Carbonization and gasification coupled sludge treatment system

Abstract

The invention provides a sludge treatment system coupling carbonization and gasification. The sludge treatment system comprises a pyrolysis unit, a combustion unit, a waste heat recovery unit and a flue gas collection unit. Wherein the pyrolysis unit is suitable for performing a pyrolysis reaction on dried sludge in fluidizing gas, the type of the pyrolysis reaction is adjusted by adjusting the oxygen content and pyrolysis temperature in the fluidizing gas, a pyrolysis product is obtained, and the type of the pyrolysis reaction comprises a gasification reaction and a carbonization reaction; the combustion unit is communicated with the pyrolysis unit and is suitable for carrying out combustion reaction on the pyrolysis gas to obtain flue gas at a first temperature; the waste heat recovery unit communicates with the combustion unit and is suitable for conducting heat exchange with the flue gas at the first temperature, and flue gas at the second temperature is obtained after heat in the flue gas at the first temperature is recovered; the flue gas collecting unit communicates with the waste heat recovery unit and is suitable for purifying and collecting flue gas at the second temperature.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of sludge harmless treatment, and particularly relates to a sludge treatment system coupling carbonization and gasification. Background Art

[0002] Sludge treatment is a key link in urban sewage treatment, and its reduction, harmlessness and resource utilization are of great significance to environmental protection and resource recycling. At present, the mainstream processes include incineration, carbonization and gasification, etc. Among them, incineration realizes sludge volume reduction through high-temperature oxidation, but faces problems of high energy consumption and secondary pollution; the carbonization process (such as rotary kiln) pyrolyzes sludge under anaerobic conditions to generate carbide, but it needs to rely on external fuel to supplement heat; the gasification process (such as fluidized bed gasification) generates combustible gas through partial oxidation, and the energy utilization efficiency is relatively high. However, existing technologies mostly focus on a single reaction mode: the carbonization process aims at solid carbon products, while the gasification process mainly focuses on the recovery of combustible gas. There are significant differences between the two in operating conditions, product characteristics and economy, and it is difficult to flexibly respond to changes in sludge composition and fluctuations in market demand.

[0003] Then, the existing sludge treatment processes have limitations in many aspects. First, the applicable scenarios are single: the incineration process is widely used in large-scale projects, but the investment in small and medium-scale projects is high and the operating economy is poor; although the carbonization process is a new direction, due to the low organic matter content of the existing sludge, the heat of the pyrolysis gas is insufficient, and a large amount of gas or biomass fuel needs to be supplemented, resulting in a cost increase. Second, the process adaptability is insufficient: for example, although the Gard gasification process can couple with flash drying to improve efficiency, it cannot be switched to the carbonization mode in the later stage; existing technologies mostly rely on fixed sludge parameter design and lack flexible adjustment means for the dynamic changes of sludge organic matter (such as future improvement trends), mainly by increasing or decreasing the gas consumption, which is poor in economy and prone to repeated investment. In addition, the performance adjustment and additional applications of carbonization products are still in the development stage, further restricting the technology popularization.

[0004] In summary, it is of far-reaching significance to develop a multi-functional sludge treatment system that combines gasification and carbonization functions and can flexibly adapt to changes in sludge quality, so as to improve the quality of sludge treatment products, solve the technical bottlenecks of the rigid, poor adaptability and low efficiency of traditional process modes. Summary of the Invention

[0005] In view of this, to solve at least one technical problem in related technologies and other aspects, the present disclosure provides a sludge treatment system coupling carbonization and gasification, including a pyrolysis unit, a combustion unit, a waste heat recovery unit, and a flue gas collection unit. Among them, the pyrolysis unit is suitable for carrying out a pyrolysis reaction on the dried sludge in a fluidizing gas, and adjusting the type of pyrolysis reaction by adjusting the oxygen content and pyrolysis temperature in the fluidizing gas to obtain pyrolysis products, where the types of pyrolysis reactions include gasification reactions and carbonization reactions; the combustion unit is connected to the pyrolysis unit and is suitable for carrying out a combustion reaction on the pyrolysis gas to obtain flue gas at a first temperature; the waste heat recovery unit is connected to the combustion unit and is suitable for exchanging heat with the flue gas at the first temperature, and obtaining flue gas at a second temperature after recovering the heat in the flue gas at the first temperature; the flue gas collection unit is connected to the waste heat recovery unit and is suitable for purifying and collecting the flue gas at the second temperature.

[0006] According to an embodiment of the present disclosure, the pyrolysis unit includes: a pyrolysis furnace, a cyclone separator, and a return feeder. Among them, a gas injection port is provided at the upper part of the pyrolysis furnace, which is suitable for introducing oxygen or air to adjust the temperature of the fluidizing gas; the cyclone separator is connected to the outlet of the pyrolysis furnace and includes a gas product outlet and a solid product outlet, and the cyclone separator is suitable for carrying out gas-solid separation on the pyrolysis products to obtain pyrolysis gas and pyrolysis carbon; the return feeder is connected to the solid product outlet of the cyclone separator and is configured to return part of the pyrolysis carbon to the pyrolysis furnace.

