Apparatus and method for separation of solids from liquid
First Claim
1. A process of separating solids from liquid, the process comprising:
- providing a settling tank having sides, a bottom and first and second ends,flowing liquid containing suspended solids into the tank'"'"'s first end;
maintaining a liquid level in the tank;
separating at least a portion of the suspended solids by gravity which settle onto the tank'"'"'s bottom;
continuously advancing a plurality of spaced-apart screens along an endless path which includes at least descending into the liquid from a first point above the liquid at the tank'"'"'s second end to a second point on the tank'"'"'s bottom, then advancing laterally to a third point on the bottom unique from the second point and adjacent the first end of the tank, and then, ascending to exit the liquid and return to the first point wherein solids are collected on the screens for clarifying the liquid, firstly by dredging solids which have settled by gravity as the screens are advanced along the bottom of the tank between the second and third points, and secondly by filtering progressively finer solids from the suspended solids through the formation of a filter cake of solids on the screens;
substantially dewatering the collected solids by firstly vibrating the solids-containing screens which lay along the ascending portion of the path and are above the liquid level and secondly by directing blasts of air onto the collected solids contained in the screens;
advancing the screens to a fourth point external to the tank;
recovering dewatered collected solids external to the tank by firstly inverting the screens at the fourth point and secondly by directing air onto the back of the inverted screens; and
withdrawing clarified liquid from the second end of the tank at a point adjacent the surface of the liquid.
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Accused Products
Abstract
Method and apparatus are provided for separating coarse and ultrafine solids from a liquid stream to produce a substantially dry solids discharge and a clarified liquid. Apparatus is provided comprising a combination of a settling tank, a plurality of filter screens spaced along an endless link-chain conveyor, a screen vibrator and directed air streams. In operation, coarse solids settle preferentially to the tank bottom. Ultrafines solids remain in suspension. Relatively coarse filter screens are conveyed from a point outside the tank to traverse a prolonged path through the liquid. Ultrafine solids are captured on the screens, by filtering the liquid through an ever finer build-up of filter cake. The relatively large number of passes of the screens through the liquid provides effective filtering of suspended solids. Further, the screens dredge settled solids from the tank bottom. After exiting the liquid, collected coarse and ultrafine solids are dewatered by vibration of the screens and directed blasts of air. Dewatered solids are dumped external to the tank and clarified water is recovered from the tank. Enhanced polymer flocculation may be practised to form flocs from ultrafine solids, after which flocs may be collected (filtered/dredged), dewatered and dumped using the invention. Dewatered solids can further be subjected to compression and decompression cycles to separate even more water from the solids.
132 Citations
33 Claims
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1. A process of separating solids from liquid, the process comprising:
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providing a settling tank having sides, a bottom and first and second ends, flowing liquid containing suspended solids into the tank'"'"'s first end; maintaining a liquid level in the tank; separating at least a portion of the suspended solids by gravity which settle onto the tank'"'"'s bottom; continuously advancing a plurality of spaced-apart screens along an endless path which includes at least descending into the liquid from a first point above the liquid at the tank'"'"'s second end to a second point on the tank'"'"'s bottom, then advancing laterally to a third point on the bottom unique from the second point and adjacent the first end of the tank, and then, ascending to exit the liquid and return to the first point wherein solids are collected on the screens for clarifying the liquid, firstly by dredging solids which have settled by gravity as the screens are advanced along the bottom of the tank between the second and third points, and secondly by filtering progressively finer solids from the suspended solids through the formation of a filter cake of solids on the screens; substantially dewatering the collected solids by firstly vibrating the solids-containing screens which lay along the ascending portion of the path and are above the liquid level and secondly by directing blasts of air onto the collected solids contained in the screens; advancing the screens to a fourth point external to the tank; recovering dewatered collected solids external to the tank by firstly inverting the screens at the fourth point and secondly by directing air onto the back of the inverted screens; and withdrawing clarified liquid from the second end of the tank at a point adjacent the surface of the liquid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A process of treating used mud from an oil well drilling rig for clarification of drilled solids from the mud, said used mud having been prepared in a mud tank and delivered downhole to aid in the drilling process, the used mud returning as liquid containing solids including coarse cuttings and fine solids, the process comprising:
