RU2411080C1 - Method of producing granulated adsorbent from sunflower shells - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to method of producing carbon adsorbents and may be used in various branches of national economy to treatment of effluents and for environmental protection. Sunflower shells are ground to 0.5-1.0 mm-fraction and polyvinyl acetate dispersion, a binder, dissolved in water to (1-3):10 weight ratio, is added thereto to obtain 8-20 wt % of polyvinyl acetate. Binder solution is mixed with shells in 4:1 ratio for them to stay in contact for 0.5 h. Then, excess solution is removed and mix is granulated. Then, granules are, first, dried at ambient temperature, and, then, in nitrogen flow at 100-120C for 0.3-0.5 h and carbonated on heating at the rate of 10-15 deg/min to 250-280C and held at final temperature for 0.25-0.5 h. ^ EFFECT: high-adsorption capacity granulated adsorbent with good mechanical strength. ^ 3 ex

Description

The invention relates to methods for producing carbon adsorbents and can be used in various sectors of the economy for wastewater treatment from various chemical contaminants, in particular for the removal of oil and oil products, as well as in environmental protection measures.

Analysis of the current level of technology showed the following:

- there is a known method of producing adsorbent from sunflower husk, including the removal of ballast substances from plant materials by solvent extraction, separating the husk from the solution, mixing it with water, freezing and thawing and drying at a temperature of 100-200 ° C (see RF patent No. 2240864 dated December 22, 2003 according to IPC B01J 20/24, published on November 27, 2004).

A disadvantage of the known technical solution is the low adsorption capacity for liquid hydrocarbons in connection with low-temperature processing and low mechanical strength. In addition, the finely dispersed form of the adsorbent limits the scope of its use in natural conditions due to the high windfall.

- there is a known method for producing activated carbon, in which the residue after biological wastewater treatment is mixed with sunflower husk, granulated, carbonized at 300-350 ° C, then suspended in 10% sulfuric acid and boiled for one hour, and then washed, dried and activated at 550-600 ° C (see RF patent No. 2036140 dated 03.24.1992 according to IPC СВВ 31/08, published in OB No. 15, 1995).

The disadvantage of this technical solution is the low adsorption capacity for liquid hydrocarbons and the low mechanical strength of the granules, which is associated with high-temperature activation. The method is multistage. Moreover, the use of sulfuric acid in the technology of producing adsorbent contributes to the corrosion of equipment.

In almost all known methods for producing carbon adsorbents from plant materials, the finished product has a small particle size, as a result of which they are subjected to windsurfing when used on open water surfaces. In this regard, losses of adsorbents are very large and, accordingly, cleaning costs increase. Common industrial adsorbents of plant origin - Lessorb (sphagnum moss), Ekolan (sawdust) - are dusty. They are almost impossible to use in filters due to the high hydraulic resistance of the layer.

As a prototype, we adopted a method for producing granules from sunflower husk, including grinding husks, introducing a binder, heating and granulating the mixture (see RF patent No. 2311224 of 06/07/2005 according to IPC B01J 2/00, published on 11/27/2007. )

The disadvantage of this method is the low adsorption capacity for liquid hydrocarbons.

The technical result that can be obtained by implementing the proposed technical solution is to obtain a granular adsorbent having a high adsorption capacity for liquid hydrocarbons and good mechanical strength.

The technical result is achieved using a known method, including grinding husks, the introduction of a binder and granulation. Moreover, according to the claimed method, a polyvinyl acetate dispersion diluted with water in the ratio, parts by weight, (1-3): 10 to a content of polyvinyl acetate of 8-20 wt.%, Mixed with husk in the ratio, parts by weight, is used as a binder, 4: 1 for contacting for 0.5 h, followed by separation of the excess solution and granulating the mixture, after which the granules are dried at ambient temperature, then dried in a stream of nitrogen at 100-120 ° C for 0.3-0.5 h and carbonate, heating at a speed of 10-15 deg / min to 250-280 ° C and maintaining at a final temperature for 0.25-0.5 hours.

Thus, the difference of the proposed method from the prototype is:

- use as a binder polyvinyl acetate dispersion, providing granules with good mechanical strength;

- the size of the obtained granules: diameter 5 mm, height 9-10 mm;

- heat treatment of granules by carbonization for the development of porosity with a predominance of macropores, as well as hydrophobization of the surface with resinous decomposition products of the organic components of the husk. These characteristics are necessary when using the finished product to remove liquid hydrocarbons from aqueous media, the molecules of which have a size from 1000 to 2000 nm, which corresponds to the radius of the macropores.

