Method for preparing new energy hydrogen through catalytic conversion of waste wood

Abstract

The invention relates to a method for preparing new energy hydrogen from waste wood, which comprises the following steps of: (1) pretreating the waste wood, baking and carbonizing, and activating and coordinating by using water vapor containing CO2 to prepare string-hole carbon; (2) reacting the string-hole carbon with superheated steam, and controlling the temperature to obtain a large amount of H2 and a small amount of CO; (3) introducing the gas product into a reactor filled with an innovative composite catalyst consisting of Fe, Au elementary substances and four metal oxides, and carrying out catalytic reaction on the gas product and overheated water vapor to convert CO into CO2 and synchronously produce H2; (4) mixing the obtained CO2 and H2, introducing the mixture into a reactor containing a cheap CO2 targeted selective absorption reactant, and removing CO2 while byproducts of high-value nano calcium carbonate whiskers and sodium carbonate nanoparticles are obtained; and (5) treating the tail gas to obtain pure H2. According to the method, the low-value waste wood is converted into high-value hydrogen through a combined process, meanwhile, a high-value product is produced as a byproduct, and the method has the advantages of being environmentally friendly, low in carbon, free of emission, high in hydrogen production rate, small in catalyst loss, low in cost, zero in CO2 emission and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of waste wood recycling and processing, and in particular relates to a method for preparing new energy hydrogen by catalytic conversion of waste wood. Background Art

[0002] With the environmental pollution caused by the use of fossil fuels, the development of clean energy is imminent. Hydrogen, as an efficient and clean new energy source and an important chemical raw material, has become the development trend of future energy. The calorific value of hydrogen is 3 to 4 times that of hydrocarbon fuels such as coke and gasoline. It can be used as an alternative fuel for internal combustion engines and gas turbines, and can operate efficiently and with ultra-low pollution in these applications. In addition, hydrogen is also considered to be the best fuel for fuel cells, with an energy efficiency of more than 90%.

[0003] At present, my country consumes about 150 million cubic meters of wood every year, of which about 100 million cubic meters are processed waste. In recent years, with the accelerated development of my country's cities and the booming development of the real estate and home improvement industries, a large number of decoration residues have appeared. It is estimated that my country's cities produce about 90 million tons of waste wood every year, including old furniture, waste wood from old house renovations, disposable wood products, waste wood from construction projects, old and rotten wood, etc. Therefore, the recycling of waste wood is imperative.

[0004] At present, the more mature hydrogen production processes in industry include water electrolysis, water-gas conversion, heavy oil and natural gas steam catalytic conversion, etc. However, these methods have disadvantages such as harsh process conditions, low hydrogen production efficiency, and high production costs. Biomass hydrogen production technology is an effective way to solve the above problems. It is expected that in the 21st century, hydrogen will play a greater role as an efficient, clean, and renewable new energy source. There are two main methods for hydrogen production from biomass energy conversion: one is microbial conversion, and the other is thermochemical conversion. Biomass thermochemical hydrogen production.

[0005] Patent CN105692551A feeds biomass and water vapor into a fluidized bed reactor, and the generated mixed gas and biochar enter the fluidized bed reactor together with water vapor for gasification reaction. The gas from the fluidized bed is then catalytically reformed with a Co / Cu-based catalyst to generate hydrogen-rich gas. This process has problems such as low reaction activity, complex raw gas, easy catalyst poisoning, high catalyst price, low service life, and low product hydrogen purity. Patent CN110155948A produces hydrogen by high-temperature steam catalytic gasification, medium-temperature adsorption enhanced steam reforming, low-temperature water-gas shift reaction, and CO2 adsorption. This process has problems such as low hydrogen purity, high energy consumption, and low product added value. Summary of the invention

[0006] A method for preparing new energy hydrogen by catalytic conversion of waste wood, the specific steps of which are as follows:

[0007] (1) Using waste wood as raw material, after pretreatment, it is placed in a high-temperature furnace for baking and carbonization, and activated with water vapor containing CO2 to produce a solid carbonization product with multi-level pores connected in series - a series of pores charcoal;

[0008] (2) The porous carbon is loaded into a fixed bed reactor to react with superheated water vapor, and a large amount of H2 and a small amount of CO gas are obtained by controlling the temperature change;

[0009] (3) The obtained gas products are mixed and introduced into an entrained flow reactor, the entrained flow reactor is equipped with a composite catalyst, and superheated water steam is introduced into the mixed gas to undergo a catalytic shift reaction to convert CO into CO2 and simultaneously produce H2;

[0010] (4) Passing the obtained CO2 and H2 mixed gas into a fluidized bed reactor containing a cheap CO2 targeted selective absorption reactant to remove CO2 while producing high-value nano calcium carbonate whiskers and sodium carbonate nanoparticles as by-products;

[0011] (5) The tail gas is dried and purified by a fixed bed dryer to obtain pure H2.

