Design of the hottest pressure swing adsorption ni

Design of pressure swing adsorption nitrogen production device in the past five or six years, with the continuous maturity of domestic pressure swing adsorption nitrogen production technology, its application fields have also been expanding, from the underground nitrogen sealing fire extinguishing of coal system, nitrogen atmosphere heat treatment of electromechanical system, raw material processing and purification nitrogen sealing protection of chemical system, to the exact difference in the quality protection of food and fruit in the food industry, and the shortage of substitute carbon dioxide gas in the fresh beer industry, And have been welcomed by users. In order to let more users understand the PSA nitrogen production technology and use the PSA nitrogen production device, this paper briefly describes the faults in the design and commissioning of the PSA nitrogen production device and the problems that should be paid attention to in use

1 working principle of pressure swing adsorption nitrogen generation device

the design basis of pressure swing adsorption nitrogen generation device is pressure swing adsorption theory. The adsorbed matrix is various adsorbents, such as aluminum glue, silica gel, activated carbon and molecular sieve. In pressure swing adsorption nitrogen generation devices, adsorbents mostly use various molecular sieves (zeolite molecular sieves, carbon molecular sieves), and various molecular sieves have their specific adsorption selectivity. For example, 3A carbon molecular sieves are often used for nitrogen generation and oxygen absorption, while 13X zeolite molecular sieves are mostly used for adsorption of H20 and C02. Working principle of pressure swing adsorption nitrogen generation device: clean pressurized air (oxygen nitrogen mixture) passes through a certain carbon molecular sieve, in which most of the oxygen and remaining trace water are adsorbed by the molecular sieve, while nitrogen is not adsorbed and discharged. This is the adsorption nitrogen generation stage. When the pressure decreases to atmospheric pressure or negative pressure, the ability of molecular sieve to adsorb oxygen decreases, and the oxygen and water adsorbed by molecular sieve under pressure are analyzed, which is the stage of analytical regeneration (oxygen production). After analysis, the molecular sieve can be carried out in the next cycle of nitrogen generation by adsorption, and the cycle is repeated, so as to obtain a certain purity of nitrogen and oxygen enriched air at the same time. See Figure 1 for the device module diagram

2design

according to the pressure swing adsorption technology and the different needs of different users, a variety of pressure swing adsorption nitrogen production devices with different technical performance parameters are designed and manufactured. Next, take the 200m3/h nitrogen production unit with purity of 99.9% used in the hydrogenation white oil project of a petrochemical plant as an example (but the process flow is shown in Figure 2), and briefly discuss the relevant aspects

2.1 main technical parameters of the device

nitrogen fish production: 200m3/h (20 ℃, 0.1MPa absolute pressure); Nitrogen purity: 99.9% (oxygen content less than 0.1%); Nitrogen supply pressure: 0.6MPa

2.2 selection and quantity determination of molecular sieves

according to previous experience, experimental data of each molecular sieve and technical parameters required by the device, the device adopts the latest 185 carbon molecular sieve of BP company in Germany, and its performance data under certain working conditions: (1) overall density: 610~630g/1; (2) Average particle diameter: 2.3~2.5mm; (3) PSA nitrogen production: more than 115m3/h · t at 99.9% N2; (4) PSA extraction rate: more than 27% N2/air

the above data have certain requirements for the pressure, dew point and oil content of the processing air. The reason for selecting BF molecular sieve is that if domestic molecular sieve is used, the required molecular sieve amount is relatively large, the volume of the configured adsorption cylinder is also correspondingly increased, and single-stage adsorption is also difficult to meet the required purity requirements. With reference to the relevant parameters of molecular sieve, the molecular sieve quantity Q1 equipped at the required pressure of 0.6MPa and purity of 99.9% N2 can be determined by comparison

2.3 determination of air compression system and cold dryer system

because molecular sieves have high requirements for the pressure, dew point and oil content of processing air, oil-free lubricated air compressors or oil lubricated air compressors plus multistage oil mist filters are often selected to ensure the requirements for oil content; Select a cold dryer to ensure its dew point requirements for the air. In this device, the oil-free lubrication air compressor is used. Its technical data: the processing air volume is 10m3/h (Q2), and the outlet pressure is 0.8MPa. The pressure dew point required by the cold dryer shall not be greater than 5 ℃

2.4 parameters and structural design of the adsorber system

the adsorber system is the core of the whole device, and its design and manufacturing quality directly affect the performance and service life of the whole device. Different parameters and structural design methods of adsorbers also have their own advantages and disadvantages. There are different views on how to achieve the best design in manufacturing business

2.4.1 parameter design of adsorber

① determination of minimum diameter d0 of adsorber

the first consideration in the design of adsorber is the empty tower speed V0 of adsorber, and the allowable empty tower speed of adsorbents with different properties also varies. The minimum diameter d0 of the adsorber can be calculated according to the processing air volume Q2 and the empty tower speed v0

② determination of adsorber volume V

adsorber volume V is composed of three parts: volume V1 required for filling molecular sieve Q1, volume V2 occupied by relevant structural members, and volume V required for buffering and uniformly distributing stable gas flow. It is mainly divided into modified polyolefins, modified ABS, plastic alloys, and other types 3; That is, v=v1+v2+v3; Among them, V is determined by parameter design, and V2 and V3 are determined by structural design

2.4.2 structural design of the adsorber

① determination of the height diameter ratio of the adsorber

the height diameter ratio of the adsorber determines whether the elongation and reduction of area of the adsorber are ductility. The often used index is whether the adsorber is short and fat or slender. With the low bed design of short and fat type, the molecular sieve has high utilization rate, small suction resistance, less pressure loss, and the manufacture of the body is relatively difficult. The slender high bed design has large suction resistance, but it can make the air flow evenly diffuse along the axial direction of the adsorber to achieve isothermal adsorption and high purity adsorption requirements

② determination of the number of adsorbers