[0007] According to an embodiment of the present disclosure, when a gasification reaction mainly occurs in the pyrolysis furnace, the gasification equivalence ratio of the fluidizing gas ≥ 0.25, the pyrolysis temperature is 700 - 900 °C, and the fluidizing gas includes at least one of N2 and O2.

[0008] According to an embodiment of the present disclosure, when a carbonization reaction mainly occurs in the pyrolysis furnace, the oxygen content of the fluidizing gas is less than 11%, the pyrolysis temperature is 300 - 650 °C, and the fluidizing gas includes at least one of N2, CO2, and water vapor.

[0009] According to an embodiment of the present disclosure, the gas flow velocity of the fluidizing gas is 0.8 - 7 m / s.

[0010] According to an embodiment of the present disclosure, the combustion unit includes a combustion chamber, and the inlet of the combustion chamber is connected to the gas product outlet of the cyclone separator.

[0011] According to an embodiment of the present disclosure, in the combustion chamber, the air excess coefficient corresponding to the combustion process of the pyrolysis gas in the combustion chamber is less than 1.05.

[0012] According to an embodiment of the present disclosure, the waste heat recovery unit includes a waste heat boiler and a first heat exchanger. The first heat exchanger is configured to connect the waste heat boiler and the pyrolysis furnace, and the heat exchanger is suitable for heating a portion of the flue gas at the second temperature to obtain the flue gas at a third temperature, and circulating the flue gas at the third temperature to the pyrolysis unit as a fluidizing gas.

[0013] According to an embodiment of the present disclosure, the aforementioned sludge treatment system further includes: a control system, including a temperature sensor, a pressure sensor, an oxygen content sensor, and a pipeline regulating valve respectively arranged in the pyrolysis furnace and the combustion chamber.

[0014] According to an embodiment of the present disclosure, the flue gas collection unit further includes a dust removal subunit and a desulfurization subunit.

[0015] According to the embodiments of the present disclosure, the sludge treatment system coupled with carbonization and gasification proposed in the present disclosure can be adapted to a variety of application scenarios through multi-unit coordination and flexible control mechanisms. The core of the system is that the pyrolysis unit can flexibly switch between gasification and carbonization reaction modes by dynamically adjusting the oxygen content and temperature of the fluidizing gas. This dual-mode design breaks through the limitations of the traditional single reaction process, can adapt to the dynamic changes of sludge organic matter, and avoid repeated investment due to the solidification of the technical route. Its flexible abundant energy storage (pyrolysis carbon) method can also better adapt to changes in external conditions, such as changes in electricity prices, matching of steam demand, long-term changes in sludge calorific value, and other high investment in energy storage / utilization. At the same time, the waste heat recovery unit efficiently recovers heat from the combustion flue gas, generates steam for front-end sludge drying, as a fluidizing gas in the pyrolysis furnace or external supply, significantly reducing external energy consumption.

[0016] In summary, the present invention solves the technical problems of single traditional process mode, poor adaptability, difficult product performance control and difficult pollution control through system structure innovation, dynamic parameter control and efficient separation technology, and realizes flexible switching of gasification-carbonization dual modes, adaptive adjustment of sludge composition and coordinated control of pollutants. It is particularly suitable for small and medium-sized sludge treatment scenarios with large organic matter fluctuations and high environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the sludge treatment system coupled with carbonization and gasification in the embodiment of the present disclosure.

[0018] [Description of Reference Numerals]

[0019] 1-sludge silo; 2-pyrolysis furnace; 3-cyclone separator; 4-returner; 5-combustion furnace; 6-first heat exchanger; 7-waste heat boiler; 8-electrostatic dust removal silo; 9-bag dust collector; 10-desulfurization spray tower; 11-chimney; 12-second heat exchanger; 21-first valve; 22-second valve; 23-third valve; 31-first induced draft fan; 32-second induced draft fan. Detailed implementation manners

[0020] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the following further describes the present disclosure in detail with reference to specific embodiments and the accompanying drawings.

[0021] In the ranges disclosed in the present disclosure, the endpoints and any values of the ranges are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present disclosure.

[0022] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0023] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those of ordinary skill in the art, unless otherwise defined. It should be noted that the terms used here should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0024] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present disclosure should have the ordinary meanings understood by those of ordinary skill in the art belonging to the field of the present disclosure. If descriptions such as "first", "second", etc. are involved throughout the text, then such descriptions of "first", "second", etc. are only used to distinguish similar objects, and cannot be understood as indicating or implying their relative importance, sequence or implicitly indicating the quantity of the indicated technical features. It should be understood that the data described by "first", "second", etc. can be interchanged under appropriate circumstances.

[0025] In the present disclosure, unless otherwise clearly specified and defined, terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection or can communicate with each other; it can be a direct connection, or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0026] In the description of the present disclosure, it should be understood that the orientation or positional relationships indicated by the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the subsystems or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present disclosure.

