Distance Measurement

Sorry if this is stupid/impractical. Can you stick a pressure transducer under the collection vessel and "weigh" the heaps?

I don't know how your furnace is set up so I'm not sure if my idea will be feasible.

How about weighing the furnace? You control your feedrate by maintaining a constant weight. There must be some relation to the height of the heap, right?

At the moment, I can't think of an instrument that can measure height in those temperatures. I had thought of video software also. What it does is monitor the height of the heap visually and software determines the height. I think National Instruments might have this technology. Again, I don't know what the conditions are in your furnace so I won't know if this is feasible as well.

An infrared camera might be able to "see" a difference in temperature between the heap and the background of the furnace, if you can get a lens to withstand the temperature at the inspection port.

Hello there, I would be agree with two previous comments that it would be possible to treat somewhat like pressure or weigh transducer (load cells). But as specialist of weighing systems I suppose that it is not so easy as it seems. First --- it maybe great "dead" weight of furnace a whole to compare with heap's (netto) weight so it's may cause troubles with sensitivity and accuracy. Second --- it is not so easy to organize such a project (at least for novice). Third --- I suppose the volume or/and height of heap might be correlated with weight but it is not just the same. Is it? Therefore I suppose you could use optic sensors which can work through thermal isolated glass. I think you need three of one (low of normal level, normal, above a normal level). Unfortunately I've not any idea how your equipment looks like in detail. So for instance you can drill hole (at wall either door) for fitting there thermal isolated glass and then sensor. You can use industrial sensor (both type reflective or active with light transmitter). Visit this link http://www.e-shj.com, write them and ask; can they help you anyway. Good luck.

I have a short and long suggestions. The short may have problems since it is coal you are using. Try a low D.C. voltage to like a light when in contact with the melt. You may need a two conductor "dip stick" if the melt does not contact a conductor.

The long suggestion:

I would try measuring the melt output (weight and volume) along with other variables.

Does it go into a bucket or device which could be weighed? If not can the flow rate be monitored or controlled?

Do variations occur at startup or other regular times like lunch breaks?

Are the melt constituents consistent or subject to significant variation which may skew results if only weight or only volume were recorded? (Scrap/Ore or materials of inconsistent composition?) Both variables may be need to be monitored.

Does the temperature of the output vary enough that volume measurements could be affected? I could not tell you if 400 degrees variation makes a difference, I have no references on that. I can only assume it would have some effect. It would depend on the volume of the melt output to be measured.

A record of input charges to melt output could be input into a spreadsheet and charted. The visual data is always easier for me to "get the picture" and see trends. I worked with a foundry many years ago and I know some complications sometimes arise when all the considered variables were the same. (This was "nodular" or "ductile" iron casting.) So you may also want to also chart the temperature of the melt, ambient air and stack air temp, and atmospheric pressure.

I know this is not real time, and more like statical analysis, but it will improve your process.

Good Luck!

As a surveyor we measure distances constantly with uncertainties in the millimeter range to almost any reflective object (out to about 400 feet). This is done with an LED within our instruments. Perhaps an EDM (Electronic Distance Measuring) device seperated from your furnace by a fused quartz lens might work. I have no idea about the melting temperature of quartz, and I don't know if an EDM would work in the extreme environment you describe. The wavelength of the heated ore might interfere with the light beam generated by the LED in the EDM.

What size is the furnace and the "Heaps" you are working with. Physical attributes may limit your options. May-be some sort of sonic distance measuring device would work. I don't know how precise you need to be or how often you need to take measurements. One could conceivably take measurements about 10-100 times a second if your measuring instrument has a short enough wavelength. Once again the wavelength of the pulse generator and the distance to the Heap may cause physical limitations.

Its seems like it would mean a lot of money to work out a systematic approach to achieving accurate and precise measurements, along with timely and appropriate responses to such variations, throughout your industry.

Your company might even want to seek out an appropriate consultant to address the relevant issues, and offer to install one or more of their more promising possible solutions...

This may be a good application for a gamma radiation / ion chamber level measurement. You mount the source (Cesium 137) to the outside of the vessel and hang a long ion chamber or scintillation counter on the other side. The coal/ore heap will attenuate the gamma signal as it gets bigger, so you have a continuous measurement.

Ultrasound is affected by temperature to tune of 0.18%/°C so you have to compensate for temp fairly accurately, so it may not work in this application.

I was thinking along the same lines, using an isotope to measurer the depth. We do this with coal heaps in the power industry. By placing the source in the bedding material under the coal stack and reading the intensity of the radiation as the stack waxes & wains.

I'm not sure that this would work in a furnace situation as there would be so much background radiation.

I have no doubt that there would be a salesman out there that would be happy to sell you some system but I wouldn't be buying without a demonstration to prove the viability. It should be easy to find someone to demonstrate the viability of their proposal with a demonstration on your furnace or to show it in use at a similar plant.

Hi all,

Thanks for the comments and suggestions, I will keep everything said in mind.

