CC BY
5UOT 333.93
Salimova N.A. Professor, Doctor of Technical Sciences, Faculty of Chemical Technology, Department of Petrochemical Technology and Industrial Ecology, Azerbaijan State Oil and Industry University, Baku, Republic of Azerbaijan Huseynova M.A.
Associate Professor, Doctor of Philosophy in Technical Sciences,
Faculty of Chemical Technology, Department of Petrochemical Technology and Industrial Ecology, Azerbaijan State Oil and Industry University, Baku, Republic of Azerbaijan Салимова Н.А. профессор, доктор технических наук, химико-технологический факультет, кафедра «Нефтехимическая технология и промышленная экология», Азербайджанский государственный университет нефти и промышленности,
Баку, Азербайджанская Республика Гусейнова М. А.
доцент, доктор философии по техническим наукам, химико-технологический факультет, кафедра «Нефтехимическая технология и промышленная экология», Азербайджанский государственный университет нефти и промышленности,
Баку, Азербайджанская Республика E-mail: [email protected]
Ecological technologies: use of mineralized waters in technical water supply Экологические технологии: использование минерализованных вод в техническом
водоснабжении
Abstract: It is known that one of the technological processes of the oil chemistry, characterized by large water consumption is the pyrolysis process. Currently the amount of water steam supplied to the reaction tubes of the furnace is 50 up to 100% (on raw material). High
process temperature (750-850°C) leads not only to coke formation, but also to the appearance of scale (scale formation). In this regard, an alternative task to ensuring pyrolysis is the use of sea water instead of fresh, possible for coastal enterprises.
Аннотация: Известно, что одним из технологических процессов нефтехимии, характеризующимся большим расходом воды, является процесс пиролиза. В настоящее время количество водяного пара, подаваемого в реакционные трубы печи, составляет от 50 до 100% (в зависимости от сырья). Высокая температура процесса (750-850°C) приводит не только к образованию кокса, но и к появлению накипи (образование накипи). В связи с этим альтернативной задачей обеспечения пиролиза является использование морской воды вместо пресной, возможной для прибрежных предприятий.
Keywords: technological; water; oil; chemistry; supply.
Ключевые слова: технологический; вода; нефть; химия; снабжение.
Introduction. To use huge stocks of mineralized waters instead of fresh water in technical water supply systems of industrial enterprises, scientific-technical tasks solving is required.
The most important of them is prevention of the scale formation by heating and during of water evaporation. One of the effective methods solving of this task is magnesium-sodium zeolite softening. Purpose of this work — is research of the base qualitative regularities of the Mg-Na-zeolite softening process the wide class of mineralized waters (with salt content from 2.5 up to 35 g/1); development of the mathematical model of the process for research and optimization the technology as a whole. In the figure 1 in the most general form, the nature of the change in the output sorption curves for cationite KU-2 tor water with ion content (in mg-eqv/1) is shown.
CCa=CMg= 1 5 CNa = 17°.
As follows from the figure, the filter operation is characterized by the formation of two volume fronts. In the first third (-12 liters of filtrate) there is a decrease not only in calcium but also in magnesium hardness (up to 2 mg-eqv/1). The magnesium (Mg) is replaced by more selective calcium cations (Ca). Specific output of water before the (Mg) breakthrough was 26 1/1 of cationite and before the Ca-
breakthrough - 46 1/1. Cation exchange capacity - 680 g-eqv/mk residual calcium concentration — 0.2 mg-eqv/1. Thus almost 99% calcium removal was achieved.
High technological indices are possible also by Mg-Na zeolite softening of other types of mineralized waters, covering class in question. Experimental Part
Results on experiments with counter current ionization of water, given in the table 1, testify to this. Here as process output indices are: cation exchange capacity
-5 -5 -5
for calcium (Ew; g-eqv/m); specific water production (d, m /m); residual concentrations of calcium and magnesium ( C^s, C^g mg-eqv/1) and also-amount of initial water salts, which may be used for regeneration (g-eqv/1.).
Table 1 — Results of experiments by Mg-Na- zeolite softening
Initial water g Ep d pres cCa pres uMg
CNa CCa C Mg
50 5 N 7.7 640 128 0.02 2
100 10 10 6.7 670 67 0.10 6
170 15 15 8.4 710 47 0.22 8
188 16 60 7.0 525 33 0.20 48
248 13 59 9.9 400 31 0.35 46
470 20 1 10 11.0 380 15 0.03 75
As follows from the data received, even for waters with a high content of counterions high values of specific output of water are reached with a degree of removal of calcium 97% or more. An important task any ion exchange technology is development of the mathematical model of process.
It is important for forecasting of the technological indices of the process, depending on water ion composition, sorption and regeneration conditions.
