Liquid ammonia conveying power recycling system of ammonia synthesis device

Abstract

The invention relates to the technical field of ammonia synthesis equipment, and particularly discloses a liquid ammonia conveying power recycling system of an ammonia synthesis device, which is used for solving the problem that power cannot be recycled in the prior art. Comprising an ammonia separator, a synthetic gas ammonia outlet separator valve is arranged at the discharging position of the upper side of the ammonia separator, a synthetic gas ammonia inlet separator valve is arranged at the feeding position of the left side of the ammonia separator, and a liquid ammonia discharging port of the ammonia separator is communicated with the feeding end of a first-stage flash tank through a liquid ammonia conveying pipeline; a discharging pipe at the top of the first-stage flash tank is provided with a flash steam delivery valve, a discharging pipe at the bottom of the first-stage flash tank is provided with a liquid ammonia delivery valve, and pressure energy in liquid ammonia produced by an ammonia synthesis device is converted into electric energy through an expansion machine; and abrasion and internal leakage damage of a valve core due to long-time operation of the liquid ammonia pressure reducing valve of the ammonia separator are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia synthesis equipment, in particular to a liquid ammonia transport power recovery and utilization system of an ammonia synthesis device. Background Art

[0002] The fresh gas from the purification with a pressure of 3.0MPa and a temperature of 30℃ and the circulating gas returned from the synthesis loop are pressurized to 14.1MPa(A) and 63℃ by the compressor and sent to the ammonia synthesis tower. The synthesis gas reacts to generate NH3 under high temperature, high pressure and catalytic action of the catalyst. Then it is cooled and condensed by the heat exchanger, and liquid ammonia is separated by the ammonia separator. The product liquid ammonia is sent out of the boundary area. The unreacted gas returns to the circulation section of the synthesis gas compressor and merges with the fresh gas. After the pressure is increased, it continues to enter the synthesis tower for reaction. At present, the working pressure of the ammonia separator is 14.5MPa, and the working pressure of the primary flash tank is 3.1MPa. According to the 100% load of the ammonia synthesis unit, the ammonia separator separates 62.5t of liquid ammonia per hour, and enters the primary flash tank through the liquid ammonia pressure reducing valve for flash evaporation; in this process, the power of liquid ammonia is wasted, and the long-term pressure reduction operation of the liquid ammonia pressure reducing valve of the ammonia separator is prone to valve core wear and internal leakage, which brings hidden dangers to normal production; therefore, it is very necessary and meaningful to design a more efficient ammonia synthesis unit liquid ammonia transportation and power recovery. Summary of the invention

[0003] The purpose of the present invention is to provide a liquid ammonia transport power recovery and utilization system for an ammonia synthesis device, which solves the problem that power cannot be recovered in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The liquid ammonia transport power recovery and utilization system of an ammonia synthesis device comprises an ammonia separator, wherein a synthetic gas outlet ammonia separator valve is provided at a discharge position on the upper side of the ammonia separator, a synthetic gas inlet ammonia separator valve is provided at a feed position on the left side of the ammonia separator, a liquid ammonia discharge port of the ammonia separator is connected with a feed end of a primary flash tank through a liquid ammonia transport pipeline, a flash gas external delivery valve is provided on a discharge pipe at the top of the primary flash tank, a liquid ammonia external delivery valve is provided on a discharge pipe at the bottom of the primary flash tank, a liquid ammonia pressure reducing valve is provided on the liquid ammonia transport pipeline, a liquid ammonia transport pipeline upstream of the liquid ammonia pressure reducing valve is connected with a feed end of an expander through a branch pipe, an expander inlet valve is provided on the branch pipe, a shaft end of the expander is transmission-connected with a shaft end of a generator through a transmission mechanism, a discharge pipe of the expander is connected with a liquid ammonia transport pipeline through a reflux pipe, an expander outlet valve is provided on the reflux pipe, and a lubrication unit for lubrication is also provided on the transmission mechanism.

[0006] On the basis of the above technical solution, the present invention also provides the following optional technical solution:

[0007] In an optional solution: the expander and the generator are both provided with a tachometer for detecting their rotation speeds.

[0008] In an optional scheme: the lubrication unit includes a lubricating oil station, and a lubricating oil delivery valve is provided on the oil outlet pipe of the lubricating oil station, the end of the oil outlet pipe is connected to the oil inlet end of the lubricating oil cooler, the oil outlet end of the lubricating oil cooler is connected to the oil inlet end of the transmission mechanism, and the oil outlet end of the transmission mechanism is connected to the oil inlet end of the lubricating oil station through a lubricating oil return pipeline.

[0009] In an optional solution: the oil outlet pipe of the lubricating oil station is also connected to the lubricating oil return pipeline through an auxiliary pipe, and a lubricating oil return valve is provided on the auxiliary pipe.

