Fluidized bed calciner

Abstract

The present invention relates to a Fluidized Bed Calcining (FBC) apparatus, a calcining plant comprising such a FBC apparatus, and a method of operating a FBC apparatus. The FBC apparatus comprising a calcination chamber having fluidizing bed zone and a calcining zone. A solid material provision means, a fluidizing means, and a solid material outlet. The solid material outlet may be configured with a gas-lock. The FBC apparatus is configured to receive a source of energy to heat the powder material to a calcination temperature. A gas outlet is located above the fluidizing bed zone to allow gases to exit the combustion chamber.

Description

FLUIDIZED BED CALCINERTECHNICAL FIELD

[0001] The present disclosure relates to a fluidized bed calciner, a calcination system comprising a fluidized bed calciner and a calcination method.BACKGROUND

[0002] Cement production is generally considered to account for 5-10% of global greenhouse gas emissions. Most of this CO2 is from clinker production. Cement clinker is produced by heat treatment of a finely pulverized mixture of about 80% limestone (CaCOa) and other mineral constituents in a kiln system which preheats and calcines the raw meal, then bums the calcined meal to form desired clinker minerals, followed by cooling. The calcination process releases about 0.55 tons of CO2 per ton of clinker produced (often termed process CO2). The energy required for calcination and heat treatment is generally provided by burning carbon containing fuels, which typically releases a further 0.2 to 0.4 tons of CO2 depending on fuel type and energy efficiency. The thermal energy consumption supplied by fuel is typically 3.5 GJ / ton clinker and the electrical energy consumption typically lOOkWh / t cement, and the formed CO2 is often termed fuel CO2. 60% of the fuel is typically burnt in the calcination stage, thereby also accounting for 60% of the fuel CO2 formation. 80 to 90% of the CO2 from clinker production thereby results from calcination.

[0003] It is desirable to capture at least some of this CO2 to reduce the CO2 emissions from the clinker production.

[0004] Calcination is generally performed by direct contact of preheated raw meal with hot flue gas, formed by either preceding or simultaneous combustion of fuel. The CO2 released from calcination is therefore mixed into the flue gas of which the main constituent is nitrogen (N2), which makes up 78% of air conventionally used to support combustion. Directly after calcination, the CO2 content in the flue gas will typically be close to 30%, depending on process details. By the time the flue gas is cooled down and via the raw mill reaches the main filter and stack, the CO2 concentration is typically in the range 10-20%.

[0005] For purpose of carbon capture processes, it is undesirable to have such low CO2 concentrations.

[0006] Several solutions exist where air is either fully or partially substituted with a gas having a high concentration of oxygen and low concentration of nitrogen. Such solutions are referred to as “oxyfuel” or “partial oxyfuel” or “pure oxyfuel”.

[0007] However, while oxyfuel systems may allow for high capture rates of the CO2, conventional oxyfuel solutions have the drawbacks of requiring recirculation of flue gas in order to make up for the missing nitrogen gas and maintain the necessary gas volume in the cement production system. Pure oxyfuel, which is oxyfuel technology without flue gas recirculation is not commonly available for retrofitting and requires substantial capex costs to provide kilns, coolers, and other equipment configured to operate in oxyfuel mode.

[0008] Partial oxyfuel, which operates a separate calciner string in oxyfuel mode is an option which allows for capture of up to about 75% of the CO2. Oxyfuel retrofit to existing kiln systems is possible, but substantial modifications are required to add new equipment and / or address both false air ingress and the need for recirculation. Other solutions like calcium looping are alternative options.

[0009] There is a need to provide alternative solutions which allow for providing a concentrated CO2 gas stream from the cement manufacturing process.SUMMARY

[0010] In one aspect of the present disclosure, the invention relates to a fluidized bed calcining apparatus comprising:• a calcination chamber having a fluidizing bed zone and a calcining zone;• a solid material provision means configured to provide a calcinable powder material to the calcination chamber, preferably providing a preheated calcinable powder material having a temperature of 400-900°C to the calcination chamber, optionally providing the calcinable powder material to the calcining zone or to a location in the calcination chamber above the calcining zone;• a fluidizing means configured to fluidize the calcinable powder material or calcined powder material in the fluidizing bed zone;• a solid material outlet connected to the calcination chamber and configured to remove the solid material from the fluidizing bed zone and thus maintain a desiredheight of the fluidizing bed, the solid material outlet additionally is configured with a gas-lock, preferably the powder outlet is located in a lower portion of the calcination chamber;• an energy provision means, configured to provide a source of energy to the calcination chamber and heat the powder material to a calcination temperature of the powder;• a gas outlet located above the fluidizing bed zone, preferably in the upper part of the calcining zone;• wherein the fluidized bed calcining apparatus is configured such that calcination of the calcinable powder primarily takes place in the calcination zone.The fluidized bed calciner allows for efficient calcination while utilizing the calcinable powder as the bed material and as a heat sink. This provides efficient heat utilization since no other bed material needs to be heated and it limits the required gas flow admission. It simultaneously maintains the temperature in the calcining zone around the calcining temperature. It thereby prevents overheating of the calcination chamber. The gas-lock and fluidization of the calcinable powder allows for efficient separation of gases and solids and restricts gas flow through the fluidized bed calciner, whereby gases formed during calcination will not or hardly be transferred to upstream process equipment or downstream process equipment together with the solids. It thus limits the loss of or dilution of formed gases from calcination of the solid phase.Calcination of limestone releases CO2. By limiting the amount of gas which is admitted and / or passes through the solid material outlet the high concentration CO2 can be sent separately to e.g., a carbon capture process. By using a high concentration oxygen gas as combustion gas, it is achievable to obtain an outlet gas that has a CO2 concentration of more than 30%, such as more than 50%, preferably more than 70% such as more than 80%, such as more than 90% (Vol%, dry). The fluidized bed calcining apparatus according to the invention thus allows for calcination and provision of a gas with a high concentration of gases released from the calcination process.The fluidizing bed zone is to be understood as a portion of the calcination chamber designed and configured to accommodate the material bed and fluidize said bed material during operation. The calcining zone is to be understood as a portion of the calcination chamber, located above the fluidizing bed, where the primary calcination takes place. During intended operating conditions at least 95% of the calcination process may take place in the calcinationzone. Alternatively, or additionally, the calcining zone may be characterized in that the solid volume fraction is less than 0.1, and / or the fluidizing zone has a solid volume fraction higher than 0.1.By “powder” is meant a solid material preferably with more than 90 w / w% of particles having a particle size less than 1000pm, preferably 90 w / w% is a Geldart-C type powder.In one or more embodiments, the fluidizing means may be mechanical means such as a moving baffle.In one or more embodiments, the fluidizing means may be one or more jets configured to inject pulses of a fluidizing gas and being suitable to fluidize a very fine calcinable powder medium which is classified as a cohesive-type powder according to the Geldart classification.

[0011] It is known that cohesive-type powders are especially hard to fluidize by injection of gases since they promote the development of gas channels in the cohesive-type powder. It has been found that injection of gases in pulses prevents the formation of channels in the powder and effectively provides fluidization. Additionally, the gas consumption required for effective fluidization is considerably lower than during constant aeration.

