CN114025864A

CN114025864A - Optimization of wet scrubber process flow by on-line measurement and control of entrained gas in scrubber liquid

Info

Publication number: CN114025864A
Application number: CN202080045312.8A
Authority: CN
Inventors: B.麦格尼斯; J.特布尔; M.麦金尼; J.库尔茨; R.达雷尔
Original assignee: Buckman Laboratories International Inc
Current assignee: Buckman Laboratories International Inc
Priority date: 2019-05-20
Filing date: 2020-05-20
Publication date: 2022-02-08
Also published as: WO2020236927A1

Abstract

Systems and methods for reducing foaming in a wet scrubber system. The system uses a device for measuring the volume of entrained gas in a wet scrubbing system and automatically or semi-automatically adjusts one or more process parameters, including: flow rate of antifoam/defoamer chemical in the wet scrubber; the flow rate of the flue gas; and fresh water flow rate. The system allows for real-time monitoring and control of foam in the wet scrubber.

Description

Optimization of wet scrubber process flow by on-line measurement and control of entrained gas in scrubber liquid

Cross Reference to Related Applications

The present invention claims priority from U.S. provisional patent application No. 62/850,396 filed on day 5/20 in 2019 and U.S. provisional patent application No. 62/948,609 filed on day 16 in 2019, both of which are incorporated herein by reference in their entireties.

Background

Technical Field

The present invention generally relates to systems and methods for improving wet scrubbing systems. More specifically, the present invention is a system as follows: the system is used to reduce foaming in a wet scrubber system based on real-time measurements of entrained gases and based on such measurements to adjust the application of chemical additives and other processing parameters.

Background

Wet scrubbers are employed in a variety of industries to remove particulate matter and harmful gases from flue or exhaust gas streams exiting the process. There are a number of different wet scrubber designs, but all rely on passing the exiting gas stream (which contains particulate or gaseous contaminants from the waste stream of an industrial process) through a scrubbing liquid to remove the target particulate and/or gas from the exiting gas stream. A variety of scrubbing liquids are known in the art for various applications, depending on the nature and quality of the particulate matter and/or gas intended to be removed. Many known liquid formulations for washing are prone to foaming under process conditions characteristic of standard wet-washing operations. Entrained gas in the scrubbing liquid in a wet scrubbing operation and foam generated from the scrubbing liquid contain gas in the form of small bubbles contained in the liquid continuous mixture.

Excessive gas entrainment and bubbling in wet scrubbing operations results in a loss of performance caused by a number of factors, including: supply pump cavitation and effluent migration and corrosion in areas not designed to handle scrubber liquids. Supply pump cavitation will reduce the recirculation flow to the scrubber, reducing the capacity of the scrubber to perform. This loss of recycle flow can lead to scrubber performance excursions and potential license violations.

Currently, wet scrubber operators rely on several different techniques to manage bubbling and cavitation around the scrubber. These techniques include: (a) loading a continuous base (base) of antifoam/antifoam chemical into the spray system or recycle liquid, (b) periodically adding fresh water to the system, provided with an additional system drain, and (c) periodically interrupting or reducing the feed to the scrubber. Of the above, the methods (b) and (c) have the obvious disadvantage that the operation of the scrubber must be stopped during the process. In many cases, this may also require a temporary suspension of the production process, the scrubber in question being designed to treat the off-gas of the production process. In addition, method (a) (continuous base loading of antifoam chemical) may limit the ability of the scrubber liquid to maintain entrained oxygen levels, which are necessary to make some scrubber oxidation reactions effective, thereby limiting the performance of the scrubber. This metering method is also responsible for the higher operating costs of the scrubber.

Unfortunately, current systems apply such foaming control techniques in an as-needed, ad hoc, or pre-programmed manner, often resulting in excessive process line shut-down to combat perceived foaming problems, excessive use of antifoam/antifoam chemicals, and/or insufficient use of the aforementioned techniques when needed, resulting in excessive foaming and consequent loss of performance.

