The present invention relates to the removal of scale build-up. More particularly, the present invention relates to the control of deposits in such systems as pulp and paper manufacturing plants.
Basically, the control of deposits is an essential part of modem pulp and paper manufacture. There is a complex interaction of fibers, water extractives, air, microorganisms, and chemical additives that produces a wide variety of deposits made worse by the mechanical processing involved in certain stages of the paper making process. These deposits cause difficulties in the operation of paper machines, cause losses in production, increase the cost of maintenance and adversely affect the product quality. Left untreated, deposit built-up in the mill can produce costly problems. The deposits can plug wires and screens, thereby interfering with the necessary free-flow of process water and chemicals.
The present invention provides a new process for the removal of the build-up of scale. These are hard deposits, usually inorganic materials, on screens, headboxes, pipes, wires, vacuum pump impellers, and etc. Scale results from the crystallization, precipitation, or coagulation of non-resinous materials. Materials involved in the formation of scale deposits can be brought in with the wood or introduced with the additives for the pulping, bleaching, and papermaking processes.
Currently, scaling, for instance in paper and pulp mills can occur in a variety of areas, such as in the bleaching stages. Scaling in such locations is an ongoing problem in the industry wherein the scaling occurs to a rapid degree on the screens used in the paper and pulp mill such as in the D1 stage. When the scale build-up reaches certain levels, the equipment must be taken off-line to do mechanical descaling because chemical boil out of the system is generally uneconomical and therefore unfeasible mainly due to the massive volume of the chemicals that would be needed for such a boil out. For instance, some tanks used in the paper and pulp mill can hold volumes such as 10,000 tons which would require enormous amounts of chemical in order to remove the scale by chemical means. When the descaling operation occurs in vessels used in such pulp mills, for instance, the mechanical or manual cleaning can take three to four weeks to clean and leads to the operation being shut down for this amount of time. Furthermore, the descaling can be required about every three months. Thus, the operating efficiency of the overall pulp mill declines significantly and further, due to the scale build-up, the quality of the pulp also degrades over time.
Accordingly, there is a desire and need in the industry to provide an alternative method and system to remove scale build-up in paper and pulp mills and other systems to avoid lengthy shut downs of the various components of the mill thus saving significant amounts of time and money and increasing the overall efficiency of the paper and pulp mill or other systems.
A feature of the present invention is to provide a system and process to remove scale build-up from a variety of systems, such as vessels used in paper and pulp mills.
Another feature of the present invention is to provide a system and method to chemically remove scale build-up in order to avoid the use of mechanical cleaning and the time delays associated with mechanical cleaning of components, for instance, used in paper and pulp mills, such as screens.
Another feature of the present invention is to provide a system and process for removing scale build-up which will avoid lengthy shut downs of paper and pulp manufacturing plants.
Additional features and advantages of the present invention will be realized and obtained by means of the elements and combinations particularly pointed out in the written description and appended claims.
To achieve these and other advantages and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to a system to remove scale build-up which includes a vessel having at least one screen and also included in the system is a cover located inside the vessel and beneath the screen to separate the screen from the rest of the vessel. The cover defines an upper portion of the vessel and a lower portion of the vessel. Furthermore, the cover is in close proximity to the screen. The system of the present invention further involves the presence of a descaler composition or boil out chemical formulation which is present in the upper portion of the vessel.
The present invention further relates to a method to remove scale build-up in a vessel having at least one screen. The method involves placing a cover inside the vessel and the cover is located beneath the screen to separate the screen from the rest of the vessel. The cover is in close proximity to the screen and defines an upper portion and a lower portion of the vessel. The method further involves introducing a descaler composition or boil out chemical formulation into the upper portion of the vessel in a sufficient amount to remove at least a portion of the scale build-up on the screen.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are intended to provide a further explanation of the present invention, as claimed.