A lime production process for CO2 recovery and utilization

Abstract

A lime production process with CO2 recycling and utilization, comprising: 1) limestone material is preheated and then enters a calcination process to continue heating and complete calcination and decomposition, generating CaO and releasing CO2 gas, and the high-temperature CaO is cooled to obtain finished lime; 2) the temperature of the CO2 cooling gas is increased after the cooling process, and the high-temperature CO2 gas discharged from the cooling process is mixed with the high-temperature CO2 gas generated in the calcination process and then sent to the preheating process, and the temperature of the high-temperature flue gas is reduced after preheating to form low-temperature hot air for discharge; 3) the low-temperature hot air discharged from the preheating process is split, with one part used as a carrier gas for fuel transportation, one part used for recycling after O2 preheating, and one part mixed with the preheated O2 to form combustion-supporting air. The present invention replaces the air combustion-supporting air commonly used in the calcination process with oxygen-enriched combustion-supporting air of an O2-CO2 mixed gas, thereby avoiding the dilution of CO2 by impurities such as N2 and significantly increasing the CO2 concentration of the tail gas during the lime production process, that is, high-purity CO2 gas can be obtained while producing lime.

Description

Technical Field

[0001] The present invention relates to a lime production process, in particular to a lime production process for CO2 recovery and utilization, belonging to the technical field of lime production. Background Art

[0002] Lime is a key industrial raw material with widespread applications in metallurgy, construction, and other fields. In 2020, domestic lime production reached approximately 300 million tons, representing a substantial industry scale. However, lime production also generates significant CO2 emissions. According to statistics, producing 1 kg of lime generates 1.1 kg of CO2. Based on this estimate, the total amount of CO2 emitted into the atmosphere during my country's lime production process exceeds 300 million tons per year. Against the backdrop of industry-wide carbon reduction and peak carbon emissions, developing low-CO2 lime production processes and technologies has become a hot topic and a key challenge in this field.

[0003] At present, industrial lime production mainly adopts a simple preheating-calcining-cooling process. The heat required for the calcination stage is provided by direct heating through the combustion of fossil fuels, the refrigerant medium in the cooling stage is room temperature air, and the preheating stage uses the high-temperature flue gas generated by the calcination and cooling stages as a heat source. Such a process design can fully utilize the waste heat of the flue gas and has a high fuel utilization efficiency. However, due to the mixing of the calcination flue gas and the cooling air, there are more impurity gases such as N2 in the exhaust gas, resulting in a low CO2 concentration in the exhaust gas, generally only (20-30%), making the enrichment and capture technology of CO2 in the exhaust gas difficult and costly. As a result, the enrichment and capture of CO2 in the exhaust gas of the lime kiln at this stage is almost zero, resulting in serious greenhouse gas emissions and waste of resources.

[0004] Figure 1 This is currently the most widely used lime production process. The room-temperature (~20°C) lime raw material (limestone CaCO3) is gradually heated to a preheating temperature (~600°C) in a preheating process. Water (free or in the form of compounds) is removed from the material before entering the calcination process. During the calcination process, high-power heat is supplied to the material, rapidly heating it to approximately 1050°C. At this high temperature, the material decomposes to form CaO and releases CO2, completing the calcination process. The resulting high-temperature CaO is cooled to 100°C in a cooling process, forming the finished lime. The heat required for heating and decomposing the material in the calcination process is typically provided by the combustion heat of solid fuels such as raw coal. The cooling process uses room-temperature air as the cooling medium. The high-temperature flue gas generated by the cooling and calcination processes enters the preheating process, providing heat for preheating the material, and finally forms a low-temperature (~120°C) exhaust gas that is discharged from the system.

[0005] Under the above-mentioned process, the combustion of fossil fuels such as raw coal and the air-based cooling process introduce large amounts of impurities such as nitrogen into the flue gas system, resulting in very low CO2 concentrations in the exhaust gas exiting the system, typically only 20-30%. The cost of CO2 enrichment and capture is negatively correlated with the initial CO2 concentration in the flue gas; the lower the CO2 concentration, the higher the enrichment and capture costs. Under the existing process, the low CO2 concentration in lime production exhaust gas leads to high enrichment and capture costs, which is a major obstacle to CO2 recovery and utilization in the lime production process. Summary of the Invention

[0006] In response to the problems of large CO2 emissions, high enrichment and capture costs, and greenhouse gas emissions causing environmental pollution and waste of resources in the above-mentioned prior art lime production process, the present invention proposes a lime production process that recycles CO2. This process breaks with convention by replacing the traditional air combustion air with oxygen-enriched combustion air formed by a mixture of O2 and CO2 gases during the calcination process, thereby avoiding the dilution of CO2 by impurities such as N2 in the prior art. As a result, the high-temperature flue gas generated in the calcination process can be recycled, achieving a self-circulating supply of CO2 gas required for processes such as cooling gas, fuel delivery carrier gas, and preheating and mixing of combustion air within the system, thereby obtaining high-purity CO2 gas while producing lime. Moreover, the specific heat of CO2 gas is higher than that of N2, which can better meet the heat transfer requirements within the system.

