Liquid purification or separation – Processes – Chemical treatment
Patent
1998-08-10
2000-08-08
Simmons, David A.
Liquid purification or separation
Processes
Chemical treatment
210218, 210219, 210319, 366289, B01D 1900, B03B 536, B01F 700
Patent
active
060997419
DESCRIPTION:
BRIEF SUMMARY
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 fertiliser 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 as used (about 425.degree. 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 generally lowered. Using external heat for gasification/drying and granulation after reaction treatment the temperature should be sufficiently low 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 and 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.
According to the invention this object is achieved through a method and an apparatus as defined in the accompanying patent claims.
SUMMARY OF THE INVENTION
The reaction processes are activated when the material is being directly beaten by the rotating beating means as it falls through the 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 a such 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 pelletising equipment.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail below, with reference to the drawings in which:
FIG. 1 is an elevational view of an apparatus according to the invention suitable for treating e.g. sewage sludge,
FIGS. 2 and 3 are successive, enlarged longitudinal sectional views of the apparatus according to the invention, and
FIGS. 4, 5 and 6 are elevational, plane and crossectional views respectively of details of a treating element.
DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to FIG. 1, the apparatus 1 according to the invention generally comprises a material treatment chambe
REFERENCES:
patent: 3788609 (1974-01-01), Toczyski
patent: 4038180 (1977-07-01), Talbert
patent: 4055494 (1977-10-01), Emmett, Jr.
patent: 5139667 (1992-08-01), Reneau, Jr.
Biopartner AS
Lawrence Frank M.
Simmons David A.
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