Method for recycling waste heat in magnesite light burning process
Technical Field
The invention relates to a magnesite smelting method, in particular to a method for recycling waste heat in a magnesite light burning process.
Background
China is one of the most abundant countries of magnesite resources in the world, and the total reserved quantity of the ores is about 30 hundred million tons, which accounts for 25 percent of the total reserve in the world. The Liaoning magnesite is the most abundant, accounts for 85.6% of the total storage in China, is mainly concentrated in large stone bridges and sea cities, and has the annual extraction amount of about 1200 plus 1500 million tons. Magnesite is a main raw material for preparing magnesium compounds, light-burned magnesium is obtained by calcining magnesite, is widely used in the fields of building materials, chemical engineering, metallurgy, medicines and the like, is an ideal material for producing fire-proof plates, light partition plates, magnesium sulfate, papermaking, a desulphurization process, furnace protection slag splashing of steel mills and the like, and is also a raw material for preparing heavy-burned magnesium, high-purity magnesite sand and electric fused magnesium.
2771 calcining furnaces for producing refractory raw materials in Liaoning, wherein the number of the light-burning furnaces is 1367, and the yield of the light-burning magnesium oxide is over 400 million tons/year. For decades, the device for preparing light-burned magnesia by calcining magnesite at high temperature continues to calcine magnesite by the traditional process of combining a water gas producer with a reverberatory furnace or a shaft kiln, and the backward production process not only causes low production efficiency and poor product quality, but also causes huge waste of energy. Because of insufficient fuel combustion, the thermal efficiency of the shaft kiln is only 26.47 percent, the temperature of the flue gas discharged by the shaft kiln is as high as more than 230 ℃, a large amount of heat is discharged along with dense smoke, the temperature of a light-burned magnesium powder product calcined by the kiln is as high as 800 ℃, the high-temperature product releases energy to the natural environment through natural cooling, and huge energy waste is caused because sensible heat cannot be recovered every year.
Chinese patent application No. 201110049511.9 discloses a heat separation method and device for light burned magnesium oxide, wherein the light burned magnesium oxide passing through a heat separation sieve enters a heat pipe heat exchanger to exchange heat with cold air, the air is heated, and the hot air is led out to heating equipment. Although the invention effectively utilizes part of the heat of the light-burned magnesia, the invention is carried out on the basis of a reflection kiln, and the heat in the flue gas is not effectively utilized. Chinese patent application No. 201310363267.2 discloses a multistage sectional mineral separation purification and comprehensive utilization method for low-grade magnesite. The invention is based on the multi-layer shaft kiln, and uses the sensible heat generated in the light burning process to heat the cold material and the furnace body, float the ore and press the ball for drying. Chinese patent publication No. CN 106587666 a discloses a device and method for producing light-burned magnesium oxide by magnesite flotation concentrate powder. The invention utilizes the waste heat of the flue gas to preheat the dried magnesite raw material by a multi-stage preheating system, however, the invention does not specifically describe the process of the multi-stage preheating system, and the waste heat of the light-burned magnesium product is not effectively utilized, thereby causing great loss of heat.
Disclosure of Invention
The invention aims to provide a method for recycling waste heat in the light burning process of magnesite. Thereby achieving the purposes of energy conservation and consumption reduction.
The purpose of the invention is realized by the following technical scheme:
a method for recycling waste heat in a magnesite light burning process is characterized in that high-temperature light burning powder products produced in the light burning process are directly contacted with and exchange heat through cyclone to preheat air and cool the products, and the preheated air is used for gas combustion in the light burning process; the magnesite powder raw material is preheated and the flue gas is cooled by directly exchanging heat through cyclone by utilizing high-temperature flue gas generated in the light burning process; the method comprises the following specific processes:
firstly, clean fuel gas is introduced into a combustor of a magnesite calciner, hot flue gas generated by combustion rapidly calcines magnesite powder through gas-solid action, a product of the clean fuel gas passes through a cyclone separator, obtained high-temperature light-burned powder is sent into a product cyclone heat exchanger, air blown by an induced draft fan is heated by using heat energy of the product, preheated air is introduced into the combustor of the magnesite calciner through filtering and dust removing, the combustion efficiency is improved, and the light-burned magnesium product subjected to filtering and dust removing and cooled by the product cyclone heat exchanger is conveyed into a storage tank; the magnesite powder as raw material is preheated by the cyclone heat exchanger, the flue gas after heat exchange is filtered and dedusted and then directly discharged, and the preheated magnesite powder and the magnesite fine powder obtained by filtering and dedusting are conveyed into the calcining furnace.
The method for recycling the waste heat in the magnesite light burning process is characterized in that the cyclone heat exchanger for preheating air by the high-temperature light burning powder product and the cyclone heat exchanger for preheating the magnesite powder raw material by the high-temperature flue gas are composed of one or more cyclones, and the treatment temperature is 1-6 levels.
