Sludge pyrolysis method and pyrolysis system

Abstract

The present invention relates to the field of sludge pyrolysis technology, specifically a sludge pyrolysis method and a pyrolysis system thereof. The pyrolysis method comprises the following steps: dehydrating the sludge and then feeding it into a pyrolysis reactor through a feeding device for pyrolysis reaction; indirectly heating the pyrolysis reactor with an external heating device so that the sludge undergoes pyrolysis reaction in an oxygen-free environment, wherein a plurality of cleaning mechanisms are equidistantly arranged on the rotating shaft within the pyrolysis reactor for cleaning the inner wall of the pyrolysis reactor. The pyrolysis reactor used in the sludge pyrolysis method of the present application has a specific cleaning mechanism that can scrape and clean attachments on the inner wall of the pyrolysis reactor, thereby improving the thermal efficiency of the overall pyrolysis process.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge pyrolysis, and in particular to a sludge pyrolysis method and a pyrolysis system. Background Art

[0002] Sludge includes municipal sludge, oily sludge, and industrial sludge. Pollutants in sludge are generally divided into four categories: First, inorganic pollutants, primarily heavy metals and salts such as copper, chromium, and mercury; second, harmful microorganisms, mostly pathogens, that coexist in the sludge; third, organic pollutants, primarily polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), phenols, and benzene series; and fourth, small amounts of radioactive elements. Pyrolysis can maximize the reduction, stabilization, detoxification, and resource utilization of sludge.

[0003] Currently, the main methods used are rotary reactors and spiral stirred reactors, which use indirect flue gas heating to provide pyrolysis heat. Common problems include low system efficiency, uneven heat transfer, and poor thermal desorption of oily sludge with high oil and water content. Pre-treatment with dehydration and oil removal is required to reduce the liquid content to below 30% before processing. This results in a long process flow, high equipment investment, and multiple polluting steps. Furthermore, each unit suffers from small processing scale and low system thermal efficiency.

[0004] Therefore, a sludge pyrolysis method and a pyrolysis system are proposed. Summary of the Invention

[0005] The object of the present invention is to provide a sludge pyrolysis method, which comprises the following steps:

[0006] The sludge is dehydrated and then fed into the pyrolysis reactor through the feeding equipment for pyrolysis reaction;

[0007] An external heating device is used to indirectly heat the pyrolysis reactor, causing the sludge to undergo a pyrolysis reaction in an oxygen-free environment, wherein the pyrolysis reaction temperature is within the range of 450-600°C. The pyrolysis reactor main body includes a pyrolysis reactor and a rotating shaft rotatably connected to the interior of the pyrolysis reactor. Both ends of the rotating shaft extend into the pyrolysis reactor, and the rotatable connection between the pyrolysis reactor and the rotating shaft is sealed. A driving member is provided at one end of the rotating shaft. Several cleaning mechanisms are equidistantly provided on the rotating shaft within the pyrolysis reactor for cleaning the inner wall of the pyrolysis reactor.

[0008] The pyrolysis reactor produces high-temperature pyrolysis oil and gas which enter the condensation device to obtain pyrolysis oil and pyrolysis gas;

[0009] The pyrolysis solids produced by the pyrolysis reaction are cooled and transported out.

[0010] Another object of the present invention is to provide a sludge pyrolysis system for implementing the above-mentioned sludge pyrolysis method, the pyrolysis system comprising a pyrolysis reactor main device and an external heating device, wherein the external heating device is arranged around the outer wall of the pyrolysis reactor main device and is used to indirectly heat the pyrolysis reactor;

[0011] The main device of the pyrolysis reactor includes a pyrolysis reactor and a rotating shaft rotatably connected to the inside of the pyrolysis reactor. Both ends of the rotating shaft extend to the pyrolysis reactor, and the pyrolysis reactor and the rotating shaft are sealed at the rotating connection. One end of the rotating shaft is provided with a driving member.

[0012] Several cleaning mechanisms are arranged at equal distances outside the rotating shaft in the pyrolysis reactor;

[0013] A feed port is provided on the upper side of the exterior of the pyrolysis reactor, and a discharge port is provided on the lower side of the exterior of the pyrolysis reactor.

[0014] In one embodiment, the number of the cleaning mechanisms is four or more groups of cleaning mechanisms, so that 60-80% of the inner wall area of ​​the pyrolysis reactor can be cleaned.

