The problem of scaling in and on process equipment used in industrial processes and particularly in those having an alkaline process stream is very well known. The scales present a significant problem when they build up on the surface of process equipment and cause a loss in the heat transfer coefficient. Thus, additional heat may be required to be provided to the evaporator equipment in these processes resulting in added cost.
An example of such an industrial process having an alkaline process stream is the Kraft recovery process for manufacturing paper which has been known for over 100 years and is eloquently described in many texts on the subject (see G. A. Smook “Handbook for Pulp and paper technologists, 3rd Edition). More recently the development of closed loop cycles in kraft paper mills has resulted in an increase in scaling problems in process equipment due to the build up of aluminum and silicon in the system as is described by P. N. Wannamaker and W. J. Frederick in “Application of solubility data to predicting the accumulation of aluminum and silicon in alkaline pulp mills”, Minimum Effluent Mills Symposium, 1996, p303. This article describes the occurrence of aluminosilicate scales in the black, green and white process liquors streams of the Kraft process. When the scales form on the surface of black liquor evaporators, tough glassy scales which are difficult and costly to remove, are formed. It has, therefore, been a well recognized need to provide a method for inhibiting the formation of aluminosilicate scales in kraft pulp mills. U.S. Pat. No. 5,409,571 describes the use of terpolymers of maleic acid, acrylic acid and hypophosphorous acid as scale inhibitor for kraft pulp mills. This type of polymer is shown to be effective against calcium carbonate scales but has not been shown to be effective for aluminosilicate scales.
USPTO Backgrounds
USPTO Backgrounds