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References:
1. Атакузиев Т. А. Физико-химические исследования сульфатсодержащих цементов и разработка низкотемпературной технологии их получения. / Ташкент, - Фан, - УзССР, - 1983, - С. 102.
2. Бутт Ю. М., Тимашев В. В. Портландцементный клинкер. - М.,/Стройиздат, - 1967, - С. 303.
Iskenderov Akhmed Maksetbaevich, Tashkent chemical technological institute, the associate professor of the faculty of chemical-technology of inorganic substances E-mail: [email protected] Erkaev Akhtam Ulashevich, Tashkent chemical technological institute, the associate professor of the faculty of chemical-technology of inorganic substances
Toirov Zokirjon Kalandarovich, Tashkent chemical technological institute, the associate professor of the faculty of chemical-technology of inorganic substances Begdullaev Akhmed Kobeysitnivich, the main specialist on the innovation and new technology UE "Kungrad Sodium Plant."
Research on the purification process of low-grade sodium chloride
Abstract: The theoretical analysis on the purification process of brine has been carried out with the usage of solubility isotherms of reciprocal systems Ca2+ ,2Na + //2Cl- ,SO] - H2O . By experimental investigations it has been determined that the purification of low-grade sodium chloride with the application of distilled fluid in the production of soda ash can increase the coefficient of sodium chloride to 0,5-2, 0% and decrease water consumption and lime to 3-8%.
Keywords: sodium chloride, distilled fluid, theoretical analysis, soda ash, water consumption.
In Uzbekistan the reserves of salt deposits of Bar- grab crane in the capacity for dissolving salt, where dis-
sakelmes, located in 30 km from UE «Kungrad Sodium solved by water (volume — 2500 m 3) with the obtaining
Plant» (UEKSP), have been chosen as the base of chlo- of crude brine, containing 26,41% NaCl. The dissolution
rine-sodium raw materials. occurs in the cylindrical apparatus with a square hopper
Salts must be subjected to the purification from ad- for receiving solid salt with the inner distributing devices
ditives of salt calcium and magnesium. For example, for for inputting water and steam and overflow the top of the
this purpose in the Crimea Sodium Plant a new two- chute. The crude brine with the temperature of 44 °C
staged lime-sodium method of brine purification [1] overflows into the container, intermediate container of
has been developed and implemented. With the pur- brine, which is cylindrical vessel with the volume flat cap
pose of intensification of this process, the suspension of 2500 m 3 [2].
of calcium hydroxide is quenched by crude brine and The initial brine is pumped in the capacity of raw
the formed suspension is fed to the mixing with brine, brine with the volume of 3500 m 3, which is delivered to
and it is subjected to the purification (purification stage the container for mixing. Solutions of lime milk and soda
of brine from magnesium). ash are delivered into this container at the temperature
In the technology of obtaining soda ash in UE KSP, of 50 °C. In the reactors the binding of cations Ca 2+ and
solid salt from storehouse is delivered with the help of Mg 2+ is occurred with the formation of insoluble combi-
nations of Mg (OH)2 and CaCO3, which are in the form of slime, are removed periodically in slime container — a cylindrical vessel with a mixer. The purification process occurs at the temperature of 43 °C.
The brine travels from reactor into the container with baffles, where it is mixed with the solution of polyacryl-amide (PAA) for better coagulation. Further, the purified solution of sodium chloride is given to the ammoniation stage. The ammoniated brine undergoes to the preliminary and final carbonation. The formed bicarbonate sodium is separated on filters and further it is delivered to the calcination for obtaining the commercial soda ash. The filtered fluid is delivered to the distillation of ammonia and carbon dioxide with the blowout of distilled fluid in wastes slurry tank.
The advantages of this method: availability, abundance, large reserves and low cost of raw materials (table salt and limestone); the basic reactions, except roasting oflimestone and calcination process, which occur at low (up to 100 °C) temperatures and at atmospheric pressure; stability of technological processes; high-quality of products; relatively low cost of soda ash.
