WASTE HEAT RECOVERY AND WATER RECYCLING IN A CRISP FACTORY

Cel

The main aim is to recycle and reuse as potable water 75% of the effluent in a crisp factory. This is to be achieved by utilising waste heat energy recovered from the frying process involved in the production of potato crisps. The result of this will be a total saving of 15.3 MW of thermal energy and a reduction in the effluent emissions of the factory. The waste heat is to be used to drive a six effect evaporator. In this way energy savings will be achieved in the crisp frying process, in the incineration of the foul gases, in the reduction of exhaust stack losses, in the reduction of water consumption and in the reduced sewage costs both in industry and local authority installations.
It is the objective of the proposers to show that effluent treatment and water recycling are economically feasible by using heat recovery and multi-effect evaporation. Also that evaporation is a viable and effective means of sewage effluent treatment for other industries and administrative authorities.
The main elements of the project that have to be designed are :
1. A new non-fouling, non-scaling tubed 'shell and tube' 'gas and vapour/water' heat exchanger; This is used to recover the available heat of condensable elements in an exhaust stream from a 'deep fat' fryer.
2. A new non-fouling, non-scaling, tubed 'shell and tube' 'gas/water' heat exchanger. This is used to collect sensible heat of the exhaust gas from an incinerator.
3. Piped connections from the above heat exchangers to a new ring main pressure hot water circuit. This is used to supply a controlled pressure drop flash steam generator capable of producing the whole thermal recovery as steam.
4. A Multiple Effect Evaporator. The vapour feed input of the evaporator is provided by the ring main pressure hot water circuit in 3. above.
All the above project elements have now been designed. Budget costs for the manufacture of the project element have been obtained from potential suppliers.
The details of the installation of the project elements have still to be finalised.

Trials have been carried out with the installed 'gas and vapour/water' heat exchanger. These trials have determined :
- design parameters for other project elements
- the overall heat transfer co-efficient.

Various trials have been carried out in parallel with the above work :
- the heat transfer properties of Mesh Plastic Composite (MPC)
- the effect of evaporation on the micro-biological loading of the effluent
Three main phases in the production of potato crisps.
Preparation - Large amounts of water are used to prepare potatoes for cooking. The potatoes arrive at the factory where soil, stones and other debris are first removed in a large water filled agilator. The cleaned potatoes then travel to the peeling machine in which an abrasive drum rotating at high speed removes the skins. In the peeling process water is used to continually wash the potatoes and wash away the skin that has been removed. Once peeled the potatoes are rinsed before entering the slicing machine. This is another high speed rotating drum which cuts slices to a fixed thickness. Water is used in this process for lubrication. The slices then proceed into a slowly rotating drum which is partly submerged in water. This is a final washing process to remove some sugars and starch before cooking. Cooling - After the preparation process the total water content of the raw potato slice is 78%. In addition there is a surface moisture content of 12% of the weight of the slice. The final crisp product has a moisture content of approximately 1.5%. In the frying process these large amounts of water are boiled off in cooking oil at 185 deg. C. This requires a high energy input. The volume of steam produced is exhausted to atmosphere and contains the large amounts of energy used for frying in the form of latent heat. At the moment most of this energy is exhausted to the atmosphere and washed.
Effluent Treatment - There are two main effluents produced from crisp production. These are noxious waste cooking gases and polluted water from the preparation process. The gases, which include steam, oil vapour and noxious smells are detoxified and removed by incineration at 700 deg. C. The incineration of these gaseous pollutants requires energy input of gas for combustion which then exhausts to atmosphere at 250 deg. C wasting some of the total energy used. The water effluent from the preparation process is partiallytreated onsite before being discharged to the local water authority for final treatment.
This project will be in the application of waste heat recovery from the cooking process. The energy recovered will be used to distil the water effluent produced by the preparation process for recycling and reuse in that.
This project is to be located in the KP Foods (UK) potato crisp factory at Billingham. At the factory KP Foods operate continuously at least 5 out of 6 semi-automatic potato crisp production lines. Each line includes potato washing, slicing, crisp frying, grading and product packing operations.
This project concentrates on the benefits which are now possible in :
i. The recovery of large quantities of heat energy from the crisp frying process which is presently discharged to the atmosphere.
ii. The reuse of this energy in an innovative heat recovery and evaporation process which is directed to the treatment of highly contaminated effluent from the preparation phases of crisp production.

Program(-y)

ENG-THERMIE 1 - Programme (EEC) for the promotion of energy technology in Europe (THERMIE), 1990-1994

Temat(-y)

2.3 - INDUSTRY

Zaproszenie do składania wniosków

Data not available

System finansowania

DEM - Demonstration contracts

Koordynator

Sulzer (UK) Ltd

Wkład UE

Brak danych

Adres

Suzler-Chemtec Division Westmead
GU14 7LP Farnborough
Zjednoczone Królestwo

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