Energy and Efficiency Characteristics of the Ejector Venturi Scrubber

The scrubbing and pumping actions in the Ejector Venturi Scrubber are two separate phenomenon occurring simultaneously. Each phenomenon requires energy and has efficiency of operation and collection efficiency. These energy and efficiency relationships are discussed and illustrated in form of numerous graphs. The scrubbing energy requirements and how they vary with particle sizes down to one micron are also discussed and presented in form of numerous graphs.     

Submicron Particulate Scrubbing with a Two Phase Jet Scrubber

The two phase jet scrubbing system utilizes waste thermal energy to provide the operating power for a two phase jet which simultaneously cleans and induces the necessary draft. Tests results have shown excellent cleaning performance and a substantially reduced operating cost.     

Correlation of Dust Scrubber Efficiency

The grid-type electrostatic precipitator¹ evolved from some basic research into the collection of airborne charged dust particles in the wake of a flat, metallic, perforated plate under the action of an externally applied electric field. In the earliest experiments in the laboratory² a flat grounded perforated plate (or grid) was placed at right angles to an air stream moving at 6 ft/sec and an electric field was created on its downstream side by the placement of a second grid, bearing high negative potential, just downstream of the first. Negatively charged dust particles, carried along by the air stream through the openings in the first of the two grids, collected on the downstream face of the upstream grid as a result of the electric force acting on them in the direction opposing the air flow. Measured values of dust collection efficiency could not be accounted for simply by resolving the directly opposing mainstream air flow and electrostatic forces. The concept of vortex-enhanced precipitation was therefore proposed in order to explain the experimental results.     

Performance of a Steam-Ejector Scrubber

The results of fractional and overall mass efficiency tests of a steam-ejector scrubber are presented. The tests were performed on one of seven modules of a full scale scrubber used for controlling particulate emissions from an open hearth furnace. Total flue gas particulate mass concentrations were determined at the inlet and outlet of the scrubber by conventional (Method 5) techniques. Inlet and outlet particulate concentrations as functions of diameter were determined on a mass basis using cascade impactors for sizes from about 0.3 μm to 5 μm, and on a number basis for diameters smaller than about 1 μm using optical and diffusional methods. Measurements were made under several scrubber operating conditions. The measured efficiencies based on total particulate mass concentrations with the scrubber operating under near optimum conditions ranged from 99.84 to 99.9%. The measured fractional efficiencies ranged from a maximum of 99.99% for particles having diameters of 1 μm to values of 97 and 99.9% for particles having diameters of 0.1, and 5 μm, respectively.     

Continuous Monitoring of FGD Wet Scrubber Corrosion

This article describes an electrochemical corrosion monitoring system developed in England that offers utilities the capability of continuously measuring power plant corrosion activity for a wide range of operating conditions.     

Status of the DOE/GEESI In-Duct Scrubbing Pilot Study

The recent promulgation of stack height regulations and possible changes in the National Ambient Air Quality Standards for sulfur dioxide and the associated dispersion model methodologies, could require older power plants to develop new compliance strategies and upgrade emission control systems. In such situations, an inexpensive, moderate removal efficiency flue gas desulfurization technology could maintain the cost effectiveness of these plants. Such a technology was selected by the Department of Energy for demonstration in its Acid Rain Precursor Control Technology Initiative. The process applies the rotary atomizer techniques developed for lime slurry dry flue gas desulfurization spray absorbers, and utilizes existing ductwork and particulate collectors. This induct scrubbing technology is anticipated to result in a dry desulfurization process of moderate removal efficiency. The critical elements for successful application are (i) adequate mixing for efficient reactant contact, (ii) sufficient residence time to produce a non-wetting product, and (iii) appropriate ductwork cross sectional areas to prevent deposition of reaction products before drying. The ductwork in many older power plants, previously modified to meet 1970 Clean Air Act requirements for particulate control, usually meets these criteria. A pilot study of the process is now in design-construct phase. Testing will start in 1987 and determine conditions under which the technology would be a cost effective approach to meeting emission reduction design criteria     

Modeling of surface tension effects in venturi scrubbing

A modified model of venturi scrubber performance has been developed that addresses two effects of liquid surface tension: its effect on droplet size and its effect on particle penetration into the droplet. The predictions of the model indicate that, in general, collection efficiency increases with a decrease in liquid surface tension, but the range over which this increase is significant depends on the particle size and on the scrubber operating parameters. The predictions further indicate that the increases in collection efficiency are almost totally due to the effect of liquid surface tension on the mean droplet size, and that the collection efficiency is not significantly affected by the ability of the particle to penetrate the droplet.     

