Incinerator Furnace Research Articles

VUV Single-Photon Ionization Ion Trap Time-of-Flight Mass Spectrometer for On-Line, Real-Time Monitoring of Chlorinated Organic Compounds in Waste Incineration Flue Gas

In this work, a sensitive and robust vacuum ultra-violet (VUV) single-photon ionization (SPI) ion trap time-of-flight mass spectrometer (VUV-SPI-IT-TOFMS) for on-line, realtime monitoring of chlorinated organic compounds in waste incineration flue gas has been newly developed. The fragment-free SPI technique with 121.6-nm VUV lamp irradiated by a microwave generator and the quadrupole ion trap to accumulate and select analyte ions were combined with a reflectron time-of-flight mass spectrometer to detect chlorinated organic compounds at trace level. This measuring system was tuned up to detect dioxins precursors with the aim at an application to monitoring trace level toxic substances in flue gases from incinerator furnaces. As a result, this technology has made it possible to analyze trichlorobenzene (T3CB), a dioxin precursor, in 18 s with a sensitivity of 80 ng/m3-N (10 pptv) using the selective accumulation of analyte substances and separation of interfering substances in the ion trap. Moreover, the first field test of the continuous monitoring T3CB in an actual waste incineration flue gas had been done for 7 months. The results show that this system has an exceeding robust performance and is able to maintain the high sensitivity in analyzing T3CB for long months of operation.

Development of an Ash Melting Furnace Utilizing the Combustion Heat of Unburned Carbon Residue in Ash

Conventional methods for treating waste and ash generated in incineration furnaces are to melt and solidify the ash at high temperature.Though various types of systems have been installed and in operation, they have some critical problems with their high operation cost including fuel cost, technical difficulties in melting mixed materials contained in ash, and practical in capability in melting iron materials and clinkers. The proposed system here is designed to utilize the combustion heat of unburned carbonaceous materials contained in discharged ash from a waste incineration furnace in order to assist melting the incineration ash to reduce fuel consumption. The furnace system has oxygen burners for burning carbon and for melting iron materials and clinkers. The test operation results conducted by 12t-ash/day test plant are reported. The test has revealed that the proposed system is capable of melting the ash containing 20-30wt.% of iron and clinker rumps of the volume size of around 15 cm3 without auxiliary fuel supply other than unburned carbon residue in ash.

Hazardous waste destruction and nitric oxide reduction with externally forced oscillation

The research described here focuses on the enhancement of hazardous waste destruction and the reduction in nitric oxide and unburned emissions in a cavity incinerator, which has externally forced acoustic oscillation. The specific configuration of the incinerator was manufactured to consist of two opposing jets and a rearward facing step [Chun, 1999]. The cavity-type incinerator warrants a sufficient residence time and effective turbulent mixing by the formation of a strong recirculation region in a combustion cavity. The experiments were carried out about combustion characteristics in a 3.2 kW laboratory scale, transportable, cavity incinerator without external oscillation. These showed that hazardous waste was destructed effectively, but unfortunately NO was increased by high gas temperature. To solve this problem, we developed an externally oscillated auxiliary burner embedded on the incinerator furnace. The external oscillation was effective to reduce NO which is produced at high temperature incineration and to destruct hazardous waste, simultaneously. Emissions of NO are seen to be decreased by nearly 60%, and DRE (destruction and removal efficiency) is above 99.99%, all with external forcing at a specific optimum conditions.

Modelling Waste Combustion in Grate Furnaces

The disposal of waste that cannot be minimized, recycled or reused is a huge international problem. In the UK, we currently landfill about 30 million tonnes of waste per year. This is environmentally unfriendly due to greenhouse gas emissions, etc., and squanders energy equivalent to about 25% of our current coal consumption. The incineration of material in energy-from-waste plants has received relatively little attention from combustion scientists and engineers in the past and this work is directed at rectifying this situation. Incinerators generally burn waste on a moving grate that transports and mixes it during combustion. The combustion process involves drying, devolatilization, gasification and char burn-out. Thus gasifiers and pyrolysers are subsets of this combustion problem. Mathematically modelling combustion on the grate requires the solution of the flow field in a reacting packed bed, including radiant heat transfer. Since the burning in the channels is mixing-limited, reactions also occur in the gas phase above the bed. The conditions evaluated at the surface of the bed are the boundary conditions for conventional computational fluid dynamic modelling of the mixing and reactions in the secondary combustion zone in the freeboard above the bed. This permits the evaluation and minimization of emissions such as dioxins to the point that dioxins from incinerators now only contribute 3% of the total UK dioxin emissions. The validation of our reacting bed modelling code (FLIC) has been achieved by measurements in a pot burner using various wastes. Furthermore, a small ‘ball instrument’ that has been specially developed to contain instruments has complemented these measurements by withstanding temperatures up to 1000°C for well over an hour. This novel device passes through industrial incinerator furnaces with the waste and records parameters such as oxygen, vibration and several temperatures onto a computer memory chip. The ball is recovered from the incinerator ash pit and the information is downloaded onto an Excel spreadsheet for detailed analysis. Incinerator combustion is obviously one of the most complex combustion physics/chemistry processes known. At the present time it is also industrially important, however it is now yielding its secrets to scientific study.

