Circulating fluidized bed reactor and process for pyrolysis reaction of ammonium chloride

Abstract

The reactor comprises an ammonia release reaction device with a gas distributor and multistage cyclone separation equipment, a riser chlorine release reactor with a heat exchange jacket, and a multistage cyclone separation chlorine release section gas-solid separation device, efficient pyrolysis separation of ammonium chloride can be achieved, ammonia gas and hydrogen chloride are produced, and a carrier material is recycled. The ammonia release reactor provides reaction heat through carrier circulation, and is provided with an efficient gas distributor and a multi-stage cyclone separator to ensure uniform mixing of gas and solid and separation of fine particulate matters; the riser chlorine release reactor completes thermal decomposition of a carrier and hydrogen chloride recovery through high-temperature flue gas dividing wall heating, and is equipped with a gas-solid separation device to realize separation and circulation of reaction products. The heat exchange efficiency, the reaction control and the system stability in the ammonium chloride pyrolysis process are remarkably improved, the method is suitable for clean recycling of ammonium chloride, and the requirement for industrial continuous production is met.

Description

Technical Field

[0001] This invention relates to the ammonium chloride pyrolysis process in chemical production, specifically to a circulating fluidized bed reactor, a matching high-temperature sealed solid feed device, and a corresponding chemical chain pyrolysis process for ammonium chloride. Background Technology

[0002] Ammonium chloride (NH4Cl) is a common ammonium salt. On the one hand, it is a major byproduct of the soda ash production process using the combined alkali process. With the continuous expansion of the soda ash industry, the byproduct output of ammonium chloride has increased year by year, far exceeding market demand. The problem of overcapacity has become increasingly prominent, becoming a key bottleneck restricting the sustainable development of the soda ash industry. On the other hand, in rare earth smelting and other chlorine-containing wastewater treatment fields, the treatment of ammonium chloride waste liquid has always been an environmental problem that urgently needs to be solved. Traditional concentration crystallization methods or calcium oxide stripping methods cannot achieve complete recovery of ammonia and chlorine resources, resulting in byproduct pollution and poor economic efficiency. Therefore, the process of pyrolyzing ammonium chloride into ammonia and hydrogen chloride can achieve efficient separation and recycling of ammonia and chlorine components in ammonium chloride, meeting the urgent needs of the soda ash and rare earth smelting industries for clean production and resource recovery. This is a key link in promoting the green upgrading of the soda ash industry.

[0003] Currently, researchers both domestically and internationally have proposed various technical pathways for the decomposition and resource utilization of ammonium chloride. Among them, the chemical loop recycling method is a representative technical route. Its basic principle is to use a carrier material (such as MgO) to break down the pyrolysis process of ammonium chloride into two sub-reactions: "ammonia release" and "chlorine release." Through the adsorption and regeneration process of the carrier, the gradual release and separation of NH3 and HCl are achieved. CN103626206A discloses a two-step thermal decomposition process based on a high-temperature adsorbent, proposing a dual-reactor design. This process introduces steam into the ammonia release section, causing ammonium chloride to react with MgO at a lower temperature to release NH3 and fix HCl to generate magnesium hydroxide (MgOHCl). Subsequently, in the chlorine release section, the MgO is regenerated by raising the temperature, releasing HCl. Theoretically, this method can achieve efficient separation and recycling of ammonia and chlorine, avoiding cross-contamination of products caused by direct heating, and has industrialization potential.

[0004] To improve heat exchange efficiency and reduce energy consumption, CN201610424828 proposes a variable gas velocity fluidized bed pyrolysis device based on cross-flow heat transfer, which achieves indirect heating through parallel material and flue gas channels. However, this design requires particles to be in a stable fluidized state, placing high demands on particle size, density, and other physical properties. Furthermore, the particle properties change with the reaction process, making it difficult to control the fluidization state and resulting in poor system stability and reliability. In addition, achieving particle fluidization requires a significant increase in the momentum input of the protective gas, increasing system operating costs. Another patent (such as CN201610111173) proposes using a multi-tube horizontal moving bed structure for ammonium chloride pyrolysis, achieving particle movement within the reactor via gravity transport. While this simplifies the reactor structure, the presence of internal heat exchange components can easily cause uneven material flow, channeling, or dead zones, affecting reaction uniformity and pyrolysis efficiency.

