A method and device for resource utilization of silicone waste liquid by staged pyrolysis

Abstract

This invention discloses a pyrolysis method and apparatus for siloxane waste liquid. The method includes: preheating and atomizing the siloxane waste liquid to obtain siloxane waste liquid vapor; mixing the siloxane waste liquid vapor with water vapor to obtain mixed vapor; hydrolyzing and filtering the mixed vapor under an inert gas atmosphere to obtain syngas and pyrolysis ash; mixing and compacting the pyrolysis ash with conductive carbon black to obtain a fixed material; placing the fixed material into a Joule thermal reactor; and flash heating the fixed material through pulse discharge to obtain a silicon carbide-graphene composite material. This method enables rapid reaction and decomposes siloxane waste liquid without generating secondary pollutants. It has the advantages of good adaptability, high speed, high efficiency, no catalyst required, no waste generation, and can realize the resource conversion of organosiloxane waste liquid.

Description

Technical Field

[0001] This invention pertains to industrial hazardous waste treatment technology, specifically relating to a method and apparatus for the staged pyrolysis and resource recovery of siloxane waste liquid. Background Technology

[0002] Organosilicon refers to siloxane organic polymers formed by the cross-linking of silicon and oxygen. It mainly includes chemicals such as silicone rubber, silicone oil, and silicone-based coupling agents. Its downstream applications are widely distributed, and the industry has a large scale and a complete industrial chain. In 2022, the product output reached 1.48 million tons and showed a rapid growth trend.

[0003] Siloxane monomers are one of the upstream basic raw materials for the deep processing of organosilicon products. They can form long-chain structures of silicon-oxygen and silicon-carbon-oxygen through various substitution or polymerization methods, enabling the synthesis of various organosilicon products such as silicone oil and silicone rubber. The synthesis process of siloxanes involves the alcoholysis and distillation separation of chlorosilanes, and waste is inevitably generated in the production process. Typical examples include waste liquids containing dimethyldiethoxysilane, hexamethylcyclotrisiloxane, and their low degree of polymerization.

[0004] On the one hand, the strong chemical stability of siloxanes is due to their unique silicon-oxygen bonds with high bond energy, making chemical oxidation methods difficult to effectively remove them; traditional incineration results in high carbon emissions, making it difficult to achieve resource utilization of waste siloxane liquids. If this type of waste liquid is directly separated by means of distillation, the separation cost is high and the separation efficiency is difficult to guarantee due to the unstable source of raw materials and complex composition.

[0005] Patent application CN 113880358 A discloses a method for effectively removing siloxanes and COD from organosilicon wastewater. This method utilizes mechanical separation, Fenton oxidation, electrocoagulation, and evaporative desalination, followed by end-of-pipe biodegradation, to remove and discharge pollutants from siloxane-containing wastewater. However, this method is highly complex, involving more than thirty unit operations. Furthermore, it is only applicable to siloxane concentrations not exceeding 10,000 ppm, and the removal process primarily relies on front-end Fenton oxidation and flocculation separation, making it difficult to treat and utilize wastewater primarily composed of organosilicon.

[0006] Patent application CN 104672452A discloses a method for recycling and reusing waste polysiloxane materials, providing a method for preparing large-scale polysiloxane materials from waste polysiloxane materials, thus achieving the reuse of waste. However, this method requires the use of precious metal catalysts and large amounts of organic solvents for more than ten hours of reaction, and also requires secondary separation by methods such as column chromatography, resulting in low waste disposal efficiency and the generation of secondary waste. The above analysis shows that existing technologies mainly target the purification of low-concentration siloxanes, and suffer from problems such as complex process operation, low resource utilization efficiency, and the generation of secondary pollutants. Summary of the Invention

[0007] This invention provides a staged pyrolysis resource recovery method for siloxane waste liquid. This method can decompose siloxane waste liquid with rapid reaction and no secondary pollutants. This method has the advantages of good adaptability, fast speed, high efficiency, no catalyst use, no waste generation, and can realize the resource recovery and transformation of organosiloxane waste liquid.

