Venturi injectors

The most frequently used contactors in full-scale waste water ozonation systems are bubble column reactors equipped with diffusers or venturi injectors, mostly operated in a reactor-in-series counter-current continuous mode. Many full-scale ozone reactors are operated at elevated pressure (2-6 barabs) in order to achieve a high ozone mass transfer rate, which in turn increases the process efficiency. 

Ozone generators convert only a small percentage of oxygen to ozone. This ozone/air mixture is dosed to a cooling water bypass loop via a venturi injector. A static mixer then ensures intimate contact of the ozone with the water before it returns to the cooling tower basin. 

The flow rates of gases are typically measured with orifice meters. Mixing of gases are achieved by various ways including venturi injectors, baffles or... 

The collection of particles larger than 1—2 p.m in Hquid ejector venturis has been discussed (285). High pressure water induces the flow of gas, but power costs for Hquid pumping can be high because motive efficiency of jet ejectors is usually less than 10%. Improvements (286) to Hquid injectors allow capture of submicrometer particles by using a superheated hot (200°C) water jet at pressures of 6,900—27,600 kPa (1000—4000 psi) which flashes as it issues from the nozzle. For 99% coUection, hot water rate varies from 0.4 kg/1000 m for 1-p.m particles to 0.6 kg/1000 m for 0.3-p.m particles. 

Main fuel injector. This unit is designed to deliver a fuel-air mixture to the catalyst that is uniform in composition, temperature, and velocity. A multi-venturi tube (MVT) fuel injection system was developed by GE specifically for this purpose. It consists of 93 individual venturi tubes arrayed across the flow path, with four fuel injection orifices at the throat of each venturi. 

Contactor design is important in order to maximize the ozone-transfer efficiency and to minimize the net cost for treatment. The three major obstacles to efficient ozone utilization are ozone s relatively low solubility in water, the low concentrations and amounts of ozone produced from ozone generators, and the instability of ozone. Several contacting devices are currently in use including positive-pressure injectors, diffusers, and venturi units. Specific contact systems must be designed for each different application of ozone to wastewater. Further development in this area of gas-liquid contacting needs to be done despite its importance in waste treatment applications. In order to define the appropriate contactor, the following should be specified ... 

Spiral mills create a high velocity helix of gas that rotates around the center of the jet mill. Solids are introduced via a venturi feed injector (Fig. 8.2) and become entrained in the turbulent helical flow. The resulting high energy collisions between particles as well as with the particles and the mill internals fracture particles to micron and submicron size. 

Feed rate 50 g/min. Injector pressure 120 psi. Milling pressure 100 psi. Venturi 316 SS. 6LOD, loss on drying. 

There are two types of two-component nozzles ejectors and injectors. The ejectors are liquid jet aspirators, which operate according to the Venturi principle and with their propulsion liquid jet in the mixing space (diffuser) attain a substantial pressure drop on the gas side. Vacuum is commonly produced by water ejectors (vacuum pumps) in the laboratory and by steam ejectors on an industrial scale. 

Many different typas of spray device have been developed and no generalized correlations are available for predicting performance. They can be categorized into two basic types (I) preformed spray, which includes countercurrent, cocurrent, and crosscurrent spray lowers, spray dryers, cyclonic spray devices, and injector venturis and (2) gas atomized spray, which consists primarily of venturi scrubbers and related designs. 

Premix duct based on a lean premixed prevaporised (LPP) concept with a venturi configuration, which has been optimized in order to obtain a good velocity profile at the inlet to the catalytic section. Fuel is injected upstream of the venturi minimum section with injectors angled relative to the airflow. Mixing is achieved with an inlet radial/axial turbulence generator in the venturi inlet. 

Wash liquid is sprayed into the gas, the gas phase remains continuous (free board scrubber without internals such as venturi srubber, injector srubber, spray smbber, annular-flow srubber, radial-... 

There is considerable information available in the hterature on the design of ejectors (steam jet ejectors, water jet pumps, air injectors, etc.) supported by extensive experimental data. Most of this information deals with its use as an evacuator and the focus is on ejector optimization for maximizing the gas pumping efficiency. The major advantage of the venturi loop reactor is its relatively very high mass transfer coefficient due to the excellent gas-liquid contact achieved in the ejector section. Therefore, the ejector section needs careful consideration to achieve this aim. The major mass transfer parameter is the volumetric liquid side mass transfer coefficient, k a. The variables that decide k a are (i) the effective gas-hquid interfacial area, a, that is related to the gas holdup, e. The gas induction rate and the shear field generated in the ejector determine the vine of and, consequently, the value of a. (ii) the trae liquid side mass transfer coefficient, k. The mass ratio of the secondary to primary fluid in turn decides both k and a. For the venturi loop reactor the volumetric induction efficiency parameter is more relevant. This definition has a built in energy... 

When filling without pressure, a vacuum is created in the conveyor tube using a venturi nozzle inside the filhng injector orifice. The filling container and the mold are vacuumized resp. vented. Due to the vacuum of the venturi nozzle, the foam particles are sucked out of the filling container and are blown into the mold cavity. 

For filling, the spindle sleeve is pneumatically retracted, and the compressed air for the venturi nozzle is turned on. A vacuum is applied to the filling injector and the material hose. This vacuum sucks the foam particles out of the filling container. 

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