Patent Application
20230288298
The present disclosure generally relates to fields of monitoring and treatment of contaminated gases, including foul air. In particular, the present disclosure is directed to systems and methods for gas monitoring and for continuous monitoring and treatment of contaminated gas streams.
Wastewater infrastructure, composting operations, industrial manufacturing and many other processes and installations can release a wide variety of contaminants to the air. These by-products can cause a variety of adverse effects, such as adverse health effects, odor production, and corrosion. Community odors remain one of the top three complaints to air quality regulators and government bodies around the U.S. and internationally. Most of all air pollution complaints are odor related.
Odors from a facility such as a wastewater treatment plant and/or related collection system, can negatively affect a surrounding community. These odors commonly lead to nuisance complaints. Estimating the effects of odors from a facility often requires laboratory odor testing. In order to accomplish this testing conventionally, air samples from the facility are collected and shipped overnight to an odor-testing laboratory. In some cases a gas sensor with a datalogger that will record the information during a certain period that is put in place is used. After the results are collected and analyzed, engineers and city managers can formulate a plan to properly address the issue.
Wastewater streams generally have variable flow and so too the concentration of odorous compounds. The flow can vary by the day of the week and hour of the day. Waste-water flow normally peaks early in the morning when people prepare for work/school, and during the night when they return to their homes. Weekends can be highly variable. Outside influences, such as storm events and snow melt can also affect the load on a wastewater treatment system.
Wastewater treatment processes release air contaminants as a byproduct of collecting, mixing, processing, transferring and treating wastewater. In wastewater treatment a common air contaminant is hydrogen sulfide (H2S). However, a wide variety of industrial processes release a wide variety of gaseous air contaminants that can present odor or more serious health risks.
Contaminant gasses such as H2S are typically monitored by specialized testing equipment that use a sensor to capture, record, and data log the level in parts per million (ppm). Electrochemical sensors are typically used. Such sensors work well for periodic checks or monitoring a space of the sudden appearance of a contaminant gas, but they are not well-suited to long term or continuous monitoring of gas streams that continually contain some amount of contaminant gas. If such a sensor is exposed continuously for an extended period, it can ‘saturate.’ In this state, products of the oxidation reaction are not able to ‘escape’ from the sensor in time for fresh gas to enter. This essentially blocks the active sites of the electrode and the sensor sensitivity will reduce (ultimately to zero). If a sensor is returned into clean air after saturation has occurred, it will usually recover. However, this recovery may take many hours (depending on the severity of saturation).
Continuous monitoring has at times been attempted by cycling two or more sensors in and out of the contaminated gas stream, such that each sensor is only exposed to the gas contaminant for a fraction of the time, and in theory recovering while out of the contaminated gas stream. However, in practice, it can be difficult to predict the time it will take for a specific sensor to reach saturation. Time to saturation depends on several factors, including sensor type, gas concentration, flow rate, gas delivery design, temperature and humidity. Additionally, the rate of saturation depends on the gas concentration. If the gas concentration exposed to the sensor is small compared to its range, then it will take longer to saturate. In some cases, sensors with larger ranges have been able to cope with continuous exposure to small amounts of gas for many months. Such systems have many drawbacks and are not widely adopted.
Poor energy efficiency is another drawback of many systems that attempt continuous monitoring of contaminant gasses because such systems require continuous operation, which may require pumps and fans to operate continuously. Every year much of the energy consumed is wasted through transmission, heat loss and inefficient technology, costing families and businesses money and leading to increased carbon footprint.
Energy efficiency is one of the easiest and most cost-effective ways to combat climate change, clean the air we breathe, improve the competitiveness of our businesses and reduce energy costs for consumers. However, it is impossible to be energy efficient in a variable process without a real time and continuous measurement able to retrofit the control system of the process.
Embodiments disclosed herein include gas monitoring systems comprising a self-cleaning and/or decontamination system with the objective to enhance the service life of a measuring gas sensor.
In one implementation, the present disclosure is directed to a gas monitoring system. The system includes a gas command circuitry and a decision logic configured to perform at least one of self-cleaning or decontamination for an electrochemical gas sensor communicating with the gas command circuitry.
In another implementation, the present disclosure is directed to a gas monitoring system for continuous gas contaminant monitoring in a gas treatment system having a gas treatment unit communicating with a contaminated gas source and outputting a treated gas. The monitoring system includes at least first and second sample gas streams receiving a gas sample from at least one of the contaminated gas source and the treated gas output; at least first and second selector valves, each communicating with one the gas sample stream, the selector valves each configured to select between the gas sample stream and an air stream to provide at least first and second sample input streams each selectively comprising the gas sample or air; and at least first and second gas sensors, each receiving one the sample input stream; and a decision logic configured to control the selector valves to switch the sample input stream from gas sample to the air after a first parameter is met and to switch from the air to the gas sample after a second parameter is met.
