Secondary Combustion Chamber Research Articles

A Three-Dimensional Numerical Model of a Waste Incinerator

A three-dimensional simulation model of the secondary combustion chamber of a waste incineration plant is presented. The model is based on a set of partial differential equations governing the transport of mass, momentum and energy, together with additional equations modelling the turbulence, heat generation by reaction and radiative heat-transfer phenomena. Because it was not possible to resolve the burner region by a grid being fine enough to describe all details and to get a grid-independent solution, profile measurements were made in a pilot-scale combustion chamber using an isotypical liquid injection burner. These results were used in order to find the parameters of the whole simulation. In order to verify the simulation model some results are compared with measurements of temperature and residence-time distribution at a real incineration plant, and two models are given for the description of the burnout behaviour. Finally the non-isothermal model is discussed and a comparison is made between the isothermal model and the non-isothermal model.

Combustion Characteristics in a Municipal Solid Waste Incinerator. 2nd Report, Combustion Improvement by Means of Computer Simulation.

The purpose of this work is to establish design and operation methods for a municipal solid waste incinerator for complete combustion of flue gas, which is essential for reducing the generation of trace hazardous substances such as dioxins. The combustion conditions of an existing incinerator, therefore, are examined, and the results demonstrate that sufficient gas mixing and oxygen concentration coupled with combustion gas temperature in the secondary combustion chamber substantially lower carbon monoxide (CO) concentration in flue gas, an indicator of complete combustion. Furthermore, from the results of investigation in conjunction with the computer simulation of gas flow distribution inside the incinerator, some modification plans are suggested and actually implemented : a nose is installed at the furnace outlet and secondary air is supplied to the secondary combustion chamber. The performance tests after the modification indicate that the gas flow distribution in the secondary combustion chamber is equalized and the concentrations of CO and dioxins are significantly lowered.

Development and Execution of a Metals Pretest Program for a Hazardous Waste Incinerator

Eastman Kodak Company owns and operates a hazardous waste incinerator at the Kodak Park Site facility, located in Rochester, New York. The incinerator consists of a rotary kiln followed by a secondary combustion chamber. Particulate and HCl control is provided by a quench chamber and a venturi scrubber. In May, 1991, a Trial Burn Plan was submitted for the incinerator as part of the NYS Hazardous Waste Management Facility Permit Application process. A key requirement of the Trial Burn was to demonstrate the hazardous waste incinerator's ability to control heavy metal emissions. To achieve this, an aqueous metals test protocol was developed to evaluate the incinerator's metals control capability under worst case conditions. Prior to the actual Trial Burn, an extensive metals pretest program was conducted at the facility to evaluate the incinerator metals control capability as a function of metal species, metals feedrate, waste chlorine content and combustion chamber temperatures. As a result of this program it was demonstrated that the high pressure differential venturi scrubber effectively controls emissions of heavy metals to levels prescribed in USEPA Guidance. Also, the program demonstrated the impact that combustion chamber temperatures and waste chlorine content have on incinerator metals control capability.

Dynamic modeling of waste incineration systems: A startup procedure

The paper deals with the development of a dynamic model which allows to describe the behavior of a rotary kiln (primary combustion chamber with heterogeneous combustion) and the corresponding afterburners system (secondary combustion chamber with homogeneous combustion). For sake of brevity, the analysis here reported will be limited to a startup procedure used, as specific application, to really check robustness and reliability of the model itself Few comparisons with experimental data available from a commercial unit will be reported to complete the model validation.

A Model to Analyze Formation of Dioxins in the High Temperature Regions of Municipal Solid Waste Incinerators

Polychlorinated dibenzo-p-dioxins (PCDD) can be formed in significant amounts in municipal solid waste incinerators. Earlier attempts at modeling their formation proposed that chlorobenzenes (CB) and chlorophenols (CP) could be precursors to PCDD formation. Most modeling studies have been largely confined to the lower temperature regions of the incinerator (450-550 K or 177-277[degrees]C). But incinerator data seem to indicate that PCDD are also formed in the region between the secondary combustion chamber and the particle collection device, a region that might be represented by a temperature range of 450-1,150 K (177-877[degrees]C). PCDD formation in this region can be predicted by the same model used for the lower temperature region by including a temperature dependence for the surface coverage of fly ash particles in the model. The effect of particle size is also discussed. 8 refs., 8 figs., 3 tabs.

Transient Suppression Packaging for Reduced Emissions from Rotary Kiln Incinerators

Abstract Experiments were performed on a 73 kW rotary kiln incinerator simulator to determine whether innovative waste packaging designs might reduce transient emissions of products of incomplete combustion due to batch charging of containerized liquid surrogate waste compounds bound on ground corncob sorbent. When containers of waste are batch charged into rotary kilns, the rupture of the container is often followed by a very rapid evolution of any volatile compounds contained therein. This flash vaporization/ pyrolysis can result in local depletion of available oxygen, as supplied from the primary burner. This can lead to a transient puff of partially combusted organic material that can pass through the primary combustion chamber, and possibly even through the secondary combustion chamber and/or downstream pollution control equipment. This phenomenon frequently leads to feed rate limitations based on the volatility or heat of combustion of organic liquids inside the containers. EPA's Air and Energy Engi...

