An Efficient Venturi Scrubber System to Remove Submicron Particles in Exhaust Gas

An efficient venturi scrubber system combining a particle growth device and a traditional venturi scrubber was designed and tested in the laboratory. Before the venturi scrubber, saturated steam at 100°C was mixed with normal temperature waste stream to achieve supersaturation conditions allowing submicron particles to grow into micron sizes. Hence the control efficiency of submicron particles was greatly enhanced at a reasonably low pressure drop as compared to that found in the literature. At a flow rate of 250L∕min and a liquid to gas ratio of 2.5L∕m3, the control efficiency of the present venturi scrubber system for NaCl particles greater than 100nm is greater than 90%, and pressure drop is only about 44cmH2O(4.3kPa). In comparison, to remove only 50% of 0.6μm particles at the same liquid to gas ratio, the pressure drop needed will be greater than 200cmH2O (or 19.6kPa). Theoretical calculation has also been conducted to simulate particle growth process and the control efficiency of the venturi scrubber considering the effects of mixing ratio (ratio of steam to waste stream by mass flow rate) and particle diameter. Theoretical results using Calvert's theory (1970) were found to agree well with the experimental data for NaCl particles greater than 50nm, and for SiO2 particles greater than 150nm.

Studying the pressure drop in venturi scrubbers had been the subject of many types of researches due to its importance for removing pollutants from polluted gas. In this study, two new approaches based on Multi-Gene Genetic Programming (MGGP) and Adaptive Neuro-Fuzzy Inference System (ANFIS) were used to predict the pressure drop in venturi scrubbers. The main parameters studied were the throat gas velocity of venturi scrubbers (Vgth), the liquid to gas flow rate ratio (L/G), and the axial distance of the venturi scrubbers (z) as the inputs to the network, while the pressure drop was as the output. One set of experimental data, which was gathered from five different venturi scrubbers including a circular and an adjustable prismatic venturi scrubber with a wetted wall irrigation, a rectangular venturi scrubber and two ejector venturi scrubbers with different throat diameters were applied for this study. The results of ANFIS and MGGP were compared with experimental data and those values from Artificial Neural Networks (ANNs) from our previous work. In this work, the coefficient of the determination (i. e. R2 value) was used to show the prediction ability of these new approaches. Results showed that MGGP and ANFIS can accurately predict the pressure drop in venturi scrubbers with R2 values of 0.9972 and 0.9734, respectively. The results also showed that MGGP has more precision than ANFIS and ANNs. Therefore, based on MGGP, two correlations were generated for two clusters of data. The comparison results between one of these correlations (i. e. correlation 1 with R2 value equal to 0.9937) and other models showed that our correlation has a very good precision and can predict the pressure drop in a more agreement with the experimental data.

Scrubbing by liquid sprayingis one of the most effective processes used for removal of fine particles and soluble gas pollutants (such as SO2, HCl, HF) from the flue gas. The primary function of venturi scrubber, which represents the first stage of the wet flue gas cleaning processes, such as in waste incineration plants, is to capture fine particles as well as remove HCl, HF or SO2 as a result of the decrease in the flue gas temperature before entering the absorption column. In this paper, a newly developed four-branch O-element is proposed as a replacement for venturi scrubber. By means of this device, sulphur dioxide (SO2) removal efficiency and pressure loss and temperature drop were experimentally calculated. The dependence of these variables on liquid–gas ratio was monitored. The simulated flue gas was prepared by the combustion of the carbon disulphide solution in toluene (1:1 vol.) in the presence of the flame in the reactor. Such prepared flue gas with temperature around 150 °C was processed in the laboratory-designed O-element scrubber. Water was used as an absorbent liquid. The maximal efficiency of SO2 removal achieved by this process was up to 70 %, which is far better in comparison with the commonly used venturi scrubbers. The pressure drop of our proposed newly designed wet scrubber is similar to that of the commonly used venturi scrubbers; nevertheless, the influence of the amount of the liquid on pressure drop is not so significant. In parallel, a mathematical model describing the mass transfer, enthalpy balance and pH change of the absorbing solution was also developed. Enthalpy balance was calculated by numerical iteration to determine the unknown outlet liquid temperature. Mass transfer calculation was used for the determination of complete Henry constant from all the subsequent SO2 absorption reactions.