[0005] Furthermore, when ammonium chloride is used as a solid feed, its easy decomposition and sublimation characteristics pose a dual challenge to sealing and stability during the feeding process. Existing circulating fluidized bed systems commonly use non-mechanical valves (such as L-valve and J-valve) or high-temperature rotary valves to transport high-temperature solid materials. However, in ammonium chloride pyrolysis scenarios, these valves often experience leaks due to insufficient gas pushing force or dust intrusion at the shaft seal, leading to the escape of ammonia and hydrochloric acid gases, equipment wear, and safety hazards. CN202411882870 discloses a leak-proof pyrolysis high-temperature solid material conveying device. By adding an extended sealing cavity between the inlet and outlet of the return feeder, employing double mechanical seals, and a water-cooled rotating shaft design, it effectively prevents high-temperature dust and pyrolysis gases from leaking along the valve stem, while simultaneously achieving reliable horizontal and short-distance return material transmission.

[0006] In summary, there is an urgent need to develop a reasonably structured, stable, energy-efficient, highly efficient, and adaptable ammonium chloride pyrolysis reactor and supporting process to achieve the recycling of ammonia and hydrogen chloride. To this end, this invention provides, on the one hand, a circulating fluidized bed reactor and its process for ammonium chloride pyrolysis, which possesses the advantages of precise flow control, high thermal efficiency, high reaction conversion rate, and continuous and stable operation. On the other hand, this invention designs a dedicated leak-proof feeding module specifically for the characteristics of ammonium chloride. This not only ensures a tight material seal and prevents the escape of solid or gas phases, but also achieves stable transmission and quantitative feeding of ammonium chloride in the feed pipeline through slow heating and segmented pressurization technology. This breakthrough overcomes several bottlenecks in existing technologies and has significant industrial application prospects. Summary of the Invention

[0007] This invention aims to overcome the problems of low reactor heat exchange efficiency, difficulty in material flow control, and easy leakage during the feeding process in the existing ammonium chloride pyrolysis process. It provides a circulating fluidized bed reactor and process for ammonium chloride pyrolysis reaction. The system integrates optimized reactor structural design, thermal coupling control of the reaction process, and a dedicated leak-proof feeding device, which effectively improves pyrolysis efficiency and system stability, and is suitable for the resource-based clean recycling of ammonium chloride.

[0008] The first aspect of this invention provides a circulating fluidized bed reactor for the pyrolysis separation of ammonium chloride to produce ammonia and hydrogen chloride, comprising:

[0009] An ammonia release reactor equipped with a gas distributor and a first-stage multi-stage cyclone separator;

[0010] A chlorination reactor equipped with a riser and a second multi-stage cyclone separator;

[0011] The regeneration carrier conveying pipeline and the chlorine carrier conveying pipeline connect the ammonia release reactor and the chlorine release reactor;

[0012] The riser pipe is located at the bottom of the chlorine release reactor and has a heat exchange jacket on its outer surface;

[0013] The chlorine release reactor is provided with a hydrogen chloride outlet at the top, a regeneration carrier outlet at the bottom of the side wall, and a gas inlet and a chlorine carrier inlet at the bottom riser.

[0014] The ammonia release reactor is provided with an ammonia outlet at the top, a carrier inlet and an ammonium chloride inlet at the bottom of the side wall, and a purge gas inlet and a chlorine carrier outlet at the bottom.

[0015] The chlorine carrier delivery pipeline connects the chlorine carrier outlet of the ammonia release reactor and the chlorine carrier inlet of the riser.

[0016] The regenerated carrier delivery pipeline connects the regenerated carrier outlet of the chlorine release reactor and the carrier inlet of the ammonia release reactor.

[0017] The present invention also provides a process for the pyrolysis separation of ammonium chloride using the above-mentioned circulating fluidized bed reactor, comprising:

[0018] (1) A mixture of raw material ammonium chloride and carrier is fed into the ammonia release reactor through the ammonium chloride inlet to carry out the ammonia release reaction, and ammonia gas and chlorine carrier are obtained. The ammonia gas is recovered from the ammonia outlet.

