Thermogravimetric analysis device and system for gas-solid reaction kinetics research

Abstract

This invention relates to a thermogravimetric analysis device and system for studying gas-solid reaction kinetics, belonging to the technical field of gas-solid reaction kinetics research equipment. It solves the problem that existing equipment cannot provide near-constant temperature conditions for gas-solid reaction experiments of fine-grained calcium hydroxide / calcium oxide material systems. The device includes a resistance furnace connected to a lifting mechanism. A reactor is installed inside the resistance furnace, with a closed top and an open bottom. A gas supply coil is fixed inside the reactor, with one end extending from the top of the reactor as an inlet and the other end connected to a purge pipe as an outlet. A sample placement mechanism is located directly below the reactor and is mounted on a weighing mechanism. Using this thermogravimetric analysis device, reaction kinetic information of fine-grained calcium hydroxide / calcium oxide material systems under fluidized bed conditions can be obtained.

Description

Technical Field

[0001] This invention relates to the field of equipment technology for gas-solid reaction kinetics research, specifically to a thermogravimetric analysis device and system for gas-solid reaction kinetics research. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Thermal energy storage is a key technology for addressing the intermittency and fluctuations of solar thermal energy and for recovering and reusing industrial waste heat. Thermal energy storage mainly includes sensible heat storage, latent heat storage, and thermochemical heat storage. Thermochemical heat storage utilizes the heat of reaction from reversible chemical reactions to store and release heat. Compared to sensible and latent heat storage, thermochemical heat storage has advantages in terms of high energy density and long storage period, making it a technology with broad application prospects.

[0004] Thermochemical thermal storage systems based on calcium hydroxide decomposition and calcium oxide hydration possess advantages such as low material cost, high energy density, reversible reaction and good cycle stability, rapid reaction kinetics, and non-toxic materials. Therefore, they are widely considered a promising thermochemical thermal storage material system for industrial applications. With the development of large-scale, high-efficiency thermal storage technologies, providing acceptable heat storage and release power requires thermal storage materials to possess excellent heat and mass transfer characteristics within the reactor. Therefore, using fluidized bed reactors for thermochemical thermal storage has become a hot topic. The fluidized bed thermochemical thermal storage process based on calcium hydroxide / calcium oxide material systems is a coupled dynamic process of material reaction kinetics and heat and mass transfer. Therefore, the reaction kinetics of the thermal storage material under fluidized bed conditions are crucial, as they will influence the selection of key design parameters for circulating fluidized bed reactors.

[0005] Fluidized bed reactors possess excellent heat and mass transfer characteristics, and the reaction process of particulate materials in fluidized bed reactors is essentially an isothermal reaction. To obtain the reaction kinetics of the calcium hydroxide / calcium oxide material system under fluidized conditions, a device capable of providing excellent heat and mass transfer characteristics for this material system is needed for reaction kinetic studies. Currently, the mainstream equipment for gas-solid reaction kinetics research is the thermogravimetric analyzer (TGA) and the micro-fluidized bed analyzer. Thermogravimetric analyzers use programmed temperature rise (the maximum heating rate is generally less than 50℃ / min) to obtain changes in sample mass. They can accurately monitor the mass change of the sample during the reaction process and precisely control the heating rate of the heater, and have already achieved widespread commercial application. However, the inventors discovered that thermogravimetric analyzers cannot study the reaction characteristics of unstable substances under isothermal conditions. For example, they cannot study the decomposition reaction of calcium hydroxide within any near-isothermal set temperature range. This is because the decomposition rate of calcium hydroxide is very fast at higher temperatures, so the calcium hydroxide in the thermogravimetric analyzer has essentially completed the decomposition reaction before reaching the expected temperature. Therefore, thermogravimetric analyzers cannot study the isothermal decomposition reaction of calcium hydroxide. Meanwhile, thermogravimetric analyzers (TGAs) are also limited by their design principles and structure, employing relatively low purge gas volumes (the maximum purge gas volume is generally less than 100 mL / min). This makes it difficult to eliminate the inhibitory effect of gas diffusion on the reaction within the reactor, resulting in significant mass transfer inhibition of the sample in the TGA. Therefore, TGAs cannot provide excellent mass transfer conditions for the sample. For these reasons, the sample quantity used in TGAs is generally small (approximately 5 mg). However, when the material composition is complex (e.g., calcium carbide slag, a multi-component mixture with calcium hydroxide as the main component), such a small sample is insufficient to represent the overall characteristics of the material. The above analysis indicates that TGAs cannot provide efficient heat and mass transfer conditions for the sample; therefore, TGAs cannot provide reliable reaction kinetic information for fluidized bed thermochemical heat storage studies of calcium hydroxide / calcium oxide material systems.

