CLIAMS:1. A photoreactor system comprising an elongated inner tube and an elongated outer tube, the inner tube being concentrically disposed within the outer tube and having substantially uniform diameter wherein the outer tube is sealed at both ends to the outer surface of the inner tube defining an annular volume between the inner tube and the outer tube, the outer tube being coupled to a feeding unit including an injection port and an adapter, the injection port having a plurality of tubular portions extending from a base portion wherein a first set of tubular portions is adapted to be in liquid communication with a source reservoir and a drain reservoir and a second set of tubular portions is adapted to be in liquid communication with a source reservoir and the annular reactor volume, the adapter having a first surface and a second surface, the first surface being secured to the outer surface of the outer tube and the second surface being provided with holes adapted to receive the tubular portions of the injection port, each tubular portion terminating at an end including an opening, the base portion of the injection port being coupled to a solenoid control segment, the solenoid control segment being adapted to control the liquid communication between the first set of tubular portions and to allow liquid communication between the second set of tubular portions, the opening at the end of at least one of the tubular portions of the second set being at least partially aligned with a perforation on the outer tube allowing the liquid flowing out of the at least one tubular portion of the second set to be fed into the annular volume of the reactor.
2. The photoreactor system as claimed in claim 1 wherein axial distance between the opening at the end of the at least one of the tubular portions of the second set and the center of the perforation is less than 3 mm
3. The photoreactor system as claimed in claim 1 or 2 wherein the adapter comprises a chemically inert polymeric material
4. The photoreactor system as claimed in any one of the claims 1 to 3 wherein the chemically inert polymeric material is polyether ether ketone
5. The photoreactor system as claimed in any one of the claims 1 to 4 wherein the injection port is coupled to a syringe drive assembly comprising a plurality of source reservoirs
6. The photoreactor system as claimed in any one of the claims 1 to 5 further comprising a Non Dispersive Infra Red (NDIR) sensor
7. The photoreactor system as claimed in claim 6 wherein the NDIR sensor is electronically coupled to a control unit adapted to provide a feedback signal to the syringe drive assembly
8. A method for determination of carbon content in an effluent, the method comprising first conveying a liquid by selective communication of one of a plurality of liquid reservoirs with a first set of tubular portions of an injection port, controlling the liquid communication between the first set by operating a solenoid control segment coupled to the injection port and allowing liquid communication between a second set of tubular portions of the injection port and the annular volume, defined between inner tube and outer tube of a photo reactor, through a perforation on the outer tube thereof.
9. The method as claimed in claim 8 wherein the analysis of inorganic carbon and the analysis of organic carbon in the effluent are performed in a single reactor.
,TagSPECI:FIELD OF THE INVENTION
The present invention relates to a photoreactor system for the determination of carbon content in an effluent stream. The invention also relates to a method for determination of carbon content using the photoreactor system
BACKGROUND
Liquid effluents from Industries are a major cause of water pollution. The high carbon content in such effluents significantly contribute to the chemical and biological oxygen demand of natural streams making the water not fit for human use. Apart from this, harmful chemicals in the effluent streams significantly disturb the aquatic ecosystem causing widespread destruction of aquatic life. The various effluent management methods currently available include treatment of the effluents making it free from polluting chemicals and thereby reducing the carbon content to the desired level before the effluent is released to the environment. Effective effluent treatment is possible only by precise determination of the carbon content of effluents before and/or after treatment. Devices for precisely determining total carbon content in effluents are much in demand. A large number of such conventional devices rely upon photochemical methods of analysis. Devices that enable photochemical oxidation of organic carbon in effluents and consequent determination of the organic carbon content are known. Many of such devices conduct analysis in batches and are not suitable for online analysis of carbon content in flowing effluent streams. Further, such conventional devices are usually complex requiring separate reactors for determination of inorganic and organic carbon in the effluent sample. Also, accuracy of analyses of carbon content using conventional devices is severely limited due to interference from dead volume of liquid samples. Online analysis of effluent streams desire operation with limited dead volume, non-corrosive materials in contact with photocatalysts, leakage-free contact between the feeding unit and the reactor tube and operation with limited human intervention. There is, therefore, a longstanding need for such a device for online determination of carbon content in effluent liquid streams with a combination of the above-mentioned multiple benefits during operation.
