CN-116715198-B - Natural gas vapor two-stage heat exchange type composite conversion hydrogen production system

CN116715198BCN 116715198 BCN116715198 BCN 116715198BCN-116715198-B

Abstract

The invention discloses a natural gas steam two-stage heat exchange type composite conversion hydrogen production system which consists of a pretreatment module, a heat exchange conversion module, a reforming conversion module, a conversion reaction module and a Pressure Swing Adsorption (PSA) hydrogen extraction module, and aims to solve the problems that in the natural gas steam conversion hydrogen production system, a conversion section is complex, the heat exchange conversion efficiency is limited, the heat transfer conversion depth is limited, the coupling synergistic effect with the rest hydrogen production/hydrogen extraction sections is small, the smoke emission and the like are still existed in the prior art, and the problems of energy cascade utilization, high methane conversion depth, self-balancing of system energy and compact and efficient reduction of smoke emission are solved, so that the heat coupling among all modules in the hydrogen production system is more reasonable, flexible and compact, the thermal efficiency of the hydrogen production system is up to 92-98%, the H2 yield is up to over 90%, the system is convenient for skid-mounted miniaturization, and the system is suitable for hydrogen production in a hydrogen station.

Inventors

ZHONG YALING
MOU SHURONG
CHEN YUN
WANG LANHAI
ZHONG YUMING
CAI YUEMING

Assignees

四川天采科技有限责任公司

Dates

Publication Date: 20260512
Application Date: 20230531

Claims (5)

