MULTI-STAGE CONTINUOUS PYROLYSIS REACTOR USING MOLTEN SALT

Abstract

Disclosed is a multi-stage continuous pyrolysis reactor using molten salt, and more specifically to a multi-stage continuous pyrolysis reactor that thermally decomposes polymer waste, such as waste plastics, under anaerobic or oxygen-deficient conditions. The multi-stage continuous pyrolysis reactor using molten salt according to the present invention comprises: a reactor body (100), a multi-stage pyrolysis furnace (200), a drive sprocket (330), a driven sprocket (340), a chain (350), a plurality of transport members (360), and a molten salt circulation unit (400).

Claims

1. A multi-stage continuous pyrolysis reactor using molten salt comprising: a reactor body (100) having an inlet (110) at one side of the upper part for introducing polymer waste and an outlet (120) on the lower part for discharging slag consisting of ash and undecomposed char; a multi-stage pyrolysis furnace (200) disposed horizontally inside the reactor body (100), configured to pyrolyze polymer waste as it moves in a zigzag path; a drive sprocket (330) coupled to a drive shaft (310) installed at one end of the molten salt circulation passages opposite the pyrolysis furnace (200); a driven sprocket (340) coupled to a driven shaft (320) installed at the other end of the molten salt circulation passages inside the pyrolysis furnace (200); a chain (350) connecting the drive sprocket (330) and the driven sprocket (340), moving in an endless loop; a plurality of transport members (360) spaced at predetermined intervals along the chain (350), circulating together with the chain to transport polymer waste; a molten salt circulation system (400) connected to the exterior of the reactor body (100) for circulating molten salt as a liquid-phase heat transfer medium; wherein the pyrolysis furnace (200) comprises: a drying section (210) located at the uppermost part, configured to remove moisture from the pores of the polymer waste within a temperature range of 80-150 C.; a melting section (220) located below the drying section (210), configured to melt and liquefy the polymer waste within a temperature range of 100-300 C.; a decomposition section (230) located below the melting section (220), configured to vaporize and decompose the molten polymer waste within a temperature range of 200-400 C.; and a carbonization section (240) located below the decomposition section (230), where slag composed of ash and undecomposed char is generated within a temperature range of 300-450 C.; wherein the pyrolysis furnace (200) is formed in a rectangular duct shape, wherein the transport member (360) is formed in a rectangular plate shape, wherein it is structured such that, through the continuous circulation of the transport members (360) together with the chain (350), the polymer waste is scraped and moved, then dropped to the next stage, and thereafter continues to move while performing pyrolysis, wherein a series of baffle plates (500) are arranged in a zigzag pattern along the flow direction of the molten salt within the molten salt circulation passages (130) of the reactor body (100); and wherein the baffle plates (500) are inclined at a predetermined angle relative to the flow direction of the molten salt, and a through passage (510) is formed between and at the ends of the baffle plates (500).

2. The multi-stage continuous pyrolysis reactor using molten salt according to claim 1, wherein the transport members (360) are in the form of plates and are arranged in a zigzag pattern with one end positioned near the inner wall of the pyrolysis furnace (200).

3. The multi-stage continuous pyrolysis reactor using molten salt according to claim 1, wherein multiple weight-reducing grooves (361) are formed on both sides and the center of the transport members (360) to reduce their weight.

4. The multi-stage continuous pyrolysis reactor using molten salt according to claim 1, wherein the molten salt circulation system (400) comprises: a molten salt tank (410) for storing the molten salt; a molten salt boiler (420) connected to the molten salt tank (410) for heating the molten salt; molten salt supply lines (430) for supplying the high-temperature molten salt heated by the molten salt boiler (420) to the molten salt circulation passages (130) of the reactor body (100); a molten salt discharge line (440) for returning low-temperature molten salt from the molten salt circulation passages (130) of the reactor body (100) back to the molten salt tank (410); a plurality of valves (450) installed on the molten salt supply lines (430) for controlling the fluid flow in each line; temperature sensors (460) installed in the pyrolysis furnace (200) for detecting the temperature of the molten salt; and a control unit (470) for adjusting the flow rate of the molten salt through the valves (450) based on the temperature values measured by the temperature sensors (460), thereby controlling the temperature of the pyrolysis furnace (200).

