Ammonia production system

Abstract

The utility model discloses an ammonia production system which comprises a gas compression module, an ammonia synthesis module and a gas circulation module, the gas compression module comprises a gas raw material introduction pipeline, a buffer tank, a compressor and a gas raw material discharge pipeline which are connected in sequence; the gas compression module further comprises a compressor control unit; the gas circulation module comprises a heat exchanger, a water cooler and a circulator; the gas circulation module further comprises a circulation machine control unit. The ammonia production system can stably operate, and the conversion rate of synthetic ammonia is improved.

Description

Technical Field

[0001] The utility model relates to an ammonia production system. Background Art

[0002] Liquid ammonia production primarily relies on fossil fuels like natural gas and coal. This process emits significant amounts of carbon dioxide for every ton of liquid ammonia produced. Natural gas-based ammonia production emits up to 4.2 tons of carbon dioxide per ton of ammonia, while coal-based ammonia production emits up to 4.2 tons of carbon dioxide per ton of ammonia. Green energy ammonia production uses green energy (such as solar and wind power) and water and air as raw materials to produce liquid ammonia, resulting in virtually zero carbon dioxide emissions throughout the entire process.

[0003] The green energy ammonia production process is an emerging green chemical process. From green energy to ammonia synthesis complete process, it is still in the exploratory stage. In order to stabilize the production of green ammonia synthesis equipment, it is necessary to stabilize green electricity to ensure the stability of chemical equipment.

[0004] At present, green energy ammonia production still has major shortcomings. For example, photovoltaic power generation can only generate electricity in stages due to the day and night factor; there are also light and weather factors, and the power generation in different time periods during the day is also very different; wind power generation also has wind fields in different time periods, and there are great differences in power generation due to wind factors; but for synthetic ammonia plants (chemical plants), the more stable the raw material supply, the more stable and safer the plant operation. The plant cannot be in a short period of time, such as suddenly reducing the load from 100% to 30%, or increasing the load from 30% to 100%. It takes a certain amount of time, but the speed cannot be too fast; under special circumstances, it must also meet the ultra-low load of 10%-30% to operate safely; the existing green energy ammonia production process is currently unable to solve the above problems, so the large-scale production of green energy ammonia is subject to great restrictions. Utility Model Content

[0005] The technical problem to be solved by the present invention is to overcome the defect that the ammonia production system in the prior art cannot operate stably, and to provide an ammonia production system that can operate stably and improve the conversion rate of synthetic ammonia.

[0006] The utility model solves the above technical problems through the following technical solutions:

[0007] The utility model provides an ammonia production system, which includes a gas compression module, an ammonia synthesis module and a gas circulation module;

[0008] The gas compression module includes a gas raw material inlet pipeline, a buffer tank, a compressor, and a gas raw material discharge pipeline connected in sequence; the gas compression module also includes a compressor control unit; a gas raw material loop is further provided between the gas raw material discharge pipeline and the buffer tank, and a gas raw material loop control valve is provided on the gas raw material loop; the compressor control unit includes a gas raw material flow meter provided on the gas raw material inlet pipeline, the gas raw material flow meter is electrically connected to the frequency converter of the compressor, and the frequency converter of the compressor is electrically connected to the gas raw material loop control valve;

[0009] The gas circulation module includes a heat exchanger, a water cooler, and a circulation machine; the gas circulation module also includes a circulation machine control unit; the heat exchanger includes a first channel and a second channel, the heat exchanger is used to heat the feed gas in the first channel and output it to the ammonia synthesis module, and the second channel, the water cooler, the circulation machine, and the first channel are connected to form a circulation gas regulation channel; the gas feed discharge pipeline is connected to the first channel, and a gas circulation branch is provided on the gas feed discharge pipeline and communicates with the pipeline between the second channel and the water cooler, and a system loop control valve is provided on the gas circulation branch; the upstream and downstream of the circulation machine are connected by a circulation gas loop, and the circulation gas loop is provided with a circulation gas loop control valve; the circulation machine control unit includes a circulation gas flow meter provided in the upstream pipeline of the circulation machine, the circulation gas flow meter is electrically connected to the system loop control valve and the frequency converter of the circulation machine, respectively, and the frequency converter of the circulation machine is electrically connected to the circulation gas loop control valve;

[0010] The ammonia synthesis module is connected to the first channel and is disposed downstream of the first channel.