喷嘴数量对文丘里除尘器性能影响的模拟

选用欧拉-欧拉多相流模型和RNG k-ε湍流模型对文丘里除尘器流动特性进行数值模拟,首先对2个喷嘴时不同液体速度下的压力降和喉管液体分布情况进行模拟,并与实验值进行了比较,得到了较好的一致性;然后比较了2个喷嘴和4个喷嘴的情况下不同液体速度时文丘里除尘器的压力降和液体分布情况。模拟结果表明：欧拉-欧拉多相流模型可准确地模拟文丘里除尘器内部流场;喷嘴数量对文丘里除尘器内部的压力降和液体分布有较大影响,当相对射流深度为0.2,喉管气速为64 m·s-1,喷嘴数量由2增加为4时,压力降增加了17.17%,在喷嘴数目为4,喉管气速为74 m·s-1,液体速度为12.5 m·s-1时可使液体在文丘里除尘器内部得到较均匀的分布。     

Comparison of the performance of a single and two-stage variable-throat venturi scrubber

The efficient removal of fine particulate matter from a gas stream by a venturi scrubber is achieved usually at the expense of a high gas-phase pressure drop with a coincident high fan running cost. It is desirable, therefore, to investigate ways of reducing venturi pressure loss for a given overall collection efficiency. This paper is principally a theoretical investigation of the effects of two-stage venturi operation. The theoretical predictions are borne out qualitatively by experimental work.The paper shows that above a certain pressure drop, which is dependent upon particle size, collection efficiencies can be increased significantly (and hence the pressure loss reduced) by using a two-stage design. The value of the main parameters in the collection efficiency—pressure drop relationship for single-stage operation determines to what extent two-stage scrubbing is an advantage. The improvement in performance becomes greater as both the particle size and system pressure drop increase. The lower efficiencies obtained with single-stage venturi operation are shown to be the result of a “diminishing returns” inherent in the scrubbing process at higher Stokes' Numbers.     

文丘里水膜除尘器除尘脱硫增效技术研究

介绍了三相流化床技术用于文丘里水膜除尘器除尘脱硫增效的原理、工艺流程以及在410t／h锅炉上的工业应用结果。工业运行测试结果表明，其脱硫效率可达85％左右，除尘效率达98％左右。该系统结构简单、运行可靠，具备了工业应用的条件。     

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

The high collection efficiencies that are required nowadays to meet the stricter pollution control standards necessitate the use of high-energy scrubbers, such as the venturi scrubber, for the arrestment of fine particulate matter from exhaust gas streams. To achieve more energy-efficient particle collection, several venturi stages may be used in series. This paper is principally a theoretical investigation of the performance of a multiple-stage venturi scrubber, the main objective of the study being to establish the best venturi design configuration for any given set of operating conditions. A mathematical model is used to predict collection efficiency vs pressure drop relationships for particle sizes in the range 0.2–5.0 μm for one-, two-, three- and four-stage scrubbers. The theoretical predictions are borne out qualitatively by experimental work. The paper shows that the three-stage venturi produces the highest collection efficiencies over the normal operating range except for the collection of very fine particles at low pressure drops, when the single-stage venturi is best. The significant improvement in performance achieved by the three-stage venturi when compared with conventional single-stage operation increases as both the particle size and system pressure drop increase.     

Flux Force Condensation Aspirative Wet Scrubbing of Submicron Particles

A novel aspirative wet scrubber system makes use of condensation forces to enhance fine particulate collection. A pressure gain of 2 to 4 inches, W.C. is generated by the system and total water pump power requirements for multistage systems are 2 horsepower per thousand scfm. of gas throughput. No fans or blowers are utilized. When scrubbing hot combustion products carrying 0.1 to 6.0 micron metal oxide particles from a kiln, total collection efficiency was 99.4%. Collection of fly ash, in the particle size range 0.1 to 10 microns, has been measured at 99.5% efficiency.     

Theoretical study of liquid droplet dispersion in a venturi scrubber

The droplet concentration distribution in an atomizing scrubber was calculated based on droplet eddy diffusion by a three-dimensional dispersion model. This model is also capable of predicting the liquid flowing on the wall. The theoretical distribution of droplet concentration agrees well with experimental data given by Viswanathan et al. for droplet concentration distribution in a venturi-type scrubber. The results obtained by the model show a non-uniform distribution of drops over the cross section of the scrubber, as noted by the experimental data. While the maximum of droplet concentration distribution may depend on many operating parameters of the scrubber, the results of this study show that the highest uniformity of drop distribution will be reached when penetration length is approximately equal to one-fourth of the depth of the scrubber. The results of this study can be applied to evaluate the removal efficiency of a venturi scrubber.     

