Method and installation for producing lime or dolime

Abstract

A method and installation for producing lime or dolime, comprising the calcination of a calcareous or dolomitic material in contact with a first flue gas obtained by the combustion of a fuel with an oxidizing gas, cooling the calcined lime or dolime with its discharge and recovery and releasing a gaseous effluent containing CO2, said method comprising the depletion of said gaseous effluent by passing it through a CaO-based sorbent material which captures the CO2 and produces a treatment material based on CaCO3-CaO, and the separation of the treatment material based on CaCO3-CaO and the CO2-depleted gaseous effluent which is withdrawn. and calcining the separated CaC03-CaO based process product in contact with a second flue gas obtained by combustion of a lean fuel with an oxidizing gas consisting of dioxygen and CO2 to produce said CaO based sorbent material. Separation between the CaO based sorbent material and the recovered CO2 enriched gas stream. Recycling of said separated CaO based sorbent material to the CO2 reduction step. Withdrawal of a value-addable portion of the CaC03-CaO based process material and compensatory introduction of fresh CaC03 in the calcination step.

Description

[Technical field]

[0001] The present invention relates to a method for producing lime or dolime as well as to an installation for producing lime or dolime, in particular an installation for carrying out such a production method. [Background technology]

[0002] The process for producing lime or dolime usually comprises the calcination of a downwardly moving calcareous or dolomitic material having a carbonate content higher than 90% by weight (CaCO3+MgCO3), in contact with a first flue gas obtained by combustion of a fuel in the presence of an oxidizing gas, cooling of the downwardly moving calcined calcareous or dolomitic material and recovery from the bottom of the main value product in the form of lime or dolime, and release of a gaseous effluent containing CO2.

[0003] Said downward movement may be performed vertically, as for example in a shaft kiln, or inclined, as for example in a rotary kiln.

[0004] The lime or dolime thus obtained consists of a pure oxide product with a CaO+MgO content higher than 80% by weight, and a specific content of impurities depending on the purity of the parent limestone or dolomite and the ash content of the fuel used in the kiln. It is important to note that additives do not necessarily need to be provided to the raw calcareous or dolomitic material to produce lime or dolime. As a general rule, marketable lime or dolime should have a high purity oxide content ranging between 98% and 80% by weight. A specific impurity that can be a "killer" for many lime or dolime applications is sulfur. For example, steel, refractory or lime slurry applications require a low to very low sulfur content.

[0005] During calcination, the raw calcareous or dolomitic materials release large volumes of CO2. Moreover, to achieve this calcination it is necessary to reach high temperatures and therefore to continue burning fuels, which in turn cause significant CO2 emissions. Overall, the calcination process has the disadvantage of actively contributing to the increase of the greenhouse effect.

[0006] Furthermore, traditional calcination processes have the drawback of providing air for the combustion of fuel and cooling the calcination products with air, resulting in the emission of gaseous effluent with a high content of diatomic nitrogen at the top of the furnace and a relatively low content of CO2 (volume concentration of 20% to 27% on a dry gas basis) that is expensive to capture due to the high abundance of nitrogen.

[0007] A method for capturing CO2 in connection with a cement clinker kiln is disclosed in US Patent Application Publication No. 2009 / 0255444. Such a method consists of thermally treating a raw material consisting of limestone, clay and iron ore to produce clinker. The gaseous effluent resulting from the clinker kiln is introduced into a CaO looping system to concentrate the CO2 in the effluent. The clinker production is adapted to high ash fuels and raw materials containing, for example, only 75% by weight of limestone. In this document, the starting material contains as a prerequisite limestone mixed with a high content of clay and iron ore that should be excluded from the production of lime or dolime. Furthermore, a residue is continuously purged from the CaO-looping system, said residue being recycled directly to the main cement clinker kiln. Impurities in this residue are therefore accumulated in the final clinker product and must be taken into account in its formulation.

[0008] The so-called "carbonate looping" CO2 capture method is also known in the coal power generation industry (see J. Hilz et al., "Long-term pilot testing of the carbonate looping in 1MWth scale," Fuel, Vol. 210, pp. 892-899 (2017)). A CaO fluidized bed in a carbonate looping system captures the CO2 present in the gaseous exhaust of a coal combustor. Fresh CaCO3 must be continuously introduced as make-up in the carbonate looping system, and the residue is also continuously purged and removed from the loop.

