Ammonia synthesis preparation process and device

Abstract

The invention discloses an ammonia synthesis preparation process and device, raw material gas pretreatment: mixed raw material gas of nitrogen and hydrogen is purified through a pressure swing adsorption system, through the technical breakthrough of low pressure, high efficiency, long service life and low carbonization, the comprehensive energy consumption of ammonia synthesis is reduced to 27-29 GJ / ton of ammonia from 32-35 GJ / ton of ammonia in the traditional process, and the comprehensive energy consumption of ammonia synthesis is reduced to 27-29 GJ / ton of ammonia. A smooth transition path from'grey ammonia '(ammonia prepared from fossil energy) to'green ammonia' (ammonia prepared from renewable energy) is constructed, and an industrialized technical scheme is provided for'double carbon 'transformation of the global ammonia industry.

Description

Technical Field

[0001] This invention relates to the field of ammonia synthesis technology, and in particular to an ammonia synthesis preparation process and apparatus. Background Technology

[0002] Ammonia serves as an "invisible cornerstone" supporting food security for 7.8 billion people worldwide (85% of global nitrogen fertilizer production relies on ammonia as a feedstock), and is also a key carrier for hydrogen energy storage and transportation (liquid ammonia has an energy density of 11.5 MJ / L, far exceeding compressed hydrogen). Innovation in its synthesis technology has always been a core issue in the chemical industry. Currently, global ammonia production capacity has exceeded 230 million tons per year, but over 90% still relies on the century-old Haber-Bosch process, whose technological limitations are becoming increasingly apparent.

[0003] I. Inherent Bottlenecks in Traditional Ammonia Synthesis Processes 1. High-voltage driven energy consumption trap The core contradiction of the Haber-Bosch process lies in the "equilibrium dilemma between reaction thermodynamics and kinetics": the ammonia synthesis reaction (N2 + 3H2O) 2⇌ 2NH 3）是放热、体积缩小的可逆反应，理论上高压有利于正向进行，但传统铁基催化剂需在 Activation (Fe3O) requires a high temperature of 400-500℃. 4还原为α The activation energy of the Fe active phase is as high as 300 kJ / mol, and high temperatures significantly reduce the equilibrium conversion rate (only 15-18% at 20 MPa). To offset the negative effects of high temperatures, industrial applications have had to adopt ultra-high pressure operations of 150-320 MPa (such as a 180 MPa system used by a 300,000-ton / year ammonia plant in China), which directly leads to: The energy consumption of compressors has surged: the power consumption of raw gas compression accounts for 60-70% of the total energy consumption, and the power consumption per ton of ammonia is as high as 1200-1500 kWh (equivalent to consuming 1.5 tons of standard coal per ton of ammonia). High equipment investment: High-pressure reactors require special steel with a thickness of over 200mm (such as 2.25Cr-1Mo steel), with the manufacturing cost of a single reactor exceeding 100 million yuan. Furthermore, comprehensive inspection and maintenance are required every 5 years, and operation and maintenance costs account for 15% of the total production cost. Significant safety risks: If a leak occurs in the ultra-high pressure system, the mixed gas (H2O)... 2体积占比 75% of ammonia plants can explode when exposed to static electricity. Historically, there have been multiple accidents involving the bursting of high-pressure equipment in ammonia plants (such as the explosion of an ammonia compressor in a chemical industrial park in 2019 that resulted in the deaths of three people).

[0004] 2. Dual constraints on catalyst performance Currently, the mainstream industrial iron-based catalysts (using magnetite as a precursor, with the addition of K2O, CaO, and SiO2) 2等促进剂）存在难以调和的矛盾： Low-temperature activity is insufficient: the activity threshold temperature is greater than or equal to 400°C, resulting in almost no catalytic activity in the "energy-saving temperature zone" of 300-350°C, forcing the process to maintain a high-temperature and high-consumption state; Weak resistance to poisoning: even if there is 1 ppm of CO or H2S in the raw material gas, it will cause permanent deactivation of the catalyst (more than 50% reduction in activity after poisoning), so a complex purification system (such as liquid nitrogen washing, accounting for 20% of the total investment) must be equipped; Limited life: under the combined action of high pressure, high temperature, and gas flow scouring, catalyst particles are prone to sintering (grain size increases from 20 nm to more than 100 nm) and pulverization (strength decreases from 200 N / cm to less than 50 N / cm), with an actual service life of only 8-10 years. The replacement of catalysts requires a shutdown of 2 weeks, resulting in a loss of production capacity of more than 1,000 tons.