[0008] This invention provides a method for the staged pyrolysis resource recovery of siloxane waste liquid, comprising:

[0009] (1) The siloxane waste liquid is preheated and atomized to obtain siloxane waste liquid vapor. The siloxane waste liquid vapor is mixed with water vapor to obtain mixed vapor. The mixed vapor is hydrolyzed and filtered under an inert gas atmosphere to obtain syngas and pyrolysis ash.

[0010] (2) The pyrolysis ash residue is mixed with conductive carbon black, ball milled and compacted to obtain a fixed material. The fixed material is placed in a Joule thermal reactor and flash-heated by pulse discharge to obtain a silicon carbide-graphene composite material.

[0011] This invention utilizes a two-stage thermal treatment waste liquid high-value utilization method through efficient steam pyrolysis reforming and electric pulse Joule thermal coupling. It can achieve the production of syngas through steam pyrolysis reforming of waste liquid without the use of catalysts, while using Joule thermal flash evaporation to convert pyrolysis ash into silicon carbide-graphene high-value-added composite material.

[0012] Preferably, the mass ratio of siloxane waste liquid vapor to water vapor is 1:1 to 3. If the water vapor content is too low, the hydrolysis will be insufficient, resulting in a significant decrease in the efficiency of syngas production from the pyrolysis of siloxane waste liquid vapor; if the water vapor content is too high, the specific heat of the mixed steam will increase, leading to a decrease in the efficiency of the pyrolysis process.

[0013] Preferably, the hydrolysis temperature is 600–900°C, and the reaction residence time is 60–600 seconds. Too low a temperature is detrimental to the steam pyrolysis process and the decomposition of hydrolysis products; too low a reaction residence time leads to incomplete hydrolysis and pyrolysis reactions, which is unfavorable for the pyrolysis of waste siloxanes to produce syngas; too high a temperature and too long a residence time have no significant promoting effect on the carbon conversion rate of the siloxane waste liquid vapor.

[0014] Preferably, the components of the siloxane waste liquid include one or more of dimethyldiethoxysilane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecylcyclohexasiloxane.

[0015] Preferably, the resistivity of the fixed material is 2.51 to 200.96 Ω·cm, and the capacitance ratio of the fixed material to the Joule thermal reactor is 0.5 to 1.5 g / F, so as to achieve efficient heating of the fixed material.

[0016] Preferably, the voltage for flash heating is 100–170V.

[0017] Preferably, the fixed material is preheated at a voltage of 20-30V to improve flash evaporation stability. Otherwise, the flash evaporation temperature may be too low or a large amount of gas may be generated during the flash evaporation process, causing the reaction quartz tube to crack.

[0018] Preferably, the main components of the obtained synthesis gas are one or more of H2, CO, CO2, CH4, C2H6, C2H4, C3H8, and C3H6.

[0019] On the other hand, the present invention also provides a staged pyrolysis resource recovery device for siloxane waste liquid, comprising:

[0020] The material pretreatment unit is used to preheat and atomize the siloxane waste liquid to obtain siloxane waste liquid vapor;

[0021] A steam generating unit is used to generate steam.

[0022] The pyrolysis gasification furnace is connected at the top to a siloxane waste liquid pretreatment unit and a steam generation unit, respectively. It is used to mix siloxane waste liquid vapor and steam to obtain mixed steam, and then hydrolyze the mixed steam under an inert gas atmosphere to obtain syngas and pyrolysis gas.

[0023] An ash filter is connected to the bottom of a pyrolysis gasifier to filter pyrolysis gas to obtain pyrolysis ash and discharge syngas.

[0024] A ball mill is used to mix pyrolysis ash collected from a filter with conductive carbon black and grind them thoroughly to obtain the material to be processed.

[0025] The Joule thermal reactor is used to compact the material to be processed to obtain a fixed material, and then flash heat the fixed material by pulse discharge to obtain a silicon carbide-graphene composite material.

