CI9-08Article Ride The Wave1
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Transcript of CI9-08Article Ride The Wave1
Ride thhe h igh- temperature mlcro-
wave processing of materials is
becoming an industrial realitY
with the avaiiability of commer-
cial microwave furnaces and the successfui
efforts to develop process know-how by
several advanced technology development
groups worldwide. The impetus for this
development is the realization that high-
temperature microwave processing can be
a faster, greener and cheaper alternative to
conventional electric- and gas-based heat-
ing technologies. Microwave processing is
often preferred over conventional meth-
ods due to substantial economic advan-
tages and comparable or better properties
of the finished product.Historicaliy in the U.S., low-temper-
ature microwave processing has been
used extensively in appl icat ions such as
food and wood processing and drying.
However, to date there are few domestic
h igh- temperal ure com merc ia l microwave
applications. A primary challenge has been
the lack of sophisticated high-temperature
rnicrowave furnaces.This obstacle is being overcome through
the availability of new high-temperature
automated microwave furnaces, including
the la test cont inuous microwave pusher
system.- Wi th a footpr i r r t in the range o l
2 x 6 to 2 x 18 m, the sYstem's maximum
output power is 9-36 kW. The maximum
temperature is 1500'C, and processing
atmospheres can be air, nitrogen' inert
gases and mixtures. This industrial micro-
wave system offers advanced industrial
direct energy transfer technology and high
efficiency that enables ceramic and metal
parts to be processed at a fraction of the
time and cost of conventional kilns.
6nl n g 6 r#en, i ilipl r.,rr*rliil g {}lal'i'y
A major advantage of high-temperature
microwave systems is their "green' nature.
Microwave furnaces generally heat oniy
the objects to be processed, not the fur-
nace walls or atmosphere. Energy-efficient
microwave furnaces produce a substan-
tially smaller carbon footprint, less poliut-
ants, and lower operating and end-prod-
uct costs. In addi t ion, microwave Process-ing can involve up to 90olo shorter process-
ing times and a corresponding decrease of
up to 80o/o in energy consumption when
compared with conventional methods for
many commercial Products.Microwaving can also yield improved
product quality with finer grain size,
higher sintered density, increased corro-
sion resistance, and greater strength of
finished parts. These advantages can be
obtained with ceramics, a range of pow-
dered metals (such as titanium, tungsten,
molybdenum and steels), and "hardmet-
als" like tungsten carbide.
> High-temperaturemicrowave processingcan be a faster, greenerand cheaper alternativeto conventiona[ electric-and gas-based heatingtechnologies.
by K. Cherian,l M.KirkseY,lP.Hu,2 L. Hurtt,2 J. Cheng,3D. Agrawal3 and R. RoY3
With the realization of not only the
technical but also the substantial economic
advantages h igh- temperal .ure microwave
processing offers, the implementation of
this new processing method began mostly
in ceramics and related industries, includ-
ing advanced ceramic/carbide wear parts,
electro-ceramics and bio-ceramics. Subse-
quently, microwave processing has begun
to migrate to other industries' such as
powder metallurgy, waste remediation,
and mater ia ls symthesis/microwave chem-
istry applications.
. . 1 | : ! ' ; ' i . '
In Iune 2006, Pennsylvania State Univer-
sity hosted the National Academy. of Engi-
neering Regional Meeting on "Immediate
Energy Savings via Microwave Usage in
Maior Materials Technologies." Several
leading microwave research, development
and application groups from Asia' Europe
and the U.S. presented reports detail ing
the technical and economic advantages
and energy savings achieved through their
implementat ion of m icrowave processing
technologies in industrial applications.For t radi t ional ceramic s inter ing,
Japan's National Institute of Fusion Sci-
ence reported that microwave use enabled
the reduction of processing time from
8 to 2 hours, energy consumpt ion reduc-
tion from 335 to 63 KWh, and reduction
I1.Spher icTechnotog ies ,Phoen ix ,Ar iz .2 .Syno-ThermCo.L td ' ,Changsha,Hunan,PR Ch ina '
3. Microwave Processing & Engineering Center, Pennsytvania State University' Pa'
16 Sep tember 2008 L www.CERAMIC INDUSTRY 'COM
ofenergy cost from $14 to $7 per batch. In the case oflarge-partalumina (up to 60 cm diameter), the sintering time was reducedfrom 96 to 20 hours, energy consumption from 5000 to 484 k\,Vhand energy cost from $420 to $70 per batch.