[0007] According to an embodiment of the present invention, a lime production process with CO2 recovery and utilization is provided.

[0008] A lime production process for CO2 recovery and utilization, the process comprising the following steps:

[0009] 1) The limestone material is preheated in the preheating process and then enters the calcination process. In the calcination process, the limestone material continues to heat up and completes calcination and decomposition, generating CaO and releasing CO2 gas. The high-temperature CaO obtained by calcination is cooled in the cooling process to obtain finished lime.

[0010] 2) The temperature of the CO2 cooling gas increases after the cooling process, and then the high-temperature CO2 gas discharged from the cooling process is mixed with the high-temperature CO2 gas generated in the calcining process. The mixed high-temperature flue gas is sent to the preheating process to participate in the preheating of the limestone material. After the preheating is completed, the temperature of the high-temperature flue gas decreases to form low-temperature hot air and is discharged from the preheating process.

[0011] 3) The low-temperature hot air discharged from the preheating process is mainly composed of CO2 gas. The low-temperature CO2 gas is divided into three gases after one diversion. One part is used as the carrier gas for the fuel required for the calcination process, one part is used for recycling after O2 preheating, and one part is mixed with the preheated O2 to form the combustion-supporting air required for the calcination process.

[0012] In the present invention, in step 3), the combustion-supporting air required for the calcination process is formed by mixing CO2 gas and O2. In the combustion-supporting air of the O2-CO2 mixed gas formed after mixing, the volume proportion of O2 is 27-31%, and the volume proportion of CO2 is 69-73%.

[0013] In the present invention, step 3) also includes a secondary diversion process, specifically: the portion of CO2 gas used for O2 preheating is further diverted to form two streams of gas, one portion of which is transported to the cooling process as cooling gas, and the other portion is transported to the high-purity CO2 finished product system.

[0014] Preferably, in step 3), a portion of the CO2 gas after the secondary diversion is cooled in a water bath process and then transported to the cooling process as cooling gas.

[0015] In the present invention, in step 3), the volume proportion of the low-temperature CO2 gas discharged from the preheating process as the carrier gas for the fuel required for the calcination process is 1-5%, preferably 2-4%.

[0016] In the present invention, in step 3), the volume proportion of the low-temperature CO2 gas discharged from the preheating process and mixed with the preheated O2 to form the combustion air required for the calcination process is 20-28%, preferably 22-26%.

[0017] In the present invention, in step 3), the volume proportion of the low-temperature CO2 gas discharged from the preheating process and transported to the cooling process for use as cooling gas is 35-45%, preferably 38-42%.

[0018] In the present invention, in step 3), the volume proportion of the low-temperature CO2 gas discharged from the preheating process to the high-purity CO2 finished product system is 30-38%, preferably 32-36%.

[0019] Preferably, in step 3), the low-temperature hot air discharged from the preheating process is first subjected to a dust removal process and then split. Preferably, the dust removal process is an electrostatic precipitator or a bag dust removal process.

[0020] In the present invention, in step 1), the temperature of the limestone material after the preheating process is 500-700°C. The temperature of the calcination process is 850-1050°C. The temperature of the finished lime obtained after the cooling process is 80-100°C.

[0021] In step 2), the temperature of the CO2 cooling gas is 15-25°C. The temperature of the high-temperature CO2 gas discharged from the cooling process is 500-700°C. The temperature of the high-temperature CO2 gas generated in the calcining process is 850-1050°C. The temperature of the low-temperature hot air discharged from the preheating process is 100-150°C.

[0022] In step 3), the temperature of the O2 before preheating is 15-25°C. The temperature of the O2 after preheating is 80-120°C. The temperature of the CO2 gas after preheating is 60-100°C. The temperature of the CO2 gas after the secondary split and cooling in the water bath is 15-25°C.

