Background

Carbon capture from industrial process plants that produce CO2 is a societal need to reduce global warming. In the production of cement clinker and other materials that are based on carbonates, thermal processing leads to conversion of the carbonates into CO2 gas. Carbon capture in the form of separation of CO2 from the flue gas can be practiced in several ways that all exhibits pro's and con's when applied as part of a clinker production process.

One of the promising routes is the so-called oxyfuel method, where the di-oxygen required for combustion is separated from the nitrogen and argon in ambient air prior to introducing it to the cement process. Thermal processing with a gas substantially free from nitrogen and argon provides a much higher concentration of CO2 in the flue gas and thus makes the flue gas much more suitable for efficient carbon capture.

The oxyfuel method does however come with some challenges. Typically, an in-line calciner system (ILC system) have been used in the manufacturing of cement clinker. This means that the cement is manufacturing in a single string comprising a preheater, calciner, rotary kiln and a clinker cooler. In a typical ILC system air is used for combustion and for conveying of solid powder in the process. Using air for combustion require approximately 1.4 kg of air per 1000 kcal fired (depending on fuel type). For a typical heat consumption of 750 kcal/kg clinker this is roughly 1.05 kg of air (minimum) per kg of cement clinker. With approximately 23% 02 (w/w) in air and an excess air factor of 1.1, 0.9 kg of N2 is provided per kg of clinker or 0.7 Nm ³ / kg clinker. The typical gas volume out of the preheater of an ILC kiln would be approximately 2 kg/kg clinker or 1.4 Nm ³ /kg clinker.

Consequently, switching to combustion in an 100 % oxygen gas would reduce the gas flow in the preheater to approximately half of the present value, while at the same time increasing the CO2 percentage (due to the lack of dilution from the nitrogen).

When requesting the same production level in the air mode and the oxyfuel method, it is necessary to recirculate gas over the preheater to keep the gas flow, leading to a more complicated system.

Oxyfuel also requires that the system is substantially gas tight such that as little air is introduced into the system. This is called false air. False air will bring Nitrogen to the system at the same time as it brings oxygen and thus the concentration of CO2 in the flue gas will be diluted. Finally cooling of the calcined clinker in a clinker cooling provides a challenge. Typically, in an ILC system 300 kcal/kg of clinker is recuperated in the clinker cooler using air. However, using air for cooling and combustion will not be possible in an oxyfuel system. Special cooling is thus required using recirculated Low N2, High CO2 gas which will require further complication of the system or by introducing high concentrated O2 to the cooler which would lead to elevated temperatures in the burning zone and thus require further remediations.

It would be desirable to provide a process and plant for calcining a carbonaceous in an efficient way and which allows to produce a flue gas stream comprising high concentrated CO2 and low concentration N2.

Summary

With this background, it is therefore an object of the present invention to provide a process and a system for calcining a carbonaceous material and simultaneous provide a gas stream comprising high concentrated CO2. Additionally, it is also an object of the present invention to provide a method and a kit for upgrading a cement manufacturing plant, in particular an ILC system in such a way that it may produce a calcined material while simultaneous provide a gas stream comprising high concentrated CO2.

In a first aspect of the invention, these and further objects are obtained by a process for calcining a carbonaceous material comprising the steps of: a) heating a carbonaceous material, in a calcining device in the presence of an oxygen-containing gas, to a calcination temperature such that the carbonaceous material releases a carbon containing species to provide a decarbonized material; b) contacting a portion of the decarbonized material with a CCh-containing gas in a carbonizing device at a temperature around a carbonization temperature to provide a carbonaceous material and a CCh-depleated gas; c) heating a portion of the carbonaceous material in a furnace device to a sintering temperature to provide a final product; d) cooling the final product; wherein i) the oxygen-containing gas having a nitrogen content of less than 78 V/V% and/or an oxygen content greater than 21 V/V % measured on dry basis; ii) gas from the furnace device is provided to the carbonizing device and substantially no gases from the furnace device is provided to the calcining device; iii) substantially no gases are provided from the calcining device to the carbonizing device; iv) a portion of the decarbonized material is provided from the calcining device to the furnace device and by-passing the carbonizing device.

