Patent Description:
Total organic carbon is a well-established water quality parameter that quantifies the overall concentration of organic substances, all of which are typically regarded as contaminants, in an aqueous environment. Total organic carbon in an aqueous sample may be composed of either one or two components-dissolved organic carbon (DOC) and particulate organic carbon. The measurement of DOC is conventionally accomplished by filtering the water sample, commonly through a <NUM>-µm filter, to remove particulate organic carbon prior to performing an analysis for DOC. The limitations of conventional apparatus and techniques for Such analysis often lead to the result that only DOC is effectively measured, instead of TOC, because the particulates in a sample containing both forms of organic carbon typically cause errors in the measurement and plug fluid passages causing hardware failures.

In the following description, DOC is used to refer to measurements in which the sample has first been filtered to remove particulates, while TOC is used herein to refer to measurements in which the sample has not been filtered. In other respects, however, the following description is relevant to both DOC and TOC measurements.

In one known approach DOC and/or TOC, the organic compounds in an aqueous sample are oxidized to carbon dioxide (CO<NUM>) and the CO<NUM> in the sample is then measured. In addition to organic carbon components, the water sample may initially contain CO<NUM> and other inorganic forms of carbon (e.g., in the form of bicarbonate and carbonate salts). Together, these forms of inorganic carbon are referred to herein as IC. Total carbon (TC) concentration in an aqueous sample is therefore the sum of the TOC and IC concentrations.

The measurement of total organic carbon in a sample relies on the conversion of organic carbon to carbon dioxide. The more common methods have been high temperature combustion, vaporizing the sample and heating the gas to over 600C. Air or oxygen is used to react with the organics at high temperature to accomplish the conversion of organic carbon to carbon dioxide. The other common method has been to mix the liquid sample an oxidizing agent such as persulfate and then activate the persulfate with heat or ultraviolet radiation. The activated persulfate will convert the organic carbon to carbon dioxide. After conversion the carbon dioxide is measured and the amount of organic carbon is calculated based on the amount of carbon dioxide measured.

Both these methods have drawbacks. Samples containing high salt concentrations such as sodium chloride in brine will cause maintenance issues with combustion techniques. Salt will deposit in high temperature furnace of combustion instruments. If these samples are repeatedly introduced to the furnace it will eventually clog and have to be cleaned. The persulfate method also suffers when high salt solutions are analyzed. The chloride is converted by the oxidizing agent to chlorine placing a high demand for the addition of oxidizer to the sample.

Furthermore, conventional measurement apparatus using high-temperature combustion trap a water sample in a reactor along with a small amount of air and oxidizing agent. A heater on the outside of the reactor heats the reactor (and sample) to the required temperature. However, the current configuration of the reactor has drawbacks. The time it takes to heat the reactor to temperature is slow and not uniform. The heater is not in contact with the reactor so the heater heats up the air around the heater and also transfers heat due to radiation. The heater is not in contact with the reactor so that after the reaction occurs it needs to be cooled down quickly to prepare for the next sample. The other drawback is that installing a temperature measuring device on the reactor may cause local heat transfer to be altered in the region where the device is attached.

Document <CIT> describes the carbon measurement in aqueous samples using oxidation at elevated temperatures and pressures. A reactor heater element has a tubular configuration open at both ends and located inside a heater housing with the reactor mounted inside the tubular portion of the heater.

These and other limitations of, and deficiencies in, the prior art approaches to IC, TOC and TC measurements are over come in whole, or at least in part, by the methods and apparatus of the described embodiments.

By contrast with the limitations of the prior approaches to making such carbon concentration determinations in aqueous samples, as discussed above, the methods and apparatus described herein are capable of measuring all of the aforementioned parameters in samples that contain concentrations of TOC, dissolved solids, and particulates. In general a sample is drawn into the analyzer described herein, reagents are added, and the sample is diluted as necessary, and then the sample enters the oxidation reactor where super critical water oxidation is used to effect the conversion of organic carbon to carbon dioxide. The critical point of water is 374C and 3200psia. To reach these temperatures and pressures the water sample is trapped in the reactor with a small amount of air and oxidizing agent. Because it is a closed system the pressure inside the tube reaches the critical point. Under these conditions organics as well as organic particles are converted to carbon dioxide.

Described herein are embodiments of a measurement apparatus and a method of sample heating wherein the reactor is resistively heated by passing electrical current directly through a tube of the reactor and measuring the temperature of the reactor using non-contact devices such as an IR sensor. Having the reactor reach the critical temperature faster allows for shorter throughput time of measurement and quicker results. While some conventional measurement apparatus take approximately <NUM> seconds to reach temperature, the use of resistive heating as described herein takes approximately <NUM> seconds. It also allows for less overshoot and a tighter temperature accuracy.

