Liquid purification or separation – Processes – Separating
Patent
1996-04-10
1998-09-22
Reifsnyder, David A.
Liquid purification or separation
Processes
Separating
210796, 210800, 210805, 210194, 210205, 210207, 210208, 210515, 210519, 210523, 2105321, B01D 2100
Patent
active
058110160
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of removing sand from a waste water loaded with sand and organic substances and which is set forth in circulation in a vertical container in which the organic substance moves upward, while the sand sinks downward toward a discharge conveyor connected to the container from beneath, and is discharged only after a certain settling period, as well as to the apparatus for effecting the method.
In clarification plants, usually, sand which is rinsed together with the waste water, is separated from likewise rinsed harmful organic substances. To this end, sand which is collected in a collecting reservoir, together with organic substances, is pumped into a sand separator. This sand separator consists essentially of a vertical mostly funnel-shaped container having an overflow for the waste water loaded with organic substances in its upper region and to which, in the region of a discharge opening, a discharge conveyor is connected from beneath. The discharge conveyor is formed as a screw conveyor and extends upward at an angle so that the discharge end is located above the height of the overflow. Due to a particular shape of the inlet for the waste water, which is loaded with sand and organic substances, a rotating stream is created inside the container in which the characteristically lighter inorganic materials are displaced upward, while the characteristically heavy sand sinks downward toward the discharge conveyor. The upward movable organic substance the ascending of which is promoted by the injection of air in the form of air bubbles, is removed from the container together with the overflowing waste water. The sand, which settled in the region of the conveyor bottom, can be removed by the discharge conveyor with the accompanying draining of the sand because the discharge end of the conveyor is located higher than the container overflow. For discharging of sand, a stepwise drive of the discharge conveyor is recommended to insure sufficient settling time for the separation of a significant amount after each introduction of waste water. A drawback of the known method of removing sand from waste water loaded with sand and organic substances consists primarily in that the discharged sand is still loaded to some extent with organic substances which excludes a further use of the sand, e.g., as a bulk material in construction. The sand removed from the waste water in this way should rather be treated as a hazardous waste and put away, which is very expensive.
Accordingly, the object of the invention is to so improve the above-described method of removing sand from waste water loaded with sand and organic substances that the discharged sand contains only an insignificant residual amount of organic substances and can be used in construction and for similar purposes.
The object of the invention is solved by mechanically stirring the settled sand with simultaneous rinsing with fresh water, which is fed from beneath, and by discharging an amount that insures a predetermined minimal height of the settled sand.
The mechanical stirring of the sand, which settled in the container bottom region, achieves not only additional stratification effect with a resulting layered formation of the deposit with characteristically heavier particles being located in the lower layer and the characteristically lighter particles being located in the upper layer, but also a mechanical purification of sand by insuring rubbing of the sand grains off each other so that the organic substance, which is adhered to the sand grains, rubs off and can be carried away from the deposit by fresh water, fed from beneath, to be removed from the container with the stream of the waste water over the overflow.
The velocity of the upward flow, which is created by the unloaded rinsing water should not exceed the sinking velocity of the sand grains in order not to disturb the deposition of the sand grain in the bottom region. In addition, the sand, which settled in the bottom region, forms a stop for the organic substance which thereby
REFERENCES:
patent: 1959917 (1934-06-01), Harrell
patent: 2933187 (1960-04-01), Old
patent: 3940252 (1976-02-01), Reinhardt et al.
Translation of Netherlands Patent 7212429, Mar. 1974.
Noggerath Holding GmbH & Co. KG.
Reifsnyder David A.
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