[0006] Miniature fluidized bed analyzers provide excellent heat and mass transfer conditions for samples through the intense relative motion between inert bed particles (typically silica sand) and sample particles. They offer rapid heating rates, enabling isothermal reactions, and are therefore widely used in fluidization. Miniature fluidized bed analyzers rely on the gas concentration signal at the reactor outlet as the primary signal to infer the reaction kinetics of the material. However, backmixing and axial diffusion of components occur within the fluidized bed reactor. Furthermore, a concentration gradient exists in the sampling pipeline between the reactor outlet and the gas analyzer inlet, further contributing to axial diffusion of gas components. Turbulent flow also causes backmixing. These factors cause the gas flow to deviate from plug flow, resulting in a degree of distortion in the gas concentration signal obtained by the gas analyzer, thus preventing the acquisition of accurate reaction kinetic information. For extremely fast gas-solid reactions like calcium hydroxide, this distortion is even more severe. The gaseous signals in the heat storage process of calcium hydroxide and the heat release process of calcium oxide are both water vapor. It is difficult for mass spectrometers or Fourier transform infrared absorption spectrometers to accurately detect water vapor in real time (for example, the calibration equipment requires standard gas of water vapor with different concentrations, and there is currently no commercially available standard gas of water vapor). Therefore, micro fluidized bed analyzers cannot be used for the study of fluidized bed thermochemical heat storage reaction kinetics of calcium hydroxide / calcium oxide material system.

[0007] Existing technologies also propose the concept of fluidized bed thermogravimetric analysis (TGA), which places the entire fluidized bed reactor on a real-time online weighing device, feeds material from the top of the reactor, and then monitors the mass change of the material under fluidized conditions. Compared with micro fluidized bed analyzers, fluidized bed TGA uses real-time mass signals as the raw signals for reaction kinetic calculations, thus allowing direct study of the material's reaction kinetic characteristics based on the mass signals. However, fluidized bed TGA has strict requirements on the particle size of the material; the particle size needs to be greater than 150 μm. Fluidized bed TGA cannot study powder materials because once the powder is added from the top of the fluidized bed, it is directly blown out by the fluidizing air flowing directly towards the powder from below, making it impossible to obtain mass information. Whether it is calcium hydroxide (analytical grade calcium hydroxide has a particle size range of 0-100 μm, with a median particle size of approximately 4 μm) or carbide slag, which is mainly composed of calcium hydroxide (approximately 80% of particles are smaller than 100 μm, with a median particle size of approximately 30 μm), fluidized bed TGA cannot reliably study it. Fluidized bed thermogravimetric analysis also suffers from pseudo-mass (i.e., the gas pipelines and temperature and pressure measuring pipelines connected to the fluidized bed reactor may have a fluctuating effect on the overall mass of the fluidized bed), which can also have an adverse effect on the measured mass signal.

[0008] In summary, there is currently a lack of equipment capable of studying the reaction kinetics of calcium hydroxide / calcium oxide material systems under fluidized conditions. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a thermogravimetric analysis device for studying gas-solid reaction kinetics, which can obtain reaction kinetic information of fine-grained calcium hydroxide / calcium oxide material systems under fluidization conditions.

[0010] To achieve the above objectives, the present invention adopts the following technical solution.

[0011] In a first aspect, embodiments of the present invention provide a thermogravimetric analysis apparatus for studying gas-solid reaction kinetics, including a resistance furnace connected to a lifting mechanism. A reactor is disposed inside the resistance furnace, with the top of the reactor closed and the bottom open. A gas supply coil is fixed inside the reactor, with one end of the gas supply coil extending from the top of the reactor to the outside of the reactor as an inlet and the other end as an outlet connected to a purge pipe. A sample placement mechanism is disposed directly below the reactor and is mounted on a weighing mechanism.

