GB2342594A - Apparatus for pH adjustment of a liquid using carbon dioxide - Google Patents

Abstract

The apparatus comprises a chamber into which liquid is fed from a reducing valve B and CO<SB>2</SB> is fed via a pressure regulator E and gas valve F. The liquid in the chamber acts as a gas seal, liquid being drawn off from the bottom of the vessel. The introduction of gas is controlled by a level control mechanism G which opens gas valve F as the level in the chamber rises and closes the valve as the liquid level falls, liquid being introduced so as to establish a gas/liquid equilibrium in the chamber. Unwanted air is removed through a purge valve H. The apparatus may be used for stabilising the pH of a water supply sample for chlorine measurement, the treatment of alkaline effluent and in food processing.

Description

APPARATUS FOR pH ADJUSTMENT WITH CARBON DIOXIDE GAS This invention relates to apparatus for pH adjustment with carbon dioxide gas.

There are many applications where it is necessary to reduce the pH of a liquid. For example, to effectively measure the chlorine residual of a water supply it is often necessary to reduce and stabilise the pH of the sample. PH reduction is also required in the treatment of alkaline effluent and in the food processing industry. Normally this is achieved by the addition of an acid solution. An alternative would be to inject carbon dioxide gas into the liquid and so produce carbonic acid.

Although effective, conventional gas injection is inefficient and escaping unused gas can pose a health and safety risk. Applying gas to the liquid within an enclose environment will improve efficiency, be environmentally friendly and minimise any health and safety risk associated with the gas.

According to the present invention, liquid is passed through a chamber filled with carbon dioxide gas. The gas combines with the liquid producing carbonic acid that reduces and stabilises the pH of the liquid. Pressure and flow control of the liquid and gas ensure a constant and sufficient supply of gas to the liquid whilst preventing the release of any unabsorbed gas into the environment.

Referring to Figure 1.

Liquid enters the top of chamber [A] via pressure reducing valve [B]. Once inside the liquid is dispersed [C] to maximise surface area. The liquid falls through and accumulates at the bottom of the chamber from where it can be drawn off at the desired rate as set by flow regulating valve [D]. The capacity of flow regulating valve [D] must always be less than the available inlet flow through pressure reducing valve [B]. As a result the liquid level in chamber [A] will rise.

A carbon dioxide gas supply is pressure regulated by [E] and connecte to chamber [A] via gas valve [F]. The gas pressure pq is set slightly higher than liquid pressure [Y]. As the level in chamber [A] rises, level control mechanism [G] opens gas valve [F]. Liquid leaving the chamber will now be replaced by gas at pressure [X] in preference to liquid at pressure [Y].

Gas is prevented from back feeding the liquid supply line by pressure reducing valve [B]. As the liquid level falls, level control mechanism [G] will start to close gas valve [F] and liquid will now replenish chamber [A] via pressure reduång valve [B]. Equilibrium is achieved.

To operate effectively air must be removed from chamber [A]. Purge valve [H] releases air/gas from chamber [A], this allows pure carbon dioxide gas to enter via gas valve [F]. Operation of purge valve [H] may be manual or automatic and may also incorporate over pressure protection for chamber [A]. Liquid passing through chamber [A] absorbs the carbon dioxide gas redudng and stabilising the pH. Level control mechanism [G] and gas valve [F] maintain the nominal liquid level in chamber [A] by automatically adding gas as it is absorbed.

Removal of the liquid supply will cause chamber [A] to empty. Level control mechanism [G] will prevent gas valve [F] from opening until the liquid level is restored and the gas seal reestablished.

Claims (7)

1. CLAIMS 1. An endosed chamber for applying carbon dioxide gas to a liquid for the purpose of pH adjustment.

   2. An endosed chamber as daimed in daim 1, wherein gas may only leave the chamber as a result of absorption into the liquid.

   3. An enclose chamber as daimed in claim 1 and daim 2, wherein a nominal liquid level maintains a seal against escaping gas.

   4. An endosed chamber substantially as described herein with reference to the accompanying drawing.

   Amendments to the claims have been filed as follows 1. An apparatus for dissolving carbon dioxide gas in a continuous water sample for the purpose of pH reduction prior to the measurement of chlorine residual, comprising: a pressure chamber for mixing the carbon dioxide gas and water, a carbon dioxide gas input regulated to pressure X and water input regulated to pressure Y where pressure X > pressure Y, an output for the release of water at reduced pH, a means of regulating the output flow to less than that available at the water input, a means of maintaining the water level within the pressure chamber by variable flow regulation of the carbon dioxide input.
2. 2. An apparatus in accordance with daim 1 wherein the carbon dioxide input is automatically shut off unless the pressure chamber output is sealed by water.
3. 3. An apparatus in accordance with daim 1 or 2 wherein no electrical supply is required.
4. 4. An apparatus in accordance with claim 1 or 2 wherein control of the carbon dioxide gas input is by means of an equilibrium float valve.
5. 5. An apparatus in accordance with daim 1 or 2 wherein the output pressure is maintained at the water input pressure Y during normal operation.
6. 6. An apparatus in accordance with claim 1 or 2 wherein the relationship of water flow to water volume is such that the time lag between water input and water output is consistent and less than 30 seconds.
7. 7. An enclose chamber substantially as described herein with reference to the accompanying drawing.