Liquid ammonia gasification process of gas-ammonia-free buffer separation tank

Abstract

The invention relates to a novel liquid ammonia gasification process, which belongs to the technical field of liquid ammonia gasification, and comprises the following steps: 1) a liquid ammonia pump is used for two purposes, liquid ammonia in a liquid ammonia tank car can be pumped to a liquid ammonia storage tank, and liquid ammonia in the liquid ammonia storage tank can be pumped to circulate through a heater; (2) the liquid ammonia is heated by a normal-temperature or low-temperature medium, the heated liquid ammonia enters the storage tank and then flashes out of the gas ammonia, and the gas ammonia can be directly led out of the liquid ammonia buffer tank to be continuously used in a gas ammonia using procedure. Normal-temperature medium heating is achieved, the system is free of over-temperature and over-pressure possibility, circulating cooling water is adopted for heating, energy consumption is not needed, the temperature of circulating water can be reduced, the heater almost does not occupy space, space occupation of a production line is reduced, and equivalently, a gas ammonia buffer tank, a water bath heater and a control system in a traditional process are omitted. The liquid ammonia buffer tank is used for separation and buffering, the temperature and pressure stability is good, the gas ammonia cleanliness is high, and the system safety is high.

Description

Technical Field

[0001] The invention relates to the technical field of liquid ammonia gasification, and in particular to a liquid ammonia gasification process of a gasless ammonia buffer separation tank. Background Art

[0002] Conventional liquid ammonia gasification refers to the process of converting liquid ammonia into gaseous ammonia after reducing the pressure and then heating it. Liquid ammonia is usually drawn from a medium-pressure liquid ammonia buffer tank, and after the pressure is reduced by a pressure reducing valve, it is sent to a hot water bath coil for heating. The gaseous liquid ammonia in the coil is completely vaporized by the hot water in the hot water tank, and then the impurities are separated by an ammonia buffer separation tank and controlled for external transportation for use. The temperature of the hot water tank is maintained stable by steam or electric heating.

[0003] The gas ammonia buffer separation tank is small in size, has limited buffering capacity, and needs to be cleaned regularly. The gasification of liquid ammonia requires the consumption of high-grade steam. Therefore, a liquid ammonia gasification process without a gas ammonia buffer separation tank is proposed to solve the above problems. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a liquid ammonia gasification process without a gaseous ammonia buffer separation tank, which has the advantages of low energy consumption, stable gas supply, good gas ammonia quality, small footprint, and low maintenance workload. It eliminates the gaseous ammonia buffer separation tank and hot water bath liquid ammonia evaporator required in the traditional process and only adds a small heater.

[0006] The new process can utilize low-temperature waste heat, and even circulating cooling water, so the heating energy consumption is basically zero. If the temperature of the heating medium is below 40°C, no control is required, and the system will not have over-temperature or over-pressure problems.

[0007] Since the liquid ammonia in the entire liquid ammonia buffer tank is heated, the heat capacity is extremely large, even if a high-temperature heating medium is used, over-temperature and over-pressure phenomena are not likely to occur.

[0008] Since the heating is carried out in the phase equilibrium state of liquid ammonia at room temperature, there is no possibility of the heating medium freezing at low temperature.

[0009] The control is simple, no energy consumption is required, the system is at normal temperature, and no additional equipment or space is required. The large medium-pressure gas ammonia buffer space is hundreds or thousands of times the buffer capacity of the original low-pressure buffer tank, which greatly reduces the control requirements of the gas-using process.

[0010] (II) Technical solution

[0011] To achieve the above object, the present invention provides the following technical solution: a liquid ammonia gasification process of a gas-free ammonia buffer separation tank, comprising the following steps:

[0012] 1) Start the liquid ammonia pump circulation, pump liquid ammonia from the liquid ammonia storage tank and return it to the liquid ammonia storage tank through the heater;

[0013] 2) Open the heating medium regulating valve to deliver the heating medium to the heater, control the pressure of the liquid ammonia storage tank to 0.6-1.5 MPa, partially vaporize the heated liquid ammonia, and separate the gas-liquid mixture by flash vaporization in the liquid ammonia storage tank. The gaseous ammonia can be delivered to the external process through the gas phase pipe;

[0014] 3) Impurities in liquid ammonia remain in the liquid phase of the liquid ammonia storage tank and are naturally precipitated and separated. The quality of the gas ammonia delivered is much higher than that of the traditional process;

[0015] 4) The heating medium can be low-temperature waste heat medium or commonly used circulating cooling water, which does not require energy consumption;

[0016] 5) Automatic control:

[0017] The pressure of the liquid ammonia storage tank is regulated by the flow of the heating medium. It is a simple single-loop control. If circulating water heating or waste heat heating with a temperature not exceeding 40°C is used, no control is required.

[0018] The liquid level alarm of the liquid ammonia storage tank. When the liquid level is low, it is necessary to add liquid ammonia from the liquid ammonia tank truck to the liquid ammonia buffer tank. The liquid ammonia pump stops pumping from the liquid ammonia tank truck and instead pumps the liquid ammonia from the liquid ammonia tank truck into the liquid ammonia storage tank through the heater.

[0019] The liquid ammonia tank truck transfers ammonia to the liquid ammonia storage tank. A compressor solution may also be used, that is, the ammonia compressor extracts the gaseous ammonia from the liquid ammonia storage tank, pressurizes it and sends it to the liquid ammonia tank truck to pressurize the liquid ammonia in the tank truck and send it to the liquid ammonia storage tank through the heater. The liquid ammonia circulation pump can be stopped here. The process of replenishing liquid ammonia does not need to stop heating.