In one aspect, the present disclosure relates to an apparatus for treating a liquid sample containing organic material. The device includes: (a) a reactor having reactor inlet and reactor outlet ports and a reactor interior for containing a liquid sample under above-ambient temperature and pressure conditions; (b) high pressure fluid reactor valve members at said reactor inlet and reactor outlet ports, said reactor valve members allowing fluid flow respectively into or out of the reactor interior when in an open-valve mode or, alternatively, capable of sealing the reactor interior when in a closed-valve mode; (c) a reactor heating system including an electrical current source operably connected to the reactor, the electrical current source configured to pass an electrical current through the reactor to rapidly and cyclically heat the reactor interior and a liquid sample sealed in the reactor interior to a temperature of about <NUM>° C. to <NUM>° C. or higher, while the reactor interior and the reactor valve members maintain the sample under sealed conditions; and, (d) a reactor cooling system adapted for rapidly and cyclically cooling the reactor interior and a reactor product sealed in the reactor interior following a heating cycle.

In one embodiment, a sensor is configured to determine a temperature value of the reactor.

In one embodiment, the sensor is configured to measure electromagnetic radiation.

In one embodiment, the sensor is configured to measure infrared radiation.

In one embodiment, the sensor is operably connected to the reactor heating system.

In one embodiment, the sensor is operably connected to the reactor cooling system.

In one embodiment, the reactor is comprised of titanium and its alloys, tantalum, Inconel <NUM>, Hastelloy C-<NUM>, or combinations thereof.

In another aspect, the present disclosure relates to a method for treating a liquid sample containing organic material utilizing a liquid sample treatment apparatus. The method includes: (a) providing a liquid sample treatment apparatus comprising the following features: (i) a reactor having reactor inlet and reactor outlet ports and a reactor interior for containing a liquid sample under above-ambient temperature and pressure conditions; (ii) high-pressure fluid reactor valve members at said reactor inlet and reactor outlet ports, said reactor valve members allowing fluid flow respectively into or out of the reactor interior when in an open-valve mode or, alternatively, capable of sealing the reactor interior when in a closed-valve mode; (iii) a reactor heating system comprising an electrical current source operably connected to the reactor, the electrical current source configured to pass an electrical current through the reactor to rapidly and cyclically heat the reactor interior and a liquid sample sealed in the reactor interior to a temperature of about <NUM>° C. to <NUM>° C or higher, while the reactor interior and the reactor valve members maintain the sample under sealed conditions; and, (iv) a reactor cooling system adapted for rapidly and cyclically cooling the reactor interior and a reactor product sealed in the reactor interior following a heating cycle. ; (b) mixing a known volume of the sample with one or more other liquids selected from oxidizer, acid and dilution water to form a sample mixture; (c) flowing at least a portion of the sample mixture into the interior of the reactor, said reactor being adapted to be alternately and repeatedly opened and sealed at the reactor inlet and reactor outlet ports; (d) sealing the portion of sample mixture in the interior of the reactor by closing the valve members at the reactor inlet and reactor outlet ports; (e) passing an electrical current through the reactor for a time sufficient substantially to oxidize the organic material and form the reactor product; (f) stopping the heating step and then rapidly cooling the interior of the reactor and the reactor product inside to substantially ambient conditions to form cooled liquid and gaseous reactor products; and, (g) opening the reactor and removing the cooled liquid and gaseous reactor products form the reactor interior.

In one embodiment, the interior of the reactor and the sample portion inside is rapidly heated to a temperature between <NUM>° C. to about <NUM>° C.

In one embodiment, a sensor is provided, the sensor configured to measure a temperature value of the reactor.

In one embodiment, a signal generated by the sensor is used to decide when to stop the heating step.

Other systems, methods, features and/or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be protected by the accompanying claims.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments and together with the description, serve to explain the principles of the methods and systems:.

<FIG> is a block schematic of one embodiment of an automated carbon measurement apparatus/analyzer illustrating five component sub-assemblies <NUM> to <NUM> that comprise the analyzer. As illustrated in <FIG>, an aqueous sample is drawn into a sample handling sub-assembly <NUM> of the apparatus, where the desired volumes of acid reagent and/or oxidizer reagent are added to a selected volume of sample. The sample may also be diluted at this stage with low-TOC dilution water if necessary before being passed to reactor sub-assembly <NUM>. Additional details about the shown and described measurement apparatus/analyzer can be found in <CIT>; <CIT>; <CIT>; and <CIT>. The sample, reagents and dilution water if any are mixed in the sample-handling portions of the apparatus to create a sample mixture comprising a substantially homogenous solution or suspension. If NPOC is to be measured, the acidified sample mixture also is sparged with CO<NUM>-free gas provided by the gas control sub-assembly/module <NUM>. The flow rate of the sparge gas is controlled to ensure that IC in the sample is removed efficiently and substantially completely. If TC or IC is to be measured, the sample mixture is mixed but not sparged.