[0012] Optionally, a first thermocouple is inserted inside the reactor, and the first thermocouple is connected to the resistance furnace temperature controller.

[0013] Optionally, the sample placement mechanism includes a crucible, which is placed on a tray. The tray is fixed to the top of a connecting rod, and the bottom of the connecting rod is connected to a weighing mechanism.

[0014] Optionally, the crucible includes a sample placement section with a flange at its edge. Correspondingly, the purge tube is horizontally positioned so that the gas blown out by the purge tube will not blow the sample out of the crucible.

[0015] Optionally, the crucible is made of platinum, the tray and connecting rod are made of quartz, and a heat-insulating pad is provided between the crucible and the tray.

[0016] Optionally, the connecting rod is a hollow rod, and a second thermocouple is installed inside the hollow rod. The second thermocouple is connected to the monitoring terminal through a temperature transmitter. The probe at one end of the second thermocouple extends into a groove opened at the bottom of the crucible. The second thermocouple is not in contact with the cavity surface of the hollow rod.

[0017] Optionally, a cooling water tray is also provided on the outer periphery of the sample placement mechanism, and the cooling water tray is connected to a chiller.

[0018] Optionally, the lifting mechanism is a screw lifting mechanism.

[0019] In a second aspect, embodiments of the present invention provide a thermogravimetric analysis system for studying gas-solid reaction kinetics, including the thermogravimetric analysis apparatus for studying gas-solid reaction kinetics described in the first aspect, wherein a gas supply coil extends from the end of the reactor and is connected to a gas supply system.

[0020] Optionally, the gas supply system includes a mixing chamber, the outlet of which is connected to the inlet of the gas supply coil via a pipeline. The inlet of the mixing chamber is connected to an air supply branch and a steam supply branch. The air supply branch includes a gas source, which is connected to the inlet of the heater. The outlet of the heater is connected to the mixing chamber. The steam supply branch includes an injection pump, the outlet of which is connected to a vaporizer. The outlet of the vaporizer is connected to the mixing chamber.

[0021] The beneficial effects of this invention are:

[0022] 1. The thermogravimetric analysis apparatus of the present invention, because the resistance furnace is connected to the lifting mechanism and the sample placement mechanism is located directly below the reactor with an open bottom, allows the reactor to reach the set temperature after the resistance furnace reaches the set temperature. The lifting mechanism then lowers the reactor, allowing the sample placement mechanism to enter the reactor, enabling the sample to quickly reach the expected temperature. Compared with current thermogravimetric analyzers, this avoids the decomposition reaction of calcium hydroxide before reaching the expected temperature due to slow heating. It achieves the decomposition reaction of calcium hydroxide within any near-constant temperature range. Furthermore, the thermogravimetric analysis apparatus of the present invention has a gas supply coil and a purge pipe, which, combined with the rapid lifting and lowering movement of the resistance furnace, enables the sample to quickly reach the expected temperature and reduces mass transfer resistance during the reaction process, providing excellent heat and mass transfer conditions for the sample. Simultaneously, reliable mass signals are used to conduct reaction kinetic studies.

[0023] 2. The thermogravimetric analysis apparatus of the present invention uses a crucible as the sample holding mechanism. Since the crucible has a flange and the purge tube is horizontally set, the gas blown out by the purge tube will not directly act on the sample in the crucible and will not blow the sample away from the crucible. Compared with the existing fluidized bed thermogravimetric analysis, it has no requirements on the sample particle size and is suitable for thermogravimetric analysis of fine-particle calcium hydroxide / calcium oxide material systems. At the same time, compared with the existing thermogravimetric analyzers, it can provide a larger purge gas volume, which can eliminate the inhibitory effect of gas diffusion in the reactor on the reaction.

[0024] 3. The thermogravimetric analysis device of the present invention uses a weighing device to directly weigh the sample, and the reaction kinetic information obtained is more accurate compared with a micro fluidized bed analyzer.