[0009] No information on the production of marketable lime or dolime can be obtained from these prior art documents. Moreover, they result in continuous purging and removal of waste materials. Summary of the Invention [Means for solving the problem]

[0010] The object of the present invention is to enable the capture, for the purpose of use or separation, of the CO2 released during the calcination process carried out in a lime or dryme kiln, while producing high quality lime or dryme, without modification of the kiln and the process embodied therein, and without the continuous removal of unusable waste products.

[0011] To solve this problem, the method presented above comprises: - transferring said gaseous effluent containing CO2 to a CO2 reduction step in which said gaseous effluent passes through a CaO-based sorbent material which captures CO2 and produces a CaCO3-CaO-based treatment material by carbonation; - separation between the treated material, mainly CaCO3-CaO, and the CO2-depleted gaseous effluent, which is extracted; - calcination of the separated CaCO3-CaO based treatment material in contact with a second flue gas obtained by combustion of a fuel selected from the group consisting of gaseous fuels and solid and liquid fuels having an ash content of less than 10% by weight and a sulfur content of less than 1.5% by weight in the presence of dioxygen and CO2 as oxidizing gases, and decarbonation of CaCO3 to produce said CaO based sorbent material and release of CO2; - separation between a sorbent material based on CaO resulting from said decarbonation and a CO2-enriched gas stream composed of a second combustion flue and the CO2 released and recovered during said decarbonation of CaCO3; - recycling the separated CaO-based sorbent material to the CO2 reduction step of the gaseous effluent; - continuous withdrawal of a portion thereof as a by-product prior to the step of calcination of the CaCO3-CaO-based process material and compensatory introduction of fresh limestone having a CaCO3 content of at least 90% by weight into said step of calcination of the separated CaCO3-CaO-based process material; Further includes:

[0012] The method is a closed loop regenerative system for CO2 capture. During carbonation, CO2 from, for example, the flue gas of a lime kiln as gaseous effluent is captured by a CaO sorbent and subjected to the following exothermic reaction CaO+CO2→CaCO3. The CO2 content of the gaseous effluent thereby drops sharply when released into the atmosphere. According to the invention, CO2-depleted gaseous effluent means a gas having a volume concentration of CO2 lower than that of the gaseous effluent of the kiln, advantageously lower than 10% on a dry gas basis, preferably lower than 5%.

[0013] In the CO2 reduction step, the CaO sorbent is advantageously in a fluidized or moving bed.

[0014] The resulting circulating CaCO3-CaO-based process material contains CaCO3 and residual CaO from which no CO2 was captured. The CaCO3 of this process material is subjected to the endothermic calcination reaction "CaCO3 + heat to CaO + CO2". According to the invention, the heat required for this calcination is generated as a result of the combustion of a fuel with low impurities in the presence of dioxygen and CO2 as oxidizing gas. This oxidizing gas can preferably be a mixture of dioxygen and CO2. Under such conditions, the combustion has the effect of producing mainly CO2 in the gas stream, optionally some impurities present only in traces in the fuel, and oxygen not consumed by the combustion of the fuel. This obviously results in a sharp increase in the CO2 content of the gas stream withdrawn from the loop. By CO2-enriched gas stream, it is to be understood that according to the invention, said gas stream has a CO2 content of at least 90%, in particular at least 95% by volume, on a dry gas basis. This gas stream rich in CO2 can then be used or captured under favorable conditions, which makes it possible to drastically reduce the contribution of lime or dry lime production to the greenhouse effect.

[0015] According to the invention, the dioxygen (hereinafter also referred to as oxygen) used is a gas with an oxygen content of more than 90%, preferably 95%, advantageously more than 98% by volume. The source of pure dioxygen can be, for example, an air separation unit which separates air into dioxygen and nitrogen, or an installed dioxygen tank.

[0016] According to the invention, the fuel for the step of calcination of the separated CaCO3-CaO-based process material is preferably gaseous, since such fuel contains neither ash nor sulfur. Such fuel can be, for example, natural gas, hydrogen, biogas, coke oven gas or gasification gas. Liquid or solid fuels, such as, for example, fuel oil, oil, liquid biofuel, petroleum coke, biomass, lignite, coal, etc., can also be selected, as long as the ash content of the fuel is <10% by weight, in particular <7%, preferably <5%, most preferably <1%, and the fuel sulfur content is <1.5% by weight, preferably <1%, most preferably 0.1% by weight. Natural gas is particularly preferred. In the following text, the term fuel with low impurities is sometimes used to summarize suitable fuels according to the invention.

[0017] In the step of calcining the separated CaCO3-CaO based treatment material, this treatment material may advantageously be in a fluidized or moving bed.