[0012] In one or more embodiments, the gas is provided in pulses having a duration (pulse time) in the range 10ms to 500ms, such as 100ms to 500 ms, 200ms to 450 ms, 250ms to 400ms or even 300ms to 400ms. The gas is preferably provided to the bed having a superficial gas velocity of less than 50cm / s calculated as the volume of admitted fluidization gas divided by the horizontal bed cross section. More preferably, gas has a superficial gas velocity of less than 25cm / s, or even 15cm / s, such as lower than lOcm / s. In some embodiments, the superficial gas velocity is between Icm / s to 5 cm / s, such as between 2cm / s to 3 cm / s., calculated at Standard Temperature and Pressure (STP).

[0013] The gas-lock should be understood as a gas seal which continuously prevents process gas from flowing freely through the solid material outlet while allowing for the powder to pass through. The solid material outlet comprising a gas-lock may be a sluice made up of alternately opening slide gates or a feed screw configured to remove the powder substantially without process gases. In one or more embodiments, the solid material outlet is configured to remove the calcinable powder / calcined powder while in a fluidized condition. A portion of the solid material outlet may be configured to inject pulses of fluidization gas. The solid material outlet may comprise a fluid trap such as a lute whichutilize trapped fluidized powder to provide a seal for the gas. The fluid trap may have a u- shaped or S-shaped or J-shaped bend.

[0014] In one or more embodiments, the fluidized bed calcining apparatus further comprises one or more suspension gas jets configured to provide a jet with sufficient velocity of gas appropriately oriented and at appropriate positions to suspend and distribute preheated calcinable powder in the calcining zone, possibly forming a spouted bed zone. This provides a higher solid loading sufficient for the calcinable powder to act as a heat sink and maintain the temperature in the calcining zone below a safety temperature, preferably a temperature at or slightly above the calcining temperature, lower than temperatures at which the solid material partially melts and becomes sticky and lower than temperatures that cause substantial damage to parts of the fluidized bed calcining apparatus. The jet may preferably inject continuous jets of gas and be adjustable to ensure that the endothermic reaction heat in the suspended calcinable powder either matches or exceeds the heat admitted to or released in different regions of the calcination zone by the energy provision means. In some embodiments, the gas jets are located at position in the calcination chamber at or around the interface between the calcining zone and the fluidizing zone. In some embodiments, the gas jets are located in the calcining zone, preferably near the top of the calcining zone. In some embodiments, the jets are oriented such that gas is provided in a horizontal direction, at an upwards direction or at a downwards direction.

[0015] In one or more embodiments, the fluidized bed calcining apparatus further comprises one or more mechanical means configured to suspend and distribute preheated calcinable powder in the calcining zone, possibly forming a spouted bed zone.

[0016] The energy provision means may be any kind of means suitable for providing any type of energy source sufficient to heat and calcine the calcinable powder. The source of energy may be any type of material which can be used as a basis or source of energy. It may be a gas burner providing a flame, an electric arc burner, heated solid elements, salt melts transferring heat through a surface. It may also be a fuel feeder suitable for providing a solid fuel to the calcination chamber. Preferably the energy provision means may be a solid fuel feeder configured to provide a solid fuel which may undergo pyrolysis and / or gasification in the fluidized bed zone. The solid fuel may be an Alternative Fuel (AF) such as municipal waste, biomass, residues, which are suitable for undergoing pyrolysis and / or gasification.

[0017] In one or more embodiments, the fluidized bed calciner is further configured to receive a solid fuel. The solid fuel may preferably be provided with substantially no or at least limited amounts of gas. In one or more embodiments, the solid material inlet is configured to provide the solid fuel to the calcination chamber substantially without any gas from upstream process equipment. The solid fuel inlet may be a mechanical feeding mechanism, such as a feed screw. The solid fuel may also be provided through a dosing feeder, screw conveyor, or rotary valve. Preferably, the feeding mechanism does not utilize pneumatic conveying. In some situations, the fuel may be directly admitted to the fluidized calcinable powder which is fluidized and transported through a gas-lock.

[0018] In one or more embodiments, the fluidized bed zone is configured to operate under conditions suitable for pyrolysis. In some embodiments, a solid fuel may be provided to the fluidized bed zone where it pyrolyzes and releases pyrolysis gases. These pyrolysis gases may be combusted in the calcining zone, which may be operated under oxidizing conditions.

[0019] In one or more embodiments, the fluidized bed calciner is fluidly connected with a gas source having an oxygen concentration above 21% and / or a nitrogen concentration below 78%. In some preferred embodiment, the gas source is substantially pure oxygen, such as a gas with more than 90% or even 99% oxygen. The use of a gas source with high oxygen concentration allows for less gas to be provided to the calcination chamber to obtain the stoichiometric amount of oxygen for combustion of the fuel. A gas source with low concentration of nitrogen allows for a higher concentration of gases formed during calcination. For calcination of limestone, this will provide an outlet gas having a high concentration of CO2. In some embodiments, a portion of the off gases from the gas outlet is recirculated and utilized as suspension gas or fluidization gas. If the source of energy is provided without requiring combustion to take place in the calcining chamber, e.g., via electric arc burner, no additional oxygen may be required in the calcining zone.

[0020] In one or more embodiments, the fluidized bed calcining apparatus is further configured to operate with a mean temperature of between 900°C and 1200°C in the calcination zone. It may in some embodiments operate with a mean temperature of between 400°C to 900°C in the fluidization zone. The higher temperature in the calcination zone is achieved and maintained through provision of heat energy balanced with heat absorption by the surroundings, particularly the endothermic calcination reaction and heating of calcinable powder. As the heated and calcined powder is provided to the fluidized bed zone, it cools.In some embodiments, the heat from the preheated calcinable powder admitted to the fluidized calcining apparatus and the calcined powder is additionally used to gasify and pyrolyze the solid fuel.

[0021] When a fuel is added to the fluidized bed zone for pyrolysis, the formed pyrolysis gases may flow into the calcination zone. To achieve good combustion of the pyrolysis gases it may be required to provide an additional supply of oxygen. It may therefore be necessary in some embodiments to inject additional gas comprising oxygen, preferably through the gas jets.

[0022] In a second aspect of the present disclosure, the invention relates to a calcination plant comprising:• a preheater device preferably comprising a plurality of cyclone preheaters and suitable for heating a solid material, such as a powder;• a fluidized bed calciner;• a cooler suitable for cooling a solid material such as a powder;• wherein the fluidized bed calciner is configured to receive preheated raw meal from the preheater device substantially without receiving any process gas from the preheater device, and• wherein calcined powder is provided from the fluidized bed calciner with limited or substantially without any gases.In some embodiments, the calcination plant is a limestone calcination plant.In some embodiments, the calcination plant is a lime-spodumene calcination plant.In some embodiments, the calcination plant is a cement clinker manufacturing plant.The calcined powder material may be provided directly from the fluidized bed calciner to the cooler. In some embodiments, the calcination plant may comprise a kiln device, configured to receive and heat the calcined powder from the fluidized bed calciner with limited or substantially without receiving any gases.Preferably less than 50 V / V% of the gases from the fluidized bed calciner is provided to the kiln or cooler. More preferably less than 10 V / V%

[0023] In one or more embodiments, substantially no gases from the fluidized bed calciner are provided to the kiln device, clinker cooler, flash calciner, re-carbonator or thepreheater device, i.e., less than 50 V / V%, preferably less than 10 V / V%. By substantially no gases is meant residual amount of gases, such as less than 10 V / V%.

