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Content archived on 2022-12-27

USE OF MECHANICAL VAPOUR RECOMPRESSION EVAPORATOR TO CONCENTRATE ACID CASEIN WHEY

Objective

By using an MVR evaporator, to concentrate acid casein whey from 6% to 55% total solids (TS), for ultimate use as an animal feed ingredient.
The innovatory aspect of the project lies in the application of MVR for the concentration of what is a highly corrosive substance, using a turbo fan instead of a centrifugal compressor.
Energy saving in comparison with conventional four-effect evaporators is estimated at 600 TOE/yr in primary energy.
This project has been completed with success.
The concentration of acid casein whey from 6% to 32% total solids content (TS) was achieved with success and according to specifications with a MVR evaporator provided by MKT Tehtaat OY of Finland.
Some minor technical problems arose during start-up and commissioning, which have now been solved. These problems are described briefly:
- build up of scale on the surfaces of the evaporator reducing the efficiency of heat transfer. This was solved by developing a new 4 hour washing programme which follows each 20 hours production run.
- fan vibration due to fouling on the impeller blades by particles of organic matter carried by the vapour from the evaporating whey and D. C. motor cut out due to vibration alarm. This was solved by cleaning the fan impeller blades at regular intervals of 500 hours operation.
- fouling of the plate heat exchanger (feed input/condensate output ) by particles carried over in the vapour from the whey. A simple solution to this problem was the installation of a stainless steel filter in the condensate inlet line to the plate heat exchanger which is cleaned at the end of each day's run.
- the concentrate density recorder has not yet performed satisfactorily.
The concentrate at 32% TS is sold as such for animal feeding.
It could be concentrated further until 55% TS with a thermal finisher evaporator, dried and sold as a powder.
During the 4,823 hours of the monitoring phase, an average of 20. 3 T of acid casein whey was produced per hour giving 3. 8 T/h of concentrate. The specific energy requirements observed were 0.
015 ton steam and 15 kWh per ton of water evaporated. The primary energy saving per year (based on a nominal 5000/year operation) would amount to 600 TOE and give a payback period of 1. 95 years. The project seems to present good prospects for replication, notably in the dairy and other agro-food industries, however taking into account the local variations for important parameters, such as number of effects of the thermal reference evaporator, price per ton of steam and per kWh.
The acid casein whey (a waste difficult to treat or dispose of) is concentrated in two steps from 6% to 55% TS content (6 to 32% by MVR; optionally 32 to 55% with a finisher).
Whey is pumped at a flow rate of 20. 5 T/h to the evaporator balance tank and, on passing through a plate heat exchanger, is heated from 30 deg. C to 54 deg. C.
Entering at the top of the evaporator, and after flowing down as a film inside the tubes, the liquid is separated, vapour from liquid, at the bottom. The liquid is then recirculated and the vapour sucked into the turbo fan (equipped with a blade wheel and, because of the corrosive nature of the raw material, specially constructed for vapour recompression) and compressed, to be used as 58 deg. C heating steam in the same stage.
At the exit of the MVR evaporator, the concentrate flow rate is 4. 125 T/h which may be fed to the finisher evaporator, where the whey increases to 55% TS.
It is foreseen that the steam requirement per ton water evaporated in the MVR stage decreases from 0. 15 to 0. 03 tons, while electricity consumption increases to 13 kWh rather than 4. 5 kWh.

Call for proposal

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Coordinator

KANTOHER CO-OP
EU contribution
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Address
KILLEEDY-BALLAGH
CO Limerick
Ireland

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