A method of treating tpu solid waste with molten sodium salt and producing nitrates

Abstract

The application provides a method for treating TPU solid waste by using molten sodium salt and preparing nitrate, and belongs to the field of solid waste treatment. The method solves the problems of high risk and high cost in traditional molten salt method for recycling TPU. The method comprises the following steps: S1, drying Na2CO3-NaOH at a certain drying temperature for a certain time to remove excess water, mixing the dried Na2CO3 and NaOH at a certain proportion to form a Na2CO3-NaOH system, and placing the Na2CO3-NaOH system in a molten salt reaction kettle; S2, heating the molten salt reaction kettle to a certain temperature and keeping the temperature for a certain time until the Na2CO3-NaOH system is completely melted; S3, putting TPU solid waste in a certain proportion with the Na2CO3-NaOH system into the molten salt reaction kettle, and reacting for a certain time to form waste salt; S4, collecting liquid products in the tail gas gas phase of the molten salt reaction kettle. The waste salt is washed with water and filtered to obtain a liquid sample, the liquid product and the liquid sample are characterized in terms of composition and content, and the content of nitrate in the liquid product and the liquid sample is determined. The method is mainly used for treating TPU solid waste.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment, and in particular relates to a method for treating TPU solid waste with molten sodium salt and preparing nitrate ester. Background Technology

[0002] Due to its excellent properties such as high-temperature stability, solubility, electrical conductivity, chemical stability and high heat capacity, molten salt has been widely used in fields such as steel smelting, chemical synthesis, electronics industry, nuclear energy, nanomaterial synthesis and thermal fluid experiments.

[0003] However, the process of recycling TPU solid waste using molten salt poses significant risks due to factors such as temperature control, oxygen contact, corrosiveness, and toxicity. To meet market demands, a safe and efficient method for extracting chemical raw materials from large quantities of TPU (thermoplastic polyurethane) waste is needed.

[0004] Therefore, it is extremely important to propose a safe, effective, and cost-efficient molten sodium salt method for recycling economically valuable components from TPU solid waste. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for treating TPU solid waste with molten sodium salt and preparing nitrate ester, so as to solve the problems of high risk and high cost of traditional molten salt method for TPU recycling.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for treating TPU solid waste with molten sodium salt and preparing nitrate ester, comprising the following steps:

[0007] S1. Dry Na2CO3-NaOH at a certain drying temperature for a certain time to remove excess moisture. Then, mix the dried Na2CO3 and NaOH in a certain proportion to form a Na2CO3-NaOH system and place it in a molten salt reactor.

[0008] S2. Heat the molten salt reactor to a certain temperature and hold it at that temperature for a certain time until the Na2CO3-NaOH system is completely melted;

[0009] S3. After adding TPU solid waste in a certain proportion to the Na2CO3-NaOH system into the molten salt reactor and reacting for a certain period of time, waste salt is formed.

[0010] S4. Collect the liquid products in the tail gas phase of the molten salt reactor. After washing and filtering the waste salt, obtain a liquid sample. Characterize the composition and content of the liquid products and liquid sample to determine the content of nitrate esters in the liquid products and liquid sample.

[0011] Furthermore, the drying temperature in step S1 is 300°C.

[0012] Furthermore, the drying time in step S1 is 24 hours.

[0013] Furthermore, in step S1, the molar ratio of Na2CO3 to NaOH is 5.6%:94.4%.

[0014] Furthermore, in step S2, the heating temperature of the molten salt reactor is 320°C.

[0015] Furthermore, the heat preservation time of the molten salt reactor in step S2 is 1 hour.

[0016] Furthermore, in step S3, the feeding ratio of the Na2CO3-NaOH system to the TPU solid waste is 10:1.

[0017] Furthermore, the reaction time in step S3 is 0.5 h.

[0018] Furthermore, in step S4, the tail gas from the molten salt reactor passes through a gas-solid separation device, a condensation device, and a gas-liquid separation device in sequence to separate the liquid products in the gas phase.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This method utilizes alkaline Na2CO3-NaOH molten salt to fully absorb the nitrogen-containing tail gas generated during the oxidation of TPU waste, and generates nitrates in the molten salt, which not only reduces the generation of acidic gases, but also further reacts with alcohols in the tail gas to produce nitrate esters.