[0015] In one embodiment, the cleaning mechanism includes a connecting rod fixedly connected to the rotating shaft, a movable inner tube is vertically fixed to the end of the connecting rod away from the rotating shaft, the two ends of the movable inner tube are sleeved and rotatably connected to the movable outer tube, a scraper is fixed to the outside of the movable outer tube, a chain is fixed to the side of the scraper, and the top of the scraper is integrally fixed with teeth. The scraper is set at an inclination angle, and one end of the scraper is in contact with the inner wall of the pyrolysis reactor, and the end of the scraper close to the inner wall of the pyrolysis reactor is designed in an arc-shaped structure.

[0016] Preferably, the pyrolysis system comprises two or more pyrolysis reactors, and the pyrolysis reactors are connected in series and / or in parallel through the communication between the discharge port and the feed port.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The sludge pyrolysis method of the present application adopts a pyrolysis system with a specially designed structure, which can clean the coke attached to the inner wall of the pyrolysis reactor in real time during the pyrolysis process. At the same time, it can realize all-round shoveling of the material in the pyrolysis reactor so that it can be fully heated and decomposed, reducing the failure rate of the pyrolysis system and improving the pyrolysis efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 Schematic diagram of the structure of the pyrolysis reactor of the present invention;

[0021] Figure 2 is a schematic cross-sectional view of a pyrolysis reactor of the present invention;

[0022] Figure 3 It is a structural schematic diagram of the cleaning mechanism of the present invention;

[0023] Description of reference numerals:

[0024] 1. Flue gas heating box; 2. Pyrolysis reactor; 21. Feed inlet; 22. Discharge outlet; 24. Rotating axis;

[0025] 3. Cleaning mechanism; 31. Connecting rod; 32. Scraper; 33. Teeth; 34. Chain; 35. Movable outer tube; 36. Movable inner tube. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Pyrolysis system

[0028] The pyrolysis device of the present application includes a pyrolysis reactor main device and an external heating device, wherein the external heating device is arranged around the outer wall of the pyrolysis reactor main device and is used to indirectly heat the pyrolysis reactor.

[0029] The external heating device can be a flue gas heating device or an electromagnetic induction heating device.

[0030] In embodiments of the flue gas heating device, hot flue gas is generally generated by burning gas. The flue gas heating device is arranged around the outer wall of the pyrolysis reactor, forming a flue gas channel between the outer wall of the pyrolysis reactor and the inner wall of the flue gas heating device for circulating the hot flue gas. For example, the flue gas heating device has a flue gas inlet and a flue gas outlet. A combustion nozzle is provided at the flue gas inlet to burn gas to generate hot flue gas, which is then discharged through the flue gas outlet. The flow rate and temperature of the hot flue gas can be controlled by adjusting the gas / air ratio of the combustion nozzle.

[0031] Preferably, the flow direction of the flue gas in the flue gas channel is opposite to the flow direction of the sludge in the pyrolysis reactor.

[0032] In an embodiment of the electromagnetic induction heating device, the rated power of the electromagnetic induction heating device can be configured to be 400-800 Kw / t, for example 800 Kw / t. In such an embodiment, 600 kWh / ton to 700 kWh / ton.

[0033] The main equipment of the pyrolysis reactor of this application is as follows Figure 1 As shown, it includes a pyrolysis reactor 2 and a rotating shaft 24 rotatably connected to the inside of the pyrolysis reactor 2. Both ends of the rotating shaft 24 extend to the pyrolysis reactor 2, and the rotatable connection between the pyrolysis reactor 2 and the rotating shaft 24 is sealed. One end of the rotating shaft 24 is provided with a driving member.

[0034] A cleaning mechanism 3 is provided at equal distances outside the rotating shaft 24 in the pyrolysis reactor 2;

[0035] A feed port 21 is provided on the upper side of the exterior of the pyrolysis reactor 2 , and a discharge port 22 is provided on the lower side of the exterior of the pyrolysis reactor 2 .

[0036] The cleaning mechanism of the present application is used to clean the coke deposits on the inner wall of the pyrolysis reactor in real time. In a preferred embodiment, the cleaning area of ​​the inner wall of the pyrolysis reactor reaches 60-80%.

[0037] The clearing agency for this application, such as Figure 2-Figure 3 As shown, the scraper 32 comprises a connecting rod 31, a scraper 32, and a chain 34. One end of the connecting rod 31 is fixedly connected to the rotating shaft 24. The connecting rod 31 is connected to the scraper 32 via a movable outer tube 35 and a movable inner tube 36. The movable inner tube 36 is vertically fixed to the end of the connecting rod 31, and the movable outer tube 35 is rotatably sleeved on both ends of the movable inner tube 36. The scraper 32 is fixed to the outer wall of the movable outer tube 35 and can rotate as the movable outer tube 35 rotates.

