Lime released carbon dioxide storage
By converting the carbon dioxide released during the cement production process into calcium oxalate, the problem of carbon dioxide difficult to capture and store in cement production is solved, and the stable storage of CO2 and low-cost transportation is achieved. It is suitable for cement production itself, reducing emissions and transportation costs. .
Patent Information
- Application Number
- CN202380035863.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-04-27
- Filing Date
- 2023-04-21
- Publication Date
- 2024-12-06
AI Technical Summary
The carbon dioxide released during cement production is difficult to effectively capture and store, resulting in environmental pollution and high transportation costs.
The carbon dioxide released in limestone is converted into calcium oxalate, and clinker is generated through high temperature treatment, and it is contacted with hydrogen to form formate, and then heat treatment is carried out to produce calcium oxalate, achieving stable storage and utilization of CO2.
Effectively prevent carbon dioxide from being released into the environment, reduce transportation costs, and convert CO2 into solid calcium oxalate that is easy to store and transport. It is suitable for cement production itself and reduces carbon dioxide emissions during cement production.
Abstract
Description
Technical Field
[0001] The present invention relates to a method for converting carbon dioxide (CO2) released by limestone during cement production into calcium oxalate. In particular, the produced calcium oxalate provides a means of storing CO2 and preventing CO2 from being released into the environment. Background Art
[0002] Carbon dioxide (CO2) is a greenhouse gas that accumulates in the atmosphere and causes global warming problems and unwanted climate change. Most of the industrial processes being carried out internationally unintentionally release significant amounts of CO2 in the exhaust gases they emit. This CO2 is accumulating in the environment, leading to increased temperatures, which in turn leads to uncontrollable climate change such as melting of polar ice caps, rising global sea levels, floods, etc.
[0003] Making cement from raw materials such as lime (calcium carbonate) and calcium hydroxide is an example of a process that emits at least 200kg or 300kg of carbon dioxide for every 1000kg of cement produced. This amount of carbon dioxide is not only harmful to the environment, but also a waste of raw materials that could be used for other purposes.
[0004] One way to address this problem is to reduce emissions by making cement production more efficient or by producing less cement. However, this is a difficult task given the growth of the global construction industry and the resulting increase in CO2 emissions. In addition, it is very costly to collect the CO2 released during cement production and transport it away from the production site, as the transportation of CO2 is not only generally expensive, but also a logistical nightmare.
[0005] Some methods disclosed in the art attempt to solve this problem. For example, CN109516912A discloses a method for utilizing and sealing carbon dioxide produced by any method known in the art. In particular, in CN109516912A, sodium carbonate is used as a chemical absorbent for CO2 to produce bicarbonate. The method has the disadvantage that a large amount of sodium carbonate must be present near the cement plant. FR-A-2669918 and JP 2003095711A attempt to use other starting materials from non-carbonate sources to make cement. However, in addition to the considerable cost of these methods, the final disposal problem of the produced carbon dioxide remains unacceptable.
[0006] WO02083591A describes a zero-emission operation of a cement plant. The carbon dioxide produced combines with calcium chloride (or other metal oxides / chlorides from sea salt or waste) to form calcium carbonate. The newly formed calcium carbonate is then processed again. Calcium oxide is produced from calcium chloride and the carbon dioxide produced is not discharged and remains in the circuit. However, this method is not only costly, but also has the disadvantage that the carbonate produced cannot usually be processed further.
[0007] EP2257362 provides an alternative solution in which carbon monoxide and / or carbon dioxide produced during cement production can be used to produce at least one oxalate. However, in the disclosed method, carbon monoxide must always be present in a higher concentration than carbon dioxide, which is not always the case in cement production.
[0008] Therefore, there is a need in the art to not only capture the CO2 emitted during cement production, but also to store the CO2 in a form that makes it both available for other uses and easy to transport. Summary of the invention
[0009] The present invention seeks to solve the above problems by providing a method for converting CO2 released from limestone during cement production into at least one oxalate. In particular, the oxalate produced is calcium oxalate. This method is particularly advantageous because CO2 is not released into the environment, and the CO2 is converted into solid oxalate without transporting the CO2 separated from the waste gas to other places, which is easier and cheaper to transport than CO2. In particular, oxalates contain a large amount of CO2 and are easy to store or transport. In addition, this is the lowest energy conversion of CO2, because only one H2 molecule is consumed for every two CO2 molecules. In particular, calcium oxalate is known to bind two moles of carbon per mole of calcium in an extremely stable form. This makes it possible to remove CO2 released from the waste gas during cement production efficiently and reliably according to any aspect of the present invention and convert CO2 into stable calcium oxalate. Compared with at least calcium carbonate, calcium oxalate, which is less water-soluble, is an extremely stable compound suitable for the production of sand and / or stone. Calcium oxalate can also be used as an additive for adhesives or hydraulic binders.
