A device and process for preparing ceramsite using municipal sludge

Abstract

The present invention provides a device for preparing ceramsite using municipal sludge, comprising a sludge pretreatment unit, a granulation molding unit and a firing unit arranged in sequence from upstream to downstream; the sludge pretreatment unit comprises a gravity concentration section, a centrifugal dehydration section and a hot air drying section. The gravity concentration section comprises a gravity concentration tank, in which a propeller blade is arranged; the centrifugal dehydration section comprises a centrifugal dehydrator, in which a drum is arranged, and the inner wall of the drum is provided with stepped protrusions to prevent the sludge from slipping and ensure the conveying and dehydration effects; the hot air drying section comprises a drying kiln, in which a spiral lifting plate is arranged, which greatly prolongs the sludge residence time; such an arrangement maximizes the use of gravity, centrifugal force and hot air to improve the dehydration and drying efficiency of the sludge. The problem of high sludge moisture content, high energy consumption and high cost of direct drying existing in the existing sludge treatment is solved.

Description

Technical Field

[0001] The invention relates to the technical field of harmless sludge treatment, and in particular to a device and a process method for preparing ceramsite by utilizing municipal sludge. Background Art

[0002] Ceramic aggregate is widely used as aggregate in the construction and building materials industry and is one of the important raw materials for lightweight aggregates due to its advantages of reasonable particle size distribution, low bulk density, low thermal conductivity, low water absorption, high refractoriness, good thermal insulation effect, and acid corrosion resistance. The general molding process of ceramsite is that the raw materials (construction impurities, stone powder, additives, etc.) are mixed and stirred in a mixer, and then granulated by a granulator. After granulation, it needs to be dried and cooled to finally form a finished product.

[0003] For example, the invention with application number CN202210157504.9 discloses a method for harmlessly treating municipal sludge and preparing ceramsite at the same time, comprising the following steps: 1) mechanically dehydrating the municipal sludge to form municipal sludge blocks; the municipal sludge blocks are dispersed by a disperser to form sludge particles, and the sludge particles are sent to a dryer for drying to form dry sludge particles; 2) the dry sludge particles are sent to a first waterfall rotary kiln, and after incineration, they are output to form incinerated sludge; 3) the incinerated sludge is ground by a vertical mill to form sludge powder; 4) the sludge powder, bentonite and water are transported to a vertical turbulent mixer for mixing and stirring to form a mixed material; 5) the obtained mixed material is made into spherical or columnar raw material balls; 6) the raw material balls are sent to a vibrating boiling dryer to form dry material balls; 7) the dry material balls are sent to a second waterfall rotary kiln for roasting to form ceramsite.

[0004] As shown in the above patent, at present, the preparation of lightweight aggregate from sludge mainly adopts the "drying-granulation-firing" process route. This process first pre-treats the sludge by drying it, and reduces its moisture content by means of thermal drying, mechanical dehydration, etc.; then, the dried sludge is formed by methods such as extrusion granulation and rolling granulation to obtain sludge green bodies; finally, the green bodies are fired at high temperature in equipment such as rotary kilns and tunnel kilns to obtain expanded clay products with a porous structure.

[0005] However, the current process has the following problems: First, the sludge has a high moisture content, and direct drying consumes a lot of energy and is costly; second, the granulation efficiency is low, the production capacity is limited, and it is difficult to meet the needs of large-scale production; third, the temperature control accuracy of the firing process is poor, the product quality is unstable, and key indicators such as strength and water absorption rate fluctuate greatly. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a device and a process method for preparing expanded clay using municipal sludge, so as to solve the technical problems existing in the current preparation of expanded clay from sludge, such as high sludge moisture content, large energy consumption for direct drying, high cost and low granulation efficiency, limited production capacity, difficulty in meeting large-scale production needs, poor temperature control accuracy during the firing process, unstable product quality, and large fluctuations in key indicators such as strength and water absorption rate.

[0007] The embodiment of the present invention discloses a device for preparing ceramsite using municipal sludge, comprising a sludge pretreatment unit A, a granulation molding unit B and a firing unit C which are arranged in sequence from upstream to downstream;

[0008] Sludge pretreatment unit A includes:

[0009] The gravity concentrating part includes a gravity concentrating tank, which has a large diameter at the top and a small diameter at the bottom and is conical. A central transmission shaft is provided in the gravity concentrating tank, and a spiral blade is installed on the central transmission shaft. The central transmission shaft is used to drive the spiral blade to rotate at a speed of 5-10 revolutions per minute.

[0010] The centrifugal dehydration part includes a high-speed centrifugal dehydrator arranged downstream of the gravity concentration tank. The high-speed centrifugal dehydrator is vertical cylindrical. A drum is arranged inside the high-speed centrifugal dehydrator. The inner wall of the drum is provided with a plurality of annular stepped protrusions. The rotation speed of the drum is 800-1200 rpm. The discharge port of the drum is also connected to a screw conveyor.

[0011] The hot air drying section includes a drying kiln, the feed port of the drying kiln is connected to the discharge port of the screw conveyor; a spiral lifting plate is arranged in the drying kiln, the cylinder of the drying kiln is inclined with respect to the horizontal direction to form a high end and a low end, and the feed port of the drying kiln is located at the high end of the drying kiln.