[0018] The CaO-based sorbent material produced during the calcination step is recycled to the CO2 reduction step.

[0019] According to the invention, the method comprises the continuous withdrawal of a portion of said CaCO3-CaO based process material before its calcination and the compensatory introduction of fresh limestone having a CaCO3 content of at least 90% by weight, preferably 95% by weight and advantageously 98% by weight, into said calcination step of the separated CaCO3-CaO based process material.

[0020] A particularity of the sorbent regeneration system is that the sorbent, here CaO, becomes less and less active with increasing number of looping cycles. This phenomenon results from increasing sintering and poisoning of the sorbent by impurities. Advantageously, a CaO sorbent capture efficiency of 30% should be maintained during the carbonation step in order to continuously obtain at least 90% by volume of CO2 capture in the gaseous effluent coming from the lime or dry lime kiln. To keep this stable performance, a certain amount of the process material based on CaCO3-CaO circulating from carbonation to calcination is withdrawn. This withdrawn circulating process material is called bleed. As indicated above, before or during the calcination of the process material based on CaCO3-CaO, new material in the form of CaCO3 with a purity higher than 90% by weight is added for compensation. This added amount is called make-up. According to the invention, the bleed is withdrawn before the calcination of the process material based on CaCO3-CaO. Thus, the recovered product reduces the calcination energy costs for its production.

[0021] According to the invention, the gaseous emissions from the lime or dry kiln in the CO2 reduction step should meet the environmental requirements as a standard, so that they are low in impurities such as ash and sulfur, and furthermore, fuels low in such impurities are used in the step of calcination of the CaCO3-CaO-based material. Furthermore, as explained above, the make-up limestone is also of high purity. As a result therefrom, the drawn-off part, called the draw-off, advantageously has a CaCO3+CaO content of at least 80% by weight, preferably 90% by weight, in particular 95% by weight. Said draw-off is a powdery material mainly based on Ca, which may contain little or no ash and little or no sulfur, is of good quality and can therefore be used as a by-value product in most of the lime markets, such as civil engineering, agriculture, wastewater treatment, papermaking, sludge treatment, etc. The draw-off is therefore not a waste product and can be used industrially or commercially. Furthermore, the amount of the withdrawn fraction may be significant, advantageously making it possible to improve the purity content of the resulting fraction and the activity of the sorbent during carbonation, without being detrimental to the production of the main and secondary value products of the process (limestone or dolime and the withdrawn fraction). Preferably, during said continuous withdrawal, a fraction of less than 15% by weight, preferably between 2 and 10% by weight, of said CaCO3-CaO based process material is withdrawn. Experiments show that an increase in said fraction results in a significant reduction of impurities in the withdrawn fraction.

[0022] Thus, according to the invention, in parallel with the production of lime or dolime, there is an additional production of a marketable Ca product, which is not extracted as in the prior art.

[0023] Advantageously, the calcination of said downwardly moving calcareous or dolomitic material is carried out at a temperature between 750 and 1750° C., preferably between 800 and 1350° C., depending on the desired characteristics of the final product.

[0024] According to an embodiment of the invention, the method comprises, during the CO2-depletion step, maintaining said carbonation at a temperature below 700°C, preferably between 600 and 670°C, in particular about 650°C, by a first heat recovery from the gaseous effluent transferred. At a temperature of 700°C, calcination of CaCO3 can begin. The carbonation is therefore operated slightly below this temperature in order to obtain a fast carbonation reaction rate while avoiding the calcination, which is a reverse reaction. As the carbonation reaction is exothermic, it is therefore necessary to extract heat from the reaction, in particular by heat exchange with an external fluid. A second heat recovery from the CO2-depleted degassed effluent is also possible after its removal from the carbonation, since the temperature of this effluent is high, in particular about 650°C.

[0025] According to a particular embodiment of the invention, the method comprises carrying out said step of calcination of the separated CaCO3-CaO based process material at a temperature between 850°C and 1200°C, preferably between about 880°C and 1050°C, more preferably between 900°C and 1000°C, for example around 920°C or 950°C, and a third heat recovery from the recovered CO2 enriched gas stream. This calcination is carried out under high CO2 partial pressure, such temperature being maintained to accelerate the calcination while producing high specific surface area CaO suitable for capturing CO2.

[0026] The first, second and / or third heat recovery may consist of converting the heat to electricity or other heat recovery uses such as drying, district heating, etc.

