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Chemical Engineering Journal 172 (2011) 835 846
Contents lists available at ScienceDirect
Chemical Engineering Journal
j ourna l ho mepage: www.elsev ier .c
Activated carbon from co-pyrolysis of particle boformal ati
K. Vanre pera NuTeC, Deparb Research Gro 3590 c Research Grou
3590 D
a r t i c l
Article history:Received 8 April 2011Received in revised form 22
June 2011Accepted 23 June 2011
Keywords:PyrolysisActivated carbEconomicsParticle boardMelamine
form
The disposal and environmental problems associated with waste
resin produced during the productionof melamine (urea) formaldehyde
and wood waste (i.e. particle board) containing these
aminoplastsrequires a processing technique which results in
products of added value and which meets both ecologicaland
economical needs. Several published results demonstrate that
nitrogen incorporation in activatedcarbon can play a signicant role
as a key parameter for the adsorption properties, as well as for
the
1. Introdu
During t(both furthboard (PB) cannot be r
In additition) of wocause pollu
CorresponE-mail add
[email protected]@sonja.schreurs
1385-8947/$ doi:10.1016/j.on
aldehyde
catalytical activity and the dispersion of carbon supported
catalysts.The production of high value nitrogenised activated
carbon, after thermal treatment in an oxygen
decient environment and subsequent activation, is considered as
a possible opportunity.This research paper investigates the
feasibility of a process design for the production of a high
added
value nitrogenised activated carbon by co-pyrolysing a mix of
particle board and melamine (urea)formaldehyde waste. A process
design and an economical model for estimating the total capital
invest-ment, the production costs, the possible revenues, the net
present value and the internal rate of return isdeveloped based on
various literature sources. In addition, Monte Carlo sensitivity
analysis has been car-ried out to determine the importance of the
main input variables on the net present value. It is assumedthat
the manufacturing facility obtains its waste from various sources
and operates continuously during7000 h a year. The study
investigates the plants protability in function of processing rate
and mixingratio.
Even though the current assumptions rather start from a
pessimistic scenario (e.g. a zero gate fee forthe melamine (urea)
formaldehyde waste, a rst plant cost, etc.) encouraging results for
a protable pro-duction of activated carbon are obtained. Moreover,
the ability to reuse two waste streams and possibleproduction of a
specialty carbon enhances the value or usefulness of the activated
carbon manufacturingfacility.
2011 Elsevier B.V. All rights reserved.
ction
he production of melamine (urea) formaldehyde resinser
abbreviated as MF) for the production of particlea considerable
amount of waste resin is produced thate-used or recycled at this
moment.on, classical thermo-chemical conversion (e.g. combus-od
waste containing these aminoplasts resins mighttion because it
results in the production of toxic gases
ding author. Tel.: +32 11 2 68 320.resses:
[email protected] (K. Vanreppelen),uhasselt.be (T.
Kuppens), [email protected] (T. Thewys),uhasselt.be (R.
Carleer), [email protected] (J. Yperman),
@xios.be (S. Schreurs).
like ammonia, isocyanic and hydrocyanic acid and nitrous
oxides[13].
A sustainable solution is more and more required to avoid
envi-ronmental problems and landlling costs, and to turn this
wastestream in a rather protable material resource. A possible
oppor-tunity, is the production of high value activated carbon (AC)
afterthermal treatment in an oxygen decient environment and
subse-quent activation.
ACs are produced for a large number of dedicated
applicationsboth as structural and functional materials. ACs are
generally usedfor air, water and gas purication, chemical and
pharmaceuticalprocessing, food processing, decolourization, solvent
vapour recov-ery, llers in rubber production, refractory materials,
catalysis andcatalyst support [46].
Marsh and Rodriguez-Reinso [5] estimated the world
annualproduction capacity of AC to be around 400 kt in 2006,
exclud-ing countries without accurately known gures like China
and
see front matter 2011 Elsevier B.V. All rights
reserved.cej.2011.06.071dehyde resin: A techno-economic evalu
ppelena,b, T. Kuppensc, T. Thewysc, R. Carleerb, J. Ytement TIW,
XIOS, Agoralaan Gebouw H, 3590 Diepenbeek, Belgiumup of Applied and
Analytical Chemistry, CMK, Hasselt University, Agoralaan Gebouw D,p
Environmental Economics and Law, CMK, Hasselt University, Agoralaan
Gebouw D,
e i n f o a b s t r a c tom/ locate /ce j
ard and melamine (urea)on
manb,, S. Schreursa
Diepenbeek, Belgiumiepenbeek, Belgium
-
836 K. Vanreppelen et al. / Chemical Engineering Journal 172
(2011) 835 846
some other Eastern countries. Furthermore the market is
increasingconstantly, due to the environmental awareness and the
growingindustrialization. Girods et al. [7] expect a growth of
5.2%/yearto 1.2 Mt by 2012. In Europe, Japan and the USA the growth
is15%/year, countries. Tduction cosspecial carbet al. [7]
staproducers w
The widof pores, hiACs. The nrial and thethat the phenced by
thetc. In normligible [4,6]positive effeadsorption acid gases
lpounds [2,3role for thecatalysts [9genised act(2.0 kEURbetween
0.8ing to Infomsaturated cato 6.0 kEURimpregnati
Becauserials result and activatis consideranitrogen comaterials
hcost [1] for ter does noMF waste, bmaterial.