[0024] In one or more embodiments, the calcination plant further comprises a calciner device fluidly coupled to the preheater device and the kiln and / or cooler such that both fluids and solids are exchanged. The calciner device may be configured to run in parallel or in series with the fluidized bed calciner. The calciner device may preferably be of another type of calciner than the fluidized bed type calciner. Preferably the calciner device may be a flash calciner.

[0025] A calciner device fluidly connected to the preheater and kiln and / or cooler is the current standard configuration for industrial calcination plants. By having a calciner device running in parallel or in series with the fluidized bed calciner it is possible to provide a hybrid calcination plant. A typical calciner device uses suspension fired fuel with air as oxidant gas. The calcination plant according to the invention can be regulated and adjusted depending on the fuel available and the desired volume of high concentration CO2 to be produced. This type of adjustment may be desired if the CO2 production should be regulated based on the amount of renewable electricity available for downstream processing of the CO2. The hybrid calcination plant may also be a good option for gradually increasing the CO2 production depending on market demand.

[0026] In a third aspect, the invention relates to a method of calcining a calcinable powder in a fluidized bed calcining apparatus. The fluidized bed calcining apparatus having a calcination chamber comprising a fluidizing bed zone and a calcining zone. The calcining zone may be located above the fluidizing bed zone. The method comprising the steps of:- providing a calcinable powder to the calcination chamber;- providing a source of energy sufficient to heat the calcinable powder to the calcining temperature and to drive the endothermic reactions thereof;- thermally contacting at least, a portion of the calcinable powder with the heat from the source of energy in the calcining zone to provide a calcined powder and a formed gas;- fluidizing at least a portion of the calcined powder and / or calcinable powder in the fluidizing bed zone as the primary bed material to form a fluidized bed;- removing at least a portion of the powder from fluidized bed through a solid material outlet to adjust the bed height, the solid material outlet may preferably be located in the fluidizingbed zone and comprising a gas-lock such that the calcined powder can pass through with only residual amounts of the formed gas passing through;- removing the formed gases through a gas outlet, said gas outlet located above the fluidizing bed zone, preferably above the calcining zone such that it receives gas from the upper part / half of the calcining zone; The gas outlet may be combined with a solid separation device such as a cyclone.In some embodiments, a portion of the removed powder from the fluidized bed calciner is un-calcined powder, i.e., calcinable powder. In some embodiments, 5-50 w / w% of the removed powder is calcined powder and the remaining un-calcined. If the fluidized bed calciner is operated in a such manner that a large fraction of the removed powder is un- calcined, the heat supplied to the calcinable powder by the energy source will match the energy required to fully calcine a fraction of the total flow of calcinable powder. It is therefore possible to maintain the temperature in the calcining zone below a safety temperature, lower than temperatures at which the solid material partially melts and becomes sticky and lower than temperatures that cause substantial damage to parts of the fluidized bed calcining apparatus, without requiring to bring essentially all the admitted calcinable powder into contact with the supplied heat. This improves process robustness and stability and has the benefit that only a fraction of the admitted solid material to the fluidized bed calcining apparatus needs to be brought into suspension and that mixing in the calcination zone is less critical to avoid exceeding a safety temperature in parts of or the whole calcining zone. Preferably less than 50 V / V% of the formed gases from the fluidized bed calciner is provided to be combined / mixed with the gas streams exiting (downstream of) the kiln and / or cooler. More preferably less than 10 V / V%.

[0027] In one or more embodiments, the calcined powder and / or calcinable powder is a cohesive-type powder according to the Geldart classification of particles. Such powders are difficult to fluidize by conventional fluidization, as channeling occurs. Geldart-C cohesive powders typically have an average particle size smaller than 20-30pm. Industrially used fluidized beds generally use bed media that are aeratable (Group A) or Sand like (Group B) for reactors, gasification units, pyrolysis units and combustion units. Industrial fluidized beds generally conventionally operate with superficial gas velocities greater than Im / s and thereby require a substantial externally induced gas flow to fluidize the particles in it. Geldart-C cohesive powders processed industrially, such as cement raw meal, are generally only processed in fast fluidized beds with superficial gas velocities greater than Im / s. Adiagram showing the different Geldart classification can be seen in Fig 1. This diagram is taken from Powder technology 428 (2023) 118861.

[0028] It is known that cohesive-type powders are especially hard to fluidize by injection of gases since they promote the development of gas channels in the cohesive-type powder. In some embodiments, the majority of the powder in the fluidized bed is the calcinable powder and / or calcined powder. Other materials may be present in the bed material together with the calcinable powder and calcined powder, but such other materials are not required for fluidization purposes. In one or more embodiments, the calcinable powder and / or calcined powder constitutes at least 50%(w / w) of solid material in the calcination chamber, preferably at least 60%(w / w), more preferably at least 70%(w / w), even more preferably at least 80%(w / w), such as at least 90%(w / w).

[0029] Preferably, no other powder material or fluidization medium is added to the process for the purpose of improving fluidization.

[0030] In some embodiments, calcinable powder is a material that releases CO2 when undergoing calcination.

[0031] In one or more embodiments, the calcinable powder is at least 50w / w% limestone. The calcinable powder may be at least 60w / w% limestone, such as at least 70w / w% limestone. The calcinable powder may comprise around 70-80w / w% limestone. The calcinable powder may be cement raw meal.

[0032] In one or more embodiments, the particles size of the calcined powder and / or calcinable powder has a particle mean average of equal to or less than 50 pm, preferably less than 30 pm, preferably less than 25 pm, more preferably less than 20pm. Cohesive Geldart C powders are typically used as raw meal for cement production sand have very different fluidization properties than coarser aeratable Geldart A and sand like Geldart B powders.

[0033] In one or more embodiments, the bed medium is fluidized by mechanical fluidization means. In one or more embodiments, the bed medium is fluidized by injecting pulses of a fluidizing gas. Preferably, the fluidizing gas is substantially pure oxygen, a gas substantially free from nitrogen or substantially pure CO2. It may also be a combination thereof. This is described in more detail in regard to the first aspect of the invention.

[0034] In one or more embodiments, the superficial gas velocity in the fluidized bed zone is no more than 50cm / s calculated as the volume of admitted fluidization gas divided by the horizontal bed cross section calculated at std pressure and temperature. More preferably gas has a superficial gas velocity of less than 25cm / s, or even 15cm / s, such aslower than lOcm / s. In some embodiments, the superficial gas velocity is between Icm / s to 5 cm / s, such as between 2cm / s to 3cm / s.The low superficial gas velocity makes it possible to limit the amount of gas required to fluidize the calcinable powder which has multiple benefits. A key advantage is that in the event of using oxygen rich gas as fluidization medium, a fluidized bed calciner can be divided into two zones. The fluidized bed can thus be used as a pyrolysis zone.

