The replacement of the existing fabric filter on the Bardon Hill Standard Havens drum mix plant presented a challenge to BG Europa (UK) Ltd. Aggregate Industries required the new installation to occupy the same area taken by the existing unit, whilst offering increased exhaust and filtration capacity.
The existing reverse air cleaning filter unit had provided several years of service, however the requirement for replacement provided the opportunity to increase capacity in preparation for the future upgrade of the drum mixer. With limited space available a bespoke solution was required to install the new filter unit within the footprint of the existing filter unit.
The BG Europa SF Pulsejet Filter allowed the opportunity to increase both filtration performance and available exhaust capacity whilst utilising the existing foundation fixings.
Using a pulse of compressed air the BG Europa SF filter generates a shock wave which cleans the filter bags. This advanced and efficient method of cleaning has been well proven in the field and does not encounter the problems associated with reverse air filters which suck atmospheric air into the bags to clean them.
The internal design of the pulse jet filter does not require provision for ducting channels within the filter body, therefore a higher density of cloth can be installed.
The new SF20/2 fabric filter installation in operation.
At Bardon Hill a total of 1280 x 500 g/m² Nomex type filter bags are installed in two ten module parallel filter units to provide a total cloth area of 1438m². Within the snap ring bags the zinc coated wire bag support cages each incorporate an integral venturi to enhance bag cleaning efficiency.
The pulse jet shock wave cleaning system sequentially cleans rows of filter bags whilst they are on line, ensuring that all of the cloth area within the filter is utilised at all times for efficient filtration. This is in contrast to the reverse air type cleaning method which takes up to 25% of the bags off line for cleaning.
An electronic pulse controller is installed within a dust tight enclosure mounted at the filter top and is pre-wired to each of the solenoid valves. This controller allows fine adjustment of cleaning pulse duration and frequency to suit operating conditions. Additionally a differential pressure monitor is installed to ensure cleaning is only performed when required, thus reducing energy requirements and maintaining the bags at their ultimate cleaning performance.
The bags and cages are factory installed within the filter unit top sections to quicken site installation. The filter top is enclosed by hand rails with safety gate access and kicking strips. Within this area access to the bags and cages is provided through full width easily removed hatch covers.
The compressed air manifold for bag cleaning is housed within the filter body ensuring protection from the elements. This arrangement provides easy access from within the hand railed area at the filter top by removal of full-length lift-off covers. The solenoid valves are also fitted on the top of the manifold allowing unrestricted access for ease of maintenance.
Collected fines fall from the filter bags into a common pyramid hopper whose dimensions were designed to allow a support structure to be fixed down to the original foundation bolt nests. The project therefore did not require any additional civils works minimising both disruption and overall costs.
Regardless of infrequency of access the existing vertical ladder, which is a common feature of most existing filter installations, did not provide the degree of safety now expected within the industry. Therefore BG Europa supplied and installed stairways and rest platforms to allow improved access to the filter top, inlet ducting and exhaust stack from ground level.
Jason Broughton – Operations Manager, Asphalt/Bardon-Croft, commented. “With no operational issues since the installation, it has been a perfect replacement and what we expected. The BG Europa bespoke design minimized any disruption and overall costs with the extra stairway and improved access bringing everything in line with the current H&S requirements.”
Fulfilling the project brief on time BG Europa has provided a modern system designed with safety as a key criteria. Additionally Aggregate Industries’ facility now has the capacity and flexibility to allow future upgrade to new clean recycling technologies as they become available.