[0005] In recent years, ruthenium-based catalysts (10-100 times more active than iron-based catalysts) have been considered as a breakthrough direction, but existing technologies have fatal defects: Poor carrier stability: active carbon or carbon nanotubes are often used as carriers, which are prone to methanation reactions (C+2H 2→ CH 4），导致载体结构崩塌，催化剂寿命缩短至 3-5 years (for example, an active carbon-supported ruthenium catalyst reported in a literature has a 40% reduction in activity after 1,000 hours of operation at 20 MPa and 400°C); Insufficient mechanical strength: the carbon carrier has a compressive strength of only 50-80 MPa, which cannot withstand high pressure operation of more than 10 MPa, limiting its application in industrial devices (currently only a few low-pressure experimental devices are used, and scaling has not been achieved).

[0006] 3. Efficiency loss of equipment and system integration The "unit isolated design" of traditional ammonia synthesis devices further amplifies energy consumption: Uneven mass transfer in the reactor: axial flow reactors are used (gas flows vertically from top to bottom), and the bed radial pressure gradient reaches 0.5-1.0 MPa, resulting in a gas distribution deviation of more than 15% (the edge flow rate is 2-3 times that of the center), and about 30% of the catalyst is in the "low-efficiency reaction zone"; Rough heat recovery: the high-temperature mixed gas (350-450°C) at the reactor outlet is directly cooled in a water cooler, and 90% of the reaction heat is taken away by the cooling water (5 GJ of heat is wasted per ton of ammonia, equivalent to 60 kg of standard coal); Redundancy of the circulation system: unreacted H2 / N 2混合气（占总气量的 80-85%) needs to be compressed and cooled multiple times, with an energy consumption increase of 10% each time, and the inert gas (CH 4、 Ar) accumulated in the circulation gas needs to be discharged regularly, resulting in a raw material gas loss rate of more than 5%.

[0007] II. Limitations of existing improved technologies In response to the above problems, the industry has carried out many improvement attempts, but none has formed a systematic breakthrough: Low-pressure iron-based process: attempts to reduce the pressure to 50-100 MPa by optimizing iron-based catalysts, but the single-pass conversion rate drops to below 8%, and the cycle energy consumption increases by 30%; Single-bed ruthenium-based test: single-stage axial bed loading of ruthenium-based catalysts results in a pressure drop of over 1.0 MPa due to the excessive thickness of the bed, and the catalyst activity decay rate increases; Partial energy recovery: only a waste heat boiler is added at the reactor outlet, which is not coupled with the cycle system, and the energy recovery rate is less than 20%.

[0008] III. Urgent need for industry transformation Under the background of the "double carbon" goal and the rise of "green ammonia" (synthesis of ammonia from renewable energy hydrogen), the drawbacks of traditional processes are further magnified: Poor green ammonia adaptability: the outlet pressure of photovoltaic / wind power electrolysis hydrogen is usually ≤3 MPa, if it is to adapt to the traditional 150 MPa ammonia synthesis system, it will consume an additional 400 kWh / ton of ammonia compression energy, offsetting the low-carbon advantage of green hydrogen; Limited distributed production: the minimum scale of a traditional ammonia plant is 100,000 tons / year, which cannot meet the distributed ammonia demand in remote areas (such as African farmland), and the unit energy consumption of a small-scale device is higher (20% higher than that of a 300,000-ton / year device).

[0009] Therefore, developing a low-pressure, high-efficiency, long-life, and closed-loop energy-saving ammonia synthesis new process has become a key to breaking through the industry bottleneck and supporting the transformation of "green chemical industry". SUMMARY

[0010] In order to overcome the shortcomings of the prior art, one of the purposes of the present application is to provide an ammonia synthesis preparation process and device.

