CN115950271A - Environment-friendly low-energy-consumption tricalcium phosphate calcining process and system - Google Patents
Environment-friendly low-energy-consumption tricalcium phosphate calcining process and system Download PDFInfo
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Abstract
The invention discloses an environment-friendly low-energy-consumption tricalcium phosphate calcining process and system, which comprises the following steps: denitration of kiln gas discharged: removing NOx in the flue gas discharged from the kiln through a denitration unit; first-stage kiln discharge flue gas heat recovery: in the combustion-supporting air heat exchange unit, the flue gas discharged from the denitration unit heats the tertiary air entering the kiln to 600-900 ℃, and then is introduced into the kiln head of the rotary kiln, and the flue gas discharged from the kiln is reduced to 600-800 ℃; and (3) second-stage discharge flue gas heat recovery: the flue gas discharged from the combustion-supporting air heat exchange unit enters a raw material preheating unit, so that the raw material is heated to 500-700 ℃ from the normal temperature, and the flue gas is reduced to 300-500 ℃; calcining raw materials: calcining the preheated powdery raw material in a rotary kiln to prepare defluorinated tricalcium phosphate clinker; cooling clinker: and cooling the discharged clinker by a kiln head cooler to obtain a finished product. The invention realizes the standard emission of the flue gas and the heat content recovery of the flue gas, reduces the heat consumption of the system, reduces the heat load of the rotary kiln and improves the yield of the kiln system.
Description
Technical Field
The invention relates to the technical field of tricalcium phosphate production, in particular to an environment-friendly low-energy-consumption tricalcium phosphate calcining process and system.
Background
Defluorinated calcium phosphate as one kind of excellent inorganic feed additive for farm animal has obvious yield increasing and weight increasing effect. The production of feed phosphate in China starts late, research and production are started from the 60 s, the production and use are really started at the end of the 80 s and are rapidly developed after the 90 s, the capacity of a device is increased to millions of tons from tens of thousands of tons, the production capacity of the device built in China currently exceeds 100 thousands of tons, and the device becomes the second world feed phosphate producing country next to the United states. Although domestic feed phosphate develops faster depending on resource advantages and energy advantages, the problems of primary products, backward technology, scattered layout, narrow application range and the like still exist. The production of defluorinated calcium phosphate by phosphoric acid method is a very complicated heterogeneous reaction process, and the degree of defluorination in the reaction is the key to influence the qualification of the product quality. The production of defluorinated calcium phosphate includes sintering defluorination process and melting defluorination process, and its basic principle is that the defluorination is carried out by steam at high temp. Because the melting method uses low-grade phosphorite as raw material, the impurities are more, the energy consumption is large, the product quality is poor, the requirement of the low-grade phosphorite as a feed-grade product can not be met, and the low-grade phosphorite is gradually eliminated. The sintering defluorination method is to sinter the ground phosphate rock and additives at high temperature and to contact with steam for reaction to defluorinate, and is a method widely adopted in the world at present.
The production process of the defluorinated tricalcium phosphate generally adopts a high-temperature method, wherein the phosphorite sodium salt phosphoric acid sintering method is technically improved in developed countries such as Europe, america, japan and the like, the product quality is reliable, the production scale is large, the production enterprises and the technology are mainly concentrated in several large companies, such as the PCS and IMC company in the United states and the Japan and Small-field chemical company, and the production process is an international mainstream production process. Compared with the foreign world, china still has a large gap in the production of the defluorinated tricalcium phosphate, which is reflected in that the defluorinated calcium phosphate in China has low yield and small device scale, and is not developed to form large-scale industry.
The calcination temperature of the defluorinated tricalcium phosphate is generally as high as 1400 ℃, and the prior art generally adopts a dry rotary kiln for calcination. After the content of phosphorus pentoxide of natural ore mined from a mine is increased by mineral separation, a small amount of industrial-grade sulfuric acid is added, the natural ore is metered and mixed into balls, and then the balls are sent into a rotary kiln to be heated and calcined by coal tar to generate high-temperature reaction, so that fluorine in phosphorite is removed, and the composite calcium-phosphorus mineral feed additive consisting of tricalcium phosphate, calcium sodium phosphate and other phosphates is generated. In the process, raw materials fed into the kiln need to be granulated into balls, so that the speed of transferring heat generated by combustion of fuels in the kiln to the materials is low, the calcination defluorination time of the balls is long, and the yield of the rotary kiln is limited; the temperature of the flue gas discharged out of the rotary kiln is often as high as above 700 ℃, the enthalpy of the flue gas discharged out of the system is very high, and the heat loss accounts for about 40% of the whole firing heat loss; meanwhile, the materials entering the kiln are not preheated, and the materials need to be preheated and dried for a long time after entering the kiln, so that the heat load in the rotary kiln is relatively large, thereby limiting the capacity improvement of the rotary kiln, and causing the production line for preparing the defluorinated tricalcium phosphate by the sintering method to be relatively small in scale, high in energy consumption, large in pollution and high in production cost. In addition, in the process, the temperature of the flue gas discharged from the kiln is about 700 ℃, the temperature window of SNCR denitration cannot be reached, NOx is difficult to remove by an SNCR method with low investment and low operation cost, so that the NOx in the flue gas is difficult to remove, and the processes of low-temperature tail gas catalytic denitration or alkali liquor absorption after ozone oxidation and the like are complex, large in investment and high in operation cost.