[0012] In step (1), the pretreatment is to crush the waste wood into particles less than 10 mm in size, and the baking and carbonization temperature in the high-temperature furnace is from 100 o C for 5-10 o C / min temperature program, when the temperature reaches 800 o C-900 o In the C range, the carbonization is kept warm for 2-4 hours, and at the same time, it is activated with water vapor containing CO2 to obtain a solid carbonization product with multi-level pores connected in series - string-porous carbon with a pore size of 0.2~55nm.

[0013] The waste wood in step (1) is one or more of waste wood from construction, forestry, material transportation and storage, and other resources.

[0014] In step (1), the CO2 / water vapor in the water vapor containing CO2 is 5-25%.

[0015] In step (2), the temperature and pressure of superheated steam are 800 o C-950 o C, 0.1-1Mpa, react with perforated carbon for 3-5h.

[0016] In step (2), the molar ratio of superheated steam to porous carbon is 8-22.

[0017] The composite catalyst in step (3) is composed of two metal elements, iron (Fe) and gold (Au), and four metal oxides, namely, a catalyst composite composed of a Fe / Fe3O4 composite, an Al2O3-loaded Au composite, and a CuO / ZnO composite. The temperature and pressure of the superheated steam introduced are 260 o C-285 o C, 0.2-0.5Mpa, catalytic conversion reaction time is 0.5-4h.

[0018] In step (3), the mass ratio of Fe / Fe3O4 is 1:2-1:10, the mass ratio of Au / Al2O3 is 1:30-1:5000000, preferably Au is added in a small proportion. The mass ratio of CuO / ZnO is 1:2-1:20.

[0019] In step (3), Au is a nano-sized particle and Al2O3 is a spherical porous hollow structure.

[0020] The fluidized bed reactor described in step (4) contains a newly prepared quicklime water and NaOH mixed solution, and the CO2 and H2 mixed gas is introduced into the reactor for full reaction. The CO2, quicklime water and NaOH generate calcium carbonate and sodium carbonate quantitatively through molecular chemical reaction, and then the mixture is separated and treated to meet the design requirements. The solid separation obtains nano calcium carbonate whiskers. Compared with nano calcium carbonate, nano calcium carbonate whiskers are less likely to agglomerate and can more effectively play the role of toughening and strengthening. Nano calcium carbonate whiskers have special columnar directionality, high whiteness and filling capacity, and higher economic and practical value. They are widely used in reinforcing polymer materials, as friction material fillers, papermaking additives and coating thickeners in the later stage. Sodium carbonate solution is evaporated to obtain sodium carbonate powder; the remaining gas is passed through a fixed bed reactor containing dry CaO to absorb water in H2, and high-purity hydrogen H2 with a purity greater than 99%-99.99% is obtained. After the CaO in the fixed bed reactor absorbs a certain amount of water, it is used in the fluidized bed reactor to absorb CO2 for recycling, turning waste into treasure, low carbon energy saving and income generation.

[0021] Compared with the prior art, the present invention has the following advantages: 1. The water vapor activator containing CO2 is a physical activation. Compared with chemical activation, the process is simpler and the cost is lower. The activator will not corrode instruments and equipment. 2. The gold-loaded catalyst not only has high catalytic activity for low-temperature oxidation of CO, but also has good water resistance, stability and humidity enhancement effect. At the same time, as a precious metal high-efficiency composite catalyst, it has a low price, a small reference and a small amount. The present invention innovatively establishes a plurality of catalyst complexes composed of two metals and four metal oxides to synergistically catalyze efficient hydrogen production, improve hydrogen conversion efficiency, increase H2 gas production and have a good overall effect. 3. Green, low-carbon, environmentally friendly and efficient conversion to produce hydrogen H2 as the main product. Nano calcium carbonate whiskers and sodium carbonate nanoparticles have high commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a process flow chart for preparing new energy hydrogen through catalytic conversion of waste wood. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] In this paper, the pore size distribution curve of the sample was obtained by nitrogen adsorption-desorption curve on Micromeritics ASAP2020 adsorption instrument, and the operating temperature was -196 o C (liquid nitrogen temperature), the sample was protected by nitrogen at 300 o C was pretreated by dehydration. The pore size distribution was calculated by BET and DFT methods.

