Condenser Vapour Load

Column configurations (NT) and separation requirements (x D) for several cases are presented in Table 3.3. The condenser holdup was fixed to 2% of the total initial charge and the column hold up is varied as a percentage of the total initial charge to the column. The initial charge to the column (Bo) is 5 kmol with a light component mole fraction (xBo) of 0.6. Also the amount of distillate product required (ZD ) is set to 3 kmol. The column operates under constant condenser vapour load strategy (section 3.2.2) with a vapour load of 3 kmol/hr for all cases. 

Condenser Vapour Load, kmol/hr Column Pressure, bar... 

Mujtaba (1989) and Mujtaba and Macchietto (1992) considered a ternary separation using Butane-Pentane-Hexane mixture. Only the optimal operation for the first main-cut and the first off-cut was considered. Table 8.7 lists a variety of separation specification (on CUT 1) and column configurations in each case. A fresh feed of 6 kmol at a composition of <0.15, 0.35, 0.50> (mole fraction) is used in all cases. Also in each case a constant condenser vapour load of 3 kmol/hr is used. For convenience Type IV-CMH model was used with ideal phase equilibrium. 

This example is taken from Mujtaba (1989) and Mujtaba and Macchietto (1992) where the same ternary mixture as in example 1 was considered for the whole multiperiod operation which includes 2 main-cuts and 2 intermediate off-cuts. The column consists of 5 (NT) intermediate plates, a total condenser and a reboiler. The column is charged with the same amount and composition of the fresh feed as was the case in example 1. Column initialisation, holdup distribution and condenser vapour load are also same as those in example 1. 

In this strategy the feed mixture is charged in the reboiler (at the beginning of the process) to its maximum capacity. For a given condenser vapour load Vc, if the reflux ratio R (which governs the distillate rate, LD, kmol/hr) and the solvent feed rate F (kmol/hr) are not carefully controlled the column will be flooded. To avoid column flooding Tran and Mujtaba (1997) developed the following necessary and sufficient condition ... 

The presence of a permanent (non-condensable) gas load together with the condensable vapour means that a smaller amount of gas ballast is required to pump vapour. The worst situation arises when no permanent gas is initially present. Under such conditions, from Equation (3.2) ... 

The reactor is an enameled apparatus with an agitator and a water vapour jacket. The production of sodium dihydroxyphenylsilanolate is carried out in butanol and toluene or ethanol and toluene medium at 35-50 °C. The consumption of other components is calculated by the amount of the loaded condensation product. After loading the product of condensation, the reactor is filled with toluene and butanol (or ethanol and toluene) from batch boxes 10 and 11. The ratio of the solvents should be 1 1.4 to obtain 10% silanol solution. The calculation takes into account toluene contained in the product of hydrolytic condensation. The loaded mixture is agitated in the reactor for 30 minutes after that it receives 20% alkali solution from batch box 12 at agitation. The reaction forms sodium dihydroxydiphenylsi-lanolate and water. 

This mode of operation demands constant rate of distillate throughout. This means that, for constant reflux ratio operation, the vapour load to the condenser is also constant. Boston et al. (1981) and Holland and Liapis (1983) considered this type of operation. 

The batch distillation column consisted of 3 internal plates, reboiler and a total condenser. The reboiler was charged with a fresh feed of 5 kmol with Benzene molefraction 0.6. The total column holdup was 4 % of the charge. Half the holdup was in the condenser and the rest was distributed over the plates. The vapour load to the condenser was 3 kmol/hr. The required product purities were x oi = 0.90 and x B2 = 0.15. The solution of Equations 8.1-8.4 therefore gives DJ = 3.0 kmol and B2 = 2 kmol. This problem is same as case 3 shown in Table 8.1. Three reflux ratio (control) intervals were used to achieve (Dl, x Di) and one control interval to achieve (B2, x B2). 

Mujtaba and Macchietto (1992) investigated how productivity (kmol of product/hr) is affected by the proposed recycle policy. Consider a fixed vapour load to the condenser (or vapour boilup rate) and fixed product compositions (e.g. xlDi and x1 B2 for recycle loop 1 of Figure 8.13). Now scale the batch times (presented as... 

If suction load contains condensable vapour, installation of a trim condenser and separator using cooling/chilled water will be beneficial... 

Is preheating of feed possible by condensing vapours This will reduce heating load and, in firm, will reduce steam/fuel consrrmption. 

The attainable ultimate pressure of such a pump set, for example during secondary drying, should not lie lower than the water vapour partial pressure of the condenser when loaded with ice since, otherwise, there is the danger of resublimation of the ice in the condenser or evaporation in the direction of the vacuum pumps. The result would be an increased water content in the pumps and this would lead to inefficient operation. 

By using the equations derived for the calculation of each parameter, it was possible to condense the extensive research material, which is discussed in the summary of the results of this work in Chap. 6. The end of each chapter contains example calculations to illustrate the individual correlations for determining the vapour load factor at the flooding point of the liquid hold-up as weU as the pressure drop of irrigated and dry random packing elements. The numerical examples are practice-oriented and explain the correlations mentioned before, based on the examples of different packings. 