Dust removal and desulphurization in a novel venturi scrubber

Venturi scrubber is very effective device for air pollution control. In an industry venturi scrubber is very efficient to remove micron size dust particles by injecting water droplet. Dust particles collide with the water droplet by inertial impaction at the throat section of venturi scrubber and deaccelerated at diffuser section to allow pressure recovery. Performance of venturi scrubber is assessed in terms of collection efficiency and pressure drop. Venturi scrubber is mostly used in Filtered Vented Containment System (FVCS) for removal of radioactive fission products in Nuclear power plant in severe accident. The purpose of the present study is to design a venturi scrubber to achieve a high overall efficiency in removing radioactive particulate iodine- 131 by CFD simulation. Mesh is developed by Gambit 2.4.6 and Ansys Fluent 15 is used to predict the pressure drop profile inside the venturi scrubber. From a physical point of view, scrubbing process follows liquid injection, the droplet formation, droplet break up and particle capturing mechanism. TAB model is considered to predict the droplet break up. Iodine of diameter 1 µm is used as dust particle. Flow field inside venturi scrubber is simulated by K-e Turbulence model and trajectory of dispersed particle is modelled using lagrangian frame of reference. Finally the results shows the effect of gas velocity and liquid mass flow rate on pressure drop and this study also investigates the overall collection efficiency of venturi scrubber for different throat gas velocities and various mass flow rate of liquid inlet.

A venturi scrubber is one of the most important devices for air pollution control. Although there are different models for predicting the pressure drop in venturi scrubbers, most of them have some defects and cannot predict the pressure drop correctly. In this study, for the first time, an Eulerian–Eulerian computational fluid dynamics (CFD) model is combined with a population balance equation to predict the pressure drop in venturi scrubbers. This simulation takes into account a multiple size group model for droplet dispersion and droplet size distribution, which is based on a population balance equation. Flow field has been calculated by solving the time averaged continuity and Navier–Stokes equations along with the standard k–e turbulence model. The equations included drag, turbulent dispersion, and buoyancy forces. The calculated pressure drop with and without considering the population balance equation was compared with the experimental data to evaluate the accuracy of the CFD modeling. The size distribution of droplets in the venturi scrubber was studied at different points for different liquid to gas ratios and throat gas velocities. The results show that the maximum break-up of droplets happens at the liquid injection point. Finally, the effects of nozzle diameter and nozzle arrangement on pressure drop in venturi scrubbers were investigated.

Estimation of pressure drop in venturi scrubbers based on annular two-phase flow model, artificial neural networks and genetic algorithm

Investigation of dust particle removal efficiency of self-priming venturi scrubber using computational fluid dynamics

Design of artificial neural networks using a genetic algorithm to predict collection efficiency in venturi scrubbers

Numerical simulation of injection characteristics, hydrodynamics and absorption of iodine vapour in a venturi scrubber operating in self-priming mode

Experimental investigation of aerosols removal efficiency through self-priming venturi scrubber

Considering roles of heat and mass transfer for increasing the ability of pressure drop models in venturi scrubbers

Maximizing the performance of a multiple-stage variable-throat venturi scrubber for particle collection

A large number of pressurized coal gasification processes being developed propose to use venturi scrubbers for particulate removal at high pressures. Theoretical predictions based on venturi scrubber performance models indicate that particle collection efficiency will decrease severely in these high gas pressure applications. An exploratory theoretical and experimental program was performed to study the effect of gas pressure on venturi scrubber performance. Experiments were done on a 0.47 m3/s (1000 acfm) pilot scale venturi scrubber. Particle collection performance was determined as a function of scrubber pressure drop for venturi scrubbers operating In the range of 1-10 atm total pressure. Experimental results confirmed that the particle collection efficiency of venturi scrubbers decreases for a given scrubber pressure drop as total gas pressure Is increased. To achieve the same particle collection efficiency, the pressure drop across a venturi scrubber operated at 10 atm Is about 10 times that of the ...

On the pressure drop across Venturi scrubbers in high temperature region, few reports are available. Precooler is sometimes used to cool hot gases, but in order to pass hot gases of over 700°C directly into Venturi scrubbers, it is necessary to know about this pressure drop.The author applied an equation Δp=kput2·γ/2g (1+L) to experimental results in which kp was the correction factor, and making a study of the relation between kp and the temperature drop across the Venturi scrubber obtained a relation kp=3 (Δt)-0.28.With the relation to dust collection efficiency, it is said that the pressure of injection water should be made higher the more the throat diameter of Venturi scrubbers is enlarged, but actually the injection pressure seems to have only slight effects on the pressure drop of Venturi scrubbers.The author performed experiments on this point, and ascertained that the pressure of injection water seems not to affect so much to the pressure drop of gas, as far as the range of water pressure is from 0.3-2.0kg/cm2, as is ordinary used.