It would be advantageous to have a system that: the system is capable of determining the appropriate level of antifoam/antifoam chemical needed in the system, and/or the appropriate discharge schedule or frequency, and automatically applying a given foam control technique, controlling that technique, or alerting the operator to the need for that technique to improve the overall efficiency of the system and associated industrial process. Such a system would ideally be able to control/limit excessive entrained gas levels while also limiting the period of low entrained gas that inhibits optimal oxidation reaction performance.

Disclosure of Invention

Accordingly, the present invention is a system and method for actively optimizing the foam control operation through real-time monitoring and control of gas content in a wet scrubber system.

The foregoing objects, features and attendant benefits of the present invention will be in part specifically pointed out and will become more readily appreciated as the following: the invention will be better understood by reference to the following detailed description of the preferred embodiments and certain modifications thereof when taken in conjunction with the accompanying drawings.

Drawings

In the drawings:

FIG. 1 is a schematic diagram of a preferred embodiment of the inventive system showing the system applied to a recirculation tank 100 for the wash liquid, which recirculation tank 100 may be used in connection with known wet scrubbing operations.

Figure 2 is a diagram of one embodiment of the inventive system applied to three recirculation tanks 100, the recirculation tanks 100 supplying fuel to three recirculation pumps, each pump supplying scrubber liquid to a wet scrubber spray tower.

Detailed Description

The present invention includes a system and method for automatically controlling entrained gas present in a recirculation system of a wet scrubber using real-time, on-line measurements. This automated measurement and control of entrained gas will increase the efficiency of the wet scrubber by reducing the negative impact that foam control measures have on the operation of the scrubber and as a result will likely enhance the performance of the industrial project in which the scrubber is applied as a whole.

This on-line measurement provides real-time advantages over current practice. The online measurement of entrained gas present allows for real-time adjustment of scrubber parameters as entrained gas levels vary. As previously described, current systems are used in an as-needed, temporary, or pre-programmed manner, often resulting in excessive process line shut-down to combat perceived foaming problems, excessive use of antifoam/antifoam chemicals (which limit the efficiency of oxidation reactions in the scrubber), and/or insufficient use of the aforementioned techniques when needed. The present invention provides real-time automated or near automated control and adjustment of antifoam/antifoam chemical dosage to control the volume of entrained gas in scrubber systems. The present invention also provides automated or near-automated control and adjustment of blowdown, air injection rate (on the equipped scrubbers), or downtime schedule or frequency to minimize such downtime as possible while preventing excessive foam buildup that can cause damage to the processing equipment and lead to washing inefficiency or license violations.

Systems according to the present invention include entrained air measurement devices such as those described in U.S. patent No. 8,109,127, which is incorporated herein by reference in its entirety. The apparatus described in us patent No. 8,109,127 uses a sonar to measure the volume of entrained gas in a liquid process stream in real time during processing. Other devices capable of providing a measure of entrained gas in the process feed may also be used in the system of the invention described herein.

In addition, the inventive system includes a processor capable of receiving, recording, and processing data received by the entrained air measurement device. In a preferred embodiment, the processor is also operatively connected to the controller for varying various process parameters in the wet scrubbing system, such as the feed rate of various additive feeds (including antifoam/antifoam chemicals, fresh water, flue gas, scrubber liquids, and/or air injection) to the wet scrubber. Also in a preferred embodiment, the processor is operatively connected to sensors of other process parameters, such as sensors for measuring the actual feed rate of the various process/additive lines mentioned earlier, sensors for measuring ambient conditions, sensors for measuring the volume of contaminants in the waste stream (exhaust stream), and sensors for measuring conductivity, chloride (chloride ions), and/or pH in the washing system.

