Technologies

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Ebara Engineering Review No.187

An Experimental Study on Vibration of the Impeller of a Centrifugal Pump

by Shijie GUO, & Yoshihiko ANDOA

An experimental study was made on the vibration of the impeller of a single stage centrifugal pump. First, the impeller was excited by an exciter when the pump was at a stop to investigate the vibration characteristics of the impeller in still water. Next, the vibration of the impeller and the pressure fluctuation acting on the pump casing were measured when the impeller was rotating in a vaneless diffuser and in a vaned diffuser respectively. The results indicate that water has a great inertia effect, and that the vibration wave travels along the circumferential direction of the impeller when the resonance of a nodal diameter mode is excited by the fluid forces induced by impeller-guide vane interaction. The resonance frequency depends on the rotating speed of the impeller and the traveling direction of the wave. As the higher harmonic components of the fluid forces induced by impeller-guide vane interaction increase with the flow rate, the resonance excited by the interaction may result in problems at high flow rates. It is also demonstrated that the resonances of nodal diameter modes may be excited even when the resonance condition of impeller-guide vane interaction is not met.

Keywords
Turbomachinery, Centrifugal pump, Impeller-guide vane interaction, Vibration, Traveling wave, Fluid force, Sideband

Air Cleaning in Clean Rooms - Super-cleaning of Mini-environments by UV/Photoelectron Method -

by Toshiaki FUJII, Tsukuru SUZUKI, Kazuhiko SAKAMOTO, Shin YOKOYAMA, & Masataka HIROSE

Prevention of wafer surface contamination is an important issue in semiconductor manufacturing as such contamination decreases LSI productivity. Although particulate contamination in work rooms is being reduced by newer clean room techniques, there are still sources of particulate contaminants, such as wafer delivering systems, wafer stockers, and load-lock chambers. Not only fine particles but also gaseous contaminants need to be controlled. The following introduces an outlook on various methods of removing such particle and gaseous contaminants.

Keywords
clean room, Air cleaning, UV/Photoelectron method, Ultraviolet irradiation, Super-clean, Gaseous contaminants, Mini-environment, Box, Particle, Si wafer

Advanced Wastewater Treatment by Biological Filter using Floating Media

by Hiroshi SAKUMA, Toshihiro TANAKA, Yasuko MAKI, Kiyomi ARAKAWA, Masato NISHIWAKI, & Takayuki KABUTO

Advanced wastewater treatment was carried out using a pilot plant to study two types of nitrogen removal processes featuring the use of floating media for biological filtration. One of the processes had a single-column, the inside of which constituted aerobic and anoxic zones. An aeration pipe was equipped inside as well. This setup allowed both nitrification and denitrification to be carried out inside a single column. A T-N removal of about 70% achieved at an LV of between 25m/day and 50m/day. The nitrogen removal by this process was found to be possible at a flow rate which was equal to that of aerobic filtration for treating secondary sewage. The other process used a column for anaerobic filtration and a separate tank for aerobic filtration. Stored sludge in the lower section of the anaerobic column was used for the denitrification. A stable nitrogen removal performance of about 70% was also attained by this setup. This process can be augmented to existing aerobic filtration systems.

Keywords
Biological filter, Nitrification, Denitrification, Floating media, Stored sludge, Nitrogen removal, Biological aerobic filter, Biological anaerobic filter

Supercritical Water Oxidation Characteristics of Organics in a Continuous Operation Reactor

by Hirokazu SATO, Shusaku HAMADA, Tatsuya NISHIMURA, Roberto Masahiro SERIKAWA, Takashi USUI, & Hideo SEKINO

The supercritical oxidation characteristics of isopropyl alcohol, hexane, and a biphenyl solution were studied using a supercritical water reaction system. The interior of the reactor was able to be visually studied through a sapphire window at the upper part of the reaction tower. Studies revealed that isopropyl alcohol enabled stable, continuous oxidation and that it was an effective supplementary fuel for maintaining the temperature inside the reactor. Continuous reaction under a high decomposition rate was confirmed even under an air ratio of 1.1, with no production of CO, NO, NO2, or soot. It was also revealed that an oxidation reaction, with an intermittent ignition of flames, progressed at an air ratio of 1.8. This ignition of flames was not a phenomenon peculiar to the use of isopropyl alcohol, but was also observed in the cases of using hexane and the biphenyl solution.