Disadvantages: low degree of raw material usage — sodium is used only by two-thirds, calcium and chloride are not used at all; the large amount of solid and liquid wastes, demanding utilization, dumping or long-term storage; significant energy resource consumption; high specific investments which lead to the long-term payback of built factories; the impossibility of carrying out the purification of low-grade sodium chloride with the content of 3-4% of insoluble part, for example, in UE KSP from sulphate ions, the content of which increases to 2.4 times of regulated amount. Besides that, it is necessary to consider that when sodium chloride is added to the solution of soda ash in the process of purification the additional amount of sulphate ion is produced due to the presence of sulphate calcium in the solution according to the reaction: CaSO4 + Na2CO3 ■ CaCO3 + Na2SO4
While producing well-dissolved salt Na2SO4 in the further process the regeneration of ammonia from filtered fluid complicates, as at the interaction of it with the limestone suspension the gypsum deposit is generated (instructing of distiller walls). Real methods of decreasing of contents of ions SO42-in crude brine to the level, excepting the generation of gypsum incrustation at the distillation stage, in the sodium industry it hasn't been yet in this sphere. Intensive works are being held though [1-10].
These shortcomings prove that the given method of brine purification is imperfect and noneconomic, especially, at the usage of low- grade sodium chloride.
The aim of the present investigations is the development of purification technology of low-grade sulphate containing sodium chloride with the partial return in the process of distiller fluid-waste production of soda ash.
So, the low-grade of sodium chloride has to dissolve in the presence of distilled fluid at 25-45 °C, and the ratio of ions SO42-/ Ca 2+ and Mg 2+/Ca 2+ must be in the interval of 0,55-0,98, which regulates the amount of distiller fluid, returned to the stage of salt dissolution from the regeneration part of the production of soda ash.
In comparison with the mentioned in [1; 2; 9; 10], the suggested purification method of low-grade sodium chloride has the series of existing essential features.
Firstly, in the suggested technology the regime of dissolving process of low-grade sulphate containing sodium chloride and the amount of return distilled fluid is regulated on the basis of isotherms of dissolution of quaternary mutual systems Ca 2+,2Na+//2Cl-, SO2- -H2O, at 25 and 45 °C (Fig. 1 and table. 1).
The given system consists of four ternary and four binary systems. Binary and ternary systems are rather highlighted in the literature [3, 8], in which the equilibrium is established in 6-7 days.
At 25 °C, lines of six fields of salts crystallization break the surface of solubility diagrams, hereupon, that five fields correspond to the release of initial components, one field to the double combinations. Fields converge in four nodal points, corresponding to the release of three different phases.
From the solubility diagram analysis of systems 2Na+, Ca 2+//2Cl-, SO42- H2O at 25 °C it is necessary that its main part belongs to the crystallization field of two dihydrate sulphate calcium, which is due to its poor solubility in water. It is clear from the diagram that solubility of sulphate calcium in the saturated solution of sodium chloride reaches to 0,598%, and with the increase of chloride calcium content to more 0,6%, it effects salting-out of chloride sodium. The solubility of sulphate calcium decreases to 0,123% with the content of 1,61% chloride calcium. However, an excessive increase in the content of the last is also not desirable, since at the purification stage of brine from calcium ions it is required the increased consumption of soda solutions.