Laboratory Evaluation of an Aldehyde Scrubber System Specifically for the Detection of Acrolein

Abstract

We demonstrate the use of an aldehyde scrubber system to resolve isobaric aldehyde/alkene interferences in a proton transfer reaction mass spectrometer (PTR-MS) by selectively removing the aldehydes from the gas mixture without loss of quantitative information for the alkene components. The aldehyde scrubber system uses a bisulfite solution, which scrubs carbonyl compounds from the gas stream by forming water-soluble carbonyl bisulfite addition products, and has been evaluated using a synthetic mixture of acrolein and isoprene. Trapping efficiencies of acrolein exceeded 97%, whereas the transmission efficiency of isoprene was better than 92%. Quantification of the PTR-MS response to acrolein was validated through an intercomparison study that included two derivatization methods, dinitrophenylhydrazine (DNPH) and O-(4-cyano-2-ethoxybenzyl)hydroxylamine (CNET), and a spectroscopic method using a quantum cascade laser infrared absorption spectroscopy (QCL) instrument. Finally, using cigarette smoke as a complex matrix, the acrolein content was assessed using the scrubber and compared with direct QCL-based detection.     

Wet Scrubber Analysis of Volatile Organic Compound Removal in the Rendering Industry

Abstract

The promulgation of odor control rules, increasing public concerns, and U.S. Environmental Protection Agency (EPA) air regulations in nonattainment zones necessitates the remediation of a wide range of volatile organic compounds (VOCs) generated by the rendering industry. Currently, wet scrubbers with oxidizing chemicals are used to treat VOCs; however, little information is available on scrubber efficiency for many of the VOCs generated within the rendering process. Portable gas chromatography/mass spectrometry (GC/MS) units were used to rapidly identify key VOCs on-site in process streams at two poultry byproduct rendering plants. On-site analysis was found to be important, given the significant reduction in peak areas if samples were held for 24 hr before analysis. Major compounds consistently identified in the emissions from the plant included dimethyl disulfide, methanethiol, octane, hexanal, 2-methylbutanal, and 3-methylbutanal. The two branched aldehydes, 2-methylbutanal and 3-methylbutanal, were by far the most consistent, appearing in every sample and typically the largest fraction of the VOC mixture.

A chlorinated hydrocarbon, methanesulfonyl chloride, was identified in the outlet of a high-intensity wet scrubber, and several VOCs and chlorinated compounds were identified in the scrubbing solution, but not on a consistent basis. Total VOC concentrations in noncondensable gas streams ranged from 4 to 91 ppmv. At the two plants, the odor-causing compound methanethiol ranged from 25 to 33% and 9.6% of the total VOCs (v/v). In one plant, wet scrubber analysis using chlorine dioxide (ClO2) as the oxidizing agent indicated that close to 100% of the methanethiol was removed from the gas phase, but removal efficiencies ranged from 20 to 80% for the aldehydes and hydrocarbons and from 23 to 64% for total VOCs. In the second plant, conversion efficiencies were much lower in a packed-bed wet scrubber, with a measurable removal of only dimethyl sulfide (20–100%).     

Mathematical Modeling of SO2 Absorption in a Venturi Scrubber

Abstract

A three-dimensional mathematical model was used to predict the removal efficiency of a venturi scrubber for SO₂ absorption into a water and alkaline solution. In order to obtain better results, nonuniform droplet concentration distribution was considered. The results of the model with nonuniform droplet concentration distribution are compared with several sets of experimental data, as well as with prediction data of a mathematical model with uniform droplet concentration distribution. Without exception, all comparisons indicated that including nonuniformity of droplet concentration distribution in the model will significantly improve the agreement between the experimental data and predicted values.     

Improved Spray Dry Scrubbing through Grinding of FGD Recycle Material

A laboratory size spray dry scrubbing unit consisting of a spray dryer and a pulse Jet baghouse was used to study the effect of grinding recycle waste on SO₂ removal across the spray dryer and on sorbent utilization. The equipment treats simulated flue gas with a dry flow rate of 1.5 m³ h^?1 (stp) and utilizes an ultrasonic nozzle for atomization. The apparatus was initially tested over a broad range of operating conditions; a close agreement in SO₂ removal was found with data from much larger units. The effect of grinding the FGD recycle material on the SO₂ removal across the spray dryer was found to be great. Grinding the recycle material can enhance the SO₂ removal efficiency to a level comparable to operation with a large excess of fresh lime.