Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2000-02-07
2001-10-09
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S218000, C210S219000, C210S319000, C422S288000, C034S368000
Reexamination Certificate
active
06299782
ABSTRACT:
The invention relates to a method and apparatus for treating liquid-containing materials based on organic waste products, particularly sludge from sewage plants. The treatment is carried out with the particular aim to make the material suitable as a fertilizer or soil improvement medium.
BACKGROUND OF THE INVENTION
Prior treatment plants are based on batchwise feeding of the material into a treatment chamber into which chemicals are added. The chemical additives cause reactions in the material resulting in heat generation and evaporation of liquid, regulation of the pH value and increase of nitrogen in the final product. Then heat is added to the thus chemically treated mass to evaporate liquid and to achieve a desired percentage of solid matter in the final product.
This prior technique suffers from several drawbacks and deficiencies. Thus, batchwise treatment is not an effective approach. Also, the relatively high temperatures which are used (about 425° C.) result in destruction of humic acid and other substances important to soil improvement.
Furthermore, when the reaction processes take place within the mass, gasification of liquid is hampered and the results of the reaction processes are generally lowered. Using external heat for gasification/drying and granulation, after reaction treatment, requires temperatures which are sufficiently low so as to avoid loss of the material substances that are valuable to soil improvement. Various low temperature technology processes may be adapted to this process. However, the properties of the material emanating from the reaction treatment would be of great importance, also for the result of this process.
The prior art also includes continuous processes for treating liquid-containing materials such as sewage sludge, as disclosed in U.S. Pat. No. 4,038,180 an EP-A-0 356 781. However, such prior processes suffer from the same drawbacks as discussed above in connection with batchwise material feeding, and in addition they tend to be less efficient owing to the slow throughput needed to ensure a sufficient sludge dwell time for the required reactions and drying to take place.
The main object of the invention is to provide an approach that permits a continuous process, and that does not require external heating of the sludge to effect the necessary evaporation, while keeping the temperature sufficiently low to avoid loss of any of the substances in the material that are valuable for improving soil.
SUMMARY OF THE INVENTION
The reaction processes are activated when the material is being directly beaten by rotating beating means as it falls through a vertical treatment chamber. Liquid and air are beaten out of the pores of the particles in the solid mass, and compact, free particles are formed under conditions promoting degasification. Also, the liberated liquid presents a relatively large surface promoting evaporation and degasification together with a cooling effect serving to keep the temperature sufficiently low, while the heat developed by the chemical reactions is sufficient to produce the desired evaporation. In such a continuous process free liquid surrounding the particles will effectively absorb heat energy supplied. Also, with compact particles, one is far more free in choosing granulating or pelletizing equipment.
Thus, briefly stated, the invention provides a continuous process for treating a liquid-containing organic waste material, comprising the steps of: adding to the material sufficient acid to achieve a pH of 2 or less in the material; subjecting the material to a beating treatment sufficient to (a) reduce the viscosity of the material, and (b) by heat-generated by friction during the beating treatment and by heat generated by reaction of the acid with the material, raise the temperature of the material so that liquid in the material is vaporized to gases; and adding to the material sufficient alkaline medium such that the pH of the material is raised to at least 5.
The invention also provides an apparatus for treating a liquid-containing organic waste material. The apparatus comprises: a substantially vertical, cylindrical treatment chamber having essentially the same open area throughout the chamber as seen from a feed direction of the material; an upper material inlet on the chamber; a chemical inlet on the chamber; a mixer disposed within the chamber; and a vent at an upper end of the chamber for venting gas from the chamber. The mixer comprises a plurality of beaters mounted on a tubular sleeve, which is rotatable about a tubular body. The beaters extend essentially to adjacent an inner cylindrical periphery of the chamber and are rotatable at speeds sufficient to so frictionally heat the material that liquid therein is evaporated to gases and the material is rendered into a higher solids content.
REFERENCES:
patent: 3788609 (1974-01-01), Toczyski
patent: 4038180 (1977-07-01), Talbert
patent: 4055494 (1977-10-01), Emmett, Jr.
patent: 5570517 (1996-11-01), Luker
patent: 5724751 (1998-03-01), Ellingsen
patent: 30 32 887 (1981-04-01), None
patent: 35 46 274 (1987-07-01), None
patent: 0 356 781 (1990-03-01), None
patent: 1521672 (1978-08-01), None
patent: 81/02888 (1981-10-01), None
Birch & Stewart Kolasch & Birch, LLP
Conterra AS
Lawrence Frank M.
Simmons David A.
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