Method of reworking silicon-containing vegetable raw material and plant for realization of this method
FIELD: reworking silicon-containing vegetable raw materials, including rice and oats.
SUBSTANCE: proposed method includes carbonization of initial raw material performed in vortex flow of oxidizing gas-heat carrier followed by separation of intermediate solid product and gaseous combustion products removed from roasting zone; proposed method includes also oxidizing roasting of carbonized intermediate product by passing the oxidizing gas through layer of product at rate ensuring "filtering layer" mode. Plant proposed for realization of this method includes two cylindrical furnaces interconnected through separation unit. First cylindrical furnace has branch pipe in its upper part for loading the raw material and pipe mounted inside furnace and used for tangential delivery of oxidizing gas-heat carrier through branch pipe fitted in lower part of said pipe. Second cylindrical furnace is provided with adjustable external heating system and oxidizing gas supply unit mounted in lower part and final product unloading unit mounted at its outlet. Separation unit includes device for removal of gaseous combustion products; initial raw material supply branch pipe, cylindrical furnaces, inner pipe and separation unit are located coaxially. Proposed method is used for production of silicon from vegetable raw material due to continuity of process at preset physico-chemical properties: purity, structure, specific furnace.
EFFECT: optimization and intensification of process.
10 cl, 1 dwg, 1 tbl
The invention relates to a method of processing silicon-containing vegetable raw materials, mainly waste rice, oats, and various species of horsetail order to obtain silicon dioxide, which, depending on the purity and structure can be used in food, pharmaceutical, perfume, paint, chemical, metallurgical, construction, oil, rubber, porcelain, glass, textile, plastic, paper and other industries.
Source raw materials for silicon dioxide is a renewable plant material, which is either a waste of processing rice or oats (straw, husk), or is a different species of horsetails.
The choice of method and equipment for processing of such silicon-containing vegetable raw materials is determined by the raw material, the content of silicon, for further use derived from raw materials of silicon dioxide, and environmental objectives for the disposal of cereal.
There is a method of ashing silicon-containing agricultural waste with silicon content up to 28%, in particular, rice husk, with the aim of obtaining as a useful product of amorphous silicon dioxide and optionally heat e is ergie. The method is carried out by burning the prepared raw material in the vortex flow at a temperature of 600-800°C, preferably at 600-680°With, in the vortex furnace in the atmosphere of hot oxidizing gas. Supplied tangentially mixture of raw material and air is ignited at the entrance to the vortex furnace and formed in the combustion process, the ash is carried by the gas flow in the vortex cleaner gas separation node), where the separation of solids (ash and unburned particles and gaseous phases (U.S. Pat. U.S. No. 3959007, publ. 25.05.1976 year).
However, low calorific value and high ash content of the raw material does not allow to implement in the apparatus, the optimum temperature range of combustion and, therefore, be obtained by a known method silica is stable homogeneous composition and quality.
Previously it was shown that to obtain silicon dioxide of high quality, you must implement two-stage temperature firing of the original plant materials (U.S. Pat. Germany No. 2416291, publ. 23.01.1975 year).
The known method for production of amorphous silica from rice husk by firing a raw material in two stages: carbonization at a temperature of 120-500°and subsequent oxidative roasting in a dynamic mode in the conditions of the fluidized-bed at a temperature of 500-800°C. Carbonized product before the second stage is crushed. To obtain the Soboh pure silica raw material before heat treatment is washed with water and/or mineral acid. The method allows to obtain amorphous silicon dioxide with a particle size of 0.5 to 10 μm, a high specific surface area and purity (U.S. Pat. Of the Russian Federation No. 2061656, publ. 10.06.1996 year).
However, the oxidative roasting in the “fluidized bed” does not allow to create optimal conditions for uniform combustion of the carbonized raw material, which ultimately reduces the quality of the formed amorphous silicon dioxide and its output due to the entrainment of fine particles from the furnace. In addition, the known method is cyclical and sequential, but also quite time-consuming, because the stage of coalification, grinding and subsequent oxidative roasting is carried out in separate process volumes.
Closest to the claimed method according to technical essence is a method of obtaining ultrafine amorphous or nanocrystalline silica from rice husk (U.S. Pat. Of the Russian Federation No. 2191159, publ. 20.10.2002,). The method includes rinsing the rice husk with water and a mineral acid, drying in the electromagnetic field of the microwave range, precalcination (charring) of the feedstock at a temperature of 520-570°, grinding formed at the stage of preliminary firing of the intermediate product and oxidative combustion in a stream of air and/or oxygen in static or dynamic mode. When dynamic mode is implemented by the creation of turbulence is entogo air flow, educated counter-tangential pulsating air flow, the result is silicon dioxide in amorphous form with a particle size of 10-60 nm, and a static mode by carrying out combustion in a laminar flow of air and/or oxygen with a fixed layer of the product, which leads to the formation of crystalline silica in the form of elongated crystals with a length of 200-400 and a diameter of 20-40 nm.
