IMPROVED CARBONATION PROCESS AND DEVICE FOR ITS IMPLEMENTATION

Description

[0001] The present invention relates to a method for producing a carbonation product from a carbonation reactant and to a device for producing a carbonation product from a carbonation reactant, in particular suitable and designed for carrying out the method according to the invention.

[0002] Carbonation plays a central role in the technological processes of a beet sugar or sugarcane sugar factory or a raw sugar refinery. Carbonation typically comprises a first carbonation step and a second carbonation step. It is a purification step in juice purification, particularly in sugarcane juice purification (whether from beets or sugarcane), or in sugar refining, especially of a raw sugar solution. Prior to carbonation, the sugarcane juice or raw sugar solution used is obtained by extraction from sugar beets (especially beet pulp) or sugarcane, or by dissolving raw sugar in water followed by pre-liming and / or main liming, also known as alkalization.During pre-liming and main liming, the extracted sugarcane juice or raw sugar solution is mixed with milk of lime, i.e., calcium hydroxide dispersion in water. This causes suspended solids contained in the extracted sugarcane juice or raw sugar solution to flocculate. Alkalization results in an alkaline sugarcane juice or an alkaline raw sugar solution. Main liming achieves a main alkalinity of approximately 0.6 to 1.2 g CaO / 100 ml in the sugarcane juice or raw sugar solution, corresponding to a pH range of 12 to 12.8 at 20 °C.

[0003] Carbonation is carried out using the alkaline sugarcane juice or alkaline raw sugar solution obtained in this way. In the first carbonation step, performed in a primary carbonation vessel, the calcium hydroxide dispersion added in excess during the main liming process and present in the alkaline sugarcane juice or alkaline raw sugar solution is neutralized by introducing freshly generated lime kiln gas, i.e., a gas containing carbon dioxide. The alkaline sugarcane juice or alkaline raw sugar solution is neutralized to a pH endpoint of approximately 11.4 to 10.8 at 20 °C, corresponding to a final alkalinity of approximately 0.06 to 0.1 g CaO / 100 ml, and the calcium hydroxide is precipitated as calcium carbonate. The precipitated calcium carbonate, particularly when precipitated as calcium carbonate crystals, has an active, positively charged surface.Without being bound to theory, the precipitated calcium carbonate, especially in the form of calcium carbonate crystals, is able to exert a purification effect through the adsorption of precipitated colloids and other non-precipitable non-sugar substances due to its active surface. Simultaneously, the precipitated calcium carbonate, particularly calcium carbonate crystals, acts as a filter aid. In the second carbonation step, carried out in a second carbonation vessel, the alkaline raw sugar juice or the alkaline raw sugar solution is neutralized by introducing freshly generated lime kiln gas to a pH endpoint of approximately 9.4 to 8.6 at 20 °C, corresponding to a final alkalinity of approximately 0.005 to 0.015 g CaO / 100 ml. The calcium hydroxide is then precipitated as completely as possible as calcium carbonate, especially in the form of calcium carbonate crystals, until the optimal alkalinity is reached.

[0004] CO₂ gas utilization rates, i.e., the utilization rates of the CO₂ content in the lime kiln gas, can reach a maximum value of approximately 90 to 95% in the first carbonation step and a maximum value of approximately 70 to 75% in the second carbonation step using novel carbonation tanks based on the state of the art. Therefore, despite comparatively high CO₂ gas utilization rates, a significant portion of the CO₂ released in the lime kiln is still present in the so-called carbonation vapors, i.e., the exhaust gas of the respective carbonation step.

[0005] DE 29 25 283 A1 relates to a process for improving the operation of the carbonation (saturation) stages of a sugar factory, wherein exhaust gas from a second carbonation stage is recycled to a first carbonation stage.

[0006] The CO₂ gas utilization rate in the carbonation steps depends primarily on the alkaline sugarcane juice level or alkaline raw sugar solution level, temperature, mixing, alkalinity of the sugarcane juice or raw sugar solution, and the CO₂ content in the lime kiln gas. It is known that a decrease in the CO₂ content of the lime kiln gas reduces the gas utilization rates in the carbonation steps and / or increases CO₂ losses. This can be observed, for example, when switching from a coke-fired lime kiln to a gas-fired lime kiln. The resulting reduction in the CO₂ content of the lime kiln gas, and the associated reduction in gas utilization, particularly in the second carbonation step (CO₂ content of exhaust gas approximately 15 to 25 vol.), significantly impacts the efficiency of the carbonation process.A CO₂ loss (-% relative to total exhaust gas volume) can lead to a CO₂ deficiency in sugar production or refining and to significant fluctuations in the operation of the carbonation steps. The lower the overall gas utilization rate or the higher the CO₂ losses during carbonation, the more CO₂ is released into the environment, causing environmental damage and, in particular, promoting the greenhouse effect.

[0007] Therefore, the technical problem underlying the present invention lies in overcoming the aforementioned disadvantages. In particular, the technical problem underlying the present invention lies in providing methods and means that make it possible to increase the overall CO₂ gas utilization rate of a carbonation process, especially carbonation in a beet sugar or cane sugar production process or raw sugar refining. Preferably, the technical problem lies in providing methods and means that make it possible to reduce the CO₂ emissions of a carbonation process, especially carbonation in a beet sugar or cane sugar production process or raw sugar refining. Furthermore, a technical problem of the present invention is to provide such methods and means that are cost-effective, environmentally friendly, and easy to handle.

[0008] The technical problem is solved by the teaching of the independent claims, the dependent claims and the teachings of the description, in particular by a process for producing a carbonation product from a carbonation reactant, comprising the process steps: a) Alkalization of a carbonation reactant to obtain an alkaline carbonation reactant and b) carbonation of the alkaline carbonation reactant comprising a first and at least one further carbonation step b1) and b2) to obtain the carbonation product, in each of which a CO2-enriched carbonation gas is introduced into the alkaline carbonation reactant and a CO2-depleted exhaust gas is discharged, characterized by c) introducing at least a proportion of the CO2-depleted exhaust gas of the at least one further carbonation step into the alkaline carbonation reactant before the first carbonation step b1).

[0009] The introduction, according to the invention, of at least a proportion of the CO2-depleted exhaust gas of the at least one further carbonation step into the alkaline carbonation reactant before the first carbonation step b1) thus constitutes a pre-carbonation step b0) which is carried out on the carbonation reactant and thus before the first carbonation step b1).

[0010] The technical problem is therefore solved by a process for producing a carbonation product from a carbonation reactant, comprising the process steps: a) Alkalization of a carbonation reactant to obtain an alkaline carbonation reactant and b) carbonation of the alkaline carbonation reactant comprising a first and at least one further carbonation step b1) and b2) to obtain the carbonation product, in each of which a CO2-enriched carbonation gas is introduced into the alkaline carbonation reactant and a CO2-depleted exhaust gas is discharged, characterized by c) introducing at least a proportion of the CO2-depleted exhaust gas of the at least one further carbonation step into the alkaline carbonation reactant before the first carbonation step, so that a pre-carbonation step b0) is carried out before the first carbonation step b1).

[0011] According to the invention, in a first process step a), a carbonation reactant is alkalized, in particular by introducing alkaline substances, especially calcium hydroxide, particularly lime milk, especially in a pre-liming and / or main liming step, and an alkaline carbonation reactant is obtained. The alkaline carbonation reactant thus contains alkaline substances, in particular calcium hydroxide, introduced by the alkalization. In a process step b), carbonation is carried out with the alkaline carbonation reactant obtained in process step a), and a carbonation product is obtained. The carbonation carried out in process step b) comprises a first carbonation step b1) and at least one further carbonation step b2). In process step b), at least two carbonation steps b1) and b2) are therefore carried out.

[0012] During each carbonation step, a CO₂-enriched carbonation gas is introduced into the alkaline carbonation reactant, and a CO₂-depleted exhaust gas is removed from the resulting alkaline carbonation intermediate or carbonation product. Without being bound to theory, the introduction of the CO₂-enriched carbonation gas into the alkaline carbonation reactant causes the CO₂ of the CO₂-enriched carbonation gas to react with the alkaline substances present in the alkaline carbonation reactant as a result of process step a), particularly calcium hydroxide, to form calcium carbonate. The calcium carbonate precipitates from the alkaline carbonation reactant as a solid, especially in the form of calcium carbonate crystals, yielding an alkaline carbonation intermediate or carbonation product.In particular, the reaction of CO₂ with calcium hydroxide to form calcium carbonate lowers the pH of the alkaline carbonation intermediate or carbonation product compared to the alkaline carbonation reactant. Preferably, the precipitated calcium carbonate, especially in the form of calcium carbonate crystals, has a positively charged surface. A purification effect is preferably achieved by adsorption of precipitated colloids and / or non-precipitable non-sugar substances present in the alkaline sugar cane juice onto the positively charged surface of the precipitated calcium carbonate. Preferably, the precipitated calcium carbonate acts as a separation agent.In particular, the precipitated calcium carbonate acts as a separation aid, since substances that cannot be separated by filtration, such as suspended solids and / or non-precipitable non-sugar substances, are adsorbed by the precipitated calcium carbonate and can thus be separated, especially by filtration, together with the precipitated calcium carbonate. Through the reaction of the CO₂ from the CO₂-enriched carbonation gas with the calcium hydroxide present in the alkaline carbonation reactant, the CO₂ content in the CO₂-enriched carbonation gas is reduced, and a CO₂-depleted exhaust gas is obtained and discharged.The CO₂-depleted exhaust gas discharged from the respective carbonation step has a lower CO₂ content than the CO₂-enriched carbonation gas introduced into the respective carbonation step, in particular at least one CO₂ content lower than that consumed in the reaction of CO₂ with calcium hydroxide to calcium carbonate in the alkaline carbonation reactant. The alkaline carbonation intermediate obtained after the first carbonation step b1) contains a lower amount of substances to be precipitated, in particular calcium hydroxide, than the alkaline carbonation reactant used in the first carbonation step b1). The alkaline carbonation intermediate obtained after the first carbonation step b1) corresponds to the carbonation reactant of at least one further carbonation step b2).According to the invention, a carbonation product is obtained after the last of at least one further carbonation step b2), in particular after the second carbonation step. The carbonation product obtained after the last carbonation step, in particular the second carbonation step, contains a smaller amount of substances to be precipitated, in particular calcium hydroxide, or in particular no substances to be precipitated, than the alkaline carbonation intermediate of the first carbonation step b1), used in the last carbonation step, in particular the second carbonation step b2), i.e., the carbonation reactant of the last, in particular the second, carbonation step b2).

