Burning chamber — combustion

Bureau of Explosives 44 Bureau of Mines 364 burning chamber - combustion chamber 60... 

In rockets burning liquid fuels the oxidizing agent (e.g., liquid oxygen) is pumped from tanks into the combustion chamber. Simultaneously, fuel (e.g., kerosene) is pumped into the chamber and burned. The combustion takes place at a constant high pressure and produces high-temperature product gases tha are expanded in a nozzle, as indicated in Fig. 8.14. 

A traditional propane burner of WS was modified for BCO combustion. The burning chandwr with the modified burner was pre heated up to 900°C with an auxiliary burner placed opposite to the BCO atomiser (Fig. 5). The nozzle was cooled down to 30°C. Once 900°C was reached in the burning chamber, the BCO injection was started. After the ignition of BCO, which occurred immediately with supply of the first amount of BCO, the auxiliary burner was turned off. The supply of BCO was started with about 2 1/h and than increased to about 9-10 1/h (liquid pressure 0.9 bar). The air supply was adjusted to about 3% O2 in the flue gases. The burning of BCO in FLOX mode continued stationary without any difficulties for several hours. Table 1 summarises the main experimental results. 

The experiments proved that BCO can be burned without any noticeable residues or soot formation and with practically no CO emission in stationary FLOX mode. Inqnovement in NO emission can be expected by varying excess air and exhaust gas recirculation ratio. However, the nitrogen content of BCO is itself a source of NOx which can not be reduced below a certain limit. The low CO concentration provides evidence for a high quality atomisation which allows a total carbon bum out. Fig. 6 shows the combustion chamber fuelled with BCO (FLOX mode). The temperatures in the burning chamber (on different places) and in the nozzle were recorded, (see Fig. 5). In order to avoid the nozzle plugging, the BCO temperature in the nozzle was controlled closed to the nozzle tip and was kept at 25-30°C, therefore a tenperature caused blocking (coke formation) can be excluded. 

After preheating the burning chamber up to 800-850 "C with an auxiliary burner, the BCO ignition and combustion were carried out without any difficulties. 

Tertiary Air. Preheated air introduced into the waste-gas flue of a kiln firing under reducing conditions, e.g. a blue-brick kiln its purpose is to burn the combustible matter in the gases leaving the kiln chamber, thus helping to minimize smoke emission from the stack (cf. PRIMARY AIR and SECONDARY AIR). Tessara(e). The small rectangular tile(s) used in mosaics. 

Flue gas of rotary kiln enters the after-burning chamber, where the combustion is completed. Next station of the flue gas is a boiler, where feed water is converted into superheated 40 bar steam. The 360°C hot steam is used for generation of electricity in the neighbouring power station. 

In order to maintain high energy efficiency and ensure a long service life of the materials of construction in the combustion chamber, turbine and jet nozzle, a clean burning flame must be obtained that minimizes the heat exchange by radiation and limits the formation of carbon deposits. These qualities are determined by two procedures that determine respectively the smoke point and the luminometer index. 

Thermal Process. In the manufacture of phosphoric acid from elemental phosphoms, white (yellow) phosphoms is burned in excess air, the resulting phosphoms pentoxide is hydrated, heats of combustion and hydration are removed, and the phosphoric acid mist collected. Within limits, the concentration of the product acid is controlled by the quantity of water added and the cooling capabiUties. Various process schemes deal with the problems of high combustion-zone temperatures, the reactivity of hot phosphoms pentoxide, the corrosive nature of hot phosphoric acid, and the difficulty of collecting fine phosphoric acid mist. The principal process types (Fig. 3) include the wetted-waH, water-cooled, or air-cooled combustion chamber, depending on the method used to protect the combustion chamber wall. 

In wetted-wall units, the walls of a tall circular, slightly tapered combustion chamber are protected by a high volume curtain of cooled acid flowing down inside the wall. Phosphoms is atomized by compressed air or steam into the top of the chamber and burned in additional combustion air suppHed by a forced or induced draft fan. Wetted-waU. plants use 25—50% excess combustion air to reduce the tail-gas volume, resulting in flame temperatures in excess of 2000°C. The combustion chamber maybe refractory lined or made of stainless steel. Acid sprays at the bottom of the chamber or in a subsequent, separate spraying chamber complete the hydration of phosphoms pentoxide. The sprays also cool the gas stream to below 100°C, thereby minimising corrosion to the mist-collecting equipment (typically type 316 stainless steel). 

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