Secondary combustion chamber

Rotary kiln systems usually have a secondary combustion chamber after the kiln to ensure complete combustion of the wastes. Airtight seals close off the high end of the kiln while the lower end is connected to the secondary combustion chamber or mixing cluimber. In some cases, liquid waste is injected into the secondary combustion chamber. The kiln acts as the primary chamber to volatilize and oxidize combustibles in the wastes. Inert ash is then removed from the lower end of the kiln. The volatilized combustibles exit the kiln and enter the secondary chamber where additional oxygen is available and ignitable liquid wastes or fuel can be introduced. Complete combustion of the waste and fuel occurs in the secondar> chamber. 

In most hazardous waste incinerators, combustion occurs in two combustion chambers. Combustion is completed in the secondary combustion chamber after the compounds have been converted to gases and partially combusted in the first chamber. 

Incineration has been used extensively in hospitals for disposal of hospital wastes containing infectious and/or hazardous substances. Most hospital incinerators (over 80%), however, are outdated or poorly designed. Modem incineration technology, however, is available for complete destmction of organic hazardous and infectious wastes. In addition, adequate air pollution control facilities, such as scmbbers, secondary combustion chambers, stacks, and so on, are needed to prevent acid gas, dioxin, and metals from being discharged from the incinerators. 

The same modern incinerators equipped with scmbbers, bag-filters, electro-precipitators, secondary combustion chambers, stacks, etc., are equally efficient for disposal of hazardous PCBs, dioxin, USEPA priority pollutants, and so on, if they are properly designed, installed, and managed. Incineration technology is definitely feasible, and should not be overlooked. The only residues left in the incinerators are small amount of ashes containing metals. The metal-containing ashes may be solidified and then disposed of on a landfill site. 

Fig. 15.4 shows a schematic representation of a nozzle throat area controller used in a VFDR. The mass flow rate from the nozzle attached to the primary combustion chamber (gas generator) to the secondary combustion chamber (ramburner) is changed by inserting a pintle. The high-temperature gas produced in the gas generator flows into the ramburner through the pintled nozzle. The pintle inserted into the nozzle moves forward and backward in order to alter the nozzle throat area. As the nozzle throat area is made small, the mass flow rate increases according to the concept described above. The fuel-flow rate becomes throttable by the pintled nozzle. 

In 1998, the DOE prepared a cost estimate of a 10-ton/day DC arc system. The system includes a furnace, waste feed system, off-gas treatment system, secondary combustion chamber, power supplies (arc power, glass overflow heating system, and metals drain), instrumentation, control systems, and product removal and handling systems. Site permitting costs and site preparation costs were also estimated (D207307). These estimates are summarized in Tables 1 and 2. 

HTTS is a completely modular, transportable incineration system. A rotary kUn heats contaminants and vaporizes hazardous organic components. The gaseous waste is then subjected to intense heat in the secondary combustion chamber. Gases are then cleaned by a wet quench and scrubber before being discharged. The ash produced by the kiln is nonhazardous and can be back-filled on site. 

IT Corporation s thermal desorption system is a commercially available, ex situ technology for the treatment of soils and sludges contaminated with organics. The process drives volatile and semivolatile organic compounds (VOCs and SVOCs) from the soil by heating the soil to temperatures greater than the boiling point temperature of the contaminants. Volatized vapors are oxidized in a secondary combustion chamber or collected for physical/chemical treatment. 

The rotational speed and angle at which it is positioned control the residence time of the solid in the kiln. Normally solid waste is converted into CO, particulate matter, or ash. For complete oxidation of flue gases and particulate matter, the kiln is also provided with a secondary combustion chamber. The volatilized combustibles exit the kiln and enter the secondary chamber where a complete oxidation tube is placed. 

An airtight stove with a catalytic afterburner and a smoke chamber such as a double-drum stove or a design that provides for improved burning in a secondary combustion chamber. 

PCC primary combustion chamber SCC secondary combustion chamber (after burner) Fig. 3 Automatic wood firing as experimental biomass furnace... 

The measuring system developed was successfully applied within various secondary combustion chambers (SCC) of biomass furnaces to determine important process parameters. With certain model assumptions for the reactor dynamics, the degree of mixing and the mean residence time are calculated from the measured residence time distribution (RTD). The determination of the fluctuating process parameters is possible with a time resolution of 15 seconds. 

The flow pattern of the vortex in the secondary combustion chamber was measured with a Laser Doppler Velocimeter (LDV). The profile measurements were performed at various feed rates and air settings as well as different hardware configurations. The LDV measured the axial and tangential velocity vectors of the flow in the hot flame simultaneously. 

The goal of the project was the development of a low emission biomass burner for boilers in the range of 50 - 500 kW thermal output [5]. The main feature of the PDU burner design is the secondary combustion chamber creating a vortex to increase gas phase turbulence in order to maximise complete combustion. The main emphasis of the burner design is to reduce the release of particulate matter. The combination of vortex and air staging techniques is supposed to reduce also the NOx-emission level. The combustion system is designed to bum preferably wood chips. 

To meet these requirements, the PDU combines a primary thermal conversion chamber with hot cyclone and a secondary combustion chamber,... 

The secondary combustion chamber creates a vortex by secondary combustion air to establish strong mixing of gas components for facilitating chemical reaction, temperature level to achieve complete combustion with low carbon particulate content and consequently low formation of PCDF and PCDD. 

Left Laser Doppler Velocimeter (LDV) for profile velocity measuring system in the secondary combustion chamber. 

Secondary combustion chamber combustion temperature > 800°C for complete combustion with low particulate emissions. 

The retention time of the hot gases in the cyclone were varied between 0.7 seconds (40 kg/h feed) up to 1.5 seconds (18 kg/h feed) and from 0.4 up to 0.7 seconds in the secondary combustion chamber. 

Primary thermal conversion chamber and hot cyclone Secondary combustion chamber ... 

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