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United Arab Emirates University (2015)

OPTIMIZATION OF A COMBINED APPROACH FOR THE TREATMENT OF DESALINATION REJECT BRINE AND CAPTURE OF CO2

Ameera Fares Mohammad Mohammad

Titre : OPTIMIZATION OF A COMBINED APPROACH FOR THE TREATMENT OF DESALINATION REJECT BRINE AND CAPTURE OF CO2

Auteur : Ameera Fares Mohammad Mohammad

Université de soutenance : United Arab Emirates University

Grade : Master of Chemical Engineering (MChE) 2015

Présentation
Carbon dioxide (CO2) is the most widespread greenhouse gas that traps heat and raises the global temperature, contributing to climate change. Existing techniques to sequester carbon dioxide have numerous environmental concerns and usually require extensive amount of energy. New technologies and methods, such as reactions with desalination reject brine according to the Solvay process, offer a new hope for the reduction of carbon dioxide concentration in the atmosphere. Brine management is another environmental concern, as many desalination plants need to find suitable approaches for the treatment or disposal of the large amounts of concentrated brine, resulting from the desalination processes. Many conventional methods are used such as disposal through deep well injection, land disposal and evaporation ponds. However these methods still suffer from many drawbacks. An alternative approach is to further process the brine to extract all the salts through reactions with carbon dioxide. This has the advantages of being environmental friendly and can produce valuable carbonate chemicals. The present work evaluates the Solvay process where carbon dioxide is passed into ammoniated brine and reacts with sodium chloride to form a precipitate of sodium bicarbonate and a soluble ammonium chloride. The process has the dual benefit of decreasing sodium concentration in the reject brine and reducing carbon dioxide emissions to the atmosphere. Process parameters were studied in a semi-batch reactor to determine their effect on CO2 capture efficiency and ions removal. These parameters included : ammonia to sodium chloride molar ratio, reaction time, temperature, gas flow rate, and pressure. Since ammonium bicarbonate is another vi important intermediate in the formation of sodium bicarbonate, its effect on ions removal was evaluated. The optimum conditions for maximum CO2 capture efficiency and ions removal have been determined using response surface methodology (RSM). In addition, continuous Solvay process has been studied at different liquid residence time. The optimum conditions for continuous Solvay process have also been evaluated for long experimental runs. In the semi-batch mode, the highest sodium removal of 33.0 % and the best CO2 capture of 86.2 % were obtained under specific conditions. The optimum CO2 capture efficiency and ions removal was found to be at temperature of 19.3oC, gas flow rate of 1.544 L/min, and 3.3NH3:1NaCl molar ratio. In the continuous Solvay process maximum ions removal were found at gas and liquid flow rates of 1.544 L/min and 12.5 ml/min, respectively, with a gas-to-liquid ratio of 123, and the reaction reached the steady state after 240 min ; the CO2 capture efficiency in 480 min was equal to 97.9% and maximum sodium removal was 32.5%. These results indicated the technical feasibility of the Solvay approach for the capture of CO2 and management of desalination reject brine.

Présentation : Scholarworks@UAEU

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Page publiée le 5 février 2017, mise à jour le 7 novembre 2017