The disadvantages of this method are cyclical, multi-stage, and the need to apply for virtually all operations of the method is distinguished technical means. In particular, at the stage of oxidative roasting to create a counter-tangential pulsating air flow (upon receipt of ultrafine amorphous silica) or laminar air flow (upon receipt of nanocrystalline silicon dioxide) also requires a variety of special equipment. It is well known that creating a laminar flow of oxidizing gas is extremely difficult to implement in practice.
For recycling of silicon-containing plant waste has developed a number of devices, such as a furnace for burning rice husk (U.S. Pat. PRC No. 86-104705, publ. 18.05.1988 year). The oven is made in the form of the combustion chamber, in which the layers are downloading raw materials, separating each layer from each other by a layer of “black m is Kini”, consisting of a carbon-containing silicon oxide. Inside the chamber there are vent pipes with holes for supplying air for combustion. Raw material is loaded so that the pipe was placed in the center layer, providing the combustion of raw materials at the same time top and bottom layer, the temperature of combustion is governed by the rate of air supply. However, the inability to provide a uniform flow of the combustion process in the entire layer leads to loss of raw materials, low purity of the product and its heterogeneity, is a mixture of amorphous and crystalline silicon dioxide.
Known furnace for burning rice husk, consisting of a feeder husk (hopper and screw feeder), chamber for burning raw materials are placed inside the mobile screw, heater, piping for air supply for combustion and flue (VZ. Japan, No. 51-10597, publ. 05.04.1976 year). However, the presence of the screw combustion chamber inner leads at high temperatures to contamination of the produced silicon dioxide.
Closest to the claimed is a device for producing silicon dioxide from vegetable raw materials, mainly from rice husk, including vortex cylindrical kiln and a vortex separator for separating solid and gaseous products of combustion, United is between the two pipes, one of which is U-shaped. In the attachment of the U-shaped pipe with oven and piping installed between the liquid shutoff valves. The upper part of the cylindrical oven made in the form of a truncated cone, and the bottom has a sloping bottom with a device for unloading in the form of a cylinder with a coaxial hole, when this furnace is equipped with located in close proximity to each other tangential inlets (nozzles) for recyclable material and oxidizing gas mixture to initiate combustion of the material (U.S. Pat. U.S. No. 3959007, publ. 25.05.1976 g).
The tangential entry of material into the atmosphere of a hot oxidizing gas into the furnace provides the movement of material in the ascending spiral trajectory towards the top of the truncated cone of the furnace in close proximity to the periphery of the furnace and initiates an exothermic reaction, allowing the input material to reach a temperature of about 600°s, which is lower than the average temperature of the oxidizing gas, so that the flow direction in the upper part of the furnace is changed to reverse, causing the material to fall down the spiral path, internal to an upward trajectory, taking all products of combustion, amorphous silicon dioxide and gases that support combustion, from the bottom part of the furnace.
At the stop permits the processing of rice husks with obtaining amorphous silicon dioxide and, if necessary, to utilize the heat of the gaseous products of combustion, if instead of a pipe separator to install equipment for heat recovery of the released gases.
However, the known device is structurally difficult and not possible to obtain silicon dioxide with the desired properties by the purity and structure, as it is not possible to implement the necessary two-stage temperature of the combustion process plant materials.
The objective of the invention is to optimize the process of obtaining silicon dioxide from the silicon-containing vegetable raw materials by developing a continuous process of refining and its intensification with the simultaneous possibility of obtaining silicon dioxide with specified physical and chemical properties: purity, structure, specific surface area, etc.
The problem is solved by the proposed method of producing silicon dioxide from plant materials, including two-stage heat treatment, consisting of a stage of carbonization of raw materials (pre-firing) and stage oxidative roasting charred intermediate product, and the method is carried out in continuous mode in a single process volume, carbonization is carried out in the vortex flow of the oxidizing gas coolant with subsequent separation of the solid intermediate product and the gaseous products of combustion, to the which derive from the burning zone, and oxidizing roasting is carried out at a temperature of 600-1200°passing an oxidizing gas through the layer formed during coalification intermediate product with speed, providing the mode filter layer.
