Method for preparing hydrogen by catalytic cracking of waste edible oil

Abstract

This invention relates to a method for producing hydrogen from waste edible oils via catalytic cracking. The method involves precipitating and filtering the waste edible oils, then converting them into C1-C5 light hydrocarbons at 350℃-380℃ using a highly active, carbon-resistant, acid-resistant, and water-resistant large-pore hydrodeoxygenation catalyst and a highly efficient n-alkane cracking catalyst. The converted hydrocarbons are then passed through a fine desulfurization reactor and into a light hydrocarbon conversion furnace for cracking to produce hydrogen. Further conversion is performed in a medium-temperature shift converter to increase the yield. Finally, the hydrogen is purified using a PSA purification system to obtain high-purity hydrogen. This method features low reaction temperatures, minimal equipment requirements, and effectively avoids coking during the reaction process. The catalyst structure and synergistic effect of this invention result in high catalytic activity, improved catalytic efficiency, abundant C1-C5 light hydrocarbon components, and higher hydrogen purity.

Description

Technical Field

[0001] This invention belongs to the field of catalytic cracking technology, and specifically relates to a method for preparing hydrogen by catalytic cracking of waste edible oils. Background Technology

[0002] Hydrogen energy is a clean, efficient, and pollution-free ideal energy source, boasting advantages such as light weight, high calorific value, and convenient transportation. With hydrogen fuel cells being tested by major automakers worldwide, the application scope of hydrogen energy is continuously expanding. Currently, most of the world's hydrogen comes from the steam reforming or partial oxidation of fossil fuels, which have drawbacks such as limited reserves and non-renewability. Therefore, finding an ideal hydrogen source with a large total quantity and abundant supply is of great significance for reducing greenhouse gas emissions, improving the natural environment, and promoting sustainable human development. Using waste cooking oil as a hydrogen source can not only enhance the economic and social benefits of resource recycling but also effectively alleviate the environmental pollution problems caused by its improper disposal.

[0003] In the prior art, CN105217569A discloses a method for producing high-purity hydrogen from waste edible oil through reforming, including the following steps: 1) Preparation of the carrier: using a metal oxide with a core-shell structure as a carrier to reform waste edible oil to produce hydrogen; 2) Pretreatment of the waste edible oil; 3) By controlling the circulation rate of the metal oxide oxygen carrier particles and the flow rate of the oil liquid, the oil liquid is subjected to an oxidation-reduction reaction in a fuel reactor to generate high-purity H2. CN111533088A discloses a method for the catalytic cracking of waste edible oil to co-produce hydrogen and carbon nanotubes. The waste edible oil is precipitated and filtered, and then catalytically cracked at 650℃-950℃ to obtain gaseous and solid products, and then the gaseous products are purified.

[0004] Although some progress has been made in the research on reaction conditions and catalytic systems for producing high-purity hydrogen from edible oil reforming, the following shortcomings still exist: (1) The catalytic cracking reaction temperature is high, which easily leads to coking; (2) The hydrogen conversion rate is not high; (3) The preparation process of metal oxide carrier is complicated and requires high-temperature sintering, which easily causes equipment wear and material loss. At the same time, it is also necessary to regulate the metal oxide, which is quite difficult. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for producing hydrogen by catalytic cracking of waste edible oils.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows:

[0007] A method for producing hydrogen by catalytic cracking of waste edible oils includes the following steps:

[0008] a) Mix the feedstock oil with hydrogen;

[0009] b) After being heated, it enters the first hydrogenation reactor, wherein the catalyst of the first hydrogenation reactor is a highly active, carbon-resistant, acid-resistant, and water-resistant large-pore hydrogenation deoxygenation catalyst.

[0010] c) After being catalyzed by the highly efficient cracking catalyst for n-alkane in the second hydrogenation reactor, the reaction continues to form more C1-C5 light hydrocarbon components;

[0011] d) The reaction temperature is between 350℃ and 380℃, and the pressure is maintained at 8 to 10 MPa;

[0012] e) The reaction products are collected after being reheated and then passed through a stripping tower and a vacuum distillation tower. The products contain C1-C5 light hydrocarbon components and unreacted oil and gas recovery products.