The carbonaceous material may be a cement clinker raw meal, a clayey material, lime, dolomite and any other material that will release CO2. The carbonaceous material may be a solid material. In one or more embodiments the carbonaceous material may be a particulate or powder material. In one or more embodiments the carbonaceous material may be a Geldart-C type powder material.

The carbonaceous material may be a material which has been decarbonized and subsequently carbonized or it may be a carbonaceous raw material. The carbonaceous material may consist of a part of a carbonaceous raw material and a part which has been decarbonized and subsequently carbonized.

In one or more embodiments the carbonaceous material may be a material that after decarbonization achieves cementitious properties.

The final product may be cement clinker, heat treated clay, quick lime, burnt dolomite, a cementitious material or other decarbonized material.

The carbon containing species that is released from the carbonaceous material may be CO2.

The CCh-containing gas provided to the carbonizing device may be exhaust gas from the furnace device and typically has a concentration of CO2 of 15-45 V/V%.

After the CO2 and the decarbonized material are contacted in the carbonizing device, the CO2- depleated gas may have a concentration of CO2 of below 30 V/V% such as between 5-30 V/V%.

The carbonizing temperature is typically at temperatures below 800°C such as 450°C -800°C.

The calcination temperature may be above 750°C such as around 750°C -1100°C.

The oxygen-containing gas may have a nitrogen content of less than 78 V/V%, such as less than 70 V/V%, such as less than 60 V/V%, such as less than 50 V/V%, such as less than 40 V/V%, such as less than 30 V/V%, such as less than 20 V/V%, such as less than 10 V/V%, such as less than 5 V/V%, preferably less than The oxygen-containing gas may additionally or alternatively have an oxygen content greater than 22 V/V%, such as 30 V/V%, such as 40 V/V%, such as 50 V/V%, such as 60 V/V%, such as 70 V/V%, such as 80 V/V%, such as 90 V/V%, such as 95 V/V%, preferably greater than 98 V/V%.

Unless otherwise specified all gas compositions are provided on dry basis.

The present invention provides a process having two process strings which are configured to exchange solid material substantially without exchanging gases. The first string may be referred to as the furnace string and comprises the furnace device and carbonizing device. The second string may be referred to as a calciner string and comprises the calcining device. This allows the furnace string to be operated with air whereas the calciner string is operated with a gas which has a low concentration of nitrogen and a high concentration of oxygen. This allows carbonated material to be transferred from the furnace string to the calciner string and in the presence of oxygen to decarbonize and produce CO2. The gas produced in the calcining device has a low concentration of nitrogen and is therefore better suited for Carbon Capture compared to a regular calcining device operated with air as a combustion gas. A first portion of the decarbonized material is returned to the carbonizer where it is carbonized again and provided to either to furnace device or to the calciner string. If the carbonized material is provided to the furnace device, it is again decarbonized, and any released CO2 gas will flow to the carbonizing device where at least some of it reacts with decarbonized material. In this way CO2 is bound in the carbonized material and is shifted from the furnace string to the calciner string. The second portion of the decarbonized material is provided directly to furnace device. The second portion of decarbonized material has a temperature around the calcination temperature and is hotter than the carbonized material provided to the furnace device from the carbonizing device, which has a temperature around the carbonization temperature. The inventors have found that it is sufficient to use only a portion of the decarbonized material for shifting CO2 from the furnace string of the process to the calciner string of the process. The remaining decarbonized material is provided directly from the calcining device to the furnace device and thus require less energy to be heated to the sintering temperature in the furnace device. The heat efficiency of the process is thereby increased.

In one or more embodiments a first fraction of 10 to 95 w/w% of decarbonized material is provided to the furnace device directly from the calcining device. In some embodiments the first fraction comprises 15 w/w%, 20 w/w%, 30 w/w%, 40 w/w%, 50 w/w%, 60 w/w%, or 70 w/w% of the decarbonized material. In some embodiments a second fraction of 5 to 90 w/w% of the decarbonized material is provided to the carbonizing device from the calcining device. In some embodiments the second fraction comprises 10 w/w%, 15 w/w%, 20 w/w% 30 w/w% 40 w/w%, 50 w/w%, 60 w/w%, or 70 w/w% of the decarbonized material. Preferably the first fraction and second fraction should substantially add up to 100 w/w%. In one or more embodiments at least one performance parameter is measured, said performance parameter being indicative of how efficient CO2 is shifted from the furnace string to the calcination string. The at least one performance parameter may be the CO2 content, fraction of CO2 shifted, the O2 content, the temperature, overall heat and power consumption. The temperature may indicate if the temperature in the carbonizing device is within a temperature range suitable for carbonizing.