Preliminary firing is accompanied by the formation of large quantities of gaseous products of combustion. It was established experimentally that the combustion of one kilogram of plant materials formed from 0.30 to 0.37 kg of gaseous products, consisting mainly of CO2and H2O. When conducting the carbonization of the raw material and subsequent oxidative roasting in one process the volume of these gaseous products block the access of oxidizing gas to the intermediate product at the stage of oxidative roasting, significantly reducing the speed of the process and impairing the uniformity of the product composition.
Proposed in the present invention the output of the gaseous combustion products at the stage of oxidative roasting allows you to avoid these disadvantages and to achieve a continuous process of obtaining silicon dioxide with specified properties and high yield in one technological scope.
Changing the temperature regime at the stage of oxidative roasting, it is possible to obtain a silicon dioxide structure. So, at a temperature not exceeding 800° C, preferably at 500-800°receive amorphous silicon dioxide, and at a temperature not higher than 1200°With, preferably, at 800-1000° - crystalline form of silicon dioxide. However, preliminary calcination is carried out in the temperature range from 200 to 600°C.
If necessary, the production of high-purity silicon dioxide (basic substance content is not less than 99.99%) vegetable raw materials are pre-treated by washing with water and/or mineral acid.
As a source of raw material use any silicon-containing vegetable raw materials, including processing waste rice husk, straw, husks of oats, various species of horsetail.
The task is also achieved by a device for producing silicon dioxide from plant material, comprising a cylindrical furnace with a pipe for supply of raw materials and socket for tangential feed of oxidizing gas-fluid separation site and located at the output of the device for discharging the final product, which, unlike known, additionally contains made adjustable by external heating of the second cylindrical furnace, attached to the bottom of the first furnace through a separator node, the first cylindrical furnace is equipped with an internal pipe, a pipe for supply of raw materials is at the top of the first the second cylindrical furnace, and the outlet for tangential feed of oxidizing gas coolant is installed in the lower part of the inner pipe, a separator node is provided with a device for outputting the gaseous products of combustion, and the second cylindrical furnace has established in the lower part of the device for supplying oxidizing gas, and the pipe for supplying raw materials, cylindrical furnace, the inner pipe and the separating node are aligned.
The invention is illustrated in the drawing, which schematically illustrates the installation in General.
The installation includes a first cylindrical furnace 1 for pre-firing (charring) plant materials installed inside the pipe 2 and pipe 3 for input of raw materials. In the lower part of the inner pipe 2 is tangential nozzle 4 for supplying oxidizing gas coolant.
Attached to the lower part of the furnace 1 separation site 5 provides the separation of the solid intermediate product from the gaseous combustion products and, in some cases, the invention may be performed either in the form of a cylinder, equipped with a cone-shaped bottom part (not shown), either in the form of a truncated cone. Performing the separation of node 5 in the form of a truncated cone is preferable because it provides more than the high yield of the final product by reducing losses.
Inside the separation of node 5 has a device 6 for outputting the gaseous combustion products of the original plant material, which constitutes the outlet branch.
To the lower narrow part of the separation of node 5 is attached a second cylindrical furnace 7, is equipped with adjustable external heating 8.
The inlet and the outlet nozzle device 6 to output gases) is located coaxially with the furnace 1 and 7.
In the lower part of the furnace 7 are device 9 for supplying the oxidative gas and the discharge device 10.
Above the inlet of the discharge pipe can be installed umbrella cover 11.
In another embodiment of the invention the inlet and the outlet nozzle can be equipped with separating blades 12.
In an optimal embodiment of the invention, the device 6 for outputting the gaseous combustion products includes umbrella cover 11 and the separating blades 12 at the same time, allowing you to more fully separate the solid particles from the gaseous combustion products, which may further be used, for example, for heating.
As the second cylindrical furnace can be used in any furnace with external heating, mainly tubular electric furnace of the type SOUL, SNA and other temperature control which is s carried out in a standard way, using, for example, thermocouples.
The flow of oxidizing gas, for example air, or mixtures thereof with oxygen in the oxidation zone of burning charred intermediate product is performed using the device 9 located in the lower part of the furnace 7. Supply carried out through, for example, installed in the lower part of the furnace 7 perforated pipe, having a form of a cross, or rings, or lattice, providing a mode filter layer, which is uniform and adequate supply of oxidizing gas through the layer of the intermediate product with no movement of the particles relative to each other. The gas flow rate is determined by the capacity of the plant, and its number is specified quality parameters of the finished silicon dioxide: the amount of oxidizing gas increases with increasing purity of the finished product, as it increases its consumption by burning formed in the preliminary firing of carbon.
