Entrainer feed temperature

The design variables to be determined in the flowsheet include the solvent-to-feed ratio (FE/FF), total stages of the extractive distillation colmnn (A i), entrainer and fresh feed tray locations (NpE and Npp) total stages of the entrainer recovery column N-2), and feed tray location of entrainer recovery column Np. As can be seen in Knight and Doherty and also summarized in Chapter 5 of Doherty and Malone, the entrainer feed temperature can also been considered as another design variable, so a cooler is included in Figure 10.10. 

There are many design variables to be determined, so to simphfy the optimization the more important and complex extractive distillation column is optimized first. We considered three different cases for the entrainer feed temperature. 

Case 1 Operating the entrainer feed temperature 5 - 15°C below the top temperature of the extractive distillation column (as suggested in Knight and Doherty ). We use 72°C in the following simulation. 

Case 2 Operating the entrainer feed temperature the same as temperature in the B2 stream (196.6°C) with no cooler. 

Case 3 Subcooling the entrainer feed temperature (from B2) to 40°C. 

Some simple regulatory control loops are determined first. The levels of the reflux drums for both columns are controlled by manipulating the distillate. Top pressures of both columns are controlled by the condenser duty. The bottom level of the extractive distillation column is controlled by manipulating the bottoms flow. The entrainer feed temperature is controlled at 72°C by manipulating the cooler duty. The initial control structure tested is one in which the reflux ratios in the two columns are controlled by manipulating the reflux. This was used in the overall control structure in Luyben. ... 

In distillation calculations, molar flowrates and compositions are usually employed. Let us assume that the fresh feed flowrate is lOOkmol/h, the feed temperature is 25°C, and the feed pressure is 1.3 atm. These are entered in the middle of the window. The feed composition is 50 mol% IPA and 50 mol% water to represent a typical waste stream from semiconductor industry. The composition can be entered in terms of mole or mass fractions, or it can be entered in terms of component molar or mass flowrates. In our example, we use the dropdown arrow to change to Mole-Frac and enter the appropriate values. Repeat the same procedure to enter the feed-stream data of the entrainer feed (FFl) as can be seen in the flowsheet given in Figure 3.1. 

Figure 13.14 (a) Dynamic response of Stage 15 liquid composition under constant reflux and constant entrainer feed operation, (b) Dynamic response of Stage 15 temperature under constant reflux and constant entrainer feed operation. 

Figure 13.14 shows the dynamic responses of the liquid compositions and temperature at Stage 15 observed in the dynamic simulation results when the reflux ratio and entrainer feed rate are constant. Since the IPA is almost completely drawn-off from the top of the column toward the end of this step, the temperature is nearly holding at some constant value until the... 

For the Stage 15 temperature control loop, initially the entrainer feed rate can be reduced without any problem in getting water into the rectifying section. Toward the end of Step 2, because the IPA is almost completely drawn-off from the system, the water composition shoots up on this stage causing the temperatore to increase drastically. As explained... 

This chapter also demonstrates that the operation of batch extractive distillation can be improved by allowing the reflux ratio and the continuous entrainer feed rate to be varied with time. The simulation results of the IPA dehydration system demonstrate that batch time and entrainer usage can be reduced by including two temperature control loops to manipulate the reflux ratio and the entrainer feed rate. All dynamic simulations used in... 

The principal advance ia technology for SASOL I relative to the German Fischer-Tropsch plants was the development of a fluidized-bed reactor/regenerator system designed by M. W. Kellogg for the synthesis reaction. The reactor consists of an entrained-flow reactor ia series with a fluidized-bed regenerator (Fig. 14). Each fluidized-bed reactor processes 80,000 m /h of feed at a temperature of 320 to 330°C and 2.2 MPa (22 atm), and produces approximately 300 m (2000 barrels) per day of Hquid hydrocarbon product with a catalyst circulation rate of over 6000 t/h (49). 

The three main types of reactors shown in Fig. 27-6 are in aclual commercial use the moving bed, the fluidized bed, and the entrained bed. The moving bed is often referred to as a. fixed bed because the coal bed is kept at a constant height. These differ in size, coal feed, reactant and product flows, residence time, and reaction temperature. 

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