Gotland’s BagVac system cleans up Jersey’s new EfW

A new centralised vacuum system powered by a Gotland BagVac has cut the time needed to clean out the Flue Gas Treatment Ducts by 50% at the new EfW plant at La Collette, Jersey. It also makes the regular removal of around five cubic meters of Flue Gas Treatment residue, as well as general housekeeping around the EfW plant, a much easier task to do, minimising the related manual handling issues.

Energy from waste
Being an island with no space for landfill and a requirement to follow the highest environmental and air pollution standards, the State of Jersey has been practicing a refuse, recycling and incineration strategy for nearly 40 years. The Island's combustible solid waste is incinerated at the new La Collette Energy from Waste (EfW) plant which is able to process over 105,000 tonnes of non-inert waste per year. Approximately 60% is household dustbin waste, the rest is shredded bulky waste (carpets, mattresses, old furniture etc).

Once as much of the refuse is recycled as possible, the La Collette plant burns the remaining rubbish using the heat to drive a steam turbine to generate 10MW/Hr of electricity at full production. This powers the new La Collette Energy from Waste (EfW) plant and excess electricity is sold to the Jersey Electricity Company (JEC).

Cleaning out the Flue Gas Treatment Ducts
A regular requirement is to clean out the Flue Gas Treatment Ducts (FGTD) of the EfW incineration plant, for which the original two inch centralised pipe work system was simply inadequate, as the State of Jersey's Waste Management Project manager Ian Coupland explains: "The FGT residue arises from the fly ash being mixed with lime and occasionally steam that has been blown through the boiler passes at specific intervals to reduce soot build up on the heat exchanger pipe work."

"This residue passes along the line, but occasionally the additional steam can make the ash and lime mix damp enough to bind into large lumps that fall out of suspension. This mixture then crusts over like cement and needs to be broken down and removed by the operators working inside the pipelines."

"Unless it was broken down almost to finings the old 2" pipe work was very prone to getting blocked. To clean out the FGTDs our operators need to use breathing apparatus and PPE equipment to ensure safety; understandably it's a very difficult and awkward job with very restricted space and movement. As such we had to find a more efficient solution and the Gotland BagVac in combination with their 4" pipe work system and inlet valves has proven to be just what we needed."

BagVac and centralised system far more efficient, minimal manual handling issues
Ian continues: "It used to take them approximately 4 days to clear around five cubic metres of FGT residue, a process repeated every 3 to 6 months using two men. Using the new Gotland system it now takes just two days as a whole. The Gotland system works very well - the FGT ducts themselves were cleared in two days and we fired up the boilers again on the Sunday. Some five cubic metres of FGT residue were removed, simply and easily into bulk bags which could then be safely disposed of in a hazardous landfill site."

"It's much easier for the operatives as well, as they have informed me when we asked them about the new equipment. As opposed to breaking down the residue with hammers, they find the 4" flexible rubber suction hose strong enough without the aluminium extension, to break the residue into small enough lumps ideal for sucking into the system and away to the BagVac's euro-bag. The use of the flexible hose for digging out the residue is very effective and does less damage to the ducting's steel construction. This system also means we've cut out the manual handling of the residue from the ducts into bags that then had to be transferred down several levels to a skip."

Minimal downtime for the installation
Besides the BagVac system itself, Ian is delighted with the speed and efficiency of the installation work: "Gotland's mechanical installation team did a superb job, very fast, efficient and with the full and correct paperwork. They also did a good job with the wiring and with the operatives' training, so we were able to put the system straight to work on blocked flue gas treatment ducts. An excellent job all round."