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Challenging Material Handling
Problem?....Consider This!
Guest Article by Paul Solt of Pneumatic Conveying Consultants
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There may not be "anything new under the
sun." but this system is really breathtaking. Recently I was privileged to
visit a very unique pneumatic conveying system. I have often been quoted as saying
"You can convey anything" and have sited for some examples 6" x 0"
coal, 3" rocks, moon surface dust, and of course live chickens. But this system
is out of the future and every bit as exciting as any of those.
Consider if you will, a conveying system that
conveys horizontally 30 feet, 180 feet vertical, 395 feet horizontal across a trestle from
one building to another, another 100 feet vertical, then 656 feet horizontal into the
receiving vessel. That in itself may not impress you, but consider the following
requirements. The material being conveyed is 3/8" diameter steel balls.
The system runs continuously. The design rate for conveying is 85 metric ton/hour,
with a capability to reach 150 metric ton/hour.
Why do I say breath taking!
Well,
walking across the trestle a distance of 395 feet at an elevation of 200 feet above the
ground is exactly that. One can not walk the conveying line without being impressed
with the engineering care and design that went into this conveying system.
Oh, did I forget to mention that the steel
balls are at a temperature of 750 degrees C (1382 degrees F)! And there is only a 20o
C loss in temperature from the beginning to the end of the conveying line! Not only
is the conveying line insulated to prevent heat loss, but the insulation is then
surrounded with a second pipe to prevent combustion. You see at this temperature the
sponge iron balls burn, and if there were a hole in the conveying line they would become a
torch and actually burn the conveying line pipe.
Had enough engineering challenges for the
day? Well add some process gas of hydrogen, carbon monoxide, etc.
Also add to
this piping arrangement the requirement to deliver these sponge iron balls to any of three
receivers, thus requiring some form of line diverter, line isolation valves, etc.
Did you ask about expansion joints? Think of the expansion of a straight pipe when
going through 700ºC temperature change and straight lengths of 400 and 650
feet.
How long does the conveying line last?
An interesting point, glad you asked. At lower temperatures, say under 450oC
wear has been measurable by using thickness readings on the pipe wall at expected points
of wear. But as the temperature of the material increases, the wear appears to have
decreased, and it is optimistically said at this point "There is no wear in the
conveying line"!
Does this system sound like a fantasy?
Well it has been operating in excess of one year, without any lost time to the operation
due to the pneumatic transport system. The driving force on this project was the
anticipate cost savings for the steel making industry. By taking the reduced iron
directly from the reactor at 750oC and conveying it to the electric arc furnace
without cooling, the energy required in the electric arc furnace and the cycle time of the
furnace were greatly reduced. This system has shown a profit to the steel plant in
excess of 57 million dollars in one year.
But what did it cost? Over 8 years of small scale
testing, development, design, scale up, retesting, redesigning and many hours of
engineering calculations, conferences, discussions and challenges. It required a
tremendous commitment by the management to invest the money into a system where there was
no back-up. The pneumatic conveying system is the only way to move the product from
the direct reduction furnace. I want to congratulate the men of this plant for their
commitment to a dream, a challenge, a night mare, but most of all to their complete
victory as a reward for unending dedication and commitment to a cause.
Paul, thank you for sharing that with us.
You can visit
Paul Solt's home page by clicking here:
Pneumatic
Conveying Consultants  .
Help others by posting your comments, suggestions and
experiences with bulk solids feeding or any other materials handling concerns you may have
on our On-Line Help Forum. For
past Ask Joe ! Articles, visit the Ask Joe! Archived Articles.
Guest articles for the Ask Joe! Column are always welcome,
for more information please contact Joe Marinelli directly at his email address:
joe@solidshandlingtech.com.
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