Limestone production

Abstract

A recycling and waste management method is disclosed that receives municipal solid waste (MSW) having a high organic content to form a supercritical water oxidation (SCWO)-based self-sustaining hydrothermal mineralization (HTM) process to receive supercritical steam and carbon dioxide having power generation potential and then form calcium carbonate suitable for use in concrete production. Hydrothermal mineralization (HTM) provides for rapid elimination of organic waste while producing emission-free and thermally stable cementitious additives for acting as carbon sinks. Hydrothermal mineralization (HTM) provides a fast handling approach for organic waste, a green power source, and a final product that can be combined with traditional and alternative cement production to reduce cement production carbon footprint.

Description

[0001] Inventors: Andrew R. Teixeira, Michael T. Timko, and David Kenney Statement on federally funded research and development: This invention was developed with the support of the U.S. government under Contract No. DE-EE0009507 issued by the Department of Energy. The government owns certain rights to this invention. Background Technology

[0002] In recent decades, carbon dioxide emissions have received considerable attention due to their harmful environmental impact. In particular, two industries are major sources of carbon dioxide emissions: (1) municipal and industrial solid waste management and (2) cement production. Municipal waste contains a large amount of organic material and is often referred to as organic municipal solid waste (MSW). Cement production is the most energy-intensive stage in the concrete production process. Both processes involve carbon dioxide (CO2), which can be utilized as a raw material for energy production and concrete production. Summary of the Invention

[0003] A recycling and waste management method receives municipal solid waste (MSW) with a high organic content to initiate a self-sustaining hydrothermal mineralization (HTM) process based on supercritical water oxidation (SCWO), thereby receiving supercritical steam and carbon dioxide with power generation potential, and then forming calcium carbonate suitable for concrete production. Hydrothermal mineralization (HTM) provides a rapid removal of organic waste while producing emission-free and thermally stable cement additives that can act as carbon sinks. Therefore, hydrothermal mineralization (HTM) offers a rapid disposal pathway for organic waste, a green power source, and an end product that can be combined with conventional and alternative cement production to reduce the carbon footprint of cement production.

[0004] This configuration is partly based on the observation that CO2 sequestration and reduction are beneficial to environmental health. Excessive CO2 emissions from fossil fuel combustion and other causes have become a major concern for governments and environmentalists. Unfortunately, conventional CO2 reduction methods focus on eliminating the sources of CO2 generation, simply reducing output by urging or forcing the elimination of sources, thus eliminating any benefits from combustion. Therefore, this configuration largely overcomes the shortcomings of conventional methods by providing a complementary consumption / receiving end arrangement for CO2-related processes. The MSW itself raises environmental concerns due to its disposal requirements; it is fed into the SCWO process. Once the water reaches a supercritical state, the CO2 generated by the SCWO undergoes a hydrothermal mineralization pathway, which is then fed into the HTM process to form calcium carbonate for cement (concrete) production. Additionally, prior to the HTM, high-pressure steam and CO2 from the supercritical reaction can be used to power turbines or for other pressurized steam applications.

[0005] More specifically, this paper presents a configuration for obtaining calcium carbonate by mineralizing a waste stream, the method comprising: heating an aqueous waste stream (such as municipal solid waste) to a temperature and pressure suitable for achieving a supercritical state of water; and reacting hydrocarbons in the waste stream with oxygen to form carbon dioxide and water derived from supercritical water oxidation. The mineralization reaction combines CO2 with calcium in the waste stream to form calcium carbonate suitable for industrial and construction purposes, such as concrete. Attached Figure Description

[0006] The above and other objects, features, and advantages of the present invention will become clear from the following description of specific embodiments of the invention as illustrated in the accompanying drawings, in which the same reference numerals refer to the same parts throughout different views. These drawings are not necessarily to scale, but rather focus on illustrating the principles of the invention.