[0012] As a specific embodiment, the granulation molding unit B includes a spiral extrusion granulation part, which includes a spiral extrusion granulator. The spiral extrusion granulator is provided with a barrel and a hopper. The hopper is in an inverted cone shape. The inlet end of the hopper is connected to the screw conveyor, and the inlet end of the hopper is connected to the barrel. A spiral shaft is arranged in the spiral extrusion granulator. The spiral shaft is a variable diameter twin-screw structure. The upstream end of the spiral shaft has a large pitch and a shallow screw depth, and the downstream end has a small pitch and a large screw depth.

[0013] As a specific implementation, it also includes an iron removal device, which is arranged between the drying kiln and the screw extrusion granulator.

[0014] As a specific embodiment, the granulation molding unit B also includes a green body pre-drying section, which includes a tunnel-type roller drying kiln. The kiln body of the tunnel-type roller drying kiln is in the shape of a long tunnel. The tunnel-type roller drying kiln is sequentially provided with an entrance area, a constant temperature area and an exit area. The entrance area, the constant temperature area and the exit area are all provided with roller conveyor belts; the tunnel-type roller drying kiln 5 is also connected to a hot air supply device, and the hot air temperature in the constant temperature zone is below 500°C.

[0015] As a specific implementation, it also includes a vibrating screen, which is arranged between the screw extrusion granulator and the tunnel roller drying kiln, the screen surface inclination angle of the vibrating screen is 15-20°, and the vibration frequency is 15-25Hz.

[0016] As a specific embodiment, the firing unit C includes a feeding and conveying section and a zoned temperature-controlled firing section. The feeding and conveying section includes a belt conveyor, and the belt conveyor is arranged between the drying kiln and the zoned temperature-controlled firing section.

[0017] As a specific embodiment, the firing unit C also includes a zoned temperature-controlled firing section, which includes a roller kiln. The roller kiln is sequentially provided with a preheating zone, a sintering zone and a cooling zone, and the preheating zone, the sintering zone and the cooling zone are respectively equipped with independent burners and temperature control systems, and the temperature control system includes a PLC control device and a real-time temperature monitoring system.

[0018] As a specific embodiment, the firing unit C includes a discharge cooling part, which includes a cooling screen. The cooling screen is arranged at the discharge end of the roller kiln. The screen surface of the cooling screen is a double-layer structure, with the upper layer being a coarse screen and the lower layer being a fine screen.

[0019] The embodiment of the present application also discloses a process for preparing ceramsite using municipal sludge. Based on the above-mentioned device for preparing ceramsite using municipal sludge, the process for preparing ceramsite using municipal sludge comprises the following steps:

[0020] S1. After the sludge is transported to the gravity thickening tank, it slowly sinks under the action of gravity. At the same time, the central transmission shaft drives the spiral blades to rotate slowly to promote the separation of mud and water. The supernatant is discharged from the overflow port, and the concentrated sludge is discharged from the mud discharge port of the gravity thickening tank;

[0021] S2. The concentrated sludge discharged from the sludge outlet of the gravity thickening tank is sent to a high-speed centrifugal dewatering machine. The sludge is separated from the water by the centrifugal force in the high-speed rotating drum. The separated water is discharged from the bottom of the drum, and the separated sludge is discharged from the outlet of the drum.

[0022] S3. The sludge is transported to the drying kiln by a screw conveyor, and is lifted and turned by the spiral lifting plate in the drying kiln, moving slowly in a spiral shape; hot air is sent in by the blower at the end of the drying kiln, and the sludge is fully in contact with the hot air. The dried sludge is discharged from the discharge port at the lower end of the drying kiln, and the moisture content is reduced to below 15%;

[0023] S4. The sludge output from the drying kiln is transported to the screw extrusion granulator. The screw shaft in the screw extrusion granulator rotates, and the sludge moves forward quickly in the large pitch shallow thread section at the upstream end, and the small pitch deep thread section at the downstream end is strongly extruded and sheared, the volume is reduced, the density is increased, and the sludge is shaped into spherical granular green ceramsite by the shear force through the die cavity, and is extruded from the discharge end of the screw extrusion granulator;

[0024] S5. The green ceramsite is transported to the vibrating screen for separation. The screen surface is vibrated by the vibrator at a high frequency to discharge the broken particles and dust through the screen holes. The complete green ceramsite is transported to the tunnel roller drying kiln.

[0025] S6. The green ceramsite slowly passes through the tunnel roller drying kiln. Hot air is sent in from the tail of the drying kiln. The hot air contacts the green ceramsite in countercurrent. When passing through the constant temperature zone, the hot air temperature is controlled below 500°C to evaporate the moisture on the surface of the ceramsite.

[0026] S7, the ceramsite pre-dried in the drying kiln enters the roller kiln through a belt conveyor, and the ceramsite passes through the preheating zone, sintering zone and cooling zone of the roller kiln in sequence; in the preheating zone, the ceramsite is heated to 800-1000℃; after entering the sintering zone, the temperature rises to 1100-1200℃, and a sintering reaction occurs inside the ceramsite; finally, it is slowly cooled to 500-800℃ in the cooling zone;

[0027] S8. The ceramsite fired in the roller kiln 6 is transported from the discharge port of the roller kiln 6 to the vibrating cooling screen, and slowly moves forward under the vibration of the cooling screen surface and the action of its own weight, and the ceramsite is cooled to the ambient temperature.