[0023] In response to the problems of large CO2 emissions, high enrichment and capture costs, and environmental pollution and resource waste caused by greenhouse gas emissions in the existing lime production process, the present invention proposes a lime production process for CO2 recovery and utilization. In the scheme of the present invention, the air combustion wind commonly used in the calcination process is replaced with oxygen-enriched combustion wind formed by a mixture of O2 and CO2 gases, and the cooling medium in the cooling process is replaced by a CO2 gas flow instead of the usual air. After such an arrangement, the two streams of high-temperature CO2 gases generated in the calcination process and the cooling process are mixed and then diverted for downstream cooling gas, coal powder transportation, preheating and mixing of combustion wind, and output of high-purity CO2 products, thereby realizing the self-circulating supply of CO2 gas required for processes such as cooling gas, fuel transportation carrier gas, and preheating and mixing of combustion wind in the system, and obtaining high-purity CO2 gas by-products while producing lime.

[0024] Generally speaking, CO2 gas is not used as a combustion-supporting component. The lime production process of the present invention breaks the convention and replaces the traditional air combustion wind with oxygen-enriched combustion wind formed by mixing O2 and CO2 gases in the calcination process. First, replacing the air combustion wind with the combustion wind of O2-CO2 mixed gas can avoid the dilution of CO2 by impurities such as N2 in the air, and the product after fuel combustion is mainly CO2, further increasing the concentration of CO2 in the flue gas generated by the calcination process; secondly, compared with the air combustion wind, the combustion wind of O2-CO2 mixed gas contains inert components CO2 and N2 respectively, and the thermal properties of CO2 and N2 are different (the specific heat capacity of CO2 is about 840j / kg-K, and the specific heat capacity of N2 is about 740j / kg-K). Moreover, diatomic molecules such as N2 and O2 have weak radiation ability, while triatomic molecules such as CO2 have strong radiation ability. That is, the radiation ability of the flue gas generated by the combustion of O2-CO2 mixed gas is stronger than that of air combustion, and the heat transfer with the material is also stronger. Therefore, the combustion wind of O2-CO2 mixed gas in the present application scheme can better meet the heat transfer requirements in the lime production system and improve production efficiency.

[0025] In addition, compared with pure oxygen combustion, the present invention uses O2-CO2 mixed gas combustion to mainly have the following advantages: ① The amount of flue gas assisted by O2-CO2 mixed gas combustion is about 4 to 5 times the amount of flue gas generated by pure oxygen combustion, while the amount of flue gas generated by pure oxygen combustion is only about 1 / 5 to 1 / 4 of the amount of flue gas generated by conventional air combustion, that is, under appropriate CO2 concentration, the amount of flue gas assisted by O2-CO2 mixed gas combustion is basically equivalent to the amount of flue gas generated by conventional air combustion. Therefore, compared with pure oxygen combustion, the scheme of O2-CO2 mixed gas combustion in this application has a higher convective heat transfer intensity with the material. ② Under the conditions of O2-CO2 mixed gas combustion, the combustion flame temperature is more suitable for the calcination and decomposition of CaCO3. The suitable calcination temperature of CaCO3 is 850-1050℃. If it exceeds 1050℃, the surface of the product CaO will be over-melted, affecting the product quality. Under pure oxygen conditions, even the flame temperature of blast furnace gas with a lower calorific value exceeds 1500℃, and the flame is short and the temperature distribution is uneven, so the calcination effect is poor. However, by using the O2-CO2 mixed gas combustion-assisted method of the present application, under suitable CO2 concentration conditions, a combustion temperature similar to that of conventional air combustion-assisted combustion (for example, 1050℃) can be obtained, and the combustion flame is longer and the temperature distribution is more uniform, so the calcination effect is better. In addition, if pure oxygen is used to assist combustion, it is very likely that the oxygen will not react completely, that is, during the fuel combustion process, impurities such as O2 will be introduced to dilute the CO2; similarly, the thermal physical properties of CO2 and O2 are different, and the specific heat capacity of CO2 is significantly greater than that of O2. That is, introducing CO2 components into the combustion-supporting air can not only ensure the heat transfer of the system and improve the calcination effect, but also greatly increase the CO2 concentration in the tail gas of the lime production process, and realize the recycling and utilization of CO2 gas while producing lime, thereby effectively overcoming the problems of large CO2 emissions and waste of resources in the existing lime production process.

