Recovery of Energy loss

Go to a previous thread "Use of heat losses of the kilns/furnances" in the CR4, this was a similar question with similar replies.

You can either use a heat exhanger to warm up dry air, pipe the exhausts to the drying line, or concievably, run your drying line through the economizer of the boiler.

If you jacket the kiln and boilers with an air gap, then piping any air in there directly to the drying line could be worth it.

Bear in mind that you are going to have to balance the cost of moving the hot air to the drying line, the insulation cost, and the value of the heat once it gets there. Cold exhaust won't do a lot of good. Consider the payback time.

You might also consider setting up your drying line so that the tiles move countercurrent to the hot air. Hot air would be manufactured at the dry end of the line, and move over the tiles towards the cold, wet end. The final objective would be to exhaust very cold air. Blow some air over the hot tiles to cool them down and preheat the combustion air.

Using some calcium hydroxide or other drying agent from time to time would dehumidify the air.

Insulation is going to be a big deal. The less heat that exits the sides, the more you have available for your processes.

Hi

your concerns are correct I want to eloborate in detail We are using vertical dryer using natural gas as a heat source to dry up the tiles I mean to to move moisture from them.The tiles are fed at one end in the dryer six in rows on the steel rods which moves up when another six tiles are fed on next steel rods automatically. The tiles are fed at one end in the dryer and after drying up comes out from other end of the vertical dryer, In this way from one end tiles are fed in and from other end tiles tiles comes out at the same time

What will be the best the boiler or the kiln/furnance

You would probably be a little better in having the driest tiles closest to the heat source. In that respect, putting the wet tiles in at the top and pulling the dry tiles out at the bottom near the burner would let you take advantage of the natural convection. It would also let you use the driest air on the driest tile, and the wettest air on the wet tile. Blowing precombustion air over the hot tiles to cool them down would let you reduce the energy needed to warm that air.

our system is such that tiles are feeded at one end, six tiles are placed on steel rods of the carrier then the carrier moves up after filling the tiles on all steel rods regularly,p filling up of the tiles is regularly and then the tiles comes out from other end on the conveyor at the same level of feeding. the tiles are very hot at other end

so please guide according to this concept for saving energy and the cost for recovery of energy loss of kiln/boiler as asked previously

If it is possible, use the heat from the hot tiles exiting the kiln to warm up air for combustion in the kiln. It would both cool the tiles down and save the energy needed to warm the air up. Concentrate your heat at the dry end of the kiln, allowing the hot air to flow countercurrent to the flow of the tiles. That way the highest value heat (the hottest air) heats up the dryest tiles, while progressively lower value heat is used to heat and dry the wet tiles. You may find that you need to make your kiln a bit longer than usual to take full advantage of all the energy you are using in the kiln.

What you want to do is to make your product tiles as cool as possible, with all their heat going back to the kiln. You want to make all the air that exits the kiln as cool and wet as possible because it gave up all its heat to warm and dry out tiles.

I've noticed that one of the best ways to use resources is to find the lowest value resource that will fill a requirement. In this case, if you don't need 1000 degree air to warm up the wet tiles, then don't use it. Use cooler air instead. Save the 1000 degree air for finishing off the hot tiles, where cooler air won't work. Make the cooler air from the hotter air as you make the cold tiles warmer.

The other posts have good suggestions as to where to recover heat. If your kiln has an exhaust, this is possibly one of the higher temperature places to recover heat. If this exhaust has low enough moisture content (since moisture is in it as a combustion by product) you could use the hot air directly for drying. Hot air with to much moisture could go thru a heat exchanger.

You would recover heat from the highest temperature source possible. Some sources may be hot enough to use directly into the dryer. If you do not have any sources hot enough to use directly, use this "pre-heated " air to feed your dryer combustors therefor using less natural gas.

