CN117208846A - Pyrolysis reforming hydrogen production method by coupling slow pyrolysis and fast pyrolysis - Google Patents
Pyrolysis reforming hydrogen production method by coupling slow pyrolysis and fast pyrolysis Download PDFInfo
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Abstract
The invention relates to the technical field of biomass pyrolysis, and provides a pyrolysis reforming hydrogen production method by coupling slow pyrolysis and fast pyrolysis. The invention carries out slow pyrolysis on the metal modified biomass to obtain modified biochar; and then carrying out fast pyrolysis on the biomass raw material, and carrying out coupling catalysis on the obtained pyrolysis gas by adopting the modified biochar and the molecular sieve catalyst to obtain hydrogen-rich gas. According to the invention, the slow pyrolysis and the fast pyrolysis are coupled, the modified biochar is prepared by utilizing the heating process of the fast pyrolysis, and the effective utilization of the heating waste heat of the fast pyrolysis can be realized; meanwhile, the invention utilizes the modified biochar and the molecular sieve catalyst to carry out coupling catalysis on pyrolysis gas obtained by fast pyrolysis, and realizes cascade catalytic reforming, thereby improving the hydrogen production yield. And moreover, the pyrolysis gas is pre-reformed by utilizing the modified biochar, so that coke deposition on the molecular sieve catalyst can be inhibited, the deactivation rate of the molecular sieve catalyst is reduced, and the use efficiency of the molecular sieve catalyst is improved.
Description
Technical Field
The invention relates to the technical field of biomass pyrolysis, in particular to a pyrolysis reforming hydrogen production method by coupling slow pyrolysis and fast pyrolysis.
Background
The biomass two-stage pyrolysis reforming hydrogen production technology is an efficient, sustainable and environment-friendly energy production method, and has various advantages and flexibility. Compared with the catalytic gasification process, the two-stage pyrolysis reforming process avoids direct contact between the raw material and the reforming catalyst; in addition, the yield of the biochar obtained by pyrolysis of the biomass raw material can reach 26 percent, which is far higher than the yield obtained by gasification, and the redundant biochar can be upgraded into value-added products, such as activated carbon and graphite, so that the economy and resource efficiency of the whole process flow can be remarkably improved.
The fast pyrolysis is to directly put the biomass raw material at high temperature for pyrolysis, the fast pyrolysis is favorable for the increase of light hydrocarbon, hydrogen and methane, and the heating process is more stable, and the method has the advantage of simple operation. However, in the heating process of the fast pyrolysis, a large amount of heat is not reasonably utilized, which causes energy waste, and the utilization of the heating waste heat during the fast pyrolysis is necessary to be explored.
In the reforming process, the stable and efficient catalyst has an important influence on the production of hydrogen, and can reduce the activation energy required by pyrolysis gas cracking reaction and realize the catalytic cracking of the pyrolysis gas to obtain a desired product. In addition, the catalyst can regulate the production process of the synthesis gas by promoting a certain reaction, help the long chain to be broken into short chains, break chemical bonds and promote the formation of small molecular gas products. Realizing macromolecular organic compounds such as alkeneEffective bond breaking and generation of more small molecular gas, is to increase H 2 Critical step of yield. Molecular sieve catalysts are considered to be the most promising gas and tar removal catalysts due to their high catalytic performance and low cost.
H in reforming process 2 Mainly from tar decomposition and C n H m The catalytic reforming reaction of (2) is easy to decompose tar to generate carbon deposit which is accumulated on the surface of the catalyst, so that the catalyst is deactivated. The catalyst needs to be regenerated after being used, the activity after regeneration is lower than the original activity, and the operation temperature of the catalyst is obviously higher than that before regeneration; in addition, the deactivated catalyst cannot be frequently regenerated endlessly and eventually will be replaced, with the total gas yield gradually decreasing with increasing regeneration times, H 2 The yield gradually decreases. Therefore, it is necessary to reduce the catalyst deactivation rate and improve the catalyst utilization efficiency.
In summary, how to realize the utilization of the heating waste heat during the fast pyrolysis and reduce the deactivation rate of the molecular sieve catalyst is a problem to be solved in the art.