A portion of the homogenous solution/suspension is then transferred to the reactor sub-assembly <NUM>. If NPOC or TC is to be measured, the solution/suspension containing oxidizer is heated in a sealed reactor to oxidize the organic compounds in the solution/suspension, and then it is cooled to near room temperature. If IC is to be measured, oxidizer is not added to the solution/suspension. In this case, the solution/suspension may be warmed to facilitate conversion of bicarbonates and carbonates to CO<NUM>. , but it is not heated so much that oxidation of organic compounds occurs.

Next, a stream of carrier gas from the gas control assembly/ module <NUM> transfers the liquid and gas products in the reactor sub-assembly <NUM> to a gas/liquid separator sub-assembly/module <NUM>. The liquid exits the analyzer from the gas/liquid separator module <NUM> while the gas product, containing the CO<NUM>, flows to the NDIR detector sub-assembly <NUM>. After the CO<NUM>, in the gas product is measured, the gas product and carrier gas mixture can be flowed through the gas/liquid separator module <NUM>, and vented to the atmosphere.

<FIG> is a schematic showing the several fluidic components of an embodiment of the apparatus in more detail. In <FIG>, sub-assemblies <NUM> to <NUM> as shown in <FIG> are delineated by broken lines. The sample-handling sub-assembly <NUM> comprises a syringe <NUM> that is connected through a three-way valve <NUM> to a coil of tubing <NUM> and a dilution water reservoir <NUM> containing low-TOC dilution water. A representative practice using the apparatus as illustrated in <FIG> is described below. It will be understood, however, that alternative sequences and methods for introducing the sample, reagent(s) and dilution water into the system could be used consistent with the scope of this invention. For example, using the apparatus illustrated in <FIG>, the oxidizer and acid reagents could be moved from coil <NUM> to a mixing location in the apparatus, such as to mixer/sparger <NUM>, prior to introducing the sample into the system in order to maintain a separation between these components until they are ready to be mixed at the mixing location.

Initially, the syringe is empty, and the valve <NUM> and coil <NUM> contain only dilution water. The volume of coil <NUM> is designed and selected to be at least as large as, and preferably larger than, the volume of syringe <NUM>, so the only liquid that can enter the syringe is dilution water from coil <NUM> or reservoir <NUM>. When an analysis begins, valve <NUM> is open, and valves <NUM>, <NUM>, and <NUM> are closed. Syringe <NUM> starts filling with dilution water drawn from a syringe end of coil <NUM>, which causes oxidizer reagent from oxidizer reagent reservoir <NUM> to be drawn through the six-way fluid element <NUM> and into a sample/reagent end of coil <NUM>. When syringe <NUM> has drawn the required volume of oxidizer into the sample/reagent end of coil <NUM>, Syringe <NUM> stops momentarily and valve <NUM> closes. Valve <NUM> opens and syringe <NUM> draws additional dilution water from the y syringe end of coil <NUM> into syringe <NUM>, which in turn draws the required volume of acid from acid reservoir <NUM> into the sample/reagent end of coil <NUM>, where it may partially mix with the oxidizer reagent already in this end of coil <NUM>. When the desired volume of acid has entered coil <NUM>, the syringe <NUM> stops momentarily, valve <NUM> closes, and valve <NUM> opens to allow the required volume of sample to be drawn into the sample/reagent end of coil <NUM>, as additional dilution water from the syringe end of coil <NUM> is drawn into syringe <NUM>. When the required volume of sample has entered the coil, syringe <NUM> stops again, and valve <NUM> closes. The coil <NUM> now contains the desired volumes of oxidizer, acid, and sample solution required for the measurement. Coil <NUM> may or may not contain a material amount of dilution water at this point, depending on the internal volume of coil <NUM> relative to the volumes of oxidizer, acid and sample drawn into coil <NUM>, and also depending upon whether or not the sample requires dilution prior to analysis.

It will be understood that, if the procedure described above took any significant amount of time to complete, there would be an opportunity for oxidizer reagent or, perhaps, even acid, from the sample/reagent end of coil <NUM> to diffuse into dilution water at the syringe end of coil <NUM>, which could lead to contamination of the syringe. In practice, however, the several steps of filling coil <NUM> are completed in a sufficiently short time that there is no opportunity for reagents drawn into the sample/reagent end of coil <NUM> to diffuse into the dilution water at the syringe end of coil <NUM>.