In one or more embodiments the first fraction of decarbonized material and second fraction of decarbonized material is adjusted based on the at least one performance parameter.

By operating the process with two different gases as combustion gases provides a system which operates with two different solids to gas ratios. The solids to gas ratios are dependent on the content of oxygen. In a preferred embodiment the solids to gas ratio in the calcining device is larger than the solid to gas ratio in the carbonizing device.

In one or more embodiments the solids to gas ratio in the calcining device is in the range of 0.5 to 7 w/w measured on dry basis. Preferably the solids to gas ratio may be 1, 2, 3, 4, 5, 6.

In one or more embodiments the solids to gas ratio in the carbonizing device is in the range of 0.25 to 7 w/w measured on dry bases. Preferably the solids to gas ratio may be 1, 2, 3, 4, 5, 6.

In one or more embodiments the furnace device is configured to operate with a gas having a nitrogen content of at least 30V/V%, such as in the range of 78 V/V%. In a preferred embodiment the furnace device is operated with atmospheric air as the combustion gas. The carbonizing device may be configured to receive the exhaust gas from the furnace device.

In one or more embodiments the majority of the carbonaceous material is initially provided to the furnace string. In one or more embodiments substantially all carbonaceous material is initially provided to the furnace string. In particular the carbonaceous material may be provided to the carbonation device or upstream of said carbonation device. By initially providing the raw material (the carbonaceous material) to the furnace string, instead of the calcining string, has the advantage that unwanted emission species released during heating of the feed material will stay in the furnace string. The amount of unwanted emission species in the calcining string (i.e. the concentrated CO2 gas) is reduced. It should be understood that solid material in the process will be transferred between the furnace string and the calcining string, but that "initially provided" means that the raw material feed (carbonaceous material) is provided to process by introducing it into the furnace string. In one or more embodiments the method further comprising the step of preheating at least a portion of the material suitable for binding carbon towards a carbonization temperature and/or preheating at least a portion of the material suitable for binding carbon to a calcination temperature. This may be achieved by having a preheating device. One example of a preheating device may be a preheating tower comprising a number of cyclone preheaters. Such a preheating tower may be connected to the furnace string or to the calciner string.

In one or more embodiments a portion of the gas from the furnace device is subjected to gas treatment before being provided to the carbonizing device. This may be achieved by a by-pass system in which some of the gases from the furnace device are extracted and provided to a by-pass system. The gas treatment may be up to 100% of furnace gasses to avoid build-up of volatiles in the process.

In one or more embodiments the feed of carbonaceous material may be provided to the calcining string, optionally to the preheating device and/or directly to the calcining device. The feed of carbonized material may additionally or alternatively be provided to the furnace string, optionally to the preheating device and/or directly to the carbonizing device. Feeding a portion of the carbonized material to both preheaters allows for better heat utilization.

In a second aspect the invention relates to a plant for producing cementitious material comprising:

- a carbonizing device

- a calcining device

- a furnace device

- a cooling device wherein the carbonizing device, furnace device, and cooling device are fluidly connected. The calcining device is substantially fluidly isolated from the carbonizing device, furnace device, and cooling device. The calcining device is configured to receive and provide a solid material to/from the carbonizing device. The calcining device may additionally be configured to operate under oxygen-enriched conditions and to additionally provide a solid material directly to the furnace device.

By oxygen-enriched conditions is meant that the oxygen-containing gas provided to the calciner may have a nitrogen content of less than 78 V/V%, such as 5 V/V%, preferably less than 2 V/V%, and additionally and/or alternatively the oxygen-containing gas may have an oxygen content greater than 21 V/V%, such as 95 V/V%, preferably greater than 98 V/V%.

The carbonizing device may be a vessel suitable for contacting a solid material with a CO2 containing gas. Preferably the contacting occurs in counter current. The solid material may be a cementitious raw material suitable for binding carbon. The carbonizing vessel may have any suitable shape and should be configured to operate under carbonizing conditions. The temperature suitable for carbonization is typically below 750°C such as around 400-750°C. In a preferred embodiment the carbonizing vessel may be configured as a flash calciner. In a preferred embodiment the carbonizing vessel is a flash calciner operated without a burner.

