METHOD OF GRANULATED SORBENT PRODUCTION
Technical field
The invention refers to sorbents production technology, particularly, to the means of binding agent production from natural glauconite for producing granulated sorbents meant for use as filtering and sorption filling capable of replacing activated carbon, anionic and cationic resins, reverse-osmosis membranes, and can be used for drinking water purification and sewage treatment from technogenic pollutant (heavy metals, oil-product, organics, pesticides, radionuclides, etc.), gases purification from atmospheric emission of pollutants, including motor transport emissions.
Prior knowledge
There is a method for the granulated sorbent production that includes mixing calcium oxide or carbonate and aluminum oxide, calcination at the temperature of 1300-1700°C, grinding, adding calcium oxide or carbonate in mixture with 0,3-4% wt of mineral fiber; the proportion of fiber length to fiber diameter is taken as 50-500; the obtained mixture is grinded additionally, then grained, and after that it is subject to hydrothermal treatment (see the Russian Federation utility patent N° 2006285, ΜΠΚ B 01J 20/04, published on 30.01.1994).
The drawback of the known method is complexity of technological process, because in the course of running it is necessary to perform high temperature calcination of mixture and its hydrothermal treatment. Besides, the granulated sorbent produced through this method has a very narrow range of use, because it can absorb only metal anions without absorbing the organic compounds, therefore its field of use is narrowed.
The original component used as a natural binding agent at producing the combination granules (granulated sorbent) according to the present invention is glauconite. It is a well-known fact that galuconite is a variable composition clay mineral with high content of divalent and trivalent ferrum, calcium, magnesium, potassium, phosphorus, which, as a rule, contains over twenty micro-elements, among which are copper, silver, nickel, cobalt, manganese, zinc, molybdenum, arsenic, chromium, stannic, beryllium, cadmium, etc. They are all in the readily retrievable form of exchangeable cations, which are substituted by the excess elements of the environment. This peculiarity, together with the layer structure, is the reason why glauconite has higher absorption characteristics than other oil-products, heavy metals, and radionuclides. At the same time it is very typical of glauconite to have a low desorption percent (removal of the adsorbed or absorbed substances from liquids or solid bodies), prolonged action, high effective heat capacity, plasticity, etc. However, with all the positive characteristics of natural glauconite, there is a problem of its isolate granulation without the use of foreign binding agent, as a consequence of its ballast fraction (quartz, field spar, etc.) composing from 40 to 90% and also a massive glauconite fraction (from 0,65 to 0,2 mm) composing from 20 to 40%.
There is a means glauconite conversion, which is radically different because of its high sorption capacity at water demineralization and capability to restore with less amount of salt. This process is carried out by heating glauconite up to the temperature over 454°C during the period of time, which is long enough to change he granules radically in terms of chemistry and physics including the removal of the most part of water with large increase in pore volume and sorption capacity and further treatment with hot sodium hydroxide concentrated solution. In the course of glauconite treatment with hot sodium hydroxide concentrated solution, which creates new and increased pore volume and sorption capacity, there occurs dissolution of quartz and deposition of sodium on the surface of glauconite pores (see USA patent for an invention N° US 2139299, ΜΠΚ C 01B 33/46, C 01B 33/00, published on 06.12.1938).
The drawback of the method described above is that treating glauconite with hot sodium hydroxide concentrated solution complicates and dears the glauconite conversion technology used narrowly for demineralizing of water. This process also decreases sorption capabilities in comparison to other pollutants, as the glauconite produced with this method can partially sorb heavy metals but cannot fully sorb the organic compounds, which narrows its area of use.
There is a method of restoring glauconite in the form of pure unchanged natural grains of the normal composition, which includes sorting and mechanical cleaning of glauconite (“green sand”) in the course of consequential water streams and chemical solutions for removing the absorbed and adsorbed impurity. In the course of preparation of pure unchanged glauconite, there is a certain amount of water, which sorts and thoroughly cleans sodium hydrate, sodium silicate, acids, removes uneven and oversized material. As a result we get normal granulated glauconite without accidentally absorbed or adsorbed foreign materials (see the USA patent for an invention N° US 1757374, ΜΠΚ C 01B 33/46, C 01B 33/00, published on 06.05.1930).
However, the result of the method described above is outwashing of the most valuable clay fractions of glauconite capable of further granulation without the use of additional binding agent components. Granulometric composition of such natural granulated glauconite is heterogeneous, which is decreasing its filtration and sorption capability. It also narrows its area of use.