[0026] Preferably, the material pretreatment unit includes:

[0027] Siloxane waste liquid storage tank, used to store siloxane waste liquid;

[0028] A material pump, connected to a siloxane waste liquid storage tank, is used to pump out the siloxane waste liquid at a set flow rate;

[0029] The material preheating device includes a vertically arranged material pipeline and a heating device installed on the outside of the pipeline. The material pipeline is connected to a material pump. The heating device heats the siloxane waste liquid in the material pipeline to obtain siloxane waste liquid vapor.

[0030] The pyrolysis gasification reactor is a vertical pyrolysis furnace, with the material inlet and carrier gas inlet at the top and the material outlet at the bottom. Heating devices are installed on the side walls. Premixed material enters the pyrolysis furnace through a pipe at the top, and the pyrolysis products flow out of the gasification furnace from the bottom. The ash filter contains multiple layers of metal mesh; pyrolysis furnace gas is filtered and collected from the mesh to obtain pyrolysis ash. The Joule heating reactor consists of a high-voltage power supply, a control system, a high-voltage capacitor, a material discharge heating tube, and discharge electrodes.

[0031] Preferably, the high-voltage capacitor of the Joule thermal reactor has a capacity of 90mF and can be controlled by the control system to achieve discharge at a maximum current of 600A under different voltages.

[0032] Preferably, the Joule thermal reactor includes a material discharge heating tube, which is made of quartz and is replaceable. The material discharge heating tube includes a graphite plug and a contact discharge electrode. After the pyrolysis ash is loaded into the heating tube and compacted, graphite plugs are added to both ends and then the contact discharge electrode is applied.

[0033] The technical principle of this invention, which couples efficient steam pyrolysis reforming and electric pulse Joule heating in a two-stage thermal treatment process to achieve the treatment and high-value utilization of siloxane waste liquid, is as follows:

[0034] (1) The organosiloxane waste liquid is preheated and atomized, then mixed with steam and fed into a pyrolysis gasification furnace for pyrolysis. On the one hand, organosiloxanes can undergo hydrolysis under this environment, promoting the breaking of Si-OC bonds and generating Si-OH and C-OH structures. This promotes the decomposition of siloxanes in the waste liquid and transforms carbon from a chemically stable siloxane form to an alcohol form that is easily thermally decomposed, thereby improving its carbon conversion efficiency. On the other hand, steam has weak oxidizing properties at high temperatures. During high-temperature pyrolysis gasification, it acts as an oxidant and a source of hydrogen and oxygen, inhibiting the formation of coke during high-temperature pyrolysis, thereby promoting the increase of syngas yield and CO and H2 content. By adjusting the amount of steam and the pyrolysis temperature, the pyrolysis atmosphere in the gasification furnace is controlled, promoting the pyrolysis of siloxanes under high-temperature conditions, realizing the pyrolysis of the main components of the siloxane waste liquid and the conversion into the main components of syngas, hydrogen and methane.

[0035] (2) The main components of pyrolysis ash are a non-conductive mixture of amorphous silicon dioxide and coke. High-temperature heat treatment can promote the reaction between silicon dioxide and carbon to generate silicon carbide, so that the residual silicon and carbon elements in the ash can be reused. The reaction process is mainly represented by the following reaction equation:

[0036] SiO2 + 2C → SiC + CO2 (1)

[0037] SiO2 + 3C → SiC + 2CO (2)

[0038] Reaction (1) can proceed spontaneously when the temperature reaches above 2500℃, and reaction (2) can proceed spontaneously when the temperature reaches above 1500℃. This indicates that a higher carbon-silicon ratio is beneficial to promoting the reduction of silicon carbide generation temperature. The pyrolysis gasification process converts a large amount of carbon into syngas components, so it is necessary to add carbon sources to the pyrolysis ash to promote silicon carbide generation.

