Low-energy-consumption hydrogen production system and method by means of reforming low-carbon hydrocarbons and steam

Abstract

The present invention belongs to the technical field of petrochemical engineering. Disclosed are a low-energy-consumption hydrogen production system and method by means of reforming low-carbon hydrocarbons and steam. According to the process of the present invention, by means of rationally and ingeniously designing a pipeline of the system, using a booster pump, additionally arranging a turbine, a power supply system and a heat exchanger, and increasing the pressure of low-carbon hydrocarbons and the pressure of the reaction of raw materials for hydrogen production, not only is the comprehensive utilization rate of liquid low-carbon hydrocarbons generated by a refinery plant and the energy in the system increased, but feeding can be carried out for raw materials in different states, and high-purity product hydrogen can be prepared with low energy consumption and low costs. Moreover, further provided in the present invention is a system which is based on an existing system for producing hydrogen from natural gas, has few changes in terms of the pipeline, low energy consumption, and a high degree of matching in terms of the process, and is particularly suitable for large-scale hydrogen production and recycling of liquid low-carbon hydrocarbons.

Description

A low-energy consumption low-carbon hydrocarbon steam reforming hydrogen production system and method Technical Field

[0001] The present invention belongs to the technical field of petrochemical industry, and in particular relates to a low-energy consumption low-carbon hydrocarbon steam reforming hydrogen production system and method. Background Art

[0002] With the widespread adoption of the cracking process (CP), the production of C3 and C4 low-carbon alkanes in the refining industry has increased, leading to a relative surplus of propane and butane. Some refineries directly burn these hydrocarbons as fuel, resulting in high-quality, low-efficiency energy. Consequently, the liquid low-carbon hydrocarbons (carbon number ≤ 6) produced as refinery byproducts are difficult to efficiently recover and utilize. Paraffin dehydrogenation (PDH) technology converts low-carbon alkanes into high-value-added olefins through catalytic dehydrogenation. However, the selectivity for the target olefins is low, and the investment and energy consumption are high, making it suitable only for large refineries and difficult for small refineries to implement.

[0003] As a chemical and energy product, hydrogen is widely used in industries such as oil refining, chemical engineering, and new energy. Generally speaking, catalytic reforming of liquid low-carbon hydrocarbons to produce hydrogen requires energy to convert them into gaseous reactants before the reaction in order to improve reaction efficiency, raw material utilization, and hydrogen conversion.

[0004] For this reason, most refineries currently use steam reforming (SR) of natural gas or refinery gas containing methane to produce hydrogen. The existing technology uses methane as the raw gas, which reacts with water vapor under high temperature and catalyst to produce hydrogen. The general reaction pressure requires 3.0MPa to 4.0MPa, so the power consumption of the raw gas pressurization is large, and the converted gas at about 800℃ to 900℃ after the reaction is only recovered by the waste heat boiler to produce steam. However, this process not only has the problem of large temperature difference at the heat exchange end of the waste heat boiler, but also has the problem of poor heat transfer. The drawbacks include high losses, as well as the ineffective recovery of pressure energy throughout the process, which results in low energy recovery efficiency during hydrogen production. Furthermore, considering the shortage of natural gas in some areas, the need to purchase liquefied natural gas as a hydrogen production feedstock, which results in high storage and transportation costs.

[0005] Therefore, there is an urgent need to develop a method for producing hydrogen through catalytic reforming that not only requires minimal changes to the existing system, but can effectively utilize liquid low-carbon hydrocarbons and has low energy consumption, high product purity, and low cost.

[0006] Summary of the Invention

[0007] The natural gas / refinery gas steam reforming hydrogen production process addresses the issues of high compressor energy consumption for the feed gas, the limited steam production from the waste heat of the reformed gas, resulting in low Second Law energy efficiency, and a relative surplus of propane and butane in some refineries. Furthermore, to overcome the existing issues of low energy recovery, low utilization of liquid low-carbon hydrocarbons, and high energy consumption for catalytic hydrogen production, one of the objectives of the present invention is to provide a low-energy method for producing hydrogen from low-carbon hydrocarbon steam reforming.

[0008] A second object of the present invention is to provide a low-energy consumption low-carbon hydrocarbon steam reforming hydrogen production system.

[0009] Key Concept / Inventive Concept of the Invention: The key to this invention lies in improving energy recovery efficiency and reducing hydrogen production feedstock costs. By rationally and ingeniously designing the system's piping and equipment, and increasing the pressure of the low-carbon hydrocarbon (liquid) feedstock to elevate the reaction pressure of the hydrogen production process, this invention not only increases the feedstock flow rate and enhances the comprehensive utilization of thermal and internal energy in the system, but also enables the feeding of liquid feedstock and the production of high-purity hydrogen product with low energy consumption.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] In a first aspect, the present invention provides a method for producing hydrogen by steam reforming low-carbon hydrocarbons with low energy consumption, comprising the following steps:

[0012] The raw materials are pressurized to 3.5-5.5 MPa, preheated and multi-stage heated to 340-380°C, then mixed with medium-pressure steam and subjected to catalytic reforming and hydrogen production reaction in the reformer to obtain reformed gas;

[0013] The converted gas undergoes a turbine expansion process and a waste heat boiler to recover internal energy and heat, undergoes a medium-temperature shift reaction at 390-420°C, and is cooled to obtain converted gas; a portion of the converted gas is used as a heat source for the preheating, and then is cooled and pressure-swing adsorbed to obtain product hydrogen and desorbed gas;

[0014] The reaction conditions of the catalytic reforming hydrogen production reaction are as follows: reaction pressure is 3.0-4.8 MPa, reaction temperature is 800-900°C; the heat source of the reformer comes from the heat generated by the combustion reaction of the desorbed gas, supplementary fuel and air.

[0015] Specifically, the medium-temperature shift reaction further produces hydrogen and converts carbon monoxide into carbon dioxide; the process recovers the waste heat of the shift gas for heating, effectively reducing the consumption of saturated steam for raw material preheating, effectively improving the utilization rate of saturated steam, and also reducing the cooling load of the shift gas.

[0016] In some embodiments, the method for producing hydrogen by steam reforming of low-carbon hydrocarbons with low energy consumption comprises the following steps:

[0017] 1) The raw materials are pressurized to 3.5-5.5 MPa, preheated and multi-stage heated to 340-380°C, desulfurized, mixed with medium-pressure steam, and then catalytically reformed in a reformer to produce hydrogen to obtain reformed gas;

[0018] 2) The converted gas is subjected to a medium-temperature shift reaction at 390-420°C by using a turbine expansion process to recover internal energy and a waste heat boiler to recover heat and produce steam, followed by cooling to obtain a first-stage converted gas. The first-stage converted gas is subjected to first-stage cooling and second-stage cooling to obtain a second-stage converted gas at 122-132°C.

[0019] 3) using the secondary shift gas of step 2) as a heat source for the preheating of step 1), followed by cooling and pressure swing adsorption to obtain product hydrogen and desorbed gas;

[0020] Wherein, the pressure of the medium-pressure steam in step 1) is 4.0-5.0 MPa and the temperature is 380-430° C.;

[0021] The reaction conditions of the catalytic reforming hydrogen production reaction in step 1) are as follows: the reaction pressure is 3.0-4.8 MPa, and the reaction temperature is 800-900°C; the heat source of the reformer in step 1) comes from the heat generated by the combustion reaction of the desorbed gas, supplementary fuel and air in step 3).

[0022] In some embodiments, the raw material in step 1) is pressurized to 4.0-5.3 MPa.

[0023] In some embodiments, step 1) further includes preheating the desulfurized raw material to 410-430° C. in a reformer, mixing it with medium-pressure steam, and then preheating it to 580-630° C. in a reformer, and then performing a catalytic reforming hydrogen production reaction in the furnace tubes of the reformer.

[0024] In some embodiments, the raw material in step 1) includes at least one of liquid propane, liquid butane, and liquid pentane.

[0025] In some embodiments, the raw material in step 1) comprises liquid propane; and the content of liquid propane is 95% to 99% (volume fraction).

[0026] In some embodiments, the raw material in step 1) further comprises gaseous alkanes, and in particular, the gaseous alkanes are selected from at least one of methane, ethane, propane, butane and pentane.

[0027] In some embodiments, the source of the liquid raw material in step 1) is one or more of a gas storage tank, an oil refinery, and a gas refinery.

[0028] Specifically, liquid propane and other low-carbon alkanes are common liquid low-carbon hydrocarbon byproducts produced in oil and gas refineries. They have a high carbon-to-hydrogen ratio, making them high-quality hydrogen production feedstocks, while also possessing high energy density. Based on these characteristics, the present invention proposes a low-energy method for producing hydrogen through steam reforming of low-carbon hydrocarbons by controlling reaction pressure and simplifying existing systems. The method also integrates a turbine and waste heat boiler to recover the pressure and thermal energy of the reformed gas, improving energy recovery efficiency.

[0029] In some embodiments, the pressure of the raw material in step 1) is 1.0 MPa to 1.8 MPa.

