Neutralising processes of municipal solid waste incineration bottom ash ina flow-through system

The neutralising processes of MSWI bottom ash in a flow-through system were investigated by pH titration in a serial batch system. A one-dimensional c oupled transport (advection) and geochemical reaction model was used to sim ulate the neutralising reactions. It has been found that the formation and movement of pH fronts are essential features of neutralising processes in f low-through systems. This characteristic and the washing-out effect makes t he neutralising capacity obtained from batch experiment difficult to apply directly to a flow-through system. The neutralising ability of the MSWI bot tom ash was significantly less in a dow-through system than in a batch syst em. It was found that the available neutralising ability of the MSWI bottom ash in the flow-through system is only a third of the neutralising capacit y in a batch system. Carbonation reactions have a large influence on the ne utralising processes of the MSWI bottom ash. The carbonation transformation plays an important role in the formation of controlling minerals for the M SWI bottom ash in the neutralising processes. Geochemical simulations combi ned with experiments provided valuable information about the neutralising p rocesses in the flow-through system. This approach provides needed insights into reaction mechanisms and helps to check the basic assumptions for a ge ochemical model. (C) 1999 Elsevier Science B.V. Ail rights reserved.