Cement, Energy and Environment July-Sep 2002

( improvi ng c linker quality and producti o.n performance. ( 'ourtesy: J Jl or!d Cement. .Jul 02, Pp. 87- 9-1. l:nquiJ)' no. -1 Fa.\" +-/-1(0) 1252 718992 [mni !: mai /fa) \I'Orldcemenf.cum ff'eh: \1'\1' \1' 11'0rldcemen/.com CLEANING TO A "SHINE" J coh Sunder[{aard. FLS Mill . Denmark The c lose proximity to the city of' Kua la Lumpur , a lso made Rawang plant necessary ro improve th e ai r qua lity to exceed mode rn sta ndnrd s. Th e main sou rce of emissions was the single preheatcr kiln stack, which is tall and clearl y visible from afar. For many years, an extreme emission level could be see n in the sky above th e plant, visuall y annou nc ing that the kiln was operating. In I992, FLS milj o was in vited to investigate what measures wo uld be required to reduce the emission level from the kiln, and it was decided to install a ne~vv ESP in parallel with the original in sta ll a ti on. Con seque ntly, th e combined emiss ion was reduced to 40 mg/Nm 3 , and was therefore no longer visibl e. The owner of the Rawa ng plant (formerly Blue Circ le Cement, now Lafa rge) decided that a fabric fi Iter wo uld be the most advantageous long-term solution to solve the emiss ion prob lem. Among many competitors, FLS milj o was awa rded the turnkey contract at the end of2000 . The main sizing criteria was a gas flow of 270 000 /NmJ/hr at 350"C to th e inlet of th e clcd usting system. At the same time, low-temperature fi lter bags should the fabric filter was not allowed to exceed 120°C. This. task required e ffi cient temperature control of the gases, which can be carried out in a number of ways: by water injection in th e coole r or in the ducti ng system, by bleed ing in cold a ir or by an air-to-air heat exchanger. The polyeste r fabric media at Rawang is protected during normal operation by th e heat exchanger. The heat ex hanger is res istant to temperatures of 600"C, and is able to suc cessfull y red uce th e tempera ture before the filt e r to I20"C. A damper is installed before the heat exchanger. which opens in the event ofan emergency situation, whereas ambient air is used to keep the temperature below the designed maximum for the system. The FLS miljo fabri c filter at Rawang is a modern type jet pulse filt e r with s ix individua l compartments and 2592 filter bags, each fi lter bag being 6 m long. The fa bri c filter is des igned to allow ma intenance o r bag re placement during operati on. J\t the test facility in England, FLS miljo continuously ~trives to imp rove gas/d ust di s tribution, whi ch is a key parameter in th e Fab ri C lea n fi Ite r de s ig n. T he company acknowledges the extreme impo t1ance of proper distribution of both dust and gases to successfully reduce air and power consumpti on and extend bag li fe. The maxi mum temperature to the fa bri c filter of 120"C a llows Rawang to use low-pri ced polyester bags without jeopa rdi s ing production. The designed air-to-ai r ratio is I.05 m/min during norma l operation, and 1.22 m/min with one compartment temporarily scaled off rat io desc ribes the re lat ionship betvveen the gas vo lum e and the installed cloth area. Fabri Ciean fi Jters have a rigid cage su pport with 360" contact with the tube sheet, which is stiffened to prevent distort ion: this is anothe r feature that allows longer fil ter bags to be used. The SmartPu lse Controller does no t only minimise ai r consum pti on , but as each bag is clea ned Jess o ften a t a lower pressure, the lifetime ofthe filter bag is also extended. The controller also fea tures offl ine cleaning. in which case the outlet dampers arc closed to iso la te th e pa rti cu lar compartment from the gas flow while a cleaning cycle is ini ti ated. The ID fan is a standard FLS– type fan. wi th a frequ ency controlled motor. FLS fan s arc low speed and stu rdily designed and do not have to be insulated for sound protection. due to the rather low speed. The fan has an impeller diameter of a li tt le over 3 m and a maximum speed of 534 rpm, which yields an efriciency of 78.5%. Fans with highe r effi ciencies may be purchased in the market; however they arc o ft e n more expensive, as they mu st be ta ilor-made to th e pa rt icular application in order to achieve high effic iency. The Rawang plant chose to purchase the bag fi Iter system on a tu rnkey bas is. and FLS milj o was ob li ged to comp le te th e e ntire installation wi thin 12 months of the rece ipt of order. The company is confident the it will operate at a far lower emission than the guaranteed 20 mg/Nm 3 . With low emi ss ion levels now from both the preheater kiln a nd the c linker coole r, the be used, whereas the temperature to fo r maintenance. The air-to-cloth Rawa ng plant is wi th out doubt a