[0011] In certain specific embodiments of the present invention, the compressor control unit is used to control the opening and closing degree of the gas raw material loop control valve and the frequency of the frequency converter according to the flow rate measured by the gas raw material flow meter.

[0012] In certain specific embodiments of the present invention, the circulation machine control unit is used to control the opening and closing degree of the system loop control valve, the frequency of the circulation machine's inverter, and the opening and closing degree of the circulation gas loop control valve according to the flow rate measured by the circulation gas flow meter.

[0013] In the present invention, preferably, the ammonia synthesis module includes an ammonia synthesis reactor and a waste heat recovery device; the first channel, the ammonia synthesis reactor, the waste heat recovery device, and the second channel are connected in sequence.

[0014] In the present invention, preferably, a cooling and separating device is further provided downstream of the water cooler, and the cooling and separating device is used to separate and obtain liquid ammonia.

[0015] Preferably, a water-cooled gas circulation loop is provided between the water cooler and the cooling and separation device, and the water-cooled gas circulation loop is used to recover the gas separated by the cooling and separation device.

[0016] The positive progress effect of this utility model is:

[0017] The ammonia production system provided by the utility model cooperates with the gas compression module, the ammonia synthesis module and the gas circulation module to form a multi-loop control, which overcomes the problem of instability of the ammonia production system caused by the unstable airflow of the raw gas, improves the safety factor of the ammonia production system, and at the same time can also improve the conversion rate of synthetic ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the ammonia production system of Example 1.

[0019] The reference numerals are as follows:

[0020] 1- Buffer tank; 2- Compressor; 3- Gas feed loop control valve; 4- Gas feed flowmeter; 5- Compressor inverter; 6- Heat exchanger; 7- Water cooler; 8- Circulator; 9- System loop control valve; 10- Circulating gas loop control valve; 11- Circulating gas flowmeter; 12- Circulator inverter; 13- Ammonia synthesis reactor; 14- Waste heat recovery device; 15- Cooling and separation device; 16- Product collection device.

[0021] 101 - Gas raw material inlet pipeline; 102 - Gas raw material discharge pipeline; 103 - Gas raw material loop; 104 - Gas circulation branch; 105 - Circulating gas loop; 106 - Water-cooled gas circulation loop. DETAILED DESCRIPTION

[0022] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. In the following examples, the experimental methods without specific conditions are selected according to conventional methods and conditions, or according to the product specifications.

[0023] Example 1

[0024] The structural diagram of the ammonia production system of Example 1 is as follows Figure 1 shown.

[0025] It includes a gas compression module, an ammonia synthesis module and a gas circulation module;

[0026] The gas compression module comprises a gas raw material inlet pipeline 101, a buffer tank 1, a compressor 2 and a gas raw material outlet pipeline 102 connected in sequence; the gas compression module further comprises a compressor control unit; a gas raw material loop 103 is further arranged between the gas raw material outlet pipeline 102 and the buffer tank 1, and a gas raw material loop control valve 3 is arranged on the gas raw material loop 103; the compressor control unit comprises a gas raw material flow meter 4 arranged on the gas raw material inlet pipeline 101, the gas raw material flow meter 4 is electrically connected with a frequency converter 5 of the compressor, and the frequency converter 5 of the compressor is electrically connected with the gas raw material loop control valve 3;

