FIELD

The disclosure relates to a chemical production system, and more particularly to a chlorine dioxide aqueous solution production system.

BACKGROUND

Chlorine dioxide aqueous solution is used for bleaching of woodpulp and the disinfection of municipal drinking water. Chlorine dioxide, when dissolved in water, is able to kill off bacteria and virus at a concentration of 2 to 10 ppm . As chlorine dioxide is less corrosive than chlorine, it is commonly used in many industrial water treatment applications as a bi ocide .

Under economical circumstances, such as avoiding product recall, the concentration of the chlorine dioxide aqueous solution from a production plant is usually higher than average, in order to ensure that it meets minimum quality standard. However, human inspection with spectrophotometry is required to conduct quality control effectively, which is not efficient for automated mass production process.

SUMMARY

Therefore, an object of the disclosure is to provide a chlorine dioxide aqueous solution production system that can alleviate the drawback of the prior art. According to the disclosure, the chlorine dioxide aqueous solution production system includes a chlorine dioxide generating device, and a mixing and measuring device. The chlorine dioxide generating device includes an electrolysis unit that is adapted for generating gaseous chlorine dioxide by electrolysis. The mixing and measuring device includes a mixing unit, a measuring unit, and a control unit.

The mixing unit has a chlorine dioxide aqueous solution mixer that is connected to the electrolysis unit, a transporting pipe that is connected to the chlorine dioxide aqueous solution mixer, a container set and a control valve set. The container set is connected to the transporting pipe such that water flowing from the container set into the chlorine dioxide aqueous solution mixer and the gaseous chlorine dioxide advanced from the electrolysis unit are mixed together to form chlorine dioxide aqueous solution which circulates through the transporting pipe and the container set. The control valve set is mounted on one of the container set and the transporting pipe, and is operable for permitting and blocking the circulation of water and the chlorine dioxide aqueous solution. The measuring unit is mounted on the transporting pipe of the mixing unit for measuring redox potential of the chlorine dioxide aqueous solution passing therethrough. The control unit is electronically connected to the control valve set of the mixing unit and the measuring unit, and compares the measured redox potential value from the measuring unit with a predetermined value for actuating and terminating operation of the control valve se t .

BRIEF DESCRI PTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which:

FIG. 1 is a partly schematic side view of a chlorine dioxide generating device of an embodiment of a chlorine dioxide aqueous solution production system according to the disclosure;

FIG. 2 is a partly schematic side view of a mixing and measuring device of the embodiment; and

FIG. 3 is a graph of relationship between redox potential and concentration of chlorine dioxide aqueous solution.

DETAILED DE SCRI PTION

Referring to FIGS. 1 to 3, an embodiment of a chlorine dioxide aqueous solution production system according to the disclosure has a chlorine dioxide generating device 1 andamixingand measuring device 2. The chlorine dioxide aqueous solution production system is adapted for producing chlorine dioxide aqueous solution from an electrolytic solution and water. The chlorine dioxide generating device 1 includes an electrolysis unit 11. The chlorine dioxide generating device 1 also includes a feeding unit 12, a cleaning unit 13, and a thermostat unit 14, each of which is connected to the electrolysis unit 11.

The electrolysis unit 11 includes an electrolytic cell 111 adapted for performing electrolysis of the electrolytic solution, a gas transporting pipe 112 that interconnects the electrolytic cell 111 with the mixing and measuring device 2, and a waste exhaust pipe 113 that is connected to the electrolytic cell 111. After gaseous chlorine dioxide is generated from the electrolytic solution in the electrolytic cell 111, it is collectedby the gas transportingpipe 112 for further uses in the mixing and measuring device 2. Byproducts of the electrolysis, primarily liquid substances, are removed from the electrolytic cell 111 through the waste exhaust pipe 113. The electrolytic cell 111 mentioned in this disclosure is a known technology and will not be discussed in further detail.

