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All over the world alternative fuels have become more

and more popular in the cement industry to cut the costs

of energy during clinker production. Due to the lack of

regulations a lot of governments – especially those of

emerging countries – raise the potential of alternative fuels

by establishing successful joint ventures with the cement

industry and its professional energy management. Therefore

ThyssenKrupp Polysius and Vecoplan established FuelTrack

as a joint venture to offer reasonable and economical solu-

tions to the cement and lime industry: Starting with identifi-

cation of combustibles and the technical assessment of the

pyro-process, the correct pre-treatment process has to be

designed. The reception of the waste material, pre-treating

waste to alternative fuel storage and feeding at the cement

works as well as technical optimization or replacement

will complete the service for a cost saving co-processing of

alternative fuels and raw materials.3

Die Verwendung von alternativen Brennstoffen beim Klin-

kerbrennen wird heute aus Kostengründen in der inter-

nationalen Zementindustrie immer wichtiger. Wegen des

Fehlens von Regularien gehen viele Regierungen – speziell

in den Entwicklungsländern – den Weg, die Potenziale von

alternativen Brennstoffen im Joint Venture mit der Zement-

industrie und deren fortschrittlichem Energiemanagement

zu heben. Durch diese Entwicklung veranlasst, etablierte

ThyssenKrupp Polysius mit Vecoplan die FuelTrack als Joint

Venture, die es sich zur Aufgabe gemacht hat, der Zement-

und Kalkindustrie akzeptable und wirtschaftliche Lösungen

beim Einsatz von alternativen Brennstoffen anzubieten.

Beginnend mit der Identifizierung eines Brennstoffs und

seiner technischen Bewertung für den Einsatz im Pyro-

Prozess, kommt der Wahl und Auslegung des richtigen

Aufbereitungsverfahrens eine wichtige Rolle zu. Die Annah-

me von Abfällen, deren Aufbereitung zu Ersatzbrennstoffen

sowie deren Anlieferung und Lagerung im Zementwerk,

die Dosierung und der Transport ebenso wie ihre techni-

sche Aufbereitung, vervollständigen den Service für eine

Kosten sparende Herstellung von alternativen Brenn- und



4Dr.-Ing. H. Baier, Dipl.-Ing. K. Menzel, Vecoplan FuelTrack GmbH, Bad Marienberg, Germany

(English text supplied by the authors)




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1 Introduction

Most of the alternative fuels used are biogenic or waste1
derived and, – despite all rumors – they have to be pre-
processed for the reduction of impurities, a constant qual-
ity and continuous mass flow behavior for utilization in the
pro cess of clinker burning.

The search for the right source and amount must start with
a look into the immediate vicinity around the cement works
where municipalities or industrial sectors are located. In gen-
eral, waste could occur in a dry, wet or pasty consistency as
well as in a hazardous2 and non-hazardous form.

Non-hazardous wastes are solids coming from industrial,
commercial or municipal sources, free of hazardous con-
tamination and consisting of plastic, paper, cardboard, tex-
tiles, biomass or composites or mixtures of these. In some
cases disposal companies collect it on behalf of the public
authority for dumping or for themselves for a first approach
of sorting and recycling.

2 How to find the right source?

Typically the market starts with “cherry picking” by seek-
ing several types of waste. On the one hand looking for an
appropriate non-contaminated waste which shows, after
pre-treatment and blending, a high similarity to the well-
known primary fuels like oil, lignite, coal etc., on the other
hand which brings a high gate fee for safe disposal.

Hazardous waste, which can be pre-treated in a simple rea-
sonable device, but due to its hazard risk it has to be han-
dled in a precautious and liable manner in order not to harm
co-workers’ health or the local environment. Due to the fact
that the waste producing companies want to reduce their
disposal costs, the amount of this hazardous waste will
decrease continuously. Therefore, FuelTrack concentrates
on non-hazardous solid waste as a feedstock for alterna-
tive fuels.

To feed the continuously running clinker burning process and
to avoid the impact of quality variation on the process and the
product, two concepts had been proved: A larger procure-
ment process picking out appropriate residues of production
or a long term contract for obtaining municipal solid waste
(MSW) as an unpredictable mixture at the end of the life cycle.