The discharge device 10 installed at the outlet of the furnace 7, should provide uniform removal of the finished product from the burning zone and can be made in the form, for example, a screw or disc feeders.
Material requirements of the installation are determined by the temperature of firing, in particular the inner tube 2, it is advisable to issue LNAT stainless steel.
A mandatory requirement in the present invention is the alignment of the pipe for the supply of raw materials, cylindrical furnaces, inner tube and the separation of the site, including the placement of the inlet and the outlet nozzle.
Thanks to the implementation of the specified location of the unit and output of gaseous products from the stage of coalification ensure continuous efficient processing of raw materials, separation of the gaseous and solid phases of the process and getting the finished product in one process volume that eliminates the use of transition pipes, manifolds, ducts and other similar devices.
The method is generally as follows.
Pre-prepared (if necessary operations of grinding, washing, drying raw materials) silicon-containing vegetable raw materials, which can be taken processing wastes, rice or oats in straw, husk, or different species of horsetail, through pipe 3, is injected into the inner tube 2 of the furnace 1. The oxidizing gas coolant, provide heat required for carbonization of the raw materials, is fed through the pipe 4 into the tube 2, where the direct combustion of raw materials in the vortex flow.
As the oxidizing gas of the coolant at stadionplein raw materials can be used, the products of combustion, for example, the products of combustion in the gas burner (not shown) a mixture of propane-butane-air”. By adjusting the flow rate of this gas-air mixture, the changes of temperature in the volume of the first cylindrical furnace within 200-600°C.
Tangential inlet gases allows you to organize the internal pipe 2 twisted (vortex) flow with intensive flow of the combustion. The use of a vortex gas flow of fluid tangentially fed into the inner tube towards the bottom of the processed raw materials provides an intensive course of the process of pre-firing (charring) due to a longer stay raw materials in suspension and better mixing it with the gas-cooled.
Charred source material of an intermediate product (ash) - silicon dioxide with a high carbon content, shall be made by the products of combustion from the pipe 2 into the outer chamber formed by the walls of the furnace 1 and the pipe 2, and arrives in the separating node 5, which due to centrifugal forces, the residual rotation of the thread there is a separation of the gaseous combustion products removed through the device 6, from the solid intermediate product, which is then fed into the second cylindrical furnace 7. Through which is formed on the bottom of the furnace 7 layer charred intermediate product making its way to the cabins oxidizing gas from the device 9 with the speed it provides a mode of “filter layer”that allows you to control stage oxidizing roasting in the process of which is burning of carbon obtained at the stage of carbonization of the intermediate product and the receipt of the silicon dioxide with the desired properties, namely a certain dispersion with the desired specific surface area, low-carbon or high-carbon, amorphous or crystalline, which is regulated by the temperature of the furnace and the residence time of the product.
Thus, the present invention allows to obtain in a continuous mode in a single process the volume of silicon dioxide preset patterns: reactive amorphous or crystalline - quartz, tridymite, cristobalite as well as necessary for different types of use of physico-chemical properties that can be adjusted over a wide range: the output of silicon dioxide, depending on the weight and type of raw materials from 10% to 21%, or from 60 to 95% depending on its content in the raw material; the content of the basic substance in the obtained product is silicon dioxide from 40 to 99.99%; loss on ignition at 1000°With from 0.1 to 6%; the value of the specific surface of from 1.1 to more than 300 m3/g; particle size of from 0.01 to more than 100 microns.
This allows in General to optimize and intensify the processing of cu is misterioso plant materials and make it manageable while simplifying hardware design method, what is the technical result of the invention.
The possibility of carrying out the invention is confirmed also by the results of experimental testing of the method and installation for its implementation.
In accordance with the invention are manufactured and tested for the processing of rice husk and oat, rice straw, stalks of horsetail pilot plant continuous output of 0.3 m3per hour, in which the height of the first furnace is 940 mm, its outer diameter is 170 mm, the height of the separation of node - 800 mm, the height of the second oven to 250 mm
If necessary raw material before heat treatment were subjected to preliminary preparation - straw and horsetail stems were ground; raw materials with mechanical impurities and/or pollution were washed with water and/or mineral acid; to ensure high purity of the final product obtained from rice husk, the leaching was carried out successively with water and acid at a temperature washing solutions 40-95° (U.S. Pat. Of the Russian Federation No. 2061656).