If the degree of superheat is large, it will be necessary to divide the temperature profile into sections and determine the mean temperature difference and heat-transfer coefficient separately for each section. If the tube wall temperature is below the dew point of the vapour, liquid will condense directly from the vapour on to the tubes. In these circumstances it has been found that the heat-transfer coefficient in the superheating section is close to the value for condensation and can be taken as the same. So, where the amount of superheating is not too excessive, say less than 25 per cent of the latent heat load, and the outlet coolant temperature is well below the vapour dew point, the sensible heat load for desuperheating can be lumped with the latent heat load. The total heat-transfer area required can then be calculated using a mean temperature difference based on the saturation temperature (not the superheat temperature) and the estimated condensate film heat-transfer coefficient. 

This is clearly a double jeopardy failure two unrelated events occurring at exactly the same time. One has nothing to do with the other. Therefore, you need to calculate the relief capacity for one scenario at a time. For the loss of power to a pump scenario, the relief load would be based on the amount of vapour generated at the normal rate of steam. For the steam control valve failure scenario, the relief capacity would be based on the amount of vapour generated by the heat provided by a wide-open steam valve even accounting for the amount of vapour condensed in this failure, the condenser would still be in operation. So the SRV should be sized for the worst condition. 

The production of pure tetraethoxysilane is basically put down to the rectification of the mixture of ethylsilicate and tetraethoxysilane. The mixture from depository 21 (see Fig.23) is poured into tank 22, the jacket of which is filled with vapour (0.9 MPa). The vapours of the product rise up, and after tower 23 enter refluxer 24, where they condense. Part of the distillate is used to to reflux the tower and the rest is sent through cooler 25 into receptacles 26 and 27. The first fraction, which boils out below 160 °C, is collected in receptacle 26 as it accumulates, it is poured into depository 28 and then re-loaded into tank 22. The second fraction (160-180 °C) is collected in receptacle 27 and is poured into depository 29 as it accumulates. This fraction is the end product, technical tetraethoxysilane. 

The raw methylphenyldimethoxysilane from collector 9 and the intermediate fraction from receptacle 15 self-flow into tank 10. After the loading is finished, the heater of the tank is filled with vapour. After the reflux appears in the box, the tower operates in the self-serving mode for 1 or 2 hours then the rest of methyl alcohol and toluene are distilled. The vapours pass through tower 11, refluxer 12 and cooler 13 the condensate enters receptacle 14. Methyl alcohol and toluene are distilled when the tern-... 

The amidation of chloromethyltrichlorosilane is carried out in steel enameled reactor 12 with an agitator and a jacket. In agitator 9, a mixture of chloromethyltriethoxysilane and toluene is prepared. Then, apparatus 12 is loaded with diethylamine from batch box 13 and with toluene from batch box 14 backflow condenser 15 is filled with water and the reactor jacket is filled with vapour. The mixture in the apparatus is heated to 35 °C and at agitation one starts to introduce ether and toluene mixture from agitator 9 at such speed that the temperature of the reactor does not exceed 50 °C. At the same time, the apparatus is constantly fed with dehydrated nitrogen. After the whole mixture has been introduced, the reactive mixture is kept at 75-85 °C for 15-18 hours. 

Reactor 1 is loaded with a necessary amount of methyltrichlorosilane, phenyltrichlorosilane and acetic anhydride from batch boxes 2, 3 and 4. Direct condenser 5 is switched on then the reactive mixture is agitated with the agitator for 15 minutes after that the reactor contents are heated to 60 °C for 30 minutes. At 50-60 °C acetylchloride is vapour-distilled it enters receptacle 6 through the run-down box the reactor contents are heated to 85-90 °C Further distillation of acetylchloride is conducted in vacuum under 550-480 GPa and at... 

Reactor 9 is used to methacrylate the acetoxysilane mixture. First, back-flow condenser 12 is switched on the agitator is switched on and the jacket of the apparatus is filled with vapour then the contents of reactor 9 are heated to 60°C. At this temperature glycolmethacrylate self-flows from batch box 10 at such speed that the temperature in the reactor does not exceed 65°C. After the glycolmethacrylate has been loaded, the contents of reactor 9 are agitated at 60-65°C for one more hour then condenser 12 is switched into the direct operation mode, vacuum is created (the residual pressure is 130-80 GPa), and acetic acid is distilled into receptacle 13 at 40-50 °C (in vapour) reactor 9 is periodically sampled to determine the acid number (a.n.). If the analysis is satisfactory (a.n. = 450-500 mg/g), reactor 9 is loaded with toluene from batch box 11. 

The CR product is sent from collector 14 into loader-unloader 15 and then into apparatus 16 the condenser cover is filled with water and the whole system is vacuumised until the residual pressure is below 1.3 GPa. The low-boiling fractions below the vapour temperature of 220-235 °C (depending on the brand of the liquid) are collected in receptacle 17. After the fraction has been separated, the distillation is stopped by turning off the electric heating of apparatus 16. Tank residue, which is the target product, IIMTC-1, IIMTC-2 or IIMTC-3 liquid, is cooled in the tank of the apparatus down to 100 °C in a vacuum of 1.3-2.6 GPa and then loaded into receptacle 15. 

The vapours of the products formed by the boiling liquid in tank 14 rise through tower 15. After the tower the vapours saturated with low-boiling products enter the built-in condenser. Part of the condensate from the top of the tower is sent back through vapour-heated (1 MPa) heater 16 to reflux the tower the other part is collected in receptacle 17. The rectification takes place under atmospheric pressure. It allows to separate two fractions HMDS (80-100 °C), concentrated PMS-lb (100-153 °C) and concentrated PMS-l,5b (153-194 °C). After the distillation the tank residue is cooled and loaded off into collector 18. 

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