US3357160A - Liquid transport and mixing system for dust - Google Patents

Description

1967 RA. DENBROEDER 3,357,160

LIQUID TRANSPORT AND MIXING SYSTEM FOR DUST Filed Dec. 28, 1965 R M E 0 0 W 0 KEN A! E 7 4 W R 1 I. l- I E F. B 0 M H P m B 4 H 4 I0 6 10 4 0 3 United States Patent 3,357,160 LIQUID TRANSPORT AND MIXING SYSTEM FOR DUST Russell A. Denbroeder, Bloomfield, Mich. (5420 Van Ness, Bloomfield Hills, Mich. 48013) Filed Dec. 28, 1965, Ser. No. 516,894 1 Claim. (Cl. 55-120) This invention relates to mechanism for separating and collecting particles entrained in flowing gas streams. The mechanism is particularly useful in the sulphate process of paper pulp production for collecting sulphur-containing ash particles which are entrained in the gas stream issuing from the sulphur recovery furnace.

Generally the gas stream having the entrained ash particles is passed through an electrostatic precipitator positioned directly above a liquid sump which receives a weak sulphate solution recovered from the pulp digestion process. As the gas stream passes through the electrostatic precipitator the entrained particles precipitate onto the collector electrodes and drop directly into the sump where they are assimilated into the weak solution by a continuously rotating paddle type agitator. The enriched solution is later fed to the recovery furnace for extraction of the recovered sulphur compounds.

In the conventional arrangement the electrostatic precipitator and sump are both rectangular in plan cross section, while the agitator blades have a circular orbit or coverage; the blades therefore cannot reach the corners of the sump, and sludge builds up in these corner areas. US. Patent 3,109,630 suggests the use of liquid jets to overcome the sludge problem. The present invention seeks to overcome the problem by the use of a circular sump.

When the precipitate is allowed to fall directly into the sump the particles near the center sump area receive little or no agitation because the agitator blade areas near the agitator axis have very small linear speeds. There is thus the possibility of sludge formation in the central areas of the sump. The present invention attempts to overcome this problem by providing a sloped shed or roof over the central sump area, said shed being effective to direct precipitate-d particles into the outer perimeter of the sump where the linear blade velocity is sufficient to assimilate the particles into the sump liquid.

A general object of the invention is to provide an arrangement of electrostatic precipitator and liquid sump wherein the precipitate is readily assimilated into the sump liquid without formation of appreciable quantities of sludge.

In the drawings the single figure is a sectional view taken through an electrostatic precipitator and sump embodying the invention. As shown, the precipitator includes a conventional elongated upright casing having four upright flat sides, two of which are shown at 12 and 14. The casing thus has a rectangular plan cross section. Arranged within the casing are the conventional ionizer wire electrodes 16 and plate type collector electrodes 18. The wires may be suspended from a charging frame 20 which is connected with the conventional insulated high voltage terminals 22. Weights 24 may be used to hold the wires in their desired spaced-apart positions.

Collector electrodes 18 may be suspended in any convenient manner, as by transverse bars 26. Rapping or vibrating mechanisms such as those shown in US. Patent 1,551,724 may be utilized to periodically dislodge precipitate from the collector electrodes. In service, particleladen gas enters the precipitator through inlet 28, whereupon the particles are ionized by wires 16 and are precipitated onto collector plates 18. Periodically, the plates are rapped to dislodge the particles, and permit them 3,357,160 Patented Dec. 12, 1967 to gravitate toward the liquid sump 30. The clean gas proceeds through gas outlet 32.

Sump 30 has a circular plan cross section. Therefore the transition duct 34 between it and casing 10 is built to a semifunnel configuration with flat upper wall surfaces gradually merging into arcuate lower wall surfaces. The duct thus guides some of the falling particles into the sump.

Overlying the central portion of the sump is a conical roof or shed 36 suitably supported from the sump side wall by three or more plate-like brackets 38. The shed intercepts a major portion of the falling particles and directs them into the outer perimetrical portion of the sump where they can be most effectively assimilated into the agitated sump liquid.