We believe that the claimed method meets the condition of novelty.

The analysis of the prior art did not reveal sources of fame: methods and compositions for producing granular adsorbent from sunflower husk using a polyvinyl acetate dispersion as a binder, followed by heat treatment of the granules in the claimed quantitative ratio of the components under these conditions and the technical result achieved. The inventive method meets the condition of an inventive step.

As a source material, use sunflower husk - waste in the process of peeling sunflower seeds before the pressing operation at oil extraction plants, accounting for 15-17% of the mass of processed seeds. The waste code according to the Federal Classification Catalog of Waste 1210020008995 (introduced by Order of the Ministry of Natural Resources of the Russian Federation dated July 30, 2003 No. 663, is attached to the application materials). The raw material fraction has a size of 1-6 mm. Raw material composition, wt.%: 32.3 - cellulose, 28.7 - lignin, 26.8 - hemicellulose polysaccharides, the rest - resins, waxy and mineral substances. Sunflower belongs to oil crops, and therefore in its husk there is an increased content of hydrophobic components. It has greater buoyancy and water-repellent properties than the fruit shells of other agricultural plants. The use of sunflower husk allows not only to obtain an adsorbent having a high absorption capacity, but also to utilize the large-tonnage waste from the oil and fat and confectionery industry. Before granulation, the husk is crushed to a fraction of 0.5-1 mm, which contributes to the production of strong uniform granules.

A coarse dispersed homopolymer polyvinyl acetate dispersion (PVAD) of the DF 51 / 10C grade (GOST 18992-80) is used as a binder. The dispersion is a plasticized product of the polymerization of vinyl acetate in an aqueous medium in the presence of an initiator and a protective colloid - polyvinyl alcohol. In the brand designation: the letter index to the numbers DF - dispersion, dibutyl phthalate plasticizer; the first two digits indicate the minimum solids content before plasticization of the dispersion, and the subsequent figures indicate the plasticizer content in terms of solids in percent; the letter index after the numbers is medium viscosity. The dispersion consists of the following components:

- polyvinyl acetate - 85%;

- plasticizer dibutyl phthalate - 10%;

- water - 5%.

The appearance of the dispersion is a homogeneous white liquid.

The specified material is mainly used to obtain water-dispersion paints, building primers, putties, etc., is cheap and affordable.

Using the granulation method with a polymer binder allows for a high adsorption capacity of the material in combination with good mechanical strength.

According to the claimed method, the polyvinyl acetate dispersion is diluted with water in the ratio, parts by weight, (1-3): 10, providing a polymer binder content of polyvinyl acetate in the amount of 8-20%. With a lower content of polyvinyl acetate, the obtained granules are characterized by low strength, and when using a dispersion of a higher concentration, a decrease in the adsorption capacity of granular adsorbents is observed due to the blocking of pores by the binder film. The use of a polyvinyl acetate dispersion containing a plasticizer, instead of a solution of one polyvinyl acetate provides a more durable, stable during transportation and operation of granular adsorbent. The binder is mixed with sunflower husk in the ratio, parts by weight, 4: 1, taking into account the bulk density of the husk (220 kg / m ³ ) and its swelling. The mixture is kept for contact for 0.5 h, which allows to facilitate the molding process and reduce mechanical stress on the granulator. Then the excess solution is separated on the filter and the mixture is granulated.

The use of granular adsorbents provides a more effective treatment of wastewater from oil pollution by reducing the hydraulic resistance of the layer in the filters, as well as eliminating surface spills of oil products, since the adsorbents obtained by the present method are coarse and molded, so they are not subjected to windsurfing like powder adsorbents .

To prevent the granules from sticking together after granulation, they are dried at ambient temperature. The drying of the obtained granules is carried out in a stream of nitrogen in the temperature range 100-120 ° C for 0.3-0.5 hours. Under these conditions, the organic husk polymers are not oxidized.