[0025] 4. In the thermogravimetric analysis apparatus of the present invention, the crucible is made of platinum and a heat insulation pad is provided between it and the tray. Platinum is resistant to high temperature, has low specific heat capacity, and has good thermal conductivity, which is conducive to the sample quickly reaching the expected temperature. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute a limitation thereof.

[0027] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention;

[0028] Figure 2 This is a graph showing the detection results of the decomposition reaction of calcium hydroxide sample in Example 2 of the present invention;

[0029] Among them, 1-gas source; 2-mass flow meter; 3-heater; 4-micro injection pump; 5-vaporizer; 6-mixing chamber; 7-resistance furnace temperature controller; 8-reactor; 9-screw lifting mechanism; 10-resistance furnace; 11-gas supply coil; 12-first thermocouple; 13-crucible; 14-quartz tray; 15-hollow quartz rod; 16-second thermocouple; 17-fixed damper; 18-chiller; 19-cooling water pan; 20-electronic scale; 21-clamping head; 22-temperature transmitter; 23-computer. Detailed Implementation

[0030] Example 1

[0031] This embodiment provides a thermogravimetric analysis apparatus for studying gas-solid reaction kinetics, such as... Figure 1 As shown, the device includes a resistance furnace 10, and a reactor 8 is disposed inside the cavity of the resistance furnace 10. The resistance furnace 10 can heat the reactor 8 so that the internal temperature of the reactor 8 reaches the set temperature, and the reactor 8 provides the set ambient temperature for the sample reaction.

[0032] In this embodiment, the constant temperature zone of the furnace body of the resistance furnace 10 is 400mm long, and the maximum heating temperature of the resistance furnace 10 is 1100℃. The resistance furnace 10 can be made using existing equipment, and will not be described in detail here.

[0033] The reactor 8 is made of stainless steel, preferably 310S stainless steel. In this embodiment, the reactor 8 adopts a cylindrical structure with a length of 600mm, an outer diameter of 89mm, and an inner diameter of 85mm. The top of the reactor 8 is provided with a top cover so that the top of the reactor 8 is closed and the bottom is open.

[0034] A sample placement mechanism is provided directly below the reactor 8 for placing samples. The resistance furnace 10 is connected to the lifting mechanism 9, which enables the resistance furnace 10 and the reactor 8 to move up and down. When the reactor 8 moves downward, the sample placement mechanism can enter the reactor because its bottom is open.

[0035] The lifting mechanism 9 adopts a screw lifting mechanism. In this embodiment, the screw lifting mechanism can drive the electric resistance furnace to move up and down at a speed of 50mm / s.

[0036] Specifically, the screw lifting mechanism 9 includes a screw with its axis set vertically. Both ends of the screw are rotatably connected to the frame. One end of the screw is connected to a drive motor, which can drive the screw to rotate. The screw is threadedly connected to a screw slider, which is fixedly connected to the outer shell of the resistance furnace. The outer shell of the resistance furnace is also slidably connected to a guide rail with its axis set vertically. The guide rail is used to guide the lifting and lowering movement of the resistance furnace.

[0037] The use of a screw lifting mechanism 9 facilitates the control of the lifting speed and position of the resistance furnace, meeting the test requirements. In other embodiments, the lifting mechanism may also be a rack and pinion lifting mechanism or a scissor lifting mechanism.

[0038] The top cover of reactor 8 is provided with a thermocouple socket and a gas supply coil inlet. A first thermocouple 12 is fixed to the top cover through the thermocouple socket. The probe end of the first thermocouple 12 extends into the interior of reactor 8 to detect the temperature inside the reactor. The first thermocouple 12 is connected to the resistance furnace temperature controller 7. The first thermocouple 12 can send the detected temperature to the resistance furnace temperature controller 7. The resistance furnace temperature controller 7 controls the operation of the resistance furnace 10 according to the received temperature so that the temperature inside reactor 8 reaches the required temperature and remains stable.

[0039] A gas supply coil 11 is installed inside the reactor 8. In this embodiment, the gas supply coil 11 is a spiral tube, located around the outer periphery of the first thermocouple 12. One end of the gas supply coil 11 extends to the outside of the reactor 8 through a gas supply coil inlet and is fixedly connected to the top cover of the reactor 8. The end of the gas supply coil 11 extending to the outside of the reactor 8 serves as the gas inlet, and the other end serves as the gas outlet, equipped with a purge pipe. The gas inlet of the gas supply coil 11 can be connected to an external gas source, and the purge pipe can blow out gas to perform high-speed purging of a predetermined area above the sample. In this embodiment, the gas supply coil is made of stainless steel, which is heat-resistant and has a long service life.