[0021] 2. This method, through reasonable proportioning and temperature control, can avoid the problems of acidic and hydrocarbon tail gas treatment that are prone to occur in existing treatment methods;

[0022] 3. The molten salt formulation provided by this method mainly consists of sodium salt, and has a low oxidation temperature. The materials are readily available, the processing method is simple, and the processing cost is low, which is conducive to the automation and industrialization of this processing method. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 This is a flowchart of a method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to the present invention;

[0025] Figure 2 Infrared spectrum of the liquid product obtained after treating TPU solid waste using this method;

[0026] Figure 3 A comparison chart of nitrate ester content in liquid products obtained after treating TPU solid waste at 320℃ using different systems;

[0027] Figure 4 The images show a comparison of the liquid products obtained after treating TPU solid waste in a Na2CO3-NaOH molten salt system at 320℃ for 0.25-1 h. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0029] It should be noted that the descriptions of "left," "right," "left side," "right side," "upper part," "lower part," "top," and "bottom" in this invention are defined based on the orientation or positional relationships shown in the accompanying drawings. They are merely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the described structure must be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] In the description of this invention, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Specific implementation method one:

[0032] Referring to the accompanying drawings, this embodiment describes a method for treating TPU solid waste with molten sodium salt and preparing nitrate esters, comprising the following steps:

[0033] S1. Dry Na2CO3-NaOH at a certain drying temperature of 300℃ for 24 h to remove excess moisture. Then, thoroughly mix the dried Na2CO3 and NaOH in a molar ratio of 5.6%:94.4% to form a Na2CO3-NaOH system and place it in a molten salt reactor.

[0034] S2. Heat the molten salt reactor to 320℃ and hold for 1 hour until the Na2CO3-NaOH system is completely melted;

[0035] S3. After adding TPU solid waste in a certain proportion to the Na2CO3-NaOH system into the molten salt reactor and reacting for 0.5 hours, waste salt is formed. The ratio of Na2CO3-NaOH system to TPU solid waste is 10:1.

[0036] S4. The tail gas from the molten salt reactor is collected and sequentially passed through a gas-solid separation device, a condenser, and a gas-liquid separation device to separate the liquid product from the gas phase. The waste salt is washed with water and filtered to obtain a liquid sample. The liquid product and the liquid sample are characterized for composition and content, and the total nitrate ester content in both the liquid product and the liquid sample is determined to be 40.3%. wt .%. Specific Implementation Method Two:

[0038] The difference between this specific embodiment and Specific Embodiment 1 is that Na2CO3-NaOH is replaced with CaCO3-NaOH, and the total content of nitrate esters in the liquid product and liquid phase sample is determined to be 28.4%. wt .%. Specific implementation method three:

[0040] The difference between this specific embodiment and Specific Embodiment 1 is that Na2CO3-NaOH is replaced with Na2CO3-Ca(OH)2, and the total content of nitrate esters in the liquid product and liquid phase sample is determined to be 15.3%. wt .%. Specific implementation method four:

[0042] The difference between this specific embodiment and Specific Embodiment 1 is that Na2CO3-NaOH is replaced with CaCO3-Ca(OH)2, and the total content of nitrate esters in the liquid product and liquid phase sample is determined to be 7.8. wt .%. Specific implementation method five:

[0044] The difference between this specific implementation method and Specific Implementation Method 1 is that the reaction time between the Na2CO3-NaOH system and the TPU solid waste is 0.25 h, and the total content of nitrate esters in the liquid product and liquid phase sample is determined to be 32.4%. wt .%. Specific implementation method six:

[0046] The difference between this specific implementation method and Specific Implementation Method 1 is that the reaction time between the Na2CO3-NaOH system and the TPU solid waste is 0.75 h, and the total content of nitrate esters in the liquid product and liquid phase sample is determined to be 40.0%. wt .%. Specific implementation method seven:

[0048] The difference between this specific implementation method and Specific Implementation Method 1 is that the reaction time between the Na2CO3-NaOH system and the TPU solid waste is 1 hour, and the total content of nitrate esters in the liquid product and liquid phase sample is determined to be 27.3%. wt .%. Detailed implementation method eight:

[0050] The difference between this specific embodiment and specific embodiment one is that, in S2, the molten salt reactor is heated to 300°C and then kept at that temperature for 1 hour until the Na2CO3-NaOH system is completely melted;

[0051] S3. After adding TPU solid waste in a certain proportion to the Na2CO3-NaOH system into the molten salt reactor and reacting for 0.5 h, waste salt is formed. The ratio of Na2CO3-NaOH system to TPU solid waste is 10:1.

[0052] S4. The total content of nitrate esters in the liquid product and liquid phase sample is determined to be 30.1. wt .%. Specific implementation method nine:

[0054] The difference between this specific embodiment and specific embodiment one is that, in S2, the molten salt reactor is heated to 310°C and then kept at that temperature for 1 hour until the Na2CO3-NaOH system is completely melted;

[0055] S3. After adding TPU solid waste in a certain proportion to the Na2CO3-NaOH system into the molten salt reactor and reacting for 0.5 h, waste salt is formed. The ratio of Na2CO3-NaOH system to TPU solid waste is 10:1.