[0027] The gas circulation module comprises a heat exchanger 6, a water cooler 7 and a circulation machine 8; the gas circulation module further comprises a circulation machine control unit; the heat exchanger 6 comprises a first channel and a second channel, and the heat exchanger 6 is used for heating raw material gas in the first channel and outputting the raw material gas to the ammonia synthesis module; the second channel, the water cooler 7, the circulation machine 8 and the first channel are connected to form a circulating gas adjusting channel; the gas raw material outlet pipeline 102 is connected with the first channel, a gas circulation branch 104 is arranged on the gas raw material outlet pipeline 102 and communicates with a pipeline between the second channel and the water cooler 7, and a system loop control valve 9 is arranged on the gas circulation branch 104; the upstream and the downstream of the circulation machine 8 are connected through a circulating gas loop 105, and a circulating gas loop control valve 10 is arranged on the circulating gas loop 105; the circulation machine control unit comprises a circulating gas flow meter 11 arranged on an upstream pipeline of the circulation machine 8, the circulating gas flow meter 11 is electrically connected with the system loop control valve 9 and a frequency converter 12 of the circulation machine respectively, and the frequency converter 12 of the circulation machine is electrically connected with the circulating gas loop control valve 10;

[0028] The ammonia synthesis module is connected with the first channel and arranged downstream of the first channel.

[0029] The ammonia synthesis module comprises an ammonia synthesis reactor 13 and a waste heat recovery device 14; the first channel, the ammonia synthesis reactor 13, the waste heat recovery device 14 and the second channel are connected in sequence.

[0030] A cooling and separating device 15 is further arranged downstream of the water cooler, and the cooling and separating device 15 is used for separating to obtain liquid ammonia.

[0031] A water-cooled gas circulation loop 106 is further arranged between the water cooler and the cooling and separating device 15, and the water-cooled gas circulation loop 106 is used for recycling gas separated by the cooling and separating device 15.

[0032] A product collecting device 16 is arranged downstream of the cooling and separating device 15.

[0033] Embodiment 2

[0034] Embodiment 2 adopts the ammonia production system of embodiment 1.

[0035] The raw material gas is nitrogen and hydrogen, the flow ratio of nitrogen and hydrogen is controlled between (2.8-3.2):1, according to the device capacity (2 million tons / year capacity, 2.5 tons / hour), the calculated flow of the raw material gas is 6600 Nm 3 / h at 100% load.

[0036] The flow of the circulating gas is the flow size at 100% load: V 循环气 =m 产 * (1+Y 出 ) / Y 出 =2.5*1000*(1+14%) / 14%=20357 Nm 3 / h; wherein V 循环气 is the flow of the circulating gas, unit: Nm 3 / h, m 产 is the capacity of the product, unit: kg / h, Y 出 is the mass content of ammonia at the outlet of the ammonia synthesis reactor, unit: %.

[0037] The ammonia production method comprises the following steps:

[0038] The raw material gas is introduced into the gas raw material pipeline and introduced into the gas compression module; the raw material gas generates liquid ammonia after passing through the ammonia synthesis module; part of the raw material gas entering the ammonia synthesis module and the residual gas after passing through the ammonia synthesis module enter the gas circulation module for circulation.

[0039] The threshold value of the flow detected by the gas raw material flow meter is 50%-110% load;

[0040] The compressor control unit operates in the following manner:

[0041] When the flow detected by the gas raw material flow meter is 10%-30% load, the frequency size of the frequency converter of the compressor and the opening and closing degree of the gas raw material loop control valve are increased; when the flow detected by the gas raw material flow meter is 30%-50% load, the frequency size of the frequency converter of the compressor and the opening and closing degree of the gas raw material loop control valve remain unchanged; when the flow detected by the gas raw material flow meter is 50%-110% load, the frequency size of the frequency converter of the compressor is adjusted according to the flow detected by the gas raw material flow meter, and the gas raw material loop control valve is closed; when the flow detected by the gas raw material flow meter is 110% above load, the gas raw material flow meter displays an over-flow alarm, and human intervention is required to reduce the supply of hydrogen and nitrogen.

