Boiler Efficiency Increase Design Project

[jaymzd]

Hi,
I am a University student working on a project that involves finding the most cost effective way of increasing the efficiency of the boiler in a local high school.
In the project we are to select one, or a combination, of three optimization strategies: increase combustion air temperature, decrease stack temperature and/or reduce XS air levels within the boiler. One other option is to look at installing a new boiler, however we are supposed to try and minimize cost as much as possible.
There are two main things that I am hoping someone might be able to help me with.
The first is that there is very little information on these boilers. All we have is that the two main boilers that are used for heating the facility are Vulcan (Vulcan Iron and Engineering Limited, Winnipeg, Canada, a company that no longer exists) gas-fired, fire-tube boilers (size A213-A) controlled using Fuel Master CG-100 control units. The control units are 4000 MBTU/hr, max 4200 MBTU/hr. However, the only real information we have on these boilers is based off of the specs for the control units, there are no drawings or spec sheets for the boilers (no expected efficiencies, XS air levels etc.). I am wondering if anyone has any experience with this type of boiler or knows of any analogous boiler's that I could get and use information from. Any information we can get, whether it is on these boilers, or boilers that would be similar to them (new and old) would be a great help.
We will also look to compare the approximate performance of these boilers to a new comparable boiler (if possible).

The retro fit option we are looking at is installing ducting that could allow us to include an air heater as well as control the air being supplied to the boiler. I am looking for any advice/experience that people have had using air heaters in a smaller application like this. How effective are they in practice?
As is, the boilers draw in ambient air from the boiler room which is fed by an open window. In the winter, the air drawn in to the boiler can be very cold since the outside temp can drop to -30degC. Does anyone have experience retrofitting a natural draft boiler to a forced draft boiler in order to control XS air levels withing the boiler?

Again, any info or experience you can offer would be a great help.

Thanks for your time.

 

[Tipper]

You won't get much advise on this forum as most of the members deal with small domestic boilers and can only just cope with the latest condensing boilers!

Get yourself into the library and research power utility boiler efficiency. They all tend to have economisers, airheaters and excess air controls, etc, for very good reasons.

Personally I would look at increasing the inlet air temperature via an airheater or just shutting the window, fitting an economiser to the flue to increase the feedwater temperature and finally controlling the excess air. Alternatively replace with a modern condensing boiler which is basically a boiler with an economiser.

What all this means is you have to get your calculator out and do some sums!

Good luck!

 

[Biggles..]

location is going to play a key part in the info you get but.

vulcan was hart/continental became stelrad and then ideal over here.

your burner is a 1.2MW forced draught burner firing into a cast iron furnace.

ideally you should be having a look at a heatloss calc first to see your required size as the burner could be too big reducing efficency plus the losses through a cast exchanger.

the ouside flueing should normally be insulated between core and outside depending upon flue height,added warming of this probably wont add much effeicency.

warming the airintake will add to the effecincey but be counter acted by the loss through the exchanger,the cost of the duct work,controls, air heater and gas train for it will probably outweigh the improvement in the boileres effeciency.

realistically id be looking into either new condensing boilers,controls etc or converting the existing furnaces to run on a more sustainable fuel.
you could with new burners convert to say waste oil,the losses of the furnace will be the same but the overall cost saving on the the fuel and installation cost when considered in the whole equation will be a money saver.