CN111285377A - System and method for producing fumed silica - Google Patents
System and method for producing fumed silica Download PDFInfo
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- CN111285377A CN111285377A CN201811497813.0A CN201811497813A CN111285377A CN 111285377 A CN111285377 A CN 111285377A CN 201811497813 A CN201811497813 A CN 201811497813A CN 111285377 A CN111285377 A CN 111285377A
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
- C01B33/181—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process
- C01B33/183—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process by oxidation or hydrolysis in the vapour phase of silicon compounds such as halides, trichlorosilane, monosilane
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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Abstract
The invention discloses a system and a method for producing fumed silica, wherein the system comprises the following components: the combustor is used for introducing raw materials of chlorosilane, hydrogen, oxygen or air for ignition and combustion; the reaction furnace is connected with the combustor, the outlet of the combustor is arranged in the reaction furnace, the reaction furnace is a closed reaction furnace, and raw materials of chlorosilane, hydrogen, oxygen or air are combusted in the reaction furnace to generate a hydrolysis reaction to generate fumed silica. The reaction furnace adopted by the system for producing the fumed silica is a closed reaction furnace, so that the influence of cold air sucked into the outside on the material concentration in the reaction furnace is avoided, the control of the reaction temperature in the reaction furnace is improved, and the problem that part of large-particle silica is generated due to low-temperature hydrolysis of chlorosilane in the reaction furnace is avoided, so that the particle size ratio and the specific surface area of the fumed silica generated by reaction in the reaction furnace are uniformly distributed, the product stability can be improved, the fluctuation range of the specific surface area of a fumed silica product is greatly reduced, and the application performance of the product is improved.
Description
Technical Field
The invention belongs to the technical field of fumed silica production, and particularly relates to a system and a method for producing fumed silica.
Background
The gas phase silicon dioxide is a fine and special amorphous powder material prepared by hydrolyzing chlorosilane at high temperature through oxyhydrogen flame, and the average primary particle size is about 7-40 nanometers. The fumed silica has small particle size, large specific surface area, strong surface adsorption, large surface energy, high chemical purity, good dispersion performance, excellent stability, reinforcement, thickening property and thixotropy, and is widely applied to various subject fields.
At present, domestic fumed silica has the following problems: (1) the product quality fluctuation is large, particularly the fluctuation range of the specific surface area of fumed silica is large, the thickening, thixotropic and reinforcing properties are unstable, and certain influence is caused on downstream production; (2) the fumed silica contains a certain amount of large-particle silica, which is mainly produced by low-temperature hydrolysis and high-temperature sintering, influences the transparency of downstream products, limits the application field of the fumed silica, and has a large gap with foreign products.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a system and a method for producing fumed silica aiming at the defects in the prior art, so that the problem that part of large-particle silica is generated by low-temperature hydrolysis of chlorosilane in a reaction furnace is avoided, and the particle size ratio and the specific surface area distribution of fumed silica generated by reaction in the reaction furnace are uniform.
The technical scheme adopted for solving the technical problem of the invention is to provide a system for producing fumed silica, which comprises the following steps:
the combustor is used for introducing raw materials of chlorosilane, hydrogen, oxygen or air for ignition and combustion;
the reaction furnace is connected with the combustor, the outlet of the combustor is arranged in the reaction furnace, the reaction furnace is a closed reaction furnace, and raw materials of chlorosilane, hydrogen, oxygen or air are combusted in the reaction furnace to generate a hydrolysis reaction to generate fumed silica.
Preferably, the burner includes: the reactor comprises a first channel, a second channel and a third channel which are sequentially arranged from inside to outside, wherein the first channel, the second channel and the third channel are all communicated with an outlet of a combustor, the first channel is used for introducing raw materials, the second channel is used for introducing combustion gas, and the third channel is used for introducing protective gas to cool the second channel and supplement oxygen in the reactor.
Preferably, a built-in mixer is further arranged in the first channel and used for mixing the gas in the first channel.
Preferably, the internal mixer is disposed at an axially central position of the first passage.
Preferably, the reaction furnace includes: the furnace chamber and set up the jacket outside the furnace chamber, the jacket is used for letting in the refrigerant and cools off the furnace chamber.
