2 replies to this topic

[Sridhar P]

Dear Sir,

Cycle of concentration in Cooling Towers for Sea Water application is generally limited to 1.25 or 1.3 in power plants. Why such a low coc and enormous pumping is practised. what are all the factor the governs the cycle of concentration in sea water application. what is the limit for Total Dissolved Solids(TDS) and how. Pl. explain.

Thanks and Regards,
P.Sridhar

Edited by Sridhar P, 28 October 2010 - 08:29 AM.

[ankur2061]

Sridhar,

Some links to address your question regarding lower CoC for seawater application as a cooling medium:

http://www.process-c...000000000597494

http://www.opc.ca.go...cle_Cooling.pdf

http://www.powergenw...chnologies.html

Additionally a very good definition of CoC is given in the GPSA Engineering Databook and is as follows:

The concentration of compounds occurring in circulating water systems that can cause scaling or corrosion of equipment must be controlled at a desirable level. This concentration level, developed on each system, is based on the quality of makeup water and the water treating chemicals used to
control corrosion or scaling. The concentration is usually reported as concentration cycles and refers to the number of times the compounds in the makeup water are concentrated in the blowdown water. For example, if the concentration in the makeup water were 125 mg/kg and the concentration of
the blowdown were 500, the concentration cycles would be 500/125 or 4 cycles. The compounds are concentrated by the loss of water through evaporation and windage. The evaporation loss in a cooling tower is calculated from the ratio of specific heat to the heat of vaporation. The specific heat of water is 4.186 kJ/(kg · °C) and the heat of vaporation is 2326 kJ/kg. The ratio 4.186/2326 = 0.0018/°C indicates that 0.18% evaporation occurs for every degree of cooling taking place across the tower.

It is obvious from the above definition that the CoC reduces if the makeup water concentration of the dissolved compounds is high which is typically true for seawater.

Hope this helps.

Regards,
Ankur.

[siva_hps]

Dear Sridhar,

As Said by Ankur, The cycle of concentraction is nothing but the ratio of the concentraction of cirulation g water to the make up water. The particular type of tube material (in the condenser) can have withstand capacity to certain level. For eg. SS tubes can with stand upto 2400 TDS and for chlorine upto 200 PPM. so based on the make up water quality, we have to limit our cycle to suit the recommendation of material. If you go for titanium in case of seawater cooling, there will be limitation on TDS and other constuents, for details check with Titanium tube material supplier for limitation on water quality.

Best regards
K.Sivakumar