For example, the schedule and frequency of blowdown in a wet scrubbing system (e.g., in a recycle tank or vessel) of a coal plant (plant) is typically driven by conductivity and chloride (chloride ions), as high levels of these measurements can inhibit reaction performance. In other applications of wet scrubbing systems, such as corn mills, the schedule and frequency of blowdown may be driven by the measured pH in the recirculation tank or vessel, as certain reactions will drive the pH to the following points: at which point the reaction does not produce the desired end product (undesired reaction).

The inventive measurement and control system is applicable to any wet scrubber, i.e. a wet scrubber using a liquid to wash contaminants from a gas stream. This includes wet scrubbers that use limestone slurry (which acts as a "builder" for scrubbing). Other scrubbing aids, such as caustic or caustic soda, may be used in the scrubber to which the inventive system is applied, as desired by those skilled in the art.

In operation, the inventive system monitors the volume of entrained gas in the wet scrubber in real time in a continuous manner and adjusts/optimizes the entrained gas volume by controlling various available processing parameters. Such control may occur as follows: the control (over controls) can occur automatically through operational control of the system or manually by an operator based on guidance received by the system for real-time adjustment of the process parameters.

FIG. 1 is a schematic illustration of an exemplary recirculation tank 100 for a liquid for scrubbing, which recirculation tank 100 may be used in connection with known wet scrubbing operations. As shown, the scrubbing liquid is received in the recirculation tank 100, and is then pumped via a recirculation pump 103 through a recirculation line 102 back to the wet scrubber tower, where the scrubbing reaction between the scrubbing liquid and the off-gas takes place. During this recycling process, in certain prior art systems, the pH of the wash liquor is sampled. Fig. 1 illustrates the following system: in this system, sample is taken from the recirculation line 102 after the pump 103, however it will be understood that other configurations are possible if not explicitly described in the prior art. As illustrated, the pH of the wash liquid is sampled (not shown), after which the wash liquid is returned to the recycle tank for eventual return to the recycle column. In this example, entrained gas measurement device 400 is located on pH sampling line 101, whereby the wash liquid flowing through pH sampling line 101 represents the wash liquid that is then present in the overall system. However, the present invention contemplates several possible locations for one or more entrained gas measurement devices 400 that can provide adequate measurements of entrained gas levels in the scrubber liquid as needed to operate the disclosed system and implement the methods of the invention described herein. The following fall within the scope of the invention: the entrained gas measurement device is positioned at any location within the system where an inline measurement or discrete sample of the scrubber liquid in the system is available, or may even be embedded in the reaction vessel or other system component. For example, the entrained gas measurement device may be installed as follows: in the existing sampling line, the pH measurement line (as shown), any other sampling line (e.g. the line that draws the sample directly from the scrubber tank), on a line adjacent to other instruments (e.g. a pH, ORP or air permeability meter), directly on the recirculation line, directly in the wall of the recirculation tank, or on the continuous discharge.

Wherever one or more entrained gas measurement devices are located within the system, they continuously (or at regular intervals) measure the entrained gas level of the scrubber liquid. Depending on the type of entrained gas measurement device used, the output from the device 400 may be transmitted to a central control station by known means (devices) compatible therewith. In fig. 1, a sensor head/transmitter unit 401 is hardwired (hard wired) to each entrained gas measurement device 400 and sends wired or wireless signals to various additional control units for implementing methods of actively controlling entrained gas levels in real time as described herein. For example, the transmitter 401 is shown in fig. 1 as being operatively connected (via the controller unit 403) to a drive unit of the antifoam pump 500 for controlling the level of antifoam/antifoam chemical supplied to the system based on readings from the entrained gas measurement device 400. Further, a connection (which may be wired or wireless) is displayed between the transmitter 401 and the main plant control center 600, where the output from the one or more entrained gas measurement devices 400 coupled with other plant data or sensor readings (available) may be processed and adjusted to determine an optimal level for the one or more antifoam pumps 500 throughout the plant (not shown), and other active control mechanisms including, but not limited to, feed rates of various additive feeds to the wet scrubber (including fresh water, flue gas, scrubber liquids, blowdown and/or air injection), or to control or inform downtime schedules or frequencies. In a preferred embodiment, the connection path between the transmitter 401 and the foam control element 500 and/or the main plant control center 600 passes through a (routed through) controller 403 that includes a processor running applications designed to output control signals to the respective foam control devices and other system-wide control devices based on inputs received from the entrained gas measurement device 400 and preprogrammed control algorithms. Also in certain embodiments of the invention, instead of an antifoam pump, element 500 in fig. 1 may represent an additional primary control mechanism operatively connected to the entrained gas measurement device 400, such as a fan (air fan), a discharge valve, an air injection valve, or similar device that may have an effect on the level of foam in the system.