[0028] As a specific implementation method, the concentrated sludge discharged from the sludge outlet of the gravity thickening tank enters the high-speed centrifugal dehydrator through the buffer tank, the liquid level gauge in the buffer tank monitors the sludge level, and the control system automatically adjusts the sludge discharge speed of the gravity thickening tank and the feed speed of the high-speed centrifugal dehydrator according to the liquid level signal;

[0029] In step S7, the expanded clay passes through the preheating zone, sintering zone and cooling zone of the roller kiln in sequence, and the temperature sensors of each zone collect the temperature of each zone in real time and transmit it to the PLC control device. The PLC control device achieves precise temperature control of the corresponding zone by adjusting the fuel amount and air-fuel ratio of the burner of each zone, so that the temperature fluctuation of each zone does not exceed ±5°C.

[0030] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0031] 1. In the sludge pretreatment stage, a conically narrowed gravity thickening tank is used, which cooperates with the rotating propeller blades set in the gravity thickening tank to promote mud-water separation while preventing interface disturbance, and the concentration effect is significantly improved; stepped protrusions are added to the inner wall of the centrifugal dehydrator drum to prevent the mud cake from slipping and ensure the transportation and dehydration effect; a spiral lifting plate is set in the drying kiln to greatly extend the sludge residence time and enhance the drying heat transfer effect. The organic combination of the three can maximize the use of gravity, centrifugal force and hot air to improve the dehydration and drying efficiency of the sludge.

[0032] 2. In the granulation stage, a variable diameter twin-screw extruder is used. The upstream section has a large pitch and a shallow screw depth, which is conducive to the rapid advancement of materials. The downstream section has a small pitch and a large screw depth to ensure that the materials are fully compacted. The axial and circumferential protrusions on the inner wall of the barrel are combined to strengthen the shearing and mixing effects, so that the sludge is continuously compacted and shaped during the extrusion process, making the green body uniform in density, smooth in surface, and significantly improved in strength. At the same time, a tunnel roller drying kiln is used to pre-dry the green body, and the hot air countercurrent contacts the material to improve the heat exchange effect, laying a solid foundation for subsequent high-temperature firing.

[0033] 3. During the firing stage, we independently developed an intelligent roller kiln system. The roller kiln is divided into zones with independent temperature control systems. With precise PLC control devices and real-time temperature monitoring systems, the whole process of heating, constant temperature and cooling of ceramsite is precisely controlled. A 45° flue gas guide plate is set in the kiln to enhance the gas-solid contact heat transfer effect. The roller conveyor makes the ceramsite move forward at a uniform speed and fully tumble for heat exchange, which greatly improves the sintering uniformity. The vibrating cooling screen at the discharge end solves the problem of finished product screening and rapid cooling, making the product quality stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0035] In the attached picture:

[0036] Figure 1 It shows a schematic structural diagram of a process flow chart for preparing ceramsite from municipal sludge according to an embodiment of the present invention;

[0037] Figure 2 It shows a schematic structural diagram of a sludge pretreatment unit according to an embodiment of the present invention;

[0038] Figure 3 It shows a schematic structural diagram of a granulation molding unit according to an embodiment of the present invention;

[0039] Figure 4 A schematic structural diagram of a firing unit according to an embodiment of the present invention is shown.

[0040] Reference numerals list

[0041] A. Sludge pretreatment unit; B. Granulation unit; C. Firing unit; 1. Gravity thickening tank; 11. Central transmission shaft; 12. Spiral blades; 2. High-speed centrifugal dehydrator; 21. Rotating drum; 22. Screw conveyor; 3. Drying kiln; 4. Screw extrusion granulator; 41. Hopper; 42. Screw shaft; 5. Tunnel roller drying kiln; 51. Vibrating screen; 6. Roller kiln; 61. Belt conveyor; 62. Cooling screen. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0043] Unless otherwise defined, all terms (including technical and scientific terms) used in the embodiments of the present disclosure have the same meanings as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It should also be understood that terms such as those defined in common dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless explicitly defined in this manner in the embodiments of the present disclosure.

[0044] The "first", "second" and similar words used in the embodiments of the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "One", "one" or "the" and similar words do not indicate a quantity limitation, but indicate that there is at least one. Similarly, "including" or "comprising" and similar words mean that the element or object appearing in front of the word covers the elements or objects listed after the word and their equivalents, without excluding other elements or objects. In the following description, spatial and directional terms such as "upper", "lower", "front", "back", "top", "bottom", "vertical" and "horizontal" may be used to describe the embodiments of the present disclosure, but it should be understood that these terms are only for the convenience of describing the embodiments shown in the figures, and do not require the actual device to be constructed or operated in a specific orientation. In the following description, the use of terms such as "connect", "connect", "fix" and "attach" may refer to two elements or structures being directly connected without other elements or structures between them, or may refer to two elements or structures being indirectly connected through an intermediate element or structure, unless otherwise clearly stated in this article.