The calcining device may be any suitable vessel configured to accommodate a solid material and a gas under calcination temperatures. The calcining vessel may have at least one burner. In one embodiment the calcining vessel is a flash calciner. In a preferred embodiment the calcining device is an oxyfuel calciner.

The furnace device is preferably a rotary kiln.

The cooling device is preferably a clinker cooler or a similar cooler configured to cool a hot cementitious material from around 1450°C to 85°C.

In one or more embodiments a solid material splitting device is connected to the calciner. The solid material splitting device being configured to provide a first portion of solid material form the calcining device to the carbonizing device and a second portion of solid material from the calcining device to the furnace device. In a particular embodiment the solid material splitter comprises two cyclones and a valve. The valve configured to adjust the amount of gas to or from at least one of the cyclones.

In one or more embodiments the material splitter is configured to provide between 5-90 w/w% of solid from the calcining device to the carbonizing device, and between 10-95 w/w% of solid material from the calcining device to the furnace device. The solid material may be the decarbonized material. In a particular embodiment the solid material is calcined cement raw meal.

In one or more embodiments the plant further comprising at least one preheating device connected to the calciner string. The calciner string preheating device being configured to receive a gas from the calciner and to contact a solid material with said gas. In a particular embodiment the preheating device is a cyclone preheater comprising a number of connected cyclones.

In one or more embodiments the plant further comprising at least one preheating device connected to the kiln string and configured to exchange gas and solids with the carbonizer. The kiln string preheating device being configured to receive a gas from the carbonizing device and to contact a solid material with said gas. In a particular embodiment the kiln string preheating device is a cyclone preheater comprising a number of connected cyclones

In one or more embodiments the calcining device is configured with a source of oxygen. The source of oxygen may be a gas tank or an oxygen manufacturing plant fluidly connected to the calcining device. The oxygen provided by the source of oxygen may have a nitrogen content of less than 78% and/or an oxygen content greater than 21 V/V %. Preferably the nitrogen content is below 5 V/V %. Preferably the oxygen content is above 95 V/V %

In one or more embodiments the plant further comprising a by-pass system fluidly connected to the kiln string. The by-pass system may be configured to receive a gas from the furnace device. In the by-pass system the gas may undergo gas treatment to remove volatiles. After gas treatment the gas is returned to the kiln string. Preferably the gas is returned to the furnace device or provided to the carbonizing device. The by-pass system may comprise gas treatment means in the form of heat exchanger and dust removing device.

In one or more embodiments the plant is fluidly connected to a carbon capture system. In particular, the calcining device may be fluidly connected to the carbon capture system such that the CO2 rich gas provided in the calcining device may be further processed in the carbon capture system.

In yet another aspect the invention relates to a retrofit system. The retrofit system provides means for converting a calcining plant operating with ambient air into a calcining plant configured to provide a concentrated gas flow of carbon dioxide. The calcining plant comprising a furnace device, a cooling device, and optionally a calciner, a kiln riser, and/or a preheating device. the retrofit system comprising at least one of the following: a) a carbonizing device; b) means for converting an existing calciner into a carbonizing device; c) means for converting an existing kiln riser into a carbonizing device.

The retrofit system further comprising: an oxy-calcining device configured with means to provide an oxygen-containing gas having a nitrogen content of less than 78% and/or an oxygen content greater than 21 V/V %; a first solids provision means configured to provide solids from a carbonizing means to the oxy-calcining device; a second solids provision means configured to provide solids from the oxycalcining device to the carbonizing means and the furnace device.

The calcining plant comprising the retrofit system may be referred to as an oxy-fired calcining plant.

The oxy-calcining device is a calcining device configured to operate with a gas having an oxygen concentration higher than ambient air.

The calcining plant may comprise a number of unit operations which may be utilized and/or converted for use in the oxy-fired calcining plant.

