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CN-121782850-B - Two-stage calcining and carbon dioxide collaborative recovery system and process for magnesite

CN121782850BCN 121782850 BCN121782850 BCN 121782850BCN-121782850-B

Abstract

The invention discloses a two-stage calcining and carbon dioxide collaborative recovery system and a process for magnesite, which relate to the technical field of efficient utilization of magnesite, and aim to solve the problem of how to realize efficient and low-consumption calcining of high-quality magnesia and efficient recovery of carbon dioxide in a same process system in a collaborative manner; the outlet end of the rotary kiln is communicated with a gas-solid separation chamber, magnesite powder is decomposed in the rotary kiln to generate carbon dioxide gas, and the carbon dioxide gas is led out by an induced draft fan through the gas-solid separation chamber to maintain micro negative pressure in the kiln. The high-temperature dust-containing carbon dioxide enters a downstream A1 carbon dioxide cyclone separator for gas-solid separation. The high temperature gas after gas-solid separation is transferred to a carbon dioxide liquefying and solidifying treatment system after heat exchange, temperature reduction and dust removal, a solid material outlet of the gas-solid separation chamber is in butt joint with a feed inlet of a suspension decomposing furnace through a high temperature airtight conveying device, and a main combustion chamber of the decomposing furnace is arranged at the bottom of the suspension decomposing furnace.

Inventors

  • CHEN DANIAN
  • MA ZHUANG
  • FAN XUPENG
  • WANG DELIANG

Assignees

  • 营口金泓源镁铝陶瓷有限公司

Dates

Publication Date
20260508
Application Date
20260305

Claims (8)