[0045] Embodiment 1:

[0046] As attached Figure 1 To Attachment Figure 4 As shown:

[0047] The embodiment of the present invention provides a device for preparing ceramsite using municipal sludge, referring to Figure 1 and Figure 2 The device is provided with a sludge pretreatment unit A, a granulation molding unit B and a firing unit C in sequence from upstream to downstream.

[0048] The sludge pretreatment unit A includes a gravity concentration section, a centrifugal dehydration section and a hot air drying section. Among them, the gravity concentration section includes a gravity concentration tank 1, which is used to perform preliminary sedimentation of the sludge and remove part of the water in the sludge by gravity effect. Specifically, the gravity concentration tank 1 has a large diameter at the top and a small diameter at the bottom, and narrows in a conical shape. A central transmission shaft 11 is provided in the tank body of the gravity concentration tank 1, and a spiral blade 12 is installed on the central transmission shaft 11. The central transmission shaft 11 can drive the spiral blade 12 to rotate at a speed of 5-10 rpm, which can prevent the disturbance of the mud-water interface and promote the separation of mud and water. The conical structure of the gravity concentration tank 1 is conducive to the centralized discharge of sludge. An overflow port is provided at the top of the gravity concentration tank 1, and the overflow port is used to discharge the supernatant produced after the mud and water separation.

[0049] The centrifugal dehydration part of the sludge pretreatment unit A includes a high-speed centrifugal dehydrator 2, which is arranged below the gravity concentration tank 1. The high-speed centrifugal dehydrator 2 is used to accelerate the separation of mud and water. Figure 2 The high-speed centrifugal dehydrator 2 is a vertical cylindrical structure, and a drum 21 is arranged in the middle position inside the high-speed centrifugal dehydrator 2. The inner wall of the drum 21 is provided with a plurality of annular stepped protrusions, and the rotation speed of the drum 21 is as high as 800-1200 rpm. A feed port is arranged at the top of the top gravity thickening tank 1, and the concentrated sludge discharged from the gravity thickening tank 1 enters the drum 21 through the feed port. Since the drum 21 rotates at a high speed, the centrifugal force generated is hundreds of times that of gravity. The sludge is subjected to a strong centrifugal force, so that the mud and water are separated quickly, and the dehydration effect is improved. At the same time, the stepped protrusions on the inner wall of the drum 21 can prevent the mud cake from slipping, thereby ensuring the conveying and dehydration effect.

[0050] The centrifugal dehydration section further includes a screw conveyor 22 , the inlet end of the screw conveyor 22 is connected to the outlet end of the bottom of the drum 21 .

[0051] In another specific embodiment, a buffer tank is provided between the gravity thickening tank 1 and the high-speed centrifugal dehydrator 2, and the buffer tank is used to adjust the material balance between the gravity thickening tank 1 and the high-speed centrifugal dehydrator 2 to avoid excess or insufficient production capacity of the centrifugal dehydrator 2. Furthermore, a liquid level gauge is provided in the buffer tank to facilitate monitoring of the material in the buffer tank. Exemplarily, the embodiment of the present application also includes a control device, which is connected to the liquid level gauge as well as the gravity thickening tank 1 and the high-speed centrifugal dehydrator 2. By obtaining the sludge capacity data monitored by the liquid level gauge, the sludge discharge speed of the gravity thickening tank 1 and the feed speed of the high-speed centrifugal dehydrator 2 can be adjusted to ensure that the material delivery volume matches the production capacity of the centrifugal dehydrator 2.

[0052] Continue to refer to Figure 2 The hot air drying part of the sludge pre-treatment unit A includes a drying kiln 3, which is rotatably arranged downstream of the screw conveyor 22 for drying the sludge. The discharge port of the screw conveyor 22 is connected to the feed port of the drying kiln 3. Specifically, the cylinder of the drying kiln 3 is inclined at a certain angle to the horizontal direction to form a high end and a low end, the feed port of the drying kiln 3 is arranged at the high end, and the discharge port of the drying kiln 3 is arranged at the low end.

[0053] like Figure 2 As shown, a lifting plate is spirally arranged along the inner wall of the drying kiln 3. The lifting plate is used to lift up the sludge input into the drying kiln and gradually sprinkle it into the hot air flow to strengthen the heat and mass exchange between the material and the hot air flow and promote the drying process. The form and number of the lifting plates are set according to the specific conditions of the sludge. For example, the arrangement of the lifting plates can be uniformly distributed lifting plates, fan-shaped lifting plates, and lifting lifting plates.

[0054] A blower (not shown in the figure) is also provided at the tail of the drying kiln 3, and the blower is used to provide hot air for the drying kiln 3. The sludge transported by the screw conveyor 22 is sent into the drying kiln 3 from the feed port of the drying kiln 3. Under the lifting and turning action of the lifting plate, the sludge moves slowly in a spiral shape from the high end to the low end of the drying kiln 3. The hot air is sent into the kiln from the tail of the drying kiln 3 by the blower. The direction of the hot air is opposite to the moving direction of the sludge, and gas-solid countercurrent contact drying is formed in the cylinder, so that the sludge is fully in contact with the hot air, and the drying effect is improved. The dried sludge is discharged from the lower end. Such a setting can control the moisture content of the sludge to be below 15%. The setting of the spiral lifting plate greatly prolongs the residence time of the sludge in the drying kiln 3 and improves the drying efficiency. Specifically, the hot air temperature, flow rate and kiln drum speed of the drying kiln 3 can be adjusted according to the sludge production requirements to ensure the drying effect.