[0010] According to one aspect of the present invention, there is provided a method for producing calcium oxalate from calcium carbonate, the method comprising the following steps:
[0011] (a) Production of CO2 from calcium carbonate;
[0012] (b) contacting the CO2 from step (a) with hydrogen to produce at least one formate; and
[0013] (c) thermally treating the formate from step (b) to produce calcium oxalate and hydrogen.
[0014] Calcium carbonate is also called limestone or lime. Since lime is abundant and relatively cheap, it is desirable to be able to treat high calcium lime with a minimum of additives so that it can be dead burned so that it can be used as a high temperature refractory without hydration or delayed slaking. Of course, it is also desirable to be able to use additives that do not substantially increase the cost of the final refractory material. Therefore, limestone is used in the production of cement and / or quicklime. More precisely, calcium oxide CaO is called quicklime or burnt lime, and calcium hydroxide Ca(OH)2 is called slaked lime. Lime suitable for the method of any aspect of the present invention relates to calcium carbonate (limestone), which is the starting material for cement and / or burnt lime production. The method according to any aspect of the present invention provides a method for converting lime into burnt lime and calcium oxalate using hydrogen. The method according to any aspect of the present invention provides a CO2 absorbent that not only prevents the CO2 generated in the cement production process from being discharged into the environment, but also allows the generated CO2 to be used in cement production itself. The CO2 captured in the form of calcium oxalate is also close to the production site, so transportation costs can be reduced.
[0015] In step (a) according to any aspect of the present invention, calcium carbonate is heated to produce CO2. In particular, clinker is produced by pyro-processing. Calcium carbonate is burned at high temperatures, first calcining the material and then clinkerizing it to produce clinker. More particularly, the calcination of limestone occurs at relatively moderate temperatures, typically about 900°C to 1100°C. The calcination of limestone refers to the thermal decomposition of limestone to produce quicklime / undigested lime (calcium oxide) and CO2. The reaction of the thermal decomposition of calcium carbonate can be expressed as:
[0016]
[0017] In another embodiment, CO2 can be produced from CaCO3 by contacting CaCO3 with at least one acid. In particular, the acid can be selected from HCl, HNO3 and H2SO4, acetic acid, formic acid, succinic acid and oxalic acid.
[0018] The CO2 produced in step (a) is first separated and then contacted with hydrogen to produce a formate. Any method known in the art can be used to produce a formate from CO2. In particular, catalytic means can be used to produce at least one formate from CO2. The formate can be an alkali metal formate, wherein the base is contacted with at least one base to produce an alkali metal formate. In particular, CO2 is hydrogenated to produce formic acid. The formic acid will be neutralized by sodium hydroxide or potassium hydroxide to produce an alkali metal formate. The base can be selected from barium hydroxide, sodium hydroxide, ammonium hydroxide, calcium hydroxide, lithium hydroxide and potassium hydroxide. More particularly, the base contacted with CO2 can be at least sodium hydroxide or potassium hydroxide, and the resulting formate produced can be sodium formate or potassium formate. Even more particularly, the base can be sodium hydroxide, and a saturated sodium formate solution can be produced at about 210°C under high pressure. The reaction equation is:
[0019] NaOH+CO2+H2→HCOONa+H2O
[0020] Depending on the base used, different formates can be formed. For example, when KOH is used, potassium formate is generated; when barium hydroxide is used, barium formate is generated, and so on. In one embodiment, calcium hydroxide can be used as the base, and the following reaction occurs:
[0021] Ca(OH)2+2CO2+2H2→(HCOO)2Ca+2H2O
[0022] In the process of catalytic production of formate from CO2, any method known in the art can be used. In addition, any catalyst known in the art to work in this method can be used. Examples of catalysts that can work in step (b) are disclosed at least in Al-Tamreh SAChem Electro Chem (2021), 8: 3207–3220. In addition, Chan, WL at least provides a bismuth-based catalyst that can also be used to produce formate from CO2 in ACS Catal. 2018, 8 (2): 931–937.
[0023] Alternatively, biotechnological methods can be used to produce formate from CO 2 . This method is disclosed at least by Alissandratos, A., in Bioresour Technol. 2014, 164: 7-1 and by Maia, LB in JJG Moura et al. (eds.), Enzymes for Solving Humankind's Problems.
[0024] In the method according to any aspect of the present invention, hydrogen is used as a reducing agent in step (b). In particular, hydrogen is used as a reducing agent in both catalytic and biotechnological methods of preparing formate from CO2.
[0025] According to any aspect of the present invention, in particular the calcium oxalate prepared in step (c) may be calcium oxalate hydrate.
[0026] The hydrogen released in step (c) is recycled to step (b) for the production of formate. Therefore, the hydrogen required for implementing the method according to any aspect of the present invention is very small. In particular, since the amount of hydrogen required for implementing the method according to any aspect of the present invention is not high, hydrogen can be produced on site. The production of hydrogen can be carried out by windmills and / or solar panels in combination with electrolyzers. In another embodiment, hydrogen can be produced using waste incineration, which also converts limestone into CaO by partial oxidation.