[0013] According to the invention, in a process step c), at least a portion of the CO₂-depleted exhaust gas discharged from the at least one further carbonation step, in particular the second carbonation step, is introduced into the alkaline carbonation reactant, preferably into a sugar cane juice or a raw sugar solution, before the first carbonation step. Introducing the portion of the CO₂-depleted exhaust gas discharged from the at least one further carbonation step, in particular the second carbonation step, into the alkaline carbonation reactant before the first carbonation step b1) in an upstream process step b0) leads to a particularly advantageous and significantly increased overall CO₂ utilization rate, since the alkalinity and thus the CO₂ requirement in the carbonation reactant is significantly higher before the first carbonation than during the first carbonation.

[0014] According to the invention, in process step c) at least a proportion of the exhaust gas of a further carbonation step, in particular a second carbonation step, carried out after the first carbonation step, is introduced into the alkaline carbonation reactant of a pre-carbonation step carried out before the first carbonation step.

[0015] According to the invention, preferably at least a portion of the exhaust gas of a further carbonation step, in particular a second carbonation step, carried out after the first carbonation step, is introduced into the alkaline carbonation reactant of the first carbonation step, and at least a further portion of the exhaust gas of the further carbonation step, in particular a second carbonation step, carried out after the first carbonation step, is introduced into the alkaline carbonation reactant of a pre-carbonation step b0) carried out before the first carbonation step.

[0016] According to the invention, preferably in process step c), at least a portion of the exhaust gas from a further carbonation step, in particular a second carbonation step, carried out after the first carbonation step, is introduced into the alkaline carbonation reactant of the first carbonation step. In this embodiment, two streams of carbonation gases are thus introduced into the first carbonation step, namely a CO₂-enriched carbonation gas and a CO₂-depleted carbonation gas, i.e., the CO₂-depleted exhaust gas, from the second or at least one further carbonation step.

[0017] Preferably, by introducing at least one portion of the exhaust gas of the at least one further carbonation step, in particular a second carbonation step, into the alkaline carbonation reactant of the first or a carbonation step carried out before the first carbonation step, in particular a pre-carbonation step, in the process step c) according to the invention, at least one portion of the unused CO 2 content in the exhaust gas of the at least one further carbonation step, in particular a second carbonation step, is used to convert at least one part of the calcium hydroxide present in the alkaline carbonation reactant of the first or a carbonation step carried out before the first carbonation step, in particular a pre-carbonation step, to calcium carbonate.Preferably, the total CO2 gas utilization rate of the carbonation according to process step b) is increased by process step c) according to the invention, in particular compared to a comparable process (hereinafter also referred to as comparative example).

[0018] Preferably, the additional use of at least a proportion of the CO2 in the exhaust gas of the at least one further carbonation step, in particular the second carbonation step, by introducing at least a proportion of the exhaust gas into the alkaline carbonation reactant of the first or a carbonation step carried out before the first carbonation step, in particular a pre-carbonation step, according to process step c) of the invention, leads to an improvement in the overall CO2 gas utilization rate of the carbonation according to process step b) of the present invention and to a reduction in the CO2 emission of the carbonation according to process step b) of the present invention compared to comparable processes.Preferably, the inventive process step c) advantageously leads to a reduction in the CO 2 emission of the carbonation according to process step b), since at least a proportion of the unused CO 2 of the CO 2-enriched carbonation gas of the at least one further carbonation step, in particular the second carbonation step, which is discharged as CO 2-depleted exhaust gas, is recycled by the inventive process step c) of the carbonation according to process step b) of the present invention, in particular reacts with calcium hydroxide to form calcium carbonate, and is therefore not emitted into the environment, in particular as in comparable processes.

[0019] According to the present invention, a pre-carbonation step b0) is carried out before the first carbonation step b1).

[0020] The present invention therefore relates in particular to a method for increasing the overall CO2 gas utilization rate in a process comprising process steps a), b) and c), in particular comprising process step b0).

[0021] The present invention therefore relates in particular to a process for reducing CO2 emissions in a process for producing a carbonation product from a carbonation reactant, comprising process steps a), b) and c), in particular b0).

[0022] In a preferred embodiment of the present invention, a second carbonation step b2) is carried out after the first carbonation step b1).

[0023] In a preferred embodiment of the present invention, at least one additional further carbonation step is carried out after the second carbonation step b2).

[0024] In a preferred embodiment of the present invention, in process step b) a total of at least 2, in particular 2, in particular at least 3, in particular 3, in particular 4, in particular 5, in particular 6, carbonation steps are carried out.

[0025] In a preferred embodiment of the present invention, a pre-carbonation step b0) is carried out before the first carbonation step b1) and a second carbonation step b2) is carried out after the first carbonation step b1).

[0026] In a preferred embodiment of the present invention, the carbonation reactant is a sugar cane juice and the carbonation product is a thin juice.

[0027] In a preferred embodiment of the present invention, the carbonation reactant is a raw sugar solution and the carbonation product is a purified raw sugar solution.

[0028] In a preferred embodiment of the present invention, the carbonation reactant is a raw sugar juice and the carbonation product is a thin juice, or the carbonation reactant is a raw sugar solution and the carbonation product is a purified raw sugar solution.

[0029] In a preferred embodiment of the present invention, in process step b) a precipitated solid, in particular comprising calcium carbonate, is obtained after each carbonation step.

[0030] In a preferred embodiment of the present invention, the precipitated solid obtained after each carbonation step comprises calcium carbonate and organic components, in particular colloidal substances, especially pectin, proteins, cellulose and hemicellulose, and in particular consists of these.

[0031] In a preferred embodiment of the present invention, in process step b) the precipitated solid, in particular comprising calcium carbonate, is separated from the alkaline carbonation intermediate, in particular sugar cane juice, or from the carbonation product, in particular thin juice, after each carbonation step.

[0032] In a preferred embodiment of the present invention, in process step b) after the first carbonation step b1), the precipitated solid, in particular comprising calcium carbonate, is separated from the alkaline carbonation intermediate, in particular sugar cane juice, by filtration or decantation.

[0033] In a preferred embodiment of the present invention, the solid separated from the alkaline carbonation intermediate, in particular sugar cane juice, after the first carbonation step b1) comprises calcium carbonate, in particular 50 to 80 wt.%, in particular 55 to 75 wt.%, in particular 60 to 70 wt.%, calcium carbonate and organic components, in particular 20 to 50 wt.%, in particular 25 to 45 wt.%, in particular 30 to 40 wt.% (in each case based on the dry matter of the separated solid).

[0034] In a preferred embodiment of the present invention, the solid separated from the alkaline carbonation intermediate or the carbonation product after the second carbonation step b2) comprises calcium carbonate, in particular 90.0 to 99.9 wt.%, in particular 95.0 to 99.9 wt.%, in particular 98.0 to 99.9 wt.%, calcium carbonate and organic components, in particular 0.1 to 10.0 wt.%, in particular 0.1 to 5.0 wt.%, in particular 0.1 to 2 wt.% (in each case based on the dry matter of the separated solid), in particular consists of these.

[0035] In a preferred embodiment of the present invention, the solid separated from the alkaline carbonation intermediate, in particular sugar cane juice, after the pre-carbonation step b0) comprises calcium carbonate, in particular 50 to 80 wt.%, in particular 55 to 75 wt.%, in particular 60 to 70 wt.%, calcium carbonate and organic components, in particular 20 to 50 wt.%, in particular 25 to 45 wt.%, in particular 30 to 40 wt.% (in each case based on the dry matter of the separated solid).

[0036] In a preferred embodiment of the present invention, in process step b) after the second carbonation step b2), the precipitated solid, in particular comprising calcium carbonate, is separated from the alkaline carbonation intermediate or the carbonation product by filtration.

[0037] In a preferred embodiment of the present invention, in process step b) after the first carbonation step b1) the precipitated solid, in particular comprising calcium carbonate, is separated by filtration from the alkaline carbonation intermediate, in particular sugar cane juice, and after the second carbonation step b2) the precipitated solid, in particular comprising calcium carbonate, is separated by filtration from the alkaline carbonation intermediate, in particular sugar cane juice, or the carbonation product, in particular thin juice.

[0038] In a preferred embodiment of the present invention, in process step b) after the first carbonation step b1) the precipitated solid, in particular comprising calcium carbonate, is separated by decantation from the alkaline carbonation intermediate, in particular sugar cane juice, and after the second carbonation step b2) the precipitated solid, in particular comprising calcium carbonate, is separated by filtration from the alkaline carbonation intermediate, in particular sugar cane juice, or carbonation product, in particular thin juice.

[0039] In a preferred embodiment of the present invention, in process step b) after the first carbonation step b1), the precipitated solid, in particular comprising calcium carbonate, is not separated from the alkaline carbonation intermediate and at least one further carbonation step b2) is carried out, wherein the precipitated solid of all carbonation steps carried out is separated from the carbonation product, in particular from the purified raw sugar solution, after the last carbonation step, in particular by filtration.

[0040] In a preferred embodiment of the present invention, in process step b) after the first carbonation step b1), the precipitated solid, in particular comprising calcium carbonate, is not separated from the alkaline carbonation intermediate, in particular from the raw sugar solution, and a second carbonation step b2) is carried out, wherein the precipitated solid, in particular comprising calcium carbonate, of the first carbonation step b1) and the precipitated solid, in particular comprising calcium carbonate, of the second carbonation step b2) are separated from the carbonation product, in particular from the purified raw sugar solution, after the second carbonation step, in particular by filtration.

[0041] In a preferred embodiment of the present invention, at least one proportion of the exhaust gas from at least one further carbonation step from process step b) according to process step c) is introduced into the alkaline carbonation reactant of the first carbonation step or the pre-carbonation step.

[0042] In a preferred embodiment of the present invention, at least one proportion of the exhaust gas from the second carbonation step according to process step c) is introduced into the alkaline carbonation reactant of the first carbonation step.

[0043] In a particularly preferred embodiment of the present invention, at least one proportion of the exhaust gas from the second carbonation step according to process step c) is introduced into the alkaline carbonation reactant of the pre-carbonation step.

