| OCR Text |
Show 3/15 Under the bubbling fluidized bed coal combustion condition, however, there exists many kinds of particles like fluidizing material, desulfurizer, char, ash, raw coal and so on. Especially the desulfurizer and char among these particles are known to decompose N20 catalytically. Therefore it seems to be difficult to discuss the detail characteristics of N20 formation/destruction by using the bubbling fluidized bed. Additionally in the previous studies N20 characteristics are discussed only by the change of gas species concentration. In the present paper the N20 formation/destruction characteristics under the low temperature pulverized coal combustion condition are studied by using an electrically heated one-dimensional laminar drop furnace. The combustion experiments are carried out by burning nine different kinds of coal with different fuel ratio and N-contnet. This experimental situation can prevent the catalytic effect on N20 decomposition since there exists only burning coal particles in the furnace. In discussing the data obtained by sampling the burning particles as well as t~e combustion gas along the furnace axis, the mass balance of nitrogen is calculated. Finally the significant parameters to promote N20 formation are explained by the obtained results of the changes of gas species concentration and components of burning particle. 1. EXPERIMENTAL APPARATUS AND PROCEDURES Figure 1 shows a schematic diagram of electrically heated one-dimensional laminar drop furnace, in which the heating length is 1.3 m. The reaction tube of 41.5 mm in inner diameter is made of quartz in order to prevent the catalytic decomposition reaction of NZO by the tube wall surface. The furnace wall temperature is controlled by three sets of temperature controllers with thyristor regulators. Coal particles are fed into the tube by using a vibration microfeeder. Both combustion gas and burning particles are sampled by a watercooled sampling probe at the tip of which an inert gas is injected to prevent the addi tiona 1 chemi ca 1 reacti ons from changi ng the compos i ti on through the sampling tube. Gas species concentrations of NO, 02' CO and CO2 are continuously measured by the respective analyzers, and HCN, NH3 and N20 concentra- |