[0055] Furthermore, the granulation molding unit B includes a spiral extrusion granulation section and a green pre-drying section. The spiral extrusion granulation section of the granulation molding unit B includes a spiral extrusion granulator 4 arranged downstream of the drying kiln 3, referring to Figure 3The screw extrusion granulator 4 includes a barrel and a hopper 41. The hopper 41 is in an inverted cone shape. The inlet end of the hopper 41 is used to connect to the discharge port of the drying kiln 3. The lower end of the hopper is connected to the barrel to transport the sludge dried by the drying kiln to the screw extrusion granulator 4.

[0056] Specifically, the inner wall of the barrel of the screw extrusion granulator 4 is provided with protrusions in the axial and circumferential directions, and a screw shaft 42 is rotatably provided in the barrel of the screw extrusion granulator 4. The screw shaft 42 is a variable diameter twin screw structure, and the upstream end thereof has a large pitch and a shallow screw depth, and the downstream end has a small pitch and a large screw depth. Such a configuration is conducive to compacting and extruding the sludge. The discharge end of the screw extrusion granulator 4 is provided with a die hole cavity for forming the sludge during extrusion.

[0057] When in use, the sludge is conveyed by the screw conveyor 22 to the barrel of the screw extrusion granulator 4 through the hopper 41, and gradually moves to the downstream end and is compacted under the push of the screw shaft 42. When passing through the die hole cavity of the screw extrusion granulator 4, the sludge is subjected to shear force during the extrusion process. At the same time, the axial and circumferential protrusions on the inner wall of the barrel enhance the shear and mixing effects, so that the sludge is finally molded into spherical granular green clay pellets.

[0058] As a specific embodiment, an iron removal device is provided between the discharge port of the drying kiln 3 and the feed port of the screw extrusion granulator 4, and the ferromagnetic substances in the sludge are sucked out by magnetic force. For example, the iron removal device can be a permanent magnet or an electromagnetic iron remover. The dried sludge enters the iron removal device through the conveyor belt between the drying kiln 3 and the screw extrusion granulator 4, and the ferromagnetic impurities in the sludge are sucked out by the permanent magnet or the electromagnet, and the purified sludge enters the hopper 41 of the screw extrusion granulator 4.

[0059] Further, see Figure 1 and Figure 3 The green pre-drying section of the granulation molding unit B includes a tunnel-type roller drying kiln 5 arranged downstream of the screw extrusion granulator 4, and the tunnel-type roller drying kiln 5 is used to pre-dry the green clay ceramsite. The kiln body of the tunnel-type roller drying kiln 5 is in the shape of a long tunnel, in which an entrance area, a constant temperature area and an exit area are arranged in sequence, and roller conveyor belts are arranged in the entrance area, the constant temperature area and the exit area. The tunnel-type roller drying kiln 5 is also connected to a hot air supply device, and illustratively, the hot air supply device is a blower.

[0060] The green clay pellets output by the screw extrusion granulator 4 are evenly delivered to the roller conveyor belt in the entrance area of ​​the tunnel roller drying kiln 5 by the feeding device in the entrance area, and then slowly move to the exit area through the roller conveyor belt in the constant temperature area. The hot air is sent into the tunnel roller drying kiln 5 by the blower. The conveying direction of the hot air is opposite to the conveying direction of the roller conveyor belt, which is conducive to the countercurrent contact between the hot air and the green clay pellets and improves the heat exchange effect. Among them, when the green clay pellets are conveyed through the constant temperature zone, the hot air temperature is controlled to be kept below 500°C, so that the residual moisture on the surface of the green clay pellets evaporates, thereby improving the drying effect of the green clay pellets.

[0061] As a specific implementation, a vibrating screen 51 is arranged between the screw extrusion granulator 4 and the tunnel roller drying kiln 5. The screen surface inclination angle of the vibrating screen 51 is 15-20°, and the vibration frequency is 15-25Hz, so as to facilitate the screening of the broken dust and the whole ceramsite in the green ceramsite output by the screw extrusion granulator 4, and ensure that the ceramsite input into the roller kiln 6 is complete ceramsite.

[0062] Reference Figure 4 The firing unit C includes a feeding and conveying section, a zoned temperature-controlled firing section, and a discharge cooling section. The feeding and conveying section includes a belt conveyor 61, and the zoned temperature-controlled firing section includes a roller kiln 6. The belt conveyor 61 is arranged between the tunnel-type roller drying kiln 5 and the roller kiln 6. The green clay pre-baked in the tunnel-type roller drying kiln 5 is conveyed to the feeding end of the roller kiln 6 by the belt conveyor 61.

