water with pretreated saline wastewater as the feedstock for hydrogen production via water electrolysis greatly reduces water resource consumption.

[0091] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for preparing a green fuel, characterized in that, Includes the following steps: 1) Gasification of biomass yields a gas mixture; 2) The gas mixture is washed to obtain crude syngas and black water; 3) The crude syngas is subjected to water-gas shift treatment and purification treatment in sequence to obtain purified syngas; 4) The black water is treated with ash water to obtain saline wastewater and ash water; 5) After pretreatment of the saline wastewater, it is then subjected to electrolytic treatment to obtain electrolytic wastewater and hydrogen gas; 6) The purified synthesis gas is mixed with the hydrogen gas and then a synthesis reaction is carried out to obtain the green fuel.

2. The preparation method according to claim 1, characterized in that, The electrical energy generated by the electrolysis process comes from wind and / or solar power generation. And / or, the biomass is obtained by grinding raw biomass into powder; And / or, the gasification process employs fluidized bed gasification.

3. The preparation method according to claim 1 or 2, characterized in that, The washing water used in the washing process comes from the water-gas conversion process.

4. The preparation method according to any one of claims 1-3, characterized in that, The pretreatment includes stripping and ion removal.

5. The preparation method according to any one of claims 1-4, characterized in that, Also includes: The greywater is then returned for washing the gas mixture.

6. The preparation method according to any one of claims 1-5, characterized in that, The water used in the ash water treatment comes from the water-gas conversion process and / or supplemental demineralized water.

7. The preparation method according to any one of claims 1-6, characterized in that, Also includes: The process of post-treatment of the electrolytic wastewater.

8. An apparatus for performing the preparation method according to any one of claims 1-7, characterized in that, It includes a gasification unit, a washing unit, a conversion unit, a purification unit, a greywater treatment unit, a pretreatment unit, a water electrolysis unit, and a synthesis unit; The gas outlet of the gasification unit is connected to the gas inlet of the washing unit; the gas outlet of the washing unit is connected to the gas inlet of the conversion unit; the liquid outlet of the washing unit is connected to the first liquid inlet of the ash water treatment unit; the gas outlet of the conversion unit is connected to the gas inlet of the purification unit; the gas outlet of the purification unit is connected to the first gas inlet of the synthesis unit; the first liquid outlet of the ash water treatment unit is connected to the liquid inlet of the pretreatment unit; the liquid outlet of the pretreatment unit is connected to the liquid inlet of the water electrolysis unit; and the hydrogen outlet of the water electrolysis unit is connected to the hydrogen inlet of the synthesis unit.

9. The apparatus according to claim 8, characterized in that, The pretreatment unit includes a stripping unit and an ion removal unit; The first liquid outlet of the ash water treatment unit is connected to the liquid inlet of the stripping unit; the liquid outlet of the stripping unit is connected to the liquid inlet of the ion removal unit, and the liquid outlet of the ion removal unit is connected to the liquid inlet of the water electrolysis unit.

10. The apparatus according to claim 8 or 9, characterized in that, It also includes a biomass milling unit; the biomass outlet of the biomass milling unit is connected to the biomass inlet of the gasification unit.

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