[0030] In some more preferred embodiments, the parameters of the raw materials in step 1) are as follows:

[0031] Main component: liquid propane, liquid propane content: 95% to 99% (volume fraction), temperature: 20 to 40° C., pressure: 1.4 to 1.6 MPa.

[0032] In some embodiments, the flow rate of the raw material in step 1) is 10 to 30 t / h.

[0033] In some preferred embodiments, the flow rate of the raw material in step 1) is 12 to 18 t / h.

[0034] In some embodiments, the pressure of the conversion gas in step 1) is 3.2-4.8 MPa.

[0035] In some embodiments, the pressure of the reformed gas at the inlet of the waste heat boiler is 2.6-3.2 MPa.

[0036] In some embodiments, the temperature of the reformed gas at the inlet of the waste heat boiler is 770-840°C.

[0037] In some embodiments, the catalyst for the catalytic reforming hydrogen production reaction in step 1) is one or more of Z417 and Z418. Specifically, Z417 and Z418 are both nickel-based catalysts.

[0038] In some embodiments, the flow rate of the medium-pressure steam in step 1) is 52 to 68 t / h.

[0039] In some embodiments, the steam flow rate used in the catalytic reforming hydrogen production reaction in step 1) is 52 to 68 t / h.

[0040] In some embodiments, the steam-to-carbon ratio of the catalytic reforming hydrogen production reaction in step 1) is 2.8 to 3.8.

[0041] In some preferred embodiments, the steam-to-carbon ratio of the catalytic reforming hydrogen production reaction in step 1) is 3.0 to 3.5.

[0042] Specifically, the steam carbon specifically refers to the ratio of the molar flow rate of water vapor to the carbon atoms in the feedstock.

[0043] In some embodiments, the hydrogen content in the conversion gas in step 1) is 65% to 73% (volume fraction, dry basis), and the CO content is 13% to 15% (volume fraction, dry basis).

[0044] In some embodiments, the process for preparing the medium-pressure steam in step 1) comprises:

[0045] The process condensed water generated by the cooling, primary cooling, and secondary cooling in step 2) is introduced into the middle of the sour water stripping tower; the process condensed water generated by the cooling in step 3) is introduced into the top of the sour water stripping tower; and heating steam is introduced into the bottom of the sour water stripping tower to separate acid gas and pure water;

[0046] The desalted water is heated to 100-112°C, mixed with a portion of pure water (i.e., recycled pure water) (to collect and deoxygenate the raw water), and then pressurized and heated to 265-282°C in the deoxygenated water heat exchanger, waste heat boiler, and saturated water evaporation section of the reformer to obtain saturated steam. The saturated steam is further heated to 400-450°C in the steam superheating section of the reformer to obtain superheated steam. The superheated steam is then cooled in the primary raw material heat exchanger to obtain medium-pressure steam.

[0047] Wherein, the pressure of the saturated steam is 4.0-5.0 MPa; the pressure of the superheated steam is 4.0-5.0 MPa.

[0048] In some embodiments, the multi-stage heating step in step 1) includes primary heating using part of the saturated steam as the heat source and secondary heating using part of the superheated steam as the heat source; the remaining part of the saturated steam is used to be heated to form superheated steam; and the remaining part of the superheated steam is directly transported outward. Specifically, for the saturated steam, the ratio of the flow rate as the heat source for primary heating and the flow rate used to be heated to form superheated steam is 1:(18-28); preferably 1:(20-26). For superheated steam, the ratio of the flow rate directly transported outward and the flow rate as the heat source for secondary heating is 1:(2.3-4.5); preferably 1:(2.5-4.2). It should be noted that the flow rate of the superheated steam used as the heat source for secondary heating is the same as the flow rate of forming medium-pressure steam.

[0049] In some embodiments, during the preparation of the medium-pressure steam, the total flow rate of the saturated steam is 65 to 95 t / h.

[0050] In some embodiments, during the preparation of the medium-pressure steam, the total flow rate of the superheated steam is 60 to 90 t / h.

[0051] In some embodiments, during the preparation of the medium-pressure steam, the steam production pressure of the waste heat boiler system is 4.0-5.0 MPa.

[0052] In some embodiments, during the preparation of the medium-pressure steam, the pressurization is specifically: pressurizing the desalted water and part of the pure water (i.e., recycled pure water) to 5.2-6.6 MPa for deoxygenation and ensuring that the steam can be transported to the next equipment, and finally participate in the catalytic reforming hydrogen production reaction.

[0053] In some embodiments, the internal energy recovered during the turbine expansion process in step 2) is converted into electrical energy and provided to the equipment in the process, thereby further reducing the energy consumption of the process.

[0054] In some embodiments, the isentropic efficiency in the turbine expansion process of step 2) is 70% to 80%, preferably 75%.

[0055] In some embodiments, the recovered energy of the turbine expansion process in step 2) is 1000 to 5000 kW.

[0056] In some embodiments, the cooling in step 3) is performed using an air cooler to cool to 40°C.

[0057] In some embodiments, the flow ratio of the product hydrogen to the desorbed gas in step 3) is 1:(8-9).

[0058] In some embodiments, the flow rate of the product hydrogen in step 3) is 4 to 6 t / h.

[0059] In some embodiments, the hydrogen in the product hydrogen of step 3) is (volume fraction is 95% to 99.9%). Preferably, the product hydrogen is 99.9% hydrogen.

[0060] In some embodiments, the flow rate of the supplementary fuel is 0.1 to 2 t / h, preferably 0.2 to 0.9 t / h.

[0061] In some embodiments, the flow rate ratio of the supplementary fuel to the desorbed gas is (20-180):1.

[0062] In some embodiments, the supplemental fuel is methane gas.

[0063] In some preferred embodiments, the air is preheated to 430-450° C. by the low-temperature air preheating section and the high-temperature air preheating section of the reformer, and then the combustion reaction occurs in the combustion chamber of the reformer.

[0064] In some embodiments, the air inlet temperature of the converter is 25°C; the temperature of the furnace tube inlet of the converter is 580-630°C; the temperature of the furnace tube outlet of the converter is 800-900°C and the pressure is 2.84-4.64 MPa; the temperature of the exhaust flue gas of the converter is 140-152°C, and the oxygen content of the exhaust flue gas is ≤3% (dry basis).

[0065] In a second aspect, the present invention provides a low-energy consumption low-carbon hydrocarbon steam reforming hydrogen production system comprising: a primary raw material heat exchanger, a secondary raw material heat exchanger, a desulfurization reactor, a reformer, a waste heat boiler system, a deoxygenated water heat exchanger, a medium-temperature shift reactor, a first shift gas separator, a hot water heat exchanger, a desalted water heat exchanger, a second shift gas separator, a shift gas cooler, a third shift gas separator, a pressure swing adsorption system, and an acidic water stripping tower; the waste heat boiler system comprises a waste heat boiler and a waste boiler steam-water separator; the combustion chamber of the reformer is provided with inlets for air and supplementary fuel;

[0066] It also includes a feed booster pump, preheating heat exchanger, turbo expander, generator, and bypass valve;

[0067] The raw material booster pump is connected to the preheating heat exchanger, the primary raw material heat exchanger, the secondary raw material heat exchanger, the desulfurization reactor, the converter, the waste heat boiler, the medium-temperature shift reactor, the deaerated water heat exchanger, and the first shift gas separator through pipelines in sequence;

[0068] A pipeline for accessing medium-pressure steam is provided on the pipeline between the desulfurization reactor and the reformer;

[0069] The turbine expander and bypass valve are connected in parallel to the pipeline between the reformer and the waste heat boiler to recover the internal energy of the reformed gas and ensure stable operation of the system;

[0070] The top of the first shift gas separator is connected to a hot water heat exchanger, a desalted water heat exchanger, and a second shift gas separator in sequence through pipelines; the top of the second shift gas separator is connected to a preheating heat exchanger, and then to a shift gas cooler and a third shift gas separator; the top of the third shift gas separator is connected to a pressure swing adsorption system, and the pressure swing adsorption system is provided with an output pipeline for product hydrogen and a pipeline for supplying desorbed gas (or fuel gas) to the reformer;

[0071] The bottom of the first shift gas separator is connected to the bottom of the second shift gas separator through a pipeline, and then connected to the middle feed port of the acidic water stripping tower.

[0072] Specifically, the waste heat boiler and waste heat separator constitute a waste heat boiler system, which is used to recover heat and generate saturated steam. Since low-carbon hydrocarbons have a high hydrogen-to-carbon ratio and are mostly in liquid phase, the raw material pressurization equipment can be replaced by a pump, significantly reducing the energy consumption of pressurization. At the same time, the operating pressure of the reformer is appropriately increased, and a turbine is installed at its outlet to first recover the pressure energy and high-temperature thermal energy of the reformed gas to directly perform work, and then recover the heat energy through the waste heat boiler to produce steam. At the same time, the thermal energy of the converted gas can be cleverly utilized to heat the raw materials. In addition, when the system is unstable, the bypass valve can be opened to stabilize the entire system. When the system is stable, the flow rate of the fluid through the bypass valve is zero.