In yet another implementation, the present disclosure is directed to a gas monitoring method, which includes providing an input stream to a gas sensor; selectively switching the input stream between a gas sample stream and a cleaning air stream, wherein the input stream is switched from the gas sample stream to the cleaning air stream based on a first parameter, and the input stream is switched from the cleaning air stream to the gas sample stream based on a second parameter; detecting a gas contaminant in the gas sample stream with the gas sensor; and cleaning the gas sensor with the cleaning air stream.
In still another implementation, the present disclosure is directed to a gas sensor cleaning kit for retrofitting an existing gas monitoring system having a gas sensor receiving a sample input stream from a contaminated gas source of a gas. The kit includes a selector valve configured to be disposed in the sample stream to selectively switch between the gas sample stream and a cleaning air stream; and a decision logic configured to switch the selector valve from the gas sample input stream to the air input stream after a first parameter is met and to switch the air input stream to the gas sample input stream after a second parameter is met.
For the purpose of illustrating the disclosure, the drawings show aspects of one or more embodiments of the disclosure. However, it should be understood that the present disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:
Embodiments disclosed herein provide autonomous systems and methods to measure contaminants in a contaminated gas stream and provide feedback to a control system to reduce the unit usage when contaminants are present in specific detectable quantities or in quantities lower than the anticipated limits. This unload of the equipment not only extends its service life, will make it more efficient by consuming less power thus making the system energy efficient, reducing operational cost and saving taxpayers money.
Disclosed embodiments monitor a gas stream input and/or input and output continuously or at predefined intervals adjustable by the user on odor control or air emission treatment equipment (new or existing). The predefined intervals may be at any time interval, and can be made effectively continuous by ganging together multiple sensors, each with its own inputs from the source air stream and ambient air for recovery. In such a multi-sensor arrangement, continuous sensing is possible by sequentially switching the air source to be tested to different sensors while switching the previously active sensor to ambient air input for recovery as described below.
Embodiments disclosed herein are configured to measure the contaminants in the input air streams at user-selected intervals to allow the odor control or air emission treatment system to reduce power consumption according to variable inlet contaminant concentrations. Disclosed monitoring systems are also designed to clean a gas sensor probe/detector once a reading is taken to avoid damage, deterioration or saturation due to continuous exposure. In other embodiments, a retrofittable monitoring system kit is provided to achieve advantages described herein with previously installed monitoring and treatment systems.
An illustrative embodiment of a monitoring system according to the present disclosure is schematically depicted in
After exiting measuring chamber 22, sampled stream 30 is exhausted at exhaust outlet 32. Exhaust may be back to atmosphere or return sampled stream 30 back to the contaminated gas source. Sensor 24 is positioned to detect contaminants in input stream 20 within measuring chamber 22. Sensor 24 produces an output signal indicative of the measured contaminants in accordance with sensor setup, which signal is delivered to decision logic 18 via communication link 34. After decision logic 18 receives the sensor signal via communication link 34, a control signal is delivered to selector valve 16 via communication link 36 switching the selector valve to change input stream 20 to atmospheric (clean) air via air intake 14. Delivery of atmospheric air to measuring chamber 22 allows self-cleaning and decontamination of sensor 24.
In some embodiments, it may be desirable to additionally provide a control signal to pump 26 with decision logic 18. For example, in some systems where gas to be sampled is provided at a relatively high pressure, pump 26 may be needed only to ensure sufficient pressure in atmospheric air supplied from air intake 14. In such systems, pump 26 may be cycled off by decision logic 18 when not needed. An additional communication link 38 may be provided for communication with pump 26.
Gas sensors used in embodiments of the present disclosure may comprise any suitable type of commercially available gas sensor as may be selected by persons skilled in the art based on the teachings of the present disclosure. In particular, embodiments described herein are well-suited for use with electrochemical sensor systems for detection of gases such as Carbon Monoxide (CO), Oxygen (O2), Hydrogen Sulfide (H2S), Sulfur Dioxide (SO2), Ammonia (NH3), Chlorine (Cl2), Hydrogen Fluoride (HF) among others.
Decision logic 18 comprises a set of instructions for determining timing and period of selection between atmospheric air and contaminated gas sample as inputs to measuring chamber 22, and may include as parameters preset or user-defined timing parameters and signal information from sensor 24. In some embodiments, decision logic 18 can be embodied in a circuit, or executed by a data processing device comprised of components such as one or more processors, memory, user interface and application interface. Alternatively, decision logic 18 may be embodied in a programmable logic controller (PLC) with both analog and digital inputs and outputs, a communications module, and a human machine interface (HMI) with a touch screen that allows the system to interact with the user. Communication links as described herein may be wired or wireless, or a combination of both and may be executed with conventional communications protocols such as LAN, WLA, WIFI, Bluetooth, etc. Controllers may include communication modules configured to communicate information to the user in many different modes such as modem or gateway to send system information to a cloud-based system, a SCADA, and/or email or text messages of alarm conditions to selected personnel.
