Olena Galkina

Water supply, sewerage and water purification Department O.M. Beketov National University of Urban Economy

 

A STATISTICAL MODEL FOR DETERMINING THE CORROSION RATE IN COKE-PLANT COOLING SYSTEMS

 

The introduction of biologically treated phenolic wastewater eliminates carbonate deposits in heat exchangers [1]. Using phenolic water with corresponding reduction in the consumption of fresh water when using corrosion protection inhibitors for byproduct-coking industry. The corrosion rate of carbon steel in the media data reaches 1.5-2 mm/yr. The method can not be used without corrosion protection. The aim of treatment is to develop a statistics model based on corrosion rate of inhibitor protection of coke-plant heat exchangers when using biologically treated phenolic wastewater in the circulating water.

Research [2] shows that the optimal ratio of artesian and phenolic waters is 80:20%. However, even at this ratio artesian and phenolic wastewater as supply water requires the addition of corrosion inhibitors to the water-circulation system. Laboratory investigations have been showed the absence of scale on the surface of the samples with increasing evaporation coefficient. Established to decrease the corrosion rate to 0.3-0.55 g/m2 h range.

Investigation was conducted on water used in Kharkiv coke-plant cooling systems. Circulating water, biochemically purified phenol wastewater and fresh water from an artesian source were used in experiments. This water was supply in the coke plant’s water-circulating system. The data on water quality have been reproduced in the laboratory as well as experiments on real objects could lead to irreversible consequences.

Chromates, silicates, and organic amines are common inhibitors. [3]. The reagent consisting of corrosion inhibitors (phosphates and silicates) and a nitrification inhibitor (based on HCNS) was established [4]. The results of reagent and optimum supplying water ratio using, slows total corrosion of carbon steel to acceptable levels of 0.2–0.3 mm/yr with unchanging corrosion.

Depending on the research of the corrosion rate of the water parameters and the corrosion inhibitor amount in the circulating water. It is well accepted that the corrosion rate can be modeled by statistics methods [5]. A model was found by using standard statistics methods. R-squared value is 98,462 pct and mean absolute error of proposed model is 3,8 pct. So proposed statistical model for determining the corrosion rate has the following form:

,       (1)

where Ding – inhibitor administered dose, mg/dm3; Ky – evaporation coefficient; S – salinity, mg/dm3; pH – pH; A – alkalinity, mmol/dm3.

Proposed statistical model for determining the corrosion rate of the water parameters and the corrosion inhibitor amount in the circulating water adequate and suitable for use in solving various tasks improve the efficiency of in coke-plant cooling systems circulating water. Further, these models can be used for corrosion rate evaluation and prediction of reverse operation of the system.

References

1.           Vinarskii, N.S. and Papkov, G.I., Using coke-plant wastewater in watercirculation systems, Express Inform., 1978, ser.10, no. 1, pp. 7–10.

2.           Smilka O. The Complex Approach to Corrosion Protection of Steel in Coke-Plant Cooling Systems / O. Smilka // Chemistry Journal. – Vol. 1, No. 4. – 2015.– pp. 124-132. Available at: http://files.aiscience.org/journal/article/html/70410025.html.

3.           The Effects and Economic Impact of Corrosion // Corrosion: Understanding the Basics. – ASM International, 2000. – Ch. 1. – 20 р. Available at: http://www.asminternational.org/documents/10192/1849770/06691G_Chapter_1.pdf.

4.           Ukrainian patent 109035 // Nesterenko S.V., Smilka O. P. and etc. – 2015.

5.           Mustaffa, Z. Developments in Reliability-Based Assessment of Corrosion / Z. Mustaffa // Developments in Corrosion Protection; Aliofkhazraei, M., Ed.; Intech, 2014. – pp 681-696.