Utilization of alternative fuels in the cement
clinker process
Die Verwendung von alternativen Brennstoffen beim Klinkerbrennen

The advantages and disadvantages of picking out appropriate
residues are listed in � Table 1.

Most of the clients working in an established waste man-
agement market, started with monofractions of industrial
products which never entered the lifecycle such as for exam-
ple overproduction, rejects, cuts or blanks, which could be
treated and blended to a high quality alternative solid fuel.

During examination of the area around a cement plant, differ-
ent waste streams may appear mixed as mentioned or sep-
arately collected from different industrial sectors, i.e. com-
ing from agriculture or from the food industry. There are also
wood or paper, cardboard, pulp, furniture, leather and tex-
tiles. There are also wastes coming from petroleum refin-
ing, from oil and solvents, from treatment of coal as well as
from coatings, paints, varnishes, adhesives, resins, sealants
or inks. There is also waste from the photographic industry,
from shaping and surface treatment of plastics, packaging,
absorbents, wiping cloths, filter materials or protective cloth-
ing, from residues of pre-treating demolition wastes or other
treatment facilities, like precipitation from process water or
waste water treatment.

However, many countries all over the world do not have
such established waste management systems and dump the
wastes as wild land filling. A potential source of alternative
fuels is a public partner – district or municipality – which due
to environmental problems has to start a sustainable waste
management system. Obviously the envisaged wastes are
products at the end of their lifecycles and in most cases
mixed and contaminated with hazardous, solid and liquid
components. The advantages and disadvantages of those
wastes are listed in � Table 2.

In an established waste management market normally pub-
lic companies operate Mechanical-Biological Treatment
Plants (MBT) firstly to split the wastes into combustibles, bio-
de gradable and recyclables to produce alternative solid fuels
from municipal waste [1]. Consequently the first step is to
assess the waste producing process, the source and the




1 Under the Waste Framework Directive (European Directive 75/442/EC as amended),
the European Union defines waste as an object the holder discards, intends to
discard or is required to discard, and anything which is discarded or otherwise
dealt with as if it were waste shall be presumed to be waste until the contrary is

2 Hazardous means that materials are at least corrosive, ignitable, reactive or toxic,
and which may have to be handled, stored, transported, and disposed of in a con-
trolled and safe manner. International companies certified according to ISO 14000
EMS will arrange a safe disposal of hazardous waste and will respect the polluter
pay principle.

Advantages Disadvantages

� Small investment

� Short depreciation time

� Modular flexible technology
while market develops and

� Tailor-made engineered fuel

� Low range of quality fluctuation

� Major efforts for acquisition

� Unstable access

� Input quality control

� Higher costs for quality

� Not suitable for a universal
waste management system

Table 1: Advantages and disadvantages of selecting appropriate
residues of production (Cherry picking)

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chemical and physical composition to discover the calorific
value etc., in order to establish exactly how the treatment
process should be designed (� Fig. 1).

As has been shown, a lot of sources might become the feed-
stock for alternative fuels or raw materials for the clinker
burning process, and after identifying the source and its
chemical composition, the envisaged waste has to be cross-
checked with the process technology, composition of raw
material, as well as the specific heat demand or the pres-
ence of alkaline or chlorine which will boost the volatility of
trace elements or can form a recirculation. � Table 3 lists
the input criteria of alternative fuels for valorization in a pre-
heater and calciner.

The key for a first indication is to monitor the input concen-
tration of the high volatile trace elements mercury, cadmium
and thallium in a sufficient way. Other medium- or non-vola-

Advantages Disadvantages

� Universal waste management
system for many types of waste

� Long term contracts with
waste producers or responsible

� Long depreciation time

� Pre-selection of feasible

� Facility and mandatory

� Management of delivered and/
or splitted streams (RDF, bio-
mass, recyclables, contamina-
ted etc.)

� High range of quality

Table 2: Advantages and disadvantages of alternative fuels derived
from mixed municipal solid wastes (MSW)

tile trace elements are dust bounded and remain in the fil-
tering system. This might become a question of cement

At least the success of cost reduction is totally interdepend-
ent on the energy demand, the resulting quality of the prod-
uct and the impact on the emissions. As a rough estimate,
the waste and its pre-treated Residue Derived Fuel (RDF) is
suitable for co-processing, when the chemical composition
and physical behavior is similar to a brown coal (� Tables 4 a
and b). � Tables 5 a and b and � Tables 6 a and b list the aver-
age chemical composition of SRF, produced from selected
industrial and municipal solid wastes (MSW).

