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Valve Hardware (Filters, Flow Controls, Positioners etc)
News Release from: Donaldson Membranes | Subject: Tetratex 6255
Edited by the Engineeringtalk Editorial
Team on 21 June 2006
Filters cut down kiln emissions
Maceira-Liz has reduced kiln emissions using baghouse filters equipped with filter bags made from Tetratex 6255 ultra-high-efficiency ePTFE membrane with woven glass fabric.
The Secil Plant of Maceira-Liz has experienced lower kiln emissions following the replacement of electrostatic filters with baghouse filters equipped with filter bags manufactured from Donaldson Membranes' Tetratex 6255 ultra-high-efficiency ePTFE membrane with woven glass fabric Secil Cement Company is the second largest cement manufacturer in Portugal and boasts a production capacity of around four million tons of cement per year, mainly for the Portuguese market
This article was originally published on Engineeringtalk on 22 Feb 2007 at 8.00am (UK)
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With a market share in Portugal of some 37%, Secil's cement is produced at three plants - Maceira-Liz, Secil-Outao and Cibra-Pataias.
With a strong local presence, growth in other countries also contributes to the worldwide development of Secil.
The company's international expansion began in 2000, with the acquisition of the Societe des Ciments de Gabes in Tunisia, which owns a cement plant with an annual capacity of more than one million tons and has a market share in Tunisia of approximately 17%.
This global expansion has continued in Angola, through the Secil Lobito, and with Secil's most recent deal - an important financial investment at Ciment de Sibline SAL, located south of Beirut, in LibaNo Secil manufactures and markets grey and white cement and operates a customer service and cement distribution for the Portuguese market.
Maceira-Liz plant has two kilns, with an actual production capacity of 1400t/d each.
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The kilns started up in 1968 and 1970, supplied by Fives Lille, with a production capacity of 900t/d.
The coolers were manufactured by Fuller and the cyclone tower by Humbolt.
Two major changes were carried out at Maceira-Liz in order to increase production capacity and optimise the process.
A new Fuller Cooler and a new double cyclone 1 in 1984-86, and in 1998-99 a cyclone tower supplied by PSP.
Further changes took place in 2000.
Originally, dedusting in the kilns was carried out by electrostatic filters.
Secil decided to have a baghouse filter built instead, made up of six compartments containing 480 bags each.
The filter was designed to operate with compartments offline to allow easy access for the maintenance staff and enabling Secil Plant's lines 5 and 6 to work continuously all year round.
The kiln of lines 5 and 6 operates by a combined system, with short breaks in direct system mode, during which the temperature of the gases entering the filter increases significantly.
In June and September 2000, baghouse filters manufactured by Redecam were installed, with the filter bags for the filters supplied by Testori using the recommended media Tetratex 6255 - Tetratex ultra-high-efficiency ePTFE membrane with woven glass fabric suitable for continuous service at temperatures up to 260C.
Tetratex ePTFE membranes are used in many parts of the cement process, giving improved airflow throughput, which translates into increased production rates.
Tetratex 6255 was suitable for this application due to its requirements for lower pressure compressed air and less frequent cleaning due to its exceptional dust cake release properties, whilst giving near zero particle emissions, increased bag life and lower maintenance costs.
After the start up of the filter in 2000, the emission was around 4 to 6mg/Nm3, with a pressure drop or around 50-60mmH2O, and these values were maintained until the end of 2002.
Following these positive results from the first set of bags, Secil decided to maintain the quality of media by continuing to use Tetratex 6255, with modifications to the filter bags designed to increase resistance to abrasion damage.
The new bags were supplied during Spring 2004 to equip the filter which receives the fumes from kiln 5 and were the first replacement set after the original supply, which successfully exceeded the 3-year warranty.
The full replacement ended in May 2004 on kiln 5 and June 2004 on kiln 6.
A total of 2880 filterbags were manufactured from Tetratex 6255.
Augusto Miragaia, Clinker and Cement Production Manager at Secil Plant Company, said: "The aim of the replacement of electrostatic filters by bag filters was to decrease the dust emissions and also to increase the reliability of the dedusting system of gases from the kiln".
"These two goals were achieved in full".
"Regarding the bag performance, the emission values agreed on the contract were 8mg/Nm3".
"We obtained between 4 and 6mg/Nm".
"We managed to keep these values constant during the first 2.5 years of functioning".
"With some partial replacements of bags it was possible to maintain a controlled emission under 2 mg/Nm3 until 3.5 years of functioning".
"During the last 6 months we have proceeded with the full replacement of the bags".
"As the filter is divided into sectors and its dimensions allow the normal functioning of the kiln with one sector out of work, the bag replacement may take place without affecting the normal functioning of the facilities".
"The experience acquired showed us that the wear of the bags occurred mainly at the base".
"The new bags installed are also Tetratex 6255, but have a reinforcement of 200mm at the base".
"With this modification we hope to increase substantially the duration of the new set of bags just installed".
"Another important factor is the bag cleaning system which takes into account the differential pressure, which allows us to avoid excessive compressed air consumption and to reduce the wear of the bags caused by excessive cleaning".
"The working pressure is between 50 and 70mmH2O".
"In global terms, we may say that the performance of the bag and filters is excellent".
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