Energy Recovery/ Heat Pump

[neweng123]

There is a biomass boilers to generate power, but the energy waste is high. They use a lot of cooling fan to cool down the saturated steam after the turbine generator. A lot of the steam is injected into the atmosphere too. No chillers were installed.

In the summer season, they can still use the excess heat to dry up paddy. But we don't any heat during summer time for heating. So most of te time, the after process steam is hard to deal with.

They are now planning to recover the wasted energy. Preferably using the excess energy for either industrial refrigiration (like cold storage for food) or even air-conditioning (cooling office space). If not, at least they can stop using so many cooling fan or inject the after process steam out of the system.

My questions are:
1. How can they do that?
2. What are chillers?
3. Is there such a thing as a compressor (in refrigeration cycle -- compressor, condensor, expension valve etc, not the same as steam compressor that add pressure to the steam) that can run from the superheated steam like the turbine generator?

It will be very much appreciated else can you direct me to the sources where I can find the solutions to the problem

 

[Goorah]

New England:

I could swear I replied to this the other day; but where it went, I have no idea.

I suggested either steam-driven ammonia/H2O absorption chillers for refrigeration applications or steam-driven LiBr/H2O absorption chillers for comfort cooling applications where chilled fluids to about 40F could be used.

Manufacturers of the LiBr units are many: Trane, Carrier, York, MqQuay, Ebra, Mitsubishi, Sanyo and many other Japanese and Korean and Indian mfcts.

Depending on your steam pressure level, either 1-stage or 2-stage could be used.

 

[neweng123]

Can I have any references or literature that I can actually refer to and help me understand about the whole process? Thank you very much.

 

[Goorah]

Here are some sites to start with: Trane.com; York.com; Carrier.com.

Here are two specific sites from Trane: first an informational piece

http://www.trane.com/commercial/library/northwood.asp

and next a technical catalog that has much useful information:

http://www.trane.com/download/equipmentpdfs/absprc005en.pdf

Happy exploring!

 

[steamman]

Have you considered steam jet refrigeration? It sounds as if you have excess steam availibility and a thermal compressor could be an option.
A thermal compressor could also use your superheated steam to produce chilled water.

 

[fredb]

Hello,

Could any of that waste steam be used to generate electricity?

 

[quark]

NewEng!

Goorah is correct in suggesting vapour absorption system for refrigeration when waste heat is available. Main problem with water.LiBr systems is crystallisation of LiBr. If the concentration is above 60% and the temperature falls down to 22deg.C LiBr crystallises. This is a problem at low temperature heat exchanger. However when compared to water/Ammonia system LiBr is better in every way.

As an alternate there are some turbines which convert steam energy to electricity. Eventhough it's a general principle you know, what I mean is a system which is used instead of Pressure Reducing Valves. The turbine will reduce the steam pressue to the required level. Generally when steam pressure is reduced, some portion of it flashes and steam becomes superheated at that particular pressure. This is a wastage of energy. These turbines utilise this energy and convert it into a useful one. (or atleast that was what I was told by one of the sales engineers) I saw, personally, the system working at one of edible oil refinery plants.

Regards,

 

[Goorah]

Quark does point out an important point to realize as you consider the LiBr absorption chiller: It's useful limit is about 38F.

Crystallization was definitely a concern about 25/30 years ago; but with today's solid state controls it is virtually stamped out (sort of like the measles was !! ).... depending upon the manufacturer)

But do you (NewEng) have any uses for medium temperature chilled fluids? I say "fluids" because remember that you can cool many things besides water: I've applied absorbers with baby oil, raw gasoline, food stuffs, glycol, sewage (yes!!! :-( )... basically anything that's has a reasonably low viscosity)

Do you (new england)produce electricty with smaller gas turbines?

In generating electricity via a gas turbine cycle, with a TIC system (Turbine Inlet Cooling... in order to improve turbine efficiency and maximize output)... in which case you could chill turbine inlet air with absorber-cooled water or glycol.

Alternatively, some producers make steam with the turbine exhaust and inject it back into the gas turbine. This is called STIG-ing the turbine (STeam Injected Gas turbine) and gives greater turbine performance improvements than a cool, "dry" turbine. This is due to the additional mass flowing thru the turbine when steam is injected. In this case it makes for sense to commit the steam to STIG tahn to TIC .... but it can be a complex economic analysis.

Also depends on the application: one must consider that absorbers, due to their chemo-mechanical nature, can take about 45 minutes after a dead stop to come up (down?) to full capacity. This wouldn't lend itself well to power peaking plants; and electric chillers (to precool air into generator/turbines (at high ambient, peak times!) typically would be used despite the parasitic electrical power load on the generator ... consider what peak power retails for !!!

