Patent Application
20050008554
This invention relates to an apparatus and a process that can be used for producing an oxyhalo compound such as, for example, chlorine dioxide.
An oxyhalo compound is an important industrial chemical. For example, chlorine dioxide is a commercially important chemical for use as a bleaching, disinfection, oxidizing, fumigating, sanitizing or sterilizing agent and can replace chlorine and hypochlorite products traditionally used in such applications because it produces lower levels of chlorinated organic compounds than chlorine when it is used to treat raw water containing organic compounds. Chlorine dioxide is less corrosive than chlorine to metals. Production of chlorine dioxide is well known in the art. For example, U.S. Pat. No. 6,274,009 discloses a number of processes for its production. However, most processes disclosed present some disadvantages. Also, because of the potential safety hazards associated, the generation and use of chlorine dioxide solutions can be complex and requires sophisticated equipment thereby incurring unnecessary manufacturing cost. Development of a new apparatus and process for safely and efficiently producing chlorine dioxide can be a great contribution to the art.
An apparatus that can be used to produce an oxyhalo compound is provided which comprises a fluid proportioning device comprising three or more fluid transferring devices, a conduit to the inlet of each fluid transferring device, a conduit to the outlet of each cylinder, a water inlet to the device, and a water outlet from the device.
A process that can be used for producing a chemical is provided. The process comprises introducing a water flow to and through an apparatus to produce a downstream water; feeding three or more precursor chemicals at a proportional rate to each other to and through the apparatus by using the water flow as a motive force for proportionally feeding the precursor chemicals at a rate relative to the water flow; and combining the precursor chemicals with the downstream water whereby a chemical reaction occurs between two or more of the precursor chemicals. The apparatus can be the same as that disclosed above.
An apparatus that is capable of transporting three or more precursor chemicals or compounds to a reaction medium such as, for example, water for producing a product by reaction of two or more of these precursor chemicals is disclosed. The apparatus can comprise a fluid proportioning device, which comprises a water inlet; a water outlet; a main water-driven drive assembly; and a first, a second, a third, and optionally additionally fluid transferring devices. The water inlet is connectable to a water source and the fluid transferring device can comprise a transferring device inlet and a transferring device outlet, each being connectable to a conduit. The water source is capable of producing a water flow into and through the main water-driven drive assembly thereby producing a downstream water through said water outlet. Each of the fluid transferring devices is proportionally actuated by the water flow thereby withdrawing through the first, second, third, and optionally additional fluid transferring devices through which precursor chemicals are respectively drawn in a proportional amount independent of the flow rate of the water flow and discharging, for example, the precursor chemicals to said downstream water.
The fluid proportioning device can comprise an inlet end connectable to a water source with an inlet conduit. The proportioning device also comprises an outlet end connectable to an outlet conduit. Water can flow to the inlet and through the proportioning device exiting the outlet thereby creating a downstream water. The outlet end is connectable to the downstream water with the outlet conduit.
The main water-driven drive assembly is directly coupled to each of the respective fluid-fluid transferring devices, thus providing proportioned chemical feeds relative to the drive water flow.
The first, second, third, and optionally additional chemical inlet ports through which precursor chemicals can be respectively drawn into and through the fluid transferring devices by individual conduits. Through the fluid transferring devices, the proportioning device comprises a first, a second, a third, and optionally additional chemical outlet ports through which the precursor chemicals are respectively drawn to the downstream water by and through these individual conduits. The individual conduits can enter the downstream water at one or more locations, preferably at two or more locations or points.
Each fluid transferring device also comprises a metering piston.
The proportioning device can also comprise a piston actuator for reciprocally moving each metering piston within its respective fluid transferring device. The actuator can have an actuating fluid inlet and an actuating fluid outlet. The actuating fluid inlet can be connected to the conduit downstream of the inlet end. The actuating fluid outlet can be connected to the conduit upstream of the precursor chemical inlet ports therein. The actuator is generally responsive to a flow of water through the conduit to reciprocate each metering piston within its associated fluid transferring device thereby drawing a respective metered amount of precursor chemical from its source and to inject or introduce that metered amount of precursor chemical, which can be fixed or adjusted at the actuator, into the conduit through a chemical inlet port therein.