Mathematical modelling of MSW incineration on a travelling bed

The rising popularity of incineration of municipal solid waste (MSW) calls for detailed mathematical modelling and understanding of the incineration process. In this paper, governing equations for mass, momentum and heat transfer for both solid and gaseous phases in a moving bed in a solid-waste incineration furnace are described and relevant sub-models are presented. The burning rates of volatile hydrocarbons in the moving bed of solids are limited not only by the reaction kinetics but also the mixing of the volatile fuels with the under-fire air. The mixing rate is averaged across a computation cell and correlated to a number of parameters including local void fraction of the bed, gas velocity and a length scale comparable to the particle size in the bed. A correlation equation is also included to calculate the mixing in the freeboard area immediately next to the bed surface. A small-scale fixed bed waste incinerator was built and test runs were made in which total mass loss from the bed, temperature and gas composition at different locations along the bed height were measured. A 2-D bed-modelling program (FLIC) was developed which incorporates the various sub-process models and solves the governing equations for both gases and solids. Thermal and chemical processes are mainly confined within a layer about 5–9 times in thickness of the averaged particle size in the burning bed. For a large part of the burning process, the total mass loss rate was constant until the solid waste was totally dried out and a period of highly rising CO emission followed. The maximum bed temperature was around 1200 K. The whole burning process ended within 60 min. Big fluctuations in species concentration were observed due to channelling and subsequent ‘catastrophic’ changes in the local bed conditions. Reasonably good agreement between modelling and measurements has been achieved. Yet the modelling work is complicated by the channelling phenomenon in the bed. Numerical simulations without consideration of the channelling effect produced very good agreement with experiments concerning the total mass loss, but significant discrepancy exists for temperature and gas composition profiles. Transient phenomena such as the breaking of waste particles and the “catastrophic” creation of new burning channels occurring during waste incineration is a vital area requiring further investigation at the fundamental level. The underlying theory of bed behaviour must be extended to include these transient events.

Improvement of combustion control through real-time measurement of O 2 and CO concentrations in incinerators using diode laser absorption spectroscopy

In order to reduce the emission of harmful substances from incinerator facilities, combustion within the incinerator furnace must be stabilized. This in turn requires accurate and rapid detection of changes in furnace combustion conditions, with appropriate control of factors such as combustion air volume. This report describes the real-time measurement of O 2 and CO concentrations in a 300 ton/day commercial incinerator furnace, as well as the improvement of combustion control using in-furnace multiple-point O 2 and CO concentration measurements. The use of diode laser absorption spectroscopy was confirmed to allow real-time (2 s) measurement of in-furnace O 2 and CO concentrations. An automated system was developed, and the results were utilized as input values for furnace combustion control. In-furnance laser measurements detected O 2 and CO concentration fluctuations 2–3 min faster than existing conventional monitors. Greater secondary combustion efficiency was achieved by using these multiple-point laser measurement results to control secondary air allocation, and CO concentration (a substitute indicator for dioxins) was reduced from 11.9 to 8.0 ppm. Fast detection of furnance information is essential for control of unbalanced furnance combustion, and this system will enable the improvement of commercial incinerator furnaces in terms of both control and emissions.

Interaction of Cadmium and Flyash Sorbents in an Experimental Waste Incineration Furnace—Flue Gas System

The interaction of cadmium and different flyash sorbents has been examined in an experimental reactor under a variety of conditions simulating those found in waste incinerator furnace—flue gas systems. The experimental system consisted of two stainless steel reactors independently heated by electrical furnaces, enabling a temperature regime of between 100 and 1000°C to be investigated. Cadmium was vaporized in the furnace section of the reactor and the cadmium species formed were passed to the flue gas section where interaction with various flyash sorbents was investigated. The sorbents examined were three different aluminium oxides, silicon oxide and two aluminium silicates and the adsorption of cadmium species under various temperatures and flue gas compositions was determined. Flyash analysis consisted of a microwave extraction—ICP procedure to determine the adsorbed cadmium. In addition, SEM-EDX analysis of the surface of the flyash sorbents was used to characterize the surface adsorption. The results showed that at lower temperatures the cadmium species were adsorbed onto the flyash through physical adsorption whereas at temperatures above 765°C chemical adsorption occurred. SEM-EDX analysis of the surface showed that discrete particles of cadmium metal were produced in the flue gas system and were deposited on the flyash. The particle size of the flyash samples was found to influence the sorption of the cadmium. The presence of HCl and O2 in the flue gas altered the sorption capacity of the cadmium.

