A production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate

Abstract

The utility model belongs to inorganic chemical production technical field especially relates to a kind of production system of magnesium sulfate direct calcination preparation high-purity magnesium oxide, including raw material storage tank, feeding station and calcinator, it is characterized in that, anhydrous magnesium sulfate is loaded in raw material storage tank, raw material storage tank bottom is connected with feeding station by air conveying pipeline;The bottom magnesium oxide outlet of calcinator, the flue gas outlet of calcinator top is connected air preheater, the flue gas outlet of air preheater is connected acid absorption tower by waste heat boiler, the top of acid absorption tower is connected concentrated sulfuric acid tank, the bottom sulfuric acid pipe of acid absorption tower sends magnesium sulfate regeneration device, the flue gas outlet of acid absorption tower is connected ammonia water circulating liquid absorption tower;The bottom magnesium oxide outlet of calcinator is connected packaging production line.Compared with prior art, the utility model has the advantages that: main product purity is improved from 98% to 99.5% or more;100% of solid waste generation is reduced, flue gas after calcination carries out two-stage acid recovery, realizes by-product resource utilization.

Description

Technical Field

[0001] This utility model belongs to the field of inorganic chemical production technology, and in particular relates to a production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate. Background Technology

[0002] Magnesium oxide, as an important inorganic chemical raw material, occupies an irreplaceable position in industrial production. Its unique physicochemical properties enable it to play a vital role in various fields such as refractory materials, environmental protection, pharmaceuticals, and food additives. Calcination is the traditional process for producing magnesium oxide, mainly through high-temperature calcination of magnesite (MgCO3) or magnesium hydroxide. The key to this process lies in controlling the calcination temperature and time, typically divided into light-calcined and heavy-calcined methods. Light-calcined magnesium oxide (active magnesium oxide) is obtained by calcination at 700-1000℃ and possesses high chemical activity; heavy-calcined magnesium oxide (dead-burned magnesium oxide) is obtained by calcination above 1500℃ and has higher density and refractory properties. This process involves simple equipment and low investment, but it has high energy consumption, and the purity of the product is greatly affected by the raw materials.

[0003] Chinese utility model patent application number 201920950350.2 discloses a horizontal rolling suspension calcination device for powder materials, including a cylinder, a rotary support mechanism, a rotary drive mechanism, a feed end sealed box, and a discharge end sealed box. The cylinder is divided into a guiding section, a calcination section, and a cooling section along the material flow direction. Multiple spiral guide plates are arranged circumferentially and longitudinally on the inner wall of the guiding section, the calcination section, and the cooling section near the calcination section. A central cylinder is located inside the cylinder of the calcination section, and multiple positive spiral baffles and negative spiral baffles are arranged circumferentially and longitudinally on the outer wall of the central cylinder. An insulation layer is provided on the inner wall of the cylinder. This utility model utilizes the spiral guide plates, positive spiral baffles, and negative spiral baffles arranged inside the cylinder to achieve suspension fluidization calcination of powder materials. The powder materials fully contact and exchange heat with hot air, resulting in high product activity and uniform quality.

[0004] Traditional magnesium oxide calcination processes generally suffer from drawbacks such as high energy consumption, low waste heat recovery efficiency, highly polluting byproducts, and magnesium oxide sintering. In particular, the highly corrosive SO3 gas produced as a byproduct of calcination generates secondary solid waste through conventional alkaline absorption methods, making green production impossible. Utility Model Content

[0005] The purpose of this invention is to provide a production system for the direct calcination of magnesium sulfate to prepare high-purity magnesium oxide, overcoming the shortcomings of existing technologies. Anhydrous magnesium sulfate raw material is dynamically suspended and calcined in a horizontal rolling suspension calcination device under precise temperature control. Through dual-mode control of co-current and counter-current flow, the thermodynamic path is adjusted, and the raw material is fully decomposed into high-purity magnesium oxide (main product) and active SO3 (byproduct) within a short and efficient reaction cycle of 20-40 minutes. Subsequently, by recovering heat from the flue gas after calcination and recovering acid in two stages, the byproducts are recycled and the waste heat is utilized in a cascade manner, meeting the national requirements for green production.

[0006] To achieve the above objectives, this utility model employs the following technical solution:

[0007] A production system for directly calcining magnesium sulfate to prepare high-purity magnesium oxide includes a raw material storage tank, a feeding station, and a calcining furnace. The calcining furnace is connected to a gas pipeline and a hot air pipeline. The raw material storage tank is filled with anhydrous magnesium sulfate, and the bottom of the raw material storage tank is connected to the feeding station via an air conveying pipeline. A metering valve is installed at the bottom outlet of the feeding station. The flue gas outlet at the top of the calcining furnace is connected to an air preheater. The hot air outlet of the air preheater is connected to the hot air pipeline of the calcining furnace. The cold air inlet of the air preheater is connected to a fan. The flue gas outlet of the air preheater is connected to an acid absorption boiler via a waste heat boiler. The steam outlet of the waste heat boiler is connected to an external pipeline, and the soft water inlet of the waste heat boiler is connected to a soft water tank. The top of the acid absorption tower is connected to a concentrated sulfuric acid tank, and the bottom sulfuric acid pipe of the acid absorption tower sends sulfuric acid to a magnesium sulfate regeneration device. The flue gas outlet at the top of the acid absorption tower is connected to an ammonia circulating liquid absorption tower. The top and bottom of the ammonia circulating liquid absorption tower are connected in series with the circulating liquid tank to form a closed-loop circulation of the circulating liquid. A circulation pump is installed on the closed-loop circulation pipe, and the top of the ammonia circulating liquid absorption tower is equipped with a flue gas exhaust port. The magnesium oxide outlet at the bottom of the calcining furnace is connected to the packaging production line.

