heat rejector

[stevechemeng]

Hi
I'm a chem eng doing some work on a boiler optimisation project. However, my background is wastewater and evaporators, not steam plant so I'm on a steep learning curve.

Our plant operates a 14 ton per hr solid-fuel, fixed-grate boiler. Depending on factory demand, the boiler load can drop to 7 ton or less for extended periods. This amount of turn down causes problems with our combustion control and can lead to stretching the capacity of the emissions control equipment.

One solution that we have been kicking around is to use run the boiler at constant load and use a heat rejector to condense unwanted steam and return condensate to the feedwater tank. We were thinking of using a forced draft finned hex and use the hot air for fuel drying. Our fuel source is very cheap, so the eff loss costs are acceptable compared to ensuring environmental due diligence.

The question I have is there anyone out there that has had experience with this sort of technology and could they share their experience?

Thanks
Steve

 

[rmw]

Wow, you live in a world that very few of us have ever seen. For the most part, most of us are trying to conserve fuel as much as we can.

First; are there any plant loads that you can use steam turbines for during these times to use excess steam? If you had an electric driven pump jor other such device that you could parallel with a steam turbine and switch to steam when the other steam demand is low, then that would be a way to use some steam. You could still condense the exhaust and heat fuel with the rejected heat.

As far as a device to condense your steam however you get it to the condenser, GEA makes such a heat exchanger. Go to

http://www.bdheat.com

and look for mention of a hybrid heat exchanger. IF not, check

http://www.geaecoflex.com

This particular type of plate heat exchanger handles air on one side and steam on the other side very easily.

rmw

 

[MikeHalloran]

I got an insider's tour of one of the local waste to energy plants, which face similar challenges. The garbage keeps coming even when the grid can't absorb the energy, or the generators are down.

So the plants are equipped to desuperheat and condense the entire steam flow that the boilers can produce.



Mike Halloran
Pembroke Pines, FL, USA

 

[stevechemeng]

Thank you for your posts. It's opened up a couple of new avenues for me.

Cheers
Steve