[0042] The threshold value of the flow detected by the circulating gas flow meter is 50%-110% load;

[0043] The circulating machine control unit operates in the following manner:

[0044] When the flow rate detected by the circulating gas flow meter is 10%-30% load, the frequency of the circulating machine inverter is maintained at the minimum control value, and the opening and closing degree of the system loop control valve and the circulating gas loop control valve are increased. The minimum control value of the circulating machine inverter frequency means the minimum frequency to maintain stable operation of the circulating machine;

[0045] When the flow rate detected by the circulating gas flow meter is 30%-50% load, the frequency of the inverter of the circulating machine is maintained at the minimum control value, the opening and closing degree of the system loop control valve is increased, and the opening and closing degree of the circulating gas loop control valve is reduced;

[0046] When the flow rate detected by the circulating gas flow meter is 50%-110% load, increase the frequency of the circulating machine's inverter, reduce the opening and closing degree of the system loop control valve, and close the circulating gas loop control valve;

[0047] When the flow rate detected by the circulating gas flow meter is above 110% load, the frequency of the circulating machine's inverter is maintained at the maximum control value, the system loop control valve is closed, and the circulating gas loop control valve is closed; among which, the maximum control value of the circulating machine's inverter frequency means the maximum frequency that maintains the circulating machine's stable operation.

[0048] The raw gas passes through the ammonia synthesis module and undergoes ammonia synthesis reaction to produce liquid ammonia. The temperature of the ammonia synthesis reaction is 350-500°C. The reacted gas is cooled and condensed to separate the liquid ammonia. The unreacted gas enters the gas circulation module, where it is pressurized by the compressor and then participates in the reaction again.

[0049] The range of the gas raw material flow meter is 10%-150% load, and the range of the circulating gas flow meter is 10%-150% load.

[0050] The device can automatically adjust in real time between 30% and 110% load, ensuring stable operation. It can also operate smoothly at 10% to 30% load, allowing for immediate resumption of production. While ensuring stable operation, the device and method can tolerate hydrogen and nitrogen fluctuations of at least 3% per minute.

[0051] Comparative Example 1

[0052] The ammonia production system of Comparative Example 1 does not contain a compressor control unit, that is, it includes a gas compression module, an ammonia synthesis module and a gas circulation module; the gas compression module includes a gas raw material inlet pipe, a buffer tank, a compressor and a gas raw material discharge pipe connected in sequence, and the gas raw material discharge pipe is connected to the first channel of the heat exchanger; the rest of the structure is the same as that of Example 1.

[0053] The kind and flow of raw material gas of the comparative example 1 are same as those of the example 2, and the ammonia production system is used.

[0054] When the device and method of the comparative example 1 are used at an ultra-low load of 10%-30%, even if the compressor control unit is started, the actual situation cannot be met, the device cannot continue to run, and the device can only be stopped.

[0055] Comparative example 2

[0056] The ammonia production system of the comparative example 2 does not contain a circulation machine control unit, that is, the ammonia production system includes a gas compression module, an ammonia synthesis module and a gas circulation module; the gas circulation module does not set a circulating gas loop, and the remaining structure is same as that of the example 1.

[0057] The kind and flow of raw material gas of the comparative example 2 are same as those of the example 2, and the ammonia production system is used.

[0058] When the device and method of the comparative example 2 are used at an ultra-low load of 10%-30%, the pressure of the whole system also greatly decreases, and the result after the decrease is that the single-pass hydrogen conversion rate is low, and the heat released by the reaction is divided into two parts, one part of the heat is taken away by radiation (the heat loss of this part is basically fixed), and the other part of the heat is taken away by the reaction gas from the ammonia synthesis reactor; since the load of the device is reduced, the reaction heat cannot meet the two parts of heat removal, and the temperature of the catalytic bed layer of the ammonia synthesis reactor will appear to be collapsed.