Preferably, the system for producing fumed silica further comprises:
and the impurity removal device is connected with the reaction furnace and is used for removing impurities in the gas-phase silicon dioxide.
Preferably, the impurity removing device includes:
the deacidification furnace is connected with the reaction furnace and is used for removing hydrogen chloride gas in the gas-phase silicon dioxide;
and the drying furnace is connected with the deacidification furnace and is used for drying and dehydrating the fumed silica to obtain the finished fumed silica.
Preferably, the deacidification furnace is heated by radiation.
Preferably, the impurity removing device further includes: a collector and a bag filter, wherein the collector and the bag filter are arranged between the reaction furnace and the deacidification furnace,
the gas-phase silicon dioxide and the tail gas in the reaction furnace enter the collector, and the collector is used for collecting the gas-phase silicon dioxide into gas-phase silicon dioxide with a preset granularity;
the inlet of the bag filter is connected with the collector, the solid outlet of the bag filter is connected with the inlet of the deacidification furnace, the bag filter is used for filtering out fumed silica, and the filtered fumed silica flows into the deacidification furnace again.
Preferably, the gas outlet of the deacidification furnace is connected with the inlet of the bag filter, and the gas discharged from the gas outlet of the deacidification furnace flows into the bag filter again for filtering.
Preferably, the system for producing fumed silica further comprises:
and the tail gas treatment device is connected with the impurity removal device and is used for treating hydrogen chloride in the gas discharged by the impurity removal device.
Preferably, the exhaust gas treatment device includes:
the hydrogen chloride absorption tower is connected with the impurity removal device and is used for absorbing hydrogen chloride in the gas discharged by the impurity removal device;
the desorption tower is connected with the tower kettle of the hydrogen chloride absorption tower and is used for desorbing hydrogen chloride in tower kettle liquid of the hydrogen chloride absorption tower;
and the basic absorption tower is connected with the top of the hydrogen chloride absorption tower and is used for absorbing residual hydrogen chloride in the gas discharged from the hydrogen chloride absorption tower.
Preferably, the bottom of the desorption tower is connected to the inlet of the hydrogen chloride absorption tower, and the bottom liquid of the desorption tower is refluxed to the hydrogen chloride absorption tower as the eluent.
The present invention also provides a method for producing fumed silica using the above system, comprising:
introducing chlorosilane, hydrogen, oxygen or air as raw materials into a combustor to ignite and burn, and introducing the raw materials into a reaction furnace, wherein the pressure in the reaction furnace is-5 kpa, the temperature is 1400-1750 ℃, and the raw materials are burnt to generate a hydrolysis reaction to generate fumed silica.
Preferably, using the system described above, the method further comprises the steps of:
introducing raw materials of chlorosilane, hydrogen, oxygen or air into the first channel;
introducing combustion gas into the second channel to ignite chlorosilane, hydrogen, oxygen or air in the first channel and perform surface modification on the generated fumed silica;
and introducing protective gas into the third channel to cool the second channel and supplement oxygen in the reaction furnace to maintain reaction balance.
Preferably, the combustion gas is hydrogen, oxygen or air; the protective gas is air or oxygen.
Preferably, using the system described above, the method further comprises the steps of:
introducing fumed silica generated after combustion in the reaction furnace into a deacidification furnace for deacidification, wherein the temperature in the deacidification furnace is 400-550 ℃;
and (3) introducing the fumed silica deacidified in the deacidifying furnace into a drying furnace for drying, wherein the temperature in the drying furnace is 200-400 ℃.
Preferably, the temperature of the deacidification gas introduced into the deacidification furnace is 450-550 ℃, and the deacidification gas is used for heating and deacidifying the gas-phase silicon dioxide introduced into the deacidification furnace.
The invention provides a system and a method for producing fumed silica, wherein the adopted reaction furnace is a closed reaction furnace, thereby avoiding the influence of cold air sucked into the outside on the material concentration in the reaction furnace, improving the control of the reaction temperature in the reaction furnace, and avoiding the generation of partial large-particle silica by low-temperature hydrolysis of chlorosilane in the reaction furnace, so that the particle size ratio and the specific surface area of the fumed silica generated by reaction in the reaction furnace are uniformly distributed, the product stability can be improved, and the fluctuation range of the specific surface area of the fumed silica product is within +/-30 m from the standard value2Lifting standard value of +/-10 m/g2And/g, the content of the sintered silicon dioxide with the particle size of more than 45um is reduced by 60 mas%, and the application performance of the product is improved.