[0010] In an optional solution: a cooling water inlet valve is provided on the cooling liquid inlet pipe of the lubricating oil cooler, and a cooling water return valve is provided on the cooling liquid outlet pipe of the lubricating oil cooler.

[0011] In an optional solution: a lubricating oil filter is further connected between the lubricating oil cooler and the transmission mechanism, and a lubricating oil cooler outlet valve is further provided between the lubricating oil cooler and the lubricating oil filter.

[0012] In an optional solution: the power connection terminal of the generator is also electrically connected to a power transmission line.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The present application converts the pressure energy of liquid ammonia produced by an ammonia synthesis device into electrical energy through an expander; avoids the long-term operation of the liquid ammonia pressure reducing valve of the ammonia separator, the wear of the valve core, and the internal leakage damage; the ammonia synthesis device is 100%, generates 2400KW.h of electricity every day, and creates an annual benefit of 396,000 yuan; the method and device of the present invention have the advantages of good treatment effect, safety and reliability, simple process, low operating cost, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the present invention.

[0016] 1. Valve for syngas outlet from ammonia separator; 2. Valve for syngas inlet from ammonia separator; 3. Inlet valve for expander; 4. Generator; 5. Electricity export line; 6. Lubricating oil return pipeline; 7. Lubricating oil station; 8. Lubricating oil export valve; 9. Cooling water return valve; 10. Cooling water inlet valve; 11. Lubricating oil return valve; 12. Lubricating oil cooler; 13. Lubricating oil cooler outlet valve; 14. Lubricating oil filter; 15. Expander outlet valve; 16. Expander; 17. Liquid ammonia pressure reducing valve; 18. Ammonia separator; 19. Liquid ammonia delivery pipeline; 20. Primary flash tank; 21. Flash gas export valve; 22. Liquid ammonia export valve. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] like Figure 1 As shown, the embodiment of the present invention provides a liquid ammonia transport power recovery and utilization system for an ammonia synthesis device, comprising an ammonia separator 18, wherein a synthesis gas outlet ammonia separator valve 1 is provided at a discharge position on the upper side of the ammonia separator 18, a synthesis gas inlet ammonia separator valve 2 is provided at a feed position on the left side of the ammonia separator 18, a liquid ammonia outlet of the ammonia separator 18 is connected to a feed end of a primary flash tank 20 through a liquid ammonia transport pipeline 19, a flash gas outlet valve 21 is provided on a discharge pipe at the top of the primary flash tank 20, a liquid ammonia outlet valve 22 is provided on a discharge pipe at the bottom of the primary flash tank 20, and the liquid ammonia outlet valve 23 is provided on the discharge pipe at the bottom of the primary flash tank 20. A liquid ammonia pressure reducing valve 17 is provided on the delivery pipeline 19. The liquid ammonia delivery pipeline 19 upstream of the liquid ammonia pressure reducing valve 17 is connected to the feed end of the expander 16 through a branch pipe. The branch pipe is provided with an expander inlet valve 3. The shaft end of the expander 16 is transmission-connected to the shaft end of the generator 4 through a transmission mechanism. The discharge pipe of the expander 16 is connected to the liquid ammonia delivery pipeline 19 through a reflux pipe. The reflux pipe is provided with an expander outlet valve 15. The transmission mechanism is also provided with a lubrication unit for lubrication. The lubrication unit can reduce the wear caused by the transmission and can also take away the heat.

[0019] The lubrication unit comprises a lubricating oil station 7, an oil outlet pipe of the lubricating oil station 7 is provided with a lubricating oil delivery valve 8, the end of the oil outlet pipe is communicated with the oil inlet end of the lubricating oil cooler 12, the oil outlet end of the lubricating oil cooler 12 is communicated with the oil inlet end of the transmission mechanism, the oil outlet end of the transmission mechanism is communicated with the oil inlet end of the lubricating oil station 7 through a lubricating oil return line 6, the liquid is sent from the lubricating oil station 7 to the lubricating oil cooler 12 through an oil pump, the cooled lubricating oil cooler 12 enters the transmission mechanism along the pipeline, so as to cool and lubricate the inside of the transmission mechanism, and the oil after working enters the lubricating oil station 7 along the lubricating oil return line 6, so as to complete the circulation work;

[0020] The oil outlet pipe of the lubricating oil station 7 is also connected to the lubricating oil return pipeline 6 through an auxiliary pipe, and a lubricating oil return valve 11 is provided on the auxiliary pipe;

[0021] The cooling liquid inlet pipe on the lubricating oil cooler 12 is provided with a cooling water inlet valve 10, and the cooling liquid outlet pipe of the lubricating oil cooler 12 is provided with a cooling water return valve 9, so that the refrigerant enters the lubricating oil cooler 12, thereby cooling the oil in the lubricating oil cooler 12;

[0022] A lubricating oil filter 14 is also connected between the lubricating oil cooler 12 and the transmission mechanism, and a lubricating oil cooler outlet valve 13 is also provided between the lubricating oil cooler 12 and the lubricating oil filter 14. The lubricating oil filter 14 is provided to remove impurities in the oil to ensure smooth flow of the oil circuit.