[0063] Furthermore, a preheating zone, a sintering zone and a cooling zone are sequentially arranged in the roller kiln 6, and the preheating zone, the sintering zone and the cooling zone are respectively equipped with independent burners and independent temperature control systems. Exemplarily, the temperature control system includes a PLC control device and a real-time temperature monitoring system, and the real-time temperature monitoring system includes a plurality of temperature sensors connected to the PLC control device. Since the preheating zone, the sintering zone and the cooling zone in the roller kiln 6 can be independently temperature-controlled, the temperature of each zone can be accurately adjusted according to the process requirements.

[0064] Exemplarily, the temperature of the preheating zone is 800-1000°C, the temperature of the sintering zone is 1100-1200°C, and the temperature of the cooling zone is 500-800°C.

[0065] The ceramsite moves slowly in the roller kiln 6, passing through the preheating zone, sintering zone and cooling zone in turn. In the preheating zone (800-1000℃), the ceramsite fully exchanges heat with the high-temperature kiln gas, and the temperature gradually increases; after entering the sintering zone (1100-1200℃), a sintering reaction occurs inside the ceramsite at this temperature, and the strength of the ceramsite is significantly improved; finally, in the cooling zone (500-800℃), the ceramsite is slowly cooled by reverse airflow to release thermal stress and avoid cracking caused by thermal stress.

[0066] Furthermore, smoke guide plates (not shown in the figure) are provided on both sides of the kiln body of the roller kiln 6. The smoke guide plates are installed at a 45° angle and can guide the rising high-temperature smoke to the surface of the ceramsite to achieve the effect of strengthening gas-solid contact and heat exchange.

[0067] Continue to refer to Figure 4 The discharge cooling part of the firing unit C is a cooling screen 62, which is arranged at the discharge end of the roller kiln 6. The screen surface of the cooling screen 62 is a double-layer structure, the upper layer is a coarse screen, and the lower layer is a fine screen. The ceramsite processed by the roller kiln 6 is output from the discharge end of the roller kiln 6 and transported to the cooling screen 62. The cooling screen 62 can accelerate the cooling speed of the ceramsite and screen it as a finished product.

[0068] Another embodiment of the present application further discloses a process for preparing ceramsite using municipal sludge. Based on the above-mentioned device for preparing ceramsite using municipal sludge, the process for preparing ceramsite using municipal sludge comprises the following steps:

[0069] After the sludge is transported to the gravity thickening tank 1, it slowly sinks under the action of gravity. At the same time, the central transmission shaft 11 drives the spiral blades 12 to rotate slowly to promote the separation of mud and water. The supernatant produced after the initial separation of the sludge is discharged from the overflow port arranged at the upper part of the gravity thickening tank 1, and the concentrated sludge enters the buffer tank through the mud discharge port of the gravity thickening tank 1.

[0070] The liquid level gauge in the buffer tank monitors the sludge liquid level, and the control device adjusts the sludge discharge speed of the gravity thickening tank 1 and the feed speed of the high-speed centrifugal dewatering machine 2 according to the liquid level signal to ensure that the sludge transportation matches the production capacity of the high-speed centrifugal dewatering machine 2.

[0071] The concentrated sludge after adjustment in the buffer tank is pumped to the feed port of the high-speed centrifugal dehydrator 2, and is quickly separated from the mud and water by the centrifugal force in the high-speed rotating drum 21. The separated water is discharged from the bottom of the drum 21, and the separated sludge cake is discharged from the discharge port of the drum 21. The sludge is transported to the drying kiln 3 by the screw conveyor 22.

[0072] Hot air is sent into the drying kiln 3 by the blower at the kiln tail. The sludge is lifted and turned by the spiral lifting plate in the drying kiln 3 and moves slowly in a spiral shape. The sludge is fully contacted with the hot air countercurrent. At the same time, the sludge is cooled along the way when being transported in the drying kiln 3. The dried sludge is discharged from the discharge port at the lower end of the drying kiln 3, and the moisture content drops to below 15%.

[0073] The sludge output from the drying kiln 3 is transported to the screw extrusion granulator 4, and then the screw shaft 42 rotates to continuously push the sludge to the discharge end of the screw extrusion granulator 4. The sludge moves rapidly in the large pitch shallow thread section at the upstream end, and is strongly squeezed and sheared in the small pitch deep thread section at the downstream end, so that the volume is reduced and the density is increased. The highly compacted sludge is subjected to shear force through the die hole cavity and is shaped into spherical granular green ceramsite, which is extruded from the discharge end of the screw extrusion granulator 4.

[0074] The green clay pellets are conveyed to the vibrating screen 51 for separation. The screen surface of the vibrating screen 51 allows broken particles and dust to be discharged through the screen holes under the high-frequency vibration of the vibrator, while the complete green clay pellets are conveyed to the tunnel roller drying kiln 5 by another conveyor belt.

[0075] The green clay pellets are slowly driven by rollers through the tunnel roller drying kiln 5. Hot air is sent in from the tail of the drying kiln 5 and contacts the clay pellets in countercurrent in the drying kiln 5. When passing through the constant temperature zone, the hot air temperature is controlled below 500°C to evaporate the moisture on the surface of the clay pellets.