[0039] (3) The Joule thermal flash evaporation of electric pulse utilizes the Joule thermal effect of electric current to allow the current generated by the instantaneous discharge of the capacitor to pass through the material. According to Joule's law, the material itself generates a large amount of heat at the moment of discharge, and the heating part is concentrated. The temperature of this area can be heated from room temperature to above 2500℃ within tens of milliseconds, reaching the spontaneous generation temperature range of silicon carbide material. When the capacitor finishes discharging, no current passes through the material. At this time, the material itself no longer generates heat, and the heating area dissipates heat quickly through air convection, allowing its temperature to return to room temperature within a few seconds.

[0040] Adding conductive carbon black to pyrolysis ash not only improves the material's conductivity, but also, as a carbon source, greatly promotes the reaction from silicon dioxide to silicon carbide. By adjusting the capacitor charging voltage, the energy input to the material region of the flash circuit can be precisely controlled, enabling millisecond-scale rapid response to control the material's heating temperature to reach the silicon carbide formation temperature range.

[0041] Based on the above principles, the yield of syngas from organosiloxane waste liquid pyrolysis and the carbon conversion rate are improved. Furthermore, the precise millisecond-level high-temperature heating of pyrolysis ash and conductive carbon black materials through Joule thermal flash evaporation enables the silicon element in the pyrolysis ash to be rapidly and efficiently converted into high-value-added carbon-silicon composite materials, thereby achieving waste reduction and control in the disposal process.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] (1) This invention utilizes all components of organosiloxane waste liquid for resource recovery and effectively controls the migration and utilization pathways of major elements such as carbon, hydrogen, oxygen and silicon.

[0044] (2) The present invention precisely controls the pyrolysis process of organosiloxane waste liquid, and improves the pyrolysis performance and carbon conversion rate of siloxane by utilizing the weak oxidizing properties of water vapor, thereby obtaining high-content syngas.

[0045] (3) This invention further utilizes the gasification by-product ash residue in a high-value manner and synthesizes SiC-graphene composite material through high-temperature heat treatment, achieving zero waste generation throughout the entire process and increasing the added value of the entire technical solution.

[0046] (4) This invention uses a direct flash electrothermal process to heat gasified ash residue. The input electrical energy is almost entirely used for high-temperature pyrolysis of the material, which has the characteristics of short processing time and high energy utilization.

[0047] (5) The method described in this invention is simple, the raw materials are readily available, the energy utilization rate is high, and the economic benefits are good. Attached Figure Description

[0048] Figure 1 A schematic diagram of the process flow for the staged pyrolysis resource recovery method of siloxane waste liquid provided in a specific embodiment of the present invention;

[0049] Figure 2 A schematic diagram of a staged pyrolysis resource recovery device for siloxane waste liquid provided in a specific embodiment of the present invention.

[0050] In the diagram: 1-Inert gas cylinder (gas source); 2-Organosiloxane waste liquid storage tank; 3-Material pump; 4-Material heater; 5-Water storage tank; 6-Water pump; 7-Steam generator; 8-Pyrolysis gasification furnace; 9-Ash filter; 10-Ball mill; 11-Joule thermal reactor. Detailed Implementation

[0051] The present invention will now be described in detail with reference to specific embodiments. These embodiments are merely examples illustrating the implementation of the present invention and do not constitute a limitation thereof. Any modifications and optimizations based on the essence and concept of the present invention fall within the protection scope of the present invention.

[0052] This invention provides a staged pyrolysis resource recovery method for siloxane waste liquid, such as... Figure 1 As shown, it includes the following steps:

[0053] (1) Preheat the gasifier to 600-900℃. During the heating process and before pumping in the siloxane waste liquid, use nitrogen, argon or helium as carrier gas and purge to fully replace the air in the gasifier, and keep the reaction residence time in the gasifier at 60-600 seconds.

[0054] (2) When the gasifier reaches the set temperature, the siloxane waste liquid containing any one or more of the following components, such as dimethyldiethoxysilane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecylcyclohexasiloxane, is preheated and atomized at a constant flow rate and then mixed with water vapor at a mass ratio of 1:1.0 to 3.0 and pumped into the gasifier. Subsequently, a pyrolysis reaction occurs, and the syngas product is obtained after purification by a gas filter. Pyrolysis ash is collected from the gasifier and the filter.