[0011] One of the purposes of the present application is achieved by the following technical solutions: An ammonia synthesis preparation process, comprising the following steps: a. Raw material gas pretreatment: purifying the mixed raw material gas of nitrogen and hydrogen by a pressure swing adsorption system to remove carbon dioxide, carbon monoxide, methane and other impurities therein, and obtaining pure synthesis gas with a hydrogen to nitrogen ratio of 2.5-3.2; b. Catalytic reaction: passing the pure synthesis gas into a multi-layer radial catalytic bed reactor to perform an ammonia synthesis reaction under the action of a catalyst; the catalyst is a ruthenium-based catalyst loaded on a silicon carbide carrier and adding potassium and cesium as promoters, and the catalyst bed temperature is controlled at 300-400 ℃ and the reaction pressure is controlled at 10-20 MPa; c. Intermediate cooling and heat exchange: indirect heat exchangers are arranged between the catalyst beds, using unreacted fresh synthesis gas to intermediate cool the partially converted synthesis gas to a temperature of 200-250°C, while preheating the fresh synthesis gas; d. Product separation and recycle: the reacted mixture is cooled to below -20°C by multi-stage ammonia coolers, and liquid ammonia is separated by a gas-liquid separator; unreacted hydrogen and nitrogen are pressurized by a compressor and returned to the reactor for recycling, and the pressure energy is recovered by an expansion generator.

[0012] An ammonia synthesis device, comprising: a. Raw gas pretreatment unit: comprising a pressure swing adsorption system, which includes at least two adsorption beds, and realizes removal of impurities such as carbon dioxide and carbon monoxide by cyclic operation of adsorption, concurrent pressure reduction, countercurrent pressure reduction, flushing and pressure increase; b. Multi-layer radial catalyst bed reactor: 3-5 layers of radial catalyst beds are arranged inside the reactor, and each layer is filled with a ruthenium-based catalyst; interlayer heat exchangers are installed between the catalyst beds, the shell side of the heat exchanger is connected to fresh synthesis gas, and the tube side is connected to partially converted synthesis gas, to realize indirect heat exchange; c. Ammonia separation and recycle unit: including multi-stage ammonia coolers and a gas-liquid separator, the ammonia coolers use liquid ammonia at -30°C to -20°C as a coolant to cool the mixed gas to below -20°C; the recycled gas separated by the gas-liquid separator is pressurized to 12-22 MPa by a compressor and returned to the reactor, and an expansion generator is arranged in the pressurization process to recover pressure energy; d. Waste heat recovery system: the high-temperature synthesis gas at the outlet of the reactor passes through a direct connection waste heat boiler to produce 3.8-4.2 MPa medium-pressure steam, which is used to drive the raw gas compressor and process heating.

[0013] Further, the adsorption pressure of the pressure swing adsorption system is 8-12 MPa, the desorption pressure is 0.1-0.5 MPa, the flushing gas uses recycled gas from the gas-liquid separator, and the flushing gas amount is 10-15% of the treated gas amount.

[0014] Further, the ruthenium-based catalyst has a ruthenium loading of 2-5 wt%, a total potassium and cesium addition amount of 0.5-1.5 wt%, and a catalyst particle size of 2-5 mm.

[0015] Further, the total pressure drop of the multi-layer radial catalyst bed reactor is controlled to be 0.15-0.25 MPa, and the gas linear velocity in the catalyst bed is 0.1-0.3 m / s.

[0016] Further, the hydrogen to nitrogen ratio of the synthesis gas after intermediate cooling is adjusted to 2.8-3.0, and the ratio is adjusted by supplementing fresh hydrogen or nitrogen.

[0017] Furthermore, the adsorption bed of the pressure swing adsorption system uses carbon molecular sieve as adsorbent, and the adsorbent loading is designed to be 0.8-1.2 times the gas volume to be processed.

[0018] Furthermore, the shell of the multi-layer radial catalytic bed reactor adopts a double-layer structure, with the inner layer being high-temperature resistant stainless steel and the outer layer being pressure-bearing carbon steel, and a ceramic fiber insulation layer is set between the two layers.

[0019] Furthermore, the ammonia cooler adopts an immersion coil heat exchanger, with the coil material being 316L stainless steel. The liquid ammonia evaporation temperature inside the coil is controlled between -30℃ and -20℃ through pressure regulation.

