Industrial Water Discharge and Biocide Fate Simulations with Nonlinear Conversion

摘要

Fouling in heat exchangers is a significant operational problem when using seawater for process cooling. It is associated with the formation of a biofilm due to the growth of micro organisms, the deposition of solid particles and organic matter as well as the growth of animals like mussels. Adding biocides to the inflowing cooling water can inhibit biofilm growth. If biocides like chlorine are added and the cooling circuit is fed with seawater the chlorine will finally be discharged into the environment at the circuit outlet. The primary biocide can undergo conversion to toxic components like halogenated organic matter within the cooling circuit itself and at the shore site environment. The environmental impact results out of both, primary biocide and forming toxic components. In different countries different boundary value regulations have to be met by industry. Therefore control of fouling using biocides has to be engineered and operated so as to satisfy process and environmental constraints. To predict whether the primary biocide and by-products exceed regulated boundary values or assess environmental fall out in general requires the simulation of transport and reaction. This work reports on the development of a plume simulation which incorporates the kinetics and fate of toxic by-products. The pollutant discharge simulation has been split into a hydrodynamic simulation and a superimposed reaction and flow field driven advection as well as dispersion system. The flow field computation has been carried out with the Finite Volume Coastal Ocean Model, FVCOM, whereas the transport and reaction simulation is based. on ADI/ADE Finite Difference algorithm. The ADI/ADE transport simulation is bound to structured grids which could be curvilinear. The FVCOM utilizes a horizontally irregular mesh consisting of triangular cells with varying vertical layer thickness, a-coordinates, along the coastal bathymetry.