耐熱鋳鋼SCH2の廃棄物焼却炉内における高温腐食機構

耐熱鋳鋼SCH2の廃棄物焼却炉内における高温腐食機構

Incinerator furnace with fire grate and air supply : Hyun Kwangsoo Sungdong Gu, Seoul, Korea

Incinerator furnace with fire grate and air supply : Hyun Kwangsoo Sungdong Gu, Seoul, Korea

Simulation numérique d'un four d'incinération d'ordures industriel coupléà une chaudière à circulation naturelle

In the context of resource conservation and the rational production and use of energy, there is growing interest in Switzerland, as elsewhere, in the incineration of domestic wastes. One of the characteristics of waste incineration cogeneration power plants is their frequent partial or excess loading. In order to describe their behavior at these non-nominal loads, there is a need for simulation tools, which predict with accuracy the behavior of the principal components of the plant at these loads. This paper presents a simulation model of an industrial waste incineration furnace coupled to a natural convection boiler. The model provides information on the internal behavior of the system, which leads to the creation of windows of operation for the incinerator/boiler system. The model was validated using measurements taken at an industrial site and forms the basis of a robust and accurate simulation tool for the description of this kind of system. With this tool, a multitude of different parametric studies can be done on geometry, waste composition, non-nominal loads, combustion gas recirculation, etc. Simulation results are given as well as results from the direct use of this model in evaluating the addition of a topping cycle to an existing waste incineration cogeneration power plant.

Fuzzy Combustion Control for Reducing Both CO and NOx from Flue Gas of Refuse Incineration Furnace.

NKK developed a new combustion controller that reduces both NOx and CO concentrations in the exhaust gas of municipal refuse incineration furnaces. We found that the manipulation of the cooling air flow rate is important because it affects the furnace temperature and the O2, NOx and CO concentrations in the exhaust gas. The new controller manipulates the cooling air flow rate. The controller monitors the furnace temperature and the O2, NOx and CO concentrations as process variables and then operates the cooling air flow rate as a manipulated variable. This multi-input / single-output controller was designed using a fuzzy control algorithm and tested on site at a municipal refuse furnace. The result of the on-site test was quite successful.

Fuzzy Combustion Control for Reducing both CO and NOx from Flue Gas of Refuse Incineration Furnace.

NKK has developed a new combustion controller that reduces both NOx and CO concentrations in the exhaust gas discharged from municipal refuse incineration furnaces. We have found that the manipulation of the cooling air flow rate is important because it affects the furnace temperature and O2, NOx and CO concentrations in exhaust gas. This controller manipulates the flow rate of the cooling air. It monitors the furnace temperature and O2, NOx and CO concentrations as process variables, and outputs the cooling air flow rate control signal as a manipulated variable. This multi-input/single-output controller was designed using by a fuzzy control algorithm and tested on site at a municipal refuse furnace. The result of the on-site test was quite successful.

Thermodynamic Behavior of Metal Chlorides and Sulfates under the Conditions of Incineration Furnaces

Thermodynamic equilibrium calculations performed with the program ChemSage reproduce the observed behavior of metals in refuse incineration furnaces and reveal general trends. Presentation of the results as a series of small graphs allows a quick overall view of the significant species. The calculations predict that all of the Hg present and most of the Cd and Pb volatilize, as is observed in practice. The amounts of Zn and Cu volatilized depend on the reduction conditions and on the amount of Cl present. As and Sb also volatilize, but Mg, Ca, Fe, and Ni do not volatilize under the prevailing oxidizing conditions. The presence of sulfur stabilizes many of the metals in sulfate phases at low temperature but has little influence above 800 °C. Under locally reducing conditions, it may favor the volatilization of Sn as SnS. More detailed studies, in which comparison is made with data from industrial furnaces with measurements carried out under well-defined conditions, are required to answer specific questions.

Analyses of polychlorinated dibenzo-p-dioxins and dibenzofurans and precursors in fly ash samples collected at different points in post-combustion zone of Japanese machida incinerator

Several samples collected at the post-combustion zone of the Machida incinerator in Japan were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated phenols (PCPs) and polychlorinated benzenes (PCBEs). All samples show lower levels of PCDDs and PCDFs in comparison to the levels of observed in other samples from various incinerators around the world. The Machida incinerator in Japan shows ten times lower levels of PCDDs/PCDFs than the Ontario incinerator in Canada. Analyses of fly ash samples collected at different points in the post-combustion zone shows higher levels of PCDDs/ PCDFs at points near the stack, and decreasing towards the combustion zone. That trend indicates the formation of PCDs/PCDFs in the electrostatic precipitator by catalytic activity of fly ash in addition to their probable formation in the incinerator furnace. Variations in normal operating conditions have no or very little effect on the amount of PCDDs/PCDFs formed. Municipal solid waste in Japan has been separated into combustible and non-combustible materials. Only the combustible materials were incinerated in the Machida incinerator, which is fluidized bed design with CaO inject into the bed.