Pilot plant development for water quality optimization by introducing carbon dioxide

Namen magistrskega dela je bil razviti pilotno napravo za kontrolirano uvajanje ogljikovega dioksida v vodo ter proučiti dejavnike, ki vplivajo na tvorbo vodnega kamna in učinkovitost dodajanja ogljikovega dioksida pri preprečevanju le-tega. Temu so sledili poskusi na pilotni napravi, izdelani za opazovanje izločanja vodnega kamna v cevovodih in v toplotnem prenosniku. V prvi fazi raziskave so bili izvedeni preliminarni poskusi na osnovni pilotni napravi. Meritve so bile izvajane periodično vsako uro na petih točkah procesa v časovnem razmiku desetih minut in so obsegale določitev sledečih parametrov: vsebnost proste ogljikove kisline, koncentracija kalcijevih ionov, koncentracija hidrogenkarbonatnih ionov, pH vrednost ter temperatura, tlak in pretok vode. Na osnovi rezultatov preliminarnih eksperimentov je bila pilotna naprava opremljena s senzorskim sistemom in ustrezno programsko opremo, ki omogoča on-line meritev raztopljenega ogljikovega dioksida, pH vrednosti, temperature in prevodnosti. Obratovalni pogoji pilotne naprave so ostali enaki kot pri preliminarnih poskusih. Ta serija je vključevala 35 meritevsedem na vsaki od merilnih točk (MT) ob dodatku treh različnih količin ogljikovega dioksida (1 l/h, 3 l/h in 5 l/h), vse z in brez uporabe ultrazvoka. Kontrola dodajanja CO2 je bila volumetrična s pomočjo merilnika pretoka plina. V tretji fazi poskusov je bila pilotna naprava dograjena še z dodatnim rezervoarjem za plin in uvedena je bila gravimetrična kontrola dodajanja ogljikovega dioksida s pomočjo tehtanja plinasistem je bil zaprt glede na dotok sveže vode. Ta serija je vključevala 9 meritev na eni merilni točki. Pridobljeni rezultati so smiselno urejeni, selekcionirani ter interpretirani. Rezultati so podani tabelarično, grafično in tekstovno. Na osnovi eksperimentalnega dela smo razvili primerno pilotno napravo za učinkovito uvajanje plinastega CO2, ki je potreben za vzpostavitev karbonatnega ravnotežja pitne vode. To nam je uspelo z več serijami eksperimentov pri različnih obratovalnih pogojih in sprotnim nadgrajevanjem pilotne naprave. Tako smo s pomočjo manometrične metode uvajanja CO2 v pitno vodo, z ultrazvočnim mešalom in s sodobno merilno-regulacijsko opremo v stanju točne določitve potrebne količine ogljikovega dioksida za optimizacijo kakovosti pitne vode.The purpose of this graduate thesis was to develop a pilot plant for the controlled supply of carbon dioxide to water and to explore the factors influencing the formation of calcium carbonate and the preventive effects of the supply of carbon dioxide on this process. This was followed by experiments on a pilot plant designed to observe the precipitation of calcium carbonate in pipelines and a heat exchanger. The first research phase consisted of preliminary experiments conducted on the basic pilot plant. The measurements were performed periodically every hour at five points of the process at ten minutes intervals and were aimed at the identification of the following parameters: concentration of free carbonic acid, concentration of calcium ions and hydrogen carbonate ions, pH-value, temperature, pressure and water flowrate. Based on the results of the preliminary experiments the pilot plant was equipped with a sensor system and an appropriate software, which enables on-line measurements of dissolved carbon dioxide, pH-value, temperature and conductibility. The operating conditions of the plant were left unchanged as compared to the preliminary measurements. This series comprised 35 measurements7 at each of the measurement points (MP). Carbon dioxide has been added in three different quantities (1 L/h, 3 L/h in 5 L/h), with as well as without ultrasound application. This set of measurements used a volumetric carbon dioxide supply control by means of a flowmeter. For the third set of experiments an additional gas tank was attached to the pilot plant and a gravimetric carbon dioxide supply control was introduced by means of weighing the gas. The system was closed in terms of fresh water input. This series comprised 9 measurements at one measurement point. The obtained results were properly structured, sorted out and interpreted. They are presented in tables, graphs and text. Based on the results of the experimental part of the research we developed a suitable pilot plant for the efficient supply of gaseous carbon dioxide, which is needed to establish the carbonate equilibrium of drinking water. This was achieved by various series of experiments at different operating conditions and a continuous development of the pilot plant. Consequently, by means of a manometric method for the supply of carbon dioxide to drinking water, an ultrasonic stirrer and modern measurement and control equipment we are able to exactly determine the quantities of carbon dioxide necessary to optimize the quality of drinking water