US 3487941 A
Description (OCR text may contain errors)
ZMEWWM P. U HMAPAMJMH PRESSURE WASHER 3 Sheets-Sheet 1 Filed May 10, 1967 lwmzar Jmm M 197G w. m. MAAPAMAMI PRESSURE WASHER 3 Sheets-Sheet 2 Filed May 10, 196'? Wm E ag W M Mm GNU .T M 0% W W W my Jam. fi, WW F. 0. HAAPAMAW r L PRESSURE WASHER Filed May 10, 1967 3 Sheets-Sheet 3 Maw/vim.- i figifi 0. Mmmmam' United States Patent 3,487,941 PRESSURE WASHER Pertti Olavi Haapamaki, Rauma-Repola 0y, Porin Tehtaat, Pori, Finland Filed May 10, 1967, Ser. No. 637,435 int. Cl. Billd 33/06 U.S. Cl. 210-404 1 Claim ABSTRACT OF THE DISCLOSURE A pressure washer used for the treatment of cellulose fiber pulp embodying a rotatable strainer disposed within a pressure chamber provided with means whereby the air which is used to aid in filtration is transferred within the pressure chamber through sealed compartments at one end of the rotating strainer.
This invention deals with a pressure washer especially intended for cellulose fiber pulp, comprising a pressure chamber inside of which is mounted a rotatable strainer drum partly submerged in a container for pulp suspension, which drum is provided with peripheral compartments and a filter screen, a pressure generator to produce overpressure in the pressure chamber, and necessary pipes for circulating the gas medium, for conducting the pulp suspension into the pressure washer and the filtered pulp and the filtrate from the washer, as well as a device inside of the pressure chamber for detaching the washed pulp layer from the surface of the strainer drum.
In previously known pressure washers of the type presented above an overpressure pressure chamber partly surrounding the strainer drum is used to obtain sufiicient pressure difference in removing the filtrate and the washings from the fiber or pulp layer accumulated on the surface of the strainer drum, at which the pressure chamber is constructed in such a way, that the strainer drum by means of a special construction packing seal is connected to the outside atmosphere at the place of pulp discharge. In these pressure washers the air from the pressure chamber going through the pulp layer is leaving at the place of pulp discharge and is conducted to the suction side of the blower fan and is again compressed into the pressure chamber above the pulp layer, at which the required pressure difference and air circulation system is accomplished. One disadvantage of a pressure washer of this kind is that it is difiicult and laborious to seal off the place of pulp discharge pressure-tight and limits the overpressure applied, and therefore it has not been possible to utilize sufiiciently the advantages gained by using overpressure to accomplish pressure difference. A generally known fact is that often a larger pressure and a higher temperature promotes filtration of wash liquid. One marked disadvantage of the known pressure washers is that the air conducted to the blower fan has to go underneath the fiber layer at the place of detachment from the strainer drum, at which it drags along with it loose fibers which tend to accumulate in the air circulation pipes and the blower fan causing clogging and unbalance in both. A cost increasing factor is also that in connecting in series pressure washers of the type mentioned, separate pulp suspension pumps are required inbetween in order to transfer the pulp from the space under the pressure of the outside atmosphere to the next overpressure washer.
The object of this invention is to eliminate the disadvantages presented above by means of the pressure washer according to the invention, which is mainly characterized in that the said device comprises a sliding arrangement fitted between the gable wall of the pressure chamber and the end of the strainer drum for conducting the gas medi- Patented Jan. 6, 1970 um from the space inside of the drum through the pressure generator either entirely or partly into the end of one or several of the compartments and further through the strainer drum and the washed pulp layer back to the pressure chamber.
With the pressure washers according to the invention many marked advantages are gained compared to corresponding previously known washers. Thus, for example, no complicated seals are needed at the point of detaching fiber or pulp layer from the strainer drum, because the pressure at the point of detachment is the same as is in the pressure chamber. In the washer according to the in vention therefore, the pressure difference affecting the pulp layer can be raised practically without limit. Contrary to suction or vacuum washers the temperature in the pressure washer according to the invention can even be raised above the atmospheric boiling point, because by increasing the pressure in the pressure chamber it is possible to compensate for a change in the point of vaporization of the pulp suspension liquid. Raising the temperature again is very favourable for filtration, because the viscosity is lowered and other filtration phenomena are promoted. Neither is there to expect foam formation caused by vaporization of the liquid to the same extent as for instance in suction washers. Furthermore, as the circulating air from the point of pulp detachment before reaching the blower fan filters through the fiber layer accumulated on the surface of the strainer drum, no piling or clogging of fibers in the piping or the fan is possible. Due to the fact that the pressure chamber and the air circulation system is completely closed, there is no fear even if complications arise that moist, hot, or poisonous gases will enter the operating room.