[0007] Figure 1 This is a context diagram of the disclosed methods for receiving and recycling municipal solid waste (MSW) for carbon dioxide sequestration and concrete production; Figure 2 Is Figure 1 Energy diagram for achieving a self-sustaining exothermic reaction in an environment; Figure 3 This is a comparison of the disclosed method with previous methods for MSW treatment and the generation of calcium carbonate or precipitated calcium carbonate (PCC) as defined herein; and Figure 4 The stoichiometric levels obtained by the disclosed method near the plateau phase are shown, while direct air capture exhibits significantly lower performance. Detailed Implementation

[0008] The following description describes several configurations associated with this method. Examples based on experimental backgrounds are disclosed to illustrate the technical aspects of converting MSW to calcium carbonate, as well as the intermediate steps and compounds.

[0009] Figure 1 This is a context diagram of the disclosed methods for receiving and recycling municipal solid waste (MSW) for carbon dioxide sequestration and concrete production. (Reference) Figure 1 In recycling environment 100, MSW 101 forms a recycling stream of organic waste containing abundant, non-specific carbon and hydrogen, mixed as waste organic matter. The waste stream from MSW 100 forms precipitated calcium carbonate (PCC) by the methods described below. PCC is the synthesized, produced calcium carbonate (CaCO3) as described below. The produced calcium carbonate can be used in concrete production 105, consumer products 107, and any suitable disposal method for calcium carbonate.

[0010] Supercritical water oxidation (SCWO) operates in an oxidizing environment at temperatures exceeding the supercritical point of water (T>374°C, P>220 bar) to decompose waste macromolecules into carbon dioxide within minutes. This is due to the high energy content (HHV) of the waste feed. 食品废物 =32.1 MJ / kg), the conversion to carbon dioxide is highly exothermic, meaning that once steady-state operation is achieved, the reaction requires no external energy to run. Once converted, the effluent is a high-pressure, high-temperature supercritical stream of carbon dioxide and water vapor. As an additional harvesting step, this stream can be expanded within a turbine to generate excess electricity, which can then be redistributed back to the grid.

[0011] After utilizing the energy potential of the outflow stream, carbon dioxide is sequestered as calcium carbonate. This reaction takes place under alkaline conditions in an aqueous medium, where CO2 is converted to bicarbonate (HCO3-). - From then on, HCO3 - Will be combined with free calcium (Ca) 2+ The reaction produces CaCO3. This conversion is thermodynamically favorable; however, it also dissolves CO2 in water to form HCO3. - This is often the rate-limiting step. By utilizing the high-pressure, high-purity effluent gas from the SCWO reaction, the disclosed method overcomes the problem related to the dissolution rate.

[0012] Figure 2 Is Figure 1 Energy diagram for a self-sustaining exothermic reaction in an environment. (Reference) Figure 1 and Figure 2The disclosed method for obtaining calcium carbonate 103 by mineralizing waste stream 101 involves heating the aqueous waste stream to temperatures and pressures sufficient to achieve supercritical water conditions in a reactor or containment. The waste stream contains significant amounts of carbon and hydrogen in the form of organic waste. The heat causes the hydrocarbons in waste stream 101 to react with oxygen in an oxidizing environment to form carbon dioxide and water derived from supercritical water oxidation. The CO2 from the waste stream dissolves in the water to form HCO3. - HCO3 - It reacts with carbon dioxide to form calcium carbonate. The disclosed pathway for hydrothermal mineralization of food waste is defined as follows:

[0013] Therefore, CO2 combines with calcium in the waste stream to form calcium carbonate. Figure 2 This mineralization originates from a negative Gibbs energy (ΔG value) change, because a positive Gibbs energy reaction would produce hydrocarbons for chemical utilization. Spontaneous or self-sustaining processes correspond to negative ΔG values, such as... Figure 2 The mineralization stage is shown in the diagram. Supercritical water (SCWO) relies on unique reactivity and transport properties that emerge when aqueous waste streams are brought above the critical point of water (374°C and 218 atm, or 704°F and 3200 psi). Supercritical water is a dense single-phase system with transport properties similar to those of gases and solvent properties comparable to those of nonpolar solvents. Oxygen is completely soluble in supercritical water, causing all organic matter to be oxidized extremely rapidly and completely to carbon dioxide, clean water (which can be reused), and some non-leached inorganic salts.