The second distinguishing feature of the controlling process is the separation in collections of salt solutions of its insoluble part and the formed calcium sulphate. That allows significantly the number of stops of sinkers to decrease for the purification and to prevent the conversion of calcium sulphate by carbonate sodium with the formation of well-soluble sulphate sodium, which
Table 1. - Dat a on solubility of components in the syste m 2Na+, Ca2+//2CI, S042 -H20 at 25°C
№ Composition points Composition of fluid phase,% Composition ( mole/1 )f fluid phase, 00gr/r Indices of Ineke Solid phase
NaCl O C/5 n z Ö n O O C/5 rt <J O (S X NaCl O C/5 n z r) Ö n O O C/5 rt <J + n O O C/5 Moles h2o /MO moles S salts
1. 26,41 - - - 73,59 0,2257 - - - - - 18,1139 NaCl
2. - 21,8 - - 78,2 - 0,1535 - - - 1 28,3023 Na,S04-10H,0
3. - - 47,10 - 53,0 - - 0,4234 - 1 - 6,954 CaCl2-4H20
4. - - - 0,21 99,79 - - - 0,0015 1 1 3695,933 CaS04.2H,0
5. 25,85 - - 0,4666 73,6834 0,2209 - - 0,0034 0,0152 0,0152 18,2501 NaCl+CaS04.2H,0
6. 23,10 6,89 - - 70,01 0,1974 0,0485 - - - 0,1972 15,817 Na,S04+NaCl
7. 13,67 14.82 - - 86,33 0,1168 0,1044 - - - 0,4727 24,53 Na,S04+Na,S04.10H,p
8. 1,02 43,59 - 55,39 0,0087 0 0,3927 - 0,9783 - 7,666 NaCl+CaCl,.6H,0
9. 21,21 0,219 78,79 - 0,149 - 0,0016 0,6288 1 29,065 Na,S04.10H,0 +CaS04-2H,0
10. 23,87 3,90 - 0,0644 72,1656 0,204 0,0275 - 0,0005 0,0022 0,1207 17,281 NaCl+3Na,S04.2CaS04+CaS04.2H,0
11. 22,21 5,66 - - 72,13 0,1898 0,0399 - - - 0,1737 17,4454 3Na SO-2CaSO+CaSO-2H O 2 4 4 4 2
12. 12,88 13.41 - - 87,12 0,1101 0,0944 - - - 0,4616 23,607 3Na,S04.2CaS04+CaS04.2H,0
13. 22,71 6,70 - - 70,59 0,1941 0,0472 - - - 0,1956 16,2524 NaCl+Na,S04+3Na,S04.2CaS04
14. 18,88 9,58 - 0,0228 71,5172 0,1614 0,0675 - 0,0002 0,0009 0,2955 17,3426 Na SO+3Na SO-2CaSO, 2 4 2 4 4
15. 16,42 12,15 - 0,0223 71,4077 0,1403 0,0856 - 0,0002 0,0009 0,3795 17,5458 Na SO+3Na SO-2CaSO, 2 4 2 4 4
16. 13,63 15,45 - 0.0251 70,92 0,1165 0,1088 - 0,0002 0,0009 0,4834 17,47 Na,S04+Na,S04.10H,0+3Na,S04.2CaS04
17. 11,78 14,42 - 0,0256 73,7744 0,1007 0,1015 - 0,0002 0,001 0,5025 20,25 Na,SO-10H 0+3Na,SO-2CaSO+CaSO • ¿ T" h T" î 1 2H20
18. 7,64 16.16 - 0,1353 92,2247 0,0653 0,1138 - 0,001 0,0056 0,6374 28,45 Na,S04.10H,0+CaS04.2H,0
19. 4,58 18,06 - 0,1570 77,203 0,0391 0,1272 - 0,0012 0,0072 0,7666 33,89 Na,S04.10H,0+CaS04.2H,0
20. 2,29 19.74 - 0,1795 97,5305 0,0196 0,1390 - 0,0013 0,0081 0,8774 33,89 Na,S04.10H,0+CaS04.2H,0
S - - - - 54,2 - - - - 1 0,015 7,20 CaCl,;4H,0+CaS04.2H,0
s, - - - - 54,3 - - - - 0,978 0,0151 7,00 CaCl,;4H,0+NaCl+CaS04.2H,0
causes incrustations of pipelines, carbo- and distillation columns in the production of soda ash.
The initial, intermediate and final solutions have been analyzed in the content of ions Cl-, Ca 2-, Mg 2+, SO2-and insoluble part with the usage of common methods of analysis [11-12]. In the researches there has been used the low-grade sodium chloride of composition mass. Mass%: NaCl - 94,01; Ca 2+ -0,49; Mg 2+ -0,115; SO2--1,15; i. r. - 4,10 and distiller fluid composition mass %: NaCl - 5,67; CaCl2 -9,57; Mg 2+ -0,03; SO2- -0,003; i. r. -0,13.
The amount of distiller fluid for 1000 kg of low-grade sodium chloride at the given weight ratio of SO2-: Ca 2+ is calculated on the formula:
Adist. f
(100 • as02_ -100N • aCg2_
N•b 2-
)
AH,O -
Ad,a.f.-bNaC1 )-100 -
(100 ■ O-NC -{(100 OnoC
+A-dit. f (1 - bNaa )}26,4
-A ■b
dist. f. uNaCl
where Adist. f; AH0 - amount of distiller fluid and recycled water, respectively for the dissolution of sodium chloride, kg; aso2_, aCa2_, aNaCl — the content of SO2- Ca 2+ and NaCl in sodium chloride %;bCa2_ ,bNaCl - contents of Ca 2+ and NaCl in distiller fluid,%; N-controlled weight ratio of SO2-; Ca 2+ at the dissolution stage, which fluctuates in the interval of 0,55-0,98.