The objerendering tFor this purcarried outduction of diagram
ofwith physicgenerated bhas been caAC has beenforming Moeconomic
fethe protab
2. Process
The prelPB waste ccan be diviand packagtion facilitysize (a few
cult to predet al. [2] de
Next, the grinded and dried waste will be transported to a
rotarypyrolysis furnace (operating at 800 C). Here the waste is
pyrol-ysed in an oxygen-free environment for a few minutes (25
min).The developed chars (solid fraction) are then transported to a
sec-
tary mperThe t conrolysy mate hnd aclonC wit
harm mullled is is s a hefter c
screr wa. A pon can thient
ens e
nom
r capn orent
t or i ma, the
are uivatioestm
valuvest
calcu
Tn=1
h:
cashitiale lifescoun
sh o expulatecounns etulate
(1 tscouthe on pre spe MFwhereas this rate is much higher in the
developinghe price of AC is a function of demand, quality, pro-t,
etc. A typical price range is 1.46 kUSD/t, but for veryons the
price can increase to 20 kUSD/t [5,8]. Girods
te that the average production cost of AC from the majoras on
average 2.5 kUSD/t.
e range of applications exists thanks to the high volumegh
surface area and the variety of surface chemistry ofal properties
of the AC are related to the precursor mate-
activation process (physical or chemical). It is
statedysicochemical properties of the ACs are strongly inu-e
presence of heteroatoms like oxygen, nitrogen, sulfur,al conditions
the amount of nitrogen in the AC is neg-. Several published results
however, demonstrate thect of nitrogen incorporation as a key
parameter for theproperties of the AC [9], especially for the
removal ofike hydrogen sulde, sulfur dioxide and phenolic com-,7].
Nitrogen incorporation can also play a signicant
catalytic activity and dispersion of carbon supported].
According to Girods et al. [2] the value of such a nitro-ivated
char from PB (in 2006) is on average 2.5 kUSD/t/t), whereas normal
ACs are sold (in 2008) at prices
kEUR/t and 1.7 kEUR/t (1.22.5 kUSD/t) [10]. Accord-il [10],
impregnated ACs (i.e. including pick-up of therbon) have a higher
selling price (in 2008) of 4.0 kEUR/t/t (5.98.8 kUSD/t) due to
higher costs incurred by theon step.
the chemical properties of the PB and MF waste mate-in in situ
nitrogen incorporation during char formationion, the production
cost of nitrogenised activated charbly reduced in comparison with
post impregnation ofntaining components on AC. In addition, these
wasteave the economic advantage of representing a negativea waste
processing company, which means that the lat-t have to pay for
obtaining resources such as PB andut instead receives a gate fee
for processing the waste
ctive of this work is to identify the crucial variables forhe
production of AC from PB and MF waste protable.pose, a preliminary
economic feasibility study has been
for a process design especially developed for the pro-AC from PB
and MF waste. After developing a process
an AC production technique (co-pyrolysis combinedal activation),
the net present value of the cash owsy an investment in
co-pyrolysis and char activationlculated. The minimum selling price
of the produced
determined, taking into account uncertainties by per-nte Carlo
sensitivity analysis. Finally, this preliminaryasibility study is
used to identify the key variables forility of the production of AC
from PB and MF waste.
design
iminary process design for the production of AC fromo-pyrolysed
with MF is shown in Fig. 1. The processded in four parts:
pretreatment, pyrolysis, activationing. After shipping the raw
materials to the AC produc-, they are rst mixed and milled into a
smaller particlemillimetre), dried and transported to a silo. It is
dif-ict the moisture content of the incoming waste. Girodstermined
the moisture in wood board to be about 7%.
ond roat a teagent. rate buthe pypied badequagases aby a
cy1000
tion ofusing acontrobut thused aator.
Abeforerecovecardedemissirated iequipmLemm
3. Eco
Pooity of ainvestmprojecgorizedcriteria(IRR), sis/actan
invtodaysof an inNPV is
NPV =
Wit
- CFn =- I0 = in- T = th- i = di
The ca(R) andTo calcinto acKuppebe calc
CFn = The dirating Taxes The lifBecauskiln furnace where they
are activated during 30 minature of 800 C in the presence of steam
as activationpyrolysis and activation are carried out in two
sepa-nected furnaces to achieve a continuous system. Both
is and activation kiln have a cross-sectional area occu-terial
which is 10% of the cylinders length to ensure aneat transfer and
mixing [11,12]. The produced pyrolysiserosols are conducted to a
thermal combustor followede for complete combustion at a
temperature of aroundh a residence time of at least 2.5 s. This
reduces forma-ful compounds or promotes their breakdown [13].
By
tiple zone oxidizer the formation of NOx can be furtherby
managing the oxygen inow in the different zones,not implemented at
this stage. The hot ue gases areat source for pyrolysis/activation
and the steam gener-ooling, the produced AC is transported to a
storage siloening and packaging. The remaining gases are cooled
toter from the steam generator. After cooling they are
dis-elletisation device and an extra gas cleaning unit beforen also
be installed, but are at the moment not incorpo-s analysis. The
possible extra investment costs for this
can be found in recent literature e.g. Lima et al. [11] andt al.
[14].
ical feasibility model
ital investment decisions can alter the future
stabil-ganisation. Investors deal with this problem by using
decision rules which evaluate the protability of thenvestment.
Biezma and San Cristbal [15] have cate-ny various investment
criteria methods. Two of these
net present value (NPV) and the internal rate of returnsed to
evaluate the economics of the MFPB pyroly-n. The NPV is the best
criterion for selecting or rejectingent, either industrial or
nancial [16,17]. The NPV ise of current and future cash ows, which
are the resultment using a predetermined discount rate [17,18].
Thelated with Eq. (1) [1720].
CFn(1 + i)n I0 (1)
ows generated in year n; total capital investment (see Table 1,
row 19) in year 0;
span of the investment;t rate.
w in a given year is the difference between revenuesenditure (E)
after tax (t) generated by the investment.
the cash ow, depreciation (D) also needs to be takent because it
lowers tax payments [19,20]. According to
al. [19] and Thewys and Kuppens [20] cash ows cand using the
following equation:
) (R E) + t D (2)nt rate of the invested money is set at 9%
incorpo-market interest rate and some risk premium [19,21].ots to
be paid amount up to 33% in Belgium (t = 0.33).an of a reactor is
described as 20 years [19,20,22].
is easy to coke, all the results are based on a rather
-
K. Vanreppelen et al. / Chemical Engineering Journal 172 (2011)
835 846 837
low averagthe year (ogeneral, whsion.
The IRR expected caexpected cacount rate tin nancialcan expect
the requirerejected.
itionhis e NPVrderonte
is repdompose
Table 1Multiplying fa
Direct costs
Indirect cost
Fixed-capitaWorking captotal capital Total capitalFig. 1.