[0026] As mentioned above, the combustion-supporting air of the O2-CO2 mixture in the present invention is compared with the combustion-supporting air of air, and the inert components of the two are CO2 and N2 respectively, and the thermal properties of CO2 and N2 are different. Under this premise, considering the control of the combustion temperature, the inventors found in practice that in the porous medium space combustion such as the lime kiln, in order to maintain a combustion temperature similar to that of air combustion, maintain a suitable combustion atmosphere, and ensure the calcination effect and product quality, in the combustion-supporting air of the O2-CO2 mixture, the concentration of O2 (volume share) is generally maintained at 27-31%, and the volume share of CO2 is 69-73%. Among them, the specific concentration value is related to the type of fuel and the calorific value. For example, when using blast furnace gas, a typical fuel on a lime kiln, the concentration of O2 is about 27-28%.

[0027] In the present invention, since the air combustion wind commonly used in the calcining process is changed to an oxygen-enriched combustion wind formed by a mixture of O2 and CO2 gases, and the cooling medium of the cooling process is changed from commonly used air to a CO2 gas flow, the main component of the high-temperature flue gas generated by both the calcining process and the cooling process is CO2 gas, that is, the dilution of CO2 by impurities such as O2 and N2 introduced in the prior art during fuel combustion and air-based cooling is avoided, the enrichment of CO2 gas is achieved, and the CO2 concentration in the lime production tail gas is greatly improved. Therefore, the present application can use the high-temperature flue gas (i.e., high-purity CO2 gas) generated by the calcining process and the cooling process for fuel transportation, mixing of combustion wind, cooling gas, and output of high-purity CO2 finished products after preheating the limestone material through flue gas circulation. The present application makes full use of the waste heat of flue gas during the flue gas circulation process. For example, before CO2 gas is mixed with O2 to form combustion-supporting air, the CO2 gas that will be used as cooling gas and high-purity CO2 finished product is first used to preheat O2. The preheated O2 is then mixed with the CO2 gas used to mix with the combustion-supporting air to form combustion-supporting air with a certain temperature, thereby improving the combustion-supporting effect, reducing fuel consumption, and improving production efficiency. The CO2 gas that has been cooled by heat exchange is then output as a product or transported to the cooling process. That is, while achieving the self-circulating supply of CO2 gas required for each process in the system, the waste heat of the flue gas is maximized and the effect of each process is guaranteed. In addition, the present application also transports the CO2 gas that has been cooled by heat exchange with O2 to the cooling process after cooling in a water bath, thereby enhancing the cooling effect on the high-temperature CaO generated by calcination to ensure that the finished lime is completely cooled.

[0028] Under the premise of making full use of the waste heat of flue gas in the above-mentioned flue gas circulation process and reducing the temperature of cooling gas to ensure complete cooling of finished lime, the fuel consumption, cooling air volume, etc. in the present invention are significantly reduced. Based on this, the present invention divides the low-temperature CO2 gas discharged from the preheating process into four air flows in proportion, among which the volume proportion of CO2 gas used for coal powder transportation is 1-5% (preferably 2-4%, for example 3%), the volume proportion of CO2 gas used for combustion air mixing (to ensure that the oxygen proportion in the mixed combustion air is 27% and CO2 proportion is 73%, so as to maintain a suitable combustion atmosphere) is 20-28% (preferably 22-26%, for example 24%), the volume proportion of CO2 gas used for cooling high-temperature CaO is 35-45% (preferably 38-42%, for example 40%), and the volume proportion of CO2 gas directly produced as a high-purity product is 30-38% (preferably 32-36%, for example 33%).

[0029] In the lime production process for CO2 recovery and utilization described in this application, Figure 2As shown in the figure, the main process includes three main processes acting on the material flow, namely preheating, calcining and cooling, and seven auxiliary processes acting on the air flow, namely primary mixing, dust removal, primary diversion, heat exchange, secondary mixing, secondary diversion and water bath. The details are as follows:

[0030] Main process (material flow process):

[0031] Preheating: Using high-temperature air (approximately 850°C) generated by the calcination and cooling processes, the limestone blocks are uniformly heated to approximately 600°C. Calcination: Using high-temperature flue gas generated by the combustion of solid fuels such as raw coal, the limestone is rapidly heated to the calcination temperature (1050°C), rapidly decomposing the CaCO3 to form CaO and release CO2. Cooling: The high-temperature CaO blocks obtained from calcination are cooled to below 100°C using a CO2 flow at approximately 20°C, resulting in finished lime CaO blocks.

