PUMP FOR CONVEYING A MOIST PULP

Abstract: The present invention relates to a device for pumping a moist pulp and may be used in the wood-pulp and paper industry for conveying a highly concentrated pulp. The proposed pump comprises a body (1) having a hopper (2) for receiving a pulp; a replaceable pipe connection (3) in which a worm feeder (5) is coaxially located; a check valve (6) mounted as viewed from a pump outlet from said pipe connection (3); and a mixing chamber (4) for mixing the pump with a carrying agent; said chamber is coupled with said pipe connection (3) and fitted with a means for supplying the carrying agent. Between the worm feeder end (5) and the check valve (6) an adjustable gap is provided. On the surface of the pipe connection, on the level of the last flight of the worm feeder there are provided longitudinal through splines (8) for evacuating air which have a length of not more than a lead of the last flight of said worm feeder, a width of about 0.2 - 1.0 mm and a total open area of from 0.5 DELTA S to DELTA S, where DELTA S means the difference between an inner sectional area of the pipe connection and a sectional area of the worm feeder rod. The proposed pump enables pumping over a moist pulp of a high concentration (16-90 %) with maximum efficiency at different sectors of production lines of paper making industry with the result that a need for using a system for the pulp dilution with water is ruled out, a total quantity of waste waters and energy expenditures to treat thereof are reduced.

Description: PUMP FOR CONVEYING A MOIST PULP FIELD OF THE INVENTION The present invention relates to a device for pumping a moist pulp and may be used in the wood-pulp and paper industry for conveying a highly concentrated pulp. In the last few years, in the field of cellulose fibre production there has been an evident tendency to use a highly concentrated pulp, since this permits the design of a more compact and a more efficient manufacturing equipment. Concentrations of the pulp in the range of 8 - 16 % are usually called as mean concentrations, or concentrations "MC". Devices used to convey the pulp with such concentrations are usually called as "MC" pumps. BACKGROUND ART The companies "A. Ahlstδm" and "Kamyur Ab" have developed a "MC" pump the operation of which is based on the centrifugal principle [see, for example, the promotional pamphlet of the company "A. Ahlstδm Osakeyukhti" - The "MC" Pumps, Esan kirijapaino Publishers, Finland, 1987]. The above pump comprises a spiral body including a feed hopper and five working zones: A - a zone for fluidizing the pulp by means of a rotor which generates intensive shearing forces; B - a zone for evacuating air a high content of which in the "MC" pulp makes its delivery by a centrifugal pump impossible; C - a zone where separation of fibres transferable with air takes place; D - a zone for evacuating a fibre-free air; E - a zone where delivery of the pulp by a pump rotor takes place. In this case, all rotors are mounted on one and the same shaft which permits using a pump having one rotor as a conventional centrifugal pump. In the Zone A, the pulp delivered from the feed hopper is thinned, that is to say, is separated into individual fibres, thereupon the use of a centrifugal pump becomes possible. Air is separated from a thinned pulp in the Zone B and is evacuated through the Zone D by means of a small-sized vacuum pump. During the entire process for pumping, the pulp remains in the thinned state. Substitution of conventional reciprocating pumps for the "MC" pumps has resulted in the reduction of a quantity of water necessary for the pulp thinning, which in turn has led to the reduction of a total quantity of waste waters and the decrease of gross energy expenditures. The closest prior art has been described in a device designed to deliver a pulp with a mean concentration ol 8 - 15 % by weight, comprising a body with pipe connections for the pulp delivery and evacuation, external and internal worm feeders and an impeller coaxially mounted on the internal worm feeder. The internal worm feeder is provided with a means for evacuating air from the pulp which is made in the form of a channel inside a shaft having a perforation as viewed from the impeller [see USSR Inventors' Certificate No. 1463332, B 01 F 7/04, 1989]. The major drawback of the abovementioned prior arts consists in a limited area of their application. In the last few years, a wide variety of novel manufacturing processes for treating a highly concentrated pulp, that is to say in the range of from 16 to 90 %, has been developed. As pointed out above, known devices are capable to convey the pulp of a limited concentration only - not more than 16 %. As a consequence, the introduction of new processing techniques, for example processes for bleaching a highly concentrated pulp, requires either an additional installation of special devices to concentrate the pulp [see. for example, Zaplatin V. B. et al., "Bleaching Cellulose With A High Pulp