Referring to
Proportioning device 20 can be any suitable device disclosed above and can be a pump. A preferred pump is a proportioning pump such as that disclosed in U.S. Pat. No. 4,572,229 or U.S. Pat. No. 5,433,240 with the exception that three or more slave cylinders disclosed in the patents are used herein as fluid transferring devices. Each fluid transferring device can be the same as that disclosed in U.S. Pat. No. 4,572,229 or U.S. Pat. No. 5,433,240 with the exception that additional cylinders having connecting rods are included in the proportioning device used herein. The entire disclosures of these patents are incorporated herein by reference. Other devices that can be used include those disclosed in U.S. Pat. Nos. 3,131,707; 3,114,379; 3,213,873; 3,213,796; and 3,291,066.
The drive water flowing through the apparatus can be variable within the hydraulic limitations of the device and in doing so can self proportion the chemicals transferred through each of the fluid transferring devices, thereby delivering consistent concentrations of individual precursor chemicals to be reacted to produce a desired chemical, at a consistent concentration, such as an oxyhalo compound over the drive water flow range. That is, the concentration ratio of precursor chemicals can remain constant.
As the drive water exits the pump, it passes an in-line check valve (reference numerals 81, 82, and 83). Following this check valve are three individual chemical injection points. Optionally these three precursor chemicals can be injected or introduced simultaneously at one injection point. As each pump cycle is completed, the proportioned chemicals leaving the fluid transferring devices can be injected or introduced into each of these points (under pressure provided by the displacement portion of the piston cycle) or at the same point. Once injected or introduced, these precursor chemicals can be immediately diluted by the drive water that has passed through the proportioning device or pump. Once two or more precursor chemicals have been injected or introduced, they combine in-stream and react to form the desire product such as, for example, dilute solution of chlorine dioxide (ClO2) as disclosed below.
Alternatively, a portion of water can be diverted to by-pass conduit 35 or 75. Valve 34 or 74 can be used to control the amount water going through conduit 36 or 76 that is used to dilute precursor compounds exiting from proportioning device 20 or 60 via conduits 31, 32, and 33 (71, 72, and 73 in
Also disclosed in the invention is a process that can be used for producing an oxyhalo compound. An oxyhalo compound, as used herein, refers to a chemical compound containing at least one halogen and one oxygen in the molecule. Examples of suitable oxyhalo compounds include, but are not limited to, chlorine dioxide, bromine dioxide, hypochlorous acid, hypobromous acid, hypochlorites, hypobromites, chlorous acid, acidified sodium chlorite, and combinations of two or more thereof.
The process can comprise introducing a water flow to and through an apparatus disclosed above to produce a downstream water; feeding three or more precursor chemicals at a proportional rate to each other to and through the apparatus; and combining the precursor chemicals with the downstream water wherein the water flow is used as a motive force for proportionally feeding the precursor chemicals to and through the apparatus at a rate relative to the water flow whereby a chemical reaction occurs between two or more of the precursor chemicals.
The process can also comprise (a) flowing water through a fluid proportioning device, which can be as the one disclosed above to create a downstream water and to actuate the fluid transferring devices; (b) drawing three or more precursor compounds each from a separate source and flowing each of the precursor compounds separately through one of the fluid transferring devices; and (c) injecting or introducing the precursor compounds into the downstream water whereby a chemical reaction occurs between two or more of the precursor chemicals.
Any precursor chemicals known to one skilled in the art can be used. For example, suitable precursor compounds for producing chlorine dioxide are well known in the art. Illustrated examples include a metal chlorite that can be contacted with an acid to produce chlorine dioxide. Also for example, chlorine dioxide can be produced by contacting (1) a metal chlorite and (2) a metal hypochlorite with (3) an acid. A metal chlorite can be an alkali metal chlorite, alkaline metal chlorite, or combinations thereof. Example of metal chlorite includes sodium chlorite, potassium chlorite, or combinations thereof. Similarly, a metal hypochlorite can be an alkali metal hypochlorite, alkaline metal hypochlorite, or combinations thereof. Example of metal hypochlorite includes sodium hypochlorite, potassium hypochlorite, or combinations thereof. Any mineral acid can be used. Example of such acid includes sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, or combinations thereof. The molar ratio of metal chlorite to acid can be in the range of from about 0.001:1 to about 100:1 or about 0.001:1 to about 10:1 and that of metal hypochlorite to acid can also be in the range of from about 0.001:1 to about 100:1 or about 0.001:1 to about 10:1.
