Optimizing membrane distillation process for triethylene glycol separation from gas separation plant waste stream | |
| Author | Pham Minh Duyen |
| Call Number | AIT Thesis no.EV-15-16 |
| Subject(s) | Membrane separation Gases--Separation |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. EV-15-16 |
| Abstract | In natural gas processing, triethylene glycol (TEG) is used as a dehumidifying agent to absorb and remove water content in the process called as dehydration. TEG should be recovered from wastewater and could be reused. Hydrophobic membrane distillation (MD) has a great potential to concentrate TEG in wastewater. This study mainly focused on optimizing the operational condition of membrane distillation process for concentrating TEG from wastewater. Two scale of hollow fiber MD were investigated (0.25 m² and 2 m²). Each membrane module was tested with three solutions: pure water, synthetic TEG and real wastewater alternately. Energy consumption analysis in all experiments was evaluated in term of the ratio of energy consumption/permeate flow. Fouling analysis was conducted to evaluate the quality of cleaning process. For bench scale study, the optimum condition in terms of energy consumption/Qp and permeate flux were achieved at feed flow rate of 2.4 (L/min), feed temperature of 70°C, and sweeping gas velocity of 4.7 m/s (gas inlet flow rate of 0.255 L/min.fiber). At this condition, pure water flux achieved was 3.14 kg/m².h, the ratio of energy consumption/Qp was 1.09 kWh/kg. During concentrating synthetic TEG from 10 to 45 %, the permeate flux was in the range from 2.1 to 2.61 kg/m².h with the ratio of energy consumption/Qp was approximately 1.29 kW/kg. The permeate flux of real wastewater investigation when concentrating TEG from 9.69 to 50% were in the range from 2.4 to 1.6 kg/m².h with the ratio of energy consumption/Qp was 1.4 kWh/kg. It could concentrate TEG in real wastewater till 98.01%. In the total resistance, membrane resistance, boundary layer resistance, fouling resistance contributed 69.2 %, 7.6%, 23.2 % respectively. The irreversible resistance accounted for 2%. The optimum condition in pilot scale study was decided at the gas velocity of 8.07 m/s (gas inlet flow rate of 0.44 L/min.fiber), feed inlet temperature of 70°C. Feed flow rate and sweeping gas temperature have less effect. The flux achieved was 1.94 kg/m².h. At this condition, the ratio of energy consumption/Qp was 0.51 kW/kg. The permeate flux was stable around 1.8 kg/m².h when the synthetic TEG concentration was less than 30 %. When the synthetic TEG concentration was in the range from 30 to 50%, permeate flux was about 1.6 kg/m².h (average). At higher TEG concentration (>50%), the flux reduced to less than 1.2 kg/m².h. When TEG concentration was in the range from 10 to 60%, the ratio of energy consumption/Qp was less than 0.7 kW/kg. Pilot scale MD module has ability to concentrate synthetic TEG till 98.7%. Investigating pilot scale MD module with real TEG wastewater, the permeate flux was higher than 1.7 kg/m².h with the TEG concentration less than 15 %. The flux reduced to the range between 1.4 and 1.65 kg/m².h at higher TEG concentration from the hour of 5thand 28th (TEG concentration less than 50%). It reached 0.9 kg/m².h at the hour of 40th (final TEG concentration was about 69.4 %). Pilot scale SGMD module had ability to concentrate TEG in real wastewater until 99.1%. The contributions of membrane resistance, boundary layer resistance and fouling resistance into the total resistance were 60.2 %, 10.4 % and 29.4% respectively. After cleaning with chemical agents, irreversible fouling resistance remained 1.3% total resistance. To concentrate real wastewater from 10 to 45 % TEG concentration, the required energy ratio was 0.62 kW/kg. The energy ratio in real wastewater and synthetic TEG were similar at 0.95 kW/kg when concentrating TEG continuously up to 65%. |
| Year | 2015 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Visvanathan, C.; |
| Examination Committee(s) | Thammarat Koottatep;Romchat Rattanaoudom; |
| Scholarship Donor(s) | Greater Mekong Subregion (GMS) Scholarship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2015 |