Numerical Simulation Study Of Performance Influencing Factors For Neutralizer

Neutralizer is a device which is used in the clean workshop section of the sulfurous method sugar mill. Its essence is a jet pump. High-speed jet of sugarcane juice forms a vacuum which inhales sulfur gas, And then reacts with CaO which is added at the preliminary grey step to form CaSO3. The adsorption effect of calcium sulfite eliminate the unsugar impurities in the mixed juice and isolate the clear juice which is limpid and light color. The work performance of neutralizer will affect the quality of the final product, so further study is necessary. CFD technology develops rapidly and is used widely in various engineering design fields in recent years. It has many advantages such as low cost, fast speed, high precision, good reliability and can simulate various working condition. Specially, CFD technology has made rapid progress in the design and study of jet pump. The researchers found that CFD technology is a good way to simulate jet pump in high precision. Simulated result can give the flow field information which cannot obtain in tests. It can make the design of the injector to conform to the use of actual production and to promote the application of the jet pump in the field of chemical industry. The design and research of neutralizer which is key equipment in sugar production still be put on the method of traditional empirical formulae.In this paper, CFD software Fluent was used to simulate a neutralizer and to explore the influence of key geometric construction on neutralizer’s performance. Firstly, the governing equation which describes two-phase flow in the neutralizer was founded and the detailed process of numerical simulation was give, include:discrete of calculation area, discrete of governing equation, solution of algebraic equation and the solving order and process of governing equation.The validation of results indicates that the numerical simulation method in this paper has high reliability. Jet Coefficient is the main performance evaluation index, meanwhile reference the velocity distribution and pressure distribution of flow field information which was obtained in numerical simulation.The geometric structure parameters studied in this paper include throat pipe diameter, throat pipe length, tail pipe diameter, tail pipe length, gas entrance diameter and jet length. It was found that:(1)When tail pipe diameter keep in constant, jet coefficient increases with the increase of throat diameter. When the tail pipe diameter is200mm, jet coefficient increased from6.93(throat diameter is90mm) to10.04(throat diameter is150mm), increased by44.9%.(2)Jet coefficient decreases with the increase of throat diameter. jet coefficient decreased from8.31(throat length is90mm) to6.78(throat length is150mm), increased by18.4%.(3)When throat pipe diameter keeps in constant, jet coefficient and gas velocity in the throat increases with the increase of tail pipe diameter.(4)Jet coefficient increases with the increase of tail pipe length, jet coefficient increased from4.23(throat length is0m) to8.11(throat length is10mm), increased by91.7%. When the tail pipe length is7m, jet coefficient is7.65, with growth of80.8%. When it has a shorter tail pipe, the static pressure at throat change slightly and the minimum of static pressure increase with the increase of tail pipe length.(5)The velocity of sulfur gas enters into the suction chamber, but jet coefficient increase linearly. jet coefficient increased from7.04(throat length is50mm)to14.27(throat length is150mm), with growth of102.7%. (6)Location of sulfur gas inlet has little influence on the jet coefficient, can be ignored.(7) Jet coefficient increases linearly with the increase of suction chamber diameter. jet coefficient decreased from7-44(throat length is400mm) to6.93(throat length is1200mm), with growth of6.8%.(8) When the diffusion pipe length is0mm and100mm (the corresponding angle is90.0°and48.6°, respectively.). jet coefficient is smaller than other angles. When diffusion pipe length decreased from200mm to500mm (angle of flare less than22°) jet coefficient increased slightly and growth is very small.(9)Jet coefficient increase with the increase of the jet length and then decrease.(10) Jet coefficient increases with the increase of the cane juice speed. For neutralizer’s geometric structure parameters in this paper, the cane juice speed of24.56-18.05m/s is ideal and larger nozzle diameter is more suitable.