Method for preparing hydrogen by thermally-electrically coupling and decomposing coal water slurry

Abstract

The invention provides a method for preparing hydrogen by thermally-electrically coupling and decomposing coal water slurry, which comprises the following steps: adding a heteropolyacid compound into water to prepare a heteropolyacid solution with the concentration of 0.05-0.5 M; the method comprises the following steps: grinding and processing pulverized coal into crude coal water slurry with the coal content of 35-65 wt% and the d (0.5) of less than 150 [mu] m; carrying out cavitation treatment on the crude coal water slurry to prepare active superfine coal water slurry with d (0.5) of less than 15 microns; preparing slurry from the heteropoly acid solution and the active superfine coal water slurry; heating the slurry, reacting for 0.5-5 hours under the condition of constant temperature, and carrying out digestion reaction on the active superfine coal water slurry; the temperature range of the digestion reaction is 150-250 DEG C; after the reaction, filtering the mixture to obtain a superfine coal water slurry digestion solution; the superfine coal water slurry digestion solution is used as an electrolyte, and hydrogen is prepared through an electrolytic reaction in an electrolytic hydrogen production device.

Description

Technical Field

[0001] The invention relates to a method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry. The invention belongs to the technical field of coal chemical industry, specifically, to the technical field of clean utilization of coal and coal-assisted-electrolysis of water to produce hydrogen. Background Art

[0002] Coal provides more than 40% of the world's electricity demand, and this share exceeds 55% in China. Due to its low cost and abundant reserves, it is expected to remain the main source of electricity production in the next few decades. However, the efficiency of coal conversion into electricity is low (usually 35-45%), and the CO2 emission load is large. Although carbon capture and storage (CCS) technology has the potential to reduce CO2 emissions into the atmosphere, it is still difficult to deploy this technology on a large scale. Therefore, a combination of solutions is needed to reduce CO2 emissions from coal-fired power generation, among which electrolysis of water-coal slurry to produce hydrogen is one of the solutions.

[0003] Most of the existing schemes for producing hydrogen by electrolysis of water-coal slurry are based on the following reactions:

[0004] Anode: C+2H2O→CO2+4H + +4e - (1)

[0005] Cathode: 4H + +4e - →2H2 (2)

[0006] Overall reaction: C+H2O→H2+CO2 (E Θ =0.21V) (3)

[0007] Although the theoretical decomposition voltage of the above reaction under standard conditions (0.21V) is much lower than the theoretical decomposition voltage of H2O under standard conditions (1.23V), due to the complex composition of coal and the fact that the above reaction belongs to multiphase electrolysis, the overvoltage of the actual electrolysis process is high and the energy efficiency of hydrogen production is low. At the same time, the above reaction still cannot avoid CO2 emissions.

[0008] There are two main methods to overcome the above problems. One method is to develop high-performance catalysts to solve the problem of high anode overvoltage; the other is the coupled preparation method: using an anode reaction with a large thermodynamic trend of reducing the Gibbs free energy to replace the high-energy-consuming anode reaction, and improving the energy efficiency of hydrogen production through reaction coupling. Among them, coupled preparation can significantly reduce the power consumption of hydrogen production, and it is possible to achieve the synergistic preparation of high-value chemicals. my country is rich in coal resources. The electrolysis of water-coal slurry to produce hydrogen and the coupled preparation of organic matter can not only reduce the power consumption of hydrogen production, but also reduce CO2 emissions and achieve high-value conversion of coal. It is a new technology for clean coal utilization with application prospects.

[0009] In the coupled hydrogen production method, how to select an oxidant with appropriate oxidizing properties and selectivity to achieve the digestion of water-coal slurry into organic compounds rather than CO2, and how to improve the reaction efficiency of water-coal slurry into organic matter and hydrogen are still the key to the further development of electrolytic water-coal slurry hydrogen production technology. Theoretically, based on the reduction properties of coal, the coupled method can select an oxidant with appropriate oxidizing properties to digest coal into organic matter, and then perform electrolytic hydrogen production, which is expected to overcome the technical limitations of multiphase reactions and the lack of CO2 emissions. Summary of the invention

[0010] The main purpose of the present invention is to break the technical limitations of the existing electrolysis of coal water slurry to produce hydrogen, which is excessive oxidation to generate CO2 and low energy efficiency of electrolysis hydrogen production. The present invention provides a method for producing hydrogen by thermal-electric coupling decomposition of coal water slurry. Through the thermal digestion of active ultrafine coal water slurry by heteropolyacid compounds (HPA), small molecular organic compounds are obtained while achieving hydrogen H2 by electrolysis of coal water slurry, thus avoiding CO2 emissions. The thermal-electric coupling decomposition of coal water slurry to produce hydrogen has high energy efficiency for hydrogen production, and provides new methods and technologies for coal-to-hydrogen production and coal chemical industry.