Process ow.
e operating time of the reactor of 7000 h, the rest ofr 20% of
the year) is used for maintenance etc. Inen the NPV is positive,
the investment is a good deci-
is the discount rate (i) at which the present value ofsh inows
from a project equals the present value ofsh outows of the project.
In other words, it is the dis-hat makes the NPV equal to zero. It
is frequently used
Addlated. Tthat th
In oNPV, Manalysous ranpresup markets because it gives the
return that the investorfor a given level of risk [17]. If the IRR
is lower thand return (discount rate) then the project should
be
in a distribuncertaintyrespondingfor the tota
ctor for the delivered-equipment cost.
Cost component
Delivered equipment InstallationPiping (installed)
Instrumentation and controls (installed) Electrical systems
(installed) Buildings (including services) Yard improvements
Service facilities (installed) Land Direct plant costs (DPC)
s Engineering, supervision Construction expenses Legal
expensesContractors fee Contingency Indirect plant costs (IPC)
l investment ital (15% ofinvestment)
investment ally the minimal selling price of the AC has been
calcu-is the minimal price at which the AC should be sold so
breaks even or in other words the NPV equals at least 0. to have
an idea about the impact of uncertainties on the
Carlo sensitivity analysis is performed. The sensitivityeatedly
calculates the NPV corresponding to numer-
draws for the value of uncertain variables following ad
distribution. Monte Carlo simulations typically result
ution of NPVs that can be declared by the degree of
of each individual variable. Each variable with its cor- range
of values and distribution is partly responsiblel uncertainty of
the NPV. The variables with the high-
Percent of equipment cost
100393126102912556
308
32344
1937
126
43476
509
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838 K. Vanreppelen et al. / Chemical Engineering Journal 172
(2011) 835 846
est inuence on NPV sensitivity should be identied and shouldbe
the subject for further research so that they can be controlledwhen
putting the project into practice. In our study 10 000 runs
arecarried out using the @Risk software from Palisade Decision
Tools.
Finally, when calcushould be sNPV.
4. Model a
The rsttial investmanalysis, thused, with a
Before asum of moequipment The total cabuilding itsing,
electricalso indireccosts for enof these inthe direct pcapital
inveraw materiabe added foing capital as a
percendetermineddisplayed in
All costsexchange raMarshall an
Cost of Equi
4.1. Total ca
The totaby the Percement cost inery allowan
One of talways avaitions can befactor rule aeven total p
Eq (YCh
Cost of unit
The actual from less ththe capacitypyrolysis fa
used as suggested by Henrich et al. [28], Tock et al. [29] and
Gassnerand Marchal [30].
The equipment cost of the pyrolysis and activation reactor(which
is on its turn a pyrolysis reactor) is derived from the
apital investment (FCI) of a pyrolysis plant presented byater et
al. [22] in Eq. (5) with Qfeed input pyrolysis the owf the feed
(ton dry matter per hour):
olysis plant = 40.8 103 (Qfeed input pyrolysis 103)0.6194
(5)
calculates the cost of the fast pyrolysis reactor, the feed-tem
and liquids recovery. Eq. (5) is a result of a regression4 cost
data preformed by Bridgwater et al. [22], and the dataumed to be
rst plant costs from a novel technology. This isant, because there
can and probably will be a considerableduction from the learning
effect. Henrich et al. [28] state
the same type of facility is designed, built and operatedl
timlly w28], two-
usedent
ausete thent
ridgwdirecidgwnd inn, 315% fes foping
the
ent
so imr is re7):
put act
h YCin Tar in tm thsis an) to fo
ect pla + 10ect plathese uncertainties have been taken into
accountlating the minimum selling price at which the ACold in order
to guarantee a 95% chance on a positive
ssumptions
step in NPV calculation is the estimation of the ini-ent
expenditure. For preliminary economic feasibility
e Percentage of Delivered-Equipment cost is commonlyn expected
accuracy of 2030%.n industrial facility can be put into operation,
a largeney needs to be spent on the necessary machinery,and their
delivery: i.e. the cost of delivered equipment.pital investment
however also consists of costs of theelf, the land on which the
equipment is installed, pip-al systems, etc. These are all direct
plant costs. Butt plant costs have to be taken into account: such
asgineering, legal expenses, contingencies, etc. The sumvestment
costs, i.e. the cost for delivered equipment,lant costs and the
indirect plant costs are called xed-stment. The amount of money
required for a stock ofls and cash kept on hand, i.e. the working
capital, shouldr estimating the total capital investment. The
work-and the direct and indirect plant costs are expressedtage of
the delivered equipment cost. The percentages
by Peters et al. [23] are used in the calculation and are Table
1.
have been updated to 2009, based on the US Dollar/Eurotio
provided by the European Central Bank [24] and thed Swift Index
[25] (see Eq. (3)):
pment (2009) = cost of Equipment (year)
Cost index (2009)Cost index (year)
(3)
pital investment
l investment cost for production of the AC is determinedntage of
Delivered-Equipment cost method. The equip-formation was provided
by literature (Table 2). A deliv-ce of 10% on the purchased
equipment cost is used [23].he problems in cost estimating is that
cost data are notlable for the particular size or capacity
involved. Predic-
made by using Eq. (4) which is known as the six-tenthsnd is
widely used in approximations of equipment androcess costs
[23].
uipment cost reactor = 40.8 103[(Qfeed input pyrolysis 103)
0.6194 +490.1%
(new) = cost of unit(ref.)
(
capacity (new)capacity (ref.)
)capacity exponent(4)
value of the cost capacity exponent in Eq. (4) can varyan 0.3 to
greater than 1.0. Yassin et al. [27] stated that
exponent is in the range of 0.60.8 for gasication andcilities.
