Method and apparatus for improving efficiency of Uhle Boxes in the process of paper production by applying a homogeneous mixture of superheated humid air
The invention comprises a method for improving efficiency of uhle boxes in the process of paper manufacturing. The essence of the invention is the use of a homogeneous mixture of superheated humid air in the press section of a paper machine. A very intense mixing of air and steam takes place in venturi injector which creates a uniform mixture, with appropriate composition and temperature, directed to a blowing nozzle. The mixture is then used in the forced flow through felt to a suction slot installed under the felt. The correct mixture composition ensures its minimum density, maximum speed and minimum time of flow through felt. It is important because the flow takes place when felt is running fast. The time ratio of the flow of homogeneous mixture of superheated humid air versus longitudinal movement of felt equals the actual working surface area of the suction slot. Extended working area directly influences the quality of felts conditioning and paper dewatering in the press section.
Currently, so called uhle boxes are used in the paper making process to condition press felts. These boxes are in fact vacuum pipes with slots of different size and shape directed towards the inside. The air flows through felt, which is moving over slots, and is then sucked off to a vacuum pump. During the process water and other contaminants from felt are sucked away together with air. This is a crucial stage for appropriate paper dewatering in the press section. Current paper machines are running at a speed much higher than the speed of air flowing through felt.
The cross-directional movement of a fast moving felt versus airflow leads to a deflection of the air stream in the direction of running felt and therefore causes considerable reduction in the working surface of uhle box.
In case of very fast paper machines this leads to a total cancellation of the open airflow surface and consequently hinders any felt conditioning.
The presented method improves the currently employed technologies in order to enhance paper production process.
BRIEF SUMMARY OF THE INVENTIONThe objective of the invention is to provide an improved felts conditioning method for paper machines with the use of a specifically prepared homogeneous mixture of superheated humid air and steam which enhances functioning of existing systems of uhle boxes used for felts cleaning and dewatering.
The invention comprises a method for improving efficiency of uhle boxes in the process of paper manufacturing.
In the paper manufacturing process there's a need to dewater and dry the end product. The degree to which paper is dewatered is of great importance because it directly impacts how much energy is saved further in the production process, particularly in the drying process. The invention comprises the method for improving efficiency of uhle boxes. Contemporary paper machines are running at a speed much higher than the speed of atmospheric air flowing through felt [
Homogeneous superheated humid air from blowing nozzle is sucked into uhle box (1) [
The dwell time of felt in the open area of uhle box is crucial because it directly impacts water and contaminants removal from felt. A portion of moisture evaporates and is sucked away. The remainder of water in the liquid form is substantially easier to suck off in higher temperature due to decrease in its viscosity and density. As a consequence, simultaneous sucking and preheating of felt by means of air-steam flow impacts the intensification of paper dewatering in the press section of the paper machine. As a result, paper web subjected to thermal drying is characterized by higher dryness.
Claims
1. The method of improving efficiency of Uhle Boxes in the process of paper production by blowing a homogeneous mixture of superheated humid air through the felt to the Uhle Box, wherein:
- said mixture (not pure steam and not hot dry air) is homogeneous and superheated by a minimum of 20 F. above the saturation point and is created in the mixing process of air with superheated steam;
- temperature of said mixture is between 175-260 F;
- absolute pressure of said mixture is between 15.5-16.5 PSI.
Type: Application
Filed: Feb 4, 2014
Publication Date: Aug 6, 2015
Inventors: Lucjan Edmund Raubic (Ottawa), Teresa Janina Raubic (Ottawa)
Application Number: 14/172,891