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separating coarse cuttings from the used mud by screening to produce a cuttings-free mud; separating fine solids from the cuttings-free mud using hydroclones to produce a clarified mud and a hydroclone underflow liquid containing fine solids; recycling the clarified mud to the mud tank for re-use and reconstitution of more mud; flowing hydroclone liquid underflow containing fine solids into a settling tank, said tank having a bottom and first and second ends and being initially charged with clear water, said hydroclone underflow flowing into said first end; maintaining a liquid level in the tank by the addition of solids-free liquid as necessary; separating at least a portion of the fine solids in the tank'"'"'s liquid by gravity; collecting fine solids by advancing a plurality of spaced-apart screens along an endless path which includes at least descending into the tank'"'"'s liquid from a first point above the liquid at the tank'"'"'s second end to a second point on the tank'"'"'s bottom, then advancing laterally to a third point on the bottom unique from the second point and adjacent the first end of the tank and then ascending to exit the tank'"'"'s liquid and return to the first point wherein solids are collected on the screens to clarify the tank'"'"'s liquid, firstly by dredging fine solids which have settled by gravity as the screens are advanced along the bottom of the tank between the second and third points, and secondly by filtering progressively finer solids from the suspended solids through the formation of a filter cake of fine solids on the screens; substantially dewatering the collected fine solids by firstly vibrating the solids-containing screens which lay along the ascending portion of the path and are above the liquid level and secondly by directing blasts of air onto the collected fine solids contained in the screens; advancing the screens to a fourth point external to the tank; recovering dewatered collected fine solids external to the tank by firstly inverting the screens at the fourth point and secondly by directing air onto the back of the inverted screens; withdrawing clarified liquid from the second end of the tank at a point adjacent the surface of the liquid; and recycling the clarified liquid to the mud tank for preparation of more mud. - View Dependent Claims (21, 22, 23)
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24. Apparatus for separating solids from liquid including a settling tank, said tank having side walls, a bottom, and first second ends, comprising;
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means for feeding liquid into the first end of the tank; means for maintaining a liquid level in the tank; a plurality of discrete means spaced on an endless loop of conveyor for screening the tank'"'"'s contents; means for advancing said conveyor and screening means through the tank; means for guiding said conveyor along a path which includes at least descending into the liquid from a first point above the liquid at the tank'"'"'s second end to a second point on the tank'"'"'s bottom for traversing the liquid and collecting solids suspended therein, then advancing laterally to a third point on the bottom unique from the second point and adjacent the first end of the tank for collecting settled solids and then ascending to exit the liquid and return to the first point for again traversing the liquid and collecting solids suspended therein; means for vibrating those screening means which lay along the ascending portion of the path and which are above the liquid level for dewatering of collected solids; means for directing stream of air onto the contents of the screening means for further dewatering the collected solids; means associated with the first path point for inverting the screening means to dump the dewatered solids external to the tank; means for directing air onto the back of the screening means for cleaning residual solids therefrom and dumping them external to the tank; and means for withdrawing a clarified liquid from the second end of the tank. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32)
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33. A process of separating solids from liquid, the process comprising:
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providing a settling tank having sides, a bottom and first and second ends; maintaining a liquid level in the tank; withdrawing clarified liquid from the second end of the tank at a point adjacent the surface of the liquid; recycling clarified liquid to the tank'"'"'s first end; feeding coarse solids contaminated with ultrafine solids to the tank'"'"'s first end; washing ultrafine solids from the coarse solids by mixing them with the recycled liquid and forming a suspension of ultrafines in the recycled liquid; flowing the liquid containing washed coarse solids and ultrafine suspension into the tank'"'"'s first end; separating the coarse solids by gravity so that the coarse solids settle onto the tank'"'"'s bottom; continuously advancing a plurality of spaced-apart screens along an endless path which includes at least descending into the liquid from a first point above the liquid at the tank'"'"'s second end to a second point on the tank'"'"'s bottom, then advancing laterally to a third point on the bottom unique from the second point and adjacent the first end of the tank, and then, ascending to exit the liquid and return to the first point, the screens having coarse screen openings for passing substantially all solids but the coarse solids, wherein coarse solids are collected on the screens for clarifying the liquid by dredging solids which have settled by gravity and which constitute the largest portion of the coarse solids as the screens are advanced along the bottom of the tank between the second and third points; advancing the screens to a point external to the tank and dumping collected solids by inverting the screens for recovery of collected, substantially ultrafine-free solids external to the tank; repeatedly feeding, washing and collecting coarse solids until the concentration of ultrafine solids in the liquid in the tank is such that the coarse solids are which are collected are no longer substantially free of ultrafine solids;
thendiscontinuing the feeding of solids to the tank; mixing a flocculant with the recycled liquid for the aggregation of at least a portion of the ultrafine solids into floc having sufficient bulk to facilitate their collection on the screens; flowing the liquid containing floc and ultrafine solids into the tank'"'"'s first end and separating at least a portion of the floc and ultrafine solids by gravity which settle onto the tank'"'"'s bottom; collecting floc and ultrafine solids by continuously advancing the plurality of spaced-apart screens along the endless path wherein floc and ultrafine solids are collected by the screens; dewatering the collected floc and ultrafine solids by vibrating the solids-containing screens which lay along the ascending portion of the path and are above the liquid level and further by directing blasts of air onto the screen contents; and advancing the screens to a point external to the tank and dumping the dewatered collected floc and ultrafine solids by inverting the buckets external to the tank and cleaning residual floc and residual ultrafine solids from the screens by directing air onto the back of the screens for recovering the dewatered floc and ultrafine solids external to the tank.
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Specification