BE1025691B1 - A BURNING PROCESS AND AN OVEN SYSTEM FOR BURNING ORGANIC MATERIALS - Google Patents

Abstract

A combustion process is provided for burning organic substances comprising the steps of: feeding an organic substance source into a first combustion zone wherein the organic substance source comprises organic substances; supplying a first oxygen source in the first combustion zone; burning the organic substances in the first combustion zone using the first oxygen source at a first operating temperature of at least 850 ° C and a first lambda value of less than 1.0, thereby forming a combustion product gas; optionally cooling the combustion product gas; supplying the optionally cooled combustion product gas to a second combustion zone; supplying a second oxygen source in the second combustion zone; burning the organics of the optionally cooled combustion product gas in the second combustion zone at a second operating temperature between 800 ° C and 950 ° C and a second lambda value higher than 1.0, thereby forming a smoke product gas.

Description

A combustion process and an oven system for burning organic substances

FIELD OF THE INVENTION

The field of the invention is focused on a combustion process and an oven system for burning organic substances.

BACKGROUND OF THE INVENTION

A combustion process for burning organic substances is generally known. For example, waste containing organic substances is incinerated in a combustion unit. The waste generally comprises nitrogen components. The combustion process can form NOx at a high level, such as higher than 200 mg / Nm ³ , in the flue gases of the combustion process. The formation of NOx in the flue gas must be reduced.

Typically, the NOx produced can be reduced by injecting ammonia or urea into the flue gases in the combustion unit with the flue gases having a temperature between 950 and 1050 ° C or by injecting ammonia or urea into the flue gases upstream of a catalyst zone which is a catalyst wherein the flue gases have a temperature between 200 ° C and 450 ° C.

The existing solutions require the consumption of a reagent (ammonia or urea) and / or additional parts, such as an injection system and / or a catalyst, for reducing the NOx produced in the flue gases.

Summary of the invention

Embodiments of the invention aim to improve the combustion process to minimize the formation of thermal and chemical NOx and to reduce or eliminate the amount of NOx in the flue gases from a combustion process of organic substances in a simple manner.

According to a first aspect of the invention, a combustion process is provided for burning organic substances, the process comprising the steps of:

(i) Feeding an organic substance source (w) into a first combustion zone wherein the organic substance source comprises organic substances;

(ii) Feeding a first oxygen source in the first combustion zone;

(iii) The burning of the organic substances in the first combustion zone using the first oxygen source at a first operating temperature of at least 850 ° C

BE2017 / 5801 and a first lambda value of less than 1.0, thereby forming a combustion product gas, the first lambda value being defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic material source in relation to the oxygen in the first incineration zone;

(iv) Optionally cooling the combustion product gas;

(v) Feeding the optionally cooled combustion product gas into a second combustion zone;

(vi) Feeding a second oxygen source into the second combustion zone;

(vii) Burning the organic substances from the optionally cooled combustion product gas in the second combustion zone at a second operating temperature between 800 ° C and 950 ° C and a second lambda value higher than 1.0, thereby forming a smoke product gas, the second lambda value is defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic matter source in relation to the oxygen in the second combustion zone.

The combustion process according to the invention provides that the organic substances are burned in the first combustion zone in a reducing environment which has a lack of oxygen (lambda is less than 1.0). As a result, in the first combustion step, essentially the carbon elements are oxidized, the combustion product gas containing carbon monoxide and optionally hydrogen gas. Free oxygen can react with hydrogen gas to form water (H ₂ O). In the first combustion zone, substantially no or little oxygen is present to combine with nitrogen to form NOx. In this step, the temperature of the gas in the first combustion zone is kept at a first operating temperature of at least 850 ° C. In this way, the organic substances are easily burned. In addition, this first operating temperature essentially allows complete elimination or destruction of smelly components.

The organic substances in the combustion product gas produced are further burned in the second combustion zone. A second oxygen source is added to the second combustion zone to provide an oxidizing environment in the second combustion zone which has a super-stoichiometric ratio (lambda value is higher than 1.0) between the organic substances and the oxygen. In this step, the temperature of the gas in the second combustion zone is kept at a second operating temperature below 950 ° C. In this way, the oxygen present will react with carbon instead of with nitrogen, wherein one

BE2017 / 5801 a reasonably low carbon monoxide content is obtained (less than 10 mg / Nm ³ ) and the amount of NOx produced in the flue gases is kept low (<150 mg / Nm ³ ). The remaining free nitrogen elements are mainly converted to nitrogen N ₂ gas.

In exemplary embodiments, the organic substances of the organic substance may contain bound nitrogen and may not contain substantially bound nitrogen.

In exemplary embodiments, a first incineration unit may comprise the first incineration zone and a second incineration unit may comprise the second incineration zone.

In an exemplary embodiment, each combustion unit may comprise a combustion chamber for housing the combustion zone.

Optionally, the combustion product gas can be cooled before the combustion product gas is supplied to the second combustion zone. For example, in the case that the first operating temperature is higher than the second operating temperature, the combustion product gas can be cooled before the combustion product gas is supplied to the second combustion zone so that the second operating temperature is kept below 950 ° C.

In one embodiment, the cooling step comprises cooling the combustion product gas in a cooling zone to a cooling set temperature which is equal to or lower than the second operating temperature. Preferably, the cooling set temperature is selected to be smaller than the second operating temperature. In an example, the cooling set temperature is between 900 and 850 ° C, preferably below 850 ° C, more preferably below 800 ° C.

The cooling zone is preferably arranged upstream of the second combustion zone. In exemplary embodiments, the cooling zone is arranged downstream of the first combustion zone and can be integrated into the first combustion unit, such as arranged within the first combustion unit downstream of a first combustion zone of the first combustion unit.

The preferred embodiments are reflected in the dependent claims.

According to a second aspect of the invention, an oven system is provided, comprising:

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- a first combustion unit comprising a first combustion zone arranged for burning an organic substance supplied from an organic substance source, thereby forming a combustion product gas;

- optionally a coolant adapted to cool the combustion product gas;

- a second combustion unit comprising a second combustion zone adapted to burn the, optionally cooled, combustion product gas;

supply means for supplying the organic substance source in the first combustion zone, a first oxygen source in the first combustion unit and a second oxygen source in the second combustion unit;

- a control system adapted to control one or more of the following: the supply means, the first combustion unit, the optional refrigerant and the second combustion unit, such that a first operational temperature in the first combustion unit is at least 850 ° C and a first lambda value is less than 1.0, the first lambda value being defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic substance source in relation to the oxygen in the first combustion zone, and such that a second operational temperature in the second combustion unit is between 800 and 950 ° C and a second lambda value is higher than 1.0, the second lambda value being defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic matter source in relation to the oxygen in the second combustion zone.

