A method of treating tpu waste with a molten salt

Abstract

The application provides a method for treating TPU waste by using molten salt, and belongs to the field of solid waste treatment.The method can solve the problems of traditional TPU waste treatment methods, such as easy generation of harmful gas, high cost and low safety.The method comprises the following steps: S1, drying a certain amount of CaCO3 and Ca(OH)2 at a certain temperature for a certain time, removing the excess water, fully mixing the dried CaCO3 and Ca(OH)2 at a certain proportion, and placing the mixture in a reaction kettle; S2, heating the reaction kettle to a certain temperature and keeping the temperature for a certain time to melt the CaCO3-Ca(OH)2 system; S3, adding TPU waste with a certain mass ratio of the melted CaCO3-Ca(OH)2 system into the reaction kettle to react, and forming waste salt after reacting for a certain time; S4, treating the waste salt after the reaction kettle discharges the waste salt to obtain a residue sample, weighing the residue sample to obtain a degradation rate, characterizing the composition and content of the waste salt sample, and determining the content of nitrate in the waste salt.The method is mainly used for treating TPU 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 waste with molten salt. Background Technology

[0002] Molten salt, as an engineering fluid, has advantages such as low vapor pressure, high melting and boiling points, high thermal conductivity and specific heat capacity, and is often used in fields such as heat storage, electrochemistry, solar energy, and waste treatment.

[0003] TPU products serve all aspects of life, but the widespread use of this material also generates a large amount of TPU waste. This waste contains a certain amount of nitrogen (N), and conventional pyrolysis and incineration methods produce NOx, leading to acid rain and even low-altitude ozone, endangering environmental safety and personal property. Furthermore, conventional pyrolysis and incineration methods often produce large amounts of tar and fly ash due to uneven heating, resulting in discontinuous treatment processes. Compared to conventional pyrolysis and incineration, the molten salt method has the advantages of lower oxidation temperatures and simpler exhaust gas treatment. The molten salt method treats organic solid waste using alkaline CaCO3-Ca(OH)2, which, compared to conventional pyrolysis and incineration methods, features uniform heating and thorough adsorption of exhaust gases.

[0004] Therefore, it is essential to provide a safe, effective, and cost-efficient method for treating TPU waste using the carbonate molten salt process. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for treating TPU waste with molten salt, in order to solve the problems of traditional methods of treating TPU products, which are prone to generating harmful gases, have high costs, and low safety.

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

[0007] S1. After drying a certain mass of CaCO3 and Ca(OH)2 at a certain temperature for a certain time to remove excess water, the dried CaCO3 and Ca(OH)2 are thoroughly mixed in a certain proportion and placed in a reaction vessel.

[0008] S2. Heat the reactor to a certain temperature and keep it at that temperature for a certain time to melt the CaCO3-Ca(OH)2 system.

[0009] S3. Add TPU waste in a certain mass ratio to the reactor and react with the melted CaCO3-Ca(OH)2 system. After a certain reaction time, waste salt is formed.

[0010] S4. After the waste salt is discharged from the reactor, the waste salt is processed to obtain a residue sample. The residue sample is weighed to obtain the degradation rate. The composition and content of the waste salt sample are characterized to determine the content of nitrate produced in the waste salt.

[0011] Furthermore, the drying temperature for CaCO3 and Ca(OH)2 in step S1 is 200°C.

[0012] Furthermore, the drying time for CaCO3 and Ca(OH)2 in step S1 is 12 hours.

[0013] Furthermore, in step S1, the mixing ratio of CaCO3 and Ca(OH)2 is 16.6 wt.% : 83.4 wt.%.

[0014] Furthermore, in step S2, the heating temperature of the reactor is 600°C.

[0015] Furthermore, the heat preservation time in step S2 is 0.5 hours.

[0016] Furthermore, in step S3, the mass ratio of the melted CaCO3-Ca(OH)2 system to the TPU waste is 10:1.

[0017] Furthermore, the reaction time in step S3 is 1 hour.

[0018] Furthermore, in step S4, the waste salt is treated by washing with water and then drying.