Drawings
FIG. 1 is a schematic configuration diagram of a system for producing fumed silica in example 2 of the invention;
FIG. 2 is a schematic view of the structure of a burner and a reactor in example 2 of the present invention.
In the figure: 1-a burner; 11-the outlet of the burner; 2-a reaction furnace; 21-furnace chamber; 22-a jacket; 3-a first channel; 31-first channel entrance; 4-a second channel; 41-second channel entrance; 5-a third channel; 51-third channel entrance; 6-a built-in mixer; 7-a vaporization heater; 8-a first mixer; 9-a first conduit; 10-a second conduit; 12-a second mixer; 13-a third conduit; 14-a fourth conduit; 15-a fifth conduit; 16-a flange; 17-a concentrator; 18-a bag filter; 19-deacidifying furnace; 20-drying in a furnace; 23-a storage bin; a 24-hydrogen chloride absorption tower; 25-a resolution column; a 26-basic absorber column; 27-a conveyor; 28-induced draft fan; 29-a reboiler at the bottom of the desorption tower; 30-meter port; 31-deacidified gas line; 32-heater.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Reference will now be made in detail to embodiments of the present patent, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present patent and are not to be construed as limiting the present patent.
Example 1
The present embodiment provides a system for producing fumed silica, comprising:
the combustor is used for introducing raw materials of chlorosilane, hydrogen, oxygen or air for ignition and combustion;
the reaction furnace is connected with the combustor, the outlet of the combustor is arranged in the reaction furnace, the reaction furnace is a closed reaction furnace, and raw materials of chlorosilane, hydrogen, oxygen or air are combusted in the reaction furnace to generate a hydrolysis reaction to generate fumed silica.
The present embodiment also provides a method for producing fumed silica using the above system, comprising:
introducing chlorosilane, hydrogen, oxygen or air as raw materials into a combustor to ignite and burn, and introducing the raw materials into a reaction furnace, wherein the pressure in the reaction furnace is-5 kpa, the temperature is 1400-1750 ℃, and the raw materials are burnt to generate a hydrolysis reaction to generate fumed silica.
The embodiment provides a system and a method for producing fumed silica, because the adopted reaction furnace is a closed reaction furnace, the influence of cold air sucked into the outside on the material concentration in the reaction furnace is avoided, the control of the reaction temperature in the reaction furnace is improved, and the generation of partial large-particle silica due to low-temperature hydrolysis of chlorosilane in the reaction furnace is avoided, so that the particle size ratio and the specific surface area of fumed silica generated by reaction in the reaction furnace are uniformly distributed, the product stability can be improved, and the application performance of the product is improved.
Example 2
As shown in fig. 1, the present embodiment provides a system for producing fumed silica, comprising:
the combustor 1 is used for introducing raw materials of chlorosilane, hydrogen, oxygen or air for ignition and combustion;
the reaction furnace 2 is connected with the combustor 1, an outlet 11 of the combustor is arranged in the reaction furnace 2, the reaction furnace 2 is a closed reaction furnace 2, and raw materials of chlorosilane, hydrogen, oxygen or air are combusted in the reaction furnace 2 to generate a hydrolysis reaction to generate fumed silica.
As shown in fig. 2, it should be noted that the burner 1 in the present embodiment includes: the reaction furnace comprises a first channel 3, a second channel 4 and a third channel 5 which are sequentially arranged from inside to outside, wherein the first channel 3, the second channel 4 and the third channel 5 are all communicated with an outlet 11 of the combustor, the first channel 3 is used for introducing raw materials, the second channel 4 is used for introducing combustion gas, and the third channel 5 is used for introducing protective gas to cool the second channel 4 and supplement oxygen in the reaction furnace 2. The first channel 3 comprises a first channel inlet 31, the second channel 4 comprises a second channel inlet 41, the third channel 5 comprises a third channel inlet 51, and the burner 1 is further provided with a meter port 30 for viewing meter readings.
In the present embodiment, an internal mixer 6 is further disposed in the first passage 3 for mixing the gas in the first passage 3.