In some instances, it may be possible to convert an existing part of the cement clinker manufacturing plant into a carbonizing device. A carbonizing device may be a vessel suitable for contacting a solid material and a CCh-containing gas, preferably in counter-flow, at a carbonization temperature. This may for instance be the case if the cement clinker manufacturing plant comprises a calcining device or a kiln riser. If these are in good condition, they may be converted into a carbonizing device. As an example, if the calcining device is a flash calciner , it may be converted into a carbonizing device by lowering its operating temperature, by e.g., shutting off the fuel supply and burner during normal operation or supplying a colder gas.

Alternatively, it is possible to provide a new carbonizing device which may be fluidly coupled to the kiln string.

When the retrofit system is connected to the cement clinker manufacturing plant in an intended manner, the complete system comprises a kiln string and a calciner string. The two strings are connected such that substantially no gases may flow between them, whereas solids are allowed to flow from the carbonizing device to the oxy-calcining device, and from the oxy-calcining device to the carbonizing device and the furnace device. In a typical air operated clinker manufacturing plant there will be some air that flows into the process due to leaky equipment, so-called false air. This is not problematic when the equipment is operated below atmospheric pressure and with ambient air. The retrofit system allows existing equipment to be operated in air mode and does not require expensive tightening. The additional equipment is on the other hand configured to be operated with an elevated oxygen concentration and a lower nitrogen content, i.e., it is more gas tight. Utilizing existing equipment in this manner allows the provision of a so-called oxyfuel cement plant in a more cost effective way. Preferably the carbonizing device is configured to receive gases directly from the kiln, such that CO2 from the kiln is provided to the carbonizing device where the carbonation reactions occur.

If the calcining plant comprises a preheating device this may be reused in the oxy-fired calcining plant. The preheating device may be a cyclone preheater. The preheating device should be located in the kiln string, such that it receives gases from the carbonizing device. The preheating device provides for efficient utilization of the heat since it preheats the raw meal towards a carbonizing temperature.

Existing equipment is configured for optimal operation with a specific amount of gas and meal flow. By dividing the existing plant into a kiln string and a calcining string, the amount of oxygen required in the kiln string is decreased, since the calcination takes place in the calciner string. However, if an existing preheating device exists in the kiln string, such a preheating device typically requires a specific volume flow of gas to work properly. To maintain the required volume flow of gas, it is required to either provide additional gas or to recirculate. Alternatively, it is required to provide a smaller preheating device which is expensive and not desired. If additional air is provided this would cool the system. The cooling could be utilized in the carbonizer to regulate the temperature. By recirculating gas leaving the preheating device back towards the carbonizing device the optimized volume flow of gas can be maintained without providing more ambient air to the system. In some embodiments of the invention, gas is recirculated and additional air is also provided to the carbonizing device for cooling.

In one or more embodiments the retrofit system further comprising a second preheating device connected to the oxy-calcining device. Preheating device connected to the oxy-calcining devices is configured to receive a gas from the oxy-calcining device and to contact a solid material with said gas. In a particular embodiment the preheating device is a cyclone preheater comprising a number of connected cyclones.

In one or more embodiments the calcining plant comprising the retrofit system is configured such that at least a portion of the meal from the carbonizer is provided directly to the kiln. In one or more embodiments the source of an oxygen-containing gas is a tank or vessel. In yet another embodiment the source of an oxygen-containing gas is an oxygen manufacturing plant. Preferably the oxygen containing gas has a nitrogen content of less than 78% and/or an oxygen content greater than 21 V/V %. More preferably the nitrogen content is below 5 V/V %. Preferably the oxygen content is above 95 V/V % In one or more embodiments the retrofit system comprises means for preheating the oxygencontaining gas. The oxygen-containing gas may be preheated by heat exchanging with gas from the cooler or heat exchanging with meal leaving the oxy-calcining device.

In one or more embodiments the retrofit system further comprising a solid material splitter. The solid material splitter may be connected to the oxy-calciner such that solid material from the oxy-calciner can be divided into two or more streams of solids. Preferably the solid material splitter being configured to provide a first portion of calcined material from the oxy-calciner to the carbonizing means and a second portion of calcined material from the oxy-calciner to the kiln.