The feeding unit 12 is operable for feeding electrolytic solution to the electrolysis unit 11. The feeding unit 12 includes a raw material tank 121 that dissolves raw salt with solvent to form the electrolytic solution, and an electrolytic solution tank 122 that interconnects the raw material tank 121 and the electrolytic cell 111 through connecting pipes. The abovement ioned raw salt may be sodium chloride or sodium chlorite, the solvent may be water , and the electrolytic solution may consequently be aqueous solution of sodium chloride or sodium chlorite. After filtration of solid particles, the electrolytic solution from the raw material tank 121 is transported to and stored in the electrolytic solution tank 122. The electrolytic solution is further fed to the electrolytic cell 111 to undergo electrolysis.

The cleaning unit 13 is operable for water-flushing the electrolysis unit 11 when it is not in use. In this embodiment, the cleaning unit 13 is a pipe that transports tap water into the electrolytic cell 111 for water- flushing . After cleaning, the tap water is also removed from the electrolytic cell 111 through the waste exhaust pipe 113.

The thermostat unit 14 is operable for controlling temperature of the electrolysis unit 11 through the process of heat exchange utilizing refrigerant. The thermostat unit 14 includes a cooler 141 that cools temperature of refrigerant, and a cooling pipe 142 that allows the refrigerant to circulate between the electrolytic cell 111 and the cooling 141. The process ofheat exchange utilizing refrigerant as aworking fluid is a known mechanical process and will not be discussed in details .

The mixing and measuring device 2 includes a mixing unit 21 that mixes the gaseous chlorine dioxide advanced from the electrolysis unit 11 with water to form chlorine dioxide aqueous solution, a measuring unit 22 that is mounted on the mixing unit 21, and a control unit 23 that is electronically connected to the measuring unit

22.

In this embodiment , the mixing unit 21 has a container set 210 that includes four containers 211, a transporting pipe 212 that is connected to and surrounds the container set 210 and that aligns the containers 211 in parallel, a water inlet 213 that has a plurality of branch pipes connected respectively to the containers 211, a chlorine dioxide aqueous solution mixer 214 that is mounted on the transporting pipe 212 and that is connected to gas transporting pipe 112 of the electrolysis unit 11, and a control valve set 215 that is mounted on the transporting pipe 212.

Each of the containers 211 stores the chlorine dioxide aqueous solution of varying concentration, ranging from zero, containing only the water from the water inlet

213, to an amount satisfactory to meet minimum standard. The transporting pipe 212 circulates the flowing fluid (chlorine dioxide aqueous solution or water) through the containers 211 and the chlorine dioxide aqueous solution mixer 214. The chlorine dioxide aqueous solution mixer 214 is operable to mix the gaseous chlorine dioxide advanced from the electrolysis unit 11 with the flowing fluid, increasing its chlorine dioxide concentration. The chlorine dioxide aqueous solution mixer 214 is a prior art disclosed in PCT publication number WO/ 2017 / 113111 , and will not be discussed in further details in this disclosure. The control valve set 215 includes a plurality of control valves 216 that are mounted on the transporting pipe 212 and that are electronically connected to the control unit 23. In this embodiment, the control valves 216 are grouped into pairs , each pair being respectively located at opposite sides of a respective one of the containers 211, being operable for permitting and blocking the circulation of the water and the chlorine dioxide aqueous solution via the respective one of the containers 211, and being able to be manually controlled when not electronically connected.

The measuring unit 22 includes an ORP (Oxidation-Reduction Potential) meter 221 mounted on the transporting pipe 212 between the chlorine dioxide aqueous solution mixer 214 and one of the containers 211 which is closest to the chlorine dioxide aqueous solution mixer 214, and a display monitor 222 digitally connected to the ORP meter 221. The ORP meter 221 of the measuring unit 22 is operable to measure redox potential of the chlorine dioxide aqueous solution passing therethrough and to process a digital signal to be sent to the display monitor 222 and the control unit 23. The display monitor 222 simply displays the redox potential value measured.