[0055] (3) After drying the pyrolysis ash residue for 24 hours, mix it evenly with carbon black and compact it so that the resistivity of the material is 2.51~200.96Ω·cm. Put the material into the Joule thermal reactor at 0.5~1.5g / F. Then, the mixed ash residue is preheated by pulse discharge at a voltage of 20~30V and flashed by discharge at a voltage of 100~170V to complete the reaction, and finally obtain silicon carbide-graphene composite material.

[0056] To achieve the above method, the present invention provides a system for the efficient pyrolysis and resource-based treatment of siloxane waste liquid, such as... Figure 2As shown, the system specifically includes: a material pump, a material preheating device, a pyrolysis gasification reactor, an ash filter, a ball mill, and a Joule heating reactor. The material preheating device is located at the front end of the pyrolysis gasification reactor. The material is pumped into the preheating device at a constant flow rate to achieve preheating. At the outlet, the material is atomized and mixed with a constant proportion of water vapor before entering the pyrolysis gasification reactor. An ash filter is located at the rear end to collect the ash produced by pyrolysis. After collection, the ash is transferred to the ball mill and uniformly mixed with conductive carbon black before being placed into the Joule heating reactor for treatment. The Joule heating reactor consists of a high-voltage power supply, a control system, a high-voltage capacitor, a material discharge heating tube, and discharge electrodes. The high-voltage capacitor has a capacity of 90mF and is controlled by the control system to achieve discharge at a maximum current of 600A under different voltages. The material discharge heating tube is made of quartz and is replaceable. The ash material to be treated is compacted after being loaded into the heating tube, and graphite plugs are added to both ends before contacting the discharge electrodes.

[0057] Example 1:

[0058] Elemental analysis of the organosiloxane waste liquid used in this embodiment was obtained through industrial analysis and ICP-OES spectroscopy. The contents of its main elements are shown in the table below:

[0059] Table 1. Elemental analysis results of organosiloxane waste liquid

[0060]

[0061] Gas chromatography-mass spectrometry analysis revealed that the waste liquid sample was a mixture of various organosiloxanes, including dimethyldiethoxysilane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecylcyclohexasiloxane.

[0062] (1) Preheat the gasifier to 900°C. Use nitrogen as a carrier gas and purge the gasifier during the heating process and before pumping in the siloxane waste liquid to fully replace the air in the gasifier and keep the reaction residence time in the gasifier at 60 seconds.

[0063] (2) When the gasifier reaches the set temperature, the siloxane waste liquid is preheated and atomized at a constant flow rate, mixed with water vapor at a mass ratio of 1:2.0 and pumped into the gasifier. Then, a pyrolysis reaction occurs. After purification by a gas filter, syngas product is obtained, and pyrolysis ash is collected from the gasifier and the filter.

[0064] (3) After drying the pyrolysis ash residue for 24 hours, it is uniformly mixed with carbon black, ball-milled, and then packed into a quartz tube with graphite plugs at both ends at a material-capacitance ratio of 1.0 g / F and compacted to make the resistivity of the material 2.51 Ω·cm. The mixture is then placed in a Joule thermal reactor, and the mixed ash residue is preheated by pulse discharge at a voltage of 20V and flashed by discharge at a voltage of 170V to complete the reaction, finally obtaining silicon carbide-graphene composite material.

[0065] Analysis of test results:

[0066] The filtered syngas was collected using a 10L aluminum foil gas sampling bag, and the syngas components and their contents were detected using gas chromatography. The total syngas yield was calculated to be 40.91 mmol / g [waste liquid], the carbon conversion rate was 72.99%, and the hydrogen volume content was 42.82%. The composite material after flash heating was characterized by powder XRD. Characteristic peaks of graphene and 3C-SiC were observed in the obtained diffraction spectrum, among which the intensity value of the characteristic peak of the (1 1 1) crystal plane of 3C-SiC was 862037 cps.