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

[0020] 1. This method utilizes alkaline CaCO3 and Ca(OH)2 molten salts to fully absorb the nitrogen-containing tail gas generated during the oxidation of TPU waste, and generates nitrates with catalytic oxidation properties in the molten salt, which not only reduces the emission of acidic gases, but also further enhances the full oxidation of TPU waste;

[0021] 2. This method solves the problems of exhaust gas treatment and incomplete oxidation that are prone to occur in the incineration process, and can improve the degradation rate of TPU solid waste by reasonably setting the oxidation temperature and time.

[0022] 3. The raw material of this method is calcium salt and its oxidation temperature is relatively low, which greatly reduces the treatment cost of waste. The preparation process is simple and easy to automate and industrialize. 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 waste with molten salt according to the present invention;

[0025] Figure 2 A comparison chart showing the NO content generated during the direct pyrolysis of TPU solid waste and its oxidation in molten salt.

[0026] Figure 3 The image shows the XRD pattern of waste salt after TPU solid waste is treated by the method described in this invention.

[0027] Figure 4 This is a photograph comparing the sample volume before and after processing using the method described in this invention. 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 waste with molten salt, comprising the following steps:

[0033] S1. After drying a certain mass of CaCO3-Ca(OH)2 at 200℃ for 12 hours to remove excess water, the dried CaCO3-Ca(OH)2 is thoroughly mixed in a ratio of 16.6wt.% to 83.4wt.% and placed in a reaction vessel.

[0034] S2. Heat the reactor to 300℃ and hold for 0.5h to melt the CaCO3-Ca(OH)2 system;

[0035] S3. Add TPU waste in a certain mass ratio to the melted CaCO3-Ca(OH)2 system to the reactor and react. The mass ratio of CaCO3-Ca(OH)2 system to TPU waste is 10:1. After 0.5 hours of oxidation reaction, waste salt is formed.

[0036] S4. After the waste salt is discharged from the reactor, a residue sample is obtained from the treated waste salt. The residue sample is weighed to obtain the degradation rate. The composition and content of the waste salt sample are characterized to determine the content of nitrates produced in the waste salt. The final degradation rate is 60.9%. Specific Implementation Method Two:

[0038] The difference between this specific embodiment and Specific Embodiment 1 is that: the reaction vessel is heated to 400°C and kept at that temperature for 0.5 hours to melt the CaCO3-Ca(OH)2 system. The oxidation reaction time between the CaCO3-Ca(OH)2 system and the TPU waste is 0.5 hours, and the final degradation rate is 77.6%. Specific implementation method three:

[0040] The difference between this specific implementation method and Specific Implementation Method 1 is that: the reaction vessel is heated to 500°C and kept at that temperature for 0.5 hours to melt the CaCO3-Ca(OH)2 system. The oxidation reaction time between the CaCO3-Ca(OH)2 system and the TPU waste is 0.5 hours, and the final degradation rate is 89.2%. Specific implementation method four:

[0042] The difference between this specific embodiment and Specific Embodiment 1 is that: the reaction vessel is heated to 600°C and kept at that temperature for 0.5 hours to melt the CaCO3-Ca(OH)2 system. The oxidation reaction time between the CaCO3-Ca(OH)2 system and the TPU waste is 0.5 hours, and the final degradation rate is 95.4%. Specific implementation method five:

[0044] The difference between this specific embodiment and Specific Embodiment 1 is that: the reaction vessel is heated to 700°C and kept at that temperature for 0.5 hours to melt the CaCO3-Ca(OH)2 system. The oxidation reaction time between the CaCO3-Ca(OH)2 system and the TPU waste is 0.5 hours, and the final degradation rate is 95.5%. Specific implementation method six:

[0046] The difference between this specific implementation method and Specific Implementation Method 1 is that: the reaction vessel is heated to 600°C and kept at that temperature for 0.5 hours to melt the CaCO3-Ca(OH)2 system. The oxidation reaction time between the CaCO3-Ca(OH)2 system and the TPU waste is 0.25 hours, and the final degradation rate is 94.2%. Specific implementation method seven:

[0048] The difference between this specific implementation method and Specific Implementation Method 1 is that: the reaction vessel is heated to 600°C and kept at that temperature for 0.5 hours to melt the CaCO3-Ca(OH)2 system. The oxidation reaction time between the CaCO3-Ca(OH)2 system and the TPU waste is 0.75 hours, and the final degradation rate is 95.4%. Detailed implementation method eight:

[0050] The difference between this specific embodiment and Specific Embodiment 1 is that: the reaction vessel is heated to 600°C and kept at that temperature for 0.5 hours to melt the CaCO3-Ca(OH)2 system. The oxidation reaction time between the CaCO3-Ca(OH)2 system and the TPU waste is 1 hour, and the final degradation rate is 95.4%. Specific implementation method nine:

[0052] TPU waste was oxidized at 600℃ for 0.5 hours, achieving a degradation rate of 70.3%.

