Rectifiers unit configurations

Figure 6.24(a) A few configurations of controlled rectifier units (for uncontrolled rectifier units the thyristors (SCRs) are replaced with diodes)... 

Both configurations can be divided into four CSs for the case of a ternary system where we wish to obtain relatively pure distillate, bottoms, and sidestream products. For the sake of consistency, the side unithas been numbered as CS4 while the internal CS is labeled as CS2 in both configurations. In the side-stripper unit, the liquid coming from CSi is divided into two streams one that is directed to the main column body and another one that is directed toward the side-stripping unit. The vapor flow in CSi is also the sum of the vapor flows from the side stripping unit and the main column. Similarly, the vapor flow from CS3 in the side rectifier is directed toward the main column and the rectifying unit, while the liquid flowrate in CS3 is the sum of the liquid flowrates in the main column and the rectifier. The location of the sidestream withdrawal and addition at the thermally coupled junction are assumed to take place at the same location. This assumption can be relaxed however, an additional CS would be created and this case will not be further discussed in this text... 

Line side Twin ARU Active Rectifier Units, 12 pulse configuration... 

The harmonic losses developed in the motor by the drive are very small in a typical mine hoist low speed synchronous motor powered from a Variable Speed Drive. In this type of configuration the Voltage Source Inverter (VSI) and Active Rectifier Unit (ARU) typically increase the motor losses by the order of 1-1.5% of the total motor losses. The low harmonic losses in this case is due to the motor s high reactance and low base frequency, the inverter technology and the switching frequency. 

A water cooled VSD for speed and torque control is used in this example to calculate the electrical losses in the drive. The drive configuration for both friction hoist and Blair hoist is a double Active Rectifier Unit (ARU) and a double Inverter Unit (INU), see Figure 5. Since there is no benefit in oversizing the VSD, only one alternative for each hoisting system is analysed. The ratings for each hoisting system are shown in Table 5. 

Figure 8.10 shows the flowsheet configuration of a column with a rectifying section liquid side draw. The multi-component feed comes from an upstream unit in the process. The benzene liquid side draw is the product stream, and has a purity specification in terms of benzene. The distillation removes n-pentane from the feed mixture and the heavies (toluene, naphthalene and biphenyl) are purged from the reboiler. A small overhead purge stream is coimected to the condenser for pressure rehef. 

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