[0013] f) C1-C5 light hydrocarbon components enter the desulfurization reactor to remove hydrogen sulfide;

[0014] g) C1-C5 light hydrocarbon components enter the light hydrocarbon conversion furnace for cracking reaction, producing a high concentration of hydrogen gas;

[0015] h) Hydrogen enters a converter for further conversion to improve yield;

[0016] i) Finally, the hydrogen is purified by the PSA system to obtain high-purity hydrogen.

[0017] Preferably, the catalyst in the first hydrogenation reactor is NiMo / γ-Al2O3.

[0018] Preferably, the catalyst in the second hydrogenation reactor includes sulfides such as Ni-S or Co-S.

[0019] Preferably, the pressure of the first hydrogenation reactor is 10 MPa, and the pressure of the second hydrogenation reactor is 10 MPa.

[0020] Preferably, the catalyst in the desulfurization reactor is ZnO / Al2O3.

[0021] Preferably, the catalyst in the light hydrocarbon conversion furnace is a composite of ZSM-5 and β molecular sieve.

[0022] Preferably, the adsorbent used in the PSA purification system is a molecular sieve.

[0023] Preferably, the unreacted oil and gas recovery product is cracked tail oil.

[0024] An apparatus for producing hydrogen by catalytic cracking of waste edible oils includes a first heating furnace, a first hydrogenation reactor, a second hydrogenation reactor, a second heating furnace, a first-stage stripping tower, a first-stage vacuum tower, a desulfurization reactor, a light hydrocarbon conversion furnace, a variable furnace, and a PSA purification system connected in sequence.

[0025] In this process, the feedstock oil is mixed with hydrogen and heated in the first heater before entering the first and second hydrogenation reactors. After being heated again in the second heater, the C1-C5 light hydrocarbon components are collected through a stripping tower and a first-stage vacuum tower. The C1-C5 light hydrocarbon components enter the desulfurization reactor to remove hydrogen sulfide and then enter the light hydrocarbon conversion furnace for cracking. The resulting high-concentration hydrogen enters the variable furnace for further conversion. Finally, high-purity hydrogen is obtained through the PSA purification system.

[0026] Advantages of this invention compared to existing technologies:

[0027] (1) In this invention, waste edible oil is precipitated and filtered, and then converted into C1-C5 light hydrocarbons at 350℃-380℃ using a highly active, carbon-resistant, acid-resistant, and water-resistant large-pore hydrodeoxygenation catalyst and a high-efficiency n-alkane cracking catalyst. Then, it is fed into a light hydrocarbon conversion furnace for cracking to produce hydrogen through a fine desulfurization reactor, further converted by a medium-temperature shift furnace to improve the yield, and finally fed into a PSA purification system to obtain high-purity hydrogen.

[0028] (2) The reaction temperature is low, the equipment requirements are low, and coking is effectively avoided during the reaction. The catalyst structure and synergistic effect of the present invention result in high catalytic activity, improved catalytic efficiency, and rich production of C1-C5 light hydrocarbon components.

[0029] (3) The first hydrogenation reactor uses a NiMo / γ-Al2O3 catalyst, which has higher catalytic activity and characteristics such as resistance to carbon buildup, high acid resistance, and water resistance. In addition, the catalyst of the second hydrogenation reactor includes sulfides such as Ni-S or Co-S, which can better and more efficiently crack the feedstock oil and form more C1-C5 light hydrocarbon components.

[0030] (4) The pressure, temperature, catalyst, and other conditions of the first and second hydrogenation reactors have also been optimized and adjusted to more effectively catalyze the cracking of waste edible oils and improve hydrogen yield and purity. In addition, the present invention also uses a PSA purification system to more thoroughly improve the purity of hydrogen.

[0031] (5) In the method of the present invention, the catalyst for producing hydrogen by catalytic cracking of waste edible oil has a limited service life and needs to be regenerated or replaced regularly. Catalyst regeneration is more convenient. The waste gas is directly burned through an air preheater and a combustion chamber to burn off the carbon deposits and degradation products accumulated on the catalyst surface, thereby achieving catalyst regeneration.

[0032] (6) The raw material oils include various waste edible oils, such as lard, chicken fat, beef tallow, palm oil, rapeseed oil, etc. These oils are effectively cracked in the method of the present invention to provide a high concentration of hydrogen products. In addition, the present invention also uses pressure swing adsorption (PSA) as a hydrogen purification method, which has a wider range of applications. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a device for producing hydrogen by catalytic cracking of waste edible oils according to the present invention.