In some cases, the source of the sample is a long distance from the analyzer, especially when embodiments of the analyzer described herein is used to monitor a process stream of an industrial operation. In such a situation, the analyzer may not provide real-time measurements if the only way of pumping the sample to the analyzer were the syringe pump. Therefore, in one of the embodiments described herein, the apparatus also includes a pump <NUM> which can rapidly draw a fresh portion of sample to the six-way union <NUM>. Once the new sample portion has been delivered to element <NUM>, it can be drawn into coil <NUM> quickly by further opening syringe <NUM> at the appropriate time.

The next step in the measurement method is to open valve <NUM>. With valve <NUM> open, the step of closing syringe <NUM> results in moving the liquids from coil <NUM> to a mixing location in the system, such as to the mixer/sparger component <NUM>, where the reagents, sample, and dilution water, if any, are thoroughly mixed. Particulate material in the sample is kept in suspension so that the solution/suspension is substantially homogeneous.

In one alternative embodiment, the acid and oxidizer are first drawn into coil <NUM> and then are transferred into mixing/sparging chamber <NUM>. The sample and dilution water (if any) are then drawn into coil <NUM> and transferred into mixing/sparging chamber <NUM> where the sample, acid, oxidizer, and dilution water are mixed. Transferring the liquids to the mixing/sparging chamber <NUM> in two steps has the advantage of preventing premature reaction of IC in the sample with the acidic reagents in coil <NUM>. Generation of gas in coil <NUM> (from reaction of IC in the sample with acid) reduces the volume of sample drawn into coil <NUM>, adversely affecting the accuracy of the measurement.

Mixer/sparger <NUM> includes a mixing and sparging chamber that also is designed to provide for sparging CO<NUM>-free gas through the solution/suspension to remove IC, if NPOC is to be measured. For sparging, after the chamber element of mixer/sparger <NUM> contains the reagents, sample and dilution water (if any), valve <NUM> opens to allow the sparge gas to bubble through the chamber element of mixer/sparger <NUM>. The gas can be provided from a pressurized gas cylinder (not shown) or from a pump (not shown) that draws ambient air through an absorber that purifies the air sufficiently for use as a CO<NUM>-free sparge gas, and/or as a carrier gas, and/or as a purge gas. In either case, the CO<NUM>-free gas is prepared for use in gas control sub-assembly module <NUM>. Sub-assembly <NUM> includes a pressure-regulating device <NUM> that adjusts the pressure of the gas to about <NUM> psig. A proportioning valve <NUM> controls the flow rate of the gas flowing through valve <NUM> by means of a sparge gas flow sensor <NUM>. Additionally, a carrier gas flow sensor <NUM> in another conduit branch can be used to monitor and control the flow rate of the carrier gas to reactor sub-assembly <NUM>. Additionally, a restrictor <NUM> in still another conduit branch can be used to provide for a small flow rate of purge gas to the NDIR detector.

In an alternative embodiment, a valve (not shown) can be used to direct the gas that exits the chamber element of mixer/sparger <NUM> through the gas/liquid separator unit <NUM> and then to the NDIR sub-assembly <NUM>. This arrangement would allow the completeness of the sparging process to be monitored. Thus, the sparging is considered complete when the NDIR indicates that the concentration of CO<NUM> in the sparge gas going to the NDIR has decreased to a very small (negligible) value.

When the sparging and/or mixing in the chamber element of mixer/sparger <NUM> is complete, valve <NUM> opens to allow all or a portion of the solution/suspension in the chamber element to be drawn into the interior of reactor <NUM> by pump <NUM>. High-pressure reactor inlet and outlet valves <NUM> and <NUM> respectively are open at this point. Valves <NUM>, <NUM>, <NUM>, and <NUM> are closed. The reactor heater <NUM> is off, and reactor <NUM> is near ambient temperature. Pump <NUM> operates until sufficient liquid from chamber <NUM> has passed through the interior of reactor <NUM> Substantially to rinse out any remaining prior sample and to fill the reactor tube inside reactor <NUM>. At this point, pump <NUM> is stopped, and valves <NUM>, <NUM>, and <NUM> close.

Reactor valves <NUM> and <NUM> allow the valve housings to be flushed after these valves are closed. The flushing step removes excess sample that contains CO<NUM> formed by the acidification of the IC in the sample. If this CO<NUM> were not flushed out of the valves, it would cause an error in the subsequent measurement. To flush the reactor valve housings, valves <NUM> and <NUM> are opened, and residual liquid and gases in these housings can then be pumped out by pump <NUM> and replaced by carrier gas.