[0073] In some embodiments, the converter includes, from the low-temperature zone to the high-temperature zone, a low-temperature air preheating section, a saturated water evaporation section, a high-temperature air preheating section, a desulfurization raw material preheating section, a steam superheating section, a conversion raw material preheating section and a radiation section; the radiation section is provided with furnace tubes and a combustion chamber.

[0074] In some embodiments, the air pipeline in the converter enters from the low-temperature air inlet, passes through the low-temperature air preheating section, the high-temperature air preheating section, and is connected to the hot air inlet of the radiation section combustion chamber.

[0075] In some embodiments, the gas outlet of the desulfurization reactor passes through a pipeline, passes through the desulfurization raw material preheating section of the converter, and is connected to the medium-pressure steam access pipeline from the secondary raw material heat exchanger; and then passes through the steam superheating section of the converter and is connected to the furnace tube of the converter.

[0076] In some embodiments, the bottom of the first shift gas separator is connected to the bottom of the second shift gas separator through a pipeline (for collecting process condensed water), and then connected to the middle feed port of the sour water stripping tower; the bottom of the third shift gas separator is connected to the top feed port of the sour water stripping tower through a pipeline; the bottom of the sour water stripping tower is provided with a steam inlet and a purified water output pipeline, and the top of the sour water stripping tower is provided with an acid gas outlet.

[0077] In some embodiments, the low-energy consumption low-carbon hydrocarbon steam reforming hydrogen production system further comprises: a feed gas compressor, a deaerator, and a deoxygenated water booster pump;

[0078] The deionized water heat exchanger is connected to the deaerator, deionized water booster pump, and deionized water heat exchanger in sequence through pipelines, and then connected to the waste heat boiler and the waste heat boiler steam-water separator to provide saturated water raw material to the waste heat boiler steam-water separator.

[0079] In some embodiments, the raw gas compressor and the raw material booster pump are connected to the system in parallel, and the raw gas compressor is connected to the primary raw material heater to achieve mixed feeding of gaseous and liquid raw materials.

[0080] In some embodiments, a pipeline passing through the saturated water evaporation section of the reformer is provided at the bottom of the residual boiler steam-water separator, so as to produce saturated steam by recycling the heat of the reformer.

[0081] In some embodiments, the pipeline at the top of the residual boiler steam-water separator is divided into two routes, one route passes through the steam superheating section of the converter to generate superheated steam; the other route is connected to the primary raw material heat exchanger and the deaerator to recover the heat in the superheated steam and use it for the primary heating of the raw material and the heating of the deaerator.

[0082] In some embodiments, the deaerator is provided with an access pipeline for a primary raw material heat exchanger; the deaerator is also provided with an access pipeline for supplementary steam for heating the desalted water.

[0083] In some embodiments, the pipeline after passing through the steam superheating section of the converter is further divided into two routes, one of which is connected to the direct external transmission pipeline for the external transmission of superheated steam; the other is connected to the secondary raw material heat exchanger for secondary heating of the raw material.

[0084] In some embodiments, the output pipeline of the purified water at the bottom of the sour water stripping tower is divided into two routes, one for direct output and the other connected to the deaerator to provide recycled pure water and mix it with deoxygenated water.

[0085] In some embodiments, the turboexpander is further connected to a generator via a wire, so as to achieve conversion of the internal energy of the conversion gas into mechanical energy and electrical energy, and improve the internal energy utilization rate of the conversion gas in the system.

[0086] In some embodiments, the generator is connected to a boosting device via a wire to provide power to the system. Specifically, the boosting device is at least one of a raw gas compressor, a raw material boosting pump, and a deoxygenated water boosting pump.

[0087] In some embodiments, the hot water heat exchanger is provided with an inlet for a heat medium, which is hot water at 65-75°C.

[0088] In some embodiments, the pressure swing adsorption system includes an adsorber, a buffer tank, a program control valve, a regulating valve, a pipeline and other equipment.

[0089] The present invention provides a catalytic reforming hydrogen production process that not only meets different feedstock feed conditions but also effectively utilizes liquid low-carbon hydrocarbons, resulting in low energy consumption, high product hydrogen purity, and low cost. Furthermore, the present invention provides a catalytic reforming hydrogen production system compatible with the aforementioned process, requiring minimal modification to existing systems, low energy consumption, high product purity, and high feedstock utilization.

[0090] Specifically:

[0091] (1) The present invention enriches the application of low-carbon hydrocarbons such as liquid propane and liquid butane in refineries, and particularly provides new high-carbon-to-hydrogen ratio high-quality hydrogen production raw materials for refineries with limited natural gas supply;

[0092] (2) The raw material pressurizing equipment of the present invention is a pump, which can be effectively used for liquid low-carbon hydrocarbons, and the power consumption of raw material pressurization is greatly reduced;

[0093] (3) The present invention recovers the waste heat of the conversion gas to vaporize the liquid raw material, thereby reducing the raw material preheating steam consumption and reducing the cooling load of the conversion gas;

[0094] (4) The present invention greatly improves the energy efficiency of the reformed gas according to the second law of thermodynamics by adding a gas expansion turbine at the outlet of the reformer. The reformed gas temperature in the prior art is 860°C, while the saturation temperature of the 3.5MPag (gauge pressure, i.e. 3.5MPa) medium-pressure steam produced is only 244°C, and the heat transfer temperature difference in the steam production process is 616°C, which is a typical high-energy, low-use. After the turbine works, the reformed gas temperature drops significantly, thereby reducing the heat transfer temperature difference in the steam production process, which can not only ensure the operation of the medium-pressure reactor, but also greatly improve the energy efficiency of the reformed gas. Although the output energy of the turbine work will reduce the output of medium-pressure steam, exchanging electricity for steam is an equivalent energy upgrade.

[0095] (5) The present invention provides an expansion turbine bypass to ensure process stability;

[0096] (6) The present invention is not only applicable to the system transformation of natural gas / methane hydrogen production, but also can reduce the energy consumption and production cost of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] FIG1 is a schematic structural diagram of a low-carbon hydrocarbon steam reforming hydrogen production system in a comparative example of the present invention.

[0098] FIG2 is a schematic structural diagram of an improved low-energy-consuming low-carbon hydrocarbon steam reforming hydrogen production system in an embodiment of the present invention.

[0099] FIG3 is a partially enlarged structural diagram of the low-carbon hydrocarbon steam reforming hydrogen production system of the present invention.

[0100] Figure 1: 1-Feed gas compressor; 2-Feed gas to saturated steam heat exchanger; 3-Feed gas to superheated steam heat exchanger; 4-Desulfurization reactor; 5-Converter; 6-Waste heat boiler; 7-Medium temperature shift reactor; 8-Deaerated water heat exchanger; 9-Shift gas first liquid separator; 10-Hot water heat exchanger; 11-Desalted water heat exchanger; 12-Shift gas second liquid separator; 13-Shift gas cooler; 14-Shift gas third liquid separator; 15-Hydrogen-rich gas pressure swing adsorption system; 16-Sour water stripping tower; 17-Deaerator; 18-Deaerated water booster pump; 19-Steam separator; 20-Feed gas booster pump; 21-Liquid feed gas to second liquid separator top gas heat exchanger; 22-Turbine to power supply system; 23-Bypass valve; 5-Converter includes: 501-radiation section, 502-conversion raw material preheating section, 503-steam superheating section, 504-desulfurization raw material preheating section, 505-high temperature air preheating section, 506-saturated water evaporation section, 507-low temperature air preheating section. DETAILED DESCRIPTION

[0101] The present invention is further described in detail below through specific examples.

[0102] Unless otherwise specified, the furnace tube in which the hydrogen production reaction occurs in the reformer 5 of the present invention is arranged in the radiation section 501 of the reformer 5, and the radiation section 501 also includes a combustion chamber; the hydrogen-rich gas pressure swing adsorption system 15 of the present invention is a pressure swing adsorption system commonly used on the market, which at least includes an adsorber, a buffer tank, a program control valve, a regulating valve and pipelines and other equipment; in the low-carbon hydrocarbon steam reforming hydrogen production system, a number of valves, flow meters, pressure gauges, thermometers, pumps and other equipment that can be used for monitoring the system can also be set according to demand (not drawn in Figures 1 or 2), but relevant personnel cannot use this as a limitation to the embodiments of the present invention. The discharge port of low-carbon hydrocarbons refers to the outlet of materials containing alkanes with 1 to 5 carbon atoms (for example, methane, ethane, propane, butane, pentane), and the source of low-carbon hydrocarbons is the pipeline of the refinery or the storage tank of low-carbon hydrocarbons; the equipment in the low-carbon hydrocarbon steam reforming hydrogen production system of the embodiment of the present invention and the comparative example are all connected by pipelines.

[0103] Unless otherwise specified, the conversion gas cooler 13 used in the comparative examples and the examples is an air cooler device with a model of GP6*3-6-128-3.0SF-23.4 / DR-Ⅲ and a manufacturer of the Hubei Electric Power Company Hankou Electric Power Equipment Factory; and the pressures in the comparative examples and the examples are all gauge pressures; the "steam carbon ratio" in the comparative examples and the examples refers to the ratio of the molar flow rate of water vapor in the converter 5 equipment to the carbon atoms in the raw material; the "low carbon hydrocarbons" in the present invention refer to one or more of methane, ethane, propane, butane and pentane.

