HOT WATER HEAT RECOVERY (HRSG) 1

[morojlu]

Dear sir,
I want to produce hot water using a HRSG. The HRSG should increase the temprature of water from 50C to 160C. The flow rate of needed water is high (about 1500~2000 ton/hr).
Can I use a Heat Exchanger like economiser in HRSG? In the other hand, I want to use a HRSG that produces hot water. Is it impossible and how can we control water outlet temprature?and if not, What is the method for obtaining this target?

 

[GenB]

It can be done,
If in he US, you have to convert your unit controls according with the Jurisdiction.
you will need an experienced hot water specialist to accomplish the task.
In order to control hot water temp you will have to have storage capacity whether in line or strage tank.
genb

 

[thermcool]

I dont understand your question fully. Do you want to use heat exchanger with hot water supply to transfer heat to the another stream of water and increase its temperature from 50 C to .... Definately to go beyond 90-100 C you need an active power supply to raise the temperature of the water. or else you can give a trying to flashing of the hot water to raise its temperature.

For the controls, if you need precise control use some digitally activated control or might be try throttling hot water with cold water to optimise the temperature.

 

[morojlu]

Dear thermcool
thanks for your reply. this hot water should produce in HRSG. it means we dont produce steam in HRSG.but the most problem is that the inlet water temperature is very low and gas turbine fuel in GASOIL with high sulfure therefore we have acid dewpoint(~120 c) corrosion.we wanted to use a simple gas to water heat exchanger (as a HRSG) but we dont know what should we do with corrosion?

 

[Manju01]

you can do as hot water boilers, the heating surface is taken as Economiser, the pressure has to be above 7bar(a),
to control the temperature by water flow (t/hr) for the same amout of heat tranfer.

 

[davefitz]

One common method of heating water without causing excessive cold end corrosion is to arrange the last several rows of cold end tubes as parrallel flow- the water would flow in the same direction as the gas ( ie from hot end to cold end). The remaining tubes ( at the hot end) would be arranged as counterflow tubes , for better overall heat transfer effectiveness.

For the cold end tubes, the parrallel flow section would be designed with the desing exhasut gas temp to be 120 C, and the water temp leaving that last cold end row as perhaps 105 C. The parrellel flow section would then be desinged to heat the water from 50-105 C. A simple ehat balance would yied the expected gas temp entering the parrallel flow section.

Another desing issue is that it will be neccesary to maintain the water pressure above the pressure that would cause the fluid to boil. The HX flow control valve would then be located at the outlet of the HX, and a safety relief valve installed upstream of that outlet valve.

 

[GenB]

Forceful you will have to recirculate to keep the temp above dew point,
it is common on condensing W boilers
genb