[0023] The power receiving end of the generator 4 is also electrically connected to the power transmission line 5, so that it can obtain power from the outside and also obtain city power;

[0024] At present, the working pressure of the liquid ammonia separator is 14.5MPa, and the working pressure of the primary flash tank is 3.1MPa. According to the 100% load of the ammonia synthesis unit, the ammonia separator separates 62.5t of liquid ammonia per hour, which is reduced in pressure by a valve and enters the primary flash tank for flash evaporation. In this process, the power of the liquid ammonia is wasted, and the long-term pressure-reducing operation of the liquid ammonia pressure-reducing valve of the ammonia separator is prone to valve core wear and internal leakage. The unit was forced to stop for maintenance due to valve core wear and internal leakage of the liquid ammonia pressure-reducing valve, which had a great impact on the overall production cost of the plant.

[0025] The invention adopts the method of expansion machine decompression and transportation. Liquid ammonia is reduced from 14.5MPa to 3.1MPa through the impeller end of the expansion machine, kinetic energy is recovered and decompression is carried out, and it is sent to the primary flash tank for downstream use; the recovered kinetic energy is converted into electrical energy through the generator and sent to the 380V power grid in the factory. According to 100% load calculation, 100KW.h is recovered per hour, and the operation is safe and reliable.

[0026] Liquid expander equipment structure introduction function:

[0027] 1. The expander speed is 18500 / min, the generator speed is 3000 / min, and the ratio of the expander speed to the generator speed is 6.

[0028] 2. The generator uses a three-phase squirrel cage 2-stage motor with a power of 120KW;

[0029] 3. The expander lubricant uses 46# turbine oil, the lubricant oil pressure is 0.25-0.35MPa, and the lubricant oil temperature is 41-48℃;

[0030] 4. The expander bearing temperature is less than 90℃ and the generator stator temperature is less than 120℃.

[0031] Specific workflow:

[0032] 1. The ammonia synthesis unit operates stably, with a load greater than 40%, and is ready for use of the expander.

[0033] 2. Check that the machines and pumps of the expander 16 are normal, there is no electrical maintenance work, and the expander 16 is ready for starting; check that the lubricating oil system is normal and the cooling water system is supplied with water; start the lubricating oil station 7, adjust the lubricating oil return valve 11 to control the lubricating oil pressure at 0.25-0.35MPa, open the lubricating oil cooler outlet valve 13 to supply lubricating oil to the expander 16. Since the lubricating oil temperature is low during the start-up process, the lubricating oil station 7 automatically starts the heater, and the lubricating oil temperature is greater than 33°C, and the heater automatically stops running.

[0034] 3. After the operation of the expander lubricating oil system is stable, open the expander inlet valve 3 by 3% for pressurization. After the pressure of the expander 16 is consistent with the system pressure, open the expander outlet valve 15 to 20% and pre-cool the expander 16 at a low speed. Pre-cool the expander 16 to below -20°C, slowly open the expander outlet valve 15 to 100%, and increase the speed of the expander 16 by adjusting the opening of the expander inlet valve 3 to less than 200 revolutions per minute. After the expander 16 reaches 3000 revolutions, check the temperature and vibration of each pump. If there is no abnormality, start the grid-connected operation. Switch the generator 4 grid-connected switch to the grid side. After the generator 4 grid-connected indication is normal, slowly close the liquid ammonia pressure reducing valve 17 to increase the load of the expander 16. Liquid ammonia is sent to the primary flash tank 20 through the expander 16 for flash separation, and the analytical gas is sent to the compressor inlet through the flash gas delivery valve from the top of the primary flash tank 20, and the liquid ammonia is sent to the downstream through the liquid ammonia delivery valve 22 from the bottom of the primary flash tank 20. In normal production, the liquid ammonia produced by the ammonia synthesis converts kinetic energy into electrical energy through the expander.

[0035] 4. Notes on the expander

[0036] (1) Before starting the machine for the first time, confirm the rotation direction of the generator when it is running electrically. Only when the rotation direction of the generator when it is running electrically is consistent with the rotation direction of the expander when it is running, can the generator and the expander be connected together.

[0037] (2) When the expander is started, the generator is not connected to the 380V grid, and the generator has no excitation system, which is equivalent to a mechanical load of the expander. There is no voltage or current in the stator and rotor windings of the generator. After the expander is started, when the speed of the expander reaches close to the rated speed of 18,500 rpm and the speed of the generator side reaches more than 3000*98%, according to the signal feedback of the speed detection module, a grid-connected closing command is issued to the 380V switch cabinet. After the 380V switch cabinet receives the grid-connected closing command, the circuit breaker is closed, the generator is successfully connected to the grid, and the generator grid-connected signal is returned to the central control DCS screen to complete the grid-connected operation.