5. The multi-stage continuous pyrolysis reactor using molten salt according to claim 1, wherein the molten salt circulation system (400) comprises: a molten salt tank (410) for storing the molten salt; a molten salt boiler (420) connected to the molten salt tank (410) for heating the molten salt; molten salt supply lines (430) for supplying the high-temperature molten salt heated by the molten salt boiler (420) to the molten salt circulation passages (130) of the reactor body (100); a molten salt discharge line (440) for returning low-temperature molten salt from the molten salt circulation passages (130) of the reactor body (100) back to the molten salt tank (410); a plurality of valves (450) installed on the molten salt supply lines (430) for controlling the fluid flow in each line; temperature sensors (460) installed in the pyrolysis furnace (200) for detecting the temperature of the molten salt; a control unit (470) for adjusting the flow rate of the molten salt through the valves (450) based on the temperature values measured by the temperature sensors (460), thereby controlling the temperature of the pyrolysis furnace (200); a preheating heater (491) installed on one side of the molten salt tank (410) for preheating the molten salt; a molten salt return line (492) for returning the molten salt heated by the molten salt boiler (420) to the molten salt tank (410); and a molten salt drain line (493) connected between the molten salt tank (410) and the molten salt supply lines (430), with a drain valve (494) installed on one side.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is an isometric view illustrating a multi-stage continuous pyrolysis reactor using molten salt according to the present invention.

[0029] FIG. 2 is a longitudinal cross-sectional view showing the multi-stage continuous pyrolysis reactor using molten salt according to the present invention.

[0030] FIG. 3 is a lateral cross-sectional view illustrating the multi-stage continuous pyrolysis reactor using molten salt according to the present invention.

[0031] FIG. 4 is a horizontal cross-sectional view of the transport member in the multi-stage continuous pyrolysis reactor using molten salt according to the present invention.

[0032] FIG. 5 is an example illustration of the transport member in the multi-stage continuous pyrolysis reactor using molten salt according to the present invention.

[0033] FIG. 6 is an example illustration of the overflow wall in the multi-stage continuous pyrolysis reactor using molten salt according to the present invention.

[0034] FIG. 7 is a figure showing another embodiment of the molten salt circulation section in the multi-stage continuous pyrolysis reactor using molten salt according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] In order to provide a detailed explanation of the present invention to an extent that a person skilled in the art to which the invention pertains can easily carry out the invention, the most preferred embodiment of the present invention will be described in detail.

[0036] As illustrated in FIGS. 1 to 3, the molten salt-based multi-stage continuous pyrolysis reactor according to the present invention includes a reactor body (100), a pyrolysis furnace (200), a drive shaft (310), a driven shaft (320), a drive sprocket (330), a driven sprocket (340), a chain (350), a transport member (360), and a molten salt circulation unit (400).

[0037] The reactor body (100) provides an environment in which polymer waste can be pyrolyzed by heating the pyrolysis furnace (200) with molten salt supplied by the molten salt circulation unit (400).

[0038] The reactor body (100) is equipped with an inlet (110) at the upper side for introducing polymer waste, and an outlet (120) at the lower side for discharging slag composed of ash and undecomposed char.

[0039] The polymer waste, such as waste plastics, introduced into the reactor body (100) is gradually heated within the temperature range of 80-450 C., undergoing processes of moisture drying, polymer waste melting, pyrolysis, and slag formation. The products of the pyrolysis reaction are separated into a mixed vapor composed of steam and pyrolysis gases, and slag consisting of ash and undecomposed char, which are discharged.

[0040] The pyrolysis furnace (200) is arranged horizontally inside the reactor body (100), and the polymer waste undergoes pyrolysis while moving in a zigzag pattern in a multi-stage structure. This pyrolysis furnace (200) includes a drying section (210), a melting section (220), a decomposition section (230), and a carbonization section (240).

[0041] In more detail, the drying section (210) is located at the uppermost part and operates within a temperature range of 80-150 C., where moisture is removed from the pores of the polymer waste.

[0042] The melting section (220) is located below the drying section (210) and operates within a temperature range of 100-300 C., where the polymer waste is melted and liquefied.

[0043] The decomposition section (230), positioned below the melting section (220), operates within a temperature range of 200-400 C., where the polymer waste melt is vaporized and and subjected to thermal decomposition.

[0044] The carbonization section (240) is located below the decomposition section (230) and operates within a temperature range of 300-450 C., where slag composed of ash and undecomposed char is formed.

[0045] The present invention involves the drying and pyrolysis of polymer waste in the aforementioned sections and temperature conditions; however, it is not limited thereto, and a pyrolysis furnace (200) may be additionally incorporated. Furthermore, various temperatures, other than those specified above, may be set as needed.