[0020] All of the above are being coordinated by automatic control devices.

[0021] The amount of gas ammonia used is determined by the gas ammonia process and does not need to be controlled in this process;

[0022] (III) Beneficial effects

[0023] Compared with the prior art, the present invention provides a liquid ammonia gasification process of a gas-free ammonia buffer separation tank, which has the following beneficial effects:

[0024] The liquid ammonia gasification process of the gas-free ammonia buffer separation tank realizes room temperature medium heating, and the system has no possibility of over-temperature and over-pressure. It uses circulating cooling water for heating, does not require energy consumption, and can also reduce the circulating water temperature. The heater takes up almost no space, reducing the space occupancy of the production line. It is equivalent to canceling the gas ammonia buffer tank, water bath heater and control system of the traditional process, and using the liquid ammonia buffer tank for separation and buffering, with good temperature and pressure stability, high gas ammonia cleanliness and high system safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1A flow chart of a liquid ammonia gasification process of a gas-free ammonia buffer separation tank proposed by the present invention; DETAILED DESCRIPTION

[0026] The following will be combined with 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.

[0027] Embodiment 1: A liquid ammonia gasification process of a gas-free ammonia buffer separation tank comprises the following steps:

[0028] 1) Move the liquid ammonia tank truck to the vicinity of the liquid ammonia buffer tank and the heater, use a liquid ammonia pump to pump liquid ammonia from the tank truck and send it to the liquid ammonia buffer tank through the heater, or use an ammonia compressor to pump gaseous ammonia from the liquid ammonia buffer tank and send it to the tank truck, press the liquid ammonia in the tank truck out and send it to the liquid ammonia buffer tank through the heater, and flash separate it in the tank;

[0029] 2) The pressure in the liquid ammonia buffer tank is related to the heating medium, which is generally 0.6-1.5MPa. The heating medium can be any room temperature medium of 10-40°C, thereby achieving room temperature medium heating liquid ammonia, thereby reducing energy consumption and making more types of media available, thereby reducing the difficulty of obtaining media.

[0030] By adopting the above technical scheme, it is possible to indirectly heat the circulating liquid ammonia through a normal temperature or low-temperature medium, and keep the temperature of the liquid ammonia in the liquid ammonia buffer tank at normal temperature. The gaseous ammonia can be directly drawn out from the liquid ammonia buffer tank, and the entire gasification process is carried out at normal temperature. Not only is the energy consumption low, but the gas supply is stable, and the gas-ammonia buffer separation tank of the traditional process is eliminated, reducing the footprint of the device.

[0031] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A new liquid ammonia gasification process, characterized in that: The following steps are involved: 1) The liquid ammonia pump can be used for both pumping liquid ammonia from the liquid ammonia tank truck and from the liquid ammonia storage tank. Both are heated by the heater and then sent to the liquid ammonia storage tank. 2) The pump transports liquid ammonia through the heater, which is indirectly heated by a 20℃-80℃ low-temperature medium. After the temperature rises, the liquid ammonia enters the storage tank and flashes out gaseous ammonia. The gaseous and liquid ammonia are separated in the liquid ammonia storage tank; 3) Since the heating is carried out at the phase equilibrium temperature of liquid ammonia, the gasification is carried out at room temperature, there is no freezing problem of the heating medium, and it is safe and energy-saving; 4) Impurities in liquid ammonia remain in the liquid phase of the liquid ammonia storage tank and can be discharged regularly; 5) The gas phase buffer space of the liquid ammonia storage tank is large, and the gas ammonia quality is good. The gas ammonia buffer separation tank required by the traditional evaporation system can be eliminated, and high-quality gas ammonia can be directly transported to the outside through the gas phase interface of the liquid ammonia storage tank; 6) Due to the large space and capacity of the liquid ammonia storage tank, a short-term failure of the gasification system will not be able to provide heating and will not affect the supply of gas ammonia; 7) The evaporation process is fully automatically controlled by PLC or DCS, which can automatically control the flow rate of the medium used to heat the liquid ammonia, ensuring that the temperature of the liquid ammonia storage tank is within the range of 10℃~40℃ and the pressure is within a safe range; 8) SIS sensors are installed, and the SIS system monitors key safety indicators, such as liquid ammonia storage tank pressure, liquid level, temperature, etc.; 9) The heater has a pressure resistance of more than 2.5MPa and can be made of either carbon steel or stainless steel.

2. The process for gasifying liquid ammonia in a gas-free ammonia buffer separation tank according to claim 1, characterized in that: The liquid ammonia buffer tank is installed with a liquid level sensor and a temperature sensor, and the liquid ammonia replenishment amount and the heat input of the heater are controlled by PLC or DCS. The heating medium pipeline, the liquid ammonia inlet and outlet of the liquid ammonia buffer tank and the gaseous ammonia output pipeline are all equipped with shut-off valves, which are connected to the SIS system. When relevant abnormalities occur in the system and the system automatic control cannot control it, the SIS system can close the relevant valves to ensure system safety.

3. The process for gasifying liquid ammonia in a gas-free ammonia buffer separation tank according to claim 1, characterized in that: The heat source for heating the liquid ammonia may be a waste heat medium at a temperature of 20-80°C or higher.

4. The process for gasifying liquid ammonia in a gas-free ammonia buffer separation tank according to claim 1, characterized in that: The liquid ammonia pump, whether extracting liquid ammonia from a tank truck or from a buffer tank, delivers the liquid ammonia to the buffer tank through the heater.

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