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Study of filtration processes at preparation of calcium-magnesium chlorate defoliant from dolomite
Khamrakulov Zohidbek, Tukhtaev Saydiahral, Askarova Mamura, Khamrakulova Hilola, Institute of General and Inorganic Chemistry of the Academy of Sciences of Uzbekistan Tashkent, Uzbekistan. E-mail: zoxid_xamro@mail.ru
Study of filtration processes at preparation of calcium-magnesium chlorate defoliant from dolomite
Abstract: The separation of the insoluble residue from the suspension of calcium and magnesium chloride obtained by decomposition of dolomite mineral with hydrochloric acid of different concentrations is investigated by the filtration methods, sedimentation and using of centrifugal force. For each method, the optimum speed is set depending on time. The filterability pulp with precipitation of calcium and magnesium chlorate, sodium chloride and sodium chlorate produced during the production of calcium-magnesium chlorate defoliant was studied.
Introduction
Uzbekistan has 22.3 million hectare of agricultural land, including more than 4.2 million irrigated hectares [1]. On basis of irrigated land over 97% of total agricultural production of the country are received. The basic crops are cotton and wheat. Annual gross yield of cotton is 3.4 million tons and 7.1 million tons of wheat. Uzbekistan takes the sixth place in the world on cotton production. The high productivity of crops, particularly, cotton, is impossible without the use of chemical fertilizers, growth regulators, herbicides, defoliants, insectoacaricides, fungicides, protectant, seed, and others.
Currently, preparations for the protection of crops, defoliants and plant growth regulators, mainly imported from abroad in the form of active ingredients or formulations. Defoliation is one of the important conditions for successful and high-quality harvest cotton before frosty period. For the production of magnesium chlorate defoliant at Incorporated Society (IS) «Ferganaazot» the initial raw source bischofite (magnesium chloride) imported from Volgograd (Russia) and Turkmenistan for the currency.
Uzbekistan has a strong mineral resource base and large prospects its increase, has real possibilities for economic recovery of the country due to the further expansion of proven reserves and mining. At present 1717 deposits revealed and about 1,000 promising manifestations of minerals, 118 kinds of minerals, of which 65 are being developed.
On the territory of Uzbekistan 1717 deposits are opened, including — 235 hydrocarbon fields, 136 — metals; 3 — coal; 55 — mining, 26 — and 30 mining and chemical — gems of raw materials; 615 — construction materials for various purposes, and 617 — fresh and mineral underground waters [2].
There is a need in the creation of domestic products based on local raw materials with the use of new approaches and technologies. Magnesium chloride in a mixture of calcium chloride can be prepared by decomposition of muriatic dolomite.
Dolomite deposits exist in Uzbekistan, particularly in Tashkent, Bukhara, Samarkand, Navoi, Ferghana, Namangan and Kashkadarya regions.
A solution of calcium chloride and magnesium can be used for the exchange reaction with sodium chlorate and thus, to obtain a calcium-magnesium chlorate defoliant. Hydrochloric acid is sufficient to use it for the decomposition of dolomite. In our conditions, the cheapest and most available reagents can be hydrochloric acid — a byproduct of large-capacity production of caustic soda at IC “Navoiazot”. Production of calcium-magnesium chlorate defoliant can be carried out on the equipment shop liquid magnesium chlorate defoliant.
Experimental part
The process of decomposition of dolomite was investigated by the example oftwo samples ofdolomite deposits Fergana “Shursu” and Kashkadarya “Pachkamar” (Uzbekistan) belonging to the group of sandy species. Their composition is shown in the table 1. In these compounds insoluble content (SiO2) is about 4-5%.
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Section 8. Chemistry
Table 1. - Chemical composition of dolomite samples (mass.%)
Mine field The content components at an air dry matter, weight.%
О и MgO ro О О <D Рн + cr> О <u Пн О CO MnO О £ О z О >-n О Рн ’"rt «М О «М ro О CO о и
Fergana «Shorsu» 31.48 19.17 0.32 0.29 2.87 0.01 0.02 0.05 0.15 0.03 0.3 45.0
Kashkadarya «Pachkamar» 30.02 19.36 0.39 0.24 2.74 0.01 0.03 0.25 0.10 0.15 0.3 45.4
In order to develop a new technology for production of calcium-magnesium chlorate defoliant experiments on the decomposition of dolomite were carried out at a ratio of T: J = 1:2 with hydrochloric acid at concentrations of 25; 31 and 35% [3].