OBJECTS OF THE INVENTION
An object of the invention is to provide a photoreactor system for on-line analysis of total carbon in flowing effluent streams
An object of the invention is to provide a photoreactor system wherein liquid sample analysis can be carried out with limited dead volume
An object of the invention is to provide a photoreactor system wherein the sample feeding unit is made durable and suitable for prolonged operation
An object of the invention is to provide a photoreactor system wherein the sample feeding unit is coupled to the photoreactor by a leakage free contact
An object of the invention is to provide a photoreactor system wherein the photo reactor system operates with limited human intervention.
An object of the invention is to provide a photoreactor system wherein both inorganic carbon and organic carbon are determined in a single reactor
Another object of the invention is to provide a photoreactor system for accurate measurement of carbon content
SUMMARY OF THE INVENTION
The invention provides a photoreactor system comprising an elongated inner tube and an elongated outer tube, the inner tube being concentrically disposed within the outer tube and having substantially uniform diameter wherein the outer tube is sealed at both ends to the outer surface of the inner tube defining an annular volume between the inner tube and the outer tube, the outer tube being provided with a feeding unit including an injection port and an adapter, the injection port having a plurality of tubular portions extending from a base portion wherein a first set of tubular portions is adapted to be in liquid communication with a source reservoir and a drain reservoir and a second set of tubular portions is adapted to be in liquid communication with a source reservoir and the annular reactor volume, the adapter having a first surface and a second surface, the first surface being secured to the outer surface of the outer tube and the second surface being provided with holes adapted to receive the tubular portions of the injection port, each tubular portion terminating at an end including an opening, the base portion of the injection port being coupled to a solenoid control segment, the solenoid control segment being adapted to control the liquid communication between the first set of tubular portions and to allow liquid communication between the second set of tubular portions, the opening at the end of at least one of the tubular portions of the second set being at least partially aligned with a perforation on the outer tube allowing the liquid flowing out of the at least one tubular portion of the second set to be fed into the annular volume of the reactor.
Typically, the axial distance between the opening at the end of the at least one of the tubular portions of the second set and the center of the perforation is less than 3 mm
Typically, the adapter comprises a chemically inert polymeric material
Typically, the chemically inert polymeric material is polyether ether ketone
Typically, the injection port is coupled to a syringe drive assembly comprising a plurality of liquid reservoirs
Typically, the photoreactor reactor comprises an NDIR sensor
Typically, the NDIR sensor is electronically coupled to a control unit
Typically, the control unit provides a feedback signal to the syringe drive assembly
The invention also provides a method for determination of carbon content in an effluent.
BRIEF DESCRIPTION OF THE DRAWINGS
The following is a detailed description of the invention with reference to the accompanying drawings, in which;
Fig 1 is a schematic view of an embodiment of the photo reactor system
Fig 2 a is a sectional view of the injection port
Fig 2 b is a sectional view of the adapter
Fig 3 is a flow path of the photoreactor system
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 schematically shows an embodiment of the photoreactor system of the invention. Referring to Figure 1, the photoreactor system is characterized by a photoreactor 1 having an inner tube 2 concentrically disposed within an outer tube 3 that is coupled to a feeding unit 4. The feeding unit 4 is connected to source reservoirs 6 through a syringe drive assembly 7 and to a drain reservoir 5. The feeding unit includes an injection port 8 and an adapter 13. Figure 2 (a) shows the detailed configuration of the injection port 8. The injection port has a base portion 9 and tubular portions 10, 11 extending from the base portion. The syringe drive assembly 7 is capable of allowing selective liquid communication between one of the source reservoirs and a set of tubular portions 10, 11. The source reservoir is selected from effluent liquid reservoir, distilled water reservoir and standard sample reservoir. Each of the tubular portion terminates at an end including an opening. During analysis of the effluent sample, the liquid communication through the tubular portions is controlled by a solenoid control segment 12. Typically, the solenoid control segment is a solenoid valve that is adapted to interrupt liquid communication through the first set of tubular portions and to allow liquid communication through the second set of tubular portions. During operation of the photoreactor system, liquid effluent sample is directed to the photoreactor through the second set of tubular portions