In summary, the prior art has the following problems:
(1) In the prior art, the rotary kiln is adopted to calcine the defluorinated tricalcium phosphate, and the flue gas discharged from the kiln carries a large amount of heat which is not effectively recycled, so that the heat consumption of a firing system is high and the fuel consumption is high.
(2) In the prior art, raw materials fed into a kiln need to be granulated into balls, the speed of transferring heat generated by combustion of fuel in the kiln to the materials is slow, the time for calcining and defluorinating the balls is long, and the yield of a rotary kiln is limited.
(3) In the prior art, raw materials entering a kiln are not preheated, the materials need to be preheated and dried for a long time after entering the kiln, and the heat load in the rotary kiln is relatively large, so that the capacity improvement of the rotary kiln is limited.
(4) In the prior art, the temperature of the flue gas discharged from the kiln cannot reach the temperature window of SNCR denitration, and NOx is difficult to remove by an SNCR method with low investment and low operation cost.
Therefore, aiming at the existing process for calcining defluorinated tricalcium phosphate in a rotary kiln, a tricalcium phosphate calcining process and a tricalcium phosphate calcining system which can realize standard emission of flue gas, recovery of heat content of the flue gas, reduction of heat consumption of the system, reduction of heat load of the rotary kiln and improvement of the yield of the kiln system need to be developed.
Disclosure of Invention
One of the purposes of the invention is to provide an environment-friendly tricalcium phosphate calcining process with low energy consumption, which comprises the steps of adding an SNCR (selective non-catalytic reduction) denitration unit at the tail of a kiln and recovering the enthalpy of flue gas by multiphase combined heat exchange, wherein after high-temperature flue gas discharged from the kiln is subjected to SNCR denitration, gas-gas heat exchange and gas-material heat exchange, the heat of the flue gas is transferred to kiln-entering combustion-supporting air and kiln-entering raw materials, so that the standard emission of the flue gas is realized, the enthalpy of the flue gas is recovered, the heat consumption of a system is reduced, the heat load of a rotary kiln is reduced, and the yield of the kiln system is improved.
Another objective of the present invention is to provide an environment-friendly tricalcium phosphate calcining system with low energy consumption.
The invention is realized in this way, a tricalcium phosphate calcining process with environment-friendly and low energy consumption, comprising the following steps:
denitration of kiln gas discharged: removing NOx in the flue gas discharged from the kiln through a denitration unit, and spraying a reducing agent at the bottom of a denitration pipeline of the denitration unit to enable the reducing agent and the NOx in the flue gas to generate a reduction reaction so as to remove the NOx in the flue gas;
first-stage kiln discharge flue gas heat recovery: flue gas discharged from the denitration unit enters a combustion-supporting air heat exchange unit through a flue gas inlet, tertiary air entering the kiln enters the combustion-supporting air heat exchange unit through the combustion-supporting air inlet, the heat of the flue gas discharged from the kiln heats the tertiary air entering the kiln to 600-900 ℃ and then is introduced into the kiln head of the rotary kiln, and the temperature of the flue gas discharged from the kiln is reduced to 600-800 ℃ from 800-1000 ℃ so as to realize the primary recovery of the heat of the flue gas;
and (3) second-stage kiln discharge flue gas heat recovery: the flue gas from the combustion-supporting air heat exchange unit enters a raw material preheating unit to heat the raw material, so that the raw material is heated to 500-700 ℃ from normal temperature, and the temperature of the flue gas is reduced to 300-500 ℃ from 600-800 ℃, thereby realizing the second-stage recovery of the heat of the flue gas;
calcining raw materials: calcining the preheated powdery raw material in a rotary kiln to prepare defluorinated tricalcium phosphate clinker;
cooling clinker: and cooling the defluorinated tricalcium phosphate clinker discharged from the kiln by a kiln head cooling machine to prepare a finished product.
Preferably, the method also comprises the following steps of flue gas dedusting: and before entering the combustion-supporting air heat exchange unit, the flue gas discharged from the denitration unit is subjected to dust collection treatment by a kiln tail cyclone dust collector, the collected dust returns to the rotary kiln, and the flue gas subjected to dust collection enters the combustion-supporting air heat exchange unit.
Preferably, the preheated powdery raw material can enter the denitration pipeline in part.
Preferably, the tertiary air entering the kiln is air or kiln head residual air discharged from the cooler, the kiln head residual air discharged from the cooler is subjected to dust collection treatment by a kiln head cyclone dust collector, the collected dust returns to the cooler, and the residual air subjected to dust collection enters the combustion-supporting air heat exchange unit.
Preferably, the raw meal entering the raw meal preheating unit is powdery, and the fineness is 80um, and the screen residue is less than 50%.