[0040] A sample placement mechanism is provided directly below the reactor 8. The sample placement mechanism includes a crucible 13, which is used to place the sample. In this embodiment, the crucible 13 is made of platinum material and includes a placement part. The placement part is horizontally arranged for placing the sample. A flange is provided at the edge of the placement part to prevent the sample from falling off the placement part.

[0041] Correspondingly, the purge tube is horizontally positioned, allowing the gas blown out to flow along the top surface of the flange without directly affecting the sample inside the crucible. This prevents the blown gas from blowing the sample away from the crucible. Compared to existing fluidized bed thermogravimetric analysis (TGA), this configuration is not limited by sample particle size and is suitable for the TGA analysis of fine-particle calcium hydroxide / calcium oxide material systems. Furthermore, compared to existing TGA analyzers, it provides a larger purge gas volume, eliminating the inhibitory effect of gas diffusion on the reaction in the reactor.

[0042] Crucible 13 is made of platinum. Platinum is resistant to high temperatures, has a low specific heat capacity, and has good thermal conductivity, which helps the sample to quickly reach the expected temperature.

[0043] The crucible 13 is placed on a tray. In this embodiment, the tray is a quartz tray 14. In order to prevent the heat of the crucible 13 from being transferred to the quartz tray 14, a heat insulation pad is provided between the crucible 13 and the quartz tray 14. The heat insulation pad is made of existing heat insulation materials, such as fiberglass, rock wool, etc.

[0044] The quartz tray 14 is fixedly connected to the top of the connecting rod, and the bottom of the connecting rod is fixed to the weighing mechanism.

[0045] In this embodiment, the connecting rod is a hollow quartz rod 15 with an internal cavity. The hollow quartz rod 15 is a cylindrical rod or a square rod. The top end of the hollow quartz rod 15 is fixedly connected to the bottom surface of the quartz tray, and the bottom end of the hollow quartz rod 15 is fixed to the weighing mechanism through the clamping head 21.

[0046] The weighing mechanism adopts an existing electronic scale 20. The weighing pan of the electronic scale 20 is provided with a clamping head that matches the hollow quartz rod 15. In one embodiment, the clamping head 21 can be a clamping block. The clamping block is provided with a slot that matches the hollow quartz rod, and the bottom end of the hollow quartz rod is inserted into the slot.

[0047] The electronic scale is connected to a monitoring terminal, which uses a computer and can collect the mass data of the sample in the crucible in real time. In this embodiment, the electronic scale has a range of 220g, a readability of 0.1mg, and a mass data acquisition frequency of 1 sample / second.

[0048] To prevent the electronic scale from being affected by the high temperature environment of the reactor, a cooling water tray 19 is provided on the outer periphery of the bottom end of the hollow quartz rod. Specifically, a through hole with a diameter larger than the outer diameter of the hollow quartz rod is opened in the center of the cooling water tray. The hollow quartz rod passes through the cooling water tray through the through hole. The cooling water tray 19 is connected to a chiller 18, which can provide cooling circulating water (10L / min, 15℃) to cool the hollow quartz rod 15 and its surrounding environment that are close to the electronic scale 20, so as to ensure that the electronic scale is not affected by the high temperature environment inside the reactor.

[0049] In this embodiment, the mass of the sample is obtained directly by using an electronic balance 20, which provides more accurate reaction kinetic information compared to a micro fluidized bed analyzer.

[0050] A second thermocouple 16 is installed inside the hollow cavity of the hollow quartz rod 15. The end of the second thermocouple 16 with the probe passes through the hole in the quartz tray 14 and the heat insulation pad, and then extends into the groove on the bottom surface of the crucible 13. The second thermocouple 16 does not contact the groove surface. The thickness of the groove at the bottom of the crucible 13 is only 1 mm. With this setting method, the temperature of the sample can be measured more accurately than that of a traditional thermogravimetric analyzer. The change in sample temperature can be measured through the second thermocouple 16.

