TONS of Waste Heat - Absorption Chilling?

[svanwag]

Hello,

I am reviewing a site with TONS of waste heat:

110 Tons of LP Steam (0.8 barg)
40 Tons of LP Steam (4.3 barg)
25 Tons of MP Steam (20.6 barg)
25 Tons of MP Steam (22.3 barg)

All of the steam is produced from process reactors.

One idea thrown about is maybe we can use all the condensing heat from the steam in some type of Ab/Ad-sorption Chiller to supply the plants with cooler cooling/chilled water and allow us to either save electricity of increase rates (obviously the latter if possible).

I have read many DIFFERENT articles (including the handbook) on absorption chilling, but really, I don't understand what the potential tonnage of "chilled" water is that I can produce from each of these waste heat streams.

For example: Can the 110 tons of LP steam produce 35 tons of chilled water at 15-20 C? Are there are quick rules of thumb for something like this? Is this even feasible with today's technology, or just a big pipe dream? We are just at the early stages, and are trying to find out if this technolgoy is something worth looking into.

Thanks,
SVW

 

[imok2]

Compared to mechanical chillers, absorption chillers have a low coefficient of performance (COP = chiller load/heat input). Nonetheless, they can substantially reduce operating costs because they are energized by low-grade waste heat, while vapor compression chillers must be motor- or engine-driven.
Low-pressure, steam-driven absorption chillers are available in capacities ranging from 100 to 1,500 tons. Absorption chillers come in two commercially available designs: single-effect and double-effect. Single-effect machines provide a thermal COP of 0.7 and require about 18 pounds of 15-pounds-per-square-inch-gauge (psig) steam per ton-hour of cooling. Double-effect machines are about 40% more efficient, but require a higher grade of thermal input, using about 10 pounds of 100- to 150-psig steam per ton-hour. So it.s feasible for you to run absorbers with the waste . I would talk to a manufcturer about this as they have the expertise to help you determine the amount of cooling you can produce.

 

[willard3]

With the advent of cogeneration, low temp (150-210F) sources can produce absorption cooling. I am doing a project using them now and they come in 10-ton increments.

I think the cost of fuel will make this a very important market.

 

[absrbrtek]

Just for simplification purposes, it takes aprox 19,000 BTU's of 12 PSI steam to get one ton of cooling out of a single stage absorber. It takes aprox 12,000 BTU's of 125 PSI steam to get one ton out of a 2 stage absorber. Yazaki makes some very nice absorbers and would be glad to help you out in sizing and potential equipment.

 

[EmeraldCoastHVACR]

The company I started out with used Absorption Chillers, and although they're COP's might be lower, it's better than nothing.

The company I worked for as a technician had it's own steam power plant to drive the forging hammers for products such as Caterpillar diesel crankshafts, landing gear for all aircraft, etc.

We recovered the heat from those processes to drive rows of 5000 ton absorption chillers for the 50,000 employee plant.

 

[mike7941]

When using waste steam keep an eye on the variablity of the cooling load. If the cooling load is constant and the waste stream is also constant everything works out great. if the cooling load varies with Outside temperature for example the you'll have to dump you waste steam or create a false cooling load when the cooling loads go away or are very small. This type of thing can eat into the planned payback quickly. For this reason some would suggest you take your MP steam through turbines running generators and backfeed the power grid. For this analysis the power grid is assumed to be infinite and can take as much or as little as your waste stream could generate.