Chlorine dioxide generation

Abstract

Devices and methods for safely using acid/chlorite ClO.sub.2 generator chemistry for water treatment, whereby a valve prevents chemical draw unless there is both vacuum within the reaction chamber as well as suitable water volume in the flow chamber for dilution, are described. The float-dependent valve can also allow for direct venting from the reaction chamber to the flow chamber in the event of elevated pressure in the reaction chamber. This approach delivers an inherently safer ClO.sub.2 generator design for systems that utilize high strength reactor zones with ClO.sub.2 concentration above 3,000 ppm.

Claims

1. A device comprising: (a) a reaction chamber wherein chemicals are mixed to generate chlorine dioxide; (b) an eductor that provides a vacuum within the reaction chamber and a motive water supply to deliver chlorine dioxide into a flow chamber; (c) the flow chamber operably connected to the reaction chamber via the motive water conduit; and (d) a float-dependent valve that provides a second connection between the reaction chamber and flow chamber and that serves as: i) a safety interlock that prevents chemical flow without having a sufficiently flooded flow chamber to dilute the generated chlorine dioxide, wherein the ratio of the flow chamber volume to the reaction chamber volume ensures chlorine dioxide concentration no higher than 3,000 ppm within the flow chamber; ii) a relief vent from the reaction chamber to the flow chamber should the reaction chamber experience a higher pressure than the flow chamber; and iii) a drainage component of the reaction chamber into the flow chamber in the absence of eductor-driven vacuum, thus preventing long-term storage of highly concentrated reactor liquor (>3,000 ppm chlorine dioxide) as well as facilitating reactor chamber maintenance or decommissioning.

2. The device of claim 1, wherein the float-dependent valve is an inverted, ball check valve and the ball component of this valve has a density lower than that of a process fluid yet has large enough mass to prevent closure of the valve under eductive vacuum alone.

3. The device of claim 1, wherein the float-dependent valve comprises a design in which a dynamic seating component of the check valve is a shape other than spherical yet its position, open or closed, is dependent upon floatation in the process fluid and vacuum in the reaction chamber.

4. The device of claim 1, wherein the float-dependent valve comprises a gasket.

5. The device of claim 4, wherein the gasket is a flexible gasket.

6. The device in claim 1, wherein an alkali metal chlorite is mixed with a mineral acid solution to generate chlorine dioxide.

7. The device in claim 1, wherein an alkali metal chlorate is mixed with a mineral acid solution to generate chlorine dioxide.

8. A device comprising: a reaction chamber having a first volume; an eductor; a flow chamber having a second volume, the flow chamber operably connected to the reaction chamber via a motive water conduit; and a float-dependent valve operably connected to the reaction chamber and the flow chamber; and wherein the float-dependent valve prevents chemical flow into the flow chamber if the flow chamber is not sufficiently flooded.

9. The device of claim 8, wherein the ratio of the second volume to the first volume is configured to prevent a concentration of chlorine dioxide from exceeding about 3,000 ppm.

10. The device of claim 8, wherein the float-dependent valve comprises an inverted ball check valve comprising a ball component.

11. The device of claim 10, wherein the ball component has a density lower than a process fluid density and a mass configured to prevent closure of the inverted ball check valve under eductive vacuum alone.

12. The device of claim 8, wherein the float-dependent valve comprises a dynamic seating component having a non-spherical shape, and wherein a position of the float-dependent valve depends upon floatation in a process fluid and a vacuum in the reaction chamber.

13. The device of claim 8, wherein the float-dependent valve comprises a gasket.

14. The device of claim 13, wherein the gasket is a flexible gasket.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic for a two-part reactor assembly with a reaction chamber upstream of the eductor.

(2) FIG. 2 shows a detailed view of the eductor and reactant feed lines that reside at the top of the reaction chamber in accordance with the present disclosure.

DETAILED DESCRIPTION

(3) The above summary of the present invention is not intended to describe each illustrated embodiment or every possible implementation of the present invention. The detailed description, which follows, particularly exemplifies these embodiments.

(4) Before the present compositions and methods are described, it is to be understood that they are not limited to the particular compositions, methodologies or protocols described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit their scope, which will be limited only by the appended claims.

(5) It must be noted that as used herein and in the appended claims, the singular forms a, an, and the include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments disclosed, the preferred methods, devices, and materials are now described.

(6) As used herein, the term chlorine dioxide (ClO.sub.2) means a chemical used as a broad-spectrum biocide and selective oxidizer that has a broad range of utility in water treatment. Due to its instability at high concentration, it is typically produced on site from precursor chemicals and immediately diluted into the process water supply being treated.