[0014] Of the 292 million tons of MSW generated in the United States, over 70% is in the form of organic waste. Most MSW organics retain varying amounts of water. Unlike traditional waste-to-energy methods (such as incineration), hydrothermal methods (such as SCWO) can process wet organic waste because their working fluid is water, thus achieving a positive energy balance when other methods require energy input.

[0015] The full benefits of integrating the disclosed methods depend on the feedstock used. This proposal is based on the use of food waste, which accounts for only 20% of all MSW generated in the United States. Through complete conversion, food waste could offset nearly 20% of the nation's demand for CaCO3.

[0016] Therefore, the disclosed method integrates SCWO and mineralization to produce CaCO3. This method satisfies at least three needs or industries: 1) CaCO3 production, 2) CO2 sequestration technology developers, and 3) the waste management industry.

[0017] In conventional methods, the demand for CaCO3 is primarily met in one of two forms. The first is direct limestone mining. The core of this process is extracting limestone from open-pit or underground mines, grinding it to the desired particle size at this stage. The second is the precipitation of CaCO3. Typically, precipitated calcium carbonate (PCC) is formed by hydrating or slaking quicklime (CaO) that already contains CO2 molecules to form calcium hydroxide (Ca(OH)2). CO2 can then be converted to HCO3. - And then react to form CaCO3.

[0018] Both conventional methods ultimately require the extraction of CaCO3, as quicklime is formed by calcining CaCO3 and producing approximately 1.3 kg CO2 / kg CaO. Emissions are slightly improved to about 1 kg CO2 / kg PCC when converted back to CaCO3. In contrast, the disclosed method does not require the extraction of CaCO3, nor any soluble form of calcium, or an alkaline environment. The example configuration uses calcium chloride (CaCl2) and sodium hydroxide (NaOH) as the calcium and alkali sources, respectively. Using conventional NaOH production, our model shows a similar emission rate of about 1 kg CO2 / kg PCC. However, when considering greener energy sources (i.e., solar, wind, biomass, etc.), it can be seen that this method can actually reduce emissions by 50%, to 0.5 kg CO2 / kg PCC.

[0019] One approach is direct air capture (DAC) / point source capture (PSC), where the purpose of DAC and PSC technologies is to remove or concentrate diluted CO2 from the atmosphere or process flue gas. These processes fall into two main chemical categories: 1) mineralization and 2) amine-based.

[0020] Mineralization focuses on the permanent removal of CO2 by forming CaCO3 or MgCO3 (two insoluble and thermally stable minerals). The deployed facilities have used mineralization technology for DAC and claim to remove significant amounts of CO2 annually. However, because the disclosed methods extract from carbon-intensive feedstocks, removal efficiencies are expected to be significantly higher than DAC if waste is utilized on a sufficiently large scale, depending on the moisture and carbon content of the process feedstock.

[0021] Figure 3 This is a comparison of the disclosed method with previous methods for MSW treatment and the formation of calcium carbonate or precipitated calcium carbonate (PCC) as defined herein. Reference Figures 1-3 , Figure 3 Several methods are compared in terms of carbon dioxide ratio.300.

[0022] Once landfilled, organic waste is destined to degrade into CO2 and CH4 and is a significant emitter of greenhouse gases (GHG), as shown in ratio 302. Conventional PCC production is typically cyclical, as it begins and ends with the extraction of CaCO3, as shown in ratio 304. The specific configuration disclosed herein provides food waste as a linear and finite end-of-life for CaCO3, with emissions comparable to conventional PCC (shown in ratio 306); however, emissions can be reduced by 50% through the use of renewable energy sources (i.e., solar, wind, etc.), as shown in ratio 308.

[0023] Back Figure 1 and Figure 2 The corresponding equations and typical use cases involve conveying a waste stream of MSW 101 or similar to a sealed containment shell or reactor suitable for pressurized operation. Applying heat, accompanied by a sufficient increase in pressure, will force the water into a supercritical state. Once the supercritical water has reached a steady state, the heat source can be removed, allowing a self-sustaining exothermic reaction to produce calcium carbonate.