Disclosure of Invention
In view of this, the present invention provides a method for producing hydrogen by pyrolysis reforming coupled with slow pyrolysis and fast pyrolysis. According to the invention, the slow pyrolysis and the rapid pyrolysis are coupled, the modified biochar can be prepared by utilizing the temperature rising process of the rapid pyrolysis, and the obtained modified biochar is used in the catalytic reforming of the subsequent hydrogen production, so that the deactivation rate of the molecular sieve catalyst can be reduced.
In order to achieve the above object, the present invention provides the following technical solutions:
a pyrolysis reforming hydrogen production method by coupling slow pyrolysis and fast pyrolysis comprises the following steps:
(1) Slowly pyrolyzing the metal modified biomass in a two-stage pyrolysis catalytic device to obtain modified biochar; the end point temperature of the slow pyrolysis is 500-800 ℃, and the heating rate from the temperature rise to the end point temperature of the slow pyrolysis is 10-30 ℃/min;
(2) After the slow pyrolysis is finished, carrying out fast pyrolysis on biomass raw materials by taking modified biochar obtained by the slow pyrolysis as a catalyst, and carrying out coupling catalysis on the obtained pyrolysis gas by adopting the modified biochar and a molecular sieve catalyst to obtain hydrogen-rich gas; the temperature of the rapid pyrolysis is 500-800 ℃;
(3) Repeating the step (2) for 10-20 times after fast pyrolysis, and carrying out in-situ regeneration on the molecular sieve catalyst, wherein the in-situ regeneration method comprises the following steps: oxygen is directly introduced into the two-stage pyrolysis catalytic device, and the molecular sieve catalyst is calcined.
Preferably, the step (2) specifically includes: after reaching the end temperature of the slow pyrolysis, placing a biomass raw material on the upstream of the modified biochar, placing a molecular sieve catalyst on the downstream of the modified biochar, performing fast pyrolysis on the biomass raw material, and performing pre-reforming and catalytic reforming on the obtained pyrolysis gas under the actions of the modified biochar and the molecular sieve catalyst in sequence to obtain hydrogen-rich gas; the fast pyrolysis time is 5-20 min.
Preferably, the two-stage pyrolysis catalytic device comprises a pyrolysis furnace and a catalytic furnace, wherein the pyrolysis furnace and the catalytic furnace are communicated, and the catalytic furnace is positioned at the downstream of the pyrolysis furnace; the molecular sieve catalyst is placed in a catalytic furnace.
Preferably, in the slow pyrolysis and the fast pyrolysis, carrier gas is introduced into the two-stage pyrolysis catalytic device, the carrier gas is nitrogen, and the flow rate of the carrier gas is 20-100 mL/min.
Preferably, the temperature of the catalytic furnace is controlled to be 700-900 ℃.
Preferably, the preparation method of the metal modified biomass comprises the following steps: acid washing is carried out on biomass raw materials to obtain acid-washed biomass; and mixing the acid-washed biomass with a metal salt solution, performing solid-liquid separation, and washing and drying the obtained solid to obtain the metal modified biomass.
Preferably, the acid for pickling is nitric acid, and the concentration of the nitric acid is 0.1-1 mol/L; the using amount ratio of the biomass raw material and nitric acid used for preparing the acid-washed biomass is 0.5-2 g/10 mL; the pickling time is 24-48 hours;
the metal salt in the metal salt solution is ferric salt or nickel salt; the concentration of the metal salt solution is 0.1-1 mol/L; the dosage ratio of the acid-washed biomass to the metal salt solution is 0.5-2 g/10 mL; and the mixing time of the acid-washed biomass and the metal salt solution is 24-48 hours.
Preferably, the molecular sieve catalyst is HZSM-5, ZSM-5, USY-1, H-beta or A-type molecular sieve.
Preferably, after the molecular sieve catalyst is regenerated in situ, repeating the steps (1) - (2), and carrying out slow pyrolysis and fast pyrolysis coupling hydrogen production again.
Preferably, in the step (3), the calcination temperature is 400-600 ℃ and the calcination time is 4-6 hours.