[0034] Figure 2 This is a flowchart of a method for producing hydrogen from waste edible oils by catalytic cracking, as described in this invention.

[0035] Explanation of reference numerals in the attached drawings: 1-raw material, 2-first heating furnace, 3-first hydrogenation reactor, 4-second hydrogenation reactor, 5-second heating furnace, 6-first-stage stripping tower, 7-first-stage vacuum tower, 8-C1-C5 light hydrocarbon components, 9-cracked tail oil, 10-dehydrogenation reactor, 11-conversion furnace, 12-variable furnace, 13-PSA purification system, 14-high-purity hydrogen, 15-raw material hydrogen. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this invention, and should not be construed as limiting this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The structure and technical solutions of this invention will be further described in detail below with reference to the accompanying drawings, and one embodiment of this invention will be given.

[0037] The present invention discloses a method for producing hydrogen by catalytic cracking of waste edible oils, comprising the following steps:

[0038] a) Mix the feedstock oil with hydrogen;

[0039] b) After being heated, it enters the first hydrogenation reactor 3, wherein the catalyst of the first hydrogenation reactor 3 is a highly active, carbon-resistant, acid-resistant, and water-resistant large-pore hydrogenation deoxygenation catalyst.

[0040] c) After being catalyzed by the high-efficiency cracking catalyst for n-alkane in the second hydrogenation reactor 4, the reaction continues to form more C1-C5 light hydrocarbon components;

[0041] d) The reaction temperature is between 350℃ and 380℃, and the pressure is maintained at 8 to 10 MPa;

[0042] e) The reaction products are collected by a first-stage stripping tower 6 and a first-stage vacuum tower 7 after being reheated. These products contain C1-C5 light hydrocarbon components and unreacted oil and gas recovery products.

[0043] f) C1-C5 light hydrocarbon components enter desulfurization reactor 10 for hydrogen sulfide removal;

[0044] g) C1-C5 light hydrocarbon components enter the light hydrocarbon conversion furnace 11 for cracking reaction, producing a high concentration of hydrogen gas;

[0045] h) Hydrogen enters the conversion furnace 12 for further conversion to improve the yield;

[0046] i) Finally, the hydrogen is purified by the PSA purification system 13 to obtain high-purity hydrogen.

[0047] The catalyst in the first hydrogenation reactor is NiMo / γ-Al₂O₃. In the hydrogen production process, waste cooking oil is first heated to 350°C and then introduced into the first hydrogenation reactor for reaction. In the first hydrogenation reactor, the waste cooking oil is first hydrogenated and cracked into smaller hydrocarbon molecules, releasing a large amount of hydrogen gas. The catalyst used is NiMo / γ-Al₂O₃. The catalyst's role is to promote the chemical reaction, increase the reaction rate and selectivity, and enable the waste cooking oil to be hydrogenated and cracked into hydrogen and hydrocarbon molecules more quickly. Since the first hydrogenation reactor is the core component of the entire hydrogen production unit, the selection and control of the catalyst are particularly critical, directly affecting the yield and quality of hydrogen.

[0048] The catalyst in the second hydrogenation reactor includes sulfides such as Ni-S or Co-S. In methods for producing hydrogen through the catalytic cracking of waste edible oils, the catalyst in the second hydrogenation reactor can use reaction products from the first hydrogenation reactor. This type of catalyst is often referred to as an in-situ catalyst for hydrogen production.

[0049] Specifically, in the first hydrogenation reactor, NiMo / γ-Al₂O₃ is used as a catalyst to hydrocracking waste edible oils, producing hydrogen and hydrocarbon molecules. Some of these reaction products can then be used as catalysts in the second hydrogenation reactor. Generally, effective catalysts among these hydrogenation products include sulfides such as Ni-S or Co-S. These sulfides possess good catalytic activity and stability, promoting hydrogen generation while also helping to maintain hydrogen purity.

[0050] Therefore, the reaction products from the first hydrogenation reactor are collected and processed to prepare a suitable sulfide catalyst, which is then loaded into the second hydrogenation reactor for further reaction. This effectively increases the yield and purity of hydrogen while reducing catalyst loss and environmental pollution during application.

