CR 13767:2001
(Main)Characterization of sludges - Good practice for sludges incineration with and without grease and screenings
Characterization of sludges - Good practice for sludges incineration with and without grease and screenings
This CEN Report describes good practice for the incineration of sludges with and without grease and screenings.
This CEN Report is applicable for sludges described in the scope of CEN/TC 308 specifically derived from :
- night soil ;
- urban wastewater collecting systems ;
- urban wastewater treatment plants ;
- treating industrial wastewater similar to urban wastewater (as defined in Directive 91/271/EC) ;
but excluding hazardous sludges from industry.
This European standard is not applicable to co-incineration of sludge and other wastes, (either urban or hazardous) (see CR 13768) and to the use of sludge in cement kilns.
Annex A gives tables of data for different typical parameters for sludge, furnace, ash, etc..
Charakterisierung von Schlämmen - Anleitung für die gute fachliche Praxis bei der Verbrennung von Schlamm mit und ohne Fett und Rechengut
Diese Europäische Norm gibt eine Anleitung für die Verbrennung von Schlamm mit und ohne Fett. Diese Europäische Norm gilt für Schlämme, die im Anwendungsbereich des CEN/TC 308 beschrieben sind, d.h. aus: - der Regenwasserbehandlung; - der Fäkalienentsorgung; - der kommunalen Abwasserkanalisation; - der kommunalen Kläranlagen; - der Behandlung ähnlicher Industrieabwässer (wie in Richtlinie 91/271/EWG festgelegt); - den Wasseraufbereitungsanlagen; - den Wasserversorgungsnetzen; mit Ausnahme von gefährlichen Industrieschlämmen.
Caractérisation des boues - Bonne pratique d'incinération des boues avec ou sans graisse et refus de dégrillage
La présente norme européenne décrit les bonnes pratiques d'incinération des boues avec ou sans graisse. La présente norme européenne s'applique aux boues décrites dans le domaine d'application du document CEN/TC 308, c'est-à-dire: - traitement des eaux pluviales; - matières de vidange; - systèmes de collecte des eaux usées urbaines; - stations d'épuration des eaux usées urbaines; - stations d'épuration des eaux industrielles assimilées (telles que définies par la Directive 91/271/CEE); - usines de production d'eau potable; - systèmes de distribution d'eau potable; à l'exception des boues industrielles dangereuses.
Karakterizacija blata - Dobra praksa za sežiganje blat z maščobami in ostanki ter brez njih
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST CR 13767:2001
01-december-2001
.DUDNWHUL]DFLMDEODWD'REUDSUDNVD]DVHåLJDQMHEODW]PDãþREDPLLQRVWDQNLWHU
EUH]QMLK
Characterization of sludges - Good practice for sludges incineration with and without
grease and screenings
Charakterisierung von Schlämmen - Anleitung für die gute fachliche Praxis bei der
Verbrennung von Schlamm mit und ohne Fett und Rechengut
Caractérisation des boues - Bonne pratique d'incinération des boues avec ou sans
graisse et refus de dégrillage
Ta slovenski standard je istoveten z: CR 13767:2001
ICS:
13.030.20 7HNRþLRGSDGNL%ODWR Liquid wastes. Sludge
SIST CR 13767:2001 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST CR 13767:2001
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SIST CR 13767:2001
CEN REPORT
CR 13767
RAPPORT CEN
CEN BERICHT
August 2001
ICS
English version
Characterization of sludges - Good practice for sludges
incineration with and without grease and screenings
Caractérisation des boues - Bonne pratique d'incinération Charakterisierung von Schlämmen - Anleitung für die gute
des boues avec ou sans graisse et refus de dégrillage fachliche Praxis bei der Verbrennung von Schlamm mit und
ohne Fett und Rechengut
This CEN Report was approved by CEN on 16 June 2001. It has been drawn up by the Technical Committee CEN/TC 308.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. CR 13767:2001 E
worldwide for CEN national Members.
