Research on Processing of Waste Water with High Ammonium Concentration by Blew-off and Absorption
|Course||Physical and chemical|
|Keywords||the treatment of wastewater Ammonia baffled HIGEE machine plate tower mass-transfer|
Serious supernutrition pollution and ecological destruction will be caused if ammonium wastewater is discharged directly to the river, lake or sea without any treatments. It is necessary to deal with ammonia in waste water. There are advantages or disadvantages in treatment of ammonium wastewater with different methods, respectively.Hypergravity technology is a new-type technology in which centrifugal forces much more than gravity ( high g or higee) can result in improving mass-trasnfer efficiency between phases by rounding packed machine (HIGEE machine). The packings in this HIGEE machine are firstly designed as barbed-web packed style, disk plate packed style, helix packed style, baffled packed style and so on, which have different ratios of surface area to volume, different pressure drop, different interphase mass-trasnfer efficiency and other properties.Ammonium wastewater is blew off by the designed whole-move baffled HIGEE machine. The whole-mobile packing of the baffled HIGEE machine is composed of two quintuplicate rings which are nested by four ?8 mm internal supporters. The packing parameters are: sole plate 50 mm in height, combination plate 65 mm in height, 380 mm in outside diameter, 135 mm in inside diameter, 10 mm space between two rings, 15 mm height difference, 170 m?1 specific surface area. The mass-transfer coefficient and gas pressure drop were investigated at different running parameters of the designed machine, such as, rotating speed, air flux, liquid flux and ammonia concentration. The experimental results show that ammonia blew off efficiency is close to 90% and mass-transfer coefficient is greater than 3.46 kmol·m?3·s?1at pH about 10, temperature about 20℃, air flux 160 m3·h?1, liquid flux 60 dm3·h?1, rotating speed 800 r·min?1 and ammonia concentration more than 3000 mg·dm?3 and the gas pressure drop was remarkably lower than that in other kinds of HIGEE machine packings and the pressure drop of wet bed was lower than that of dry bed. The regression equations of mass-transfer coefficient and gas pressure drop by matlab analysis are obtained:The vortex plate tower has the following advantages: wide opreation range, low gas pressure drop, simple construction, low investment cost and so on. In order to avoid re-pollution, the above-mentioned stripped gaseous ammonia should be absorbed in the designed vortex plate tower. The designed vortex plate tower is 1300 mm tower high, 150 mm tower diameter, 147 mm outside diameter of vortex plate, 50 mm blind plate diameter, 170 mm space between two plates, 25 degrees elevation , 20 blades, 3 mm blade thickness, 22% open area.The absorbent efficiency of gaseous ammonia is over 81% by the designed vortex plate tower and the average number of theoretical plates is 3.5 under the conditions of the gaseous ammonia concentration 0.5~1.0%, air flux 0.8 m3·min?1 and pure water used as the absorbent. Its hydraulic loading is 1.62 m3·m?2·h?1. The absorbing efficiency is over 90% and the average number of theoretical plates is 4.5 at the same conditions except sulfuric acid absorbents. The regression equations of the number of theoretical plates by matlab analysis are expressed as: NT=9.85×10-7б-5.7646G0.1105H0.1510Y10.0395 (water absorbent) NT=1.1983б-0.4780G0.2581H0.1354ρ0.0116Y10.0017 (sulfuric acid absorbent)Some surfactants in the absorbents is used to improve absorbent efficiency. The experimental results indicate that the average number of theoretical plates is changed from 3.5 to 4.3 at the above-mentioned conditions with 1.0 g·dm?3 octanol and isooctylal in water absorbent and no remarkable influence on mass-transfer in sulfuric acid absorbent with octanol and isooctylal. The regression equations of the number of theoretical plates in water absorbent with 1.0 g·dm?3 octanol and iso-octylal by matlab analys are expressed as: NT=1.0767б-0.2988G0.1547H0.0888Y10.4002The technique of the blow-off by HIGEE machine and absorption by vortex plate tower are suitable for treating wastewater with high ammonium concentration. It is economical and practical technology with high efficiency, simplicity of the process.