[0035] In one or more embodiments, a portion of the bed material may be removed through the solid material outlet. Preferably, the majority of the bed material may be removed through the solid material outlet. Preferably, at least 90% of the bed material may be removed through the solid material outlet.

[0036] Preferably, the bed material may be removed from the fluidizing bed zone while in a fluidized condition to maintain a constant bed level in the calcination chamber. Preferably, the majority of the bed material is removed in this way.

[0037] In one or more embodiments, the formed gases are removed through the gas outlet substantially without any calcinable powder and / or calcined powder. This should be understood as meaning that at least 95V / V% of the formed gas is removed through the gas outlet. Preferably, the solid loading in the gas outlet is less than 500 g / kg.

[0038] In one or more embodiment, the formed gases constitute at least 60V / V% of the total gases removed from the calcination chamber through the gas outlet. It may in some embodiments constitute above 70 V / V%, more preferably above 80 V / V%. In some embodiments, the formed gases may constitute above 90 V / V% of the total gases removed through the gas outlet. The formed gases may comprise CO2 from calcination of the calcinable powder and CO2 from combustion and include H2O evaporated from moist fuel and H2O produced from combustion of fuel.

[0039] In some embodiments, especially when operating with an additional calciner in parallel or in series, it may be desirable to calcine only a portion of the calcinable powder in the fluidized bed calciner.

[0040] In one or more embodiments, at least 5% of the calcinable powder is calcined, such as at least 10%. Preferably, at least 20% of the calcinable powder is calcined, more preferably, at least 40%. In some embodiments, preferably at least 50% or more preferably at least 60% is calcined. In some embodiments, preferably at least 70%, or even preferably80%, is calcined. In some embodiments, at least 90%, more preferably at least 95% or even around 100%, is calcined. The suitability of the fluidized bed calciner to operate with a broad range of degrees of partial calcination allows for flexibility of the process which may be desirable dependent on the availability of fuel or the demand of high concentration CO2. If the source of energy is provided by electricity, such as with an electric arc burner the production may be dependent on the availability of renewable electricity.

[0041] In one or more embodiments, the mean temperature in the calcining zone may be between 900°C and 1200°C. This is a temperature which is suitable for calcining limestone. The mean temperature in the fluidized bed zone may be between 400°C and 900°C. This temperature is measured as an average temperature through the depth of the bed. A temperature in this range is sufficient for heating any solid fuels in the bed.

[0042] In some embodiments, the fluidized bed zone has reducing conditions. The reducing conditions may be achieved by adding a fuel to the fluidized bed while providing no or a limited amount of oxidizing gases. Reducing conditions may even be provided by introducing high concentration oxygen into the fluidized bed as long as it is provided in low amounts, such as with the superficial gas velocity previously described.

[0043] In embodiments where it is desirable to combust a fuel in the calcining zone, it may be necessary to provide an oxidizing gas. This gas may be different from the pulsating gas. The oxidizing gas may be provided directly to the calcining zone. In theory, any gas comprising oxygen may be provided, but to obtain a high concentration CO2 outlet gas it is desirable to provide a gas having a high concentration of oxygen and / or a low concentration of Nitrogen. It may as an example comprise more than 21 v / v% oxygen and less than 78v / v% nitrogen. Preferably, the gas comprises more than 90v / v% oxygen. Preferably, the gas comprises less than 10v / v% nitrogen.

[0044] In one or more embodiments, a fuel may be provided to the calcining zone. The fuel provided to the calcining zone is preferably a gas such as Natural gas, pyrolysis gas, methane.

[0045] In some embodiments, a solid fuel may be provided to the calcination chamber. The solid fuel enters the fluidized bed where it is pyrolyzed under reducing conditions and provides pyrolysis gases. The pyrolysis gases then bubble through the bed and are combusted upon reaching the calcining zone.

[0046] In one or more embodiments, it may be desirable to provide a suspension gas. The suspension gas may be provided through a jet in the calcination chamber wall to suspendand distribute calcinable powder in the calcining zone. The gas jet may be located near the interface between the fluidizing zone and the calcining zone. The calcinable powder may be suspended and entrained by the suspension gas up into the calcining zone. The suspension gas may be introduced in such a way that the calcinable powder is effectively mixed with the gases in the calcining zone. This ensures effective usage of the combustible gases and oxidizing gas. The properly distributed calcinable powder also acts as a heat sink to avoid overheating of the calcination chamber walls.

[0047] In one or more embodiments, the volume ratio of gas provided as suspension gas and fluidizing gas is at least 5:1, preferably at least 10: 1 and most preferably at least 20: 1. The suspension gas and the fluidizing gas may be the same type of gas, but it may also be different gas compositions.

[0048] The gases may in particular comprise oxygen, methane, CO2 and / or dihydrogen. It may be required to recirculate some CO2 to provide a high concentration CO2 gas stream applicable as fluidization gas, cooling gas for heat provision means and / or as suspension gas to suspend calcinable powder. This can particularly be relevant if the source of energy is not combustion.

[0049] In one or more embodiments, the fluidized bed calcining apparatus comprises one or more mechanical means such as moving baffle plates along the inlet flow stream of calcinable powder configured to suspend and distribute preheated calcinable powder in the calcining zone. This can particularly be relevant if the source of energy is not combustion.

[0050] In yet another aspect of the invention, the fluidized bed calciner apparatus may be operated in different modes based on the demand and price of CO2, the availability or type of fuel, and / or the availability and price of an oxidizing a gas having a high concentration of oxygen.

[0051] If the demand of CO2 is low, or the availability of oxygen is low, the fluidized bed may be operated in pyrolysis mode. In this operation mode, the fluidized bed calciner should be operated under reducing conditions, i.e., with a deficit amount of oxygen compared to fuel. Air may thus be used as fluidization gas. As the solid fuel enters the calcination chamber and the fluidized bed of hot calcinable powder, the fuel is pyrolyzed into char and pyrolysis gases are formed. The pyrolysis gases can be provided to the calcining device, or the kiln device for combustion through a gas outlet suitable for this purpose.

[0052] The fluidized bed calciner apparatus may be switched into calcination mode upon a change in demand.

[0053] Once it is decided to operate the fluidized bed calcining apparatus in calcining mode, at least a stoichiometric amount of oxygen, preferably high concentration oxygen, is provided to the calcining chamber, and the gas jets are utilized to maintain a good mixing of powder and gas in the calcination zone to utilize the calcinable powder as a heat sink. In this configuration, the fluidized bed zone is utilized for pyrolyzing the solid fuel and the calcination zone is utilized for combusting the pyrolysis gases and calcining the calcinable powder. The formed gases comprise a high amount of CO2 which can be extracted for further processing and optionally carbon capture through a gas outlet dedicated for this purpose.

[0054] Which of the two gas outlets to use may be controlled by one or more fans which can be adjusted based on gas analysis of the outlet gases.