The utility model provides a system is calcined to environment-friendly low energy consumption tricalcium phosphate, includes that rotary kiln, cooler, kiln tail smoke chamber, denitration unit, combustion-supporting wind heat transfer unit and raw preheat the unit, kiln tail smoke chamber, rotary kiln and cooler link to each other in proper order, the exhanst gas outlet of kiln tail smoke chamber links to each other with the flue gas inlet of denitration unit, the exhanst gas outlet of denitration unit links to each other with combustion-supporting wind heat transfer unit's flue gas inlet, combustion-supporting wind heat transfer unit's flue gas outlet links to each other with the flue gas inlet that the unit bottom was preheated to the raw material, the combustion-supporting wind export of stating combustion-supporting wind heat transfer unit links to each other with the kiln hood of rotary kiln, the raw material preheat the discharge gate of unit bottom with kiln tail smoke chamber links to each other, the kiln head department of rotary kiln is provided with kiln head combustor.
Preferably, the denitration unit comprises a denitration pipeline, a denitration system and a spray gun, the denitration pipeline is positioned above the kiln tail smoke chamber, a smoke outlet at the top of the denitration pipeline is connected with a smoke inlet of the combustion-supporting air heat exchange unit, the denitration system is connected with the spray gun, and the spray gun is arranged at the bottom of the denitration pipeline.
Further preferably, a discharge hole at the bottom end of the raw meal preheating unit is connected with the denitration pipeline.
Preferably, a kiln tail cyclone dust collector is arranged between a flue gas inlet of the combustion-supporting air heat exchange unit and a flue gas outlet of the denitration unit, the flue gas inlet of the kiln tail cyclone dust collector is connected with the flue gas outlet of the denitration unit, the flue gas outlet of the kiln tail cyclone dust collector is connected with the flue gas inlet of the combustion-supporting air heat exchange unit, and a discharge port of the kiln tail cyclone dust collector is connected with a kiln tail smoke chamber.
Preferably, a combustion-supporting air inlet of the combustion-supporting air heat exchange unit is connected with a low-temperature residual air outlet of the cooling machine.
Preferably, a kiln head cyclone dust collector is arranged between a combustion air inlet of the combustion air heat exchange unit and the cooling machine, a residual air inlet of the kiln head cyclone dust collector is connected with a low-temperature residual air outlet of the cooling machine, a discharge hole of the kiln head cyclone dust collector is connected with the cooling machine, and a residual air outlet of the kiln head cyclone dust collector is connected with a combustion air inlet of the combustion air heat exchange unit.
Preferably, the combustion-supporting air heat exchange unit comprises a gas-gas heat exchanger, a flue gas inlet of the gas-gas heat exchanger is connected with a flue gas outlet of the denitration unit, a flue gas outlet of the gas-gas heat exchanger is connected with a flue gas inlet of the raw material preheating unit, and a combustion-supporting air outlet of the gas-gas heat exchanger is connected with a kiln head cover of the rotary kiln.
Preferably, an air inlet valve and a fan are arranged on the pipeline of the combustion-supporting air inlet of the air-air heat exchanger, and an air outlet valve is arranged on the pipeline of the combustion-supporting air outlet of the air-air heat exchanger.
Preferably, the raw meal preheating unit comprises at least one stage of cyclone preheater, and the cyclone preheater comprises a cyclone cylinder, and an air pipe and a material pipe which are connected with the cyclone cylinder.
The invention has the following advantages and beneficial effects:
1. according to the invention, raw materials are preheated and fed into the kiln, so that the temperature of flue gas discharged from the kiln is increased, the temperature window of SNCR denitration is met, the denitration pipeline is arranged at the tail of the kiln, and the SNCR denitration system is arranged, so that the flue gas NOx reaches the environment-friendly standard emission, and the method has the advantages of low investment and low operation cost.
2. The invention fully recovers the heat content of the flue gas discharged from the kiln by arranging multiphase combined heat exchange at the kiln tail. The first-stage heat exchange is gas-phase heat exchange, high-grade flue gas heat is transferred to tertiary air entering the kiln, and the temperature of combustion-supporting air in the kiln is increased; the second stage is gas phase-solid phase heat exchange, and transfers the heat of the cooled flue gas to the raw material entering the kiln to raise the temperature of the raw material entering the kiln. Through two-stage heat exchange heat recovery, the heat load in the rotary kiln is reduced, and the heat loss brought away by the flue gas is reduced, so that the heat consumption of the kiln system is reduced, and the fuel consumption is saved.
3. According to the invention, the raw material preheating unit is arranged at the kiln tail, so that the raw material entering the kiln is powder and is directly calcined in the kiln, the problems of low heat transfer speed of the material balls in the kiln and long time for calcining and defluorinating the material balls after granulation are avoided, and the calcining capacity of the rotary kiln is improved.
4. The invention arranges the raw material preheating unit at the tail of the kiln, heats the raw material entering the kiln to 500-700 ℃ after preheating treatment, saves the drying and heating time required after the material enters the kiln, reduces the heat load in the rotary kiln, improves the calcining capability of the rotary kiln, replaces the prior dry-process long kiln process, can reduce the specification of the kiln with the same output, and is beneficial to the large scale of a single line scale.