In exemplary embodiments, the supply means comprise first supply means for supplying the organic substance source in the first combustion unit, first oxygen supply means adapted for supplying a first oxygen source in the first combustion unit and / or second oxygen supply means adapted for supplying a first oxygen source in the second combustion unit.

In exemplary embodiments, the furnace system comprises a cooling zone arranged upstream of the second combustion unit, wherein the combustion product gas is cooled by the optional cooling means in the cooling zone.

In exemplary embodiments, the first combustion unit comprises one of a vertical or horizontal static oven, a rotary drum, such as a rotary oven, a fluidized bed oven, a static grill oven, or a moving grill oven.

Preferred embodiments are reflected in the dependent claims.

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In an exemplary embodiment, the combustion product gas has a calorific value of at least 2.0 MJ / Nm3 and most 5.0 MJ / Nm3, preferably a calorific value of at least 2.5 MJ / Nm3 and most 4.5 MJ / Nm3.

In an exemplary embodiment, the feed ratio of the organic matter source to the oxygen source of feed steps (i) and (ii) is controlled such that the first lambda value in the first combustion zone is less than 1.0.

In an exemplary embodiment, the first operating temperature is in the range between 850 and 1350 ° C, preferably between 900 and 1100 ° C, more preferably about 1050 ° C, and / or wherein the first lambda value is less than 0.9, preferably less than 0.8, more preferably between 0.7 and 0.5.

In an exemplary embodiment, the first combustion step (iii) comprises partially recirculating the combustion product gas in the first combustion zone.

In an exemplary embodiment, during the first combustion step (iii) the first combustion zone is cooled by a cooling step, preferably comprising cooling the smoke product gas downstream of the second combustion zone and supplying the cooled smoke product gas into the first combustion zone for maintaining of the first operating temperature below 1150 ° C, preferably at about 1050 ° C.

In an exemplary embodiment, the optional cooling step (iv) comprises cooling the combustion product gas to a cooling set temperature, which is equal to or lower than the second operating temperature.

In an exemplary embodiment, the second operating temperature is at least 850 ° C, preferably at least 900 ° C, more preferably between 920 and 930 ° C.

In an exemplary embodiment, the feed ratio of the combustion product gas and the oxygen source of feed steps (v) and (vi) is controlled such that the second lambda value in the second combustion zone is greater than 1.0, preferably between 1.1 and 1.3.

In an exemplary embodiment, the process additionally includes the step:

BE2017 / 5801 (viii) Supplying a support fuel to the first combustion zone and / or the second combustion zone.

In embodiments, the support fuel may be a fuel gas, such as a hydrogen gas and a natural fossil gas, and may be a liquid fuel, such as diesel.

In an exemplary embodiment, the optional cooling step (iv) includes cooling the smoke product gas downstream of the second combustion zone and using the cooled smoke product gas (cF) to cool the combustion product gas (P).

In an exemplary embodiment, the optional cooling step (iv) comprises supplying water, such as spraying water into a cooling zone downstream of the first combustion zone.

In an exemplary embodiment, the optional cooling step (iv) is controlled as a function of the second operational temperature.

In an exemplary embodiment, a heat-recovering boiler is provided and integrated into at least one of the first incineration zone, the cooling zone and the second incineration zone, additionally comprising the step of recovering heat from at least one of the first incineration zone, the cooling zone and the second incineration zone by the heat recovery boiler.

In an exemplary embodiment, the heat-recovery boiler comprises a heat-recovery fluid adapted to cool at least one of the first combustion zone, the cooling zone and the second combustion zone, and wherein a flow of the heat-recovery fluid is controlled as a function of a temperature in the first combustion zone, the cooling zone and the second combustion zone, respectively.

In an exemplary embodiment, a residence time in the first combustion zone is at most 4 s, preferably at most 2 s, more preferably less than 1 s.

In an exemplary embodiment, a residence time in the second combustion zone is at most 4 s, preferably at most 2 s, more preferably less than 1 s.

In an exemplary embodiment, the second oxygen supply step (vi) is controlled such that the flue product gas comprises less than 5 vol%, preferably less than 3 vol% oxygen. A lower oxygen level is advantageous when using cooled smoke product gas cF as the coolant of the combustion product gas P. In this way, the cooled smoke product gas cF can

BE2017 / 5801 are used for cooling the combustion product gas P while the oxygen level in the corresponding first combustion zone and / or second combustion zone is substantially not affected.

In an exemplary embodiment, wherein the second oxygen supply step (vi) comprises adjusting the second oxygen stream based on a step of measuring the oxygen volume concentration in the flue product gas.

In an exemplary embodiment, the oxygen flow from the second oxygen supply step (vi) is predetermined based on a step of theoretically calculating a concentration of oxygen in the flue product gas based on a predetermined comparison, the calculation preferably being based on an oxygen concentration of 3% maximum.

In an exemplary embodiment, additionally comprising a start-up process prior to the combustion step (iii), which start-up process comprises the steps of: (ix) controlling the feed steps (i), (ii), optionally including the feed step (viii), such that the temperature in the first combustion zone reaches a substantially stable start-up temperature of at least 850 ° C and a first lambda value of at least 1.0; (x) reducing the first oxygen source stream from the feed step (ii) while keeping the organic matter source stream from the feed step (ii) substantially constant so that the first lambda value is reduced to less than 1.0, preferably less than 0.9, more preferably about 0.85, even more preferably less than 0.8, thereby reaching the first operating temperature between 900 and 1100 ° C.

In an exemplary embodiment, the time of the step (x) of reducing the oxygen source stream is less than 10 s. This supports a rapid reduction of the oxygen level in the first combustion zone and limits the maximum temperature reached in the first combustion zone during the reduction step (x) while the first lambda value is reduced from above 1.0 to below 1.0 in the first combustion zone.

In an exemplary embodiment, the organic substance source comprises at least one selected from a gas phase, a liquid phase, a sludge phase and a solid phase.

In an exemplary embodiment, the organic matter source comprises a solid phase, wherein the first incineration zone comprises a grid or the first incineration zone is provided with a

BE2017 / 5801 rotary drum, such as a rotary oven, or wherein the organic matter source comprises a sludge phase, the first combustion zone comprising a fluidized bed.

In an exemplary embodiment, the supply means comprise first supply means for supplying the organic matter source in the first combustion unit, first oxygen supply means adapted for supplying a first oxygen source in the first combustion unit and / or second oxygen supply means adapted for supplying a first oxygen source in the second combustion unit.

In an exemplary embodiment, the first combustion unit comprises one of a rotary drum, such as a rotary oven, a fluidized bed or a grid system.