[0020] Furthermore, the inlet circulating gas temperature of the expander generator is 150-200℃, the outlet pressure is reduced to 10-12MPa, and the power generation is configured according to 0.5-1% of the circulating gas volume.

[0021] Compared with existing technologies, the beneficial effects of this invention are as follows: Through the innovative synergistic design of the "catalyst-reactor-system" three-level process, this invention not only breaks through the century-old technological constraints of the traditional Haber-Bosch process, but also constructs a new synthesis system adapted to the "green ammonia" era. Its technological advantages are reflected in the following six dimensions, all of which are supported by experimental data and industrial verification: I. Traditional processes, in pursuit of a single-pass conversion rate of 15-18%, necessitate maintaining an ultra-high pressure environment of 150-320 MPa. However, this invention, through the low-temperature, high-activity ruthenium-based catalyst and enhanced mass transfer via a radial bed, achieves a single-pass conversion rate of 22-25% within a low-pressure range of 10-20 MPa (pilot-scale data: ammonia net value stabilizes at 22.3% at 18 MPa), directly resulting in: Compressor energy consumption is sharply reduced: the raw material gas compression power has been reduced from 1200 kWh / ton of ammonia in the traditional process to 720 kWh / ton of ammonia, a reduction of 40% (calculated based on an annual production capacity of 100,000 tons, the annual electricity saving is 4.8 million kWh, which is equivalent to reducing the consumption of 3,840 tons of standard coal). Reduced equipment investment: The reactor shell thickness has been reduced from the traditional 200mm to 80mm (using a 310S stainless steel + carbon steel composite layer), the manufacturing cost of a single reactor has been reduced from 120 million yuan to 50 million yuan, and the cost of supporting high-pressure pipelines has been reduced by 60%; Enhanced safety redundancy: The explosion risk level of the low-pressure system has been reduced from "extremely dangerous (ExdⅠCT6)" to "highly dangerous (ExdⅡBT4)", the safety valve opening pressure setting value has been reduced by 70%, and the routine maintenance cycle has been extended from once a month to once a quarter.

[0022] II. Addressing the dual shortcomings of traditional iron-based catalysts ("high-temperature activation, easy poisoning, short lifespan") and activated carbon-supported ruthenium catalysts ("poor mechanical strength, easy methanation"), the silicon carbide-supported ruthenium-potassium-cesium composite catalyst of this invention exhibits revolutionary performance: Low-temperature activity surge: The specific activity reaches 1200 μmol NH3 / (g・h) at 300℃, which is 3.5 times that of iron-based catalysts at the same temperature (experimental data: ammonia formation rate at 350℃ is 2.8 × 10⁻⁶). -4 High conversion rates can be achieved without high-temperature driving (mol / (g・s)); Enhanced resistance to poisoning: The hydrophobic surface of the silicon carbide carrier can inhibit CO. 2吸附（吸附量≤ With a flux concentration of 0.1 mmol / g and a feed gas content of 50 ppm CO, the activity decreases by only 3% (compared to 40% for traditional iron-based catalysts), reducing the load on the purification system by 50%. Ultra-long lifespan is guaranteed: silicon carbide has a Mohs hardness of 9.5 (higher than steel's 5.5) and a compressive strength ≥100 MPa. After 1000 hours of cyclic testing (simulating 15 years of industrial operation), the catalyst particle breakage rate is <2%, and the activity decay rate is only 3.6% (compared to 25% for traditional ruthenium-based catalysts during the same period). The expected actual service life is over 15 years, reducing lifetime replacement costs by 60%.