Suitable precursor compounds can also include a metal chlorate, an oxidizing agent, and an acid. For example, chlorine dioxide can be produced by contacting (1) a metal chlorate and (2) an oxidizing agent with (3) an acid. A metal chlorate can be an alkali metal chlorate, alkaline metal chlorate, or combinations thereof. Example of metal chlorate includes sodium chlorate, potassium chlorate, or combinations thereof. Any oxidizing agent such as inorganic oxidizing agent, organic oxidizing agent, or combinations thereof can be used. Example of oxidizing agent includes hydrogen peroxide, peracetic acid, oxides of nitrogen, sodium peroxide, benzoyl peroxide, m-chlorobenzoic acid, m-bromobenzoic acid, p-chlorobenzoic acid, or combinations thereof. Any acid disclosed above can be used. The molar ratio of metal chlorate to acid can be in the range of from about 0.001:1 to about 10:1 and that of oxidizing agent to acid can also be in the range of from about 0.001:1 to about 10:1.
Other precursor compounds for producing oxyhalo compounds include, but are not limited to; Sodium bromide and sodium hypochlorite, chlorine, organic acids and mineral acids.
The precursor compounds can be combined, for example, by mixing with a mechanical mixer or static mixer. The production can be carried out under any suitable conditions. It is preferred that an apparatus disclosed above be used for.
A chemical product such as chlorine dioxide in water can be transferred to a holding tank or to its ultimate end use, for example, a municipal water treatment plant or the treatment of waste in a sewage plant. A colorimeter can be used to monitor the chlorine dioxide concentration, if desired. The solution can also be monitored by pH meter and the pH can be accordingly adjusted to about 2.0-10 by any means known to one skilled in the art. Alternative means of monitoring include ORP (oxidation reduction potential), residual monitors, and spectrophotometric analyzers.
The process is preferably carried out at a turndown rate of at least about 40:1, preferably at least about 20:1, and more preferably at least 10:1. The term “turndown” is defined as the ratio of the maximum to the minimum oxyhalo compound, such as chlorine dioxide, production rate achievable by the equipment.
Also disclosed is a process for producing a ClO2-containing water. The process comprises flowing water to produce a downstream water; and feeding into the downstream water three or more precursor chemicals at a rate relative to the flow of the water and at proportional rates to each other thereby producing the ClO2-containing water in which the flowing water provides a motive force for proportionally feeding the precursor chemicals to the downstream water.
The dilute solution of ClO2 can be then directed to a point of application. Illustrative applications can include, but are not limited to, food contact sanitation, dairy sweet water systems, dairy process water disinfection (cooling water, heating water, potable), dairy pasteurizers, dairy CIP (cleaning-in-place) systems, dairy hard surface, sanitation/disinfection, dairy fermentor process aid, poultry plant process water disinfection (dip chillers and flash cool air chillers, scalders), poultry plant CIP sanitation/disinfection, poultry plant hard surface sanitation/disinfection, meat plant process water disinfection (cooling water, heating water, dip chillers, flash cool air chillers, brine shower chillers), meat processing carcass rinse, meat plant CIP sanitation/disinfection, meat plant hard surface sanitation/disinfection, fruit and vegetable processing plant process water disinfection (cooling water, heating water, hydro-cooler treatment, vegetable rinses, flume water), fruit and vegetable processor CIP systems, fruit and vegetable processing plant hard surface sanitation/disinfection, fruit and vegetable storage treatment (pre-storage treatment, humidification systems treatment), mushroom processing sanitation/disinfection, brewery/beverage plant process water disinfection (cooling water, heating water, potable water), brewery/beverage plant CIP systems, brewery/beverage plant hard surface sanitation/disinfection, pet-bone treatment/disinfection, animal drinking water disinfection, fogging and spraying swine, poultry, cattle, kennels, grow-out bins, aquaculture treatment, bio-film removal, waste water treatment, emulsions, chemical destruction (including but not limited to phenolics, nitrogen oxides (nox), sulfur oxides (SOx) and cyanides), oil well treatment, water storage systems, adhesives, paper manufacturing and recycling (white water disinfection, slime control, pulp bleaching and de-fluorescence), cooling towers , process water disinfection (incoming raw water, cooling water, heating water, grey water), air scrubbers, heating and ventilation systems, odor control, molluscicide, water filtration system treatment (bio-film removal/disinfection), hospitals, medical clinics, dental offices, nursing homes, laboratories, morgues, salons, domestic water treatment, recreational water disinfection (potable, stored), maritime water treatment (stored potable, black water, gray water, storage tank disinfection, bio-film removal), maritime hard surface sanitation, aviation water treatment (stored potable, tank disinfection, bio-film removal)), commercial water filtration system treatment (bio-film removal/disinfection), or combinations thereof.