[0024] In this instance configuration, the waste stream is an organic waste stream, and a supercritical water oxidation (SCWO) reaction to generate CO2 is initiated in a containment shell by heating to at least 373°C at a pressure of at least 220 bar in an oxidizing environment. Prior to mineralization, a gaseous stream of carbon dioxide and water can be harvested by connecting a container or turbine inlet to the containment shell to power external loads. Pressurized gas containing carbon dioxide and water vapor is received by connecting a container or conduit to the containment shell; this high-pressure steam can be used to power mechanical loads.

[0025] Besides mineralization, amine-based removal has proven effective in stripping CO2 from gas streams. However, the reversibility of amine reactions limits their ability to sequester CO2. Amine-based removal is better suited for CO2 purification and delivery. Furthermore, amines are expensive and corrosive, making them impractical for many applications. Conventional methods have not yet combined SCWO and mineralization in this way to produce CaCO3. CO2 is efficiently sequestered in bicarbonate, and then mineralization consumes CO2 and free calcium to produce calcium carbonate.

[0026] Figure 4 The diagram shows the stoichiometric levels achieved by the disclosed method near the plateau phase, while direct air capture exhibits significantly lower performance. (Reference) Figure 4 The running conditions depicted by the dotted line above are for SCWO, where: •

[0027] •

[0028] The dashed line below shows Direct Air Capture (DAC): •

[0029] •

[0030] At 150 psi, the process begins to plateau at approximately 10% conversion within 20-120 minutes. This is a result of the alkali level dropping below stoichiometry and the pH falling below 5.5. (The text abruptly shifts to a seemingly unrelated topic about alkali and Ca.) 2+ Under stoichiometric conditions, the process produces a complete or near-complete transformation. Once supercriticality is achieved, mineralization becomes a self-sustaining, spontaneous reaction with a negative ΔG.

[0031] While the systems and methods defined herein have been specifically shown and described with reference to their embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as covered by the appended claims.

Claims

1. A method for obtaining calcium carbonate by mineralizing a waste stream, the method comprising: The aqueous waste stream is heated to a temperature and pressure suitable for achieving the supercritical state of water in the aqueous waste stream; The hydrocarbons in the waste stream react with oxygen to form carbon dioxide and water derived from supercritical water oxidation; as well as The CO2 combines with calcium in the waste stream to form calcium carbonate.

2. The method of claim 1, further comprising: CO2 from the waste stream dissolves into the water to form HCO3. - ,as well as The HCO3 formed - It reacts with the carbon dioxide to form the calcium carbonate.

3. The method of claim 1, further comprising: The waste stream is then transported to a sealed containment housing suitable for pressurized operation; After the supercritical water reaches a steady state; as well as The heat source is removed to allow a self-sustaining exothermic reaction to produce the calcium carbonate.

4. The method of claim 3, further comprising: The gaseous stream of carbon dioxide and water is harvested to power external loads.

5. The method of claim 1, wherein, The waste stream is an organic waste stream, and the method further includes: The supercritical water oxidation (SCWO) reaction to produce CO2 is initiated by heating to at least 373°C under a pressure of at least 220 bar in an oxidizing environment. The CO2 is encapsulated in bicarbonate; and The CO2 and free calcium are mineralized to form calcium carbonate.

6. The method of claim 5, wherein, This mineralization originates from negative Gibbs energy variations.

7. The method of claim 6, wherein, Mineralization is a self-sustaining spontaneous reaction with negative ΔG.

8. The method of claim 6, wherein, Mineralization produces CO3 2- .

9. An apparatus for supercritical water oxidation and mineralization, comprising: A sealed container suitable for withstanding pressure and temperature, the sealed container being used to contain a stream of aqueous waste and heat it to the temperature and pressure required to achieve a supercritical state of water in the stream of aqueous waste; The supercritical water causes the hydrocarbons in the waste stream to react with oxygen to form carbon dioxide and water derived from supercritical water oxidation. as well as The containment shell allows for a self-sustaining exothermic reaction to produce calcium carbonate by combining the CO2 with calcium in the waste stream.

10. The method of claim 9, further comprising a container coupled to the housing for receiving pressurized gases comprising carbon dioxide and water vapor for powering mechanical loads.

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