In an exemplary embodiment, the rotary drum comprises a sealing system for preventing air leakage in the rotary drum.

In an exemplary embodiment, the furnace system comprises a cooling zone arranged upstream of the second combustion unit, wherein the combustion product gas is cooled by the optional cooling means in the cooling zone.

In an exemplary embodiment, the second combustion unit and optionally the cooling zone are adapted to remove ash on the bottom side of the second combustion unit and the cooling zone, respectively.

In an exemplary embodiment, the first combustion unit comprises a temperature sensor for measuring the first operational temperature and wherein the control system is adapted to control the first operational temperature in response to the measured first operational temperature.

In an exemplary embodiment, the first combustion unit comprises cooling means for cooling the first combustion unit, the cooling means comprising at least one of supply means for supplying cooled smoke product gas and supply means for supplying water into the first combustion unit, such as a spraying device for spraying water in the first combustion unit.

In an exemplary embodiment, the first combustion unit comprises recirculation means for partially recirculating the combustion product gas in the first combustion zone.

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In an exemplary embodiment, the recirculation means comprises a mixing wall arranged at a downstream end of the first combustion unit and having a plurality of openings adapted to direct the combustion product gas downstream of the mixing wall along a plurality of flow paths which are substantially parallel to each other.

In an exemplary embodiment, the second combustion unit comprises a temperature sensor for measuring the second operational temperature and wherein the control system is adapted to control the second operational temperature in response to the measured second operational temperature.

In an exemplary embodiment, the optional cooling means are controlled in response to the measured second operating temperature.

In an exemplary embodiment, the furnace system additionally comprises at least one support fuel supply means adapted to supply a support fuel in at least one of the first combustion zone and the second combustion zone, and wherein the at least one support fuel supply means is controlled by the control system in response to a measurement of the first operating temperature and / or in response to a measurement of the second operating temperature.

In an exemplary embodiment, the furnace system additionally comprises a heat recovery boiler integrated in at least one of the first combustion unit, comprising the optional cooling means and the second combustion unit.

In an exemplary embodiment, the first combustion unit comprises a combustion chamber for accommodating the combustion zone having a length to diameter ratio between 3 and 8, more preferably having a length to diameter ratio of about 4.

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Brief description of the figures

The accompanying figures are used to illustrate presently preferred non-limiting exemplary embodiments of devices according to the present invention.

The above and other advantages of the elements and objects of the invention become apparent and the invention can be better understood from the following detailed description when read in conjunction with the accompanying figures in which:

FIG. 1 is a schematic drawing of an exemplary embodiment of an oven system for burning organic substances;

FIG. 2 is a schematic drawing of another exemplary embodiment of an oven system for burning organic substances;

FIG. 3 is a schematic drawing of another more detailed exemplary embodiment of an oven system for burning organic substances;

FIG. 4 is a schematic drawing of another more detailed exemplary embodiment of an oven system for burning organic substances;

Detailed description of the illustrated embodiments

The figures are only schematic and not restrictive. In the figures, the size of some elements may be exaggerated and are not drawn to scale for illustrative purposes. Reference marks in the claims are not intended to limit the scope of protection. In the figures, the same reference characters are used to refer to the same or corresponding elements.

FIG. 1 illustrates an exemplary embodiment of an oven system for burning organic substances. The system comprises a first combustion unit 100, a second combustion unit 200 and a control system 10. The system further comprises first supply means 110 adapted for supplying an organic material source W in the first combustion unit 100, first oxygen supply means 120 adapted for supplying a first oxygen source O1 in a first combustion zone 105 of the first combustion unit 100 and second oxygen supply means 320 adapted to supply a second oxygen source O2 in a second combustion zone 205 of the second combustion unit 200. The control system controls the first combustion unit 100, the second combustion unit 200 , first supply means 110, first oxygen supply means 120 and the second oxygen supply means 320 (for simplicity, not all control lines are shown in Figure 1).

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The organic material source W can be any waste source, including gaseous waste, liquid waste, such as contaminated water, solid waste or sludge waste. The first oxygen source 01 and the second oxygen source O2 can be any of air, oxygen, or any other suitable oxidizing agent-containing source. Although the first oxygen source 01 and the second oxygen source O2 are illustrated as two completely separate streams, it is clear to those skilled in the art that both of the first oxygen source 01 and the second oxygen source O2 may originate from one and the same oxygen source in an alternative embodiment. Compositions of the first oxygen source 01 and the second oxygen source O2 may therefore be substantially identical or may be different depending on the current configuration of the first and second oxygen supply means 120, 220.

The first oxygen supply means 110 may be any suitable means, such as a fan, a supply control valve or a pressure system adapted to supply the first oxygen source 01, such as air, oxygen, etc., into the first combustion zone 105 of the first combustion unit 100.

The first combustion unit is adapted to receive the organic substance source W and the first oxygen source 01 in the first combustion zone 105. The first combustion unit comprises a first combustion means, such as a burner, for burning an organic substance supplied from the organic substance source W into the first combustion zone 105 of, thereby producing a combustion product gas P, also called flue gas. Burning in the sense of this invention can also be described as incineration.

The first combustion unit, the first supply means 110 and the first oxygen supply means 120 are controlled by the control system 10 for operating at a first operational temperature of at least 900 ° C and a first lambda value of less than 1.0.

The first lambda value is defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic material source in relation to the oxygen in the first combustion zone.

At the first lambda value 1.0, the molar ratio of the organic matter source to the oxygen in the combustion unit is equal to the stoichiometric ratio. When the first lambda value is less than 1.0, the molar ratio of the organic matter source to the oxygen in the combustion unit is less than 1.0 (sub-stoichiometric).

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When the first lambda value is higher than 1.0, the molar ratio of the organic matter source to the oxygen in the combustion unit is greater than 1.0 (superstoichiometric).

In fact, when the first lambda value is less than 1.0, a reducing environment is provided in the first combustion unit which is deficient in oxygen. As a result, in the first combustion step, primarily the carbon elements are oxidized, the combustion product gas P containing carbon monoxide and optionally hydrogen gas. Free oxygen can react with hydrogen to form water. In the first combustion unit, substantially no or little oxygen is present for combining with nitrogen to form NOx. In this step, the temperature of the gas in the first combustion unit is kept at a first operating temperature of at least 850 ° C. In this way, the organic substances are easily burned.