[0027] Throughout the drawings, the same elements are denoted by the same or similar reference numerals. When it may cause confusion in the understanding of the present disclosure, conventional structures or configurations will be omitted. Moreover, the shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual sizes, proportions, and actual positional relationships. Additionally, in the present disclosure, any reference signs located between parentheses should not be construed as a limitation to the present disclosure.

[0028] Similarly, in order to streamline the present disclosure and assist in understanding one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0029] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present disclosure.

[0030] How to reduce the operating costs throughout the project cycle, taking into account the short - and long - term economic benefits and development directions, is the direction that current sludge treatment methods are more concerned about and is also a problem to be solved. According to the requirements of the end - of - line outlet, flexibly adjusting the product form is also a difficulty for existing devices. After the project is put into production, generally only the treatment capacity (load) can be adjusted within a certain range, and it is very difficult to adjust to different end - of - line products, or major technical improvements are required.

[0031] In the process of realizing the present disclosure, it was found that: adopting a fluidized bed method with good adaptability and adjusting the process can be used for gasification and incineration to improve the current high cost problem of sludge pyrolysis carbonization; at the same time, it can also take into account the changes in long-term market demand. When the benefits of sludge charcoal or carbon emission reduction increase in the future, the system can be used as a carbonization pyrolysis furnace 2 by adjusting the reserved conditions, thereby realizing the change of the final product.

[0032] The present disclosure proposes a sludge treatment system coupled with carbonization and gasification, including a pyrolysis unit, a combustion unit, a waste heat recovery unit and a flue gas collection unit. The pyrolysis unit is suitable for performing a pyrolysis reaction on the dried sludge in a fluidizing gas, and adjusting the type of pyrolysis reaction by adjusting the oxygen content and the pyrolysis temperature in the fluidizing gas to obtain a pyrolysis product, wherein the type of pyrolysis reaction includes a gasification reaction and a carbonization reaction; the combustion unit is connected to the pyrolysis unit, and is suitable for performing a combustion reaction on the pyrolysis gas to obtain flue gas at a first temperature; the waste heat recovery unit is connected to the combustion unit, and is suitable for performing a heat exchange with the flue gas at the first temperature, and recovering the heat in the flue gas at the first temperature to obtain the flue gas at a second temperature; the flue gas collection unit is connected to the waste heat recovery unit, and is suitable for purifying and collecting the flue gas at the second temperature. The first temperature and the second temperature are relative concepts, and the first temperature is higher than the second temperature.

[0033] According to the embodiments of the present disclosure, the sludge treatment system coupled with carbonization and gasification proposed in the present disclosure can be adapted to a variety of application scenarios through multi-unit coordination and flexible control mechanisms. The core of the system is that the pyrolysis unit can flexibly switch between gasification and carbonization reaction modes by dynamically adjusting the oxygen content and temperature of the fluidizing gas. This dual-mode design breaks through the limitations of the traditional single reaction process, can adapt to the dynamic changes of sludge organic matter and market demand fluctuations, and avoids repeated investment due to the solidification of the technical route. At the same time, the waste heat recovery unit efficiently recovers heat from the combustion flue gas, generates steam for front-end sludge drying, as a fluidizing gas in the pyrolysis furnace 2 or for external supply, significantly reducing external energy consumption.

[0034] Specifically, in the carbonization mode, part of the energy is stored in the form of solid carbon, reducing the demand for gas supplementation and coping with fluctuations in electricity prices and changes in steam demand.

[0035] Specifically, the gasification mode can be used when the calorific value of the sludge is low to maximize heat recovery; when the calorific value of the sludge is increased or the added value of the carbonized product is increased, the carbonization mode can be switched to (mainly inert gas, furnace temperature 300-650°C) to generate high-porosity sludge charcoal. For example, the specific surface area of sludge charcoal is about 300-500m 2 / g.

[0036] According to an embodiment of the present disclosure, the pyrolysis unit includes: a pyrolysis furnace 2, a cyclone separator 3 and a returner 4. Among them, a gas injection port is provided at the top of the pyrolysis furnace 2, which is suitable for introducing oxygen or air to adjust the temperature of the fluidizing gas; the cyclone separator 3 is connected to the outlet of the pyrolysis furnace 2, including a gas product outlet and a solid product outlet, and the cyclone separator 3 is suitable for gas-solid separation of the pyrolysis product to obtain pyrolysis gas and pyrolysis carbon; the returner 4 is connected to the solid product outlet of the cyclone separator 3, and is configured to return part of the pyrolysis carbon to the pyrolysis furnace 2.