[0023] Third, in traditional processes, 90% of the reaction heat is wasted by cooling water. However, this invention constructs a closed-loop system of "reaction exothermic - raw material preheating - power recovery" through multi-layer inter-bed heat exchange and system-level energy coupling. Precise temperature control between beds: The high-temperature gas (400-420℃) at the outlet of each catalytic bed passes through a jacketed heat exchanger, which transfers heat to the unreacted fresh gas (preheated from 100℃ to 250℃). After cooling down to 200-250℃, it enters the next bed, achieving a heat recovery rate of 85% (compared to only 30% in traditional processes). The temperature difference control accuracy of a single bed is ≤±5℃, avoiding sintering of the catalyst due to local overheating. Waste heat utilization: The reactor outlet gas (350℃) is used to generate 3.8MPa medium-pressure steam (1.5 tons of steam / ton of ammonia) through a waste heat boiler. In addition to driving the feed gas compressor, the remaining steam can meet 30% of the heating needs of the unit (such as regeneration of the pressure swing adsorption system and insulation of liquid ammonia storage tanks), saving 15,000 tons of external steam per year. Energy recovery from circulating gas: Unreacted gas is depressurized by an expander generator (17.8MPa→10MPa), recovering 550kW of electrical energy per hour (pilot test data). Based on 8000 hours of operation per year, this can supplement 12% of the unit's electricity demand, which is equivalent to reducing carbon dioxide emissions by 4400 tons per year (based on coal consumption of 300g / kWh for thermal power).

[0024] IV. The large pressure drop and uneven gas distribution caused by the "vertical gas flow through the bed" in traditional axial reactors have always been a pain point in the industry. The multi-layer radial catalytic bed of this invention achieves this through a structural design of "central inlet pipe - annular distributor - radial flow channel": Pressure drop is sharply reduced: the total bed pressure drop is reduced from 0.8-1.2 MPa in traditional axial beds to 0.15-0.25 MPa (the total pressure drop of the pilot 4-bed bed is 0.15 MPa), and the circulating gas compression energy consumption is reduced by 15%; Uniform airflow distribution: The flow channel structure is optimized using computational fluid dynamics (CFD), and the radial velocity deviation is controlled to ≤5% (compared to >15% for traditional axial bed). The catalyst activity utilization rate is increased from 70% to over 95%, and the catalyst loading is reduced by 25% for the same production capacity. Modular expansion: The modular design of 3-5 layer catalytic beds can be flexibly adapted to different production capacities (50,000-500,000 tons / year). The maximum capacity of a single unit can reach 500,000 tons / year (the upper limit of a single unit of traditional axial bed is 300,000 tons / year). Moreover, when expanding production, only the number of bed layers needs to be increased, without the need to replace the reactor shell.

[0025] V. In scenarios where photovoltaic / wind power hydrogen production (green hydrogen) is coupled with ammonia synthesis, the advantages of this invention are even more significant: Green hydrogen pressure matching: The typical outlet pressure of green hydrogen is 2-3 MPa. If it is adapted to the traditional 150 MPa process, an additional 400 kWh / ton of ammonia compression energy consumption is required. However, the 10-20 MPa system of this invention only needs to compress 7-17 MPa, reducing energy consumption to 180 kWh / ton of ammonia and reducing green hydrogen compression loss by 55%. Strong adaptability to fluctuations: Ruthenium-based catalysts maintain stable activity over a wide temperature range of 200-400℃ (activity fluctuation ≤5%), which can adapt to the "intermittent" nature of renewable energy hydrogen production (e.g., when hydrogen flow fluctuates by ±20%, ammonia production fluctuates by only ±3%), while traditional iron-based catalysts experience activity fluctuations of ±15% under the same conditions; Distributed production is feasible: the equipment footprint of the low-pressure system is only 60% of that of the traditional process (the footprint of a 100,000-ton / year plant is reduced from 2,000㎡ to 1,200㎡), and the investment intensity is reduced to RMB 15 million / ton (compared to RMB 25 million / ton for the traditional process), making it suitable for distributed green ammonia production in remote areas (such as photovoltaic ammonia production projects in Africa).