[0055] In a preferred embodiment, the method of operating the fluidized bed calcining apparatus in calcining mode comprising the steps of:

[0056] Specifying and providing an amount of fuel based on desired CO2 production;

[0057] Providing a continuous flow of hot calcinable powder such that only a portion of the calcinable powder is calcined;

[0058] Specifying and providing an excess amount of oxygen based on the oxygen required for combustion of the fuel.BRIEF DESCRIPTION OF DRAWINGS

[0059] A better understanding of embodiments of the present disclosure (including alternatives and / or variations thereof) may be obtained with reference to the detailed description of the embodiments along with the following drawings, in which:

[0060] FIG. 1 shows a diagram indicating the Geldart classification of particles;

[0061] FIG. 2 is a schematic cross-sectional view of an exemplary fluidized bed calciner, according to an embodiment of the present disclosure;

[0062] FIG. 3 is a schematic cross-sectional view of an exemplary fluidized bed calciner, according to an embodiment of the present disclosure;

[0063] FIG. 4 is a schematic cross-sectional view of an exemplary fluidized bed calciner, according to an embodiment of the present disclosure;

[0064] FIG 5 is a schematic plan view of a portion of a calcination plant comprising a fluidized bed calciner, according to an embodiment of the present disclosure;

[0065] FIG. 6 is a schematic plan view of a part of a calcination plant comprising a first and second fluidized bed calciner according to different embodiments of the present disclosure;

[0066] FIG. 7 is a schematic plan view of a part of a separate-line-calciner (SLC) plant comprising a plurality of fluidized bed calciners, according to different embodiments of the present disclosure.DETAILED DESCRIPTION

[0067] Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. Moreover, references to various elements described herein are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be construed to relate to the plural and vice- versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claim.

[0068] Referring to FIG. 2, which is an example of a fluidized bed calcining apparatus 1. The fluidized bed calcining apparatus 1 has a gas sealing inlet portion in the form of aloop seal 10 connected to a calcining vessel 18 in such a way that solids can flow from the loop seal 10 to the calcining vessel 18. During intended use of the fluidized bed calcining apparatus 1, preheated raw meal having a temperature of around 600-900°C is provided to the pulse aerated loop seal 10 through the inlet 8. The loop seal 10 makes up a first fluidized bed. In the current configuration, the loop seal 10 has a U-formed cross-sectional shape. During intended use of the loop seal 10, it comprises fluidized meal bed 12 that forms a gas barrier preventing gas streams from flowing through the loop seal 10. When the loop seal 10 is loaded with meal that is aerated during intended operating conditions, an amount of meal equal to the amount of admitted meal flows out of the loop seal 10 into the calcining vessel 18 through the connecting conduit 14, more particularly into the calcination chamber 15.

[0069] The calcining vessel 18 has an inlet leg 16 (left hand side on Fig. 2) and an outlet leg 22 (right hand side on Fig. 2). In the calcination chamber 15, the meal further flows down into the fluidized bed zone, which during intended use comprises a fluidized bed 20 of meal. In the current configuration, the fluidized bed 20 is pulse aerated by gas inlets (not shown) provided on an interior lower surface 21 of the calcining vessel 18. A meal stream also flows through the fluidized bed 20 either leaving via the overflow point (24) which is connected to the solid outlet 25, or through the lower drain point 30. The meal stream leaving the fluidized bed calcining apparatus may be admitted to a kiln system of a cement manufacturing plant from which the preheated meal originally may have been extracted. A solid fuel may be admitted through the top of the calcination chamber through the fuel inlet I la. Subsequently, most of the admitted fuel drops by gravity into the fluidized bed 20 of hot meal in which it is heated, dried and pyrolyzed by heat transfer from hot meal in the fluidized bed 20. A fraction may be entrained, heated, dried, pyrolyzed and / or combusted by contact with an upward going gas stream in the calcination chamber 15. A source of oxygen, preferably a high concentration oxygen gas, may be provided to the calcination chamber 15 by one or more admission points 17 which are located on the inlet leg of the calcining vessel 18 at a vertical position approximately corresponding to the overflow level on the outlet leg (ref) of the fluidized bed zone (ref). Oxygen is preferably admitted by jets whereby the gas also acts as a suspension gas. Preheated raw meal from the fluidized bed 20 and / or meal that flows out of the loop seal 10 through the connecting conduit 14 into the calcining chamber 15 is thereby suspended by the gas into the calcination chamber 15 above the fluidized bed. The gas in the calcination chamber 15 comprises meal which is entrained in an upward going gas flow together with aeration gas, evaporated water, pyrolysis gas, oxygen and / orcombustion products. In a preferred embodiment, the raw meal is a calcium carbonate containing material, such as limestone and cement raw meal. By substantial entrainment of preheated raw meal particles, the fine calcium carbonate containing particles will absorb heat from the gas phase extremely effectively, whereby heat release in the gas phase will cause the temperature of the raw meal to rise until the calcination temperature at which they will continue to absorb heat as long as calcium carbonate is present. A temperature buffer is thereby established in the calcining chamber 15 preventing the temperature from substantially exceeding the calcination temperature, which for calcium carbonate at a CO partial pressure of about 1 Bar is around 950°C. As the raw meal particles are calcined, CO2 is released and flows upwards through the calcination zone 15 to the gas outlet 26 and to the connecting duct 23, as the fluidized beds 20 and 12 prevent downwards flow or draught of the gases. The upward flowing gas will entrain some of the particles that are present, potentially forming a spouting zone. By providing oxygen to the calcining zone, heat is generated, since oxygen is mixed with the pyrolysis gases from the fuel or with char particles causing a combustion. CO2, water, and other combustion products form from the combustion. The oxygen jets are preferably introduced in a manner whereby they cause intense mixing with pyrolysis gases and simultaneously suspend raw meal and combustible solids, such as char, in the gas phase, whereby combustion and calcination proceed rapidly. Above the fluidized bed 20, the cross-sectional area of the calcination chamber 15 may gradually increase whereby the gas velocity decreases and the amount of particles that can be entrained in the gas flow decreases. This may cause solid particles to sediment out and flow down along the walls returning into the fluidized bed 20 or form a spouted bed. The zone with the cross-sectional area increase may be referred to as the spouting zone. It is not visible in Fig. 2. Additional jets for providing oxygen may be located further up in the calcining chamber 15. The jets may be positioned such that they maximize gas phase mixing to ensure full combustion and can be used to entrain part of the meal stream provided directly from the loop seal 10 into the gas phase as a means to ensure a temperature buffer in the calcining chamber 15. A gas flow is extracted in the upper part of the calcination chamber through the gas outlet 26. The outlet gas stream has a concentration of CO2 produced by combustion and calcination using the high concentration oxygen gas. The gas stream may be mixed with additional oxygen if more oxygen is needed to complete combustion. Dust may also be removed from the gas stream and returned to the fluidized bed calcining apparatus 1 or a downstream kiln system. A residual gas stream not extracted through thegas outlet 26 may flow into the kiln system through the solid outlet 25. If the amount of gas extracted through the gas outlet 26 is slightly less than the gas flow leaving the calcining chamber 15 the residual gas stream may be very limited due to the configuration of the fluidized bed calcining apparatus 1. The residual gas stream may be provided to a kiln system together with the meal stream at a location from which the preheated meal originally was extracted and to which the preheated meal from the fluidized bed calciner is admitted. In one method of operating the fluidized bed calciner 1, a substantial excess of raw meal is admitted to the fluidized bed calciner 1 when considering the calcination heat generated from admitted fuel. This helps to stabilize temperature control in the fluidized bed calcining apparatus 1. Further calcination of the remaining non-calcined meal is subsequently achieved in the kiln system to which the meal and any residual gas stream is admitted.

