Method for liquid-state deslagging of household garbage ash

Abstract

The invention belongs to the field of garbage treatment, and particularly relates to a liquid-state deslagging method for household garbage ash. The method for liquid-state deslagging of the household garbage ash comprises the following steps: component determination: determining components of the household garbage ash; selecting a fluxing agent: selecting one fluxing agent or a mixture of at least two fluxing agents as an inorganic fluxing agent according to the components of the household garbage ash; and gasification reaction: mixing the household garbage and the inorganic fluxing agent, carrying out gasification reaction on the obtained mixture, and discharging ash. According to the method provided by the invention, a small amount of inorganic fluxing agent can be added, the melting temperature of the household garbage during gasification reaction is reduced, the energy consumption and the equipment operation cost are reduced, and the fluctuation temperature of a slag discharge port can be met, so that the gasification furnace is free of slag bonding and corrosion and smooth in liquid slag discharge, and the equipment operation stability and operation safety are improved; and smooth liquid deslagging is realized.

Description

Technical Field

[0001] This application belongs to the field of waste treatment, specifically relating to a method for discharging liquid ash from municipal solid waste. Background Technology

[0002] Since 2019, my country's annual municipal solid waste collection volume has exceeded 240 million tons. Sanitary landfill and incineration still account for over 90% of my country's municipal solid waste treatment. Current simple and singular methods of municipal solid waste treatment not only fail to meet the ever-increasing volume of waste but also generate secondary pollution during the process. Furthermore, municipal solid waste contains enormous energy potential, and simple treatment methods lead to energy waste. Compared to incineration, high-temperature gasification technology can achieve the resource conversion of municipal solid waste, and the generated gas components (mainly CO and H2) are simple, clean, and have fewer impurities, which is beneficial for the conversion of downstream products (such as methanol and ethanol). At the same time, the fly ash and other pollutants generated during high-temperature gasification are significantly less than those produced by incineration, and the solid residue rate is low, making it less likely to cause secondary pollution. This gives it significant advantages in terms of processing scale and operating costs.

[0003] Currently, most high-temperature fluidized bed gasifiers employ liquid ash discharge. To ensure stable operation of liquid ash discharge, a series of conditions must be met. Specifically, firstly, the operating temperature must be significantly higher than the ash melting temperature to ensure the ash is discharged in liquid form; secondly, the high-temperature viscosity of the ash must be consistently maintained between 5.00 and 25.00 Pa·s to reduce corrosion of the furnace wall by the molten slag. Currently, to avoid excessive energy consumption and operational safety issues caused by excessively high operating temperatures in high-temperature gasification units, a certain amount of flux is often added to the raw ash to lower the ash melting point. Existing fluxes for controlling the ash melting temperature are mostly designed for coal ash, which has a higher content of acidic oxides than basic oxides. However, municipal solid waste ash has a higher content of basic oxides than acidic oxides, easily causing slagging and corrosion in high-temperature gasifiers, and there is also the problem of excessive flux addition. Therefore, researching composite fluxes specifically for municipal solid waste ash is crucial for ensuring stable gasification of municipal solid waste over a long period during the high-temperature gasification process. Summary of the Invention

[0004] The purpose of this application is to provide a liquid ash discharge method for municipal solid waste to solve at least one of the above-mentioned technical problems.

[0005] To achieve the above objectives, this application adopts the following technical solution: This application provides a method for liquid discharge of municipal solid waste ash, comprising the following steps: composition determination: determining the composition of municipal solid waste ash; flux selection: selecting one flux or a mixture of at least two fluxes as an inorganic flux based on the composition of municipal solid waste ash; gasification reaction: mixing municipal solid waste and inorganic flux, subjecting the resulting mixture to a gasification reaction, and discharging the ash residue.

[0006] In some embodiments of this application, the main components of municipal solid waste ash in the composition determination step include CaO, SiO2, and Al2O3, with CaO having the highest content. Based on the mass fraction of CaO, one flux or a mixture of at least two fluxes is selected as an inorganic flux in the flux selection step. The mixing ratio of various fluxes in the flux mixture is adjusted to the mixing ratio of municipal solid waste and inorganic flux in the gasification reaction step, so that the inorganic flux reacts with CaO to generate low-melting-point compounds and produce a low-temperature eutectic effect, thereby adjusting the physicochemical properties of the ash slag in the gasification reaction step.

[0007] In some embodiments of this application, a particular flux is selected from non-metallic oxides, alkali metal oxides, alkaline earth metal oxides, and transition metal oxides.

[0008] In some embodiments of this application, the inorganic flux is selected from substances whose main components are at least one of SiO2, Al2O3, K2O, Na2O and Fe2O3.

[0009] In some embodiments of this application, the inorganic flux is selected from substances that can be prepared by calcination to contain at least one of SiO2, Al2O3, K2O, Na2O and Fe2O3.

[0010] In some embodiments of this application, the inorganic flux is selected from complexes or salts containing at least one of SiO2, Al2O3, K2O, Na2O and Fe2O3.

