High Temperature Air Combustion Technology Research Articles

1501 高温雰囲気中における単一石炭粒子の自発点火に及ぼす酸素濃度の影響

Considering exhaustion of natural resources, the vast quantities of coal are very attractive for human beings and expected to play an important role in the future. On the other hand, the amount of environmental pollutant is more discharged than any other fossil fuels in combustion. Therefore, high temperature air combustion technology of pulverized coal is under development as an innovative combustion technology in order to decrease amounts of environmental pollutant. In this study, effects of oxygen concentration on ignition process of a single coal particle in high temperature were investigated.

236 廃棄物の高温空気燃焼に関する研究

High-Temperature Air Combustion Technology is an attractive method for producing surplus electric power and reducing environmental disruption materials such as NOx and dioxins especially in combustion process of Municipal Solid Waste (MSW) incinerator. The objective is to develop an energy-saving system for the MSW incinerator and to lower the emission pollutant. The experimental study is carried out systematically with simulated MSW furnaces (500kg-waste/h) to study the thermal degradation, the distribution of temperature and gas concentrations in the furnaces. Blowing the mixture of high temperature air and the flue gas to the primary combustion space brings extremely stable combustion. Moreover, it reduces not only the NOx, CO and the other toxic products, but also more than 20% of the excess air.

237 都市ごみ焼却炉内燃焼挙動の予測

High-temperature air combustion technology is applied to produce surplus electric power and reduce dioxins, NOx and CO in combustion process of a stoker-type MSW (Municipal Solid Waste) incinerator. The macro-patterns of flow and combustion are analyzed numerically with an approximate combustion analysis code using physical model. Present simulation data, general distributions of the temperature, the velocity, and the chemical species, were approximately related to the experimental data measured using a simulated MSW incinerator. We found that blowing mixed gas of high-temperature air and exhaust gas to combustion beginning space was effective for the decrease of air for waste combustion.

1504 フラクタル・モデルを用いた高温空気燃焼場における微粉炭燃焼特性の解析

High-Temperature Air Combustion Technology (HiCOT) of pulverized coal combustion is expected to improve the combustion efficiency of coal and to reduce NO_x emission. The objective of this research is to predict the combustion behavior of the pulverized coal in such a furnace with optimum design, which fully utilizes the advantage of HiCOT technique. Especially, char combustion behavior under high-temperature air condition is numerically calculated using the Fractal Reaction Model and compared with the experimental data. From the results of the calculation, this new reaction model in high temperature air combustion condition predicts the conversion of the pulverized coal more highly than the conventional model. Comparing with the experimental data, the new model can predict the char conversion better than the conventional model in the early stage of char combustion.

A study of combustion behavior of pulverized coal in high-temperature air

High-temperature air combustion is a promising technology to increase the usage of combustion energy and to improve combustion efficiency. This technology has been mainly developed for gaseous fuels, and recently application of this technology to solid fuels like pulverized coal has also become of interest. For the development of high-temperature air combustion technology for pulverized coal, it is important to experimentally investigate the combustion behavior of pulverized coal in high-temperature air. In this study, high-temperature air is applied to a pulverized coal burner to investigate the effect of air temperature on ignition, coal burnout, and NO x emission. Pulverized coal is introduced into a cylindrical furnace of 1 m diameter and 3 m height using a water-cooled stainless nozzle of 15 mm diameter. Combustion air is preheated using a heat exchanger with a gas burner and electrical furnace. The temperatures of the combustion air are set to 623 or 1073 K in order to compare the effect of air temperature. It is observed that ignition delay decreases as the air temperature increases, which is due to the more rapid devolatilization caused by higher particle heating rates. It is possible to form a stable flame even for low-volatile coals like anthracite. The difference in measured peak flame temperatures between 623 and 1073 K air is about 100 K, which is smaller than expected. Coal burnout is improved in the 1073 K air condition, which seems to be due to the increase of porosity of the particle. NO x concentration decreases for higher temperature due to enhancement of the reduction zone by rapid devolatilization of coal, as the volatile and fuel nitrogen release is enhanced in high-temperature air.

00/00945 High efficiency power generation from coal and wastes utilizing high temperature air combustion technology. (Part I: Performance of pebble bed gasifier for coal and wastes)

00/00945 High efficiency power generation from coal and wastes utilizing high temperature air combustion technology. (Part I: Performance of pebble bed gasifier for coal and wastes)

99/03876 High efficiency power generation from coal and wastes utilizing high temperature air combustion technology. (Part II: Thermal performance of compact high temperature air preheater and MEET boiler): Iwahaski, T. et al. FACT (Am. Soc. Mech. Eng.), 1998, 22, (1), 489–494

99/03876 High efficiency power generation from coal and wastes utilizing high temperature air combustion technology. (Part II: Thermal performance of compact high temperature air preheater and MEET boiler): Iwahaski, T. et al. FACT (Am. Soc. Mech. Eng.), 1998, 22, (1), 489–494

Numerical Study of NOx Emission in High Temperature Air Combustion.

The characteristics of NOx emission in the high-temperature air combustion technology were investigated numerically. Two kinds of methods were used. Detailed chemistry and transport properties were used for a two-dimensional laminar diffusion flame, and a simplified reaction scheme was used for calculating a turbulent flame in a furnace. Results show that the thermal mechanism dominates NOx emission in high-temperature air combustion. If only the preheated air temperature is increased, NOx emission will rise significantly. However, the combination of air preheating and flue gas recirculation not only improves the combustion efficiency, but also suppresses NOx emission in the combustion process.