[0076] After being pre-dried in the drying kiln 5, the ceramsite enters the roller kiln 6 via the belt conveyor 61. The ceramsite slowly moves to the kiln tail in the roller kiln 6 and continues to roll, so that the ceramsite and the flue gas can fully exchange heat. The ceramsite passes through the preheating zone, sintering zone and cooling zone of the roller kiln 6 in turn; in the preheating zone, the ceramsite is heated to 800-1000℃; after entering the sintering zone, the temperature rises to 1100-1200℃, and a sintering reaction occurs inside the ceramsite; finally, it is slowly cooled to 500-800℃ in the cooling zone. At the same time, the temperature sensors of each partition collect the temperature of each partition in real time and transmit it to the PLC control device. The PLC control device realizes precise temperature control of the corresponding partition by adjusting the fuel amount and air-fuel ratio of the burner of each partition, so that the temperature fluctuation of each partition does not exceed ±5℃. If there is any abnormality, the PLC control device can alarm in time.

[0077] In this process, the flue gas guide plate located on the side wall of the roller kiln 6 guides the hot flue gas to the surface of the ceramsite to enhance the heat exchange. At the same time, the ceiling of the roller kiln 6 radiates the heating of the ceramsite, and the ceramsite itself is provided with water cooling to prevent overheating and deformation.

[0078] The ceramsite fired by the roller kiln 6 is transported from the discharge port of the roller kiln 6 to the vibrating cooling screen 62. The ceramsite slowly moves forward under the vibration of the screen surface of the cooling screen 62 and the action of its own weight. At the same time, the ceramsite is quickly cooled to the ambient temperature by the cold air.

[0079] The above are only specific implementations of the present disclosure, but the protection scope of the present disclosure is not limited thereto, and the protection scope of the present disclosure shall be based on the protection scope of the claims.

Claims

1. A device for preparing ceramsite using municipal sludge, characterized in that: It includes a sludge pretreatment unit (A), a granulation molding unit (B) and a burning unit (C) which are arranged in sequence from upstream to downstream; The sludge pretreatment unit (A) comprises: The gravity concentrating section comprises a gravity concentrating tank (1), wherein the gravity concentrating tank (1) has a large diameter at the upper part and a small diameter at the lower part, and is in a conical shape; a central transmission shaft (11) is provided in the gravity concentrating tank (1), and a spiral blade (12) is installed on the central transmission shaft (11); the central transmission shaft (11) is used to drive the spiral blade (12) to rotate at a speed of 5-10 revolutions per minute; The centrifugal dehydration section comprises a high-speed centrifugal dehydrator (2) arranged downstream of the gravity concentration tank (1); the high-speed centrifugal dehydrator (2) is vertically cylindrical; a rotating drum (21) is arranged inside the high-speed centrifugal dehydrator (2); the inner wall of the rotating drum (21) is provided with a plurality of annular stepped protrusions; the rotating speed of the rotating drum (21) is 800-1200 revolutions per minute; and the discharge port of the rotating drum (21) is also connected to a screw conveyor (22); The hot air drying section comprises a drying kiln (3), wherein the feed port of the drying kiln (3) is connected to the discharge port of the screw conveyor (22); a spiral lifting plate is provided in the drying kiln (3), the cylinder of the drying kiln (3) is inclined with respect to the horizontal direction to form a high end and a low end, and the feed port of the drying kiln (3) is located at the high end of the drying kiln (3); The granulation molding unit (B) comprises a spiral extrusion granulation section, and the spiral extrusion granulation section comprises a spiral extrusion granulator (4); the spiral extrusion granulator (4) is provided with a barrel and a hopper (41), and the hopper (41) is in an inverted cone shape, and the inlet end of the hopper (41) is connected to the spiral conveyor (22), and the inlet end of the hopper (41) is connected to the barrel; a spiral shaft (42) is provided in the spiral extrusion granulator (4), and the spiral shaft (42) is a variable diameter twin-screw structure, and the upstream end of the spiral shaft (42) has a large pitch and a shallow screw depth, and the downstream end has a small pitch and a large screw depth; The granulation molding unit (B) further comprises a green pre-drying section, the green pre-drying section comprises a tunnel-type roller drying kiln (5), the tunnel-type roller drying kiln (5) is provided with an entrance area, a constant temperature area and an exit area in sequence, the hot air temperature of the constant temperature area is below 500°C; It also includes a vibrating screen (51), the vibrating screen (51) being arranged between the screw extrusion granulator (4) and the tunnel-type roller drying kiln (5), the screen surface inclination angle of the vibrating screen (51) being 15-20°, and the vibration frequency being 15-25 Hz; The firing unit (C) further comprises a zoned temperature-controlled firing section, the zoned temperature-controlled firing section comprising a roller kiln (6), wherein the roller kiln (6) is provided with a preheating zone, a sintering zone and a cooling zone in sequence; the temperature of the preheating zone is 800-1000° C., the temperature of the sintering zone is 1100-1200° C., and the temperature of the cooling zone is 500-800° C.; The firing unit (C) further comprises a discharge cooling section, wherein the discharge cooling section comprises a cooling screen (62), wherein the cooling screen (62) is arranged at the discharge end of the roller kiln (6), and wherein the screen surface of the cooling screen (62) is a double-layer structure, wherein the upper layer is a coarse screen and the lower layer is a fine screen.