[0011] In some embodiments of this application, the inorganic flux is selected from kaolin, quartz, bentonite, potassium feldspar, sodium feldspar, nepheline, hematite, limonite and siderite.

[0012] In some embodiments of this application, the inorganic flux is selected from SiO2, Al2O3, K2O, Na2O, Fe2O3 and K2CO3.

[0013] In some embodiments of this application, the inorganic flux contains SiO2:Al2O3:K2O:Na2O:Fe2O3=(0~1):(0~1):(0~1):(0~1):(0~1).

[0014] In some embodiments of this application, the ratio of SiO2:Al2O3 in the inorganic flux is 2 to 5.

[0015] In some embodiments of this application, the SiO2:Al2O3 ratio in the inorganic flux is 3.5.

[0016] In some embodiments of this application, the component determination step includes a preparation step, namely, ashing treatment: ashing the domestic waste to obtain domestic waste ash.

[0017] In some embodiments of this application, the component determination step includes establishing a ternary phase diagram: establishing a SiO2-Al2O3-CaO ternary phase diagram based on the main components of municipal solid waste ash, and adjusting the mixing ratio of various fluxes in the flux mixture in the flux selection step and the blending ratio of municipal solid waste and inorganic flux in the gasification reaction step based on the SiO2-Al2O3-CaO ternary phase diagram.

[0018] In some embodiments of this application, the gasification reaction step includes homogenization treatment: crushing and sieving municipal solid waste and inorganic flux separately to obtain municipal solid waste fragments and inorganic flux fragments, thoroughly mixing the municipal solid waste fragments and inorganic flux fragments to obtain homogenized material, and feeding it into a gasifier for gasification reaction, and discharging ash and slag.

[0019] In some embodiments of this application, the particle size of both the municipal solid waste fragments and the inorganic flux fragments in the homogenization process is less than 0.2 mm. The particle size of both the municipal solid waste fragments and the inorganic flux fragments is less than 0.2 mm to ensure uniform mixing of the two materials, thus preventing incomplete combustion or coking during the subsequent gasification reaction.

[0020] In some embodiments of this application, the homogenization process includes mechanical mixing and / or pyrolytic mixing.

[0021] In some embodiments of this application, the gasifier is a fluidized bed.

[0022] In some embodiments of this application, the flow temperature of the ash is below 1500°C.

[0023] This application provides a method for liquid ash discharge of municipal solid waste, which can add a small amount of inorganic flux to reduce the melting temperature of municipal solid waste during gasification reaction, thereby reducing energy consumption and equipment operating costs. It can also meet the temperature fluctuations at the ash discharge port, so that the gasifier does not slag or corrode, improve the stability and safety of equipment operation, and achieve smooth liquid ash discharge. Attached Figure Description

[0024] Figure 1 The ternary phase diagram of SiO2-Al2O3-CaO in municipal solid waste provided in this application.

[0025] Figure 2 The viscosity-temperature characteristics curve of municipal solid waste provided in this application.

[0026] Figure 3 Viscosity-temperature characteristic curves of Example 1 provided in this application.

[0027] Figure 4 Viscosity-temperature characteristic curves of Example 2 provided in this application.

[0028] Figure 5 Viscosity-temperature characteristic curves of Example 3 provided in this application.

[0029] Figure 6 Viscosity-temperature characteristic curves of Example 4 provided in this application.

[0030] Figure 7 Viscosity-temperature characteristic curves of Example 5 provided in this application. Detailed Implementation

[0031] In this application, the numerical range represented by "~" means the range in which the numerical values ​​recorded before and after "~" are respectively the minimum and maximum values.

[0032] In the numerical ranges described in this application, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in different stages. In the numerical ranges described in this application, the upper or lower limit value recorded in a certain numerical range can be replaced with the value shown in the embodiments.

[0033] Unless the context clearly indicates otherwise, when used in this specification, the terms "comprising," "including," or "containing" specify the presence of the said element, but do not exclude the presence or addition of one or more other elements.

[0034] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0035] Glossary / Explanation: Kaolin (chemical formula Al2Si2O5(OH)4) mainly consists of approximately 39.5% Al2O3, 46.5% SiO2, 14% H2O, 0.5-2% Fe2O3, 0.1-1% TiO2, and small amounts of CaO and MgO. Quartz mainly consists of approximately 95% SiO2, with less than 5% total content of Al2O3, Fe2O3, CaO, and MgO. Bentonite (chemical formula Na, Ca) 0.33 (Al,Mg)2Si4O 102 •nH2O, main components: SiO2 content 60-70%, Al2O3 content 15-25%, MgO content 2-5%, Na2O and K2O content approximately 1-3%. Potassium feldspar chemical formula KAlSi3O8, sodium feldspar chemical formula NaAlSi3O8, nepheline chemical formula NaKAl2Si2O8, hematite chemical formula Fe2O3, limonite chemical formula FeO(OH)・nH2O, siderite chemical formula FeCO3.

[0036] The term "domestic waste" in this application refers to solid waste generated by people in their daily lives or in activities that provide services for daily life, as well as solid waste that is considered domestic waste under laws and administrative regulations. It mainly includes residential waste, market and commercial waste, waste from public places, street cleaning waste, and waste from enterprises and institutions.