[0104] It should also be noted that "to 19," "from 8," "to 17," and "from 2" in Figures 1 and 2 respectively represent "pipeline connected to the waste heat boiler steam-water separator 19," "pipeline connected to the deaerated water heat exchanger 8," "pipeline connected to the deaerator 17," and "pipeline connected to the hydrogen-rich gas pressure swing adsorption system 15." Regarding "to 19," it should also be noted that the waste heat boiler system in this comparative example includes the waste heat boiler 6 and the waste heat boiler steam-water separator 19, which are connected by a pipeline. The raw water (desalted water and recycled purified water) is actually introduced into the waste heat boiler system from the deaerated water heat exchanger 8, and ultimately forms saturated steam in the waste heat boiler steam-water separator 19 using the heat from the saturated water evaporation section 506 of the reformer 5.

[0105] In an embodiment, the hydrogen content in the reformed gas is 65% to 73% (volume fraction, dry basis), and the CO content is 13% to 15% (volume fraction, dry basis);

[0106] The combustion reaction occurs in the reformer's combustion chamber after air is preheated to 430-450°C in the reformer's low-temperature and high-temperature air preheating sections. The reformer's air inlet temperature is 25°C; the reformer's tube inlet temperature is 580-630°C; the reformer's tube outlet temperature is 800-900°C and the pressure is 2.84-4.64 MPa. The reformer's exhaust gas temperature is 140-152°C, and the exhaust gas oxygen content is ≤3% (dry basis).

[0107] Comparative Example 1

[0108] Low carbon hydrocarbon steam reforming hydrogen production system:

[0109] This comparative example provides a low-carbon hydrocarbon steam reforming hydrogen production system (see Figure 1), including a feed gas compressor 1; a feed-to-saturated steam heat exchanger 2; a feed-to-superheated steam heat exchanger 3; a desulfurization reactor 4; a reformer 5; a waste heat boiler 6; a medium-temperature shift reactor 7; a deaerated water heat exchanger 8; a first shift gas separator 9; a hot water heat exchanger 10; a desalted water heat exchanger 11; a second shift gas separator 12; a shift gas cooler 13; a third shift gas separator 14; a hydrogen-rich gas pressure swing adsorption system 15; an acidic water stripping tower 16; a deaerator 17; a deaerated water booster pump 18 and a residual boiler steam-water separator 19;

[0110] The structure of the low-carbon hydrocarbon steam reforming hydrogen production system of this comparative example (see Figures 1 and 3) specifically includes:

[0111] The outlet of the raw gas of low-carbon hydrocarbons is connected to the raw gas compressor 1, the steam heat exchanger 2, the raw material-superheated steam heat exchanger 3, and the desulfurization reactor 4 in sequence through pipelines, passes through the desulfurization raw material preheating section 504 of the converter 5, the conversion raw material preheating section 502 of the converter 5, and is then connected to the furnace tube of the converter 5, the waste heat boiler 6, the medium-temperature conversion reactor 7, the deoxygenated water heat exchanger 8 and the first conversion gas separator 9.

[0112] The gas outlet at the top of the first conversion gas separator 9 is connected to the hot water heat exchanger 10, the desalted water heat exchanger 11, and the second conversion gas separator 12 in sequence through pipelines; the gas outlet at the top of the second conversion gas separator 12 is connected to the conversion gas cooler 13, the third conversion gas separator 14 and the hydrogen-rich gas pressure swing adsorption system 15 through pipelines, and is used to cool, separate and purify the mixed gas to obtain higher-purity product hydrogen and fuel; the hydrogen-rich gas pressure swing adsorption system 15 is provided with two pipeline outlets, one pipeline outlet is used to output the product hydrogen outlet; and the other pipeline outlet is connected to the combustion chamber of the reformer 5 for providing fuel.

[0113] The bottom of the third shift gas separator 14 is connected to the top feed port of the sour water stripping tower 16. The liquid outlet at the bottom of the first shift gas separator 9 is connected to the liquid outlet at the bottom of the second shift gas separator 12, and then connected to the middle (center) feed port of the sour water stripping tower 16 via a pipeline. The bottom of the sour water stripping tower 16 is provided with an inlet for heating steam (1.0 MPa steam) and a discharge pipe for purified water, which are used to remove acidic substances such as carbon dioxide and obtain recycled purified water. Specifically, the top of the sour water stripping tower 16 is provided with an acid gas outlet for discharging trace acidic gases (such as carbon dioxide). The purified water discharge pipe at the bottom of the sour water stripping tower 16 is divided into two routes: one route is connected to the second feed port of the deaerator 17, used to provide recycled purified water to the deaerator 17, and the other route is discharged as wastewater (essentially water, with little pollution).

[0114] The deaerator 17 is connected to the heat source outlet of the steam heat exchanger 2 to provide a heat source for heating the deaerator 17; at the same time, the deaerator 17 is also provided with a steam supplementary pipeline for supplementing the heat source (not used in this comparative example).

[0115] The desalted water heat exchanger 11 is provided with a desalted water inlet; the desalted water heat exchanger 11 is also connected to the first feed inlet of the deaerator 17, the deoxygenated water booster pump 18, the deoxygenated water heat exchanger 8, and the waste heat boiler system (including the waste heat boiler 6 and the waste heat boiler steam-water separator 19), and is used to provide saturated water to the waste heat boiler steam-water separator 19; the bottom of the waste heat boiler steam-water separator 19 is provided with a pipeline passing through the saturated water evaporation section 506 of 5, which is used to recover and utilize the heat of the converter 5 and generate saturated steam.

[0116] The steam-water separator 19 is also equipped with two saturated steam outflow pipelines. One pipeline is connected to the feedstock-to-saturated steam heat exchanger 2 and the deaerator 17, providing a heat source and heat to these two units. Another pipeline is connected to the steam superheating section 503 of the reformer 5, recovering heat from the higher-temperature flue gas to generate superheated steam. The steam superheating section 503 pipeline is then similarly split into two: one is directly discharged (or transported externally); the other is connected to the feedstock-to-superheated steam heat exchanger 3 and then to the pipeline located between the desulfurization feedstock preheating section 504 and the reformer feedstock preheating section 502 of the reformer 5. This pipeline is used to mix the superheated steam with light hydrocarbons and provide the steam reforming reaction gas for hydrogen production in the reformer 5 tubes.

[0117] It should also be noted that the converter 5 (see Figure 3) includes, from the high-temperature section (about 900°C) to the low-temperature section (about 150°C), a radiation section 501 (including a combustion chamber, a supplementary fuel gas inlet, a hot air inlet and a desorption gas inlet), a conversion raw material preheating section 502, a steam superheating section 503, a desulfurization raw material preheating section 504, a high-temperature air preheating section 505, a saturated water evaporation section 506 and a low-temperature air preheating section 507 (including an air inlet and a smoke exhaust port).

[0118] All of the above devices are connected through pipelines.

[0119] Method for producing hydrogen by steam reforming of low-carbon hydrocarbons:

[0120] This comparative example provides a method for producing hydrogen by steam reforming low-carbon hydrocarbons in an existing refinery. 4 Nm 3 / h) as an example, the specific steps include the following (see Figure 1 and Figure 3):

[0121] Raw gas (component: CH4, purity: methane mole fraction ≥ 97.5%, total sulfur ≤ 20 mg / m 3 、Temperature: 25℃、Pressure: 0.6MPa、Flow rate: 13.1t / h, i.e. 18303.3Nm 3 / h) is pressurized to 3.5MPa (pressure at the compressor outlet, gauge pressure) by the raw gas compressor 1, heated to 380℃ by the raw material-saturated steam heat exchanger 2 (heat source: saturated steam, 244℃) and the raw material-superheated steam heat exchanger 3 (heat source: superheated steam, 430℃), and desulfurized in the desulfurization reactor 4 until the sulfur content is less than 0.05-0.1ppm. The desulfurized raw material preheating section 504 of the reformer 5 is preheated to 430℃ and mixed with medium-pressure steam ( The raw materials are mixed (pressure: 3.5 MPa, temperature: 365°C, flow rate: 44.1 t / h), and then heated to 630°C in the reforming raw material preheating section 502 of the reformer 5. Then, a catalytic reforming reaction for hydrogen production is carried out in the furnace tubes of the reformer 5 (reaction temperature: 860°C, reaction pressure: 3.0 MPa, catalyst Z418, reaction steam consumption: 44.1 t / h, steam-to-carbon ratio: 3.0), to produce reformed gas (temperature: 860°C, pressure: 2.84 MPa, flow rate: 57.2 t / h, H2 content: 72.7%, CO content: 13.1%, dry basis);

[0122] The reformed gas is heat recovered by the waste heat boiler 6 until the temperature is reduced to 340°C, and then enters the medium temperature shift reactor 7 to remove carbon monoxide (temperature: 410°C, catalyst: B113-2, converting carbon monoxide and water into hydrogen and carbon dioxide), and is cooled to 160°C by the cold fluid of the deoxygenated water heat exchanger 8. The first-stage reformed gas (temperature: 160°C, pressure: 2.78MPa, flow rate: 51.7t / h) and process condensate are obtained in the first liquid separation tank 9 of the reformed gas; the first-stage reformed gas is heated to 400°C and then heated to 800°C. The gas is cooled to 130°C by the heat exchanger 10 (cold source: 65°C hot water, flow rate of the cold source: 75t / h) and the desalted water heat exchanger 11, and the secondary conversion gas (130°C, 2.63MPa, flow rate: 41.2t / h) and process condensate are obtained in the second conversion gas separator 12; the secondary conversion gas is cooled to 40°C by the conversion gas cooler 13, and the tertiary conversion gas (40°C, 2.52MPa, flow rate: 34.7t / h) and process condensate are obtained in the third conversion gas separator 14.