[0037] According to the embodiments of the present disclosure, the gas injection port at the top of the pyrolysis furnace 2 can accurately control the pyrolysis atmosphere in the pyrolysis furnace 2 by dynamically adjusting the oxygen intake, thereby realizing free switching between gasification and carbonization reaction modes in a single device. The cyclone separator 3 efficiently separates the gaseous components (pyrolysis gas) and solid components (pyrolysis carbon) in the pyrolysis products through centrifugal force, reducing the gas-solid entrainment phenomenon. The return device 4 can return some of the incompletely reacted pyrolysis carbon (such as semi-coke) to the pyrolysis furnace 2, and promote the secondary cracking reaction by extending the residence time of the carbon particles, thereby significantly improving the carbon conversion rate. The synergistic effect of oxygen regulation, efficient separation and return material circulation enables the system to have the advantages of both energy recovery and resource utilization, solves the core problems of traditional process product mixing, low carbon conversion rate, and rigid operation mode, and has significant advantages in flexibility, energy efficiency and environmental protection.

[0038] In some specific embodiments, oxygen supplementation in the gasification mode promotes partial oxidation of organic matter to generate combustible gas, thereby improving heat recovery efficiency; low-carbon gasification slag is quickly separated and directly discharged to avoid residual carbon affecting combustion efficiency; in the gasification mode, return material is reduced to accelerate carbon consumption.

[0039] In some specific embodiments, oxygen input is reduced in the carbonization mode to maintain an anaerobic environment to promote sludge cracking to generate high-porosity carbonized products; after separation, the sludge carbon is flexibly controlled through the return device 4 to go (partial return or external storage); increasing the return material is beneficial to maintaining the stability of the fluidized bed material layer in the furnace and avoiding temperature fluctuations.

[0040] In some specific embodiments, the pyrolysis furnace 2 may be in the form of a fluidized bed.

[0041] In some specific embodiments, the return device 4 can be a two-way return device that is easy to disassemble and seal. The return device 4 can be flexibly set to adjust the return amount, thereby matching the flow rate to jointly adjust the residence time of the material in the pyrolysis furnace 2. When the sludge processing amount is small, no material may be returned to the pyrolysis furnace 2.

[0042] In some specific embodiments, the corresponding furnace body (diameter, height and other parameters) can be designed according to different sludge processing scales. For example, the ratio of the furnace body diameter to the furnace body height of the pyrolysis furnace can be 0.1-0.2.

[0043] According to an embodiment of the present disclosure, when the gasification reaction mainly occurs in the pyrolysis furnace 2, the gasification equivalence ratio of the fluidizing gas ≥ 0.25, the pyrolysis temperature is 700 - 900 °C, and the fluidizing gas includes at least one of N2 and O2.

[0044] According to an embodiment of the present disclosure, sufficient oxygen in the fluidizing gas (oxygen gasification equivalent ≥ 0.25) and a high-temperature environment (700 - 900 °C) act synergistically to promote the rapid partial oxidation reaction of organic matter in the sludge, generating combustible gas (pyrolysis gas) mainly composed of CO and H2.

[0045] In some specific embodiments, when the sludge treatment system operates in the gasification reaction state, the first valve 21 is closed (or reduced), the second valve 22 is opened to an appropriate position, the first induced draft fan 31 is adjusted to an appropriate air volume, the mixed gas composition is mainly N2 and O2 (when the first valve 21 has an opening, there is also some water vapor and CO2), and after heating, the flow rate and gasification equivalent of the gas entering the furnace are both within an appropriate range. The temperature of the pyrolysis furnace 2 is maintained at 700 - 900 °C, and the gasification reaction mainly occurs in the furnace. The carbon content of the gasification residue is very low. The surplus heat is mainly utilized in the form of steam after gas combustion.

[0046] According to an embodiment of the present disclosure, when the main carbonization reaction occurs in the pyrolysis furnace 2, the oxygen content of the fluidizing gas is less than 11%, the pyrolysis temperature is 300 - 650 °C, and the fluidizing gas includes at least one of N2, CO2, and water vapor.

[0047] According to an embodiment of the present disclosure, a low-oxygen or oxygen-free environment (oxygen content ≤ 0.1) combined with medium and low temperatures (300 - 650 °C) promotes the pyrolysis carbonization rather than complete oxidation of organic matter in the sludge, generating sludge carbon with a relatively high carbon content and high porosity. Inert gases (such as N2 and recycled flue gas) are used as the fluidizing medium to reduce the heat release caused by the introduction of oxygen, thereby reducing the external fuel demand. The tail flue gas (containing CO2 and water vapor) is passed into the furnace after being heated by the first heat exchanger 6, which not only provides the heat required for carbonization but also realizes the internal energy cycle. In addition, the introduction of water vapor can promote the evaporation of water and the release of volatile components in the sludge in the low-temperature section (300 - 450 °C), reducing the risk of coking.

[0048] According to an embodiment of the present disclosure, the design of the fluidizing gas composition and temperature parameters provides seamless connection for the gasification-carbonization mode switching. For example, when switching to the mainly gasification mode, only the oxygen ratio needs to be increased and the temperature needs to be raised to 700 - 900 °C, without equipment modification. This "one furnace with dual functions" design significantly improves the equipment utilization rate, especially suitable for small and medium-sized projects to cope with sludge quality fluctuations and market changes.