Hope this helps, NewEng, and makes you take a deep look at all the energy flows into and out of your facility.

 

[Goorah]

NewEng: How large are the numbers we you are talking about and can you be more specific: How many lbs/hr of steam are being generated/wasted by the biomass generator and at what saturated temp are each available. Would be much better able to make suggestions if this were know.

 

[ChasBean1]

How much does the excess steam vary? If the excess steam doesn't provide a constant, reliable energy source for another component (such as an absorption chiller), look into replacing the turbine with a more efficient model. A turbine that's efficient and well-sized and staged correctly for the application discharging to a condenser under vacuum should be very efficient.

 

[quark]

Goorah!

I don't think any other liquid can be used in LiBr system for in it water is used as refrigerent. In ammonia systems ammonia is used as refrigerent and water as absorbent. If I am wrong please send me some details of the systems you have developed and let me know what is the COP value?

Anticipating reply from you.

Regards,

 

[Goorah]

Hello Quark:

Please go to the third post from the top in this thread where you'll find links to the sites which will give you the details you're looking for. I believe in the paper mill case study, they'r cooling chlorine dioxide using stainless stell tubing in the evaporator.

You are certainly correct in stating "in LiBr system for in it water is used as refrigerent."; however, the refrigerant is on the refrigerant side of the HX; while the fluid being cooled (gasoline, baby oil, human blood, maple syrup, whatever) is on the other side of the HX.

Since H2O is in fact the refrigerant in "aqueous" LiBr absorbtion chillers and since it has a funny way of becoming solid at 0 C, I had mentioned earlier that the practical limit for the fluid being chilled is 38 F in these systems: assuming a 3 degree Tapproach in evap, the refrigerant (water) would be at 38-3 = 35 F.... BULK AVERAGE temp. Allowing for colder spots in areas of eddy flow or "dead spots" and some margin (35-32 = 3 F0 had better be allowed!!!

 

[Jessee]

I work at a forge shop in the midwest. Cooling of the shop has been a perpetual problem, since the forging process requires heating steel to over 2000 degrees, and then cooling it back to ambient. My question is this: is there a safe and robust system of absorbtion cooling that could utilize the heat (radiant and convection) that is constantly being lost by the tubs of hot steel to spot cool the operators? Are there any companies or groups that might be working on this very application. Most of the commercial chillers seem to be aimed at gas or steam fired, whereas I would like to use the direct heat from the "piles" of red hot steel. Any insight would be helpful.

 

[quark]

Jessee!

I have seen applications where steam coming from cooling the furnace walls is utilized for refrigeration system using vapor absorption techinques. Try to contact Trane people.

Regards,

 

[PacificSteve]

An absorption chiller loses overall capacity greatly at 45F and below, so if there are applications where 48F or higher can be useful, you will get way more cooling BTUH out.

Also, rather important to have technically competent operations staff, or as others have suggested, you can crystallize your lithium bromide and have one real big headache.

Interesting to note however, that you don't "get rid" of the heat you started with, you get it all back, plus whatever heat was taken out of the system to be cooled, plus pumping energy if you want to get real picky.

After all that, these are still real cool machines that can have paybacks in the 4 to 8 year range compared to efficient electric driven chillers, maybe quicker payback if high electric rate is present.

Pacific Steve

 

[quark]

Steve!

One simple idea I consider always in energy conservation is " what type of energy is being used?"

Heat is a low grade energy and electricity is high grade energy. The conversion of high grade to low grade energy is always inefficient (but required -)

In refrigeration the ultimate effect is to remove heat and using electricity to do this less efficient. In vapor absorption system you are using heat to remove heat. (yes, for pumping of cooling and chilled water and for absorbent and refrigerant pumps you do use electricity). So both the systems cannot be compared literally.

Note: If you are installing a boiler to run a vapor absorption system then there is a real need to compare with vapor compression system.

 

[quark]

Steve!

One simple idea I consider always in energy conservation is " what type of energy is being used?"

Heat is a low grade energy and electricity is high grade energy. The conversion of high grade to low grade energy is always inefficient (but required -)

In refrigeration the ultimate effect is to remove heat and using electricity to do this less efficient. In vapor absorption system you are using heat to remove heat. (yes, for pumping of cooling and chilled water and for absorbent and refrigerant pumps you do use electricity). So both the systems cannot be compared literally.

Note: If you are installing a boiler to run a vapor absorption system then there is a real need to compare with vapor compression system.

Regards,

 

[Fayaz]

Hello, you people seems to have knowledge of biogas, I need help on producing biogas, pit design, on a very small scale. For a house about 3000 sq. ft. I want to be energy idependent from utilities companies.
ANY HELP?