[0046] In case of a fire in the pyrolysis furnace (200), nitrogen purging can be used to suppress the fire. If the molten salt flow is insufficient during the molten salt drainage (drain), nitrogen can be supplied to improve the flow of the molten salt. Additionally, if urgent drainage of molten salt is required due to valves failures or other issues, nitrogen purging can be used to push the molten salt out before it solidifies, thus reducing the drainage time.

[0047] Furthermore, before the pyrolysis starts, the oxygen in the pyrolysis furnace must be removed. To remove oxygen, nitrogen can be supplied to displace the oxygen, or steam can be supplied to push out the oxygen. Specifically, to expel oxygen from the pyrolysis zone before the pyrolysis begins, instead of injecting steam, water can be supplied, and as the pyrolysis furnace heats up, the water will evaporate into steam, which will displace the oxygen.

[0048] In the event that the molten salt is not drained and accumulates in the pyrolysis furnace, pipes or other components, steam is introduced into the molten salt zone inside the pyrolysis furnace and the pipes to melt the molten salt, thereby ensuring smooth flow of the molten salt and preventing any obstruction in its flow.

[0049] A drive sprocket (330) coupled to a driving shaft (310) installed on one side of the pyrolysis furnace (200).

[0050] A driven sprocket (340) coupled to a driven shaft (320) installed on the other side of the pyrolysis furnace (200).

[0051] In this system, the drive sprocket (330) is driven by power transmitted from the motor (370) mounted on the exterior of the reactor body (100). A gearbox (380) is operatively coupled to the motor shaft (370) and transmits the reduced rotational speed to the driving shaft (310), thereby causing the drive sprocket (330) to rotate when the motor (370) is activated.

[0052] The chain (350) connects the drive sprocket (330) and the driven sprocket (340), forming a continuous loop for transmission.

[0053] The number of installed drive shafts (310), driven shafts (320), drive sprockets (330), driven sprockets (340), and chains (350), as well as their diameters and gear ratios, may be varied according to the characteristics of the device to which the drive system is applied, and are not specifically limited.

[0054] The transport members (360) are installed at predetermined intervals along the chain (350) and move in a circulating motion with the chain (350), thereby transporting the polymer waste. That is, through the continuous circulation of the transport members (360) along with the chain (350), the polymer waste is conveyed through the multi-stage pyrolysis furnace (200) and undergoes pyrolysis.

[0055] With the configuration as described above, the polymer waste introduced into the reactor body (100) is scraped and moved, then dropped to the next stage, where it continues to move, allowing for smooth transport and uniform distribution of the polymer waste. This prevents clogging or sticking caused by foreign substances in the polymer waste.

[0056] As shown in FIG. 4, it is preferable that the transport members (360), shaped as plates and arranged in a zigzag pattern, have one end positioned in close proximity to the inner wall of the pyrolysis furnace (200). The transport members (360) may be arranged such that only a portion of the transport members are in a zigzag pattern, as required.

[0057] By arranging a plurality of transport members (360) in a zigzag pattern and scraping along the inner wall of the pyrolysis furnace (200), polymer waste is prevented from accumulating in the gap between the transport members (360) and the inner wall, thereby avoiding blockages.

[0058] Without a zigzag arrangement, friction between the transport members and the inner wall of the pyrolysis furnace can lead to motor overload. However, when arranged in a zigzag pattern, the transport members reduce friction, ensure uniform scraping, lower motor load, and prevent polymer materials from accumulating on and adhering to the inner wall.

[0059] As shown in FIG. 5, multiple weight-reducing grooves (361) may be formed on both sides and the center of the conveying member (360) to reduce its weight.

[0060] The formation of these grooves (361) decreases the weight of the conveying member (360), thereby reducing noise during operation and lowering the conveying load.

[0061] In general, the lower part of the pyrolysis zone is the area that requires the most heat transfer and also has the largest surface area. Therefore, enhancing heat transfer in the lower part is crucial. To improve heat transfer in the lower part, a significant amount of heat must pass through this area. However, since heat typically moves upwards, it passes through without adequately heating the lower part. In other words, the heat required to heat the lower part is transferred through the turbulent flow of heat rising towards the upper part.

[0062] As shown in FIG. 6, a series of baffle plates (500) can be continuously arranged in a zigzag pattern along the flow direction of the molten salt in the circulation passages (130) of the reactor body (100).

[0063] It is preferable that the baffle plates (500) are inclined at a predetermined angle relative to the flow direction of the molten salt, and through holes (510) are formed between the baffle plates (500) and at their ends.

[0064] When the molten salt does not fully fill the upper regions of the molten salt circulation passages (130), heat transfer to these regions is diminished. To address this issue, the invention arranges a series of baffle plates (500) in a zigzag pattern along the molten salt circulation passages (130), redistributing the flow and enhancing thermal transfer to the upper regions.