[0011] The specific principle of the present invention is as follows: Tungsten / molybdenum heteropoly acid and its salt (HPA) have multiple electron donation and acceptance properties, and are called "electron sponges". The redox performance can be easily selectively regulated. Therefore, by selectively regulating the composition and structure of HPA, the selective oxidation and digestion of water-coal slurry by HPA can be achieved to avoid the production of CO2. At the same time, HPA is converted into heteropoly blue (HPB) after reacting with water-coal slurry. HPB and water-coal slurry digestion liquid are electrolyzed to produce hydrogen H2 at a voltage far lower than 1.23V (theoretical decomposition voltage of H2O), and HPB is restored to HPA (see the following formula (4)). The mediating compound HPA of the thermal-electric coupling reaction is recycled.

[0012]

[0013] The entire technical chain of the present invention realizes the production of hydrogen by decomposing water-coal slurry and the clean utilization of coal through thermal-electric coupling. The HPA used is non-toxic and environmentally friendly. The method can not only realize low-power hydrogen production and reduce CO2 emissions, but also convert multiphase reactions into homogeneous reactions, reducing the loss of electrolytic components. The hydrogen obtained in the present invention is pure hydrogen, does not contain other gases, does not require additional purification treatment, and has promotion and application value.

[0014] In order to achieve the above object, the present invention provides a method for producing hydrogen by thermal-electric coupled decomposition of coal-water slurry, comprising the following steps:

[0015] Step S1, preparation of a heteropolyacid solution: adding a heteropolyacid compound into water to prepare a heteropolyacid solution with a concentration of 0.05-0.5M;

[0016] Step S2, preparation of water-coal slurry: grinding coal powder into a coarse water-coal slurry with a concentration of 35wt% to 65wt% coal and d(0.5) less than 150μm; preparing the coarse water-coal slurry into an active ultrafine water-coal slurry with d(0.5) less than 15μm by cavitation treatment;

[0017] Step S3, preparation of ultrafine coal water slurry digestion liquid: prepare slurry with the heteropoly acid solution of step S1 and the active ultrafine coal water slurry of step S2; heat the slurry, react for 0.5 to 5 hours under constant temperature conditions, and digest the active ultrafine coal water slurry; the temperature range of the digestion reaction is 120 to 250° C., preferably 150 to 250° C.; after the reaction, filter the mixture to obtain the ultrafine coal water slurry digestion liquid;

[0018] Step S4, electrolyzing water-coal slurry digestion liquid to produce hydrogen: using the ultrafine water-coal slurry digestion liquid as an electrolyte, hydrogen is produced by electrolysis reaction in an electrolysis hydrogen production device.

[0019] In this article, "d(0.5)" is a parameter that expresses the particle size distribution, also known as the median particle size, which indicates the particle size corresponding to when the cumulative particle size distribution percentage of the sample reaches 50%. In a physical sense, this means that particles with a particle size greater than d(0.5) account for 50%, and particles with a particle size less than d(0.5) also account for 50%. There are many ways to measure d(0.5), such as laser diffraction. "d(0.1)" and "d(0.9)" that appear below correspond to the particle sizes of 10% and 90%, respectively.

[0020] More specifically, in step S2, the coal powder can be ground into a crude water-coal slurry with a concentration of 35 wt% to 65 wt% coal and d(0.5) less than 150 μm by a known process. For example, the crude water-coal slurry can be prepared by a dry pulverizing-wet slurry mixing method.

[0021] Additives can be optionally added in the preparation of crude water-coal slurry. Additives include dispersants and / or stabilizers. Dispersants can reduce the interfacial tension between coal powder and water, enhance the hydrophilicity of coal powder, and make coal powder particles evenly dispersed in water, thereby improving the fluidity and stability of the slurry; stabilizers can enhance the interaction between coal powder particles and improve possible precipitation and aggregation. Dispersants can be selected from one or more of lignin sulfonates, naphthalene sulfonates and humates; stabilizers can be selected from one or more of carboxymethyl fiber, polyacrylamide, xylan, plant gum and inorganic minerals. The amount of additives added is 0.1% to 2% of the weight of coal powder.

[0022] The active ultrafine coal water slurry can be prepared by known process methods, for example, one or more of the methods that can produce ·OH, such as hydrodynamic cavitation, ultrasonic cavitation, arc micro-explosion, microwave radiation, etc.

[0023] In step S3, the heteropoly acid solution and the ultrafine coal water slurry are prepared into a slurry in a certain ratio, and the residue is removed by filtration after the reaction to obtain an ultrafine coal water slurry digestion solution. The mass ratio of the heteropoly acid to the coal can be 0.1-1.