[0044] By introducing at least a portion of the exhaust gas from at least one further carbonation step, in particular the second carbonation step, into the alkaline carbonation reactant of the pre-carbonation step, the overall CO₂ gas utilization rate of the carbonation is advantageously increased. In particular, the overall CO₂ gas utilization rate of the carbonation of the process according to the invention is higher than the overall gas utilization rate of comparable processes. Preferably and advantageously, the overall CO₂ gas utilization rate of the carbonation of the preferred process according to the invention, in which the exhaust gas from the at least one further carbonation step, in particular the second carbonation step, is introduced into the alkaline carbonation reactant of a pre-carbonation step according to process step c) of the invention, is higher than in a carbonation process in which the exhaust gas from the at least one further carbonation step,in particular the second carbonation step, into the alkaline carbonation reactant of the first carbonation step, especially since the gas utilization rate of a first carbonation step is already at least 80%. This is because the calcium hydroxide contained in the alkaline carbonation reactant of the first carbonation step preferably reacts largely with the CO₂ of the CO₂ of the CO₂-enriched carbonation gas used for the first carbonation step, in particular fresh, i.e., freshly obtained, for example, from a lime kiln or present as boiler house gas, to form calcium carbonate. Therefore, by introducing, in particular in addition to the fresh CO₂-enriched carbonation gas, at least a portion of the exhaust gas of at least one further carbonation step, in particular the second carbonation step, into the alkaline carbonation reactant of the first carbonation step according to the invention,The overall CO₂ gas utilization rate of the carbonation according to process step b) of the present invention cannot be increased to the same extent as by introducing at least one portion of the exhaust gas from at least one further carbonation step, in particular a second carbonation step, into the alkaline carbonation reactant of the pre-carbonation step, as the sole, i.e., into which no fresh CO₂-enriched carbonation gas is introduced. The calcium hydroxide present in the alkaline carbonation reactant of the pre-carbonation step is characterized by the fact that it does not come into contact with CO₂ from a fresh CO₂-enriched carbonation gas, and in particular is not thereby converted to calcium carbonate. Preferably, the pre-carbonation step introduces at least one portion of a carbonation gas already used from the at least one further carbonation step b2), in particular a second carbonation step.The sole CO₂-enriched carbonation gas is introduced into a fresh alkaline carbonation reactant, i.e., an alkaline carbonation reactant into which no fresh CO₂-enriched carbonation gas has been introduced, and the calcium hydroxide present therein is converted to calcium carbonate. Preferably, in a first carbonation step, fresh CO₂-enriched carbonation gas, which is not CO₂-enriched carbonation gas previously obtained as CO₂-depleted exhaust gas from at least one further carbonation step according to process step b2), is introduced into the alkaline carbonation intermediate or alkaline carbonation reactant obtained from the pre-carbonation step. In particular, this advantageously increases the overall CO₂ gas utilization of the carbonation according to process step b) of the present invention, especially also in comparison to comparable processes.

[0045] In a preferred embodiment of the present invention, an alkaline carbonation intermediate is obtained after the pre-carbonation step b0) which has fewer substances to precipitate, in particular comprising calcium hydroxide, than the alkaline carbonation reactant before the pre-carbonation step.

[0046] In a preferred embodiment of the present invention, after the first carbonation step b1) an alkaline carbonation intermediate is obtained which has fewer substances to precipitate, in particular comprising calcium hydroxide, than the alkaline carbonation reactant before the first carbonation step.

[0047] In a preferred embodiment of the present invention, a carbonation product is obtained after the last carbonation step.

[0048] In a preferred embodiment of the present invention, a carbonation product is obtained after the second carbonation step b2).

[0049] In a preferred embodiment of the present invention, the invention relates to a method for producing a carbonation product from a carbonation reactant, comprising the process steps: a) Alkalization of a carbonation reactant to obtain an alkaline carbonation reactant and b) carbonation of the alkaline carbonation reactant comprising, in particular, a first and a second carbonation step b1) and b2) to obtain a carbonation product, in each of which a CO2-enriched carbonation gas is introduced into the alkaline carbonation reactant and a CO2-depleted exhaust gas is discharged, characterized by c) introducing at least a proportion of the exhaust gas of the second carbonation step into the alkaline carbonation reactant during the first carbonation step.

[0050] In this embodiment, two different carbonation gases are introduced into the first carbonation step, namely a CO2-enriched carbonation gas and a CO2-depleted carbonation gas, in particular exhaust gas, from the second or further carbonation step.

[0051] In a preferred embodiment of the present invention, the invention relates to a method for producing a carbonation product from a carbonation reactant, comprising the process steps: a) Alkalization of a carbonation reactant to obtain an alkaline carbonation reactant and b) carbonation of the alkaline carbonation reactant comprising, in particular, a pre-carbonation step b0), a first carbonation step b1) and a second carbonation step b2) to obtain a carbonation product, in each of which a CO2-enriched carbonation gas is introduced into the alkaline carbonation reactant and a CO2-depleted exhaust gas is discharged, characterized by c) introducing at least a proportion of the exhaust gas of the second carbonation step into the alkaline carbonation reactant before the first carbonation step, in particular into the alkaline carbonation reactant during the pre-carbonation step, in particular as the sole CO2-enriched carbonation gas.

[0052] In a preferred embodiment of the present invention, the method is carried out in a device for producing a carbonation product from a carbonation reactant comprising at least one first carbonation vessel and at least one further carbonation vessel.

[0053] In a preferred embodiment of the present invention, the process is carried out in a beet sugar or cane sugar processing apparatus for the production of thin juice from raw sugar juice comprising at least one first carbonation vessel and at least one further carbonation vessel.

[0054] In a preferred embodiment of the present invention, the process is carried out in a sugar refining apparatus for the production of a purified raw sugar solution from a raw sugar solution comprising at least one first carbonation vessel and at least one further carbonation vessel.

[0055] In a preferred embodiment of the method of the present invention, the device has at least one pre-carbonation vessel upstream of the first carbonation vessel.

[0056] In a preferred embodiment of the method of the present invention, the device has a second carbonation container downstream of the first carbonation container.

[0057] In a preferred embodiment of the method of the present invention, the device has a pre-carbonation vessel upstream of the first carbonation vessel and a second carbonation vessel downstream of the first carbonation vessel.

[0058] In a preferred embodiment of the method of the present invention, each carbonation step is carried out in a separate carbonation vessel.

[0059] In a preferred embodiment of the method of the present invention, all carbonation steps are carried out in a carbonation vessel.

[0060] In a preferred embodiment of the method of the present invention, the first carbonation step is carried out in a first carbonation vessel and the second carbonation step is carried out in a second carbonation vessel.

[0061] In a preferred embodiment of the method of the present invention, the first carbonation step is carried out in a first carbonation vessel, the second carbonation step in a second carbonation vessel, and the pre-carbonation step in a pre-carbonation vessel.

[0062] In a preferred embodiment of the method of the present invention, the first carbonation step, the second carbonation step and the pre-carbonation step are each carried out in a carbonation vessel.

[0063] In a preferred embodiment of the method of the present invention, the device has at least one line from the at least one further carbonation vessel, in particular a second carbonation vessel, to an upstream carbonation vessel, in particular a first carbonation vessel or pre-carbonation vessel, in order to introduce at least a part of the exhaust gas of the at least one further carbonation step, in particular a second carbonation step, into the alkaline carbonation reactant before or during the first carbonation step.

[0064] In a preferred embodiment of the method of the present invention, the device has at least one line from the second carbonation vessel to the first carbonation vessel in order to introduce at least a part of the exhaust gas of the second carbonation step into the alkaline carbonation reactant during the first carbonation step, in particular in addition to carbonation gas enriched by CO2 obtained in a lime kiln or present at least partially in a boiler house gas.

[0065] In a preferred embodiment of the method of the present invention, the device has at least one line from the second carbonation vessel to the at least one pre-carbonation vessel in order to introduce at least a part of the exhaust gas of the second carbonation step into the alkaline carbonation reactant before the first carbonation step, in particular the pre-carbonation step, in particular as the sole CO2-enriched carbonation gas.

[0066] In a preferred embodiment of the present invention, the exhaust gas of the first carbonation step has a CO2 content of 1 to 10 vol.%, in particular 1 to 8 vol.%, in particular 2 to 6 vol.%, in particular 3 to 4 vol.%, (based on the total volume of exhaust gas of the first carbonation step).

[0067] In a preferred embodiment of the present invention, the exhaust gas of the at least one further carbonation step, in particular the second carbonation step, has a CO2 content of 1 to 40 vol.%, in particular 5 to 35 vol.%, in particular 10 to 30 vol.%, in particular 15 to 27 vol.%, in particular 26.3 vol.%, in particular 21.4 vol.%, in particular 17.9 vol.%, in particular 15.7 vol.% (based on the total volume of exhaust gas of at least one further carbonation step).

[0068] In a preferred embodiment of the present invention, the exhaust gas of the pre-carbonation step has a CO2 content of 1 to 10 vol.%, in particular 2 to 8 vol.%, in particular 3 to 6 vol.%, (based on the total volume of exhaust gas of the pre-carbonation step).

[0069] In a preferred embodiment of the present invention, the exhaust gas of the at least one further carbonation step, in particular the second carbonation step, is mixed with a CO2-enriched carbonation gas after process step b) and before process step c).

[0070] In a preferred embodiment of the present invention, the CO2-enriched carbonation gas of a beet sugar or cane sugar processing apparatus is obtained by a lime kiln powered by coke or gas.

[0071] In a preferred embodiment of the present invention, the CO2-enriched carbonation gas of a sugar refining device is at least a proportion of a boiler house gas.

[0072] In a preferred embodiment of the present invention, the CO2-enriched carbonation gas is obtained by a lime kiln powered by coke or gas or is at least a proportion of a boiler house gas.

[0073] In a preferred embodiment of the present invention, the CO2-enriched carbonation gas obtained by a coke- or gas-operated lime kiln has a CO2 content of 1 to 99 vol.%, in particular 10 to 70 vol.%, in particular 20 to 50 vol.%, in particular 25 to 45 vol.%, in particular 26 to 42 vol.%, in particular 41.5 vol.%, in particular 35.0 vol.%, in particular 30.1 vol.%, in particular 26.0 vol.% (based on the total volume of CO2-enriched gas).

[0074] In a preferred embodiment of the present invention, the CO2-enriched carbonation gas of at least one portion of the boiler house gas has a CO2 content of 1 to 99 vol.%, in particular 10 to 70 vol.%, in particular 20 to 50 vol.%, in particular 25 to 45 vol.%, in particular 26 to 42 vol.%, in particular 41.5 vol.%, in particular 35.0 vol.%, in particular 30.1 vol.%, in particular 26.0 vol.%, in particular 20.0 vol.%, in particular 15.0 vol.%, in particular 10.0 vol.% (based on the total volume of CO2-enriched gas).

[0075] In a preferred embodiment of the present invention, the CO2-enriched carbonation gas obtained by a coke- or gas-operated lime kiln or the CO2-enriched carbonation gas of at least a portion of the boiler house gas is mixed with air, in particular ambient air, in particular to adjust the CO2 content of the CO2-enriched carbonation gas.

[0076] In a preferred embodiment of the present invention, the retention time of the CO2-enriched carbonation gas in the respective carbonation container, in particular pre-carbonation container, first carbonation container and / or at least one further carbonation container, in particular second carbonation container, is 1.0 to 15.0 minutes, in particular 2.0 to 12.0 minutes, in particular 2.5 to 10.0 minutes, in particular 2.5 minutes, in particular 4 minutes, in particular 6 minutes, in particular 8 minutes, in particular 10 minutes.

[0077] In a preferred embodiment of the present invention, the sugar cane juice is obtained from sugar beets or sugar cane.

[0078] In a preferred embodiment of the present invention, a raw sugar solution is obtained by dissolving raw sugar in water.