To ensure an optimum mode of the manufacturing process, the resulting solution of chlorides of calcium and magnesium were separate from the insoluble residue by filtration, settling and centrifugation to maximize extraction of the decomposition products in the liquid phase.
Investigation of the filtering process of the insoluble residue performed on installation model consisting of nodes drive reactor with adjustable temperature and vacuum filter. The filter was used in the capacity of dense filter cloth — belting.
The ability of the slurry to separate into solid and liquid phases can be described by filtration filterability denoted (F). Filterability pulp, forming incompressible precipitation should not depend on external conditions generated for the filtering process is a function of the physical state of the solid and liquid phases at the time of filtering [4]. In equations 1 and 2, expressing the fundamental law of filtering the pulp forming incompressible sediments on the filter septum, a quantity characterizing the state of the liquid and solid phases of pulps represented as p-rQ:
V = VS/(V*c) (!)
Vf = apSt/(^t0x0) (2)
where, Vf- filtrate volume, m 3; r0 - sediment volume resistivity, l/m 2; S - filtering surface, м 2; т - duration of filtration, sec; ДР - pressure difference N/м 2; ^ -viscosity of the liquid phase of the suspension, n-c-м 2 with; R - the resistance of the filter septum 1/m; x0 -the ratio of sediment to the volume of the filtrate.
With the increase of one of the factors filterability suspension worsens, therefore, this parameter is the inverse of the filterability — resistance to filtration:
1/f = b-ro (3)
Taking into account incompressible nature of rainfall,
little resistance, currently applied in the production of
filter walls, expressing (x0) by the height of the sediment layer (hsl) and substituting the value of resistance to filtration (4), we obtain:
Vf = ДР • S • т •F/hsl W here we find the filterability:
F =
Vf • hsi
AP • S •t
(4)
(5)
Filterability is numerically equal to the height of the product formed on the filter cake layer on volume of filtrate through the unit time when differential pressure per unit time.
The filtration process has been studied in the laboratory at temperatures of 303 and 313K, the residual pressure 0,1471T0-3 N/m 2 and the filter area 0,6936-10-2 m 2.
Results and discussion
The results of determining the filterability hydrochloric acid drawing dolomite deposit «Shorsu» are given in table 2.
The data show that at 303K with increasing amounts of pulp, the increase filtration time observed in 2.9 times. To accelerate the filtration process is carried out at a temperature of 313 K. This acceleration of the filtration time is observed in 1.08 times.
A method ofsettling was used to remove the insoluble precipitates. The process of settling of the insoluble residue from the processing of dolomite hydrochloric acid products studied in a measuring cylinder versus time. For the study hydrochloric acid pulp was used, which obtained by particulate decomposition of dolomite with a particle size + 3 ^ - 5, + 5 ^ - 7 and +7 ^ - 10 mm and a weight ratio of the individual fractions of1:1:1 and the standard grinding dolomite flour. The deposition time was recorded by the number of suspension clarified slurry at a temperature of298K. After a settling time of the pulp particles are deposited at the bottom of the cylinder. Early particles settle faster, but after some time, when the resistance force is the driving force of the medium, the particles settle slowly and evenly with a constant speed. The dependence of the degree of brightening pulp of HCl from time and concentration is shown in fig. 1 from which follows that one of the factors influencing
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Study of filtration processes at preparation of calcium-magnesium chlorate defoliant from dolomite
the process of settling is the concentration of acid. With increasing initial acid concentrations, rate of settling reduced. For example, for 5 minutes with the increasing concentration of hydrochloric acid for the decomposition of dolomite from 25 to 35%
decreases in sedimentation velocity 1.7-2 times (for example, particulate dolomite for 5 min 29.80 and 17.80%, respectively, for 60 min 78.05 and 70.30%). To ensure continuity of the process the particles in the slurry should be deposited not less than 50-60%.
