Chemical Engineering Dissertaion. Designing a venturi scrubber Essay

Chemical Engineering Dissertaion. Designing a venturi scrubber - Essay Example This happens in the bottleneck of the venturi. Behind this bottleneck, the pressure drops, reducing flow velocity back to normal. At this point, contaminant particles are collected and removed. A venture scrubber is the simplest but most compact but efficient wet dust collector. It collection efficiency is rated from 0.2 Â µ particles when high linear gas velocities ranging 50 to 150m/s reach the throat as the gas is contacted with water. Therefore, collection efficiency of a venture scrubber depends on the pressure drop experienced during the operation. The scrubber is made of a long tube with consecutive converging and diverging sections with steep rising velocity in the convergent section. This enables the scrubbing liquor to get in contact with the throat and convert the kinetic energy into pressure in the downstream divergent diffuser. When gas flow is a variable, it is necessary to adapt the cross-section of the throat to maintain constant velocity as well as collection efficiency. In a simple tubular design, the throat is made of rubber and pinched pneumatically. Other types consider mechanical control to adapt the cross-sectional area. Amount of water injected is also varied. As water moves in the closed circuit, a settling basin is incorporated that separates the collected dust as slurry. The high velocity of the gas makes it important to consider erosion and abrasion factors as well as corrosion due to the absorption of acid gas compounds. Water treatment of the collected water pose considerable costs to venture dust collectors. The water droplets coalesce to a size of 0.1mm and are separated by centrifugal forces (conventional cyclones), lamellae separator, sick-sack flow, inertial forces and wetted collecting surfaces, or wire or fibre gauge packages. The droplets from venturi scrubbers require entrainment. Therefore droplet separators are required. A two step arrangement is preferred with a first contact using recycled water while the