The invention provides a pyrolysis reforming hydrogen production method by coupling slow pyrolysis and fast pyrolysis, which comprises the following steps: (1) Slowly pyrolyzing the metal modified biomass in a two-stage pyrolysis catalytic device to obtain modified biochar; the end point temperature of the slow pyrolysis is 500-800 ℃, and the heating rate from the temperature rise to the end point temperature of the slow pyrolysis is 10-30 ℃/min; (2) After the slow pyrolysis is finished, carrying out fast pyrolysis on biomass raw materials by taking modified biochar obtained by the slow pyrolysis as a catalyst, and carrying out coupling catalysis on the obtained pyrolysis gas by adopting the modified biochar and a molecular sieve catalyst to obtain hydrogen-rich gas; the temperature of the rapid pyrolysis is 500-800 ℃; (3) Repeating the step (2) for 10-20 times after fast pyrolysis, and carrying out in-situ regeneration on the molecular sieve catalyst, wherein the in-situ regeneration method comprises the following steps: oxygen is directly introduced into the two-stage pyrolysis catalytic device, and the molecular sieve catalyst is calcined. According to the invention, slow pyrolysis and fast pyrolysis are coupled, and modified biochar is prepared by utilizing the heating process of the fast pyrolysis (namely, metal modified biomass is subjected to slow pyrolysis), so that the effective utilization of the heating waste heat of the fast pyrolysis is realized; meanwhile, the invention utilizes the modified biochar and the molecular sieve catalyst to carry out coupling catalysis on pyrolysis gas obtained by fast pyrolysis to realize cascade catalytic reforming, wherein the modified biochar is used as a pre-reforming catalyst to decompose heavy molecular oxygen-containing compounds into small molecular compounds, and the molecular sieve catalyst is used as a reforming catalyst to convert all small molecules into H 2 Thereby improving the hydrogen production yield. And is combined withAnd moreover, the pyrolysis gas is pre-reformed by utilizing the modified biochar, so that coke deposition on the molecular sieve catalyst can be inhibited, the deactivation rate of the molecular sieve catalyst is reduced, and the use efficiency of the molecular sieve catalyst is improved.
Furthermore, when the molecular sieve catalyst is regenerated, the molecular sieve catalyst does not need to be taken out, and the catalyst is directly regenerated in the furnace, so that the operation is convenient, and the production efficiency is improved.
Drawings
FIG. 1 is a schematic diagram of a slow pyrolysis and fast pyrolysis coupled pyrolysis reforming hydrogen production process according to the present invention.
Detailed Description
The invention provides a pyrolysis reforming hydrogen production method by coupling slow pyrolysis and fast pyrolysis, which comprises the following steps:
(1) Slowly pyrolyzing the metal modified biomass in a two-stage pyrolysis catalytic device to obtain modified biochar; the end point temperature of the slow pyrolysis is 500-800 ℃, and the heating rate from the temperature rise to the end point temperature of the slow pyrolysis is 10-30 ℃/min;
(2) After the slow pyrolysis is finished, carrying out fast pyrolysis on biomass raw materials by taking modified biochar obtained by the slow pyrolysis as a catalyst, and carrying out coupling catalysis on the obtained pyrolysis gas by adopting the modified biochar and a molecular sieve catalyst to obtain hydrogen-rich gas; the temperature of the rapid pyrolysis is 500-800 ℃;
(3) Repeating the step (2) for 10-20 times after fast pyrolysis, and carrying out in-situ regeneration on the molecular sieve catalyst, wherein the in-situ regeneration method comprises the following steps: oxygen is directly introduced into the two-stage pyrolysis catalytic device, and the molecular sieve catalyst is calcined.
FIG. 1 is a schematic diagram of a slow pyrolysis and fast pyrolysis coupled pyrolysis reforming hydrogen production process according to the present invention. The method of the present invention will be described in detail.
According to the invention, metal modified biomass is subjected to slow pyrolysis in a two-stage pyrolysis catalytic device to obtain modified biochar; the final temperature of the slow pyrolysis is 500-800 ℃, and the heating rate from the temperature rising to the final temperature of the slow pyrolysis is 10-30 ℃/min. In the present invention, the preparation method of the metal-modified biomass preferably includes: pickling a biomass raw material (marked as a first biomass raw material) to obtain pickled biomass; and mixing the acid-washed biomass with a metal salt solution, performing solid-liquid separation, and washing and drying the obtained solid to obtain the metal modified biomass.