[0024] Furthermore, the heteropolyacid is selected from one or more of a keggin structure or Dawson structure tungsten / molybdenum-based heteropolyacid compound, and a keggin structure or Dawson structure tungsten / molybdenum-based heteropolyacid embedded with a highly oxidizable transition metal atom, preferably a keggin structure or Dawson structure tungsten / molybdenum-based heteropolyacid compound embedded with a highly oxidizable transition metal atom.

[0025] Heteropolyacids decompose the coal-water slurry into small molecular organic compounds.

[0026] Further, the cation of the heteropolyacid is selected from H + 、Na + , K + NH4 + One or more of .

[0027] Furthermore, in step S3, the concentration of coal in the mixture is 30 g / L to 180 g / L.

[0028] Furthermore, in the electrolytic hydrogen production device, the electrolyzer is a PEM electrolyzer or a sealed H-type electrolyzer and is equipped with a cell separator membrane.

[0029] Preferably, the battery separator membrane is a proton exchange membrane or a semipermeable membrane.

[0030] Furthermore, the cathode in the electrolytic hydrogen production device is an electrode that can undergo a hydrogen evolution reaction. Specifically, the electrolytic hydrogen production device is equipped with a Pt electrode, a Pt / C electrode, or an electrode loaded with a hydrogen evolution (HER) catalyst as the cathode, and the cathode electrolyte is selected from one or more of a phosphoric acid solution, a sulfuric acid solution, and a hydrochloric acid solution. The electrode reaction produces H2.

[0031] Furthermore, the electrolytic hydrogen production device is equipped with a hydrophilic carbon felt as an anode and an ultrafine coal water slurry digestion solution as an electrolyte. The electrode reaction converts HPB into HPA.

[0032] Furthermore, the electrolysis reaction is carried out in an oxygen-free environment, the electrolysis voltage is less than 1.23V, and the electrolysis temperature is 25-120°C.

[0033] Furthermore, the method further comprises step S5, circulation of the HPA-containing electrolyte: transferring the heteropolyacid-containing electrolyte in the electrolytic hydrogen production device to the system containing the active ultrafine water-coal slurry through a circulation pump; filtering after the digestion reaction, and then transferring to the electrolytic hydrogen production device through a circulation pump. Specifically, the digestion reaction is carried out under constant temperature conditions for 0.5 to 5 hours, and the reaction temperature range is 150 to 250°C.

[0034] Furthermore, the cavitation treatment in step S2 is a hydrodynamic cavitation or an ultrasonic cavitation method.

[0035] Furthermore, the particle size of the coal powder in step S2 is less than 200 meshes.

[0036] Specifically, in step S1, the raw coal may be crushed, ground, and sieved to obtain coal powder with a particle size of less than 200 meshes. The raw coal may be one or more of bituminous coal, sub-bituminous coal, lignite, and the like.

[0037] Furthermore, the heating method in step S3 is a hydrothermal reaction, or water bath heating, oil bath heating, tracing heating or platform contact heating in an oxygen-free environment.

[0038] Specifically, in step S3, the slurry is transferred into a heating container or a hydrothermal reactor, and the reaction time is 0.5 to 5 hours under constant temperature conditions, the water-coal slurry is digested into organic matter, and the heteropoly acid is converted into heteropoly blue. The organic matter includes humic acid, formic acid, oxalic acid, aromatic acid, olefinic acid and other organic matter.

[0039] Furthermore, the electrolytic hydrogen production device in step S4 is a proton exchange membrane or semipermeable membrane closed electrolytic cell in an oxygen-free atmosphere.

[0040] In summary, compared with the prior art, the advantages of the present invention are at least reflected in the following aspects:

[0041] 1) The electrolysis process of the present invention does not generate CO2, and the remaining organic solution after electrolysis can be used as a chemical material or fuel, providing a new method for the clean utilization of coal.

[0042] 2) The present invention adopts cavitation technology to prepare ultrafine activated water-coal slurry to improve the reaction conversion rate of coal-to-hydrogen.

[0043] 3) The oxidant heteropoly acid (HPA) used in the present invention is non-toxic and recyclable, and the conditions required for the entire technology are mild, harmless and environmentally friendly.

[0044] 4) The present invention can efficiently electrolyze water-coal slurry digestion liquid to produce hydrogen at a voltage significantly lower than the theoretical decomposition voltage of water (1.23V).

[0045] 5) The decomposition voltage of the water-coal slurry digestion solution of the present invention can be as low as about 0.58V, and the digestion solution can extract hydrogen under the low bias voltage generated by a small solar PV panel, which has the characteristics of low carbon, low cost, mild conditions, and green environmental protection.

[0046] 6) The present invention provides a new method for the clean utilization of coal coupled with water electrolysis to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0048] Figure 1 The technical flow chart of the present invention is shown.

[0049] Figure 2 The infrared spectra of the vacancy-directed synthesis of tungsten-based heteropoly acids of Examples 1-6 of the present invention are shown.

