Patent Publication Number: US-2005129578-A1

Title: Fast system for detecting detectible combustion products and method for making and using same

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an analytical instrument for fast detection of non-vacuum assisted detectible oxides and methods for making and using same.  
      More particularly, the present invention relates to an analytical instrument for fast detection of non-vacuum assisted detectible oxides, where the instrument includes a sample supply unit, an oxidizing agent supply unit, a combustion unit maintained at a first elevated temperatue, a transfer line, a detection chamber, a detector and an analyzer, where the transfer line and the detector chamber are maintained at a second elevated temperature, where the first elevated temperature is sufficient to convert all or substantially all of the oxidizable components in a sample to their corresponding oxides and where the second temperature is sufficient to reduce or eliminate water vapor condensation in the transfer line and detector chamber. The present invention also relates to methods for making and using same.  
      2. Description of the Related Art  
      Many instruments have been designed to perform on-line studies of compositions in reactor and/or refinery effluents or other effluents. Many of these instruments have considerably long cycle rates with most having cycle time of four (4) minutes or more.  
      Although many of these systems do an adequate job at monitoring effluent compositions, their considerable cycle time is not sufficient to allow tighter control over reactor, refinery and/or other chemical transformation processes. Thus, there is a need in the art for a faster analytical instrument for detecting and measuring detectible combustion products for non-vacuum assisted detection from effluents from reactors, refineries or other chemical transformation processes to allow improved process control and monitoring.  
     SUMMARY OF THE INVENTION  
      The present invention provides an analytical instrument for fast on-line monitoring of effluents comprised of at least one combustible components detectible by a non-vacuum assisted detection system, where the instrument includes a sample supply system, an oxidizing agent supply system, a combustion chamber maintained at a first elevated temperature, a detection chamber, a transfer line connecting the two chambers, a detector and an analyzer, where the detection chamber and the transfer line are maintained at a second elevated temperature, where the first elevated temperature is sufficient to convert all or substantially all oxidizable sample components into their corresponding oxides and the second elevated temperature is sufficient to prevent or eliminate water vapor condensation in the transfer line and detection chamber.  
      The present invention also relates to an analytical instrument including a sample supply system, an oxidizing agent supply system, a combustion chamber maintained at a first elevated temperature, a UV fluorescence detection chamber, an excitation light source in optical communication with the detection chamber, a transfer line connecting the two chambers, a photo detector and an analyzer, where the detection chamber and the transfer line are maintained at a second elevated temperature, where the first elevated temperature is sufficient to convert all or substantially all oxidizable sample components into their corresponding oxides and the second elevated temperature is sufficient to prevent or eliminate water vapor condensation in the transfer line and detection chamber.  
      The present invention relates to a sulfur analytical instrument including a sample supply system, an oxidizing agent supply system, a combustion chamber, a UV fluorescence detection chamber adapted to detect fluorescent light emitted from electronically excited sulfur dioxide, a transfer line connecting the two chambers, a detector adapted to detect the fluorescent light and an analyzer adapted to convert the detected light into a concentration of sulfur in the sample. The combustion chamber is maintained at a first elevated temperature sufficient to convert or oxidize all or substantially all oxidizable sample components into their corresponding oxides. The detection chamber and the transfer line are maintained at a second elevated temperature sufficient to prevent or eliminate water vapor condensation in the transfer line and the detection chamber. The heated transfer line and detector chamber allows a cycle time to be about twice to four times faster than a conventional on-line instrument designed to measure sulfur concentration in samples. In one preferred embodiment, the cycle time of the system of this invention is less than or equal to about 2 minutes. In another preferred embodiment, the cycle time of the system of this invention is less than or equal to about 1.5 minutes. In another preferred embodiment, the cycle time of the system of this invention is less than or equal to about 1 minute. In yet another preferred embodiment, the cycle time of the system of this invention is less than 1 minute. The term cycle time is defined as the elapsed time between sample introduction into the analytical system and the concentration determination in the analyzer. A faster analysis is critical in many chemical and refinery processes and is especially well suited of measuring sulfur content during final fuel formulating and blending.  
