The Experts below are selected from a list of 42 Experts worldwide ranked by ideXlab platform

Rakesh Govind - One of the best experts on this subject based on the ideXlab platform.

  • advances in biotreatment of acid mine drainage and biorecovery of metals 2 membrane bioreactor system for sulfate reduction
    Biodegradation, 2003
    Co-Authors: Henry H Tabak, Rakesh Govind
    Abstract:

    Several biotreatmemt techniques for sulfate conversion by the sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing acid mine drainage (AMD). This research deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of acid mine water from the Berkeley Pit, Butte, MT, using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase sparged gas bioreactor systems are: large microporous membrane surface to the liquid phase; formation of hydrogen sulfide outside the membrane, preventing the mixing with the pressurized hydrogen gas inside the membrane; no requirement of gas Recycle Compressor; membrane surface is suitable for immobilization of active SRB, resulting in the formation of biofilms, thus preventing washout problems associated with suspended culture reactors; and lower operating costs in membrane bioreactors, eliminating gas recompression and gas Recycle costs. Information is provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in anaerobic digester sludge and sediment master culture reactors and with SRB biofilms in bench-scale SRB membrane bioreactors. Biokinetic parameters have been determined using biokinetic models for the master culture and membrane bioreactor systems. Data are presented on the effect of acid mine water sulfate loading at 25, 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25, 35 and 40 °C) to determine and optimize sulfate conversions for an effective AMD biotreatment. Pilot-scale studies have generated data on the effect of flow rates of acid mine water (MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion in those systems. The pilot-scale data indicate that the SRB membrane bioreactors systems can be applied toward field-scale biotreatment of AMD and for recovery of high purity metals and an agriculturally usable water.

Beenackers, A.a C M - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of two-phase and three-phase methanol synthesis processes
    1996
    Co-Authors: Van De Graaf, G.h, Beenackers, A.a C M
    Abstract:

    A comparison is made between the ICI (two-phase) methanol synthesis process and a three-phase slurry process based on a multi-stage agitated reactor. The process calculations are based on a complete reactor system consisting of the reactor itself, a recycling system and a gas-liquid separator. The basic kinetic and thermodynamic data were taken from previous studies carried out in our laboratory. The results show that both reactor systems produce comparable methanol yields under the same process conditions except for the reactor temperature. Carbon conversion to methanol values close to 100% can be achieved. The three-phase process is more efficient in terms of heat recovery and power consumption. This is primarily caused by the fact that the three-phase process generates high-pressure steam and the ICI two-phase process yields boiler feed water of 90 degrees C. Furthermore, the pressure drop in the three-phase reactor is smaller than in the two-phase reactor, resulting in a smaller duty of the Recycle Compressor. However, for the present low energy prices, the annual financial savings, coupled with these energetic aspects, are not sufficient to compensate for the higher capital investment of the three-phase reactor system relative to the ICI two-phase reactor system. A relatively high natural gas price of US $4.1 per gigajoule is needed to reach the economical break-even point between the two processes. More active catalysts may be developed in the near future. Our results show that a relative increase in the catalyst activity by a factor of 1.5 or more (for both processes) will make the three-phase process of economic interest at a natural gas price of US $2.5 per gigajoule

Sinopec Beijing - One of the best experts on this subject based on the ideXlab platform.

Leader, Malcolm E. - One of the best experts on this subject based on the ideXlab platform.

  • Improving The Reliability Of A High Speed Refrigeration Compressor.
    'Biophysical Society of Japan', 2007
    Co-Authors: Kelm, Ray D., Leader, Malcolm E.
    Abstract:

    LecturePg. 21-30A high speed (15,200 rpm) refrigeration centrifugal Recycle Compressor was experiencing severe reliability problems resulting in short run times between major overhauls. Typical run times were one to 12 weeks. The symptoms identified at the start of the project included oil foaming in the closed loop oil sump on the end of the Compressor, sudden and severe damage to the balance piston and interstage seals shortly after startup, high thrust bearing oil drain temperature (due to high balance piston leakage), and high levels of process contaminant fouling on the impellers during operation. A solution was pursued using a systems approach including review of repair practices, hardware installation, operating practices, lubrication system design, and rotordynamic analysis of the rotorbearing system. Review of casing vibration during a startup cycle of the Compressor was found to include evidence of surging, and generally high amplitude casing vibration even though the casing to rotor weight ration was very large (~40:1). Inspection and review of the lubrication system indicated that the system had previously been modified on several occasions from the original equipment manufacturer (OEM) design in various attempt to improve the Compressor reliability. In addition, several grades of oil including synthetic were used at various times. However, the oil sump continued to exhibit heavy foaming not just during startup but under normal continuous operation. Although the rotor design appeared to be consistent over the life of the machine, the journal bearings were reported to have been changed to several different styles, including pressure dam bearings, fixed lobe, and with various bearing materials of construction. Oil foaming problems under continuous operating conditions were eliminated by repair of clogged oil mist coalescing elements in the oil sump, and improving the oil/refrigerant flow paths into the oil sump. A complete lateral rotordynamics study found that the existing bearings were not a good choice and that the rotor was operating on the first critical speed. New bearings were optimized and a “dummy” impeller was added to the rotor to reduce the critical speed to well below operating speed. The results of the bearing and rotor modifications reduced the amplification factor from 19 to less than 2.5 at the first critical speed, and predicted a 90 percent reduction in center-span operating speed vibration amplitudes for a given level of rotor unbalance, greatly reducing the risk for internal rubs. The tremendous success of this project emphasizes the clear requirement to address problems of this sort using a systematic, engineered approach as opposed to a trial and error solution strategy. The charge of the reliability improvement team was to identify positive changes that could be reasonably implemented to lengthen run time to repair. The final solution included some rather simple maintenance modifications (oil system) as well as some very sophisticated hardware modifications (bearing and rotor design changes). However, review of the whole system was necessary to identify the key components that would lead to rapid success in the plant

Henry H Tabak - One of the best experts on this subject based on the ideXlab platform.

  • advances in biotreatment of acid mine drainage and biorecovery of metals 2 membrane bioreactor system for sulfate reduction
    Biodegradation, 2003
    Co-Authors: Henry H Tabak, Rakesh Govind
    Abstract:

    Several biotreatmemt techniques for sulfate conversion by the sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing acid mine drainage (AMD). This research deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of acid mine water from the Berkeley Pit, Butte, MT, using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase sparged gas bioreactor systems are: large microporous membrane surface to the liquid phase; formation of hydrogen sulfide outside the membrane, preventing the mixing with the pressurized hydrogen gas inside the membrane; no requirement of gas Recycle Compressor; membrane surface is suitable for immobilization of active SRB, resulting in the formation of biofilms, thus preventing washout problems associated with suspended culture reactors; and lower operating costs in membrane bioreactors, eliminating gas recompression and gas Recycle costs. Information is provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in anaerobic digester sludge and sediment master culture reactors and with SRB biofilms in bench-scale SRB membrane bioreactors. Biokinetic parameters have been determined using biokinetic models for the master culture and membrane bioreactor systems. Data are presented on the effect of acid mine water sulfate loading at 25, 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25, 35 and 40 °C) to determine and optimize sulfate conversions for an effective AMD biotreatment. Pilot-scale studies have generated data on the effect of flow rates of acid mine water (MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion in those systems. The pilot-scale data indicate that the SRB membrane bioreactors systems can be applied toward field-scale biotreatment of AMD and for recovery of high purity metals and an agriculturally usable water.