A system for generating electricity from excess pressure in the production of ammonia

Abstract

A kind of surplus pressure energy-saving power generation system in ammonia synthesis production, including sequentially connected ammonia synthesis loop, high-pressure ammonia separator and medium-pressure ammonia separator, the outlet of the high-pressure ammonia separator is communicated with the medium-pressure ammonia separator by medium-pressure pressure reducing valve;It further includes liquid ammonia expansion generator set and the drive turbine matched with the liquid ammonia expansion generator set, the inlet side pipeline of the medium-pressure pressure reducing valve is communicated with the inlet of the drive turbine, the outlet side pipeline of the medium-pressure pressure reducing valve is communicated with the outlet of the drive turbine, and the drive turbine is drivingly connected with the liquid ammonia expansion generator set by transmission device.Using the above structure, the utilization rate of surplus pressure energy is high, which is converted into electric energy and put on the grid without additional input of external energy, and the energy recovery efficiency is high;Simple structure, small floor area, convenient operation of matched equipment, high running stability;Strong adaptability, realize continuous operation all day round.

Description

Technical Field

[0001] This utility model relates to the field of synthetic ammonia production technology, and in particular to a residual pressure energy-saving power generation system in ammonia synthesis production. Background Technology

[0002] Ammonia is a key raw material for fertilizer production, and coal-to-ammonia is currently one of the mainstream ammonia preparation processes. With industry development, reducing energy consumption in ammonia synthesis and simplifying the synthesis process have become core development trends in ammonia synthesis technology. New or expanded petrochemical projects must meet energy efficiency benchmarks; by the end of 2025, the proportion of synthetic ammonia production capacity above the energy efficiency benchmark level must exceed 30%, and capacity below the energy efficiency benchmark level must undergo technological upgrades or be phased out. These requirements place higher demands on energy conservation and carbon reduction in the synthetic ammonia industry.

[0003] In actual ammonia synthesis production, process conditions must be strictly controlled: the optimal temperature for ammonia synthesis is 400.0–500.0℃, and the space velocity needs to be controlled between 10,000 and 30,000 h⁻¹. -1 (Corresponding system pressure 15-30 MPa); the ammonia separation section requires pretreatment by an ammonia condenser (-15℃, 15 MPa), followed by sequential passage through a high-pressure ammonia separator (-10℃, 15 MPa), a medium-pressure ammonia separator (-8℃, 5.2 MPa), and an atmospheric pressure ammonia separator (-33℃, 0 MPa), ultimately delivering the liquid ammonia to a storage tank. Currently, the pressure reduction process from the outlet of the high-pressure ammonia separator (15 MPaG) to the inlet of the medium-pressure ammonia separator (5.2 MPaG) generally uses pressure-reducing valves or orifice plates for direct pressure reduction. This method results in the complete waste of pressure energy in the high-pressure liquid ammonia, making energy recovery impossible and severely contradicting the industry's energy conservation and carbon reduction requirements. Therefore, developing a system that can efficiently recover the residual pressure energy in this process is of significant practical importance for reducing energy consumption in ammonia synthesis plants and improving the industry's energy efficiency. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to provide a residual pressure energy-saving power generation system in ammonia synthesis production. The system has a simple structure, high residual pressure energy utilization rate, can be operated continuously and stably, and has strong equipment operation reliability. It realizes the conversion of pressure energy into electrical energy and reduces the energy consumption of ammonia synthesis plant.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a residual pressure energy-saving power generation system in ammonia synthesis production, comprising an ammonia synthesis circuit, a high-pressure ammonia separator, and a medium-pressure ammonia separator connected in sequence, wherein the outlet of the high-pressure ammonia separator is connected to the medium-pressure ammonia separator through a medium-pressure reducing valve; It also includes a liquid ammonia expansion generator set and a drive turbine that is matched with the liquid ammonia expansion generator set. The inlet side pipeline of the medium pressure reducing valve is connected to the inlet of the drive turbine, the outlet side pipeline of the medium pressure reducing valve is connected to the outlet of the drive turbine, and the drive turbine is connected to the liquid ammonia expansion generator set through a transmission device.

[0006] In a preferred embodiment, the high-pressure ammonia separator is provided with a first gas outlet at the top, and the medium-pressure ammonia separator is provided with a second gas outlet at the top. Both the first gas outlet and the second gas outlet are connected to the ammonia synthesis circuit to achieve recirculation of circulating gas.

