Ash Removal System Research Articles

WEAR OF THE FUEL SUPPLY SYSTEM OF CFB BOILERS

The advantages of circulating fluidized bed (CFB) boilers over other boiler types include the possibility to fire fuels of low calorific value and rich in mineral matter like oil shale. However, particle-surface interactions may cause wear of surfaces submerged in ITREX, of the walls inside the furnace, of chrome-plated panels in separators, and of heat surfaces in boiler convection passes. This takes place directly in the boiler, but particle-surface interactions begin in the fuel supply system already and end in the ash removal system. The present article deals with wear in the fuel supply system on the basis of practical experience.

Formation of mineral deposits in hydraulic ash removal systems

Selection of design schemes for the water supply (straight through, or circulating) of hydraulic ash-removal (HAR) systems for thermal electric power plants (TPP) is examined as a function of the character of mineralization of the water in a specific system. Causes are outlined for the formation of mineral deposits on equipment of the HAR system, which transports ash slurries of different types of solid fuels. The cause of the high rate of seasonal growth formation in the circulating HAR systems of TPP burning fuel with highly alkaline ash slurries is established experimentally in an example of a shale electric power plant. Measures are developed for rapid slow-down of the rate of growth formation in these systems. Measures are proposed for prevention of growth formation for other types of ash slurries.

Results of studying the ash pneumatic transport from ash trap hoppers in a pulse-mode

The results of studying the effects of ash layer density and the method of dynamic impact on the ash ability to flow are presented. A scheme of a pneumatic impulse pump and that of an impulse-type ash removal and transport system of high operating performance are proposed.

00/03386 Improving hot gas filtration behavior in PFBC power plants

According to a previous paper, a laboratory-scale cold flow model of the hot gas filtration system in Escatron PFBC power plant has been built. The main objectives were to establish the validity of the scaling laws for cyclone separator systems (cyclone and dipleg) and to perform detailed room temperature studies in a rapid and cost effective manner. In Escatron PFBC power plant, the hot gas filtration equipment is a two-stage process performed in nine streams between the fluidized bed and the gas turbine. Due to the unsteadiness in the dipleg and the suction nozzle, and the effect of sintered deposit, the cyclone performance is modified. The performances of cyclone separator system and suction nozzle diplegs are scarcely reported in the open literature. This paper presents the results of a detailed research in which some important conclusions of well known studies about cyclones are verified. Also remarkable is the increase in cyclone efficiency and decrease in pressure drop when the solid load to the cyclone is increased. The possibility to check the fouling by means of pressure drop has not been previously addressed. Finally, the influences of gas input velocity to the cyclone, the transport gas to the ash conveying lines,more » the solid load and the cyclone fouling have been analyzed. This study has allowed characterizing the performance of the full-scale ash removal system, establishing safe limits of operation and testing design improvements as the two suction nozzle dipleg, pointing out important conclusions for the filtration process in PFBC power plants.« less

Experience with coal-fired boilers in the amer power station

Coal-fired boilers have operated in the Amer Power Station of PNEM, at Geertruidenberg, since 1952. Presently, two 230 MW units and one 600 MW are fired with coal. A survey is presented of: the raw coal transportation, handling and storage systems; the characteristics of the mill types used and the experiences with these mills; the characteristics of the furnace and coal burners; and the ash removal system.

Evaluation of the George Neal electrostatic precipitator

The Electric Power Research Institute (EPRI) is currently supporting a major research program characterizing the performance of high efficiency electrostatic precipitators (ESP). One such effort evaluating the George Neal ESP of Iowa Public Service Company is described in this paper. Results show that under well tuned conditions the ESP overall collection efficiency was 99.7% at a specific collecting area of 745 ft 2/kacfm (147 m 2/m 3/s) (520 MW) with associated mass concentrations of 0.025 lb/10 6 Btu and stack opacity of 4.6%. The boiler outlet size distribution was found to be bimodal with submicron and large particle peaks at 0.2 and 5 microns diameter, respectively. Consequently, an apparent bimodal fractional efficiency curve results with efficiencies of 99.6%, 98%, and 90% measured for 20, 2 and 0.2 micron diameter particles, respectively. Rapping reentrainment losses were found to be insignificant except during episodes of high ash hopper levels resulting from a malfunctioning ash removal system, when large rapping puffs were observed. In addition, outlet emissions increased dramatically to 0.08 lb/10 6 Btu (34 ng/J) during these periods, suggesting that an emission level more representative of daily operation lies somewhere between 0.025–0.08 lb/10 6 Btu (10.8–34 ng/J).