1. The natural gas water vapor two-stage heat exchange type composite conversion hydrogen production system is characterized by comprising a pretreatment module, a heat exchange conversion module, a reforming conversion module, a conversion reaction module and a PSA hydrogen extraction module, wherein, The pretreatment module comprises a material conveying pipeline, a conveying pump and/or a booster, a preheating unit and a hydrodesulfurization unit, wherein the natural gas is taken as raw material gas and enters the preheating unit of the pretreatment module, the pretreatment module receives the raw material gas of the natural gas, and enables the raw material gas of the natural gas to enter the hydrodesulfurization unit after being subjected to steam to the reaction temperature required by hydrodesulfurization to form purified natural gas, the purified natural gas is mixed with a certain proportion of steam to form mixed steam, the mixed steam enters a downstream heat exchange conversion module, hydrogen of the hydrodesulfurization unit comes from the downstream PSA hydrogen extraction module, and the desulfurization depth is required to meet the specification requirements of catalytic conversion or conversion reaction of various catalysts of the downstream convection pre-conversion, heat exchange conversion, reforming conversion and conversion reaction module; A heat exchange conversion module, which comprises a convection pre-conversion unit and a heat exchange conversion unit, wherein the heat exchange conversion module receives mixed steam and high-temperature reforming conversion gas from a downstream reforming conversion module, the mixed steam enters a tube array of the convection pre-conversion unit and carries out convection heat transfer with the combined conversion gas which is from the heat exchange conversion unit and flows out of the tube array of the convection pre-conversion unit to obtain heat required by a pre-conversion reaction, so that the mixed steam removes components with more than C 5 which are harmful to downstream heat exchange conversion and reforming conversion, and part of purified natural gas in the mixed steam and light hydrocarbon components with less than C 5 carry out the pre-conversion reaction with water vapor in the mixed steam to form the pre-conversion gas, part of the pre-conversion gas flows out of the heat exchange conversion module and enters the downstream reforming conversion module, part of the raw material enters a heat exchange conversion unit and flows into a tube array loaded with a reforming conversion catalyst to perform heat exchange conversion reaction to form heat exchange conversion gas, heat required by the heat exchange conversion reaction is obtained from convection heat transfer of high-temperature reforming conversion gas flowing out of the tube array, the temperature of the heat exchange conversion reaction is 780-900 ℃, part of the heat exchange conversion gas flowing out of the tube array of the heat exchange conversion unit is mixed with reforming conversion gas cooled by the convection heat transfer of the heat exchange conversion unit to form combined conversion gas, the combined conversion gas enters a convection pre-conversion unit and performs convection heat transfer with mixed steam entering the convection pre-conversion unit, the temperature of the mixed steam is 450-650 ℃ after the mixed steam is subjected to the pre-conversion by the convection pre-conversion unit, the combined conversion gas is cooled to 150-350 ℃ after the convection heat transfer of the convection conversion gas to form final conversion gas, and the final conversion gas enters a downstream conversion reaction module, a part of heat exchange conversion gas flowing out of the heat exchange conversion unit and the final conversion gas cooled after convection heat transfer by the convection pre-conversion unit are mixed and enter a downstream conversion reaction module, and the proportion of the heat exchange conversion gas into two parts depends on the reaction temperature required by the middle-high temperature or middle-low temperature conversion reaction adopted by the downstream conversion reaction module and the content of more than C 5 components in the mixed steam and the corresponding temperature required by the convection pre-conversion; The reforming conversion module comprises an oxyhydrogen combustion reforming conversion unit, the oxyhydrogen combustion reforming conversion unit comprises a reforming conversion tube array reactor and an oxyhydrogen combustion reaction chamber at the upper part of the tube array reactor, the reforming conversion module receives pre-conversion gas, rich oxygen, water vapor containing hydrogenolysis gas 2 from a downstream PSA hydrogen extraction module, water vapor for adjusting the water-carbon ratio and the hydrogen-carbon ratio of the reforming conversion module and carbon dioxide containing desorption gas 1 from the downstream PSA hydrogen extraction module, high-temperature reforming conversion gas formed by the reforming conversion module directly flows into an upstream heat exchange conversion unit, the introduced rich oxygen and the pre-conversion gas and the hydrogenolysis gas containing hydrogenolysis gas 2 generate oxyhydrogen combustion reaction in the oxyhydrogen combustion reaction chamber to generate huge combustion reaction heat, the generated combustion reaction heat is directly carried into a tube array filled with a reforming conversion catalyst in the reforming conversion unit by the participation reforming conversion reaction gas to be converted, the reforming conversion temperature reaches 850-990 ℃, the methane conversion rate is 99-100%, and the high-temperature reforming conversion gas flowing out through the reforming conversion reaction directly flows into the heat exchange conversion unit in the upstream heat exchange conversion module to perform convection, and heat required by heat exchange conversion is provided for heat transfer conversion; the shift reaction module is arranged to receive the final conversion gas from the heat