[0026] Example 1 1kg of waste wood crushed to 5mm in size was put into a high temperature furnace for baking and carbonization. The temperature was from 100 o C together 8 o C / min, when the temperature reaches 810 o C for 2 hours, and activated with 10% CO2 steam, a solid carbonization product with multi-level pores connected in series, namely, porous carbon, was obtained. The mesoporosity was 33% and the pore size ranged from 0.3 to 52 nm as measured by physical adsorption instrument. The skeletal carbon was loaded into a fixed bed reactor and reacted with superheated water vapor. The molar ratio of superheated water vapor to skeletal carbon was 10. The temperature and pressure of the superheated water vapor were 850 o C, 0.5Mpa, react with perforated carbon for 4h. A large amount of H2 and a small amount of CO gas are obtained, and the obtained gas products are mixed and introduced into an entrained flow reactor. The entrained flow reactor is equipped with a catalyst complex composed of a Fe / Fe3O4 complex, an Al2O3-loaded Au complex and a CuO / ZnO complex. The Fe / Fe3O4 mass ratio is 1:5, and the Au / Al2O3 mass ratio is 1:200000. The CuO / ZnO mass ratio is 1:10. Superheated steam is introduced to react with the mixed gas to undergo a catalytic conversion reaction to convert CO into CO2. The temperature and pressure of the superheated steam are 270 o C, 0.4Mpa, the catalytic conversion reaction time is 3h. The obtained CO2 and H2 mixed gas is passed into a fluidized bed reactor, and the fluidized bed reactor contains a newly prepared quicklime water and NaOH mixed solution. The CO2 and H2 mixed gas is passed into the reactor for full reaction. CO2, quicklime water and NaOH quantitatively generate calcium carbonate and sodium carbonate through molecular chemical reaction, which are treated, solid separation to obtain nano calcium carbonate whiskers, and sodium carbonate solution is evaporated to obtain sodium carbonate powder. The remaining gas passes through a fixed bed reactor containing dry CaO to absorb moisture in H2, and obtain high-purity hydrogen H2 with a purity of 99.65%. The biomass hydrogen production rate of the entire process is 138g hydrogen / kg construction waste wood, and the hydrogen conversion rate is 57%. After the CaO in the fixed bed reactor absorbs a certain amount of moisture, it is used in the fluidized bed reactor to absorb CO2 for recycling, turning waste into treasure, low-carbon energy saving and income generation.

[0027] Example 2 1kg of waste wood from transportation and storage, crushed to 4mm in particle size, is put into a high temperature furnace for baking and carbonization. The temperature is from 100 o C together 9 o C / min, when the temperature reaches 850 o C for 2 hours, and activated with water vapor containing 12% CO2, thereby obtaining a solid carbonization product with multi-level pores connected in series, namely, porous carbon. The mesoporosity is 35% and the pore size ranges from 0.5 to 53 nm as measured by physical adsorption instrument. The skeletal carbon was loaded into a fixed bed reactor and reacted with superheated water vapor. The molar ratio of superheated water vapor to skeletal carbon was 15. The temperature and pressure of the superheated water vapor were 900 o C, 0.6Mpa, react with perforated carbon for 3.5h. A large amount of H2 and a small amount of CO gas are obtained, and the obtained gas products are mixed and introduced into an entrained flow reactor. The entrained flow reactor is equipped with a catalyst complex composed of a Fe / Fe3O4 complex, an Al2O3-loaded Au complex and a CuO / ZnO complex. The Fe / Fe3O4 mass ratio is 1:6, and the Au / Al2O3 mass ratio is 1:300000. The CuO / ZnO mass ratio is 1:15. Superheated steam is introduced to react with the mixed gas to undergo a catalytic conversion reaction to convert CO into CO2. The temperature and pressure of the superheated steam are 275 o C, 0.3Mpa, the catalytic conversion reaction time is 2h. The obtained CO2 and H2 mixed gas is passed into a fluidized bed reactor, and the fluidized bed reactor contains a newly prepared quicklime water and NaOH mixed solution. The CO2 and H2 mixed gas is passed into the reactor for full reaction. CO2, quicklime water and NaOH quantitatively generate calcium carbonate and sodium carbonate through molecular chemical reaction, which are treated, solid separation to obtain nano calcium carbonate whiskers, and sodium carbonate solution is evaporated to obtain sodium carbonate powder. The remaining gas passes through a fixed bed reactor containing dry CaO to absorb moisture in H2, and obtain high-purity hydrogen H2 with a purity of 99.76%. The biomass hydrogen production rate of the entire process is 141g hydrogen / kg material transportation and storage waste wood, and the hydrogen conversion rate is 59%. After the CaO in the fixed bed reactor absorbs a certain amount of moisture, it is used in the fluidized bed reactor to absorb CO2 for recycling, turning waste into treasure, low-carbon energy saving and income generation.