Fig. 2 is a diagram of a system applied to three recirculation tanks 100 that supply fuel for three recirculation pumps (not shown in fig. 2), each of which supplies scrubber liquid to a wet scrubber spray tower. Fig. 2 illustrates how data from multiple entrained gas measurement devices 400 (each installed on a pH sampling line of a separate recirculation tank 100, although other configurations or locations of the entrained gas measurement devices 400 are possible, as previously described) may be used to provide control signals to a single antifoam pump 500 or other control device. As shown, transmitters 401 (wired or wireless) for three entrained gas measurement devices 400 are connected to an optional receiver 402 (which is associated with a controller 403) and an antifoam pump 500 (which supplies antifoam chemical to the gas scrubbing system) or other foam control device as previously described. Although not shown in fig. 2, each of the entrained gas measurement devices 400 (or its associated transmitters 401) may be connected, either wired or wirelessly, with a main plant control center or a sub-center dedicated to that part of the operation, thereby collecting signals received from the plurality of entrained gas measurement devices (and other available sensors) and performing any calculation or analysis operations to provide control signals to the antifoam pump 500 or other active control mechanism as described herein.

Thus, the system continuously receives inputs from: at least entrained gas measurement devices, and in certain embodiments, other sensors associated with the operation of the wet scrubber (such as one or more of those described herein), including conductivity, chloride (chloride ion), and pH sensors. In response to those measurements, the inventive system provides one or more output(s) to control or direct control of foam control measures or other process parameters.

In some preferred embodiments, the system operates automatically. Thus, the controller 403 according to the present invention includes a processor running a software application with one or more control algorithms to control in real time at least one of: flow rate to the antifoam/antifoam chemical in the wet scrubbing system; flow rate of fresh water into the wet scrubbing system; a feed rate to the flue gas in the wet scrubbing system; the feed rate of the compressed gas used for the blowdown of the wet scrubbing system. In a preferred embodiment, and as described, antifoam dosing control is achieved using a controller paired with a variable frequency drive connected to an antifoam dosing pump. To control other process parameters, such as blowdown, the entrained gas measurement device (or a controller receiving signals therefrom) will be operatively connected to: the controller is capable of controlling the automatic valve position or pump speed (% open or% speed) relative to the parameter being controlled. In other embodiments, the controller 403 sends a signal to the master plant control center 600 that is equipped with a (house) processor running a software application having one or more control algorithms to implement the functions as previously described. Alternatively, one or more of the controllers 403 and/or the master plant control center 600 may be installed or located in the cloud, the internet or intranet, or elsewhere on a remote server operatively connected to the inventive system.

In another preferred embodiment, the system operates by: real-time feedback is provided to an operator of the wet scrubbing system regarding the level of parameters (e.g., flow rate of fresh water or flow rate of anti-foaming agent to the wet scrubbing system) that should be met to reduce or otherwise optimize the level of entrained gas in the wet scrubbing system, whereby the operator can monitor the system in real-time or near real-time and manually adjust the indicated parameters.