5. According to the invention, the flue gas and the combustion-supporting air entering the combustion-supporting air heat exchange unit are subjected to dust collection treatment, so that the combustion-supporting air heat exchange unit is prevented from being blocked due to dust accumulation in the long-term use process.
Drawings
FIG. 1 is a schematic diagram of a calcination system provided in accordance with one embodiment of the present invention;
FIG. 2 is a schematic diagram of a calcination system provided in example two of the present invention.
In the figure:
a-air; g 2-secondary air; g 3-tertiary air entering the kiln; g 4-kiln head residual air; g 5-low temperature flue gas; r-raw meal; f-pulverized coal; k-defluorinated tricalcium phosphate clinker;
1-raw meal preheating unit; 101-first stage cyclone; 102-a second stage cyclone; 103-a material distributing valve;
2-combustion-supporting air heat exchange unit; 201-gas heat exchanger; 202-a fan; 203-an air inlet valve; 204-an air outlet valve; 205-kiln tail cyclone dust collector; 206-kiln head cyclone dust collector;
3-a denitration unit; 301-a denitration pipeline; 302-a spray gun; 303-a denitrification system;
4-kiln tail smoke chamber; 5-a rotary kiln; 6-a cooling machine; 7-a kiln head burner; 8-kiln head cover.
The dotted line with an arrow is the airflow direction; the solid line with arrows indicates the flow direction of the raw material or pulverized coal.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, e.g., as being fixed or detachable or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The embodiment of the invention provides an environment-friendly tricalcium phosphate calcining process with low energy consumption, which comprises the following steps:
denitration of discharged flue gas: before the flue gas discharged from the kiln enters the kiln tail cyclone dust collector 205, NOx in the flue gas is removed through the denitration unit 3, the concentration of NOx in the flue gas entering a denitration pipeline is generally 800-1500 ppm, the temperature of the flue gas is 800-1000 ℃, a reducing agent (ammonia water) is sprayed into the bottom of the denitration pipeline 301 of the denitration unit 3, and the reducing agent in the denitration pipeline 301 and NOx in the flue gas are subjected to a reduction reaction, so that the removal of NOx in the flue gas is realized;
and (3) flue gas dedusting after discharging the kiln: high-temperature flue gas discharged from the kiln contains dust, the flue gas treated by the denitration unit 3 is subjected to dust collection treatment by a kiln tail cyclone dust collector 205 before entering the combustion-supporting air heat exchange unit 2, the collected dust returns to the rotary kiln 5, and the flue gas subjected to dust collection enters the combustion-supporting air heat exchange unit 2;
first-stage kiln discharge flue gas heat recovery: flue gas treated by the kiln tail cyclone dust collector 205 enters one channel in the combustion-supporting air heat exchange unit 2 through a flue gas inlet, tertiary air g3 entering the kiln enters the other channel in the combustion-supporting air heat exchange unit 2 through the combustion-supporting air inlet, high-temperature flue gas discharged from the kiln is a heating source, the tertiary air entering the kiln is a heat absorption source, the flue gas discharged from the kiln heats the tertiary air entering the kiln, the tertiary air entering the kiln is heated to 600-900 ℃ by utilizing the heat of the flue gas discharged from the kiln and then is introduced into the head of the rotary kiln 5, and the flue gas discharged from the kiln is reduced to 600-800 ℃ from 800-1000 ℃ to realize the primary recovery of the heat of the flue gas;
and (3) second-stage kiln discharge flue gas heat recovery: the flue gas from the combustion-supporting air heat exchange unit 2 enters a raw material preheating unit 1, and the raw material is heated, so that the raw material is heated to 500-700 ℃ from the normal temperature, and the flue gas is cooled to 300-500 ℃ from 600-800 ℃, and the secondary recovery of the heat of the flue gas is realized; the raw material entering the raw material preheating unit 1 is powdery, the fineness is 80um, and the screen residue is less than 50%;
calcining raw materials: calcining the preheated powdery raw material in a rotary kiln 5 to prepare defluorinated tricalcium phosphate clinker K; the preheated powdery raw material can also enter the denitration pipeline 301 partially, and because the temperature of the flue gas in the denitration pipeline 301 is 800-1000 ℃, the temperature of the materials entering the kiln can be increased, and the heat load of the rotary kiln 5 is reduced;
cooling clinker: and (5) cooling the defluorinated tricalcium phosphate clinker discharged from the kiln by a kiln head cooling machine 6 to prepare a finished product.
The kiln-entering tertiary air g3 is air or kiln-head residual air g4 discharged from the cooler 6, the kiln-head residual air discharged from the cooler 6 is subjected to dust collection treatment by the kiln-head cyclone dust collector 206, collected dust returns to the cooler 6, and the residual air subjected to dust collection enters the combustion-supporting air heat exchange unit 2.
The utility model provides an environment-friendly low energy consumption tricalcium phosphate system of calcining, includes rotary kiln 5, cooler 6, kiln tail smoke chamber 4, denitration unit 3, kiln tail cyclone 205, combustion-supporting wind heat transfer unit 2 and raw material preheating unit 1, kiln tail smoke chamber 4, rotary kiln 5 and cooler 6 link to each other in proper order, kiln tail smoke chamber 4, denitration unit 3, kiln tail cyclone 205, combustion-supporting wind heat transfer unit 2 and raw material preheating unit 1 link to each other in proper order.