There are means of glauconite granulation with preliminary mixing with different types of binding agents. For example, there is a method for producing granulated glauconite (versions) according to which the natural glauconite is parched, riddled, cleaned from quartz impurities, crushed, re-riddled with fractionation less than 40 pm and the binding agent additive is introduced. In the first version it is zirconium dioxide sol, in the second version it is aluminophosphate sol; after doing the graining the product is dried, heat-treated, cooled down to 40-50°C, and then packed (see the Russian Federation patent for an invention N° 2348453, ΜΠΚ B 01J 20/12, B 01J 20/30, published on 10.03.2009).
However, the drawback of the method described above is the necessity to use a foreign binding agent, which makes for increase in power consumption and decrease in sorption capacity. As a result, the prime cost of the final product rises because of the high price of the foreign binding agent. As a consequence, it seriously affects the competitive ability of the product and narrows its area of use.
In terms of technical essence, the closest to the suggested invention method of granulated nanosorbent production involves mixing of the original components with the further adding of water until the plastic material is formed, granulation of this mass, heat-treatment of granules with their further cooling. As the original components we use bentonite clay, thermal expanded carbon, and glauconite with the following proportion of components, wt%: bentonite clay - 10-40, glauconite - 10-50, thermal expanded carbon - 10-60; at this thermal treatment includes drying of grains put into the closed thermal insulating volume made of quartz ceramic up to the temperature not higher than 1000°C (see the Russian Federation application for the grant of a patent for an invention No. 2009126840/05, ΜΠΚ B01J 20/20, B01J 20/16, B82B 3/00, published on 20.01.2011).
The drawback of the described method is the necessity to use the foreign binding agent. It complicates the technology of producing the glauconite granules, increases the prime cost of the final product because of the high price of the foreign binding agent. As a consequence, it greatly affects the competitive ability of the product and narrows its area of use.
The objective of the present method is to invent a method of granulated sorbent production based on the binding agent from glauconite.
Technical results achieved at the present problem solving is the increase in sorption and absorption capacity of the granulated sorbent through using magnetic fraction of glauconite as a binding agent. DISCLOSURE OF INVENTION
In broad terms in one aspect the invention comprises a method for producing a granulated sorbent based on glauconite without a foreign binding agent, comprising glauconite sand preheating, screening, separating magnetically into a nonmagnetic and a magnetic fractions, wherein the glauconite magnetic fraction concentration should not be less than 95%, milling the glauconite magnetic fraction, mixing the milled glauconite magnetic fraction with water to obtain a plastic mass, granulating the mass, drying the obtained granules, splitting the granules, screening the granules to the fraction range of 0.8 up to 100 mm, kilning the fractioned granules with their subsequent cooling, and packing the end product.
Optionally the method further includes the step of milling the glauconite magnetic fraction down to the size of glauconite particles from 1 to 100 pm.
Optionally the milled glauconite magnetic fraction is mixed with water before granulation to obtain a plastic mass with humidity not below 28%.
Optionally the granules drying after the granulation is performed naturally at positive ambient temperature not lower than 20°C and humidity not exceeding 10%
Optionally after the splitting and screening the granules, the waste is returned for secondary milling and further utilization as a binding agent for granulation.
Glauconite is a multipurpose material by its structural and geochemical characteristics. However, the use of non-processed glauconitic sand as a sorbent with its increased sorption characteristics seems to be impossible because of peptisation of glauconite clay fraction.
The use of glauconite magnetic faction from glauconitic sand as a binding agent, while producing the granules, allows to obtain granulated sorbent, which possesses increased sorption and adsorption capacities which can widen its area of use.
Glauconitic sand comes from quarry in wet or frozen and chunked condition etc. and contains different rubbish in the form of grass roots, gaize etc., that is why it is preheated (dried), with the optimal temperature in the range from 70 to 100°C. The main condition for this is that sand must be dry and easily sifted through a sieve to separate mechanical admixture and gaize. The sieve may have mesh from 0,8 to 0,25 mm, the main condition is that fracture of glauconite must be sieved, and maximum fracture of glauconite must be from 0,65 mm and lower.