Keywords
Supercritical water oxidation, Continuous reactor, Sapphire window, Flame, Air ratio, Isopropyl alcohol, Hexane, Biphenyl

Analysis of Membrane Foulants in Water Treatment Process (Ⅰ) - Evaluation on Fouling Materials and Filtration Resistances -

by Yoshihide KAIYA, Yoshikazu ITOH, Satoshi TAKIZAWA, Kenji FUJITA, & Tadashi TAGAWA

A filtration experiment was done using a hollow fiber microfiltration membrane to study membrane fouling characteristics. The raw water was drawn from Lake Kitaura. The membrane after the filtration was brown in color due to manganese. Results of analysis on membrane fouling elements revealed organic matter (measured by a TOC analyzer), manganese, iron, calcium, magnesium, and silica. The attachment of manganese and TOC was one order of magnitude higher than that of other elements, indicating that manganese and TOC were dominant fouling materials. However, the flux measured after chemical washing of micro-modules revealed that the decline in membrane permeability was mainly caused by organic matter. The chromatogram of the liquid extracted from the fouled membrane had a void peak and five peaks below 6000daltons, which include proteins, polysaccharides, and aromatic compounds which constitute humic substances.

Keywords
Membrane treatment, Membrane fouling material, Organic matter, Manganese, Filtration resistance

Analysis of Membrane Foulants in Water Treatment Process (Ⅱ) - Chemical Cleaning of Fouled Membranes -

by Yoshihide KAIYA, Yoshikazu ITOH, Satoshi TAKIZAWA, Kenji FUJITA, & Tadashi TAGAWA

A study was conducted on the chemical cleaning of fouled membranes. The membranes were those used for the filtration of raw water drawn from Lake Kitaura. Micro-modules were cut out from fouled membranes and changes in the clean water flux through the modules were measured before and after chemical cleaning. Oxalic acid, sodium hydroxide, sodium hypochlorite, hydrogen peroxide, enzymes and detergents were used as cleaning agents. Out of these, sodium hypochlorite, hydrogen peroxide, and sodium hydroxide were found to be effective for the recovery of permeability of the fouled membranes. In most of the experiments, the higher the cleaning temperature, the higher the effectiveness of chemical cleaning. However, chemical cleaning by a mixture of 1%-sodium hypochlorite and 4%-sodium hydroxide showed a comparable cleaning efficiency even at a low temperature (5°C). Merely applying the solution on the membrane surface, such as intermittent immersion, resulted in high washing efficinency.

Keywords
Membrane treatment, Membrane fouling, Membrane fouling material, Chemical cleaning, Micro-module

Analysis of Membrane Foulants in Water Treatment Process (Ⅲ) - Effect of Prechlorination on Membrane Fouling Prevention -

by Yoshihide KAIYA, Yoshikazu ITOH, Satoshi TAKIZAWA, Kenji FUJITA, & Tadashi TAGAWA

A constant rate filtration experiment was done using hollow fiber microfiltration membranes to study membrane fouling suppression effects by prechlorination. The raw water was drawn from Lake Kitaura. The average increase rate in Trans-Membrane Pressure of the prechlorinated process was less than 10% of that without prechlorination. A significant effect of prechlorination on membrane fouling prevention was verified, which indicated that bio-fouling also occurred in the membrane filtration processes for potable water treatment. Evaluation on fouling organics by Pyrolysis-GC-MS identified pyrolysis fragments such as hydroxy propanone, acetonitrile, acetamide, benzene, and phenol. Research results suggested that the fouling organics found in this research included, polysaccharides, proteins, amino sugars, and aromatic compounds which constitute humic substances.

Keywords
Membrane treatment, Microorganism, Organic matter, Molecular weight distribution, Pyrolysis-GC-MS

Wall Cabinet Type Booster Pump System for Direct Water Supply

by Kaoru YAGI

A new wall cabinet type, booster pump system, model PND, has been released into the market. This system features a high-efficiency motor, the integration of a ball valve and a check valve, as well as a non-flow switch control function which enables a pump operation to automatically stop when there is a decrease in the amount of water being pumped. These features achieve compactness (66% in size of conventional system) and space-saving. Maintenance of the system can be done from the front side of the system, such as is the case of conventional such systems. Protective functions have lessened the need to exchange parts due to damage. Model PND has also inherited features of conventional models, such as low noise, indoor and outdoor usage, and energy-saving.

Keywords
Direct water supply, Booster pump, Wall cabinet, Save space, Protective functions, High-efficiency motor, Non-flow switch, Low noise, Estimated constant end-pressure control

Dry Gas Seal with Ductile Rotating Ring

by Takao TAKEUCHI, Tadashi KATAOKA, Hiroshi NAGASAKA, Momoko KAKUTANI, & Nobuyasu IWASAKI

EBARA has developed and released a new dry gas seal, named NF9, equipped with a mating ring made of ductile material. Dry gas seals are widely used as shaft seals in compressors and conventional seals use mating rings made of sintered material. Cases have been reported of ring breakage causing critical damage to the compressor. The mating ring of NF9 features an enhanced tribological property. The surface of the ductile material is coated with titanium nitride using dynamic ion beam mixing, a leading edge technique for surface modification. A new technique has been used by which minimized deformation of the ring is enabled. The NF9 features the same performance of that of a conventional dry gas seal, but the ductile material used for its mating ring enables it to withstand breakage due to brittle fractures. The techniques applied can be adopted more widely and actively in heightening the reliability of compressors.