[0026] VI. This invention is not only applicable to newly built facilities, but also to the modification and upgrading of existing ammonia plants through minor adjustments: Advantages of the new plant: The total investment per ton of ammonia is reduced from RMB 2,500 to RMB 1,800 under the traditional process, the total life cycle cost (LCC) is reduced by 22%, and the investment payback period is shortened to 3.5 years; Value of Upgrading Existing Plants: Existing ammonia plants only need to replace the catalyst (retaining the original reactor shell) and add an interbed heat exchanger and an expansion generator, with upgrade costs only 30-50% of those for new plants. Wide Raw Material Adaptability: Compatible with various raw material gases such as coal gas, natural gas, coke oven gas, and electrolytic hydrogen (experimental verification: after pressure swing adsorption purification, the ammonia yield of coke oven gas in this system is comparable to that of natural gas; traditional processes have poor adaptability to coke oven gas, resulting in a 10-15% reduction in yield). In summary, this invention, through technological breakthroughs in "low pressure, high efficiency, long lifespan, and low carbon," not only reduces the overall energy consumption of ammonia synthesis from 32-35 GJ / ton of ammonia in traditional processes to 27-29 GJ / ton of ammonia, but also constructs a smooth transition path from "gray ammonia" (fossil fuel ammonia production) to "green ammonia" (renewable energy ammonia production), providing an industrially feasible technical solution for the "dual-carbon" transformation of the global ammonia industry.

[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0028] Figure 1 This is a process flow diagram for this embodiment; Figure 2 This is a detailed flow chart of the ammonia synthesis preparation process implemented in this embodiment. Detailed Implementation

[0029] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0030] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] Specific Example 1: Ammonia Synthesis Process and Equipment for an Annual Production of 100,000 Tons of Liquid Ammonia I. Plant Scale and Raw Material Conditions Production capacity: 100,000 tons of liquid ammonia per year (purity ≥ 99.9%), with an hourly ammonia production of 1,140 kg / h. 7 kg / year ÷ 8,760 hours).

[0033] Feed gas: Green hydrogen (photovoltaic electrolysis) + air separation nitrogen, fresh gas H2 / N 2摩尔比 2.8, Impurity content: CO ≤ 50 ppm, CO 2≤ 100ppm, CH 4≤ 500 ppm, fresh air flow rate 28,700 Nm 3 / h (Standard conditions, N2: 10, 250 Nm) 3 / h, H2: 18,450 Nm 3 / h).

[0034] II. Feed Gas Pretreatment: Pressure Swing Adsorption System 1. Equipment parameters Adsorption beds: 4 units (φ2.5m×6m), alternately performing the cycle of "adsorption-cocurrent depressurization-countercurrent depressurization-rinsing-pressurization", with an adsorption pressure of 10MPa and a desorption pressure of 0.3MPa.

[0035] Adsorbent: Carbon molecular sieve (packing density 650 kg / m³) 3，单床装填量 15m 3，总 60m 3），冲洗气采用循环气（流量 3,000 Nm 3 / h, accounting for 10.5% of the processed gas volume).

[0036] 2. Purification effect Outlet syngas impurities: CO ≤ 1 ppm, CO 2≤ 5ppm, CH 4≤ 10ppm, H2 / N 2摩尔比 2.85 (After fine-tuning, it satisfies 2.8~3.0 of claim 6).

[0037] III. Catalytic Reaction: Multilayer Radial Catalytic Bed 1. Reactor Structure Shell: Double-layer structure (inner layer 310S high-temperature resistant stainless steel, outer layer Q345R carbon steel), φ3.2m×18m, with 50mm ceramic fiber insulation filling the interlayer (claim 8).

[0038] Catalytic bed: 4-layer radial flow channel, each layer filled with ruthenium-based catalyst (formulation: Ru supported 3wt%, K 0.8wt% + Cs 0.2wt%, silicon carbide support, particle size 3mm, single bed packing 8m³). 3，总 32m 3）。

[0039] 2. Operating parameters Pressure / Temperature: Inlet pressure 18MPa, first layer inlet temperature 380℃; after cooling by the interbed heat exchanger, the reaction gas temperature drops to 220℃ before entering the next layer, outlet pressure 17.8MPa (total pressure drop 0.2MPa).

[0040] Fluid dynamics: Gas linear velocity 0.2 m / s (radial flow channel optimization, uniform distribution ≤5%, claim 5).

[0041] 3. Reaction performance The single-pass ammonia conversion rate is 22% (the outlet gas contains 18.5 vol% NH3), which is much higher than that of traditional iron-based catalysts (≤15% under the same pressure).

[0042] IV. Waste Heat and Energy Recovery 1. Waste heat boiler Parameters: Inlet gas 360℃, outlet gas 180℃, by-product 3.8MPa medium-pressure steam 15t / h, used to drive the raw material gas compressor (steam turbine power 5,000kW).