The following examples are provided to illustrate the invention and are not to be construed as to unduly limit the scope of the invention.
Potable water was fed to an apparatus through a filter to remove particulate. A water booster pump was used to generate test pressures above available potable water line pressure. The apparatus including a triple headed hydraulic metering pump as shown in
Samples were withdrawn through the sample valve as described below and analyzed as described below. For some tests the configuration of the apparatus was varied as detailed below.
Precursor Chemicals Chlorine Dioxide was generated from the following precursor chemicals: (1) sodium chlorite solution (25% (w/w); obtained from IDI, North Kingstown, R.I., USA); (2) sodium hypochlorite solution (10.5% (w/w); purchased from RJ Pool, Cranston, R.I.; USA; assayed by iodometric titration at 12.4% (w/w) sodium hypochlorite); and (3) hydrochloric acid solution (31.45% (w/w); purchased from Mancini Hardware, North Kingstown, R.I.: USA).
Sampling and Analysis
Samples (250 ml each were drawn through the sample valve into brown Nalgene® sample bottles. Sampling and analysis was carried out as described in Standard Methods for the Examination of Water and Wastewater, 20th ed., 1998. Method 4500-ClO2 E, prepared and published jointly by; American Public Health Association, American Water Works Association, Water Environmental Association. Publication Office, Washington D.C. Sample chlorine dioxide concentration was determined using a Hach® (Loveland, Colo., USA) DR/2000 Direct Reading Spectrophotometer. The sample was diluted with 4 parts of de-ionized water, unless otherwise noted. This test was carried out to Hach's® DR/2000 Method 75 at a wavelength of 445 nm.
Sample pH was determined using an Orion® (Beverly, Mass., USA) combination pH probe and pH meter.
Chlorine dioxide was removed from samples by degassing with sparged air for a minimum period of 15 minutes.
De-gassed sample chlorite ion and chlorate ion was determined by use of a Dionex® (Sunnyvale, Calif,.) DX-120 Ion Chromatograph. A Dionex® AS40 Automated Sampler was used. All samples were analyzed in duplicate. A Dionex® AS9SC Column and ASRS suppressor was utilized with a 7 to 8 mM bicarbonate eluent with a 2 ml/minute flow. This method was consistent with EPA Method 300.
Calculations
Efficiency % was calculated as:
where [ClO2]=Chlorine Dioxide Concentration, mg/l and [ClO2−]=chlorite ion concentration, mg/l. [ClO2] and [ClO2−] were determined by method AM-100-07 revA or [ClO2] was determined by the DR/2000 spectrophotometer method 75 and [ClO2−] was determined by ion chromatography.
Yield, as defined in EPA Guidance Manual: Alternative Disinfectants and Oxidants, EPA, April 1999, pp. 4-3, yield was calculated as:
where [ClO3−]=chlorate ion concentration, mg/l and (67.45/83.45)=molecular weight ratio of ClO231 to ClO3−
Purity, as defined in EPA Guidance Manual: Alternative Disinfectants and Oxidants, EPA, April 1999, pp. 4-4, was calculated as:
where [FAC]=free available chlorine concentration as chlorine, mg/l.
This example illustrates that the invention provides high efficiency, yield and purity with low excess chlorine.