[0051] The pressure of the first hydrogenation reactor is 10 MPa, and the pressure of the second hydrogenation reactor is 10 MPa.

[0052] The catalyst in the desulfurization reactor 10 is ZnO / Al2O3.

[0053] The catalyst in the light hydrocarbon conversion furnace 11 is a composite of ZSM-5 and β molecular sieve.

[0054] The adsorbent used in the PSA purification system is a molecular sieve.

[0055] Unreacted oil and gas recovery products are cracked tail oil.

[0056] The present invention provides an apparatus for producing hydrogen by catalytic cracking of waste edible oils, comprising a first heating furnace 2, a first hydrogenation reactor 3, a second hydrogenation reactor 4, a second heating furnace 5, a first-stage stripping tower 6, a first-stage vacuum tower 7, a desulfurization reactor 10, a light hydrocarbon conversion furnace 11, a transformation furnace 12, and a PSA purification system 13 connected in sequence.

[0057] In this process, the feedstock oil and hydrogen are mixed and heated in the first heater 2 before entering the first hydrogenation reactor 3 and the second hydrogenation reactor 4. After being heated again in the second heater 5, the C1-C5 light hydrocarbon components are collected through a stripping tower 6 and a first-stage vacuum tower 7. The C1-C5 light hydrocarbon components enter the desulfurization reactor 10 to remove hydrogen sulfide and then enter the light hydrocarbon conversion furnace 11 for cracking reaction. The high-concentration hydrogen produced enters the transformation furnace 12 for further conversion. Finally, high-purity hydrogen is obtained through the PSA purification system 13.

[0058] For the PSA process of hydrogen adsorption, precise control and monitoring of system temperature is one of the key factors for achieving more accurate and reliable control. To achieve this goal, a temperature control strategy based on Model Predictive Control (MPC) algorithm is adopted. By optimizing the control input, the system achieves the desired temperature response, including the following steps:

[0059] S1: Establishing a hydrogen adsorption model

[0060] A hydrogen adsorption model was established as the input to the control algorithm. The model is based on the gas separation principle and adsorption kinetic equations, including processes such as adsorption, desorption, elution and regeneration. The model was used to simulate and optimize the PSA process.

[0061] (1)

[0062] in, q i Indicates the first i The mass adsorption capacity of the adsorbent. q max,i Indicates the first i The maximum adsorption capacity of the adsorbent K i,1 and K i,2 Let these represent the adsorption constants for the first and second adsorption steps, respectively. n i,1 and n i,2 The adsorption indices for the first and second adsorption steps are respectively represented. E a,i Indicates the first i The activation energy of the adsorbent R Represents the gas constant. T Indicates the system temperature. P i This indicates the pressure of the adsorbent.

[0063] S2: Determine the control objective

[0064] After determining the hydrogen adsorption model, it is necessary to define the control objectives of the PSA process. The PSA process is affected by many factors, such as gas flow rate and pressure, adsorbent type and quality, and system temperature. The control system temperature should be determined, and the control objective should be set to achieve the desired temperature while ensuring system stability and reliability.

[0065] S3: Establish a temperature model for the PSA system

[0066] To design a temperature control algorithm, a temperature model of the PSA system needs to be established. This model is based on physical principles and governing equations to describe the system's dynamic characteristics and response. The temperature changes of the PSA system are described using heat transfer and energy balance equations. The model is expressed as:

[0067] (2)

[0068] in, C p Indicates the enthalpy capacity of a gas mixture. T Indicates the system temperature. h 1 and h 2 They respectively represent the positions located at the th 1 The adsorption bed and the first 2 Enthalpy of the mixed gas at the interface between adsorption beds A j This represents the cross-sectional area of ​​the adsorption bed. Q′ This represents the system's heat input. In actual operation, it is usually affected by factors such as ambient temperature, cyclic compression heat, and adsorption / desorption of the mixed gas, thus requiring adjustment and optimization based on specific application conditions.