[0079] In a preferred embodiment of the present invention, a raw sugar solution comprises 10 to 95 wt.%, in particular 20 to 90 wt.%, in particular 30 to 85 wt.%, in particular 40 to 80 wt.%, in particular 50 to 70 wt.%, in particular 55 to 65 wt.%, in particular 60 wt.%, raw sugar and 5 to 90 wt.%, in particular 10 to 80 wt.%, in particular 15 to 70 wt.%, in particular 20 to 60 wt.%, in particular 30 to 50 wt.%, in particular 35 to 45 wt.%, in particular 40 wt.%, water (in each case based on the total weight of raw sugar solution).

[0080] In a preferred embodiment of the present invention, the CO2 gas utilization rate of the first carbonation step is at least 80%, in particular at least 85%, in particular at least 90%, in particular 90 to 95%, in particular 92%, in particular 95%.

[0081] In a preferred embodiment of the present invention, the retention time of the CO2-enriched carbonation gas in the first carbonation vessel is 1.0 to 15.0 minutes, in particular 2.0 to 12.0 minutes, in particular 2.5 to 10.0 minutes, in particular 2.5 minutes, in particular 4 minutes, in particular 6 minutes, in particular 8 minutes, in particular 10 minutes, and the gas utilization rate of the first carbonation step is at least 80%, in particular at least 85%, in particular at least 90%, in particular 90 to 95%, in particular 92%, in particular 95%.

[0082] In a preferred embodiment of the present invention, the CO2 gas utilization rate of the at least one further carbonation step, in particular the second carbonation step, is at least 20%, in particular at least 30%, in particular at least 40%, in particular at least 45%, in particular 47 to 60%, in particular 47%, in particular 49%, in particular 50%.

[0083] In a preferred embodiment of the present invention, the retention time of the CO2-enriched carbonation gas in the at least one further carbonation vessel, in particular a second carbonation vessel, is 1.0 to 15.0 minutes, in particular 2.0 to 12.0 minutes, in particular 2.5 to 10.0 minutes, in particular 2.5 minutes, in particular 4 minutes, in particular 6 minutes, in particular 8 minutes, in particular 10 minutes, and the gas utilization rate of the at least one further carbonation step, in particular a second carbonation step, is at least 20%, in particular at least 30%, in particular at least 40%, in particular at least 45%, in particular 47 to 60%, in particular 47%, in particular 49%, in particular 50%.

[0084] In a preferred embodiment of the present invention, the CO2 gas utilization rate of the pre-carbonation step is at least 70%, in particular at least 75%, in particular at least 80%, in particular more than 80%, in particular 80 to 88%, in particular 80%, in particular 81%, in particular 82%, in particular 83%, in particular 84%, in particular 85%, in particular 86%, in particular 87%, in particular 88%.

[0085] In a preferred embodiment of the present invention, the retention time of the CO2-enriched carbonation gas in the pre-carbonation vessel is 1.0 to 15.0 minutes, in particular 2.0 to 12.0 minutes, in particular 2.5 to 10.0 minutes, in particular 2.5 minutes, in particular 4 minutes, in particular 6 minutes, in particular 8 minutes, in particular 10 minutes, and the gas utilization rate of the pre-carbonation step is at least 70%, in particular at least 75%, in particular at least 80%, in particular more than 80%, in particular 80 to 88%, in particular 80%, in particular 81%, in particular 82%, in particular 83%, in particular 84%, in particular 85%, in particular 86%, in particular 87%, in particular 88%.

[0086] In a preferred embodiment of the present invention, the total CO2 gas utilization rate of the carbonation according to process step b) is at least 50%, in particular at least 55%, in particular at least 60%, in particular at least 70%, in particular at least 80%, in particular at least 90%, in particular 50 to 99%, in particular 60 to 98%, in particular 70 to 97%, in particular 80 to 96%, in particular 90 to 95%, in particular 92%, in particular 95%.

[0087] In a preferred embodiment of the present invention, the total CO2 gas utilization rate of the carbonation according to process step b) is improved by at least 3%, in particular at least 5%, in particular at least 7%, in particular 7%, in particular 8%, in particular 9%, compared to a comparable process without carrying out process step c) according to the invention.

[0088] In a preferred embodiment of the present invention, the CO2 emission of the carbonation according to process step b) is reduced by at least 20%, in particular at least 30%, in particular at least 40%, in particular 43%, in particular 44%, in particular 46%, in particular 54%, in particular 56%, in particular 57%, compared to a comparable process without carrying out process step c) according to the invention.

[0089] The present invention also relates to a device for producing a carbonation product from a carbonation reactant, in particular suitable and designed for carrying out a process according to the invention, comprising at least one first carbonation vessel, at least one further carbonation vessel and at least one line from the at least one further carbonation vessel into an upstream carbonation vessel, in particular a pre-carbonation vessel, which is suitable for introducing at least a part of an exhaust gas from the at least one further carbonation vessel into an alkaline carbonation reactant, presently in an upstream carbonation vessel, wherein a pre-carbonation vessel is upstream of the first carbonation vessel and wherein the upstream carbonation vessel is the pre-carbonation vessel.

[0090] In a preferred embodiment of the present invention, the device according to the invention comprises at least one alkalization container, in particular at least one liming container, in particular a pre-liming container and a main liming container.

[0091] In a preferred embodiment of the device according to the invention, a second carbonation container is connected downstream of the first carbonation container.

[0092] In a preferred embodiment of the device according to the invention, a pre-carbonation vessel is connected upstream of the first carbonation vessel and a second carbonation vessel is connected downstream.

[0093] In a preferred embodiment of the present invention, the device according to the invention comprises a total of at least 2, in particular 2, in particular at least 3, in particular 3, in particular 4, in particular 5, in particular 6, carbonation vessels.

[0094] In a preferred embodiment of the present invention, the device according to the invention has at least one line from the second carbonation vessel to the first carbonation vessel, which is suitable for introducing at least a part of an exhaust gas from the second carbonation vessel into an alkaline carbonation reactant present in the first carbonation vessel.

[0095] In a preferred embodiment of the present invention, the device according to the invention has at least one line from the second carbonation vessel to the at least one pre-carbonation vessel, which is suitable for introducing at least a part of an exhaust gas from the second carbonation vessel into an alkaline carbonation reactant present in the pre-carbonation vessel, in particular as a single, sole CO2-enriched carbonation gas.

[0096] In a preferred embodiment of the present invention, the device for producing a carbonation product from a carbonation reactant, in particular suitable and designed for carrying out a process according to the invention, comprises a first carbonation vessel, a second carbonation vessel downstream of the first carbonation vessel, and a line from the second carbonation vessel to the first carbonation vessel upstream of the second carbonation vessel, which is suitable for introducing at least a part of an exhaust gas from the second carbonation vessel into an alkaline carbonation reactant, in particular in addition to carbonation gas enriched by CO2 obtained in a lime kiln or present as CO2 in a boiler house gas.

[0097] In a preferred embodiment of the present invention, the apparatus for producing a carbonation product from a carbonation reactant, in particular suitable and designed for carrying out a process according to the invention, comprises a first carbonation vessel, a second carbonation vessel downstream of the first carbonation vessel, a pre-carbonation vessel upstream of the first carbonation vessel, and a line from the second carbonation vessel to the pre-carbonation vessel upstream of the first carbonation vessel, which is suitable for introducing at least a part of an exhaust gas from the second carbonation vessel into an alkaline carbonation reactant, in particular into the pre-carbonation vessel upstream of the first carbonation vessel, in particular as a single, sole CO2-enriched carbonation gas.

[0098] In a preferred embodiment of the present invention, the device according to the invention is a beet sugar or cane sugar processing device for producing thin juice from raw sugar juice.

[0099] In a preferred embodiment of the present invention, the device according to the invention is a sugar refining device for producing a purified raw sugar solution from a raw sugar solution.

[0100] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a separation device, in particular a filtration device, is connected downstream of each carbonation container.

[0101] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a feed container is connected downstream of each separation device, in particular a filtration device.

[0102] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a feed container is placed upstream of each carbonation container.

[0103] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a feed container is placed upstream of the second carbonation container.

[0104] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a first separation device, in particular a filtration device, is connected downstream of the first carbonation container.

[0105] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a first separation device, in particular a filter device, is connected downstream of the first carbonation container and a feed container is connected downstream of the first separation device.

[0106] In a preferred embodiment of the device according to the invention, a second separation device, in particular a filtration device, is connected downstream of the second carbonation vessel.

[0107] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a separation device, in particular a filtering device, is connected downstream of the pre-carbonation container.

[0108] In a preferred embodiment of the device according to the invention, in particular a sugar refining device, no separation device, in particular a filtering device, is connected downstream of the pre-carbonation vessel.

[0109] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, at least one pre-carbonation container is connected upstream of the first carbonation container and a separation device, in particular a filter device, is connected between the first carbonation container and the pre-carbonation container.

[0110] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a pre-carbonation container is connected upstream of the first carbonation container, a separation device, in particular a filter device, is connected between the first carbonation container and the pre-carbonation container, a second carbonation container is connected downstream of the first carbonation container, and a first separation device is connected between the first carbonation container and the second carbonation container, in particular a feed container is connected between the first separation device and the second carbonation container.

[0111] In a preferred embodiment of the device according to the invention, a pre-carbonation vessel is connected upstream of the first carbonation vessel, no separating device is connected between the first carbonation vessel and the pre-carbonation vessel, a second carbonation vessel is connected downstream of the first carbonation vessel, and a first separating device is connected between the first carbonation vessel and the second carbonation vessel; in particular, a feed vessel is connected between the first separating device and the second carbonation vessel.

[0112] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a pre-carbonation container is connected upstream of the first carbonation container, a separation device, in particular a filter device, is connected between the first carbonation container and the pre-carbonation container, a second carbonation container is connected downstream of the first carbonation container, a first separation device, in particular a filter device, is connected between the first carbonation container and the second carbonation container, and a second separation device, in particular a filter device, is connected downstream of the second carbonation container.

[0113] In a preferred embodiment of the device according to the invention, a pre-carbonation vessel is connected upstream of the first carbonation vessel, no separation device is connected between the first carbonation vessel and the pre-carbonation vessel, a second carbonation vessel is connected downstream of the first carbonation vessel, a first separation device, in particular a filtering device, is connected between the first carbonation vessel and the second carbonation vessel, and a second separation device, in particular a filtering device, is connected downstream of the second carbonation vessel.

[0114] In a preferred embodiment of the device according to the invention, in particular a sugar refining device, a pre-carbonation container is connected upstream of the first carbonation container, no separation device is connected between the first carbonation container and the pre-carbonation container, a second carbonation container is connected downstream of the first carbonation container, no first separation device is connected between the first carbonation container and the second carbonation container, and a second separation device, in particular a filter device, is connected downstream of the second carbonation container.