[0007] In a preferred embodiment, the medium-pressure reducing valve is a level control valve, and the valve control signal of the medium-pressure reducing valve and the operating status signal of the driving turbine are jointly associated with the level controller of the high-pressure ammonia separator to regulate the level stability of the high-pressure ammonia separator.

[0008] In a preferred embodiment, the driving turbine is a liquid ammonia expander, which receives high-pressure liquid ammonia and releases pressure energy through expansion to drive the liquid ammonia expander generator set.

[0009] In a preferred embodiment, a liquid ammonia storage tank is also included, which is connected to the outlet of the medium-pressure ammonia separator and is used to store liquid ammonia after medium-pressure separation. In a preferred embodiment, the crude ammonia pressure output from the outlet of the ammonia synthesis circuit is 11–15 MPaG, and the pressure difference between the inlet and outlet sides of the medium-pressure reducing valve is 8–12 MPaG.

[0010] In a preferred embodiment, the transmission device includes a speed reducer, an asynchronous generator, and a grid-connected cabinet connected in sequence. The drive turbine is connected to the asynchronous generator via the speed reducer, and the asynchronous generator is connected to the power grid via the grid-connected cabinet.

[0011] The residual pressure energy-saving power generation system in ammonia synthesis production provided by this utility model, by adopting the above-described structure, has the following beneficial effects: (1) The residual pressure energy utilization rate is high. The pressure energy of the high-pressure liquid ammonia decompression process is directly recovered and converted into electricity for grid connection. No additional external energy input is required. The energy recovery efficiency can reach more than 85%. (2) It has a simple structure, small footprint, convenient operation of supporting equipment, and high operational stability; (3) It can be used for both new ammonia synthesis plants and energy-saving retrofits of existing plants, with low retrofit costs and short cycles; (4) By coordinating the control of the liquid level control valve and the driving turbine operation signal, the liquid level of the high-pressure ammonia separator is kept stable, and the ammonia separation efficiency is avoided due to the fluctuation of the pressure reduction process, so as to achieve continuous operation throughout the day. Attached Figure Description

[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the overall structure and process of this utility model.

[0013] In the diagram: 1. Ammonia synthesis circuit; 2. High-pressure ammonia separator; 3. Medium-pressure ammonia separator; 4. Liquid ammonia storage tank; 5. Medium-pressure pressure reducing valve; 6. Drive turbine; 7. Liquid ammonia expansion generator set. Detailed Implementation

[0014] Example 1: like Figure 1 This invention discloses a residual pressure energy-saving power generation system for ammonia synthesis production. The system's core design objective is the recovery of pressure energy from the ammonia synthesis process, achieving both energy cascade utilization and energy conservation and carbon reduction. Its main components include an ammonia synthesis loop 1, a high-pressure ammonia separator 2, and a medium-pressure ammonia separator 3, connected in series to form the process flow path. The ammonia synthesis loop 1 completes the synthesis reaction of crude ammonia, and its output ammonia-containing material enters the high-pressure ammonia separator 2 for gas-liquid separation. The outlet of the high-pressure ammonia separator 2 is connected to the medium-pressure ammonia separator 3 via a medium-pressure reducing valve 5, forming a conventional pressure-reducing and conveying path for liquid ammonia. To achieve the residual pressure recovery function, the system is also specially equipped with a liquid ammonia expansion generator set 7 and a drive turbine 6 that is matched with the liquid ammonia expansion generator set 7. The inlet side pipeline of the medium pressure reducing valve 5 is connected to the inlet of the drive turbine 6, and the outlet side pipeline of the medium pressure reducing valve 5 is connected to the outlet of the drive turbine 6, forming a parallel operation architecture from the pressure reducing valve to the turbine. The drive turbine 6 transmits mechanical energy to the liquid ammonia expansion generator set 7 through a transmission device, completing the conversion of pressure energy into electrical energy.

[0015] In a preferred embodiment, the high-pressure ammonia separator 2 has a first gas outlet at its top for discharging the recirculated gas rich in unreacted components after separation; the medium-pressure ammonia separator 3 has a second gas outlet at its top for discharging the small amount of gas generated during this separation stage. Both the first and second gas outlets are connected to the ammonia synthesis loop 1 to achieve closed-loop reflux of the recirculated gas, which not only improves the utilization rate of raw materials but also reduces emission losses, meeting industry requirements for energy conservation and carbon reduction.