Keywords
Dry gas seal, Dynamic ion beam mixing method, Titanium nitride (TiN), Ductile material, Brittle fracture, Mating ring, Deformation control technique, Bi-directional

Modular Ice Generator

by Katsuhiro KUBO, Yasuo IKEZAKI, & Susumu SAKAIDA

EBARA's modular ice generator is a heat source for a dynamic type ice storage system. This generator is made up of compact modules and is therefore space-saving. Its energy-saving feature, including ice generation during nighttime hours when the electric demand is low, contributes to a reduction in running cost. The refrigerant used by the generator is HFC-134a, a substance know to have zero effect on the ozone layer. The generator causes minimal effect on global warming. All in all, this modular ice generator is contributing to overall global-scale environmental protection. The following outlines this user-friendly generator.

Keywords
Ice Storage, Dynamic (Ice Storage), Screw Compressor, Plate Heat Exchanger, Super chiller, Refrigerant, Global Environment, Ozone Layer (Protection), HFC-134a, Economizer

Development of Turbomolecular Pump with Valve

by Shigekazu YAMAMOTO, Hiroshi SOBUKAWA, Matsutaro MIYAMOTO, Atsushi SHIOKAWA, Toshiharu NAKAZAWA, Koichi KIDO, & Atsushi OOYAMA

A new turbomolecular pump with a valve has been developed. This pump features an integration of a gate valve which is also capable of adaptive pressure control. This design allows significant space-saving and a great improvement in the effective pumping speed. Various performance tests have been carried out successfully and this reliable, compact turbomolecular pump, featuring an integrated dual-function valve system, has been released into the market.

Keywords
Turbomolecular pump with valve, Adaptive pressure control valve, Gate valve, Pumping system, Effective pumping speed, Servomotor drive, Valve disk actuator, Clean vacuum, Vacuum pump, Semiconductor

ntroduction of Vertical Gas Turbines for Driving a Pumping Station and Wastewater Treatment Plant - Vertical Gas Turbines used at Itabashi Pumping Station & Sanpou Wastewater Treatment Plant -

by Chikara KUBOTA, Yuichi HISAI, Nobuyoshi TAKITA, & Kou SHINOHARA

The following introduces vertical gas turbines used at Itabashi Pumping Station and Sanpou Wastewater Treatment Plant. That for the former is used for driving a 1-floor type, vertical axial flow pump (for transmitting river water) while that for the latter is used for driving a 2-floor type, vertical mixed flow pump (for transmitting urban runoff). The use of these turbines is achieving a saving in construction cost, more reliable operation, and less impact on the environment.

Keywords
Vertical gas turbine, Horizontal gas turbine, Twin shaft type gas turbine, Vertical axial flow pump, Vertical mixed flow pump, Environment, Speed control, Concentration of dust, Concentration of nitrogen oxide

Effective Utilization of Waste Sludge from Water Purification Plant

by Naoto KIMURA, & Kouji KASHIMADA

EBARA's sludge treatment system for treating waste sludge from a water purification plant has been installed at Yokohama City's Waterworks facility. This system includes a filter press, a dehydrator, a heat generator, a cake feeder, sludge cake crusher, a scrubber, and an activated carbon tower for deodorization. The filter press, a long-term operation type with a compression function, has a filtration area of 950 m2 and is the largest of its kind in Japan. The crusher controls the particle size of the crushed sludge cakes and features a cylindrical screen and a vertical rotating blade. The heat generator is a fluidized layer type featuring superior thermal efficiency and easy maintenance. The entire output of treated sludge is used effectively as gardening soil. This system has now been operating for almost two years and excellent feedback is reported.

Keywords
Gardening soil, Sludge from water purification plant, Filter press, Effective utilizaton, Fluidized bed dryer

Control System of EBARA Fujisawa Plant No.2 Power Station

by Akira USUI, Toshiaki MIYASHITA, Akio SATOO, & Hisaki OKAMURA

The No. 2 Power Station of EBARA's Fujisawa Plant began commercial operation as an independent provider of electricity since June 1999. This facility features a DSS (Daily Start & Stop) operation for combined cycle power generation by gas and steam turbines. The startup and shutdown of this power station is done by an automatic sequence function. The time necessary for the gas turbine generator to reach full power output is about 50 minutes from a synchronous startup. The time for the same to reach a parallel shutdown from a full power output is about 30 minutes.

Keywords
Independent power producer, Combined cycle, Gas turbine, Steam turbine, Heat recovery steam generator, Distributed control system, Start-up and shut down seqnence, Plant trip logic