[0032] Auxiliary process (air flow process):

[0033] Primary mixing: The two high-temperature CO2 gases (1050°C and approximately 600°C, respectively) generated by the calcination and cooling processes are evenly mixed. The mixed gas temperature reaches approximately 850°C. The mixed high-temperature flue gas is used to preheat the room-temperature limestone (approximately 20°C). Dust removal: After the preheating process, the temperature of the high-temperature flue gas drops from 850°C to approximately 120°C. At this point, the flue gas is mixed with a large amount of CaCO3 and CaO dust. Before entering the downstream process, the dust is removed through an electrostatic precipitator or bag filter. Primary diversion: The flue gas (primarily composed of CO2 gas) after dust removal and purification is diverted into three streams, which are used for downstream pulverized coal transportation, oxygen preheating, and combustion air mixing. Specifically, a portion of the CO2 gas is used as the carrier gas for pulverized coal transportation, a portion of the CO2 gas is sent to the downstream heat exchange process to preheat the pure oxygen used for combustion, and the remaining CO2 gas is used as a component of the combustion air and mixed with the preheated O2 (i.e., the secondary mixing process). Heat Exchange: Industrial pure oxygen (normal temperature, approximately 20°C) is exchanged with the primary diverted flue gas, raising the oxygen temperature to approximately 100°C and further cooling the flue gas to approximately 80°C. Secondary Diversion: The flue gas is split into two streams, one of which is fed into the downstream water bath process, and the other is directly produced as high-purity CO2 product. Water Bath: After passing through the water bath, the secondary diverted flue gas' temperature is further reduced to approximately 20°C before being fed as cooling gas to the cooling process.

[0034] Compared with the prior art, the present invention has the following beneficial technical effects:

[0035] 1. The present invention changes the air combustion air commonly used in the calcination process into an oxygen-enriched combustion air formed by a mixture of O2 and CO2 gases, and at the same time changes the cooling medium in the cooling process from common air to CO2 flow, thereby avoiding the dilution of CO2 by impurities such as N2 in the prior art, and greatly improving the CO2 concentration of the tail gas in the lime production process, that is, high-purity CO2 gas by-product can be obtained while producing lime.

[0036] 2. The present invention mixes the two streams of high-temperature CO2 gases generated in the calcination process and the cooling process and then diverts them for use in downstream cooling gas, coal powder transportation, preheating and mixing of combustion-supporting air, and output of high-purity CO2 products. By enriching and circulating the CO2 gas, the self-circulating supply of CO2 gas required for processes such as cooling gas, fuel transportation carrier gas, and preheating and mixing of combustion-supporting air in the system is achieved, and high-purity CO2 gas is obtained at the same time, that is, resource utilization of CO2 gas is achieved, thereby avoiding the problems of large CO2 emissions and waste of resources in the existing lime production process.

[0037] 3. The present invention breaks the convention and adopts a combustion-supporting air of an O2-CO2 mixed gas, and limits the concentration of the two gases in the combustion-supporting air, thereby avoiding the dilution of CO2 by impurity components such as N2 or O2 in the existing technology. Moreover, the specific heat capacity of CO2 is greater than the specific heat capacity of N2 and O2. That is, the introduction of CO2 components into the combustion-supporting air can not only ensure the heat transfer of the system, but also greatly increase the CO2 concentration in the exhaust gas during the lime production process, thereby realizing the recycling and utilization of CO2 gas while producing lime. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of the lime production process in the prior art;

[0039] Figure 2 This is a flow chart of the lime production process using CO2 recovery and utilization in Application Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The technical solutions of the present invention are illustrated below with examples, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0041] According to an embodiment of the present invention, a lime production process with CO2 recovery and utilization is provided.

[0042] A lime production process for CO2 recovery and utilization, the process comprising the following steps:

[0043] 1) The limestone material is preheated in the preheating process and then enters the calcination process. In the calcination process, the limestone material continues to heat up and completes calcination and decomposition, generating CaO and releasing CO2 gas. The high-temperature CaO obtained by calcination is cooled in the cooling process to obtain finished lime.

[0044] 2) The temperature of the CO2 cooling gas increases after the cooling process, and then the high-temperature CO2 gas discharged from the cooling process is mixed with the high-temperature CO2 gas generated in the calcining process. The mixed high-temperature flue gas is sent to the preheating process to participate in the preheating of the limestone material. After the preheating is completed, the temperature of the high-temperature flue gas decreases to form low-temperature hot air and is discharged from the preheating process.

[0045] 3) The low-temperature hot air discharged from the preheating process is mainly composed of CO2 gas. The low-temperature CO2 gas is divided into three gases after one diversion. One part is used as the carrier gas for the fuel required for the calcination process, one part is used for recycling after O2 preheating, and one part is mixed with the preheated O2 to form the combustion-supporting air required for the calcination process.

[0046] In the present invention, in step 3), the combustion-supporting air required for the calcination process is formed by mixing CO2 gas and O2. In the combustion-supporting air of the O2-CO2 mixed gas formed after mixing, the volume proportion of O2 is 27-31%, and the volume proportion of CO2 is 69-73%.