[0019] (2) The chlorine carrier is fed into the riser through the chlorine carrier conveying pipeline to release chlorine and obtain hydrogen chloride and regenerated carrier. The hydrogen chloride is recovered from the hydrogen chloride outlet and the regenerated carrier is fed into the ammonia release reactor through the regenerated carrier conveying pipeline for recycling.

[0020] The ammonia release reaction device equipped with a gas distributor and a multi-stage cyclone separator undergoes an ammonium chloride pyrolysis reaction (ammonia release reaction). The carrier is generally an alkali metal oxide, such as magnesium oxide. The final gaseous material is ammonia, and the solid material is hydroxyl chloride after absorbing hydrogen chloride and unreacted metal oxides. The reaction is as follows.

[0021] NH4Cl→HCl↑+NH3↑ (1)

[0022] MgO + HCl → Mg(OH)Cl (2)

[0023] The ammonia release reactor has a purge gas inlet at the bottom. Purge gas is introduced to enhance the mixing of NH4Cl with the magnesium oxide support.

[0024] Preferably, the purging gas is high-temperature water vapor generated by waste heat recovery;

[0025] Preferably, the purge gas velocity ranges from 0.05 to 0.1 m / s;

[0026] Preferably, the temperature of the ammonia release reactor is controlled at 300-400℃.

[0027] More preferably, the temperature of the purge gas and its flow rate are measured and adjusted by a temperature sensor to control the temperature inside the reactor.

[0028] The multi-stage cyclone separator uses a multi-stage cyclone separator structure to capture fine dust and solid particles in the reaction products in stages, ensuring that the particulate matter content in the exhaust gas is reduced to within the emission standards, while avoiding corrosion and blockage of downstream equipment by particles.

[0029] Preferably, the cyclone separator adopts a two-stage separation. The gas outlet material of the first-stage cyclone separator enters the second-stage cyclone, and the solid outlet material passes through the gas distributor and enters the stockpile. The inlet of the second-stage cyclone separator is product gas containing a small amount of solid particles. The gas outlet material enters the ammonia recovery section, and the solid outlet material passes through the gas distributor and enters the stockpile.

[0030] Preferably, the cyclone separator is made of Hastelloy, which has the characteristics of high temperature resistance and corrosion resistance, and is suitable for the acidic gas environment generated during the pyrolysis of ammonium chloride;

[0031] The ammonia release reactor is equipped with a high-efficiency gas distributor to ensure uniform mixing and good fluidization of gas and solid carrier within the reactor.

[0032] The gas distributor adopts a porous plate structure with precisely designed pore size and pore density to ensure uniform gas distribution, prevent gas short-circuiting and dead zone formation, and improve the heat exchange efficiency and reaction rate of fluidized bed reaction.

[0033] Preferably, the gas distributor is a perforated plate gas distributor with a perforated pore size distribution design. The pore size is 1.5–3.0 mm, uniformly distributed on the plate surface, and the thickness is 5–10 mm. This design ensures strength while reducing pressure drop. The pore density (number of pores / unit area) is approximately 2000–4000 pores / m². 2 This ensures uniform gas distribution and moderate resistance.

[0034] Preferably, the gas velocity (perforation gas velocity) is controlled below 2 m / s to avoid high-speed gas jets damaging the fluidized bed particles;

[0035] The inlet material of the riser chlorine release reactor device with heat exchange jacket is the carrier that adsorbs hydrogen chloride and the unreacted carrier, such as MgOHCl and MgO, which comes from the ammonia release reactor and is located at the bottom side of the riser. The outlet material is HCl produced after the decomposition of the adsorbent carrier and the regenerated carrier, which are fed into the gas-solid separation device of the chlorine release section for separation.