[0049] In some specific embodiments, when the sludge treatment system is mainly operating in a carbonization reaction state, the second valve 22 and the third valve 23 are closed. At this time, the medium entering the pyrolysis furnace 2 is the tail gas (mainly composed of N2, CO2, and water vapor). After being heated to 600 - 700 °C in the first heat exchanger 6, it is sent into the pyrolysis furnace 2 to provide heat for pyrolysis carbonization; and the temperature inside the furnace is maintained at 300 - 650 °C, and mainly cracking and carbonization reactions occur inside the furnace.

[0050] According to an embodiment of the present disclosure, the gas flow velocity of the fluidizing gas is 0.8 - 7 m / s.

[0051] According to an embodiment of the present disclosure, on the one hand, the gas flow velocity of the fluidizing gas ensures that the bed particles are fully suspended, avoiding local coking or reaction dead zones caused by deposition, especially when treating high-ash or viscous sludge, maintaining a stable fluidization state; on the other hand, it also prevents excessive entrainment of particles, reducing the load of the cyclone separator 3 and the loss of fine powder.

[0052] According to an embodiment of the present disclosure, the combustion unit includes a combustion chamber, and the inlet of the combustion chamber is connected to the gas product outlet of the cyclone separator 3.

[0053] In some specific embodiments, an oxygen content monitor and a temperature monitor are provided behind the combustion furnace 5, and an over-temperature water spraying and cooling facility is provided.

[0054] According to an embodiment of the present disclosure, in the combustion chamber, the air excess coefficient corresponding to the combustion process of the pyrolysis gas in the combustion chamber is less than 1.05.

[0055] According to an embodiment of the present disclosure, by precisely controlling the air excess coefficient, while ensuring efficient combustion, it significantly reduces pollutant emissions, improves energy utilization efficiency, and reduces operating costs. At the same time, it is also beneficial to reduce the amount of tail gas and reduce the oxygen content in the tail gas (increasing the inert components of the recirculating gas).

[0056] According to an embodiment of the present disclosure, the waste heat recovery unit includes a waste heat boiler 7 and a first heat exchanger 6. Among them, the first heat exchanger 6 is configured to be connected to the waste heat boiler 7 and the pyrolysis furnace 2. The first heat exchanger 6 is suitable for heating part of the flue gas at the second temperature to obtain flue gas at the third temperature, and circulating the flue gas at the third temperature to the pyrolysis unit as the fluidizing gas. Among them, the second temperature and the third temperature are relative concepts, and the third temperature is the temperature at which the flue gas is circulated and introduced into the pyrolysis furnace 2.

[0057] In some specific embodiments, by introducing flue gas mainly composed of an inert medium and reheating it as the medium for heat reflux, it can be used as the main means to adjust the flow rate inside the furnace.

[0058] In some specific embodiments, by adjusting the air content in the fluidizing gas entering the pyrolysis furnace 2 (controlling the second valve 22 and the second induced draft fan 32) and the temperature of the gas entering the furnace (controlling the third valve 23), the temperature in the furnace (combustion reaction) is mainly adjusted, and the ratio and composition of the solid and gas products can also be affected.

[0059] According to an embodiment of the present disclosure, the aforementioned sludge treatment system further includes a control system, including a temperature sensor, a pressure sensor, an oxygen content sensor, and a pipeline regulating valve respectively arranged in the pyrolysis furnace 2 and the combustion chamber.

[0060] According to the embodiments of the present disclosure, the temperature sensor can monitor the temperature of the pyrolysis furnace 2 and the combustion chamber in real time, and adjust the fluidizing gas heating temperature or water spraying amount through feedback to ensure that the reaction is in the optimal temperature window. The oxygen content sensor dynamically detects the oxygen concentration of the fluidizing gas and the combustion flue gas, and the linkage regulating valve controls the oxygen input to maintain the reaction atmosphere accurately and controllably. The pressure sensor is used to monitor the pressure difference of the pyrolysis furnace 2, and automatically adjusts the fluidizing gas flow rate in combination with the sludge feed amount and particle size changes to prevent bed collapse or excessive particle entrainment. The multi-parameter coordinated regulation capability of the control system has achieved a leap from "extensive operation" to "fine intelligent control", while improving product quality, reducing energy consumption costs, and ensuring environmental protection standards. It provides a basic basis for the efficient management of the sludge treatment system throughout the entire cycle.

[0061] According to an embodiment of the present disclosure, the flue gas collection unit further includes a dust removal subunit and a desulfurization subunit.

