Patent ID: 6322705
Filing Date: 2001-11-27
Classification: B01D

Abstract:
A method for purification of water flowing in a water-based heating or cooling plant as a circulating liquid thermal energy carrier, said method comprising:passing water to be filtered through a tank containing filter materials, the filter materials including:pH changing material for changing the pH value of the water to a value exceeding neutral; anda plurality of layers of different granulated substances, including at least one layer of mechanical filter substances including fine grain sand and at least one layer of chemical reacting filter substances, the chemical reacting filter substances including at least one of granulated magnesium oxide and granulated calcium carbonate; the layers being located in an upright column having a top, said layers of mechanical filter substances and chemical reacting filter substances having respective densities, said layers of filter substances being located in the upright column in reverse order of their densities, the layer of filter substances having the lowest density being located at the top of the column and the remaining layers of filter substances following therebelow in order to density and being in contact with adjacent layer(s), with the layer of filter substances having the highest density being the lowermost layer in the column in the tank, each layer of mechanical filter substances being in direct contact with at least one layer of chemical reacting filter substances;wherein the step of passing water comprises:passing the circulating water to be purified through the top of the tank, then through all of the filter substances of said material layers, to subject the circulating water to a combined effect of mechanical and chemical purification treatment, said layers of filter substances accumulating at least one of sludge, corrosion residues and other contaminating particles during the purification treatment; andpassing raw water through the column from the bottom of the tank to the top of the tank when the tank needs to be cleaned, for forcing the filter substances to swirl in the tank, and disposing of the raw water from the upper part of the column through a drain, to free said filter substances of sludge, corrosion residues and other contaminating particles accumulated on said substances and to convey the sludge, corrosion reside and other contaminating particles from the tank with used raw water, and stopping the flow of raw water, and allowing the cleaned granulated substances from the filter material layers to settle, wherein the granulated filter substances settle into place to form the column with the substances arranged in reverse order of the respective densities within the tank.