In the present invention, the first biomass material is preferably an agricultural waste, the present invention has no special requirement on the type of the agricultural waste, and the agricultural waste is well known to those skilled in the art, and in the specific embodiment of the present invention, the agricultural waste is corn straw; the first biomass feedstock is preferably pre-treated prior to use, the method of pre-treatment preferably comprising: sequentially shearing, drying, grinding and sieving biomass raw materials; the drying temperature is preferably 105-120 ℃, and the drying time is preferably 3-12 hours; the grinding is preferably carried out in a pulverizer; the pore diameter of the screen mesh for sieving is preferably 60-100 μm, and the undersize material is taken out. The invention ensures that the biomass raw material has uniform size and good heat conductivity through pretreatment.
In the present invention, the acid for acid washing is preferably nitric acid, and the concentration of the nitric acid is preferably 0.1 to 1mol/L, more preferably 0.3 to 0.5 mol/L; the dosage ratio of the first biomass raw material to the nitric acid is preferably 0.5-2 g/10mL, more preferably 1 g/10 mL; the pickling time is preferably 24-48 hours, more preferably 24-36 hours; after the pickling is completed, the biomass after pickling is preferably washed with water, until the pH value is no longer changed, and dried at a temperature of preferably 105-120 ℃ for preferably 24-48 hours. According to the method, impurities and partial metals in the biomass raw material are removed through acid washing, so that the interference of the impurities and other metal components in the biomass raw material on the loaded metal is reduced.
In the present invention, the metal salt in the metal salt solution is preferably an iron salt or a nickel salt, preferably iron nitrate or nickel nitrate; the concentration of the metal salt solution is preferably 0.1-1 mol/L, more preferably 0.3-0.5 mol/L; the dosage ratio of the acid-washed biomass to the metal salt solution is preferably 0.5-2 g/10mL, more preferably 1 g/10 mL; the mixing time of the acid-washed biomass and the metal salt solution is preferably 24-48 hours, more preferably 24-36 hours; the solid obtained by solid-liquid separation is preferably washed with water until the pH value is no longer changed; the temperature of drying the washed solid is preferably 105-120 ℃ and the time is preferably 24-48 hours. According to the invention, the metal catalyst is introduced into the biochar to enhance the speed and selectivity of the pyrolysis reaction, the biochar can be used as a carrier to provide support for the active metal catalyst, so that the dispersibility and stability of the active metal catalyst are improved, the efficiency of the catalytic hydrogen production reaction is improved, and the yield of hydrogen is increased; and the modified biochar has the advantages of low cost, effective tar removal, carbon deposition resistance and the like.
In the invention, the end temperature of the slow pyrolysis is 500-800 ℃, preferably 600-800 ℃, and the heating rate from the temperature rise to the end temperature of the slow pyrolysis is 10-30 ℃/min, preferably 15-20 ℃/min.
In the invention, the two-stage pyrolysis catalytic device comprises a pyrolysis furnace and a catalytic furnace, wherein the pyrolysis furnace and the catalytic furnace are communicated, and the catalytic furnace is positioned at the downstream of the pyrolysis furnace; the invention preferably places the metal modified biomass in a pyrolysis furnace of a two-stage pyrolysis catalytic device for heating, and slowly pyrolyzes the metal modified biomass in the heating process to obtain the modified biochar.
After the slow pyrolysis is finished, the modified biochar obtained by the slow pyrolysis is used as a catalyst to carry out the fast pyrolysis on biomass raw materials, and the modified biochar and a molecular sieve catalyst are used for carrying out coupling catalysis on the obtained pyrolysis gas to obtain hydrogen-rich gas. In a specific embodiment of the present invention, preferably after reaching the end point temperature of the slow pyrolysis, the present invention places a biomass raw material (denoted as a second biomass raw material) upstream of the modified biochar, places a molecular sieve catalyst downstream of the modified biochar, carries out fast pyrolysis on the biomass raw material, and the obtained pyrolysis gas is subjected to prereforming and catalytic reforming under the actions of the modified biochar and the molecular sieve catalyst in sequence to obtain a hydrogen-rich gas; the temperature of the fast pyrolysis is 500-800 ℃, preferably 600-700 ℃, and the time of the fast pyrolysis is preferably 5-20 min, more preferably 5-15 min. In the invention, after the temperature is raised to the end point temperature of the slow pyrolysis, preferably, the biomass raw material is placed into a pyrolysis furnace of a two-stage pyrolysis catalytic device, is placed at the upstream of modified biochar, and is subjected to fast pyrolysis under the condition of heat preservation; the molecular sieve catalyst is preferably placed in a catalytic furnace of a two-stage pyrolysis catalytic device.