that is removably engaged into the receiving holes 16,17 of the adapter 13 shown in figure 2 (b). The middle hole 16 of the adapter receives a tubular portion (of the injection port), the opening at the end of which is at least partially aligned to a perforation on the outer tube of the photoreactor system. Further, axial distance between the center of this opening and the perforation on the outer tube is less than 3 mm ensuring negligible dead volume during analysis of each sample. Each of the front holes 15, 17 of the adapter form a flow channel to a lateral portion of the adapter that is adapted to be in liquid communication with either the source reservoirs 6 or to the drain reservoir 5. During operation, the liquid sample is first drawn into a lateral hole 14 of the adapter and is communicated to the drain reservoir through the first set of tubular portions 10 on the injection port 8 and through the other lateral hole 18 of the adapter. The adapter comprises a material that is resistant to corrosion upon contact with photocatalyst suspension. Preferably, the adapter comprises Polyether ether ketone (PEEK). The adapter-injection port configuration enables precise positioning of the injection port with respect to the perforation on the outer tube of the photoreactor allowing feeding of liquid samples into the annular volume of the photoreactor with negligible dead volume. It also allows leakage-proof contact between the feeding unit and the photoreactor. The adapter, being itself chemically inert, shields the injection port from being in contact with the corrosive photocatalyst contained in the annular volume of the reactor. During the commencement of the analysis, the liquid communication from source reservoir 6 to drain reservoir 5 is interrupted by means of the solenoid control segment 12. The solenoid control segment 12 directs liquid drawn from source reservoir 6 to the photoreactor 1 through the second set 11 of tubular portions. Such liquid communication extends through the middle hole 16 of the adapter that is at least partially aligned with the perforation on the outer tube 3 of the reactor.
The sample liquid fed into the annular volume defined between the outer tube 3 and the inner tube 2 of the reactor is first contacted with an oxidant acid to enable release of all inorganic carbon in the form of carbon dioxide that is analysed to determine the inorganic carbon content. The photoreactor system of the invention is an online system which is pre-programmed and does the analyses automatically drawing a fixed volume of sample from the effluent stream and injecting it into the photo reactor 1. Perchloric acid is the oxidant acid preferably used for determination of inorganic carbon. The CO2 gas that is generated gets collected in the closed-loop sampling line and passes over the NDIR sensor 21. The concentration maxima at the end of the reaction is noted and related to the carbon content in the sample. This result is then displayed on the digital display. After the determination of the inorganic carbon content is completed, the UV (Ultra Violet) lamp is switched on, for determining the organic carbon in the liquid sample. Under UV irradiation in the presence of the photocatalytic suspension, all organic carbon is photo catalytically oxidized to CO2. The photocatalytic suspension typically contains TiO2 catalyst. The measured amount of CO2 generated is converted into Total Organic Content (TOC). The result is then displayed on the digital display. The analysis cycle is repeated with a frequency as programmed. The system is completely automated. Once the photoreactor system is turned on it carries out automatically all the steps involved in the analysis and displays the final reading on digital display. Thus, the photoreactor system of the present invention operates with limited human intervention. Also, since the system allows determination of both inorganic as well as organic carbon, determination of total carbon in the liquid is made possible without requiring separate reactors for individually determining organic or inorganic carbon.
The photoreactor system essentially operates in two modes:
1) Calibration mode: In this mode, the photoreactor system is calibrated
2) Analysis mode: In this mode, the total carbon content in the liquid effluent sample is determined
Calibration of the photoreactor system:
The photoreactor system is pre-calibrated with known standards. For this, the photoreactor system is switched on and the calibration mode is chosen. Once selected, the catalyst suspension of TiO2 and HClO4 acid are homogenized by bubbling fresh air after which photoreactor is filled with this suspension.
Before actual analysis of the liquid sample from the effluent stream, the photoreactor system draws a standard liquid sample from one of the source reservoirs 6 with the help of syringe drive system 7 and oxidizes it respectively by HClO4 and by photocatalytic means to carbon dioxide. The amount of CO2 generated at the end of the reaction is converted to carbon content in the standard and stored in the memory as the calibration data. This stored calibration data serves to determine Total organic content (TOC) and Total Inorganic Content (TIC) of unknown liquid samples. This step is repeated with the second standard and the data is stored.