      The present invention relates to a method for rapid determination of a concentration of an element capable of generating a detectible combustion product or oxide, where the method includes the steps of supplying a sample to a combustion chamber of an analytical instrument of this invention and simultaneously, collectively or sequentially supplying an oxidizing agent to the combustion chamber. Once in the combustion chamber, oxidizable components in the sample are converted into their corresponding oxides and water vapor, where the combustion chamber is maintained at a first elevated temperature above an ignition temperature for an oxidizing agent-sample mixture or sufficient to oxidize all or substantially all oxidizable sample components into their corresponding oxides. Generally, the first elevated temperature is above about 300° C., preferably above about 600° C., and particularly above about 900° C. Preferably, the elevate temperature is between about 300° C. and about 2000° C. Particularly, the elevated temperature is between about 600° C. and about 1500° C. More particularly, the elevated temperature is between about 800° C. and about 1300° C. The combustion apparatuses of this invention can be operated at ambient pressure, at reduced pressure down to ten of millimeters of mercury, or at higher than ambient pressures up to a 1000 or more psia. The term substantially all means that at least 95% of the oxidizable components in the combustible material have been converted to their corresponding oxides, preferably, at least 98% of the oxidizable components in the combustible material have been converted to their corresponding oxides, particularly, at least 99% of the oxidizable components in the combustible material have been converted to their corresponding oxides and especially, at least 99.9% of the oxidizable components in the combustible material have been converted to their corresponding oxides.  
      Transferring the oxidized mixture via a transfer tube to a reaction chamber while maintaining the transfer tube at a second elevated temperature sufficient to reduce or prevent water vapor condensation in the transfer line or the detection chamber. The second elevated temperature is generally between about 30° C. and about 120° C. and preferably between about 40° C. and about 100° C. The method also includes the steps of irradiating the mixture with excitation light from an excitation light source to form electronically excited, detectible oxides, detecting fluorescent light emitted by the electronically excited detectible oxides and deriving a concentration of the detectible oxide, which comprises an element of interest, in the effluent and relate it to a concentration of the element in the sample. 
    
    
     DESCRIPTION OF THE DRAWINGS  
      The invention can be better understood with reference to the following detailed description together with the appended illustrative drawings in which like elements are numbered the same:  
       FIG. 1  depicts a block diagram of a preferred embodiment an apparatus of this invention; and  
       FIG. 2  depicts a block diagram of a preferred embodiment of a detection system of this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The inventor has found that a fast analytical technique can be developed for rapid systematic analysis of routine samples and especially for systematic analysis and monitoring of reactor effluent compositions or refinery effluent compositions to ensure conformity with either governmental or industrial standards of quality. The technique includes a combustion chamber maintained at a first elevated temperature to ensure complete or substantially complete oxidization or conversion of all oxidizable sample components into their corresponding oxides and water and a post combustion chamber system maintained at a second elevated temperature sufficient to reduce or eliminate water vapor condensation in the post combustion chamber system. The technique also includes a detection system designed to detect and quantify a concentration of an element in the sample from a concentration of a detectible oxide in the combustion products.  
      The inventor has found that by heating the system downstream of the combustion chamber, the cycle time for sample analysis can be reduced from about 4 minutes per sample to about 1 minute or less. This nearly 4 time reduction in cycle time, the time between each sample injection and an output result, greatly improves monitoring of effluents of chemical and/or refinery processes on-line. For example, the fuel blending is commonly performed by refiners to produce fuel that meets or exceeds governmental levels of sulfur. Generally, the refiners will produce to a very low level sulfur feedstock (expensive) and a high level sulfur feedstock (less expensive). The low level sulfur feedstock has a sulfur content well below governmental standards, while the high level sulfur feedstock has a sulfur content well above governmental standards. The refiners then blend the two feedstocks together in a ratio designed to generate a blended feedstock having a sulfur level at or slightly below the governmental standard. However, to do this blending and maintain the desired sulfur level, the refiners need fast and accurate analytical data. The faster the accurate analytical data the better because a few minutes of producing an out-of-spec material cost refiners a lot of money and lowers throughput—the out-of-spec product must be reblended to a desired low sulfur content. Therefore, fast and accurate analytical data can improve product conformity, uniformity and product throughput. Of course, the need to monitor output composition quickly is sought in many industrial areas including the chemical industry, the pharmaceutical industry, the nutraceutical industry, and the food industry to name a few.  
