Concentrating evaporators – Fluid feed or discharge devices
Patent
1997-05-29
1999-05-18
Manoharan, Virginia
Concentrating evaporators
Fluid feed or discharge devices
159 15, 159 262, 165147, 202239, B01D1/30;3/00
Patent
active
059048077
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a liquid distributor in an evaporator, which distributor is intended in particular for liquid suspensions containing solid ingredients. The distributor includes at the upper end of the heat exchange surface a transverse conduit frame which includes liquid conduits for distributing over the entire width of the surface a liquid introduced from the side of the evaporator.
BACKGROUND OF THE INVENTION
In an evaporator in which the liquid flows as a thin film on the heat exchange surface, the surface should be covered with liquid throughout in order to achieve an efficient transfer of heat. When a liquid suspension which contains solid ingredients is being evaporated, increasing concentrations of solids at the boundaries of the dry and liquid-covered areas of the heat exchange surface would additionally cause very rapid soiling of the heat exchange surface. An even distribution over the heat exchange surface of the liquid to be evaporated is thus an absolute prerequisite for efficient operation of the evaporator.
The keeping of the heat exchange surface covered with liquid can be promoted by increasing the liquid amount fed onto the surface. However, this increases the consumption of energy for pumping and increases the thickness of the flowing liquid film, thus lowering the heat transfer coefficient. For this reason, very narrow liquid conduits have generally been resorted to in liquid distributors in evaporators, but such conduits tend to become clogged when solids-containing liquid suspensions are being evaporated.
From Finnish lay-open print 86961 there is known a heat exchanger intended for the evaporation of liquid, the heat exchanger having adjacently positioned bags formed from plastic membrane, the membrane surfaces of the bags serving as heat exchange surfaces. The liquid to be evaporated is introduced onto the outer surfaces of the bags from conduits adjacently positioned in honeycombs at the upper end of the evaporator and distributed over the entire width of the bags. The heating medium used is vapor directed via the same honeycombs to the inside of the bags, the vapor being vapor produced during evaporation and compressed in a compressor.
The apparatus described in FI publication 86961 is intended for the distillation of seawater. In addition, the publication mentions as an intended use of the apparatus the concentration of solutions and suspensions, such as bleaching effluents. However, in this case the apparatus has the deficiency that the fiber material and other solids present in the suspension tend to clog the obliquely oriented narrow liquid conduits in the honeycombs.
SUMMARY OF THE PRESENT INVENTION
An object of the present invention is to provide a liquid distributor for an evaporator; more particularly, a liquid distributor in which the problem of prior-art systems, the clogging of conduits by solids present in the suspension, is avoided. The liquid distributor of the present invention is therefore especially suitable for the treatment of wood-processing industry waste waters which contain fiber materials, such as the waste liquor from pulping or bleaching effluents, or for the treatment of food-industry waste waters which form carbonate, oxalate and other precipitates. The liquid distributor according to the invention is characterized in that it has an obliquely downwards slanted feed conduit and a plurality of distribution conduits branching out therefrom and leading to the heat exchange surface at each branching point of the feed conduit and a distribution conduit the common wall surface of the conduits, downstream relative to the feed flow, is rounded so that the dividing of the flow takes place on the curved dividing surface formed by the wall.
In a manner deviating from the oblique liquid conduits starting from the side of the evaporator in accordance with FI publication 86961, the liquid distributor according to the present invention comprises a common oblique feed conduit which divides the liquid into distribution conduits de
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Eriksson Hemmo
Koistinen Peter
Ramm-Schmidt Leif
Tiainen Veli
Hadwaco Ltd. Oy
Manoharan Virginia
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