Note that, in the present embodiment, the internal mixer 6 is provided at an axially central position of the first passage 3.
In this embodiment, the reaction furnace 2 includes: the oven cavity 21 and the jacket 22 arranged outside the oven cavity 21, wherein the jacket 22 is used for introducing a cooling medium to cool the oven cavity 21.
Specifically, the system for producing fumed silica in the present embodiment further includes:
the vaporization heater 7 is used for vaporizing and heating the raw material chlorosilane;
the first mixer 8 is connected with a first pipeline 9 and a second pipeline 10, the first pipeline 9 is used for introducing raw material hydrogen into the first mixer 8, and the second pipeline 10 is used for introducing raw material oxygen or air into the first mixer 8;
a second mixer 12 arranged between the first mixer 8 and the burner 1, wherein the inlet of the second mixer 12 is connected with the outlet of the first mixer 8, the outlet of the second mixer 12 is connected with the first channel 3, the inlet of the second mixer 12 is also connected with the vaporization heater 7, and the second mixer 12 is used for mixing raw material chlorosilane, hydrogen, oxygen or air;
the third pipeline 13 is connected with the second channel 4, and the third pipeline 13 is used for introducing combustion gas air into the second channel 4;
the fourth pipeline 14 is connected with the second channel 4, and the fourth pipeline 14 is used for introducing combustion gas hydrogen into the second channel 4;
and the fifth pipeline 15 is connected with the third channel 5, and the fifth pipeline 15 is used for introducing shielding gas into the third channel 5.
Specifically, the burner 1 and the reaction furnace 2 in this embodiment are connected by a flange 16, and are in sealed connection, the reaction furnace 2 and the burner 1 are tightly combined to be in sealed connection, and no gap exists between the two. The reaction furnace 2 can not suck cold air from the outside, the air or oxygen to be supplemented is supplemented by the combustor 1 after being metered, and the flow of each reaction material can be accurately metered, so that the reaction ratio and the reaction temperature are controlled, the particle size and the specific surface area of the generated fumed silica product are more uniformly distributed, and the product quality is more stable. In addition, no cold air enters the reaction furnace 2, so that the low-temperature hydrolysis of chlorosilane can be avoided, and the generation of large-particle silicon dioxide can be effectively reduced.
It should be noted that the system for producing fumed silica described in this embodiment further includes:
and the impurity removal device is connected with the reaction furnace 2 and is used for removing impurities in the gas-phase silicon dioxide.
It should be noted that, in this embodiment, the impurity removing device further includes:
the collector 17 is connected with the reaction furnace 2, the fumed silica and the tail gas in the reaction furnace 2 enter the collector 17, and the collector 17 is used for collecting the fumed silica into fumed silica with a preset particle size;
a bag filter 18, wherein the inlet of the bag filter 18 is connected with the collector 17, the bag filter 18 is used for filtering out fumed silica, and the filtered fumed silica flows into the deacidification furnace 19 again;
an inlet of the deacidification furnace 19 is connected with a solid outlet of the bag filter 18, the deacidification furnace 19 is used for removing hydrogen chloride gas in the gas-phase silicon dioxide, and the heating mode of the deacidification furnace 19 is radiation heating in the embodiment; 19 bottoms of deacidification stove are equipped with the deacidification gas entry, let in deacidification gas in to deacidification stove 19 through the deacidification gas entry, and deacidification gas includes water vapor and compressed air and constitutes, and deacidification gas pipeline 31 and deacidification gas access connection are provided with heater 32 on the deacidification gas pipeline 31, and heater 32 is used for carrying deacidification gas in to deacidification stove 19 through deacidification gas pipeline 31 to heating deacidification gas. The deacidification gas forms superheated steam after being heated, so that the deacidification steam can be prevented from being liquefied and contacting with the fumed silica to cause the fumed silica to agglomerate to form large-particle fumed silica.
The drying furnace 20 is connected with the solid outlet of the deacidification furnace 19, and the drying furnace 20 is used for drying and dehydrating the fumed silica to obtain a finished product fumed silica;
and a storage bin 23 connected with the drying furnace 20 and used for storing the finished fumed silica.
Specifically, the deacidification furnace 19 in this embodiment is a secondary deacidification furnace 19, two deacidification furnaces 19 are connected in series, and the drying furnace 20 is a primary drying furnace 20.