[0115] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a second carbonation container is connected downstream of the first carbonation container and a first separation device, in particular a filter device, is connected between the first carbonation container and the second carbonation container.

[0116] In a preferred embodiment of the device according to the invention, in particular a sugar refining device, a second carbonation container is connected downstream of the first carbonation container, no first separation device is connected between the first carbonation container and the second carbonation container, and a second separation device, in particular a filtration device, is connected downstream of the second carbonation container.

[0117] In a preferred embodiment of the device according to the invention, in particular a beet sugar or cane sugar processing device, a second carbonation container is connected downstream of the first carbonation container, a first separation device, in particular a filtering device, is connected between the first carbonation container and the second carbonation container, and a second separation device, in particular a filtering device, is connected downstream of the second carbonation container.

[0118] In a preferred embodiment, the device according to the invention, in particular a beet sugar or cane sugar processing device, comprises a lime kiln powered by coke or gas.

[0119] In a preferred embodiment, the device according to the invention, in particular a sugar refining device, comprises a boiler house, in particular a gas-powered boiler house.

[0120] The technical problem is also solved by, in particular, a process for producing a carbonation product from a carbonation reactant, comprising the process steps: a) Alkalization of a carbonation reactant to obtain an alkaline carbonation reactant and b) carbonation of the alkaline carbonation reactant comprising a first and at least one further carbonation step b1) and b2) to obtain the carbonation product, in each of which a CO2-enriched carbonation gas is introduced into the alkaline carbonation reactant and a CO2-depleted exhaust gas is discharged, characterized by c) introducing at least a proportion of the CO2-depleted exhaust gas of the at least one further carbonation step into the alkaline carbonation reactant before or during the first carbonation step, preferably before the first carbonation step.

[0121] In the context of the present invention, "carbonation reactant" means the reactant used for carrying out a carbonation reaction. Preferably, the carbonation reactant is raw sugar juice. More preferably, the carbonation reactant is a raw sugar solution. Preferably, a carbonation reactant contains a larger quantity of substances to be precipitated and / or suspended solids than the carbonation product obtained from the carbonation reactant by carrying out a carbonation reaction.

[0122] In the context of the present invention, the term "carbonation product" is understood to mean the product obtained by carrying out a carbonation reaction. Preferably, the carbonation product is a thin juice. More preferably, the carbonation product is a purified raw sugar solution. Preferably, a carbonation product resulting from a carbonation reaction contains a smaller amount of substances to be precipitated, in particular comprising calcium hydroxide, and / or suspended solids than the carbonation reactant. More preferably, the carbonation product resulting from a carbonation reaction contains no substances to be precipitated, in particular no calcium hydroxide, and / or suspended solids. Preferably, the carbonation product is obtained after the last carbonation step, in particular the second carbonation step.Preferably, after the last carbonation step, the carbonation product contains solid material, in particular calcium carbonate, that was not separated by the last carbonation step.

[0123] In the context of the present invention, "raw sugar solution" is understood to mean raw sugar dissolved in water. Preferably, a raw sugar solution contains a larger quantity of substances to be precipitated and / or suspended solids than the purified raw sugar solution obtained from the raw sugar solution by carrying out carbonation.

[0124] In the context of the present invention, "raw sugar" is understood to mean unrefined sugar. Preferably, the raw sugar is processed into refined sugar in a sugar refining process. Preferably, raw sugar has a brownish color.

[0125] In the context of the present invention, "refined sugar" is understood to mean sugar obtained from raw sugar by refining. Refined sugar preferably has a white color.

[0126] In the context of the present invention, "purified raw sugar solution" is understood to mean the raw sugar solution obtained from a raw sugar solution after carbonation. Preferably, a purified raw sugar solution resulting from carbonation has a lower quantity of substances to be precipitated, in particular comprising calcium hydroxide, and / or suspended solids than the raw sugar solution used in the carbonation, in particular alkaline raw sugar solution. Preferably, the purified raw sugar solution resulting from carbonation has no substances to be precipitated, in particular no calcium hydroxide, and / or suspended solids. Preferably, the purified raw sugar solution is obtained after the last carbonation step.Preferably, after the last carbonation step, the purified raw sugar solution contains solid material, particularly calcium carbonate, that was not separated by the last carbonation step.

[0127] In the context of the present invention, "sugar raw juice" is understood to mean the juice obtained after extraction from a solid sugar source, in particular sugar beets, especially sugar beet pulp, or sugar cane. Preferably, the sugar raw juice from sugar beets, especially sugar beet pulp, or sugar cane is extracted with hot water, in particular water heated to 70 °C, in an extraction tower. Preferably, the sugar raw juice is cloudy. Preferably, after extraction, up to 99 wt.% of the sugar from the sugar beet or sugar cane (based on the total weight of sugar in the sugar beet or sugar cane) is present in the sugar raw juice. Preferably, the sugar raw juice comprises, in addition to sugar, other substances, in particular suspended solids and non-precipitable non-sugar substances.

[0128] In connection with the present invention, "suspended particles" are understood to mean solid substances, in particular mineral or organic solids, which do not dissolve in an surrounding medium, in particular water, and are kept suspended due to their small size and low weight.

[0129] In connection with the present invention, "non-precipitable non-sugar substances" means non-sugar substances, i.e. substances that are not sugars, which cannot be precipitated by the liming carried out in sugar production or sugar refining, in particular pre-liming and main liming.

[0130] In the context of the present invention, "liming" is understood to mean a process step prior to carbonation. Preferably, liming comprises a pre-liming and / or a main liming; in particular, it consists of both. Preferably, in a liming step, a carbonation reactant is alkalized to an alkaline carbonation reactant. Preferably, "liming" is also understood to mean alkalization.

[0131] In the context of the present invention, "preliming" is understood to be a process step in sugar production, in particular juice purification, or sugar refining, in which the pH value of a carbonation reactant, in particular raw sugar juice or raw sugar solution, is increased to pH 10.6 to 11.6 by the use of milk of lime. Preferably, preliming precipitates colloids and insoluble salts from the carbonation reactant.

[0132] In connection with the present invention, "main liming" refers to a process step in sugar production, particularly juice purification or sugar refining, in which the pH value of a carbonation cation obtained from a preliminary liming step is further increased to pH 12 to 12.6 by the use of lime milk, thereby obtaining an alkaline carbonation cation. Preferably, the main liming step cleaves the invertase and acid amides present in the carbonation cation.

[0133] In the context of the present invention, "lime milk" is understood to mean a calcium hydroxide dispersion in water. Lime milk is preferably used in the pre-liming and main liming stages of sugar production or sugar refining. Lime milk is preferably used for the precipitation of non-sugar substances and suspended solids. Preferably, the non-sugar substances and suspended solids are adsorbed by the solid calcium hydroxide present in the lime milk.

[0134] In the context of the present invention, "thin juice" also refers to sugar thin juice. In the context of the present invention, "thin juice" is an intermediate product in sugar production, particularly obtained from sugar beets or sugar cane. Preferably, thin juice is obtained from raw sugar juice by the process according to the invention. Preferably, the thin juice contains 10 to 20% raw sugar (based on the total composition of the thin juice). Preferably, the thin juice is clear and light yellow in color.

[0135] In connection with the present invention, "sugar" is understood to mean a mono- or disaccharide, in particular glucose and sucrose, especially sucrose.

[0136] In the context of the present invention, "alkalization" is understood to mean an increase in the pH value of a carbonation reactant. Preferably, the pH value of the carbonation reactant is increased to pH 11 to 12 by alkalizing it. Preferably, the alkalization comprises pre-liming and / or main liming, and in particular consists of both. Preferably, the pH value of the carbonation reactant is increased in the alkalization process by the use of lime milk. Preferably, an alkaline carbonation reactant is obtained by alkalizing a carbonation reactant. Preferably, alkaline sugar cane juice is obtained by alkalizing a raw sugar solution. Preferably, an alkaline raw sugar solution is obtained by alkalizing a raw sugar solution.

[0137] In the context of the present invention, "adsorption" is understood to mean the accumulation, in particular the adhesion, of a substance, especially a non-sugar substance and / or suspended solid, to the surface of a solid, especially calcium hydroxide and / or calcium carbonate. Preferably, the substances interact with the surface of the solid through non-covalent interactions. According to the invention, adsorption is thus also understood to mean physisorption.

[0138] In the context of the present invention, "primary liming alkalinity" refers to the alkalinity of the alkaline carbonation reactant obtained by primary liming. Preferably, primary liming alkalinity is understood to be an alkalinity of 0.6 to 1.2 g CaO / 100 mL.

[0139] In the context of the present invention, "alkaline carbonation reactant" means a carbonation reactant obtained after alkalization according to process step a) of the process according to the invention. Preferably, a pre-liming and / or a main liming is carried out to obtain an alkaline carbonation reactant. Preferably, an alkaline carbonation reactant contains calcium hydroxide. Preferably, an alkaline carbonation reactant is an alkaline raw sugar juice. Preferably, an alkaline carbonation reactant is an alkaline raw sugar solution.

[0140] In the context of the present invention, "alkaline carbonation intermediate" means an alkaline intermediate obtained after carrying out a pre-carbonation step, a first carbonation step, or at least one further carbonation step that is not the last carbonation step. In the context of the present invention, the alkaline carbonation intermediate obtained after each carbonation step, in particular a pre-carbonation step, a first carbonation step, or at least one further carbonation step that is not the last carbonation step, is simultaneously the alkaline carbonation reactant used in the subsequent carbonation step.

[0141] In the context of the present invention, "carbonation" is understood to mean the purification of an alkaline carbonation reactant to obtain a carbonation product, in particular by introducing CO₂ and separating it from a precipitated solid. Preferably, the carbonation of the present invention comprises at least two carbonation steps. More preferably, the carbonation of the present invention comprises a first carbonation step, a second carbonation step, and optionally a pre-carbonation step. More preferably, the carbonation of the present invention comprises at least one separation step of a solid precipitated by a carbonation step from an alkaline carbonation intermediate to obtain an alkaline carbonation reactant, in particular one containing fewer substances to be precipitated than the alkaline carbonation reactant before the carbonation step.Preferably, the carbonation process of the present invention comprises a separation step of a solid precipitated by a carbonation step from a carbonation product, yielding the carbonation product separated from the solid formed by the carbonation step. Preferably, "carbonation" process step b) of the present invention comprises at least two introductions of a CO₂-enriched carbonation gas into an alkaline carbonation reactant, at least two discharges of a CO₂-depleted exhaust gas, separation of a solid from a carbonation product, yielding the carbonation product, and optionally, separation of a solid from an alkaline carbonation intermediate.

