GB1033599A - Improvements relating to falling film type evaporators - Google Patents

Abstract

1,033,599. Evaporators; falling-film type. A..E.ROSENBLAD. Sept. 23,1964 [Sept. 23, 1963], No. 38830/64. Heading B1B. The heat transfer element of an evaporator of the falling-film type comprises a pleated wall made of light gauge, heat-transmissive material in the form of vertically-elongated plates arranged in a row with interspaces between them. The housing of the evaporator is divided into two compartments by partitions 122,123. On one side of the wall, the liquid to be concentrated is introduced through pipes 46 on to the opposite faces 2, 4 of the interspaces 5 between the plates so that the liquid flows down the plates in film-form, while heating medium is passed through the interspaces 9 between the plates on the opposite side of the wall. The evaporator shown is of the recompression type. The vapour evolved from the falling- films of liquid flows out of interspaces 5 into chamber 126, and rises through entrainment separator 127 into compartment 128. The vapour is then drawn through pipe 129 into compressor 130, and the compressed vapour is conducted through pipe 131 into chamber 29 as heating-medium for the interspaces 9 of the pleated wall. The condensate is discharged through pipe 124. The evaporation side of the pleated wall is divided into two compartments by partition 105. The feed liquor is sprayed on to the upper part of the plates in compartment 106, and some of the partially concentrated liquor which collects on shelf 114 overflows the lip of the shelf and is recirculated, together with fresh feed, to the upper part of the plates in compartment 106. The remainder of the partially concentrated liquor on shelf 114 flows through pipe 115 for further concentration as flowing films on the plates of compartment 107. The liquor reaching the lower part of the compartment 107 is recirculated to the upper parts of the plates and, when the liquor has been concentrated to the desired extent, the valve (not shown) for withdrawing product from the evaporator is opened. Non- condensable gases reaching interspaces 9 pass, together with some vapour, through perforated plates 135 which extend from top to bottom of each interspace 9 near the rounded end wall 3. These gases flow up chambers 136, and are withdrawn through vent pipe 138. The Specification also describes in detail a multiple effect evaporator wherein a continuous pleated heat transfer element extends throughout the length of the evaporator, but partitions are arranged so that the vaporization from the liquor is carried out in six stages at diminishing pressure.