Specifically, the denitration unit 3 is used for removing NOx in high-temperature flue gas discharged from the kiln, a flue gas inlet at the bottom of the denitration unit 3 is connected with a flue gas outlet of a kiln tail flue gas chamber 4, a flue gas outlet at the top of the denitration unit 3 is connected with a flue gas inlet of a kiln tail cyclone dust collector 205, a discharge port of the kiln tail cyclone dust collector 205 is connected with the kiln tail flue gas chamber 4, a flue gas outlet of the kiln tail cyclone dust collector 205 is connected with a flue gas inlet of a combustion-supporting air heat exchange unit 2, a flue gas outlet of the combustion-supporting air heat exchange unit 2 is connected with a flue gas inlet at the bottom end of a raw material preheating unit 1, a combustion-supporting air outlet of the combustion-supporting air heat exchange unit 2 is connected with a kiln head 8 of the rotary kiln 5, a flue gas outlet at the top end of the raw material preheating unit 1 discharges low-temperature flue gas, a feed inlet at the top end of the raw material preheating unit 1 is used for raw material feeding, a discharge port at the bottom end of the raw material preheating unit 1 is connected with the kiln tail flue gas chamber 4, and a kiln head burner 7 is arranged at the kiln head of the rotary kiln 5.
And the combustion-supporting air heat exchange unit 2 is positioned behind the denitration unit 3, and the high-temperature kiln discharge flue gas heats the tertiary air entering the kiln in the combustion-supporting air heat exchange unit 2. The raw material preheating unit 1 is positioned behind the combustion-supporting air heat exchange unit 2, the flue gas discharged from the combustion-supporting air heat exchange unit 2 enters the raw material preheating unit 1 to preheat the raw material, and the raw material from the raw material preheating unit 1 enters the rotary kiln 5 through a material pipe. The head of the kiln head burner 7 is positioned in the center of the kiln head of the rotary kiln 5, and fuel is sprayed from the kiln head of the rotary kiln 5. A kiln tail cyclone dust collector 205 is arranged between the denitration unit 3 and the combustion-supporting air heat exchange unit 2, dust in the kiln discharge smoke can be collected and returned to the rotary kiln 5, the dedusted smoke enters the combustion-supporting air heat exchange unit 2, and blockage caused by dust accumulation in the long-term use process of the combustion-supporting air heat exchange unit 2 is prevented.
The combustion-supporting air heat exchange unit 2 comprises a gas-gas heat exchanger 201, a smoke inlet of the gas-gas heat exchanger 201 is connected with a smoke outlet of a kiln tail cyclone dust collector 205, a smoke outlet of the gas-gas heat exchanger 201 is connected with a smoke inlet of the raw material preheating unit 1, and a combustion-supporting air outlet of the gas-gas heat exchanger 201 is connected with a kiln head cover 8 of the rotary kiln 5. An air inlet valve 203 and a fan 202 are arranged on a pipeline of a combustion-supporting air inlet of the air-air heat exchanger 201, and an air outlet valve 204 is arranged on a pipeline of a combustion-supporting air outlet of the air-air heat exchanger 201.
And a combustion-supporting air inlet of the gas-gas heat exchanger 201 is connected with a low-temperature residual air outlet of the cooler 6. A kiln head cyclone dust collector 206 is arranged between a combustion-supporting air inlet of the gas-gas heat exchanger 201 and the cooling machine 6, a residual air inlet of the kiln head cyclone dust collector 206 is connected with a low-temperature residual air outlet of the cooling machine 6, a discharge hole of the kiln head cyclone dust collector 206 is connected with the cooling machine 6, and a residual air outlet of the kiln head cyclone dust collector 206 is connected with a combustion-supporting air inlet of the combustion-supporting air heat exchange unit 2.
The combustion-supporting tertiary air is composed of air or kiln head residual air which is discharged from the cooler 6, the combustion-supporting tertiary air is blown into the air-air heat exchanger 201 through the fan 202, and an air inlet valve 203 and an air outlet valve 204 are respectively arranged in front of and behind the air-air heat exchanger 201, so that the air inlet and outlet amount of the combustion-supporting tertiary air is adjustable; the heated combustion-supporting tertiary air is connected with a kiln head cover 8 of the rotary kiln 5 and enters the rotary kiln 5.