In this calculation a capacity exponent of 0.7 is
xed-cBridgwratio o
FCI pyr
Eq. (5)ing sysfrom 1are assimportcost rethat, ifseveranentiaet
al. [about cost isinvestm
Beccalculainvestmcost. Bof the that Brbe fouerectiotems,
5expensand picost of
Equipm
It is alreactoin Eq. (
Qfeed in
Witfound reacto
Fropyroly(5)(7
1
Dir31%
Dirar Qfeed input pyrolysis 103)0.6194
(8)
es the investment and operating costs decrease expo-ith the
number of built plants. According to Henrichit is reasonable to set
the total capital investment atthirds of the rst plant cost. In
this paper the rst plant. Therefore, it may be inferred that a
rather pessimistic
cost scenario is applied. Bridgwater et al. [22] used other and
less factors toe indirect plant cost and direct costs, the xed
capital
of the pyrolysis plant is recalculated to the equipmentater et
al. [22] stated that the total plant cost is 169%t plant cost. The
percentages of the direct cost factorsater et al. [22] used are not
dened, but the factors can
Peters et al. [23]. So they are assumed to be 39% for% for
piping, 26% for instruments, 10% for electrical sys-or civil works
and 29% for structures and buildings. Ther lagging are included
under the equipment installationcosts like Peters et al. [23]
suggested. The equipmentpyrolysis reactor can thus be calculated by
Eq. (6).1
cost pyrolysis reactor = Direct plant cost290%
= FCI pyrolysis plant490.1%
(6)
portant to note that the feed input of the activationlated to
the feed input of the pyrolysis reactor as dened
ivation = YChar Qfeed input pyrolysis (7)
har the char yield from the pyrolysis step which can beble 4 and
Qfeed input activation the input of the activation/h dry matter.e
foregoing discussion the total equipment cost for thed activation
reactor can be calculated by combining Eqs.rm Eq. (8).
nt cost = equipment cost pyrolysis reactor (100% + 39% + 26%+% +
29% + 55%) = 290% equipment cost pyrolysis reactor)nt cost = FCI
pyrolysis plant
169%
.
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K. Vanreppelen et al. / Chemical Engineering Journal 172 (2011)
835 846 839
Table 2Major equipment cost an their scaling factors used.
Item Sizing parameter Unit cost year Reference
Crusher 2 t/h 44.94 kUSD (2002) [13]Dryer 10 t/d 51.27 kUSD
(2002) [13]Silo (raw material) 500 m3 380 kEUR (2009) [26]Nitrogen
storage tank 1.92 m3 19.26 kUSD (2002) [13]Pyrolysis and activation
reactor / Eq. (8)Steam boiler and condenser 3781 kg/h 116.84 kUSD
(2002) [13]Thermal combustor 1000 N m3/h 40 kEUR (2004) [14]Cyclone
1000 N m3/h 1.5 kEUR (2004) [14]Silo (activated carbon) 500 m3 380
kEUR (2009) [26]Screening and Grading 139.9 kg/h 25.0 kUSD (2005)
[11]Packing of activated carbon 139.9 kg/h 25.0 kUSD (2005)
[11]
The formula is used in the assumption that condensable
gases(pyrolysis liquids) will not be condensed (i.e. direct
diversion to thecombustion system), but instead the AC needs to be
cooled. There-fore it is assumed that the cost of the liquids
recovery of Bridgwateret al. [22], is the same as for the AC
cooling.
The produced gases can be considered as a mixture of
ammable(toxic) comenvironmencombustiopounds. Thbe performa cyclone.
Ttained at reduces thewill be destthrough a cLemmens eWith a
max1000 N m3/respectively
4.2. Expend
The totacost and thassumed thyearly interBelgostat [3than 5
yearan amountof 4.0% is apcosts of pyinsurance, oare
generalinvestment
A summary of literature percentages to calculate the
annualoperating cost is displayed in Table 3.
In this model, the annual maintenance cost is accounted for
3%,the annual overhead and insurance cost for 2% of the total
xed-capital investment. The cost for maintenance labour is
incorporatedin Eq. (9) (Labour cost) [19,20].
labo2]. T
/h) Q
cost
onomyed R in uros
to bed thAC pr
delie MFaid, DispR/t (aste cilitys tha
the io.rovi
as a put (gwa
the
Table 3Summary of th
Annual oper
Maintenance
Insurance
Insurance an
Overheadspounds at enhanced temperature. From an energy andtal
point of view there is a need to (re)use this heat orn energy and
decompose or separate the toxic com-ermal treatment of the volatile
combustible gases willed by a direct red thermal oxidizer combined
withhe temperature of the combustion chamber is main-1000 C with a
residence time of minimum 2.5 s. This
formation of NOx and harmful materials, like dioxins,royed [13].
For complete combustion, the ue gases passyclone where possible
solid particles are separated out.t al. [14] calculated a cost
estimate for these systems.imum cost of 40 kEUR and 1.5 kEUR for a
gas stream ofh for the combustion chamber and the cyclone is
used.
iture
l expenditure of the project consists of the operatinge yearly
interest payments. Thewys and Kuppens [20]at an investment is
nanced by means of a loan with aest of 4.60% in Belgium. The
macro-economic database1] gives an average initial interest
provision for mores of 3.9% on new credits (in 2009) for the euro
area for
of more than 1 MEUR. In this model an interest rateplied as a
realistic compromise. The annual operating
rolysis and activation consist of maintenance, labour,verhead,
delivered feed, energy and water costs whichly expressed as a
percentage of the total xed-capital
[20] except the last three items.
Theet al. [2feed (t
Labour
FPS Ecemplo48 kEUfrom Ematedassumof the
Theand th[7] is pplant. 220 EUthis wtion fapay
lesmodelscenar
To pto act feed in
Bridcooling
e xed annual operating factors.
ating cost Expressed as
3% of xed-capital investment
5% of xed-capital investment (for a gasication sy3% of
xed-capital investment (for a combustion p4% of xed-capital
investment 6% of xed-capital investment 2.5% of xed-capital
investment 2% of xed-capital investment
2% of xed-capital investment 1% of xed-capital investment
d general 1% of xed-capital investment
4% of xed-capital investment 2% of xed-capital investment ur
costs are calculated with Eq. (9) based on Bridgwaterhe calculation
is in function of the ow rate of the dryfeed input pyrolysis and
will always be rounded up.