Table 2. - Filterability of dolomite hydrochloric acid drawing
Temperature, K Pulp quantity, g Pressure (ДР), N/m 2-10-3 Time (t), sec. Thickness of firm residue (X mm Filterability (F), m 4/N-t Speed filterability, kg/m 2-s
by filtrated
303 250 0.1471 1200 1.8 1.53835 0.04538
400 0.1471 2760 2.8 1.64085 0.03160
500 0.1471 3480 3.2 1.86075 0.03135
313 250 0.1471 1110 1.8 1.50128 0.04039
400 0.1471 2700 2.7 1.59543 0.03242
500 0.1471 3330 3.1 1.66981 0.03173
The degree of clarification by decomposition of dolomite with hydrochloric acid concentration of 25; 31 and 35% at 70-90 minutes is suitably 58.8564.10%, 53.84-61.82% and 51.65-59.60%. And when using lump dolomite through 70-90 minutes degree of clarification is 81.92-85.72%, respectively, 79.6582.22% and 74.80-80.20%.
It is known that the process of settling has a number of disadvantages: low rate of deposition of particles (<0.5 m/h); large size settlers — indoors at their diameter is 12-20 m, and in open areas up to 120 m (takes a large amount of the production site and the time when loading and shipping); due to the difficulty
of separating the fine particles in a gravitational field, this method is acceptable for primary settling, i. e. before supplying the slurry to the centrifuge or filter [5].
The first period of clarification for dolomite (before 70 min) and particulate dolomite (before 20 minutes) are carried out with virtually a constant rate, as evidenced by almost a straight line, depending on the degree of clarification settling time. Further clarification process speed decreases. The ratio of the height of the stabilized layer of sediment to the initial height of the suspension layer has a bulk concentration of sediment in suspension. Dolomite flour for this value is close to 0.22.
Fig. 1. Dependence of degree brightening pulp of hydrochloric acid time and concentration of HCl; 1 — for dolomite flour; 2 — for lump dolomite
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Section 8. Chemistry
Velocity curve lightening of hydrochloric acid lump from pulp raw material consists of three segments, characterized by different sedimentation rate sediment, depending on the particle size. The speed of the pulp brightening particulate materials is significantly higher than the pulp from dolomite flour. So in 20 minutes the degree of lightening the pulp obtained by the decomposition of lump dolomite 25, 31 and 35% hydrochloric acid, was respectively 64.05, 59.60 and 50.80%, and in 60 minutes — 78.05, 75.70 and 70.30%, i. e. with increasing viscosity decrease in the degree of clarification pulp is observed. Stabilized layer height in the decomposition of the particulate materials is less than dolomite flour and is
0.14, which is characterized by a dense packing of particles in the sediment.
To separate the insoluble particles have also used the method of centrifugal forces in the devices — centrifuges and hydrocyclones. Separating insoluble matter from the slurry by centrifugal force can be carried out not only in centrifuges but only hydrocyclones, as well. In these devices, due to significant circumferential velocity of the flow along the axis of the hydrocyclone column is formed dispersion liquid or the gas whose pressure is lower than at the periphery. This kernel limits on the inside of the ascending flow of fine particles and has a significant influence on the effect of separating cyclones. They are widely used for clarifying suspensions (concentration slurries), as well as the classification (the separation into fractions of materials grain size) solid particles having a diameter from 5 to 150 microns.
The smaller the diameter of the hydrocyclone, the more developed in its centrifugal force and hence the smaller the particles separated. The experiment model
of hydrocyclone installation was used consisting of a cylindrical (60 mm diameter) and conical part with an
1 - cylindrical part;
2 - supply pipe;
3 - flare section;
4 - sealing leg;
5 - hopper for the insoluble residue;
6 - drain connections.
Fig. 2. The experimental hydrocyclone installation for separation of the insoluble residue
The results of the study of separation insoluble particles of dolomite decomposition products are shown in Table 3.
