5.+Prevention

__Prevention Methods __
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The prevention of fouling is an important consideration to many industries. Due to the varying operating conditions, chemical feeds, process flows and numerous other variables, the platforms of prevention are very different depending where the fouling is occurring. The following are examples of methods currently used in different processes.

=Methane Steam Reforming =

In this very important, common process catalytic fouling plays a large role in the efficiency and operation of the process stream. Due to the nature of the feed(methane) and the high operating conditions, fouling can either envelope the catalyst or form whiskers on the surface blocking pores and eventually damaging the catalyst. To prevent this engineers have found that increasing the steam to methane ratio has reduced the formation of the unwanted coke. Another alternative which is used is the alkylation of the feed stream as this reduces the acid pores effect on the carbon compounds(Esther et al. 1987).

=Catalyst Beds =

Catalysts beds are found in many locations, there are many different approaches to reduces and preventing fouling. One example where one would find a catalyst bed would be in a catalytic converter on the end of a car. One method is to grade the catalyst bed by having more pores near the inlet to trap the majority of particulates and coke in the entrance region. A complicated but effective approach is to add a high voidage macroporous ceramic filter which is added to the catalyst to remove particulates before they can accumulate of the bed. A third approach being used is the selective distribution of pores throughout the catalyst bed. This selective pore spacing allows for a longer use of catalyst before it deactivates and also increases the tortuosity of the bed to increase the chance of gas particles knocking off fouling (Dunleavy 2005).

=Selective Catalytic Reduction =

In these NOx reducing catalysts, the main cause of fouling is unwanted impurities within the flue gas. To avoid the build up of the particulates, the process is designed with a high exit speed to force reduced the chance of fouling(the speed isn’t high enough to damage the catalyst itself). In extremely dusty processes and high particulate matter within the stack gas soot blowers are added to physically remove the soot which finds it way onto the catalyst.(Fu 1998)