[0038] (3) After being connected to the grid, a three-phase symmetrical current is added to the generator stator, generating a rotating magnetic field with a speed of 3000 rpm in the internal space of the generator. The generator has an excitation magnetic field. Since the generator speed is less than 2970 rpm at this time, the generator works in an electric state, absorbing power from the grid and driving the expander to accelerate rotation together with the expansion work. When the generator speed reaches 3000 rpm, there is no relative motion between the rotor conductor and the rotating magnetic field, and no induced electromotive force is generated in the rotor conductor. Therefore, the generator neither generates electricity nor absorbs electricity from the grid. As the speed of the expander increases, the speed of the generator rotor is higher than that of the rotating magnetic field, and the rotor conductor and the rotating magnetic field generate relative motion, cutting the magnetic lines of force to generate induced electromotive force and induced current. The magnetic field of the induced current acts on the stator winding, converting the mechanical energy of the expander expansion work into electrical energy, and the generator generates electricity.

[0039] (4) By finely controlling the opening degree of the expander inlet valve, the liquid level in the ammonia separator is maintained at a stable state, thereby ensuring that the generator is in a continuous, stable and efficient power generation condition.

[0040] (5) In the event of an electrical short circuit, the 380V switch cabinet circuit breaker can directly trip, disconnecting the generator from the power grid.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A liquid ammonia transport power recovery and utilization system for an ammonia synthesis device, comprising an ammonia separator (18), wherein a synthesis gas inlet ammonia separator valve (2) is provided at the left feed position of the ammonia separator (18), and a liquid ammonia outlet of the ammonia separator (18) is connected to a feed end of a primary flash tank (20) through a liquid ammonia transport pipeline (19), characterized in that: The discharge pipe at the top of the primary flash tank (20) is provided with a flash gas delivery valve (21), the discharge pipe at the bottom of the primary flash tank (20) is provided with a liquid ammonia delivery valve (22), the liquid ammonia delivery pipeline (19) is provided with a liquid ammonia pressure reducing valve (17), the liquid ammonia delivery pipeline (19) upstream of the liquid ammonia pressure reducing valve (17) is connected to the feed end of the expander (16) through a branch pipe, the branch pipe is provided with an expander inlet valve (3), the shaft end of the expander (16) is transmission-connected to the shaft end of the generator (4) through a transmission mechanism, the discharge pipe of the expander (16) is connected to the liquid ammonia delivery pipeline (19) through a reflux pipe, the reflux pipe is provided with an expander outlet valve (15), and the transmission mechanism is also provided with a lubrication unit for lubrication.

2. The liquid ammonia transport power recovery and utilization system of an ammonia synthesis device according to claim 1, characterized in that: The expander (16) and the generator (4) are both provided with a tachometer for detecting their rotation speeds.

3. The liquid ammonia transport power recovery and utilization system of an ammonia synthesis device according to claim 1, characterized in that: The lubrication unit comprises a lubricating oil station (7), an oil outlet pipe of the lubricating oil station (7) is provided with a lubricating oil delivery valve (8), the end of the oil outlet pipe is connected to the oil inlet end of a lubricating oil cooler (12), the oil outlet end of the lubricating oil cooler (12) is connected to the oil inlet end of a transmission mechanism, and the oil outlet end of the transmission mechanism is connected to the oil inlet end of the lubricating oil station (7) via a lubricating oil return pipeline (6).

4. The liquid ammonia transport power recovery and utilization system of an ammonia synthesis device according to claim 3, characterized in that: The oil outlet pipe of the lubricating oil station (7) is also connected to the lubricating oil return pipeline (6) through an auxiliary pipe, and a lubricating oil return valve (11) is provided on the auxiliary pipe.

5. The liquid ammonia transport power recovery and utilization system of an ammonia synthesis device according to claim 3, characterized in that: The cooling liquid inlet pipe on the lubricating oil cooler (12) is provided with a cooling water inlet valve (10), and the cooling liquid outlet pipe of the lubricating oil cooler (12) is provided with a cooling water return valve (9).

6. The liquid ammonia transport power recovery and utilization system of an ammonia synthesis device according to claim 3, characterized in that: A lubricating oil filter (14) is also connected between the lubricating oil cooler (12) and the transmission mechanism, and a lubricating oil cooler outlet valve (13) is also provided between the lubricating oil cooler (12) and the lubricating oil filter (14).

7. The liquid ammonia transport power recovery and utilization system of an ammonia synthesis device according to claim 1, characterized in that: The power connection end of the generator (4) is also electrically connected to the power transmission line (5).

Images