[0027] The method according to the invention may advantageously comprise a step of mixing pure dioxygen with a part of the recovered CO2 enriched gas stream to generate said oxidizing gas for said combustion of the calcination step. Combustion of fuel with pure oxygen produces flame temperatures that are too high for normal equipment. It is also advantageously planned to simultaneously introduce CO2 to dilute the oxygen. Advantageously, a part of the recovered gas stream rich in CO2 is taken and mixed with oxygen. Thus, an O2 + CO2 mixture with a suitable flame temperature is obtained instead of the usual air oxidizing mixture O2 + N2, while producing a gas stream increasingly enriched in CO2 during the calcination step.

[0028] The present invention includes at least one kiln, each of which comprises: a top feed for calcareous or dolomitic material; a calcination zone in which the calcareous or dolomitic material moves downwards and comes into contact with a first flue gas obtained by the combustion of a fuel in the presence of an oxidizing gas, whereby it is calcined into lime or dolomitic material; a cooling zone for cooling the calcined lime or lime moving downwards; a bottom discharge for recovering the cooled lime or dry lime as a main value product; a top outlet for the gaseous exhaust containing CO2 to be released; The present invention also relates to an installation for the production of lime or dolime, comprising:

[0029] According to the present invention, the facility further comprises: a carbonation reactor containing a sorbent material based on CaO; - means for transporting said gaseous effluent containing CO from said top outlet of said at least one kiln to said carbonation reactor, said gaseous effluent passing through said sorbent material for capturing CO and carbonating to produce a treatment material based on CaCO3-CaO and a CO2-depleted gaseous effluent; a first separation device for separating said CaCO3-CaO based treatment material from a CO2-depleted gaseous effluent at the top of the carbonation reactor and for removing said gaseous effluent; a calcination reactor, supplied by a transfer duct with the CaCO3-CaO-based material coming from the first separation device, in which the CaCO3-CaO-based material comes into contact with a second flue gas obtained by combustion of a fuel selected from the group consisting of a gaseous fuel and a solid fuel and a liquid fuel having an ash content of less than 10% by weight and a sulfur content of less than 1.5% by weight in the presence of dioxygen and CO2 as oxidizing gases, with the formation of the CaO-based sorbent material by decarbonation of CaCO3 and the release of CO2; a second separation device for separating, at the top of the calcination reactor, the sorbent material based on CaO resulting from the decarbonation and a CO2-enriched gas stream formed by the second combustion fumes and the CO2 released during the decarbonation of CaCO3, and for withdrawing this CO2-enriched gas stream for recovery; a recycle duct through which the CaO-based sorbent material from the second separation device is fed to the carbonation reactor; - a withdrawal duct arranged to withdraw and recover a portion of the CaCO3-CaO based process material from the transfer duct as a by-product value, the withdrawal duct being provided with a compensatory fresh supply of CaCO3 to feed the calcination reactor; Includes.

[0030] In the installation according to the invention, the gaseous emissions containing CO2 may be generated by one or several kilns capable of producing lime or dolime, in which the raw materials are fed at the top of the kiln and the calcined material is discharged at the bottom after cooling. Such kilns are, for example, rotary kilns, shaft kilns, such as vertical shaft kilns, annular shaft kilns, parallel flow regenerative kilns, etc., in which the calcareous or dolomitic material moves downwards by a vertical or inclined direction.

[0031] Depending on the ash or sulfur content of the CO2-containing gaseous effluent released at the top outlet of the at least one kiln, the means for transporting the gaseous effluent may be solely in the duct connecting the top outlet to the carbonation reactor or may further comprise a suitable pollution prevention device.

[0032] The plant may also include any separation device, such as a cyclone, capable of separating certain solid materials from a gas.

[0033] In the carbonation reactor, the sorbent material may advantageously be in the form of a fluidized or moving bed. In the calcination reactor, the treatment material based on CaCO3-CaO may also advantageously be in the form of a fluidized or moving bed.

[0034] Preferably, the installation may further comprise a first heat exchanger arranged in the carbonation reactor to allow recovery by an external fluid of the amount of heat released during carbonation. The temperature in the carbonation reactor may therefore be maintained at a temperature lower than 700°C. At least one second heat exchanger may be arranged to allow heat recovery by an external fluid from the CO2-depleted gaseous effluent withdrawn from the first separation device. At least one third heat exchanger may be arranged to allow heat recovery by an external fluid from the CO2-enriched gas stream withdrawn from the second separation device. The external fluid is in particular water, which may become steam in the first, second and / or third heat exchanger and be fed to a steam turbine to generate electricity.

