The Hiep Thanh Seafood fish processing factory includes energy intensive facilities with an average specific energy consumption of 414 kWh per ton of fish input, or 1400 kWh per ton of fish product. Energy is therefore a significant expense in a fish processing plant, which can be mitigated by recycling some wastes for energy purpose on site. The ENERFISH project demonstrates the potential of conversion of the fish cleaning wastes into final energy: cold, heat and electricity, but also extra biodiesel which can be retailed on the biofuel market (see BY-PRODUCTS).
Figure 1: Example of a Cummins diesel generator set for heat and power production
Conventional refrigeration systems account for about 80% of the energy consumption and require large refrigerant charges and circulation. Hundreds of meters of piping, and many valves and brazed joints provide significant amount of refrigerant and energy losses.
Environmental and energy efficient issues have stimulated the development of new refrigeration systems that require less quantity of conventional refrigerant and saves electricity: Cascade type system where main compressor circuit is based on NH3 refrigerant, and CO2 based distribution circuits for cooling/freezing energy. CO2 refrigerant is a non-toxic product having high heat capacity and low viscosity. The low pressure drop enables the use of small diameter pipes which is an asset especially if the needed piping is extensive. The high heat transfer coefficient enables efficient heat transfer solutions.
Figure 2: Principle of the VAHTERUS NH3/CO2 refrigeration system
Figure 3: Pre-existing Bitzer ammonia compressors
Figure 4: VAHTERUS NH3/CO2 refrigeration system
The electricity needs of a fish processing factory can be covered by running a generator fuelled by biodiesel produced from fish cleaning wastes. The factory is energy self-sufficient and using energy efficient cooling/freezing systems, a remarkable part of energy can be sold for other purposes.
Figure 5: Freezing storage >
Producing electricity in co-generation mode, the total efficiency of the energy production can reach the value of 88-90%.
Figure 6: Energy flow diagram in maximum heat & power cogeneration mode
Figure 7: Energy flow diagram in mode adjusting heat & power to the fishery needs