Table 3. - Characteristics of the clarification process of hydrochloric acid pulp dolomite flour in a hydrocyclone
The degree of lightening pulp% obtained by the decomposition of dolomite with hydrochloric acid concentration
Time, minute 25% HCl 31% HCl 35% HCl
1 29.95 29.21 28.57
2 39,92 38,64 36,42
3 47.27 47.14 45.72
4 59.73 59.36 58.20
5 73.30 72.10 70.92
10 85.42 85.30 84.22
15 93.80 93.30 92.97
20 99.87 99.84 98.46
From the table it follows that at 4 minutes the acid concentration of25, 31 and 35 is respectively 59.73%,
precipitation rate of the particles of the insoluble residue 59.36% and 58.20. And for 20 minutes, these values are
from the decomposition products ofdolomite hydrochloric respectively 99.87, 99.84 and 98.46%.
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Study of filtration processes at preparation of calcium-magnesium chlorate defoliant from dolomite
Fig. 3. Diffraction pattern of the sample insoluble residue hydrochloric acid hoods Figure 3 shows a diffraction pattern of insoluble residue Based on the results of studies on the process of
dolomite. It can be seen that the phase composition of filtering the insoluble residue from the decomposition
the insoluble residue consists mainly of natural quartz. It of dolomite products we proposed a schematic diagram
clearly manifested diffraction peaks SiO2 4.30; 3.36; 2.46; of a separation under centrifugal force (fig. 4).
2.29; 2.24; 2.13; 1.98; 1.82; 1.67; 1.54Ao. The presence of According to the slurry after which the 2 nd stage of diffraction lines 7.77; 3.81; 3.08; 3.02; 2.85; 2.83 indicates decomposition with a centrifugal pump (1) is supplied
that there are halfas dolomite and calcium sulfate dehydrate. under pressure through a tangential inlet (2) to the upper
Thus, principled practicability of the usage schematic part of the hydrocyclone (3), where the separation of
for the continuous separation of insoluble residues the insoluble residue from the liquid phase, i. e. solution
of hydrochloric acid dolomite slurry with the help of of calcium chloride and magnesium chloride.
centrifugal forces was offered in this study
1 - centrifugal pumps; 2 - pipe; 3 - hydrocyclone; 4 - sump; 5, 6 - reactors; 7 - chalk dispenser; 8 - patronova filter; 9 - fine filter; 10 - collection. ChCM - solution of calcium chloride and magnesium, VP4 - saturated steam, CD4 - condensate.
Fig. 4. Schematic scheme of the separation o insoluble residue by centrifugal forces
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Section 8. Chemistry
Suspension through the cylindrical portion moves along a helical trajectory in the conical part of the hydrocyclone. Simultaneously with the pulp to move the solids deposited in the walls and at the bottom of the apparatus. The thickened suspension (sludge) is supplied through the nozzle to the sump (4). The purified solution through the nozzle located on the side of the equipment, is returned to the process. Precipitation derived from a lower portion of the settler. The sludge from the settling tank is collected in the tailings pond.
The flow of the purified solution rises up and through the pipe (2) is fed to the upper part of the reactor (5). For neutralizing the solution of chlorides of calcium and magnesium to pH 5-6 at the same time here through the dispenser (7) CaO is added.
Reactors (5, 6) are vertical cylindrical apparatus with conical bottom. The device is equipped with a jacket and equipped with a helical stirrer. The temperature in the reactor is maintained at 363K.
For purification from mechanical impurities neutralized solution ofcalcium chloride and magnesium at 363K ofthe bottom of the reactor (5, 6) by a centrifugal pump (1) is pumped into the filter cartridge (8). Here the solution is circulated in the reactor (6) to complete purification. The solid mass accumulates on the surface of the filter pack and withdrawn from the bottom of the dump.
The filtrate flows down through the peripheral filter pipe going into the collection chamber and sent to the filter (9).
Clarified solution ofcalcium chloride and magnesium passes through the filter (9) and collected in a storage solution of calcium chloride and magnesium (10) — a vertical cylindrical apparatus with internal heating coils. Heating unit is operated by steam in the coil. The mixed solution of chlorides of calcium and magnesium at a temperature 363K centrifugal pump (1) is fed into the conversion reactor (RIC).
The next step in the process is the conversion of chlorides of calcium, magnesium and sodium chlorate, thus obtaining a liquid calcium-magnesium chlorate defoliant.