Introduction of liquid, such as weak sulphate solution, may be accomplished through inlet opening 40 located some distance above outlet opening 42 to establish a liquid level approximately even with the upper edges of agitator blades 44. The drive for the agitator blades may be effected from a powered shaft 46 disposed within a tubular support 48 which projects upwardly from the sump bottom wall. Affixed to the upper end of shaft 46 is a sleeve 50 which carries agitator blades 44 and scraper blades 52. Suitable bearings (not shown) may be provided to support the end thrust of shaft 46 and the side thrust of sleeve 50. In any event, the arrangement should preferably be designed to give continuous rotary movement of agitator blades 44 and scraper blades 52 from a single powered shaft.

As blades 52 move along the surface of conical shed 36 their serrated lower edges dislodge any particles otherwise tending to cling to the shed upper surface. The particles are thus discharged into the outer perimeter of the sump without excessive particle buildup on the shed upper surface. The outer portions of agitator blades 44 can be made to have fairly substantial linear velocities, even with small rotational speeds of shaft 46. Therefore the particles fed to the outer blade areas tend to be quickly dissolved or assimilated in the sump liquid. Shed 36 thus keeps the particles away from the central area of the sump without excessive particle buildup on the prevent sludge formation. The circular plan cross section of the sump is also effective to prevent sludge since it eliminates the corner areas of rectangular sumps which cannot be reached with a circular motion agitator.

I claim:

In combination, an electrostatic precipitator comprising an upright multi-walled casing having a substantially square plan cross section; an inlet in one of the casing walls for admitting particle-laden gas into the casing; an outlet in another casing wall for discharging clean gas out of the casing; vertically disposed ionizer electrodes and collector electrodes arranged in the casing to intercept gas flowing from the inlet to the outlet, whereby solid particles are caused to precipitate onto the collector electrodes; said electrodes being spaced from one another to define vertical passages for allowing precipitate to fall into the lower portion of the casing; a sump having a circular plan cross section disposed below the rectangular casing; a convergent particleguiding duct connecting the lower portion of the casing with the upper portion of the sump; the diameter of the sump being only slightly less than the side-to-side dimension of the precipitator whereby the convergent duct is steeply sloped for easy guidance of particles into the sump perimeter; flushing liquid supply means fluidly communicating with said sump for admitting liquid to the sump; means at the perimeter of the sump for discharging liquid from the outenperimeter of the sump; a conical particle-distributing shed overlying the central portion of the sump; said shed having a downwardly-outwar'clly sloping upper surface whereby particles deposited on the shed upper surface are directed toward the outer perimeter of the sump; the diameter of the shed being only slightly less than the diameter of the sump whereby all of the precipitate will 'enter the sump immediately adjacent its outer perimeter; the aforementioned liquid discharge means being located below the level of the shed, whereby the shed will be entirely above the sump liquid level; rotary agitator means centrally arranged in the sump for mixing precipitated particles with the sump liquid; said'agitator means having a diameter approximately that of the sump whereby to effectively reach the sump perimeter where the particles are deposited; powered scraper means arranged to rotate about the axis of the shed, said scraper means being located to traverse the shed upper surface whereby to push particles toward the shed surface perimeter a tubular support projecting upwardly withinthe sump beneath the central portion of the shed; a sleeve surrounding the tubular support; a drive shaft extending upwardly within the tubular support to a driving connection with the sleeve; and said scraper means being connected with an upper portion of the sleeve, and said agitator means being connected with a lower portion of the sleeve.

References Cited UNITED STATES PATENTS 1,551,724 9/1925 Anderson -112 X 1,573,376 2/1926 Dickerson et 211. 55-145 X 1,668,063 5/1928 Force 210-528 X 1,736,842 11/1929 Wilcox 210-528 X 1,798,510 3/1931 Winslow et a1. 55-426 1,944,523 1/1934 Miller 55-118 X 2,336,017 12/1943 Jewell et a1 55-431 X 2,373,154 4/1945 Welp 210-528 X 2,603,307 7/1952 Richardson 55-108 2,614,652 10/1952 Sultzer 55-120 2,682,314 6/1954 Davis 55-120 2,689,019 9/1954 Roberts et al 55-120 X 2,749,212 6/1956 Crowder 55-112 X 3,109,630 11/1963 Nichols 55-101 X FRANK W. LUTTER, Primary Examiner.

HARRY B. THORNTON, Examiner.

D. TALBERT, Assistant Examiner.

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