Concentrating evaporators – Film type – Moving film
Patent
1996-02-09
1998-12-15
Lithgow, Thomas M.
Concentrating evaporators
Film type
Moving film
159 172, 159 201, 159 271, 159 274, 159 431, 159 49, 159DIG8, 134 2216, 134 2217, 134 2219, 134170, 165 95, 426588, B01D 122, B01D 126, B01D 124
Patent
active
058491481
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a distributor plate for a falling film evaporator for use in preparing concentrated liquids or powders such as powdered milk or the like, to an evaporator including such a distributor plate and to a method of use of the evaporator.
BACKGROUND
Falling film evaporators are widely used in the food processing industry to concentrate liquids such as milk, fruit juice, sugar solutions and the like. Evaporation occurs on the inner surfaces of tubes as the liquid falls as a film on their inner surfaces. The tubes may also be referred to as callandria. A perforated plate, known as a distributor plate, is mounted over the callandria so that a head of the liquid to be evaporated is produced on the plate resulting in an even distribution of liquid from the inlet above the plate to the openings of the callandria. Evaporator systems of this type often include a series of evaporative units each unit called an effect and including an inlet for the liquid to be evaporated, callandria within which evaporation is effected and a distributor plate disposed above the callandria to distribute the liquid to be evaporated to the openings of the callandria.
The distributor plate of the invention is particularly suited to use with evaporators which are used in the manufacture of concentrated milk products such as powdered milk and will be described with reference to that exemplary application. The evaporator of the invention is not however limited to that application and may be used in evaporation and concentration of other liquids such as sugar solutions, fruit juice and other beverages.
The evaporators used in concentration of milk and milk products such as skim milk and whey generally include a series of at least three and typically four effects and a finishing effect. The milk is passed through the callandria in each effect in the series to provide progressive concentration, the system being maintained under a vacuum and the callandria heated to facilitate evaporation.
During use of the evaporation system a crust known as "milk stone" forms on the surfaces of the equipment, particularly in the evaporation tubes and distributor plate, which if not removed results in reduction in efficiency of evaporation, reduction in product quality and blockage of the callandria which require expensive maintenance procedures. Washing of evaporator systems with wash solutions can reduce build up of contaminants however in order to keep the system clean regular washings of several hours each must be carried out together with frequent servicing. This significantly reduces production and involves high maintenance costs. There is a need for a system which provides efficient evaporation but which requires less maintenance and down time for cleaning.
SUMMARY OF THE INVENTION
The invention provides a distributor plate which provides efficient operation and improved system maintenance reducing the down time associated with maintenance and cleaning of equipment.
In one aspect the invention provides a distributor plate for a falling film evaporator the distributor plate including an essentially planar plate member having a multiplicity of distribution holes therein, the distributor plate being adapted to maintain a head of liquid thereon during evaporation to thereby regulate liquid flow and distribute liquid to be evaporated to callandria via said distribution holes, the distributor plate further comprising a series of overflow conduits for providing a flow of liquid through the plate during washing, the inlets of the overflow conduits being disposed above the surface of the plate to provide a further means of liquid flow to callandria during washing.
Preferably the inlets of the overflow conduits are at a height above the upper surface of the plate member greater than the head of liquid produced during evaporation. This is particularly preferred as it enables the distributor plate to regulate flow during evaporation to provide the appropriate flow rate and distribution for efficient evaporat
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Chemical Engineer's Handbook, fifth Edition, Perr & Chilton McGraw-Hill Kogakusha Ltd. 18-31.
Brochure Rall Evaporator Cleaning Systems ("RECS") 1985 Europe.
Ancon Chemical Pty. Ltd.
Lithgow Thomas M.
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