[0050] Figure 3 The particle size distribution diagram of the ultrafine water-coal slurry of Example 1 of the present invention is shown.

[0051] Figure 4 The LSV curve of the ultrafine water-coal slurry digestion liquid of Example 1 of the present invention is shown.

[0052] Figure 5 The VT curve of hydrogen production by electrolysis of ultrafine water-coal slurry digestion liquid of Example 1 of the present invention is shown.

[0053] Figure 6 The VT curve diagram of hydrogen production by electrolysis of crude water-coal slurry digestate according to Example 1 of the present invention is shown.

[0054] Figure 7 The VT curve of hydrogen production by electrolysis of ultrafine water-coal slurry digestion liquid of Example 2 of the present invention is shown.

[0055] right Figure 1 The reference numerals in the figures are described as follows:

[0056] 1. Electrolyzer; 2. Cathode; 3. Proton exchange membrane; 4. Anode; 5. Pump; 6. Pump. DETAILED DESCRIPTION

[0057] The present application is further described in detail below in conjunction with examples. These examples are intended to better further understand the present invention, are not limited to the best mode of implementation, and do not limit the content and protection scope of the present invention. Any product that is the same or similar to the present invention and is obtained by anyone under the inspiration of the present invention or by combining the present invention with the features of other prior arts falls within the protection scope of the present invention.

[0058] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The experimental methods used in the following embodiments are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments, unless otherwise specified, can all be obtained from commercial sources.

[0059] The core of the technical solution of the present invention is composed of a water-coal slurry activation system, a water-coal slurry oxidation digestion reaction system, and a water-coal slurry digestion liquid electrolysis system, wherein the water-coal slurry oxidation digestion reaction system and the water-coal slurry digestion liquid electrolysis system can be connected through a circulation pump. A specific embodiment of the circulation preparation of the present invention can be referred to the attached Figure 1 , Figure 1 The technical process of the present invention is shown. The electrolytic hydrogen production device includes an electrolytic cell 1, which is equipped with a proton exchange membrane 3. The cathode 2 reacts to produce H2, and the anode 4 converts HPB into HPA through an electrolytic reaction. The HPA-containing electrolyte is transferred to a system containing active ultrafine water-coal slurry through a pump 5, a digestion reaction occurs under heating conditions, and then the electrolyte is transferred to the electrolytic hydrogen production device through a pump 6. The active ultrafine water-coal slurry is obtained by cavitation activation of the water-coal slurry. Figure 2 In the figure, the infrared spectra of the vacancy-directed synthesis of tungsten-based heteropoly acids of Examples 1-6 of the present invention are shown respectively.

[0060] Example 1

[0061] This embodiment provides a method for producing hydrogen by decomposing coal-water slurry with thermal-electric coupling, which is specifically implemented as follows:

[0062] 1. Preparation of heteropolyacid compounds (HPA):

[0063] This example adopts the strategy of vacancy-oriented synthesis to synthesize heteropolyacid catalyst. First, 350g of sodium molybdate and 25g of sodium silicate are used to synthesize vacancy-type molybdenum-based heteropolyacid under acidic conditions, and then sodium vanadate is added to embed vanadium atoms into the vacancy heteropolyacid structure to form vanadium-doped molybdenum-based heteropolyacid, and then the heteropolyacid compound is obtained by ether extraction.

[0064] 2. Preparation of Junneng 5500 Ultrafine Coal Water Slurry

[0065] According to the proportion, 360g of Junneng 5500 coal powder, 226.2g of water and 2g of lignin were weighed. The lignin was dissolved in water and then fully mixed with the coal powder. The slurry was mechanically ball-milled to d (0.5) of 56 μm to prepare a crude water-coal slurry.

[0066] The crude water-coal slurry was cavitated by a hydrodynamic cavitator with a shearing machine speed of 16000-18000 rpm to prepare an active ultrafine water-coal slurry with a d (0.5) of 3.573 μm. Figure 3The particle size distribution diagram of the ultrafine water-coal slurry of this embodiment is shown, where d(0.1)=0.459 μm, d(0.5)=3.573 μm, and d(0.9)=54.766 μm.

[0067] 3. Oxidative digestion of superfine water-coal slurry of 5500 coal

[0068] Take an ultrafine coal-water slurry containing 6.66g of coal, add 60ml of a heteropolyacid compound with a concentration of 0.1M. After the two types of substances are mixed and homogenized, transfer them into a 200℃ reactor for hydrothermal reaction for 5h to digest the coal in the coal-water slurry as much as possible. Filter the reaction product to remove the residue and obtain the digestion solution of the ultrafine coal-water slurry.