The control unit 23, which is a computer in this embodiment, receives and compares the measured redox potential value from the ORP meter 221 with a predetermined value for actuating and terminating operation of the control valve set 215.

To determine the predetermined value for the control unit 23, it is recommended to make a graph establishing relationship between redox potential and concentration of the chlorine dioxide aqueous solution, similar to the one shown in FIG. 3, by sampling a set amount of data to plot a best-fit curve. In this embodiment, By assigning variable y as the redox potential (mV) and variable x as the concentration of the chlorine dioxide aqueous solution (ppm) , an equation of the best-fit curve with y = 74.8681n (x) +670.95 (eq.l) is established with R ² = 0.9764, representing an almost perfect fit. The abovement ioned formula (eq.l) may also be expressed in terms of x as well : x = exp [ ( y- 670.95 ) / 74.868 ] ( eq . 2 ) .

One may simply utilize interpolation and exterpolation , or use professional data processing applications such as Origin or SigmaPlot to determine the abovement ioned relationship. With the graph and the equation on hand, it is easier to build a chart (shown below) to select the predetermined value for the control unit 23.

CIO ₂ Concentration (ppm) Redox Potential (mV) 2000 1211

1500 1206

1000 1192

750 1178

500 1154

250 1113

100 1049

50 915

25 902

10 846

5 794

To begin the operation of the disclosure, one is ought to initiate the mixing unit 21 by filling the containers 211 with water from the water inlet 213 first, which in turns circulate the water throughout the transporting pipe 212 and the chlorine dioxide aqueous solution mixer 214. Then, the chlorine dioxide generating device 1 is initiated, such that the feeding unit 12 feeds electrolytic solution to the electrolytic cell 111, which in turns generates gaseous chlorine dioxide by electrolysis. The gaseous chlorine dioxide is collected by the gas transporting pipe 112 and is transported to the chlorine dioxide aqueous solution mixer 214 of the mixing unit 21, while the byproducts of the electrolysis is transported out of the system through the waste exhaust pipe 113. The gaseous chlorine dioxide is mixed together with the water in the chlorine dioxide aqueous solution mixer 214 to form chlorine dioxide aqueous solution, which circulates into the containers 211. The chlorine dioxide aqueous solution in the container 211, driven by the ongoing fluid circulation throughout the transporting pipe 212, is then driven back into the chlorine dioxide aqueous solution mixer 214 yet again, mixing with more gaseous chlorine dioxide to increase its concentration. The process repeats.

The measuring unit 22 constantly measures the redox potential passing therethrough and sends the signal to the control unit 23 for value comparison. Once the measured value exceeds or equals to the predetermined value, the concentration of the chlorine dioxide solution has reached minimal standard, in which the control unit 23 is operable to send signals to terminate operation of the control valves 216 and to stop the circulation of fluid in the mixing and measuring device 2. The containers 211 would have the finished products ready for shipping, and may be replaced with a new set of containers 211 for the next production. The automated measurement of the measuring unit 22 and the control unit 23 alleviate the need for human sampling.

When setting up a predetermined value, one may assign the redox potential value that corresponds to the desired concentration value. It is also possible to assign the value in concentration value, by having the control unit 23 convert the redox potential value into the equivalent concentration value when it compares values. In other embodiments, the measuring unit 22 may be assigned to directly convert the redox potential value into the equivalent concentration instead when sending signals to the display monitor 222 and the control unit 23.

In addition, the number of containers 211 is subject to change, and is not restricted to the four containers 211 mentioned in this embodiment. Likewise, the number of control valves 216 should corresponds to the number of the containers 211. Lastly, it should be mentioned that, while the electronic communication in this embodiment is connected directly by wires, it may also be wireless in other embodiments.

In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details.

It should also be appreciated that reference throughout this specification to "one embodiment," "an embodiment," an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects.

While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.