[0037] This application discloses a method for liquid ash discharge from municipal solid waste. The purpose is to address the issues of energy consumption, operating costs, and safety concerns arising from the need for high operating temperatures during the gasification process of municipal solid waste. Furthermore, existing fluxes for controlling the melting temperature of waste ash are primarily designed for ash types like coal ash, where the content of acidic oxides is greater than that of basic oxides. However, municipal solid waste ash contains more basic oxides than acidic oxides, which can easily cause slagging and corrosion in high-temperature gasifiers. Additionally, excessive amounts of flux can lead to a surge in the ash content of the raw materials.

[0038] In the embodiments of this application, the flow temperature (FT) of municipal solid waste ash is determined by an ash fusion tester. The flow temperature (FT) of ash is determined according to GB / T219-2008. The prepared triangular ash cone is placed in the ash fusion tester and heated from room temperature to 900°C at a heating rate of 15°C / min. Then, the temperature is continued to rise at a rate of 5°C / min until it reaches 1500°C. The temperature of the ash cone in different states is observed and recorded based on the changes in the shape of the ash cone. The main values ​​include deformation temperature (DT), softening temperature (ST), hemisphere temperature (HT), and flow temperature (FT). Flow temperature (FT) refers to the critical temperature at which a mixture (such as ash) begins to have obvious fluidity during the heating process. The melting temperature includes deformation temperature, softening temperature, hemisphere temperature, and flow temperature. The high-temperature viscosity curve of municipal solid waste ash was determined by a high-temperature viscometer. To simulate the flow of molten slag in a fluidized bed, the ash sample was placed in a high-temperature electric furnace for pre-melting. The pre-melting temperature was 100℃~200℃ higher than the ash melting flow temperature. After naturally cooling to room temperature, the crucible was removed and crushed to obtain ash. The obtained ash was then subjected to viscosity testing. The viscosity testing process included the following steps: (1) 50~55g of ash sample was placed in the test crucible and placed on the viscometer support, and then covered with a corundum protective tube; (2) The vacuum pump switch was turned on, and the exhaust switch and air inlet switch were turned off. (2) Turn off the vacuum pump and evacuate for about 5 minutes. When the vacuum gauge shows a pressure close to -0.1 MPa, turn off the vacuum pump. (3) Introduce the atmosphere required for the test (air atmosphere, weak reducing atmosphere) and control the flow rate at 100 ml / min. (4) Set the heating program and start heating. When the sample reaches the highest set temperature (pre-melting temperature), put the rotor into the sample and start the cooling test. The cooling rate is 2℃ / min. (5) The computer automatically records the temperature and viscosity. (6) After the test is completed, lift the rotor out of the liquid surface according to the instrument prompts and continue cooling the high-temperature furnace to room temperature. Plot the high-temperature viscosity curve according to the specific temperature, and obtain the temperature that meets the industry standard system viscosity of 2.5~25 Pa·s for liquid slag discharge according to the high-temperature viscosity curve of ash slag. The high-temperature molten slag in this temperature range has less slagging and corrosion on the furnace wall.

[0039] This application addresses the complex and variable composition of municipal solid waste ash by proposing a method for liquid ash discharge. This method allows for the selection of appropriate fluxes to address the high CaO, low SiO2, and low Al2O3 characteristics of municipal solid waste ash, thereby reducing the ash's melting temperature and improving its viscosity-temperature characteristics, thus meeting the requirements for liquid ash discharge after the gasification reaction of municipal solid waste in an entrained bed.

[0040] This application provides a method for discharging liquid ash from municipal solid waste, which includes the following steps. Composition analysis: Determining the composition of municipal solid waste ash; Flux Selection: Based on the composition of municipal solid waste ash, one flux or a mixture of at least two fluxes is selected as the inorganic flux. In the embodiments of this application, the specific flux is selected from SiO2, Al2O3, K2O, Na2O, and Fe2O3, and the inorganic flux is selected from substances with at least one of SiO2, Al2O3, K2O, Na2O, and Fe2O3 as the main component, or from substances that can be prepared by calcination to contain at least one of SiO2, Al2O3, K2O, Na2O, and Fe2O3, or from complexes or salts containing at least one of SiO2, Al2O3, K2O, Na2O, and Fe2O3. In some embodiments of this application, the inorganic flux is also selected from kaolin, quartz, bentonite, potassium feldspar, sodium feldspar, nepheline, hematite, limonite, and siderite, or from SiO2, Al2O3, K2O, Na2O, Fe2O3, and K2CO3. In some embodiments of this application, the inorganic flux contains SiO2:Al2O3:K2O:Na2O:Fe2O3=(0~1):(0~1):(0~1):(0~1):(0~1) or SiO2:Al2O3=2~5; preferably, the inorganic flux contains SiO2:Al2O3=3.5.

[0041] Gasification reaction: municipal solid waste and inorganic flux are mixed, and the resulting mixture is subjected to a gasification reaction to discharge ash and slag.

