US3681191A

US3681191A - Paper pulp digester blowdown method

Info

Publication number: US3681191A
Application number: US88359A
Authority: US
Inventors: Frank Williams Farrelly
Original assignee: Process Evaluation and Development Corp
Current assignee: Process Evaluation and Development Corp
Priority date: 1970-11-10
Filing date: 1970-11-10
Publication date: 1972-08-01
Anticipated expiration: 1989-08-01
Also published as: BR7107414D0; AU3549371A; FR2113358A5; ES396824A1; AU462550B2

Abstract

THIS INVENTION RELATES TO A METHOD OF MAINTAINING A CONTINUOUS BLOWDOWN FLOW OF PAPER PULP BETWEEN A PULP DIGESTER AND A HOT STOCK REFINER OR OTHER DOWNSTREAM EQUIPMENT COMPRISING THE STEPS OF PASSING DIGESTED PULP MATERIAL THROUGH A MODIFIED DIGESTER BLOW VALVE, TRAPPING LARGE, SOLID FOREGN OBJECTS THEREBY PREVENTING SAID OBJECTS FROM BECOMING LODGED IN THE ORIFICE OF SAID VALVE ROTATING THE BLOW VALVE, AND EXERTING A FLUID PRESSURE ON THE ORIFICE THUS BLOWING SAID FOREIGN OBJECTS INTO A BLOW TANK OR A TRASH BIN.

Description

United States Patent 3,681,191 PAPER PULP DIGESTER BLOWDOWN METHOD Frank Williams Farrelly, Merrick, N.Y., assignor to Process Evaluation and Development Corporation, New York, N.Y.

Filed Nov. 10, 1970, Ser. No. 88,359 Int. Cl. D21c 7/08 US. Cl. 162-52 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method of maintaining a continuous blowdown flow of paper pulp between a pulp digester and a hot stock refiner or other downstream equipment comprising the steps of passing digested pulp material through a modified digester blow valve, trapping large, solid foreign objects thereby preventing said objects from becoming lodged in the orifice of said valve rotating the blow valve, and exerting a fluid pressure on the orifice thus blowing said foreign objects into a blow tank or a trash bin.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a method of conveying fluid pulp between a pulp digester and associated downstream equipment such as a hot stock refiner, and more particularly to a method of maintaining a substantially continuous flow of fluid pulp between a pulp digester and the downstream equipment and thereby preventing the digester plug valve from becoming clogged by foreign material, and subsequently costly operation shutdowns.

Prior art The process of this invention is designed with particular reference to use in a system for conveying fluid pulp between a continuous pulp digester and associated downstream equipment such as a hot stock refiner, although it can be adapted to various kinds of systems for conveying fluids from one vessel to another.

In the production of paper pulp from sugarcane bagasse or similar fibrous plant materials fibers are digested to produce pulp of a quality suitable for manufacture into paper. The digestion process includes dissolving the lignin, sugars, and resins content of the fibers, thereby separating the cellulose from the cementing materials with as little damage as possible to the cellulose. Problems arise due to the presence of rocks and trash in the fiber feed to the pulp digesters. This foreign material, after passing through the digester becomes clogged in the digester blow valve causing many costly shutdowns.

The present invention eliminates the problems arising from foreign material becoming clogged in the orifice of the digester blow valve, and prevents many costly opera tional shutdowns for the purpose of cleaning the orifice.

SUMMARY OF THE INVENTION Generally speaking, this invention relates to a method of maintaining a substantially continuous flow of fluid pulp between a pulp digester and associated downstream equipment such as a hot stock refiner, thereby preventing large, solid foreign objects from becoming lodged in the orifice of the digester blow or blowdown valve, and subsequent operational shutdowns due to clogging.

The method of this invention comprises the steps of reducing the cross-sectional area of the valve flow path of the digester blow valve over a portion of the length of the said flow path; positioning the reduced orifice of the blow valve on the downstream side of the flow, thus pro- 3,681,191 Patented Aug. 1, 1972 viding a trap pocket in the pulp flow line between the digester discharge and subsequent processing equipment; passing digested material through the discharger and digester blow valve, capturing large foreign objects in said trap pocket, rotating the reduced valve orifice so that the digester pressure is exerted on the opposite side of the reduced orifice, thus discharging said foreign objects into a blow tank or into a by-pass line around the downstream equipment and then into a blow tank, thereby clearing the plug; and returning said orifice to its original position thereby resuming normal flow of the digested pulp. It is also a variation of this invention to discharge the rocks or foreign materials into a separate trash container by means of a stream or air jet.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the present process of this invention may be best understood by reference to the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic drawing of pulp digester and digester blow valve;

FIGS. 2 and 3 are more detailed elevational sectional views of the digester blow valve of FIG. 1;

FIGS. 4, 5, 6 and 7 are elevational sectional views of a digester blow valve used in the process of the invention embodying further modifications.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates pulp digester 10 in which depithed fibers of sugarcane bagasse or similar fibrous materials are processed to separate the' fibrous constituents from nonfibrous materials by dissolving the latter. When this process is completed, the digester contents are blown through discharger 11 and digester blow valve 12 into the top of a blow tank where the digested contents are kept stirred by an agitator assembly and the stock is maintained at a uniform consistency.

