Efficiency of Power Generation 1

[SpikeMorgan]

Only need a ball park answer on this one.

What percent of power can one expect to produce from a givin feed stock? I know it is vague, but I would expect coal, LNG, NG, etc. would all produce roughly the same output relitive to their energy content.

 

[davefitz]

based on currently implemented technology, there is a wide range in efficiency of conversion. Newer proposed techologies will widen this gap. The fuel used, age of the technology, location of the plant ( Europe + japan vs US) all represent variables that effect the efficiency installed capacity .Basically, evaluated cost of fuel , including import fuel taxes and externality taxes ( carbon tax) tend to drive some nations to implement higher efficiency technology.

For clean fuels such as nat gas, LNG, gas fired combined cycles range in LHV effiencies from 50-61%, excluding transmission losses. Simple cycle gas turbines may range from 28-43% LHV efficiency.

coal fired boilers feeding a rankine cycle may have a range of LHV efficiency from 27-43%

 

[a2bekhit]

hi thnks for all your help
but i have question why there is a divergence in pressure lines in the h-s diagram

 

[MJCronin]

Spike,

Your question is very general, but should be posed in the mechanical engineering terms of "thermal efficiency" and "heat rate" for a given fuel. Not in terms of feedstock.

Some good information here about fossil plants:

http://en.wikipedia.org/wiki/Fossil_fuel_power_plant

The decision about the particular type of plant to construct and its operating costs is based upon the availabilty of fuel contracts, emissions limits, licensing and business risk.

Why are you asking this question and what do you want to do with this information ?

-MJC

 

[SpikeMorgan]

Wow my question was poorly written! Thanks for the link; it confirmed the information from Dave.

I have a potential fuel that is a by product of our processing system. We produce something on the order of 250 tons per day. From what I've been told, it has a LHV that is close to that of coal. I wanted to get a number that I could use to approximate the revenue generated from the production of electricity. So in essence, I was asking what the thermal efficiency of a typical power plant would be from the boiler to the meter.

 

[EdStainless]

It all depends on the type of plant.
Fueling boilers and then using the steam to drive a train of turbines (HP, IP, LP)will get you to the high 30%s, if you run high pressures. If you run lower pressures you will be lucky to make the low 20%s.

A better option might be IGCC, Integral gassification combined cycle. Take your fuel and make a synthetic gas out of it. At this point you can clean it (much easier than cleaning turbine exhaust), store it , sell it, or what ever. Then to make power burn it in a gas tubine with a heat recovery steam generator.
Even after making the syn gas and all of the polution controls you can reach 40% eff with this system.
The catch is capital costs. IGCC plants are expensive.

Depending on where you are located and what your feedstock is you may be agle to get grants and R&D money to do this. If you are reducing overall polution there may be other savings.

http://www.coal21.com.au/IGCC.php

http://www.iea-coal.org.uk/content/default.asp?PageId=74

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[taylorg]

What is your by-product? We might be able to help you avoid the ususal pitfalls.
Reciprocating gas engines are also good contenders for using by-products and have open cycle efficiencies of around 46%.

 

[SpikeMorgan]

Foams and fabrics, most is 1.5" in diameter or less.

 

[stinems]

Spike,
Foams and fabrics would probably be best burnt up in a fluidized bed boiler, which allegedly burn most things you throw at them while capturing most of the nasty pollutants before they go out the stack. I think 'foam and fabic (polyester?)' and I think NOx and VOCs. Costs alot of money to pay for pollution allowances these days (google 'clean air interstate rule'). Plants would also have to modify their Title V air permit with the state (paperwork and hoops to jump thru).

Gasification would be an option as well, but to my knowledge gasification-based power plants of any magnitude are on the rare side these days.

Ballpark guesstimate:
Assuming your product has about the same caloric content as coal (say, 8800 BTU/lb like a subbituminous coal) and a plant heat rate of 10,000 BTU/kWh (or 34% efficient like an 80's vintage pulverized coal plant), you'll get maybe ~440MWh/day of production out of your 250 ton/day byproduct.

Realize your byproduct would probably be best co-fired with standard fuel, maybe a 10% blend for a 200MW fluidized bed coal plant. I am not sure if your scraps are directly burnable at ~1.5", may or may not need to be finer for a fluidized bed boiler.

Best of luck to you!

 

[EOIT]

Spike,

All the power plants that I know of base what they will pay for a alternate fuel off of $/mmBTU. So if you know the BTU/lb you should be able to get a good ballpark on what kind of revenue you can generate. The biggest problem that I have seen is shipping. 250 tons is ~10 truckloads a day which isn't much for a decent sized plant.

stinems is right that you are looking for a fluidized bed boiler such as a CFB or BFB (Circulating vs Bubbling). Unless you have a way to backhaul it out of your facility I would look for one of these types of plants in your area.

Good luck,

EOIT

 

[ccfowler]

Spike,

Your foams and fabrics are likely to be difficult for handling and firing without additional processing in the form of shredding or pulverizing. As mentioned above, environmental issues are likely to be controlling factors that will determine the true economics of the proposed system. If chlorine or other troublesome substances are involved, then serious corrosion issues can be added to the list of potential physical and regulatory problems.

Bulk handling and transportation are likely to be troublesome to avoid contamination by water, dirt, or trash. What happens to the materials of your foams and fabrics when their temperature rises? Do they liquify, vaporize, become stringy or gooey, ...?

What about the potential to re-process these materials into some other form? Does simply firing them as power generation fuel really offer the greatest value? Are they necessarily combined, or can they be kept segregated for more coherent processing, transportation, and storage?

Are there daily, weekly, monthly, or seasonal variations in the quantities or proportions of these materials? Storage of raw or processed materials could be another matter of much consequence.

If firing these materials as fuels is really the best option, it seems most likely that either gasification or fluidized bed combustion will be the most practical options.

Since you seem to be looking to electric power generation as the ultimate use, it will be important to consider the value of that power. Peak, mid-range, and base-load power have greatly different values. If you are considering generating the power, you would do well to pay attention to the part-load efficiency of the power plant and not just its maximum efficiency. Start-up and standby fuel consumption of the power plant can also be major issues.

 

[EdStainless]

I supposed htat htere would be a lot of unwanted chemicals involved (Cl, S, solvent...).
That is why I figured that gasification would be the best option. There is a lot of this work that has been done with everything from coal (clean coal technology) to tires.
Then you can scrub the gas and use it however. Fire a small cogen turbine or just make steam.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[rmw]

But not cheaply.

rmw