These technological indices include: working exchange capacity оf сationite by
Ca
ions and residual content of these cations in treated water. There are several approaches to solving such problems [6]:
Figure 1 — Output curvers of the Mg-Na-zeolite softening of the water 1-CCa - f(V); 2-CMg = f(V); 3- can = f(V); 4-4 Cfa
—1 development of the functional (experimental-statistical) model, describing process without considering its mechanism;
—>2 development of the semi-empirical models which describe the whole process and reflect individual aspects of the mechanism of the studied process;
—3 development of purely deterministic models, reflecting sufficiently fully the mechanism of the studied process.
The latter approach is the most effective and at the same time the most complex.
Semi-empirical approach is based on the following initial formula, used tor calculation of the base technological index of the process-working exchange capacity of cationite (Ew):
"5
Ew = Op ■ Eeq[1-hp.l.(1-8) / ho], g-eqv/m (1)
where:
a — is regeneration efficiency coefficient;
Eeq — is the full equilibrium exchange capacity of cationite by calcium cations,
"3
g-eqv/m ;
A — is coefficient, taking into account incompleteness use of cationite exchange capacity in protective layer;
hp.i. — is height of the cationite protective layer, m;
h0 — is total height of the cationite layer, m.
According to calculation of the ion equilibrium, the Ca2+ residual concentrations, reliably eliminating CaCO3 and CaSO4 precipitation by heating and evaporation of mineralized water are 0.1-0.3 mg-eqv/1.
Deeper Ca2+ removal is achieved by filtration in the second stages.
Therefore, by development of the mathematical model of the process, can be limited to obtaining a system of ratios, allowing to calculate working exchange capacity of cat ionite, turning on the depth of Ca2+ removal in the category of indices, to which restrictions are imposed.
Analysis of the formula (1) indicates its universality (from the point of view of solution of applied tasks in particular - suitability for calculating the ionization process of mineralized waters of arbitrary composition).
Table 2 — Levels and intervals of factors variation
Levels Factors
Co(xi) mg-eqv/1 H(x2) mg-eqv/1 ACa (x3) u (x) m/h
Upper(+) 200/550 30/120 0.5/0.5 20/20
Lower (-) 40/200 10/30 0.2/0.2 5 5
zero 120/375 20/75 0.35/0.35 12.5/12.5
Note: in numerator — the value of the factors on brackish waters, in the denominator — on salt water.
Determination of the hp.l. value for every experiment carried out according to the methodic [1].
Since the equation (2) is linearized after logarithm, then processing the results of calculation was carried out, by logarithm received values of hpl.
Dependence hpl f (C0, H0, ACa, v) can be approximated with high accuracy by the power equation of the type:
hpe = a C a1- H a2- ACaa3 -0a4 (2)
where: a, a1, a2, a3, a4- are the empirical coefficients.
As a result of statistical processing the sum of experimental data, following the recommendation [3] the following polynomial was received (for brackish water):
y =1.36 + 0.079x1 + 0.146 x2 T 0.0445x3 + 0.0824x4 (3)
Therefore, research came down to getting functional dependences a^ hp.j., Eeq from the determining factors of the process.
- total salt content of initial water (Co);
- total hardness (Ho);
- calcium share in total hardness (ACa);
- rate of water filtration (0).
The object of research were mineralized waters with salt content from 2.5 up to 35g/l, by hardness 30-120 mg-eqv/1, calcium component 20+50% of total hardness. On base of preliminary experiments, it was area accepted to down the studied area into two parts within each of which a more accurate approximation of the desired functional dependences is possible [3].
Research was carried out on the cationite KU-2 by method of mathematical planning of experiment. Factors affecting the height of cationite protective layer and its levels are presented in the table 2.
The following expression was used to transition the equation (3) to natural scale [4].
_ 2 (igxj - lgxf ) ,
(4)
where xi — is coded value of i - factor;
x f, x f — are natural values of the upper and lower level of i-factor.
As a result of the transition from coded values of factors to natural, it was obtained:
lgY = 0.0678 + 0.234 lgQ)+ 0.524lgHo0.325lgACa+0.33lgu (5)
After potentiation:
hp.e. =1.17-Cq ■ 2 3- H0-5 2 -AC 03 3-u0- 3 3 (6)
Similar formula but with other empirical coefficients was derived for salt waters:
hp.e. =1.19-c00-3 5- //o0-24 -AC £ 1 5-u0- 3 8 (7)
Interpretation of the obtained formulas showed that for brackish waters hp.e. value is changed within 10 —50cm for salt waters — 40 —90cm, i.e. doubled on average.
The nature of the influence of all factors on hpe is the same: the rise of each of them contributes to growth of hp.e..
At the same time for both types of waters from 4 considered factors total hardness of water has a more noticeable effect on hp.e..