[0008] Furthermore, the calcining furnace is a horizontal rolling suspension calcining device, and the combustion gas and hot air participating in the calcination have two flow directions: co-current and counter-current.

[0009] Furthermore, the magnesium oxide outlet at the bottom of the calcining furnace is connected to the packaging production line via a grading device.

[0010] Furthermore, the finished product specifications of the grading device are D50 particle sizes in the range of 1-10 micrometers.

[0011] Furthermore, the saturated steam generated by the waste heat boiler is connected to an external delivery pipe and a reuse pipe, respectively, and the reuse pipe is connected to the steam-driven fan and / or steam-driven pump of this production system.

[0012] Furthermore, an expansion joint is provided on the connecting pipeline between the feeding station and the calcining furnace.

[0013] Furthermore, at least one outlet pipeline of the raw material storage tank and the feeding station is equipped with a relevant air valve.

[0014] Compared with the prior art, the beneficial effects of this utility model are:

[0015] 1) Anhydrous magnesium sulfate raw material is dynamically suspended and calcined in a horizontal rolling suspension calcination device under precise temperature control. By controlling the thermodynamic path through co-current / countercurrent dual modes, the raw material is fully decomposed into high-purity magnesium oxide (main product) and active SO3 (byproduct) within a short and efficient reaction cycle of 20-40 minutes, which solves the problem of local overburning and increases the purity of the product from 98% to over 99.5%.

[0016] 2) Environmental breakthrough: The first closed-loop path of SO3 → fuming sulfuric acid → regenerated magnesium sulfate is created, which reduces solid waste generation by 100% compared with the traditional alkaline absorption method. The flue gas after calcination is subjected to two-stage acid recovery to realize the resource utilization of by-products.

[0017] 3) Energy efficiency upgrade: The waste heat cascade utilization system (external steam supply + self-driven equipment + hot air circulation) reduces the overall energy consumption by 30%, breaking through the industry's cost bottleneck;

[0018] 4) Advantages of critical control: The horizontal rolling suspension calcination device accurately controls the temperature at the critical temperature of 1200℃, avoiding magnesium oxide sintering and solving the technical problem of crystal defects caused by traditional processes when the temperature exceeds 1200℃. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow stage one of the embodiments of this utility model;

[0020] Figure 2 This is a schematic diagram of the second stage of the process flow of this utility model embodiment;

[0021] Figure 3 This is a schematic diagram of the three-stage process flow of an embodiment of this utility model.

[0022] In the diagram: 1-Raw material storage tank, 2-Feeding station, 3-Calcination furnace, 4-Pneumatic conveying pipeline, 5-Metering valve, 6-Air preheater, 7-Waste heat boiler, 8-Acid absorption tower, 9-Ammonia water circulating liquid absorption tower, 10-Expansion joint, 11-Air shut-off valve. Detailed Implementation

[0023] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0024] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] The components of the present invention embodiments described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0026] See Figure 1-3 This is a schematic diagram of the process flow structure of a production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate according to this utility model. It includes a raw material storage tank 1, a feeding station 2, and a calcining furnace 3. The calcining furnace 3 is connected to a gas pipeline and a hot air pipeline. The raw material storage tank 1 contains anhydrous magnesium sulfate with a purity ≥99% and a particle size ≤1mm. The bottom of the raw material storage tank 1 is connected to the feeding station 2 via a pneumatic conveying pipe 4. A metering valve 5 is installed at the bottom outlet of the feeding station 2. At least one outlet pipeline in the raw material storage tank 1 and the feeding station 2 is equipped with a control valve 11 to reduce dust escape from the system while conveying raw materials. The magnesium oxide outlet at the bottom of the calcining furnace 3 is connected to a packaging production line, and the flue gas outlet at the top of the calcining furnace 3 is connected to an air preheater 6. An expansion joint 10 is installed on the connecting pipeline between the feeding station 2 and the calcining furnace 3 to reduce the adverse effects of high temperature on the equipment. The hot air outlet of air preheater 6 is connected to the hot air pipe of calcining furnace 3, and the cold air inlet of air preheater 6 is connected to a fan. The flue gas outlet of air preheater 6 is connected to acid absorption tower 8 via waste heat boiler 7. The steam outlet of waste heat boiler 7 is connected to an external pipeline, and the soft water inlet of waste heat boiler 7 is connected to a soft water tank. The top of acid absorption tower 8 is connected to a concentrated sulfuric acid tank, and the bottom sulfuric acid pipe of acid absorption tower 8 sends sulfuric acid to a magnesium sulfate regeneration device. The flue gas outlet at the top of acid absorption tower 8 is connected to ammonia circulating liquid absorption tower 9. The top and bottom of ammonia circulating liquid absorption tower 9 are connected in series with the circulating liquid tank to form a closed-loop circulation of the circulating liquid. A circulation pump is installed on the closed-loop circulation pipe, and a flue gas exhaust port is provided at the top of ammonia circulating liquid absorption tower 9. The magnesium oxide outlet is high-purity magnesium oxide with a purity ≥99.5%. After classification, high-purity magnesium oxide can be obtained as ultrafine powder with an adjustable D50 particle size of 1-10 micrometers.