[0036] The thermal decomposition reaction of magnesium hydroxide occurs within the riser-type chlorination reactor equipped with a heat exchange jacket, thereby recovering the carrier and hydrogen chloride. The reaction is as follows:

[0037] Mg(OH)Cl→MgO+HCl↑ (main) (3)

[0038] Mg(OH)Cl + HCl → MgCl2 + H2O↑ (substitute) (4)

[0039] The gas conveying gas of the riser chlorination reactor device with heat exchange jacket is an inert protective gas containing water vapor to suppress the above reaction (4);

[0040] Preferably, the temperature inside the riser reactor is controlled within the range of 550–680°C;

[0041] Preferably, the riser reactor outlet is equipped with a baffle to buffer the separation of the gas and solid phases;

[0042] Preferably, the molar ratio of inlet water vapor to MgOHCl is between 0.5 and 2, and the inlet temperature is between 500 and 600°C;

[0043] The heat exchange jacket uses high-temperature flue gas to heat the riser reactor, which flows counter-currently with the material.

[0044] Preferably, the temperature of the high-temperature flue gas is 900–1100°C;

[0045] More preferably, the low-temperature flue gas after heat exchange can be recycled and used for heating the loose gas in the ammonia release reaction device.

[0046] The gas-solid separation device in the chlorine release section with multi-stage cyclone separator is similar in structure to the separation section of the aforementioned ammonia release reactor. The inlet is the regeneration carrier and gaseous HCl from the riser reactor outlet. The gas outlet material is HCl, and the solid outlet material is the regeneration carrier, which is recycled to the ammonia release reactor.

[0047] The present invention also provides a special leak-proof feeding device suitable for continuous high-temperature feeding of ammonium chloride solid, including a rotary joint, a double bearing seat, a double-chamber leak-proof sealing system, an inlet flange, a corrosion-resistant shell, an inspection port, a rotating shaft, a wear-resistant and corrosion-resistant castable lining, conveying blades, a support platform, an outlet flange, and a drive assembly.

[0048] The support platform is preferably placed horizontally to support the entire device; the shell is arranged horizontally above the support platform, and an inlet flange is provided at the top of the shell, which is connected to the feed hopper or buffer silo; an outlet flange is provided at the bottom of the shell, which is sealed to the inlet of the ammonia release reactor to form a closed transition channel and effectively prevent gas leakage.

[0049] Preferably, a double-chamber leak-proof sealing system is installed at the axial left end of the housing. The sealing system combines an inert gas shield with a two-stage mechanical seal to limit the escape of ammonia and hydrogen chloride gas.

[0050] The rotating shaft extends into the inner cavity of the housing through the double-chamber leak-proof sealing system. The outer end of the rotating shaft is supported and installed on the support platform by two sets of high-temperature resistant bearings. A rotary joint is provided at the shaft end to transmit power and introduce cooling medium.

[0051] Preferably, the inner walls of the housing cavity, inspection port, and flange interface are lined with wear-resistant and corrosion-resistant castable to enhance the durability of the device;

[0052] Preferably, spiral conveying blades are installed on the inner wall of the rotating shaft to slowly and evenly convey solid ammonium chloride material, reducing the risk of local overheating and blockage.

[0053] More preferably, the outer shell of the feeding device is equipped with a temperature control system, which can be a jacketed cooling device or a heat tracing device, used to maintain the temperature of the feeding section below the decomposition temperature of ammonium chloride, to prevent the material from decomposing or sublimating prematurely during the conveying process, and to ensure the stability and sealing performance of the material conveying process.

[0054] Compared with the prior art, the present invention has the following advantages:

[0055] 1) It realizes the continuous and industrialized operation of the entire process of ammonium chloride "ammonia release-chlorine release" pyrolysis reaction, and meets the needs of by-product ammonium chloride resource recovery in rare earth, soda ash and other industries;

[0056] 2) The problem of easy volatilization and blockage of ammonium chloride at high temperature has been solved. The new rotary feeder improves the safety and airtightness of feeding and is suitable for continuous feeding of solid ammonium chloride.

[0057] In the following specific embodiments of the present invention, the above features will be further explained in detail. Attached Figure Description

[0058] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0059] Figure 1 The effect of temperature on the ammonia and chlorine release reactions is shown.

[0060] Figure 2 The effect of water vapor molar concentration on the chlorine release reaction is shown.

[0061] Figure 3 A schematic diagram of the process structure for a circulating fluidized bed reactor used in ammonium chloride pyrolysis is shown. Detailed Implementation

[0062] The present invention will be further described below with reference to the embodiments and accompanying drawings. However, the present invention is not limited to the listed embodiments, but should also include equivalent improvements and modifications to the technical solutions defined in the appended claims of the present invention.