2. The device for preparing ceramsite using municipal sludge as claimed in claim 1, characterized in that: It also includes an iron removal device, which is arranged between the drying kiln (3) and the screw extrusion granulator (4).

3. The device for preparing ceramsite using municipal sludge as claimed in claim 1, characterized in that: The kiln body of the tunnel-type roller drying kiln (5) is in the shape of a long tunnel, and the entrance area, the constant temperature area and the exit area are all provided with roller conveyor belts; the tunnel-type roller drying kiln (5) is also connected to a hot air supply device.

4. The device for preparing ceramsite using municipal sludge as claimed in claim 3, characterized in that: The firing unit (C) comprises a material feeding and conveying section and a zoned temperature-controlled firing section. The material feeding and conveying section comprises a belt conveyor (61). The belt conveyor (61) is arranged between the tunnel-type roller drying kiln (5) and the zoned temperature-controlled firing section.

5. The device for preparing ceramsite using municipal sludge as claimed in claim 4, characterized in that: The preheating zone, the sintering zone and the cooling zone are respectively equipped with independent burners and temperature control systems, and the temperature control system includes a PLC control device and a real-time temperature monitoring system.

6. A process for preparing ceramsite using municipal sludge, characterized in that: Based on the device for preparing ceramsite using municipal sludge as described in any one of claims 1 to 5, the process for preparing ceramsite using municipal sludge comprises the following steps: S1, after the sludge is transported to the gravity thickening tank (1), it slowly sinks under the action of gravity, and at the same time, the central transmission shaft (11) drives the spiral blade (12) to slowly rotate, thereby promoting the separation of mud and water, and the supernatant is discharged from the overflow port, and the concentrated sludge is discharged from the mud discharge port of the gravity thickening tank (1); S2, the concentrated sludge discharged from the sludge outlet of the gravity thickening tank (1) is sent to the high-speed centrifugal dewatering machine (2), and the sludge is separated from the water by the centrifugal force in the high-speed rotating drum (21), the separated water is discharged from the bottom of the drum (21), and the separated sludge is discharged from the discharge port of the drum (21); S3, the sludge is transported to the drying kiln (3) by the screw conveyor (22), and is lifted and turned by the spiral lifting plate in the drying kiln (3), and moves slowly in a spiral shape; hot air is sent into the drying kiln (3) by the blower at the kiln tail, and the sludge is fully in contact with the hot air. The dried sludge is discharged from the discharge port at the lower end of the drying kiln (3), and the moisture content is reduced to less than 15%; S4, the sludge output from the drying kiln (3) is transported to the screw extrusion granulator (4), the screw shaft (42) in the screw extrusion granulator (4) rotates, the sludge moves forward rapidly in the large pitch shallow thread section at the upstream end, and the small pitch deep thread section at the downstream end is subjected to strong extrusion and shearing action, the volume is reduced, the density is increased, and the sludge is subjected to shearing force through the die hole cavity, and is shaped into spherical granular green clay pellets, which are extruded from the discharge end of the screw extrusion granulator (4); S5, the green ceramsite is transported to a vibrating screen (51) for separation, and the screen surface is vibrated at a high frequency by a vibrator to discharge broken particles and dust through the screen holes, and the complete green ceramsite is transported to a tunnel roller drying kiln (5); S6, the green ceramsite slowly passes through the tunnel type roller drying kiln (5), hot air is sent into the tunnel type roller drying kiln (5) from the kiln tail, the hot air contacts with the green ceramsite in countercurrent, and when passing through the constant temperature zone, the hot air temperature is controlled below 500° C., so as to evaporate the moisture on the surface of the ceramsite; S7, the ceramsite pre-dried in the tunnel roller drying kiln (5) enters the roller kiln (6) via a belt conveyor (61), and the ceramsite passes through the preheating zone, sintering zone and cooling zone of the roller kiln (6) in sequence; in the preheating zone, the ceramsite is heated to 800-1000° C.; after entering the sintering zone, the temperature rises to 1100-1200° C., and a sintering reaction occurs inside the ceramsite; and finally, it is slowly cooled to 500-800° C. in the cooling zone; S8. The ceramsite fired in the roller kiln (6) is transported from the discharge port of the roller kiln (6) to the vibrating cooling screen (62), and slowly moves forward under the vibration of the screen surface of the cooling screen (62) and the action of its own weight, and the ceramsite is cooled to ambient temperature.

7. The process for preparing ceramsite using municipal sludge as claimed in claim 6, characterized in that: The concentrated sludge discharged from the sludge outlet of the gravity thickening tank (1) enters the high-speed centrifugal dehydrator (2) through the buffer tank. The liquid level gauge in the buffer tank monitors the sludge liquid level, and the control system automatically adjusts the sludge discharge speed of the gravity thickening tank (1) and the feed speed of the high-speed centrifugal dehydrator (2) according to the liquid level signal. In step S7, the ceramsite passes through the preheating zone, sintering zone and cooling zone of the roller kiln (6) in sequence, and the temperature sensors of each zone collect the temperature of each zone in real time and transmit it to the PLC control device. The PLC control device achieves accurate temperature control of the corresponding zone by adjusting the fuel amount and air-fuel ratio of the burner of each zone, so that the temperature fluctuation of each zone does not exceed ±5°C.

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