[0047] In the present invention, step 3) also includes a secondary diversion process, specifically: the portion of CO2 gas used for O2 preheating is further diverted to form two streams of gas, one portion of which is transported to the cooling process as cooling gas, and the other portion is transported to the high-purity CO2 finished product system.

[0048] Preferably, in step 3), a portion of the CO2 gas after the secondary diversion is cooled in a water bath process and then transported to the cooling process as cooling gas.

[0049] In the present invention, in step 3), the volume proportion of the low-temperature CO2 gas discharged from the preheating process as the carrier gas for the fuel required for the calcination process is 1-5%, preferably 2-4%.

[0050] In the present invention, in step 3), the volume proportion of the low-temperature CO2 gas discharged from the preheating process and mixed with the preheated O2 to form the combustion air required for the calcination process is 20-28%, preferably 22-26%.

[0051] In the present invention, in step 3), the volume proportion of the low-temperature CO2 gas discharged from the preheating process and transported to the cooling process for use as cooling gas is 35-45%, preferably 38-42%.

[0052] In the present invention, in step 3), the volume proportion of the low-temperature CO2 gas discharged from the preheating process to the high-purity CO2 finished product system is 30-38%, preferably 32-36%.

[0053] Preferably, in step 3), the low-temperature hot air discharged from the preheating process is first subjected to a dust removal process and then split. Preferably, the dust removal process is an electrostatic precipitator or a bag dust removal process.

[0054] In the present invention, in step 1), the temperature of the limestone material after the preheating process is 500-700°C. The temperature of the calcination process is 850-1050°C. The temperature of the finished lime obtained after the cooling process is 80-100°C.

[0055] In step 2), the temperature of the CO2 cooling gas is 15-25°C. The temperature of the high-temperature CO2 gas discharged from the cooling process is 500-700°C. The temperature of the high-temperature CO2 gas generated in the calcining process is 850-1050°C. The temperature of the low-temperature hot air discharged from the preheating process is 100-150°C.

[0056] In step 3), the temperature of the O2 before preheating is 15-25°C. The temperature of the O2 after preheating is 80-120°C. The temperature of the CO2 gas after preheating is 60-100°C. The temperature of the CO2 gas after the secondary split and cooling in the water bath is 15-25°C.

[0057] Example 1

[0058] A lime production process for CO2 recovery and utilization, the process comprising the following steps:

[0059] 1) The limestone material is preheated in the preheating process and then enters the calcination process. In the calcination process, the limestone material continues to heat up and completes calcination and decomposition, generating CaO and releasing CO2 gas. The high-temperature CaO obtained by calcination is cooled in the cooling process to obtain finished lime.

[0060] 2) The temperature of the CO2 cooling gas increases after the cooling process, and then the high-temperature CO2 gas discharged from the cooling process is mixed with the high-temperature CO2 gas generated in the calcining process. The mixed high-temperature flue gas is sent to the preheating process to participate in the preheating of the limestone material. After the preheating is completed, the temperature of the high-temperature flue gas decreases to form low-temperature hot air and is discharged from the preheating process.

[0061] 3) The low-temperature hot air discharged from the preheating process is mainly composed of CO2 gas. The low-temperature CO2 gas is divided into three gases after one diversion. One part is used as the carrier gas for the fuel required for the calcination process, one part is used for recycling after O2 preheating, and one part is mixed with the preheated O2 to form the combustion-supporting air required for the calcination process.

[0062] Example 2

[0063] A lime production process for CO2 recovery and utilization, the process comprising the following steps:

[0064] 1) The limestone material is preheated in the preheating process and then enters the calcination process. In the calcination process, the limestone material continues to heat up and completes calcination and decomposition, generating CaO and releasing CO2 gas. The high-temperature CaO obtained by calcination is cooled in the cooling process to obtain finished lime.

[0065] 2) The temperature of the CO2 cooling gas increases after the cooling process, and then the high-temperature CO2 gas discharged from the cooling process is mixed with the high-temperature CO2 gas generated in the calcining process. The mixed high-temperature flue gas is sent to the preheating process to participate in the preheating of the limestone material. After the preheating is completed, the temperature of the high-temperature flue gas decreases to form low-temperature hot air and is discharged from the preheating process.

[0066] 3) The low-temperature hot air discharged from the preheating process is mainly composed of CO2 gas. The low-temperature CO2 gas is divided into three gases after one diversion. One part is used as the carrier gas for the fuel required for the calcination process, one part is used for recycling after O2 preheating, and one part is mixed with the preheated O2 to form the combustion-supporting air required for the calcination process.

