DE4200916C2 - Process for the partial decarbonization of water - Google Patents

Description

The invention relates to a method for partial decarbonization of water according to the preamble of claim 1.

Such a method is known from DE-PS 29 13 287, in which the partial decarbonization of water by means of a filter bed made of trigonal filter material such as lime, dolomite or the like, taking the water to be treated through the filter bed under the same early vacuum application trickles. Here is the Entcar The stronger the vacuum used, the stronger the bonus. Dement speaking with the latter also increases the energy expenditure for the Ent carbonization.

From the patent application of Automatic Pump and Softener Corporation, Rockford, file number A 135, is a partial decarbonizer sation of water known, the water to be treated is a primary ren and is subjected to a secondary degassing. The primary outcome Solution is found by pressure atomizing the water using a diffuser instead, the effect of which is also that he the pressure in the Ko lonne drops below atmospheric pressure. In the column in Ge Genstrom to the partially degassed what trickles down on a coke filter bed this flowing air is sucked through the vacuum. Here is the through the negative pressure generated by the diffuser is responsible for the secondary degassing Lich.

The object of the invention is a method according to the Oberbe handle of claim 1 to create an improved decarbonization degree achieved with constant vacuum.

This task is performed according to the characteristic part of the Claim 1 solved.

Further refinements of the invention are as follows Description and the dependent claims.  

The inert gas expan introduced during the decarbonization diert in the partial vacuum prevailing in the filter bed (one works before preferably with an absolute pressure of approx. 100 mbar or less) considerable increase in its fluidity. This causes that water and inert gas within the fine-grained material tung  of the filter bed without flooding the latter (as long as corresponding flow rates of both media are not exceeded become). The inert gas, which acts as an entraining gas, provides another Reduction of the partial pressure of CO₂ already reduced by the vacuum and thus for an accelerated forwarding of the CaCO₃ precipitation from the calcite-oversaturated under the process conditions in a vacuum, aqueous solution in principle

Ca (HCO₃) ₂-CO₂ → CaCO₃ + H₂O

formed carbon dioxide.

As CO₂-free inert gas come for example in the present case as nitrogen, oxygen or air in question, the latter preferred is practically exempt from CO₂. Mechanically, for example, by filtering cleaned inert gas is due to the vacuum from the bed trigonal filter material made of pure lime, dolomite or the like sucks, preferably in countercurrent, d. H. that the matter pouring water down from the bottom evenly onto the loading distributed inert gas is opposed. However, too be worked in direct current, but then the effect is because of the lower CO₂ partial pressure drop.

The inert gas and in particular atmospheric if necessary CO₂-free air is in a water / inert gas volume ratio of preferably about 1: 0.5 to 1: 1.5, in particular about 1: 1 (measured under Normal conditions) added.

It was determined experimentally that with a contact time of about 12 min between water and filter material in a vacuum of about 100 mbar absolute pressure by adding atmospheric air to the water in the Volume ratio of about 1: 1 (measured under normal conditions) the same partial decarbonization effect can be achieved as without inert gas only with a vacuum of about 50 mbar.

Apart from that, the following advantages were achieved:

• - Energy savings for pumping gas and water by around 25 to 30%,
• - Crystallize and firm adhesion of the CaCO₃ on the trigona len filter material to over 90% and thus
• - Reduction of rinse water consumption and sludge.  
• - Improved usability of the coarsened grain of calcium carbonate, for example for wastewater neutralization or path fixing gung,
• - Possibility z. B. the oxidative iron and manganese deposition in one process step with the partial decarbonization because of the O₂-Lö solution in the water,
• - Elimination of volatile chlorinated hydrocarbons around is a factor of 10 to 100 higher than without inert gas.
• - Partial use of the CO₂-containing exhaust gases to eliminate the Calcite oversaturation in the treated water.

Claims (4)

1. A process for the partial decarbonization of water, especially drinking water, by precipitation of calcium carbonate in the presence of crystallization nuclei in the form of calcium carbonate-containing material in a filter bed made of granulated solid substances, the water being trickled through the filter bed with simultaneous negative pressure and in particular the filter bed in this way backwashing that about 10 to 20% of the calcium carbonate precipitated during the decarbonization remain in the filter bed, characterized in that CO₂-free inert gas in a volume ratio of water to inert gas of 1: 0.5 to 1: 1.5 during the decarbonization by Can flow through the filter bed. 2. The method according to claim 1, characterized in that as Inert gas air is used. 3. The method according to any one of claims 1 to 2, characterized records that the inert gas is conducted in countercurrent to the water. 4. The method according to any one of claims 1 to 3, characterized records that a volume ratio of water to inert gas of 1: 1 ver is applied.