Claims

1. A method for preparing new energy hydrogen by catalytic conversion of waste wood, the specific steps of which are as follows: (1) Using waste wood as raw material, after pretreatment, it is placed in a high-temperature furnace for baking and carbonization, and activated with water vapor containing CO2 to produce a solid carbonization product with multi-level pores connected in series - a series of pores charcoal; (2) The porous carbon is loaded into a fixed bed reactor to react with superheated steam, and a large amount of H2 and a small amount of CO gas are obtained by controlling the temperature change; (3) The obtained gas products are mixed and introduced into an entrained flow reactor, in which a composite catalyst is installed, and superheated water steam is introduced to react with the mixed gas to undergo a catalytic shift reaction to convert CO into CO2 and simultaneously produce H2; (4) Passing the obtained CO2 and H2 mixed gas into a fluidized bed reactor containing a cheap CO2 targeted selective absorption reactant to remove CO2 while producing high-value nano calcium carbonate whiskers and sodium carbonate nanoparticles as by-products; (5) The tail gas is dried and purified by a fixed bed dryer to obtain pure H2.

2. The method for preparing new energy hydrogen by catalytic conversion of waste wood according to claim 1, characterized in that: The raw material waste wood comes from one or more types of waste wood from construction, forestry, material transportation and storage, and other resources.

3. The method for preparing new energy hydrogen by catalytic conversion of waste wood according to claim 1, characterized in that: In step (1), the pretreatment is to crush the waste wood into particles less than 10 mm in size, and the baking and carbonization temperature in the high-temperature furnace is from 100 o C for 5-10 o C / min temperature program, when the temperature reaches 800 o C-900 o In the C range, the carbonization is carried out for 2-4 hours under heat preservation, and at the same time, water vapor containing CO2 is used for activation and coordination, thereby obtaining a solid carbonization product with multi-level pores interconnected in series - string-porous carbon with a pore size of 0.2~55nm.

4. The method for preparing new energy hydrogen by catalytic conversion of waste wood according to claim 3, characterized in that: The CO2 / water vapor ratio in water vapor containing CO2 is 5~25%.

5. The method for preparing new energy hydrogen by catalytic conversion of waste wood according to claim 1, characterized in that: The temperature and pressure of the superheated steam introduced in step (2) are 800 o C-950 o C, 0.1-1Mpa, react with perforated carbon for 3-5h.

6. The method for preparing new energy hydrogen by catalytic conversion of waste wood according to claim 6, characterized in that: The molar ratio of superheated steam to porous carbon is 8-22.

7. The composite catalyst according to claim 1, characterized in that: The composite catalyst in step (3) is composed of two metal elements, iron (Fe) and gold (Au), and four metal oxides, namely, a catalyst composite composed of a Fe / Fe3O4 composite, an Al2O3-loaded Au composite, and a CuO / ZnO composite. The temperature and pressure of the superheated steam introduced are 260 o C-285 o C, 0.2-0.5Mpa, catalytic conversion reaction time is 0.5-4h.

8. The method for preparing new energy hydrogen by catalytic conversion of waste wood according to claim 8, characterized in that: The mass ratio of Fe / Fe3O4 is 1:2~1:10, the mass ratio of Au / Al2O3 is 1:30~1:5000000. The mass ratio of CuO / ZnO is 1:2~1:

20.

9. The method for preparing new energy hydrogen by catalytic conversion of waste wood according to claim 8, characterized in that: Au is a nano-scale particle, Al2O3 is a spherical porous hollow structure, and Au nanoparticles cover the surface of Al2O3 particles and internal pores to form a composite structure catalyst material.

10. The method for removing CO2 and drying H2 according to claim 1, characterized in that: The fluidized bed reactor described in step (4) contains a newly prepared quicklime water and NaOH mixed solution, and the CO2 and H2 mixed gas is introduced into the reactor for full reaction. The CO2, quicklime water and NaOH react quantitatively to generate calcium carbonate and sodium carbonate, and then separate and treat them to meet the design requirements. The solid-liquid heterogeneous separation obtains nano calcium carbonate whiskers. Compared with nano calcium carbonate, nano calcium carbonate whiskers are less likely to agglomerate and can more effectively play the role of toughening and strengthening. Nano calcium carbonate whiskers have special columnar directionality, high whiteness and filling capacity, and higher economic and practical value. They are widely used in reinforcing polymer materials, as friction material fillers, papermaking additives and coating thickeners in the later stage. Sodium carbonate nanoparticles are obtained by evaporating the sodium carbonate solution; the remaining gas is passed through a fixed bed reactor containing dry CaO to absorb water in H2 to obtain high-purity hydrogen H2 with a purity greater than 99%-99.99%. After the CaO in the fixed bed reactor absorbs a certain amount of water, it is used in the fluidized bed reactor to absorb CO2 for recycling, turning waste into treasure, low carbon energy saving and income generation.

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