Whey Recovery in Dairy Plants
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Date
2018-05-21
Authors
Abdulhadi, Nada
Samaneh, Noor
Sawalha, Wassan
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Abstract
The dairy factories produce large amount of waste and most wasted by product is whey, so the main concern of this study assesses the possibility of whey recovery in diary factories , accordingly the process of manufacturing whey and converted it into protein (liquid or powder) will be discussed with the lowest visible energy cost. Al –Safa diary factory was selected as the case study.
In Al-Safa factory, about 67200 𝐿/𝑦𝑒𝑎𝑟 of whey is disposed through sewage network.
Samples of whey are collected and concentrated through the falling film evaporator, which was the best visible available method for the evaporation process.
The type of falling film evaporator that is used in this study called single stage evaporator Mod. UMEC-EV. Evaporation process was the main concern; it was studied to concentrate feed whey from 6.35% to 14%.
It was observed that in the first pass (concentrated once) evaporation system with the thermal load was 17568.1 kJ per kilogram solid content while the second pass 20679.7 kJ/kg.. The final results indicated that the third pass evaporation system with 19175 kJ/kg is more effective and feasible to be adopted.
After evaporation, whey concentrate is then further dried in a spray dryer, the influence of the spray-drying conditions on the energy and production cost was investigated. The factors investigated were the inlet air temperature 160–250°C, air speed at the exhaust and liquid flow rate 3.0-4.3 m/s, 280-362 mL/h, respectively. Stated that, the optimal operation conditions were at a flow rate 0.71 L/h and an inlet air temperature 160°C.
The raw whey was taken and entered directly in the spray dryer with a solid content of 6.35% according to that the thermal load was 65770 kJ/kg solid content. While for 8.0% solid content that is concentrated once, the thermal load was 52170 kJ/kg, however as increasing the solid content from 10.89% to 14.0%, the thermal load decreases form 38360 kJ/kg to 30410 kJ/kg, respectively, as the amount of moisture in samples decreases too.
For each pass, an energy summation process was calculated for both falling film evaporator and spray dryer in order to obtain the total energy consumption, after that cost calculation was achieved relatively to the cost of kilogram diesel. The cost for the raw whey was 12.06 Nis/kg solid while for passes one, two, and three were 12.83, 10.88, 9.12 Nis/kg solid, respectively.
The best optimum case is selected to be pass three based on our studies, this was done according to the lowest total thermal load which was 49585 kJ/kg, with the lowest cost 9.12 Nis per solid whey.