= 1.04 ([1 + YChar] Qfeed inputplrolysis)0.475 3shiftsannual
salary (9)
y [36] states that the annual salary of one person,in the
industrial sector in Belgium was on average2004. By using the
annual nominal unit labour cost datatat [37] the average annual
salary in industry is esti-e around 55 kEUR in the year 2009. In
this model it isat 3 shifts are sufcient for a good and secure
operationoduction facility.vered feed cost consists of the cost of
the PB waste
waste. For processing PB waste a gate fee of 70 EUR/twhich is an
incoming cash ow for the AC productionosing of MF waste to a landll
site costs a MF factoryincluding transport) in Belgium. This could
mean thatalso represents an income stream for the AC produc-, as
the MF factory is already satised when it has ton 220 EUR/t for
disposing its MF waste stream. In thiscost of the MF is set at 0
EUR/t to have a worst case
de an oxygen free environment, nitrogen gas is appliedpurging
gas. In this study a rate of 8 kg nitrogen gas/tbased on [35]) with
a cost of 2.5 EUR/kg is applied.ter et al. [22] used 18.5 m3
water/t input material forproduced pyrolysis liquid and Ko et al.
[35] used 13.5 m3
Reference
[19,20,32,33]
stem) [13,27,30]rocess) [27]
[34][35][22][11]
[20,33][35]
[32]
[34][20,33]
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840 K. Vanreppelen et al. / Chemical Engineering Journal 172
(2011) 835 846
Table 4Estimated costs and yields of the input feed.
Ratio (MF/wood) 4 MF1 PB 3 MF2 PB 2 MF3 PB 1 MF4 PB 0 MF5 PB
Yield Chara 22% 29% 36% 43% 50%Yield active carbona (vis--vis
char) 44% 45% 47% 48% 50%
a Girods et al. [7] determined the carbon yield after pyrolysis
(400 C) typically 50% and again 50% after pyrolysis combined with
steam activation (800 C).Own laboratory experiments on MF give a
yield of 15 and 42% respectively (800 C).
water/t input material to generate steam for the activation
andcooling water for the produced pyrolysis liquid. The quantity
ofcooling water (from surface water 20 C) needed to cool the
pro-duced AC from 800 C to 20 C is 13 t/h. In this calculation it
isassumed that the specic heat capacity of AC is equal to the
specicheat capacity of graphite (709 kJ/(t C)) and the maximum
tem-perature of
dened by are assume1.5 EUR/m3
Anothersplit in twomated thatelectricity. consumptioity is set
atsolid wastebiomass a rture [3942and the actalso neededFor the
dryIn most pyrrequired hethe char. Inonly AC anbe thermallsented
modis assumed.
4.3. Revenu
It is expeand 4.5 kEUprocessing MF resin an(see Table
4incurred.
Table 4 shown thatin the mixtratio and th
In someical (gover. . ., recover
production of green electricity and heat. However, these are
nottaken into account in this process because these are mostly
meantas temporary regulations, which differ from country to
coun-try.
5. Results and discussion
onom
NPV Fig
The ted in
us a lnd onsatghere (4tal oalys
ing c PB
minoduc
shaeeds
kEUR0 MF.y thee disF5
ccepsharePB) alear vbles ixturows en se
price NPVs a o bre
Table 5Summary of co
1 t/h F3 P
Total capital 263 kEOperating co 641 kEGate fee deliTotal
operatProduced acMinimal sell cooling water that needs to be
discharged is 30 C asthe Belgian legislation. Here, the water
requirementsd to be 15 m3 water/t input material with a cost
of.
utility required in the process is energy which can be parts,
power and heat requirements. Ko et al. [35] esti-
a 1.25 t/h processing plant producing AC uses 200 kWSo it is
assumed that for a 1 t/h facility the electricityn is 160 kW. In
this estimation the price of electric-
0.0725 EUR/kWh. The heat of pyrolysis for municipal is
calculated by Baggio et al. [38] as 1.8 MJ/kg. Forange of 2 MJ/kg
to 3.47 MJ/kg can be found in litera-]. In our case a value of 2.5
MJ/kg for both the pyrolysisivation step is taken. In the
activation step steam is. Heating water from 20 C to 800 C requires
5.5 MJ/kg.ing process 2.67 MJ/kg water in the wood is needed.olysis
reactors (for the production of pyrolytic oil) theat is provided by
the combustion of the gas and/or
this application, as explained before in Section 4.1,d gases (as
by-product) are produced. The gases willy destroyed and provide the
required heat. In the pre-el a higher heating value of 1617 MJ/kg
for the gases
es
cted that the AC can be sold at a price between 1 kEUR/tR/t AC.
Net present values have been calculated forcapacities of 1 t/h and
2 t/h waste in different ratios ofd PB waste. Different ratios
result in different yields) and different qualities and hence
different costs are
provides a guideline for the char and AC yields. It is the AC
yield increases when the share of PB increasesure. So the highest
yield is obtained by the 0 MF5 PBe lowest by the 4 MF1PB.
countries subsidies can be applied such as ecolog-nmental)
premium, a discount for waste treatment,y and selling of other
possible by-products, possible
5.1. Ec
Thelined inratios.displayand thment acompeand higate fethe toThe
anoperatMF 1NPV.
Thethe pring thethat nto 1.7and a Table 6
Onlthan thand 0 Min an amajor MF2
A cand Tafeed mcash AC whsellinga 0 EURrequireorder t
sts for the production of active carbon by this model.