[0035] Further details and features of the method and the installation according to the invention may result from the claims. [Brief description of the drawings]

[0036] The installation according to the invention is now disclosed by means of FIG. 1, which is a schematic flow chart of a non-limiting embodiment. [Figure 1] 1 is a schematic flow diagram of a non-limiting embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] [Example 1] The illustrated installation comprises a conventional lime kiln 1, producing 175 tpd (tons per day). 12.5 tph (tons per hour) of limestone with a CaCO3 content of 96% by weight is introduced through a top feed 2 and calcined to lime in contact with 1.6 tph of flue gas obtained by the combustion of biomass, supplied at 3, in the presence of primary air as carrier gas and secondary air supplied at 4. Cooled by cooling air introduced at 6, 7.3 tph of lime with a CaO content of 93% by weight is discharged through a bottom discharge 5. A gaseous effluent is released from the kiln through a top outlet 7 and is transported by means of a connecting duct 9 to a carbonation reactor 8 through a purification system 16, including a dust collector, a dryer and / or a desulfurizer.

[0038] [Table 1]

[0039] As can be seen from Table 1, the CO2 volume concentration in the gaseous effluent is very low relative to the N2 concentration (65%). In such conditions, separation of both components is not easily feasible and is costly due to the large gas volumes to be treated.

[0040] The carbonation reactor 8 comprises a fluidized bed of sorbent material, mainly CaO, supplied by a recycle duct 10. There, 90% of the CO2 of the gaseous effluent is captured by the CaO, which is carbonated to CaCO3 by an exothermic reaction. In the carbonation reactor 8, the temperature of the gaseous effluent must be maintained at a value of about 650°C by a heat exchanger 11 in communication with a turbine 12 in order to convert the heat into electricity, in the event that the reverse reaction, calcination, is initiated. 2.3 MWe of electricity are thus obtained.

[0041] From the carbonation reactor 8, the gaseous effluent carrying the treated material mainly composed of CaCO3-CaO is fed through a transfer duct 13 to a cyclone 14, from the top of which a CO2-depleted gaseous effluent is discharged.

[0042] [Table 2]

[0043] Here, the gaseous effluent leaving the top of the cyclone 14 contains only traces of CO2 and may be removed in the atmosphere. Before this removal, this gas passes through a heat exchanger 15 in communication with a turbine 17 to convert heat into electricity. 1.5 MWe of electricity is thus obtained.

[0044] The separated solid particles of the treated material, mainly CaCO3-CaO, exit the bottom of the cyclone 14 and are fed to the bottom of the calcination reactor 19 using a transfer duct 18.

[0045] The calcination reactor 19 is also supplied with fuel containing few impurities. In the illustrated case, 1857 Nm 3 / h of natural gas (i.e., ash- and sulfur-free fuel) is introduced into the calcination reactor 19 through an inlet 20, and 23 tph of oxidizing gas containing dioxygen and CO2 is supplied through an inlet duct 21. The calcination reactor is operated at a temperature of about 900°C to accelerate the calcination of the treated material, mainly CaCO3-CaO, and to produce high specific surface area CaO.

[0046] From the calcination reactor 19, the gaseous effluent carrying the activated CaO is fed from the top through a transfer duct 22 to a cyclone 23 where a CO2 enriched gas stream is recovered.

[0047] [Table 3]

[0048] The CO2 concentration in the gas stream leaving the cyclone 23 is very high. Such gas may be industrially value-added, for example for technical CO2 production or separation. Before recovery, the gas stream passes through a heat exchanger 24 in communication with a turbine 25 to convert heat into electricity. 3.17 MWe of electricity is thus obtained.

[0049] The active CaO-based sorbent material leaves the bottom of the cyclone 23 separately and is recycled to the bottom of the carbonation reactor 8 by means of the recycle duct 10 .

[0050] Prior to said combustion of lean fuel in the presence of an oxidizing gas containing dioxygen and CO2, the dioxygen is mixed with the recovered CO2-enriched gas stream. 5 tph of oxygen produced at 90% concentration by air separation unit 26 is mixed with 18 tph of CO2-enriched gas recycled using recycle duct 27 and introduced as oxidizing gas into calcination reactor 19 by inlet duct 21. Obviously, the recycled CO2-enriched gas and pure dioxygen may be fed separately to the calcination reactor, where their mixing takes place in situ.

[0051] During capture of CO2 in carbonation reactor 8, there is the production of CaCO3 as explained above, but the CaO in the fluidized bed only partially participates in the carbonation. Thus, the CaCO3-CaO based process material circulating between carbonation reactor 8 and calcination reactor 19 contains particles of CaO as well as particles of CaCO3.

