Evaporators
All GEA Niro systems provide pre-heating and heat treatment to kill
bacteria, reduce energy consumption and ensure that the correct functional
properties are achieved in the feed concentrate.
The low residence
time, often down to as low as 6-10 minutes, provides the following benefits:
- Minimum heat load on product
- Short start-up and shut-down times
- Low product losses
- Reduced cleaning time and costs
MVR Evaporation (Mechanical Vapour Recompression)
For applications where the availability of steam is restricted or expensive,
the MVR system is recommended. This system uses high-pressure fans to compress
the vapour generated by the evaporation to a higher temperature and return it
to the same effect. Excess vapour from this effect is either lead to a
condenser or utilized in a finisher.
The MVR evaporator can also be fitted with the wrap-around separator that
considerably reduces space requirements while matching or even improving the
high efficiency of the traditional tangential separator.
The
advantages of the MVR evaporator are:
- Low energy consumption. This applies to both heating and cooling
requirements as the plant produces cold condensate suitable for cooling
purposes.
- Recompression power supplied electrically thus reducing steam requirement
- Ease of operation. The fan allows for full and rapid control of evaporation
within the entire range of the plant without reconfiguration of the plant.
- TVR Evaporation (Thermal Vapour Recompression)
- In multiple effect TVR evaporators the evaporative energy in the first
effect is supplied from a steam injector that compresses vapour from one of the
associated effects to a higher temperature.
The heating medium in any subsequent effect is the vapour generated in the
previous effect. Vapour from the final effect is condensed by heating the
incoming product and in the condenser. The hot condensate can be reused for
boiler water and/or CIP liquid.
The choice between MVR and TVR depends
on the local prices of different energy sources, the possibility of using the
condensate, the depreciation of the capital cost (including capital cost of the
building), and the cost of product losses during cleaning.
Direct Contact Heating
In the early 1980s it was proved that even
minimum residence time above 70°C had major impact on product properties.
Heating in indirect heaters proved to have too long and uncontrolled residence
time for many applications.
Niro's new direct contact heating systems
however heat the product instantly by condensing steam directly in the product.
The heating can take place with or without regenerative steps depending on the
energy costs and/or the required heating duty and can be designed to give
exactly the time/temperature combination required by the product.
Today
Direct Contact Heating is the worldwide standard within the dairy industry.
Some of the benefits of Direct Contact Heating systems are:
- Low viscosity of concentrate, resulting in better SI of the powders
- Improved quality of instant whole milk powders
- Improved coffee stability test
- Low heat powders, applying highest heat treatment temperatures, resulting
in better bacteriological properties
- Tailor making the WPNI of medium heat powders
- Improved heat stability of high heat, heat stable powders