1. Application in the chemical industry
High pressure reaction system: In some chemical synthesis reactions, such as high-pressure hydrogenation reactions, nitrogen needs to be compressed to a higher pressure to provide an inert environment and prevent explosions during the reaction process. The piston compressor can output high pressure, which can increase the nitrogen pressure to tens of megapascals or even higher, meeting the requirements of high-pressure environment inside the reactor. For example, in the synthetic ammonia industry, nitrogen is one of the raw materials that needs to be compressed by a piston compressor before the reaction, and then mixed with hydrogen to undergo the reaction under high temperature, high pressure, and the action of a catalyst.
Low flow gas transportation: In chemical laboratories or small-scale chemical facilities, piston compressors are a good choice when low flow, high-pressure nitrogen supply is required. It can accurately control the output and pressure of nitrogen gas, providing a stable nitrogen source for experiments or small-scale production. For example, in the research and development process of some fine chemical products, a small amount of high-purity nitrogen is required for purging, replacement, or as a protective gas. Piston compressors can meet this small flow rate and high pressure demand.
2. Applications in the electronics industry
Chip manufacturing process: In the semiconductor chip manufacturing process, there are strict requirements for the purity and pressure of nitrogen gas. In some specific process steps, such as photolithography, etching, and cleaning of chips, high-purity and stable pressure nitrogen gas is required. A piston compressor can compress nitrogen to the appropriate pressure and provide the required nitrogen for chip manufacturing through appropriate filtration and purification systems. For example, in the photolithography process, nitrogen is used as the carrier gas, and the stable pressure provided by the piston compressor can ensure that the photoresist is evenly coated on the surface of the silicon wafer, ensuring the accuracy of chip manufacturing.
3. Application in the food industry
Food packaging: During the food packaging process, nitrogen gas needs to be compressed and filled into the food packaging bag to extend the shelf life of the food. A piston compressor can compress nitrogen gas to an appropriate pressure, allowing it to be smoothly filled into the packaging bag, eliminating oxygen from the bag and preventing food oxidation and moisture. For example, in the packaging of snack foods such as potato chips, nuts, etc., the nitrogen compressed by the piston compressor can fill the packaging bag to the fullest, protecting the food and extending its shelf life.
4. Application in the metallurgical industry
Metal melting protection: During the melting process of non-ferrous metals such as aluminum, copper, etc., nitrogen gas is required to prevent metal oxidation. A piston compressor can compress nitrogen gas and transport it above the melting furnace, forming a nitrogen protective layer on the surface of the metal melt. For example, in the process of aluminum melting, the nitrogen gas provided by the piston compressor can effectively reduce the contact between aluminum liquid and oxygen, reduce metal oxidation loss, and improve product quality.
Mixing and alloying in steel production: During the steelmaking process, piston compressors can be used to blow nitrogen into the molten steel, playing a role in stirring the molten steel and making its composition more uniform. Meanwhile, in some special steel production, nitrogen can also be added as an alloying element to the steel. The piston compressor can control the pressure and flow rate of nitrogen to ensure the smooth progress of the alloying process.
The working principle of a piston compressor for compressing industrial nitrogen gas is based on the compressibility of the gas, which is achieved through the reciprocating motion of the piston in the cylinder. The specific process is as follows:
1. Expansion process: The piston moves away from the intake and exhaust valves, increasing the cylinder volume and decreasing pressure. The residual air left in the cylinder from the previous cycle continues to expand and the pressure decreases, creating conditions for the upcoming intake process.
2. Inhalation process: When the pressure inside the cylinder drops slightly below the nitrogen pressure in the intake pipe, the nitrogen in the intake pipe pushes open the suction valve and enters the cylinder. As the piston continues to move, gas continues to enter the cylinder until the piston reaches the end of its stroke. At this point, the amount of nitrogen inhaled depends on factors such as the cylinder volume and intake pressure.