[0142] In the context of the present invention, the term "carbonation step" refers to the introduction of a CO₂-enriched carbonation gas into an alkaline carbonation reactant and the discharge of a CO₂-depleted exhaust gas from the alkaline carbonation intermediate or carbonation product formed by the carbonation step. Preferably, a carbonation step is carried out in a carbonation vessel. Preferably, in a carbonation step, a solid is precipitated from the alkaline carbonation reactant by introducing a CO₂-enriched carbonation gas into the alkaline carbonation reactant. Preferably, the solid precipitated from the alkaline carbonation reactant comprises calcium carbonate and optionally non-precipitable non-sugar substances and / or suspended solids.Preferably, in a carbonation step, the CO₂ of the introduced CO₂-enriched carbonation gas reacts with the calcium hydroxide contained in the alkaline carbonation reactant to form calcium carbonate, thereby yielding a CO₂-depleted exhaust gas and an alkaline carbonation intermediate containing a lower amount of precipitates than before the carbonation step, or a carbonation product. Preferably, the CO₂-depleted exhaust gas obtained in the carbonation step is discharged from the carbonation vessel.

[0143] In connection with the present invention, "CO₂-enriched carbonation gas" is understood to mean a gas containing CO₂ produced for carbonation. Preferably, the CO₂-enriched carbonation gas is produced by a lime kiln powered by coke or gas. Preferably, the CO₂-enriched carbonation gas is at least a portion of a boiler house gas. Preferably, the CO₂-enriched carbonation gas can be at least a portion of the exhaust gas discharged from at least one further carbonation step, in particular a second carbonation step, and is introduced into the alkaline carbonation reactant before or during the first carbonation step according to process step c) of the invention.This CO₂-depleted exhaust gas, or carbonation gas, can therefore be understood as CO₂-enriched carbonation gas, since the CO₂ content in the carbonation gas decreases during the execution of the first carbonation step or a carbonation step prior to the first carbonation step, in particular a pre-carbonation step. Preferably, the CO₂ content of the CO₂-enriched carbonation gas can be adjusted by adding air. Preferably, the CO₂-enriched carbonation gas has a CO₂ content of at least 40.0 vol%, in particular 41.5 vol%, (based on the total volume of carbonation gas) without the addition of air. Preferably, the CO₂-enriched carbonation gas is introduced into an alkaline carbonation reactant present in a carbonation vessel during a carbonation step.Preferably, the CO₂ of the CO₂-enriched carbonation gas reacts with the calcium hydroxide present in the alkaline carbonation reactant to form calcium carbonate, resulting in a CO₂-depleted exhaust gas. Preferably, the CO₂-enriched carbonation gas has a higher CO₂ content than the CO₂-depleted exhaust gas (in each case based on the total volume of carbonation gas or exhaust gas).

[0144] In connection with the present invention, "CO₂-depleted exhaust gas" is also understood to mean carbonation vapors. Preferably, "CO₂-depleted exhaust gas" is understood to mean exhaust gas obtained in a carbonation step. More preferably, "CO₂-depleted exhaust gas" is understood to mean CO₂-depleted exhaust gas obtained after a reaction of CO₂ present in a CO₂-enriched carbonation gas with calcium hydroxide present in an alkaline carbonation reactant to form calcium carbonate. Preferably, the CO₂-depleted exhaust gas is discharged from an alkaline carbonation intermediate or carbonation product present in a carbonation vessel in a carbonation step according to process step b) of the invention.Preferably, according to the invention, the CO₂-depleted exhaust gas discharged from an alkaline carbonation intermediate or carbonation product present in a carbonation vessel according to process step b) is introduced into an alkaline carbonation reactant present in a carbonation vessel upstream of the carbonation vessel as CO₂-enriched carbonation gas according to process step c) of the invention. Preferably, the CO₂-depleted exhaust gas discharged from a second carbonation vessel according to process step c) of the invention is introduced into an alkaline carbonation reactant present in a first carbonation vessel as CO₂-enriched carbonation gas, in particular in addition to CO₂-enriched carbonation gas obtained in a lime kiln or present at least partially in a boiler house gas.Preferably, the CO2-depleted exhaust gas discharged from a second carbonation vessel is introduced into an alkaline carbonation reactant present in a pre-carbonation vessel as CO2-enriched carbonation gas, in particular as the sole CO2-enriched carbonation gas, according to process step c) of the invention.

[0145] In connection with the present invention, "fresh CO₂-enriched carbonation gas" is understood to mean CO₂-enriched carbonation gas obtained from a lime kiln, in particular one powered by coke or gas, or present at least partially in a boiler house gas, and which has not already been used in a carbonation step. Preferably, "fresh CO₂-enriched carbonation gas" is understood to mean CO₂-enriched carbonation gas that cannot also be understood as CO₂-depleted exhaust gas, in particular gas obtained from a carbonation step.

[0146] In the context of the present invention, "CO₂ content" is also understood to mean CO₂ concentration. Preferably, "CO₂ content" is understood to mean the CO₂ volume fraction of a gas relative to the total volume of the gas.

[0147] In connection with the present invention, "pre-carbonation step" is understood to mean a carbonation step which is carried out before the first carbonation step and in which a CO2-depleted exhaust gas of a further, in particular second, carbonation step is introduced as the sole CO2-enriched carbonation gas into an alkaline carbonation reactant.

[0148] In the context of the present invention, "at least one further carbonation step" means at least one further carbonation step that is or are carried out after the first carbonation step. Preferably, the at least one further carbonation step is a second carbonation step, and no further carbonation step is carried out after the second carbonation step.

[0149] In connection with the present invention, "beet sugar or cane sugar processing device" is understood to mean a device that processes beet sugar and / or cane sugar into raw sugar. Preferably, the process according to the invention is carried out in the beet sugar or cane sugar processing device according to the invention. Preferably, thin juice is produced from raw sugar juice in the beet sugar or cane sugar processing device.Preferably, the beet sugar or cane sugar processing device according to the invention comprises a first carbonation vessel, at least one further carbonation vessel, and at least one line from the at least one further carbonation vessel to an upstream carbonation vessel, wherein the at least one line is suitable for introducing at least a portion of an exhaust gas from the at least one further carbonation vessel into an alkaline raw juice, presently in an upstream carbonation vessel. Preferably, the beet sugar or cane sugar processing device according to the invention includes an alkalization vessel.

[0150] In the context of the present invention, "sugar refining apparatus" is understood to mean an apparatus that refines raw sugar into refined sugar. Preferably, the inventive method is carried out in the sugar refining apparatus according to the invention. Preferably, a purified raw sugar solution is produced from a raw sugar solution in the sugar refining apparatus according to the invention. Preferably, the sugar refining apparatus according to the invention comprises a first carbonation vessel, at least one further carbonation vessel, and at least one line from the at least one further carbonation vessel to an upstream carbonation vessel, wherein the at least one line is suitable for introducing at least a portion of an exhaust gas from the at least one further carbonation vessel into an alkaline raw sugar solution, as is the case here in an upstream carbonation vessel.Preferably, the sugar refining apparatus according to the invention has an alkalization vessel.

[0151] In the context of the present invention, a "carbonation vessel" is understood to be a vessel in which a carbonation step is carried out. Preferably, a "carbonation vessel" is also understood to mean a carbonation reactor. Preferably, a carbonation vessel contains an alkaline carbonation reactant, an alkaline carbonation intermediate, or a carbonation product. Preferably, a separation device is connected downstream of a carbonation vessel. Preferably, a CO₂-enriched carbonation gas is fed into a carbonation vessel via one line, and a CO₂-depleted exhaust gas is discharged via another line.

[0152] In the context of the present invention, a "pre-carbonation vessel" is understood to be a vessel in which a pre-carbonation step is carried out, in particular into which a CO₂-depleted exhaust gas from a further, in particular a second, carbonation step or further, in particular a second, carbonation vessel is introduced as the sole carbonation gas into an alkaline carbonation reactant. A pre-carbonation vessel can also be a conduit or other vessel into which the CO₂-depleted exhaust gas from a further, in particular a second, carbonation step or further, in particular a second, carbonation vessel can be introduced as the sole carbonation gas into an alkaline carbonation reactant.The pre-carbonation vessel is located upstream of the first carbonation vessel and is designed so that a carbonation reactant can be directed from the pre-carbonation vessel into the first carbonation vessel.

[0153] In connection with the present invention, the "gas utilization rate" of a carbonation step is calculated using the following formula: 10000 * CO 2 − Gas − CO 2 − Abgas / CO 2 − Gas * 100 − CO 2 − Abgas , where the value of the CO2 gas corresponds to the CO2 content in the CO2-enriched carbonation gas (based on the total volume of CO2-enriched carbonation gas) and the value of the CO2 exhaust gas corresponds to the CO2 content in the CO2-depleted exhaust gas of the carbonation step (based on the total volume of CO2-depleted exhaust gas).

[0154] In connection with the present invention, "CO2 total gas utilization" means the total gas utilization of the carbonation process according to the invention and is calculated using the following formula:

[0155] Where quantitative information, in particular percentages, of components of a product or composition is given in connection with the present invention, these, unless explicitly stated otherwise or it is evident to a person skilled in the art, add up together with the other explicitly stated or evident further components of the composition or product to 100% of the composition and / or the product.

[0156] In the context of the present invention, the term "at least one" is understood to mean a quantity that expresses a number of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and so on. In a particularly preferred embodiment, the designation "at least one" can represent exactly the number 1. In a further preferred embodiment, the term "at least one" can also mean 2, 3, 4, 5, 6, or 7.

[0157] Insofar as the "presence", "contain", "exhibit" or "content" of a component is expressly mentioned or implied in connection with the present invention, this means that the respective component is present, in particular in a measurable quantity.

[0158] Insofar as the "presence", "containment" or "existence" of a component in an amount of 0 [unit], in particular mg / kg, µg / kg or wt.%, is expressly mentioned or implied in connection with the present invention, this means that the respective components are not present in a measurable amount, in particular are not present.

[0159] The number of decimal places given corresponds to the precision of the measurement method used.

[0160] If, in connection with the present invention, the first and second decimal places or the second decimal place are not specified for a number, they shall be set to zero.

[0161] In the context of the present invention, the term "and / or" means that all members of a group connected by the term "and / or" are disclosed both alternatively to one another and cumulatively to one another in any combination. For the expression "A, B and / or C", this means that the following disclosure content is to be understood: a) A or B or C, or b) (A and B), or c) (A and C), or d) (B and C), or e) (A and B and C).

[0162] In the context of the present invention, the terms "comprising" and "comprising" are understood to mean that, in addition to the elements explicitly covered by these terms, further, unmentioned elements may be present. In the context of the present invention, these terms are also understood to mean that only the explicitly mentioned elements are covered and no further elements are present. In this particular embodiment, the meaning of the terms "comprising" and "comprising" is synonymous with the term "consisting of." Furthermore, the terms "comprising" and "comprising" also encompass compositions that, in addition to the explicitly mentioned elements, contain further unmentioned elements that are, however, of a functionally and qualitatively subordinate nature. In this embodiment, the terms "comprising" and "comprising" are synonymous with the term "essentially consisting of."