The second combustion unit 200 is arranged downstream of the first combustion unit 100. The combustion product gas P is supplied to the second combustion zone 205 of the second combustion unit 200. The second oxygen supply means 220 can be any suitable means, such as a fan, a supply control valve or a pressure system, arranged for supplying the second oxygen source O2, such as air, oxygen, etc., into the second combustion zone 205 of the second combustion unit 200. The second combustion unit 200 is adapted to receive the combustion product gas P and the second oxygen source O2 in the second combustion zone 205 The second combustion unit 200 comprises a second combustion means, such as a burner, for burning an organic substance supplied from the organic material source into the second combustion zone 205, thereby producing a smoke product gas F. The second combustion unit 200 and the second acid-fuel supply means and 220 are controlled by the control system for operating at a second operating temperature of at least 950 ° C and a second lambda value higher than 1.0.

The second lambda value is defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic matter source to the oxygen in the second combustion unit.

The first operating temperature at which the first combustion unit 100 operates in the first combustion zone 105 is in the range between 850 ° C and 1350 ° C, preferably between 900 and 1100 ° C, more preferably between 920 and 930 ° C. The lambda value at which the first

BE2017 / 5801 combustion unit operating is less than 0.9, preferably less than 0.8, more preferably between 0.7 and 0.5.

The second operating temperature at which the second combustion unit 200 operates in the second combustion zone 205 is in the range between 800 and 950 ° C, preferably at least 900 ° C, more preferably between 920 and 930 ° C.

The second lambda value at which the second combustion unit operates is higher than 1.0, preferably between 1.1 and 1.3.

When the first operating temperature is selected between 850 ° C and 950 ° C and the second operational temperature is selected between 850 ° C and 950 ° C, the produced combustion product gas can be supplied to the second combustion unit 200 without cooling the combustion product gas P prior to supplying the produced combustion product gas P to the second combustion unit 200.

Optionally, the furnace system comprises a recirculation system 600 for the flue product gas F, the recirculation system comprising cooling means for cooling the flue product gas cF. Such a coolant may, for example, be a heat recovery unit, such as a heat recovery boiler.

The smoke product gas F is cooled downstream of the second combustion unit 200 and a portion of the cooled smoke product gas cF is recycled and supplied to the first combustion unit 100 to maintain the first operating temperature in the first combustion unit in the desired range. Additionally or alternatively, a portion of the cooled smoke product gas cF is recycled and supplied to the second combustion unit 200 to maintain the second operating temperature in the second combustion zone 105 of the second combustion unit 200 in the desired area.

In this example, a smoke product gas fan and / or a smoke gas supply control valve 650 is provided in the recirculation system 600, which is controlled by the control system 10 for supplying the cooled smoke product gas cF.

Rough water, low calorific liquids, steam, nitrogen or any other refrigerant can be used as a relapse refrigerant in the event that the cooling with recirculated flue product gas cF fails or is insufficient and such refrigerant can be injected through spray nozzles in the first combustion unit 100 and / or the second combustion unit 200, respectively.

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Using the furnace system of Fig. 1, the combustion process can be optimized for burning the organic substances while reducing the amount of NOx produced. In this way, low emission levels in flue product gases can be achieved.

In all embodiments described herein, the first combustion unit 100 may be a vertical or horizontal static oven, a rotary oven, a fluidized bed oven, a static grill oven, or a moving grill oven. Typically, solid waste and / or sludge are thermally processed in a rotary oven, a fluidized bed oven or a grid oven where the combustible fraction is gasified and "flared" from the inert fraction. The inert fraction and residues (bottom ash) are collected and removed via an embedded chain conveyor at the end of the rotary oven. The temperature inside the rotary oven is controlled at a predefined set point, for example between 850 ° C and 1000 ° C, by a combustion air stream.

In all embodiments described herein, the first combustion unit 100 is controlled such that the residence time during the first combustion step in the first combustion unit 100 is at most 4 s, preferably at most 2 s, more preferably less than 1 s. In a particular example, the residence time in the first combustion unit 100 is controlled by applying an underpressure, such as an underpressure in the first combustion unit 100 between -10 mbarg and 0 mbarg.

In a particular example, the residence time in the first incineration unit 100 can be controlled by any of a step of controlling the speed of the waste to be less than 5 m / s or by a step of controlling the energy released to be less than 0.3-0.5 MW / Nm ³ .

In all embodiments described herein, the second combustion unit is controlled such that the residence time during the second combustion step in the second combustion unit 200 is at most 4 s, preferably at most 2 s, more preferably less than 1 s. Preferably, in an effective zone of the second combustion unit 200, there may be a temperature above 850 ° C for 2 seconds to ensure good burn-out.

In a particular example, the residence time in the second combustion unit 200 can be controlled by controlling injection rates of injected second oxygen source O2 provided by the second oxygen supply means 220 and controlling injection rates of injected refrigerant, such as injected cooled smoke product gas cF.

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In all embodiments described herein, the second oxygen supply means 220 may be controlled by the control system 10 such that the flue product gas comprises less than 5 volume% oxygen, preferably less than 3 volume%. The furnace system comprises an oxygen level sensor adapted to measure the oxygen volume concentration in the flue product gas.

The volume percentage (vol%) of oxygen as defined herein is the volume percentage of oxygen in a wet state of the gas.

Additionally, the control system 10 can be arranged to predetermine the oxygen flow for supplying the second oxygen source O2 in the combustion unit 200 based on a step of theoretically calculating a concentration of 3% oxygen by volume in the flue product gas F based on a predetermined comparison. The second oxygen supply means 220 are controlled to provide the predetermined oxygen flow to the second combustion unit 200. This is called the supply advance control loop.

The oxygen level sensor provides a signal to the control system 10 which describes the measured oxygen volume concentration in the flue product gas F. The control system 10 adjusts the volume flow provided by the second oxygen supply means 220 based on the measured oxygen volume concentration in the flue product gas F such that a concentration of about 3 volume% oxygen or less than 3 volume% oxygen in the smoke product gas is achieved. This is called the feed-back control loop.

FIG. 2 illustrates another exemplary embodiment of an oven system for burning organic substances. As in Figure 1, the system comprises a first combustion unit 100 comprising a first combustion zone 105, a second combustion unit 200 comprising a second combustion zone 205, a first supply means 110, a first oxygen supply means 120, a second oxygen supply means 220 and a control system 10.

The furnace system further comprises a cooling zone 300 such as a cooling chamber, which is arranged downstream of the first combustion unit 100 and upstream of the second combustion unit 200.

The first supply means 110 are adapted for supplying the organic substance source W into a first combustion zone 105 of the first incineration unit 100. The organic substance source W can be any of waste sources, including gaseous waste, liquid-shaped waste such as contaminated water, solid-dust waste or sludge waste.

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The first oxygen supply means 120, such as a fan, are adapted to supply a first oxygen source Ol, such as air, oxygen, etc .; in the first combustion unit 100.