The composition of glauconiteore depends on mine field, at that concentration of glauconite in ore may be from 15% to 75%, all the rest is ballast in the form of quartz, feldspar etc. Glaucotite can be magnetized at high magnetic field strength. When glauconite ore is passed through magnetic separator, glauconite is separated from ballast fracture. The presence of metal in glauconite indicates high concentration of glauconite. This can be seen from Table 1, which represents the elemental composition of the separated magnetic by separation of glauconite on the magnetic and non-magnetic fraction. Table 1 also shows that the magnetic metal fraction is considerably more than the non-magnetic one. Thus, the obtained mixture with the concentration of glauconite in separated magnetic fraction is not less than 95%.
The milling of magnetic fraction is carried out in order to obtain the flour for making grains from magnetic fraction (mainly for grains glauconite milling with the size of fractions in the range from 30 to 50 microns).
Table 1
Milled magnetic fracture is mixed with water in order to form plastic mass. The graining mass is carried out to give cylindrical grains, which have the size in diameter from 0.8 to 100 mm and the length from 50 to 100 mm, thus, the "noodles", which according to the usage of die may have different diameter and length, are obtained. Grains of different diameter size and length are needed and the obtained “noodles” are dried naturally at positive surrounding air not lower than 20 °C and air humidity not more than 10%. It is necessary in order to remove the excessive humidity before the operation of milling of the obtained “noodles”, from which granules of needed granulometric size are produced. If the milling of “noodles” is done after baking under 650 °C for at least 1 hour, then, as a result of milling these grains, the obtained waste is hard to utilize, and during the drying to humidity of 10%, the obtained waste as the result of milling “noodles” is sent back to milling and second obtainment of “noodles” for production of grains of necessary size. Waste is not formed with such a technology.
Graining and screening of granules is done in order to get fractions, which have size in diameter and length from 0,8 to 100 mm, because consumer sizes of granules for water purifying have these granulometric parameters, and the form of granules must be of irregular shape, but closer to the round shape. The maximum filtration capacity of the final product is achieved by getting irregular round form of granules for any granulometric composition.
Baking of granules is carried out in a furnace at the temperature not exceeding 650 °C, in the course of not longer than 1 hour, because at this temperature granules have consumer hardness and do not fall into pieces when they get into water and stay hard. The period, which is long enough for baking, can be not less than 1 hour.
Isolation of magnetic fraction of glauconite from the main mass allows us to obtain the binding agent, which is the main material of granulated sorbent production.
We suggest a method of granules production on the basis of natural glauconite binder, which can be used as full sorbent. The presence of ballast fraction and high percentage of large fraction composition of glauconite hampers direct granulating of glauconite sand without any additives. That is why glauconite granulation in known technical solutions was made with different blinders, for example, zirconium dioxide or bentonite, which, on the one hand facilitated normal granulating of glauconite, and on the other hand contributed to decrease of its sorbent characteristics.
The proposed technical solution provides an opportunity of getting separated milled fraction of glauconite with the help of magnetic separation, which is used as a binding agent for granulation. This achieves the maximum sorbent effect of the final product for extended range of pollutants.
Experimental measurements of sorption indice of combined grains were carried out, in the composition of which we used: bentonite clay, glauconite and thermally expended carbon at the ratio of components, mass %: bentonite clay - 40, glauconite - 40, thermally expended carbon - 20; where bentinite clay was the binding agent, in comparison with glauconite granules on the basis of glauconite binder, where the concentration of glauconite was 95%. Measurements were carried out on ferrous metal sorption from water before and after passing through granules. Passing model solution of ferrous metal through combined and glauconite grains was carried out simultaneously. Underwater production unit of metal in potable water is 0,3 mg/l. Used equipment is photometer of creatine phosphokinase-3. Results of measurements are represented in Table 2.
Table 2 shows that sorption of glauconite granules on the basis of glauconite binder is three times higher than sorption of combined granules with bentinite clay, glauconite and thermally expended carbon, therefore, the sorption capacity increases.
Table 2
Short description of ketches
The invention is illustrated with a photograph, which shows the morphology of glauconite granules (side view of the surface of the powder sample of glauconite, amplification - 20 kt). Morphology research was done on the scanning electronic microscope TESCAN MIRA II LMU. The sample consists of glauconite, which contains not less than 95% of magnetic fraction of glauconite, and is made with SHF expansion and has the form of elongated structures, light-brown color, hard. The sample surface is comprehensive, developed and nanostructured. There are disseminations of crystallized structure in the sample.
