Project REM – Chicken litter CleanPulse bag filter with offline cleaning

Project REM – Chicken litter CleanPulse bag filter with offline cleaning

‘Cleanpulse’ CPB 38/43 for Chicken Litter Incineration. Norfolk

Global Sustainable Energy Solutions

bhsl supply and operate fluidised bed combustion heating systems suitable for low-value biomass such as poultry litter, wet wood chips and spent mushroom compost.

Installations include an innovative fuel handling system called a toploader which can be purchased separatley to address a variety of bulk materials handling needs.

The waste to energy market is expanding rapidly as industry recognises the financial benefits as well as the environmental impact of the world’s increasing fossil fuel energy consumption. Often renewable energy plants are on a grand scale, producing Mega Watts of energy to provide heat and power to large manufacturing facilities. In this plant the scale is smaller and the benefits are more localised.

Jack O’Connor – the founder of bhsl – was active in the poultry industry, owning and operating his own farm. His vision was to find a solution to the increasing number of challenges facing the poultry industry in its operating methodologies – management and cost of litter disposal, regulatory and environmental factors and low margins with a high dependency on energy.

The BHSL enquiry required 2 filters to suit 2 of BHSLs FBC 500s to be built on site. The site is ‘Farmers Weekly - 2011 Poultry Farmer Of The Year’ Mike Joice’s Uphouse Farm in Norfolk.

As energy is one of the biggest costs in rearing poultry, he and his son have invested in a major on-farm biomass plant. The farm’s energy plant is fuelled by poultry manure to heat water, which is pumped around a 4.7km network of underground pipes to the 16 poultry houses on two sites.

Since the farm’s energy centre was built last year, it has made it possible to replace a fossil fuel, liquid propane gas, by using a mix of poultry manure and wood chip to fuel two 500kw burners. All the heat for the chicken housing is now produced on farm and the next phase will involve selling surplus heat to generate electricity for the National Grid, probably next year.

The pair of filters required were fairly simple, using a front entry distribution chamber and requiring insulation and cladding but no trace heating. No incorporated means of accessing the top of the filter was required in FDL scope.

The relatively small size of the required CPB filters meant that the design was altered from our standard to incorporate fitting the insulation and cladding at the fabrication stage prior to despatch to site. The design information available from client was limited due to the original nature of the application. Therefore, a decision was reached with the client that each filter would be supplied with a total of 64 bags in place, but with the capacity to accept a further 8 bags. This would allow an increase in filter capacity from a CPB 38 to a CPB 43 (total filtration area 38 or 43m²) should this be required once the plant became operational. Dust discharge was to be via the clients enclosed trough conveyor.

The image to the left shows the offset steel angle around the hopper which forms a stiffener for the cladding following the insertion of insulation material.

Following an operational period of 6 months it was discovered that the extremely fine nature of the dust handled by the filter was causing pulse cleaning issues. The addition of the extra 8 bags lowered the filtration velocity but the core issue was re-entrainment.

Re-entrainment is a descriptor for the process by which dust can be pulse cleaned off the filter media, but instead of falling into the filter hopper it returns back to the filter bag surface. This can occur when dust is fine and does not agglomerate.

The pulse cleaning pressure was reduced, but the re-entrainment issue persisted. As this was a pioneering plant, no dust sample or particles size distribution information was available.

A plan was devised to adapt the filter as simply and efficiently as possible to an off-line cleaning arrangement, whereby the top and the bag sections are compartmentalised. The outlet of the top section was also revised to include four individual outlets with a butterfly damper attached to each, the four ducts then combining in a single plenum chamber on to the flange to which the fan is then bolted.

In order for the system to be effective the jet pulse controller is configured to close 1 of the dampers prior to pulsing the two corresponding rows of filter bags.

By closing the damper of one section to isolate ¼ of the filter media, the air flow and differential pressure in the closed section is removed allowing the dust adhering to the bags under negative pressure (suction) to be released and fall into the hopper below and avoiding the re-entrainment that was occurring previously.

Designer: Roger Callis

Project Manager: Stewart Callis

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