Then, to increase the adsorption capacity, the granules are also subjected to carbonization in a stream of nitrogen. A necessary requirement for obtaining a hydrophobic and oleophilic carbon sink is the implementation of thermal decomposition of husks in an oxygen-free environment. At a high temperature, oxygen promotes hydrophilic activation of the surface, it acquires an acidic character, which contributes to increased water absorption upon contact of the adsorbent with water. In addition, during the heat treatment of raw materials in an oxygen-containing atmosphere, a decrease in the yield of the finished product and an increase in the degree of burning of the surface are observed.

Carbonization is carried out by raising the temperature at a speed of 10-15 deg / min to 250-280 ° C. At a final temperature, isothermal exposure is carried out in a nitrogen atmosphere for 0.25-0.50 hours. Heat treatment of granules from sunflower husk is organized under the indicated conditions in accordance with a number of features:

- the heating rate has a significant effect on the total porosity of the carbonizate. Its increase leads to a more active release of volatile compounds, while the formation of macropores with a size of 200-10000 nm and a decrease in the proportion of pores with a size of less than 5 nm are observed. With slow heating, a highly developed micropore system is created with a minimum total volume of meso- and macropores. It has been experimentally established that the optimal rate of temperature rise during heat treatment of sunflower husk, which allows one to obtain macroporous adsorbents, is in the range of 10-15 deg / min. This achieves an almost uniform porous structure due to the uniform removal of volatile compounds from the husk, as well as the distribution of resinous substances on the adsorbent surface to give it additional water-repellent properties and increase oleophilicity. The heating rate of less than 10 deg / min, in addition to obtaining an adsorbent with a pore size insufficient for large molecules of liquid hydrocarbons to penetrate into them, increases the duration of the heat treatment process. Raising the temperature at a speed of more than 15 deg / min leads to uneven heating of the entire volume of the reaction chamber. In addition, the output velocity of the volatile components of the sunflower husk increases, which causes thinning and rupture of the pore walls, a consequence of this is a decrease in the mechanical strength of the finished adsorbent;

- the choice of temperature conditions for carbonization is associated with the peculiarity of the occurrence of chemical transformations of organic polymers in the composition of sunflower husk under the influence of a binder. Its presence in the composition of the granules causes the breakdown of husk polymers at lower temperatures. The properties of granular adsorbents obtained under the claimed temperature conditions are similar to the properties of non-granulated adsorbents from sunflower husk obtained at 300-400 ° C. Based on the temperature dependence of the mechanical strength of granular adsorbents and their adsorption capacity, the temperature range of 250-280 ° C was selected. To a temperature of 250 ° C, a sufficiently high porosity does not develop, and above 280 ° C there is a decrease in the yield of granules and their strength;

- isothermal aging is carried out for 0.25-0.50 hours. Less time is not enough to complete chemical transformations at a given temperature and to distill decomposition products from pores. With a treatment duration of more than 0.50 hours, there is a slight increase in the absorption capacity of the adsorbent, but this fact does not justify the energy consumption.

At the end of the isothermal exposure, a temperature is reduced to 40 ° C in order to prevent oxidation of the surface of the adsorbent in the air.

In more detail, the essence of the claimed invention is described by the following examples.

Example 1

Sunflower husk is crushed to a fraction of 0.5-1 mm. Connect 1 wt.h. (40 g) of polyvinyl acetate dispersion brand DF 51 / 10C and 10 wt.h. (400 g) of water, after which the prepared binder solution with husk is mixed in the ratio, parts by weight, 4: 1 (440 g and 110 g, respectively) and incubated for 0.5 h; Then the excess solution is separated from the husk on the filter and the mixture is formed to obtain granules with a diameter of 5 mm, a height of 9-10 mm. The granules obtained are dried at ambient temperature.

Then the granules are loaded into a muffle furnace with programmed control and dried at 100 ° C for 0.3 h in a stream of nitrogen. Then the temperature is raised at a speed of 10 deg / min to 250 ° C and held for 0.25 hours. At the end of the isothermal exposure, the temperature is reduced to 40 ° C and the finished product is unloaded.

The yield of granular adsorbent is 60% based on the initial husk.