In this embodiment, the gas outlet of the deacidification furnace 19 is connected to the inlet of the bag filter 18, and the gas discharged from the gas outlet of the deacidification furnace 19 is filtered by the bag filter 18.
It should be noted that the system for producing fumed silica described in this embodiment further includes:
and the tail gas treatment device is connected with the impurity removal device and is used for treating hydrogen chloride in the gas discharged by the impurity removal device.
It should be noted that, the exhaust gas treatment device in this embodiment includes:
a hydrogen chloride absorption tower 24 connected to the gas outlet of the bag filter 18, the hydrogen chloride absorption tower 24 being configured to absorb hydrogen chloride in the off-gas discharged from the gas outlet of the bag filter 18;
the desorption tower 25 is connected with the tower kettle of the hydrogen chloride absorption tower 24, the desorption tower 25 is used for desorbing hydrogen chloride in the tower kettle liquid of the hydrogen chloride absorption tower 24, and the purity of the desorbed hydrogen chloride is not lower than 98 mas%; the hydrogen chloride is separated from other components in the tail gas through the analysis of the analysis tower 25, the hydrogen chloride is delivered, the problem of treatment of by-product low-concentration hydrochloric acid is avoided, and the problems of high storage and transportation risks and difficult sale of the low-concentration hydrochloric acid are solved.
The basic absorption tower 26 is connected with the top of the hydrogen chloride absorption tower 24, the basic absorption tower 26 is used for absorbing residual hydrogen chloride and chlorine in the gas discharged from the hydrogen chloride absorption tower 24, and the tail gas obtained after the treatment of the basic absorption tower 26 can be directly discharged.
Of course, the hydrogen chloride absorption tower 24 may be single-stage or multi-stage, the desorption tower 25 may be single-stage or multi-stage, and the basic absorption tower 26 may be single-stage or multi-stage.
Specifically, the system for producing fumed silica in the present embodiment further includes:
and a conveyor 27 arranged between the bag filter 18 and the deacidification tower, wherein the conveyor 27 is respectively connected with the bag filter 18 and the deacidification tower, and the conveyor 27 is used for conveying fumed silica.
Specifically, the system for producing fumed silica in the present embodiment further includes:
and the induced draft fan 28 is arranged between the bag filter 18 and the hydrogen chloride absorption tower 24, the induced draft fan 28 is respectively connected with the bag filter 18 and the hydrogen chloride absorption tower 24, and the induced draft fan 28 is used for conveying tail gas.
Specifically, the system for producing fumed silica in the present embodiment further includes:
the desorption tower kettle reboiler 29 is connected to the desorption tower 25, and the desorption tower kettle reboiler 29 is used for heating the tower kettle liquid of the desorption tower 25 and then conveying the heated tower kettle liquid back to the desorption tower 25.
In the present embodiment, the bottom of the desorption tower 25 is connected to the inlet of the hydrogen chloride absorption tower 24, the bottom of the desorption tower 25 is dilute hydrochloric acid, the bottom of the desorption tower 25 is refluxed to the hydrogen chloride absorption tower 24 to be used as a leacheate to continuously absorb hydrogen chloride in the tail gas, and concentrated hydrochloric acid generated after hydrogen chloride absorption enters the desorption tower 25.
The present embodiment also provides a method for producing fumed silica using the above system, comprising:
(1) heating and vaporizing raw material chlorosilane in a vaporization heater 7, wherein the vaporization pressure is 0.05-0.25 MPa, and the temperature is 70-110 ℃;
introducing raw material hydrogen into a first mixer 8 through a first pipeline 9, introducing raw material air into the first mixer 8 through a second pipeline 10, drying and preheating the air, controlling the dew point to be lower than-50 ℃ and the temperature to be 120-170 ℃, uniformly mixing the gas in the first mixer 8, then introducing the gas into a second mixer 12, introducing vaporized chlorosilane into the second mixer 12, mixing the gas in the second mixer 12 at the temperature of 90-180 ℃, uniformly mixing the gas in the second mixer 12, then introducing the gas into a first channel 3, and mixing the gas through a built-in mixer 6 in the first channel 3;
introducing combustion gas air into the second channel 4 through the third pipeline 13, introducing combustion gas hydrogen into the second channel 4 through the fourth pipeline 14, mixing the combustion gas air and the hydrogen in the second channel 4, and controlling the gas flow velocity in the second channel 4 to be 80-120 m/s;
introducing protective gas air into the third channel 5 through a fifth pipeline 15, wherein the temperature of the protective gas is 120-170 ℃;
(2) igniting the combustor 1, igniting and burning chlorosilane, hydrogen and air in the first channel 3 by combustion gas air and hydrogen introduced into the second channel 4, performing surface modification on the generated fumed silica, and cooling the gas in the first channel 3; the protective gas air introduced into the third channel 5 cools the second channel 4 and supplements oxygen in the reaction furnace 2 to maintain reaction balance.