[0069] 4. Electrolysis of water-coal slurry digestion liquid to produce hydrogen H2

[0070] The water-coal slurry digestion liquid was transferred to the closed anode tank of the H-type electrolyzer by using a flow pump to isolate the air, and used as the anode liquid for hydrogen production reaction. Carbon felt was used as the working electrode, commercial Pt / C was used as the counter electrode, and phosphoric acid was used as the cathode liquid. The water-coal slurry digestion liquid could be electrolyzed to stably produce hydrogen H2 at an applied voltage of 0.58V.

[0071] 5. Circulation of HPA-containing electrolyte

[0072] After the hydrogen production reaction is completed, the molybdenum-based heteropoly blue is converted into molybdenum-based heteropoly acid. After the electrolysis residual organic matter is separated, the heteropoly acid is pumped back to the thermal digestion reaction system for the next round of thermal digestion of water-coal slurry-electrolysis of water-coal slurry digestion liquid coupled cycle reaction.

[0073] Figure 4 The LSV curve of the ultrafine water-coal slurry digestion liquid of this embodiment is shown. Figure 5 The VT curve of hydrogen production by electrolysis of ultrafine water-coal slurry digestion liquid of this embodiment is shown. Figure 6 The VT curve of hydrogen production by electrolysis of crude water-coal slurry digestion solution of this embodiment is shown. Under the same reaction conditions, it can be seen that the ultrafine water-coal slurry digestion solution of this embodiment can release more hydrogen than the crude water-coal slurry digestion solution.

[0074] Example 2

[0075] This embodiment provides a method for producing hydrogen by decomposing coal-water slurry with thermal-electric coupling, which is specifically implemented as follows:

[0076] 1. Preparation of heteropolyacid compounds (HPA):

[0077] This example adopts the strategy of vacancy-oriented synthesis to synthesize heteropolyacid catalyst. First, 360g of sodium tungstate and 20g of sodium silicate are used to synthesize vacancy-type tungsten-based heteropolyacid under acidic conditions, and then sodium vanadate is added to embed vanadium atoms into the vacancy heteropolyacid structure to form vanadium-doped tungsten-based heteropolyacid, and then the heteropolyacid compound is obtained by ether extraction.

[0078] 2. Preparation of Shenhua coal ultrafine water-coal slurry

[0079] According to the ratio, 360g Shendong coal powder (Baode coal from Shanxi), 226.2g water and 2g lignin were weighed. Lignin was dissolved in water and then fully mixed with coal powder. The slurry was mechanically ball-milled to d (0.5) of 45 μm to prepare a crude water-coal slurry.

[0080] The crude water-coal slurry was cavitated by a hydrodynamic cavitator with a shearing machine speed of 16000-18000 rpm to prepare an active ultrafine water-coal slurry with a d (0.5) of 3.436 μm.

[0081] 3. Oxidative digestion of activated ultrafine water-coal slurry of Shendong coal

[0082] Take ultrafine coal-water slurry containing 6.66g of coal, add 60ml of heteropolyacid compound with a concentration of 0.1M. After the two types of substances are mixed and homogenized, transfer them into a reactor at 200℃ for hydrothermal reaction for 5h to digest the coal in the coal-water slurry as much as possible. Filter the reaction product to remove the residue and obtain the digestion solution of ultrafine coal-water slurry.

[0083] 4. Electrolysis of water-coal slurry digestion liquid to produce hydrogen H2

[0084] The water-coal slurry digestion liquid was transferred to the closed anode tank of the H-type electrolyzer by a flow pump to isolate the air, and used as the anode liquid for hydrogen production reaction. Carbon felt was used as the working electrode, homemade Pt / WC / HS was used as the counter electrode, and phosphoric acid was used as the cathode liquid. Under the bias voltage of ~0.6V generated by a small PV solar panel, the water-coal slurry digestion liquid could be electrolyzed to stably produce hydrogen H2.

[0085] 5. Circulation of HPA-containing electrolyte

[0086] After the hydrogen production reaction is completed, the tungsten-based heteropoly blue is converted into tungsten-based heteropoly acid. After the electrolysis residual organic matter is separated, the heteropoly acid is pumped back to the thermal digestion reaction system for the next round of thermal digestion of water-coal slurry-electrolysis of water-coal slurry digestion liquid coupled cycle reaction.

[0087] Figure 7 The VT curve of hydrogen production by electrolysis of ultrafine water-coal slurry digestion liquid of this embodiment is shown.

[0088] Example 3

[0089] This embodiment provides a method for producing hydrogen by decomposing coal-water slurry with thermal-electric coupling, which is specifically implemented as follows:

[0090] 1. Preparation of heteropolyacid compounds (HPA):

[0091] This example adopts the strategy of vacancy-oriented synthesis to synthesize heteropolyacid catalyst. First, 360g of sodium tungstate and 20g of sodium silicate are used to synthesize vacancy-type tungsten-based heteropolyacid under acidic conditions, and then sodium molybdate is added to embed molybdenum atoms into the vacancy heteropolyacid structure to form molybdenum-doped tungsten-based heteropolyacid, and then the heteropolyacid compound is obtained by ether extraction.