A cementitious raw material suitable for binding carbon may be utilized to transfer CO2 from the kiln string to the oxy-calciner string. The solid material splitter may thus be used to provide a sufficient amount of decarbonized cementitious raw material from the oxy-calcining device to the carbonizing device. The remaining decarbonized cementitious raw material may be provided from the oxy-calcining device directly to the furnace device to improve the heat utilization of the plant. In one or more embodiments the solid material splitter may be configured to adjust the first portion and second portion of calcined material. In a preferred embodiment the solid material splitter is connected to a control system. One or more CO2 sensors may be located in the plant such that they may measure the CO2 in the gas. A CO2 sensor may be a sensor that measures a parameter indicative of the CO2 content. Preferably it measures the CO2 content before and after the carbonizing device. A CO2 sensor may also be located in the carbonizing unit. The sensor being coupled to and being in communication with the control system, and based on the measurements from the one or more sensors, the control system may adjust the first portion and second portion. In a preferred embodiment the control system is configured to minimize the amount of CO2 flowing out of the carbonizing device to the preheating device. Alternatively or additionally the plant may comprise one or more sensors for measuring 02, temperature, moisture and control system may optionally adjust the first portion and second portion based on a combination of measured parameters.

In one or more embodiments sensors are located near the solid transfer points, i.e. in the calcining device, carbonizing device, furnace device, preheating device and/or in the cooling device. The sensors may be connected to and being in communication with the control system.

In addition to the solid material splitter, the first solid provision means and/or second solid provision means may be connected to the control system to adjust the transfer of solids between the furnace string and the calcining string.

The feed of carbonized material may also be adjusted by the control system. As an example, if a temperature measurement in the carbonizer is too low, an increased amount of calcined material may be provided from the calcining device to the carbonizing device.

As another example, if the measurement of CO2 in the carbonizing device ( or in the preheater coupled to the carbonizing device), is too high, an increased amount of calcined material may be provided to the carbonizing device from the calcining device. Alternatively, if the measurement of oxygen in the carbonizing device is low, this may indicate that an unnecessary amount of calcined material is provided to the carbonizing device. In this situation the amount of solid material to the carbonizing device from the calcining device may be decreased and consequently the amount of solid material from the calcining device to the furnace device is increased and the heat utilization is improved. It should be said that the measurement may not only be a direct measurement of oxygen, but also an indirect measurement, i.e., a measurement of another parameter which is indicative of the oxygen concentration. This applies for all the possible parameters which may be measured.

In one or embodiments the retrofit system comprising a by-pass system configured to be fluidly connected to furnace device such that a portion of the gases from the furnace device is provided into the bypass system. In the by-pass system gases may undergo gas treatment to remove volatiles. After gas treatment the gas is returned to either the furnace device and/or the carbonizing device. The by-pass system may comprise gas treatment means in the form heat exchanger and dust removing device.

In one or more embodiments the retrofit system further comprising carbon capture system suitable for being fluidly connected to the oxy-calciner.

In yet another aspect the invention relates to a method of retrofitting a cement clinker manufacturing plant with means to provide a gas stream with concentrated CO2. Said cement clinker manufacturing plant may be a regular air operated plant. The cement clinker manufacturing plant comprising one or more of: a) a preheating device b) a calcining device c) a furnace device kiln d) a cooling device.

The method comprising: providing an oxy-calcining device configured with a with a source of an oxygencontaining gas, said oxygen containing gas having a nitrogen content of less than 78% and/or an oxygen content greater than 21 V/V %; providing a carbonizing device or means for converting an existing part of the cement clinker manufacturing plant into a carbonizing device; providing a first solids provision means configured to provide solids from the carbonizing means to the oxy-calciner substantially without exchanging any gas between the carbonizing means and the oxy-calciner and connecting said first solids provision means to the oxy- calcining device and carbonizing device; providing a second solids provision means configured to provide solids from the oxy-calciner to the carbonizer and kiln substantially without exchanging any gas between the carbonizing means and the oxy-calciner and kiln and connecting said second solids provision means to the oxy-calcining device and carbonizing device.

By having the oxy-calcining device and the carbonizing device separated such that substantially no gases can flow between them, provides two different strings which can be operated with different gas compositions. It is thus possible to operate the existing parts of the clinker manufacturing system with ambient air as the combustion gas, whereas the oxy-calciner may be operated using a different gas. The carbonizing device is preferably coupled to the furnace device such that gases may flow from the furnace device to the carbonizing device and optionally further to the preheating device.