[0062] According to the embodiments of the present disclosure, the dust removal subunit (such as a bag filter 9 or a ceramic filter element) can efficiently capture particulate matter (such as unburned carbon powder, ash, etc.) in the flue gas, reduce the dust concentration, and avoid dust pollution to the atmosphere and the surrounding environment. The desulfurization subunit (such as a wet desulfurization tower or dry calcium spraying) is used to remove acidic gases such as SO2 in a targeted manner. The dust removal and desulfurization subunits adopt a modular design (such as the electrostatic dust removal chamber 8 and the chamber cleaning of the bag filter 9, and the multi-stage spraying of the desulfurization spray tower 10), and the operating parameters can be dynamically adjusted according to the flue gas volume and pollutant concentration. With the synergistic effect of the dust removal and desulfurization subunits, the flue gas can also be discharged through the chimney 11, which not only greatly reduces pollutant emissions and meets the requirements of environmental protection regulations, but also improves the system economy through resource recovery and equipment protection, providing a key guarantee for the greening and sustainability of the sludge treatment process.

[0063] In some specific embodiments, a second heat exchanger 12 is connected after the desulfurization spray tower 10 to recover and utilize heat energy.

[0064] In some specific embodiments, the operation process of the sludge treatment system coupled with carbonization and gasification proposed in the present disclosure includes:

[0065] Step 1: The dried sludge is first transported to the feed hopper or sludge bin 1 of the pyrolysis furnace 2, and enters the pyrolysis furnace 2 through the feed screw for reaction. The pyrolysis furnace 2 adopts a fluidized bed furnace, and the bottom fluidized air comes from the tail flue gas and air after heating (the proportion is adjustable). The fine ash after pyrolysis (gasification) is returned to the furnace for further gasification after cyclone separation. At the same time, the return device 4 has an interface condition for direct discharge, and the carbon ash collected by the cyclone separator 3 can be directly discharged into the buffer bin according to the setting.

[0066] Step 2: The pyrolysis gas separated by cyclone enters the hot blast furnace after high-temperature dust removal, and is mixed with the incoming air for combustion; the outlet high-temperature flue gas enters the first heat exchanger 6 to heat the reflux tail flue gas / air mixture, and the heated mixed gas is provided with a cross-over pipe, and the temperature of the mixed gas entering the furnace can be adjusted by a valve. After the flue gas is cooled in the heat exchanger, it enters the waste heat boiler 7, and further heat is recovered to generate steam. Part of the steam is introduced into the pyrolysis furnace 2 (adjustable), and the rest is used for front-end sludge drying or external sales.

[0067] Step 3: After the flue gas leaves the waste heat boiler 7, its temperature drops to about 200°C, and then it enters the flue gas collection unit for treatment and is discharged after meeting the standards.

[0068] Step 4: The purified flue gas is led by the recirculation fan to the first heat exchanger 6 for heating and then enters the pyrolysis furnace 2; at the same time, an air intake port is left at the inlet pipe of the recirculation fan, and the ratio of the recirculated flue gas to air can be controlled by a regulating valve.

[0069] In some specific embodiments, when the sludge treatment system coupled with carbonization and gasification proposed in the present disclosure is used for powdered activated carbon regeneration, a high-temperature ceramic dust collector is arranged after the combustion furnace 5 to collect more fine powdered activated carbon.

[0070] It should be noted that the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, other embodiments obtained by ordinary technicians in the field without creative work are all within the scope of protection of the present disclosure.

[0071] The sludge treatment system coupled with carbonization and gasification proposed in the present disclosure is applied to the sludge gasification / carbonization system. Taking 40 tDS / d (equivalent to 200 t / d of sludge with a moisture content of 80%) as an example, the sludge dry basis parameters are as follows (ignoring other small elements such as phosphorus and chlorine): the current dry basis element composition is: C: 21.5%, H: 4.05%, O: 17.49%, N: 5.72%, S: 2%, and ash content is 49.24%; the dry basis element composition in future development will be C: 39.18%, H: 5.34%, O: 20.94%, N: 6.99%, S: 0.96%, and ash content is 26.59%.

[0072] To meet the industrial requirements of complete sludge treatment, the sludge treatment system integrating carbonization and gasification proposed in this disclosure can also be equipped with a sludge deep dewatering device (such as a drying device and a sludge bin 1). The existing system mainly focuses on gasification heat utilization; in the later stage, with the development of high-value-added sludge carbon and the increase in sludge calorific value, the sludge treatment system mainly based on carbonization has more promising benefits, and at the same time, the benefits of subsequent carbon emissions reduction will become clearer. This system can be flexibly adjusted in various ways according to different external conditions in the short and long term to meet market demands and bring higher benefits throughout the cycle.

[0073] The following will describe two operating modes: mainly gasification (using low calorific value of current sludge and low added value of carbide) and mainly carbonization (high calorific value of sludge and high added value of carbide).

[0074] Example 1: Mainly gasification: maximizing heat energy utilization (the current mainstream direction)

[0075] In this Example 1, after the front-end wet sludge is dried, the moisture content of the sludge is 30%. About 2.4t of dry sludge enters the pyrolysis furnace 2 per hour on average, and about 7.85t / h of saturated steam is required. If a sludge drying device is added at the front end and the process is changed to deep dewatering + drying, after deep dewatering to a moisture content of 60% - 65%, the steam used for drying is reduced to about 3.5t / h and enters this system.