[0038] One end of the chain 34 is fixed to the connecting rod 31 , and the other end of the chain 34 is fixed to the side surface of the scraper 32 . The rotation degree of the scraper is controlled by the elastic deformation of the chain.

[0039] The end of the scraper 32 that contacts the pyrolysis reactor is arc-shaped and has teeth 33. The arc is such that the curvature of the arc can achieve tangential contact with the inner wall of the pyrolysis reactor.

[0040] Since the coke produced by sludge pyrolysis is of high hardness and easy to agglomerate, and the sludge raw material itself is generally filtered during the dehydration stage, the particle size of the sludge raw material after filtration is relatively large (generally 1-4 cm), so the tooth spacing of the teeth 33 can be within the range of 1-2 cm, so that the sludge particles and lumpy coke can be completely picked up to avoid omission, thereby achieving comprehensive removal.

[0041] The effect of chain 34 is to make buffer for the rotation of scraper. The length of chain 34 is 4-6cm, for example 5cm.

[0042] In one embodiment, the scraper 32 rotates at an angle of 30-120°.

[0043] By controlling the rotation angle of the scraper 32 through the chain 34, the scraper 32 can be flexibly rotated according to the filling degree of the sludge material and the thickness of the coke, thereby achieving an efficient cleaning effect throughout the sludge depyrolysis process.

[0044] The scraper can be a quadrilateral, such as a square, an irregular trapezoid, etc. The width of the scraper can be in the range of 8-30 cm, such as 20 cm, 23 cm, 25 cm, 28 cm. The length of the curved side of the scraper can be 15-20 cm.

[0045] In some embodiments, four or more cleaning mechanisms may be arranged on the rotating shaft along the length of the rotating shaft.

[0046] In some embodiments, one or two to four cleaning mechanisms may be arranged on the same radial cross-section of the rotating shaft, and the angles between the cleaning mechanisms may be 90°, 120°, or 180°.

[0047] When the pyrolysis system of the present application is used to perform pyrolysis of sludge, the pyrolysis method includes the following steps:

[0048] The sludge is dehydrated and then fed into the pyrolysis reactor through the feeding equipment for pyrolysis reaction;

[0049] An external heating device is used to indirectly heat the pyrolysis reactor, so that the sludge undergoes pyrolysis reaction in the absence of oxygen, wherein the pyrolysis reaction temperature is within the range of 450-600°C;

[0050] The pyrolysis reactor produces high-temperature pyrolysis oil and gas which enter the condensation device to obtain pyrolysis oil and pyrolysis gas;

[0051] The pyrolysis solids produced by the pyrolysis reaction are cooled and transported out.

[0052] In an embodiment where the external heating device is a flue gas heating device, to ensure a pyrolysis reaction temperature of 450-600°C, the flue gas inlet temperature is 600-800°C, and the flue gas outlet temperature is controlled within the range of 300-400°C. Using the pyrolysis system of the present application, the flue gas outlet temperature can be maintained stably at 300-400°C for 30 days, thereby ensuring the stability of the pyrolysis reaction.

[0053] In an embodiment where the external heating device is an electromagnetic induction heating device, the power of the electromagnetic induction heating device can be 400-800 kW / t, for example, 800 kW / t. In this embodiment, the energy consumption of the pyrolysis system per ton of processing capacity is 600-700 kWh / t, and can be maintained at less than 620 kWh / t for 30 days.

[0054] In one embodiment, in order to reduce the overall energy consumption of the pyrolysis method and reduce equipment investment, the water content of the sludge after dehydration is below 30% by weight.

[0055] The pyrolysis method of the present application is used to pyrolyze sludge. The resulting pyrolysis products are largely converted into pyrolysis oil and pyrolysis gas. The yield of pyrolysis solids is significantly reduced compared to existing technologies, significantly improving the quality of the pyrolysis products. Furthermore, the pyrolysis system of the present application, through the design of a specific cleaning mechanism, can clean the inner walls of the pyrolysis reactor in real time, reducing the risk of equipment failure and saving equipment maintenance costs. This is highly beneficial for continuous industrial sludge pyrolysis.

[0056] The present application is described in detail below with examples.

[0057] The sludge used in the following examples is Beijing municipal sludge. After drying, the industrial analysis data is shown in Table 1 below.

