Droplet impingement problem

Direct water spray cooling must be carried out with care. The spray chamber must be designed to ensure complete evaporation of all Hquid droplets before the gas enters the baghouse. Spray impinging on the chamber walls can result ia a dust mud iaside the chamber and any increase ia gas dewpoint may result in baghouse problems or atmospheric plume condensation. Spray nozzle wear can result in coarse or distorted spray and wetted bags, and water pressure failure can cause high temperature bag deterioration. 

COMMENTS The Carnot vapor cycle as illustrated by Example 2.1 is not practical. Difficulties arise in the isentropic processes of the cycle. One difficulty is that the isentropic turbine will have to handle steam of low quality. The impingement of liquid droplets on the turbine blade causes erosion and wear. Another difficulty is the isentropic compression of a liquid-vapor mixture. The two-phase mixture of the steam causes serious cavitation problems during the compression process. Also, since the specific volume of the saturated mixture is high, the pump power required is also very high. Thus, the Carnot vapor cycle is not a realistic model for vapor power cycles. 

If a carry-over problem has been traced to entrainment, the use of a demister will probably help. The qualitative effect of a demister on entrainment is also shown in Table 21-1. A demister is a pad placed in front of the KO drum outlet nozzle, as indicated in Figure 21-2. The droplets of liquid impinge and are coalesced on the Brillo-like fibers of the demister pad. 

With the present configuration, the frozen droplets are not yet uniform, but further improvements can be achieved by systematic evolutionary optimization of the process parameter settings. The small diameter of the current swirl tube sets an upper limit to the velocity of the gas flow beyond a threshold, the yield decreases because incompletely frozen particles impinge upon the walls and form crusts. Trying to solve this problem merely by experimentation would not be economical, this is the domain of computational fluid dynamics. 

Injecting 3%, instead of 40% NaOH solution minimizes the problem of soda corrosion of the crude transfer line. If caustic is injected too close to an elbow of the transfer line, impingement by droplets of caustic can cause severe attack and a hole-through at the elbow. 

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