Countermeasures to Decrease and Stabilize Pressure Drop across Ceramic Tube Filter (CTF)

Abstract

Pressurized Fluidized Bed Combustion (PFBC) combined cycle system which has high plant efficiency due to installed steam turbine and gas turbine, and high performance for environment, becomes a subject of world attention.
Two configurations of cyclones and ceramic tube filter (CTF) were examined for gas purification in 71MWe PFBC plant at Wakamatsu, Electric Power Development CO., LTD. where whole cyclones removed all coarse ashes not sent to CTF in one configuration and the cyclones were partially bypassed in order to send a part of the coarse ash to CTF in another configuration.
The first configuration suffered a larger pressure drop across the CTF, which reached 40 to 45KPa (4, 000mmAq to 4, 500mmAq), and several times of ash plugging, leading to filter breakage during a couple of weeks operation . Increased pressure drop required frequent back pulse cleaning to remove accumulated ash on CTF . Partial bypass of the cyclones reduced very much the pressure drop even if more ash was introduced to CTF, and hence frequency of back pulse cleaning was decreased by the configuration with bypass. No filter breakage was experienced at all, since the cyclone bypass system has been introduced. Thus around 800 hours continuos operation was achieved by the configuration, increasing the efficiency of power generation by 0.5% due to saved auxiliary power for back pulse cleaninig.
The roles of coarse ash sent to CTF with cyclone bypassed are discussed in the pressure drop due to the accumulated ash on the CTF.