[0067] Example 2

[0068] The siloxane waste liquid described in this embodiment is the same as that described in Example 1.

[0069] (1) Preheat the gasifier to 800°C. Use argon as a carrier gas and purge the gasifier during the heating process and before pumping in the siloxane waste liquid to fully replace the air in the gasifier and keep the reaction residence time in the gasifier at 150 seconds.

[0070] (2) When the gasifier reaches the set temperature, the siloxane waste liquid is preheated and atomized at a constant flow rate, mixed with water vapor at a mass ratio of 1:1.0 and pumped into the gasifier. Then, a pyrolysis reaction occurs. After purification by a gas filter, syngas product is obtained, and pyrolysis ash is collected from the gasifier and the filter.

[0071] (3) After drying the pyrolysis ash residue for 24 hours, mix it evenly with carbon black and fill it into a quartz tube with graphite plugs at both ends with a material-capacitance ratio of 0.5 g / F. Compact the material so that the resistivity is 10.15 Ω·cm. Place it into a Joule thermal reactor and then perform preheating discharge at 30 V and flash heating discharge at 150 V by pulse discharge to complete the reaction. Finally, silicon carbide-graphene composite material is obtained.

[0072] Analysis of test results:

[0073] The filtered syngas was collected using a 10L aluminum foil gas sampling bag, and the syngas components and their contents were detected using gas chromatography. The total syngas yield was calculated to be 18.49 mmol / g [waste liquid], the carbon conversion rate was 37.81%, and the hydrogen volume content was 35.20%. The composite material after flash heating was characterized by powder XRD. Characteristic peaks of graphene and 3C-SiC were observed in the obtained diffraction spectrum, among which the intensity value of the characteristic peak of the (1 1 1) crystal plane of 3C-SiC was 553704 cps.

[0074] Example 3

[0075] The siloxane waste liquid described in this embodiment is the same as that described in Example 1.

[0076] (1) Preheat the gasifier to 700°C. Use helium as a carrier gas and purge the gasifier during the heating process and before pumping in the siloxane waste liquid to fully replace the air in the gasifier and keep the reaction residence time in the gasifier at 300 seconds.

[0077] (2) When the gasifier reaches the set temperature, the siloxane waste liquid is preheated and atomized at a constant flow rate, mixed with water vapor at a mass ratio of 1:2.0 and pumped into the gasifier. Then, a pyrolysis reaction occurs. After purification by a gas filter, syngas product is obtained, and pyrolysis ash is collected from the gasifier and the filter.

[0078] (3) After drying the pyrolysis ash residue for 24 hours, mix it evenly with carbon black and fill it into a quartz tube with graphite plugs at both ends with a material-capacitance ratio of 1.5 g / F. Compact the material so that the resistivity is 53.65 Ω·cm. Place it into a Joule thermal reactor and then perform a preheating discharge at a voltage of 20 V and a flash heating discharge at a voltage of 130 V on the mixed ash residue through pulse discharge to complete the reaction. Finally, silicon carbide-graphene composite material is obtained.

[0079] Analysis of test results:

[0080] The filtered syngas was collected using a 10L aluminum foil gas sampling bag, and the syngas components and their contents were detected using gas chromatography. The total syngas yield was calculated to be 32.01 mmol / g [waste liquid], the carbon conversion rate was 73.30%, and the hydrogen volume content was 28.08%. The composite material after flash heating was characterized by powder XRD. Characteristic peaks of graphene and 3C-SiC were observed in the obtained diffraction spectrum, among which the intensity value of the characteristic peak of the (1 1 1) crystal plane of 3C-SiC was 362845 cps.

[0081] Example 4

[0082] The siloxane waste liquid described in this embodiment is the same as that described in Example 1.

[0083] (1) Preheat the gasifier to 600°C. Use nitrogen as a carrier gas and purge the gasifier during the heating process and before pumping in the siloxane waste liquid to fully replace the air in the gasifier and keep the reaction residence time in the gasifier at 600 seconds.

