Evaluation of hydrothermal carbonization reactions for faecal sludge treatment and hydrochar production | |
| Author | Krailak Fakkaew |
| Call Number | AIT Diss. no.EV-16-05 |
| Subject(s) | Carbonization Sewage sludge Biomass energy |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-16-05 |
| Abstract | Faecal sludge management is a serious problem in developing countries which has caused environmental pollution and health risks. Hydrothermal carbonization (HTC) is a thermal conversion process which can be appli e d to treat faecal sludge (FS) and convert i t into a valuable solid product called hydrochar. This research determined the applicability of conventional and two - stage HTC processes for FS treatment with respect to energy consumption and efficiency in hydrochar production. To investigate effects of p rocess parameters, mass and energy balances, l aboratory - scale HTC experiments were conducted with a 1 - L high pressure reactor . Optimum conditions of HTC processes which could convert FS to hydrochar at the relatively high energy content and yield were determined and verified. HTC product characteristics were analyzed to identify their applications and post - treatment options. Experimental r esults of the conventional HTC process indicated the significance of moisture content on energy con tent of the produced hydrochar . Likewise, increasing temperatures and reaction times resulted in increased energy contents of the produced hydrochar. O ptimum conditions of the conventional HTC of FS to produce the highest normalize d energy yield were moisture content of 80% , reaction time of 5 h and temperature of 250 C. In these conditions, t he energy content and hydrochar yield were 19 - 20 MJ/kg and 70 - 73 % , respectively . In addition, a mathematical model which could estimate the energy content of the produced hydrochar using the relevant parameters such as moisture content of FS, temperature, reaction time an d volatile solid concentration in FS was developed and validated satisfactorily with the literature data. A low - energy HTC process named “Two - stage HTC” comprising of hydrolysis and carbonization stages using FS as feedstock was developed and optimized. The experimental results indicated the hydrolysis reaction time and carbonization temperature had significant effect s on energy content of the produced hydrochar. O ptimum conditions of the two - stage HTC of FS were hydrolysis temperature of 1 70 C, hydrolysis reaction time of 155 min, carbonization temperature of 215 C, and carbonization reaction time of 100 min. In thes e conditions, t he energy content and hydrochar yield of 20 - 21 MJ/kg and 70 - 73 % , respectively, could be achieved. The e nergy required for the two - stage HT C was about 25% lower than conventional HTC process . The e nergy efficiency of the two - stage HTC for treating faecal sludge was higher than that of conventional HTC and other thermal conversion processes such as pyrolysis and gasification. The two - stage HTC could be considered as a potential technology for treating FS and producing hydrochar. |
| Year | 2016 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-16-05 |
| Type | Dissertation |
| 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) | Thammarat Koottatep |
| Examination Committee(s) | Visvanathan, Chettiyappan ;Shrestha, Rajendra Prasad ;Chongrak Polprasert |
| Scholarship Donor(s) | Bill & Melinda Gates Foundation under the framework of the SaniUP Project |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2016 |