Calandria Evaporator The Swenson calandria evaporator is applied less often today than it was years ago, though there are still a number of companies that prefer this evaporator for various applications. For most applications, however, the lower equipment costs for other designs have prompted the replacement of calandria evaporators with long-tube vertical rising-film, long-tube vertical falling-film, and forced-circulation evaporators. The calandria evaporator has a heat exchanger with tubes usually less than six feet long integral with the vapor body. Circulation is created by the difference in specific gravity between the body liquor and the heated liquor and vapor generated inside the tubes, plus a vapor lift effect. The calandria evaporator can be used for salting-type applications; however, an agitator located inside or beneath the downcomer is recommended to suspend the salt crystals in the lower portion of the body.
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Theory: Evaporators are used in evaporation of volatile solvents usually water from a solution and its purpose is to concentrate non-volatile solutes such as organic compounds, inorganic salts, acids or bases.
In some applications the evaporators are also used to recover solvents such as potable water from saline water. The relatively pure condensed water recovered using evaporators can be used for boiler feed makeup, salt washing, salt dissolving, instrument purges, equipment and line washing and other uses.
Evaporators can be classified in three main categories: 1. Apparatus heated by direct fire 2. Vapour heated evaporators with tubular heating surfaces. Apparatus with heating medium in jackets and double walls. The Calandria evaporator falls in the second category. It has a heat exchanger and vapour body forming an integral part of the equipment. The circulation pattern is up through the tube and down through a circular pattern called the downcomer.
The circulation is created by the difference in density between the liquid in the vessel and the vapour-liquid mixture in the tubes and also the vapour lift effect. Procedure: We were provided with a Calandria evaporator with tubes, shell, side inlet, and vapour outlet made of stainless steel.
A vessel continuously feeds the solution to the Calandria. An insulated tank is provided below with a heater along with a temperature indicator cum controller to control the hot fluid temperature. The power supply was switched on after all the necessary connections were made. The suction line of the cold fluid circulation was then connected to the cold water supply line. Flow rate was fixed ensuring efficient condensation. It was ensured that the drain valve was closed.
Now the circulation of the hot fluid is started and the heater was switched on. The temperature of hot fluid was set to 0C. System was left for a few minutes until the hot fluid attained the desired temperature mark. Now we kept a vessel beneath the condensate and the Solution was allowed to fill the vessel for 3 minutes. Mark up to which the vessel was filled was then noted.
Table for observed readings: Volume of condensate Time of collection Sr.
Expt. 5 Calandria Evaporator