[0084] (2) When the gasifier reaches the set temperature, the siloxane waste liquid is preheated and atomized at a constant flow rate, mixed with water vapor at a mass ratio of 1:3.0 and pumped into the gasifier. Then, a pyrolysis reaction occurs. After purification by a gas filter, syngas product is obtained, and pyrolysis ash is collected from the gasifier and the filter.

[0085] (3) After drying the pyrolysis ash residue for 24 hours, mix it evenly with carbon black and fill it into a quartz tube with graphite plugs at both ends with a material-capacitance ratio of 1.0 g / F. Compact the material so that the resistivity is 200.96 Ω·cm. Place it into a Joule thermal reactor and then perform preheating discharge at 30V and flash heating discharge at 100V on the mixed ash residue through pulse discharge to complete the reaction. Finally, silicon carbide-graphene composite material is obtained.

[0086] Analysis of test results:

[0087] The filtered syngas was collected using a 10L aluminum foil gas sampling bag, and the syngas components and their contents were detected using gas chromatography. The total syngas yield was calculated to be 19.59 mmol / g [waste liquid], the carbon conversion rate was 43.83%, and the hydrogen volume content was 29.63%. The composite material after flash heating was characterized by powder XRD. Characteristic peaks of graphene and 3C-SiC were observed in the obtained diffraction spectrum, among which the intensity value of the characteristic peak of the (1 1 1) crystal plane of 3C-SiC was 221583 cps.

[0088] Comparative Example 1

[0089] Referring to Specific Example 1, except that no water vapor is added, the other material amounts, reaction conditions and operating procedures are the same as in Example 1.

[0090] Comparative Example 2

[0091] Referring to Specific Example 1, except for not adding conductive carbon black to adjust the conductivity of the gasification ash, the other material dosages, reaction conditions, and operating procedures remain the same as in Example 1.

[0092] Performance Analysis:

[0093] The same operation and testing were performed. The results of Comparative Example 1 showed that the total syngas yield was 4.96 mmol / g [waste liquid], and the carbon conversion rate was 11.86%, but the carbon monoxide content was significantly reduced, and the volume content of the high molecular weight C3+ component increased from less than 0.20% to 3.27%. Characteristic peaks of graphene and 3C-SiC could still be observed in the powder XRD diffraction spectrum, with the intensity value of the characteristic peak of the (1 1 1) crystal plane of 3C-SiC being 669529 cps.

[0094] Comparative Example 2: The total syngas yield is not less than 40 mmol / g [waste liquid], the carbon conversion rate is not less than 70%, and the hydrogen volume content is not less than 40%; however, the preheating and flash heating discharge described in step (3) cannot be performed, and the powder XRD diffraction spectrum of the obtained material does not contain graphene and 3C-SiC characteristic peaks.

[0095] The analysis results of the various embodiments and comparative examples show that the syngas production efficiency and carbon conversion rate of Comparative Example 1 decreased, and the SiC content in the composite material obtained by flash evaporation decreased; Comparative Example 2 could not achieve electric pulse flash heating, resulting in no composite material formation. These results indicate that steam pyrolysis can simultaneously promote the pyrolysis of siloxane waste liquid, increase the syngas content, and improve the quality of the flash-obtained material. The control of the resistivity of the material by conductive carbon black directly determines whether electric pulse flash heating is feasible. Therefore, using steam-assisted pyrolysis and using conductive carbon black to control the resistance of the pyrolysis ash can achieve better waste liquid pyrolysis efficiency and composite material yield.

[0096] Analysis of the various embodiments shows that the two-step thermal conversion method proposed in this invention can achieve the pyrolysis conversion of organosiloxane waste liquid and produce two products: syngas and silicon carbide-graphene composite materials. This invention provides a graded resource utilization method for organosiloxane waste liquid based on a two-step thermal conversion method, which fully utilizes the carbon and silicon elements in this type of waste liquid, reducing carbon emissions and secondary ash generation problems in traditional pyrolysis incineration processes. Simultaneously, the produced syngas product can be used for hydrogen production and organic synthesis through conversion reactions, Fischer-Tropsch synthesis, etc.; the silicon carbide-graphene composite material prepared from the thermal treatment of ash can be used as a novel functional material in high-value-added fields such as the preparation of high-performance electrode materials. Therefore, this invention is a technology for the treatment and resource utilization of organosilicon waste liquid with promising industrial applications and economic benefits.