[0123] Process condensate (temperature: 160°C, total flow rate: 16.1 t / h) from the first and second shift gas separators 9, 12, and 1.0 MPa steam (temperature: 185°C, flow rate: 0 t / h) from the third shift gas separator 14 are fed into the middle, top, and bottom of the sour water stripping column 16, respectively, to produce acid gas and water (flow rate: 22.5 t / h). Part of this water is directly discharged as wastewater, while the remaining part is recycled as purified water (flow rate: 22.5 t / h, temperature: 112°C) and mixed with heated desalted water in the deaerator 17 for use as raw material.

[0124] The three-stage conversion gas is subjected to the pressure swing adsorption (PSA) process of the hydrogen-rich gas pressure swing adsorption system 15 (key process parameters: hydrogen recovery rate ≥ 90%, adsorbent: porous solid material) to obtain product hydrogen (flow rate: 4.54t / h, 2×10 4 Nm 3 / h, in terms of volume fraction, the purity of hydrogen is 99.9%) and desorbed gas (composition: 99.9% hydrogen, flow rate: 30.15t / h, 24002Nm 3 / h, calorific value: 2234.0kcal / Nm 3 ).

[0125] Air (flow rate: 102 t / h, temperature: 25°C) is heated to 430°C by the low-temperature air preheating section 507 and the high-temperature air preheating section 505 of the converter 5. The three gases, desorbed gas (flow rate: 30.15 t / h) and supplementary fuel gas (component: CH4, flow rate: 1.53 t / h), are mixed and burned in the combustion chamber of the converter 5 to produce high-temperature flue gas (about 900°C), which provides heat to the converter 5. The exhaust gas temperature of the converter 5 (i.e., the temperature of the exhaust gas) is 150.4°C, and the dry basis oxygen content is 3% (volume fraction).

[0126] Desalted water (flow rate: 42.84 t / h, temperature: 30°C) is heated to 110°C in desalted water heat exchanger 11 and mixed with recycled purified water (flow rate: 22.5, temperature: 112°C) produced at the bottom of tower 16. The water is then deoxygenated in deaerator 17, pressurized to 5.2 MPa by deoxygenated water booster pump 18, heated to 265°C in deoxygenated water heat exchanger 8, and further heated to 267°C in waste heat boiler 6. Heat from the saturated water evaporation section 506 of the reformer 5 is then used to generate 3.5 MPa saturated steam (flow rate: 67.5 t / h, temperature: 244°C) in the waste heat boiler separator 19. The waste heat boiler system, consisting of waste heat boiler 6 and waste heat boiler separator 19, produces 3.5 MPa steam.

[0127] The saturated steam is heated by the flue gas in the steam superheating section 503 of the reformer 5 to obtain superheated steam (flow rate: 65.3 t / h, temperature: 430°C); the remaining saturated steam (flow rate: 2.2 t / h) is used as a heat source to provide heat to the raw material-saturated steam heat exchanger 2. This part of the saturated steam (244°C) is used as the heat source for the raw material-saturated steam heat exchanger 2, and then as the heat source (220°C) of the deaerator 17 for heat recovery and utilization, which can heat the raw material in the deaerator 17 to 118°C.

[0128] The superheated steam is divided into two parts, one part (flow rate: 21.2t / h) is output; the other part (flow rate: 44.1t / h) is used to cool the raw material ~ superheated steam heat exchanger 3 to obtain medium-pressure steam, which is used for catalytic reforming hydrogen production reaction.

[0129] Supplementary explanation of system and process:

[0130] The sour water stripping tower 16 is actually a 20m high packed tower; the flow rate of 1.0MPa steam in the sour water stripping tower 16 is 0.1t / h; the sour water stripping tower 16 removes trace impurities such as CO2, and finally the carbon dioxide is discharged from the top of the sour water stripping tower 16 in the form of acid gas.

[0131] The desorbed gas is used as the main fuel to provide heat for the converter, and natural gas is used as the auxiliary fuel. After being mixed with the preheated high-temperature air, it is sent into the converter combustion chamber for combustion. The high-temperature flue gas provides heat for the steam reforming reaction in the radiation section 501, and then passes through the conversion raw material preheating section 502, the steam superheating section 503, the desulfurization raw material preheating section 504, the high-temperature air preheating section 505, the saturated water evaporation section 506, and the low-temperature air preheating section 507 for cooling, and the oxygen content of the flue gas at the converter outlet is controlled to be 3% (dry basis).

[0132] The specific process of pressure swing adsorption (PSA) is: adsorption, forward pressure reduction, reverse pressure release, flushing, and pressure increase.

[0133] Example 1

[0134] Compared with Comparative Example 1, the low-energy-consuming low-carbon hydrocarbon steam reforming hydrogen production system of this embodiment further includes a liquid-phase raw material-second liquid separation tank top gas heat exchanger 21, a turbine-power supply system 22 and a bypass valve 23, and changes the access method of the conversion gas cooler 13.

[0135] Low-energy-consuming low-carbon hydrocarbon steam reforming hydrogen production system:

[0136] The structural diagram of the low-energy-consuming low-carbon hydrocarbon steam reforming hydrogen production system of this embodiment is specifically shown in Figures 2 and 3; and the structure of the low-energy-consuming low-carbon hydrocarbon steam reforming hydrogen production system of this embodiment is modified based on the comparative example; the modifications are as follows:

[0137] 1) Stop the raw gas compressor 1 and install a raw material booster pump 20 at the corresponding position for feeding, pressurizing and heating liquid low-carbon hydrocarbons;

[0138] 2) A liquid phase raw material to second liquid separation tank top gas heat exchanger 21 is added to the pipeline between the raw material booster pump 20 and the raw material to saturated steam heat exchanger 2;

[0139] 3) The gas outlet pipeline at the top of the second shift gas separator 12 is modified to connect sequentially to the liquid-phase feedstock to the second split tank top gas heat exchanger 21, the shift gas cooler 13, and the third shift gas separator 14. This is used to recover heat from the second shift gas separator 12 to heat the liquid-phase feedstock to the second split tank top gas heat exchanger 21 and reduce the energy consumption of the shift gas cooler 13 (see Table 1), thereby obtaining tertiary shift gas and process condensate.

[0140] 4) A turbine-power supply system 22 and a bypass valve 23 are added between the reformed gas outlet of the reformer 5 and the waste heat boiler 6; the turbine-power supply system 22 and the bypass valve 23 are connected in parallel to facilitate the pressure of the turbine-power supply system 22 and to recover part of the internal energy in the reformed gas.

[0141] The raw material booster pump 20 used in this embodiment is a centrifugal pump.

[0142] The turbine-power supply system 22 used in this embodiment includes a turbine expander and a generator. The turbine expander and the generator are connected via a driveable link. The turbine expander converts internal energy into mechanical energy, while the generator converts mechanical energy into electrical energy. Furthermore, the generator can be connected to an energy storage device or electrical energy output conductors to store energy, directly output electrical energy, or directly use it in the devices of this embodiment, further reducing energy consumption.

[0143] It should also be noted that the low-carbon hydrocarbon steam reforming hydrogen production system of this embodiment retains the original pipeline and equipment functions by means of deactivating the raw gas compressor 1 and its related pipelines, and adding pipelines and valves; and the raw gas compressor 1 and the raw material booster pump 20 are connected to the system in parallel, and a gas-liquid separator can be added between the two through the pipeline to further create conditions for gas-liquid mixed feeding. If the raw materials include gaseous and liquid low-carbon hydrocarbons, the gaseous and liquid low-carbon hydrocarbons can be mixed and fed by opening the relevant equipment (such as the raw gas compressor 1) and the corresponding valves, and the flow of the relevant pipelines can be adjusted to achieve a process of low-carbon hydrocarbon catalytic reforming hydrogen production with reduced energy consumption.