The denitration unit 3 comprises a denitration pipeline 301, a denitration system 303 and a spray gun 302, the denitration pipeline 301 is positioned above the kiln tail smoke chamber 4, a smoke outlet at the top of the denitration pipeline 301 is connected with a smoke inlet of the combustion-supporting air heat exchange unit 2, the denitration system 303 is connected with the spray gun 302, the spray gun 302 is arranged at the bottom of the denitration pipeline 301, a reducing agent (ammonia water) is sprayed into the denitration pipeline 301 through the denitration system 303 via the spray gun 302, and NOx in kiln tail smoke is reduced into N 2 。
The raw material preheating unit 1 comprises at least one stage of cyclone preheater, and the cyclone preheater comprises a cyclone cylinder, and an air pipe and a material pipe which are connected with the cyclone cylinder. The discharge hole at the bottom end of the raw material preheating unit 1 is also connected with the denitration pipeline 301. In this embodiment, two-stage cyclone preheaters, namely a first-stage cyclone 101 and a second-stage cyclone 102, are provided, a flue gas inlet of the second-stage cyclone 102 is connected with a flue gas outlet of the gas-gas heat exchanger 201, a discharge port of the second-stage cyclone 102 is connected with the kiln tail smoke chamber 4 and the denitration pipeline 301 through a material distributing valve 103, a flue gas outlet of the second-stage cyclone 102 is connected with a flue gas inlet of the first-stage cyclone 101, and a discharge port of the first-stage cyclone 101 is connected with a connecting pipeline between the second-stage cyclone 102 and the gas-gas heat exchanger 201.
And refractory materials are arranged in the cyclone preheater, the rotary kiln 5, the cooler 6, the denitration pipeline 301 and the combustion-supporting air inlet pipeline and the combustion-supporting air outlet pipeline of the gas-gas heat exchanger 201.
The present invention is described in further detail below.
Example 1
Referring to fig. 1, the present embodiment provides an environment-friendly tricalcium phosphate calcining system with low energy consumption. The device mainly comprises a rotary kiln 5, a cooler 6, a kiln tail smoke chamber 4, a denitration pipeline 301, a kiln tail cyclone dust collector 205, a gas-gas heat exchanger 201 and a cyclone preheater.
The front end of the rotary kiln 5 is provided with a kiln head cover 8, and the front of the kiln head cover 8 is connected with a kiln head burner 7; fuel is sprayed into the rotary kiln 5 through a kiln head burner 7 for combustion, and heat is provided for the calcination of the materials in the rotary kiln 5. The kiln tail of the rotary kiln 5 is connected with a kiln tail smoke chamber 4, smoke generated by combustion in the rotary kiln 5 is discharged through the kiln tail smoke chamber 4, and the concentration of NOx in the combustion smoke is generally 800-1500 ppm. The calcining temperature of the materials in the kiln is about 1400 ℃, the clinker discharged from the kiln enters a cooler 6, air a is introduced into the cooler 6, and the clinker is cooled to be below 150 ℃. The hot air at the front end of the cooler 6 is secondary air g2, the temperature is 800-1200 ℃, and combustion-supporting air is provided for the calcination in the kiln.
The gas-gas heat exchanger 201 is located after the denitration duct 301. A kiln tail cyclone dust collector 205 is arranged between the denitration pipeline 301 and the gas-gas heat exchanger 201, dust in the flue gas is collected and returned to the rotary kiln 5, and the dedusted flue gas enters the gas-gas heat exchanger 201, so that the blockage caused by dust accumulation in the long-term use process of the gas-gas heat exchanger 201 is prevented. The high-temperature flue gas heats the tertiary air g3 entering the kiln in the gas-gas heat exchanger 201, the high-temperature flue gas of the cyclone dust collector 205 at the tail of the kiln as a heating source, the tertiary air g3 entering the kiln as a heat absorption source, the tertiary air entering the kiln is heated to 600-900 ℃ by utilizing the heat of the high-temperature flue gas exiting the kiln, and then the tertiary air entering the kiln is introduced into the rotary kiln 5, and the temperature of the flue gas exiting the kiln is reduced to 600-800 ℃ from 800-1000 ℃, so that the primary recovery of the heat of the flue gas is realized. The preheated tertiary air g3 is connected to a kiln hood 8 through a pipeline, is mixed with the secondary air g2 and then enters the kiln, and provides combustion-supporting air for fuel combustion.
The cyclone preheater has two stages, and after gas-solid heat exchange and cyclone separation, the raw material temperature is raised and the flue gas temperature is reduced to 300-500 deg.C. The raw meal is preheated in a secondary cyclone preheater. The raw material R is powder with fineness of 80um and screen residue less than 50 percent and is at normal temperature. Raw materials are fed into an outlet air pipe of the second-stage cyclone 102 through a pipeline to perform gas-solid heat exchange, the raw materials enter the first-stage cyclone 101 under the drive of airflow, after the gas-solid separation is performed in the first-stage cyclone 101, the materials are fed into the outlet air pipe of the gas-gas heat exchanger 201 from a feeding pipe of the first-stage cyclone 101, the raw materials enter the second-stage cyclone 102 under the drive of airflow, and after the gas-solid separation is performed by the second-stage cyclone 102, the raw materials are fed into a kiln tail smoke chamber 4.
And after entering a kiln tail smoke chamber 4, the raw material discharged from the cyclone preheater is calcined in a rotary kiln 5, the raw material is sintered into clinker, and the clinker discharged from the kiln is cooled by a cooler 6 to prepare a clinker product. Part of the hot air out of the cooler 6 enters the kiln as high-temperature secondary air g2; the other part is discharged from the kiln head and is used as kiln head residual air g4, the temperature of the kiln head residual air is 200-400 ℃, and a drying heat source is provided for the grinding link of the raw materials and the fuel.