Successful pilot-scale investigations have been completed in
fapan for using microwaves in steel production. The U.S. Depart-ment of Energy estimates that conversion of domestic steelmak-ing from conventional to microwave-assisted processing wouldsave up to 14 million tons of coal burned for energy, thus reduc-ing pollutant emissions by over 30 million tons of carbon mon-oxide and carbon dioxide annualh
Total processing timewas decreased from 1-500hours using corrventionalprocessing to around 50hours with a microwave-
assisted route.
Britain's Loughborough University investigated microwave-assisted hybrid processes for the sintering and chemical vaporinfiltration (CVI) of ceramic matrix composites (CMCs). Fora 13-mm-thick woven fabric preform, the total processing timewas decreased from 1500 hours using conventional processing toaround 50 hours with a microwave-assisted route.
Canada's Ontario Energy Agency estimated that if the ceramicindustry started using microwave instead of conventional processesfor various ceramic products, the industry would save 412 millionKWh per year, or the equivalent of one 350 MW coal-fired powerplant. When extrapolated to all applications in North America,annual energy savings could be measured in Gigawatt hours.
The Penn State Microwave Processing and Engineering Cen-ter cut the sintering cycle time for cemented carbides from 2.5hours to 15 minutes, producing parts with improved abrasionand corrosion resistance. This has now developed into a frrll-scalecommercial technolo gy.
Additional studies comparing high-temperature microwaveprocessing with traditional methods have been carried out for anumber of applications and are summarized below.
PTC Electronic Ceramic Heating Parts
ConventionalFootprint (square meters) 50Furnace hotding power (kW) 35Power consumption (kWh/10,000 pieces) 300Productivity (pieces/year) 24 mittionEnergy costs per 10,000 pieces (@ $0.1/kwh) $lOAnnuaI maintenance costs $3750Total savi n gs/ y ear (24 m illion pieces) : 548,000
MicrowaveI O
1,2100
24 milt ion$ro
$3750
Footprint (sq uare meters)Furnace input power (kW)Power consumption (kWh/ton of product)Productivity (tons/year)Energy costs per ton of product ($0.1/kwh)
Total savings/year (100 tons): S70,000
Footprint (sq uare meters)Furnace input power (kW)Power consumption (kWh/ton of product)Productivity (tons/year)Energy costs per ton of product ($0.1/kwh)
Total savings/year (200 tons): 596,000
120180
9000100
$9oo
100100
6000200
$ooo
4050
2000100
$200
4024
1200200
$120
Footprint (square meters) 200Furnace input power (kW) 550Productivity (tons/yeaO 2ooPower consumption (kWh/ton of product) 13,500Nitrogen gas consumption (m3/hr) 240Annual maintenance costs $150,000Energy costs per ton of product ($0.1/kWh) $fffOAnnual maintenance costs per ton of products $750Nitrogen gas use per ton of products $tOll
Total savings/year (200 tons): 5358,800
6080
1004500
60$37,500
$4sb$tts$sre
The debinding and sintering of positive temperature coeffi- AluminaGrindingSandscient (PTC) electronic ceramic heating parts was carried out in For alumina grinding sand processing with microwaves, thea continuous tunnel microwave furnace. Each PTC ceramic part required microwave sintering temperature was lower (by approx-weighed 7 g and the maximum temperature used was 1240'C. imately 100"C) and the hold time significantly shorter (by about*SPHERIC/SYNO-THERMTM computer-controlled microwave furnace with the AMPS pusher system,marketed in the U.S. by Spheric Technologies, Phoenix, Ariz..