Concentration In A Gaseous Phase", The Express Information Service "Cellulose. Paper, And Card" , Moscow, 1982, Issue 8, VNIIPIEIlesprom, pp. 1 - 37], or the development of new pumps permitting a direct delivery of a highly concentrated pulp. SUMMARY OF THE INVENTION The present invention is made in order to solve the above problems included in the prior arts, and an object of this invention is to provide a special device which enables pumping over a moist pulp of a high concentration (16 - 90 %) with maximum efficiency at different sectors of production lines of paper making industry. The above technical result is achieved in accordance with the present invention by a pump for conveying a moist pulp which comprises a body having a hopper for receiving a pulp; a replaceable pipe connection in which a worm feeder is coaxially located; a check valve mounted as viewed from a pulp outlet from said pipe connection; and a mixing chamber for mixing the pulp with a carrying agent; the chamber is coupled with said pipe connection and fitted with a means for supplying the carrying agent; wherein an adjustable gap is provided between the worm feeder end and the check valve; on the surface of the pipe connection, on the level of the last flight of said worm feeder there are provided longitudinal through splines having a width of about 0.2 - 1.0 mm, a length of not more than a lead of the last flight of said worm feeder, and a total open [clear] area of from 0.5 ^S to A S, where^S means the difference between an inner sectional area of the pipe connection and a sectional area of the worm feeder rod. The proposed pump differs from the prior art pump in that a body of the pump is provided with a replaceable pipe connection in which a worm feeder is coaxiallv located: a check valve mounted as viewed from a pulp outlet from said pipe connection; and a mixing chamber for mixing the pulp with a carrying agent; said chamber is coupled with said pipe connection and fitted with a means for supplying the carrying agent; wherein an adjustable gap is provided between the worm feeder end and the check valve: said means for evacuating air is made in the form of longitudinal through splines being located on the surface of the pipe connection, on the level of the last flight of said worm feeder and having a width of about 0.2 - 1.0 mm, a length of not more than a lead of the last flight of said worm feeder, and a total open area of from 0.5 Δ S U_> Δ S, whereλS has the above defined meanings. The use of a replaceable pipe connection in the design of the proposed pump enables, during its installation, to choose a desired gap size between the check valve and an end of a rigidly fastened rod of a worm feeder. A gap size depends on the pulp quality and technological features of the process and may be of about 10 - 50 mm. Moreover, the use of said replaceable pipe connection significantly simplifies operation of the pump; in case where it is clogged up due to contaminants in the pulp, the pipe connection is easy to remove followed by withdrawal of contaminants. Through splines provided on the surface of the pipe connection are intended to be used to evacuate air which is displaced from the pulp in the process of its compaction in a space between the last flight of the worm feeder and the check valve. In this case, dimensions of the splines and a total open area are chosen such that, on the one hand, a possibility of squeezing-out the pulp through the splines (at the expense of a limitation on maximal sizes and areas) be ruled out and, on the other hand, a maximally efficient air evacuation from a compressed pulp (at the expense of limitation on maximal sizes and areas) be attained. When incorporating length of through splines in the design, only the size of a lead of the last flight of the worm feeder is to be taken into account, since precisely this lead serves to perform function of compacting the pulp, whereas remaining flights just move the pulp forward. In doing this, a lead of the worm feeder flight may be both constant and variable, depending upon a particular fibre type and technological features of the process in which the present conveying device is implemented. BRIEF DESCRIPTION OF THE DRAWINGS Further features and other objects of this invention will become clear from the following detailed description made with reference to the drawings in which: Figure 1 is a sectional view of a pump; and Figure 2 shows A - A section of Figure 1. DESCRIPTION OF THE PREFERRED EMBODIMENT The pump comprises a body 1 having a hopper 2 for receiving a pulp; a replaceable pipe connection 3 and a mixing chamber 4 for mixing the pulp with a carrying agent. The pipe connection 3 is provided with a worm feeder 5 which is coaxially located therein. A check valve 6 is mounted as viewed from a pulp outlet from said pipe connection. The worm feeder has two zones - a loading zone 5a located within said feed hopper and a delivery zone 5b located directly in the pipe connection 3. The worm feeder 5 is driven into rotation