In the invention, in the slow pyrolysis and fast pyrolysis processes, carrier gas is introduced into a two-stage pyrolysis catalytic device, wherein the carrier gas is nitrogen, and the flow rate of the carrier gas is preferably 20-100 mL/min, more preferably 40-60 mL/min; in the present invention, the "upstream" and "downstream" refer to the direction of flow of the carrier gas, which is introduced from the pyrolysis furnace inlet of the two-stage pyrolysis catalytic device and flows out from the outlet of the catalytic furnace.
In the invention, the temperature of the catalytic furnace is preferably controlled to 700-900 ℃, preferably 800 ℃.
In the present invention, the type of the second biomass raw material is consistent with that of the first biomass raw material, and will not be described herein again, the second biomass raw material is preferably pretreated before use, and the pretreatment mode is consistent with the above scheme, and will not be described herein again; the dosage ratio of the second biomass raw material to the first biomass raw material is preferably 1:1; the mass ratio of the second biomass feedstock to the molecular sieve catalyst is preferably 1:1.
In the present invention, the molecular sieve catalyst is preferably HZSM-5, ZSM-5, USY-1, H-beta or A-type molecular sieve, more preferably HZSM-5 molecular sieve; the silicon-aluminum ratio of the HZSM-5 molecular sieve is preferably 25; before the molecular sieve catalyst is used, roasting, crushing and sieving are preferably carried out sequentially; the roasting temperature is preferably 500 ℃, the time is preferably 4 h, the pore diameter of the sieving screen is preferably 60-100 μm, and the undersize product is taken out.
In the invention, the second biomass raw material is introduced into a pyrolysis furnace and subjected to fast pyrolysis, generated pyrolysis gas flows downwards, and sequentially passes through modified biochar and a molecular sieve catalyst to be subjected to prereforming under the action of the modified biochar, so that the heavy molecular oxygen-containing compound is decomposed into small molecular compounds, and the molecular sieve is inhibitedCoke deposition on the catalyst, and reforming the pre-reformed gas under the action of a molecular sieve catalyst to convert all small molecules into H 2 Thereby improving the hydrogen production yield; in the specific embodiment of the invention, after the second biomass raw material is introduced into the pyrolysis furnace, collecting hydrogen-rich gas at the outlet of the catalytic furnace by utilizing a gas collecting bag; in the present invention, the hydrogen content in the hydrogen-rich gas is preferably 30vol% or more, more preferably 60vol% or more.
In the present invention, after the rapid pyrolysis is completed, the temperature is preferably maintained, and then the next batch of biomass raw material is fed into the pyrolysis furnace to perform the rapid pyrolysis of the next batch.
After repeating the step (2) for 10-20 times by fast pyrolysis, the invention carries out in-situ regeneration on the molecular sieve catalyst, and the in-situ regeneration method comprises the following steps: oxygen is directly introduced into the two-stage pyrolysis catalytic device, and the molecular sieve catalyst is calcined. In the invention, the calcination temperature is preferably 400-600 ℃, preferably 500-550 ℃, and the calcination time is preferably 4-6 h, more preferably 5h. In the specific embodiment of the invention, when the molecular sieve catalyst is regenerated, the modified biochar in the two-stage pyrolysis catalytic device is not required to be taken out, and oxygen is directly introduced for calcination. During calcination, the modified biochar becomes partially gaseous.
The method preferably comprises the steps of repeating the steps (1) - (2) after the molecular sieve catalyst is regenerated in situ, and carrying out the slow pyrolysis and fast pyrolysis coupling hydrogen production again.
The following description of the embodiments of the present invention will clearly and fully describe the technical solutions of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the following examples, corn stalks were used as the test material, the dust on the surface of the corn stalks was washed with deionized water and then dried in the sun for 3 days, and then the corn stalks were chopped into 1 cm 3 The small pieces were dried in an oven at 105℃for 3 h. The dried corn stalks were crushed and sieved to obtain 100 μm dry powder for subsequent testing. The molecular sieve catalyst used in the following examples was HZSM-5 having a silica to alumina ratio (Si/Al) of 25, and HZSM-5 was calcined in a muffle furnace at 500℃for 4 h, followed by pulverizing and sieving to obtain 60 μm HZSM-5 powder. The devices employed in the following examples are two-stage pyrolysis catalytic devices, including a pyrolysis furnace and a catalytic furnace, which are in communication, and the catalytic furnace is located downstream of the pyrolysis furnace.
