Inedible Rendering by Means of the Wet Pressing Process. Demonstration Project

摘要

The rendering of offal and waste materials from slaughtering and meat processing is based traditionally on batchwise dry rendering followed by separation of meat and fat by means of solvent extraction. The energy consumption in such a process is high, i.e. of the order of 75 kg fuel oil per ton raw materials having an average water content of nearly 60%. A new energy-saving process has been developed based on a conditioning and prepressing of the raw materials at temperatures of the order of 60 deg C. The pressing procedure divides the materials into a solid phase with low fat content and a fluid phase containing more than 60% of the total water and nearly all the fat. The solid phase is dried in an indirectly heated drier. The fat from the fluid phase is removed in a tricanter. 80-90% of the water in the resulting liquid phase is removed in a three-stage vacuum evaporator using waste heat from the driers as heating medium. Pilot experiments have indicated that such a process is feasible and that the energy consumption in the process would be of the order of 35 kg fuel oil per tonne. The objective of the present project was to design and construct a full-scale production line using the wet pressing system, to demonstrate the feasibility of the process in full-scale operation and to obtain key figures for the energy consumption. The project was carried out at the Danish cooperative rendering plant KOFO in Losning. It was proven that the process - with minor modifications - is highly feasible in large-scale operation. The measuring of energy consumption showed the following figures: (i) 33.2 kg fuel oil per tonne offal or 60.1 kg per tonne water evaporated, and (ii) 69.1 kWh per tonne offal or 125 kWh per tonne water evaporated. An annual energy saving of 1632 toe was recorded for the wet pressing system compared to the conventional process formerly used at KOFO and based on a throughput of 50,000 t offal per year. (ERA citation 13:007590)