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Spray Tower Optimization
Published in Kenneth Schifftner, Air Pollution Control Equipment Selection Guide, 2021
Spray towers basically disperse by using pressurized spray a high surface area liquid stream counterflow (primarily) into a gas stream containing contaminants and/or heat. The purpose of the design is to efficiently affect the transfer of mass and/or heat into the liquid. The liquid is then constantly drained from the spray tower. The word “primarily” is used because some of the liquid is inherently carried upward in the vessel (sometimes called “back-mixing”) given the movement of the gases. Unless the contaminant is absorbed quickly and is rapidly neutralized (retained in solution by being converted to a low partial pressure salt or oxide), movement of the liquid upward can reduce the net efficiency of the spray tower. The optimization goal is therefore to minimize the amount of liquid moving up with the gas stream.
Role of Incineration in the Production of Persistent Organic Pollutants: Is It Safe?
Published in Narendra Kumar, Vertika Shukla, Persistent Organic Pollutants in the Environment, 2021
Gagandeep Kour, Kajol Goria, Ashish Pathak, Richa Kothari, Deepak Pathania, Sunil Dhar, V. V. Tyagi
The waste is collected and transported to the incinerator plant, where it is stored in a bunker before being transferred to the incineration chamber, as shown in Figure 4.5. The waste is combusted at a temperature above 850°C. Fossil fuels such as natural gas are used for the start-up and to maintain the high combustion temperatures. Urea, hydrated lime, and activated carbon are injected into the flue gas to control the nitrogen oxides and sulfur oxides emitted from the incinerator stacks. Filter bags, scrubbers, electrostatic precipitators, spray towers, and other control measures are used to remove particulate matter.
Gas–Liquid Reactors
Published in Salmi Tapio, Mikkola Jyri-Pekka, Wärnå Johan, Chemical Reaction Engineering and Reactor Technology, 2019
Salmi Tapio, Mikkola Jyri-Pekka, Wärnå Johan
Gas scrubbers are a special type of gas–liquid reactors. Two main constructions exist: the spray tower and the Venturi scrubber. These reactor types are shown in Figures 7.14 and 7.15. The gas phase is dispersed into the liquid phase with a Venturi tube. The gas flows through the Venturi tube at a high velocity (Figure 7.15). In a spray tower, the liquid is distributed with a distributor and sprayed downwards in the form of small droplets. The gas flows countercurrently upwards. Due to high gas velocities, these kinds of reactors are only useful for very fast reactions.
Experimental study of the temperature distribution and water evaporation in an axial dual-zone vortex chamber spray dryer
Published in Drying Technology, 2022
Juray De Wilde, Subhajit Dutta, Jnyana Ranjan Pati, Axel de Broqueville
Spray drying is widely used for the production of particles in the chemical, biochemical, food and feed and pharmaceutical industries.[1–3] The production of milk powder and detergents are well-known examples. Despite decades of experience with spray towers, efficiency is still limited resulting in high volume requirements, and related high capital and operational costs.[4] Typically, operation is single zone, with all air fed at the same temperature. Furthermore, the air temperature is limited to prevent degradation of the product.[5,6] The slip velocity between the drying air and the droplets is limited to prevent entrainment of the particles and the droplet concentration in the chamber is relatively low. The limited slip velocity is detrimental for interfacial mass and heat transfer, which are essential in the initial drying phase. In this phase, evaporation at the external surface of the droplets leads to shrinkage of the droplets and formation of a thin shell of solute material. In the next phase of final drying, diffusion limitations in the forming particle determine the observed evaporation rate. Depending on the composition of the droplets and the operating conditions and the eventual overlap between the formation of a shell and the introduction of intra-particle diffusion limitations, a cavity can be formed inside the particles.[2,5]