[0042] The component determination procedure also includes the following preparation steps: Ashing treatment: Ashing household waste to obtain household waste ash; Establish a ternary phase diagram: Based on the main components of municipal solid waste ash, establish a SiO2-Al2O3-CaO ternary phase diagram. Based on the SiO2-Al2O3-CaO ternary phase diagram, adjust the mixing ratio of various fluxes in the flux mixture in the flux selection step and the mixing ratio of municipal solid waste and inorganic flux in the gasification reaction step.

[0043] The gasification reaction process also includes the following steps: Homogenization treatment: Municipal solid waste and inorganic flux are crushed and sieved separately to obtain fragments of municipal solid waste and inorganic flux. The fragments of municipal solid waste and inorganic flux are thoroughly mixed to obtain homogenized material, which is then fed into a gasifier for gasification reaction, and ash is discharged. In some embodiments of this application, the particle size of both the fragments of municipal solid waste and inorganic flux is less than 0.2 mm. During homogenization treatment, the thorough mixing methods include mechanical mixing and / or pyrolytic mixing. The fragments of inorganic flux are mixed with the fragments of municipal solid waste at mass fractions of 2%, 3%, 5%, 6%, and 8% to obtain homogenized material with different mixing ratios.

[0044] The main components of municipal solid waste ash in the composition determination step include CaO, SiO2, and Al2O3, with CaO having the highest content. Based on the mass fraction of CaO, one flux or a mixture of at least two fluxes is selected as the inorganic flux in the flux selection step. The mixing ratio of various fluxes in the flux mixture is adjusted to the blending ratio of municipal solid waste and inorganic flux in the gasification reaction step, so that the inorganic flux reacts with CaO to generate low-melting-point compounds and produce a low-temperature eutectic effect, thereby adjusting the physicochemical properties of the ash in the gasification reaction step. In the embodiments of this application, the physicochemical property indicators of the ash include melting temperature (mainly FT temperature), the temperature range corresponding to a viscosity of 2.5-25 Pa·s, and the temperature interval for a viscosity of 2.5-25 Pa·s; preferably, the melting temperature is less than 1500℃ for the FT temperature and the temperature interval for a viscosity of 2.5-25 Pa·s is greater than 100℃. Based on the composition analysis of municipal solid waste ash, CaO, SiO2, and Al2O3 account for over 75% of the ash, and their influence is far greater than that of other substances. Therefore, the melting temperature variation of ash under different SiO2 / Al2O3 / CaO ratios in the SiO2-Al2O3-CaO ternary phase diagram of municipal solid waste is of guiding significance. Furthermore, since alkali metal and alkaline earth metal compounds have low melting points, they can cause high-melting-point substances (such as CaO) in the ash to form a eutectic, leading to earlier melting of these high-melting-point substances. Additionally, metal oxides (especially transition metal oxides, such as Fe2O3) can act as "network modifiers," disrupting the aluminosilicate or silicon-oxygen structure in the ash and forming low-melting-point compounds. Therefore, this application can effectively reduce the melting temperature of ash and expand the temperature range for viscosities of 2.5-25 Pa·s.

[0045] The composition of municipal solid waste ash was determined according to the national standard GB / T30725-2014 "Determination Method of Composition of Solid Biomass Fuel Ash", and the results are shown in Table 1. The main components of municipal solid waste ash include CaO, SiO2, Al2O3, TiO2, K2O, Na2O, Fe2O3, MgO, P2O5, and SO3. Among them, CaO, SiO2, and Al2O3 account for more than 75% of the composition of municipal solid waste ash, and each of the three has a dual role and its influence is far greater than that of other substances. The alkaline oxides in municipal solid waste ash are represented by CaO, while the acidic oxides are represented by SiO2. The CaO content of municipal solid waste ash (especially incineration ash) exceeds 50%, and it is generally alkaline. The melting temperature, viscosity and chemical properties of the ash are determined by the addition of acidic oxides or amphoteric oxides. For example, adding SiO2, Al2O3 or K2CO3 fluxing agents can improve the content of alkaline oxides and acidic oxides in municipal solid waste ash, so that the content tends to be balanced. This content balance is an important factor in avoiding slagging, corrosion and other problems, and ensuring the efficient, stable and safe operation of the gasifier.