[0027] The thermal treatment of the formate to produce oxalate in step (c) involves heating the formate at a temperature of about 360° C. to 420° C. In one embodiment, the heating is done rapidly so that the reaction proceeds efficiently. More particularly, according to any aspect of the invention, the formate is heated at a temperature of about 360°C to 390°C, 360°C to 385°C, 360°C to 380°C, 360°C to 375°C, 360°C to 365°C, 365°C to 390°C, 365°C to 385°C, 365°C to 380°C, 365°C to 375°C, 365°C to 370°C, 370°C to 390°C, 370°C to 385°C, 370°C to 380°C, 370°C to 375°C, 375°C to 390°C, 375°C to 385°C, 375°C to 380°C, 380°C to 390°C or 385°C to 390°C. In one embodiment, the thermal treatment of the formate in step (c) is conducted at at least or about 360° C., 365° C., 370° C., 375° C., 380° C., 385° C., or 390° C. These lower temperatures better achieve higher selectivity for desired products than temperatures previously conducted.
[0028] Specifically, sodium formate undergoes the following reaction to form sodium oxalate:
[0029] 2HCOONa→NaOOC-COONa+H2
[0030] The sodium oxalate obtained after the above steps can then be converted to calcium oxalate by reacting the sodium oxalate with calcium hydroxide to form calcium oxalate:
[0031] Na2C2O4+Ca(OH)2-CaC2O4+2NaOH
[0032] In this embodiment, sodium oxalate or potassium oxalate is converted to calcium oxalate, which precipitates, releasing sodium hydroxide or potassium hydroxide. In particular, calcium oxalate precipitates because its solubility is much lower than that of sodium oxalate or potassium oxalate.
[0033] In another embodiment, calcium formate undergoes the following reaction to form calcium oxalate:
[0034] (HCOO)2Ca→CaC2O4+H2
[0035] The hydrogen produced according to this process may then be recycled in step (a) and the calcium oxalate may be separated using methods known in the art.
[0036] In particular, no or measurable amounts of CO are present in any of steps (a), (b) and (c).
[0037] According to another aspect of the present invention, there is provided a method for storing CO2, the method comprising the following steps:
[0038] (a) contacting the separated CO2 with hydrogen to produce at least one formate; and
[0039] (b) thermally treating the formate from step (a) to produce calcium oxalate and hydrogen
[0040] The CO2 is produced by calcium carbonate.
[0041] The oxalate in step (b) may be calcium oxalate hydrate.
[0042] In particular, according to any aspect of the present invention, CO2 is produced during the production of burnt lime and / or cement. In particular, CO2 is stored in close proximity to a CO2 source and / or a calcium carbonate source.
Claims
1. A method for producing calcium oxalate from calcium carbonate, the method comprising the following steps: (a) Producing CO2 by heating calcium carbonate; (b) contacting the CO2 from step (a) with hydrogen to produce at least one formate; and (c) thermally treating the formate of step (b) to produce calcium oxalate and hydrogen Wherein the heat treatment of the formate in step (c) involves heating the formate at a temperature of about 360°C to 390°C to produce oxalate.
2. The method according to claim 1, wherein the calcium oxalate in step (c) is calcium oxalate hydrate.
3. The process according to claim 1 or 2, wherein the formate in step (b) is produced by catalytic or biotechnological means using hydrogen as a reducing agent.
4. A process according to any one of the preceding claims, wherein the hydrogen released in step (c) is recycled to step (b) to produce formate.
5. A process according to any one of the preceding claims, wherein the formate in step (b) is produced by catalytic means, wherein the CO2 is contacted with at least one base in the presence of hydrogen.
6. A process according to any one of the preceding claims, wherein the formate produced in step (b) is an alkali metal formate.
7. A process according to any one of the preceding claims, wherein the formate produced in step (b) is sodium formate or potassium formate.
8. A method according to any one of the preceding claims, wherein no or measurable amounts of CO are present in any of steps (a), (b) and (c).
9. A method for storing CO2, the method comprising the following steps: (a) contacting the separated CO2 with hydrogen to produce at least one formate; and (b) thermally treating the formate of step (a) to produce calcium oxalate and hydrogen wherein the CO2 is produced from calcium carbonate; and Wherein the heat treatment of the formate in step (c) involves heating the formate at a temperature of about 360°C to 390°C to produce oxalate.
10. The method according to claim 9, wherein the oxalate in step (b) is calcium oxalate hydrate.
11. The method according to claim 9 or 10, wherein the CO2 is generated during the production of burnt lime and / or cement.
12. The method according to any one of claims 9 to 11, wherein the CO2 is stored in close proximity to a CO2 source and / or a calcium carbonate source.
13. The method according to any one of claims 9 to 12, wherein CO is absent or not present in measurable amounts in step (a).