After the reactor tube of reactor <NUM> has been filled with sample and reactor valves <NUM> and <NUM> have been flushed, valve <NUM> closes and valve <NUM> opens to allow carrier gas to flow from sub-assembly <NUM> through valve <NUM>, pass through the gas/liquid separator <NUM>, and then pass to the NDIR detector sub-assembly <NUM>. Flow of carrier gas at this time is necessary to allow the NDIR detector to reach a steady baseline prior to the subsequent CO<NUM> measurement. An in-line filter <NUM> may be provided between gas/liquid separator <NUM> and the NDIR unit to prevent aerosols from the reactor <NUM> and/or from gas/liquid separator <NUM> from entering the optical path <NUM> of the NDIR detector.

To measure NPOC or TC, the organics contained in the sample portion in the reactor tube of reactor <NUM> must be oxidized. This oxidation can be made to occur by heating the interior of reactor <NUM> with a heater <NUM>, and/or by resistive heating as described herein, while controlling the temperature using a temperature sensor <NUM>. The sealed reactor can be heated, for example, to a temperature between about <NUM>° C. and <NUM>° C. (preferably between about <NUM>° C. and <NUM>° C. , and between about <NUM>° C. and <NUM>° C. in one embodiment). The heating period may be between about one to thirty minutes, preferably between about two and four minutes, and approximately <NUM> minutes in one embodiment. During this period, organics are oxidized in the sample portion in the reactor. At the end of that period, heating element <NUM> is turned off, and fan unit <NUM> is turned on to blow ambient air over reactor <NUM>, cooling it rapidly to near room temperature. Because of the small mass of reactor <NUM>, it is typically cooled by this cooling step to near ambient temperature in less than about <NUM> seconds.

To measure IC, the liquid inside reactor <NUM> is not oxidized. The reactor is filled as described above, but reactor <NUM> is heated only to a temperature sufficient to facilitate formation of CO2 from bicarbonates and carbonates (i.e., typically to no more than about <NUM>. The subsequent cooling step may in this case be abbreviated or omitted entirely. Furthermore, the oxidizer reagent is not required for IC measurements, and its addition to the sample prior to the reactor step can thus be omitted to reduce operating cost and make the analysis faster.

When the heating and cooling of reactor <NUM> is completed (or the comparable IC reactor sequence is completed), Valves <NUM> and <NUM> close, and valves <NUM>, <NUM>, <NUM>, and <NUM> open. This apparatus configuration allows carrier gas to flow through the reactor tube of reactor <NUM>, and carry the reactor products through gas/liquid separator <NUM>, to the NDIR sub-assembly and along the NDIR optical path <NUM>.

The NDIR measures the absorbance of the CO<NUM> in the gas flowing along NDIR optical path <NUM> at a wavelength of approximately <NUM>, e.g., <NUM> ± <NUM>. As the CO<NUM> carried from reactor <NUM> enters and passes through the NDIR. the absorbance measurement begins at a baseline level, rises up to and passes through a maximum level, and then returns to the baseline level that existed before the valves associated with reactor <NUM> opened. Either the height of the absorbance peak (or the depth of the intensity trough) or the cone-shaped area of the absorbance response curve can be calibrated and used to determine the amount of CO<NUM> contained in the gas product coming from the reactor.

The NDIR detector is comprised of three chambers, as seen in <FIG> and <FIG>. One chamber <NUM> contains the IR source. The central chamber, which is the NDIR optical path <NUM>, is the chamber through which the carrier gas and the gas product from reactor <NUM> (which includes the CO<NUM>) flow. The third chamber <NUM> contains the IR detector. Chambers <NUM> and <NUM> are flushed by CO<NUM>-free gas provided through the conduit that includes flow controller <NUM> so that CO<NUM>in the ambient air does not affect the measurements made with the NDIR. The NDIR further includes an associated temperature sensor <NUM> and an associated pressure sensor <NUM>. proximately located relative to the NDIR, which monitors atmospheric pressure outside the NDIR (which is essentially the same as the pressure of the CO<NUM> in the NDIR). The temperature and pressure measurements made respectively by temperature sensor <NUM> and pressure sensor <NUM> can be used to compensate the response of the NDIR for variations in the temperature and pressure of the gas being measured. Alternatively, sensors <NUM> and/or <NUM> may be omitted if the measurement does not require temperature and/or pressure compensation.

One of the several components of embodiments of the apparatus described herein is the mixer/sparger <NUM>. As shown in greater detail in <FIG>, the mixer/sparger includes a liquid inlet/gas outlet section <NUM>, a middle section <NUM>, and a liquid outlet/gas inlet section <NUM>. The top section <NUM> contains a liquid inlet 43a and the Sparge gas outlet 43b.