  1. 1. The magnesite two-stage calcination and carbon dioxide collaborative recovery system comprises a raw material preheating cyclone cylinder (1), and is characterized in that the discharge end of the raw material preheating cyclone cylinder (1) is connected to a rotary kiln (2) which maintains a micro negative pressure state, the rotary kiln (2) is arranged in a rotary kiln combustion chamber (3), and the rotary kiln combustion chamber (3) heats the outer wall of the rotary kiln by using gaseous fuel; The outlet end of the rotary kiln (2) is communicated with a gas-solid separation chamber (4), a negative pressure is formed at the gas outlet of the gas-solid separation chamber (4) through a draught fan (5), dust-containing high-temperature carbon dioxide is conveyed to an A1 carbon dioxide cyclone separator (6), and the high-temperature gas after gas-solid separation of the A1 carbon dioxide cyclone separator (6) is conveyed to a carbon dioxide liquefying and solidifying treatment system after being cooled and dedusted through a heat exchange mechanism; the solid material outlet of the gas-solid separation chamber (4) is in butt joint with the feed inlet of the suspension decomposing furnace (7) through a high-temperature airtight conveying device, a main decomposing furnace combustion chamber (8) is arranged at the bottom of the suspension decomposing furnace (7), the top of the suspension decomposing furnace (7) is communicated with a C3 cyclone (9) through a gooseneck, the solid material outlet of the C3 cyclone (9) is connected with the feed end of a multistage cooling mechanism, and the discharge end of the multistage cooling mechanism is connected with a finished product conveying device and is conveyed to a clinker finished product warehouse; The heat exchange mechanism comprises an A2 heat exchanger (10), a gas inlet of the A2 heat exchanger (10) is connected with a gas outlet of the A1 carbon dioxide cyclone separator (6), a cold air inlet of the A2 heat exchanger (10) is connected with a blower (11), a hot air outlet of the A2 heat exchanger (10) is connected with an air inlet of a rotary kiln combustion chamber (3), a gas outlet of the A2 heat exchanger (10) is connected with a dust collection bag (12), a gas outlet of the dust collection bag (12) is connected with a draught fan (5), an outlet end of the draught fan (5) is sequentially connected with a water cooling device (13) and a booster fan (14), and an outlet end of the booster fan (14) is used for conveying cooled and dedusted carbon dioxide to a carbon dioxide liquefaction and solidification treatment system; the carbon dioxide liquefying and solidifying treatment system comprises at least one pretreatment unit for filtering and/or adsorbing and purifying carbon dioxide gas, a compression condensing unit consisting of one or more compressors and condensers and an optional rectifying unit for further purifying liquid carbon dioxide or a solidifying unit for converting the liquid carbon dioxide into solid dry ice.
  2. 2. The two-stage magnesite calcination and carbon dioxide co-recovery system according to claim 1, wherein a pressure sensor for collecting the pressure difference between the interior of the rotary kiln (2) and the external atmospheric pressure in real time is installed in the rotary kiln (2), the pressure sensor signals are transmitted to an external PLC system, and the PLC system outputs instructions according to the pressure difference, and the rotary kiln maintains a micro negative pressure state by adjusting the frequency of a frequency converter of an induced draft fan (5) to change the rotating speed.
  3. 3. The magnesite two-stage calcination and carbon dioxide co-recovery system according to claim 1 is characterized in that the multi-stage cooling mechanism comprises a C3 cyclone (9) discharge port, an L1 cyclone cooler (15), an L2 cyclone cooler (16) and an L3 cyclone cooler (17) which are sequentially connected, high-temperature clinker collected by the C3 cyclone (9) is conveyed to an inlet pipeline of the L1 cyclone cooler (15) through a high-temperature feeder to be subjected to first-stage gas-solid heat exchange cooling, materials cooled by the L1 cyclone cooler (15) are conveyed to an inlet pipeline of the L2 cyclone cooler (16) through a medium-temperature feeder to be subjected to second-stage gas-solid heat exchange cooling, materials cooled by the L2 cyclone cooler (16) are conveyed to an inlet pipeline of the L3 cyclone cooler (17) through a low-temperature feeder to be subjected to third-stage gas-solid heat exchange cooling, and cooled clinker separated and collected by the L3 cyclone cooler (17) is conveyed to a finished product warehouse through downstream conveying equipment.
  4. 4. The magnesite two-stage calcination and carbon dioxide co-recovery system according to claim 3, further comprising a high-temperature gas recovery loop, wherein the rotary kiln combustion chamber (3) is provided with a gas outlet and is connected to a suspension decomposing furnace (7) through a high-temperature pipeline, and the high-temperature gas is used as an auxiliary heat source of the decomposing furnace; The medium-temperature heat exchange loop is characterized in that a gas outlet of the C3 cyclone (9) is connected with a multi-tube cooler (18), a hot air channel and a combustion air channel which are not communicated with each other are separated from each other in the multi-tube cooler (18) through a heat exchange element, the hot air channel is connected with a gas outlet of the C3 cyclone (9) and a gas inlet of the raw material preheating cyclone (1) to preheat raw materials, one end of the combustion air channel is provided with a cold air inlet, the other end of the combustion air channel is provided with a preheating air outlet, and the preheating air outlet is connected to a gas inlet of the rotary kiln combustion chamber (3) through a pipeline; And medium-low temperature gas exhausted from a gas outlet of the L1 cyclone cooler (15) is led to the main combustion chamber (8) of the decomposing furnace through a pipeline.
  5. 5. The two-stage magnesite calcination and carbon dioxide co-recovery system of claim 1, wherein the gaseous fuel is fuel gas or natural gas.
  6. 6. The magnesite two-stage calcination and carbon dioxide collaborative recovery system according to claim 1 is characterized by comprising a feeding mechanism, an iron removing mechanism and a drying and scattering machine which are sequentially connected, wherein the feeding mechanism comprises a feeding hopper and a belt scale arranged below an outlet of the feeding mechanism and is used for feeding and metering materials, the iron removing mechanism is arranged at the downstream of the belt scale and is used for removing metal impurities in the materials, the drying and scattering machine is arranged at the downstream of the iron removing mechanism and is used for drying and scattering the materials, the raw material preheating cyclone (1) comprises a C1 cyclone and a C2 cyclone, a discharge port of the drying and scattering machine is connected with a feed port of the C1 cyclone through a pipeline, a discharge port of the C1 cyclone is connected with a feed port of the C2 cyclone, and a discharge port of the C2 cyclone is connected with a feed end of a rotary kiln (2) and is used for feeding the preheated materials into the kiln for subsequent treatment.
  7. 7. A process using the magnesite two-stage calcination and carbon dioxide co-recovery system as claimed in any one of claims 1 to 6 is characterized by comprising the following steps that S1, raw magnesite is preheated by a raw material preheating cyclone (1) and is conveyed to a rotary kiln (2) which dynamically maintains a micro negative pressure state; S2, under the indirect radiant heat effect of 950-1000 ℃ provided by a rotary kiln combustion chamber (3), maintaining the temperature in the rotary kiln (2) at 650-700 ℃ for one-stage pre-decomposition to generate a partially decomposed intermediate product and gas with carbon dioxide concentration of more than or equal to 75 vol%; s3, enabling high-temperature gas generated by one-stage pre-decomposition to enter a gas-solid separation chamber (4) from an outlet of a rotary kiln (2) for preliminary separation, conveying separated dust-containing gas to an A1 carbon dioxide cyclone separator (6) for efficient collection through a draught fan (5), and enabling the obtained high-temperature gas to enter a heat exchange mechanism; s4, the high-temperature gas sequentially flows through an A2 heat exchanger (10) to recover waste heat, a dust collection bag (12) to remove dust and a water cooling device (13) to cool, and then is conveyed to a carbon dioxide liquefaction and solidification treatment system by a booster fan (14) to be recycled; S5, delivering the intermediate product separated by the gas-solid separation chamber (4) into a suspension decomposing furnace (7) through a high-temperature airtight conveying device, simultaneously, introducing gaseous fuel through a gaseous fuel nozzle arranged in a main combustion chamber (8) of the decomposing furnace to form high-temperature flame, introducing high-temperature gas generated by the rotary kiln combustion chamber (3) into the main combustion chamber (8) of the decomposing furnace as an auxiliary heat source and an air source, directly contacting the intermediate product with the high-temperature flame, and performing instant fluidization calcination reaction to complete final decomposition at 1100-1200 ℃.
  8. 8. The two-stage magnesite calcining and carbon dioxide co-recovery process according to claim 7, further comprising the following steps of S6, enabling the calcined material in the suspension decomposing furnace (7) to rise to a gooseneck along with the air flow and enter a C3 cyclone (9) for gas-solid separation, and introducing the separated medium-temperature gas into a raw material preheating cyclone (1) as a heat source to preheat the raw material; and S7, enabling the solid high-temperature magnesium oxide clinker separated by the C3 cyclone (9) to enter a multi-stage cooling mechanism, and sequentially carrying out multi-stage gas-solid heat exchange cooling through an L1 cyclone cooler (15), an L2 cyclone cooler (16) and an L3 cyclone cooler (17), and finally conveying the cooled clinker to a finished product warehouse.