      The present invention broadly relates to an improved analytical instrument for rapid and accurate sample analysis including a combustible material (fuel or sample) supply system, an oxidizing agent supply system (of course, the two systems can be combined into a single supply system) and a combustion chamber. The combustible material supply system supplies the sample to the combustion chamber, while the oxidizing agent supply system supplies an amount of an oxidizing agent sufficient to completely or substantially completely oxidize all oxidizable components in the sample to their corresponding oxides. The combustion chamber, which is maintained at a first elevated temperature sufficient to promote complete or substantially complete combustion, oxidizes the oxidizable components of the sample into their corresponding oxides and water forming an oxidized mixture. The mixture is then transferred to a reaction chamber via a transfer line. The transfer line and the reaction chamber are maintained at a second elevated temperature. In the reaction chamber, one or more oxides in the mixture are detected and a concentration of an element in each of the oxides is determined and converted to a concentration of that element in the sample. In the reaction system, the oxidizes are generally exposed to an agent that causes the oxides to be converted to an analytically active state. The preferred agent is excitation light and the preferred analytically active state is an electronically excitation state. Thus, the preferred detection system is a light amplification device such as a photo-multiplier tube (PMT) or any other photo-counting device that produces an electronic signal proportional to the concentration of the oxide of interest in the mixture such as a Charge-coupled Device (CCD) or an Intensitifed Charge Coupled Devise (ICCD).  
      The sample supply system can be any sample supply system including an auto-sampler, a septum for direct injection, a sampling loop for continuous sampling, an analytical separation system such as a GC, LC, MPLC, HPLC, LPLC, or any other sample supply system used now or in the future to supply samples to analytical instrument combustion chambers or mixture or combinations thereof.  
      The present invention broadly relates to a method for fast and accurate sample analysis including the steps of feeding a combustible composition and an amount of oxidizing agent in excess of all combustible components of the combustible composition to a combustion chamber maintained at a first elevated temperature sufficient to covert all of the combustible components in the combustible composition completely or substantially completely, preferably completely, to their corresponding oxides and water to produce an oxidized mixtures. Transferring the oxidized mixture to a reaction chamber via a transfer line, where the transfer line and reaction chamber are maintained at a second elevated temperature sufficient to reduce or prevent water vapor condensation in the transfer line or the reaction chamber. Exposing the mixture in the reaction chamber to an agent that converts a portion of at least one oxide in the mixture to an analytically active state. Measuring the at least one oxide in its analytically active state to produce a signal proportional to a concentration of the at least one oxide in its analytically active state. Converting this signal into a concentration of an element in the sample, where the element is an atomic constituent of the at least one oxide. A cycle time for the entire process represents a reduce period of time, up to four times faster than traditional methods, with equivalent or better accuracy.  
      The combustion chamber useful in this invention can be any conventional packed or unpacked combustion tube. However, one preferred combustion chamber for use in this invention is a combustion chamber having a combustion zone with at least one static mixer along a length of the combustion zone for increasing oxidation efficiency without increasing a combustion volume and/or a residence time in the combustion zone. The mixing combustion chamber can also be used to increase throughput.  
