Design and construction of facilities for handling of ashes at the sludge incineration plant
The task comprises the characterization and use of two different types of bio ashes. This is due to the different incinerator types at the wastewater treatment plants (WWTPs) operated by LYNIS and AWS, respectively. At LYNIS WWTP the sludge is incinerated in conventional multiple hearth furnaces; ashes production approx. 7,000 t/year. At AWS WWTP the sludge is incinerated in a fluidized bed oven, and the ashes collected as fly ashes; ashes production approx. 3,000 t/year.
At both WWTPs the bio ashes are wetted prior to the transfer to a local controlled land fill site to prevent occupational health and environmental problems with the ashes action like dust powder.
It is essential for maintaining the pozzolanic characteristics of the bio ashes to avoid wetting. Thus, an outlet system for the dry ashes has to be designed and constructed at both WWTPs, and each one allowing for a dust free transfer of dry ashes in full scale quantities to vehicles acceptable for a convenient unloading at the concrete production plant.
It is the responsibility of LYNIS and AWS, respectively, to install the two outlet systems. UNICON will contribute with expertise from the concrete industry on handling of dry powders in the design phase of the outlets. The operation of the outlets will be integrated in the SCADA systems at the WWTPs in order to obtain a user-friendly operation and on-line documentation. The method, which will be based on screw conveyors, is a well-known transport system for dry powders and a relatively simple open transfer system with dust control into a closed container.
Progress indicators – 1) outlet design approved, 2) outlets constructed and tested for functionality.
Expected results – The expected results will be two demonstration facilities for collection of dry bio ash at WWTPs with incinerator the two types: multiple hearth furnace and fluidized bed oven, respectively. These are the two predominant bio solids incinerator types in Europe. The targets are to obtain facilities, which are acceptable to the operator in terms of being user-friendly and are safe for occupational health and safety and environmental quality by preventing dust pollution.
Constraints - As there is already much expertise in the concrete industry on the handling of dry powders it assumed that a proper design is relatively straight forward in this new application. In case that the anticipated solutions will not be adequate for a dust free transfer, this will not be a constraint for the entire project. As a contingency plan transport by vacuum trucks is a possibility, however, being a more expensive solution.