Furthermore, by maintaining the air circulation closed as far as possible, heat losses and particularly the amounts of leaving gases stay low, which is a matter of extreme importance, for instance, in the sulphate pulp industry where the discharging gases still have to go through a separate treatment to eliminate odour. For instance, in using open suction washers the problems of ventilation and odour elimination are very diificult to solve on account of the large amounts moist and leaking air to deal with.
The invention is further clarified below and in the enclosed schematical drawings, in which FIG. 1 presents from the end the pressure washer according to the invention with the end plate removed,
FIG. 2 presents a longitudinal section of the other end of the pressure washer according to FIG. 1, taken along the line IIII in FIG. 1,
FIG. 3 presents schematically that end of the washer which is connecting to the gas circulation system, and
FIG. 4 presents a longitudinal section of the end of a pressure washer, according to another application of the invention, corresponding to that in FIG. 2.
According to the drawings the pressure washer includes a pressure chamber 1, a trough for pulp suspension 2 connecting pressure-tight to the lower end of the pressure chamber, as well as a rotatable strainer drum 3 partly submerged in the pulp suspension of the trough, at which that part of the strainer drum which is situated above the surface of the pulp suspension is surrounded pressure tight by the pressure chamber 1. The strainer drum is mounted on a concentrical shaft 4 running through it, which shaft in the cases presented is rotated clockwise, at which fibers from the pulp suspension in the trough 2 accumulate on the surface of the rotating strainer drum. The drum has a perforated outer mantle 5 topped by a filter screen 6. Inside of the drum at a distance from the outer mantle 5 there is an inner mantle 7, at which both mantles 5 and 7 are connected by plates 8 running lengthwise along the strainer drum, so that compartments 9 of the same length as the drum are formed side by side between both mantle surfaces. The open ends of the compartments are sealed against the gable wall of the pressure chamber 1 by means of the circular seal 12, and the end of the strainer drum again, seen in the drawing, is leaving an intermediate space 11 between itself and the gable wall of the pressure chamber 1. The above presented drum construction is previously known and devices according to the invention differing from this construction, for obtaining overpressure in the pressure chamber 1 and detaching the fiber layer from the surface of the strainer drum 3, are described below:
In the sliding area of the strainer drum, the length of which can be changed or varied, the inner mantle 7 is separated from the intermediate space 11 by means of the circular seal 13 and the slide seals 14 and 15. If necessary, the inside space of the slide can be divided into parts by means of the additional slide seal 16. The part of the slide which is situated between the slide seals 14 and 16 operates only as part of the air circulation system, and the part between the seals 15 and 16 serves as initial felting zone, as described below in connection with the operation of the pressure Washer.
In the drawing the path of the pulp suspension is marked by arrows a, the path of the air by arrows b, and the path of the filtrate by arrows c.
When the pressure washer operates pulp suspension is conducted to the container 2 through the connection piece 17, at which on the surface of the rotating strainer drum 3 a pulp or fiber layer is formed. This is washed with wash liquid coming from spray pipes 19 fitted into the pressure chamber. At the same time gas by means of the pressure generator 20' is pressed through the connection piece 21 and the chamber 22, which is located between the intermediate plates 14 and 16 serving as compartment seals and which is part of the above-mentioned slide construction, into the compartments adjacent to the chamber 22. From these compartments air is passing through the strainer surface of the drum 3 into the pressure chamber 1, detaching at the same time from the strainer drum a fiber layer 18, which by means of the knife 23 is conducted into the trough 24 situated outside of the strainer drum and communicating with the pressure chamber 1. If necessary, additional air by means of the pressure generator may also be conducted into the pressure chamber through the connection piece 25. The air conducted into the pressure chamber passes through the fiber layer accumulated on top of the strainer drum, and through the strainer drum, into the compartment 9, and by way of the open gable ends of the compartments into the intermediate space 11, and is conducted from here through the pipe fitting 26 into the pressure generator 20, and by means of this through the pipe connections 21 and back into the pressure chamber 1. A shortage or an excess of circulating air can be adjusted by way of the pipe connection 27, which is fitted to the inlet side of the pressure generator and is communicating with the outside atmosphere.