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Contents
Foreword.3
Introduction .4
1 Scope .5
2 References.5
3 Terms and definitions.5
4 Sludge properties .5
4.1 Chemical characteristics.6
4.2 Physical-chemical characteristics .7
5 Combustion fundamentals.9
6 Equipment characteristics.10
6.1 Incineration systems .10
6.2 Support components.16
6.3 Design aspects.21
7 Operational procedures .22
7.1 General.22
7.2 Specific .22
8 Management of residues.25
8.1 Flue gas.25
8.2 Ashes .26
8.3 Wastewater .27
9 Environmental impact assessment.27
Annex A.28
Bibliography .32
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Foreword
This document has been prepared by CEN /TC 308, "Characterization of sludges".
This document is currently submitted to the CEN BT.
The status of this document as CEN Report has been chosen because the most of its content is not completely in
line with practice and regulation in each member state. This document gives recommendations for a good practice
but existing national regulations concerning the sludges incineration remain in force.
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Introduction
The purpose of this CEN Report is to describe good practice of the sludge incineration in order to ensure a safe
and economical operation. The main goals are to :
describe the principal design parameters relevant to different process schemes ;
assess the operating procedures able to perform optimal energy consumption, emissions control and
equipment durability ;
provide the responsible authorities with well established and easily applicable protocols for control purposes ;
promote the diffusion of this practice and favouring the formation of a public opinion consensus ;
potential advantages of high temperature processes include :
reduction of volume and mass of sludge ;
destruction of toxic organic compounds, if present ;
energy recovery.
Anyway, priority should be given to reduction of pollutants at the origin and to recover ,
if technically and economically feasible, valuable substances (phosphorous and potassium) in sludge and derived
products.
The following abbreviated terms necessary for the understanding of this report apply :
COD Chemical oxygen demand
LOI Loss On Ignition
MHF Multiple Hearth Furnace
FBF Fluidised Bed Furnace
RKF Rotary Kiln Furnace
EF Electric Furnace
CF Cyclone Furnace
PCDF Polychlorodibenzofurans
PCDD Polychlorodibenzodioxins
PCB Polychlorinated biphenyls
PAH Polycyclic aromatic hydrocarbons
GCV Greater Calorific Value
LCV Lower Calorific Value
VOC Volatile organic carbon
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1 Scope
This CEN Report describes good practice for the incineration of sludges with and without grease and screenings.
This CEN Report is applicable for sludges described in the scope of CEN/TC 308 specifically derived from :
night soil ;
urban wastewater collecting systems ;
urban wastewater treatment plants ;
treating industrial wastewater similar to urban wastewater (as defined in Directive 91/271/EC) ;
but excluding hazardous sludges from industry.
This European standard is not applicable to co-incineration of sludge and other wastes, (either urban or hazardous)
(see CR 13768) and to the use of sludge in cement kilns.
Annex A gives tables of data for different typical parameters for sludge, furnace, ash, etc.
2 References
EN 1085, Wastewater treatment – Vocabulary.
EN 12832, Characterization of sludges – Utilisation and disposal of sludges – Vocabulary.
EN 12255-8, Wastewater treatments plants – Part 8 : Sludge treatment and storage.
CR 13768, Characterization of sludges – Good practice for combined incneration of sludge and household wastes.
prEN 13965-1, Characterization of waste – Terminology – Part 1 : Material related terms and dEFinitions.
prEN 13965-2, Characterization of waste – Terminology – Part 2 : Management related terms and dEFinitions.
3 Terms and definitions
For the purposes of this CEN Report, the following terms and definitions which apply are those given in :
Directive 91/271/EC (Concerning urban waste water treatment) ;
Directive 75/442/EEC (The Waste Framework Directive) as amended by EU Directive 91/156/EEC ;
Directive 89/369/EEC (Concerning prevention of atmospheric pollution derived from urban solid waste
incineration plants) ;
EN 1085, EN 12832, and prEN 13965-1 and 2.
4 Sludge properties
Sludge characterisation for the assessment of combustion processes involves the evaluation of chemical and
physical parameters and specific properties.
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4.1 Chemical characteristics
The main chemical characteristics to be taken into account are :
organic and inorganic chlorine ;
sulfur ;
phosphorus and nitrogen ;
other halogens ;
organic micropollutants with main regard to chlorinated hydrocarbons, phenols and polyphenols,
polychlorinated biphenyls (PCB), pesticides and polycyclic aromatic hydrocarbons (PAH) ;
elemental analysis of loss on ignition (LOI) ;
trace elements.
