Counter-current Washing of Filter Cakes
Tang, Haiyan (2009)
Tiivistelmä
The main objective of this thesis was to compare the efficiency of counter-current and co-current filter cake washing techniques. Filter cake washing is a common unit operation which is used in the chemical process industry for improving the recovery of the liquid phase or for purifying the solid phase of the filter cake. Counter-current displacement washing is more difficult to arrange and it requires additional process equipment but the advantage of counter-current method is that the consumption of wash water that is required for achieving certain filter cake purity may be considerably decreased when compared to the co-current washing method. This is true especially for materials that are difficult to wash.
The literature part of this thesis consists of a review of filter cake washing in general, including the basic principles of co-current and counter-current techniques, and a description of the structure and operation of a horizontal vacuum belt filter, which is the equipment considered in the experimental part of this thesis. Also the most common cake washing models are introduced.
The experiments were performed by washing wheat apatite filter cakes in a laboratory scale vacuum filter by using both co-current and counter-current washing methods. The main results of these tests were the washing curves that relate the purity of the filter cake to the amount of wash liquid used. Comparison between the obtained washing curves showed that both washing methods could be efficiently applied for achieving good washing results. The differences between the wash liquid consumptions in the co-current and counter-current washing methods were found to be surprisingly small but this is most probably explained by the relatively good washing characteristics of the apatite cakes. The washing models introduced in the literature part were compared with the results obtained from the experiments and it was found out that the studied cake washing processes could be described
The literature part of this thesis consists of a review of filter cake washing in general, including the basic principles of co-current and counter-current techniques, and a description of the structure and operation of a horizontal vacuum belt filter, which is the equipment considered in the experimental part of this thesis. Also the most common cake washing models are introduced.
The experiments were performed by washing wheat apatite filter cakes in a laboratory scale vacuum filter by using both co-current and counter-current washing methods. The main results of these tests were the washing curves that relate the purity of the filter cake to the amount of wash liquid used. Comparison between the obtained washing curves showed that both washing methods could be efficiently applied for achieving good washing results. The differences between the wash liquid consumptions in the co-current and counter-current washing methods were found to be surprisingly small but this is most probably explained by the relatively good washing characteristics of the apatite cakes. The washing models introduced in the literature part were compared with the results obtained from the experiments and it was found out that the studied cake washing processes could be described