Description

Two-stage calcining and carbon dioxide collaborative recovery system and process for magnesite Technical Field The invention relates to the technical field of high-efficiency utilization of magnesite, in particular to a two-stage calcining and carbon dioxide collaborative recovery system and process for magnesite. Background Magnesium oxide is an important inorganic chemical product, is widely used as a core raw material of refractory materials to manufacture inner liners of high-temperature industrial kilns, and has important applications in the fields of environmental protection, agriculture, building materials and the like, such as soil improvement, animal feed additives, magnesia cementing materials and the like. Currently, magnesia is mainly prepared by calcining magnesite, and conventional methods mostly use single calcining equipment, such as an external-combustion rotary kiln (e.g., comparative document 1: CN1060827125B) or a fluidized-bed cracking furnace (e.g., comparative document 2: CN110526597B). D1 discloses a method for preparing light-burned magnesia by using an external combustion rotary kiln, which improves the hydration activity and the burning loss rate of the light-burned magnesia by controlling the parameters of wind speed, calcination temperature, time and the like of primary wind and secondary wind. However, the method still has the following problems that the combustion chamber of the rotary kiln needs to be maintained at an ultra-high temperature (1200-1300 ℃), the kiln body refractory material is easy to be seriously lost after long-time operation, the service life of equipment is short, carbon dioxide is not effectively recovered, and is directly discharged to the atmosphere, so that resource waste and environmental pollution are caused, and heat and energy consumption are increased. D2 provides a method for preparing light burned magnesia by a fluidized bed cracking method, which utilizes high-temperature carbon dioxide gas flow to realize quick cracking, reforms carbon dioxide generated by the cracking with methane to prepare methanol, and realizes the primary utilization of carbon resources. Firstly, the large-scale electric heating fluidized bed is very rare in industrial-scale application, the heating efficiency, the temperature uniformity and the long-period running stability of the large-scale electric heating fluidized bed are difficult to match with the industrial continuous and high-productivity requirements, the actual application requirements of a large-scale industrial production line cannot be met, the electric heating mode is high in cost, the carbon dioxide recovery depends on the subsequent chemical conversion, and the methanol market requirements are limited. Therefore, there is a need in the art for an integrated system and process that can not only efficiently calcine magnesite to produce high quality magnesia, but also achieve efficient recovery and recycling of carbon dioxide. Disclosure of Invention In order to solve the problems, namely the problems proposed by the background technology, the invention provides a magnesite two-stage calcination and carbon dioxide collaborative recovery system and process, which comprises a raw material preheating cyclone, wherein the discharge end of the raw material preheating cyclone is connected to a rotary kiln which maintains a micro negative pressure state, the rotary kiln is arranged in a rotary kiln combustion chamber, and the rotary kiln combustion chamber heats the outer wall of the rotary kiln by using gaseous fuel; The outlet end of the rotary kiln is communicated with a gas-solid separation chamber, a gas outlet of the gas-solid separation chamber forms negative pressure through a draught fan, dust-containing high-temperature carbon dioxide is conveyed to an A1 carbon dioxide cyclone separator, the high-temperature gas trapped by the A1 carbon dioxide cyclone separator is cooled and dedusted through a heat exchange mechanism and then conveyed to a carbon dioxide liquefying and solidifying treatment system, a solid material outlet of the gas-solid separation chamber is in butt joint with a feeding port of a suspension decomposing furnace through a high-temperature airtight conveying device, a main combustion chamber of the decomposing furnace is arranged at the bottom of the suspension decomposing furnace, the top of the suspension decomposing furnace is communicated with a C3 cyclone through a gooseneck, a solid material outlet of the C3 cyclone is connected with a feeding end of a multi-stage cooling mechanism, and a discharging end of the multi-stage cooling mechanism is connected with a clinker finished product warehouse. The rotary kiln is further provided with a pressure sensor for collecting the pressure difference value between the rotary kiln and the external atmosphere in real time, the pressure sensor is transmitted to an external PLC system, the PLC system outputs an instruction according to the pres