[0065] The baffle plates (500) partially obstruct the flow of the molten salt, dissipating its kinetic energy and guiding the molten salt into a uniform and stable flow. This improves the thermal transfer efficiency in both the lower and upper regions of the molten salt circulation passages (130).

[0066] The through-holes (510) allow the molten salt to flow downstream without passing over the baffle plates (500), maintaining the continuous flow of the molten salt.

[0067] As shown in FIGS. 1 and 2, the molten salt circulation unit (400), located on the exterior of the reactor body (100), circulates molten salt, which functions as the heat transfer medium.

[0068] In pyrolysis reactors that use hot air as the heat source, the temperature of the entire pyrolysis furnace is determined by the hot air supplied from the burner. However, due to the gradual decrease in temperature from the upper to the lower part, it becomes difficult to manage the temperature of each layer to match the specific characteristics of that layer.

[0069] The present t invention enables efficient operation by differentially controlling the temperature of each stage of the pyrolysis furnace (200) through the molten salt circulation system (400).

[0070] The molten salt circulation system (400) includes a molten salt tank (410), a molten salt boiler (420), molten salt supply lines (430), a molten salt discharge line (440), valves (450), a temperature sensor (460), and a control unit (470).

[0071] The molten salt tank (410) stores the molten salt to be supplied to the pyrolysis furnace (200). The molten salt used in the pyrolysis reactor according to the embodiment of the present invention may be a fluid in which salts such as NaNO.sub.3, KNO.sub.3, NaNO.sub.2, and the like are mixed in appropriate proportions. This molten salt is a substance that exists as a solid but undergoes a phase change to a liquid at temperatures above its melting point.

[0072] The molten salt boiler (420) is connected to the molten salt tank (410) and heats the molten salt to the pyrolysis reaction temperature.

[0073] The molten salt boiler (420) can be heated using a heater or any of gas, liquid, or solid fuels, depending on its capacity.

[0074] A first pump (490) is installed between the molten salt tank (410) and the molten salt boiler (420), and the first pump (490) is responsible for supplying the molten salt stored in the molten salt tank (410) to the pyrolysis reactor (200).

[0075] The molten salt supply lines (430) supply the high-temperature molten salt, heated by the molten salt boiler (420), to the molten salt circulation passages (130) in the reactor body (100).

[0076] The ultrasonic flow meters (480) and the valves (450) are installed on the molten salt supply lines (430) to control the flow of molten salt to the circulation passages (130).

[0077] Previously, embodiments were described in which multiple molten salt supply lines (430) are configured in parallel to supply molten salt to the reactor body (100), and accordingly, the molten salt circulation passages (130) connected to the molten salt supply lines (430) are also configured in parallel; however, they may alternatively be configured in series. As in the previous embodiments, when the molten salt supply lines (430) and the molten salt circulation passages (130) connected thereto are configured in parallel, the flow rate is low and the flow velocity is slow, resulting in a significant temperature difference between the two ends of the molten salt circulation passages (130). However, when the molten salt supply line (430) and the molten salt circulation passage (130) are connected in series from the lower part to the upper part, and the flow rate and flow velocity of the molten salt are increased while supplying the molten salt at an appropriate temperature, the molten salt is transferred from the lower part to the upper part. As a result, the temperature of the upper part can be controlled to be lower than that of the lower part, and the temperature difference between both ends of the molten salt circulation passage (130) is reduced.

[0078] The molten salt discharge line (440) returns the low-temperature molten salt from the molten salt circulation passages (130) of the reactor body (100) back to the molten salt tank (410).

[0079] The valves (450) are installed at multiple locations along the molten salt supply lines (430) to regulate the fluid flow within each line.

[0080] By employing electrically controlled valves (450), the control unit (470) can manage the operation of the valves, facilitating ease of operation and enabling automatic temperature control by inputting a desired set point. To achieve this, ultrasonic flow meters (480) are provided to detect variations in flow rate resulting from the operation of the valves (450) and to monitor corresponding temperature changes, thereby driving the valves (450) to adjust in accordance with the set temperature.

[0081] The temperature sensing sensors (460) are installed in the pyrolysis reactor (200) to detect the temperature of the molten salt. The temperature sensors (460) may also be installed in the molten salt circulation passages (130) as depicted in FIG. 1 and in other locations as deemed necessary, which would be apparent to those skilled in the art.

[0082] The control unit (470) adjusts the molten salt flow rate through the valves (450) based on the temperature values measured by the temperature sensing sensors (460), thereby controlling the temperature of the pyrolysis reactor (200).