Igniting and burning raw materials of chlorosilane, hydrogen and air, and feeding the raw materials into a reaction furnace 2, wherein the pressure in the reaction furnace 2 is-5 kpa, the temperature is 1400 ℃, a hydrolysis reaction is carried out to generate fumed silica and hydrogen chloride, the tail gas of the reaction furnace 2 is obtained at an outlet of the reaction furnace 2, and the tail gas of the reaction furnace 2 comprises: the chlorine-containing gas comprises 50-80 mas% of nitrogen, 1-7 mas% of oxygen, 1-8 mas% of water vapor, 15-30 mas% of hydrogen chloride and 0.5-2 mas% of chlorine.
The combustor 1 is provided with a built-in mixer 6 for mixing raw materials, reaction air, reaction hydrogen and chlorosilane steam are mixed after being accurately metered, the influence of the three material ratios on the specific surface area of a product is great, and fumed silica products of different models can be produced by adjusting the three material ratios.
Specifically, the reaction furnace 2 in this embodiment is a jacket 22 type water cooling structure, and coolant water is introduced into the jacket 22, and the temperature of the coolant water is 80 to 95 ℃. The reaction furnace 2 is provided with an ignition port, a flame observation port, a temperature measurement port and a pressure measurement port.
(3) The fumed silica and the tail gas in the reaction furnace 2 are introduced into the collector 17, the fumed silica is collected into fumed silica with preset granularity through the collector 17, and specifically, the nano-powder fumed silica is collected into the micro-powder fumed silica, so that the gas-solid separation of a subsequent system is facilitated.
(4) Micron-sized powder fumed silica and tail gas are introduced into a bag filter 18 for gas-solid separation to obtain separated fumed silica and tail gas,
(5) the gas-phase silicon dioxide is discharged from a solid outlet of the bag filter 18 and is conveyed into a two-stage deacidification furnace 19 for deacidification treatment by a conveyor 27, the temperature in the deacidification furnace 19 is 400 ℃, and hydrogen chloride gas in the gas-phase silicon dioxide is removed; and then the silicon dioxide enters a drying furnace 20 for drying and dehydration, wherein the temperature in the drying furnace 20 is 300 ℃, and the finished product of the fumed silica is obtained.
As the fumed silica can be sintered at 800 ℃, the deacidification furnace 19 adopts the radiation type heating, so that the fumed silica is prevented from being directly contacted with a heat source to cause high-temperature sintering, and large-particle silica is formed. The bottom of the deacidification furnace 19 is provided with a deacidification gas inlet, the main components of the deacidification gas are water vapor and compressed air, the volume ratio of the water vapor to the compressed air is 1 (5-1), the deacidification gas is heated to 450-550 ℃ by the heater 32 and enters the deacidification furnace 19, and the deacidification gas is the hydrogen chloride adsorbed on the surface of the fumed silica removed by the compressed air. The deacidification gas is heated to form superheated deacidification steam, so that the deacidification steam can be prevented from being liquefied and contacting with the fumed silica to cause the fumed silica to agglomerate to form large-particle silica.