[0056] S4. The total content of nitrate esters produced in the liquid product and liquid phase sample was determined to be 29.8%. wt .%. Specific Implementation Method Ten:

[0058] The difference between this specific embodiment and specific embodiment one is that, in S2, the molten salt reactor is heated to 330°C and then kept at that temperature for 1 hour until the Na2CO3-NaOH system is completely melted;

[0059] S3. After adding TPU solid waste in a certain proportion to the Na2CO3-NaOH system into the molten salt reactor and reacting for 0.5 hours, waste salt is formed. The ratio of Na2CO3-NaOH system to TPU solid waste is 10:1.

[0060] S4. The total content of nitrate esters in the liquid product and liquid phase sample was determined to be 39.8%. wt .%.

[0061] Comparing specific implementation methods one through four, it can be seen that, under 320°C conditions, the nitrate ester content in the liquid products obtained from the treatment of TPU waste in different systems is as follows: Figure 2 As shown, liquid phase infrared spectroscopy was performed on the liquid products of the four systems, and the results are as follows. Figure 3 As shown, this demonstrates that nitrate esters containing -CH3 and -O-NO2 structures were produced in all four systems. Compared to the Ca(OH)2 system, the liquid product had a higher nitrate ester content when NaOH was present. The liquid product and liquid phase sample had the highest nitrate ester content when the system was Na2CO3-NaOH. This indicates that treating TPU solid waste using a sodium-containing molten salt system can produce liquid products with high nitrate ester content.

[0062] Comparing specific implementation methods one, five, six, and seven, it can be seen that in the Na2CO3-NaOH system, when the treatment temperature is 320℃, the nitrate ester content in the liquid product and liquid phase sample first increases and then decreases with the increase of treatment time. When the treatment time is 0.5 h, the nitrate ester content in the liquid product and liquid phase sample reaches its peak, and when the treatment time is 1 h, the nitrate ester content in the liquid product and liquid phase sample decreases significantly.

[0063] Comparing specific implementation methods one, eight, nine, and ten, in the Na2CO3-NaOH system, TPU solid waste was treated under different temperature conditions near the system's melting point. It was found that when the temperature was 320℃, the nitrate ester content in the liquid product and liquid phase sample was the highest. That is, when the treatment temperature is slightly higher than the melting point of NaOH, the melting of salt is conducive to the generation of nitrate esters.

[0064] Therefore, the optimal solution proposed in this patent for treating TPU solid waste and preparing nitrate ester using the Na2CO3-NaOH (5.6%: 94.4%) sodium salt system is to treat it at 320℃ for 0.5 h.

[0065] The experimental equipment that may be involved in the above description, including but not limited to molten salt reactors, gas-solid separation devices, condensation devices, and gas-liquid separation devices, as well as the methods for characterizing the composition and content of liquid products and liquid phase samples, are all existing equipment and methods, and are not the essence of this invention. Therefore, they will not be described in detail.

[0066] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A method for treating TPU solid waste with molten sodium salt and preparing nitrate ester, characterized in that, Includes the following steps: S1. Dry Na2CO3-NaOH at a certain drying temperature for a certain time to remove excess moisture. Then, mix the dried Na2CO3 and NaOH in a certain proportion to form a Na2CO3-NaOH system and place it in a molten salt reactor. S2. Heat the molten salt reactor to a certain temperature and hold it at that temperature for a certain time until the Na2CO3-NaOH system is completely melted; S3. After adding TPU solid waste in a certain proportion to the Na2CO3-NaOH system into the molten salt reactor and reacting for a certain period of time, waste salt is formed. S4. Collect the liquid product in the tail gas phase of the molten salt reactor. After washing and filtering the waste salt with water, obtain a liquid sample. Characterize the composition and content of the liquid product and the liquid sample to determine the content of nitrate ester in the liquid product and the liquid sample.

2. The method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to claim 1, characterized in that: The drying temperature in step S1 is 300°C.

3. The method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to claim 2, characterized in that: The drying time in step S1 is 24 hours.

4. The method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to claim 3, characterized in that: In step S1, the molar ratio of Na2CO3 to NaOH is 5.6%:94.4%.

5. The method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to claim 1, characterized in that: The heating temperature of the molten salt reactor in step S2 is 320°C.

6. The method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to claim 5, characterized in that: The heat preservation time of the molten salt reactor in step S2 is 1 hour.

7. The method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to claim 1, characterized in that: In step S3, the feeding ratio of the Na2CO3-NaOH system to the TPU solid waste is 10:

1.

8. The method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to claim 6, characterized in that: The reaction time in step S3 is 0.5 h.

9. The method for treating TPU solid waste with molten sodium salt and preparing nitrate ester according to claim 1, characterized in that: In step S4, the tail gas from the molten salt reactor passes through a gas-solid separation device, a condensation device, and a gas-liquid separation device in sequence to separate the liquid products in the gas phase.

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