Cleaning and liquid contact with solids – Processes – With treating fluid motion
Reexamination Certificate
1999-10-05
2002-09-17
El-Arini, Zeinab (Department: 1746)
Cleaning and liquid contact with solids
Processes
With treating fluid motion
C134S026000, C134S030000, C134S095300, C134S199000
Reexamination Certificate
active
06451126
ABSTRACT:
BACKGROUND AND SUMMARY OF INVENTION
The present invention relates to a system and method for cleaning a pulp paper processing dryer, and more specifically an apparatus and method for automatically cleaning the machine frames of a pulp paper processing dryer utilizing a plurality of directional nozzles positioned adjacent to the machine frames, means for pumping cleaning solution to the directional nozzles for application onto the machine frames, means for selectively communicating cleaning solution between the pumping means and the directional nozzles, and means for automatically controlling the operation of the cleaning system.
The operation of the dryer section of a pulp and paper mill utilizing a wet process wherein paper is manufactured by continuous sheet forming and drying is critical to the economic viability of a pulp and paper mill. The dryer section of a pulp and paper manufacturing plant is often the production bottleneck. In the increasingly competitive pulp and paper industry, where margins are tight, more emphasis is being placed on the importance of achieving a high capacity utilization of the dryer section to allow a manufacturing facility an opportunity to meet production goals. Within the pulp and paper industry there is a vital need to improve the efficiency of every aspect of operating the pulp paper processing dryer while maintaining high standards for worker safety.
Paper is typically manufactured from a dilute mixture of paper fibers and water. Water is removed from this dilute mixture in three basic steps; including 1) screening or forming wherein the dilute mixture is passed through fine screens to form a sheet of wet paper fibers, 2) removing water from the wet sheet by mechanical means utilizing a series of press rolls, and, 3) removing additional water by evaporative drying utilizing a series of drying rolls heated internally by steam. Although each of these basic steps involves the removal of water, the dryer section of a pulp and paper mill refers to the later step wherein a continuous paper web is dried as it passes over a series of heated rolls before the final dried paper product is wound onto reels. The dryer section is comprised of a complex series of large spinning cylindrical dryer cans over which the paper web travels. On each side of the dryer cans are machine frames that support the dryer cans. Dryer sections are often operated within a protective enclosure that contains heat released during the drying process allowing for lower energy consumption by the drying process. The protective enclosure, or dryer hood, remains closed when the dryer is operating. When the dryer is out of service, large doors in the dryer hood are opened to allow access to and inspection of the dryers.
Because of economic pressures it has become vital for a pulp and paper mill to improve the efficiency of every aspect of the operation of pulp processing dryers. An important but often overlooked operational aspect of these machines is the process by which the pulp paper processing dryers are cleaned. In particular, the machine frames of a pulp and paper processing dryer must be routinely cleaned to remove oil, grease, and paper fines that accumulate thereon during operation of the equipment. Keeping the machine frames of a pulp paper dryer clean of accumulated oil, grease, and paper fines is important to maintain a safe work environment and to reduce the risk of a fire, which could injure workers and destroy operating equipment causing a reduction in the facility's capacity utilization. Another important benefit of frequent cleaning of machine frames is the removal of paper fines from the dryer section of a pulp paper mill that could otherwise contaminate, and reduce the quality of, the mill's paper products.
Although there is an overriding need to improve the efficiency of every aspect of the pulp processing dryer cleaning process, the industry continues to rely on time-consuming and inefficient methods for cleaning pulp paper processing dryers. The conventional method of cleaning the machine frames of pulp and paper dryers is labor intensive. A small portable tank of cleaning solution and a small portable cleaning solution pump are positioned near a machine frame to be cleaned. Plant personnel connect the hose and spray nozzle to the cleaning solution pump, then spray cleaning solution onto the machine frames. After the cleaning solution is left on the machine frames for a period of time, the hose and spray nozzle is connected to a source of water and water is then sprayed on the surface of the machine frames to rinse off cleaning solution, oil and grease. The primary drawback of the conventional cleaning method is its time-consuming nature. Dryer sections of pulp and paper mills can be very large, having lengths in excess of 300 hundred feet, and these sections contain a large number of machine frames. A cleaning method that requires a person to clean each of the many machine frames in succession is a lengthy process, one that often cannot be completed during a short period of time.
For most pulp and paper mills it is important to minimize the periods that its dryer section is not in service. When a dryer has been taken out of service, many tasks must be performed to place the equipment back in service, and to minimize downtime these tasks must be completed as efficiently as possible. Unfortunately, during these downtimes manpower is often at a premium. In some cases, pulp and paper dryers normally cannot be cleaned after maintenance work on the dryer has begun. As a general rule, pulp and paper dryers can be cleaned using conventional methods only when there are no significant limitations on both the time available for cleaning and the manpower available to clean.
Under these constraints, it is not unusual for the portions of the equipment to be cleaned most frequently to be the most visible, easiest ones. More difficult sections are typically cleaned less frequently, such as the side of the machine frames facing the dryer cans (i.e., back sides of the machine frames). The back sides of the machine frames are seldom cleaned because of the difficulty involved in cleaning these sections utilizing the conventional cleaning method. A conventional method of cleaning the back sides of machine frames is to stand on a walkway above the machine frames and spray cleaning solution downward onto the back sides of the machine frames. This task cannot be performed for several hours after the dryer section has been taken out of service because of unsafe high temperatures. Plant personnel cannot clean the back sides of the machine frames until the dryer section has sufficiently cooled. This delay in commencing this work causes the work to be performed infrequently, if at all. Cleaning machine frames utilizing a more efficient cleaning method would result in more frequent and more thorough cleaning of machine frames and would result in a safer work environment and a reduced risk of property damage from a fire caused, in part, by the accumulation of oil, grease, and paper fines on machine frames.
Another problem with the conventional cleaning method is that all machine frames are cleaned in succession, and all machine frames cannot be cleaned simultaneously soon after a pulp and paper processing dryer has been taken out of operation. It would be advantageous to clean all machine frames shortly after the machines have been taken out of operation before the machines and the oil, grease, and paper fines accumulated thereon have cooled down. A more efficient cleaning method that allowed for the simultaneously cleaning of all machine frames before the machine frames have cooled down would be a significant improvement over conventional cleaning methods.
SUMMARY OF THE PRESENT INVENTION
With the foregoing in mind, it is the principal object of this invention to provide an apparatus and method for automatically cleaning the machine frames of a pulp paper processing dryer.
It is a further object of this invention to provide an apparatus and method for cleaning the machine frame
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