Apparatus and Materials - Free Essay on a Shell Heat Exchanger Calandria

Calandria is a shell heat exchanger designed to concentrate sugar solutions. It consists of a shell, tubes and three passes, each consisting of 7 tubes. A sugar-concentrated steam is fed at the top of the Calandria, losses the heat through the walls and exits at the bottom as the condensate. Since the steam is at a higher temperature than the sugar solution, it also transmits heat to the sugar solution. The transmitted heat is known as calibrating heat, owing to the fact that the steam does not alter its temperature. The high pressure in the Calandria tube which can be regulated by the operator prevents the sugar solution from evaporating.

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The heat of evaporation is then transmitted to the calandria so that the sugar solution does not evaporate in the heat exchanger as it moves through the tubes because it does not gather sensible heat and also due to high back pressure. This pressure can be regulated by the butterfly valve. The valve separates the top of the calandria from a vapor-liquid separator. When the liquid crosses the butterfly valve, part of it becomes vapor due to reduced temperature and pressure. This is called flashing. Then, the vapor-liquid mixture separates in the separator. The liquid flows through the bottom of the separator while the vapor exits through the top. The liquid that is collected from the bottom of the separator is slightly more concentrated than the one passing through the calandria tubes.

Between the Calandria and the pump, a small amount of thick liquor is drawn as a liquor product, after which a thin liquor feed is fed back to the system. The recycling is done at a much higher flow rate that the feed rate. An electronic flow meter is used to measure the recycle flow rate. When the mixture of the thick liquor and the vapor condensate are pumped back to the feed tank at constant steam pressure the evaporator reaches a steady state.

Some of the risks that may result in using the shell and heat exchangers is the possibility of causing fire (Standard Operating Procedure and Safety Guide for Shell and Tube Heat Exchanger Apparatus, 2011). Although not at a higher risk of causing fire, it is important for the users to be prepared. In the event of fire, the users should leave the room immediately as directed on the fire exit. It is important to raise the fire alarm usually located outside the room. Additionally, users should only attempt to use fire extinguisher if they know how to use it. In such a case, only one attempt should be made. If unable to use it, one should leave to a safer place.

Even though the equipment does not pose great kinetic danger, sometimes the water needed to run it may heat beyond 85 degree Celsius which could be a health risk as it can cause burn (Standard Operating Procedure and Safety Guide for Shell and Tube Heat Exchanger Apparatus, 2011). To ensure no user gets burn, no one should touch the equipment during the operation and immediately after it is shut down. One should also be careful to avoid touching the connectors and tubing to the heat exchanger as they gets hot.

Due to the extensive usage of liquids while working with this equipment, there is high possibility of the users to fall as the floor may become too slippery. Users are advised to ware appropriate shoes and to walk carefully while working with the equipment so that they do not fall as they can break their arm, or can be injured.

References

Standard Operating Procedure and Safety Guide for Shell and Tube Heat Exchanger Apparatus. (2011) (1st Ed.). Retrieved from https://www.unb.ca/fredericton/engineering/depts/mechanical/_resources/pdf/sop/heat-exchanger-che.pdf