[0051] The other end of the second thermocouple 16 extends out of the hollow quartz rod 15 through a hole in the rod wall and is fixedly connected to the fixed damper 17, which is fixed on the cooling water pan 19.

[0052] By setting the fixed damper 17, the second thermocouple 16 can be kept fixed, thereby preventing the second thermocouple 16 from contacting the cavity surface of the hollow quartz rod 15, thus avoiding the problem of inaccurate mass signal caused by contact friction.

[0053] Specifically, the fixed damper 17 is provided with a fixing hole, the second thermocouple 16 is inserted into the fixing hole and fixed to the fixed damper 17, the end of the second thermocouple 16 inserted into the fixing hole extends to the outside of the fixed damper 17 and is connected to the temperature transmitter 22 through a signal line, the temperature transmitter 22 is connected to the monitoring terminal through the signal line, and the monitoring terminal is a computer 23.

[0054] By setting the fixed damper 17, on the one hand, the second thermocouple 16 is prevented from contacting the hollow quartz rod 15. On the other hand, when the signal line is shaken by external influences, the fixed damper 17 will prevent the second thermocouple 16 from shaking, thus avoiding affecting the normal operation of the second thermocouple 16.

[0055] The second thermocouple 16 is connected to the computer 23 via the temperature transmitter 22 to record the temperature data of the sample in the crucible 13 in real time. The temperature data acquisition frequency is 1 sample / second.

[0056] When the thermogravimetric analysis apparatus of this embodiment is working, the resistance furnace 10 is first raised to the top, the heat insulation pad is placed on the quartz tray 14, the crucible 13 is placed on the heat insulation pad, the electronic scale 20 performs the tare weighing operation, the resistance furnace 10 is started, and the temperature inside the reactor 8 is heated to the reaction temperature required for the experiment. Depending on whether the experiment is a heat storage reaction kinetics experiment or an exothermic reaction kinetics experiment, it is determined whether to introduce compressed air or a mixture of compressed air and water vapor into the reactor through the gas supply coil. After the reading of the first thermocouple 12 reaches the required experimental temperature and stabilizes, the chiller 18 is turned on. A predetermined amount of sample is weighed using a laboratory analytical balance (readable 0.1 mg) and spread evenly in the crucible 13. In this embodiment, the sample is a calcium hydroxide or calcium oxide material system. The computer 23 begins collecting mass data from the electronic scale 20 and data from the second thermocouple 16, controlling the lead screw lifting mechanism 9 to lower the resistance furnace 10 to a predetermined position at a speed of 50 mm / s. The predetermined position is such that the distance between the bottom of the first thermocouple 12 and the upper surface of the crucible 13 is 5 mm, and the axis of the purge tube is aligned with the bottom of the first thermocouple, i.e., the distance between the axis of the purge tube and the upper surface of the crucible is 5 mm. This ensures that the temperature at the location of the crucible 13 meets the research requirements. After the resistance furnace 10 lowers to the predetermined position, the sample begins to react. When the mass measured by the electronic scale 20 no longer changes, the reaction is considered complete. After the sample experiment is completed, a blank experiment without the sample needs to be conducted under the same experimental conditions. The thermogravimetric curve of the sample can be obtained by subtracting the mass data of the blank experiment from the mass data of the sample experiment. By comparing the sample mass obtained by the laboratory analytical balance before the experiment with the sample mass of the rapid reaction thermogravimetric analysis system before the reaction, the accuracy of the mass signal obtained by the system was confirmed.

[0057] After the resistance furnace 10 reaches the set temperature inside the reactor 8, the reactor 8 is lowered by a lifting mechanism, allowing the sample placement mechanism to enter the reactor 8. This enables the sample to quickly reach the expected temperature. Compared with current thermogravimetric analyzers, this avoids the decomposition reaction of calcium hydroxide before reaching the expected temperature due to slow heating. It realizes the decomposition reaction of calcium hydroxide under a set temperature range that is close to constant temperature at any fixed point. At the same time, the thermogravimetric analysis device in this embodiment has a gas supply coil 11 and a purge pipe. Combined with the rapid lifting and lowering movement of the resistance furnace 10, it enables the sample to quickly reach the expected temperature and reduces the mass transfer resistance during the reaction process, providing excellent heat and mass transfer conditions for the sample. Meanwhile, reliable mass signals are used to conduct reaction kinetic studies.