In any of these embodiments, the inventive system may also provide an output having properties of an optimized discharge plan and/or frequency designed to reduce or otherwise optimize the volume of entrained gas in the system. Thus, the system of the present invention may be operated in a "check" mode for a period of time shortly after installation and/or at regular or predetermined intervals to record and analyze the effect of various levels of various process parameters, or existing blowdown schedules, on the level of entrained gas in the system. Thus, the system may suggest an "optimal" level for each of the parameters of the system and/or a discharge plan that will minimize or otherwise optimize the level of entrained gas in the system, and optionally continue to monitor and suggest adjustments to a predetermined "optimal" level in real time to control foaming.

In summary, the system provides a means for adjusting the antifoam or antifoam chemical dosage in real time to control entrained gases present. The inventive system may also be used to actively control discharge schedules or other operating parameters (e.g., air injection rates) for a wide range of wet scrubbing applications.

Although the apparatus disclosed herein is particularly useful in wet scrubbers that are predominantly used in many other industrial operations (energy, steel, petrochemical, etc.), the apparatus is suitable for use in other fields within the scope of the invention disclosed herein.

This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.

Statement of industrial applicability

Wet scrubbing systems are widely used technology in various industries and are necessary or highly useful to assist the industry in complying with federal and state air emission requirements. There is great industrial applicability in improving the operation of wet scrubbing systems used in various types of industrial operations, including energy, steel, petrochemical, and the like. The present invention not only improves the operation of the scrubber, but also reduces the operating cost of the scrubber and extends the life of the equipment.

Claims

1. A system, the system comprising:

a wet scrubber;

a sensor for measuring the volume of entrained gas in the fluid;

one or more controllers for controlling one or more process parameters; and

a processor operatively connected to the sensor.

2. The system of claim 1, wherein the one or more processing parameters are selected from the group consisting of: the flow rate of the antifoam/antifoam chemical in the wet scrubber, the flow rate of the flue gas, the flow rate of the fresh water, the conductivity level, the chloride level, the rate of air injection, and/or the pH of the liquid in the wet scrubber.

3. The system of claim 1, wherein the processor is operatively connected to at least one of the one or more controllers and is capable of automatically or semi-automatically adjusting at least one of the one or more controllers in real-time.

4. The system of claim 3, wherein the processor is capable of automatically or semi-automatically adjusting at least one of the one or more controllers in real-time in response to data received from the sensor representative of the volume of entrained gas in the fluid.

5. The system of claim 1, wherein the sensor is capable of measuring the volume of entrained gas in a recirculating fluid of the wet scrubber in real time.

6. The system of claim 1, wherein the sensor is positioned to measure a volume of entrained gas in a pH test line of the wet scrubber.

7. The system of claim 1, wherein the sensor is positioned to measure a volume of entrained gas in a recirculation line carrying a scrubber liquid to the wet scrubber.

8. The system of claim 1, further comprising one or more additional sensors for measuring the volume of entrained gas in the fluid, and wherein the sensors are operatively connected to one or more of the one or more additional sensors.

9. The system of claim 8, wherein the processor collects and analyzes entrained gas measurement data from each of the sensors and provides control signals to the one or more controllers based on a totality of the entrained gas measurement data.

10. The system of claim 9, wherein the one or more controllers comprise an anti-foam or anti-foam metering pump.

11. The system of claim 9, wherein the one or more controllers comprise an automated valve to control the rate of discharge and/or air injection into the wet scrubber system.

12. A method for reducing foaming in a wet scrubber system, the method comprising:

measuring a volume of entrained gas in the wet scrubber system;

automatically or semi-automatically adjusting one or more process parameters to control an amount of foam in the wet scrubber system.

13. The method of claim 12, wherein the one or more processing parameters are selected from the group consisting of: the flow rate of the antifoam/antifoam chemical in the wet scrubber, the flow rate of the flue gas, the flow rate of the fresh water, the conductivity level, the chloride level, and/or the pH of the liquid in the wet scrubber.