Effects of highly preheated combustion air on characteristics of burner operation and fuel consumption in controlled-air incinerator (original) (raw)
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International Journal of Energy Research, 2005
Experiments have been carried out to study the effect of secondary air supply rate on the combustion of volatile gas in a controlled-air incinerator. The secondary air supply was varied at flow rates of 0.56, 1.026, 1.73 Nm3/min. The waste in this study was categorized into three types: namely those containing low, medium and high combustible matter. The significant results of the experimental investigation shown that increasing secondary air supply rate reduces the chamber temperature in both chambers and strong effect on CO reduction for waste with high combustible content. NO formation increases slightly as secondary air supply increases and SO2 formation depends on the sulfur content in the waste and insensitive to secondary air for the range of flow rate tested. Copyright © 2005 John Wiley & Sons, Ltd.
An experimental study has been conducted with a fixed bed reactor to simulate, in a laboratory scale, industrial municipal waste incineration using moving grates. Carbon monoxide, nitrogen oxide, temperatures and mass loss rate measurements have been used to establish the importance of the operating parameters of a municipal waste incinerator in the characteristics of the combustion process. The present work is concerning the study of the impact of the airs of combustion. Two different regimes have been identified and that are controlled by the airflow through the fuel (primary airflow). The two combustion regimes established has served to show the potential impact of the operating conditions on the comportment of the combustion, the temperatures and the yields of carbon monoxide and nitrogen oxide : the production of NO seems to be controlled only by the oxygen concentration in the secondary zone of combustion. An increase in total airflow, thus, results in an increase in the yield of NO.
Effects of operating parameters on the combustion of medical waste in a controlled air incinerator
… and management, 2005
Experiments have been performed to investigate the effects of primary chamber preheating temperature and batch size of the waste feed on the combustion of medical waste in a two chamber controlled air incinerator of 50 kg/h nominal capacity. The primary purpose is to determine qualitatively the functional relationships between the key incinerator performance indicators and the above two parameters so that optimum preheating conditions of a pilot incinerator, which has been in trial use at a hospital, may be defined. Three batch sizes were used, namely: 5, 7.5 and 10 kg, with the primary chamber preheating temperature varied from 500 to 800°C at 100°C intervals for each batch. The secondary chamber temperature control was set at 900°C. The results showed that increasing the waste charging temperature and the weight of charge tend to accelerate the rate of volatile gas release, causing a ''bottleneck effect'' in the secondary chamber and, hence, a negative effect on the overall performance of the incinerator, as reflected in the residual unburned CO in the gases leaving the chamber. Higher charging rates could have been achieved by increasing the combustion air supplied to the chambers. Using CO measurement as a criterion for good combustion makes it possible to determine the optimum incinerator temperature control settings and operating conditions, as well as to assure continuous, efficient, environmentally satisfactory operation. The optimum operating condition for the range of experiments tested appears to be a batch size of 5 kg and a primary chamber preheating temperature in the vicinity of 700°C.
Combustion Simulation in the Secondary Chamber of a Pilot-Scale Incinerator
Environmental Engineering Science, 2007
A numerical analysis of combustion in the secondary chamber (thermoreactor) of a two-stage pilot scale incinerator using computational fluid dynamics (CFD) is presented in detail. Various versions of the CFD program package CFX were used, which offer different combustion models for specific types and forms of combustion processes. The present study was focused on those physical conditions that assure complete combustion, that is, temperature, residence time, and turbulent mixing. The selection of an appropriate combustion model was based on a comparison of the numerical results and experimental values of some combustion macro parameters in a thermoreactor. Combustion models based on one-step bimolecular chemical reaction and models based on multistep reactions were used. These models enabled a more detailed prediction of the combustion process in the secondary chamber of a pilot-scale incinerator. The products of incomplete combustion that are significantly important for the designing and optimization of combustion devices can be predicted by applying multistep reaction models more accurately, especially in a transient regime of combustion.