[0058] Example 2

[0059] This embodiment provides a thermogravimetric analysis system for studying gas-solid reaction kinetics, such as... Figure 1As shown, it includes the thermogravimetric analysis apparatus for gas-solid reaction kinetics research described in Example 1.

[0060] The air inlet of the air supply coil 11 is connected to the air supply system, which provides the air supply coil 11 with air or a mixture of air and water vapor at a set pressure.

[0061] The gas supply system includes a mixing chamber 6. The outlet of the mixing chamber 6 is connected to the inlet of the gas supply coil 11 via a pipeline. The mixing chamber 6 has two inlets, one of which is connected to an air supply branch and the other is connected to a steam supply branch. The air supply branch includes a gas source 1, a mass flow meter 2, and a heater 3 connected in sequence via pipelines. The outlet of the heater 3 is connected to the inlet of the mixing chamber 6 via a pipeline. The gas source 1 is a gas cylinder that can inject air at a set pressure into the mixing chamber 6. The heater 3 is used to heat the air.

[0062] In this embodiment, gas source 1 can provide gas at 0.15 MPa. The gas flow rate is adjusted to 500 mL / min by mass flow meter 2, and the heater is set to 180°C to preheat the gas.

[0063] To meet the research requirements of calcium oxide hydration reaction, a steam supply branch was set up. The steam supply branch includes an injection pump and a vaporizer 5 connected in sequence through a pipeline. The steam outlet of the vaporizer 5 is connected to another air inlet of the mixing chamber 6 through a pipeline.

[0064] The syringe pump is a micro-injection pump 4, which injects liquid water (0.184 nL / min - 83.318 mL / min) into the vaporizer 5, which generates continuous and stable water vapor at a temperature of 280°C. The gas exiting the heater 3 mixes thoroughly with a certain amount of water vapor in the mixing chamber 6 to form a mixed gas with a certain water vapor partial pressure.

[0065] The gas exiting the mixing chamber 6 enters the gas supply coil 11 inside the reactor 8. After sufficient heat exchange within the gas supply coil 11, the gas will purge the surface of the sample inside the crucible 13. The gas supply coil 11 is a spiral tube to increase the heat exchange area and ensure that the temperature of the gas reaching the surface of the crucible 13 is consistent with the set temperature inside the reactor 8. The connecting pipes between the vaporizer 5 and the mixing chamber 6, the connecting pipes between the heater 3 and the mixing chamber 6, the exterior of the mixing chamber 6, and the connecting pipes between the mixing chamber 6 and the gas supply coil 11 inside the reactor 8 are all covered with heating tape (heating temperature of 180℃).

[0066] The working process of the system of the present invention will be explained below by taking the analysis of the heat storage reaction of the decomposition of pure calcium hydroxide as an example.

[0067] The screw lifting mechanism 9 moves the reactor 8 to its initial position at the top of the guide rail. A heat insulation pad is placed on the quartz tray 14, and the crucible 13 is placed on the heat insulation pad. The electronic scale 20 performs a tare weighing operation. The resistance furnace 10 is started to heat the reactor 8 to the required reaction temperature. Gas (air, 500 mL / min) is introduced into the air supply branch. The temperature inside the reactor 8 is stabilized using the first thermocouple 12. Once the reading of the first thermocouple 12 reaches the required level and stabilizes, the chiller 18 is turned on. An appropriate amount of analytically pure calcium hydroxide sample is weighed using a laboratory analytical balance (readable 0.1 mg) and spread evenly in the crucible 13. In this embodiment, the sample mass of calcium hydroxide is 70.5 mg. The computer begins to collect the mass data from the electronic scale 20 and the temperature data from the second thermocouple 16. The screw lifting mechanism 9 is controlled to lower the resistance furnace 10 to the designated position at a speed of 50 mm / s, after which the sample begins to react. The reaction is considered complete when the mass signal no longer changes. After the sample experiment is completed, a set of blank experiments without the sample are performed under the same experimental conditions. For example... Figure 2 As shown, the thermogravimetric curve of the sample can be obtained by subtracting the mass data of the blank experiment from the mass data of the sample experiment. Furthermore, the collected mass data can be used to calculate the reaction kinetic parameters of the decomposition of analytically pure calcium hydroxide. This will provide more reliable reaction kinetic information for the fluidized bed thermochemical heat storage research of calcium hydroxide.