The bottom section <NUM> includes the inlet port 45b for the sparge gas and the outlet 45a for liquid. The middle section <NUM> includes a chamber element 44a located inside an annular solenoid coil 44b, which is activated by passing a series of current pulses through it. Such current waveform pulsing causes a magnetic stirrer <NUM> positioned inside chamber 44a to rapidly move up and down inside chamber 44a. In one embodiment, the magnetic stirrer <NUM> is coated with a corrosion-resistant outer layer, and its up-and-down action under the influence of the solenoid-generated waveform pulses causes the sample, reagents and dilution water, if any, inside chamber 44a to be rapidly mixed, typically in about <NUM> seconds or less. The bottom section <NUM> of mixer/sparger <NUM> includes a porous gas disperser <NUM>, through which sparge gas is directed on its way into chamber 44a. The pore diameter in the gas disperser <NUM> may be about <NUM> to <NUM> in. , e.g., preferably about <NUM> to <NUM>, and about <NUM> in one embodiment. The small bubbles produced by passing the sparge gas through disperser <NUM> results in efficient removal of IC from the liquid in chamber 44a, generally in about <NUM> seconds to <NUM> minutes at sparge gas flow rates ranging from about <NUM> to about <NUM> cc/min. , typically and preferably in about one minute or less at a sparge gas flow rate of about <NUM> cc/min.

Another of the components of one of the embodiments of the apparatus are the high-pressure reactor valves <NUM> and <NUM> as shown in <FIG>, and as illustrated in greater detail in <FIG>. As seen in <FIG>, a polymeric or elastic Seal <NUM> is attached to or comprises a front end or section of a moveable plunger element <NUM>, which is designed to move back and forth inside the housing/valve body <NUM> when motor <NUM> is activated. The rear portion of seal <NUM> is adapted to retain first and second O-rings <NUM> and <NUM> respectively, which seal the interior of housing <NUM>. The front end of seal <NUM> is sized and shaped to mate with and plug an opening (i.e., an inlet opening or an outlet opening) of reactor <NUM> when the valve is closed by advancing plunger element <NUM>. Reactor <NUM> may be attached to valve housings <NUM>, for example, using fittings <NUM> (as seen in <FIG>), which provide a seal that is essentially leak-free at the pressure produced in reactor <NUM> when the solution/suspension is sealed inside reactor <NUM>, and reactor <NUM> is heated.

Seal <NUM> is enclosed by a seal chamber defined by the valve housing <NUM> extending from the sealed opening of reactor <NUM> at least to first O-ring <NUM>. This chamber can be continuously or periodically flushed with gas using seal chamber ports <NUM> and <NUM> as shown in <FIG>. (Reactor valves <NUM> and <NUM> also each have a third port that is not seen in <FIG>. The sample solution/suspension enters or exits the valve and the interior of reactor <NUM> through that third port. ) This apparatus configuration makes it possible to remove any IC or free CO<NUM> that may be present in the valve housing <NUM> while the sample is being oxidized/treated in reactor <NUM>.

<FIG> is a schematic illustration of reactor valves <NUM> and <NUM> mounted at either end of a reactor <NUM>. In one embodiment, the reactor heater element <NUM> has a tubular configuration open at both ends and located inside a heater housing with the reactor <NUM> mounted inside the tubular portion of heater <NUM>. In one embodiment, heater <NUM> comprises a thick-film heating element deposited on an electrically insulating coating on the tubular portion of heater <NUM>, as shown in <FIG>. The tubular portion of heater <NUM> may be constructed of stainless steel, titanium, or other suitable materials. The two ends of reactor <NUM> pass respectively through slots (not shown in <FIG>) in the sidewall of the tubular portion of heater <NUM>. In one embodiment, reactor <NUM> is a tube generally constructed of titanium; however, stainless steel, ceramics, and other materials that are sufficiently corrosion resistant and compatible with the oxidation temperatures required can be used including titanium and its alloys grade <NUM> and grade <NUM>, tantalum, Inconel <NUM>, Hastelloy C-<NUM>, and the like. As previously discussed, the reactor assembly may also include a fan component to cool the reactor <NUM> after a heating/oxidation step. As seen in <FIG>, the outlet (downstream side) of fan <NUM> may be positioned close to one open end of the heater <NUM>, and is oriented so that a flow of cooling air during a cooling step passes through the heater housing and over both the exterior and interior of heater <NUM>, and also such that the airflow going through the interior of the tubular portion of the heater <NUM> during a cooling step passes over the portion of reactor <NUM> contained within the tubular portion of heater <NUM>.