[0092] 2. Preparation of Junneng 4000 Ultrafine Coal Water Slurry

[0093] According to the ratio, 180g of 4000 coal powder, 175g of water and 1g of lignin were weighed. The lignin was dissolved in water and then fully mixed with the coal powder. The slurry was mechanically ball-milled to d (0.5) of 52 μm to prepare a crude water-coal slurry.

[0094] The crude water-coal slurry was cavitated by a hydrodynamic cavitator with a shearing machine speed of 18000-22000 rpm to prepare an active ultrafine water-coal slurry with a d(0.5) of 3.760 μm.

[0095] 3. Oxidative digestion of superfine water-coal slurry of 4000 coal

[0096] Take ultrafine coal water slurry with a coal content of 2.00g, add 20ml of heteropolyacid compound with a concentration of 0.1M. After the two types of substances are mixed and homogenized, transfer them to a reactor at 180℃ for hydrothermal reaction for 5h to digest the coal in the coal water slurry as much as possible. Filter the reaction product to remove the residue and obtain the digestion solution of ultrafine coal water slurry.

[0097] 4. Electrolysis of water-coal slurry digestion liquid to produce hydrogen H2

[0098] The digestion liquid of the water-coal slurry was transferred to the closed anode tank of the H-type electrolyzer by a flow pump to isolate the air and used as the anode liquid for hydrogen production reaction. Carbon felt was used as the working electrode, commercial Pt / C was used as the counter electrode, and sulfuric acid was used as the cathode liquid. The water-coal slurry digestion liquid could be electrolyzed to stably produce hydrogen at an applied voltage of 0.52V.

[0099] 5. Circulation of HPA-containing electrolyte

[0100] After the hydrogen production reaction is completed, the tungsten-based heteropoly blue is converted into heteropoly acid. After the electrolysis residual organic matter is separated, the heteropoly acid is pumped back to the thermal digestion reaction system for the next round of thermal digestion of water-coal slurry-electrolysis of water-coal slurry digestion liquid coupling cycle reaction.

[0101] Example 4

[0102] This embodiment provides a method for producing hydrogen by decomposing coal-water slurry with thermal-electric coupling, which is specifically implemented as follows:

[0103] 1. Preparation of heteropolyacid compounds (HPA):

[0104] This example adopts the strategy of vacancy-oriented synthesis to synthesize heteropolyacid catalyst. First, 350g of sodium molybdate and 25g of sodium silicate are used to synthesize vacancy-type molybdenum-based heteropolyacid under acidic conditions, and then sodium tungstate is added to embed tungsten atoms into the vacancy heteropolyacid structure to form tungsten-doped molybdenum-based heteropolyacid, and then ether extraction is used to obtain heteropolyacid compound.

[0105] 2. Preparation of Ultrafine Coal-Water Slurry of Junneng 5500 Coal

[0106] According to the ratio, 360g of 5500 coal powder, 226.2g of water and 2g of lignin were weighed. The lignin was dissolved in water and then fully mixed with the coal powder. The slurry was mechanically ball-milled to d (0.5) of 52 μm to prepare a crude water-coal slurry.

[0107] The crude water-coal slurry was cavitated by a hydrodynamic cavitator with a shearing machine speed of 14000-16000 rpm to prepare an active ultrafine water-coal slurry with a d(0.5) of 9.252 μm.

[0108] 3. Oxidative digestion of 5500 active ultrafine coal water slurry

[0109] Take ultrafine coal water slurry with a coal content of 3.33g, add 30ml of heteropolyacid compound with a concentration of 0.1M. After the two types of substances are mixed and homogenized, transfer them into a 200℃ reactor for hydrothermal reaction for 5h to digest the coal in the coal water slurry as much as possible. Filter the reaction product to remove the residue and obtain the digestion solution of ultrafine coal water slurry.

[0110] 4. Electrolysis of water-coal slurry digestion liquid to produce hydrogen H2

[0111] The water-coal slurry digestion liquid is transferred to the closed anode tank of the H-type electrolyzer by a flow pump to isolate the air, and used as the anode liquid for hydrogen production reaction. Carbon felt is used as the working electrode, Pt electrode is used as the counter electrode, and phosphoric acid is used as the cathode liquid. Under the bias voltage of ~0.6V generated by a small PV solar panel, the water-coal slurry digestion liquid can be electrolyzed to stably produce hydrogen H2.

[0112] 5. Circulation of HPA-containing electrolyte

[0113] After the hydrogen production reaction is completed, the molybdenum-based heteropoly blue is converted into molybdenum-based heteropoly acid. After the electrolysis residual organic matter is separated, the heteropoly acid is pumped back to the thermal digestion reaction system for the next round of thermal digestion of water-coal slurry-electrolysis of water-coal slurry digestion liquid coupled cycle reaction.