[0046] Table 1. Composition determination results of municipal solid waste ash

[0047] Based on the composition analysis of municipal solid waste ash, CaO, SiO2, and Al2O3 account for over 75% of the ash, with their influence far exceeding that of other substances. Using FactSage software to study the high-temperature melting properties of the ash, the main components were simplified to a ternary system of SiO2-Al2O3-CaO, ignoring the influence of other minor components (such as Fe2O3 and MgO). The complete liquidus temperature at phase equilibrium was calculated based on the principle of minimizing the system's Gibbs free energy. Furthermore, the measured contents (mass fractions, such as w(Ca), w(Si), w(Ca), w(Al2O3), and w(Al2O3)) of calcium, silicon, and aluminum were then analyzed. (Al) is converted to the composition of corresponding oxides (CaO, SiO2, Al2O3) through atomic weight conversion, and the complete liquidus temperature under phase equilibrium is calculated using thermodynamic software (such as FactSage). Combined with the chemical composition (e.g., mole fraction) of each oxide in the equilibrium liquid phase, a CaO-SiO2-Al2O3 ternary phase diagram suitable for the silicate melting system of municipal solid waste is constructed, marking the liquidus line, eutectic point, and main crystalline phase regions, such as... Figure 1 As shown in the figure, the melting temperature changes of ash residue under different SiO2 / Al2O3 / CaO ratios are analyzed in the ternary phase diagram. Considering that the CaO content of municipal solid waste ash (ash residue after gasification reaction, etc.) exceeds 50%, the amount of additional SiO2 and / or Al2O3 to be added to municipal solid waste is determined to improve the melting temperature of municipal solid waste.

[0048] Specifically, by adding flux to municipal solid waste, the amount of flux used can be reduced while effectively lowering the melting temperature of ash, thereby reducing costs and controlling the viscosity-temperature characteristics of the ash. On one hand, based on the melting temperature variations of ash under different SiO2 / Al2O3 / CaO ratios in the SiO2-Al2O3-CaO ternary phase diagram of municipal solid waste, adding as little SiO2 and / or Al2O3 flux as possible to the municipal solid waste allows it to react with CaO in the ash (municipal solid waste ash) to generate low-melting-point compounds and produce a low-temperature eutectic effect, thus keeping the melting temperature within a lower isothermal section and effectively reducing the ash melting temperature. On the other hand, given the low melting points of alkali metal and alkaline earth metal compounds, adding low-melting-point alkaline oxides such as K₂CO₃ (melting point approximately 891℃) to form a eutectic with high-melting-point substances in ash and slag allows the high-melting-point substances to melt earlier, and the formation of the eutectic lowers the overall melting temperature. Alternatively, adding metal oxides (transition metal oxides) such as Fe₂O₃ (melting point approximately 1565℃) in an alkaline environment, with Fe... 3+ It exists in the form of a “network modifier” that destroys the aluminosilicate or silicon-oxygen structure in ash and forms low-melting-point compounds (such as calcium aluminoferrite, with a melting point of about 1415℃) with CaO, Al2O3, etc., synergistically reducing the melting temperature of municipal solid waste ash.

[0049] The SiO2-Al2O3-CaO ternary phase diagram, used in FactSage software to study the high-temperature melting properties of municipal solid waste ash, simplifies the composition into different oxide systems. Based on the principle of minimizing the Gibbs energy of the system, the complete liquid phase temperature, mineral types and contents, and the chemical composition of the liquid phase under phase equilibrium are calculated. In the equilateral triangle of the SiO2-Al2O3-CaO ternary phase diagram, the three vertices represent pure components (SiO2, Al2O3, CaO), the three sides represent binary systems (such as SiO2-Al2O3, Al2O3-CaO, CaO-Al2O3), and the interior region represents the phase state of the ternary mixture. The mass fraction of each component in the "mass fraction coordinates" is determined by the geometric position of the triangle. Common methods include: "perpendicular line method"—drawing perpendicular lines from a point to the three sides, with the length of the perpendicular corresponding to the mass fraction ratio of each component; and "parallel line method"—reading the proportion of the corresponding component through line segments parallel to a side. "Temperature axis" - In a three-dimensional phase diagram, the vertical axis represents temperature, but in practice, it is often simplified by using isothermal sections (fixed temperature) or projection diagrams.

[0050] In this embodiment, the municipal solid waste ash is taken from the ash residue after the municipal solid waste has undergone a complete gasification reaction in a municipal solid waste incineration plant. Without adding flux, XRD (X-ray Diffraction) analysis shows that the main forms of calcium in the ash are CaO (melting point 2570℃) and Ca2SiO4 (melting point 2130℃). The ash residue is formed by the high-temperature gasification reaction of municipal solid waste. Since the ash residue is mainly composed of a mixture of various components exhibiting a eutectic melting effect, forming a calcium-silicon eutectic, the FT temperature of the calcium-silicon eutectic is greater than 1500℃. This corresponds to a viscosity of 2.5-25 Pa·s within a temperature range of 1300℃ to 1340℃, with a temperature interval of 40℃. The viscosity-temperature characteristic curve is shown in the attached figure. Figure 2 As shown in the figure. The following examples illustrate the changes in the ash flow temperature and viscosity-temperature characteristics of slag when flux is added.