An embodiment of the NDIR detector sub-assembly <NUM> is shown in greater detail in <FIG>. The NDIR consists of an optical system and an associated NDIR electronic system (as illustrated in the block diagram of <FIG>). The NDIR optical system generally has three sections: an IR source compartment <NUM>, a sample cell/NDIR optical path <NUM>, and an IR detector compartment <NUM>. Collimating lenses <NUM> located at either end of sample cell <NUM> separate the adjacent sections. In one embodiment, the lenses <NUM> are constructed of silicon.

In one embodiment, the IR source <NUM> is a thin-film heater. It may be mounted in plates <NUM> that are attached to an IR source heater and an IR source temperature sensor. Using the associated NDIR electronic system, the plates <NUM> and IR source <NUM> are controlled to a temperature of about <NUM>° C. in one embodiment.

In one embodiment, the IR detector <NUM> is a pyro electric, lithium tantalate sensor element. A <NUM> filter is mounted in the IR detector in front of the sensor element. This filter selectively passes infrared radiation at the wavelength that is absorbed by CO<NUM>. Thus, the IR detector <NUM> measures the IR radiation that passes through the optical path39 and the filter without being absorbed by CO<NUM>.

The IR detector <NUM> may be mounted in plates <NUM> attached to an IR detector heater and an IR detector temperature sensor. In one embodiment, the IR detector <NUM> is controlled at a temperature of about <NUM>° C. using the associated NDIR electronic system.

Carrier gas and the gas product from reactor <NUM>, including the CO<NUM>, flow through the center section <NUM> of the NDIR. IR source <NUM> and IR detector <NUM>, located in their separate compartments, are isolated from water vapor and potentially corrosive oxidation products by the compartment separation lenses <NUM>. The chambers <NUM> and <NUM> are also sealed, and CO<NUM> from ambient air is prevented from entering, or at least from remaining in, those chambers by flowing purge gas provided by the gas control sub-assembly <NUM>. The center section <NUM> of the NDIR has a gas inlet port <NUM> and a gas outlet port <NUM>, through which the carrier gas and the gas product from the reactor, including the CO<NUM>, flow. As illustrated in <FIG>, the gas inlet port <NUM> may be located proximate to the IR detector end of the NDIR, while the gas outlet port <NUM> is located proximate to the IR source end of the NDIR. However, the reverse orientation also is effective.

The electronic system for operating the NDIR sub-assembly in one embodiment is schematically illustrated in <FIG>. As seen in <FIG>, the electronic system includes electronic devices selected to provide power to the IR source, the IR source heater, the IR detector, the IR detector heater, and other electrical components. In one embodiment, the electronics control system modulates the power to the IR source at a frequency of <NUM>. Signals may be generated at other frequencies for operation of other components, such as the bandpass filter and analog-to-digital converter, from a field-programmable gate array (FPGA) as is known in the art.

The FPGA can be adapted or adjusted to generate a <NUM> clock for the IR source, with a duty cycle suitable for its operation. The IR source driver converts the logic-level clock signal into the pulsed power required by the IR source. The IR source emits infrared light, modulated at <NUM>. This light reaches the IR detector, attenuated by any CO<NUM> present in the center section <NUM> of the NDIR. The IR detector converts the infrared light that it receives back into an electrical signal, with signal content at <NUM> that is proportional to the infrared light that it receives. The detector bandpass filter is selected or adapted to remove harmonics of the <NUM> signal and DC offset, lowfrequency noise, and high-frequency noise generated by the IR detector. A synchronous circuit, such as a Switched-capacitor filter, is used in the detector bandpass filter, with a clock provided by the FPGA at a multiple of <NUM>. The analog-to-digital converter samples the waveform from the detector bandpass filter, also using a clock provided by the FPGA at a whole number multiple of <NUM>. For example, a clock of <NUM> provides <NUM> waveform samples per cycle of the IR detector waveform. The FPGA and the microprocessor perform further bandpass filtering of the digitized IR detector signal, centered at the modulation frequency of <NUM>, to remove detector noise and noise from the AC mains at <NUM> or <NUM>. The amplitude of the <NUM> signal at the output of the digital bandpass filter is then measured. The response of the IR detector is adjusted for temperature, pressure, and flow rate as necessary, and the CO<NUM> concentration is calculated in the manner described above. Based on the description provided herein, the processing steps described above could readily be implemented by one of ordinary skill in this art using an apparatus in accordance with the described embodiments.

<FIG> illustrates a typical response curve of an NDIR during a carbon measurement sequence. The output is in instrument counts, and the counts are proportional to the amount of IR radiation that strikes the IR detector <NUM>. When there is no CO<NUM> in section <NUM>, the response is at its maximum or baseline level. As soon as CO<NUM> enters section <NUM>, the response decreases until it reaches a minimum (trough) that <NUM> corresponds to when the amount of CO<NUM> in section <NUM> has reached its maximum (maximum absorbance). As the CO<NUM> passes out of section <NUM>, the response returns to its original baseline level.