After assessing the technical potential of
the kiln and the chemistry of the waste,
the physical behavior has to be prepared
for process neutral utilization. The first
treatment step is to separate the High
Caloric Fraction (HCF) with a grain size of
max. 300 mm. In the next step this HCF
will be processed to a Residue Derived
Fuel (RDF) with a grain size of max.
80 mm only for feeding a properly de-
signed calciner.

So far it is clear that for feeding the main
burner coal has to be ground or deliv-
ered with a degree of fineness of 2 %
sieve retention on 90 µm, but due to the Figure 1: The FuelTrack AFR Approach

Element Content

CaO in ash

Single or in total

≥ 50 mass %

SiO2 in ash

Al2O3 in ash

Fe2O3 in ash

Mercury (Hg) ≤ 2 ppm dry substance

Cadmium (Cd) ≤ 50 ppm dry substance

Thallium (TI) ≤ 45 ppm dry substance

Other trace elements ≤ 20 000 ppm dry substance

Table 3: Indication for input criteria of alternative fuels for valorization
in a preheater and calciner

Designation Value

Caloric value 21 800 MJ/kg

C 25.2 ... 28.8

H 2

O 10.0 ... 11.5

N 0.2

S 0.1 ... 0.5

Volatiles 46 ... 48

Ash 2 ... 20

CaO 1.6 ... 2.0

SiO2 0.3 ... 0.4

Al2O3 0.5 ... 0.6

Fe2O3 1.0 ... 1.4

Table 4 a: Average chemical composition of German lignite in % [2]

Designation Value

As 0.2 ... 2.5

Be 0.04 ... 0.40

Pb < 0.01 ... 2.20

Cd 0.01 ... 1.50

Cr 0.01 ... 15.00

Ni 1.0 ... 9.3

Hg 0.11 ... 0.90

Tl 0.027 ... 0.200

V 1…13

Zn 3.9 ... 22.0

Table 4 b: Trace elements of German lignite in ppm

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economy of pre-treating it is commonly
accepted to process the quality controlled
Solid Recovered fuel (SRF) in a third step
to a grain size less than 30 mm.

In some cases a further comminution
process to produce RDF-meal with less
than 3 mm may even also be beneficial for
high substitution rates at the main burner.
The close interconnection between pre-
treatment and conversion technology is
the economical answer. � Fig. 2 shows
the way from waste to treated tailor-made
alternative fuels.

3 Treatment of AFR

Residues, wastes and biomass of almost
undefined size and form are typically either
separately or jointly treated to remove minerals, organic,
metals, glass, ash or other constituents from the fuel, which
might harm the treatment process as well as the clinker burn-
ing process or the emission balance. After shredding, siev-
ing, screening and/or ballistic separation, a Highly enriched
Caloric Fraction (HCF) with a lump size of less than 300 mm
is received (� Fig. 3).The HCF is either the basis material for
further processing of RDF or can be fed directly into a spe-
cialized calciner, called a step combustor (� Fig. 4). Storage
and handling of this material should be relatively simple but
it is necessary to consider the large size and the low bulk
density. For separate pre-treatment at a distance from the
cement plant it might be necessary to bale it. Beside bale-
opening in the plant itself, it needs no further treatment,
just rough dosing and transportation to the step combustor.

4 The step combustor

The step combustor is designed for large-sized alternative
fuels. Retention time and transportation conditions in a
standard calciner are not sufficient for the safe burnout of
such coarse and slow-reacting alternative fuels [4].

The retention time of 4 to 8 s in a typical suspension flow cal-
ciner is grossly insufficient for the safe burnout of such slow-

reacting coarse alternative fuels. As a function of the alter-
native fuel quality, the transport and discharge rates in the
step combustor can be separately controlled and retention
times extended up to 15 min. Transporting with controlled
air blast nozzles, an elegant side effect is that no mechani-
cal internal fittings or moving parts are necessary inside the
reaction chamber. Fig. 4 shows the principle of a step com-
bustor. This type of step combustor can be fed with up to
70 % of the amount of the calciner fuel. The coarse alterna-
tive fuel will be thermally comminuted and might burn out
in the stages 70 to 90 %. The remaining coke fraction is fine
enough to achieve the final burnout within the calciner itself.
So the coarse HCF can build the basic fuel load of the cal-
ciner. For controlling the calciner operation in any case either
primary fuel or higher quality RDF is required. This can be an
RDF in the next treatment step.

