A research of different composition and structure inhibitors’ effectiveness using a cooling scale  loop modeling equipment in dynamic conditions. Simulated conditions of water circulating two  industries. The optimal molecular weight for carboxylic polyacids as well as the optimal dose for  carboxylic polyacids and organophosphorus compounds for use in these systems were estimated

Cherednichenko, D. V.

Dormeshkin, О. B.

Vorobiov, А. D.

A research of different composition and structure inhibitors’ effectiveness using a cooling scale loop modeling equipment in dynamic conditions. Simulated conditions of water circulating two industries. The optimal molecular weight for carboxylic polyacids as well as the optimal dose for carboxylic polyacids and organophosphorus compounds for use in these systems were estimated

Belarusian State Technological University

Chemistry and Technology of Inorganic Materials and Substances 63 УДК 628.16  О. B. Dormeshkin, D. Sc. (Engineering), assistant professor, vice-rector for research (BSTU); А. D. Vorobiov, PhD student (BSTU),  D. V. Cherednichenko, PhD (Chemistry), senior researcher (IGIC NASB) EVALUATION METHOD OF SCALING INHIBITORS ACTION EFFECTIVENESS A research of different composition and structure inhibitors’ effectiveness using a cooling scale loop modeling equipment in dynamic conditions. Simulated conditions of water circulating two industries. The optimal molecular weight for carboxylic polyacids as well as the optimal dose for carboxylic polyacids and organophosphorus compounds for use in these systems were estimated. Introduction. To ensure optimal temperature rate in industrial production water cycles are wide-ly used. All water circulating systems can be roughly classified into one of three types of struc-tures that represent a set of water facilities and the sequence of their location on the terrain: open re-circulating systems (direct-flow with water reuse), direct-flow systems and closed recirculating sys-tems (reverse).  Continual tightening of ecological regulations and the rising cost of water abstracted from natural sources cause the reduction of water consumption by industrial enterprises by the way of upgrading water circulation systems with increasing evaporation rate. Therefore the issue of scale deposits in the pipes of the cooling water circulation systems, and especially on the heat exchanging surfaces of the equipment is a very topical. The rate of formation of scale deposits in water circulation systems, and their quantity directly de-pends on the operating system parameters, as well as on water quality indicators such as hardness, alkalinity, pH value, TDS (total dissolved solids), etc. In general case, a water stability indicator is used. Water is considered to be stable, if it does not form and dissolve hardness depositions and thus enables continuous operation of a cooling circulat-ing system for a long time [1]. The deviation scope of the water system from the stable state shows its disposition to scale formation or corrosion. Thus, it is possible to predict to some extent the speed and the quantity of scale deposits being produced. To simplify practical calculations empirical criteria are introduced to determine the saturation index, or water stability, for example Langelier saturation index, etc. [2]. Langelier saturation index (LSI) is calculated by the formula  LSI pH pH ,s   where in pH  measured water pH value; рНs – pH value corresponding to the equilibrium СО2 con-tent in the solution depending on the temperature and the concentration of Са2+  cations, the total al-kalinity level and salinity. The latter figure (pHs) is determined using nomograms. The aggressiveness of water is evaluated by the value of Langelier saturation index. If the index value is less than 0, then this water can dissolve calcium carbonate, eliminating the possibility of a protective carbonate film formation on the surface of pipelines and equipment, which causes corro-sion process. At a positive index value water is non-aggressive and promotes the carbonate deposits formation. If the value of Langelier saturation in-dex is close to 0, water is considered to be stable. The value of the saturation index grows with in-creasing of evaporation coefficient value, and ac-cordingly, the tendency to form scale deposits in-creases dramatically. To compensate this negative effect the specific chemical compounds are brought in water composition – scale formation-inhibitors the use of which allows the water system to remain stable at elevated saturation index for a long period of time. There are various methods for effectiveness evalu-ating of the inhibitory effect of reagents [3]. However, most methods are characterized by complexity, strin-gent demands for test conditions and purity of the rea-gents being used. A common shortcoming is the lack of study possibilities of sedimentation processes in dynamic environments and the associated