[0144] Low-energy method for producing hydrogen by steam reforming of low-carbon hydrocarbons:

[0145] This embodiment provides an improved low-energy-consuming process for producing hydrogen from steam reforming of low-carbon hydrocarbons. 4 Nm 3 / h) as an example, the details are as follows (see Figure 2 for the process flow):

[0146] Raw materials (components: liquid C3H6, purity: propane mole fraction ≥ 95%, total sulfur ≤ 10mg / m 3、Temperature: 35℃、Pressure: 1.5MPa、Flow rate: 14.7t / h, i.e. 7466Nm 3 / h) is pressurized to 4.0 MPa (pressure at the compressor outlet, gauge pressure) by the raw material booster pump 20, and heated to 380°C by the liquid-phase raw material-second liquid separation tank top gas heat exchanger 21 (heat source: secondary conversion gas, 130°C), the raw material-saturated steam heat exchanger 2 (heat source: saturated steam, 252°C), and the raw material-superheated steam heat exchanger 3 (heat source: superheated steam, 430°C). The desulfurization reactor 4 performs desulfurization treatment, and the desulfurization raw material preheating section 504 of the reformer 5 is preheated to 430°C and mixed with medium-pressure steam (pressure: 4.0 MPa). a, temperature: 375 ℃, flow rate: 54t / h) are mixed, and then heated to 630 ℃ by the conversion raw material preheating section 502 of the reformer 5, and then a catalytic reforming hydrogen production reaction (temperature: 860 ℃, reaction pressure: 3.5MPa, catalyst: Z418, reaction steam consumption: 54t / h, steam-to-carbon ratio 3.0) is carried out in the furnace tube of the reformer 5 to obtain reformed gas (temperature: 860 ℃, pressure: 3.34Mpa, flow rate: 68.7t / h, H2 content 68.1%, CO content 14.7%, dry basis);

[0147] The reformed gas first passes through the parallel turbine-power supply system 22 and bypass valve 23 to recover and recycle its internal energy (recovered energy / external work: 1510.45 kW, isentropic efficiency η = 75%). The outlet gas of the turbine-power supply system 22 (832°C, 2.84 MPa) is then cooled to 340°C by waste heat boiler 6 for heat recovery. It then enters the medium-temperature shift reactor 7 for carbon monoxide removal and is cooled to 160°C by the cold fluid of the deoxygenated water heat exchanger 8. The first-stage reformed gas (temperature: The first-stage shift gas is cooled to 130°C through a hot water heat exchanger 10 (cold source: 65°C hot water, cold source flow rate: 77.2 t / h) and a desalted water heat exchanger 11, and the second-stage shift gas (130°C, 2.63 MPa, flow rate: 49.1 t / h) and process condensate is obtained in the second shift gas separator 12.

[0148] The secondary conversion gas is pre-cooled to 115°C through the conversion gas filter 21, and then cooled to 40°C through the cooler 13. The tertiary conversion gas (40°C, 2.52MPa, flow rate: 42.2t / h) and process condensate are obtained in the conversion gas third liquid separator 14.

[0149] Process condensate (temperature: 133°C, total flow rate: 19.7 t / h) from the first and second shift gas separators 9, 12, and 1.0 MPa steam (temperature: 184°C, flow rate: 0.1 t / h) from the third shift gas separator 14 are fed into the middle, top, and bottom of the sour water stripping column 16, respectively, to produce acid gas and water (flow rate: 26.5 t / h). Part of this water is directly discharged as wastewater, while the remaining part is recycled as purified water (flow rate: 26.5 t / h, temperature: 115°C) and mixed with heated desalted water in the deaerator 17 for use as raw material.

[0150] The three-stage conversion gas is subjected to the pressure swing adsorption (PSA) process of the hydrogen-rich gas pressure swing adsorption system 15 to obtain product hydrogen (flow rate: 4.54t / h, 2×10 4 Nm 3 / h, in terms of volume fraction, the purity of hydrogen is 99.9%) and desorbed gas (composition: 99.9% hydrogen, flow rate: 37.63t / h, 28112.2Nm 3 / h, calorific value: 2034.3kcal / Nm 3 ).

[0151] Air (flow rate: 98 t / h, temperature: 25°C) is heated to 430°C by the low-temperature air preheating section 507 and the high-temperature air preheating section 505 of the converter 5. The three gases, desorbed gas (flow rate: 37.63 t / h) and supplementary fuel gas (component: CH4, flow rate: 0.83 t / h), are mixed and burned in the combustion chamber of the converter 5 to produce high-temperature flue gas (about 900°C), which provides heat to the converter 5. The exhaust gas temperature of the converter 5 (i.e., the temperature of the exhaust gas) is 150.4°C, and the dry basis oxygen content is 3% (volume fraction).

[0152] Desalted water (flow rate: 41.4 t / h, temperature: 30°C) is heated to 125°C in desalted water heat exchanger 11 and mixed with recycled purified water (flow rate: 26.5 t / h, temperature: 115°C) produced at the bottom of tower 16. It is then deoxygenated in deaerator 17, pressurized to 5.2 MPa by deoxygenated water booster pump 18, heated to 265°C in deoxygenated water heat exchanger 8, and further heated to 267°C in waste heat boiler 6. Heat from the saturated water evaporation section 506 of the reformer 5 is then utilized to produce 4.0 MPa saturated steam (flow rate: 70.9 t / h, temperature: 252°C) in the waste heat boiler separator 19. The waste heat boiler system, consisting of waste heat boiler 6 and waste heat boiler separator 19, produces steam at a pressure of 4.0 MPa.

[0153] 4.0MPa saturated steam is heated by the flue gas of the steam superheating section 503 of the reformer 5 to obtain superheated steam (flow rate: 68t / h, temperature: 430℃); the remaining 4.0MPa saturated steam (flow rate: 2.9t / h) is used as a heat source to provide heat to the raw material-saturated steam heat exchanger 2. This part of 4.0MPa saturated steam (252℃) is used as the heat source of the raw material-saturated steam heat exchanger 2, and then as the heat source (248℃) of the deaerator 17 for heat recovery and utilization, which can heat the raw material in the deaerator 17 to 126℃.

[0154] The superheated steam is divided into two parts, one part (flow rate: 14t / h) is discharged directly; the other part (flow rate: 54t / h) is used for the raw material-superheated steam heat exchanger 3 to obtain medium-pressure steam, which is used for catalytic reforming hydrogen production reaction.

[0155] The embodiments are improvements based on the comparative examples. Other equipment and parameters not specifically described are essentially the same as those in the comparative examples. Unless otherwise specified, the equipment, devices, or system connections in the embodiments and comparative examples are generally pipeline connections, which are conventional in the art. Furthermore, to facilitate system operation, the system pipelines are also equipped with flow meters, thermometers, and pressure gauges, which are also conventional in the art.

[0156] Energy consumption comparison

[0157] Since the source of the low-carbon hydrocarbons in the raw materials of Comparative Example 1 and Example 1 can be a pipeline or product of an oil refinery, the main energy consumption of Comparative Example 1 and Example 1 is shown in Table 1.

[0158] Table 1 Main energy consumption of Comparative Example 1 and Example 1

[0159] Note: The changes in Table 1 are calculated by subtracting the amounts in Comparative Example 1 from those in Example 1; the cooling water load in Table 1 is calculated by summing the cooling loads for the shift gas cooler 13 and the interstage cooling for the feed gas compressor 1; and the steam production in Table 1 is calculated by subtracting the steam production from the feed-to-superheated steam heat exchanger 3 and the steam production from the de-feed-to-saturated steam heat exchanger 2 from the total saturated steam production of the waste heat boiler system. In addition to the changes, positive numbers in Table 1 represent factors that affect the system's work or energy supply, while negative numbers represent factors that affect the system's external work or energy loss.

[0160] As shown in Table 1, under the premise of the same hydrogen production and purity, compared with Comparative Example 1, the energy consumption of Example 1 is as follows:

[0161] 1. After calculation, the power consumption of raw material supercharging was reduced from 1349.41kW in Comparative Example 1 to 28.57kW in Example 1, a reduction of 1320.84kw;

[0162] 2. The turbine produces 1510.45 kW of power (isentropic efficiency η = 75%), which is used for transmission to the external power grid or to drive other power-consuming devices within the device.

[0163] 3. The hydrogen production raw materials increased by 1.6t / h, but the desorption gas production increased, which reduced the reformer supplementary firing by 0.7t / h;

[0164] 4. Medium-pressure steam production decreased by 7.27t / h.

[0165] 5. Based on GB / T50441-2016 "Petrochemical Design Energy Consumption Calculation Standard" energy consumption indicators:

[0166] 5.0 MPa steam 90 kg EO / t, 3.5 MPa steam 88 kg EO / t, electricity 0.22 kg EO / kwh, desalted water 1.0 kg EO / t, and raw materials and fuels converted into standard oil based on low calorific value (methane 1195.2 kg EO / t, propane 1107 kg EO / t) and hydrogen production 4.54 t / h, the comprehensive energy consumption of Example 1 is reduced by 135.8 kg EO / t H2.

[0167] Example 2

[0168] The low-energy-consuming low-carbon hydrocarbon steam reforming hydrogen production system used in this embodiment is the same as that in Example 1.