PERFORMANCE OF THE INTEGRAL ROCKET-RAMJETS

The work aims at the experimental and theoretical determination of the effect of the air addition on the performance of solid propellant Integral Rocket-Ramjet Motors 1RRM's. An experimental investigation was carried out to determine the specific impulse dependence on the air equivalence ratio, using an 80 mm motor with exchangeable external and intermediate nozzles. Air inlets and secondary combustion chamber were kept unchanged. The ducted air by ram effect was simulated in this ground testing by feeding pressurized air into the secondary combustion chamber. The experimental investigation showed that the motor specific impulse was increased by about 85% when the air equivalence ratio was increased from zero to ..bout 0.7.A simple one dimensional mathematical model of a solid propellant IRRM atsteady state is presented. The numerical calculations based onthe presented model showed good agreement with the test results.

Thermal treatment for the removal of PCBs and other organics from soil

AbstractThermal separation is an emerging technology for the treatment of contaminated soils and solids. The process removes organic contaminants by indirectly heating the soils and olids to temeratures sufficient to vaporize the harazdous components. The organic vapors in the desorber off‐gas are treated either by oxidation in a RCRA‐standard secondary combustion chamber or by condensation and conventional treatment of the small amount of the resultant condensate.This process had its first successful pilot demonstrations in treating Herbicide Orange contaminated soils at the Naval Construction Battalion Center and at Johnston Island, where dioxin contamination was reduced to less than 1 ppb.This paper summarizes the results of a series of pilot tests, conducted under a TSCA R&D permit, on 3 soils contaminated with PCBs at concentrations ranging from 250 ppm to 4%. To demonstrate the process on an engineering scale, IT made 13 runs in the pilot thermal separator at rates ranging from 18 to 32 kg/hr. Reported are results on the effect of temperature and residence time on the quality of treated soil. The report also summarizes pilot results on a mixed waste soil and soils contaminated with PAHs.

The incineration system “Thermal siphon” effect

AbstractAn anomalous phenomenon known as the “thermal siphon” effect has been observed in four operational incinerators with vertical secondary combustion chambers (SCCs). The kiln and air pollution control (APC) system pressures in all four cases have, under certain conditons, been observed to be negative while the pressure at the top of the SCC is positive. This paper will focus on an explanation of this unusual fluid flow phenomenon.

Flow measurements in a model ramjet secondary combustion chamber

Experimental studies were conducted on a typical secondary combustion chamber of a ramjet to understand the influence of various inlet parameters such as primary nozzle configuration, secondary air injection angle, and flow Reynolds numbers on the secondary combustion chamber (SCC) performance. Cold flow studies were made with air as the flow medium for both primary and secondary jets followed by similar studies with hot primary jets. The general flow structure in the SCC obtained from surface oil film technique showed recirculation zones near the head end. The combustor length required for jet mixing was found to be unrelated to recirculation zone length confirmed by selective temperature and total pressure profile measurements. The calculated fFictional loss from the momentum balance consideration was found to be small. That significant improvement in mixing can be achieved by a choice of multiple-hole primary nozzle configuration has been demonstrated.

Cleanup of contaminated soils by pyrolysis in an indirectly heated rotary kiln

AbstractThe destruction of hazardous waste and cleanup of contaminated soils by pyrolysis in an indirectly heated rotary kiln system, followed by combustion of the volatiles in a secondary combustion chamber, has been tested in a pilot plant and demonstrated in an industrial scale plant. Deutsche Babcock Anlagen AG conducted comprehensive tests in a pilot plant with throughput rates of 0.5 to 1 ton/hour. Following these tests, Deutsche Babcock designed and constructed the industrial scale demonstration plant with a throughput rate of 7 tons/hour for Bergbau AG Westfalen near Dortmund, West Germany.

Remediation of PCB soil contamination by on-site incineration

Throughout the world, sites have been discovered which contain hazardous wastes. To completely destroy the contaminants in the soil, incineration remains the primary option for soils containing organics with high boiling points. This paper deals with operational aspects of the Transportable Incineration System, including specific procedures which were developed during the incineration of PCB-contaminated soils at the Lauder salvage yard in Beardstown, Illinois. Some of the issues treated in this paper include: • • Prescreening of soil to remove oversize materials. • • Process description. • • Treated soil material handling at elevated temperatures. • • Slag formation in the kiln and secondary combustion chamber. • • Development of procedures required for trial burn testing. Some of these procedures may require special system design consideration.

