Toluene hydrodealkyl, process

Figure 2.11 Input/output structure by toluene hydrodealkylation process.

Be able to use the process simulators systematically during process creation, following sequences similar to those illustrated later in this chapter for a toluene hydrodealkylation process. The reader will learn to simulate portions of the process (the reactor section, the distillation section, etc.) before attempting to simulate the entire process with its recycle loops. Many examples and exercises enable the reader to master these techniques. 

Figure 4.19 Reaction section for the toluene hydrodealkylation process with the temperature-, pressure-, and phase-change operations.

Figure 4.20 Flowsheet showing a task integration for the toluene hydrodealkylation process.

Figure 4.22 Toluene hydrodealkylation process-distillation section.

Toluene hydrodealkylation process—separation section. As discussed in Section 4.3, the following stream at 100°F and 484 psia is to be separated by two distillation columns into the indicated products. 

Return to the design of the toluene hydrodealkylation process, as it is presented in Section 4.3. In the reactor section, after heuristics are utilized to set (1) the large excess of H2 in the hydrodealkylation reactor, (2) the temperature level of the quenched gases that enter the feed-product heat exchanger, and (3) the temperature in the flash vessel, the simulator is used to complete the material and energy balances and to examine the effects of these heuristics on the performance of the reactor section. In the distillation section, after heuristics are used to set (1) the quahty of the feed, (2) the use of partial or total condensers, (3) the use of cool-... 

Often small quantities of chemicals are produced in side reactions, such as the reaction of benzene to form biphenyl in the toluene hydrodealkylation process. When the reaction proceeds irreversibly, small quantities of byproducts must be separated away, as in Figure 4.20, or purged otherwise they will build up in the process until the process must be shut down. 

This example follows the simulation of the complete toluene hydrodealkylation process at the end of Section 4.3 and is presented without a solution because it is the basis for Exercise 5.4. To recycle the biphenyl to extinction, the flowsheet in Figure 4.20 is modified to eliminate the last distillation column, and unreacted toluene from the second column is recycled with biphenyl. This is accomplished by the reversible reaction... 

Heuristic 32 Quench a very hot process stream to at least l,15(fF brfore sending it to a heat exchanger for additional cooling and/or condensation. The quench fluid is best obtained from a downstream separator as in Figure 4.21 for the toluene hydrodealkylation process. Alternatively, if the process stream contains water vapor, liquid water may be an effective quench fluid. 

In Figure 4.20 for the toluene hydrodealkylation process, the pressure of the recycle gas leaving the flash drum at 100°F and 484 psia is increased with a compressor to 569 psia, so that, after pressure drops of 5 psia through the heat exchanger and 70 psia through the furnace, it enters the reactor at a required pressure of 494 psia. 

Revamp of a toluene hydrodealkylation process. This prob-lan considers some waste-minimization concepts. Our operating toluene hydrodealkylation unit, shown in Figure 5.13, involves the hydrogenation of toluene to benzene and methane. An equi-lihium side reaction produces a small quantity of biphenyl. To be more competitive, and eliminate waste, the process needs to be studied for a possible revamp. The customer for our small production of biphenyl has informed us that it will not renew its contract with us, and we have no other prospective buyer for biphenyl. Also, a membrane separator company believes that if we install their equipment, we can reduce our makeup hydrogen requirement. Make preliminary process design calculations with a simulator to compare the two alternatives below, and advise me of the technical feasibility of the second alternative and whether we should consider such a revamp further. For your studies, you will have to perform mainly material balance calculations. You will not make detailed distillation calculations, and liquid pumps need not be modeled. For the second alternative, calculate the required area in square feet of the membrane unit and determine if it is reasonable. 

Vapor-liquid case. The reactor effluent for a toluene hydrodealkylation process, of the type discussed in Section 4.3, is a gas at 1,150°F and 520 psia. When brought to 100°F at say 500 psia by a series of heat exchangers, the result is a vapor phase in equilibrium with a single liquid phase. A two-phase flash calculation using the SRK equation of state gives the following results ... 

Reactor Effluent Phase Equilibrium for a Toluene Hydrodealkylation Process... 

In a toluene hydrodealkylation process, 25,000 Ib/hr of toluene feed is pumped from 75°F and 30psia to 570 psia. Use a process simulator to compute the capacity in gpm, the pump head in feet of tolueM, the exit temperature, and brake horsepower (BHp) for ... 

Make an order-of-magnitude estimate of the total capital investment, as of the year 2001 (MS = 1,110), to produce benzene according to the toluene hydrodealkylation process shown in Figure 5.13. Assume an overall conversion of toluene to benzene of 95% and 330 days of operation per year. Also, assume the makeup gas enters at the desired pressure and a clay adsorption treater must be added to the flow sheet after the stabilizer. The treater removes contaminants that would prevent the benzene product from meeting specifications. In addition, in order for the reactor to handle the high temperature, it must have a brick lining on the inside, so take a material factor of Fm = 15. Otherwise, aU major equipment is constructed of carbon steel. The plant will be constructed outdoors with major additions to existing facilities. 

Toluene Hydrodealkylation Process—Capital Cost Estimation. See Exercise 17.21 for a complete economic analysis, including equipment sizing, cost estimation, and calculation of the total capital investment. 

Figure 2.5 Recycle Structure of Hydrogen Stream in Toluene Hydrodealkylation Process. Methane Is...

For the toluene hydrodealkylation process, establish the primary flow pathway for... 

Table 5.1. Process Description of the Toluene Hydrodealkylation Process (Refer to Figures 5.3 and...

Table 6.6 Equilibrium and Reaction Kinetics Data for the Toluene Hydrodealkylation Process Reaction Stoichiometry...

Table E8.2 Results for the Estimation of Operating Labor Requirements for the Toluene Hydrodealkylation Process Using the Equipment Module Approach...

The PFD for the toluene hydrodealkylation process (Figure 1.51 represents the battery-limits plant. The equipment necessary to produce the various service or utility streams, which are used in the process and are necessary for the plant to operate, are not shown on the PFD. However, the utility streams such as cooling water and steam for heating are shown on the PFD. These streams, termed utilities, are necessary for the control of stream temperatures as required by the process. These utilities can be supplied in a number of ways. 

Consider the benzene recovery column in the toluene hydrodealkylation process shown in Figure 1.5. This column is redrawn in Figure E13.2. The purpose of the column is to separate... 

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