[0051] Example 1 SiO2 and municipal solid waste were separately crushed and sieved to obtain municipal solid waste fragments and SiO2 fragments with a particle size of less than 0.2 mm. The SiO2 fragments were mixed with the municipal solid waste fragments at mass fractions of 2%, 3%, 5%, 6%, and 8% to obtain homogenized materials of SiO2 and municipal solid waste with different blending ratios. These homogenized materials were then fed into an entrained flow bed for gasification. The ash slag after gasification was tested for flow temperature and viscosity-temperature curves, and the results are shown in Table 1. With the appropriate addition of SiO2, the ash slag flow temperature decreased because the high-melting-point CaO (melting point 2570°C) reacted with SiO2 (melting point 1713°C) to form Ca3Si2O7 (melting point 1458°C) and CaSiO3 (melting point 1540°C). Meanwhile, due to the small grain size of SiO2, the small-grained SiO2 enhances the interfacial effect, adjusts the complexity of the network structure, and disperses the activation energy distribution, thus reducing the rate of viscosity change of the melt during heating and widening the temperature range corresponding to 2.5-25 Pa·s. Therefore, adding SiO2 will widen the temperature range interval corresponding to the viscosity of 2.5-25 Pa·s. However, when excessive SiO2 is added, unreacted SiO2 (melting point 1650℃) will exist in the ash, leading to an increase in the ash flow temperature and a shift of the viscosity temperature range to the higher temperature region. Table 2 shows that considering the blending ratio, FT temperature (ash flow temperature), and the temperature point corresponding to a viscosity of 2.5 Pa·s (T... 2.5Pa∙s The temperature point corresponding to a viscosity of 25 Pa·s (T) 25Pa∙s Considering factors such as the temperature range, temperature interval, and cost corresponding to a viscosity of 2.5-25 Pa·s, the optimal condition is a SiO2 mass fraction of 6%, which results in a maximum decrease in the FT temperature of the ash slag of 389℃; the viscosity-temperature curve is attached. Figure 3As shown, the temperature range corresponding to a viscosity of 2.5-25 Pa·s is from 1149℃ to 1268℃, with the temperature interval becoming 119℃.

[0052] Table 2. Experimental results of SiO2 mixing

[0053] Compared to municipal solid waste raw materials, the flow temperature of municipal solid waste ash after adding SiO2 is significantly reduced, and the temperature interval is significantly widened. This is beneficial for reducing the reaction temperature of the fluidized bed and increasing the adaptability of the slag discharge port to temperature fluctuations, thereby reducing energy consumption and improving equipment stability and operational safety.

[0054] Example 2 Al2O3 and municipal solid waste were separately crushed and sieved to obtain fragments of municipal solid waste and Al2O3 with a particle size of less than 0.2 mm. The Al2O3 fragments were then mixed with the municipal solid waste fragments at mass ratios of 2%, 3%, 5%, 6%, and 8% to obtain homogenized materials of Al2O3 and municipal solid waste with different blending ratios. These homogenized materials were then fed into an entrained gasification bed for gasification. The ash residue after gasification was subjected to ash flow temperature and viscosity-temperature curve tests, and the results are shown in Table 3. With the addition of an appropriate amount of Al2O3, CaO reacted with Al2O3 to form CaAl2O4 (melting point 1600℃), which lowered the ash residue flow temperature and broadened the temperature range for viscosity conforming to 2.5-25 Pa·s. However, when Al2O3 was in excess, it reacted with MgO to form MgAl2O4 (2130℃), causing the ash residue flow temperature to rise. The temperature point (T) corresponding to the combined blending ratio, FT temperature, and viscosity of 2.5 Pa·s. 2.5Pa∙s The temperature point corresponding to a viscosity of 25 Pa·s (T) 25Pa∙s Considering factors such as the temperature range, temperature interval, and cost associated with a viscosity of 2.5-25 Pa·s, the optimal scenario is achieved when the Al2O3 mass fraction is 3%, resulting in a maximum decrease in slag flow temperature of 296℃. The viscosity-temperature curve is shown in the attached figure. Figure 4 As shown, the temperature range corresponding to a viscosity of 2.5-25 Pa·s is from 1124℃ to 1226℃, and the temperature interval becomes 102℃.

[0055] Table 3 Results of Al2O3 mixing experiments

[0056] Compared to municipal solid waste raw materials, the ash residue after adding Al2O3 shows a significant decrease in flow temperature and a significant widening of temperature interval. This helps to reduce the reaction temperature of the fluidized bed and increase the adaptability of the ash discharge port to temperature fluctuations, thereby reducing energy consumption and improving equipment stability and operational safety.

[0057] Example 3 A mixture of SiO2 / Al2O3 with a mass ratio of 3.5 was prepared. SiO2 / Al2O3 and municipal solid waste were separately crushed and sieved to obtain municipal solid waste fragments and SiO2 / Al2O3 fragments with particle sizes all less than 0.2 mm. The SiO2 / Al2O3 fragments were then mixed with the municipal solid waste fragments at mass fractions of 2%, 3%, 5%, 6%, and 8% to obtain homogenized materials of SiO2 / Al2O3 and municipal solid waste with different blending ratios. These homogenized materials were then fed into an entrained flow bed for gasification. The ash slag after gasification was tested for flow temperature and viscosity-temperature curves, and the results are shown in Table 4. With the appropriate addition of SiO2 and Al2O3, the high CaO content in the slag was converted into anorthite (melting point 1551℃), resulting in a decrease in the ash slag flow temperature. Meanwhile, due to the small grain size of SiO2, adding SiO2 will widen the temperature range that corresponds to a viscosity of 2.5-25 Pa·s. However, when excessive amounts of SiO2 and Al2O3 are added, the excess SiO2 and Al2O3 will react with MgO in the ash to form MgAl2Si2O8 (melting point 1890℃), thus increasing the ash flow temperature and shifting the viscosity temperature range towards higher temperatures. The optimal blending ratio, FT temperature, and temperature point corresponding to a viscosity of 2.5 Pa·s are considered. 2.5Pa∙s The temperature point corresponding to a viscosity of 25 Pa·s (T) 25Pa∙s Considering factors such as the temperature range, temperature interval, and cost corresponding to a viscosity of 2.5-25 Pa·s, the optimal situation is when the mass fraction of SiO2 / Al2O3 mixture is 3%, which reduces the slag flow temperature by 292℃. The viscosity-temperature curve is shown in the attached figure. Figure 5 As shown, the temperature range that meets the viscosity of 2.5-25 Pa·s is from 1135℃ to 1246℃, and the temperature interval becomes 111℃.