The Washed pulp is discharged from the trough 24 located inside of the pressure chamber 1, by means of a heater arrangement or a spiral conveyor 28, either through the connecting piece 29 into a pulp suspension pump operating as a pressure lock, or through the connecting piece 30 diluted with wash liquid or water coming from the dilution pipe 31, directly to another washer under pressure or by Way of a liquid lock into an evacuated space.
The filtrate runs due to the pressure difference through the fiber layer and the strainer surface 5 and 6 into the compartments 9, and discharges from here through the open ends of the compartments by Way of the connecting piece 32.
Further according to the FIGURES l and 3 the same overpressure as in the pressure chamber 1 is effective through the fiber-free strainer surface in the compartments separated by the slide seals 15 and 16 of the slide construction. In these compartments only a careful preliminary felting of pulp fibers can take place due to the hydrostatic pressure difference, independent of the pressure in the washer, at Which small fibers are prevented from going with the washings through the strainer surface in the area following the compartment seal 15 due to the effect of the much greater pressure than the hydrostatic pressure difference.
The above presented mode of applying the invention according to the FIGURES l-3 is the most suitable in such cases where the storage and pumping tank for filtrate dis charging from the washer is situated immediately beside or below the Washer, whereas in such cases where the said tank has to be placed considerably lower, the most favourable solution, for instance from the point of view of power economy, is the mode of applying the invention according to FIG. 4. In FIG. 4 the same parts are marked with the same symbols as in the FIGURES 1-3. In this mode of application attempts are made to obtain vacuum in the open compartments 9 by means of the potential energy of the filtrate, aided by the barometer tube 33, in order to maintain the pressure difference sufficiently large. Such a vacuum has not been possible to accomplish in previous pressure washers.
In the mode of application according to the FIGURE 4 the air or part of it can be taken to the circulation from the air separation tank 34, at which for instance the storage tank for filtrate may serve for this purpose.
The circulating air can be connected to the outer atmosphere through the connecting piece 27.
The accomplishment of vacuum, however, is not limited to the above presented mode of application only, but can be accomplished also by other known methods, at which the air to the pressure generator to be brought to circulate is taken from the gas discharge side of the generator of vacuum.
Naturally the invention is not restricted to the above working example, but it can be varied considerably as to details within the scope of the idea of the invention. This concerns in particular the type of slide construction including slide seals.
What is claimed is:
1. In a pressure washer apparatus for the continuous treatment of fibrous materials, embodying:
a pressure chamber;
a cylinder rotatably mounted within said pressure chamber;
a perforated strainer-mantle of larger diameter than said cylinder;
mounting means for said strainer-mantle comprising fluid-tight sections running the length of said cylinder and extending perpendicularly from the surface of said cylinder to said strainer-mantle, said arrangement forming compartments on the exterior of said cylinder open at only one end thereof;
connecting means to said chamber for the supply of material to be treated;
connecting means to said chamber for the outlet of treated material; a pressure generator; gas supply means extending from said generator to said chamber for conducting gas for de-watering a fibrous mat accumulated on said strainer-mantle;
gas return means to said generator from said chamber for conducting gas which has passed through a fibrous mat accumulated on said strainer-mantle for re-pressurization and recirculation;
separate gas supply means for conducting gas into said pressure chamber from said pressure generator for removal of a fibrous mat accumulated on said strainer-mantle;
the improvement of sealing means comprising a first portion, located at the end of said strainer-mantle which has the open ends of said compartments, ex-
tending from said pressure chamber to the end of said strainer-mantle, thereby providing a gas-tight seal separating gas to be returned to said pressure sure on the mantle side of said mat greater than the pressure on the other side of said mat, said second portion separating said removal gas from other generator on one side of said seal from gas which has been supplied to said pressure chamber on the 5 other side of said seal; References Cited and a second portion extending from said chamber to UNITED STATES PATENTS said cylinder at the end having the open ends of said gas in said chamber.
compartments, located adjacent said connecting 1,512,321 10/1024 Wait 210-67 means for the outlet of treated material, and con- 10 2,963,158 12/1960 Junz nected with said first portion to form a gas-tight 3,029,948 4/1962 McKay 210412 X enclosure for conducting gas to said open ended compartments for the removal of the fibrous mat accumulated 0n the strainer-mantle by creating a pres- REUBEN FRIEDMAN, Primary Examiner T. A. GRANGER, Assistant Examiner