Comparative example 1 fast pyrolysis of corn stover to produce hydrogen
Placing a corn stalk sample of 10g in a pyrolysis furnace, placing 10g of molecular sieve catalyst in a catalytic furnace, pyrolyzing at 800 deg.C (both the pyrolysis furnace and the catalytic furnace are controlled at 800 deg.C) for 10 min, and introducing N 2 ，N 2 The flow is 60 mL/min, the gas collecting bag is used for recycling the hydrogen-rich gas, and the GC-MS is used for recycling H in the produced gas 2 And (5) analyzing the content.
Comparative example 2 omitting the molecular sieve catalyst
The pretreated corn stalks are fully mixed with 0.5 mol/L nitric acid solution by using a constant temperature stirring device according to the proportion of 1 g/10mL for 24 h, the mixture is filtered, and the obtained solid product is washed by deionized water until the pH of the washing liquid is not changed any more. The washed solid product was dried in an oven at 105 ℃ for 24 h to yield an acid washed biomass.
The pickled biomass was mixed with 0.5 mol/L ferric nitrate solution at a ratio of 1 g/10mL and stirred 24 h. The mixture was filtered and the resulting solid product was washed with deionized water until the pH of the wash solution was no longer changing. The washed solid product is dried in an oven at 105 ℃ for 24 h to obtain the modified corn stalk.
Placing a 10g modified corn stalk sample into a pyrolysis furnace, wherein the heating rate is 10 ℃/min, the end temperature of heating is 800 ℃, and the pyrolysis atmosphere is N 2 ，N 2 The flow is 60 mL/min, and the modified biochar is obtained.
Heating to 800 deg.C, placing 10g corn stalk sample in pyrolysis furnace, and placing on the upstream of modified biochar(molecular sieve catalyst is not put in the catalytic furnace), pyrolysis is carried out for 10 min at 800 ℃ (the temperature of the pyrolysis furnace and the catalytic furnace are controlled to be 800 ℃), and N is introduced 2 ，N 2 The flow is 60 mL/min, the gas collecting bag is used for recycling the hydrogen-rich gas, and the GC-MS is used for recycling H in the produced gas 2 And (5) analyzing the content.
Example 1 combination of corn stover slow pyrolysis and fast pyrolysis
The preparation method of the modified corn stalk is the same as that of comparative example 2.
Placing a 10g modified corn stalk sample into a pyrolysis furnace, wherein the heating rate is 10 ℃/min, the end temperature of heating is 800 ℃, and the pyrolysis atmosphere is N 2 ，N 2 The flow is 60 mL/min, and the modified biochar is obtained.
Heating to 800 ℃, placing a corn stalk sample of 10g in a pyrolysis furnace, placing the corn stalk sample in the upstream of modified biochar, placing 10g of molecular sieve catalyst in a catalytic furnace, pyrolyzing at 800 ℃ (both the pyrolysis furnace and the catalytic furnace are controlled at 800 ℃) for 10 min, and introducing N 2 ，N 2 The flow is 60 mL/min, the gas collecting bag is used for recycling the hydrogen-rich gas, and the GC-MS is used for recycling H in the produced gas 2 And (5) analyzing the content.
Test results:
gas production H by GC-MS 2 The results of three parallel tests show that the hydrogen content in the hydrogen-rich gas obtained in the comparative example 1 is 9.73-9.86 vol%, the hydrogen content in the hydrogen-rich gas obtained in the comparative example 2 is 15.68-16.02 vol%, and the hydrogen content in the hydrogen-rich gas obtained in the example 1 is 38.56-40.38 vol%, and it can be seen that the hydrogen production method by combining the slow pyrolysis and the fast pyrolysis can remarkably improve the hydrogen production yield of biomass, the modified biochar is not adopted for prereforming in the comparative example 1, the molecular sieve catalyst is not used in the comparative example 2, and the hydrogen content in the produced gas is lower than that in the example 1.
After the comparative example 1 and example 1 were subjected to rapid pyrolysis 10 times (10 g of biomass raw material amount each time), the apparent morphology of the modified biochar and the molecular sieve catalyst was analyzed by SEM, and the spent catalyst was subjected to Temperature Programmed Oxidation (TPO) analysis using a thermogravimetric analyzer to detect carbonaceous deposits.