by means of a motor drive 7. On the surface of the pipe connection 3, on the level of the last flight of the worm feeder 5, longitudinal through splines 8 are provided. Between an end of a rigidly fastened worm feeder 5 and the check valve, there is provided a gap 9 which size is adjusted by means of the pipe connection 3. The mixing chamber 4 is provided with a means 10 for supplying a carrying agent. This means may be made in the form of a supply pipeline. The pump body is disposed on special supports 1 1. Specific dimensions and materials of individual elements of the pump are governed by a particular type of the pulp and production conditions. The pump operates as follows. A moist pulp having a high concentration (16 - 90 %) is supplied from the feed hopper 2 via the loading zone 5a into the delivery zone 5b, further conveyed to the pipe connection 3 outlet and within the gap 9 between an end of the worm feeder 5 and the check valve 6. Here, by means of the last flight of the worm feeder 5, the pulp is compacted and shaped into a "pulp plug". In the process for shaping a "pulp plug" , air is displaced therefrom and evacuated outwards via through splines 8 located on the surface of the pipe connection 3. The formation of a "pulp plug" is accompanied by an increase in pressure affecting the check valve 6. As soon as this pressure becomes more than an external pressure in the mixing chamber 4, the check valve 6 opens up and a portion of a fibrous material enters the mixing chamber 4. A carrying agent (usually, it is air or its mixture with another gas) supplied under a high pressure into the mixing chamber 4 through a supplying means 10 breaks up the pulp into separate fibres. From the mixing chamber 4, the pulp divided into separate fibres is fed, by means of the carrying agent, via a pipeline (not shown in the drawing) to any section of the production line. As pointed out above, a gap between the last flight of the worm feeder 5 and the check valve 6 is easy to adjust when mounting the pipe connection 3, which enables formation of a "pulp plug" of different thickness, for example from about 10 to 50 mm, depending on a particular type of raws and technological features of the process. Just the same factors influence the choice of optimal dimensions of through splines and an open area. The selection of an optimal thickness of a "pulp plug", through spline dimensions and an open area permits pumping over a moist pulp with maximum efficiency. The use of the proposed conveying device permits reduction in energy expenditures to pump over a moist pulp due to the fact that the water content in this pulp may be decreased from 84 % to 10 % (which corresponds to the pumping over a moist pulp at the concentration of an absolutely dry substance of from 16 % to 90 % by weight). The introduction into practice of the proposed desing of the pump offers ample scope to solve the problem concerning the pumping over a pulp in paper shops. The use of pumps will allow to distribute the pulp among separate paper machines without using a white return water as a carrying agent. The proposed pump may be installed at different sectors of production lines of paper-making industry to convey a highly concentrated pulp at long distances with the result that a need for using a system for the pulp dilution with water is ruled out, a total quantity of waste waters and energy expenditures to treat thereof are reduced. Having described presently preferred embodiments of the invention, it is to be understood that it may be otherwise embodied within the scope of the appended claims.

Claims: CLAIMS A pump for conveying a moist pulp comprising a body having a hopper for receiving a pulp; a worm feeder; and a means for evacuating air, characterized in that the body is provided with a replaceable pipe connection in which said worm feeder is coaxially located; a check valve mounted as viewed from a pulp outlet from said pipe connection; and a mixing chamber for mixing the pulp with a carrying agent; the chamber is coupled with said pipe connection and fitted with a means for supplying the carrying agent; wherein an adjustable gap is provided between the worm feeder end and the check valve; said means for evacuating air is made in the form of longitudinal through splines being located on the surface of the pipe connection, on the level of the last flight of said worm feeder and having a width of about 0.2 - 1.0 mm, a length of not more than a lead of the last flight of said worm feeder, and a total open area of from 0.5 Δ S to Δ S, where^S means the difference between an inner sectional area of the pipe connection and a sectional area of the worm feeder rod.

Inventors: GRUDININ VLADIMIR PAVLOVICH, GRUDININ, VLADIMIR PAVLOVICH
Applicants: ANISIMOV ALEXANDR PAVLOVICH, GRUDININ ALEXANDR VLADIMIROVIC, GRUDININ VLADIMIR PAVLOVICH, ANISIMOV, ALEXANDR PAVLOVICH, GRUDININ, ALEXANDR VLADIMIROVICH, GRUDININ, VLADIMIR PAVLOVICH
Application year: 1996
Main classification: F04D7
IPC codes: D21D5, F04D3, F04D7, F04D9