3-D Flow Modeling of a Hazardous Waste Incinerator

A three-dimensional flow model of a hazardous waste incinerator kiln and vertical secondary combustion chamber arrangement was constructed to evaluate critical system parameters. The chamber wall configuration, location and arrangement of burners, and the positioning of the outlet duct were examined to determine the critical secondary combustion chamber gas residence time and mixing of the combustion flows. The scale model consisted of the rotary kiln as a primary combustion chamber, the secondary combustion chamber, two burners, and the exhaust ducting. Flue gas velocities in the model inlets and outlet were maintained to provide a Reynolds numbers equal to the full size unit. Patterns of smoke which were injected into the model inlets were viewed to evaluate flow mixing. Slow motion playback of video tape was used to determine the minimum residence time of flow in the high temperature combustion zone. The results of the model study were used to complete the engineering of a waste incineration system.

Microcomputer Control of a Two-Stage Combustor

ABSTRACT Amicrocomputer-based feedback control system was constructed to operate a two-stage, updraft, wood chip gasifler-combustor. Two separate controllers were implemented on a single microcomputer, providing a proportional control loop for the secondary combustion chamber temperature and a predictive, state-estimating loop for the output temperature. Tests verified controller stability and accuracy during set point tracking and process disturbances. Mean output temperature was held within 1 C of a constant set point, and within 3 C of a ramp input. The output temperature controller, developed from existing algorithms, is applicable to a wide range of single input, single output problems.

Predicting Ash Particulate Emission from Updraft Biomass Gasifier-Combustors

ABSTRACT A0.3 GJ/h wood chip gasifier with a cyclonic secondary cyclonic secondary combustion chamber was used to burn debarked pine wood chips. A complete mass and energy balance was conducted on the system and particular emissions measured. Ash emission rates were found to be an order of magnitude lower than previously reported rates for corn cob gasification-combustion. Ash emission for corn cobs and wood chips when adjusted for ash content and gasification rates were found to be proportional to the second power of gasification rate. Results imply that ash emissions are less for low ash fuels and can be predicted by a common mathematical equation.

Verbrennungsanlage mit Rauchgaswäsche für die Beseitigung von Chemie‐Abfällen

AbstractIncineration plant with flue‐gas scrubbers for disposal of chemical waste. Incineration plant No. II installed at the Bayer Facilities at Leverkusen/Germany has been in regular operation since November 1977 after a previous one‐year period of testing. About 25 000 t of industrial waste per year can be burnt in this plant, simultaneously producing nearly 140 000 t of steam. The plant consists of a bunker building, a rotary kiln and secondary combustion chamber, including all the feeding equipment for solid, viscous, and liquid wastes, as well as a boiler, an electrostatic dust precipitator, and a wet gas cleaning unit. This latter unit consists of an injection cooler (quencher), two rotary scrubbers, and a jet scrubber. The cleaned flue gas is reheated in two heat exchangers and is discharged from a suction blower through a 100 m high chimney into the atmosphere. Around the chimney several measuring instruments are installed to check and continuously record the type and amount of emission. The scrubber water is sent to the company waste water treatment plant; the solid ashes and dust are dumped separately. The average incineration costs are DM 400 per ton of waste.

Flame Quenching by Rectangular Channels as a Function of Channel Length for Methane-Air Mixture

Abstract Flame quenching distance data for a thin plate forming a variable long side of multi-layer and a single rectangular channel have been obtained for a methane and air mixture. The quenching distance was affected by the channel length and the volume of the primary and secondary combustion chamber. The relation between the quenching distance G and the length of the channel L is given by where B', B, and K are constants, and e is the base of natural logarithms. It is shown that above equation may be used successfully to determine the quenching distance.

A study of NO x emission characteristics in two stage combustion

To suppress the emission of NOx a new technique for two stage combustion has been developed and the formation of NOx by this combustion process examined by changing the combustion mode. The combustion is divided into two parts, a primary and a secondary stage. In the primary stage, partial combustion is carried out for a much higher fuel-air equivalence ratio than that of usual staged combustion. After promoting partial combustion, secondary air is supplied to complete combustion in the secondary combustion chamber. Nitrogen compounds such as HCN, NH3, and NO are formed in the primary stage, and these are converted to NOx in the exhaust gas at a high conversion rate. When NO is added to a fuel, the greater part is converted to HCN in the primary fuel-rich combustion, and a relatively small quantity of NH3 is also formed. Interactions between NO, HCN, NH3 and other species, including carbon compounds, are strongly suggested in fuel-rich flames. HCN and NH3 may be formed through several different reactions. These nitrogen compounds can be reduced by carrying out the primary combustion at a high fuel-air equivalence ratio and premixed rate. The rate of conversion of the nitrogen compounds to NOx is not affected but Thermal NO is significantly suppressed by the combustion modifications in the secondary stage. By applying this combustion technique to a practical boiler, successful reduction of NOx is obtained.