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VOL.20 NO.1 (published in Jun-2012)

VOL.20 NO.1 (published in Jun-2012)
CO2 Separation and Capture by Membrane Technologies,
and The Application to The Flue Gas in Waste Incineration Plants
Muneharu FUJIKAWA*
(*Energy and Environmental Development Dept.)

(Abstract)

CO2 separation and capture technology from flue gas is considered an extremely viable technology for reducing emissions of greenhouse gases, and its practical application is highly anticipated. Waste incineration plants are relatively small in size and have a low energy conversion efficiency compared to thermal power stations or blast furnaces. This means that membrane-based separation technology is best suited if CO2 is to be separated and captured from the flue gas in waste incinerators due to its advantages of space-efficient and energy-efficient design, and low cost. This report first provides an introduction into CO2 separation and capture by membrane technologies, and outlines calculations when using the technology for exhaust gas from waste incineration plants. The results conclude that the membrane contactors method is the best technology current available for the separation and capture of CO2 from flue gas in waste incineration plants. Further improvements to heat-resistance and acid-resistance of the membrane and absorption fluid could make the membrane contactors method more energy-efficient for separating and capturing CO2. If the heat-resistance and acid-resistance of membranes used in the membrane-gas absorption hybrid method and facilitated transport membrane methods, as well as the reliability of separation performance can be improved into the future, the technology is expected to become even more space and energy-efficient, while also available at a lower cost.

Case Study of Delivery of Industrial Waste Incineration Plants Suited to
Treatment of Various Types of Waste
Hiroyuki HIKITA*and Hiroaki HYUGA*
(*Energy Technology Division 1)

(Abstract)

There have been major advances in reducing and reusing and recycling, industrial waste. Yet industrial waste is being generated in small quantities and large varieties, which has increased the demand placed on industrial waste disposal operators by consumers disposing of industrial waste. Our company has delivered and installed a growing number of step grate stoker incineration plants since 2006, however there has been an increase in orders for industrial waste incineration plants with rotary kiln and stoker incineration plants following increased demand for the amount of fluid and high-calorific waste disposed of by consumers that cannot be treated adequately using stoker incinerator. Operation of the particular plant was transferred at the end of November, 2011, after conducting plant performance tests and checking that all performance guaranteed items had been adhered to. These two incineration plants have resulted in an incineration plant system that is capable of processing various types of waste, including solids, liquids, sludge, high-calorific, low-calorific, and bulk waste.

Nitrogen Removal by combination of Nitritation and
Anaerobic Ammonium-Oxidation Process using Fixed-bed Reactor
Keita TAKAKI*and Masahiko OKUDA*
(*Sewerage Engineering Dept.)

(Abstract)

Using anaerobic ammonium oxidation process as a novel biological process for nitrogen removal from wastewater containing high concentrations of ammonium has attracted much attention. It makes possible to reduce the operational costs of aeration and carbon sources (e.g. methanol) compared with the conventional nitrification/denitrification process. This study focuses on the potential for removing nitrogen from reject water in a municipal wastewater treatment plant using a combined nitritation/anaerobic ammonium oxidation process with fixed-bed reactors.

In a bench-scale plant that was fed reject water, the nitrite conversion efficiency was above 80% for about 210 days during the nitritation operation. Nitrate production was negligible during this period. We found that the NO2- - N/NH4+ - N ratio of the anaerobic ammonium oxidation reactor influent could be maintained easily by controlling the flow rate of bypass wastewater according to the nitritation performance. For the anaerobic ammonium oxidation reactor, significant nitrogen removal was observed immediately after the start-up and a maximum nitrogen removal rate of 2.90kg - N/m3/d was obtained 80 days after start-up.

Technology Development to Simultaneously Control Chlorinated Aromatics
and Nitrogen Oxide in Flue Gases via Addition of Urea
Kazuyuki OSHITA*,Madoka NAKAMURA*,Yoshihiro NISHIMOTO*,Masaki TAKAOKA*,
Masaharu OUE**and Hitoshi HARADA**
(*Department of Environmental Engineering, Graduate School of Engineering, Kyoto University
**Energy and Environmental Development Dept.
)

(Abstract)

To improve waste-to-energy electrical power generation at a municipal solid waste incinerator (MSWI), a new flue gas treatment system that includes a ceramic filter for dust removal at 300℃ and a selective catalytic reduction process (SCR) for NOx removal was developed. However, dust removal at 300℃ could produce chlorinated aromatics, which might increase dioxins and PCBs in ash. In this study, we added urea into this system as an inhibitor of dioxins and PCBs and the NOx reducing agent, and examined whether urea could inhibit dioxins and PCBs with simultaneously reducing NOx. At first, a lab-scale fundamental test was carried out by heating model fly ash, adding 1% urea at 300℃ and adjusting the oxygen concentration between 5% and 20% in a tube reactor. As a result, PCBs were inhibited by the presence of urea and lower oxygen concentrations. PCBs decreased by 87% with the addition of 1% urea and with a 5% oxygen concentration compared with a treatment without urea and a 10% oxygen concentration. After this first test, a bench-scale test was carried out using the experimental flue gas treatment device. As a result, 11% to 23% of PCBs, 22% of dioxins and approximately 53% of NOx were simultaneously inhibited by the addition of 1% urea.

Study of the SO3 Generation Process During Combustion, and Field Surveys
of the SO3/SO2 Conversion Ratio at Waste Incineration Plants
Masaharu OUE*and Keiji TATSUMI*
(*Energy and Environmental Development Dept.)

(Abstract)

In laboratory testing, the generation of SO3 could be limited by using two-stage combustion, however this limitation was not observed when the primary air ratio was decreased in two-stage combusion. The results were the same as those achieved in field surveys conducted at existing waste incineration plants. The relationship between the SOx concentration and SO3/SO2 conversion ratio was also studied, with results indicating a positive proportional relation in laboratory testing, however there was no correlation observed during field surveys. And field survers showed that the SO3/SO2 conversion ratio of waste incineration plants constructed within the last 10 years was around 0.1% to 1.0%.

Latent Heat Recovery Type Vacuum Gas Water Heater
Tomoo MIURA*
(*Nippon Thermoener Co., Ltd.)

(Abstract)

There has been an increased awareness amongst the general public to save energy and reduce their environmental impact, with much attention focused on high-efficiency water heaters. Our company has developed the latent heat recovery type vacuum gas water heater (VACOTIN HEATER) to meet these demands.

This development has resulted in an individual afficiency of 95% (based on lower heating value) through the use of a new fin water tube layout within the actual structure of the VACOTIN HEATER. The addition of an economizer to further increase the recovery of latent heat results in an overall efficiency of 105%. The installation of a proportional combustion control burner with the turndown rario of 5:1 has drastically improved system efficiency when used under patr-load operation.