Effects of Access of Secondary Air on Operation of an Atmospheric Burner
International Journal of Energy for a Clean Environment, 2011
The major advantage of atmospheric burners, which are applied both in households and in industry, is their noncomplexity, i.e., primary combustion air is entrained, so there is no need for a fan. Consequently, the main designing task is to provide optimal amounts of primary and secondary air to the burner, which will lead to a stable and efficient burner operation. This research was focused on investigating the influence of access of secondary air on the operation of a novel, fully premixed atmospheric burner, which has an advantage of low NOx emissions (due to lean fuel conditions), but is prone to flame instabilities. This investigation helps predict the performance of the fully premixed atmospheric burner within the chamber, initially designed for a partially premixed atmospheric burner. For this purpose, an experimental setup with controllable accesses of primary and secondary air was built. Experimental investigation showed that for a constant primary excess air ratio the availability of the secondary air significantly increased the emission of CO. Thus, besides reducing the heat efficiency of the combustion unit, the availability of the secondary air reduced the overall performance of the burner. The availability of the secondary air showed to be important for the burner operation in the current setup, i.e., when secondary air was not available, the chimney draft induced strong changes in the entrainment of primary air, which led to conditions under which the burner was not operable.
Fuel, 2021
Air preheating is generally used to improve moisture evaporation and boiler efficiency in waste incineration systems. This study employs FLIC-FLUENT coupling procedure to investigate the influence of primary air preheating on municipal solid waste (MSW) combustion characteristics in a moving grate incinerator. The MSW properties, incinerator specifications and operating parameters were acquired from an incineration plant in Zhejiang Province, China. The MSW combustion modelling was carried out with air preheating temperatures in a range of 453-513 K. The simulation results were compared with measurements data from the incinerator and literature. It was found that higher primary air temperature caused a larger layer of evaporation at the bottom of the bed. When the evaporation layer comes in contact with the ignition front, the remaining mass burned instantaneously, resulting in a faster complete combustion. Peak bed temperature was observed during the complete combustion, it was highly influenced by heat flux from the primary air and the combustion. Higher primary air temperature also resulted in increased devolatilization rate and peak flame temperature. The peak flame temperature reached 1961 K under 513 K air temperature. Boiler efficiency increased by 5.6% when remaining flue gas heat was utilized to preheat the air to 453 K compared to the unutilized. However, high primary air temperatures also have negative influences, for example, accelerated thermal NOx generation and locally high bed temperature. Condensation of acid gases could also occur if the remaining flue gas heat was over-utilized. Therefore, the determination of the suitable primary air temperature is essential.
Combustion and Heat Calculations for Incinerator
The design of industrial and municipal incinerators is based on combustion and heat considerationsl The procedures are given for calculating the quantities of air, flue gas, water and heat, as well as the gas temper atures. To assist the reader, a municipal incinerator is used as an example. The relation between refuse analysis and flue gas analysis is explained. Sections on dry and wet dust collection are included.
Thermal analysis of an enriched flame incinerator for aqueous residues
Energy, 2006
The use of oxygen to enrich the combustion air can be an attractive technique to increase capacity of an incinerator originally designed to operate with air. If incinerator parameters such as operation temperature, turbulence level and residence time are fixed for a certain fuel supply rate, it is possible to increase the residue consumption rate using enriched air. This paper presents the thermal analysis for operation with enriched air of an aqueous residue experimental incinerator. The auxiliary fuel was diesel oil. The theoretical results showed that there is a considerable increase in the incineration ratio up to approximately 50% of O 2 in the oxidiser. The tendency was confirmed experimentally. Thermal analysis was demonstrated to be an important tool to predict possible incinerator capacity increase.
2014
This research aims to study for the double-chambered incinerator using biomass producer gas derived from gasification process by adjust the optimal combustion characteristics that can efficiently prevent emissions from being released. 30 kilowatt-thermal of gasifier that can generate an average of 18 m 3 per hour of producer gas at the maximum fuel input rate of 15 kg per hour. The incinerator prototype consists of 2 combustion chambers with 2 gas burners installed, one for sample meat combustion and one for pollution elimination. The calculated proper volume of the primary chamber and secondary chamber were 0.10 m 3 and 0.03 m 3 , respectively, in order to maintain an adequate combustion residence time. The experiment shows the temperature of the primary and secondary rooms can achieve a maximum of 750 o C and 500 o C, respectively, when 100% of excess air condition was carried out. Meanwhile, a large input of excess air decreased the temperature inside the combustion chambers and ...