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# Concrete Plant

Member Posts: 6
I have a concrete plant that wants to heat 50F water to 200F using a boiler or water heater. They are using 20 gallons every 5 to 6 minutes to mix with the concrete. How do I go about sizing the unit? I'm an air guy so I don't get into wet heat much. Thanks for the help

• Member Posts: 2,542
Doing the math....

Gallons times pounds times delta T equals BTU's.

So, in your case, 20 gallons every 5 to 6 minutes = 240 gallons per hour.

Throw in a few gallons to CYA, and call it 250 GPH.

250 X 8.33 = 2083 LBS.

2083 LBS times 150 degree delta T = 313,000 BTUH, net.

Assuming you're at sea level, using an 80 % efficient appliance, you'd take the 313,000 and divide by .80 to determine the required input to deliver those btu's.

So, 313,000 / .8 = 391,250, rounded up to 400,000 btuH.

If the actual draw is 20 gallons, and you can only expect 80% hot water draw from any vertical tank before mix and dilution overcome you, then take the 20 gallons and divide by .8 and you end up with a storage tank of 50 gallons.

Now, in order to stuff all those btus' into that tank, it will need some pretty healthy tappings on it to guarantee you can put the heat where it's needed.

Expect short cycling...

If in doubt, contact one of the hot water boiler manufacturers, like Raypak. They offer "FREE" software on line that wil assist you in your decision.

G'Luck!

ME
• Member Posts: 277
Steam

Our local plant uses a steam boiler with a tube and shell hx. The water is stored in 2 tanks about 10'high and 10' in diameter. Temp is about 110. I think 200 might be to high. Raw steam is fed to the sand pile to keep the sand warm.
• Member Posts: 16
Small?

Rich,
That does not seem like a lot of water for a concrete plant. Is this a small facility? Most plants that I have worked with can use 100 gallons at a time without a problem.
The direct steam application is not used for mixing cement. They do shoot steam directly in to the piles of mix from underneath to keep it from freezing. It is then put in a hopper and mixed with water to make the final product.
• Member Posts: 3,782
Consider a condensing boiler...

...some boilers are built just to make hot water. The Munchkin VHW series from heat transfer products is a good example. One 399 unit coupled with a buffer tank should keep your plant very happy, and economically too. Just be sure to install the Munchkin per the manufacturers instructions!
• Member Posts: 414
Check with HTP on this

Constantin,

I had the same thought but am not so sure.

It might be tough for an indirect to heat the water to 200F. At any reasonable delta T across the coil and between the coil and the tank, the inlet water seems to want to be above boiling.

Am also wondering about the levels of dust in a concrete plant. I'd tend toward a less critical combustion setup that would take the abuse of such an environment.

jerry
• Member Posts: 9,514
Concrete Plant

> I have a concrete plant that wants to heat 50F

> water to 200F using a boiler or water heater.

> They are using 20 gallons every 5 to 6 minutes to

> mix with the concrete. How do I go about sizing

> the unit? I'm an air guy so I don't get into wet

> heat much. Thanks for the help

• Member Posts: 3,782
Good Points, for sure!

It is my understanding that the VWH doesn't use an indirect tank with a hermetic HX, instead the tank is used as a pure buffer. If you look at page 22 of the VWH installation manual, you'll see a diagram that shows a constantly circulating tank with cold water tie-in feeding the same pipe as the boiler supply.

However, using a Munchkin to constantly circulate near 200°F water seems like a waste, it's unlikely to ever condense. Plus, it's maximum design temp is 185°F, so that's a double-whammy.

To make this work, it would have to be a two-stage cascading system where the Munchkin feeds a small buffer tank to 140°F, which then feeds into a second water boiler that takes it up the last 60°F. I doubt this much equipment for efficiency is worth the up-front cost though.

Furthermore, you're absolutely right WRT a concrete plant being a punishing environment to work in (for machinery and mammal alike). A condensing boiler might not last long enough to make the whole excercise worthwhile.

On the other hand, considering the possibly high contamination with lye, grit, and other exoctica, what boiler is likely to last longest while still giving you decent efficiency?
• Member Posts: 9,514
Concrete Plant

I would take a good look at their daily operation, 20 gals every 5 or 6 min. seems low. A yard load of concrete takes around 35 gals of water depending on mix design they are looking for. Also those trucks will be filling their water tanks to boot for the job site, adding more water to mix and washing out. 5 to 6 min. is about right to batch out a truck. They probably are looking for 200* water so by the time it is mixed with the heated sand,aggregate,portland and cold truck, Haul time ect. It gets tempered to the temperature they are looking for once it gets to the job site typically 60* to 65*.

I don't know the size of the plant, but I would figure each truck is going to use "AT LEAST" 55 gal a yard if not more. When those trucks are making round trips they will be filling their truck tanks also if depleted. I would definetly CYA on this one. To install an undersized water heating setup that can't produce under extreme conditions, will definetly hinder the plant operation if they have to wait for hot water. The dispatcher and plant manager will get an ear full if the contractor is waiting on trucks. Maybe even lose their business.

Gordy
• Member Posts: 6,232
What boiler do they currently have in place?

what currently has been preforming this work at the batch plant? Perhaps you already have what you need just needs some ajudication of the applicabilities:)
• Member Posts: 10
concrete plant

We installed a system in a plant about 10 years ago we had 2 800 gallon storage tanks 1 very large expansion tank and 2 a.o. smith copper fin boilers approx. 300,000 btu each can't recall exactly. Will look up the info in the files and see next week. But it does look like your water use is low. The plant was pouring concrete for a series of large bridges so maybe their needs were higher than normal
• Member Posts: 277

Don,The two tanks are about 5800 gallons each. The boiler is about 1,000,000 btu.They are looking for some new tanks though. Black iron does rust.LOL
• Member Posts: 6,106
It takes @ 30

gallons of H2O to mix one yard of redi mix. Not sure how much hot water could be used per yard.

Concrete trucks can run 6-8 yards or more, so count on 180- 240 gallons per truck batch. If they use all hot and trucks run back to back... That is a bit of water.

They often use water to clean return trucks and even hose down leaving trucks at some yards.

Better get a real accurate number from them on what they expect for continous HW use.

Hate to see you miss the boat on sizing. I think storage would be needed.

hot rod

• Member Posts: 6,232
heres a thought..........Day Tank,.

get a large day tank put a Real pump on it with camlock fittings and valves...... if they want to run the place 24 /7 get a week tank to hold the supply for the day tank so it has beacoup d leau.then all you need is to have the week tank topped off by truck.the water arrives warm and you aint freezing that quantity of water off quick. what have they already in place?
• Member Posts: 6
Tahnk You

I just wanted to say thanks for all the ideas. I have a lot to mull over and you have been very helpful. This is my first use of The Wall and I think it's great that this place is here.
• Member Posts: 1
Look at Aerco

look at the aerco kc1000 water heater boiler it can do anywhere from 60deg rise @ 1860 gph to 140deg rise @ 797 gph with a 96% total efficency no storage tank needed. This boiler uses feed forward temp sensing technology to modulate the firing rate from 140,000btu to 1,000,000. I have replaced many installs of an 80 gal storage tank and a 199,000btu boiler with this unit, customers are all verry pleased all report an unexhaustable supply of hot water and appx 25-30% savings in gas consumption. eric
• Member Posts: 6,106
If they service their own trucks

a waste oil boiler would be a good match!

I use Clean Burns at trucking, car wash/ Quick Lube facilities.

A very inexpensive way to heat DHW, especially if they pay to have crankcase drain oil hauled away

hot rod