Process water heat recovery

[PMTM]

We are plastic foam product manufacturer and for this purpose we use molding machines. This kind of process uses steam for heating plastic and water for cooling purposes.
Returning water after process has the temperature of about 70-75 deg C. Cooling water flow is 120 m3/hr. To reuse this water it needs to be cooled down to about 30 deg C. Cooling towers are used to evaporate some water and bring temperature down to required level. Certain percent of returning water is reheated to fulfill our plant steam requirements. We recognize the amount of energy that possibly can be recovered and reused to produce steam, but we are still looking for suitable solution to produce steam and cool process water at the same time.
We are really open to any help and suggestions.

 

[HEC]

Put a regeneration heat exchanger on the feed to the cooling tower (70-75C water). On the other side of the regen heat exchanger put the boiler feed water. You will heat the boiler feed water from the nominal 30C to around 65 - 72C. You have not stated the boiler feed flow so cannot make comment on how much the cooling tower feed temperature will drop.

Mark Hutton

 

[PMTM]

Boiler already uses the hottest water, but I am looking for way to utilize about 5 MW of energy in post process water to create steam and end up with 100-110 m3/min of cooled water down to about 30 degC at the same time. Use of heat pump is imagined as most efficient way.

 

[willard3]

If you have a domestic water use, ie, bathrooms and etc, this is well within the range for domestic water.

Incoming domestic water will be in the range of 50-55F.

 

[HEC]

PMTM,
For full recovery of heat you will generate around 8,000kg/hr at 120C/0.198MPa steam. However the condensor for this heat pump would need to operate at around 130C. Most refrigerants at that temperature have very high pressure, so this system may not be economical. As an example for ammonia you would be looking at pressure ratio of around 10. The CoP for a heat pump reduces as pressure rato increases, hence the energy input for compressor and capital cost would not make this attractive.


Mark Hutton

 

[PMTM]

We have heard Lithium Bromide heat pump might work, but We cannot find manufacturers for more info.

 

[ChrisConley]

McQuay has a product called a Templifier, which is a heat recovery heat pump. I've heard of the product being used on cooling tower lines, I know that the discharge temperatures of the product have recently been increased (although I don't think it has been increased to 130C...)

http://www.mcquay.com/McQuay/ProductInformation/WaterCooledChiller/Templifier-Scroll

http://www.mcquay.com/McQuay/Produc...Chiller/TemplifierandHeatRecovery-Centrifugal

 

[Zesti]

"Lithium Bromide heat pump" ... I think you are refering to an Absorption Chiller.

Your excess heat might also be of use to your neighbours.
I have heard of projects where excess heat from one company is used by other companies in the same industrial area.

But such a thing might be a large step to take...

5MW would heat a fairly large greenhouse for instance.