5 Processing of RDF/SRF

� Fig. 5 demonstrates the processing of RDF < 80 mm or SRF
< 30 mm. To create such well-defined RDF, the HCF needs a
second shredding step. Particularly, when it will be used as
controlling fuel for the calciner or needs to be fed pneumati-
cally, it is a must to have a good quality monitored pre-sorted
and air classified SRF where the large and heavy 3-D parti-

Figure 2: The way from waste to treated/tailor-made alternative fuels

Figure 3: Preprocessing the highly enriched calorific fraction

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cles have been eliminated. � Fig. 6 shows a typical arrange-
ment: processing of sorted material with a 2-shaft coarse
shredder, a ballistic separation followed by a fine shredder
and a subsequent storage system for RDF/SRF.

6 RDF/SRF handling and dosing

The RDF/SRF handling to feed the calciner and/or the kiln
burner is, of course, dependent on the situation of plant

and treatment site, but may consist of a truck receiving and
unloading station, an appropriate storage system, the trans-
port equipment to the calciner, main burner and a dosing sta-
tion as close as possible to the calciner or main burner.

For the calciner feeding, pneumatic feeding is not recom-
mended, because the pneumatic transport requires more
energy. As well as for the main burner fuel mechanical
transportation and a straight blow line without any bend-

ing avoid energy losses and wear. Often
a police filter for insufficient quality due
to heavy and oversize particles is needed.
Experience shows that not a screening,
but an air classifier is recommended for a
right quality fuel to the main burner (� Fig. 7).

If RDF/SRF is received in different qua l-
ities and/or from different sources, good
sampling and quality monitoring is man-
datory. Furthermore it is recommend
to have a modular storage system – as
shown here – which can be extended
and gives the option of blending differ-
ent qualities.

The Truck Unloading and Loading System
(TULS) shown here can take RDF/SRF
feed material at one side and is able to
unload to a screw and chain conveyor sys-

Designation Value

Caloric value 21 800 ... 32 200 MJ/kg

C n.d.

H n.d.

O n.d.

N n.d.

S 0.1 … 0.8

Volatiles n.d.

Ash 9 … 39

CaO n.d.

SiO2 n.d.

Al2O3 n.d.

Fe2O3 n.d.

Cl 0.39 … 2.20

F 0.1 … 1.7

Table 5 a: Average chemical composition of SRF (preselected industrial
waste components) [2] in %

Designation Value

As 0.68 ... 15.32

Pb 27 ... 4406

Cd 0.75 ... 162.00

Cr 19.10 ... 187.00

Ni 5.41 ... 1622.00

Hg 0.09 ... 1.62

Tl 0.23 ... 1.96

V 2.17 ... 164.00

Table 5 b: Trace elements of SRF (preselected industrial waste compo-
nents) in ppm

Figure 4: The principle of a step combustor

Designation Value

Caloric value 16 700 ... 25 700 MJ/kg

C 48.2 ... 54.1

H 7.3 ... 8.5

O 32.5 ... 34.1

N 0.76 ... 1.35

S 0.1 ... 1.0

Volatiles n.d.

Ash 13.6 ... 46.7

CaO 26.0 ... 32.1

SiO2 22.6 ... 30.5

Al2O3 7.82 ... 60.00

Fe2O3 4.26 ... 6.75

Cl 0.8 ... 4.3

F 0.02 ... 0.09

Table 6 a: Average chemical composition of SRF (out of municipal solid
waste) [1, 2] in %

Designation Value

As 0.48 ... 7.33

Pb 131 … 30176

Cd 2.1 ... 55.0

Cr 82.73 ... 3029.00

Ni 14.19 ... 3658.00

Hg 0.28 ... 3.39

Tl 0.18 ... 5.90

V 5.19 … 135.00

Table 6 b: Trace elements of SRF (out of municipal solid waste) in ppm

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tem at the same time. With the help of a flexible wide chain
scraper – freely self-controlled in height – the RDF can be
distributed over the whole rectangular box and filled into the
speed-controlled extraction screw at the same time. Typically
required, more than one box opens the possibility of stor-
ing and locating different fuel qualities and blends them at
the extraction in a favorable way. � Fig. 8 shows the Truck
Unloading and Loading System (TULS), fed by a truck unload-
ing station and discharging to calciner transport.