The charring of the feedstock in the vortex gas flow of fluid into the first furnace flows with high intensity. So, empirically it is shown that the duration of this process until the silicon dioxide with a high carbon content is not more than 3-4 seconds, and the duration of heat treatment on the Tadei oxidation firing in the second furnace to obtain a low-carbon silicon dioxide is no more than 10 minutes.
In the presented table shows the characteristics of the feedstock, the temperature conditions of oxidative roasting, as well as the average yields of the final product and its quality characteristics in the processing of raw materials from the following regions:
rice husk - from Krasnodar and Primorsky territories, Astrakhan region, some regions of China, Vietnam, South Korea;
straw rice - from Primorsky Krai;
the husk of the oat - of Primorsky Krai and Amur oblast;
various species of horsetail - of Primorsky Krai.
The value of the specific surface of the silica was determined by the method (Bviusaa. - Workshop on the chemistry of surface phenomena and adsorption. M.: Higher school, 1973, 206 C.) using methylene blue.
Raw material and characteristics of the obtained silicon dioxide
|Raw materials||The content of SiO2in the feedstock, %||Output SiO2with a basic substance content 99%, %||The structure of SiO2after firing at a temperature (°)||The value of specific surface SiO2after firing at a temperature (°C), m2/g|
|The husks of oats||3-5||70-90||Amorphous||Amorphous||Crystal||123-129||5-8|
|The stems of horsetail||14-19||Pp.63-72||Amorphous||A mixture of amorphous and crystalline phases||Crystal||235-242||1.1-3.3|
1. A method of producing silicon dioxide from plant materials by two-stage heat treatment, including the stage of carbonization of raw materials and the stage of oxidative roasting charred intermediate product, wherein the method is carried out in continuous mode in a single process, while the charring of the feedstock is carried out in the vortex flow of the oxidizing gas coolant with subsequent separation of the solid intermediate product and the gaseous products of combustion, which is removed from zone is beige, and stage oxidative roasting of the intermediate product is carried out at a temperature of 600-1200°passing an oxidizing gas through the layer of product with speed, providing the mode filter layer.
2. The method according to claim 1, characterized in that the preliminary calcination is carried out at a temperature of 200-600°C.
3. The method according to claim 1, characterized in that the phase oxidation firing is carried out at a temperature of 500-800°C.
4. The method according to claim 1, characterized in that the phase oxidation firing is carried out at a temperature of 800-1000°C.
5. The method according to claim 1, wherein the plant material is pre-washed with water and/or acid.
6. Device for producing silicon dioxide from plant material, comprising a cylindrical furnace with a pipe for supply of raw materials and socket for tangential feed of oxidizing gas-fluid separation site and located at the output of the device for discharging the final product, characterized in that the installation further comprises made adjustable by external heating of the second cylindrical furnace, attached to the bottom of the first furnace through the separation unit; a first cylindrical furnace is equipped with an internal pipe; a pipe for supplying raw materials is located in the upper part of the first cylindrical furnace and the inlet to the Tangenziale the Noi filing oxidizing gas coolant is installed in the lower part inner tube; separation Assembly is provided with a device for the withdrawal of gaseous products of combustion; and a second cylindrical furnace has established in the lower part of the device for supplying oxidizing gas, and the pipe for supplying raw materials, cylindrical furnace, the inner pipe and the separating node are aligned.
7. Installation according to claim 6, characterized in that the separation unit is designed in the form of a truncated cone.
8. Installation according to claim 6, characterized in that the device for outputting the gaseous combustion products is an outlet pipe, the inlet of which is located coaxially with the furnaces.
9. Installation according to claim 8, characterized in that above the inlet of the discharge pipe is installed umbrella cover.
10. Installation according to claim 8 or 9, characterized in that the inlet of the discharge pipe is equipped with separating blades.
FIELD: interaction substance technology.
SUBSTANCE: preparation of porous nanostructure of silicon consists in forming pores in silicon-containing base wherein silicon is present in the form of one of three stable isomers, summary content of the two remaining isotopes not exceeding half their natural occurrence. For example, if 28Si is present, base can include 29Si and 30Si isotopes in sum not exceeding 3.5%; if 29Si is present, base can include 28Si and 30Si isotopes not exceeding in sum 47%; and if 30Si is present, base can include 28Si and 29Si isotopes not exceeding in sum 48%.
EFFECT: increased atomic homogeneity of porous silicon nanostructure resulting in improved quality of porous layer, which enables realization of certain nuclear physical effects.
4 cl, 2 ex