The toxicity of emissions (gaseous, liquid, solid) from incineration generally depends on the presence of above
chemicals at origin, when improper operating conditions occur.
a) Sulfur
The sulfur content of sewage sludge ranges generally from 0,5 % to 2 % by dry mass. Because a fraction of the
sulfur is present in the oxidised sulfate form, not all of this sulfur is converted to sulfur dioxide during combustion.
Sulfur dioxide then combines with moisture, either in the waste gas treatment system or in the atmosphere, to form
sulfuric and sulfurous acids.
b) Phosphorus and nitrogen
Phosphorus can be present in sewage sludge in concentration ranging from 1 % to 5 % by dry mass. This
concentration mainly depends on the phosphorus load in the wastewater system and on the level of phosphorus
removal accomplished in the treatment plant. Nowadays in some countries the phosphorus concentration in urban
wastewater is decreasing due to substitution of phosphorus in detergents with other products. During combustion
phosphorus and phosphorus compounds are converted to calcium phosphate which can be present in the furnace
ash up to 15 % mass fraction of P O in certain conditions, leaching of phosphorus from ashes should be taken
2 5
into account.
Nitrogen content of sewage sludge (2 % to 12 % dry mass) can be converted during combustion to molecular
nitrogen or to NO , depending on the temperature and atmosphere inside the furnace. NO formation from fuel
x x
bound nitrogen can be controlled by restricting the air flow to the minimum excess above the stoichiometric
requirement and by staging the air flow to the furnace (see 8.1).
1)
c) Chlorine and other halogens
Organic and inorganic chlorine compounds play an important role in the combustion processes for the tendency of
the chlorine radicals to bind to active radicals, like O*, H* and OH*. This determines a decrease in the combustion
rate with the possibility of toxic compounds formation. Chlorine and other halogens are also responsible for the
presence in the exhaust gases of acidic compounds which are undesirable for corrosion problems involved,
especially at high temperatures. The presence of organic chlorine in sewage sludge is generally negligible (less
than 50 mg/kg dry mass) but the concentration of inorganic chlorine can be some units per cent dry mass
depending on chlorine presence in the sludge water fraction and on the use of inorganic conditioners. The
industrial sludges similar to sewage sludge mentioned in Directive 91/271/EC, which derive from food and/or
1) Bromine can exert similar effects than chlorine but the organic compounds are easier formed and they can also be easier
destroyed at high temperatures.
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beverage transformation and production, do not contain organic chlorine. As for swage sludge, inorganic chlorine
can be present in such sludges if FeCl is used as conditioner.
3
d) Organic micropollutants
Although the presence of organic micropollutants in sewage sludge can be in some cases noticeable, they
generally do not pose problems in incineration. Chemical analysis should can include, for particular cases of
contaminated sludges, the compounds which are recognised to be recalcitrant to a thermal degradation.
e) Elemental analysis
Elemental analysis of loss on ignition (C, H, N, S, O) is important to predict flow rate and composition of flue gas
and therefore to design the purification gas line. Typical elemental analysis of primary, secondary, mixed and
digested sludge is given in Table A.1.
f) Trace elements
Trace element presence in sewage sludge has to be considered for their potential tendency to be transferred in the
gaseous phase (especially for mercury). They (except mercury) can be concentrated in fly ashes collected in bag
and electrofilters (arsenic, lead, cadmium and zinc). Mercury generally escapes with flue gases but can be
condensed in scrubbers or captured by activated carbon filters.
Trace elements are generally present in sewage sludge in very variable concentrations depending on the presence
of industrial effluents in the wastewater. Table A.2 gives an indication of the most common range of variation and
the typical values of trace element concentrations, but it has to be pointed out that, currently, the trace element
presence in sewage sludge is decreasing due to a more effective control of undesirable pollutants input to the
sewerage system.
4.2 Physical-chemical characteristics
The main physical-chemical characteristics to be taken into account are :
dry matter ;
physical consistency ;
loss on ignition (LOI) ;
calorific value ;
presence of grease, scum and screenings.