complexity of phase study of carbonate sedimentation on the sur-face of various materials. In this work, the installation simulating the sedi-mentation processes under dynamic conditions РМАС SCL-30P-2A (UK) was used to evaluate the effective-ness of the reagents as scale inhibitors (Fig. 1). The operation principle of the apparatus is a dy-namic measurement increasing as a result of scale formation, a differential pressure in the metal capillary at varying or constant experiment parameters. Solutions of calcium and magnesium chloride, and sodium bicarbonate of certain concentration from the containers 1 and 2 are fed via peristaltic pumps 3, 4 the capillary 6 with a constant volume velocity. Before mixing and feeding to a capillary the solutions pass through heat exchangers (not shown in the diagram) placed in a thermostat 7, for achieving a predetermined temperature. The for-mation and sediment deposition takes place in the 64 ISSN 1683-0377. Proceedings of BSTU. 2013. No. 3. Chemistry and Technology of Inorganic Substances capillary under dynamic conditions. Thickness growth of deposits on capillary walls increases the hydrodynamic resistance of the system that is fixed by means of a differential manometer 5.   Fig.1. Installation scheme,  simulating sedimentation processes: 1, 2 – containers; 3, 4 – pumps; 5 – differential pressure gauge; 6 – capillary; 7 – thermostat  The time interval, during which the scale layer, leading to an increase of differential pressure in the capillary from zero to a certain value is formed, is used as an index characterizing the effectiveness of preventing or slowing down (inhibition) sedimen-tation. The given value is a relative value – it indi-cates the inhibiting process of sedimentation in the capillary compared to the control non-reagent op-tion. The smaller is the pressure increase in a capil-lary within a certain period of time, the more effec-tive is the reagent and more optimal the used dose. This installation allows to evaluate the tendency of the water used in a particular water recirculation systems to scale formation.  In industry, the water enters the water recircu-lation systems from natural surface or underground sources. Depending on the origin the impurity con-tent in the water can vary considerably. So, the company PJSC "Mineral Wax Plant" uses water from artesian wells, and the PJSC "Grodno Azot)" – river water (Table) The aim of this work is to simulate the opera-tion of the cooling water circulating cycles, as well as the effectiveness study of scaling inhibi-tors of different composition under dynamic con-ditions.  Main part. As model systems solutions of so-dium hydrogen carbonate, calcium and magnesium chlorides were used, taken in amounts correspond-ing to the water parameters from the real water circulation systems of enterprises "Mineral Wax Plant" and PJSC "Grodno Nitrogen". The pH value was adjusted by means of sodium hydroxide. As scaling inhibitors the following set of compounds was used: succinic acid, adipic acid, sebacic acid, polyacrylic acid having a molecular weight (MW) 2,000–16,000 polymethacrylic acid (MW 5,100) hydroxyethylenediphosphon (HEDP) amintrimetilphosphon (ATMP), 2-phosphonbutan 1,2,4-tricarboxylic acid (PBTK). The scaling in-hibitor was fed to the unit separately. The inhibi-tor concentration quantity in the solutions being studied is selected in such a way as to ensure a pressure change in the capillary within an hour. The reagent doses being used are equal within the same system. As a comparative characteristics of the reagent effectiveness there served a relative indicator  time interval (), during which in the capillary there is formed the scale layer, which leads to a differential pressure increase from zero to a certain value, simi-lar for all experiments (in our case  to 4 psi). The results of studies are presented in Fig. 2. Experiments have shown that when bringing the dicarboxylic acids (succinic acid, adipic acid, sebacic acid) in the system, the inhibition duration does not increase substantially as compared with the control. Carrying the polymeric carboxylic acids (poly-acrylic acid, polymethacrylic acid, and their copol-ymers) leads to an increase of inhibiting duration by 1.2-1.3 times. When using as inhibitors organo-phosphorus compounds (hydroxy-ethylenedipho-sphon, amintrimetilphosphon 2-phosphonbutan-1,2,4-tri-carboxylic acid) the system work duration increases by 2,6-3 times compared with the con-trol, reagentless option. Quality values of the circulating water samples at enterprises  Water Alkalinity, mmol / l Са2+, mg/l Mg2+, mg/l pH LSI PJSC ”Mineral Wax Plant” (artesian water)  Feeding (Ку = 1) 5 49.9 12.7 7.46 0.9 Cycle (Ку = 2) 7.84 100.1 25.3 8.8 2.5 Cycle (Ку = 3) 10.6 149 37.9 9 3.1 PJSC “Grodno Asot (Nitrogen) (river water)  Feeding (Ку = 1) 2.83 154 55.5 8 1.5 Cycle (Ку = 2) 5.07 308 111 8.4 2.5 Cycle (Ку = 3) 7.61 462.1 166.6 8.7 3 1 5 3 2 4 6 7 Chemistry and