[0070] The loop seal 10 and the calcining vessel 18 are configured with a sluice system 31 connected to a lower drain points 13 and 30. The sluice system 31 may comprise one or several sluice gates which can be opened to drain the fluidized bed 12 and 20 for any material accumulating in the fluidized beds 12 and 20. In the configuration shown in Fig. 2 where fuel is only provided to the inlet let, the gases from the outlet leg 22 mainly comprise aeration gases. It may comprise some pyrolysis gases from solid fuel pyrolyzed in the outlet leg part of the fluidized bed 20.

[0071] The inlet leg 16 and the outlet leg 22 are fluidly connected by means of the gas conduit 23, such that aeration gases and any additional gases from the outlet leg 22 can flow into the gas outlet 26.

[0072] Referring to FIG. 3, which is another example of a fluidized bed calcining apparatus 100 configured to increase the calcination capacity compared to the embodiment referring to FIG. 2. Preheated raw meal is admitted into the loop seal 110 through the inlet 111 from where it is provided into the calcination chamber 115a of the calcination vessel 118 substantially without any process gases. The meal flows from the calcination chamber 115a into the fluidized bed 120 where the meal is fluidized by gas injected through the gas inlets (not shown) on the lower interior surface 121. The inlet leg 116 operates similarly to the embodiment in Fig. 2. The fluidized bed calcining apparatus 100 in Fig. 3 is characterized in that fuel and oxygen are also provided to the outlet leg 122. A solid fuel may be provided through the inlet 111b and falls into the fluidized bed 120 in the second leg 122. Oxygen gas is provided through jets 117b which are provided in the outlet leg 122 and located near the bed-gas interface and positioned such that they maximize gas phase mixing to ensure fullcombustion of fuel. The jets 117b may be used to entrain part of the meal stream into the gas phase as a means to ensure a temperature buffer in the calcining zone (51), while at the same time effectively exposing meal to heat from combustion, whereby intended calcination takes place. The calcination chamber 115b volume above the outlet leg 122 fluidized bed 120 is also sized and shaped to accommodate mixing, combustion, and calcination. The gas stream from the first leg 116 calcination chamber 115a is combined with the gas stream from the second leg 122 calcination chamber 115b in a duct 140. After the two streams are united, a gas flow is extracted through the common gas outlet 141 in the upper part of the duct 140 to remove a stream of concentrated CO2 produced by oxyfuel combustion and calcination. Any dust present in the outlet gas may be removed from the gas stream and returned to the fluidized bed calcining apparatus 100 or a kiln system. Some residual gas stream may not be extracted through the common gas outlet 141 and is extracted through the meal outlet 125 where it flows into the kiln system from which the preheated meal originally may have been extracted and to which the preheated and at least partially calciner meal from the fluidized bed calciner is provided. The extracted gas stream from common gas outlet 141 may be mixed with additional oxygen if more oxygen is required to complete combustion of any gases - before or after dust removal in a cyclone (not shown).

[0073] FIG 5 shows an embodiment with a fluidized bed calciner 501 being integrated in a kiln system 500 for cement clinker production. The fluidized bed calciner 501 is configured to receive preheated cement raw meal at approximately 800°C. The kiln system 500 comprising a kiln 502 and a calciner 504. The kiln 502 being connected to the calciner 504 by the kiln riser 503. It further comprises a preheater tower comprising four cyclone preheater stages 511, 512, 513, 514. In the embodiment shown, the meal is extracted from the 2nd lowest preheater stage 512. The CO2 rich gas stream is extracted through gas outlet 526 and may be provided to separate cooling, cleaning and / or carbon capture (not shown). The residual gas stream not extracted through the gas outlet flows with the discharged meal into the kiln riser duct 503 and calciner 504 of the kiln system 500. Additional calciner fuel and preheated meal are admitted to the calciner 504 where combustion and calcination are completed to the extent desired upon introduction of hot tertiary air provided from the clinker cooler (not shown) through the tertiary air gas duct 506.

[0074] FIG 4 shows a smaller and less complex example of a fluidized bed calciner 401 with a pulse fluidized bed 420 through which preheated meal (600-900°C) flows. It has a calcination chamber 415 above the fluidized bed 420 in the outlet leg 422. Hot meal fromthe preheater is provided to the inlet leg 416. The fluidized bed calciner 401 has a calcination vessel 418 which has a substantially U-shaped cross section. It has an overflow point 424 at which most meal leaves the fluidized bed calciner 401 during normal operation. It also has a lower drain point 430 through which batches of meal and debris may be extracted during operation. The specific design of the calcination vessel 418, which has the lowest upper point of the U-shape 426 at a lower vertical height than the overflow point 424, prevents gas from flowing through the U-shaped vessel from meal outlet 425 to inlet 411 or the opposite direction. The outlet leg 422 is designed similarly to the previous embodiments. Fuel 411b and oxygen 417b are provided to the outlet leg 422 of pulse aerated meal in a manner such that they maximize gas phase mixing to ensure full combustion. It may also be used to entrain part of the meal stream from the pulse fluidized bed 420 into the gas phase as a means to ensure a temperature buffer in the calcining zone 415. Above the fluidized bed on the outlet leg 422 in the cross-sectional area may gradually increase in the calcination zone 415. This may improve separation of solid / gas since the gas velocity decreases and the amount of particles that can be entrained in the gas flow decreases, whereby some solid particles may sediment out and flow down along the walls returning into the fluidized bed zone 420 or sediment out into the outlet 425. A gas flow is extracted in the upper part of the calcination chamber 415 through the gas outlet 426 to remove a stream of concentrated CO2 produced by combustion and calcination. Dust may also be removed from the gas stream and returned to the fluidized bed calcining apparatus 401 or the kiln system (not shown) with which it may be integrated. Dust entrainment through the gas outlet 426 may be limited or reduced by making the cross section of the gas outlet 426 sufficiently large to sediment out dust or removed in a subsequent cyclone. Any residual gas stream not extracted flows out of the calcining apparatus 401 with the meal through the solid outlet 425. The extracted gas stream may be mixed with additional oxygen if more oxygen is needed to complete combustion downstream of the fluidized bed calcining apparatus 401 - optionally before or after dust removal in a cyclone (not shown). This smaller and less complex configuration has the advantage of being able to integrate within a limited preheater height - particularly for retrofits, it is less costly as less equipment needs to be installed. The configuration may be less suitable for fuels with large fuel and debris particles and substantial fuel drying requirements but may be well suited for more readily combustible fuels such as fine saw dust and liquid fuels admitted at or slightly above the pulse fluidized meal bed.