[0052] [Table 4]

[0053] CaO becomes less and less active with increasing cycles. There is an increase in particle sintering. Then, in order to maintain at least 30% CO2 capture efficiency of the active CaO in the CaO-based sorbent, a withdrawal flow rate of 0.8 tph of CaCO3-CaO-based process material (2% by weight of CaCO3-CaO-based process material) is withdrawn from the transfer duct 18 through withdrawal duct 28. For compensation, 1.06 tph of fresh limestone make-up with a CaCO3 content of 96% by weight is introduced into the calcination reactor through inlet 29. Since the fuel used in the calcination reactor 19 does not contain any ash or sulfur and the make-up compensation limestone has a high purity, the recycled CaO-based sorbent is very pure while the circulating CaCO3-CaO-based process material contains only Ca-based components. The bleed-off material is therefore not a waste product and can be used in several areas, such as gas or water purification, agriculture, paper manufacturing, civil engineering, etc.

[0054] The CO2 captured in the gas stream recovered from the calcination reactor is summarized in Table 5.

[0055] [Table 5]

[0056] At the same time, the gas stream recovered from the calcination reactor is highly enriched in CO2 and can be used or captured, a draw off is a valuable Ca product produced in parallel with the production of lime or dolime, and the electrical needs of the facility, particularly the air separation unit, are met by the output of the turbine.

[0057] [Example 2] We now describe the process according to the invention in a lime plant comprising several kilns, producing 2000 tpd of lime and fuelled by lignite. The gaseous emissions of all the kilns are collected together and sent into a carbonator-calciner system as illustrated in FIG.

[0058] [Table 6]

[0059] [Table 7]

[0060] [Table 8]

[0061] 66 tph of oxygen produced at a concentration of 90% by the air separation unit 26 and 222 tph of CO2-enriched gas recycled by the recirculation duct 27 are mixed as the oxidation gas and introduced into the calcination reactor. 3 / h of natural gas (i.e., a fuel without ash or sulfur) is also fed to the reactor as fuel.

[0062] [Table 9]

[0063] In order to maintain at least 30% CO2 capture efficiency of the active CaO in the CaO-based sorbent material, a withdrawal flow rate of 10 tph of CaCO3-CaO-based treatment material (2% by weight) is withdrawn from the transfer duct 18 through withdrawal duct 28. For compensation, a make-up of 13 tph of fresh limestone with a CaCO3 content of 98% by weight is introduced into the calcination reactor.

[0064] The power generated by the steam turbines is 30 MWe for turbine 12, 21 MWe for turbine 17 and 39 MWe for turbine 25.

[0065] The CO2 captured in the gas stream recovered from the calcination reactor is summarized in Table 10.

[0066] [Table 10]

[0067] [Example 3] We now disclose the method according to the invention in the same lime plant as in Example 2. The gaseous effluents of all the furnaces are collected together and fed to a carbonator-calciner as illustrated in Figure 1, but the fuel used in the calciner reactor is lignite with an ash content of 3.8% by weight and a sulphur content of 0.4% by weight.

[0068] As can be seen, the gaseous effluent entering the carbonation reactor 8 and the CO2 depleted gaseous effluent leaving the cyclone 14 exhibit the same characteristics as in Tables 6 and 7 of Example 2, respectively.

[0069] [Table 11]

[0070] 65 tph of oxygen produced at 90% concentration by the air separation unit 26 and 220 tph of CO2-enriched gas recycled through the recirculation duct 27 are mixed as oxidation gas and introduced into the calcination reactor. 40 tph of the above-mentioned lignite is also fed to this reactor as fuel.

[0071] [Table 12]

[0072] In order to maintain at least 30% CO2 capture efficiency of the active CaO in the CaO-based sorbent material, a withdrawal flow rate of 16 tph of CaCO3-CaO-based treatment material (3% by weight) is withdrawn from the transfer duct 18 through withdrawal duct 28. To compensate, 20 tph of fresh limestone make-up with a CaCO3 content of 98% is introduced into the calcination reactor. The withdrawal contains 16% by weight of impurities and is still a valuable product.

[0073] The power generated by the steam turbines is 31 MWe for turbine 12, 21 MWe for turbine 17 and 39 MWe for turbine 25.

[0074] The CO2 captured in the gas stream recovered from the calcination reactor is summarized in Table 13.

[0075] [Table 13]

[0076] [Example 4] We now disclose the process according to the invention in the same lime plant as in Example 2. The gaseous effluents of all the furnaces are collected together and fed to a carbonator-calciner as illustrated in Figure 1, but the fuel used in the calciner reactor is lignite as in Example 3.