Here also the process of separating crystal from slurry of sodium chloride formed during the exchange reaction of the starting components. The purpose of the process is the removal of the crystalline sodium chloride and unreacted sodium chlorate. For this, we used the method of filtration, which was carried out in a laboratory, consisting of nodes drive the reactor at a constant temperature and filtered. The filter used dense filter cloth — belting.
The results of experiments on the filtering pulp precipitation ofcalcium and magnesium chlorate, sodium chlorate and chloride residue and sodium chlorate, calcium, magnesium, sodium vacuous presented in table 4.
Table 4. - Filterability pulp with chlorate precipitation of calcium, magnesium, and sodium chloride
Temperature, K Pulp quantity, g Pressure (ДР), N/m 2.10-3 Time (гХ sec. Thickness of firm residue (h Л mm Filterability (F), m 4/N-t Speed filterability, kg/m 2-s
on solid phase by filtrated
Pulp with sediments of sodium chloride
363 150 0.1471 10 4.4 153.20 0.7075 1.3643
200 0.1471 14 6.0 196.93 0.6737 1.1517
300 0.1471 18 7.5 243.21 0.6551 1.1197
Pulp with sediments of sodium chlorate
293 150 0.1471 11 4.6 130.19 0.6751 1.2403
200 0.1471 16 6.4 158.57 0.6189 1.0036
300 0.1471 21 8.2 187.82 0.5894 1.0002
These data indicate the usefulness of the filter pulp formed during the conversion of chlorides of calcium and magnesium and sodium chlorate residue of calcium and magnesium and sodium to the layer thickness regulating solid. In this case, the optimal temperature of the pulp filtration of sodium chloride is 363K, and for sodium chlorate 293K.
Based on the results of studies recommended the following diagram of a filtration of sodium chloride and sodium chlorate of conversion products (fig.5).
Where by the pulp resulting from the conversion of the solution of calcium chloride and magnesium with sodium chlorate, with the temperature at 363K using a centrifugal pump is directed to a vacuum belt filter (1). Under the influence of the vacuum in the first filtering section for separating a filtrate from the “cake”. Separated from the filtrate “cake” is subjected to two-stage washing. In the first washing step is performed after the water washing of the filter cloth and filter belts delivered by the pump (10) from the receptacle (7).
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Study of filtration processes at preparation of calcium-magnesium chlorate defoliant from dolomite
Fig. 5. Process flow diagram of the filtering unit of the pulp with precipitation of calcium and magnesium chlorate, chloride and sodium chlorate
1,11 - vacuum belt filters, reactors 2,3, 4 a/b, 9,10,17 - centrifugal pumps, separators, 5.12, 6.13, - fans, 7,8,14,16 -collectors, 15 - filling machine of installation, a heat exchanger 18. SCd - sodium chloride, SCt - sodium chlorate, DI - demineralized water, CW (R) - recycled water.
The second rinsing step is performed with demineralized water. The content of “cake" to leaching: Cl- — 25-35%; ClO3- — 30-38%; Ca+2-1-1.8%; Mg+2-
0.5-1%; Na+ — 20-26%.
The washing water after the second wash the filter cake is collected in the separator. Then, the wash water is fed by gravity into the tank water trap (7). Yield washing water is carried through the overflow tube to the collection (16) (in the step of dissolving sodium chlorate), which is used as a solvent.
Filtered “cake" (returnable salt), consisting mainly of sodium chloride containing small amounts of calcium,
magnesium and sodium chlorate, is transported to the electrolysis (part of “cake" after flushing: Cl- - 26-36%; ClO3- - 25-30%; Ca+2-0.5%; Mg+2-0.27%; Na+ - 23-27%).
The filtrate after filtration on a vacuum filter belt (1) by gravity with temperature 363 K enters the successive reactors (2, 3).
Cooling of the filtrate from the temperature 363K to 293K temperature takes place in two stages:
— the reactor (2) is ensured by reducing the temperature of the filtrate 363K to 323K in a shirt nutrient supply cooling water at a temperature of300K;
— the reactor (3) is ensured by reducing the
temperature of the filtrate to a temperature from 323K to 293K by conveying into the peeling water at 280K.
The pulp, after cooling to 280K using a centrifugal pump (4 a/b) is pumped to a vacuum belt filter (11).
