| OCR Text |
Show diameters between 0.2 to 0.5 microns are generally collected less efficiently by ESP than larger particles. Ammonia is a typical example of this category of chemicals. This paper describes the study conducted at Ontario Hydro's 640 MJ /h combustion research f~cility where S03' water and a proprietary chemical were used to condition low sulphur coal ashes and sorbent injection wastes in order to improve the performance of electrostatic precipitators. EXPERIMENTAL COMBUSTION RESEARCH FACILITY The study was conducted at Ontario Hydro's Combustion Research Facility (CRF) designed for a maximum coal feed rate of abo~t 20 kg/h (44 Ib/h) US bituminous coal at a firing rate of 640 MJ/h (6.1 x 10 BTU/h) (Figure 1). The furnace is a refractory-lined cylindrical chamber, fully equipped for monitoring gas and wall temperatures. There are multiple ports for flame observation and for insertion of solid sampling probes. There are also probes to determine slagging and fouling rates. The pulverized coal is delivered down-draft to the burner with the combustion air which can be electrically preheated to temperatures up to 350°C (662~). Gas burners on each side of the coal burner are used to heat the furnace to operating temperatures before beginning to feed to coal. The coal burner, designed and constructed by Research Division staff, is equipped with a vortex generator and four air vanes to assure good mixing and adequate residence time of the fuel-air mixture in the combustion zone. The combustion gases in the furnace are cooled by water and/or air circulating in a cylindrical inconel jacket around the furnace. This cooling system is equipped with temperature sensors and flow meters to control furnace quenching rates. The combustion gases leaving the furnace are further cooled by a series of air-cooled heat exchangers prior to entering the resistivity probe housing and ESP. The ESP consists of a cubic stainless steel chamber, and is equipped with two sets of interchangeable cells. One set has an II-plate electrode with 2.5 cm (1 in) spacing, the other a 5-plate electr~de with 5 cm (2 in) spacing. The design sp~cific collection area~ (SCA, m2/m Is) for the two sets of cells are 39 (0.2 ft /cfm) and 17 (0.09 ft /cfm) respectively for base line firing conditions using a high volatile US bituminous coal. The CRF instrumentation permits system temperatures, and flue gas compositions (02' CO2 , CO, S02 and NOx) to be monitored continuously. Gas temperature in the furnace are measured with a suction pyrometer and flame temperatures with an optical pyrometer. Flow rates and pressures are measured by flow meters and manometers. All measuring and monitoring systems are linked to a computerized data acquisition system. Particulate mass loading in the flue gas before and after the ESP is measured with an isokinetic sampling system. In-situ resistivity is measured with a point-plane resistivity probe situated in the resistivity probe housing and particle size distribution of the ash is measured with a Pilot Mark 3 Cascade Impactor. |