[0068] The analytical system of this embodiment can provide a reliable research tool for the study of the reaction kinetics of fluidized bed thermochemical storage of calcium hydroxide / calcium oxide. It is understood that the analytical system of this embodiment can also be applied to the study of the reaction kinetics of fluidized bed thermochemical storage of carbide slag with calcium hydroxide as the main component and the study of the reaction kinetics of fluidized bed thermochemical storage of magnesium hydroxide / magnesium oxide.

[0069] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A thermogravimetric analysis apparatus for studying gas-solid reaction kinetics, characterized in that, It includes an electric resistance furnace, which is connected to a lifting mechanism. The electric resistance furnace has a reactor inside, which is closed at the top and open at the bottom. A gas supply coil is fixed inside the reactor. One end of the gas supply coil extends from the top of the reactor to the outside of the reactor as the gas inlet, and the other end is connected to a purge pipe as the gas outlet. A sample placement mechanism is set directly below the reactor and is installed on the weighing mechanism. The gas-solid reaction kinetics are the reaction kinetics of the fine-particle calcium hydroxide / calcium oxide material system under fluidization conditions; The sample placement mechanism includes a crucible, the crucible includes a sample placement part, the edge of the sample placement part is provided with a flange, and the purge tube is horizontally arranged so that the gas blown out of the purge tube will not blow the sample out of the crucible. A first thermocouple is inserted inside the reactor; The crucible is placed on a tray, and the tray is fixed to the top of the connecting rod. The connecting rod is a hollow rod, and a second thermocouple is installed inside the hollow rod. The probe of one end of the second thermocouple extends into a groove opened at the bottom of the crucible.

2. The thermogravimetric analysis apparatus for studying gas-solid reaction kinetics as described in claim 1, characterized in that, The first thermocouple is connected to the resistance furnace temperature controller.

3. The thermogravimetric analysis apparatus for gas-solid reaction kinetics research as described in claim 1, characterized in that, The bottom end of the connecting rod is connected to the weighing mechanism.

4. The thermogravimetric analysis apparatus for studying gas-solid reaction kinetics as described in claim 1, characterized in that, The crucible is made of platinum, while the tray and connecting rod are made of quartz. A heat-insulating pad is placed between the crucible and the tray.

5. The thermogravimetric analysis apparatus for studying gas-solid reaction kinetics as described in claim 1, characterized in that, The second thermocouple is connected to the monitoring terminal via a temperature transmitter, and the second thermocouple is set in a non-contact manner with the cavity surface inside the hollow rod.

6. The thermogravimetric analysis apparatus for studying gas-solid reaction kinetics as described in claim 1, characterized in that, A cooling water tray is also installed around the sample placement mechanism, and the cooling water tray is connected to a chiller.

7. The thermogravimetric analysis apparatus for gas-solid reaction kinetics research as described in claim 1, characterized in that, The lifting mechanism is a screw lifting mechanism.

8. A thermogravimetric analysis system for studying gas-solid reaction kinetics, characterized in that, The thermogravimetric analysis apparatus for studying gas-solid reaction kinetics, as described in any one of claims 1-7, includes a gas supply coil extending from the end of the reactor and connected to a gas supply system.

9. The thermogravimetric analysis system for gas-solid reaction kinetics research as described in claim 8, characterized in that, The gas supply system includes a mixing chamber. The outlet of the mixing chamber is connected to the inlet of the gas supply coil via a pipeline. The inlet of the mixing chamber is connected to an air supply branch and a steam supply branch. The air supply branch includes a gas source, which is connected to the inlet of the heater. The outlet of the heater is connected to the mixing chamber. The steam supply branch includes an injection pump, the outlet of which is connected to a vaporizer. The outlet of the vaporizer is connected to the mixing chamber.

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