The first combustion unit 100 is adapted to receive the organic substance source W and the first oxygen source Ol in the first combustion zone 105. The first combustion unit 100 comprises a first combustion means, such as a burner, for burning an organic substance supplied from the organic substance source W, thereby producing a combustion product gas P. The first combustion unit 100, the first supply means 110 and the first oxygen supply means 120 are controlled by the control system 10 for operating at a first operational temperature of at least 900 ° C at a first lambda value of less than 1.0.

In a particular example, the first operating temperature in the first combustion unit 100 is greater than 950 ° C, preferably between 950 and 1100 ° C, more preferably between 1000 and about 1100 ° C.

In particular, higher temperatures may be advantageous if the first combustion chamber is to be operated in a slag-forming mode or if stubborn chemicals are present. Also, when operating the first chamber at a high temperature, the entire stoichiometric ratio of oxygen (lambda) can be minimized since less cooling air is required.

In exemplary embodiments, the first operational temperature is selected such that the resulting solid residues, such as shafts, are substantially inert and / or are substantially fully reacted. In particular exemplary embodiments, the first combustion unit 100, as provided by a rotary oven, is operated in a slag forming mode such that the shafts are melted and can flow into an ash collection apparatus.

The cooling zone 300 or cooling chamber is arranged downstream of the first combustion unit 100. The combustion product gas P is led into the cooling zone 300. In the cooling zone 300, the combustion product gas P is cooled to a cooling set temperature that is equal to or lower than the second operating temperature of the second combustion unit 200. Preferably, the cooling set temperature is selected to be lower than the second operating temperature. In an example, the cooling set temperature is between 900 and 850 ° C, preferably below 850 ° C, more preferably below 800 ° C.

The cooling zone 300 comprises cooling means adapted to cool the combustion product gas P in the cooling zone 300. The control system 10 controls the cooling means. The control system 10 controls the cooling means to obtain the cooling set temperature.

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In an example shown in Fig. 2, the furnace system comprises a recirculation system 600 for flue product gas F, the recirculation system comprising cooling means for cooling the flue product gas cF. Such a cooling means can, for example, be a heat recovery unit, such as a heat exchanger or a heat recovery boiler.

The cooled smoke product gas cF is recycled to be supplied to at least one of the first combustion unit 100, the second combustion unit 200 and / or the cooling zone 300.

In this example, a smoke product gas fan and / or a smoke gas supply control valve 650 is provided in the recirculation system 600 for supplying the cooled smoke product gas into the cooling zone 300. The supply of the cooled smoke product gas cF into the cooling zone 300 is controlled by the control system 10 in response to a measured second operating temperature of the second combustion unit 200.

The second operating temperature in the second combustion unit 200 is controlled to be between 800 and 950 ° C, preferably at least 850 ° C.

In an example, in the case that the measured temperature in the second combustion unit 200 drops below 850 ° C, the flow of the cooled flue product gas cF in the cooling zone 300 can be reduced to reduce the cooling in the cooling zone 300.

In another example, in the case that the measured second operational temperature in the second combustion unit 200 rises above 950 ° C, the flow of the cooled flue product gas cF in the flow zone 300 can be increased to increase the cooling in the cooling zone 300. Additionally or alternatively, in the case of supplying the cooled flue product gas cF to the cooling zone 300 is insufficient or fails, unmixed water can be supplied to the cooling zone 300 as a fall-back cooling agent. In a special example, the furnace system comprises water spraying means for spraying (waste) water into the cooling zone 300. The water spraying means are controlled by the control system.

The recirculation system 600 can additionally be used for cooling the first combustion unit 100. In this example, a flue product gas fan and / or a flue gas supply control valve is provided in the recirculation system for supplying the cooled flue product gas cF in the first combustion unit 100. The supply of the cooled smoke product gas cF in the first combustion unit 100 is controlled by the control system 10 in response to a measured first operating temperature of the first combustion unit 100.

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Because the sub-stoichiometric combustion process in the first combustion unit 100 can produce a lot of energy, the first combustion unit 100 can be cooled with the recirculated cooled smoke product gas cF.

In one example, in the case that the measured first operational temperature in the first combustion unit 100 drops below 1050 ° C, the flow of the cooled flue product gas cF in the first combustion unit 100 can be reduced to reduce the cooling in the first combustion unit 100 .

In another example, in the case that the measured first operational temperature in the first combustion unit 100 rises above 1100 ° C, the flow of the cooled product gas cF in the first combustion unit 100 can be increased to increase the cooling in the first combustion unit 100.

Additionally or alternatively, the cooled smoke product gas cF is recycled and supplied to the second combustion unit 200 to maintain the second operating temperature in the second combustion zone 205 in the second combustion unit 200 in the desired area. Unmixed water can be used as a relapse cooling agent in the event that the cooling with recirculated cooled flue product gas cF fails or is insufficient.

The furnace system additionally comprises a first support fuel supply means 130 adapted for supplying support fuel E1 into the first combustion unit 100 and a second support fuel supply means 230 adapted for supplying a support fuel E2 into the second fuel unit separately. The support fuel E1, E2 may contain a hydrogen gas, such as a support fuel produced by a batch of hydrogen reactor. In embodiments, the support fuel may be a fuel gas, such as a hydrogen gas and a natural fossil gas, and may be a liquid fuel, such as diesel.

Although the support fuel E1 and the support fuel E2 are illustrated as two completely separate streams, it is obvious to those skilled in the art that both of the support fuel E1 and the support fuel E2 may originate from one and the same support fuel source in an alternative embodiment. Compositions of the support fuel E1 and the support fuel E2 may therefore be substantially identical or may be different depending on the configuration of the support fuel supply means 130, 230.

Each support fuel supply means 130, 230 is controlled by the control system 10 separately in response to the measured temperature in the first combustion unit 100 and in response to the measured temperature in the second fuel unit 200, respectively.

BE2017 / 5801

In an example, in the case that the first operating temperature in the first combustion unit 100 drops too far below the first desired operating temperature, for example at 1050 ° C, the support fuel flow provided by the support fuel supply means 130 can be amplified by the control system 10 to prevent that the temperature in the first combustion unit 100 drops further. This is typically advantageous when incinerating waste sources containing material having reasonably low calorific values, such as dewatered sludge, rejected plastics from pulp operations of recycled paper, wet municipal solid waste or municipal solid waste with high organic content. Waste with reasonably low calorific values typically have heating values below 7000 MJ / kg, more preferably below 3500 MJ / kg.

In another example, in the event that the second operating temperature in the second combustion zone 205 of the second combustion unit 200 drops too far below the desired second operational temperature, e.g., 925 ° C, the support fuel flow provided by the support fuel supply means 230 will be enhanced by the control system 10 to prevent the temperature in the second combustion unit 200 from falling further.

