Selective Removal Of H₂S In A Impinging Stream Absorber

The gas produced by the fermentation process of wastewater treatment in thepharmaceutical industry, containing a certain amount of H₂S and CO₂, must be refinedbefore further emissions or use, especially very strict requirements on theconcentration of H₂S. When the concentration of the H₂S in the air was higher than³00ppm can endanger life. Adsorption-desorption method was widely used toremoval H₂S at present. The packed absorption columns were used as the equipment.Because of the gas stay a long time in columns, H₂S and CO₂were absorbed at thesame time, resulting in larger absorbent consumption, tower load increases and theenergy consumption increases. The desorbed gas as raw material for subsequent sulfurrecovery unit, the large amount of CO₂desorption decreases H₂S concentration,resulting in sulfur recovery unit in the state of the low efficiency of operation inlong-term, greatly increased the device operation and maintenance costs. The subjectof this topic is theoretical study of impinging streams absorber for selectivedesulfurization performance.A³D fluid dynamics mathematical model of impinging stream absorber wasestablished. The hydrodynamic properties of the absorber and the effects of impingingdistance, impinging velocity on the pressure drop and the maximum radial velocity ofthe absorber were investigated. The motion law of the droplet in the flow field and theeffects of impinging velocity, droplet diameter, droplet injection speed on theresidence time of the droplet were also investigated.Results show that the velocity andpressure distribution of the absorber were in line with the mirror model which isdefined by Powell and the droplet motion was in line with the theoretical analysis andexperimental research.The pressure drop and the maximum radial velocity which didnot change significantly when L/d≥2, increased as the impinging velocity increase.The suggestion of the diameter of the single air out absorber was D/d≥8.5. Theresidence time of the droplet was increase as the impinging velocity increase, but itdid not change significantly when the impinging velocity was greater than14m/s. Theresidence time of the droplet decreased first then and then increased as the dropletinjection speed increase, but it increase as the droplet diameter increase. The fluid dynamics model and the mass transfer model were coupled firstly. Theeffects of impinging distance, impinging velocity, droplet diameter, droplet injectionspeed, liquid-gas ratio and Na/S molar ratio on the selectivity coefficient and thedesulfurization rate were investigated. The effect of impinging velocity on volumetricmass transfer coefficient was also investigated. Results show that when the impingingdistance was L/d=4, the impinging velocity was20m/s, the droplet diameter was40μm, the droplet injection speed was³0m/s, liquid-gas ratio was0.05⁰.1L/m³andNa/S molar ratio was³, the selectivity coefficient could reach³0, the rate ofdesulfurization was more than99%and the volumetric mass transfer coefficient wasin the1.05¹.75s^-1. The theoretical research could guide the design of the impingingstreams absorber and the choice of the operating parameters.The results show that the impinging streams absorber exhibits highdesulfurization rate, high selectivity, low liquid-gas ratio, high mass transfercoefficient and low energy consumption, there is good potential for industrialapplication in the field of selective desulfurization.