Rake mechanism

Circular raking mechanisms are sometimes also used ia square basias with horizontal flow across the basia. Such designs have to iacorporate supplementary rake arms that reach iato the corners of the square vessel (Fig. 3). 

A thickener has several basic components a tank to contain the slurry, feed piping and a feedwell to allow the feed stream to enter the tank, a rake mechanism to assist in moving the concentrated sohds to the withdrawal points, an underflow solids-withdrawal system, and an overflow launder. The basic design of a bridge-supported thickener mechanism is illustrated in Fig. 18-86. 

FIG. 18-91 Rake-mechanism designs employed for specific duties. (EIMCO Process Equipment Co.)... 

Thickener control philosophies are usually based on the idea that the Iindertlow density obtained is the most important performance criterion. The o ertlow clarity is also a consideration, but this is generally not as critical. Additional factors which must be considered are optimization of tlocciilant usage and protection of the raking mechanism. 

Typical diameters are up to 150 ft. and machines have operating torques to 750,000 fir-Lbs. The Bridge - or Beam or Truss - spans the diameter of the tank and supports the drive and rake mechanisms. The underflow is removed from the discharge cone at the bottom center. 

The diameters on these machines are over 400 ft., with operating torques to 2,400,000ft.-Lbs. The stationary center pier supports the drive and rake mechanisms. The truss extends from the center pier to the tank periphery supports walkway, power lines and feed lasunder. 

These rate constants are representative of the rake mechanism of Germain [24],... 

A general scheme of hydrogenation of 1,3-butadiene, the rake mechanism, is given in Scheme 7. Two kinds of selectivity for the intermediate butenes can be defined. Selective formation of butenes can be expected if > 4 (mechanistic selectivity). On the other hand, if k /k- > kj,/k, adsorption of the diene prevents the readsorption of butenes and hence the consecutive hydrogen addition cannot take place (thermodynamic... 

Settled solids rheology (for raking mechanism design and drive torque specification)... 

Ultrahigh-Rate Thickeners This type of thickener uses a tall, deep tank with a steep bottom cone and may be used with or without a raking mechanism. This combines the functions of a thickener (to... 

---