[0058] Table 1

[0059] Element All water ash content Volatile matter Fixed carbon weight% 30 21.28 41.58 7.14

[0060] Example

[0061] In the pyrolysis system of this embodiment, the pyrolysis reactor (sectional view as shown in FIG. Figure 2 The cleaning machine (shown) is horizontal, 9m long and 1.5m in inner diameter. 42 cleaning mechanisms are arranged at equal distances along the length of the rotating shaft. The rotating shaft rotates at a speed of 3r / min.

[0062] The width of the scraper is 15 cm, the tooth spacing of the teeth on the scraper is 1 cm, and the original length of the chain is 5 cm.

[0063] With a working efficiency of 1500kg / hour, the municipal sludge is transported to the pyrolysis reactor for continuous pyrolysis. The high-temperature pyrolysis oil and gas produced enter the condensation device (shell and tube heat exchanger, heat exchange surface 300m 2 ) to obtain pyrolysis oil and pyrolysis gas; the pyrolysis solids produced are discharged through cooling and transportation (indirect cooling spiral, spiral diameter DN350mm, length 6m).

[0064] The pyrolysis reactor is heated by flue gas and the pyrolysis temperature is maintained at 500 ° C. In order to ensure that the pyrolysis temperature is maintained at 500 ° C, the flue gas inlet temperature is controlled at 700 ° C, the flue gas outlet temperature is controlled at 300 ° C, and the flue gas flow rate is 5000 Nm 3 When the flue gas outlet temperature is higher than 350°C, stop the pyrolysis system and check the coking condition on the inner wall of the pyrolysis reactor.

[0065] The temperature conditions at the flue gas outlet are summarized in Table 2 below.

[0066] Table 2

[0067] Number of days Day 5 Day 10 Day 20 Day 30 Day 40 Day 45 Day 50 temperature 300℃ 300℃ 305℃ 315℃ 330 341℃ 355℃

[0068] The pyrolysis reactor operated continuously for 40 days without significant fluctuations in the flue gas outlet temperature, indicating good performance. However, significant temperature fluctuations occurred on the 45th day, reaching 341°C. The temperature reached 355°C on the 50th day. Operation was stopped on the 50th day, and inspection of the inner wall of the pyrolysis reactor revealed an average thickness of 0.1 cm of coke deposits.

[0069] The analysis of the pyrolysis products during the operation of the pyrolysis system is shown in Table 3.

[0070] Table 3

[0071] Day 10 Day 20 Day 30 Day 40 Day 45 Day 50 Pyrolysis oil 36.8 wt% 36.8 wt% 36.7% by weight 36.5 wt% 36.1 wt% 30.1 wt% Pyrolysis coke 30.6 wt% 30.6 wt% 30.7 wt% 30.9 wt% 31.5 wt% 37.2% by weight

[0072] As can be seen from Table 3, within 45 days when the flue gas outlet temperature fluctuated slightly, the yield of pyrolysis oil was relatively stable and maintained at the same level. However, on the 50th day when the temperature fluctuated significantly, the yield of pyrolysis oil fluctuated significantly.

[0073] Comparative Example

[0074] In this comparative example, a rotary kiln (9 m long, 1.5 m diameter) was used as the pyrolysis reactor for sludge pyrolysis. The same pyrolysis conditions as in Example 1 were employed, with flue gas heating. The flue gas outlet temperatures are summarized in Table 4.

[0075] Table 4

[0076] Number of days Day 5 Day 7 Day 10 Day 15 Day 17 Day 20 Day 25 Day 30 temperature 300℃ 310℃ 308℃ 315℃ 320℃ 335℃ 350℃ 380℃

[0077] Table 4 shows that during the first 15 days of operation, the flue gas outlet temperature fluctuated and was not very stable. After 15 days, it began to steadily increase, reaching a high of 380°C on the 30th day. The pyrolysis system of this comparative example was shut down, and the inner wall of the rotary kiln was inspected, revealing that the average thickness of the coke deposits on the inner wall reached 0.8 cm.

[0078] The analysis of pyrolysis products after the rotary kiln was operated continuously for 30 days is shown in Table 5.