(7) As used herein, the term floating ball check valve means a check valve that uses a ball as the internal component that seals against the valve body to stop flow and in which the ball has a density lower than the fluid medium being processed such that the ball floats.

(8) As used herein, the term flow chamber means a vessel that either fully or partially surrounds the reaction chamber and through which a bulk of the process water being treated flows. It is sized to allow for adequate dilution of the reaction chamber, such that in a non-flow condition, complete emptying of the reaction chamber contents into the flow chamber would render a ClO.sub.2 concentration no higher than 3,000 ppm.

(9) As used herein, the term reaction chamber means a vessel in which precursor chemicals are combined to generate ClO.sub.2.

EXAMPLES

(10) Using 7.5 wt % NaClO.sub.2 and 15 wt % HCl precursor solutions, maximum and minimum ClO.sub.2 production flows were determined according to inlet pressure, outlet pressure, motive water flow rate, and process water flow. The system hardware was fixed although manual flow rate control valves were used for the precursors to vary the PPD ClO.sub.2 generated. The system achieved 6-36 PPD ClO.sub.2 production rates. After verifying acceptable conversion efficiency in the system, several scenarios were tested to validate the safety features of the device, as further described below.

Example 1: Process Flow Interruption

(11) After the device had produced ClO.sub.2 for 30 minutes, the process water was turned off to simulate a system that was shut down before it had time to be purged or emptied. With the process flow supply interrupted, the flow to the eductor was also interrupted, and the vacuum on the reaction chamber halted. At this point, the float-dependent valve 18 opened and allowed the contents of the reaction chamber to slowly drain into the flow chamber. This safety measure minimizes the risk of ClO.sub.2 vapors building up in an enclosed reaction chamber volume.

Example 2: Low Acid Flow and Extended Dwell Time

(12) In a more extreme set of circumstances, the acid feed was lowered to simulate a system that had not been properly configured to correct precursor feed ratios. When the acid feed is low, the ClO.sub.2 concentration within the reaction chamber can be considerably higher if there is sufficient dwell time to convert the chlorite to ClO.sub.2. In a shutdown scenario, the ClO.sub.2 can continue to form over time after shutdown. Under these conditions, the float-dependent valve 18 sufficiently drained and diluted the reaction chamber 10 contents into the flow chamber 16 before any decomposition events occurred.

Example 3: Pressure Event Within the Reaction Chamber

(13) A test was conducted in which water was forced through the acid feed at a rate of 310 gallons per day (GPD) while the pressure of the reaction chamber was monitored. With the float-dependent valve 18 in place, the maximum pressure achieved in the flow chamber was 1.2 psig. The check valve was then replaced by a plug to prevent venting, and the test was repeated. Applying the same flow rate of 310 GPD, the reaction chamber pressure increased to 4.4 psig, which is a nearly 4 times greater pressure differential between the reaction chamber 10 and the flow chamber 16. In these tests, the flow chamber 16 was being emptied to an open container, and did not have significant back pressure.

(14) The iteration without the float-dependent valve 18 is similar to traditionally constructed AC ClO.sub.2 generators, in which the reaction chamber consists of only two feed inlets and a single outlet being diluted into a process water supply. Therefore, in the case of a decomposition event within the reaction chamber 10, the modified design would readily release its contents into the process water flow, providing much quicker dilution and lower internal shock pressures as compared to a traditionally designed AC ClO.sub.2 generator.

Example 4: Insufficiently Filled Flow Chamber

(15) In this experiment, we attempted to start the ClO.sub.2 generator without having sufficient fluid level in the flow chamber 16. In this case, no chemical flow occurred, because no vacuum could be maintained within the device. Without a sufficiently filled flow chamber 16, the float-dependent valve 18 did not seal and did not allow a vacuum to be established within the reaction chamber 10.

Example 5: Reaction Chamber Drainage

(16) The float-dependent valve 18 also allows for faster and easier drainage when preparing the device or system for maintenance or inspection. Upon draining the flow chamber 16, the check valve float-dependent valve 18, flow out of the reaction chamber 10 would slow to a trickle, or may even require complete disassembly to empty its contents.

(17) While the present disclosure has been illustrated by the description of exemplary embodiments thereof, and while the embodiments have been described in certain detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the disclosure in its broader aspects is not limited to any of the specific details, representative devices and methods, and/or illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the Applicant's general inventive concept.