exchange conversion module and perform shift reaction to output shift gas, and is used for reacting carbon monoxide in the final conversion gas with steam in a shift reaction bed loaded with a middle-high temperature or middle-low temperature shift reaction catalyst to form shift gas taking hydrogen and carbon dioxide as main components, part of the shift gas returns to the heat exchange conversion module to adjust the hydrogen-carbon ratio of the heat exchange conversion gas flowing out of the heat exchange conversion module, and the other part of the shift gas enters the downstream PSA hydrogen extraction module, the heat required by the shift reaction module is directly carried in by the final conversion gas from the upstream heat exchange conversion module, and the shift reaction process corresponding to different shift reaction catalysts in the shift reaction module is adapted by adjusting the distribution proportion of two heat exchange conversion gases in the heat exchange conversion module; a PSA hydrogen module comprising a PSA decarbonization unit and a PSA purification unit.
2. The two-stage heat exchange type composite conversion hydrogen production system for natural gas and water vapor as claimed in claim 1, wherein the upstream and downstream connection among the pretreatment module, the heat exchange conversion module, the reforming conversion module, the conversion reaction module and the PSA hydrogen extraction module is formed by splicing and assembling corresponding pipelines, valves and equipment interfaces in each module, and the hydrogen production system further comprises one or more auxiliary equipment selected from a compressor, a delivery pump, a buffer tank, a steam tank and an auxiliary pipeline, wherein the hydrogen production capacity of the hydrogen production system is 50Nm 3 /h at the minimum and 5000Nm 3 /h at the maximum, and the operating pressure range of the hydrogen production system is 0.3-3.5 MPa.
3. The system for producing hydrogen by two-stage heat exchange type composite conversion of natural gas and water vapor as claimed in claim 1, wherein high-temperature reforming conversion gas flowing out of the reforming conversion module does not directly enter the heat exchange conversion unit, but firstly enters the preheating unit for convection heat transfer and then enters the heat exchange conversion unit for convection heat transfer, the heat exchange conversion gas flowing out of the heat exchange conversion unit is not divided into two parts, but is completely mixed with reforming conversion gas flowing out after convection heat transfer by the heat exchange conversion unit to form combined conversion gas, a low-temperature reforming conversion catalyst is filled in a heat exchange conversion unit tube array in the heat exchange conversion module, the low-temperature reforming conversion catalyst takes nickel/cobalt as a main active component, rare earth metal and oxides thereof as a cocatalyst component, the reforming conversion temperature of the low-temperature reforming conversion catalyst is 450-600 ℃, and a high-temperature nickel-series reforming conversion catalyst is filled in a reforming conversion tube array reactor of the reforming conversion module; the high-temperature reforming conversion gas carries out convection heat transfer with the natural gas raw gas at normal temperature in the preheating unit so that the temperature of the natural gas raw gas rises to the operation temperature required by hydrodesulfurization, the reforming conversion gas subjected to convection heat transfer by the preheating unit enters the heat exchange conversion unit of the heat exchange conversion module and flows out of the tube array filled with the low-temperature reforming conversion catalyst by the heat exchange conversion unit, carries out convection heat transfer with the pre-conversion gas flowing through the tube array, provides heat required for conversion for the low-temperature reforming conversion catalyst bed layer in the heat exchange conversion tube array, flows out heat exchange conversion gas after carrying out low-temperature reforming conversion reaction in the tube array, and is mixed with the reforming conversion gas flowing out after the convection heat transfer by the heat exchange conversion unit to form combined conversion gas, the combined conversion gas enters a convection pre-conversion unit of the heat exchange conversion module again, and carries out convection heat transfer with mixed steam flowing into the convection pre-conversion unit, so that the mixed steam is heated in a tube array of the convection pre-conversion unit and subjected to pre-conversion reaction, high hydrocarbon components in the mixed steam are removed, and partial reforming conversion reaction is carried out to form pre-conversion gas, the pre-conversion temperature is 280-350 ℃, the combined conversion gas is cooled to 160-280 ℃ after the convection heat transfer of the convection pre-conversion unit, the final conversion gas is formed, and finally the conversion gas directly enters a downstream conversion reaction module to carry out conversion reaction, and at the moment, a conversion reaction catalyst is selected as a medium-low temperature conversion catalyst.