[0097] Furthermore, after reading the above description of the present invention, any applications, additions, modifications, or variations made by those skilled in the art without departing from the meaning and scope of the present invention shall fall within the scope defined by the appended claims.

Claims

1. A method for the staged pyrolysis resource recovery of siloxane waste liquid, characterized in that, include: (1) The siloxane waste liquid is preheated and atomized to obtain siloxane waste liquid vapor. The siloxane waste liquid vapor is mixed with water vapor to obtain mixed vapor. The mixed vapor is hydrolyzed and filtered under an inert gas atmosphere to obtain syngas and pyrolysis ash. (2) The pyrolysis ash residue is mixed with conductive carbon black, ball milled and compacted to obtain a fixed material. The fixed material is placed in a Joule thermal reactor and flash-heated by pulse discharge to obtain a silicon carbide-graphene composite material. The mass ratio of the siloxane waste liquid vapor to water vapor is 1:1 to 3; The hydrolysis temperature is 600–900℃, and the reaction residence time is 60–600 seconds.

2. The method for staged pyrolysis resource recovery of siloxane waste liquid according to claim 1, characterized in that, The components of the siloxane waste liquid include one or more of dimethyldiethoxysilane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecylcyclohexasiloxane.

3. The method for staged pyrolysis resource recovery of siloxane waste liquid according to claim 1, characterized in that, The resistivity of the fixed material is 2.51–200.96 Ω•cm, and the capacitance ratio of the fixed material to the Joule thermal reactor is 0.5–1.5 g / F.

4. The method for staged pyrolysis resource recovery of siloxane waste liquid according to claim 1, characterized in that, The voltage for flash heating is 100–170V.

5. The method for staged pyrolysis resource recovery of siloxane waste liquid according to claim 1, characterized in that, Before flash heating, the fixed material is preheated, and the preheating voltage is 20-30V.

6. The method for staged pyrolysis resource recovery of siloxane waste liquid according to claim 1, characterized in that, The main components of the obtained synthesis gas are one or more of H2, CO, CO2, CH4, C2H6, C2H4, C3H8, and C3H6.

7. A staged pyrolysis resource recovery device for siloxane waste liquid, characterized in that, include: The material pretreatment unit is used to preheat and atomize the siloxane waste liquid to obtain siloxane waste liquid vapor; A steam generating unit is used to generate steam. The pyrolysis gasification furnace is connected at the top to a siloxane waste liquid pretreatment unit and a steam generation unit, respectively. It is used to mix siloxane waste liquid vapor and steam to obtain mixed steam, and then hydrolyze the mixed steam under an inert gas atmosphere to obtain syngas and pyrolysis gas. An ash filter is connected to the bottom of a pyrolysis gasifier to filter pyrolysis gas to obtain pyrolysis ash and discharge syngas. A ball mill is used to mix pyrolysis ash collected from a filter with conductive carbon black and grind them thoroughly to obtain the material to be processed. The Joule thermal reactor is used to compact the material to be processed to obtain a fixed material, and then flash heat the fixed material by pulse discharge to obtain a silicon carbide-graphene composite material.

8. The staged pyrolysis resource recovery device for siloxane waste liquid according to claim 7, characterized in that, The material pretreatment unit includes: Siloxane waste liquid storage tank, used to store siloxane waste liquid; A material pump, connected to a siloxane waste liquid storage tank, is used to pump out the siloxane waste liquid at a set flow rate; The material preheating device includes a vertically arranged material pipeline and a heating device installed on the outside of the pipeline. The material pipeline is connected to a material pump. The heating device heats the siloxane waste liquid in the material pipeline to obtain siloxane waste liquid vapor.

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