[0076] First, the system designs a dedicated pyrolysis furnace 2, heat exchanger according to the sludge quality and quantity, and configures the corresponding waste heat boiler 7 and flue gas purification facilities. The inner diameter (flow velocity) of the furnace, the area of the high-temperature heat exchanger, and the flue gas volume of the waste heat boiler and flue gas purification facilities all meet the requirements within the range of carbonization and gasification operating modes.

[0077] The dry sludge rapidly heats up under the heating of the fluidizing gas and bed material in the pyrolysis furnace 2, mainly undergoing gasification reactions.

[0078] At this time, the temperature of the fluidizing air (air) entering the pyrolysis furnace 2 is 600 - 650°C, 3600 Nm 3 / h; (the O2 gasification equivalent in the furnace is about 0.8); the furnace temperature is about 700 - 750°C (partial combustion reactions occur to supplement heat). The generated syngas enters the combustion chamber for combustion after passing through cyclone dust removal, and the ash collected by cyclone separation is returned to the pyrolysis furnace 2 through the return feeder 4. A slag discharge port is provided at the bottom of the furnace.

[0079] The combustion chamber is provided with an air injection port; the pyrolysis gas and air are completely burned inside (temperature greater than 900°C), the residence time is greater than 2S, the air volume entering the chamber can be adjusted, and a water spraying cooling device is provided. An oxygen content monitoring facility is provided at the outlet of the combustion chamber, and then the high-temperature flue gas enters the first heat exchanger 6 to heat the fluidizing air, while the high-temperature flue gas is cooled, and then enters the waste heat boiler 7.

[0080] The waste heat boiler 7 generates about 4 t / h of saturated steam at 1 MPa and 180 °C for use in the front-end sludge drying. After adding deep dehydration at the front end, there is a small surplus of steam for drying. The pressing time in the previous stage can be reduced or the pyrolysis furnace 2 can be adjusted to keep some fixed carbon in the gasification slag.

[0081] After the flue gas exits the waste heat boiler 7, the temperature drops to about 200 °C, and then it enters the flue gas purification systems such as bag dust removal and wet deacidification. After being treated to meet the standards, it is discharged through the chimney 11.

[0082] At this time, the first valve 21 of the second induced draft fan 32 is in the closed state; the main air source is air. Since the current sludge has a low calorific value and a large amount of steam is required for front-end drying, gasification mainly occurs in the pyrolysis furnace 2, and the lower the carbon content in the pyrolysis ash slag, the better.

[0083] Example 2: Carbonization-based: Produce more sludge carbon (future development trend)

[0084] In the future, the dry-base carbon content and calorific value of the sludge will increase significantly. For specific values, refer to the aforementioned sludge quality. There is heat surplus in the system; at the same time, the added value of the sludge carbon increases, and benefits such as carbon emission reduction also appear. In this example, the adjustment is made to mainly focus on pyrolysis carbonization.

[0085] At this time, the fluidizing gas in the pyrolysis furnace 2 is mainly flue gas. The second valve 22 of the second induced draft fan 32 is nearly closed (the oxygen supply is about 0.1 - 0.15 oxygen equivalent), and the first valve 21 is in the open state; that is, the main components of the air entering the furnace are N2 and CO2.

[0086] The amount of hot mixed gas entering the pyrolysis furnace 2 is 5000 - 6000 Nm 3 / h, and the temperature is 650 - 700 °C. The temperature at the bottom of the pyrolysis furnace 2 is relatively low, about 400 - 500 °C; air is injected through the air inlet reserved at the upper part of the furnace, so as to raise the temperature of the furnace top flue and cyclone to 800 - 850 °C, providing temperature conditions for the activation of the sludge carbon (with a water vapor and CO2 atmosphere itself), and improving parameters such as its porosity. After cyclone separation, most of the sludge carbon is collected and discharged through the return feeder 4 (not returned to the furnace chamber, and the return leg of the furnace chamber is sealed with a blind plate at this time). A small part of the fine powder enters the combustion chamber with the pyrolysis combustible gas and burns. The generated sludge carbon has a calorific value of about 7 - 8 MJ / kg and a specific surface area of 300 - 500 m 2 / g. It can be used as auxiliary fuel or low-quality activated carbon.

[0087] The steam generated in the waste heat boiler 7 aims to meet the heat demand of this project. By adjusting the pyrolysis (gasification) conditions, the total heat output of the system is balanced with the demand, and the remaining surplus energy is stored in the pyrolysis carbon slag (which is convenient for storage and reuse).

[0088] When the value of the produced pyrolytic carbon is very high, the pyrolysis conditions can be further controlled, including using external energy (gas) to reduce the consumption of carbon-based materials and generate as much high-value sludge carbon as possible.

[0089] Both the first induced draft fan 31 and the second induced draft fan 32 are frequency conversion regulated, and need to be adjusted to achieve a new system pressure balance.

[0090] The remaining process is the same as before, and the actual process may be between the two states in Example 1 or this example.