Shown in the embodiment, the control system 10 controls the first combustion unit 100, the second combustion unit 200, the first supply means 110, the first oxygen supply means 120, the second oxygen supply means 220, the first support fuel supply means 130, the second support fuel supply means 230 and the cooling means (for simplicity not all control lines are shown in the schematic figure).

FIG. 3 illustrates another more detailed exemplary embodiment of an oven system for burning organic substances. As in Figure 2, the system comprises a first combustion unit 100 comprising a first combustion zone 105, a cooling zone 300, a second cooling unit 200 comprising a second combustion zone 205, a first supply means 110, a first oxygen supply means 120, a second oxygen supply means 220, a recirculation system 600 for recycling cooled smoke product gas to at least one of the first combustion unit 100, a cooling zone 300 and a second combustion unit 200, a support fuel supply means 130 for supplying a support fuel into the first combustion unit 100 and a control system 10.

BE2017 / 5801

In all of the described embodiments, the support fuel supply means 130 can be used for a start-up process of the combustion process in the first combustion unit 100. In the start-up process, the following steps are performed prior to the regular combustion: in a first step, controlling the first combustion unit 100 for operating in an oxidizing mode (first lambda higher than 1.0) using the support fuel supply means 130 for supplying a support fuel E1 in the first combustion unit 100 and using the first oxygen supply means 120 such as a fan, for supplying a first oxygen source 01, such as air, oxygen, etc., in the first combustion unit 100.

In a second step, once a stable start-up temperature, such as 850 ° C, is achieved, the first supply means 110 are controlled for supplying the organic matter source into the first combustion unit 100 while the support supply means 130 is controlled for reducing the supply of the support fuel E1 in the first combustion unit 100. In the second step, the first combustion unit 100 is still operated in the oxidizing mode (first lambda higher than 1.0). A stable start-up temperature herein is a temperature above the auto-ignition point of the organic substances from the organic material source. In the second step, the flow of the organic matter source in the first combustion unit 100 can be boosted to a nominal flow rate (set point) and the first oxygen source flow is controlled to operate the first combustion unit 100 under oxidizing conditions.

In a third step, reducing the first oxygen source stream provided by the first oxygen supply means 120 while the organic substance source stream provided by the first supply means 110 is maintained at a substantially constant level such that the first lambda value is reduced to be less than 1.0 , preferably less than 0.9, more preferably about 0.95, even more preferably less than 0.8, wherein the first operating temperature is reached, such as between 900 and 1100 ° C. The required amount of first oxygen source stream can be calculated so that the sub-stoichiometric reducing factor (e.g., the desired lambda value of 0.85) will be achieved.

Preferably, the time of the reducing step for reducing the first oxygen source stream and obtaining a sub-stoichiometric environment in the first combustion unit 100, wherein the first lambda value is reduced to less than 1.0, is less than x seconds. Lowering the first oxygen source stream causes the temperature to rise in the first heating unit 100 to reach a maximum high peak level. When the first oxygen source stream is further reduced, less will

BE2017 / 5801 supporting fuel E1 are burned. This will further lower the temperature below the above-mentioned maximum temperature peak level.

The first oxygen source stream will be reduced as quickly as possible, thereby reducing the first lambda in the first combustion unit 100, to pass through the maximum temperature zone without actually reaching the maximum temperature.

Downstream of the second combustion unit 200, the furnace system additionally comprises a heat recovery unit 400, such as a heat recovery boiler. The heat-recovering boiler is adapted to extract heat from the smoke product gas F, thereby cooling the smoke product gas cF.

Downstream of the heat recovery unit 400, the furnace system additionally comprises a cleaning unit 500 adapted to clean the cooled smoke product gas cF. The cleaning unit, for example, may comprise a catalytic reactor adapted for a catalytic oxidation of dioxins and furans and / or a catalytic reactor adapted for a catalytic reduction of NOx. A catalytic reactor adapted for a catalytic reduction of NOx is generally known in the art and can typically be performed by injecting ammonia or urea into the flue product gases upstream of a catalytic zone comprising a catalyst, wherein the flue product gases have a temperature have between 200 ° C and 450 ° C.

FIG. 4 illustrates another more detailed exemplary embodiment of an oven system for burning organic substances. As in Fig. 3, the system comprises a first combustion unit 100 comprising a first combustion zone 105, a cooling zone 300, a second combustion unit 200 comprising a second combustion zone 205, a first supply means 110, a first oxygen supply means 120, a second oxygen supply means 220, a recirculation system 600 for recirculating cooled flue product gas to at least one of the first combustion unit 100, a cooling zone 300 and a second combustion unit 200, a heat recovery unit 400, a cleaning unit 500 and a control system 10 (for simplicity, not all control lines in FIG. 4 shown).

The first combustion unit of the oven system is provided by means of a rotary oven. The solid waste and / or sludge are thermally processed in the rotatable furnace whereby the combustible fraction is gasified and burned off from the inert fraction. The inert fraction and residues (bottom ash) are collected and removed via a submerged chain conveyor at the end of the rotary oven.

BE2017 / 5801

The furnace system is additionally controlled in a similar manner by the control system as the furnace system shown in Fig. 3. In addition, the cooling zone 300 and the second combustion unit 200 have a conical bottom leading to an underlying extraction tank. Solid shafts and optionally molten shafts and salts can leave the cooling zone and the second combustion unit 200 via the conical bottom to the lower extraction tank. A chain conveyor, preferably at least partially submerged in this extraction tank, can additionally transport the combustion residues to an open removable container. A constant water level in the extraction tank can guarantee airtightness and the prevention of unwanted intake of fresh air. The combustion residue can still glow when it leaves the cooling zone 300 and the second combustion unit 200. The water in the extraction tank cools the residue and additionally stabilizes the degradation process.

The heat recovery unit 400 may be a heat recovery boiler. The heat-recovering boiler is adapted to extract heat from the smoke product gas F, thereby cooling the smoke product gas cF.

The system of FIG. 4 additionally includes a recirculation line 600 connected between an output of the cleaning unit 500 and an input of the cooling zone 300; and a control means 650 for controlling a flow through the recirculation line 600 as a function of a desired temperature in the second combustion unit 200. The control means 650 may comprise a valve. In this way, a suitable amount of cooled smoke product gas cF exiting the heat recovery unit 400 can be injected into a cooling chamber 300.

In one embodiment (not shown), the heat-recovering boiler 400 is integrated in the second combustion unit 200. The heat-recovering boiler 400 is arranged for controllably recovering heat from the second combustion unit 200. The first boiler 100 comprises a heat-recovering liquid, such as boiler supply water, arranged for cooling the second combustion unit 200, and wherein a flow of the heat recovery fluid is controlled as a function of a temperature in the second combustion unit 200.