[0058] Table 4 Results of SiO2 / Al2O3 = 3.5 Blending Experiment

[0059] Compared to municipal solid waste raw materials, the ash slag with added Al2O3 and SiO2 exhibits a significant decrease in flow temperature and a marked widening of temperature intervals. This helps to reduce the reaction temperature of the fluidized bed and increase the adaptability of the slag discharge port to temperature fluctuations, thereby reducing energy consumption and improving equipment stability and operational safety.

[0060] Example 4 Kaolin and municipal solid waste were crushed and sieved separately to obtain municipal solid waste fragments and kaolin fragments with a particle size of less than 0.2 mm. The kaolin fragments were then mixed with the municipal solid waste fragments at mass ratios of 2%, 3%, 5%, 6%, and 8% to obtain homogenized materials of kaolin and municipal solid waste with different blending ratios. These homogenized materials were then fed into an entrained gasification bed for gasification. The ash slag after gasification was tested for ash flow temperature and viscosity-temperature curves, and the results are shown in Table 5. With the addition of an appropriate amount of kaolin, the proportion of low-melting-point substances such as CaAl2Si2O8, CaAl2O4, and CaSiO3 in the slag continuously increased, thus decreasing the ash flow temperature of the slag. However, when kaolin was added in excess, high-melting-point substances such as SiO2, MgAl2Si2O8, and MgAl2O4 appeared in the slag, leading to an increase in the ash flow temperature of the slag. The temperature point (T) corresponding to the combined blending ratio, FT temperature, and viscosity of 2.5 Pa·s. 2.5Pa∙s The temperature point corresponding to a viscosity of 25 Pa·s (T) 25Pa∙s Considering factors such as the temperature range, temperature interval, and cost corresponding to a viscosity of 2.5-25 Pa·s, the optimal situation is when the kaolin mass fraction is 3%, the slag flow temperature decreases by 301℃. The viscosity-temperature curve is shown in the attached figure. Figure 6 As shown, the temperature range corresponding to a viscosity of 2.5-25 Pa·s is from 1133℃ to 1241℃, with the temperature interval becoming 108℃, which is in a relatively low temperature range.

[0061] Table 5 Results of Kaolin Blending Experiment

[0062] Compared to municipal solid waste raw materials, the ash residue after adding kaolin exhibits a significant decrease in flow temperature and a marked widening of temperature intervals. This helps to reduce the reaction temperature of the fluidized bed and increase the adaptability of the ash discharge port to temperature fluctuations, thereby reducing energy consumption and improving equipment stability and operational safety.

[0063] Example 5 K2CO3 and municipal solid waste were crushed and sieved separately to obtain municipal solid waste fragments and K2CO3 fragments with a particle size of less than 0.2 mm. The K2CO3 fragments were mixed with the municipal solid waste fragments at mass fractions of 2%, 3%, 5%, 6%, and 8% to obtain homogenized materials of K2CO3 and municipal solid waste with different blending ratios. These homogenized materials were then fed into an entrained gasification bed for gasification. The ash residue after gasification was subjected to flow temperature and viscosity-temperature curve tests, and the results are shown in Table 6. K2CO3 has a low melting point of only 891℃, which leads to low-temperature eutectic melting, causing high-melting-point CaO and Ca2SiO4 to melt at relatively low temperatures. Therefore, as the K2CO3 content increases, the ash residue flow temperature decreases, and the viscosity-temperature interval first increases and then decreases. The temperature points corresponding to the combined blending ratio, FT temperature, and viscosity at 2.5 Pa·s (T0) are shown in Table 6. 2.5Pa∙s The temperature point corresponding to a viscosity of 25 Pa·s (T) 25Pa∙s Considering factors such as the temperature range, temperature interval, and cost corresponding to a viscosity of 2.5-25 Pa·s, the optimal situation is when the K2CO3 mass fraction is 3%, resulting in a maximum decrease in slag flow temperature of 402℃. The viscosity-temperature curve is attached. Figure 7 As shown, the temperature range corresponding to a viscosity of 2.5-25 Pa·s is from 1050℃ to 1156℃, with the temperature interval becoming 106℃.