Recovering heat off the skin of the kiln is sometimes used. One caution is that if your kilns are lined (depending on what you are making as to the temperature of the kiln core) you must recover heat fast enough to not elevate your refractory lining temperature. Some kiln shells must stay under a certain temperature so the refractory lining stays cool enough or the liner will degrade quickly.

The other posts have good suggestions as to where to recover heat. If your kiln has an exhaust, this is possibly one of the higher temperature places to recover heat. If this exhaust has low enough moisture content (since moisture is in it as a combustion by product) you could use the hot air directly for drying. Hot air with to much moisture could go thru a heat exchanger.

You would recover heat from the highest temperature source possible. Some sources may be hot enough to use directly into the dryer. If you do not have any sources hot enough to use directly, use this "pre-heated " air to feed your dryer combustors therefor using less natural gas.

Recovering heat off the skin of the kiln is sometimes used. One caution is that if your kilns are lined (depending on what you are making as to the temperature of the kiln core) you must recover heat fast enough to not elevate your refractory lining temperature. Some kiln shells must stay under a certain temperature so the refractory lining stays cool enough or the liner will degrade quickly.

HI

I would like to know how can I check or calculate "exhaust has low enough moisture content" (since moisture is in it as a combustion by product)

If there is moisture then how could I design the heat exchanger

Large and very long rotating steel kilns are used to "cook" limestone from the virgin raw material. Such plants require enormous amounts of heat to do this.

In order to help keep the process cost-effective, these kilns use the heat discharge end of the kiln to preheat the untreated crushed material, before it enters the kiln. This effectively shortens the amount of time needed for the chemical reaction to occur.

I've helped in the mechanical design of the subsystems on these giant machines and while I am not a chemical engineer, I have enough experience with ceramics to where I see no reason why this highly effective recovery technology can't be used to dry the tiles.

Large engineering firms like F. L. Smidth are specialists in this field and have an enormous international client base for kilns and cement plants.

However, you are more likely to get greater attention, faster and spend a lot less money, if you speak to smaller niche engineering firms like "High Temp Technology."

High Temp is also international in scope but because they are a smaller firm, can respond much more quickly to these concerns than most big ones who inevitably have a lot of corporate inertia.

They have a web site: www.hitemptech.com

Obviously, an initial capital investment will be necessary. However, a properly designed system almost always rewards you with a fast ROI, especially so in a market where energy costs are rising exponentially.

Over the long term, such a system could perhaps even increase production volumes with virtually no escalation in energy costs.

If you are really lucky, you may even find yourself the beneficiary of a government energy grant with no payback requirements. That depends on where you live.

Governments here in the US, at both the Federal and State level, are looking hard for viable energy conservation opportunities and are happy to work with you, provided you are prepared to deal with the flood of nonsensical minutia that so often accompanies government programs.

L. J.

How can you help in designing tho recover of heat loss from the kiln or boiler to use as a soucre of heat to heat up the tiles in vertical dryer from where the six tiles are automatically feeded in one row from one end on steel rods and then it goes up filling the dryer and comes out after drying making a one cyle and it comntiously work as six tiles are feeded in the dryer and at the same time six tiles comes out of the dryer from other end after drying

one can find the heat required to dry the the tiles and time required per batch if it is a continious process , than we can control the fuel and air compositon by cascading convection zone draft pressure and temp of the outlet exhaust this optimisation can reduce approximately 10 to 15% of saving

Hi

I appreciate your reply

Will you help out in finding the method for finding heat required for drying the tiles

The tile dryer is a vertical dryer feeding of tiles at one end and exit of tile after drying from other end it is a continious process having a cyle of from 45 minutes to 2 hours depends on feeding the dryer

dryer contains about 3600 tiles of 8" x 8" size continous feeding and exit. The tiles are fed in the dryer through conveyor received from the hydraulic press

it is a continous process feeding the tiles at one end six in one row on steel rods then automatically feeding of tiles in the tiles and then the tiles comes out of the dryer at the same time time from the other end of the dryer after drying up