Separated by vacuum from the “cake" filtrate collected in the separator (12). The filtrate is then fed by gravity into the collection (14) for storage of the finished liquid calcium magnesium chlorate defoliant. Next, a solution of calcium and magnesium chlorate centrifugal pump (4 a/b) is fed to the station bay drums.
Obtained after filtration “cake" is directed to the stage of dissolution of sodium chlorate in the collection (16). The composition of the “cake" obtained after filtration:
Cl- — 3-3.7%; NaClO3-60-65%; Ca+2-0.5%; Mg+2-
0.27%; Na+ — 9-10%.
In addition, the tank (16) enters liquor separated from the second section belt vacuum filter (1). In the tank (16), the resulting solution was continuously stirred. Then the solution using a centrifugal pump (17) is supplied to the heat exchanger (18) and heated to 363K. The heated 50% solution was pumped into the buffer tank and the resulting 60% solution of sodium chlorate enters RIC for subsequent conversion.
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Section 8. Chemistry
Conclusions
Thus, the filtration process was studied insoluble residue of decomposition products of natural dolomite solyanokislotnogo various methods. The basic feasibility of using was shown for continuous separation of insoluble residues hydrochloric acid pulp dolomite using centrifugal forces.
The process of filtering the slurry formed in the conversion of a solution of calcium chloride and
magnesium with sodium chlorate. The obtained results show the need for filtration of the pulp produced during the conversion of chlorides of calcium and magnesium and sodium chlorate residue of calcium and magnesium and sodium to the layer thickness regulating solid. In this case, the optimal temperature of the pulp filtration of sodium chloride is 363K, and for sodium chlorate 293K. The data obtained concepts filtration units in the preparation of calcium-magnesium chlorate defoliant were suggested.
References:
1. Kurbanov E., Kuziev R., Current status of soil fertility in Uzbekistan and some ways to improve it, Mining Bulletin of Uzbekistan, 1, 2001, 94-96, (in Russian).
2. Turamuratov I. B., The mineral raw material base of Republic Uzbekistan, Materials of the International scientific and technical conference, «Science and practice integration as the mechanism of effective development of geological field of Republic Uzbekistan», 2014, Tashkent, Uzbekistan, 2014, 7-9, (in Russian).
3. Hamrakulov Z. A., Tukhtaev S., Tadjiev S. M., Askarova M. K. Kinetics of decomposition of dolomite with hydrochloric acid, Journal Uzbek Chemica, Tashkent, 1, 2011, 6-9.
4. Zhuzhikov V. A. Filtration. Theory and practice of separation of the suspension, Moscow, 1971 (in Russian).
5. Aynshteyn V. G., Zakharov M. K., Nosov G. A., and others, The general course ofprocesses and devices of chemical technology, Moscow, 2003, (in Russian).
Kholiqov Abduvali Jonizoqovitch, National University of Uzbekistan, Senior Lecturer of the Department of Physical and Colloid Chemistry
E-mail: habduvali@rambler.ru
Phisico-chemical properties alkilaminomethylenfosfonovyh inhibitors
Abstract: Protective affectivity of some inhibitors relative to carbon steel in acid mediums has been investigated. Used inhibitors besides inhibition of common corrosion also have decreased librarian of hydrogen in steel and also have promoted to preservation of it's plastical properties.
Keywords: inhibitor, electrochemical corrosion protection, plastic properties, the degree of filling, adsorption equilibrium.
Холиков Абдували Жонизокович, Национальный университет Узбекистана им. Мирзо Улугбека, ст. преподаватель кафедры физической и коллоидной химии
E-mail: habduvali@rambler.ru
Физико-химические свойства алкиламинометиленфосфоновых ингибиторов
Аннотация: Исследована защитная эффективность ряда ингибиторов по отношению к углеродистой стали в кислых средах. Исследуемые ингибиторы помимо торможения общей коррозии, вызывают снижение диффузии водорода в сталь и способствуют сохранению ее пластических свойств.
Ключевые слова: ингибитор, коррозия, защита, пластические свойства, степень заполнения, адсорбционное равновесие.
Поиск эффективных методов противокоррозион- ущербом, наносимым коррозией в технологическом ной защиты металлов и сплавов обусловлен не только и электрохимическом плане, но и ухудшением эколо-
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