Alternatively, the heat-recovering boiler 100 can be integrated into any of the first combustion unit 100 and the cooling zone 300.

Examples

In the following examples, variations in combustion yield and cooling with coolants, cooled smoke product gas cF, are shown in these examples. The examples are indicative of one

BE2017 / 5801 incineration process in an oven system as shown and described in relation to figures 2, 3 and 4, in which a cooling zone is used for controllably cooling the combustion product gas P. In these examples, the waste is incinerated in a first incineration zone in a reducing environment (first lambda value is less than 1.0). As a result, the carbon elements are substantially oxidized, the combustion product gas containing carbon monoxide and optionally containing hydrogen. Free oxygen can react with hydrogen gas to form water (H ₂ O). In the first combustion zone essentially no or little oxygen is left to combine with nitrogen or to form NOx. Table I below shows the composition of the combustion product P (also called syngas).

Example # Example 1 Example 2 Power yield 60% from 22 MW 110% of 22 MW Cooled flue gas cF Temperature (K) 523 K 523 K Combustion air Temperature (K) 283 K 283 K Combustion product gas P Composition (V%) CO - 11.71% CO ₂ - 4.47% H ₂ - 4% H ₂ O-25% N ₂ - 54.82% CO-11.71% CO ₂ -4.47% H ₂ - 4% H ₂ O-25% N ₂ - 54.82% Combustion product gas P - current (kg / h) 14580 26791 Combustion air Injection (kg / h) 8673 15921 Cooled flue gas cF Injection (kg / h) 12571 21188 Second operating temperature (K) 1161 K 1196 K Flue gas F Composition (V%) N ₂ - 65.92% O ₂ - 3.24% H ₂ O - 20.04% CO ₂ - 10.79% N ₂ - 65.92% O ₂ - 3.24% H ₂ O - 20.04% CO ₂ - 10.79%

Table I: Variations in power yield and cooling flows

BE2017 / 5801

Table I further gives an indication of the temperatures of the cooled flue gas cF and the temperature of the combustion air that have been used. As visible, the combustion air is introduced to provide an oxidizing environment in the second combustion zone of the second combustion unit.

The combustion air can already be used to reduce the temperature in the combustion product gas P. As shown in Table I, the amount of combustion air that is introduced substantially scales with the amount of power output (or amount of burnt waste). However, at a certain point, more combustion air cannot be added. The cooled flue gas is injected to further cool the product gas P, such that a second operating temperature of at most 1200 K (at most about 930 ° C) is achieved. As can be seen in Example 2, a higher injection flow of cooled flue gas cF is required to maintain the second operating temperature below 1200 K.

In these examples 1 and 2, the resulting flue gas F has an oxygen content of about 3 vol. % (wet), essentially no carbon monoxide (<10 mg / Nm ³ ) and a NOx content of less than 150 mg / Nm ³ .

In all embodiments described herein, the cooling means can be any of cooled recycled flue gases, steam, waste water and low calorific liquids or combinations thereof.

For example, in a modified embodiment of the embodiment shown in Fig. 2, the cooling means may be steam or waste water, which are controlled by the control unit 10 to be injected into at least one of the first combustion unit 100, the cooling zone 300 and the second combustion zone 200 instead of injecting cooled recirculated flue gases cF.

Additionally or alternatively, cooling can also be achieved by flowing the combustion product gas P from the reducing first combustion unit 100 into a heat exchanger. This heat exchanger can be a water pipe boiler (either self-circulated or using controlled circulation) or can be a higher temperature air / gas heat exchanger.

Claims (5)