Example 2
Referring to fig. 2, the difference from the embodiment 1 is that the tertiary air g3 entering the kiln is hot air from the cooling machine 6, the temperature is 200-400 ℃, and the enthalpy of the tertiary air is higher than that of normal temperature air, which is beneficial to increasing the temperature of the tertiary air entering the kiln and reducing the heat consumption. The embodiment is suitable for the conditions that the raw and fuel water is little and the kiln head residual air g4 has rich heat. After the tertiary air g3 entering the kiln is induced from the kiln head cooler 6, the tertiary air is subjected to dust collection treatment by the kiln head cyclone dust collector 206 and enters the gas-gas heat exchanger 201, so that the blockage caused by dust accumulation in the long-term use process of the gas-gas heat exchanger 201 is prevented.
The material pipe of the second-stage cyclone cylinder 102 is provided with a material distributing valve 103, the material pipe is divided into two branches, one branch is connected with the kiln tail smoke chamber 4, and the other branch is connected with a denitration pipeline 301. The opening degree of the material distributing valve 103 can be adjusted between 0 percent and 100 percent, so that the material distribution of raw materials is realized, and after the raw materials are distributed into the denitration pipeline 301, the temperature of the materials entering the kiln can be increased and the heat load of the rotary kiln 5 is reduced because the temperature of the flue gas in the denitration pipeline 301 is 800-1000 ℃.
In conclusion, the invention preheats the raw materials into the kiln, thereby improving the temperature of the flue gas discharged from the kiln, meeting the temperature window of SNCR denitration, ensuring that the NOx in the flue gas reaches the environmental protection standard and is discharged, and having less investment and low operation cost. The heat enthalpy of the smoke discharged from the kiln is fully recovered by arranging multiphase combined heat exchange at the kiln tail. The first-stage heat exchange is gas-phase heat exchange, high-grade flue gas heat is transferred to tertiary air entering the kiln, and the temperature of combustion-supporting air in the kiln is increased; the second stage is gas-solid phase heat exchange, and the heat of the cooled flue gas is transferred to the kiln raw material to increase the temperature of the kiln raw material. Through two-stage heat exchange heat recovery, the heat load in the rotary kiln is reduced, and the heat loss brought away by the flue gas is reduced, so that the heat consumption of the kiln system is reduced, and the fuel consumption is saved. The raw material preheating unit is arranged at the tail of the kiln, the temperature of the raw materials entering the kiln is raised to 500-700 ℃ after the raw materials enter the kiln, the drying and heating time required after the materials enter the kiln is saved, the heat load in the rotary kiln is reduced, the calcining capacity of the rotary kiln is improved, the existing dry-process long-kiln process is replaced, the specification of the kiln with the same output can be reduced, and the single-line-scale large-scale production is facilitated.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: it is to be understood that modifications may be made to the technical solutions described in the foregoing embodiments, or some or all of the technical features may be equivalently replaced, and the modifications or the replacements may not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (14)
1. An environment-friendly tricalcium phosphate calcining process with low energy consumption is characterized in that: the method comprises the following steps:
denitration of kiln gas discharged: removing NOx in the flue gas discharged from the kiln through a denitration unit, and spraying a reducing agent at the bottom of a denitration pipeline of the denitration unit to enable the reducing agent and the NOx in the flue gas to perform a reduction reaction so as to remove the NOx in the flue gas;
first-stage kiln discharge flue gas heat recovery: flue gas discharged from the denitration unit enters a combustion-supporting air heat exchange unit through a flue gas inlet, tertiary air entering the kiln enters the combustion-supporting air heat exchange unit through the combustion-supporting air inlet, the heat of the flue gas discharged from the kiln heats the tertiary air entering the kiln to 600-900 ℃ and then is introduced into the kiln head of the rotary kiln, and the temperature of the flue gas discharged from the kiln is reduced to 600-800 ℃ from 800-1000 ℃ so as to realize the primary recovery of the heat of the flue gas;
and (3) second-stage discharge flue gas heat recovery: the flue gas from the combustion-supporting air heat exchange unit enters a raw material preheating unit to heat the raw material, so that the raw material is heated to 500-700 ℃ from the normal temperature, and the temperature of the flue gas is reduced to 300-500 ℃ from 600-800 ℃, thereby realizing the secondary recovery of the heat of the flue gas;
calcining raw materials: calcining the preheated powdery raw material in a rotary kiln to prepare defluorinated tricalcium phosphate clinker;
cooling clinker: and (5) cooling the defluorinated tricalcium phosphate clinker discharged from the kiln by a kiln head cooling machine to prepare a finished product.
2. The calcination process of environment-friendly tricalcium phosphate with low energy consumption according to claim 1, further comprising the steps of removing dust from kiln flue gas: and before entering the combustion-supporting air heat exchange unit, the flue gas discharged from the denitration unit is subjected to dust collection treatment by a kiln tail cyclone dust collector, the collected dust returns to the rotary kiln, and the flue gas subjected to dust collection enters the combustion-supporting air heat exchange unit.
3. The process of calcining green tricalcium phosphate with low energy consumption as claimed in claim 1, wherein the preheated powdered raw material can be partially fed into the denitration pipeline.