4. The natural gas steam two-stage heat exchange type composite conversion hydrogen production system according to claim 1, wherein the natural gas is not used as fuel gas in its entirety, but is used as a part of raw gas to enter a preheating unit of a pretreatment module, and is used as a part of fuel gas to enter a reforming conversion module; the reforming conversion unit of the reforming conversion module is not an oxyhydrogen combustion reforming conversion unit, but is a radiant heat reforming conversion unit, and the reforming conversion module receives the intermediate pre-conversion gas, the natural gas fuel gas, the air, the hydrogenolysis inhalation 2 from the downstream PSA hydrogen extraction module, the carbon dioxide-containing desorption 1 from the downstream PSA hydrogen extraction module, and the natural gas fuel gas, The steam, radiant heat reforming conversion unit includes reforming conversion reactor composed of tube array loaded with nickel series reforming conversion catalyst and combustion chamber set on the upper part or side part or bottom of reforming conversion reactor, part of natural gas is used as fuel gas and air is used as combustion improver to make combustion reaction, high temperature combustion gas produced by combustion reaction is sprayed out by nozzle and makes radiant heat transfer to tube array, the conversion temperature of reforming conversion catalyst bed in tube array is up to 770-950 deg.C, high temperature flue gas is produced after being combusted by reforming conversion module, flows into pre-conversion unit and is used as heat source of preheating unit after the pre-conversion unit and mixed steam are made convection heat transfer, natural gas raw gas is preheated by preheating unit and then enters hydrodesulfurization unit to make desulfurization to produce purified natural gas, purified natural gas is mixed with steam to form mixed steam, the mixed steam enters a pre-conversion unit of a heat exchange conversion module and carries out convection heat transfer with high-temperature flue gas from the reforming conversion module, so that the mixed steam forms pre-conversion gas, the temperature of the formed pre-conversion gas is 250-350 ℃, the formed pre-conversion gas enters the convection pre-conversion unit of the heat exchange conversion module and carries out convection heat transfer with the combined conversion gas of the heat exchange conversion unit from the heat exchange conversion module, so that the pre-conversion gas forms intermediate pre-conversion gas, the temperature of the intermediate pre-conversion gas is 450-650 ℃, the intermediate pre-conversion gas enters the heat exchange conversion unit to carry out heat exchange conversion reaction, wherein a nickel series reforming conversion catalyst is loaded in a tube array of the heat exchange conversion unit, the heat exchange conversion reaction temperature of the intermediate pre-conversion gas is 750-880 ℃, the intermediate pre-conversion gas carries out convection heat transfer with the reforming conversion gas which comes from the reforming conversion module and flows out the tube array of the heat exchange conversion unit to provide a heat source for the heat exchange conversion unit, the intermediate pre-conversion gas is reformed and converted in the heat exchange conversion unit tube, the heat exchange conversion gas is mixed with the reformed conversion gas flowing out of the heat exchange conversion unit tube after convection heat transfer to form combined conversion gas, the combined conversion gas enters the convection pre-conversion unit of the heat exchange conversion module and is subjected to convection heat transfer with the pre-conversion gas from the pre-conversion unit, so that the pre-conversion gas is further heated and pre-converted to form intermediate pre-conversion gas, the intermediate pre-conversion gas is divided into two fluids and respectively enters the heat exchange conversion unit of the heat exchange conversion module and the radiant heat reforming conversion unit of the reforming conversion module to be reformed and converted, the combined conversion gas is cooled after the convection heat transfer is carried out by the convection pre-conversion unit to form final conversion gas, and is mixed with a part of the heat exchange conversion gas through the heat recovery system and enters the conversion reaction module after meeting the operation temperature required by the medium-high temperature or medium-low temperature conversion reaction of the downstream conversion reaction module, after the conversion reaction is carried out, conversion gas is formed, after the conversion gas is subjected to further heat exchange and temperature reduction to the operation temperature required by the PSA hydrogen extraction module through the heat recovery system, the conversion gas enters the PSA hydrogen extraction module so as to obtain H 2 product gas with purity more than or equal to 99.99 percent, wherein the added heat recovery system can generate water vapor to meet the requirement of the hydrogen production system, part of conversion gas which is not subjected to heat exchange and temperature reduction through the heat recovery system is used as adjusting gas for adjusting the water-carbon ratio and the hydrogen-carbon ratio of the heat exchange conversion module, part of H 2 product gas from the PSA purification unit of the PSA hydrogen extraction module is returned to the hydrodesulfurization unit in the pretreatment module to hydrodesulfurize the natural gas raw material gas flowing out of the preheating unit, the hydrogenolysis inhalation 2 from the PSA purifying unit of the PSA hydrogen extracting module is used as fuel gas of the reforming conversion module to partially replace natural gas feed gas, and enters a combustion chamber of a radiant heat reforming conversion unit of the reforming conversion module to burn, so as to provide a heat source for the reforming conversion module, and the carbon dioxide-containing desorption 1 from the PSA decarbonizing unit of the PSA hydrogen extracting module is partially mixed with water vapor, The intermediate pre-converted gas is taken as the water-carbon ratio and hydrogen-carbon ratio adjusting gas in the reforming conversion module conversion process, and a part of the intermediate pre-converted gas is output as the raw gas for extracting high-concentration CO 2 or is discharged.
5. The system for producing hydrogen by two-stage heat exchange type composite conversion of natural gas and water vapor as claimed in claim 1, wherein the PSA decarbonization unit and the PSA purification unit of the PSA hydrogen extraction module adopt a rotary pressure swing adsorption system consisting of more than 7-channel multi-channel rotary valves and more than 5 adsorption towers, wherein the carbon molecular sieve is added by 10-20% in the composite adsorbent filled in the adsorption towers.

