Civil and Environmental Engineering - Master's degree
http://hdl.handle.net/1721.1/7652
Thu, 25 Aug 2016 03:02:38 GMT2016-08-25T03:02:38ZEvaluation of membrane filtration for treatment of black liquor in small-scale pulp and paper mills in India
http://hdl.handle.net/1721.1/103846
Evaluation of membrane filtration for treatment of black liquor in small-scale pulp and paper mills in India
Ren, Xiaoyuan, S.M. (Xiaoyuan Charlene). Massachusetts Institute of Technology
Black liquor, a strongly polluting byproduct from the kraft pulping process in pulp and paper mills, is traditionally treated by being passed through multiple effect evaporators and burned in a recovery boiler to produce energy and recover chemicals. However, the traditional treatment of black liquor is not economically viable for the small-scale kraft paper mills in India that uses waste agricultural products as raw material to produce brown paper. Membrane ultrafiltration treatment has been advocated by many scholars as a possible alternative treatment method for black liquor, and this study attempts to address industrial concerns on the cost-effectiveness of membranes for black liquor concentration and treatment. Utilizing a cross-flow hollow fiber membrane module in a recirculation system operating under constant pressure, black liquor is recirculated through the system over an extended period of time to observe the quantity and quality of the lignin in the concentrate and the permeate, and how they vary over time. Additionally, the permeate flux rate change over time is also observed to determine the required frequency of cleaning membranes from reversible fouling of membranes, as well as the frequency to replace membranes due to irreversible fouling. Cost of cleaning and changing membranes, as well as the profit gained from lignin retained can be estimated and compared with literature to determine the cost-effectiveness of ultrafiltration membranes in treating black liquor. Experimental results suggest that operating at a pressure of 207 kPa and a cross-flow velocity of 1.06 m/s, the average permeate flux of black liquor is 7-21 LMH when concentrating lignin in black liquor from a concentration of 38 g/L to 185 g/L, which compares favorably to literature results. However, a membrane cleaning frequency of every 4 to 6 hours and an estimated membrane lifetime of several weeks, predicted by experimental results, significantly raises the cost of cleaning and changing membranes in comparison to the commonly estimated membrane cleaning frequency of once per day and lifetime of 1.5 year in literature. The permeate lignin concentration, which increased up to 40 g/L at the end of a concentration cycle, would also decrease the profit gained from reusing the permeate stream in the cooking process. The increased cost factors associated with both intense membrane fouling and the need for permeate stream retreatment require to be addressed in future research, in order to more comprehensively evaluate membrane filtration process as a cost-effective alternative for treating black liquor.
Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 153-157).
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/1721.1/1038462016-01-01T00:00:00ZVulnerability analysis of electricity distribution networks with large-penetrations of PEVs and DERs
http://hdl.handle.net/1721.1/103845
Vulnerability analysis of electricity distribution networks with large-penetrations of PEVs and DERs
Shelar, Devendra (Devendra Anil)
This thesis focuses on the vulnerability assessment of radial electricity distribution networks (DNs) under large-scale integration of Distributed Energy Resources (DERs) and Plug-in Electric Vehicles (PEVs). We formulate a two-player Stackelberg security game involving an attacker (external threat agent) and the defender (network operator). First, the attacker targets a subset of the insecure DER or PEV nodes, and strategically manipulates their set-points by attacking the DER/PEV controller logic at the nodes. Next, the defender responds to the resulting supply-demand mismatch by triggering network control operations, which includes direct load control and control of available non-compromised DERs/PEVs. The attacker's (resp. defender's) objective is to maximize (resp. minimize) the weighted sum of the cost of active and reactive power supply, costs of DER/PEV and load control, and the cost due to loss of voltage regulation. This composite cost captures the key trade-offs that the network operator faces in balancing power supply and quality during a broad range of contingency conditions. The choice of this cost in the security game reflects the attacker's overall goal of comprising the DER/PEV nodes to maximize the minimum composite cost for the network operator. Solving the sequential game with nonlinear power flow constraints is a computationally hard problem. To address this challenge, we introduce two auxiliary sequential game problems each with linear power flow constraints. We prove that the values of these relaxed problems upper and lower bound the value of the original game. Next, we introduce a greedy algorithm that can be utilized to efficiently compute an optimal attack strategy for both auxiliary games. Our main result is that, under a set of assumptions, the set of optimal attacker strategies is identical for these games, and hence we obtain a tractable solution to compute an optimal attack for the original game. Furthermore, the optimal attack strategy exhibits an interesting structural property: the downstream nodes are more critical for limiting costs of reactive power supply and maintaining voltage regulation. This insight is useful for vulnerability assessment of DNs under DER/PEV node compromises. Finally, we also exploit the structure of optimal attack to design a distributed control strategy for defender response.
Thesis: S.M. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 95-98).
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/1721.1/1038452016-01-01T00:00:00ZIntrusion dynamics of small oil droplets from a deep ocean blowout
http://hdl.handle.net/1721.1/103844
Intrusion dynamics of small oil droplets from a deep ocean blowout
Wang, Dayang, S.M. Massachusetts Institute of Technology
This paper presents an experimental study of the behavior of oil plumes in ambient stratification and a mild current, in which the flow is classified as stratification-dominated. Experiments are conducted in an inverted framework by releasing a continuous stream of dense glass beads from a carriage towed in a salt-stratified tank. Non-dimensional particle slip velocity UN ranged from 0.1 to 1.9. While particles of all sizes were affected by the stratification, only those with UN less or equal to 0.5 were observed to enter the intrusion layer. The spatial distributions of beads, collected on a bottom sled towed with the source, present a Gaussian distribution in the transverse direction and a skewed distribution in the along-current direction. Dimensions of the distributions increase with decreasing UN. The spreading relations can be used as input to far-field models describing subsequent transport. The average particle settling velocity, Uave, was found to exceed the individual particle slip velocity, Us, which is attributed to the initial plume velocity near the point of release. Additionally, smaller particles exhibit a "secondary plume effect" as they exit the intrusion as a swarm. The secondary effect becomes more prominent as UN decreases. These findings might explain the observations from the 2000 Deep Spill field experiment where oil was found to surface more rapidly than predicted based on Us. An analytical model predicting the particle deposition patterns, was developed based on findings above and validated against experimental measurements. The model estimates near-field oil transport under the Deepwater Horizon spill conditions, with and without chemical dispersants.
Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 44-46).
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/1721.1/1038442016-01-01T00:00:00ZA price prediction method In real estate market
http://hdl.handle.net/1721.1/103843
A price prediction method In real estate market
Li, Heng, S.M. Massachusetts Institute of Technology
Current housing price prediction usually employs hedonic or repeat-sales models. The objective is to build a statistical model which is more focused on statistic methods. Neither ordinary nor regularized regression model haven been applied to the field of real estate, even though they are rather well-known statistical procedures. This thesis concludes lots of ordinary and regularized regression models. A theoretical review was performed for these models, and Boston Housing data was used to evaluate their performance. The results were found to be reasonable, from a statistical perspective.
Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 71-75).
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/1721.1/1038432016-01-01T00:00:00Z