[0163] Further advantageous embodiments result from the dependent claims.

[0164] The invention is described in more detail below, without limiting the general concept of the invention, by means of examples and accompanying drawings. Reference symbol list:

[0165] 100 Comparison device 200 Device according to the invention 101, 201 Alkalinization tank 202 Pre-carbonation tank 103, 203 First carbonation tank 104, 204 Second carbonation tank 110, 210 Filtration device 111, 211 Storage tank 120, 220 Supply line 130, 230 Line transporting fresh CO2-enriched carbonation gas 131, 231 Exhaust line 240 Line according to the invention 241 Exhaust line

[0166] The figures show: Figure 1 a schematic setup of a comparison device (100) in which no method according to the invention can be carried out, Figure 2a bar chart showing three CO2 gas utilization rates from three initial carbonation steps, in which three different CO2-enriched carbonation gases with 41.5 vol%, 30.1 vol% or 26.0 vol% (each based on total volume of carbonation gas) were used, Figure 3 a bar chart showing CO2 gas utilization rates of three second carbonation steps, in which three different CO2-enriched carbonation gases with 41.5 vol%, 30.1 vol% or 26.0 vol% (each based on total volume of carbonation gas) were used, Figure 4 a schematic structure of a device (200) according to the invention in which a method according to the invention can be carried out, and Figure 5A diagram showing CO2 gas utilization rates of four pre-carbonation steps at different retention times, 10, 8, 6, 4 and 2.5 minutes, of the CO2-enriched carbonation gas in the pre-carbonation vessel, using four different CO2 contents, 41.5 vol%, 35.0 vol%, 30.0 vol% and 26.0 vol% (each based on total volume of carbonation gas). Examples: Example 1: CO2 gas utilization rates of a first and a second carbonation step as a comparison example

[0167] In Figure 1A comparison device (100) is shown. After alkalizing sugar cane juice to obtain alkaline sugar cane juice in an alkalizing vessel (101) (alkalinity 0.75 g CaO / 100 ml), three carbonation reactions, each comprising two carbonation steps, in particular a first and second carbonation step, were carried out with CO2-enriched carbonation gas having different CO2 contents, and the CO2 gas utilization rate was calculated and compared in each case. A process step c) according to the invention was not carried out.

[0168] The three CO₂-enriched carbonation gases, each with a different CO₂ content, were produced using a coke-fired lime kiln and the addition of air. The CO₂ content of the three CO₂-enriched carbonation gases was determined to be 41.5 vol%, 30.1 vol%, and 26.0 vol% (based on the total volume of carbonation gas) using a gas analyzer that analyzes CO₂ content via a non-dispersive infrared sensor. The three CO₂-enriched carbonation gases are subsequently referred to as 41.5% CO₂ gas, 30.1% CO₂ gas, and 26.0% CO₂ gas, or more generally as CO₂ gases.

[0169] The analysis of the CO2 gases was carried out using a Horiba Pg350 gas analyzer and the NDIR method (non-dispersive infrared sensor).

[0170] The respective CO₂-enriched carbonation gases are conveyed via a line (130) carrying fresh CO₂-enriched carbonation gas to the respective carbonation vessel and into the corresponding alkaline sugarcane juice. The alkaline sugarcane juice is transported via supply lines (120) between the respective vessels and the filtration device (110), which is located downstream of the first carbonation vessel (103) and upstream of a storage vessel (111).

[0171] With the three CO2 gases, a first carbonation step was carried out in a first carbonation vessel (103) and subsequently a second carbonation step with fresh CO2 gas was carried out in a second carbonation vessel (104) and the respective CO2 content of the CO2-depleted exhaust gas obtained in the respective carbonation step was measured and the CO2 gas utilization rate was calculated using the following formula: 10000 * CO 2 − Gas − CO 2 − Abgas / CO 2 − Gas * 100 − CO 2 − Abgas , where the value of the CO2 gas corresponds to the CO2 content in the CO2-enriched carbonation gas of the respective carbonation step (based on the total volume of CO2-enriched carbonation gas) and the value of the CO2 exhaust gas corresponds to the CO2 content in the CO2-depleted exhaust gas of the respective carbonation step (based on the total volume of CO2-depleted exhaust gas).

[0172] The results are shown in Table 1 and Figure 2 for the first carbonation step as well as Table 2 and Figure 3 summarized for the second carbonation step.

[0173] Table 1 shows that with a lower CO₂ content of the CO₂ gas at the inlet of the first carbonation vessel of the first carbonation step, the CO₂ content of the CO₂-depleted exhaust gas at the outlet of the first carbonation vessel of the first carbonation step decreases (second row, Table 1: 3.6 vol%, 3.4 vol%, and 2.7 vol% CO₂ content in the exhaust gas of 41.5 vol% CO₂ gas, 30.1 vol% CO₂ gas, and 26.0 vol% CO₂ gas). The CO₂ gas utilization rate also decreases (third row, Table 2: 95%, 92%, and 91% CO₂ gas utilization rates of 41.5% CO₂ gas, 30.1% CO₂ gas, and 26.0% CO₂ gas). Table 1: CO2 content in the CO2-enriched carbonation gas at the inlet and CO2-depleted exhaust gas at the outlet of the first carbonation vessel of the first carbonation step, as well as calculated values ​​of the CO2 gas utilization rate in each case. 1. Carbonation step 1. Carbonation step 1. Carbonation step CO2 content (input) [Vol.-%] 41,5 30,1 26 CO2 content (initial) [Vol.-%] 3,6 3,4 2,7 CO2 gas utilization rate [%] 95 92 92

[0174] In Figure 2A bar chart is shown, where each bar represents the respective CO₂ gas utilization rate (y-axis) of the first carbonation step using a CO₂-enriched carbonation gas (x-axis, 41.5% CO₂ gas, 30.1% CO₂ gas, and 26.0% CO₂ gas). The CO₂ gas utilization rate of the first carbonation step using the 41.5% CO₂ gas is 95%, that of the first carbonation step using the 30.1% CO₂ gas is 92%, and that of the first carbonation step using the 26.0% CO₂ gas is also 92%.

[0175] A lower CO₂ content of the CO₂ gas in the first carbonation step leads to a lower CO₂ gas utilization rate in the first carbonation step. The same behavior is observed in the second carbonation step (Table 2 and Figure 3In the second carbonation step, the CO₂ content of the CO₂-depleted exhaust gas at the outlet of the second carbonation vessel is also lower, due to the lower CO₂ content of the CO₂ gas at the inlet of the second carbonation vessel. The CO₂ gas utilization rate decreases with decreasing CO₂ content of the CO₂ gas. Table 2: CO2 content in the CO2-enriched carbonation gas at the inlet and CO2-depleted exhaust gas at the outlet of the second carbonation tank of the second carbonation step, as well as calculated values ​​of the CO2 gas utilization rate in each case. 2. Carbonation step 2. Carbonation step 2. Carbonation step CO2 content (input) [Vol.-%] 41,5 30,1 26,0 CO2 content (initial) [Vol.-%] 26,3 17,9 15,7 CO2 gas utilization rate [%] 50 49 47

[0176] In Figure 3A bar chart is shown, with each bar representing the respective CO₂ gas utilization rate (y-axis) of the second carbonation step using a CO₂-enriched carbonation gas (x-axis, 41.5% CO₂ gas, 30.1% CO₂ gas, and 26.0% CO₂ gas). The CO₂ gas utilization rate of the second carbonation step using the 41.5% CO₂ gas is 50%, that of the second carbonation step using the 30.1% CO₂ gas is 49%, and that of the second carbonation step using the 26.0% CO₂ gas is 47%.

[0177] Table 3 shows the total volume of CO₂ gas used in each carbonation step, as well as the volume distribution of the respective total CO₂ gas volume between the first and second carbonation steps. The last two rows of Table 3 show the CO₂ consumption and the exhaust gas volume of the second carbonation step in m³. Table 3: Carbonation gas volume and exhaust gas volume of the carbonations CO2 content (input) [Vol.-%] 41,5 35,0 30,1 26,0 Total lime kiln gas volume for carbonation [m³ / h] 2900 3500 4200 5200 Lime kiln gas volume of first carbonation step [m³ / h] 2470 2980 3593 4470 Lime kiln gas volume of second carbonation step [m³ / h] 430 520 607 730 CO2 consumption second carbonation step [m3 / h] 89 89 89 89 Exhaust gas second carbonation step [m³ / h] 341 431 518 641 Example 2: CO2 gas utilization rates and total CO2 gas utilization rates of a process according to the invention in a device according to the invention

[0178] In Example 2, after obtaining alkaline sugar cane juice according to process step a) of the present invention, a carbonation according to process step b) of the present invention comprising a pre-carbonation step, a first and a second carbonation step and a process step c) according to the invention was carried out in a device (200) according to the invention. Figure 4 carried out.

[0179] Figure 4Figure 1 shows a device (200) according to the invention. According to the device (200) according to the invention, an alkalization vessel (201) (alkalinity 0.75 g CaO / 100 ml), in which process step a) is carried out according to the method according to the invention, is connected downstream of a pre-carbonation vessel (202), in which a pre-carbonation step b0) is carried out according to the method according to the invention, wherein the alkalization vessel (201) is connected to the pre-carbonation vessel (202) via a feed line (220), through which the alkaline carbonation reactant or alkaline carbonation intermediate is transferred.A first carbonation vessel (203), in which a first carbonation step b1) is carried out according to the method according to the invention, is connected downstream of the pre-carbonation vessel (202). The pre-carbonation vessel (202) is connected to the first carbonation vessel (203) via a feed line (220) in which an alkalinity of 0.73 g CaO / 100 ml is present at this position. A filtration device (210) is connected downstream of the first carbonation vessel (203), and the first carbonation vessel (203) is connected to the filtration device (210) via a feed line (220). A feed vessel (211) is connected downstream of the filtration device (210), and the filtration device (210) is connected to the feed vessel (211) via a feed line (220).A second carbonation vessel (204), in which a second carbonation step b2) is carried out according to the inventive method, is connected downstream of the feed vessel (211), the feed vessel (211) being connected to the second carbonation vessel (204) via a feed line (220). Fresh CO2-enriched carbonation gas is introduced into the alkaline carbonation reactant present in the first carbonation vessel (203) via a line (230) transporting fresh CO2-enriched carbonation gas, and CO2-depleted exhaust gas is discharged via an exhaust line (231).Fresh CO2-enriched carbonation gas is introduced into the alkaline carbonation reactant present in the second carbonation vessel (204) via a line (230) transporting fresh CO2-enriched carbonation gas, and the CO2-depleted exhaust gas from the second carbonation vessel (204) is discharged via a line (240) according to the invention and introduced as CO2-enriched carbonation gas into the alkaline carbonation reactant present in the pre-carbonation vessel (202) according to process step c) according to the invention and discharged as CO2-depleted exhaust gas from the pre-carbonation vessel (202) via an exhaust gas line (241).