      Referring now to  FIG. 1 , a preferred embodiment of an instrument of this invention, generally  100 , is shown to include a sample supply unit  102 . The sample supply unit  102  includes a heated sample valve housing  104  including a first heater  106  having a temperature sensor  107  and a first heater temperature controller  108  having a power supply line  109   a  and a temperature sensor line  109   b , and a sample valve  110  having a sample in line  112 , a sample out line  114 , a carrier gas in line  116  and a sample valve outlet line  118 . The first heater  106  and the first controller  108  are designed to maintain the sample supply unit  102  at an elevated injection temperature to allow for adequate sample injection. The instrument  100  also includes an oxidizing agent supply line  120  connected to a source of oxidizing agent (not shown) and a furnace  122  having a combustion tube or chamber  124  including a combustion zone  126 . The combustion chamber  124  also includes a sample inlet  128  connected to the sample valve out line  118 , an oxidizing agent inlet  130  connected to the oxidizing agent supply line  120  and an oxidized sample outlet  132 . The furnace  122  also includes a second heater  134  having a second temperature sensor  135 , where the second heater surrounds the combustion zone  126  and a second temperature controller  136  having a power supply line  137   a  and a temperature sensor line  137   b . The second heater  134  and the second controller  136  are adapted to maintain a temperature of the combustion zone  126  at a temperature sufficient to convert all or substantially all oxidizable components in the sample into their corresponding oxides and water forming an oxidized mixture which exits the chamber  124  via the outlet  132 .  
      After the oxidized mixture exits the combustion chamber outlet  132  it enters a transfer line or tube  138  having a third heater  140  including a third temperature sensor  141 , where the third heater surrounds all or a majority of a length of the transfer line or tube  138  and a third temperature controller  142  having a power supply line  143   a  and a temperature sensor line  143   b . The third heater  140  and the third controller  142  are designed to maintain the transfer line or tube  138  at a temperature sufficient to prevent or eliminate water vapor condensation in the transfer tube  138 . The transfer tube  138  is connected to a detector system  144  having a detector chamber  145   a  and an detector/analyzer  145   b  via a detector chamber inlet  146 . The detector chamber  145   a  includes a fourth heater  148  having a fourth temperature sensor  149  and a fourth temperature controller  150  having a power supply line  15   la  and a temperature sensor line  151   b  and a vent line  152 . The fourth heater  148  and the fourth controller  150  are designed to maintain the detector chamber  145   a  at an elevated temperature sufficient to prevent or eliminate water vapor condensation in the detector chamber  145   a . The detector/analyzer  145   b  is adapted to convert a single produced in the reaction chamber  145   a  into a concentration of an oxide in the oxidized mixture and convert that concentration of an element concentration in the sample of the element of interest in the detected oxide. The preferred heater for the transfer tube or line is to heat trace the line with a heating sleeve.  
      Referring now to  FIG. 2 , a preferred embodiment of a UV detection system of this invention, generally  200 , is shown to include a detector chamber  202 , a detector chamber oxidized sample inlet  204 , a detector chamber outlet or vent  206  and a detector chamber heater  208 . The detector chamber  202  also includes a excitation light port  210  connected to an excitation light source  212  and a detector port  214 . The UV detection system  200  also includes a filter  216  and a detector  218 , where the filter  216  is connected to the detector port  214  so that a desired bandwidth of UV fluorescent light emitted from oxides in the sample excited by light from the light source  212  and where the detector  218  converts the light passing through the filter  216  into an output signal. The UV detection system  200  also includes an analyzer  220  adapted to convert the output signal from the detector  218  into a concentration of an element in the sample. The preferred elements are sulfur and/or nitrogen. If both nitrogen and sulfur are to be analyzed simultaneous, then the oxidized sample can be split into two parts, one part going to a sulfur detection system and the other part going to a nitrogen detection system. The analyzer is generally a digital processing system including a digital processing unit, memory (cache, RAM, ROM, etc.), a mass storage device, peripheral or the like. The analyzer takes as input the output from the detector such as a PMT and converts the signal into a concentration of an element of interest in the original sample. The data can then be displayed, printed, or the like.  
      All references cited herein are incorporated by reference. While this invention has been described fully and completely, it should be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. Although the invention has been disclosed with reference to its preferred embodiments, from reading this description those of skill in the art may appreciate changes and modification that may be made which do not depart from the scope and spirit of the invention as described above and claimed hereafter.