The product quality was found to be as good as that in parts sin-tered by a conventional furnace.
For an annual production level of 24 million pieces of theproduct, lab/field trials demonstrated potential yearly savings ofapproximately $48,000 by using a microwave processing routerather than a conventional processing route. Additional compar-ative data is detailed in Thble 1.
Conventional Microwave
ConventionaI Microwave
Conventiona[ Microwave
CERAMIC INDUSTRY ) Seotember 2005 17
RIDE THE WAVE
ffi suNRocK cERAMtcsSpecia/ists in hish alumina kiln furniture
Saggers, setters, tile, rings/disks& pusher plates
-MW -Conv
Sunrock Geramlcs ComPanY, LLC2625 S. 21-st Ave. Broadview, lL 60155PH: 708.3 44.7 600, FX: 708.34 4.7 636
Time {Hrsl
Figure 1. Alumina gr inding sand processing.
-MW -Conv
1400
1200
1000
800
600
400
200
0
Tim€ {Hrs}
Figure 2. Ni-Zn ferrite parts sintering.
-MW -Cony
part
L8001600
O 1400
; 1200
E 1000
$ sooE U U U
f +oo200
0
U
o
o
Eo
€
Eo
F
1600
14001200
1000800
600
40c
200
T ime lHrs ) : : i : .
Figure 3. Vanadium nitride synthesis and sintering.
one-sixth) in comparison to a conventional continuous sinter-
ing furnace for a similar product. The overall process time' from
room temperature to room temperature' was reduced by more
than660/o (see Figure l). Table 2lists additionalbenefits..)
Ni-Zn Ferrite PartsIt was found that the required microwave sintering temperature forr
Ni-Zn ferrite parts was lower (by about 100oC), and the hold time
was significantly shorter (by approximately one-third) in compari-
son to a conventional continuous sintering furnace for a similar
product. Figure 2 illustrates the 50% reduction in overall process
time that resulted with microwave processing. For an annual pro-
duction of 200 tons of Ni-Zn ferrite parts, lab/field trials demon-
strated that a potential savings of $96,000 could be achieved by uti-
lizing microwave vs. conventional processing (see Table 3).
4 to 6 week standard lead time
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Vanadium NitrideVanadium nitride (VN) synthesis andsintering through microwave process-ing was also investigated. The requiredmicrowave sintering temperature waslower (by - 50 'C) and the hold t imewas s igni f icant ly shor ter (about one-s ix th) compared to a convent ionalp rocess ( l i ke a tmosphe r i c p ressu recarbothermic reduction) for a similarproduct. Microwave processing reducedthe overall process time by at least 50olo(see Figure 3) , and potent ia l savingscould reach $358,000 per year for anannual production of 200 tons. Table 4lists additional details.
A Hot FutureHigh-temperature microwave process-ing can provide substantial economicand envi ronmental advantages overt radi t ional processes as a resul t o f acombination of several factors, includ-ing reduced processing t imes, lower
processing temperatures, reduced con-sumable costs in cer ta in cases, fewerp o l l u t a n t s , a n d e n e r g y s a v i n g s - i naddi t ion to improvements in prod-uct propert ies. Also, the appl icat ionof microwaves involves substantiallyreduced or near-zero product ion ofenvi ronmental ly harmful emiss ions,the reby mak ing th i s an env i ronmen-tally friendlier-or "greener"-tech-
nology as well.With a smaller physical footprint and
a substantially smaller carbon footprint,microwave furnaces offer lower operat-ing and end-product costs. Thus, micro-wave processing technology is a faster,greener and more energy-efficient alter-native for industry. @
For more information regarding microwayeprocessing contact Spheric Technologies, Inc.at 4708 E. Van Buren St., Phoenix AZ 85008;(602) 2 1 S-9292; e-mail [email protected];or visit www. SohericTbch. mm.
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CERAMIC INDUSTRY l September 2008 t9