Rheological properties also play an important role, especially as far as the design of feeding system is concerned.
a) Dry matter
In incineration of sewage sludge dry matter is a variable affecting both fuel requirement and exhaust gas
production. Generally any increase in dry matter is believed to be beneficial in the combustion for the reduction in
fuel requirement. Until the condition for autogenous combustion is reached the increase in dry matter corresponds
also to a decrease in combustion gases production. It should be pointed out that any further increase of dry matter
beyond the limit of autogenous combustion could be not very convenient because this entails a more abundant gas
production, especially if dilution air is used instead of water for the control of the combustion chamber temperature.
The use of water, on the contrary, reduces the quantity of recoverable heat in the boiler.
Moreover, if after burning of combustion gases should be accomplished, the feeding of too dry a sludge to the
furnace implies also very abundant fuel requirements in the after burning chamber due to high gas production.
Therefore, thermal drying of sludge before incineration has to be properly designed and operated in order to attain
an optimal drying level. Dried and dewatered sludges can be mixed, if necessary, to avoid too high not needed dry
matter concentrations.
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b) Physical consistency
Physical consistency of sludge should be adapted to furnace and its feeding system.
Depending on the dewatering device a crumbly product could be needed before feeding the incineration furnace.
c) Loss on ignition and calorific value
Calorific value of sludge is probably the most important parameter for the evaluation of combustion processes. It
represents the heat quantity developed in the combustion by the unit mass of material in standard conditions.
As a first approximation the Greater Calorific Value (GCV) can be evaluated by the Du Long equation, if the
elemental analysis of combustible material is known :
GCV = 32 810 C + 142 246 (H – O/8) + 9 273 S (1)
where
GCV is in kJ/kg LOI ; and
C, H, O and S are the mass fraction of the elements in the loss of ignition.
The above formula gives an overestimation of the heat value of sludges with high organic nitrogen content
because : a) the nitrogen will be associated with the hydrogen as an amine, b) the production of nitrogen oxide in
the amine combustion reduces the hydrogen heat release.
The following equation can be used to take into account the above effects :
GCV = 32 810 C + 142 246 (H – O/8) + 9 273 S – [2 189 N (1 – ) + 6 4894N ](2)
where
represents conversion (mass fraction) of nitrogen to nitrogen oxide, generally in the range 2 % to 7 %.
Lower calorific value (LCV) can be also evaluated (Nielsen and Simonsen, 1994) by measuring the chemical
oxygen demand COD and the total Kjeldahl nitrogen (TKN) (ammoniacal + organic nitrogen) and using the
formula :
LCV = 13 700 COD + 19 000 TKN (3)
where
LCV is in kJ/kg LOI ; and
COD and TKN are expressed in kg/kg LOI.
COD of sludge generally varies in the range of 1,5 kg to 1,8 kg O /kg LOI and TKN in the range 0,02 kg/kg LOI
2
to 0,09 g/kg LOI.
Typical calorific values of municipal wastewater sludges range from 22 100 kJ/kg LOI to 24 400 kJ/kg LOI
(anaerobically digested primary) to 23 300 to 27 900 (raw primary). Secondary sludges display values between
20 700 kJ/kg LOI and 24 400 kJ/kg LOI.
The variability of the calorific value mainly depends on the elemental analysis of sludges : when the hydrogen
content is higher also the calorific value displays higher values as for primary sludge in comparison with secondary
and with digested sludge.
LCV can be estimated considering the water present in the sludge (1 – X), being X the fraction of dry solids, and
the combustion water (9 H LOI) :
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LCV (kJ/kg sludge) = GCV X LOI – 2 440 (9 H LOI + 1 – X)(4)
where
LOI is the loss on ignition with respect to dry solids (kg/kg).
If the lower calorific value of loss on ignition is known (LCV ) the lower calorific value of wet sludge can be easily
LOI
evaluated by :
LCV = LCV X LOI – 2 440 (1 – X)(5)
LOI
As a first approximation for LCV a value of 23 000 kJ/kg LOI can be assumed.
LOI
d) Presence of grease, scum and screenings
Grease, scum and screenings can be incinerated together with sludges but generally they pose several problems.
Screenings clog feed mechanisms for certain types of furnace and therefore a grinding or shredding process is
advisable before feeding.
Screenings also contain bulky and non-combustible materials, which create problems in the ash disposal system.