[0091] Example 3: Applied to the regeneration of powdered activated carbon

[0092] In this example, the sludge treatment system that couples carbonization and gasification is applied to the field of powdered activated carbon regeneration. The moisture content of the recovered waste powdered activated carbon is related to the industry. When the moisture content is relatively high, it is generally dried to less than 20% moisture content at the front end and then enters this sludge treatment system.

[0093] The steps in this example are the same as those in the aforementioned Example 2. After the waste activated carbon is fed into the pyrolysis furnace 2, the fluidizing gas is mainly the heated tail gas (mainly composed of N2 and CO2), and it is mainly in the carbonization state as before. The temperature in the lower part of the pyrolysis furnace 2 is 400 - 600 °C, and a gas injection port is provided in the upper part of the furnace. The reaction temperature with the volatile matter rises to 800 - 850 °C. The saturated powdered carbon is dried and thermally desorbed at the bottom. When it is carried to the upper middle part, the temperature and the conditions of the activating agent (CO2, water vapor) are both available, and it is further activated in the latter half of the gas flow. After being collected by the cyclone, the activated carbon does not return to the pyrolysis furnace 2 (the connecting pipe from the return feeder 4 to the pyrolysis furnace 2 is sealed with a blind plate), but enters the regenerated powdered carbon bin (coarse particles). A high-temperature dust collector (ceramic membrane) is provided after the cyclone to collect fine powder and enter the fine regenerated powdered carbon bin. Then the pyrolysis gas enters the combustion chamber for combustion. The insufficient part of the heat is supplemented by the gas in the combustion chamber, and finally the system heat balance is achieved, thereby reducing the operating cost.

[0094] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not used to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A sludge treatment system coupling carbonization and gasification, comprising: A pyrolysis unit, adapted to perform a pyrolysis reaction on the dried sludge in a fluidizing gas, and adjusting the type of pyrolysis reaction by adjusting the oxygen content and pyrolysis temperature in the fluidizing gas to obtain pyrolysis products, wherein the types of pyrolysis reaction include gasification reaction and carbonization reaction; A combustion unit, connected to the pyrolysis unit, adapted to perform a combustion reaction on the pyrolysis gas to obtain flue gas at a first temperature; A waste heat recovery unit, connected to the combustion unit, adapted to exchange heat with the flue gas at the first temperature, and obtain flue gas at a second temperature after recovering the heat in the flue gas at the first temperature; A flue gas collection unit, connected to the waste heat recovery unit, adapted to purify and collect the flue gas at the second temperature.

2. The sludge treatment system according to claim 1, wherein, The pyrolysis unit includes: A pyrolysis furnace, the upper part of the pyrolysis furnace is provided with a gas injection port, adapted to introduce oxygen or air to adjust the temperature of the fluidizing gas; A cyclone separator, connected to the outlet of the pyrolysis furnace, including a gas product outlet and a solid product outlet, the cyclone separator is adapted to perform gas-solid separation on the pyrolysis products to obtain pyrolysis gas and pyrolysis carbon; A return feeder, connected to the solid product outlet of the cyclone separator, configured to return part of the pyrolysis carbon to the pyrolysis furnace.

3. The sludge treatment system according to claim 2, wherein, When the gasification reaction mainly occurs in the pyrolysis furnace, the gasification equivalence ratio of the fluidizing gas ≥ 0.25, the pyrolysis temperature is 700 - 900 °C, and the fluidizing gas includes at least one of N2 and O2.

4. The sludge treatment system according to claim 2, wherein, When the carbonization reaction mainly occurs in the pyrolysis furnace, the oxygen content of the fluidizing gas is less than 11%, the pyrolysis temperature is 300 - 650 °C, and the fluidizing gas includes at least one of N2, CO2, and steam.

5. The sludge treatment system according to claim 2, wherein The gas flow velocity of the fluidizing gas is 0.8 - 7 m / s.

6. The sludge treatment system according to claim 1, wherein, The combustion unit includes a combustion chamber, and the inlet of the combustion chamber is connected to the gas product outlet of the cyclone separator.

7. The sludge treatment system according to claim 6, wherein, In the combustion chamber, the air excess coefficient corresponding to the combustion process of the pyrolysis gas in the combustion chamber is less than 1.

05.

8. The sludge treatment system according to claim 1, the waste heat recovery unit includes: A waste heat boiler; A first heat exchanger, configured to connect the waste heat boiler and the pyrolysis furnace, the heat exchanger is adapted to heat part of the flue gas at the second temperature to obtain flue gas at a third temperature, and circulate the flue gas at the third temperature to the pyrolysis unit as the fluidizing gas.

9. The sludge treatment system according to claim 1 further comprises: A control system, including temperature sensors, pressure sensors, oxygen content sensors respectively arranged in the pyrolysis furnace and the combustion chamber, and pipeline regulating valves.

10. The sludge treatment system according to claim 1, the flue gas collection unit further includes a dust removal sub-unit and a desulfurization sub-unit.

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