4 MF1 PB 3 MF2 PB 2 M
investment 10 221 kEUR 10 764 kEUR 11 st (without feed cost)
1547 kEUR 1595 kEUR 1
vered feed 98 kEUR 196 kEUR 294 kEing cost 1449 kEUR 1399 kEUR
1347 kEtivated carbon 678 t/year 914 t/year 1184 t/ying price
activated carbon 4.2 kEUR/t 3.2 kEUR/t 2.5 EUic evaluation of the
base case
s corresponding to a 1 t/h processing facility are out-. 2 as a
function of the selling price of AC and the MFPBotal investment and
operating costs for this facility are
Table 5. A higher AC yield (i.e. less MF in the feed mix)arger
installation are the cause of slightly higher invest-perating
(without feed cost) costs. This small increase ised by the income
provided by the gate fee of the waste
yield (revenue) of AC: i.e. in the 0 MF5 PB ratio the90
kEUR/year) is responsible for a decrease of 30% ofperating cost
(1726490 kEUR/year = 1236 kEUR/year).is of Table 5 and Fig. 2
illustrates that the lowerosts and higher AC yields in the
successive range (4
0 MF 5 PB) of ratios are responsible for the higher
imal selling price (NPV = 0 EUR, break-even point) ofed AC can
be found in Table 5 and Fig. 2. By increas-re of PB in the ratio
the minimal selling price for AC
to be achieved gradually decreases from 4.2 kEUR/t/t which
corresponds respectively to a 4 MF1 PB5 PB ratio. The accompanying
IRRs are presented in
cases in the green box (full line) where the IRR is highercount
rate can be accepted. The 2 MF3 PB, 1 MF4 PB
PB feed mixture appear to be the most likely to resulttable
investment project (i.e. when IRR > 9%). When the
in the mix comes from MF waste (i.e. 4 MF1 PB or 3n investment
is only acceptable a high AC prices.iew on the situation can be
made by combining Fig. 25 and 6. For example: a 1 t/h processing
facility with ae of 1 unit MF and 4 units PB would yield a NPV of
theof 4.2 MEUR, an IRR of 14% and a yearly output of 1.4 ktlling
the product at a price of 2.5 kEUR/t. The minimum
of a mixture of 1 unit MF and 4 units PB to yield at least is
2.0 kEUR/t. A feed mixture of 3 MF and 2 PB however
higher minimum selling price of at least 3.2 kEUR/t inak
even.
B 1 MF4 PB 0 MF5 PB
UR 11 733 kEUR 12 180 kEURUR 1684 kEUR 1726 kEUR
UR 392 kEUR 490 kEURUR 1292 kEUR 1236 kEURear 1445 t/year 1750
t/yearR/t 2.0 kEUR/t 1.7 kEUR/t
-
K. Vanreppelen et al. / Chemical Engineering Journal 172 (2011)
835 846 841
5.2. Econom
When loone could aBecause thiand the higcompared tity of the
reand RodriguFig. 2. Net present value for a 1 t/h processin
Fig. 3. Net present value for a 2 t/h processin
ic impact of the nitrogen content of the AC
oking at the previous analysis (and Fig. 2 and Tables 46)rgue
that it is only usefull to study the 0 MF5 PB ratio.s mix has the
lowest minimal selling price of 1.7 kEUR/thest output of AC (1.7
kt/year), it results in higher NPVso mixes with a higher share of
MF. However, the qual-sulting AC needs to be considered. Bandosz
[4], Marshez-Reinoso [5], Menndes-Dias and Martn-Gulln [6]
state that aformance ocan be seenin the succeet al. [7] ha1.52
wt% whigher nitrovation condand thus yieg facility.
g facility.
higher nitrogen content corresponds to a better per-f the AC
resulting in higher attainable selling prices. It
that the nitrogen content of the resulting AC decreasesssive
range (4 MF1 PB 0 MF5 PB) of ratios. Girodsve produced an AC from
PB with a nitrogen content ofith an estimated value of 2.0 kEUR/t.
They state that agen content could be obtained by optimizing the
acti-itions, and hence probably better adsorption propertiesld a
higher value. Therefore, if AC production from pure
-
842 K. Vanreppelen et al. / Chemical Engineering Journal 172
(2011) 835 846
Table 6IRR for the 1 t/h feed input factory.
PB is optimized, a somewhat higher selling price with an
expectedmaximum of 2.5 kEUR/t corresponding to an NPV of 8.8 MEUR
canbe achieved.
In our case of mixing the PB with MF, AC with an even
highernitrogen content could easily be achieved. In recent
literature, theestimated selling value of specialty (impregnated)
carbons is inthe range of 4.06.0 kEUR/t (incl. pick-up of the
saturated carbonand sellingAC is imprcase, providof the AC
tion, in some extra specialty cases even higher prices can
beachieved.
Therefore, one should take the nitrogen content into
account,which is the highest in the feed mixture of 4 MF1 PB and
gradu-ally decreases as the share of MF in the ratio decreases. It
meansthat the mixtures with a higher share of MF have a higher
chanceof reaching a selling price of 4.0 kEUR/t to 6 kEUR/t. From
Fig. 2
ble 5s a o bre
valu prices of 2008) [10]. An example of such a
specialtyegnation with NaOH to trap acidic components. Oures the
incorporated nitrogen for the basic properties
thus a similar sales value can be expected. In addi-
and Tarequireorder ta salesFig. 4. Importance of the distinct
expenditu, it can be seen that, a feed mixture of 3 MF and 2
PBhigher minimum selling price of at least 3.2 kEUR/t inak even.
However, this mixture is more likely to reache of 5.0 kEUR/t with a
NPV of 10.2 MEUR (comparedre items.
-
K. Vanreppelen et al. / Chemical Engineering Journal 172 (2011)
835 846 843
to pure PB 18.4 MEUR so this pricthat the mixa NPV of 7.the
situatiothe NPV of price of theaccount, it Fig. 5. Mean NPV output
after Monte Carlo
Fig. 6. Average sensitivity of the crucial variables on the
NPV of 8.8 MEUR). In the case of 2 MF3 PB a NPV ofis achieved.
However, its nitrogen content will be lower,e (of 5.5 kEUR/t) may
not be achievable. A key point isture of 4 MF1 PB at a selling
price of 6.0 kEUR obtains
3 MEUR. This is somewhat smaller than the pure PB inn of a
selling price of 2.5 kEUR/t, at a price of 2.0 kEUR/tthe pure PB
(3.5 MEUR) is lower. Taken the expected
0 MF5 PB (between 2.0 kEUR/t and 2.5 kEUR/t) intois possible to
select the ratios in function of their sell-
ing prices wmixture. Thin Table 6 iand in the d(2.5 kEUR/tTable
6, thenor in the dshaded areand more. analysis.