Sample analysis:
During the actual analysis of the liquid sample, the photocatalyst suspension is drawn from a reservoir 22 to the annular volume of the photoreactor system. The catalyst suspension is fed into the photo reactor system by creating a vacuum at the outlet 25 of the photo reactor system using a vacuum pump 19 while the inlet 24 is connected to TiO2 catalyst reservoir 22 through a solenoid control segment. The catalyst suspension fills the annular volume of the photo reactor 1 up to a pre-determined lower limit. This catalyst suspension will be used for a few samples till the suspension in photoreactor system crosses a pre-determined upper limit. After this, the photoreactor system is prepared to be in the circulation mode. In the circulation mode, the photo reactor, filter, halogen trap 20 and NDIR sensor 21 are in the path of closed loop. Air is circulated in closed loop. The level of CO2 is monitored continuously by NDIR sensor 21. The NDIR sensor 21 is electronically coupled to a control unit that is adapted to provide the syringe drive assembly 7 with a feedback signal that allows continuous operation with limited human intervention.
After the measurement is completed, purging of the reactor is started. The CO2 generated in the closed loop during the oxidation is removed and filled with fresh ambient air. After this, the catalyst suspension is drained by using vacuum generated by the pump 19. The drain reservoir 23 is connected to inlet 24 of photoreactor through a set of solenoid valves. Through this path the suspension in the photoreactor is drawn to drain reservoir 23. Photo reactor outlet 25 is opened to air through a solenoid valve so that the top of the solution in photo reactor is at atmospheric pressure. After draining, distilled water is fed into the reactor using syringe drive assembly 7. The distilled water is then drained out to the drain 5. A pre-programmed amount of next liquid sample from the effluent is then fed into the photoreactor and inorganic as well as organic carbon content is determined.
With every sample injection, the level of catalyst suspension in the annular volume of the photoreactor system rises. When it reaches a pre-determined upper limit, no more sample injection is possible. The photoreactor system then automatically goes into the drain operation. The entire catalyst suspension is drained into the drain reservoir 23. It is then rinsed by feeding the photo reactor system with distilled water, and the water is drained into the drain reservoir 5 and a fresh catalyst suspension is filled. The photoreactor system is now ready for analysis. While injecting the sample (or standard) into the photoreactor, care is taken to clean the sampling line with distilled water as well as to rinse with the sample to be analyzed. After such cleaning and rinsing, the liquid effluent sample is injected into the photoreactor. This ensures sample integrity and reproducibility. After every cycle of operation the photoreactor system goes into sleep mode and becomes active after a preprogrammed time for analyzing the next liquid sample from the effluent stream.
The present invention provides a photoreactor system suitable for determination of organic content in effluent streams wherein the photoreactor system comprises a feeding unit including an injection port and an adapter that allows determination of carbon content with low dead volume, high accuracy and with negligible human intervention. Apart from minimizing the dead volume, the feeding unit of the photoreactor system of the present invention allows leakage free contact with the photoreactor. This is enabled by a configuration where tubular portions of the injection port is received inside an adapter that is secured to the reactor tube in such a way that precise positioning of the injection port opening with respect to the perforation on the photoreactor tube is made possible. Further the feeding unit of the photoreactor system of the present invention is resistant to corrosion even on exposure to corrosive photocatalysts. This is made possible by separating the injection port and the photoreactor tube by a corrosion resistant adapter. Thus, the present invention provides a photoreactor system that is durable, thereby ensuring prolonged and uninterrupted operation. The photoreactor system of the present invention also allows determination of total carbon content in effluent streams with high accuracy and precision. Further, by allowing the determination of carbon content in a continuous process using an NDIR sensor and a control unit that provides a feedback loop with the syringe drive system, the photoreactor system of the invention provides ease of operation with limited human intervention. Furthermore, by enabling determination of both the organic and inorganic carbon content of the effluent streams using a single reactor, the photoreactor system of the invention has a less complex design.
The above description is illustrative only and is not limiting. The present invention is defined by the claims that follow and their full range of equivalents.