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Ebara Engineering Review No.185

Numerical Simulation of Multi-phase Flows for Studying a Proposed Method for the Prevention of Adhesion on Inner Surfaces of Combustion System Exhaust Ducts

by Xinming WANG, & Hirokuni HIYAMA

A numerical simulation was made to study a proposed method for preventing the adhesion of exhaust gas constituents on the inner walls of combustion system (incinerator, melting furnace, waste recovery reactor, etc.) exhaust ducts, caused by phase changes of molten salts. The proposed method features the injection of air for constituting a layer of air inside a duct for the prevention of adhesion. Analyses were made on exhaust gases which contained molten salt mist and vapor. The distribution of flow velocity, concentration and distribution of molten salt vapor, as well as the behavior of mist inside exhaust ducts were analyzed and the results used for devising optimal conditions for maintaining a layer of air for the prevention of the said adhesion. It was revealed that injecting air without any swirling components was effective for adhesion prevention. An optimal flow rate of air for maintaining a maximum length of the prevention layer was also found. Another finding was that making the air supplying slit as wide as permissible was effective for adhesion prevention.

Multiphase flow, Numerical simulation, Exhaust duct, Adhesion, Particle motion, Diffusion, Mass transfer, Mist of molten salt, Vapor of molten salt, Concentration distribution

Methane Fermentation Treatment of Organic Waste by the Mebius Demonstration Plant

by Yutaka YONEYAMA, Kenichi ISHIDA, Norio YAMADA, Yoshihiro NAKAMORI, & Yoshiro SUZUKI

Experiments were carried out on methane fermentation treatment of organic waste by a waste treatment and recovery system (named the Mebius system). A mixture of household garbage and night soil sludge (TS ratios: 1:1, 1:2.5, and 1.5) was treated using a demonstration plant to test the methane fermentation performance of the system. The temperature and retention time inside the reactor were maintained at 55°C and 16 days, respectively. Three runs were carried out, each for the different TS ratio. The CODcr decomposition was between 56% and 64.8% during Runs 1 & 3, increasing along higher sludge and garbage ratios. The decomposition of CODcr was 70% for the garbage, 35% for septic tank sludge, and 30% for excess activated sludge. The amount of recovered energy (estimated), resulting from treating both a sludge/garbage mixture or sludge alone, was found to be sufficient for heating the system's methane fermentation equipment.

WAASA process, Night soil, Septic tank sludge, Garbage, Methane fermentation, Electric power generation, Bio-gas, Compost, MS, TR

PCDD/PCDF Monitoring System with Ion Trap-GC/MS/MS

by Yukio KEMMOCHI, & Akihiro ARIKAWA

A new system has been developed for monitoring PCDDs (Poly Chlorinated Dibenzo-p-Dioxins) and PCDFs (Poly Chlorinated Dibenzo Furans) in fly ash. The monitoring by this system is done in three stages. The first features extraction by the ASE (Accelerated Solvent Extraction) method, the second features scrubbing in a pre-packed silica gel column, and the third features quantitative measurement using Ion Trap-GC/MS/MS. An analysis of one air-dried fly ash sample takes about six hours. The precision of the analyses is controlled using 13C-labeled internal standard reference material. Good correlation was indicated between analytical results obtained by this system and those obtained by conventional dioxin analysis using an HRMS (High Resolution Mass Spectrometer). The threshold of detection by the present system is about 10 pg-TEQ/g.

Dioxins, Ion Trap, MS/MS, Monitoring, Analysis

Water-cooled, Energy-saving Pump Controller

by Yoshio MIYAKE, & Keita UWAI

A water-cooled, energy-saving controller has been developed for manual control of pump speed. The use of this controller, which can be simply attached to an existing pump system, can be an alternative to the replacement of pumps by inverter-equipped ones. This cost-effective controller can be used for both new and existing submersible deep-well pumps, water supply pumps, as well as circulation pumps of air conditioning systems. Energy saving is achieved by eliminating idle operation of pumps.

Water-cooled, Inverter, Energy-saving, Real duty point, Installation near the pumps, Electric power consumption, Circulation pump, Group of pumps, Energy-consumption, Inverter-motor-pump

Heat Exchange Promotion Method for a Water-on-tube Thermal Storage Tank

by Kaki YOSHIDA, Shinji KANAI, Hideaki YAGISHITA, Masaru KOJIMA, & Noriyuki KOSUGI

A method of promoting the heat exchange of a water-on-tube storage tank was tested. The main components of the experimental apparatus were a brine chiller, a heat exchanger, and an ice storage tank. A computer and a data logger were also utilized for the tests. Comprehensive studies were made using different types of air nozzles to establish which type, hole and nozzle arrangement, injection rate, and timing yielded the optimal heat radiation. Similar studies were done concurrently for water injection and the results compared. The comparison revealed that air-injection was more favorable for promoting heat exchange. All in all, test results indicated that there was a possibility of a saving in the number of heat exchange modules by use of the present method.

Ice storage tank, Water-on-tube, Heat exchanger, Air injection, Discharge

Remote Maintenance Management System for Small-scale Water Purification Plants

by Hiromasa KAIHATSU, & Masao AYUKAWA

A new remote maintenance management system has been developed for small-scale water purification plants. This system is computerized and enables centralized management of small-to-medium scale water purification plants. Various operational data, such as on treatment, water quality, mechanical parts, etc. are retrieved and stored in a database. This system is also capable of giving instant warnings of failures and other irregularities. This system is extremely cost-effective in that data transmission can be done through the public telephone line and using personal computers.

Personal computer, Remote maintenance, Network communication, Microcomputer, Database, Water treatment unit

Engineering Seminar on Fluid Acoustics - Lecture 5: Harmony between Flow and Sound -

by Yoshiyuki MARUTA

This is the fifth of a series of lectures for an engineering seminar on fluid acoustics and focuses on the control and utilization of sound generated from unsteady flows. Simulation and estimation of fluid dynamic sounds, as well as control techniques of fluid acoustics are discussed. The final part discusses the relationship between unsteady flows and sounds. Also included is an introduction of numerical simulation methods by CAA (Computational AeroAcoustics), which has been proven to be somewhat inferior for simulating cases of complicated flows. It is discussed that conventional acoustic engineering methods are effective for flow noise reduction, and that controlling the flow itself is imperative for direct control over noise sources. It is concluded that a harmony between flow and sound is a dominating factor for controlling fluid acoustics.

Fluid acoustics, Noise control, Low noise acoustic wind tunnel, Experimental simulation, Computed fluid dynamics, Computational aeroacoustics, Turbulence control, Acoustical engineering, Transmission control, Unsteady flow