Recycling Energy from an Annealing Furnace

Hi Hector,

Have you thought of pre-heating the zinc, the air in the plant and/or office (in winter)? Do you use steam for anything? Is there anywhere else in the plant you heat anything that you could either heat or pre-heat with this exhaust.

The only things I think you need to keep in mind are whether you are going to impede the flow of the exhaust leaving the building or leak exhaust into inhabited areas.

While you're at it you could look for processes where you are heating up water and then dumping it down the drain. Install a heat exchanger and use the waste water to pre-heat the incoming water.

Now that I think of it, you could use your exhaust gas to preheat the combustion air.

Have fun thinking of new variations.

Gordie.

Tanks for your advice, i wanna tel you that in the continuos annealing furnace i told you we use radian tubes to generate heat power, it uses about 2710M3/hr og NG gas and 33600M3/hr of combustion air, so it's a big amount of combustion waste gas, i wanna used this gas to preheat another equipment that uses steam to heat up air in order to dry some sheet metal, my question is , can I use this waste gas to heat up the air insted of steam, the steam is at 120°C, and the waste gas is at 350°C, another thing is that what would happen with the exhaust gas because it has NOx and SOx.

Because my burner has a recuperator so i have already used the waste gas to preheat the combustion air.

but as i told you i have 3 air dryers and i wanna use the waste gas to heat up the air.

While the steam has a lot more energy per unit volume at 120C than the hot exhaust at 350C (heat of condensation), You could only heat a lot of air to 100C with the steam but you could conceivably heat the air close to 350C using a counterflow exchanger.

The exhaust gas probably also has a lot of H2O in addition to the NOx and SOx. so your heat exchange would need to be acid resistant as there will be condensation. (You might be able to get some brownie points for reducing your emissions.)

If your air dryers are currently heated with steam then perhaps you could continue to use the steam but then heat the 100C air with the exhaust gas and reduce the number of air dryers to 2.

Later,

Gordie.

As already advised you can use the heat in hot gases to heat the incoming air or producing steam/hot water.
Introduction of new equipment in the gas circuit could lead to higher draft loss. This point should be considering your planning.

Hi Hector

In order to give you some suggestion I need to know where your factory is located and how much is the waste gas flow rate?

I work for Altran that is a consulting company in the energy field and I could give you good suggestion

You can contact me on francesco.mole@altran.it

Bye

Tanks for your advice, i wanna tel you that in the continuos annealing furnace i told you we use radian tubes to generate heat power, it uses about 2710M3/hr og NG gas and 33600M3/hr of combustion air, so it's a big amount of combustion waste gas, i wanna used this gas to preheat another equipment that uses steam to heat up air in order to dry some sheet metal, my question is , can I use this waste gas to heat up the air insted of steam, the steam is at 120°C, and the waste gas is at 350°C, another thing is that what would happen with the exhaust gas because it has NOx and SOx.

Increase the recuperator capacity. You are still getting out 350°C so there is margin for improvement. Check with your recuperator supplier. Or contact ACTE SA (ask for Luc Prieels) as I mentioned before. They may have cost effective equipment for you.

Why dont you think to change your air/gas burner system with oxygas and recuperative burner systems ? So you will save all waste heat vhenever you operate your furnace.

Regards,

Taner Mersin

This company utilises waste heat to produce electrical energy, plus they manage carbon credits on your behalf. However efficiency in transforming waste heat into electricity are not great.It would be much better for you to use it as space/air heater or in some other industrial process.

http://www.biothermenergy.com/

Hi Hector, can you use the combustion gases to preheat the air used for combustion? That is usually the easiest solution.

You could use ORC or Kalina machines to make electricity but efficiency is limited.

www.heat2power.net/kalina

Feel free to contact me if you need more info.

You can try google as well.

Heating your incoming air is a very good one. Low cost and robust. Have a look at heat exchangers from ACTE SA in Belgium. They make great stuff.

http://www.acte-sa.be/

If the heatflow is steady you can think of installing a hot water circuit and heat the buildings around. Just like city heating systems do. Sell your heat.

Tanks for your advice, i wanna tel you that in the continuos annealing furnace i told you we use radian tubes to generate heat power, it uses about 2710M3/hr og NG gas and 33600M3/hr of combustion air, so it's a big amount of combustion waste gas, i wanna used this gas to preheat another equipment that uses steam to heat up air in order to dry some sheet metal, my question is , can I use this waste gas to heat up the air insted of steam, the steam is at 120°C, and the waste gas is at 350°C, another thing is that what would happen with the exhaust gas because it has NOx and SOx.