[0069] S4: Design Model Predictive Control Algorithm Framework

[0070] After establishing the temperature model of the PSA system, the framework of the control algorithm needs to be determined. Since the PSA process is affected by multiple input variables and exhibits nonlinear and time-varying properties, the Model Predictive Control (MPC) algorithm is chosen as the control strategy. The MPC algorithm transforms the optimal control problem into an optimization problem and solves for the optimal control input using a predictive model and constraints. The MPC algorithm consists of the following three steps:

[0071] S41. Predictive Model: Update the PSA system temperature model based on real-time measurement data and make predictions for several future time steps.

[0072] (3)

[0073] in, T ( k+j∣k ) indicates in k At that moment, by the first j The predicted temperature value obtained from each sampling point h in ( k+j | k ) indicates in k At that moment, by the first j The input flow obtained from each sampling point C pIndicates the enthalpy capacity of a gas mixture. T ( k ) represents the actual temperature at time k.

[0074] S42. Optimize control input: Calculate the control input sequence that enables the temperature to reach the desired value through an optimization algorithm, while ensuring that all constraints are met.

[0075] (4)

[0076] in, u ( k+j | k ) indicates in k At that moment, by the first j The control input value obtained from each sampling point, Δ u ( k+j | k ) indicates in k At that moment, by the first j The input control increment is obtained from each sampling point.

[0077] S43. Implement control input: Execute the first control input in the control input sequence, and recalculate the control input sequence on the next sampling to achieve precise temperature control.

[0078] (5)

[0079] in, u ( k ) indicates in k The actual control input at any given moment.

[0080] S5: Design Control Strategies

[0081] After determining the MPC algorithm framework, the control strategy needs to be designed. This involves selecting the types and number of control inputs, and defining parameters such as constraints and weighting factors. The control inputs are set as flow rate and adsorbent temperature, while considering constraints such as adsorption bed pressure, adsorbent selection, regeneration cycle, and hydrogen storage tank capacity. To make temperature control more precise and reliable, the constraints and weighting factors are adjusted and optimized according to actual needs.

[0082] S6: Collect data and preprocess it.

[0083] To achieve precise temperature control, relevant data needs to be collected and preprocessed. This data includes real-time monitoring data of the PSA system, such as temperature, flow rate, and pressure, as well as control input and output parameters. During preprocessing, the data needs to be cleaned, normalized, and standardized to improve the model's training effectiveness and generalization ability.

[0084] S7: Training the Model

[0085] After data preprocessing, the MPC model is trained. By adjusting model parameters and constraints, it is made capable of quickly and accurately predicting temperature response and optimizing control inputs such as adsorbent selection and cyclic operation in the PSA process. During training, stochastic gradient descent is employed to improve the model's convergence speed and accuracy.

[0086] S8: Test the model and perform real-time dynamic optimization.

[0087] After training the MPC model, it is tested. The model's generalization ability and performance are verified by inputting unknown operating conditions. If the model's predictions match the actual situation, it is applied to the real-time optimization of the PSA process to improve hydrogen separation efficiency and economic benefits. Specifically, in the real-time dynamic optimization process, control inputs such as flow rate and adsorbent temperature are optimized based on the model's predictions to maximize the separation effect and economic benefits of the PSA process.

[0088] In summary, the PSA system temperature control strategy based on the Model Predictive Control (MPC) algorithm comprises eight steps: establishing a hydrogen adsorption model, determining the control objective, establishing a PSA system temperature model, designing the MPC algorithm framework, designing the control strategy, collecting and preprocessing data, training the model, and testing the model and performing real-time dynamic optimization. This algorithm enables precise control and monitoring of the system temperature, achieving more accurate and reliable control during adsorption and desorption processes, thereby improving process efficiency and economic benefits.

[0089] The PSA process includes seven steps: feed pressurization (PR), adsorption (AD), depressurization equalization (DPE), blowing (BD), vacuum equalization (VA), purging (PG), and pressurization equalization (PPE) to reduce vacuum energy and mechanical costs.

[0090] The PSA system includes adsorption bed 1 and adsorption bed 2. The process steps and corresponding times for adsorption bed 1 and adsorption bed 2 are shown in the table.

[0091]

[0092] The two adsorption beds employing the PSA process achieve high purification efficiency. In adsorption bed 1, after the feed gas is pressurized by the feed pressurization (PR) process and enters the adsorber, it undergoes adsorption (AD), pressure equalization (DPE), blowing (BD), and vacuum (VA) steps, removing impurities and resulting in a high-quality gas. In adsorption bed 2, similar steps further enhance the gas purity. Therefore, the two adsorption beds using the PSA process effectively improve gas purification efficiency and represent an effective method for gas purification.

