Teaching Document - Essay Example

Teaching Document The purpose of this document is to explain a particular process in chemical engineering. It seeks to explain the industrial process of starch to glucose hydrolysis. The learner should be able to explain various operations in the conversion process and its significance at the end. The process is majorly a conversion biochemical process operation, but also contains these process operations; Phase separation operation, mixing the operation and material transfer operations (Silla 10).
The process uses corn-starch slurry (liquid with 30%-40% solid) that contains the starch to be converted to glucose. The other chemicals used include: alpha amylase enzyme, gluco-amylase enzyme and carbon which is used in the adsorbers as a decolorizer. The process occurs in five main stages; two hydrolysis processes that convert about 100% of the starch in the slurry into glucose and three evaporation processes to dry up the glucose. The starch slurry first flows into the first hydrolyser, R1, which converts 25% of the starch into glucose using alpha-amylase enzyme that catalyzes the hydrolysis process. After the first hydrolysis process, the viscosity of the slurry is reduced, and the slurry is then passed through a centrifuge, PS-1, which removes any proteins and oils present.
The slurry is then passed through the second hydrolyser, R-2, which completes the hydrolysis process using the gluco-amylase enzyme that leads to the overall conversion of starch to glucose to almost 100%. The viscosity reduction of the slurry after the first hydrolysis process ensures proper mixing with the gluco-amylase and prevents the formation of unhydrolyzable gelatinous material in the second hydrolyser. After the second process of hydrolysis, the slurry is decolorizes in an adsorber, CS-1, parked with carbon (Silla 23).
After the conversion of starch to glucose the rest of the process dehydrates the glucose. A dry product is then obtained using the process of evaporation. The glucose solution is pumped into the first stage of evaporation where a portion of the water is removed. To conserve energy (heat), the first stage of evaporation uses mechanical re-compression of the vapor evolved and since glucose is heat sensitive the process is conducted in a vacuum produced by a vacuum pump, C-1. The first evaporation stage is carried out in two steps; in the first step, energy is transferred to the solution in the boiler to evaporate some water concentrating the glucose. In the next step vapor and liquid are separated in a phase separator.
After the initial stage of evaporation, the solution is then decolorized again in adsorber. Little amounts of organic acid is removed in an ion exchanger, R-3, which replaces anions with hydrogen ions and cations with hydroxyl ions thereby replacing the organic acid with water. The next two stages of evaporation are conducted in a vacuum. The water vapor from the phase separator is first removed by direct contact with water in a barometric condenser. The condensates develop static pressure in the condenser which enables it to flow out through pipes. To obtain the glucose powder, it is separated from the solution in horizontal cylindrical crystallizers, CS-10, by cooling and gradually mixing at 1.5 rpm. The solution is then transferred to perforated-screen centrifuge (PS-1) where the solution is partially separated from the crystals. The wet crystals containing about 14% water are then conveyed to a rotary drier, CS-11, which removes the remaining water (Silla 27). From the diagram in fig 1.3 shown, as provided by Silla (2003), the process is described as follows (p 24):
Key
1. 1st hydrolyser – R-1
2. 2nd hydrolyser – R-2
3. Vacuum pump –P-1
4. Centrifuge – Ps-1
5. 1st Adsorber – CS-1
6. 2nd Adsorber –CS-3
7. Ion exchanger – R-3
8. Rotary – Cs-11
9. Crystallizer – CS-10
10. Evaporator – CS-2
11. Pumps - P-1, P-2, P-3, P-4, P-7
10. Heater – H-2
11. Tank- S-2
Barometric condenser – CS-5, CS6
The logic and significance of this process is that it takes place in the body of animals and human beings to convert the starch back glucose to aid the process of respiration. The process relies on enzymes to convert the starch to glucose, and it occurs in stages. This technique was borrowed by chemical engineers to manufacture glucose in large scale for commercial purposes. The industrially manufactured glucose is used for industrial fermentation to produce ethanol and to soften the food texture. In addition it adds volume, prevent the crystallization of sugar and finally enhance the flavor.
Work cited
Silla, Harry. Chemical process engineering: design and economics. CRC Press, 2003 Read More