[0114] Example 5

[0115] This embodiment provides a method for producing hydrogen by decomposing coal-water slurry with thermal-electric coupling, which is specifically implemented as follows:

[0116] 1. Preparation of heteropolyacid compounds (HPA):

[0117] This example adopts the strategy of vacancy-oriented synthesis to synthesize heteropolyacid catalyst. First, 240g sodium tungstate and 6mL phosphoric acid are used to generate vacancy tungsten-based heteropolyacid in an acidic environment, and then sodium vanadate is added to embed vanadium atoms into the vacancy heteropolyacid structure to prepare vanadium-doped tungsten-based heteropolyacid, and then the heteropolyacid is obtained by ether extraction.

[0118] 2. Preparation of ultrafine lignite water-coal slurry

[0119] According to the ratio, 180g Shuangyashan lignite powder, 150g water and 1g lignin were weighed. The lignin was dissolved in water and then fully mixed with the coal powder. The slurry was mechanically ball-milled to d (0.5) of 46 μm to prepare a crude water-coal slurry.

[0120] The crude water-coal slurry was cavitated by a hydrodynamic cavitator with a shearing machine speed of 16000-18000 rpm to prepare an active ultrafine water-coal slurry with a d (0.5) of 5.379 μm.

[0121] 3. Oxidative digestion of superfine water-coal slurry of 5500 coal

[0122] Take ultrafine coal water slurry with a coal content of 3.00g, add 30ml of heteropolyacid compound with a concentration of 0.1M. After the two types of substances are mixed and homogenized, transfer them to a reactor at 180℃ for hydrothermal reaction for 5h to digest the coal in the coal water slurry as much as possible. Filter the reaction product to remove the residue and obtain the digestion solution of ultrafine coal water slurry.

[0123] 4. Electrolysis of water-coal slurry digestion liquid to produce hydrogen H2

[0124] The water-coal slurry digestion liquid was transferred to the closed anode tank of the H-type electrolyzer by using a flow pump to isolate the air, and used as the anode liquid for hydrogen production reaction. Carbon felt was used as the working electrode, commercial Pt / C was used as the counter electrode, and hydrochloric acid was used as the cathode liquid. The water-coal slurry digestion liquid could be electrolyzed to stably produce hydrogen H2 at an applied voltage of 0.6V.

[0125] 5. Circulation of HPA-containing electrolyte

[0126] After the hydrogen production reaction is completed, the molybdenum-based heteropoly blue is converted into molybdenum-based heteropoly acid. After the electrolysis residual organic matter is separated, the heteropoly acid is pumped back to the thermal digestion reaction system for the next round of thermal digestion of water-coal slurry-electrolysis of water-coal slurry digestion liquid coupled cycle reaction.

[0127] Example 6

[0128] This embodiment provides a method for producing hydrogen by decomposing coal-water slurry with thermal-electric coupling, which is specifically implemented as follows:

[0129] 1. Preparation of heteropolyacid compounds (HPA):

[0130] This example adopts the strategy of vacancy-oriented synthesis to synthesize heteropolyacid catalyst. First, 350g of sodium molybdate and 25g of sodium silicate are used to synthesize vacancy-type molybdenum-based heteropolyacid under acidic conditions, and then sodium vanadate is added to embed vanadium atoms into the vacancy heteropolyacid structure to form vanadium-doped molybdenum-based heteropolyacid, and then the heteropolyacid compound is obtained by ether extraction.

[0131] 2. Preparation of Xinjiang coal ultrafine water-coal slurry

[0132] According to the ratio, 180g Xinjiang coal powder, 175g water and 1g lignin were weighed. Lignin was dissolved in water and then fully mixed with coal powder. The slurry was mechanically ball-milled to d (0.5) of 102 μm to prepare a crude water-coal slurry.

[0133] The crude water-coal slurry was cavitated by a hydrodynamic cavitator with a shearing machine speed of 16000-18000 rpm to prepare an active ultrafine water-coal slurry with a d (0.5) of 3.015 μm.

[0134] 3. Oxidative digestion of Xinjiang coal activated ultrafine water-coal slurry

[0135] Take ultrafine coal-water slurry containing 6.66g of coal, add 60ml of heteropolyacid compound with a concentration of 0.1M. After the two types of substances are mixed and homogenized, transfer them into a reactor at 200℃ for hydrothermal reaction for 5h to digest the coal in the coal-water slurry as much as possible. Filter the reaction product to remove the residue and obtain the digestion solution of ultrafine coal-water slurry.