[0063] Figure 3 This is a schematic diagram of the process structure of the circulating fluidized bed reactor of the present invention, as shown below. Figure 3 As shown, the circulating fluidized bed reactor includes: an ammonia release reactor with a gas distributor and a multi-stage cyclone separator; a riser chlorine release reactor with a heat exchange jacket; and a chlorine release section gas-solid separation device with a multi-stage cyclone separator.

[0064] The ammonia and chlorine release reactors are circulating fluidized bed reactors. The solid discharge from the ammonia release reactor is conveyed to the inlet of the riser-type chlorine release reactor, where it is reacted and separated from the raw material ammonium chloride before being conveyed to the riser reactor. The riser chlorine release reactor is heated by high-temperature flue gas through the partition wall, while the heat for the ammonia release reactor is provided by a high-temperature carrier circulating from the carrier.

[0065] The ammonia release reaction device equipped with a gas distributor and multi-stage cyclone separator has ammonium chloride as the raw material and a regenerated carrier separated by the gas-solid separation device in the subsequent chlorination stage as the gas outlet material. The gas outlet material is ammonia produced by the reaction, and the solid outlet material is a carrier that adsorbs hydrogen chloride.

[0066] Example 1

[0067] In the rotary moving bed experimental device, MgO is used as the chemical chain carrier, with a processing capacity of 4.2 kg ammonium chloride / hour. The ammonia release and chlorine release processes for the chemical chain recycling of ammonium chloride to recover ammonia and hydrogen chloride are carried out in batches within the experimental device. The rotary moving bed experimental device includes a quartz tube reactor, a high-temperature electric heating furnace, a magnetohydrodynamic sealed feeding and discharging system, a raw material / carrier silo, and an atmosphere control system. The device uses industrial by-product ammonium chloride (particle size 0.5–2 mm) as raw material. In the initial operation stage, ammonium chloride and magnesium oxide are mixed at a molar ratio of 3:1 and fed into the feed silo. Under gravity, the feed screw conveys the mixture into the quartz tube. Resistance wire heating is used inside the furnace, and the furnace temperature is controlled at 350±50℃. At this time, ammonium chloride undergoes a pyrolysis reaction to generate NH3 and HCl. HCl is adsorbed by the magnesium oxide solid phase to generate Mg(OH)Cl. Under gravity, the product is collected in the discharge silo, and the gaseous product (mainly NH3) is discharged from the top and absorbed and collected by the absorption device. After the ammonia release reaction is completed, the product is fed back into the feed silo for the chlorine release reaction. The furnace temperature is controlled at 600±50℃, and steam is introduced at the outlet to control the hydrogen chloride concentration and reduce side reactions. After the chlorine release reaction, magnesium hydroxide decomposes to produce HCl and magnesium oxide carrier. The former is absorbed and quantitatively measured using an absorption device, while the latter is recycled.

[0068] Figure 1 The effect of different temperatures on the conversion rates of ammonia and chlorine release reactions is shown in the figure. As can be seen from the figure, the reaction rate increases with increasing temperature. For the ammonia release reaction, the reaction reaches its endpoint in about 20 minutes at 350℃. For the chlorine release reaction, the reaction reaches its endpoint in about 40 minutes at 600℃. The yields of gaseous products NH3 and HCl are both greater than 90%. Figure 2 The effect of the presence of water vapor in the gas phase on the reaction was demonstrated. The presence of water vapor in the gas phase had no effect on the ammonia release reaction, but a significant effect on the chlorine release reaction. Figure 2 It can be seen that when there is no water vapor in the gas phase, the yield of HCl is low, only about 0.4; when the mole fraction of water vapor in the gas phase increases from 0 to 0.16, the yield of HCl increases, but the influence of side reactions still exists; when the mole fraction of water vapor is further increased to 0.276, the experimental data are consistent with the reaction mechanism, and it can be considered that the influence of side reactions has been eliminated.