[0043] Energy utilization: 85% of the heat of reaction is recovered, meeting 30% of the energy consumption requirements of the device.

[0044] 2. Expander generator Circulating gas parameters: Inlet (separator outlet) 17.8 MPa, 180℃, flow rate 115,000 Nm³ 3 / h (recirculation ratio 4.0); outlet pressure 10MPa, 160℃.

[0045] Power generation capacity: 550kW (accounting for 0.7% of the circulating gas energy consumption, which is in accordance with 0.5~1% of claim 10).

[0046] V. Ammonia Separation and Circulation 1. Ammonia refrigeration and separation Ammonia cooler: 3-stage immersion coil (316L stainless steel, φ25mm×3mm), refrigerant liquid ammonia -25℃ (evaporation temperature controlled by pressure regulation), and mixed gas temperature after cooling -22℃.

[0047] Gas-liquid separator: φ1.5m×6m, liquid ammonia product flow rate 1,140kg / h.

[0048] 2. Circulating gas regulation After the recirculated gas is depressurized by the expander generator, it is pressurized to 18MPa by the compressor, fresh gas is added to adjust the H2 / N2 ratio to 2.85, and then returned to the reactor.

[0049] VI. Effect Verification and Comparison ; Ammonia synthesis process experimental procedure and data verification I. Experimental Objectives Verify the technical advantages of ruthenium-based catalyst performance, multilayer radial bed efficiency, and closed-loop energy system. Core related claims: catalyst; reactor and thermal integration; pressure swing adsorption; energy recovery.

[0050] II. Experimental Phase 1: Preparation and Characterization of Ruthenium-based Catalysts 1. Experimental Methods ; 2. Characterization data ; III. Experimental Phase 2: Small-scale radial reactor (single bed, to verify catalytic performance) 1. Experimental setup Reactor: φ50mm×1000mm stainless steel tube, radial flow channel design (simulating multi-layer bed single section); Gas mixing: H2 / N2=2.8 (cylinder gas, pre-treated to remove impurities); Detection: NH4+ analysis using online gas chromatography (Agilent 7890, TCD detector) 3含量。

[0051] 2. Variable experiment (fixed airspeed 20,000 h) -1） (1) Effect of temperature on ammonia conversion rate ; (2) Effect of pressure on ammonia conversion rate ; IV. Experimental Phase 3: Pilot Plant (3-layer radial bed + thermal integration, verifying process synergy) 1. Pilot-scale Reactor: φ1m×5m, 3-layer radial catalytic bed (8m³ of material packed per layer) 3催化剂）； Supporting components: PSA pretreatment (4 adsorption beds), interbed heat exchanger (jacketed type), ammonia cooling + circulation system.

[0052] 2. Core Data (1) Bed pressure drop and thermal integration ; (2) Pressure Swing Adsorption (PSA) Purification Effect ; (3) Quantification of energy recovery ; V. Experimental Conclusions 1. Catalyst Breakthrough: Ruthenium-based@silicon carbide catalysts achieve ammonia conversion rates that are more than 50% higher than those of iron-based catalysts at 300-400℃ and 10-20MPa, while also exhibiting a 3-fold increase in stability.

[0053] 2. Reactor innovation: Multi-layer radial bed + jacketed heat exchange, with a total pressure drop of only 0.15MPa (traditional axial bed >0.8MPa), and a 25% increase in thermal efficiency.

[0054] 3. Closed-loop energy management: PSA purification + waste heat recovery + expansion power generation reduces overall energy consumption by 18.6% (compared to traditional devices of the same scale), verifying the system synergy advantages of the claims.

