A poultry abattoir required a re-evaluation of their waste process.
The abattoir mainly processed chicken meat which they package for human consumption. The process is completely automated. The factory employs about 200 people and processes between 65,000 and 125,000 chickens per day.
The problem centred on what to do with the high amount of animal wastes generated by the process and a re-evaluation was required. The abattoir opted to process the waste by crushing and cooling it for eventual sale as pet food.
This process not only solved their animal waste issue but also provided a value-add solution with an economic return.
The processing plant was initially designed to cool 1,800 kg/h of minced poultry waste (this capacity was subsequently increased to 5,000 kg/h) for its transformation into a product which was suitable for consumption by other animals.
The cooling process is a critical step to preserve the features of the animal waste and ensures the preservation of the product in optimal conditions for transportation to the abattoir’s facilities. The waste was taken from 30oC and cooled to 5/10oC for storage and subsequent refrigerated transport.
The abattoir also requested a skid mounted CIP system to provide the automated cleaning of the product line and other components.
The particular product in this case study was a heterogeneous mixture of waste (composed of viscera, heads, feet, wings and bones) from poultry meat.
For the correct thermal design of the plant, the proper determination of the product’s physical properties is essential: density, specific heat, thermal conductivity and viscosity.
To ascertain these properties (mainly viscosity-temperature curves) several pumping tests were carried out in an existing installation in the abattoir’s facilities.
Based on these tests, the product’s physical properties were understood and agreed with the abattoir and then compared to a large database of physical properties for different types of meat waste ensuring the optimal thermal design of processing plants.
A complete “turnkey” system was provided with its scope including:
Thermal treating section for cooling by means of tubular heat exchangers
Flanged and automated product side valves
Skid mounted CIP system
Regulation & control using automation
Start-up carried out with the plant in operation
On site training for correct handling of the installation
DESIGN OF TUBULAR HEAT EXCHANGER
The CT-20 model was used for this project. Its features include:
The CT-20 model consists of 2 concentric tubes. Waste flows through the inner corrugated tube and the refrigerant flows through the outer annular space. This design removes the risk of blockage of the heat exchangers that can be caused by the presence of the large particulate solids content in the product.
The design was a solution involving increased diameter to prevent blockages, processing the meat at an acceptable velocity to enhance the thermal exchange and to keeping the pressure drop within reasonable values.
Flanged connections were chosen to enable the dismantling of the units for easy maintenance and cleaning and the use of modules to enable the duty to be increased if required.
Meat wastes are very viscous and the pressure drop in the inner tube can be quite high. An accurate determination of pressure drop allows a correct selection for the pump and the design pressure. A positive displacement pump was chosen in this instance.
The system supplied was capable of being adapted to variable capacities by means of a pump with a frequency converter allowing the system to run with variable process flow rates between 1,800 kg/h and 5,000 kg/h.
The inner tubes were SOFT corrugated to increase the turbulence of the product without significantly increasing the pressure drop.