[0075] FIG 6 shows two different embodiments of a fluidized bed calcining apparatus installed on a kiln system 600 with at least one preheater string 660 without a tertiary air duct connected to it. In the preheater string, the lowest cyclone 661 and second lowest cyclone 662 are shown. So-called Suspension Preheater kilns, ILC-E kilns (In-Line Calciner with Excess air) and the kiln-string of SLC kilns (Separate Line Calciner) are examples of such kiln system types. The embodiment of the fluidized bed calcining apparatus 630 shown in FIG 2 (with the overall integration as shown in FIG 6) is integrated between the second lowest stage 662 and the kiln riser duct 673. The embodiment of the calcining bed apparatus 640 shown in FIG 4 is integrated between the lowest stage cyclone 661 and the kiln feed inlet 675. The embodiment has multiple benefits. Firstly, CO2 rich gas streams can be extracted from the kiln system 600 for utilization or storage. One or two streams can be extracted. An increased degree of calcination of meal admitted to the rotary kiln 671 can be achieved by firing a range of different fuel types, particularly cost-effective fuels with a large volatile content and moisture content such as refuse derived fuel, but also suited for more readily combustible fuels such as fine saw dust and liquid fuels admitted at or slightly above the pulse fluidized meal bed. The increased degree of calcination can be achieved without the need for installation of a tertiary air duct - because the oxygen required for combusting the calcination fuel is supplied as substantially pure oxygen. Furthermore, additional combustion air does not need to be conveyed through the kiln 671, which could cause unacceptable cooling of the clinker burning zone and raising the cyclone preheater temperatures as well as the heat loss form the preheater 660. Increased clinker production in the kiln 671 can also be achieved without needing to make changes to the existing kiln system to accommodate a higher gas flow, except for the extracted CO2 rich gas stream (raw meal feed capacity, clinker cooling capacity and clinker handling capacity need to match the increased capacity).

[0076] FIG 7 shows a kiln system 700 designed to concentrate and extract essentially all of the CO2 from all calcination and combustion in a kiln system 700 for clinker production by utilizing at least two fluidized bed calcining apparatus 715 and 730 and a re-carbonator 772. The embodiment shown has a two-string Separate Line Calciner (SLC) kiln system retrofit where limited changes are made to the existing kiln system 700, whereby the kiln system 700 largely can be reused and uncertainties avoided, without needing to recirculate flue gas. Particularly the rotary kiln 771 remains, except for the temperature of hot meal admitted to it being up to 100°C higher than in a conventional kiln due to a higher CO2partial pressure during calcination. Approximately 50% of the hot meal from the second lowest kiln string preheater stage 712 (700-800°C) is each admitted to a first fluidized bed calcining apparatus 730 with the balance being admitted directly to the re-carbonation unit 772 on the kiln riser duct. Approximately 50% of the meal from cyclone stage 721 is admitted to fluidized bed calcination unit 731, while the remaining fraction is admitted to the re-carbonation unit 772. The re-carbonation unit 772 is a gas suspension re-carbonator in which CaO continuously admitted in a stream from the first pair of fluidized bed calcining apparatus 730 and 731 is suspended in the CO2 containing gas stream from the rotary kiln 771 while controlling the temperature of the gas-solid suspension so that it remains below the calcination temperature corresponding to the CO2 partial pressure at the given point in the process. The hot meal admitted directly from preheater cyclones 712 and 721 is admitted at two different vertical positions in the re-carbonation unit 772 to maintain the temperature below the calcination temperature despite heat release by re-carbonation - and supplemented by hot meal from the third lowest kiln string preheater stage 713. As the meal from preheater cyclone stages 721, 712, and 713 has a temperature lower than the calcination temperature below which the temperature must be maintained, the hot meal from the preheater cyclone stages 721, 712 and 713 serves as a cooling medium. If further cooling is required, meal from preheater cyclones with lower temperature, such as 722 can be admitted to the recarbonation unit 772. The meal from the re-carbonator separation cyclone 711 is divided in two streams, preferably equal streams, which each are admitted to a second fluidized bed calcining apparatus 715 and 716. Two parallel second fluidized bed calcining apparatuses 715 and 716 are installed to ensure sufficient calcination capacity, while limiting the height requirement. A CO2 rich gas stream is extracted from each of the two second fluidized bed calcining apparatuses 715 and 716 and the meal stream is admitted to the rotary kiln 771 for further processing. The solid stream admitted to the rotary kiln 771 is 90-95% calcined, whereby the final calcination takes place in the rotary kiln 771 in the conventional manner. The first and second fluid bed calcining apparatuses 715, 716, 730, 731 are configured in the same way as for the embodiment above in FIG 3; i.e. configured to increase the calcination capacity by admitting both a fuel and oxygen to both the inlet legs 116 and outlet legs 122 and extracting CO2 rich streams of the combined gas generated by calcination at the inlet leg 116 and outlet legs 122 through a cyclone (not shown) which admits the solid meal stream to the kiln system 700, while removing the CO2 rich gas stream. The meal passing through the first decarbonation unit 730 and 731 is about 75% calcined when it enters the re-carbonator 772, thus providing a stoichiometric excess of CaO compared to the amount of CO2 entering the re-carbonator 772 from the kiln 771. The partly re-carbonated meal from the re-carbonator 772 is 90-95% calcined in the two second fluidized bed calcining apparatuses 715 and 716 as described above. Air from the clinker cooler conveyed through the tertiary air duct 706 is admitted to the cyclone preheater string 720 not connected to the rotary kiln 771 utilizing hot air from the cooler (not shown) to preheat heat the raw meal. Decarbonated flue gas from the rotary kiln 771 is utilized to preheat the kiln preheater string 710. CO2 rich streams are extracted from each of the fluidized bed calcining apparatus 715, 716, 730, 731. The embodiment shown in FIG 7 makes it possible to capture CO2 without requiring major modifications to the existing kiln system because gas flows through all major existing processing units (kiln 771, preheater strings 710 and 720 and the clinker cooler) can be maintained within 30% of the design values for nominal clinker production capacity, which is generally considered to be a viable turndown ratio for a kiln system 700. Similar retrofit and operation can be achieved with In Line Calciner kiln systems with one or more preheater strings such as 500 shown in FIG 5 with a single preheater string. This can be achieved by introducing one or more second fluidized bed calcining apparatuses (corresponding to 715 and 716 on FIG 7) between the lowest preheater cyclone 511 and the kiln 502 shown on FIG 5.