[0093] By employing an axially dispersed plug flow model, the mass balance of each component in the adsorption bed is calculated, which helps to deepen the understanding of the adsorption process, optimize the PSA process system, and determine the reasonable range of design parameters. The mass balance of each component in the adsorption bed is calculated using the axially dispersed plug flow model as follows:

[0094] (6)

[0095] The overall mass balance is:

[0096] (7)

[0097] The energy balance between the gas and solid phases is:

[0098] (8)

[0099] Where Kz is the effective axial thermal conductivity.

[0100] Due to the small diameter of the adsorption bed, heat loss through the wall and heat accumulation within the wall are not negligible. While the temperature change is small due to the low impurity content, another energy balance exists at the adsorption bed wall:

[0101] (9)

[0102] (10)

[0103] Calculate the pressure drop, where v is the surface velocity, then:

[0104] (11)

[0105] ,

[0106] The adsorption rate of the adsorbent particles was modeled using a linear driving force model, which employed a single lumped mass transfer parameter. w Assuming this parameter is constant, it is obtained by fitting the experimental breakthrough curve.

[0107] (12)

[0108] Since the content of each impurity in the feed is very small, a loaded phase ratio model is used for multi-component adsorption equilibrium, then:

[0109] (13)

[0110] (14)

[0111] in, k1 、k 2 、k 3 、k 4 The relevant model parameters can be obtained through experiments; A is the cross-sectional area; B is the isotherm parameter; C p Let d be the heat capacity, d be the diameter, and D be the diameter. ax Where is the axial dispersion coefficient of mass, and h is the heat transfer coefficient. H ads For the average heat of adsorption, K z For the effective axial thermal conductivity, L is the adsorption bed length, P is the pressure, and q, q , For adsorption capacity, equilibrium adsorption capacity, and average adsorption capacity, q m Here are the isotherm parameters, R is the radius or gas constant, t is time, and T is the temperature of the solid and gas phases. atm For ambient temperature, T w denoted as wall temperature, u as interstitial velocity, y as gas phase mole fraction, ε as interparticle void fraction, μ as viscosity, v as surface velocity, ρ as density, and w as a coefficient.

[0112] By employing an axially dispersed plug flow model, the mass balance of each component in the adsorption bed is calculated, which helps to deepen the understanding of the adsorption process, optimize the PSA process system, and determine the reasonable range of design parameters. First, this model helps to deepen the understanding of the adsorption process. It treats the adsorption bed as a series of uniform discrete segments and considers the interaction between the adsorbent and the gas, thus simulating the separation, adsorption, and elution processes of each component during adsorption, which helps to deepen the understanding of the internal physical phenomena and chemical mechanisms of the adsorption bed. Second, this model is used to optimize the PSA process system. By simulating and calculating the mass balance of each component in the adsorption bed, the gas purification efficiency and yield under different operating conditions are evaluated, the performance differences of different schemes are compared, and the optimal scheme is selected, thereby achieving the goal of optimizing the PSA process system. Finally, the reasonable range of design parameters is also determined by calculating the mass balance of each component in the adsorption bed. The design parameters of the adsorption bed include feed flow rate, adsorption tower size, adsorbent type, and storage capacity. The selection of these parameters has a significant impact on gas purification efficiency and yield. By calculating the mass balance of each component in the adsorption bed, the performance indicators of the system under different design parameters are determined, and thus the reasonable range of design parameters is determined. In summary, employing an axially dispersed plug flow model to calculate the mass balance of each component in the adsorption bed helps deepen the understanding of the adsorption process, optimize the PSA process system, and determine the reasonable range of design parameters. This plays a crucial role in improving the efficiency and economy of gas purification.

[0113] Advantages of this invention compared to existing technologies:

[0114] (1) In this invention, waste edible oil is precipitated and filtered, and then converted into C1-C5 light hydrocarbons at 350℃-380℃ using a highly active, carbon-resistant, acid-resistant, and water-resistant large-pore hydrodeoxygenation catalyst and a high-efficiency n-alkane cracking catalyst. Then, it is fed into a light hydrocarbon conversion furnace for cracking to produce hydrogen through a fine desulfurization reactor, further converted by a medium-temperature shift furnace to improve the yield, and finally fed into a PSA purification system to obtain high-purity hydrogen.