[0016] In the preferred embodiment, the medium-pressure reducing valve 5 is a level control valve. Its core function is to control the liquid ammonia flow rate by adjusting the valve opening, thereby stabilizing the liquid level in the high-pressure ammonia separator 2. To improve control accuracy and system stability, the valve control signal of the medium-pressure reducing valve 5 and the operating status signal of the drive turbine 6 are jointly linked to the level controller of the high-pressure ammonia separator 2, forming a coordinated control mechanism. When the load of the drive turbine 6 changes, causing a change in the liquid ammonia flow rate, the level controller can synchronously adjust the opening of the medium-pressure reducing valve 5 to ensure that the liquid level in the high-pressure ammonia separator 2 is always maintained within the process requirements, avoiding the impact of liquid level fluctuations on subsequent separation effects.

[0017] In a preferred embodiment, the driving turbine 6 is a liquid ammonia expander, whose structural design is adapted to the physical properties and process parameters of liquid ammonia, and is used to receive high-pressure liquid ammonia discharged from the high-pressure ammonia separator 2. The high-pressure liquid ammonia undergoes an expansion process inside the driving turbine 6, rapidly reducing its pressure and releasing a large amount of pressure energy, driving the turbine impeller to rotate at high speed. This, in turn, drives the liquid ammonia expander generator set 7 through mechanical transmission, achieving efficient recovery and utilization of pressure energy.

[0018] In a preferred embodiment, a liquid ammonia storage tank 4 is also included for temporary storage and transfer of liquid ammonia. The liquid ammonia storage tank 4 is connected to the outlet of the medium-pressure ammonia separator 3 and is used to store liquid ammonia that meets the purity requirements after medium-pressure separation. This arrangement creates a buffer connection between the discharge of the medium-pressure ammonia separator 3 and the storage of liquid ammonia in the liquid ammonia storage tank 4, avoiding the impact of subsequent transportation fluctuations on the stable operation of the separation section and ensuring the continuity of the entire production process.

[0019] In the preferred embodiment, the crude ammonia output from the outlet of the ammonia synthesis loop 1 has a high pressure, providing a basic condition for subsequent pressure energy recovery; the inlet and outlet sides of the medium-pressure reducing valve 5 form a stable pressure difference, which is both the power source for the flow of liquid ammonia and the core prerequisite for driving the turbine 6 to achieve energy conversion, ensuring that the residual pressure recovery system has sufficient energy supply.

[0020] In the preferred embodiment, the transmission device adopts a multi-stage transmission and grid-connected control architecture, including a reducer, an asynchronous generator, and a grid-connected cabinet connected in sequence. The output speed of the drive turbine 6 typically does not match the rated speed of the asynchronous generator. The reducer enables precise speed adjustment, ensuring stable transfer of mechanical energy to the asynchronous generator. After the asynchronous generator converts mechanical energy into electrical energy, the voltage, frequency, and other parameters need to be adjusted through the grid-connected cabinet to ensure that the output electrical energy meets grid connection standards, ultimately achieving safe and stable connection with the grid and enabling efficient utilization of recovered electrical energy.

[0021] Example 2: like Figure 1 The working principle of this utility model is as follows: Check the sealing of all pipelines in the system (using helium mass spectrometry for leak detection; leak rate ≤ 1 × 10⁻⁶). -9 (Pa・m³ / s), ensuring that the medium-pressure reducing valve 5 is at its normal opening (initial opening 50%), and that the drive turbine 6 is in a stopped state; Start ammonia synthesis circuit 1 to allow crude ammonia (pressure 13 MPaG, temperature 450℃) to enter high-pressure ammonia separator 2, where high-pressure liquid ammonia (purity ≥99.5%) is separated at -10℃. The circulating gas returns to ammonia synthesis circuit 1 via the return pipeline. Slowly reduce the opening of the medium-pressure reducing valve 5 (reducing it by 5% every five minutes), and at the same time open the shut-off valve of the inlet branch pipe of the drive turbine 6 to allow some high-pressure liquid ammonia (initial flow rate 10m³ / h) to enter the drive turbine 6. High-pressure liquid ammonia expands inside the drive turbine 6, depressurizing from 13MPaG to 5.2MPaG, driving the turbine rotor to rotate, and the speed gradually increases to 3000r / min. The speed is then increased to 3000r / min, which drives the asynchronous generator to generate electricity through the reducer. The electricity is then connected to the power grid through the grid-connected cabinet. The liquid level of the high-pressure ammonia separator 2 is monitored in real time by the liquid level controller. If the liquid level is higher than the set value, the liquid inlet of the drive turbine 6 is increased, and the opening of the medium-pressure reducing valve 5 is appropriately reduced. If the liquid level is lower than the set value, adjust it accordingly; Gradually adjust all high-pressure liquid ammonia flow to stabilize at 50 m³ / h and enter medium-pressure ammonia separator 3 through drive turbine 6. At this time, the opening of medium-pressure pressure reducing valve 5 drops to 10%, drive turbine 6 runs stably, and generator output power stabilizes at 120 kW. The medium-pressure ammonia separator 3 further separates liquid ammonia at -8℃ and 5.2MPaG. The small amount of circulating gas separated is returned to the ammonia synthesis circuit 1, and the qualified liquid ammonia (purity ≥99.8%) is sent to the liquid ammonia storage tank 4 for storage.