[0067] In step 3), a secondary diversion process is also included, specifically: the part of CO2 gas after being used for O2 preheating is further diverted to form two gases, one part is transported to the cooling process as cooling gas, and the other part is transported to the high-purity CO2 finished product system.

[0068] Example 3

[0069] Example 2 was repeated, except that in this example, blast furnace gas was used as the fuel for the calcination process. In step 3), the combustion air required for the calcination process was formed by mixing CO2 gas with O2. In the resulting O2-CO2 mixture, the volume fraction of O2 was 28% and the volume fraction of CO2 was 72%.

[0070] Example 4

[0071] Example 2 was repeated, except that in this example, the fuel required for the calcination process was raw coal. In step 3), the combustion air required for the calcination process was formed by mixing CO2 gas and O2. In the resulting O2-CO2 mixture, the volume of the combustion air was 27% by volume of O2 and 73% by volume of CO2.

[0072] Example 5

[0073] Example 4 was repeated, except that in step 3), a portion of the CO2 gas after the secondary diversion was cooled in the water bath process and then transported to the cooling process as cooling gas.

[0074] Example 6

[0075] Example 5 was repeated, except that in step 3), the low-temperature hot air discharged from the preheating process was first subjected to electrostatic precipitator treatment and then diverted.

[0076] Example 7

[0077] Example 5 was repeated, except that in step 3), the low-temperature hot air discharged from the preheating process was first subjected to bag dust removal treatment and then diverted.

[0078] Example 8

[0079] Example 7 was repeated, except that in step 1), the temperature of the limestone material after the preheating process was 612° C. The temperature of the calcination process was 1045° C. The temperature of the finished lime obtained after the cooling process was 94° C.

[0080] In step 2), the temperature of the CO2 cooling gas was 25°C. The temperature of the high-temperature CO2 gas discharged from the cooling process was 619°C. The temperature of the high-temperature CO2 gas generated in the calcination process was 1045°C. The temperature of the low-temperature hot air discharged from the preheating process was 126°C.

[0081] In step 3), the temperature of the O2 before preheating was 25°C. The temperature of the O2 after preheating was 103°C. The temperature of the CO2 gas after preheating was 82°C. The temperature of the CO2 gas after the secondary split and cooling in the water bath was 25°C.

[0082] Example 9

[0083] Example 8 was repeated, except that in step 3), of the low-temperature CO2 gas discharged from the preheating process, the volume proportion of the CO2 gas used as a carrier gas for the fuel required for the calcination process was 3%, the volume proportion of the CO2 gas mixed with the preheated O2 to form the combustion-supporting air required for the calcination process was 22%, the volume proportion of the CO2 gas transported to the cooling process for use as cooling gas was 41%, and the volume proportion of the CO2 gas transported to the high-purity CO2 finished product system was 34%.

[0084] Application Example 1

[0085] like Figure 2 As shown, a lime production process for CO2 recovery and utilization comprises the following steps:

[0086] 1) 1.7 tons of limestone material with an initial temperature of 20°C is preheated to about 600°C and then enters the calcination process. In the calcination process, the limestone material is further heated to 1050°C to complete calcination and decomposition, generating CaO and releasing CO2 gas. The high-temperature CaO obtained by calcination is cooled to about 95°C in a cooling process to obtain about 1 ton of finished lime.

[0087] 2) 700Nm 3 / t-CaO CO2 cooling gas (20 ℃) ​​after the cooling process to increase the temperature to about 600 ℃, and then the high temperature CO2 gas discharged from the cooling process and the high temperature CO2 gas generated in the calcination process (1050Nm 3 / t-CaO, about 1050℃) are mixed, and the mixed high-temperature flue gas (1750Nm 3 / t-CaO, about 850℃) is sent to the preheating process to participate in the preheating of limestone materials. After the preheating is completed, the temperature of the high-temperature flue gas is reduced from 850℃ to about 120℃ to form low-temperature hot air, which is discharged from the preheating process.