Description

Natural gas vapor two-stage heat exchange type composite conversion hydrogen production system Technical Field The invention belongs to the technical field of hydrogen preparation in hydrogen energy, and particularly relates to a natural gas water vapor two-stage heat exchange type composite conversion hydrogen production system. Background Hydrogen energy is one of the most promising clean energy sources at present, the current hydrogen preparation process mainly comprises the steps of obtaining and discharging CO 2 or CO or other pollutants from fossil raw materials containing hydrocarbon through catalytic pyrolysis reforming conversion and hydrocarbon separation, wherein the raw materials comprise natural gas, methanol, coal, heavy oil, methane and the like, and the preparation of 'gray hydrogen' through natural gas steam reforming conversion (SMR) is the method with the largest global standard, the most mature and the lowest hydrogen production cost at present. The method for preparing the 'ash hydrogen' by taking the natural gas as the raw material mainly comprises steam reforming conversion (SMR), partial Oxidation Reforming (POR), autothermal reforming (ATR), heat exchange conversion (HTER), plasma reforming and the like, wherein SMR conversion hydrogen production is the most mature and common traditional hydrogen production method, the core technology is a reformer or a conversion reactor, and a radiation chamber (section) generally provides heat to enable the conversion temperature required by the catalytic reforming conversion reaction of methane and steam in a tube array in the furnace to be up to 700-900 ℃, and the typical conversion heat efficiency is only about 70 percent because the tube array type reformer or the reactor is limited by a radiation heat transfer mode, the miniaturization difficulty of the device is increased, a certain amount of natural gas is consumed as fuel gas, a large amount of surplus steam is generated, and further, the natural gas consumption and the smoke emission are increased. Therefore, at present, aiming at the problems existing in the hydrogen production of natural gas or hydrocarbon steam conversion (SMR) at home and abroad, a plurality of novel technologies for completely or partially replacing a radiation section in the SMR conversion section are provided so as to reduce the fuel consumption of the natural gas and the emission of smoke, improve the thermal efficiency of the hydrogen production process and the yield of H 2 product gas, and simultaneously facilitate the skid-mounted miniaturization of the device. Among them, the series of technologies related to hydrocarbon vapor reforming hydrogen production including natural gas, including US2015/0175416A1、CN111433151A、CN101056817A、CN101208264A、CN200480009024.8、CN200580038308.4、CN00106514.9、CN113474282A, which have been developed by danish tropsh (Topsoel) corporation and chinese branches, which are the world-leading technologies for hydrocarbon vapor reforming hydrogen production, are most typical. The typical process of the series of patents of the topline company mainly comprises the following two main types, namely, first, partially replacing the radiation type conversion load and improving the conversion heat efficiency. In the traditional hydrocarbon steam SMR conversion process using natural gas as raw material, the heat exchange type heat transfer conversion technology (HTER) of the topline company fully utilizes high-temperature process gas at a radiant type (section) conversion outlet as a heat source for heat exchange type conversion, and performs heat exchange conversion on pre-converted gas which enters a non-combustion chamber heat exchange type conversion connected in parallel with the SMR conversion furnace, thereby reducing the consumption of fuel gas of a radiant type conversion unit, increasing the yield of H 2 product gas, enabling the conversion heat efficiency to reach 70-90% and above, and reducing the radiant type conversion load by 30% on average, but HTER heat transfer conversion is still based on the heat given by the high-temperature process gas flowing out from the radiant section. To further reduce SMR conversion loads, the Topso company uses an electric or autothermal conversion (ATR) in combination with SMR and HTER to form a first, second, third conversion, a second, a third conversion, a fourth conversion, a fifth conversion, a fourth conversion, a fifth conversion, a sixth conversion, and a fourth conversion, such as in the CN113474282A patent, The fourth conversion and other complicated and serial converter/reactor processes are realized, thereby completely adopting the desorption gas of the PSA purification H 2 process to be the fuel gas of the combustion type reformer (SMR), saving natural gas, leading the conversion load of the SMR to be reduced to 30 percent at maximum, simultaneously realizing that the conversion heat efficiency and the yield of H 2 product gas ar