[0077] As can be seen, the gaseous effluent entering the carbonation reactor 8 and the CO2 depleted gaseous effluent leaving the cyclone 14 exhibit the same characteristics as shown in Tables 6 and 7 of Example 2, respectively.

[0078] [Table 14]

[0079] 78 tph of oxygen produced at 90% concentration by the air separation unit 26 and 265 tph of CO2-enriched gas recycled through the recirculation duct 27 are mixed as oxidation gas and introduced into the calcination reactor. 48 tph of the above-mentioned lignite is also supplied to this reactor as fuel.

[0080] [Table 15]

[0081] A withdrawal flow rate of 50 tph of CaCO3-CaO-based treatment material (10% by weight) is withdrawn from the transfer duct 18 through withdrawal duct 28 in order to maintain at least 30% CO2 capture efficiency of the active CaO in the CaO-based sorbent material. For compensation, 66 tph of fresh limestone make-up with a CaCO3 content of 98% is introduced into the calcination reactor. The withdrawal contains 8.25% by weight of impurities and is a valuable product.

[0082] The power generated by the steam turbines is 32 MWe for turbine 12, 21 MWe for turbine 17 and 47 MWe for turbine 25.

[0083] The CO2 captured in the gas stream recovered from the calcination reactor is summarized in Table 13.

[0084] [Table 16]

[0085] A comparison between Example 3 and Example 4 shows that increasing the withdrawal rate of treated material with a main component of CaCO3-CaO from 3% to 10% results in a significant reduction in the withdrawal impurities (ash + CaSO4 + other impurities) from 16.43% to 8.25%.

[0086] Other embodiments and variations of the invention may be construed within the scope of the claims.

[0087] For example, the heat recovery can be of any type and is not limited to electrical.

[0088] In summary, such a plant avoids high contribution to the greenhouse effect, material flows and power generation are at desirable levels, makes make-up supply from the plant quarry possible locally, makes the extraction highly valuable, and makes the power generation a benefit to the local community.

Claims

1. - a carbonate content of more than 90% by weight (CaCO ３ + MgCO ３ sintering of the downwardly moving calcareous or dolomitic material with - cooling of the downwardly moving calcined calcareous or dolomitic material and recovery from the bottom of the main value product in the form of lime or dolime; -CO ２ and releasing a gaseous effluent containing 1. A method for producing lime or dolime comprising: -CO ２ of the gaseous effluent containing CO ２ was collected and converted to CaCO by carbonation. ３ - passing said gaseous effluent through a CaO-based sorbent material which produces a CaO-based treatment material; ２ Transfer to the reduction step, - CaCO ３ - A processing material mainly composed of CaO and CO ２ and separating the reduced gaseous effluent. - Dioxygen and CO as oxidizing gases ２ and a second flue gas obtained by combustion of a fuel selected from the group consisting of a gaseous fuel and a solid and liquid fuel having an ash content of less than 10% by weight and a sulfur content of less than 1.5% by weight in the presence of said separated CaCO. ３ - Calcination of the treatment material mainly composed of CaO, and CaCO ３ and forming the CaO-based sorbent material by decarbonation of CO. ２ and the step of - the sorbent material based on CaO resulting from the decarbonation, a second combustion flue and CaCO ３ The CO released and recovered during the decarbonation of ２ CO is made up of ２ and separating the enriched gas stream. - the CO of the gaseous effluent of the separated CaO-based sorbent material ２ Recycling to the decreasing steps, - CaCO ３ - before the step of calcination of said treated material, mainly CaO, a part of it is continuously withdrawn as a by-product of value, and the separated CaCO ３ - at least 90% by weight of CaCO in the step of calcining the treatment material mainly composed of CaO ３ Introduction of compensation for new limestone with a content of limestone; The method of claim 1, further comprising:

2. The method comprises: ２ 2. A method according to claim 1, characterised in that it comprises maintaining the carbonation at a temperature below 700°C, preferably between 600 and 670°C, in particular 650°C, by first recovering heat from the transferred gaseous effluent during the feedstock step.

3. The removed CO ２ 10. The method of claim 1 including a second heat recovery from the reduced gaseous effluent.

4. The method comprises: ３ - carrying out the step of calcining the separated treatment material, mainly CaO, at a temperature of 850 to 1200 ° C, in particular 880 to 1050 ° C, preferably 900 to 1000 ° C, and ２ and a third heat recovery from the enriched gas stream.