[0069] Example 2

[0070] In a pilot plant with an annual processing capacity of 10,000 tons / year, MgO is used as the chemical loop recycling carrier. The ammonia release process and the chlorine release process for the recovery of ammonia and hydrogen chloride through the ammonium chloride chemical loop recycling are carried out in stages within the pyrolysis unit of this invention. The reaction process is as follows: Figure 3As shown, the system mainly consists of two parts: a chlorine-releasing reactor and an ammonia-releasing reactor. Magnesium oxide and magnesium hydroxide circulate between the two reactors, and the flow rate is controlled by a solid flow rate controller. The chlorine-releasing reactor is heated by high-temperature flue gas at 1200±50℃. The flue gas is generated by a flue gas generator and flows in through a jacket. After the outlet temperature drops to 800±20℃, it is introduced into the jacket of the ammonia-releasing section furnace, where it is further cooled to 550±25℃. Ammonium chloride, a byproduct of the soda ash process for ammonia synthesis, is used as raw material. The particle size of the raw material is controlled within the range of 0.5–2 mm, requiring no special screening treatment. During the start-up phase, the raw material ammonium chloride and magnesium oxide carrier are mixed at a molar ratio of 3:1 and fed into the ammonia-releasing reactor through a high-temperature ammonium chloride feeder. After the process stabilizes, the magnesium oxide carrier is recycled, 20 times. At this point, the molar ratio of the inlet raw material ammonium chloride to magnesium oxide carrier is 60:1. Inside the ammonia-releasing reactor, the temperature is heated to 350±50℃, and the residence time of the material in the reactor is controlled at 1.5±0.2 hours. In this stage, ammonium chloride decomposes into NH3 and HCl, with HCl being adsorbed by magnesium oxide to form Mg(OH)Cl. The main gaseous component of the reaction is NH3, which is drawn out by a two-stage cyclone separator and sent to an ammonia condensation or absorption system, while the solid material enters the chlorination release reactor. The temperature of the chlorination release reactor is raised to 600±50℃, and water vapor is introduced. The particle residence time is controlled at 1.5±0.3 hours, allowing Mg(OH)Cl to pyrolyze to generate HCl and magnesium oxide. After the chlorination release reactor completes the decomposition of magnesium hydroxide, it generates magnesium oxide carrier, which is returned to the ammonia release reactor for carrier recycling. The device is purged with an inert protective gas containing water vapor, and each inlet is equipped with an MFC and a product concentration feedback closed-loop regulation to suppress the occurrence of side reactions.

[0071] Taking the chlorine-releasing reactor as an example, in the rotary kiln reactor of the chlorine-releasing section, the energy consumption for the decomposition process of the reactants is H1 = 160 kJ / mol NH4Cl, of which the sensible heat of heating is 60 kJ / mol NH4Cl and the endothermic heat of reaction is about 100 kJ / mol NH4Cl. The molar ratio of magnesium hydroxide to magnesium oxide during the chlorine release process is 2:1. The flue gas has similar physical properties to air and can be treated approximately as air. The flue gas flow rate is 30 m³ / h. 3 Based on a flow rate of / s and a flue gas inlet temperature of 1200℃, the parameters of the ammonium chloride pyrolysis converter reactor in the chlorination release section are shown in Table 1:

[0072] Table 1. Design parameters of the rotary kiln reactor for the chlorination release section.

[0073]

[0074] According to the calculations in Table 1, a material conversion rate of 96.7% can be obtained in the reactor shown in Table 2.

[0075] Table 2. Structural parameters of the chlorine release reactor

[0076]

[0077]

[0078] Comparative Example 2

[0079] The throughput is the same as in Example 2, i.e., 10,000 tons / year, but the moving bed reaction process described in patent CN201610111173 is used. A comparison of the two processes is shown in Table 3.

[0080] Table 3. Structural parameters of the chlorine release reactor

[0081]

[0082] Table 3 shows that the two processes have a small difference in reaction yield, but the circulating fluidized bed (CFB) process has a significant advantage in terms of equipment investment and maintenance costs. In terms of equipment structure, the CFB adopts a vertical integrated reactor structure, which requires less space and has a compact layout, resulting in a much lower investment cost compared to the complex tube bundle arrangement of the horizontal tube reactor. Regarding operational stability, the horizontal tube process is susceptible to material flow deviation, scaling, and dead zones, leading to system instability; the CFB, on the other hand, possesses strong self-cleaning properties and uniform flow. At the same production capacity, the annual total operating cost of the CFB process is approximately 35%–40% lower than that of the horizontal tube process, demonstrating a significant economic advantage.