FIG. 2 illustrates an elevational, sectional view of a digester blow valve 12 of FIG. 1, modified in accordance with the present invention, in its normal flow position. After the digester processes are completed, the digester contents are blown through inlet 14, and valve flow path 17 including a reduced orifice 15 which has been sized for normal discharge from the digester. The material blown through reduced orifice 15 continues through blow line 16 into the blow tank. When a large solid foreign object becomes lodged in orifice 15, clogging the digester discharge, valve flow path 17 is rotated 180 as shown in FIG. 3. The digester pressure exerted on the other side of orifice 15 blows the rock or foreign object into the blow tank thus clearing valve flow path 17. The flow path is then returned to its normal position illustrated in FIG. 2 and the blowdown process continued.

FIG. 4 is a sectional view of the digester blow valve 25 used in the process of this invention modified to operate when a hot stock refiner is installed to further process digested pulp immediately after the digester. Pressure of the digester forces the digested pulp through inlet 20 and rotatable valve flow path 23 with a reduced orifice 21, then into the outlet flow path 22 leading to the hot stock refiner. Large, solid, foreign objects becoming lodged in reduced orifice 21, plugging the digester discharge, are removed by rotating valve flow path 23, as shown in FIG. 5. The digester pressure now being exerted on the other side of reduced valve orifice 21 blows the rock or foreign object through bypass outlet 24 into-the blow tank thus clearing valve flow path 23. The reduced valve orifice 21 is then returned to its normal position, and the blowdown process continued.

FIG. 6 is a sectional view of digester blow valve 31 of this invention further modified to discharge foreign objects plugging the digester blow valve into a separate trash bin. After the digester processes are completed, the digester contents are blown through inlet 26 and rotatable valve flow path 28 with reduced orifice 27 which has been sized for normal discharge from the digester. The material blown through said orifice 27 continues through blow line 32 into the hot stock refiner. When a large solid foreign object becomes lodged in the reduced orifice 27, clogging the digester discharge, the valve flow path 28 is rotated 90 clockwise as shown in FIG. 7. By means of a live steam or pressurized air jet through line 29, the rocks or foreign materials are blown through outlet line 30 into a separate trash bin. The valve fiow path 28 is then returned to its normal position illustrated in FIG. 6 and the blow-down process continued.

It is apparent to those skilled in the art that various changes, modifications, additions and substitutions may be made in the methods described and structures illustrated herein without departing from the spirit and scope of the appended claims.

What is claimed is:

1. A method of maintaining a substantially continuous blowdown flow of solids contaminated paper pulp from a pulp digester discharge through a digester blowdown valve and then to a subsequent pulp processing vessel comprising the steps of reducing the cross sectional size of the valve flow path of the digester blowdown valve over a portion of the length of the said flow path to form a reduced valve orifice in said flow path; positioning the reduced valve orifice on the downstream side of the blowdown flow thus providing a trap pocket in the valve flow path; passing the contaminated digested pulp material through the blowdown valve; trapping solid foreign objects in said trap pocket; rotating the blowdown valve and '4 exerting a fluid pressure on the opposite side of the reduced valve orifice to discharge the trapped solid foreign objects from the trap pocket and clear the valve flow path; and returning said blowdown valve to its original flow position thereby resuming normal blowdown flow of the digested pulp.

2. The method of claim 1 wherein the valve is rotated so that the digester blowdown pressure is the pressure exerted on the opposite side of the reduced valve orifice to clear the valve flow path.

3. The method of claim 2 wherein the solid foreign objects are discharged into a collecting tank or trash bin separate from the subsequent pulp processing vessel.

4. The method of claim 1 wherein the fluid pressure exerted to discharge trapped objects from the trap pocket is provided by pressurized steam or pressurized air flowing through the valve flow path when the valve is rotated out of its normal blowdown flow position.

5. The method of claim 4 wherein the solid foreign objects are discharged into a collecting tank or trash 'bin separate from the subsequent pulp processing vessel.

References Cited UNITED STATES PATENTS 3,486,516 12/1969 Stoertz 162-52 X 2,115,675 4/1938 Tremmel 251209 X 2,621,012 12/1952 Graham 251207 X S. LEON BASHORE, Primary Examiner A. L. CORBIN, Assistant Examiner US. Cl. X.R.