5. 3. The method of claim 2, wherein the first, second and / or third heat recovery comprises a conversion of a thermal quantity into electricity.

6. 2. The method according to claim 1, characterized in that the fuel for the calcination step is selected from the group consisting of natural gas, hydrogen, biogas, coke oven gas, gasification gas, fuel oil, oil, liquid biofuel, petroleum coke, biomass, lignite and coal.

7. To generate the oxidizing gas for the combustion of the calcination step, pure dioxygen is added to the recovered CO ２ The method of claim 1 including the step of mixing with a portion of the enriched gas stream.

8. During the continuous withdrawal, CaCO ３ 2. A method according to claim 1, characterised in that a portion of the treatment material, mainly CaO, less than 15%, preferably between 2 and 10%, by weight is withdrawn.

9. CaCO ３ The portion of the CaO-based treatment material that is withdrawn is at least 80% by weight of CaCO ３ 2. The method according to claim 1, characterized in that it has a CaO content.

10. At least one kiln (1), each of which comprises: - a top feed (2) for calcareous or dolomitic material, a calcination zone in which said calcareous or dolomitic material moves downwards and comes into contact with a first flue gas obtained by the combustion of a fuel in the presence of an oxidizing gas, whereby it is calcined to lime or dolomitic material; a cooling zone for cooling the downwardly moving calcined lime or dram; - a bottom outlet (5) for recovering the cooled, calcined lime or dolime as a main value product; -CO ２ a top outlet (7) for the discharged gaseous effluent containing 1. An installation for the production of lime or dolime comprising: a carbonation reactor (8) containing a sorbent material based on CaO; from the top outlet (7) of the at least one kiln ２ The gaseous effluent (9) containing CO ２ was collected and converted to CaCO by carbonation. ３ -CaO-based treatment material and CO ２ a means for transferring said gaseous effluent to said carbonation reactor (8) through said sorbent material producing a reduced gaseous effluent; At the top of the carbonation reactor (8), ２ The CaCO from the reduced gaseous effluent ３ a first separator (14) for separating the treated material, mainly CaO, and for extracting its gaseous effluent; said CaCO coming from said first separation device (14) through a transfer duct (18); ３ - A processing material mainly composed of CaO is supplied, and the CaCO ３ - The treatment material is mainly CaO, and the oxidizing gas is dioxygen and CO ２ and contacting a second flue gas obtained by combustion of a fuel selected from the group consisting of a gaseous fuel and a solid fuel and a liquid fuel having an ash content of less than 7% by weight and a sulfur content of less than 1.5% by weight in the presence of CaCO ３ and CO ２ a calcination reactor (19) with the release of - at the top of the calcination reactor (19), the CaO-based sorbent material resulting from the decarbonation and the second combustion fumes and CaCO ３ The CO released during the decarboxylation of ２ CO generated from ２ and separating the CO ２ a second separation apparatus (23) for removing an enriched gas stream for recovery; a recycle duct (10) through which the CaO-based sorbent material from the second separation device (23) is fed to the carbonation reactor (8); - the CaCO from the transport duct (18) ３ - A part of the treated material, mainly CaO, is extracted and recovered as a by-product, and fresh CaCO ３ a withdrawal duct (28) through which a source of (29) is provided to feed the calcination reactor (19); The facility comprising:

11. 11. The installation according to claim 10, further comprising at least one first heat exchanger (11) arranged in said carbonation reactor (8) to enable recovery by an external fluid of the amount of heat released during carbonation.

12. The CO removed from the first separation device (14) ２ 11. The installation according to claim 10, further comprising at least one second heat exchanger (15) arranged to allow heat recovery with an external fluid from the reduced gaseous effluent.

13. The CO recovered from the second separation device (23) ２ 11. The installation of claim 10, further comprising at least one third heat exchanger (24) arranged to allow heat recovery from the enriched gas stream with an external fluid.

14. 12. The installation according to claim 11, characterized in that the external fluid is water which passes into a steam state in the first, second and / or third heat exchanger, and the installation further comprises at least one steam turbine (12, 17, 25) to which this steam is supplied in order to generate electricity.

15. CO from the top outlet (7) of the at least one kiln. ２ 11. Installation according to claim 10, characterized in that the means for transferring the gaseous effluent (9) containing comprises a purification system (16).

16. The CaCO according to any one of claims 1 to 9. ３ - The use of said continuously withdrawn portion of the treated material consisting essentially of CaO for civil engineering, agriculture, papermaking or waste water or waste air treatment.

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