[0169] This embodiment provides a low-energy-consuming process for producing hydrogen through steam reforming of low-carbon hydrocarbons. 4 Nm 3 / h) as an example, compared with Example 1, its key process parameters are as follows:

[0170] 1) Raw material propane (16.1 t / h, 35° C., 1.5 MPa, liquid) is pressurized to 5.3 MPa by raw material booster pump 20, consuming 47.46 kW of power.

[0171] 2) Control the reaction pressure of the catalytic reforming hydrogen production reaction at 4.8 MPa, the steam-to-carbon ratio of the furnace tubes in the reformer 5 at 3.0, and the reformed gas at the reformer outlet (temperature: 860° C., pressure: 4.64 MPa, H2 content 66.1%, CO content 13.8%, dry basis).

[0172] 3) The energy recovered by the expansion turbine is 4744.1 kW. The outlet gas of the turbine-power supply system 22 is 778.6°C and 2.84 MPa. The steam-water separation in the waste heat boiler 19 of the waste heat boiler system produces 5.0 MPa saturated steam (81.6 t / h), of which 4.0 t / h is used to heat the feedstock, and 77.6 t / h is used to heat the flue gas in the steam superheating section 503 of the reformer 5 to 430°C to obtain superheated steam.

[0173] 4) The superheated steam is divided into two parts. One part (flow rate: 18.6 t / h) is directly output; the other part (flow rate: 59 t / h) is used to cool the raw material-superheated steam heat exchanger 3 to obtain medium-pressure steam, which is used for catalytic reforming hydrogen production reaction; finally, the product hydrogen (H2 purity: 99.9%, flow rate: 2×10 4 Nm 3 / h (4.54t / h) and desorbed gas (used as fuel for the reformer, flow rate: 30211.9Nm 3 / h is 39.71t / h, calorific value: 2374.12kcal / Nm 3 ).

[0174] 5) Auxiliary fuel (composition: CH4, 0.23 t / h). Reformer exhaust gas 150.4°C, dry basis oxygen content 3%v. Reformer feed air (flow rate: 110 t / h, temperature: 25°C).

[0175] 6) The amount of desalted water and recycled purified water needs to be adjusted. In this case, the flow rate of desalted water is 46.6 t / h and the recycled purified water is 30.8 t / h. The other process conditions are basically the same as those in Example 1.

[0176] Energy consumption comparison

[0177] Since the source of the low-carbon hydrocarbons in the raw materials of Comparative Example 1 and Example 2 can be a pipeline or product of the refinery, the same calculation method and calculation basis as Table 1 are used. The main energy consumption of Comparative Example 1 and Example 2 is shown in Table 2.

[0178] Table 2 Main energy consumption parameters of Comparative Example 1 and Example 2

[0179] Note: The changes in Table 2 are calculated by subtracting the amounts in Comparative Example 1 from those in Example 2; the cooling water load in Table 2 is calculated by summing the cooling loads for the shift gas cooler 13 and the interstage cooling for the feed gas compressor 1; and the steam production in Table 2 is calculated by subtracting the steam production from the feed-to-superheated steam heat exchanger 3 and the steam production from the de-feed-to-saturated steam heat exchanger 2 from the total saturated steam production of the waste heat boiler system. In addition to the changes, positive numbers in Table 2 represent factors that affect the system's work or energy supply, while negative numbers represent factors that affect the system's external work or energy loss.

[0180] As shown in Table 2, under the premise of the same hydrogen production and purity, compared with Comparative Example 1, the energy consumption of Example 2 is as follows:

[0181] 1. After calculation, the power consumption of raw material supercharging was reduced from 1349.41kW in Comparative Example 1 to 47.46kW in Example 1, a reduction of 1301.95kw;

[0182] 2. The expansion turbine produces 4744.11 kW of power (isentropic efficiency η = 75%), which is used for transmission to the external power grid or to drive other power-consuming devices in the device;

[0183] 3. The hydrogen production raw materials increased by 2.95t / h, but the desorption gas production increased, which reduced the reformer supplementary firing by 1.29t / h;

[0184] 4. Medium-pressure steam production decreased by 2.58t / h.

[0185] 5. Based on GB / T50441-2016 "Petrochemical Design Energy Consumption Calculation Standard", the energy consumption indicators are: 90kgEO / t for 5.0MPa steam, 88kgEO / t for 3.5MPa steam, 0.22kgEO / kWh for electricity, and 1.0kgEO / t for desalted water. Raw materials and fuels are converted into standard oil based on their low calorific value (1195.2kgEO / t for methane and 1107kgEO / t for propane), and the hydrogen production is 4.54t / h. The overall energy consumption of the device is reduced by 212.53kgEO / t H2.

[0186] Example 3

[0187] The low-energy-consuming low-carbon hydrocarbon steam reforming hydrogen production system used in this embodiment is the same as that in Example 2 or Example 1.

[0188] This embodiment provides a low-energy-consuming process for producing hydrogen by steam reforming of low-carbon hydrocarbons. 4 Nm 3 / h) as an example, the process of this embodiment is based on Example 2, reducing raw material consumption, improving steam-to-carbon ratio, and adjusting fuel gas consumption.

[0189] Compared with Example 2, the key process parameters of this embodiment are as follows:

[0190] 1) Raw material propane (14.9 t / h, 35° C., 1.5 MPa, liquid) is pressurized to 5.3 MPa by raw material booster pump 20, consuming 44.07 kW of power.

[0191] 2) The reaction pressure of the catalytic reforming hydrogen production reaction is controlled to be 4.8 MPa, the steam-to-carbon ratio of the furnace tube in the reformer 5 is 3.5, and the reformed gas at the reformer outlet is (temperature: 860°C, pressure: 4.64 MPa, H2 content 67.9%, CO content 13%, dry basis).

[0192] 3) The energy recovered by the expansion turbine is 4930.1 kW. The outlet gas of the turbine-power supply system 22 is 778.2°C and 2.84 MPa. The waste heat boiler steam-water separator 19 of the waste heat boiler system produces 5.0 MPa saturated steam (91 t / h), of which 3.6 t / h is used to heat the raw materials, and 87.4 t / h is used to heat the flue gas from the steam superheating section 503 of the reformer 5 to 430°C to obtain superheated steam.

[0193] 4) The superheated steam is divided into two parts. One part (flow rate: 23.4 t / h) is directly output; the other part (flow rate: 63.9 t / h) is used to cool the raw material-superheated steam heat exchanger 3 to obtain medium-pressure steam, which is used for catalytic reforming hydrogen production reaction; finally, the product hydrogen (H2 purity: 99.9%, flow rate: 2×10 4 Nm 3 / h (4.54t / h) and desorbed gas (used as fuel for the reformer, flow rate: 28448.2Nm 3 / h is 38.25t / h, calorific value: 2069.29kcal / Nm 3 .

[0194] 5) Auxiliary fuel for the reformer (composition: CH4, 1.62 t / h). Reformer exhaust gas: 150.4°C, oxygen content: 3%v on a dry basis. Reformer feed air (flow rate: 120 t / h, temperature: 25°C).

[0195] 6) In this case, the desalted water flow rate is 51.3 t / h, the recycled purified water is 36 t / h, and the other process conditions are basically the same as those in Example 2.

[0196] Energy consumption comparison

[0197] Since the source of the low-carbon hydrocarbons in the raw materials of Comparative Example 1 and Example 3 may be a pipeline or product of an oil refinery, the main energy consumption of Comparative Example 1 and Example 3 is shown in Table 3.

[0198] Table 3 Main energy consumption parameters of Comparative Example 1 and Example 3

[0199] Note: The changes in Table 3 are calculated by subtracting the amounts in Comparative Example 1 from those in Example 3; the cooling water load in Table 3 is calculated by summing the cooling loads for the shift gas cooler 13 and the interstage cooling for the feed gas compressor 1; and the steam production in Table 3 is calculated by subtracting the steam production from the feed-to-superheated steam heat exchanger 3 and the steam production from the de-feed-to-saturated steam heat exchanger 2 from the total saturated steam production of the waste heat boiler system. In addition to the changes, positive numbers in Table 3 represent factors that affect the system's work or energy supply, while negative numbers represent factors that affect the system's external work or energy loss.

[0200] As shown in Table 3, under the premise of the same hydrogen production and purity, compared with Comparative Example 1, the energy consumption of Example 3 is as follows:

[0201] 1. After calculation, the power consumption of raw material supercharging was reduced from 1349.41kW in Comparative Example 1 to 44.07kW in Example 3, a reduction of 1305.34kw;

[0202] 2. The expansion turbine produces 4930.11 kW of power (isentropic efficiency η = 75%), which is used for transmission to the external power grid or to drive other power-consuming devices in the device;

[0203] 3. The hydrogen production raw materials increased by 1.8t / h, but the desorption gas production increased, which increased the reformer supplementary combustion by 0.09t / h;

[0204] 4. Medium-pressure steam production increased by 2.2t / h.