(6) The tail gas discharged from the gas outlet of the bag filter 18 enters the hydrogen chloride absorption tower 24 through the induced draft fan 28, the induced draft fan 28 provides power for the whole system, the hydrogen chloride absorption tower 24 absorbs the hydrogen chloride in the tail gas,
the gas discharged from the top of the hydrogen chloride absorption tower 24 enters the basic absorption tower 26, the basic absorption tower 26 absorbs the residual hydrogen chloride in the gas discharged from the hydrogen chloride absorption tower 24, and the tail gas obtained after the treatment by the basic absorption tower 26 reaches the standard and can be directly discharged;
the tower bottom liquid of the hydrogen chloride absorption tower 24 enters an analytical tower 25, the analytical tower 25 analyzes the hydrogen chloride, and the purity of the analyzed hydrogen chloride is not lower than 99 mas%. The hydrogen chloride is separated from other components in the tail gas through the analysis of the analysis tower 25, the hydrogen chloride is delivered, the problem of treatment of by-product low-concentration hydrochloric acid is avoided, and the problems of high storage and transportation risks and difficult sale of the low-concentration hydrochloric acid are solved. The tower bottom liquid of the desorption tower 25 is dilute hydrochloric acid, the tower bottom liquid of the desorption tower 25 flows back to the hydrogen chloride absorption tower 24 to be used as leacheate to continuously absorb hydrogen chloride in the tail gas, and concentrated hydrochloric acid generated after hydrogen chloride is absorbed enters the desorption tower 25.
Three batches of T-200 type fumed silica produced by the open type reaction furnace 2 in the comparison experiment are compared with T-200 type fumed silica produced by the closed type reaction furnace 2 of the system for producing fumed silica in the embodiment (see table 1), the fluctuation range of the specific surface area of the product produced by the closed type reaction furnace 2 is obviously reduced, and the content of screen residues (an index for measuring the amount of large-particle silica in the product, and the content of screen residues indicates that the content of large-particle impurities is high) is obviously reduced.
TABLE 1
The embodiment provides a system and a method for producing fumed silica, because the adopted reaction furnace 2 is a closed reaction furnace 2, the influence of cold air sucked into the outside on the material concentration in the reaction furnace 2 is avoided, the control of the reaction temperature in the reaction furnace 2 is improved, and the generation of part of large-particle silica due to low-temperature hydrolysis of chlorosilane in the reaction furnace 2 is avoided, so that the particle size ratio and the specific surface area distribution of the fumed silica generated by reaction in the reaction furnace 2 are uniform, the product stability can be improved, compared with the use of an open reaction furnace in the prior art, the system in the embodiment improves the fluctuation range of the specific surface area of a fumed silica product from a standard value of +/-30 m2/g to a standard value of +/-10 m2/g, reduces the content of sintered silica with the particle size larger than 45um by 60mas, and improves the application performance of the product. In the embodiment, the bag filter 18 is adopted to perform gas-solid separation through bag filtration, the whole system adopts an absorption and analysis combined technology to realize the separation of the hydrogen chloride and other components in the tail gas, the hydrogen chloride gas is delivered out, the hydrochloric acid is not by-produced, and the problems of large risk of hydrochloric acid storage and transportation and difficulty in selling the hydrochloric acid are solved.
Example 3
This example provides a method for producing fumed silica using the system of example 2, differing from the method of example 2 by:
the pressure in the reaction furnace in the step (1) is 5kpa, and the temperature is 1750 ℃; introducing raw material oxygen into the first mixer through a second pipeline;
the temperature in the deacidification furnace in the step (5) is 550 ℃, and the temperature in the drying furnace is 400 ℃.
Example 4
This example provides a method for producing fumed silica using the system of example 2, differing from the method of example 2 by:
the pressure in the reaction furnace in the step (1) is-2 kpa, and the temperature is 1550 ℃; introducing combustion gas oxygen into the second channel through a third pipeline; introducing protective gas oxygen into the third channel through a fifth pipeline;
the temperature in the deacidification furnace in the step (5) is 450 ℃, and the temperature in the drying furnace is 200 ℃.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (14)
1. A system for producing fumed silica, comprising:
the combustor is used for introducing raw materials of chlorosilane, hydrogen, oxygen or air for ignition and combustion;
the reaction furnace is connected with the combustor, the outlet of the combustor is arranged in the reaction furnace, the reaction furnace is a closed reaction furnace, and raw materials of chlorosilane, hydrogen, oxygen or air are combusted in the reaction furnace to generate a hydrolysis reaction to generate fumed silica.