A combustion process for burning organic substances, the process comprising the steps of: (i) Feeding an organic substance source (W) into a first combustion zone (105), wherein the organic substance source comprises organic substances; (ii) supplying a first oxygen source (01) in the first combustion zone; (iii) Burning the organic substances in the first combustion zone (105) using the first oxygen source (01) at a first operating temperature of at least 850 ° C and honoring first lambda value less than 1.0, thereby forming a combustion product gas (P), wherein the first lambda value is defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic substance source in relation to the oxygen in the first combustion zone; (iv) Optionally cooling the combustion product gas; (v) Feeding the optionally cooled combustion product gas (P) into a second combustion zone (205); (vi) Feeding a second oxygen source (O2) into the second combustion zone; (vil) Burning the organic substances from the optionally cooled combustion product gas in the second combustion zone (205) at a second operating temperature between 800 ° C and 950 ° C and a second lambda value higher than 1.0, thereby forming a smoke product gas (F), wherein the second lambda value is defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic substance source in relation to the oxygen in the second combustion zone. The combustion process according to claim 1, wherein the combustion product gas has a calorific value of at least 2.0 MJ / Nm ³ and at most 5.0 MJ / Nm ³ , preferably has a calorific value of at least 2.5 MJ / Nni ³ and at most 4.5 MJ / 30 Nm ³ . The combustion process according to any of the preceding claims, wherein the feed ratio of the organic matter source to the oxygen source of the feed steps (i) and (ii) is controlled such that the first lambda value in the first 35 combustion zone is less than 1.0. BE2017 / 5801 The combustion process according to any of the preceding claims, wherein the first operating temperature is in the range between 850 and 1350 ° C, preferably between 900 and 1100 ° C, more preferably about 1050 ° C, and / or wherein the first lambda value is less than 0.9, preferably less than 0.8, more preferably between 0.7 and 0.5. The combustion process according to any of the preceding claims, wherein the first combustion step (iii) partially recycled the combustion product gas into the first combustion zone. The combustion process according to any of the preceding claims, wherein during the first combustion step (iii) the first combustion zone is cooled by a cooling step, preferably comprising cooling the smoke product gas downstream of the second combustion zone and supplying the cooled smoke product gas (cF in the first incineration zone, for maintaining the first operating temperature below 1150 ° C, preferably at about 1050 ° C. The combustion process according to any of the preceding claims, wherein the optional cooling step (iv) comprises cooling the combustion product gas to a cooling set temperature that is equal to or lower than the second operating temperature. The combustion process according to any of the preceding claims, wherein the second operating temperature is at least 850 ° C, preferably at least 900 ° C, more preferably between 920 and 930 ° C. The combustion process according to any of the preceding claims, wherein the feed ratio of the combustion product gas and the oxygen source of the feed steps (v) and (vi) is controlled such that the second lambda value in the second combustion zone is greater than 1.0, preferably between 1.1 and 1.3. The combustion process according to any of the preceding claims, wherein the process additionally comprises the step of: (viii) Feeding a support fuel (E1, E2) in the first combustion zone and / or the second combustion zone. The combustion process of any one of the preceding claims, wherein the optional cooling step (iv) cooling the flue product gas downstream of the second BE2017 / 5801 combustion zone and using the cooled smoke product gas (cF) for cooling the combustion product gas (P). The combustion process according to any of the preceding claims, wherein the optional cooling step (iv) comprises supplying water, such as spraying water into a cooling zone downstream of the first combustion zone. The combustion process according to any of the preceding claims, wherein the optional cooling step (iv) is controlled as a function of the second operating temperature. The incineration process according to any of the preceding claims, wherein a heat recovery boiler (400) is provided and integrated in at least one of the first incineration zone, the cooling zone and the second incineration zone, further comprising the step of recovering heat from at least one from the first combustion zone, the cooling zone and the second combustion zone by the heat recovery boiler. The combustion process of claim 14, wherein the heat-recovering boiler comprises a heat-recovering fluid adapted to cool at least of the first combustion zone, the cooling zone and the second combustion zone, and wherein a flow of the heat-recovering fluid is controlled as a function of a temperature in the first combustion zone, the cooling zone and the second combustion zone, respectively. The combustion process according to any of the preceding claims, wherein a residence time in the first combustion zone is at most 3 s, preferably at most 2 s, more preferably less than 1 s. The combustion process according to any of the preceding claims, wherein a residence time in the second combustion zone is at most 3 s, preferably at most 2 s, more preferably less than 1 s. The combustion process according to any of the preceding claims, wherein the second oxygen supply step (vi) is controlled such that the flue product gas comprises less than 5 vol%, preferably less than 3 vol% oxygen. BE2017 / 5801 The combustion process according to claim 18, wherein the second oxygen supply step (vi) comprises adjusting the second oxygen flow based on a step of measuring the oxygen volume concentration in the flue product gas. The incineration process according to any of the preceding claims, further comprising a start-up process prior to the incineration step (iii), which start-up process comprises the steps of: (ix) controlling the supply steps (i), (ii), optionally including the supply step ( viii) such that the temperature in the first combustion zone reaches a substantially stable start-up temperature of at least 850 ° C and a first lambda value of at least 1.0; (x) reducing the first oxygen source stream from the feed step (ii) while keeping the organic matter source stream from the feed step (ii) substantially constant so that the first lambda value is reduced to less than 1.0, preferably less than 0.9, more preferably about 0.85, even more preferably less than 0.8, thereby reaching the first operating temperature between 900 and 1100 ° C. The incineration process according to any of the preceding claims, wherein the organic material source comprises at least one selected from a gas phase, a liquid phase, a sludge phase and a solid phase. The incineration process according to any of the preceding claims, wherein the organic substance source comprises a solid phase, wherein the first incineration zone comprises a grid or the first incineration zone is provided with a rotatable drum, such as a rotating oven, or wherein the organic material source comprises a sludge phase wherein the first incineration zone comprises a fluidized bed. 23. An oven system comprising: - a first combustion unit (100) comprising a first combustion zone (105) arranged for burning an organic substance supplied from an organic substance source, thereby forming a combustion product gas (P): - optionally a coolant adapted to cool the combustion product gas; - a second combustion unit (200) comprising a second combustion zone (205) adapted to burn the optionally cooled combustion product gas; supply means for supplying the organic substance source in the first combustion zone, a first oxygen source 01 in the first combustion unit and a second oxygen source O2 in the second combustion unit; - an operating system designed to control one or more of the following: the BE2017 / 5801 supply means, the first combustion unit, the optional refrigerant and the second combustion unit, such that a first operational temperature in the first combustion unit is at least 850 ° C and a first lambda value is less than 1.0, the first lambda value being is defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic matter source in relation to the oxygen in the first combustion zone, and such that a second operating temperature in the second combustion unit is between 800 and 950 ° C and a second lambda value is higher than 1.0, the second lambda value being defined as the molar ratio to a stoichiometric ratio of the organic substances from the organic material source in relation to the oxygen in the second combustion zone. The furnace system of claim 23, wherein the feed means first feed means (110) for feeding the organic matter source into the first combustion unit, first oxygen feed means (120) adapted to feed a first oxygen source into the first combustion unit and / or second oxygen feed means (220) arranged for supplying a first oxygen source in the second combustion unit. The furnace system of any one of claims 23 to 24, wherein the first combustion unit comprises one of a rotary drum, such as a rotary oven, a fluidized bed or a grid system. The furnace system of any one of claims 23, wherein the rotary drum comprises a sealing system for preventing air leakage in the rotary drum. The furnace system according to any of claims 23 to 26, wherein the furnace system comprises a cooling zone (300) arranged upstream of the second combustion unit, wherein the combustion product gas is cooled by the optional cooling means in the cooling zone. The furnace system of claim 27, wherein the second combustion unit and optionally the cooling zone (300) are adapted to remove ash (S) on the bottom side of the second combustion unit and the cooling zone (300), respectively. The furnace system according to any of claims 23 to 28, wherein the first combustion unit is a temperature sensor for measuring the first operational BE2017 / 5801 temperature and wherein the control system is adapted to control the first operational temperature in response to the measured first operational temperature. The furnace system according to any of claims 23 to 29, wherein the first combustion unit comprises cooling means for cooling the first combustion unit, the cooling means at least one of supply means for supplying cooled smoke product gas (650) and supply means for supplying water comprising in the first combustion unit, such as a spraying device for spraying water in the first combustion unit. The furnace system according to any of claims 23, wherein the first combustion unit comprises recirculation means for partially recirculating the combustion product gas in the first combustion zone. The furnace system of claim 31, wherein the recirculation means comprises a mixing wall arranged at a downstream end of the first combustion unit and having a plurality of openings adapted to direct the combustion product gas downstream of the mixing wall along a plurality of flow paths which are substantially parallel to being together. The furnace system of any one of claims 23 to 32, wherein the second combustion unit comprises a temperature sensor for measuring the second operational temperature and wherein the control system is adapted to control the second operational temperature in response to the measured second operational temperature . The furnace system of claim 33, wherein the optional cooling means is controlled in response to the measured second operating temperature. The furnace system of any one of claims 23 to 34, further comprising at least one support fuel supplying means (130, 230) adapted to feed a support fuel (E1, E2) into at least one of the first combustion zone and the second combustion zone, and wherein the at least one support fuel supply means (130, 230) is controlled by the control system in response to a measurement of the first operational temperature and / or in response to a measurement of the second operational temperature. BE2017 / 5801 The furnace system of any one of claims 23 to 35, further comprising a heat recovery boiler integrated in at least one of the first combustion unit, including the optional cooling means (300) and the second combustion unit. 37. The furnace system according to any of claims 23-36, wherein the first combustion unit comprises a combustion chamber for accommodating the combustion zone having a length-to-diameter ratio between 3 and 8, more preferably a length-to-diameter ratio of around 4.