[0022] The beneficial effects of this utility model are: high utilization rate of residual pressure energy, directly recovering the pressure energy of the high-pressure liquid ammonia decompression process and converting it into electricity for grid connection, without the need for additional external energy input, and the energy recovery efficiency can reach over 85%; simple structure, small footprint, convenient operation of supporting equipment, and high operational stability; it can be used for new ammonia synthesis plants or for energy-saving retrofitting of existing plants, with low retrofitting costs and short cycles; through the coordinated control of the liquid level control valve and the driving turbine operation signal, the liquid level of the high-pressure ammonia separator is ensured to be stable, avoiding the impact of ammonia separation efficiency on the decompression process, and realizing continuous operation throughout the day.

Claims

1. A residual pressure energy-saving power generation system in ammonia synthesis production, characterized in that: It includes an ammonia synthesis circuit (1), a high-pressure ammonia separator (2) and a medium-pressure ammonia separator (3) connected in sequence. The outlet of the high-pressure ammonia separator (2) is connected to the medium-pressure ammonia separator (3) through a medium-pressure reducing valve (5). It also includes a liquid ammonia expansion generator set (7) and a drive turbine (6) that is matched with the liquid ammonia expansion generator set (7). The inlet side pipeline of the medium pressure reducing valve (5) is connected to the inlet of the drive turbine (6), the outlet side pipeline of the medium pressure reducing valve (5) is connected to the outlet of the drive turbine (6), and the drive turbine (6) is connected to the liquid ammonia expansion generator set (7) through a transmission device.

2. The residual pressure energy-saving power generation system in ammonia synthesis production according to claim 1, characterized in that: The high-pressure ammonia separator (2) is provided with a first gas outlet at the top, and the medium-pressure ammonia separator (3) is provided with a second gas outlet at the top. Both the first gas outlet and the second gas outlet are connected to the ammonia synthesis circuit (1) to achieve circulating gas reflux.

3. The residual pressure energy-saving power generation system in ammonia synthesis production according to claim 1, characterized in that: The medium-pressure reducing valve (5) is a level control valve, and the valve control signal of the medium-pressure reducing valve (5) and the operating status signal of the drive turbine (6) are jointly associated with the level controller of the high-pressure ammonia separator (2) to regulate the level stability of the high-pressure ammonia separator (2).

4. The residual pressure energy-saving power generation system in ammonia synthesis production according to claim 1, characterized in that: The driving turbine (6) is a liquid ammonia expander, which is used to receive high-pressure liquid ammonia and release pressure energy through expansion to drive the liquid ammonia expander generator set (7).

5. The residual pressure energy-saving power generation system in ammonia synthesis production according to claim 1, characterized in that: It also includes a liquid ammonia storage tank (4), which is connected to the outlet of the medium-pressure ammonia separator (3) and is used to store liquid ammonia after medium-pressure separation.

6. The residual pressure energy-saving power generation system in ammonia synthesis production according to claim 1, characterized in that: The crude ammonia pressure output from the outlet of the ammonia synthesis circuit (1) is 11-15 MPaG, and the pressure difference between the inlet and outlet sides of the medium pressure reducing valve (5) is 8-12 MPaG.

7. The residual pressure energy-saving power generation system in ammonia synthesis production according to claim 1, characterized in that: The transmission device includes a speed reducer, an asynchronous generator and a grid-connected cabinet connected in sequence. The drive turbine (6) is connected to the asynchronous generator via the speed reducer, and the asynchronous generator is connected to the power grid via the grid-connected cabinet.

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