초록 ▼

A small flow of a water with a high carbon dioxide content (normally a carbon-dioxide-saturated water) is produced using hollow-fiber membranes, and is uniformly mixed with a large flow of untreated water with constant proportions. Since the hollow-fiber membrane module has a reserve capacity for ad

A small flow of a water with a high carbon dioxide content (normally a carbon-dioxide-saturated water) is produced using hollow-fiber membranes, and is uniformly mixed with a large flow of untreated water with constant proportions. Since the hollow-fiber membrane module has a reserve capacity for adding carbon dioxide to the water, the resistivity of the mixed water is maintained at a constant level by maintaining constant proportions of the small and large flows, even if the total flow rate fluctuates due to fluctuations in the rate of water used in a subsequent process. Accordingly, no automated control device is particularly necessary in order to maintain the resistivity at a constant level. Therefore, a compact and simple apparatus can be produced which can operate at a low cost.

대표청구항 ▼

[ What is claimed is:] [1.] An apparatus for adding carbon dioxide gas to ultra pure water comprising:a housing to house a gas permeable membrane, the gas permeable membrane dividing the interior of the housing into an ultra pure water path and a carbon dioxide gas path, the housing having an openin

[ What is claimed is:] [1.] An apparatus for adding carbon dioxide gas to ultra pure water comprising:a housing to house a gas permeable membrane, the gas permeable membrane dividing the interior of the housing into an ultra pure water path and a carbon dioxide gas path, the housing having an opening for injecting carbon dioxide gas through which the carbon dioxide gas path communicates with the exterior of the housing,an inlet in fluid communication with a source of a fluctuating flow of untreated ultra pure water which communicates with the ultra pure water path,a distributing portion provided between the ultra pure water path and the inlet for untreated ultra pure water,an outlet for resistivity-controlled ultra pure water which communicates with the ultra pure water path,a combining portion which is provided between the ultra pure water path and the outlet for resistivity-controlled ultra pure water, anda bypass line through which the distributing portion communicates with a combining portion,wherein a fluctuating flow of untreated ultra pure water introduced from the inlet for untreated ultra pure water is divided into a flow for the ultra pure water path and a flow for the bypass line at constant flow rate proportions, and the gas permeable membrane supplies carbon dioxide gas to the untreated ultra pure water which passes through the ultra pure water path up to the saturation concentration or up to an approximately constant concentration near the saturation concentration at any flow rate in an expected fluctuation range. [12.] A process for adding carbon dioxide gas to ultra pure water comprising the steps of:dividing a fluctuating flow of untreated ultra pure water into two flows with constant proportions,producing carbon-dioxide-added ultra pure water by adding carbon dioxide gas to one of the flows of the untreated ultra pure water via a gas permeable membrane up to the saturation concentration or up to an approximately constant concentration near the saturation concentration, andcombining the carbon-dioxide-added ultra pure water and the other flow of untreated ultra pure water. A process for adding carbon dioxide gas to ultra pure water to produce a resistivity-controlled ultra pure water at a rate corresponding to a fluctuating rate of ultra pure water used in a subsequent process, the process for adding carbon dioxide to ultra pure water comprising the steps of:dividing a fluctuating flow of untreated ultra pure water, which is supplied at a rate corresponding to a rate of resistivity-controlled ultra pure water used in the subsequent process, into two flows, one of which is larger than the other, with constant proportions, by a distributing device,supplying the smaller flow to a hollow-fiber membrane module, in which the smaller flow and the flow of carbon dioxide gas are separated by a hollow-fiber membrane, so as to produce a carbon-dioxide-added ultra pure water, in which ultra pure water contains carbon dioxide at the saturation concentration or at an approximately constant concentration near the saturation concentration at any flow rate in an expected fluctuation range,combining the carbon-dioxide-added ultra pure water with the larger flow of the untreated ultra pure water, anduniformly mixing the combined water to produce ultra pure water which has a predetermined controlled resistivity. A process for adding carbon dioxide gas to ultra pure water according to claim 13, wherein the larger flow of untreated ultra pure water is made to flow in a bypass pipe line which is provided inside the hollow-fiber membrane module. A process for adding carbon dioxide gas to ultra pure water according to claim 13, wherein the proportion of the smaller flow to the larger flow is less than 1/50. A process for adding carbon dioxide gas to ultra pure water according to claim 13, wherein the carbon-dioxide-added ultra pure water is ultra pure water saturated with carbon dioxide. A process for adding carbon dioxide gas to ultra pure water according to claim 16, wherein the pressure of the carbon dioxide gas which is in contact with the hollow-fiber membrane is maintained at a constant level using a pressure regulating valve so as to maintain the concentration of the carbon-dioxide-added ultra pure water at the saturation concentration or at an approximately constant concentration near the saturation concentration, and wherein the flow of carbon dioxide gas is supplied at rates varied according to fluctuations in the smaller flow of the untreated ultra pure water.