[0059] When the device and method of the example are used at a load of 30%-110%, the single-pass hydrogen conversion efficiency, power consumption and heat recovery of the device of the example are same as those of the traditional ammonia device in the prior art. Generally, when the load of the traditional device is increased or reduced, when the hydrogen and nitrogen fluctuation is greater than 3% / min, a planned advance plan needs to be handled; however, when the green energy fluctuates at a high amplitude and a high frequency, there is no predictability in a short time, and the hydrogen and nitrogen fluctuation is often greater than 3% / min, so that the device cannot be stably operated. After the control of the example is used, real-time automatic adjustment can be realized, and the device can be stably operated; at the same time, the device can also be stably operated at a load of 10%-30%, and production can be restored at any time.

[0060] Compared with the comparative example 1, the example 2 can meet the situation that the device can be stably operated at an ultra-low load of 10%-30%, the device is in a hot state, and full-load production can be restored at any time according to the conditions of the front-end nitrogen and hydrogen.

[0061] Compared with Comparative Example 2, Example 2 shows that at an ultra-low load of 10%-30%, by reducing the gas volume of the ammonia synthesis reactor and the corresponding reaction gas volume, the total gas volume of the entire system is increased, forming a pressure effect. The system pressure increases, which also improves the hydrogen conversion efficiency in the ammonia synthesis reactor. At the same time, since the inlet gas volume of the ammonia synthesis reactor is reduced, the heat carried away by the reaction gas will be reduced, and the reaction heat can be effectively retained in the ammonia synthesis reaction tower, which can effectively solve the temperature collapse problem of the catalytic bed temperature of the ammonia synthesis reactor and prepare for the subsequent rapid increase in the production load of the device.

Claims

1. An ammonia production system, characterized in that: It includes a gas compression module, an ammonia synthesis module and a gas circulation module; The gas compression module includes a gas raw material inlet pipeline, a buffer tank, a compressor, and a gas raw material discharge pipeline connected in sequence; the gas compression module also includes a compressor control unit; a gas raw material loop is further provided between the gas raw material discharge pipeline and the buffer tank, and a gas raw material loop control valve is provided on the gas raw material loop; the compressor control unit includes a gas raw material flow meter provided on the gas raw material inlet pipeline, the gas raw material flow meter is electrically connected to the frequency converter of the compressor, and the frequency converter of the compressor is electrically connected to the gas raw material loop control valve; The gas circulation module includes a heat exchanger, a water cooler, and a circulation machine; the gas circulation module also includes a circulation machine control unit; the heat exchanger includes a first channel and a second channel, the heat exchanger is used to heat the feed gas in the first channel and output it to the ammonia synthesis module, and the second channel, the water cooler, the circulation machine, and the first channel are connected to form a circulation gas regulation channel; the gas feed discharge pipeline is connected to the first channel, and a gas circulation branch is provided on the gas feed discharge pipeline and communicates with the pipeline between the second channel and the water cooler, and a system loop control valve is provided on the gas circulation branch; the upstream and downstream of the circulation machine are connected by a circulation gas loop, and the circulation gas loop is provided with a circulation gas loop control valve; the circulation machine control unit includes a circulation gas flow meter provided in the upstream pipeline of the circulation machine, the circulation gas flow meter is electrically connected to the system loop control valve and the frequency converter of the circulation machine, respectively, and the frequency converter of the circulation machine is electrically connected to the circulation gas loop control valve; The ammonia synthesis module is connected to the first channel and is disposed downstream of the first channel.

2. The ammonia production system according to claim 1, characterized in that The ammonia synthesis module includes an ammonia synthesis reactor and a waste heat recovery device; the first channel, the ammonia synthesis reactor, the waste heat recovery device, and the second channel are connected in sequence.

3. The ammonia production system according to claim 1, wherein: A cooling and separating device is further provided downstream of the water cooler, and the cooling and separating device is used to separate and obtain liquid ammonia.

4. The ammonia production system according to claim 3, characterized in that: A water-cooled gas circulation loop is further provided between the water cooler and the cooling and separation device, and the water-cooled gas circulation loop is used to recover the gas separated by the cooling and separation device.

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