The method for recycling the waste heat in the magnesite light burning process comprises a cyclone heat exchange system for gas-solid separation, high-temperature flue gas preheating of magnesite powder, a cyclone heat exchange system for high-temperature light burning powder product preheating air, a filtering and dust removing system, a flue gas discharging system and a cooled light burning powder product storage tank, wherein the preheated air is fed into a combustor of the magnesite powder calcining furnace, and the preheated magnesite powder raw material is fed into the magnesite powder calcining furnace.
According to the method for recycling the waste heat in the light burning process of the magnesite, the filtering and dedusting of the magnesite powder preheated by the high-temperature flue gas after cyclone heat exchange is low-temperature filtering and dedusting, and the flue gas subjected to low-temperature filtering and dedusting is discharged after reaching the standard; the filtering and dedusting system after cyclone heat exchange of the preheated air of the high-temperature light burning powder product filters and removes dust at high temperature, and the air after high-temperature filtering and dedusting is used for gas combustion in the light burning process.
The invention has the advantages and effects that:
1. the invention uses the product heat energy to heat air as fresh air to be blown into the calcining furnace, and changes the original cold air blowing into hot air to reduce the fuel consumption and improve the combustion efficiency, wherein part of the heat energy can also be used for heating in winter, bathing and the like to reduce the consumption of coal. Thereby achieving the purposes of energy conservation and consumption reduction.
2. According to the invention, the heat energy of the flue gas is transferred to the raw material by the heat exchange between the high-temperature flue gas and the raw material magnesite, so that the recycling rate of the heat energy of the flue gas is improved, the purpose of preheating the raw material is achieved, and the heat energy consumed by calcining the raw material is reduced.
Drawings
FIG. 1 is a schematic illustration of example 1 of a process flow of the present invention;
FIG. 2 is a schematic illustration of example 2 of the process flow of the present invention;
FIG. 3 is a schematic representation of the process flow of example 3 of the present invention.
Detailed Description
The present invention will be described in detail with reference to the embodiments shown in the drawings.
Example 1
As shown in fig. 1, firstly, clean fuel gas is introduced into a combustor of a magnesite calciner, hot flue gas generated by combustion rapidly calcines magnesite powder through gas-solid action, a product of the clean fuel gas passes through a cyclone separator, obtained high-temperature light calcined powder is sent into a product cyclone heat exchanger, air blown by a draught fan is heated by using heat energy of the product, the preheated air is introduced into the combustor of the magnesite calciner through filtering and dust removing, the combustion efficiency is improved, the number of the product cyclone heat exchangers is 1, and the light calcined magnesium product subjected to filtering and dust removing and cooled by the product cyclone heat exchanger is conveyed into a storage tank; the magnesite powder as raw material is preheated by a smoke cyclone heat exchanger with the number of 1, the smoke after heat exchange is filtered and dedusted and then directly discharged after reaching the standard, and the preheated magnesite powder and the magnesite fine powder obtained by filtering and dedusting are conveyed into a calcining furnace.
Example 2
As shown in fig. 2, firstly, clean gas is introduced into a combustor of a magnesite calciner, hot flue gas generated by combustion rapidly calcines magnesite powder through gas-solid action, a product of the clean gas passes through a cyclone separator, obtained high-temperature light calcined powder is sent into a product cyclone heat exchanger, air blown by a draught fan is heated by using heat energy of the product, the preheated air is introduced into the combustor of the magnesite calciner through filtering and dust removing, the combustion efficiency is improved, the number of the product cyclone heat exchangers is 1, and the light calcined magnesium product subjected to filtering and dust removing and cooled by the product cyclone heat exchanger is conveyed into a storage tank; the magnesite powder as raw material is preheated by a smoke cyclone heat exchanger with the number of 2, the smoke after heat exchange is filtered and dedusted and then directly discharged after reaching the standard, and the preheated magnesite powder and the magnesite fine powder obtained by filtering and dedusting are conveyed into a calcining furnace.
Example 3
As shown in fig. 3, firstly, clean gas is introduced into a burner of a magnesite calciner, hot flue gas generated by combustion rapidly calcines magnesite powder through gas-solid action, a product of the clean gas passes through a cyclone separator, obtained high-temperature light calcined powder is sent into a product cyclone heat exchanger, air blown by a draught fan is heated by using heat energy of the product, the preheated air is introduced into the burner of the magnesite calciner through filtering and dust removal, the combustion efficiency is improved, the number of the product cyclone heat exchangers is 2, and the light calcined magnesium product subjected to filtering and dust removal and cooled by the product cyclone heat exchanger is conveyed into a storage tank; the magnesite powder as raw material is preheated by a smoke cyclone heat exchanger with the number of 4, the smoke after heat exchange is filtered and dedusted and then directly discharged after reaching the standard, and the preheated magnesite powder and magnesite fine powder obtained by filtering and dedusting are conveyed into a calcining furnace.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.