Embodiment of invention
The proposed method of producing granulated sorbent on the basis of natural binder of glauconite is as follows.
Previously glauconite binder basis is made in the form of glauconite flour according to the following technology.
Feebly magnetic mineral glauconite is obtained from glauconite sand (with the help of magnetic separation), which has been preheated at the temperature of 70-100°C and screened through the sieve, which has the size from 0,8 to 0,25mm. During the separation ballast fractions (quartz, feldspar, glauconite non-magnetic, etc.) separate from magnetic glauconite. Separated magnetic glauconite is reduced to fragments in any milling equipment, which allows to get glauconetic flour fraction from 1 to 100 microns. Obtained glauconetic flour fraction from 1 to 100 microns are mixed in homogenizer with addition of water in order to obtain clay glauconite mass with humidity not less than 28%, which is used in obtaining of sorption granules based on natural glauconite.
The obtaining of grains based on milled magnetic fraction of glauconite is done according to the following technology.
Glauconite binder in the form of flour obtained after separation of magnetic glauconite fractions and its milling is mixed with water to humidity of the obtained mass not less than 28%. The obtained mass is directed into the granulating machine, from which granules with the diameter from 0,8 to 100mm and length from 50 to 100mm come. After leaving the granulating machine they are naturally dried at above-zero surrounding temperature not lower than 20°C with humidity not more than 10%. Dried grains are directed to the milling machine, where they become granules of irregular form, which have size in diameter from 0,8 to 100mm and length from 0,8 to 100mm. As a result of milling, different types of granulometric composition are formed. Granules are screened through sieves, which have the size from 0,8 to 100 mm. Screened granules are sorted according to their granulometric composition and directed into the furnace for baking at the temperature not more that 650°C in the course of not longer than 1 hour. After thermal treatment, natural cooling of granules is carried out until they reach the temperature of the environment, then granules are packaged in containers.
Defective grains, siftings and flour, which are formed during the fragmentation rocess, are directed back into the granulating machine, which allows to get glauconite flour fraction from 1 to 100 microns. After milling, glauconite flour is directed to the stage of mixing with water. With this technology no waste is formed.
Preferred Embodiment
Glauconitic ore, which is represented by glauconitic sand, is preliminarily dried under temperature not higher than 100°C to the point of reaching humidity not less than 8% throughout the volume. Dried glauconitic ore is screened with screen plates of various granulometric sizes, in order to separate mechanical impurities, i.e. grass roots, gaize, etc. from glauconitic sand. Screened glauconitic sand is sent for separation, which is performed with the help of high-intensity magnetic roller separator CBMI/I with the induction of 1,5 tesla, or with the help of dry magnetic beneficiation system MECOY-154/200. In the course of magnetic separation, the process of separation of glauconitic magnetic fraction from the non-magnetic part, which is a ballast fraction consisting of quartz, feldspar, etc., takes place. Separated magnetic glauconitic fraction is then delivered to the milling system (e.g. three-stage centrifugal mill ML|-700 produced by ZAO “TZDO”, city of Tula), which allows to reduce glauconite to fractions not more that 50 micron. Water is added into the milled magnetic fraction of glauconite and the obtained mass is mixed with the help of homogenizer until it reaches residual humidity not less than 28%. The obtained mass is delivered to mixing extrusion-type granulating system of any type for obtaining granules with a diameter of 1.4 mm, length of 80 mm, which can be achieved through installing nozzles with openings (opening diameter 1.4 mm). For other sizes nozzles with the required openings are to be installed. The remaining ballast fraction (quarz, feldspar, etc.) is deposited and stored for utilization in other types of technology for scavenging. The obtained granules are naturally dried under positive surrounding temperature not less than 20°C and humidity no more than 10% and are then delivered to the hammermill, where they are broken into smaller fractions, with the cross-sectional size ranging from 1.2 to 1.4 mm; the granules are screened and sorted according to their granulometric compositions. The granules are then baked under the temperature not higher than 650°C in the course of 1 hour. The output of the finished granules is 15%. Defective granules, plus mesh, and powder formed in the course of breaking are sent back to the milling system, which allows to obtain glauconite powder with a fraction from 1 to 100 micron. After milling the obtained glauconite powder proceeds to the stage of mixing with homogenizer with water and for secondary granulation. There is no waste when this technology is used. The applied technology allows to obtain glauconite granulated sorbent, which reaches high sorptive capacity.
In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variation such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.