Date of Award
Master of Science in Chemical Engineering (MSChE)
Chemical and Petroleum Engineering
Muftah Hassan El-Naas
Dr. Naeema Ibrahim Aldarmaki
J. Paul Chen
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 an extensive amount of energy. New technologies and methods, such as reactions with desalination reject brine according to the Solvay process, offer 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 good 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 environmentally 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 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 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, the continuous Solvay process has been studied at different liquid residence times. The optimum conditions for the 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 a 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.
Mohammad, Ameera Fares, "OPTIMIZATION OF A COMBINED APPROACH FOR THE TREATMENT OF DESALINATION REJECT BRINE AND CAPTURE OF CO₂" (2015). Theses. 751.