In one or more embodiments the solid provision means may be a rotating screw feeder or a loop seal where the solid material is fluidized. In one particular embodiment of the loop seal the solid material is fluidized with an oxygen-rich gas. In embodiments where the solid material is a Geldart-C type powder it may be beneficial to fluidize the solid material using pulsated gas to avoid channeling.

In one or more embodiments the method comprising the step of converting an existing calciner into a carbonizing device or converting an existing kiln riser into a carbonizing device.

The calcining device, which typically is part of the cement clinker manufacturing plant, may be converted into a carbonizing unit by at least lowering the operating temperature of the calcining device from a calcining temperature to a carbonizing temperature. This is achieved by shutting of the fuel provision means to the calcining device, and optionally by provided a cooling gas. The cooling gas may be ambient air. The kiln riser, which typically also is part of the cement clinker manufacturing plant, may be converted into a carbonizing device by at least lowering the operating temperature in the kiln riser from a temperature near a calcining temperature to a carbonizing temperature.

In one or more embodiments the method further comprising the step of providing a preheating device and connecting said preheating device to the oxy-calciner such that the preheating device is suitable for meal and gas exchange with the oxy-calciner.

In one or more embodiments the method comprising the step of providing a solid material splitter and connected said solid material splitter to the oxy-calciner, the furnace device, and either the carbonizing device or the second solids provision means. The solid material splitter may be configured to provide a first portion of calcined material from the oxy-calciner to the carbonizing device and a second portion to the furnace device.

In one or more embodiments the method further comprising the step of providing a by-pass system and fluidly connecting said by-pass system to the furnace device and the carbonizing device. The by-pass system comprising gas-treating means.

In one or more embodiments the method further comprising the step of providing a carbon capture system and fluidly connected said carbon capture system to the to the oxy-calcining device or optionally the preheater located in the calcining string.

Brief description of drawings

The invention will be described in more details below by means of non-limiting examples of presently preferred embodiments and with reference to the drawings. In the figures thick arrows indicate gas transfer and thin lines indicate transfer of solids.

Fig. 1 shows a flow chart of a process for manufacturing a cementitious material according to one embodiment of the invention,

Fig. 2 shows a flow chart of a process for manufacturing a cementitious material according to a further embodiment of the invention,

Fig. 3 shows a flow chart of a process for manufacturing a cementitious material according to a further embodiment of the invention,

Fig. 4 shows a flow chart of a process for manufacturing a cementitious material according to yet a further embodiment of the invention, Fig. 5 shows a flow chart of a process for manufacturing a cementitious material according to yet a further embodiment of the invention.

Detailed Description

Fig. 1 shows a process chart for a plant 100 for producing a cementitious material from at least a carbonaceous material. The plant 100 comprising a carbonizing device 4, a calcining device 3 a furnace device

2 and a cooling device 1.

The cooling device 1, the furnace device 2, and the carbonizing device 4 are located in a furnace string 20 and are fluidly connected. The calcining device 3 is located in a separate calcining string 21 and is substantially fluidly isolated from components in the furnace string 20. The calcining device 3 is connected to the carbonizing device 4 such that solid material transfer is possible. The calcining device 3 is further configured to provide a solid material to the furnace device 2. During intended operation a cementitious raw material 10 is provided to the carbonizing device 4. The cementitious raw material may be a carbonaceous material, such as cement raw meal. A portion of the carbonized material is provided from the carbonizing unit to the calcining device 3. Cementitious raw material 11 may additionally be added to the calcining device