The dissolution process of salt has been carried out at the temperature 45 °C with the settling of obtained suspension for 120 min. After release of the clarified part of the produced thick suspension has been filtrated, the wet residue has been expressed with the obtaining of clarified desulfated solution. It can be seen on the experimental data (tables 2,3) that at the salt dissolution by only the recycled water the clarified solution of sodium chloride with the content is obtained, mass%: NaCl - 26,41; Ca 2+ -0,13; Mg 2+ -0,03; SO2- -0,32; i. r. -0.13 and ratio SO42-/ Ca 2+, equal to 2,46.
By salt dissolution in the presence of distiller fluid and ratio of SO42-/ Ca 2+ = 0,86 it is obtained the dissul-fated clarified solution of sodium chloride with the content, mass %: NaCl — 26,20; Ca 2+ -0,29; Mg 2+ -0,04; SO42- -0,20; i. r. -0,14. With the decrease of SO42-/Ca 2+ to 0,55 the content of ion SO2- decreases to 0,15%, however, the content of ion Ca 2+ is more than 0.44%. Therefore, the decrease of ratio SO42-/Ca 2+ is lower to 0,55 undesirably.
The decrease of ratio of ions SO2-/Ca 2+ and Mg 2+/ Ca 2+ at the dissolution stage to less than 0,55 leads
to the increase of content of chloride calcium in the solution, which requires the increased consumption of sodium solution at the purification stage from calcium ions, at the indicated ratio more than 0,98 it is observed incomplete desulfation.
The fall of temperatures to 25 °C leads to the minor decrease of content of ions SO2- in clarified solution. As
4
analysis of isotherms shows the volume diagram of solubility systems
Na+ ,1 Ca2+ / /2SO2;,Cl~ - H2O at 25 °C, occupying
CaSO4- 2H2O the volume is more than at 45 °C. The increase of content of SO42+ is defined due to the formation of small crystals CaSO4- 2H2O and the slow precipitation due to the viscosity of brine.
At the temperature less than 25 °C the reduction of solubility of sodium chloride occurs.
The increase of temperature more than 45 °C practically does not affect to the solubility of sodium chloride and leads to the overspending of heating steam.
Therefore, it is desirable to carry out the dissolution process at 40-45 °C temperature.
Various factors influence on the kinetics of sedimentation and condensation of sludge. Thus, by the purification of brine from calcium ions and magnesium sludge, which is rich with calcium carbonate, it can be gelatinous and have a large volume at the beginning of condensation.
For achieving high sedimentation rates and minimum final volume of sludge, it is desirable that the ratio of ions Ca 2+ and Mg 2+ in the suspension has been as large as possible.
Therefore, at the purification of brine, which is rich with magnesium, more rationally the usage of lime, as at the purification from Mg 2+ ions Ca 2+, forming during dissociation Ca (OH)2, transit in the final result to CaCO3, increasing the ratio of calcium and magnesium ions in the suspension [9; 10].
Implementation of the obtaining process of soda ash from low-grade sulphate containing halites on the suggested technology provides all the primary requirements on the creation of conditions for the formation of large well precipitating crystals with the obtaining purified brine, according to the technological regulations [2; 9; 10].
Composition of purified brine: NaCl — no less than 100 n.d, Ca 2+ — no more than 10 mg/l, Mg 2+ — no less than 5 mg/l, insoluble residue — no more than 40 mg/dm 3, temperature of brine — 35-40 °C [2].
