Fredrick Kitalekwa’s scientific contributions

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Figure 1. Five-effect evaporator station showing vapor bleeding configurations studied with heat exchange between bled vapors with the feed.
Figure 2. Variation of the steam requirement with percent bleeding in effects.
Figure 12. Variation of (a) total heat transfer surface area, and (b) steam economy with pressure in the last effect at various vapor bleeding configurations e) Effect of pressure in the last effect on steam economy for different bleeding configurations Steam economy is the number of kilograms of water vaporized from all the effects per kilogram of steam use (Chantasiriwan, 2017). Pressure in the last effect is related to the steam requirement of the system, as discussed above. An increase in pressure in the last effect increases steam requirement of the system as the system is trying to compensate for the lost overall temperature difference driving force. Also, an increase in steam requirement, decreases steam economy of the system. The variation of steam economy with pressure in the last effect is presented in Figure 12 (b) where different bleeding configurations are compared. Increasing pressure in the last effect decreases the steam economy of the system as shown in Figure 12 (b). With incorporation of vapor bleeding, steam economy of the system is restored and improved more. Again, simulation results show that, bleeding by a combination of E1&E3gives the highest steam economy in the system as compared to other bleeding configurations. Furthermore, bleed E3 and bleed E4show similar results of steam economy in the system. Similarly, bleed E1 and a combination of E2&E4 give same results. Therefore, for the five-effect evaporator system, with a concern to improve its performance, vapor bleeding is the method to use as it reduces steam consumption and improves steam economy of the system as shown in Figure 12(b). With a well selected and implemented bleeding configuration such as combination of E 1 &E 3 the system performance is highly improved than using other configurations.
Comparison of the ratio of steam consumption at 0% and 75% bleeding at different bleeding configurations.
Steam economy values at different steam pressure for 30% bleeding and bleeding configurations.
Effect of vapor-bleeding and its configurations on multiple-effect sugarcane juice evaporator performance
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September 2024

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International Journal of Engineering Science and Technology

Fredrick Kitalekwa

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Improving process performance is always important in any processing industry with the aim of reducing operation costs and improving the profit.Vapor bleeding may be used in processing industries using multiple-effect evaporatorsto reduces steam consumption and increases steam economyThe effect of vapor bleeding on separation performance using multiple-effect sugarcane juice evaporator was analyzed. The effect of increasing percent of vapor bled and determination of the most effective bleeding configuration in terms of energy efficiency and operating costs. The performance factors assessed were: steam requirement, total heat transfer area (At), steam economy, total utilized heat (Qt), mass flow rate of bottoms (Bi), percent solids in the bottoms (XBi), and mass flow rate of vapors. To carry out this work, a five-effect evaporator, forward feed computer model was developed based on mass and energy balance equations, calibrated by data from steam tables. Simulations incorporating different configurations of vapor bleeding were carried out. Bleeding from each of the first four effects, Ei , and from a combination of effects (E1&E3, E2&E4) were carried out. The E1&E3 configuration showed a highest decrease in steam consumption by 23.73% and improved steam economy by 31.28%. Also, vapor bleeding reduced At and XBi while increasingBi. This work suggests that to improve energy efficiency during separation of mixtures using evaporators, vapor bleeding should be practiced while maintaining a balance between vapors used to preheat the feed and that used for heating the subsequent effects.

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