[0088] 3) The low-temperature hot air discharged from the preheating process is electrostatically precipitated to remove the mixed CaCO3 and CaO dust in the flue gas, and the clean flue gas with a temperature of about 110°C is obtained, whose main component is CO2 gas. The low-temperature CO2 gas is split into three gases after a split, which are used for downstream pulverized coal transportation, oxygen preheating, and combustion air mixing. Among them, 60Nm 3 / t-CaO CO2 gas is used as the carrier gas for the raw coal required for the calcination process, 1260Nm 3 / t-CaO CO2 gas enters the downstream heat exchange process, preheating the O2 (160Nm 3 / t-CaO, 20℃), remaining 430Nm 3 The CO2 gas from the calcined CaO is mixed with preheated O2 (raised to approximately 100°C after heat exchange with CO2) to form the combustion air required for the calcination process. The volume ratio of the combustion air is 27% by volume of O2 and 73% by volume of CO2.

[0089] Then, the CO2 gas used for O2 preheating (the temperature is reduced to about 80℃ after heat exchange with O2) is split twice to form two gases, of which 700Nm 3 The CO2 gas of / t-CaO is cooled to about 20℃ in a water bath and then transported to the cooling process as cooling gas, 560Nm 3 / t-CaO CO2 gas is transported to the high-purity CO2 finished product system.

Claims

1. A lime production process for CO2 recovery and utilization, the process comprising the following steps: 1) The limestone material is preheated in a preheating process and then enters a calcination process. In the calcination process, the limestone material continues to heat up and completes calcination and decomposition, generating CaO and releasing CO2 gas. The CaO obtained by calcination is cooled in a cooling process to obtain finished lime; 2) The temperature of the CO2 cooling gas increases after the cooling process. The CO2 gas discharged from the cooling process is then mixed with the CO2 gas generated in the calcining process. The mixed flue gas is sent to the preheating process to participate in the preheating of the limestone material. After the preheating is completed, the flue gas temperature decreases to form hot air and is discharged from the preheating process. 3) The hot air discharged from the preheating process is mainly composed of CO2 gas. The CO2 gas is divided into three gases after the first diversion. The volume proportion of the CO2 gas is 1-5% and used as the carrier gas for the fuel required for the calcination process. The volume proportion of the CO2 gas is 20-28% and mixed with the preheated O2 to form the combustion air required for the calcination process. The remaining part is used for O2 preheating and then recycled. The CO2 gas used for O2 preheating is further divided into two gases after the second diversion. The volume proportion of the CO2 gas is 35-45% and is transported to the cooling process as cooling gas, and the volume proportion of the CO2 gas is 30-38% and is transported to the CO2 finished product system. In step 3), the combustion-supporting air required for the calcination process is formed by mixing CO2 gas and O2. In the combustion-supporting air of the O2-CO2 mixed gas formed after mixing, the volume proportion of O2 is 27~31%, and the volume proportion of CO2 is 69~73%.

2. The lime production process according to claim 1, wherein: In step 3), a portion of the CO2 gas after the secondary diversion is cooled in a water bath process and then transported to the cooling process as cooling gas.

3. The lime production process according to claim 1, characterized in that: In step 3), the volume of the CO2 gas discharged from the preheating process, which is used as the carrier gas for the fuel required for the calcination process, accounts for 2-4% of the CO2 gas.

4. The lime production process according to claim 1, characterized in that: In step 3), the volume of the CO2 gas discharged from the preheating process and mixed with the preheated O2 to form the combustion air required for the calcination process accounts for 22~26%.

5. The lime production process according to claim 1, characterized in that: In step 3), the volume of the CO2 gas discharged from the preheating process and transported to the cooling process for use as cooling gas accounts for 38-42%.

6. The lime production process according to claim 1, characterized in that: In step 3), the volume of the CO2 gas discharged from the preheating process that is transported to the CO2 finished product system accounts for 32-36%.

7. The lime production process according to any one of claims 1 to 6, characterized in that: In step 3), the hot air discharged from the preheating process is first subjected to dust removal treatment in the dust removal process and then diverted.

8. The lime production process according to claim 7, characterized in that: The dust removal process is electrostatic precipitator or bag dust removal.

9. The lime production process according to claim 2, characterized in that: In step 1), the temperature of the limestone material after the preheating process is 500-700°C; the temperature of the calcination and decomposition process is 850-1050°C; the temperature of the finished lime obtained after the cooling process is 80-100°C; In step 2), the temperature of the CO2 cooling gas is 15-25°C; the temperature of the CO2 gas discharged from the cooling process is 500-700°C; the temperature of the CO2 gas generated in the calcining process is 850-1050°C; the temperature of the hot air discharged from the preheating process is 100-150°C; In step 3), the temperature of O2 before preheating is 15~25℃; the temperature of O2 after preheating is 80~120℃; the temperature of the CO2 gas after preheating O2 is 60~100℃; the temperature of the CO2 gas after secondary diversion and cooling in a water bath process is 15~25℃.

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