[0115] (2) The reaction temperature is low, the equipment requirements are low, and coking is effectively avoided during the reaction. The catalyst structure and synergistic effect of the present invention result in high catalytic activity, improved catalytic efficiency, and rich production of C1-C5 light hydrocarbon components.

[0116] (3) The first hydrogenation reactor uses a NiMo / γ-Al2O3 catalyst, which has higher catalytic activity and characteristics such as resistance to carbon buildup, high acid resistance, and water resistance. In addition, the catalyst of the second hydrogenation reactor includes sulfides such as Ni-S or Co-S, which can better and more efficiently crack the feedstock oil and form more C1-C5 light hydrocarbon components.

[0117] (4) The pressure, temperature, catalyst, and other conditions of the first and second hydrogenation reactors have also been optimized and adjusted to more effectively catalyze the cracking of waste edible oils and improve hydrogen yield and purity. In addition, the present invention also uses a PSA purification system to more thoroughly improve the purity of hydrogen.

[0118] (5) In the method of the present invention, the catalyst for producing hydrogen by catalytic cracking of waste edible oil has a limited service life and needs to be regenerated or replaced regularly. Catalyst regeneration is more convenient. The waste gas is directly burned through an air preheater and a combustion chamber to burn off the carbon deposits and degradation products accumulated on the catalyst surface, thereby achieving catalyst regeneration.

[0119] (6) The raw material oils include various waste edible oils, such as lard, chicken fat, beef tallow, palm oil, rapeseed oil, etc. These oils are effectively cracked in the method of the present invention to provide a high concentration of hydrogen products. In addition, the present invention also uses pressure swing adsorption (PSA) as a hydrogen purification method, which has a wider range of applications.

[0120] (7) The MPC algorithm is used to achieve precise control and monitoring of the temperature of the PSA system, so as to achieve more accurate and reliable control during adsorption and desorption, thereby improving process efficiency and economic benefits.

[0121] (8) By adopting the axially dispersed plug flow model, the mass balance of each component in the adsorption bed is calculated to help deepen the understanding of the adsorption process, optimize the PSA process system, and determine the reasonable range of design parameters.

[0122] The parts of this invention not described in detail are common knowledge in the field.

[0123] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A method for producing hydrogen by catalytic cracking of waste edible oils, characterized in that, Includes the following steps: (a) Mixing the feedstock oil with hydrogen; (b) After being heated, it enters the first hydrogenation reactor (3), wherein the catalyst of the first hydrogenation reactor (3) is NiMo / γ-Al2O3, which has high activity, acid resistance, water resistance and carbon deposition resistance, and is used for hydrogenation deoxygenation; (c) It enters the second hydrogenation reactor (4) and is cracked under the action of Ni-S or Co-S sulfide catalyst to generate C1-C5 light hydrocarbons; (d) The reaction temperature is between 350℃ and 380℃, and the pressure is maintained at 8-10 MPa; (e) The reaction products are heated and then enter a first-stage stripping tower (6) and a first-stage vacuum tower (7) to collect C1-C5 light hydrocarbon components. The unreacted oil and gas are recovered as cracked tail oil. (f) C1-C5 light hydrocarbon components enter the desulfurization reactor (10) and are desulfurized under the action of ZnO / Al2O3 catalyst; (g) After desulfurization, the light hydrocarbons enter the light hydrocarbon conversion furnace (11) and are cracked under the action of ZSM-5 / β molecular sieve composite catalyst to produce hydrogen. (h) Hydrogen enters the converter (12) for further conversion to increase the yield; (i) The final hydrogen is purified by the PSA purification system (13) to obtain high-purity hydrogen.

2. The method for producing hydrogen by catalytic cracking of waste edible oils according to claim 1, characterized in that, The pressure of the first hydrogenation reactor is 10 MPa, and the pressure of the second hydrogenation reactor is 10 MPa.

3. The method for producing hydrogen by catalytic cracking of waste edible oils according to claim 1, characterized in that, The adsorbent used in the PSA purification system is a molecular sieve.

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