Claims

CLAIMS1. A fluidized bed calcining apparatus comprising:- a calcination chamber having a lower fluidizing bed zone and an upper calcining zone;- a solid material provision means configured to provide a calcinable powder material to the calcination chamber;- a fluidizing means configured to fluidize the calcinable powder material or calcined powder material in the fluidizing bed zone;- a solid material outlet connected to the calcination chamber and configured to remove the solid material from the fluidizing bed zone and thus maintain a desired height of the fluidizing bed, the solid material outlet additionally is configured with a gas-lock;- an energy provision means, configured to provide a source of energy to the calcination chamber and heat the powder material to a calcination temperature of the powder;- a gas outlet located above the fluidizing bed zone, preferably in the upper part of the calcining zone; wherein the fluidized bed calcining apparatus is configured such that calcination of the calcinable powder primarily takes place in the calcination zone.

2. The fluidized bed calcining apparatus according to claim 1 wherein the fluidizing means configured to inject pulses of a fluidizing gas and is suitable to fluidize a powder medium which is classified as a cohesive-type powder according to the Geldart classification.

3. The fluidized bed calcining apparatus according to claims 1 to 2 wherein the solid material outlet is configured to remove the powder material while in a fluidized condition, preferably wherein a portion of the solid material outlet is configured to inject pulses of fluidization gas.

4. The fluidized bed calcining apparatus according to any previous claim further comprising a suspension gas jet inlet configured to suspend and distribute calcinable powder in the calcining zone to provide a solid loading sufficient for the calcinable powder to act as a heat sink.

5. The fluidized bed calcining apparatus according to any previous claims further configured to receive a solid fuel.

6. The fluidized bed calcining apparatus according to any previous claim wherein the fluidized bed zone has conditions suitable for pyrolyzing the solid fuel, and wherein the pyrolysis gas released from the fuel is combusted in the calcining zone.

7. The fluidized bed calcining apparatus according to any previous claim wherein it is fluidly connected with a gas source having an oxygen concentration above 21% and / or a nitrogen concentration below 78%.

8. The fluidized bed calcining apparatus according to any previous further configured to operate with a mean temperature of between 900°C and 1200°C in the calcination zone, and a mean temperature of between 400°C to 850°C in the fluidization zone.

9. A cement manufacturing plant comprising: a preheater device, preferably comprising a plurality of cyclone preheater suitable for heating a solid material; a fluidized bed calciner according to any of claims 1 to 7, a kiln device, configured to received and heat treat the calcined meal from the fluidized bed calciner such as to form the cement clinker, a clinker cooler configured to receive and cool cement clinker from the kiln,- wherein the calciner is configured to receive preheated raw meal from the preheater device substantially without receiving any process gas from the preheater device or kiln device, and- wherein the calcined meal from the fluidized bed calciner is provided to the kiln device.

10. The cement manufacturing plant according to claim 9, wherein substantially no gases from the fluidized bed calciner are provided to the kiln device, clinker cooler or the preheater device.

11. The cement manufacturing plant according to claims 9 or 10 further comprising a calciner device coupled to the preheater device and the kiln device such that exchange of both fluids and solids are possible, said calciner device running in series or in parallel withthe fluidized bed calciner and configured to receive a solid material from the fluidized bed calciner and preferably wherein the calciner device is of another type of calciner than a fluidized bed type calciner, such as a flash calciner.

12. A method of calcining a calcinable powder in a fluidized bed calcining apparatus, the apparatus having a calcination chamber comprising a fluidizing bed zone and a calcining zone, said calcining zone located above the fluidizing bed zone, the method comprising the steps of- providing the calcinable powder to the calcination chamber;- providing a source of energy sufficient to heat the calcinable powder to the calcining temperature and to drive the endothermic reactions thereof;- thermally contacting at least a portion of the calcinable powder with the heat from the source of energy in the calcining zone to provide a calcined powder and a formed gas;- fluidizing at least a portion of the calcined powder and / or calcinable powder in the fluidizing bed zone as the primary bed material to form a fluidized bed;- removing the calcined powder from fluidized bed through a solid material outlet to adjust the bed height thereof, said solid material outlet may comprise a gas-lock such that the calcined powder is removed substantially without any of the formed gas;- removing the formed gases through a gas outlet, said gas outlet located in the upper part of the fluidizing bed zone.

13. The method according to claim 12 wherein the calcined powder and / or calcinable powder is a cohesive-type powder according to the Geldart classification of particles.

14. The method according to claim 12 or 13 wherein the calcinable powder is at least 50w / w% limestone, preferably the calcinable powder is cement raw meal.

15. The method according to any of claims 12 to 14 wherein the superficial gas velocity in the fluidized bed zone calculated as the volume of admitted fluidization gas divided by the horizontal bed cross section is no more than 50 cm / s, more preferably 2cm / s to 50cm / s, such as 2cm / s to 5 cm / s.

16. The method according to any of claims 12 to 15 wherein the calcinable powder and / or calcined powder constitutes at least 50%(w / w) of solid material in the calcination chamber, preferably at least 60%(w / w), more preferably at least 70%(w / w), even more preferably at least 80%(w / w), such as at least 90%(w / w).

17. The method according to any of claims 12 to 16 wherein the bed medium is fluidized by injecting pulses of a fluidizing gas, preferably wherein the fluidizing gas is substantially pure oxygen, a gas substantially free from nitrogen or substantially pure CO2.

18. The method according to any of claims 12 to 17 wherein an amount of bed material substantially equal to the admitted amount of bed material is removed from the fluidizing bed zone while in a fluidized condition to maintain a constant bed level in the calcination chamber.

19. The method according to any of claims 12 to 18 wherein at least 5% of the calcinable powder is calcined, such as 10%, preferably 20% of the calcinable powder is calcined, preferably at least 40%, preferably at least 50%, preferably at least 60%, more preferably at least 70%, preferably 80%, more preferably at least 90%, more preferably at least 95% or even around 100%.

20. The method according to any of claims 12 to 19 wherein the mean temperature in the calcining zone is between 900°C and 1200°C and wherein the mean temperature in the fluidized bed zone is between 400°C and 900°C.

21. The method according to any of claims 12 to 20 wherein the formed gases constitute at least 60V / V% of the total gases removed from the calcination chamber, preferably above 70 V / V%, more preferably above 80 V / V%, most preferably above 90 V / V%.

22. The method according to any of claims 12 to 21 wherein the fluidized bed zone has reducing conditions.

23. The method according to any of claims 12 to 22 wherein a gas comprising oxygen is provided to the calcining zone and wherein the calcining zone has oxidizing conditions.

24. The method according to any of claims 12 to 23 wherein a fuel is provided to the calcining zone and wherein the source of energy is provided by combusting the fuel in the calcining zone.

25. The method according to any of claims 12 to 24 wherein a solid fuel is provided to the calcination chamber and wherein the fuel is pyrolyzed in the fluidized bed zone to release pyrolysis gases and wherein the pyrolysis gases are combusted in the calcining zone.

26. The method according to any of claims 12 to 25 wherein a suspension gas is provided to the calcination chamber to suspend and distribute calcinable powder in the calcining zone.

27. The method according to any of claims 12 to 26 wherein the solids fraction in an upper portion of the calcining zone is less than 0.5 and most preferably less than 0.

2.

28. The method according to any of claims 12 to 27 previous claim wherein volume ratio of gas provided as suspension gas and fluidizing gas is at least 5: 1, more preferably 10: 1, most preferably at least 20: 1.

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