Skimming generally contains more than 95 % moisture and therefore they should be thickened to at least 25 %
solids before incineration. Skimming is difficult to handle in the thickened state due to their viscosity and a heating
process to 70 °C to 80 °C is generally requested to get skimming pumpable. This scum solids should be ground to
a size not exceeding 6 mm. GCV of skimming and screenings are in the range 37 000 kJ/kg to 44 000 kJ/kg dry
solids and 23 000 kJ/kg to 25 600 kJ/kg dry solids, respectively.
-6 3 3
Quantities of screenings are strictly dependent on the screen opening : they can vary in the range of 3x10 m /m
-6 3 3
to 40x10 m /m of sewage for opening of 12 mm to 25 mm (the upper limits apply to the reduced openings). As
3
dewatered sludge production can be approximately evaluated in 1 l/m of sewage the screenings production can
be accounted in approximately 0,2 % to 4 % in mass of sludge production, considering that the density of wet
3 3
screenings is 640 kg/m to 1 000 kg/m .
Quantities of scum are very much dependent on the quality of the sewage and on the collecting system in the
wastewater treatment plant : the highest values can be as high as 17 g of dry solids by cubic meter of sewage
which means up to 1,7 % of sludge production. At a concentration of 25 % this value increases to 6,8 %.
Addition of scum and grease can result in operating and safety problems : due to their high energy content an
increased volume of exhaust gases are suddenly produced in the heating space. It could happen that suction
blowers, responsible for vacuum production in the furnace are not able to draw off the developed explosive gas
immediately, which, therefore, can escape in the ambient air.
An operator has to take measures against such a situation and has to control appropriately any addition of
combustible material different from sewage sludge.
5 Combustion fundamentals
Combustion is an oxidation reaction carried out at high temperature: the union of oxygen with carbon, hydrogen
and sulfur yields energy and products of combustion, namely, carbon dioxide (CO ), water (H O) and sulfur
2 2
dioxide (SO ). Organic nitrogen is preferentially converted to nitrogen gas but a certain amount (2 % to 7 %) can
2
also be further oxidised to nitrogen oxide (NO).
The nitrogen in the air is also candidate to be converted to oxides of nitrogen (NO ). This phenomenon begins to
x
be noticeable at temperatures higher than 1 100 °C and increases with any further increase of temperature.
The maximum temperature achieved by the combustion of a fuel will result from the balance between the energy
produced and/or the energy input and that of combustion products. The heat released by the combustion of a
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substance is then used to increase the temperature of the combustion products to the equilibrium temperature. The
amount of heat required to raise a unit weight of gas, liquid, or solid of one degree is the specific heat of the
material. In Tables A.3 and A.4, the main properties of gaseous products of combustion are shown.
All oxidising combustion reactions require some excess air to ensure that the reaction proceeds rapidly to
completion. The amount of excess air required is a function of time of stay, temperature and turbulence, commonly
referred to as the "3Ts of combustion". Generally as turbulence is maximised, excess air can be decreased.
Turbulence provides more opportunities of contact between fuel and oxygen and changes substantially for various
types of combustion units. High efficiency burners may employ as low as 20 % to 30 % excess air while less
efficient furnaces, like multiple hearth and rotary kiln furnaces, need 100 % to 125 % excess air at least. As excess
air quenches the combustion temperature it is desirable to minimise the quantity to be employed especially when
auxiliary fuel is needed to sustain combustion. This effect can be reduced by air pre-heating. If insufficient excess
air is added to the furnace or if one or more of the "3Ts" concepts are lacking, the combustion operation will
generate smoke and products of incomplete combustion, thus making incineration operation not acceptable.
6 Equipment characteristics
6.1 Incineration systems
The type of incinerator most commonly in use for sludge incineration is the Fluidised Bed Furnace (FBF). Other
types are : Multiple Hearth Furnace (MHF), Rotary Kiln Furnace (RKF), combination of MHF and FBF, Electric
Furnace (EF) and Cyclone Furnace (CF).
They can be combinated with a dryer.
a) Fluidised Bed Furnace (FBF)
It is a cylindrical refractory lined shell containing a sand bed fluidised during operation by air through a distributor
plate below the bed. The temperature of the bed is controlled at about 750 °C. FBFs fall into two categories :
bubbling and circulating. They are based on the same principle, but in the circulating bed unit a higher fluidisation
velocity creates very intensive mixing of air and fuel. Particles are carried out of the vertical combustion chamber by
the flue gas and are removed in a cyclone to be returned to the FBF through a loop seal. A cross section of a
bubbling FBF is shown in Figure 2. Typical design parameters of a bubbling FBFs, which are much more common
than circulating types, are reported in Table A.5.