[0083] Example 3

[0084] Taking a circulating fluidized bed device with a processing capacity of 100 kg ammonium chloride / day as an example, the structural parameters of the conveying device can be designed as shown in Table 4:

[0085] Table 4. Structural parameters of the ammonium chloride conveying device

[0086]

[0087] In terms of sealing performance, the device employs a dual-chamber leak-proof sealing system, combining inert gas shielding and a two-stage mechanical seal, effectively preventing the escape of harmful gases and improving the device's airtightness. After 50 hours of operation, the sealing system did not require replacement, with leakage of <0.01kg / year, resulting in virtually zero emissions. Regarding thermal control and material stability, the device uses a water-cooled jacket and heat tracing control system, maintaining the shell temperature stably between 60 and 803℃, with no sublimation or crystallization during the conveying process. After 50 hours of operation, the actual conveying stability was >99.9%, with no record of blockage shutdowns. In terms of safety and maintenance costs, the annual maintenance of the device only requires inspection of the bearings and sealing gas source, without replacing the main structure, significantly reducing maintenance costs.

[0088] Comparative Example 2

[0089] The process conditions and conveyor dimensions are the same as in Example 2, except that a commonly used high-temperature rotary valve is used for feeding. Regarding sealing performance, after 50 hours of use, a trace amount of ammonia gas escaped from the shaft seal area, with an estimated annual leakage of 0.5 kg / year. In terms of thermal control and material stability, the conveying channel lacks active temperature control, and the measured temperature of the equipment casing rose above 170°C, causing ammonium chloride to sublimate prematurely in the feeding section by approximately 1.8 kg / year, resulting in one instance of crystallization blockage and a 3-hour shutdown for cleaning. Regarding safety and maintenance costs, the shaft seal is expected to need replacement every six months, with an average annual maintenance cost of approximately 3500 yuan (including downtime losses and material costs).

[0090] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are within the spirit and scope of the present invention.

Claims

1. A circulating fluidized bed reactor for the production of ammonia and hydrogen chloride by pyrolytic separation of ammonium chloride, characterized in that, The application relates to a chlorine carrier conveying pipeline and a regenerated carrier conveying pipeline connecting an ammonia releasing reactor and a chlorine releasing reactor. The application relates to a chlorine releasing reactor with a riser and a second multi-stage cyclone separator device. The application relates to a chlorine carrier conveying pipeline and a regenerated carrier conveying pipeline connecting an ammonia releasing reactor and a chlorine releasing reactor. The riser is arranged at a bottom position of the chlorine releasing reactor and is provided with a heat exchange jacket on an outer surface. A top portion of the chlorine releasing reactor is provided with a hydrogen chloride outlet, a bottom portion of a side wall is provided with a regenerated carrier outlet, and the bottom riser is provided with a gas inlet and a chlorine carrier inlet. A top portion of the ammonia releasing reactor is provided with an ammonia outlet, a bottom portion of a side wall is provided with a carrier inlet and an ammonium chloride inlet, and a bottom portion is provided with a purge gas inlet and a chlorine carrier outlet. The chlorine carrier conveying pipeline is connected with the chlorine carrier outlet of the ammonia releasing reactor and the chlorine carrier inlet of the riser. The regenerated carrier conveying pipeline is connected with the regenerated carrier outlet of the chlorine releasing reactor and the carrier inlet of the ammonia releasing reactor. The ammonium chloride inlet of the ammonia releasing reactor is connected with a leakage-proof feeding device, which comprises a supporting platform, a cylindrical shell arranged horizontally above the supporting platform, a rotating shaft arranged horizontally and penetrating into an inner cavity of the shell, and conveying blades mounted on the rotating shaft.