NPV for a 1 t/h facility.
hich yield an equal or more positive result than thisese ratios
with their accompanying IRRs are presentedn the shaded area in the
case of a price of 2.0 kEUR/tashed box in the case that the maximum
selling price
) for the AC of the pure PB is reached. As illustrated by 4 MF1
PB ratio neither appears in the shaded area,ashed box. This ratio
would only be comprised in the
a if Table 6 would be expanded to prices of 5.5 kEUR/tThe 4 MF1
PB ratio would only appear in the dashed
-
844 K. Vanreppelen et al. / Chemical Engineering Journal 172
(2011) 835 846
Table 7Variables with their protability distribution.
Input variable Protability distribution Most likely value
Variance of the distribution
Delivered feed cost Triangular Dependent of the ratio
10%Discount rat 9%Electricity co 0.0Cost of wate 1.5Char output
SeActive carbo SeStaff cost/sh 55Total Capita DeLiquid nitrog
2.5
box if Tableimportant tinteresting which mean
5.3. Econom
Anothercapacity, i.epyrolysis). Dowaste/h to Fig. 2).
Thisincorporatepower expobling the pinput pyrolysistotal equipmthe
total casequently, athe height oto 52% (depsequence thwith 24%.
5.4. Share o
Fig. 4 pexpressed ae Triangularst Triangular r Triangular
(%) (pyrolysis) Triangular n output (%) (activation) Triangular
ift Triangular l Investement Triangular en Triangular
Table 8Percentage of Monte Carlo simulation runs that gain a
positive NPV. 6 is expanded to contain prices above 6.5 kEUR/t. It
iso keep this in mind, as the 4 MF1 PB ratio is potentiallyif
higher nitrogen content can be scientically proved,s that these
high selling prices can be attained.
ies of scale
important factor affecting the NPV is the processing. the hourly
ow ratio of the input material (Qfeed inputubling the processing
rate of the AC plant from 1 t2 t waste/h results in higher NPVs
(compare Fig. 3 to
is a consequence of the economies of scale that ared in the
total equipment cost equation (Eq. (8)). As thenent in Eq. (8) is
smaller than one (0.6194 < 1), dou-rocessing capacity (in other
words multiplying Qfeedby 2) does not result in a proportional
increase of theent cost. Doubling the processing rate thus
augments
pital investment with only 57% instead of 100%. Con-lso the
total operating costs which partly depend onf the total capital
investment increase with only 39%ending on the mix ratio of MF and
PB waste). As a con-e break-even selling price of AC decreases on
average
f expenditure items in total expenditure
resents the share of the distinct expenditure itemss an average
percentage for all ratios of the total dis-
counted exrepresents deviation dand maintetively a shaand a
maxideviation dest paymenclosely folloelectricity. payments,
lifetime of investmentuid nitrogeSection 5.5
5.5. Monte
As descr100% certaiare uncertathe NPV if texpected toplant are
sechange folllikely, a minare performdraws a ran10%725 EUR/kWh
10%
EUR/m3 10%e Table 4 10%e Table 4 10%
kEUR 10%pendent of the ratio 10%
EUR/kg 10%penses (over 20 years). The total capital investmenton
average the major share of 42.9% (with a maximumown of 0.9% and a
maximum deviation up of 0.7%). Staffnance present the main
operating costs with respec-re of 11% (with a maximum deviation
down of 0.7%mum deviation up of 0.8%) and 10% (with a maximumown
and up of 0.2%) of the total expenses. The inter-ts amount to 8%
(0.2%; +0.1%) of the total expenditurewed by insurance, overhead,
liquid nitrogen, water andThe xed operating costs (insurance,
overhead, interestmaintenance) are considered as unchanging during
thethe project (20 years). The impact of the total capital
and the cash ows generated by the staff cost, liq-n, water and
electricity on the NPV will be analysed in
by means of Monte Carlo sensitivity analysis.
Carlo sensitivity analysis
ibed in Section 3, results are only valid in the case ofnty of
the base case variables. Some variables howeverin by denition,
other variables might strongly inuenceheir value changes slightly.
Nine main variables that are
affect the economic attractiveness of the productionlected. The
variables, listed in Table 7, are allowed to
owing a triangular distribution characterized by a mostimum and
a maximum value. Monte Carlo simulationsed, in which each run of
the Monte Carlo simulationdom value for each of these variables,
between the min-
-
K. Vanreppelen et al. / Chemical Engineering Journal 172 (2011)
835 846 845
Table 9Minimal selling price at which the AC should be sold to
guarantee a 95% chance on a positive NPV.
Ratio (MF/wood) 4 MF1 PB 3 MF2 PB 2 MF3 PB 1 MF4 PB 0 MF5 PB
Minimal selling price 5.0 kEUR/t 3.7 kEUR/t 2.9 kEUR/t 2.5
kEUR/t 2.5 kEUR/t
imum and distributionues drawn f(10 000 perresult in a N
Fig. 5 illuthe Monte Cfor the 1 t/hrates can be
By meanobtaining aTable 8.