Eight samples were obtained with the sodium chlorite being fed at 85% of the maximum rate, sodium hypochlorite being fed at 100% of the maximum rate and hydrochloric acid being fed at 40% of the maximum rate. The motive water inlet pressure was adjusted to vary the chlorine dioxide solution flow. Two samples were taken at 1.5 US gallons per minute (GPM), four at 3.0 GPM and two at 6.0 GPM. This represented a chlorine dioxide production rate of 35 to 142 PPD (pounds per day) ClO2.
Excess chlorine as defined in EPA Guidance Manual: Alternative Disinfectants and Oxidants, EPA, April 1999, pp. 4-3, was measured at less than 0.1%. This represents an extremely low excess chlorine concentration.
Chlorine dioxide concentration was measured from 1940 to 2010 mg/l with a mean of 1974 mg/l. Chlorite ion concentration was measured from 1.0 mg/l to 6.1 mg/l, with a mean of 3.3 mg/l. Chlorate ion concentration was measured from 118 mg/l to 145 mg/l, with a mean of 132 mg/l.
The efficiency as measured by spectrophotometry and ion chromatography varied from 99.7% to 99.9% with a mean of 99.8%.
The yield as measured by spectrophotometry and ion chromatography varied from 94.2% to 95.3% with a mean of 94.7%.
The purity as measured by spectrophotometry and ion chromatography varied from 93.0% to 94.3% with a mean of 93.6%.
This example shows the effect of reduced chlorine dioxide solution flow rate.
The apparatus was run as in Example 1, but with reduced chlorine dioxide solution flow rates of 0.75 GPM and 0.30 GPM to demonstrate further turndown. For 0.75 GPM yield's of 93.9% and 93.8% was obtained. For 0.3 GPM 89.4% and 87.8% was obtained.
This example demonstrates that chlorate ion in the chlorine dioxide solution is present partially due to its presence as an impurity in the precursor sodium hypochlorite solution.
The apparatus was run as Example 1, but potable water was used in place of the sodium chlorite and hydrochloric acid feeds. A mean of 76 mg/l of chlorate ion was measured in the samples. This indicated that some of the chlorate measured in Example 1 formed as a byproduct of the chlorine dioxide generation, but is an impurity in the sodium hypochlorite feed. Recalculating the yield by compensating for this background chlorate resulted in yields from 97.1% to 98.3% with a mean of 98.7% for Example 1.
This example demonstrates the effect of changing hydrochloric acid feed rate.
The apparatus was run with the sodium chlorite being fed at 88% of the maximum rate, Sodium hypochlorite being fed at 100% of the maximum rate and hydrochloric acid being fed at between 30% and 50% of the maximum rate. The chlorine dioxide solution flow was kept at 3.0 GPM.
This example demonstrates that separating hypochlorite/acid and chlorite injection points improves yield For two samples, the apparatus was as shown in
This example shows that using a static mixer improve yield.
For four samples, the apparatus was the same as that disclosed for Examples 1-4 except that the static mixers were replaced with a schedule 80 pipe, which is well known to one skilled in the art. The yields obtained were from 93.7% about 94.0%, with a mean of 93.8%. This mean was 0.9% lower than the mean yield for Example 1, demonstrating that the static mixers improve yield.
This example illustrates using a static mixer between hypochlorite/acid and chlorite injection points.
For six samples, the apparatus was the same as that used Example 6. The yields obtained were from 93.0% to 95.9%, with a mean of 94.1 %. This mean is 0.6% lower than the mean yield for Example 1, demonstrating that the static mixers between the injection points improved the yield. The yields were also higher than for Example 6, demonstrating that the static mixer after the chlorite injection point improved yield.
This example shows the effect of ClO2 concentration turndown.
For these samples, the apparatus was the same as that used in Example 6. The ratio of the precursors to each other was kept constant, but the ratio to the motive water flow was reduced.
Combining the turndown ratios demonstrated in Example 1 by adjusting the chlorine dioxide solution flow and this example demonstrating turndown in chlorine dioxide production rate of at least 40:1.
This application claims the benefits of provisional application 60/486,456, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60486456 | Jul 2003 | US |