There are two ways that the response peak (trough) can be used to calculate carbon concentrations in an aqueous sample being tested. The response curve can be mathematically integrated, and the resulting cone-shaped area of the response curve can be related to carbon concentration by one type of mathematical calibration correlation. Alternatively, the height of the peak (depth of the trough) can be measured and related to carbon concentration by another type of mathematical calibration correlation. These mathematical calibration correlations can be developed for a particular instrument by performing tests on samples containing known concentrations of IC, OC and/or TC. Basing computations on the measurement of peak height has the advantage that it is relatively unaffected by changes in gas flow rate.

In accordance with the invention, as shown in <FIG>, the reactor <NUM> is heated by the use of electrical current <NUM>, passed directly through all or a portion of the reactor <NUM>. Direct heating by electrical current may be used either in place of, or in addition to a heater <NUM> (as shown in <FIG>). A power source <NUM> is used to pass the electrical current <NUM> through all or a portion of the reactor <NUM>. The reactor material has a resistance R, that is inherent to the reactor material.

Electrical energy is dissipated as heat when an electrical current passes through reactor material. The heat dissipated can be characterized by the formula P = I<NUM>R, where P is the power dissipated, I is the current flow through the material, and R is the resistance of the material the electrical current flows through. When the electrical current flows through the reactor, the resistance of the reactor material causes electrical energy to dissipate as heat. Therefore, passing an electrical current through the reactor <NUM> heats the reactor <NUM>. The rate of heating is proportional to the resistance of the reactor and the square of the current passing through the reactor <NUM>. As a result, no separate heater <NUM> or heating element is required to heat the reactor <NUM>, and increased efficiency is possible.

To monitor and control the heating of the reactor <NUM> using an electrical current, sensing techniques as previously described may be applied. These include, but are not limited to, directly sensing the temperature of the reactor <NUM> using a temperature sensor <NUM> such as, for example, a RTD, detecting electromagnetic emissions produced by the reactor <NUM>, and using an infrared (IR) sensor to measure the temperature of the reactor <NUM>, and the like. Sensor <NUM> measurements produced may be used by a control circuit <NUM> to apply electrical current to the reactor <NUM>, determine the magnitude or the applied current, and/or determine when to stop the flow of electrical current through the reactor <NUM>. The control circuit <NUM> can use various inputs <NUM> to make these determinations in addition to sensed temperature of the reactor <NUM>, including positions of valves, status of the measurement apparatus, and the like.

<FIG> illustrates a schematic diagram of either all or part of an exemplary circuit <NUM> for heating and controlling the reactor <NUM>. <FIG> includes instrumentation amplifiers and DC converters configured to implement a reactor heating system.

<FIG> also illustrates a schematic diagram of either all or part of an exemplary circuit <NUM> for heating and controlling the reactor <NUM>. <FIG> includes amplifiers, and an optoisolator, configured to implement a reactor heating system.

<FIG> also illustrates a schematic diagram of either all or part of an exemplary circuit <NUM> for heating and controlling the reactor <NUM>. <FIG> includes a configuration of comparators used to implement an exemplary reactor heating circuit. Finally, <FIG> illustrates a schematic diagram of either all or part of an exemplary circuit <NUM> for heating and controlling the reactor. <FIG> includes a configuration of amplifiers used to implement an exemplary reactor heating circuit. The schematics disclosed in <FIG>, <FIG>, <FIG>, and <FIG> are intended to be non-limiting examples, which may be applied separately or in various combinations.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

Claim 1:
An apparatus for treating a liquid sample containing organic material, said apparatus comprising:
a reactor (<NUM>) having reactor inlet and reactor outlet ports and a reactor interior for containing a liquid sample under above-ambient temperature and pressure conditions;
high-pressure fluid reactor valve members (<NUM>, <NUM>) at said reactor inlet and reactor outlet ports, said reactor valve members (<NUM>, <NUM>) allowing fluid flow respectively into or out of the reactor interior when in an open-valve mode or, alternatively, capable of sealing the reactor interior when in a closed-valve mode;
a reactor heating system comprising an electrical current source operably connected to the reactor (<NUM>), the electrical current source configured to pass an electrical current (<NUM>) through the reactor (<NUM>) to rapidly and cyclically heat the reactor interior and a liquid sample sealed in the reactor interior to a temperature of about <NUM>° C. to <NUM>° C. or higher, while the reactor interior and the reactor valve members (<NUM>, <NUM>) maintain the sample under sealed conditions; and,
a reactor cooling system adapted for rapidly and cyclically cooling the reactor interior and a reactor product sealed in the reactor interior following a heating cycle.