4. The process for calcining the environment-friendly tricalcium phosphate with low energy consumption as claimed in claim 1, wherein the tertiary air entering the kiln is air or kiln head residual air coming out of a cooler, the kiln head residual air coming out of the cooler is subjected to dust collection treatment by a kiln head cyclone dust collector, the collected dust returns to the cooler, and the residual air after dust collection enters the combustion-supporting air heat exchange unit.
5. The process of calcining environment-friendly tricalcium phosphate with low energy consumption as claimed in claim 1, wherein the raw material fed into the raw material preheating unit is in powder form with fineness of 80um and a mesh size of less than 50%.
6. The utility model provides a tricalcium phosphate system of calcining of low energy consumption of environment-friendly, its characterized in that, preheats the unit including rotary kiln, cooler, kiln tail smoke chamber, denitration unit, combustion-supporting wind heat transfer unit and raw material, kiln tail smoke chamber, rotary kiln and cooler link to each other in proper order, the exhanst gas outlet of kiln tail smoke chamber links to each other with the flue gas inlet of denitration unit, the exhanst gas outlet of denitration unit links to each other with the flue gas inlet of combustion-supporting wind heat transfer unit, the exhanst gas outlet of combustion-supporting wind heat transfer unit links to each other with the flue gas inlet of raw material preheating unit bottom, the combustion-supporting wind outlet of stating combustion-supporting wind heat transfer unit links to each other with the kiln hood of rotary kiln, the raw material preheat the discharge gate of unit bottom with kiln tail smoke chamber links to each other, the kiln head department of rotary kiln is provided with kiln head combustor.
7. The environment-friendly type tricalcium phosphate calcining system with low energy consumption as claimed in claim 6, wherein said denitration unit comprises a denitration pipeline, a denitration system and a spray gun, said denitration pipeline is located above the kiln tail smoke chamber, the top smoke outlet of said denitration pipeline is connected with the smoke inlet of the combustion-supporting air heat exchange unit, said denitration system is connected with the spray gun, said spray gun is arranged at the bottom of the denitration pipeline.
8. The environment-friendly tricalcium phosphate calcining system with low energy consumption as claimed in claim 7, wherein the discharge outlet at the bottom end of the raw meal preheating unit is connected with the denitration pipeline.
9. The environment-friendly tricalcium phosphate calcining system with low energy consumption as claimed in claim 6, wherein a kiln tail cyclone dust collector is arranged between the flue gas inlet of the combustion-supporting air heat exchange unit and the flue gas outlet of the denitration unit, the flue gas inlet of the kiln tail cyclone dust collector is connected with the flue gas outlet of the denitration unit, the flue gas outlet of the kiln tail cyclone dust collector is connected with the flue gas inlet of the combustion-supporting air heat exchange unit, and the discharge port of the kiln tail cyclone dust collector is connected with the kiln tail smoke chamber.
10. The system for calcining environment-friendly tricalcium phosphate with low energy consumption as claimed in claim 6, wherein the combustion air inlet of said combustion air heat exchange unit is connected with the low-temperature residual air outlet of the cooling machine.
11. The system for calcining tricalcium phosphate of environment protecting type and low energy consumption as claimed in claim 10, wherein a kiln head cyclone dust collector is arranged between the combustion air inlet of said combustion air heat exchange unit and the cooler, the residual air inlet of said kiln head cyclone dust collector is connected with the low temperature residual air outlet of the cooler, the discharge port of said kiln head cyclone dust collector is connected with the cooler, and the residual air outlet of said kiln head cyclone dust collector is connected with the combustion air inlet of the combustion air heat exchange unit.
12. The environment-friendly tricalcium phosphate calcining system with low energy consumption as claimed in claim 6, wherein said combustion-supporting air heat exchange unit comprises a gas-gas heat exchanger, the flue gas inlet of said gas-gas heat exchanger is connected with the flue gas outlet of the denitration unit, the flue gas outlet of said gas-gas heat exchanger is connected with the flue gas inlet of the raw meal preheating unit, and the combustion-supporting air outlet of said gas-gas heat exchanger is connected with the kiln head cover of the rotary kiln.
13. The system for calcining tricalcium phosphate with environment protection and low energy consumption as claimed in claim 12, wherein an air inlet valve and a fan are disposed on the pipeline of the combustion-supporting air inlet of the gas-gas heat exchanger, and an air outlet valve is disposed on the pipeline of the combustion-supporting air outlet of the gas-gas heat exchanger.
14. The environment-friendly type low energy consumption tricalcium phosphate calcining system of claim 6, wherein the raw meal preheating unit comprises at least one stage of cyclone preheater, the cyclone preheater comprises a cyclone cylinder, and an air pipe and a material pipe connected with the cyclone cylinder.
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| CN117213227A (en) * | 2023-09-15 | 2023-12-12 | 中材建设有限公司 | Method and system for obtaining high-concentration carbon dioxide flue gas based on calcined cement clinker |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117213227A (en) * | 2023-09-15 | 2023-12-12 | 中材建设有限公司 | Method and system for obtaining high-concentration carbon dioxide flue gas based on calcined cement clinker |
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