[0205] 5. Based on GB / T50441-2016 "Petrochemical Design Energy Consumption Calculation Standard", the energy consumption indicators are: 90kgEO / t for 5.0MPa steam, 88kgEO / t for 3.5MPa steam, 0.22kgEO / kWh for electricity, and 1.0kgEO / t for demineralized water. Raw materials and fuels are converted into standard oil based on their low calorific value (1195.2kgEO / t for methane and 1107kgEO / t for propane), and the hydrogen production is 4.54t / h. The overall energy consumption of the device is reduced by 235.18kgEO / t H2.

[0206] Energy consumption conversion for long-term operation or large-scale hydrogen production:

[0207] Based on the standard of producing 20,000 to 50,000 cubic meters of product hydrogen (99%) and after decomposition according to the relevant standards in Tables 1 to 3, the total energy consumption of Comparative Example 1 and Examples 1 to 3 are 6368.9 kgeo / h, 6009.6 kgeo / h, 5604.8 kgeo / h, and 5477.3 kgeo / h, respectively.

[0208] Compared with Comparative Example 1, Examples 1 to 3 use liquid propane as the raw material, which not only has lower power consumption during pressurization, but also utilizes a turbine to convert the internal energy of the reformed gas into electrical energy. Therefore, the overall energy consumption of Examples 1 to 3 is reduced. Moreover, by pressurizing the raw material, utilizing the heat in the system to vaporize and heat the raw material to a specific reaction temperature, and increasing the steam-to-carbon ratio, a highly efficient catalytic reforming hydrogen production reaction can be achieved under higher reaction pressure conditions. This also has the advantages of increasing the utilization rate of liquid propane and requiring less fuel replenishment.

[0209] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for producing hydrogen by steam reforming of low-carbon hydrocarbons with low energy consumption, characterized in that: The following steps are involved: The raw material is pressurized to 3.5-5.5 MPa, preheated and multi-stage heated to 340-380°C, and then mixed with medium-pressure steam to undergo catalytic reforming and hydrogen production reaction in the reformer to obtain reformed gas; The conversion gas is subjected to a turbine expansion process and a waste heat boiler to recover internal energy and heat, and is subjected to a medium-temperature conversion reaction at 390-420°C and cooling to obtain conversion gas; a portion of the conversion gas is used as a heat source for the preheating, and then subjected to cooling and pressure swing adsorption to obtain product hydrogen and desorbed gas; The reaction conditions of the catalytic reforming hydrogen production reaction are as follows: the reaction pressure is 3.0-4.8 MPa, and the reaction temperature is 800-900°C; the heat source of the converter comes from the heat generated by the combustion reaction of the desorbed gas, supplementary fuel and air.

2. The method for producing hydrogen by steam reforming of low-carbon hydrocarbons with low energy consumption according to claim 1, characterized in that: The method further comprises: Before mixing with medium-pressure steam at a pressure of 4.0-5.0 MPa and a temperature of 380-430°C, a desulfurization treatment is provided; After medium-temperature shift reaction and cooling, a primary shift gas is obtained; the primary shift gas is subjected to primary cooling and secondary cooling to obtain a secondary shift gas of 122-132°C; the secondary shift gas is used as a heat source for the preheating in step 1), and then cooled and subjected to pressure swing adsorption to obtain product hydrogen and desorbed gas.

3. The method for producing hydrogen by steam reforming of low-carbon hydrocarbons with low energy consumption according to claim 2, characterized in that: The medium-pressure steam preparation process comprises: The process condensed water generated by the cooling, primary cooling and secondary cooling is introduced into the middle of the acidic water stripping tower; the process condensed water generated by the cooling is introduced into the top of the acidic water stripping tower; and heating steam is introduced into the bottom of the acidic water stripping tower to separate acidic gas and pure water; The desalted water is heated to 100-112°C, mixed with a portion of pure water, and pressurized, and heated to 265-282°C in the deoxygenated water heat exchanger, the waste heat boiler, and the saturated water evaporation section of the converter to obtain saturated steam; the saturated steam is further heated to 400-450°C in the steam superheating section of the converter to obtain superheated steam; part of the superheated steam is cooled by the primary raw material heat exchanger to obtain medium-pressure steam; Among them, the pressure of the saturated steam is 4.0-5.0 MPa; the pressure of the superheated steam is 4.0-5.0 MPa; the raw material includes at least one of liquid propane, liquid butane, and liquid pentane; the pressure of the raw material is 1.0 MPa-1.8 MPa.

4. The method for producing hydrogen by steam reforming of low-carbon hydrocarbons with low energy consumption according to claim 3, characterized in that: The multi-stage heating step includes: primary heating using part of saturated steam as a heat source and secondary heating using part of superheated steam as a heat source; the remaining part of saturated steam is used to be heated to form superheated steam; and the remaining part of superheated steam is directly transported outward.

5. The method for producing hydrogen by steam reforming low-carbon hydrocarbons with low energy consumption according to claim 2 or 3, characterized in that: The feedstock also includes gaseous alkanes.

6. The method for producing hydrogen by steam reforming of low-carbon hydrocarbons with low energy consumption according to claim 3 or 4, characterized in that: The pressure of the reformed gas is 3.2-4.8 MPa; the pressure of the reformed gas at the inlet of the waste heat boiler is 2.6-3.2 MPa; In the process of preparing the medium-pressure steam, the pressurization is specifically: mixing the desalted water and part of the pure water, and pressurizing them to 5.2-6.6 MPa.

7. The method for producing hydrogen by steam reforming of low-carbon hydrocarbons with low energy consumption according to claim 2 or 3, characterized in that: The isentropic efficiency in the turbine expansion process is 70% to 80%.

8. The method for producing hydrogen by steam reforming of low-carbon hydrocarbons with low energy consumption according to claim 2 or 3, characterized in that: The flow rate ratio of the product hydrogen to the desorbed gas is 1:(8-9); the flow rate of the product hydrogen is 4-6 t / h; the flow rate ratio of the supplementary fuel to the desorbed gas is (20-180):1; the product hydrogen is 99.9% hydrogen.

9. A low-energy consumption low-carbon hydrocarbon steam reforming hydrogen production system, comprising: A primary raw material heat exchanger, a secondary raw material heat exchanger, a desulfurization reactor, a converter, a waste heat boiler system, a deoxygenated water heat exchanger, a medium-temperature conversion reactor, a conversion gas first liquid separator, a hot water heat exchanger, a desalted water heat exchanger, a conversion gas second liquid separator, a conversion gas cooler, a conversion gas third liquid separator, a pressure swing adsorption system and an acidic water stripping tower; the waste heat boiler system includes a waste heat boiler and a waste boiler steam-water separator; the combustion chamber of the converter is provided with an inlet for air and supplementary fuel; It is characterized in that It also includes a feed booster pump, a preheating heat exchanger, a turbo expander, a generator and a bypass valve; The raw material booster pump is connected to the preheating heat exchanger, the primary raw material heat exchanger, the secondary raw material heat exchanger, the desulfurization reactor, the converter, the waste heat boiler, the medium temperature shift reactor, the deoxygenated water heat exchanger, and the first shift gas separator in sequence through pipelines; A pipeline for accessing medium-pressure steam is provided on the pipeline between the desulfurization reactor and the reformer; The turbine expander and bypass valve are connected in parallel to the pipeline between the reformer and the waste heat boiler to recover the internal energy of the reformed gas and ensure stable operation of the system; The top of the first conversion gas separator is connected to the hot water heat exchanger, the desalted water heat exchanger, and the second conversion gas separator in sequence through pipelines; the top of the second conversion gas separator is connected to the preheating heat exchanger, and then connected to the conversion gas cooler and the third conversion gas separator; the top of the third conversion gas separator is connected to the pressure swing adsorption system; the pressure swing adsorption system is provided with an output pipeline for product hydrogen and a pipeline for providing desorption gas to the converter; The bottom of the first shift gas separator is connected to the bottom of the second shift gas separator through a pipeline, and then connected to the middle feed port of the acidic water stripping tower.

10. The system for producing hydrogen by steam reforming low-carbon hydrocarbons with low energy consumption according to claim 9, characterized in that: Also includes: Raw gas compressor, deaerator and deaerated water booster pump; The deionized water heat exchanger is connected to the deaerator, the deionized water booster pump, and the deionized water heat exchanger in sequence through pipelines, and then connected to the waste heat boiler and the waste heat boiler steam-water separator to provide saturated water to the waste heat boiler steam-water separator; The bottom of the steam-water separator is provided with a pipeline passing through the saturated water evaporation section of the converter, and saturated steam is produced by recycling the heat of the converter; The pipeline at the top of the residual boiler steam-water separator is divided into two routes, one of which passes through the steam superheating section of the reformer to generate superheated steam; the other is connected to the primary raw material heat exchanger and the deaerator to recover the heat in the superheated steam and use it for the primary heating of the raw material and the heating of the deaerator; the deaerator is provided with an access pipeline to the primary raw material heat exchanger; The pipeline after passing through the steam superheating section of the converter is divided into two routes. One route is connected to the direct external transmission pipeline for the external transmission of superheated steam; the other route is connected to the secondary raw material heat exchanger for secondary heating of the raw materials.

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