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Key
1 Exhaust and ash
2 Pressure tap
3 Sight glass
4 Burner
5 Tuyeres
6 Fuel gun
7 Pressure tap
8 Start-up preheat burner for hot windbox
9Windbox
10 Fluidizing air inlet
11 Refractory arch
12 Fluidised sand bed
13 Freeboard
14 Sludge inlet
15 Thermocouple
16 Sand inlet
Figure 1 — Bubbling fluidised bed furnace (typical cross section)
Advantages of FBFs are low excess air requirement, due to the high turbulence, low NO production, due to
x
effective control of combustion temperature, reliability (no moving parts), flexibility for shock load, adaptability to
sludges at different moisture content (dewatered, partially dried, full dried), heat storage capacity by sand bed, and
possible abatement of acidic compounds within the bed using additives, like limestone and dolomite.
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Disadvantages include ash and sand carry-over, and possible formation of a block of vitrified sand when salts with
low melting points are present. This problem can be attenuated by an addition of chemicals to bind the alkaline
salts.
b) Multiple Hearth Furnace (MHF)
It consists in a vertical cylindrical-refractory lined reactor containing a number of horizontal hearths. Rabble arms,
supported by a single central shaft, rake the sludge radially across the hearths from the top to the bottom, in
counter-current with air and hot gases. A cross section of a multiple hearth furnace is shown in Figure 2. Three
zones can be distinguished in the furnace: drying, with gas temperature up to 400 °C, burning (temperatures of gas
and solid phases of 850 °C to 900 °C), ash cooling (temperatures of ashes and air generally lower than 200 °C).
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Key
1 Sludge cake, screenings and grit
2 Burners
3 Supplemental fuel
4 Combustion air
5 Shaft cooling air return
6 Solids flow
7 Drop holes
8 Rabble arm drive
9 Shaft cooling air
10 Ash discharge
11 Clinker breaker
12 Gas flow
13 Rabble arm (2 or 4 per hearth )
14 Auxiliary air ports
15 Scum
16 Exhaust gas
17 Cooling air discharge
18 Damper
19 In Hearth
20 Out Hearth
Figure 2 — Multiple hearth furnace (typical cross section)
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Typical design values of a MHF are : 2 m to 8 m (diameter), 4 to 14 (hearths, at least 8 desirable), 30 kg to 60 kg
2
wet sludge/m ·h (hearth loading rate), 100 % to 125 % (excess air).
Advantages are flexibility with respect to feed quality and loading rates, durability, low fuel consumption due to
effective heat recovery inside the equipment.
Disadvantages are possible odour problems and emissions of volatile substances, due to the low temperature of
exhaust gas, high need of excess air, due to the low turbulence and high maintenance costs, due to many moving
parts. Moreover, high fuel consumption is needed, if afterburning of exhaust gases has to be accomplished, to take
their temperature from 400 °C to 450 °C to at least 850 °C.
c) Combination of multiple hearth furnace and fluidised bed furnace
Essentially, it consists of a cylindrical brick-faced vertical combustion chamber, in whose lower part a sand bed is
kept fluidised with the aid of combustion air. The fluidised bed is streamed with hot air from below via the windbox
and the tuyeres.
The predrying layers with variable rpm rotating hollow shaft and stirring arms are located in the upper part of the
fluidised bed furnace.The lowest layer serves additionally as distributor level for the even feed of the predried,
crumbly sludge into the underlying fluidised bed. The flue gases, enriched with water vapour and odour laden
components, are fed back into the baking zone of the fluidised bed for after burning in the fluidised bed.
The degree of drying of the MHF can be easily regulated, thus improving the overall performance of the process
reducing the excess air amount.
As a result of the described process there is an extremely stable, self-sustaining incineration process characterised
by low nitrogen oxide and carbon monoxide values in the flue gas. An advantage of this combination is also the
possible reduction of the grate surface of the FBF, in comparison with a process where only a FBF is applied. The
multi-layer fluidised bed furnace can be operated wit
...
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