Technology of Inorganic Materials and Substances 65  Fig.2. Time interval for scaling ()  in the modal system without additions (1)  with reagents (2–8): 1 – without additions; 2 - PMAA (0.1 mg / l, МW2,100);  3 - PAA (0.1 mg / l, МW2,100) 4 - HEDP (0.1 mg / l);  5 - ATMP (0.1 mg / l) 6 - succinic acid (0.1 mg / l);  7 - adipic acid (0.1 mg / l) 8 - sebacic acid (0.1 mg / l)   The study of PAA samples with different mo-lecular weights (500, 2,100, 5,100, 8,100 and 15,100) results into the fact that the inhibitory action effectiveness with increasing molecular weight ini-tially increases and then decreases (Fig. 3). Fig. 3. Differential pressure value  in the system for carboxyl polyacids  with different molecular weights  at a given point of time   Thus, the carrying of samples PAA of MW 8,100 and 15,100 in the system reduces the inhibi-tion time due to the fact that polymers with such a molecular weight value begin to show flocculant properties. In this case there is not only the interac-tion of  the polyelectrolyte polar groups with the calcium and magnesium carbonate crystal  surface , but also the bond formation between the remain-ing in free state "tails" of macromolecules that en-tails coarsening, the particle aggregation and sub-sequent sedimentation. In the case of PAA with MW of 500 and less the inhibition time is also reduced compared with MW 2,1005,100 because of the fact that the size of the macromolecules does not allow to form an adsorption layer on the surface of the formed crys-tals, hindering their further correct formation and growth.  To determine the optimal inhibitor dose the number of experiments are carried out and the de-pendences of the inhibition time on the dose of the input polyelectrolyte are obtained. The graph of dependence is shown in Fig. 4. Fig. 4. Scaling duration ()  in a model system at various reagents dosages   Fig. 4 shows that the polyelectrolyte dose in-crease from 0.25 to 3 mg/l greatly improves the inhibiting effect. When increasing PAA concentra-tions from 3 to 8 mg/l and more  is rising slightly. Therefore, we can conclude that the optimal value of the carboxyl substances concentration in the system is 3.5 mg/l, of phosphorus compounds –  5.8 mg / l.  In the investigated compound series organo-phosphorus inhibitors showed maximum inhibitory potency that is probably due to their ability to form stable complexes with calcium and magnesium ions. Polymeric carboxylic acids also affect the system stability, but to a lesser extent. From the study results of the sedimentation in-hibiting effectiveness in model systems follows that the use of these substances as inhibitors under practical conditions at PJSC "Mineral Wax Plant" and PJSC "Grodno Azot" will significantly slow down the processes of sedimentation and  ensure non-stop operation of the cooling water circulating cycles. 00,511,522,533,540 10 20 30 40 50dP, psiτ, min     PAA 2,100      PAA 5,100     PAA 8,100      PAA 15,100    PAA 500....1 234 56 7 8020406080100120τ, min 0.1   0.25    0.5       1       3         5      8Dosage, ppmcarboxylic acidsorganophosphorous compounds  dicarboxylic acids τ, min66 ISSN 1683-0377. Proceedings of BSTU. 2013. No. 3. Chemistry and Technology of Inorganic Substances Conclusion. A comparative analysis of the rea-gents-inhibitors of different composition and struc-ture is carried out under dynamic conditions using the described method of efficiency evaluation, which provides a higher accuracy and reliability of the results in comparison with other methods. According to the research of the inhibitory ac-tion effectiveness of some compounds it has been found that organophosphates are the most effec-tive  sedimentation rate is decreased by 2.6– 3 times. In a series of carboxyl compounds the polyacrylic acid with molecular weights from 2,100 to 5,100 has the greatest effect. The optimal dose of the reagents in the system is 5–8 mg/l for phosphorus-containing compounds, 35 for car-boxylic polyacids. Comparative characteristics of these substances inhibitory potency, obtained using this method, can serve as a basis for the development of water treatment reagent modes for cooling circulating cycles of industrial enterprises.  References  1. Фрог, Б. Н. Водоподготовка / Б. Н. Фрог, А. П. Левченко. – М.: Ассоциация строит. вузов, 2007. – 681 с.  2. Flynn, D. J. Nalco Water Handbook /  D. J. Flynn. – McGraw-Hill, 2009. – 1280 p. 3. Чаусов, Ф. Ф. Влияние кристалличе-ской структуры солей на эффективность ин-гибирования их кристаллизации органофос-фонатами / Ф. Ф. Чаусов // Химия и химиче-ская технология. – 2008. – Т. 51, вып. 5. –  С. 63–67. Received 22.02.2013   Chemistry and Technology of Inorganic Materials and Substances 67  

Evaluation method of scaling inhibitors action effectiveness

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Evaluation method of scaling inhibitors action effectiveness

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