[0027] Calcining furnace 3 is a horizontal rolling suspension calcining device with a temperature setting range of 850℃-1200℃ and a calcination cycle of 20-40 minutes. The combustion gas and hot air involved in calcination switch between co-current and counter-current channels, ensuring thorough mixing and combustion of the combustion gas and hot air. The horizontal rolling suspension calcining device solves the problem of localized overburning in traditional vertical calcining furnaces through dynamic suspension technology, increasing the product purity from 98% to over 99.5%.

[0028] Air preheater 6 heats cold air into hot air at over 600°C and returns it to the combustion chamber of calcining furnace 3, reducing gas consumption by ≥16%. Saturated steam generated by waste heat boiler 7 is preferentially used to drive the steam-driven fans and pumps of this process system; the remainder is exported. In this embodiment, exported steam accounts for no less than 30% of the total steam production.

[0029] This invention represents a significant breakthrough in environmental protection: it pioneers a closed-loop pathway from SO3 → fuming sulfuric acid → regenerated magnesium sulfate, reducing solid waste generation by 100% compared to traditional alkaline absorption methods. Energy efficiency is greatly enhanced: the four-stage waste heat utilization system (external steam supply + self-driven equipment + hot air circulation) reduces overall energy consumption by 30%, breaking through the industry's cost bottleneck. It also boasts critical control advantages: precise temperature control at a critical temperature of 1200℃ avoids magnesium oxide sintering (traditional processes require temperatures exceeding 1200℃, leading to crystal defects), significantly improving the quality of magnesium oxide products.

[0030] SO3 gas in the flue gas inside acid absorption tower 8 is converted into fuming sulfuric acid by concentrated sulfuric acid absorption, with an absorption efficiency of ≥98%. This product is recycled as a raw material for the regeneration of magnesium sulfate.

[0031] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate, comprising a raw material storage tank, a feeding station, and a calcination furnace, wherein the calcination furnace is connected to a gas pipeline and a hot air pipeline, characterized in that, The raw material storage tank contains anhydrous magnesium sulfate. The bottom of the raw material storage tank is connected to the feeding station via an air conveying pipe. A metering valve is installed at the bottom outlet of the feeding station. The flue gas outlet at the top of the calcining furnace is connected to an air preheater. The hot air outlet of the air preheater is connected to the hot air pipe of the calcining furnace. The cold air inlet of the air preheater is connected to a fan. The flue gas outlet of the air preheater is connected to an acid absorption tower via a waste heat boiler. The steam outlet of the waste heat boiler is connected to an external pipeline. The soft water inlet of the waste heat boiler is connected to a soft water tank. The top of the acid absorption tower is connected to a concentrated sulfuric acid tank. The sulfuric acid pipe at the bottom of the acid absorption tower sends sulfuric acid to a magnesium sulfate regeneration device. The flue gas outlet at the top of the acid absorption tower is connected to an ammonia circulating liquid absorption tower. The top and bottom of the ammonia circulating liquid absorption tower are connected in series with the circulating liquid tank to form a closed-loop circulation of the circulating liquid. A circulation pump is installed on the closed-loop circulation pipe. The top of the ammonia circulating liquid absorption tower is equipped with a flue gas exhaust port. The magnesium oxide outlet at the bottom of the calcining furnace is connected to the packaging production line.

2. The production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate according to claim 1, characterized in that, The calcining furnace is a horizontal rolling suspension calcining device, and the combustion gas and hot air participating in the calcination have two flow directions: co-current and counter-current.

3. The production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate according to claim 1, characterized in that, The magnesium oxide outlet at the bottom of the calcining furnace is connected to the packaging production line via a grading device.

4. The production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate according to claim 3, characterized in that, The finished product specifications of the grading device are D50 particles with a diameter in the range of 1-10 micrometers.

5. A production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate according to claim 1, characterized in that, The saturated steam generated by the waste heat boiler is connected to an external delivery pipe and a reuse pipe, respectively. The reuse pipe is connected to the steam-driven fan and / or steam-driven pump of this production system.

6. The production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate according to claim 1, characterized in that, An expansion joint is installed on the connecting pipeline between the feeding station and the calcining furnace.

7. The production system for preparing high-purity magnesium oxide by direct calcination of magnesium sulfate according to claim 1, characterized in that, At least one of the outlet pipelines of the raw material storage tank and the feeding station is equipped with an air valve.

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