Performance characteristics of granular adsorbent:

- oil intensity and water absorption were determined according to TU 214-10942238-03-95. The tests used Grozny oil, the diesel fraction (DT) extracted from it, and motor oil (MM). The resulting adsorbent has the following indicators: adsorption capacity for oil - 3.6 g / g, for MM - 3.4 g / g, for the fraction of DT - 3.3 g / g; water absorption is 1.0 g / g;

- the mechanical strength of the granules in crushing was determined using an IPG-1 extensometer. The resulting adsorbent has a strength of 3.6 kgf / cm ² ;

- the efficiency of water purification from oil by the obtained adsorbent was determined by the results of adsorption of Grozny oil from wastewater under dynamic conditions. For this, an adsorbent in an amount of 5 g is loaded into an adsorption column with a diameter of 25 mm and a height of 300 mm. 1000 ml of waste water containing 500 mg of Grozny oil is passed through an adsorption column with an adsorbent. Wastewater is filtered in a downward direction at a constant speed of 1.8 m / h. The duration of the process was 1.13 hours. The residual mass concentration of oil in the last 100 ml of the filtrate was determined by the IR photometric method (RD 52.24.476-95) using a KN-2m oil analyzer. The efficiency of water purification from oil is 94%.

Example 2

In example 1, take chopped husk. Connect 2 parts by weight (80 g) of polyvinyl acetate dispersion brand DF 51 / 10C and 10 wt.h. (400 g) water. Further, according to example 1, granules are obtained and dried in air. Then the granules are dried at 110 ° C for 0.4 hours in a stream of nitrogen, heated at a speed of 12 deg / min to 260 ° C and incubated for 0.35 hours. Next, according to Example 1, the finished product is obtained.

The adsorbent yield is 57% based on the initial husk. The obtained granular adsorbent has the following indicators: adsorption capacity for oil - 4.1 g / g, for MM - 4.0 g / g, for the DT fraction - 3.8 g / g; water absorption is 0.8 g / g; the mechanical strength of the granules is 4.0 kgf / cm ² .

After treatment of the wastewater obtained with the adsorbent in the adsorption column, as described in Example 1, the efficiency of oil water purification is 96%.

Example 3

In example 1, take chopped husk. Connect 3 parts by weight (120 g) polyvinyl acetate dispersion brand DF 51 / 10C and 10 wt.h. (400 g) water. Then, according to example 1, granules are obtained and dried in air. Then the granules are dried at 120 ° C for 0.5 h in a stream of nitrogen, heated at a speed of 15 deg / min to 280 ° C and incubated for 0.50 h. Next, according to Example 1, the finished product is obtained.

The adsorbent yield is 44% based on the initial husk. The obtained granular adsorbent has the following indicators: adsorption capacity for oil - 4.8 g / g, for MM - 4.6 g / g, for the DT fraction - 4.4 g / g; water absorption is 0.7 g / g; the mechanical strength of the granules is 4.0 kgf / cm ² .

After treatment of the wastewater obtained with the adsorbent in the adsorption column, as described in Example 1, the oil treatment efficiency is 98%.

To confirm the conditions of industrial applicability, the carbon adsorbent obtained in example 3 was used for wastewater treatment at a gas station in the city of Stavropol. For this, the adsorbent is loaded into a two-stage non-pressure sorption filter of the FSD-01 brand. The mass of loading is 14 kg (7 kg of adsorbent in each of the steps). Overall dimensions of the device, m: diameter - 0.70, total height - 1.14. The filtering speed is 2.0 m / h. The filter performance is 1.0 m ³ / h. The oil content in the wastewater entering the filter is 110.00 mg / l. The residual concentration of oil products in the treated effluents is 0.27 mg / l, which does not exceed the MPC of oil and oil products for water bodies for household and cultural purposes, equal to 0.30 mg / l.

Spent adsorbent can be disposed of by burning as solid fuel.

Claims (1)

A method of producing a granular adsorbent from sunflower husk, including grinding husk, introducing a binder and granulating, characterized in that a polyvinyl acetate dispersion diluted with water in the ratio (1-3): 10 parts by weight is used as a binder. to a polyvinyl acetate content of 8-20 wt.%, mixed with husk in a ratio of 4: 1 wt.h. for contacting for 0.5 h, followed by separation of the excess solution and granulating the mixture, after which the granules are dried at ambient temperature, then dried in a stream of nitrogen at 100-120 ° C for 0.3-0.5 h and carbonized heating at a speed of 10-15 deg / min to 250-280 ° C and keeping at a final temperature for 0.25-0.5 hours