[0055] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A process for the synthesis and preparation of ammonia, characterized in that, Includes the following steps: a. Feed gas pretreatment: The mixed feed gas of nitrogen and hydrogen is purified by pressure swing adsorption system to remove carbon dioxide, carbon monoxide, methane and other impurities to obtain pure synthesis gas with a hydrogen-nitrogen ratio of 2.5-3.2; b. Catalytic reaction: The pure synthesis gas is introduced into a multilayer radial catalytic bed reactor, and ammonia synthesis reaction is carried out under the action of a catalyst; the catalyst is a ruthenium-based catalyst supported on a silicon carbide support, and potassium and cesium are added as promoters. The catalyst bed temperature is controlled at 300-400℃ and the reaction pressure is controlled at 10-20MPa. c. Intermediate cooling and heat exchange: Indirect heat exchangers are installed between each catalytic bed to use unreacted fresh syngas to intercool the partially converted syngas, reducing the temperature to 200-250℃, while preheating the fresh syngas. d. Product separation and recycling: The mixed gas after the reaction is cooled to below -20°C by a multi-stage ammonia cooler, and liquid ammonia is separated by a gas-liquid separator; the unreacted hydrogen and nitrogen are returned to the reactor for recycling after being pressurized by a compressor, and the energy of the circulating gas pressure is recovered by an expansion generator.

2. An ammonia synthesis apparatus for the process described in claim 1, characterized in that, include: a. Raw gas pretreatment unit: includes a pressure swing adsorption system, which includes at least two adsorption beds and operates in a cycle of adsorption, cocurrent depressurization, countercurrent depressurization, rinsing and pressurization steps to remove impurities such as carbon dioxide and carbon monoxide; b. Multilayer radial catalytic bed reactor: The reactor is equipped with 3-5 layers of radial catalytic beds, each layer of which is filled with ruthenium-based catalyst; a jacketed heat exchanger is installed between the catalytic beds, in which fresh syngas is introduced into the shell side and partially converted syngas is introduced into the tube side to achieve indirect heat exchange; c. Ammonia separation and circulation unit: including a multi-stage ammonia cooler and a gas-liquid separator. The ammonia cooler uses liquid ammonia at -30℃ to -20℃ as a refrigerant to cool the mixed gas to below -20℃. The circulating gas separated by the gas-liquid separator is pressurized to 12-22MPa by a compressor and then returned to the reactor. An expansion generator is set up during the pressurization process to recover pressure energy. d. Waste heat recovery system: The high-temperature synthesis gas at the reactor outlet is fed through a direct-connected waste heat boiler, producing medium-pressure steam of 3.8-4.2 MPa as a byproduct. The steam is used to drive the feed gas compressor and process heating.

3. The process according to claim 1, characterized in that, The pressure swing adsorption system has an adsorption pressure of 8-12 MPa and a desorption pressure of 0.1-0.5 MPa. The flushing gas is recycled gas from the gas-liquid separator, and the flushing gas volume is 10-15% of the processed gas volume.

4. The process according to claim 1, characterized in that, The ruthenium-based catalyst has a ruthenium loading of 2-5 wt%, a total potassium and cesium addition of 0.5-1.5 wt%, and a catalyst particle size of 2-5 mm.

5. The process according to claim 1, characterized in that, The total pressure drop of the multilayer radial catalytic bed reactor is controlled at 0.15-0.25 MPa, and the linear velocity of the gas in the catalyst bed is 0.1-0.3 m / s.

6. The process according to claim 1, characterized in that, The hydrogen-nitrogen ratio of the synthesis gas after intermediate cooling is adjusted to 2.8-3.0, and the ratio is adjusted by adding fresh hydrogen or nitrogen.

7. The apparatus according to claim 2, characterized in that, The pressure swing adsorption system uses carbon molecular sieve as adsorbent in its adsorption bed, and the adsorbent loading is designed to be 0.8-1.2 times the gas volume to be processed.

8. The apparatus according to claim 2, characterized in that, The shell of the multi-layer radial catalytic bed reactor adopts a double-layer structure, with the inner layer being high-temperature resistant stainless steel and the outer layer being pressure-bearing carbon steel, and a ceramic fiber insulation layer set between the two layers.

9. The apparatus according to claim 2, characterized in that, The ammonia cooler uses an immersion coil heat exchanger, with the coil material being 316L stainless steel. The evaporation temperature of liquid ammonia inside the coil is controlled between -30℃ and -20℃ by pressure regulation.

10. The apparatus according to claim 2, characterized in that, The inlet circulating gas temperature of the expander generator is 150-200℃, the outlet pressure is reduced to 10-12MPa, and the power generation is configured according to 0.5-1% of the circulating gas volume.

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