Using the RDF for calciner firing, all suitable designed cal-
ciner types are possible. Multistage combustion or a sepa-
rate combustion chamber may be an advantage. At least RDF
and the calciner just have to fit together: Either the RDF is
made fit for the given calciner or the calciner fits for the given
alternative fuel. � Fig. 9 illustrates a well-designed standard
calciner for using 100 % RDF.

The RDF consists of 50 mm tire chips. Sometimes separate
biomass is available. Coal/petcoke is normally on standby,
the calciner operation control is done with the on short dis-
tance pneumatically injected RDF.

To run the calciner coal-free with 100 % alternative fuel is not
magic, but to increase the thermal substitution rate to above
50 to 60 % it is necessary to go to the main burner as well.
The well-cleaned HCF, other pre-sorted or mono-industrial
residue fractions can be the basic material to prepare quality –
assured SRF for the main burner. For an accept able burn-
out and correct clinker quality, the RDF compounds must
be comminuted into finer particles. Due to the economical
limits, the fineness of the main burner fuel is not as typical
as for a coal dust.

Figure 5: Processing RDF < 80 mm or SRF < 30 mm

Figure 6: Treating HCF and processing and storage of RDF

Figure 7: RDF/SRF handling and dosing at the cement plant

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An ideal quality SRF for the main burner should basically con-
sist of 2-D material only. The SRF particles have to be within
a limited range of density and burning behavior. Otherwise
the particles of the alternative fuel mixtures are burning at
different levels: While thin, large-area particles are consumed
during floating in the flame, three-dimensional particles, e.g.
hard plastic, rubber, wood, etc. can accumulate in the tip of
the flame or fly beyond it into the clinker bed which leads
to reducing conditions, sulfur cycles and bad clinker causing
loss of strength. Because the quality of the SRF cannot be
guaranteed no screening will help. Due to the open sieving
floor three dimensional disruptions will pass. Only appropri-
ate quality control or an air classifier will fulfill the require-
ments for a police filter [5].

The burner itself should be a multi-channel type with sufficient
momentum and flexibility, particularly if the target is to substi-
tute more than 50 % of fuel at the main burner by SRF [6].

7 Using RDF meal at the main burner

In practice, alternative fuels are not always well defined as
required by external parties. The preparation process may
have some weaknesses, the burning behavior of the mixed
SRF is insufficient, the heating value may be too low or the
moisture content too high for good clinker burning.

In this case, a further option is to increase the thermal sub-
stitution rate by a subsequent treating and fining of the RDF
to get better conditions for the combustion process [4].

8 Final remarks

Based on many years of experience in cement plant engi-
neering, it is now possible to offer a sustainable concept
for all types of solid alternative fuels. This could and should
include the whole process chain from treating and refining
the potential of alternative fuels, tailored storage and dosing
arrangements up to adaptations of the calciner, main burner
or clinker production process itself.
This competence in pre-treating and handling is now concen-
trated in the newly founded company, Vecoplan FuelTrack
GmbH, a joint venture of ThyssenKrupp Polysius AG and
Vecoplan AG, acting internationally with a long background
of experience in cement plant engineering and engineering
in the handling of alternative fuels.

Figure 8: Truck Unloading and Loading System (TULS) fed by a truck
unloading station and discharging to calciner transport

Figure 9: Well-designed standard calciner for using 100 % AFR

It all began on the basis of a great idea. With the development of the customised burner over 45 years ago, we gave technological advance a
decisive push. And every day we focus on promoting the competitive edge of our customers – by continuously improving the combustion process
with proven Austrian technology: more effi cient, more simple, more safe. The outcome: Intelligent Combustion Solutions.

can reinvent it.


Inte l l igent Combust ion Solut ionsAustria – Brasil – China – Mexico – Malaysia – Poland – Spain

52_59_Baier.indd 58 02.03.2012 7:15:14 Uhr

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