[0064] Table 6 Results of K2CO3 Blending Experiment

[0065] Compared to municipal solid waste raw materials, the ash residue after adding K2CO3 shows a significant decrease in flow temperature and a significant widening of temperature interval. This helps to reduce the reaction temperature of the fluidized bed and increase the adaptability of the ash discharge port to temperature fluctuations, thereby reducing energy consumption and improving the stability and safety of equipment operation.

[0066] The ash discharge port of the high-temperature gasifier is a certain distance from the central heating zone of the gasifier. This results in the ash discharge port temperature being lower than the actual reaction temperature of the fluidized bed and exhibiting some fluctuation. A wider temperature interval not only reduces the requirements for the reaction temperature but also accommodates the temperature fluctuations at the ash discharge port, increasing the stability and safety of equipment operation and enabling smooth liquid ash discharge.

[0067] This application provides a method for liquid slag discharge of municipal solid waste ash, which can add a small amount of inorganic flux to reduce the melting temperature of municipal solid waste during gasification reaction, thereby reducing energy consumption and equipment operating costs. It can also meet the temperature fluctuations at the slag discharge port, while greatly reducing the increase in the content of raw material ash. Furthermore, when the content of alkaline oxides and acidic oxides in the municipal solid waste ash tends to be in equilibrium, the fluidized bed gasifier will not slag or corrode, improving the stability and safety of equipment operation and achieving smooth liquid slag discharge.

[0068] The specific advantages of this application are as follows: 1. The selection of flux type and dosage in this application can effectively reduce the ash melting temperature of municipal solid waste and improve the ash viscosity-temperature characteristic curve, so that the flow temperature of municipal solid waste ash drops from above 1500℃ to below 1300℃, and the ash viscosity-temperature characteristic curve meets the operating standards of fluidized bed gasification technology.

[0069] 2. This application addresses the impact of seasonal and regional factors on the composition of municipal solid waste ash. It starts by adjusting the proportion of ash components in municipal solid waste ash and adjusts the amount of flux added according to the different ash components of different raw materials. It is highly flexible and widely applicable.

[0070] 3. The flux used in this application to reduce the ash melting temperature is widely available and inexpensive, and the amount added is only 1 to 10% of the raw material mass fraction, which will not significantly increase the raw material cost of production.

[0071] The above description of the embodiments disclosed in this application enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for discharging liquid ash from municipal solid waste, characterized in that, Including steps, Composition analysis: Determining the composition of municipal solid waste ash; Flux selection: Based on the composition of municipal solid waste ash, select one flux or a mixture of at least two fluxes as the inorganic flux; Gasification reaction: municipal solid waste is mixed with flux or mixture, and the resulting mixture is subjected to a gasification reaction to discharge ash and slag.

2. The method according to claim 1, characterized in that, The main components of the municipal solid waste ash in the composition determination step include CaO, SiO2, and Al2O3, with CaO having the highest content. Based on the mass fraction of CaO, one flux or a mixture of at least two fluxes is selected as an inorganic flux in the flux selection step. The mixing ratio of various fluxes in the flux mixture is adjusted to the blending ratio of municipal solid waste and inorganic flux in the gasification reaction step, so that the inorganic flux reacts with CaO to generate a low-melting-point compound and produce a low-temperature eutectic effect, thereby adjusting the physicochemical properties of the ash in the gasification reaction step.

3. The method according to claim 2, characterized in that, The inorganic flux is selected from substances whose main components are at least one of SiO2, Al2O3, K2O, Na2O and Fe2O3.

4. The method according to claim 2, characterized in that, The inorganic flux is selected from substances that can be prepared by calcination to contain at least one of SiO2, Al2O3, K2O, Na2O and Fe2O3.

5. The method according to claim 2, characterized in that, The inorganic flux is selected from complexes or salts containing at least one of SiO2, Al2O3, K2O, Na2O and Fe2O3.

6. The method according to claim 2, characterized in that, The inorganic flux contains SiO2:Al2O3 with a ratio of 2 to 5.

7. The method according to claim 2, characterized in that, The component determination step includes establishing a ternary phase diagram: establishing a SiO2-Al2O3-CaO ternary phase diagram based on the main components of the municipal solid waste ash, and adjusting the proportion of the inorganic flux in the flux selection step and the mixing ratio of the municipal solid waste and the inorganic flux in the gasification reaction step based on the SiO2-Al2O3-CaO ternary phase diagram.

8. The method according to claim 1, characterized in that, The gasification reaction step includes: Homogenization process: The municipal solid waste and the inorganic flux are crushed and sieved separately to obtain fragments of municipal solid waste and inorganic flux. The fragments of municipal solid waste and inorganic flux are thoroughly mixed to obtain homogenized material, which is then fed into a gasifier for gasification reaction and ash is discharged.

9. The method according to claim 8, characterized in that, In the homogenization process, the particle size of both the municipal solid waste fragments and the inorganic flux fragments is less than 0.2 mm.

10. The method according to claim 8, characterized in that, During the homogenization process, the homogenization steps include thorough mixing via mechanical mixing and / or pyrolytic mixing.

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