3. Compression process: The piston rotates back and the cylinder volume gradually decreases. Due to the anti reverse effect of the intake valve, nitrogen gas in the cylinder cannot flow back into the inlet pipe, and the gas pressure in the outlet pipe is higher than that inside the cylinder. The gas in the cylinder cannot escape from the exhaust valve to the outside of the cylinder, and the amount of nitrogen gas in the cylinder remains constant. The piston continues to move and reduce the volume inside the cylinder, causing the pressure of nitrogen to continuously increase.
4. Discharge process: As the piston moves, the pressure of compressed nitrogen gas increases to slightly higher than the gas pressure in the outlet pipe. The nitrogen gas in the cylinder pushes open the spring of the exhaust valve and enters the outlet pipe, continuously discharging until the piston moves to the end of this stroke.
The piston continuously reciprocates in the cylinder, allowing the above four processes to cycle, thereby achieving continuous compression of industrial nitrogen gas. In order to improve compression efficiency and meet different pressure requirements, piston compressors in practical applications may adopt multi-stage compression, which means that nitrogen gas passes through multiple cylinders in sequence and is gradually compressed in each cylinder to achieve the required nitrogen pressure.
Advantages and disadvantages of piston compressors
1. Advantages
Wide pressure range: Piston compressors can provide high pressure output. It can compress gases such as nitrogen to high pressures through multi-stage compression, with a maximum pressure of several hundred megapascals, making it widely used in industrial scenarios that require high-pressure gases. For example, in the chemical process of high-pressure hydrogenation reaction, a piston compressor can compress nitrogen gas to meet the requirements of the high-pressure environment inside the reaction vessel, providing a safe inert environment for the reaction.
High flexibility: The displacement adjustment range of piston compressors is wide. By changing the stroke and speed of the piston or using a gas volume adjustment device, the flow rate and pressure of the output gas can be flexibly adjusted within a certain range to meet different working requirements. For example, in a laboratory environment, when a low flow, high pressure nitrogen supply is required, a piston compressor can accurately control the output and pressure of nitrogen, providing a stable gas source for the experiment.
Strong adaptability: The piston compressor has a certain tolerance to the properties and impurity content of the compressed gas. It can process industrial nitrogen containing small amounts of impurities, and the requirements for nitrogen purity and humidity are relatively less strict than those of centrifugal compressors. This enables it to work relatively stably in some situations where gas pretreatment requirements are not high, such as small-scale industrial production or general nitrogen application scenarios.
Simple structure: The basic structure of a piston compressor is relatively intuitive, mainly composed of a cylinder, piston, intake valve, exhaust valve, and crankshaft connecting rod mechanism. This simple structure makes its manufacturing process relatively mature and cost-effective. And in terms of maintenance and repair, technicians are relatively easy to understand its working principle and structure, and it is also relatively convenient to repair and replace parts.
2. Disadvantages
Gas with oil stains: During the operation of a piston compressor, lubricating oil is required between the piston and cylinder wall for lubrication and sealing, which may result in the presence of lubricating oil in the compressed gas. For some industrial applications that require extremely high gas purity, such as the electronic chip manufacturing industry, these oil stains may have a serious impact on product quality, so complex gas purification treatment is required after compression to remove oil stains.
Discontinuous exhaust: The exhaust of a piston compressor is intermittent, and the exhaust process is periodic as the piston moves back and forth. This can cause certain fluctuations in gas pressure. In some application scenarios that require high stability of gas pressure, such as continuous reactions in precision chemical production processes, such pressure fluctuations may have adverse effects on pipeline systems or ongoing chemical reactions, and may even cause damage to mechanical components.
There are many vulnerable parts: The piston compressor has many moving parts, such as piston rings, air valves, connecting rod large end pads, etc., which are prone to wear and tear during long-term reciprocating motion and frequent working processes. Regular maintenance and replacement of vulnerable parts are necessary, otherwise it will affect the performance and service life of the compressor. Moreover, the large number of vulnerable parts also increases the workload and cost of maintenance.
Speed limitation: Due to the working mode of the piston compressor, where the piston reciprocates within the cylinder, its speed is limited to a certain extent. Compared with centrifugal compressors, piston compressors may have larger external dimensions and footprint under the same displacement requirements, which may cause inconvenience for some industrial sites with limited space.