Dispersion analysis showed that, by research of effect of the base factors on coefficient of effectiveness of cationite regeneration (a2) in the study area, significant for the regeneration of cationite are 3 factors: C0, CCa and specific salt consumption. This dependence also may be approximated by equation of power type: Two calculation formulas were obtained: a) for brackish waters
b) for salt waters
„ — (\ r 0.04 0.24 rs -0.078 /0\
a2 = 0.6Ca ■ g C0 (8)
„ — r\ ¿r n 0.04. „0.31 ^ -0.078
a2 = 0.65CCa ■ g C0 (9)
In the first case: CCa= 5 -15, C0= 40—200 mg-eqv/1, in the second- 10—50 and 200 —6 0 mg-eq v/1 respectively.
For the whole range g = 4 —10 g-eqv/1 of cationite.
Calculation by above formulas show that in studied are a; values are changed within 0.7—0.97 and the most significant of the considered factors is specific salt consumption.
Method of mathematical planning was used also by study of dependence of the equilibrium exchange capacity of cationite on base factors.
On base of preliminary research an expediency of approximation of this dependence have been determined by equation of linear regression [5].
As a result, the following regression equations have been obtained:
a) for brackish waters:
Ee.q. = 4.27-2 - C0 + 0.1Ho + 490- ACa + 46.3H0 ACa (10)
b) for salt waters:
Ee.q. = 238- 0.77-Co + 2.8 H0 + 149 ACa + 7.7H0 ACa - 0.76Co ACa (11) Analysis of the equations (10) and (11) shown that the Eeq values are changed
-5
within 450— 1300 g-eqv/m in field of the brackish waters and within 240— 1200 g-
-5
eqv/m in field of salt waters. By the significance of the influence on Eeq value, factors are arranged in the following order: ACa, C0, H0.
Totality of equations (1) and (2) represent mathematical model of the process of Mg-Na-zeolite softening of wide class mineralized water [2]. Results and Discussion
Taking into account the features of the organization of the process in periodic filters and for reasons of technological expediency this model is supplemented by a system of restrictions:
- rate of water filtration (0);
- height of cationite layer (u);
- specific consumption ofthe magnesium and sodium salts on regeneration of cationite (g);
- residual content of calcium ions (Caraed)
3-5<u 25 - 30 m/h (12)
1.5 < h0 < 6 m (13)
2 < g < gcoh,g - eqv/l (14)
CH s< 0.1 mg - eqv/l (15)
In the equation (14) disposable quantity of salts (gCO4) is calculated as follows:
= 0 - 3 (l6)
where k — is coefficient, taking into account reuse of the worked regeneration solution. Value of Kr are changed within 1.1-1.4.
Table 3 — Results of the estimated and experimental determination of E2
Initial water Ee.q. g a E2
Co Go CCa g-eqv/m3 estimated experim
60 10 5 906 10.8 0.89 660 640
120 20 10 898 4.4 0.71 586 560
200 30 15 964 1 1.8 0.89 730 680
312 76 26 690 8.3 0.91 512 525
320 72 13 518 12 0.97 408 1 400
380 130 20 445 12 0.95 327 300
Adequacy of the resulting model was vertified by comparison of calculated values of E2 with experimental data, given earlier in table l.
Calculation of E2 was made on computer as method above, by method of consistent approximation, namely by preliminary accepted E2 value the g, hp.e., a were calculated, then the E2 value was specified.
For the condition that the calculation is completed, the discrepancy between adjacent values of the exchange capacity was taken, following the inequality:
E2 < 1 % from E2
Analysis of the obtained results (table3) shown that average deviation of experimental and estimated values of E2 does not exceed 7%, which is quite acceptable for implementation of practical calculation.
Received model was used for study of the height of cationite layer on the exchange capacity of cationite within values of specified factor which cannot be sustained under laboratory conditions.
It has been determined, that by increase of catalyst layer from 1 up to 3 m a working exchange capacity is increased by 1 8%, 12% and 20% respectively by processing of mineralized waters (look the table 3).
Conclusions
Thus, the mathematical model of the Mg-Na zeolite softening process of wide of mineralized waters was obtained, allowing:
- comprehensively research and optimal process;
- solve practical problems by calculation and projection of the water supply plants ensuring non-scale regime work of the heat-engineering systems:
- the same for enterprises of oil production oil refining and other branches of industry.
References
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3. Shirinova D.B., Bayramova A.S., Allahverdiyeva U.E. Study of biological cleaning of water contaminated with aromatic hydrocarbons. Journal "Oil Economy of Azerbaijan". — Baku, SOCAR, — No.3, — 2022, — P.54-58. DOI.10.37474/0365-8554/2022-03-54-58.
4. Senyavin M.M. Ion exchange in technology and analysis of inorganic substances. — M: Chemistry, — 1980, — 272 p.
5. Spiridonov A.L. Experiment planning in the study of technological processes. — M.: Mechanical Engineering, — 1981, — 184 p.
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