[0053] Comparing specific implementation methods one to five, it can be seen that when TPU waste is treated in the CaCO3 and Ca(OH)2 system at different temperatures, the degradation rate of TPU waste is 95.4% when the temperature is above 600℃. Further increasing the temperature to 700℃ has little effect on increasing the degradation rate, only increasing it by 0.1%.

[0054] Comparing specific implementations four, six, seven, and eight, it can be seen that at 600℃, when the oxidation time is greater than 0.5h, further increasing the oxidation time does not affect the degradation rate at 95.4%. That is, under this temperature condition, further increasing the oxidation time has no effect on the further oxidation of TPU waste.

[0055] Comparing Examples 4 and 9, it is evident that using molten salt significantly improves the degradation rate of TPU waste, specifically increasing it from 70.3% to 95.4%. Furthermore, component analysis of the exhaust gases from both examples yielded the following results: Figure 2 As shown, the molten salt method significantly reduces the NO content in the exhaust gas compared to direct oxidation. The waste salt obtained after molten salt treatment was characterized by XRD, and the results are as follows. Figure 3 As shown, sodium nitrate was clearly detected in the waste salt. This proves that molten salt can effectively adsorb NO tail gas. Furthermore, the molten salt method for treating TPU solid waste also has the advantage of a significant volume reduction. Comparing the TPU waste before and after oxidation, for example... Figure 4 As shown, the molten salt method can effectively treat TPU waste.

[0056] Given that excessively high temperatures can easily lead to the generation of fly ash and volatile products.

[0057] Therefore, the optimal solution proposed in this patent for treating TPU waste using a CaCO3 and Ca(OH)2 (16.6 wt.%) system is to treat it at 600°C for 0.5 h.

[0058] The experimental equipment and tools involved in the above methods, the methods for characterizing the composition and content of waste salt samples, and the methods for determining the content of nitrates generated in waste salt all adopt existing technologies, and will not be elaborated here.

[0059] 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 of treating TPU waste with molten salt, characterized in that, Includes the following steps: S1. After drying a certain mass of CaCO3 and Ca(OH)2 at a certain temperature for a certain time to remove excess water, the dried CaCO3 and Ca(OH)2 are thoroughly mixed in a certain proportion and placed in a reaction vessel. S2. Heat the reactor to a certain temperature and keep it at that temperature for a certain time to melt the CaCO3-Ca(OH)2 system. S3. Add TPU waste in a certain mass ratio to the molten CaCO3-Ca(OH)2 system into the reactor and react for a certain period of time to form waste salt. S4. After the waste salt is discharged from the reactor, the waste salt is processed to obtain a residue sample. The residue sample is weighed to obtain the degradation rate. The composition and content of the waste salt sample are characterized to determine the content of nitrate produced in the waste salt. The drying time for CaCO3 and Ca(OH)2 in step S1 is 12 hours. In step S1, the mixing ratio of CaCO3 and Ca(OH)2 is 16.6 wt.% : 83.4 wt.%; The heating temperature of the reactor in step S2 is 600℃; The heat preservation time in step S2 is 0.5 hours; In step S3, the mass ratio of the melted CaCO3-Ca(OH)2 system to the TPU waste is 10:

1. The reaction time in step S3 is 1 hour. The waste salt in step S4 is treated by washing with water and then drying. The CaCO3 and Ca(OH)2 molten salts fully absorb the nitrogen-containing exhaust gas generated during the oxidation of TPU waste, and produce nitrates with catalytic oxidation properties in the molten salts. This not only reduces the emission of acidic gases, but also further enhances the full oxidation of TPU waste.

2. The method of claim 1, wherein: The drying temperature for CaCO3 and Ca(OH)2 in step S1 is 200℃.

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