For examsales value If the produmore, 100%summarizein 95% of
thscenarios fothe selectedof the ratioMF1 PB at by the MonNPV is
highminimal 95
These sdened in tsider uncertBased on thpoint of viewith an
evethese resultprice of the
The shadan equal ofthe Monte the dashedfor this ratithe dashed
for respectistarts at 5.5
Neverthresent a ratMF-waste awill probabpositive. Ana specialty
described in
5.6. Identi
Finally, tis determinfor further iable is dendependent For each
vaFig. 6 for a 1by the stand
inpuut vaectedacto
vity =
tive e in tive e cha
for this me in ons o
moointhe in
charhe Ansitivlearl
the w liqui
factpita
clus
asibias bon vant mlity oulatent
A senhe mestmlly en of isticobabof nit
a higfulneeusecans at ng th
the m sensnsiti
pricmaximum value and in accordance with the selected. Each run
results in a NPV corresponding to the val-or each of the nine
uncertain variables. Numerous runs
ratio in this research) of the Monte Carlo simulationPV
distribution.strates this distribution, characterized by the mean
ofarlo analysis with their respective standard deviations
processing plant. Similar results for the other input
calculated.s of Monte Carlo simulations also the probability of
positive NPV is calculated. The results are listed in
ple, a 1 MF4 PB ratio that yields an AC quality with aof only
2.0 kEUR/t has a 42% chance on a positive NPV.ct is of better
quality and can be sold at 2.5 kEUR/t or
of the cases have a positive NPV. The green full line boxs the
ratios and selling prices that would yield at leaste cases a
positive NPV. These are the most promisingr an AC production
facility put into practice. Comparing
cases (full line green box) of Tables 6 and 8 the scenario 2 MF3
PB with a selling price of 2.5 kEUR/t and the 4a selling price of
4.5 kEUR/t are supplementary rejectedte Carlo simulation, because
the chance on a negativeer than 5%. The minimal price corresponding
to this% chance on a positive NPV is determined (see Table
9).elling prices are somewhat higher than the valueshe base case
(see Table 5) because the latter did not con-ainties in the assumed
values of the base case variables.ese results one can say that it
is, from an economicalw, not interesting to study the 4 MF1 PB and
ratiosn higher MF portion. Nevertheless, in order to analyses, one
should follow the same consideration (expected
0 MF5 PB ratio) as in Section 5.1.ed area in Table 8 represents
the scenarios which yield
more positive NPV than the 0 MF5 PB mixture (fromCarlo
simulation, Fig. 5) at a price of 2.0 kEUR/t and in
box the cases where the maximum price (2.5 kEUR/t)o is applied.
For the 3 MF2 PB and the 4 MF1 PB ratiobox starts at a sales value
of 5.5 kEUR/t and at 6.5 kEUR/tvely. In addition, for the 4 MF1 PB
ratio the shaded area
kEUR/t. The conclusions in Section 5.1 thus still hold.eless, we
need to keep in mind that these results rep-her worst case
scenario, with a zero income from thend rst plant costs. In normal
conditions the MF wastely yield a gate fee and will make the
projections moreother important fact is the likelihood of
producingcarbon of very high added value 4.06.0 kEUR/t (as
Section 5.5).
cation of the key variables
he sensitivity of the NPV to the diverse input variablesed, in
order to identify the crucial process parametersnvestigation. The
sensitivity of the NPV for a given vari-ed as the extent to which
the variability of the NPV isto the variability of the variable
under consideration.
of the an inpthe selevery f
sensiti
A posiincreasa nega(1) Thfactors0.55. Tincreasdeviatithe 3rdA
key pprice, tAC andyield, tage secosts cfee forwater,sitivitytotal
ca
6. Con
A feof AC hbased differefeasibiby calcinvestmof AC. mine tthe
inv
Reaductiopessimwill prration sold ator useity to ra
signicarbondoubli24% of
Thevery sesellingriable of Table 7 an average NPV sensitivity is
given in
t/h facility. The coefcients on the graph are normalizedard
deviation of the output and the standard deviation
Future rcreate a mat and not in actual euros. The higher the
coefcient ofriable (the longer the bar), the greater the impact
that
variable has on the NPV. The variability of the NPV forr can be
calculated by using Eq. (10).
NPV/NPVvariable/variable
(10)
value (the bar extending to the right) means that anthe variable
leads to an increasing NPV. In the case ofsign the NPV decreases by
an increase of the variable.r and AC yield are on average the most
determininghe NPV variability, both have an average sensitivity
ofeans that for every k fraction of a standard deviation
char/AC yield, the NPV will increase by 0.55k standardf the NPV.
(2) The total capital investment is on average
st important variable in declaring the NPVs sensitivity. is
that, depending on the mix ratio and the AC sellingvestment cost is
sometimes more important than the
yield, but the three main variables are always the charC yield
and investment expenditure. The negative aver-ity results of the
discount rate and the delivered feedy indicate that a lower
discount rate and a higher gateaste respectively result in a higher
NPV. (3) The cost of
d nitrogen, electricity and staff have also negative sen-ors.
However these are almost negligible relative to thel investment,
discount rate, char and AC yield.
ion
lity study to process MF and PB waste for the productioneen
performed. A preliminary process design has beenrious literature
sources, for an input feed of 1 t/h andixing ratios of the two
waste products. The economicf the preliminary process design has
been investigated,ing the NPV and IRR of the cash ows incurred by
an
in a pyrolysis and activation plant for the productionsitivity
analysis has been performed in order to deter-ost crucial variables
that inuence the protability ofent.ncouraging results are obtained
for a protable pro-AC, as the current assumptions start from a
rather
scenario: e.g. a zero gate fee for the MF waste (whichly be
higher in practice). Besides that, the in situ incorpo-rogen can
result in a high quality product which can beh price or even in a
niche market. In addition, the valuess of the AC production plant
is enhanced by its abil-
two waste streams. Also the processing capacity playst role. A
larger manufacturing plant is able to producea lower cost despite
the higher initial investment. Bye input rate to 2 t/h (dry matter)
a reduction of averageinimal selling price is obtained.
itivity analysis reveals that the AC plant economies areve to
the investment cost, the product yield and the ACe which is an
indication for product quality.
esearch needs to focus on these prime properties torketable high
value product.
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846 K. Vanreppelen et al. / Chemical Engineering Journal 172
(2011) 835 846
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Activated carbon from co-pyrolysis of particle board and
melamine (urea) formaldehyde resin: A techno-economic evaluation1
Introduction2 Process design3 Economical feasibility model4 Model
assumptions4.1 Total capital investment4.2 Expenditure4.3
Revenues
5 Results and discussion5.1 Economic evaluation of the base
case5.2 Economic impact of the nitrogen content of the AC5.3
Economies of scale5.4 Share of expenditure items in total
expenditure5.5 Monte Carlo sensitivity analysis5.6 Identification
of the key variables
6 ConclusionReferences