2. The system for producing fumed silica according to claim 1, wherein the burner comprises: the reactor comprises a first channel, a second channel and a third channel which are sequentially arranged from inside to outside, wherein the first channel, the second channel and the third channel are all communicated with an outlet of a combustor, the first channel is used for introducing raw materials, the second channel is used for introducing combustion gas, and the third channel is used for introducing protective gas to cool the second channel and supplement oxygen in the reactor.
3. The system for producing fumed silica according to claim 2, wherein an internal mixer is further disposed within the first passage for mixing the gases within the first passage.
4. The system for producing fumed silica according to claim 1, wherein the reaction furnace comprises: the furnace chamber and set up the jacket outside the furnace chamber, the jacket is used for letting in the refrigerant and cools off the furnace chamber.
5. The system for producing fumed silica according to any one of claims 1 to 4, further comprising:
and the impurity removal device is connected with the reaction furnace and is used for removing impurities in the gas-phase silicon dioxide.
6. The system for producing fumed silica according to claim 5, wherein the purging device comprises:
the deacidification furnace is connected with the reaction furnace and is used for removing hydrogen chloride gas in the gas-phase silicon dioxide;
and the drying furnace is connected with the deacidification furnace and is used for drying and dehydrating the fumed silica to obtain the finished fumed silica.
7. A system for producing fumed silica according to claim 6, wherein the deacidification furnace is heated by radiation.
8. The system for producing fumed silica according to claim 6 or 7, wherein the purging device further comprises: a collector and a bag filter, wherein the collector and the bag filter are arranged between the reaction furnace and the deacidification furnace,
the gas-phase silicon dioxide and the tail gas in the reaction furnace enter the collector, and the collector is used for collecting the gas-phase silicon dioxide into gas-phase silicon dioxide with a preset granularity;
the inlet of the bag filter is connected with the collector, the solid outlet of the bag filter is connected with the inlet of the deacidification furnace, the bag filter is used for filtering out fumed silica, and the filtered fumed silica flows into the deacidification furnace again.
9. A system for producing vapor phase dioxidation according to claim 8, wherein the gas outlet of the deacidification furnace is connected to the inlet of a bag filter, and the gas discharged from the gas outlet of the deacidification furnace is filtered by the bag filter.
10. The system for producing fumed silica according to claim 5, further comprising:
and the tail gas treatment device is connected with the impurity removal device and is used for treating hydrogen chloride in the gas discharged by the impurity removal device.
11. The system for producing fumed silica according to claim 10, wherein the tail gas treatment device comprises:
the hydrogen chloride absorption tower is connected with the impurity removal device and is used for absorbing hydrogen chloride in the gas discharged by the impurity removal device;
the desorption tower is connected with the tower kettle of the hydrogen chloride absorption tower and is used for desorbing hydrogen chloride in tower kettle liquid of the hydrogen chloride absorption tower;
and the basic absorption tower is connected with the top of the hydrogen chloride absorption tower and is used for absorbing residual hydrogen chloride in the gas discharged from the hydrogen chloride absorption tower.
12. A method for producing fumed silica using the system of any of claims 1-11, comprising:
introducing chlorosilane, hydrogen, oxygen or air as raw materials into a combustor to ignite and burn, and introducing the raw materials into a reaction furnace, wherein the pressure in the reaction furnace is-5 kpa, the temperature is 1400-1750 ℃, and the raw materials are burnt to generate a hydrolysis reaction to generate fumed silica.
13. The method according to claim 12, characterized in that, using the system as claimed in claim 2, the method further comprises the steps of:
introducing raw materials of chlorosilane, hydrogen, oxygen or air into the first channel;
introducing combustion gas into the second channel to ignite chlorosilane, hydrogen, oxygen or air in the first channel and perform surface modification on the generated fumed silica;
and introducing protective gas into the third channel to cool the second channel and supplement oxygen in the reaction furnace to maintain reaction balance.
14. Method according to claim 12 or 13, characterized in that, using the system described in claim 6, the method further comprises the steps of:
introducing fumed silica generated after combustion in the reaction furnace into a deacidification furnace for deacidification, wherein the temperature in the deacidification furnace is 400-550 ℃;
and (3) introducing the fumed silica deacidified in the deacidifying furnace into a drying furnace for drying, wherein the temperature in the drying furnace is 200-400 ℃.
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