[0083] With this configuration, the molten salt circulation system (400) allows for precise differential control of the temperature of each stage of the pyrolysis reactor (200), enabling g efficient operation and improving the heat transfer efficiency of the molten salt.

[0084] As shown in FIGS. 1 and 7, The molten salt circulation unit (400) may include a molten salt tank (410) for storing molten salt, a molten salt boiler (420) connected to the molten salt tank (410) for heating the molten salt, the molten salt supply lines (430) that supply the high-temperature molten salt heated by the molten salt boiler (420) to the molten salt circulation passage (130) of the reactor body (100), a molten salt discharge line (440) that returns the low-temperature molten salt from the molten salt circulation passage (130) of the reactor body (100) back to the molten salt tank (410), a plurality of valves (450) installed on the molten salt supply lines (430) to control the fluid flow in each line, a temperature sensor (460) installed in the pyrolysis furnace (200) to detect the temperature of the molten salt, a control unit (470) that adjusts the flow rate of the molten salt based on the temperature readings from the temperature sensor (460) to regulate the temperature of the pyrolysis furnace (200), a preheating heater (491) installed on one side of the molten salt tank (410) to preheat the molten salt, a molten salt return line (492) that returns the molten salt heated by the molten salt boiler (420) to the molten salt tank (410), and a molten salt drain line (493) connected between the molten salt tank (410) and the molten salt supply lines (430), having a drain valve (494) on one side.

[0085] Since the molten salt tank (410), molten salt boiler (420), molten salt supply lines (430), molten salt discharge line (440), valves (450), temperature sensor (460), and control unit (470) have the same configuration and function as those described in the previous embodiment, further detailed explanation thereof will be omitted.

[0086] By incorporating the preheating heater (491), molten salt return line (492), and molten salt drain line (493) into the aforementioned configuration, the molten salt stored in the molten salt tank (410) can be preheated, enabling the flow of molten salt, which is solid at room temperature. Once the molten salt is partially liquefied and becomes pumpable, the molten salt boiler (420) is activated. Instead of supplying the preheated molten salt to the pyrolysis reactor, it is returned to the molten salt tank (410), ensuring that the entire molten salt within the tank remains flowable. This reduces the operating time of the molten salt boiler and allows the molten salt to be heated at a lower cost. Furthermore, by rapidly liquefying the molten salt, the heating time is minimized, leading to an increase in yield.

[0087] The molten salt circulation system (400) operates the preheating heater (491), and once a portion of the molten salt in the molten salt tank (410) has melted, it then activates the second pump (495). Then, the molten salt boiler (420) is operated to heat the molten salt, which is circulated through the molten salt return line (492) to further heat the molten salt in the molten salt tank (410). Once the molten salt in the molten salt tank (410) is sufficiently heated, the drain valve (494) of the molten salt drain line (493) is closed, and the first pump (490) is activated to supply the molten salt to the pyrolysis furnace (200). When stopping the operation of the pyrolysis reactor, the molten salt boiler (420) is turned off, the first pump (490) and the second pump (495) are stopped, and the drain valve (494) is opened.

[0088] Although the present invention has been described with reference to the preferred embodiments in the accompanying drawings, it is evident that various modifications can be made without departing from the scope of the invention as understood by those skilled in the art. Therefore, the scope of the present invention should be interpreted in accordance with the claims, which encompass various modifications.

DESCRIPTION OF REFERENCE NUMERALS

[0089] 100: reactor body [0090] 110: inlet [0091] 120: outlet [0092] 130: molten salt circulation passages [0093] 200: pyrolysis furnace [0094] 210: drying section [0095] 220: melting section [0096] 230: decomposition [0097] 240: carbonization section [0098] 310: drive shaft [0099] 320: driven shaft [0100] 330: drive sprocket [0101] 340: driven sprocket [0102] 350: chain [0103] 360: transport members [0104] 361: weight-reducing grooves [0105] 370: motor [0106] 380: gearbox [0107] 400: molten salt circulation unit [0108] 410: molten salt tank [0109] 420: molten salt boiler [0110] 430: molten salt supply lines [0111] 440: molten salt discharge line [0112] 450: valves [0113] 460: temperature sensors [0114] 470: control unit [0115] 480: ultrasonic flow meters [0116] 490: first pump [0117] 491: preheating heater [0118] 492: molten salt return line [0119] 493: molten salt drain line [0120] 494: drain valve [0121] 495: second pump [0122] 500: baffle plates [0123] 510: through passage