[0136] 4. Electrolysis of water-coal slurry digestion liquid to produce hydrogen H2

[0137] The water-coal slurry digestion solution was transferred to the closed anode tank of the H-type electrolyzer by using a flow pump to isolate the air, and used as the anode liquid for hydrogen production reaction. Carbon felt was used as the working electrode, the homemade Pt / WC / HS was used as the counter electrode, and phosphoric acid was used as the cathode liquid. Under an external voltage of ~0.6V, the water-coal slurry digestion solution could be electrolyzed to stably produce hydrogen H2.

[0138] 5. Circulation of HPA-containing electrolyte

[0139] After the hydrogen production reaction is completed, the molybdenum-based heteropoly blue is converted into molybdenum-based heteropoly acid. After the electrolysis residual organic matter is separated, the heteropoly acid is pumped back to the thermal digestion reaction system for the next round of thermal digestion of water-coal slurry-electrolysis of water-coal slurry digestion liquid coupled cycle reaction.

[0140] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing hydrogen by thermal-electric coupled decomposition of coal-water slurry, characterized in that: The method comprises the following steps: Step S1, preparation of a heteropolyacid solution: adding a heteropolyacid compound into water to prepare a heteropolyacid solution with a concentration of 0.05-0.5M; Step S2, preparation of water-coal slurry: grinding coal powder into a coarse water-coal slurry with a concentration of 35wt% to 65wt% coal and d(0.5) less than 150μm; preparing the coarse water-coal slurry into an active ultrafine water-coal slurry with d(0.5) less than 15μm by cavitation treatment; Step S3, preparation of ultrafine coal water slurry digestion liquid: prepare slurry with the heteropoly acid solution of step S1 and the active ultrafine coal water slurry of step S2; heat the slurry, react for 0.5 to 5 hours under constant temperature conditions, and digest the active ultrafine coal water slurry; the temperature range of the digestion reaction is 150 to 250° C.; after the reaction, filter the mixture to obtain ultrafine coal water slurry digestion liquid; Step S4, electrolyzing water-coal slurry digestion liquid to produce hydrogen: using the ultrafine water-coal slurry digestion liquid as an electrolyte, preparing hydrogen through an electrolytic reaction in an electrolytic hydrogen production device.

2. The method for producing hydrogen by thermal-electric coupled decomposition of coal-water slurry according to claim 1, characterized in that: The heteropoly acid is selected from one or more of a tungsten / molybdenum-based heteropoly acid compound with a keggin structure or a Dawson structure, and a tungsten / molybdenum-based heteropoly acid with a keggin structure or a Dawson structure embedded with a highly oxidizable transition metal atom. Preferably, the cation of the heteropoly acid is selected from H + 、Na + , K + NH4 + One or more of .

3. The method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry according to claim 1 or 2, characterized in that: The concentration of coal in the mixture in step S3 is 30 g / L to 180 g / L. Preferably, the heating method in step S3 is hydrothermal reaction, or water bath heating, oil bath heating, heat tracing heating or platform contact heating in an oxygen-free environment.

4. The method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry according to claim 1 or 2, characterized in that: In the electrolytic hydrogen production device, the electrolytic cell is a PEM electrolytic cell or a sealed H-type electrolytic cell and is equipped with a battery separator membrane. Preferably, the electrolytic hydrogen production device is a proton exchange membrane or semipermeable membrane sealed electrolytic cell in an oxygen-free atmosphere.

5. The method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry according to claim 1 or 2, characterized in that: The electrolytic hydrogen production device is equipped with a Pt electrode, a Pt / C electrode or an electrode loaded with a hydrogen production catalyst as a cathode, and the cathode electrolyte is selected from one or more of a phosphoric acid solution, a sulfuric acid solution and a hydrochloric acid solution.

6. The method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry according to claim 1 or 2, characterized in that: The electrolytic hydrogen production device is equipped with a hydrophilic carbon felt as an anode, and the ultrafine water-coal slurry digestion solution is an electrolyte.

7. The method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry according to claim 1 or 2, characterized in that: The electrolysis reaction is carried out in an oxygen-free environment, the electrolysis voltage is less than 1.23V, and the electrolysis temperature is 25-120°C.

8. The method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry according to claim 1 or 2, characterized in that: The method further comprises step S5, circulation of the HPA-containing electrolyte: transferring the heteropolyacid-containing electrolyte in the electrolytic hydrogen production device to a system containing active ultrafine water-coal slurry via a circulation pump; filtering after digestion reaction, and then transferring to the electrolytic hydrogen production device via a circulation pump.

9. The method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry according to claim 1 or 2, characterized in that: The cavitation treatment in step S2 is a hydrodynamic cavitation or ultrasonic cavitation method. Preferably, the particle size of the coal powder in step S2 is less than 200 meshes.

10. The method for producing hydrogen by thermal-electric coupled decomposition of water-coal slurry according to claim 1 or 2, characterized in that: In the digestion reaction of step S3, the active ultrafine water-coal slurry is digested into organic matter, and the heteropoly acid is converted into heteropoly blue.

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