[0180] For the first and second carbonation steps, fresh CO₂-enriched carbonation gases were used, with the CO₂ contents of the CO₂-enriched carbonation gases of the first and second carbonation steps being 41.5 vol%, 35.0 vol%, 30.0 vol%, and 26.0 vol% respectively (based on the total volume of carbonation gas). According to the invention, the CO₂-depleted exhaust gas obtained from the second carbonation step was discharged from the second carbonation vessel (204), introduced into an alkaline sugar cane juice present in the pre-carbonation vessel (202) as the sole CO₂-enriched carbonation gas (CO₂ gas) according to process step c) of the invention, a pre-carbonation step was carried out, and CO₂-depleted exhaust gas was discharged from the pre-carbonation vessel (202).

[0181] The CO₂ content of the CO₂-depleted exhaust gas from the second carbonation step, which represents the CO₂-enriched carbonation gas from the pre-carbonation step (hereinafter referred to as CO₂ gas), was determined to be 26.3 vol%, 21.4 vol%, 17.9 vol%, and 15.7 vol% (based on the total gas volume of CO₂-depleted exhaust gas from the second carbonation step and CO₂-enriched carbonation gas from the pre-carbonation step, respectively), in particular by means of a gas analyzer that analyzes the CO₂ content via a non-dispersive infrared sensor. This gas was introduced via a line (240) from the second carbonation vessel into an alkaline sugar cane juice present in the pre-carbonation vessel (202) as the sole CO₂-enriched carbonation gas, and a pre-carbonation step was carried out (see Figure 4The retention time of the respective CO₂ gas in the pre-carbonation vessel (202) during the pre-carbonation step was 10, 8, 6, 4, or 2.5 minutes. Subsequently, the CO₂ content of the CO₂-depleted exhaust gas from the pre-carbonation step (hereinafter referred to as CO₂ exhaust gas) was determined, and the CO₂ gas utilization rate was calculated using the following formula: 10000 * CO 2 − Gas − CO 2 − Abgas / CO 2 − Gas * 100 − CO 2 − Abgas , where the value of the CO2 gas corresponds to the CO2 content in the CO2-enriched carbonation gas of the pre-carbonation step (based on the total volume of CO2-enriched carbonation gas) and the value of the CO2 exhaust gas corresponds to the CO2 content in the CO2-depleted exhaust gas of the pre-carbonation step (based on the total volume of CO2-depleted exhaust gas).

[0182] The respective CO2 gas utilization rates are in Figure 5 summarized.

[0183] In Figure 5A diagram is shown in which each data point corresponds to a CO2 gas utilization rate (y-axis) of a pre-carbonation step with a corresponding retention time (x-axis) of the CO2-enriched carbonation gas during the pre-carbonation step in a pre-carbonation vessel (202).

[0184] The calculations and the diagram in Figure 5 show that the CO2 gas utilization rate of the pre-carbonation step according to the invention is ≥80%.

[0185] Figure 5 Furthermore, it shows the tendency that the CO₂ gas utilization rate in the pre-carbonation step according to the invention decreases with an increase in the CO₂ content in the CO₂-enriched carbonation gas. Furthermore, in Figure 5 the tendency to see that the CO2 gas utilization rate in the pre-carbonation step according to the invention decreases with a shorter retention time.

[0186] Example 2 shows in particular: The CO₂ content in the CO₂-depleted exhaust gas of the pre-carbonation step is 2.5 to 5.5 vol% (based on the total volume of CO₂ exhaust gas). The CO₂ content in the CO₂-depleted exhaust gas of the pre-carbonation step decreases with the decrease in the CO₂ content in the CO₂-enriched carbonation gas of the pre-carbonation step. The CO₂ content in the CO₂-depleted exhaust gas of the pre-carbonation step decreases with the increase in the retention time of the CO₂-enriched carbonation gas in the pre-carbonation vessel (202) during the pre-carbonation step. The alkalinity in the alkaline sugar cane juice used in the pre-carbonation step according to the invention was reduced by 0.02 g CaO / 100 mL (from 0.75 g CaO / 100 mL to 0.73 g CaO / 100 mL). Example 3: Comparison of the results from Example 1 and Example 2

[0187] Table 4 compares the CO2 gas utilization rates and total CO2 gas utilization rates of the example according to the invention (Example 2) and the comparison example (Example 1). According to the invention (Example 2) Comparison (Example 1) CO2 content in lime kiln gas % 41,5 30,1 26,0 41,5 30,1 26,0 Total lime kiln gas per hour m³ / h 2900 4200 5200 2900 4200 5200 CO2 density kg / m³ < 1,98 1,98 1,98 1,98 1,98 1,98 Total CO2 content in lime kiln gas kg / h 2383 2503 2677 2383 2503 2708 Lime kiln gas in the 1st carbonation step m³ / h 2470 3593 4470 2470 3593 4470 CO2 content in lime kiln gas in the 1st carbonation step kg / h 2030 2141 2301 2030 2141 2328 CO2 gas utilization rate of the 1st carbonation step % 95 92 92 95 92 92 CO2 content in the exhaust gas of the 1st carbonation step kg / h 101 171 184 101 171 186 Lime kiln gas in the 2nd carbonation step m³ / h 430 607 730 430 607 730 CO2 content in lime kiln gas in the 2nd carbonation step kg / h 353 362 376 353 362 380 CO2 gas utilization rate of the 2nd carbonation step % 50 49 47 50 49 47 CO2 content in the exhaust gas of the 2nd carbonation step kg / h 177 184 199 177 184 201 Exhaust gas from the 2nd carbonation step for the pre-carbonation step m³ / h 341 517 641 - - - CO2 content in the carbonation gas of the pre-carbonation step % 26,3 17,9 15,7 - - - CO2 content in the carbonation gas of the pre-carbonation step kg / h 177 183 199 - - - CO2 gas utilization rate of the pre-carbonation step (average of residence times from 2.5 to 10 min) % 84,5 83,4 83,2 - - - CO2 content in the exhaust gas of the pre-carbonation step kg / h 28 30 33 - - - Total CO2 content (i.e., emission) in the exhaust gases of carbonation kg / h 129 202 218 278 356 388 CO 2 total gas utilization rate of carbonation % 95 92 92 88 86 86

[0188] Table 4 shows that the CO2 emission of the carbonation carried out according to the inventive method and in an inventive device is reduced by 54% during carbonation with the 41.5-CO2 gas, by 43% with the 30.1-CO2 gas and by 44% with the 26.3-CO2 gas.

[0189] The total CO2 gas utilization rate of the respective carbonation ations is calculated using the following formula:

[0190] The overall CO2 gas utilization rate of the carbonation processes according to the inventive method and carried out in an inventive device is improved by 8% for carbonation with 41.5-CO2 gas, by 7% with 30.1-CO2 gas and by 7% with 26.3-CO2 gas.

[0191] It is therefore evident that the production of a carbonation product from a carbonation reactant by means of a method according to the invention, in particular carried out in a device according to the invention, has a higher overall CO2 gas utilization rate and reduced CO2 emissions compared to a comparison method, in particular carried out in a comparison device.

Claims

1. A process for producing a carbonatation product from a carbonatation educt, comprising the process steps: a) alkalisation of a carbonatation educt to obtain an alkaline carbonatation educt and b) carbonatation of the alkaline carbonatation educt comprising a first and at least one further carbonatation step b1) and b2) to obtain the carbonatation product, in the course of each of which a CO2-enriched carbonatation gas is introduced into the alkaline carbonatation educt and a CO2-depleted waste gas is discharged, characterised in that c) introducing at least a proportion of the waste gas of the at least one further carbonatation step into the alkaline carbonatation educt prior to the first carbonatation step, so that a pre-carbonatation step b0) is carried out prior to the first carbonatation step b1).

2. The process of claim 1, wherein the carbonatation educt is a raw sugar juice and the carbonatation product is a thin juice or the carbonatation educt is a raw sugar solution and the carbonatation product is a purified raw sugar solution.

3. The process of one of the preceding claims, wherein the process is carried out in an apparatus for producing a carbonatation product from a carbonatation educt comprising at least one first carbonatation vessel (203) and at least one further carbonatation vessel.

4. The process of one of the preceding claims, wherein the apparatus (200) has a pre-carbonatation vessel (202) upstream of the first carbonatation vessel (203).

5. The process of one of the preceding claims, wherein the apparatus has at least one line (240) from the at least one further carbonatation vessel to an upstream pre-carbonatation vessel (202) to introduce at least a part of the waste gas of the at least one further carbonatation step into the alkaline carbonatation educt prior to the first carbonatation step.

6. The process of one of the preceding claims, wherein the waste gas of the at least one further carbonatation step has a CO2 content of 1 to 40 vol%, in particular 15 to 27 vol% (based on the total volume of waste gas).

7. The process of one of the preceding claims, wherein the waste gas of the at least one further carbonatation step after process step b) and prior to process step c) is mixed with a CO2-enriched carbonatation gas.

8. The process of one of the preceding claims, wherein the CO2-enriched carbonatation gas is obtained from a coke- or gas-operated lime kiln or is at least a proportion of a boiler house gas.

9. The process of one of the preceding claims, wherein the CO2-enriched carbonatation gas obtained according to claim 9 has a CO2 content of 1 to 99 vol% (based on total volume of CO2-containing gas).

10. The process of one of the preceding claims, wherein the carbonatation educt is obtained from sugar beet or sugar cane.

11. The process of one of the preceding claims, wherein the CO2 gas utilisation rate of the at least one further carbonatation step is at least 20 %.

12. The process of one of the preceding claims, wherein the total CO2 gas utilisation rate of the carbonatation is at least 70 %.

13. An apparatus for producing a carbonatation product from a carbonatation educt, in particular suitable and designed for carrying out a process according to any one of the preceding claims 1 to 12, comprising at least one first carbonatation vessel (203), at least one further carbonatation vessel and at least one line (240) from the at least one further carbonatation vessel to an upstream carbonatation vessel, which is suitable for introducing at least a part of a waste gas from the at least one further carbonatation vessel into an alkaline carbonatation educt present in an upstream carbonatation vessel, wherein a pre-carbonatation vessel (202) is connected upstream of the first carbonatation vessel (203), and wherein the upstream carbonatation vessel is the pre-carbonatation vessel (202).

14. The apparatus of claim 13, wherein the apparatus is a beet sugar or sugar cane sugar processing apparatus for producing thin juice from raw sugar juice.

15. The apparatus of claim 13 or 14, wherein the apparatus is a sugar refining apparatus for producing a purified raw sugar solution from a raw sugar solution.