[0079] Table 5

[0080] Day 5 Day 7 Day 10 Day 15 Day 17 Day 20 Day 25 Day 30 Pyrolysis oil 36.8 wt% 36.7% by weight 36.8 wt% 36.1 wt% 35.6% by weight 32.3% by weight 29.3 wt% 27.5 wt% Pyrolysis coke 30.6 wt% 30.7 wt% 30.6 wt% 30.9 wt% 31.4 wt% 35.1% by weight 38.5 wt% 39.8% by weight

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sludge pyrolysis method, characterized in that: The steps include: The sludge is dehydrated and then fed into the pyrolysis reactor through the feeding equipment for pyrolysis reaction; An external heating device is used to indirectly heat the pyrolysis reactor, causing the sludge to undergo a pyrolysis reaction in the absence of oxygen, wherein the temperature of the pyrolysis reaction is within the range of 450-600°C. The pyrolysis reactor includes a pyrolysis reactor body and a rotating shaft rotatably connected to the interior of the pyrolysis reactor body, with both ends of the rotating shaft extending to the exterior of the pyrolysis reactor, and the rotatable connection between the pyrolysis reactor and the rotating shaft being sealed. A driving member is provided at one end of the rotating shaft. A plurality of cleaning mechanisms are equidistantly provided on the rotating shaft within the pyrolysis reactor for cleaning the inner wall of the pyrolysis reactor. The pyrolysis reactor produces high-temperature pyrolysis oil and gas which enter the condensation device to obtain pyrolysis oil and pyrolysis gas; The pyrolysis solids produced by the pyrolysis reaction are cooled, conveyed and discharged; The cleaning mechanism includes a connecting rod fixedly connected to the rotating shaft, a movable inner tube is vertically fixed to the end of the connecting rod away from the rotating shaft, the two ends of the movable inner tube are sleeved and rotatably connected to the movable outer tube, a scraper is fixed to the outside of the movable outer tube, a chain is fixed to the side of the scraper, the other end of the chain is fixed to the connecting rod, the top of the scraper is integrally fixed with teeth, the scraper is set at an inclination angle, and one end of the scraper is in contact with the inner wall of the pyrolysis reactor, and the end of the scraper close to the inner wall of the pyrolysis reactor is designed in an arc-shaped structure.

2. The sludge pyrolysis method according to claim 1, characterized in that: The external heating device is a flue gas heating device, an electromagnetic induction heating device, or an electric heating wire heating device.

3. The sludge pyrolysis method according to claim 2, characterized in that: The flue gas heating equipment is provided with a flue gas inlet and a flue gas outlet. The flow direction of the flue gas in the flue gas heating equipment is opposite to the flow direction of the sludge in the pyrolysis reactor. The temperature of the flue gas inlet is 600-800°C, and the temperature of the flue gas outlet remains stable at 300-400°C within 30 days.

4. The sludge pyrolysis method according to any one of claims 1 to 3, characterized in that: The water content of the sludge after dehydration is below 30% by weight.

5. A pyrolysis system for implementing the sludge pyrolysis method according to any one of claims 1 to 4, characterized in that: The pyrolysis system includes a pyrolysis reactor and an external heating device, wherein the external heating device is used to indirectly heat the pyrolysis reactor; The pyrolysis reactor includes a pyrolysis reactor body and a rotating shaft rotatably connected to the interior of the pyrolysis reactor body. Both ends of the rotating shaft extend to the exterior of the pyrolysis reactor, and the rotatable connection between the pyrolysis reactor and the rotating shaft is sealed. A driving member is provided at one end of the rotating shaft. Several cleaning mechanisms are arranged at equal distances outside the rotating shaft in the pyrolysis reactor; The pyrolysis reactor is provided with a feed port on the upper side of its exterior, and a discharge port on the lower side of its exterior; The cleaning mechanism includes a connecting rod fixedly connected to the rotating shaft, a movable inner tube is vertically fixed to the end of the connecting rod away from the rotating shaft, the two ends of the movable inner tube are sleeved and rotatably connected to the movable outer tube, a scraper is fixed to the outside of the movable outer tube, a chain is fixed to the side of the scraper, the other end of the chain is fixed to the connecting rod, the top of the scraper is integrally fixed with teeth, the scraper is set at an inclination angle, and one end of the scraper is in contact with the inner wall of the pyrolysis reactor, and the end of the scraper close to the inner wall of the pyrolysis reactor is designed in an arc-shaped structure.

6. The pyrolysis system according to claim 5, characterized in that: Four or more cleaning mechanisms are arranged along the length direction of the rotating shaft, so that 60-80% of the inner wall area of ​​the pyrolysis reactor can be cleaned.

7. The pyrolysis system according to claim 5, characterized in that: The pyrolysis system includes two or more pyrolysis reactors, and the pyrolysis reactors are connected in series and / or in parallel through the communication between the discharge port and the feed port.

Images