2. The circulating fluid bed reaction apparatus according to claim 1, wherein An inlet is arranged at a top portion of the shell, an inlet flange is arranged on the inlet, the inlet flange is connected with a feeding hopper or a buffer bin, an outlet is arranged at a bottom portion of the shell, an outlet flange is arranged on the outlet, and the outlet flange is sealingly connected with an inlet of the ammonia releasing reactor to form a closed transition channel. A double-chamber leakage-proof sealing system is arranged at an axial end of the shell, the sealing system is combined with inert gas shielding and double-stage mechanical sealing, and gas leakage is limited. The rotating shaft penetrates into the inner cavity of the shell through the double-chamber leakage-proof sealing system, an outer end of the rotating shaft is supported and mounted on the supporting platform through two groups of high-temperature resistant bearings, and a rotating joint is arranged at an axial end of the rotating shaft to transmit power and introduce cooling medium. Wear-resistant and corrosion-resistant castable is attached to inner walls of the shell and joints; and spiral conveying blades are arranged on inner walls of the rotating shaft and used for slowly and uniformly conveying ammonium chloride solid materials. A maintenance opening is further arranged on the shell. The leakage-proof feeding device is provided with a temperature control system, the temperature control system is a jacket cooling device or a heating device, and the temperature control system is used for maintaining a temperature of a feeding section to be lower than a decomposition temperature of ammonium chloride.

3. The circulating fluid bed reaction apparatus of claim 2 wherein, The application relates to a chlorine carrier conveying pipeline and a regenerated carrier conveying pipeline connecting an ammonia releasing reactor and a chlorine releasing reactor.

4. A process for the pyrolytic decomposition of ammonium chloride using the circulating fluid bed reactor according to any one of claims 1 to 3, characterized in that, (1) a mixture of raw ammonium chloride and a carrier is input into the ammonia releasing reactor from the ammonium chloride inlet to carry out an ammonia releasing reaction, ammonia gas and a chlorine carrier are obtained, and the ammonia gas is recovered from an ammonia outlet; (2) the chlorine carrier is input into the riser through the chlorine carrier conveying pipeline to carry out a chlorine releasing reaction, hydrogen chloride and a regenerated carrier are obtained, the hydrogen chloride is recovered from a hydrogen chloride outlet, and the regenerated carrier is input into the ammonia releasing reactor through the regenerated carrier conveying pipeline to be recycled and used. The carrier in the ammonia releasing reactor is alkali metal oxide, preferably magnesium oxide; 5. The process of claim 4, wherein, The ammonia releasing reaction is a pyrolysis reaction of ammonium chloride, a reaction formula is NH4Cl -> HCl + NH3, and a reaction formula of the carrier adsorbing hydrogen chloride is MgO + HCl -> Mg(OH)Cl. ​ 6. The process of claim 4, wherein, The purge gas inlet of the ammonia releasing reactor bottom is connected to a purge gas, which is high-temperature water vapor generated by waste heat recovery, and the gas velocity is controlled at 0.05-0.1 m / s, and the temperature of the ammonia releasing reactor is controlled at 300-400 DEG C.

7. The process of claim 4, wherein, The gas distributor adopts a multi-hole plate structure, the aperture is 1.5-3.0mm, the hole density is 2000-4000 holes / m 2 , the thickness is 5-10mm, and the designed gas velocity is controlled below 2m / s.

8. The process of claim 4, wherein, The hydroxyl magnesium chloride thermal decomposition reaction occurs in the lifting pipe chlorine releasing reactor device, carrier recovery and hydrogen chloride recovery are realized, the reaction formula is Mg(OH)Cl→MgO+HCl↑(main reaction); Mg(OH)Cl+HCl→MgCl2+H2O↑(side reaction).

9. The process of claim 8, wherein, The inert protective gas containing water vapor is introduced into the lifting pipe chlorine releasing reactor to inhibit the side reaction, the temperature is controlled at 550-680 DEG C, the inlet water vapor and MgOHCl molar ratio is 0.5-2, and the inlet temperature is controlled at 500-600 DEG C.

10. The process of claim 4, wherein, The lifting pipe chlorine releasing reactor is provided with a heat exchange jacket, and is heated by 900-1100 DEG C high-temperature flue gas, and the low-temperature flue gas after heat exchange is recycled and used for heating the loose gas of the ammonia releasing reactor.

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