Firstly, to weigh the furnace will not help me, we already know exactly how much material is in the furnace and how much is added. Weigh feeders are used and we have a very fancy smancy accounting balance model. And we know exactly how much is tapped. It is the production tempo that is the unknown, so at the same feed rate we can find that the heaps "grow" and the next day that it "shrink". We would like to keep the heaps constant to ensure stability.

The idea of using isotopes have been in the back of my mind ..... still have to do some homework.

Guest's proposal to get a consultant is against my principle. In this instance myself and the internet is as good a consultant as my company will get. (Technically I am the consultant .... employed to provide solutions).

Regarding the size. The furnace is round with a diameter of 10 meters. The distance from the roof to the top of the heaps is 4 meters. So it is not so huge. But as most of you realised, the temperature is the major factor.

The idea to put a lence between the atmosphere and the probe is not so viable, as the "dirty" atmosphere makes the lense so dirty so fast that it is not a good idea. So the best would be to have a hole, and insert a probe every now and then. That probe can be watercooled to withstand the atmosphere.

Regards,

TC

You've got a fascinating problem there! Wish I could say that I know what you need but I don't, really.

My suggestion about weighing actually doesn't have anything to do with accounting of materials. All you're after is maintaining a constant weight. As melt exits, more raw material is instroduced. The rate that you feed your material should equal the outlet to maintain the weight. The actual weight is irrelevant.

However, caramba's point about the deadweight of the furnace being so much more than the netweight (weight of the materials - both raw and melt) is valid. One way out (which complicates things) is to use a counterweight. This will effectively zero out the deadweight so that all you're left with is the netweight. For a project this size though, I won't be willing to guarantee the results!

Vulcan,

Good point, but what I did not mention is that we do batch tapping. Thus, we tap every two hours and in between we build up material and metal in the furnace.

Another point is that we want the heaps to stay there and to be constant in surface area, so would like to feed more (or less) to maintain that.

Yes, as you said, an fascinating problem. That is why I love my job .... ;)

TC

Hi everybody! As I could realize the weight is not a problem, though additional information along processing won't be superfluous ever.

As regards counterweight, here is a problem:

(i)lever system or something like should be installed on site;

(ii) construction might appear extremely unstable with trend having come into dangerous resonance regime invoked low frequency acting force factors. It brings longterm duration of measuring but without desired accuracy so often.

As for any optic sensor placed at drilled hole. I so sorry about mentioned "optic" but LED sensors have quite wide spectrum frequency range so there would be placed for instance special designed (i suppose infrared) sensor behind isolated screen at furnace's wall hole.

Nontheless idea to employ "isotop" approach looks quite workable though palpable expensive (I've meant not money only)

I do like approach make your work as consultant. Why not? To inflame a great discussion for gathering the best idea. Good Luck!

The extreme environment makes for a real challenge for sensor. It is dirty, it is extremely hot, and it is not a liquid (At least not until you melt it.) Using flow rates is a bit of a challange because it not like you have a metered pump or a flowmeter that can measure what is coming in or out. You just have feed rates.

Being a dirty environment probably precludes optical and ultrasonic. I know UV pulsed lasers have been used in similar applications but you would have to talk to a vendor to see if it would work in your case. You probably have to go with a non-contacting microwave sensor. I would consider nuclear as a last resort.

Here is an example of a supplier for microwave blast furnace "Burden level" sensor.

http://www.vegacontrols.co.uk/application_details.asp?fixedRangeID=01&applicationID=140

Hi,

one solution that will work:

Make a chopped infrared (or visible) light source inside a long tube so that the dust is not blocking the light but blown into the furnace chamber by a slight air feed. Make the diameter of the light bundle by a parabolic reflector some (10 or so)cm.

Select the wavelength so that the dust is not blocking too much of the light (long wavelength recommended.

Attach a second tube opposite and at the end a second (concentrating mirror and a photodetector or a retroreflector (cube corner) and the photodetector in the first tube.

As the heap is growing it will block more and more of the chopped light, easily detected as the detector will see only the chopped light.

Another possibility is by lighting vertical from above and looking at the lighted spot on-top of the heap from 45° with an arrangement that is available for measurement of small distances (mm to cm) by many producers: triangulation sensor. This is imaging the lighted spot on a PSD or a linear photo-diode array.

If you want to buy one i know a commercial source where you can get singular solutions in this field.

RHABE

Caramba, Accudave and RHABE,

Thank you for the comments and suggestions. My solution is slowly becoming more and more defined.

Thanks Caramba for the thoughts on the counterweight. A furnace weighing in the order of 100tons will take a seriously interesting system to make suspended. if we ever go that route you will definitely be in the loop.

Accudave, I had a look at Vega controls, if I look at some of their other applications, then they could be a viable supplier, so i will contact them.

RHABE, interesting concept to use mirrors etc. But at 1500 degrees C I don't think it will be possible. Any visible light is "absorbed" by the atmospheric radiation. Infra Red might work.

Greetings,

TC