3 through a dedicated inlet. The calcining device is provided with an oxygen containing gas 12. The carbonized material is heated to a calcination temperature in the presence of oxygen to form a decarbonized material and CO2. Because the calciner string 21 may be operated with a gas 12 with a low concentration of nitrogen, the CO2 may be removed from the calcining devices as an CCh-rich exhaust gas 15. A portion of the decarbonized material is returned to the carbonizer 4 where it achieves a carbonization temperature in the presence of a CCh-containing gas. As the decarbonized material contacts the CO2 gas it re-carbonates into a carbonized material. As material is re-carbonated the gas becomes at least partially depleted from CO2. The at least partially CCh-depleated gas 16 is removed from the carbonizer. A portion of the carbonized material may again be provided to calcining device 3 whereas another portion is provided to the furnace device 2. In the furnace device 2 the carbonized material is heated to a sintering temperature to provide a cementitious material. During this process CO2 is released and provided to the carbonizer where it may react with decarbonated material. The cementitious material is then provided to a cooling device 1 where it is cooled and extracted 14. The cooler receives a cooling gas 13, which is heated by contacting the hot cementitious material. It is then provided to the furnace device 2 as a combustion gas. If an excess amount of cooling gas 13 is provided to the cooling device a portion of the cooling gas may be removed as hot gas 18. The hot gas 18 may be used for heat exchange. Another portion of the decarbonized material is provided from the calcining device 3 to the furnace device 2. In this way an excess amount of decarbonized material which is not required for sufficient transfer of CO2 from the furnace string 20 to the calciner string 21 is directly provided to the furnace device 2. The decarbonized material provided directly from the calcining device 3 to the furnace device 2 is hotter than carbonized material from the carbonizer. Thus, the direct provision of decarbonized material from the calcining device to the kiln provides a more energy efficient process.

Fig. 2 shows a process chart for a plant 101 for producing cementitious material. The plant 101 is similar to that shown in 100, but additionally comprises a preheating device 5 located in the furnace string 20 and a preheating device 6 located in the calcining string 21. The preheating device 5 is configured to receive a gas from the carbonizing device 4. A cementitious raw material 10 is provided to the preheating device 5 and is in counter flow contacted with and heated by the gas from the carbonizer 4. An example of a preheating device 5 may be a cyclone preheating tower comprising a plurality of cyclones. The preheating device 6 is configured to receive a gas from the calcining device 3. A cementitious raw material 10 is provided to the preheating device 6 and is in counter flow contacted with and heated by the gas from the calcining device 3. An example of a preheating device 6 may be a cyclone preheating tower comprising a plurality of cyclones. The plant 101 thus provides a process having better heat utilization.

Fig. 3 shows a process chart for a plant 102 for producing cementitious material. The plant 102 is similar to that shown in 101, but additionally comprises a by-pass system 7. A portion of the gases from the furnace device 2 may be provided to the by-pass system 7 where it is subjected to gas treatment. By-pass dust and volatiles 17 may be removed from the gas before it may be reintroduced to the furnace device 2 or to the carbonizing device 4.

Fig. 4 shows a process chart for a plant 103 for producing cementitious material. The plant 103 is similar to that shown in 101, but additionally comprises a system (8,9,10) for splitting solid material from the calcining device 3 into two separate streams. The solid material splitter comprises a first cyclone 8, a second cyclone 9, a valve 10, and optionally a valve 11. Exhaust gas 15 and decarbonized material is together provided into the first cyclone 8 or the second cyclone 9. The amount of exhaust gas 15 and decarbonized material to each of the cyclones is determined by the valve 10 and valve 11. If the valve 11 is shut and valve 10 is open, all decarbonized material is provided to the cyclone 8 and further to the carbonizer 4. If the valve 10 is shut and valve 10 is open, all decarbonized material is provided to the cyclone 9 and further directly to the furnace device 2. In an embodiment the valve 10 and valve 11 is coupled to a control system. Based on measurements of CO2 content in the exhaust gas 16 the valve 10 and valve 11 may be adjusted to provide a desired transfer of CO2 from the furnace string 20 to the calcining string 21. Fig. 5 shows a process chart for a plant 101'. This design is similar to the plant 101. The plant 101' additionally comprises a heat exchanger 7' for preheating the oxygen-containing gas provided to the calcining device 3. The oxygen-containing gas is heat exchanged with the calcined meal provided from the calcining device 3 to the carbonizer 4. Alternatively, the oxygen-containing gas may be heat exchanged with the hot gas 18 provided from the cooler 1.

The plant 101' additionally comprises gas recirculation means, configured for recirculating exhaust gas 16 back to the carbonizer 4. The recirculated exhaust gas 16 may be provide to the carbonizer as illustrated, provided before the carbonizer 4 but after the kiln 2, after the carbonizer 4 but before the preheating device 5. The recirculation of exhaust gas provides a larger flow velocity in the preheating device 5 and can be used to maintain a desired temperature in the carbonizer 4.