If the gas speed is very small, the size of the adsorber is large and uneconomical.
If the gas velocity is too large, the pressure drop will increase and the adsorption efficiency will be affected.The optimum gas velocity was determined by experiment.
The adsorption design can not pursue too high adsorption efficiency, the empty tower speed value is reduced, it will make the adsorption bed volume, the amount of adsorbent and equipment cost increased greatly;On the contrary, it is not appropriate to take too large empty tower gas speed. Although the equipment cost is low, the adsorption efficiency drops a lot, and the pressure drop of the system will rise rapidly with the increase of the empty tower speed, resulting in excessive power consumption. Therefore, due to the selection of the appropriate air speed of the empty tower, the most suitable air speed of the empty tower is 0.8~1.2m/s"21, according to the empirical conclusion, this design determines
conditions:Treatment air volume :Q=20000 m'h, design temperature is 35° C, pressure is 1.01325×103Pa  Since the proportion of air in exhaust gas is far greater than that of pollutants, the properties of exhaust gas can be approximately viewed as the thermophysical properties of dry air. Please refer to Appendix 9 of Principles of Chemistry to obtain the following data:Properties of air mixture:Fluid density P;=1.147kg/ m', viscosity u,= 1.94×10-5 Pa.S, specific heat capacity C,=1.005kJ/(kg."C)Under certain operating conditions, the gas mixture by adsorption bed, adsorption by adsorption, adsorption after a period of time, when starting from the adsorbent in the laminar flow of the gas adsorbed mass (or its concentration reaches a specified value), think bed fire, adsorption properties of adsorbent adsorption quantity at this time is called dynamic activity of adsorbent.
The activity is not only related to the characteristics of adsorbents and adsorbents, but also related to temperature, concentration and operating conditions.
The kinetic activity value of adsorbent is the main basis for the design of adsorption system.
The adsorption rateThe adsorption process often takes a long time to reach equilibrium, and the contact time is limited in the actual production process.Therefore, the amount of adsorption depends on the adsorption rate, and the adsorption rate is related to the adsorption process, the adsorption process can be divided intoThe adsorption process often takes a long time to reach equilibrium, and the contact time is limited in the actual production process.Therefore, the amount of adsorption depends on the adsorption rate, and the adsorption rate is related to the adsorption process, which can be divided into the following steps
(1) External diffusion, the adsorbate from the main air flow through the air film around the particles to the outer surface of the adsorbent; (2) Internal diffusion, the adsorbate from the outer surface through micropores to the surface of the adsorbent micropores
(3) adsorption, the adsorbent reached the microporous surface of the adsorbent is adsorbedhttps://www.activated-carbon-pellets.com
(4) The desorbed adsorbate diffuses to the main body of the gas phase through internal and external diffusionPhysical adsorption process is generally controlled by internal and external diffusion, chemical adsorption is controlled by both surface dynamics and internal and external diffusion.Because of the complexity of the adsorption process and many influencing factors, it is difficult to derive the rate theoretically, so it is generally determined by experience or model experiment.
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