Patent Application
20110247497
The invention relates in accordance with the preamble of claim 1 to an apparatus for implementing water separation in the vacuum system of a paper machine. Furthermore, the invention relates to a method in accordance with claim 7.
It is generally known to use vacuum for dewatering a web at the upstream end of a paper/cellulose/cardboard-making machine. The removed water must be separated from the vacuum flow prior to passing the air to a vacuum pump or blower. To this end, a steel tank has conventionally been employed wherein the flow is retarded and water is separated from air utilizing a cyclone concept. For greater air flow volumes concrete tanks have been developed in which separation of water occurs by retarding the flow velocity and then passing the air-water aerosol via droplet separation lamella plates. In the appended drawing (
In the state of the art, this construction is employed in conjunction with vacuum systems equipped with turbo blowers. In practice the system is relatively functional, but needs a lot of maintenance by the operator. A particular problem arises from the adherence of pulp to the walls of the tank structure as well as to the droplet separation lamella plates. The separation efficacy is substantially deteriorated when the lamella plates gather a layer of pulp. Resultingly, fiber can pass along with the air flow to the vacuum pump/blower. In turbo blowers the pulp fibers cling to the blade wheel that may thus become unbalanced. Pulp also adheres to the flow passageways of the blower thereby causing loss of vacuum efficacy. Moreover, in certain blower constructions pulp has penetrated into the labyrinth seals between the blade wheels thus causing damage in the blower.
It must further be noted that the prior-art construction has lamella plates located in the center of the separation tank. During system maintenance the operating personnel thereof must have access to the space behind the lamella plates for cleaning the entire tank. The lamella plate compartment must be provided with a door that can be opened during a maintenance shutdown. Cleaning the lamella plates is an extremely lengthy process and, moreover, they are expensive to fabricate.
Another disadvantage is that in practice a long piping must used to connect this kind of concrete separator tank to the blowers. As the vacuum flow takes place at 100% RH and air is cooled in the long piping, condensation occurs. Subsequently, the condensed water causes erosion in the blade wheels of the blower. These problems need be overcome.
Now the present invention offers a solution through a novel kind of apparatus that uses an improved method of water separation in a vacuum system.
The essential features of the invention are an import asset of the apparatus and the method utilizing the same as specified in the claims. More precisely, the invention is characterized by what is disclosed in the appended claims.
The invention is next described in more detail by making reference to the annexed drawings wherein
An essential feature of the invention is that the inlet pipe of the concrete separation tank is provided with a guiding baffle structure 1 that directs water and pulp to the bottom of the separator tank. In this preseparator, the air flow is retarded gradually without invoking a vacuum loss. The guiding baffle structure 1 has a multisectional construction, most advantageously comprising two sections 1A and 1B displaced apart from each other by a gap 10. In gap 10 the flow cross section is twice as large as the flow cross section of inlet pipe 8. In gap 11 the flow cross section is twice as large as the flow cross section of gap 10. The retarding flow directs the water gravitationally down. On the bottom of the preseparator is located a water trap vessel 2 serving to prevent air flow 12 from reaching the tank bottom. In this fashion, air flow 12 is forced to stream along the walls and ceiling of the separator tank, whereby the residual water in the air flow 12 is further separated and thereupon flows down along the tank walls to its bottom.
The tank has no lamella plates at its center, but instead, a droplet separation cell 4 is located at the mouth of the outlet pipe. In droplet separation cells used in the art, air flows in narrow slots thus forcing the droplets to coalesce, whereupon the droplets grown in size fall gravitationally down. The cross-sectional structure of cell 4 can be fabricated using automated manufacturing techniques. According to the invention, the plates of the droplet separation cell are coated with PTFE or some other dirt-repelling material. When required, a small amount of clean water can be sprayed to in front of the cell. In front of the cell and at the outlet pipe end are located plates 6 and 7 serving to prevent direct air flow into the outlet pipe 9.
In
On the basis of the above description, the invention clearly provides significant benefits. Hence, the droplet separation system according to the invention can be manufactured at a lower cost than the prior-art construction illustrated in
To a person skilled in the art it is obvious that the invention is not limited by the above-described exemplary embodiments, but rather may be varied within the inventive spirit and scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20105361 | Apr 2010 | FI | national |