Fig.l.Diagram of the solubility of reciprocal systems 2Na+, Ca 2+//2CI-, SO42- -H2O at 25oC Table 2. - The influence of technological parameters on technical-analytical indicators of dissolution process
№ Technical-analytical indicators of the process Existing technology Develoi ped technology
1 2 3
1 2 3 4 5 6
1 Composition of low-grade sodium chloride, mass.% NaCl 94,01 - - -
H. 0. 4,64 - - -
so2- 1,15 - - -
Ca 2+ 0,49 - - -
Mg 2+ 0,115 - - -
Amount of low-grade sodium chloride, g 1000 947.74 958,99 958,99
1 2 3 4 5 6
2 Composition of distiller fluid, mass% NaCl 5,67 - - -
n. r. - - - -
SO 2- - - -
CaCl2 9,57 - - -
Mg 2+ 0,027 - - -
3 Additive of distiller fluid, g - 394,36 237,19 237,19
4 Amount of circulating water, g 2559 2164,64 2321,81 2321,8
Ratio of ions in the suspension, formed at the dissolution of SO42-/Ca 2+ 2,347 0,597 0,86 0,86
6 Composition of crude brine after separation i. r. and produced sulphate calcium from suspension, mass.%: NaCl 26.41 26,15 26,20 26,18
i. r. 0,13 0,14 0,13 0,15
SO42- 0.32 0,155 0,20 0,23
Ca 2+ 0.14 0,44 0.29 0,30
Mg 2+ 0.03 0.03 0,04 0,041
7 Temperature of dissolution, °C 44 44 43 25
8 Ratio of ions:
SO 2-/Ca 2+ 2,856 0,354 0,689 0,74
Mg 2+/Ca 2+ 0,21 0.066 0.138 0,14
9 Mass of residue, g 139,2 201,0 198,0 196,0
10 Mass of clarified solution, g 3419,8 3358 3320,0 3318,0
£AJl/UU
* J 1 , -. A , i
Figure.2 X-rayogram of samples. Sodium chloride from deposits of Karaumbet
-1 ■--■■■■■.—1—f * *
-i----1-1—(-r-r-,-i^i 'I i ............. ■ I -----........i-I-—I-'T-.-M. |-r-,-----
10 20 30 40 50 60 7:
Figure.2 X-rayogram of samples. Sodium chloride from deposits of Barsakelmes
5DDC -
.--J-JL,—Л-- JJU J Lnilll ifS/sJ^ . п-^УЛн,.^ ..„ ■
10 20 30 40 50
Figure.2 X-rayogram of samples. Insoluble part after dissolution of salt
60
20 CO
wivi ........... 0 20 к : : 4 aULAM, 5 u в С 7D
Figure.2 X-rayogram of samples. Insoluble part after the purification of crude brine from magnesium and calcium ions
In order to determine the salt composition of residue, produced by the dissolution of low-grade sulphate containing sodium chloride and its purification from ions of magnesium and calcium, chemical [11] and physico-chemical methods of analysis have been used [13-17]. The results of researches show that low-grade sodium chloride mainly consists of NaCl, and certain amount of sulfate calcium and muds (figure 2, curves 1 and 2). The residue, generating by the dissolution of salt mainly consists of calcium sulphate, NaCl and muds (curve 3). The residue, generating at the purification of crude brine from magnesium and calcium ions consists of carbonates
of calcium and magnesium (dolomite) and magnesium hydroxide (curve 4).
Based on the above-mentioned investigations we can conclude that the suggested method of the purification of low-grade sodium chloride can be positively in general and in the production of soda ash:
- the efficiency of the usage of initial components is increased in the production of soda ash;
- distiller fluid of 5-10%, which is waste of sodium production, is used with the increasing of the usage coefficient of sodium chloride to 0,5-2,0% and decreasing of the consumption of water and lime to 3-8%.
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3. Бодалева Н. В., Ленешков И. Н. Исследование растворимости в системе K2SO4-MgSO4-CaSO4-H2O при 55 С-ЖНХ. т. 1, 1956, - № 5. C. 995-1007.
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Mamedov Shakir Ahmad, PhD, Azerbaijan University of Architecture and Construction, Department Test and seismic stability of construction,
Azerbaijan, Baku, E-mail: [email protected] Hasanova Tukezban Jafar, PhD, Azerbaijan University of Architecture and Construction, Department Test and seismic stability of construction,
Azerbaijan, Baku, E-mail: [email protected] Imamalieva Jamila Nusrat, PhD, Azerbaijan University of Architecture and Construction, Department Test and seismic stability of construction,
Azerbaijan, Baku, E-mail: [email protected]
Reserch of movement of the viscous elastic fixed vertically located cylinder in liquid with the free surface under the influence of the seismic waves
Abstract: The problem about movement of the rigid cylinder keeping vertical position under the influence of running superficial waves in a liquid is considered. The indignation of a falling wave caused by presence of the cylinder which moves is thus considered. Special decomposition on a falling harmonious wave is used. The problem dares an operational method. For a finding of the original the decision, considering that the image denominator represents tabular function, Voltaire's integrated equation of the first sort which dares a numerical method is used.
Cylinder movement in the continuous environment under the influence of waves is considered in work [1]. Problems are solved by an operational method, thus originals of required functions are looked for by numerical definition of poles of combinations of transcendental functions and calculation of not own integrals.
Using specificity of a task below, decisions are under construction the numerical solution of the integrated equation of Volter of the first sort that doesn't create computing problems of the complex roots of transcendental functions [2; 3] connected with search. Keywords: cylinder, liquid, wave, movement, surface.