An exemplary embodiment of decision logic 18 is illustrated in
After the system configuration is set, sensors are activated 44, the pump (where present) is activated 45, and the selector valve is switched to gas sample mode 46 to deliver the gas sample stream to the measuring chamber. After a defined time typically based on system configuration (configuration factors such as type and size of conducting tubing, pump parameters and distance from sampling inlet to measuring chamber), the sample of contaminated gas will reach and flow through the measuring chamber for detection by the sensor 47. After the sensor reading stabilizes and the measured contaminant value determined, the selector valve is switched to atmospheric air putting the system into cleaning mode 48. In some embodiments, sensing time 47 may be a predefined time period based on parameters such as sensor type/performance and user preferences in specific applications, or, alternatively, sensing time may be dynamic based on setpoint values of measured contaminants.
In cleaning mode 48, the pump delivers fresh air to allow the sensor to be cleaned and decontaminated. The decontamination time will typically be a preset time period defined by the user based on the sensor type and specifications. In some embodiments, output from additional sensors indicating the main sensor state may be dynamically incorporated into the determination of decontamination time. After the decontamination time, the pump is turned off 49. Typically, system components will be maintained in an off state until the next monitoring cycle. Particularly in long sampling cycles turning the system off is a good energy saving practice facilitated by embodiments disclosed herein.
In a simplified embodiment, after measuring contaminants in the gas sample stream, decision logic 18 will send a signal to the machine or process control and jump to the alarm condition check. In some more advanced alternative embodiments (e.g., as shown in
Optional or additional checks of different contaminants 52, 53 can be done in processes with more than one contaminant or otherwise where several measurements must be performed to identify the additional contaminants. Overall, the process with optional or additional checks is generally the same in terms of the cycle, after the first contaminant measurement the system will check for the second contaminant, will determine the level of the second contaminant, and will send a signal 54 according to the presets in a process as described before. After the measuring cycle, an alarm check is performed 55 and if there is any specified alarm condition detected, an alarm warning is sent 56. The determination of whether monitoring is complete 57 may be based on user-set preferences such as time or a specified number of measuring cycles. When the user-set preference for completion of monitoring is met, the control sequence ends 58 until re-initiated.
Measuring chamber 76 is the point of the system where a detecting element of gas sensor 78 contacts the gas sample stream to generate an electric signal delivered to controller 80 via communication link 82 proportional to contaminants detected within the sampled gas stream. In this embodiment, controller 80 contains decision logic 18 as described above. Controller 80 delivers a control signal to gas treatment system 60 to modulate treatment control based on level of sampled contaminants via communication link 84. One example of a gas treatment system is disclosed in U.S. patent publication No. 2020/0406189A1, entitled “Multi-Stage Treatment System and Methods for Removal of Target Vapor Compounds from Contaminated Air Streams,” which is incorporated by reference herein in its entirety. Controller 80 may comprise one or more processors, memory, user interface and application interface. Controller 80 further may be configured to execute control algorithms stored in memory based on inputs from the sensor probe and other inputs as may be required by persons of ordinary skill based on the teachings contained herein. After controller 80 takes the measurement of the contaminant, based on decision logic 18 controller 80 switches selector valve 74, closing the intake of contaminated gas from sampling inlet 69 to switch to atmospheric air from air intake 86 to self-clean and decontaminate gas sensor 78.
Gas monitor control kit 100 includes many of the same components as described above in connection with
The teachings of the present disclosure can be used in many other applications or embodiments. For example, as depicted in
In a further alternative embodiment shown in
As will be appreciated by persons of ordinary skill in the art, the embodiment shown in
Further features and advantages of embodiments disclosed herein include:
The foregoing has been a detailed description of illustrative embodiments of the disclosure. It is noted that in the present specification and claims appended hereto, conjunctive language such as is used in the phrases “at least one of X, Y and Z” and “one or more of X, Y, and Z,” unless specifically stated or indicated otherwise, shall be taken to mean that each item in the conjunctive list can be present in any number exclusive of every other item in the list or in any number in combination with any or all other item(s) in the conjunctive list, each of which may also be present in any number. Applying this general rule, the conjunctive phrases in the foregoing examples in which the conjunctive list consists of X, Y, and Z shall each encompass: one or more of X; one or more of Y; one or more of Z; one or more of X and one or more of Y; one or more of Y and one or more of Z; one or more of X and one or more of Z; and one or more of X, one or more of Y and one or more of Z.
Various modifications and additions can be made without departing from the spirit and scope of this disclosure. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present disclosure. Additionally, although particular methods herein may be illustrated and/or described as being performed in a specific order, the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this disclosure or of the inventions as set forth in following claims.
The present application claims priority to U.S. Provisional Application No. 63/051,501, filed Jul. 14, 2020, entitled “Continuous Monitoring Odor Control Systems and Methods,” which is incorporated by reference herein in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US21/41220 | 7/12/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63051501 | Jul 2020 | US |