The results show that the molecular sieve catalyst of example 1 has a weight loss of less than 10% and the molecular sieve catalyst of comparative example 1 has a weight loss of 20%, indicating that the modified biochar prereforming is beneficial to reducing the molecular sieve catalyst deactivation rate. In addition, SEM results showed that the presence of a portion of the char fragments was observed on the molecular sieve catalyst of example 1, indicating that the pyrolysis gas crushed a portion of the modified biochar into small fragments and carried to the molecular sieve catalyst layer.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The pyrolysis reforming hydrogen production method by coupling slow pyrolysis and fast pyrolysis is characterized by comprising the following steps of:
(1) Slowly pyrolyzing the metal modified biomass in a two-stage pyrolysis catalytic device to obtain modified biochar; the end point temperature of the slow pyrolysis is 500-800 ℃, and the heating rate from the temperature rise to the end point temperature of the slow pyrolysis is 10-30 ℃/min;
(2) After the slow pyrolysis is finished, carrying out fast pyrolysis on biomass raw materials by taking modified biochar obtained by the slow pyrolysis as a catalyst, and carrying out coupling catalysis on the obtained pyrolysis gas by adopting the modified biochar and a molecular sieve catalyst to obtain hydrogen-rich gas; the temperature of the rapid pyrolysis is 500-800 ℃;
(3) Repeating the step (2) for 10-20 times after fast pyrolysis, and carrying out in-situ regeneration on the molecular sieve catalyst, wherein the in-situ regeneration method comprises the following steps: oxygen is directly introduced into the two-stage pyrolysis catalytic device, and the molecular sieve catalyst is calcined.
2. The method according to claim 1, wherein the step (2) is specifically: after reaching the end temperature of the slow pyrolysis, placing a biomass raw material on the upstream of the modified biochar, placing a molecular sieve catalyst on the downstream of the modified biochar, performing fast pyrolysis on the biomass raw material, and performing pre-reforming and catalytic reforming on the obtained pyrolysis gas under the actions of the modified biochar and the molecular sieve catalyst in sequence to obtain hydrogen-rich gas; the fast pyrolysis time is 5-20 min.
3. The method of claim 1, wherein the two-stage pyrolysis catalytic device comprises a pyrolysis furnace and a catalytic furnace, the pyrolysis furnace and catalytic furnace being in communication, and the catalytic furnace being downstream of the pyrolysis furnace; the molecular sieve catalyst is placed in a catalytic furnace.
4. The method of claim 3, wherein in the slow pyrolysis and fast pyrolysis processes, a carrier gas is introduced into the two-stage pyrolysis catalytic device, the carrier gas is nitrogen, and the flow rate of the carrier gas is 20-100 mL/min.
5. A method according to claim 3, wherein the temperature of the catalytic furnace is controlled to 700-900 ℃.
6. The method of claim 1, wherein the method of producing the metal-modified biomass comprises: acid washing is carried out on biomass raw materials to obtain acid-washed biomass; and mixing the acid-washed biomass with a metal salt solution, performing solid-liquid separation, and washing and drying the obtained solid to obtain the metal modified biomass.
7. The method according to claim 6, wherein the acid for pickling is nitric acid, and the concentration of the nitric acid is 0.1-1 mol/L; the using amount ratio of the biomass raw material and nitric acid used for preparing the acid-washed biomass is 0.5-2 g/10 mL; the pickling time is 24-48 hours;
the metal salt in the metal salt solution is ferric salt or nickel salt; the concentration of the metal salt solution is 0.1-1 mol/L; the dosage ratio of the acid-washed biomass to the metal salt solution is 0.5-2 g/10 mL; and the mixing time of the acid-washed biomass and the metal salt solution is 24-48 hours.
8. The process of claim 1 wherein the molecular sieve catalyst is HZSM-5, ZSM-5, USY-1, H-beta or a-type molecular sieve.
9. The method of claim 1, wherein steps (1) - (2) are repeated after the molecular sieve catalyst is regenerated in situ, and the slow pyrolysis and fast pyrolysis coupling hydrogen production is performed again.
10. The method according to claim 1, wherein in the step (3), the calcination temperature is 400 to 600 ℃ and the calcination time is 4 to 6 hours.
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