Patent Description:
In the chemical pulping industry, mill operators treat lignocellulosic material with either strong acids or strong bases to disassociate the lignin from the cellulosic fibers. Operators may then separate, wash, and further process the cellulosic fibers into pulp or other pulp-based products. Chemical process examples include: the Kraft process (also known as the "sulfate process"), the sulfite process, the soda pulping process, and the sulfite semi-chemical pulping process.

While the processing chemicals for each type of chemical process may vary, mill operators frequently recover and recycle these process chemicals to operate the mill economically. For example, in the Kraft process, mill operators digest lignocellulosic material (commonly wood chips) in large pressurized vessels with "white liquor" comprising sodium hydroxide (NaOH) and sodium sulfide (Na<NUM>S). During the digestion step, the white liquor reacts with lignin and other compounds in the lignocellulosic material and takes on a dark color. Unsurprisingly, this reacted liquor is known as "black liquor. " Whereas the white liquor comprises the reactants sodium hydroxide (NaOH) and sodium sulfide (Na<NUM>S), the black liquor contains the chemical products sodium carbonate (Na<NUM>CO<NUM>) and sodium sulfate (Na<NUM>SO<NUM>). While sodium hydroxide (NaOH) and sodium sulfide (Na<NUM>S) are generally inexpensive, it is generally cost prohibitive to purchase new solutions of sodium hydroxide (NaOH) and sodium sulfide (Na<NUM>S) to maintain production. For this reason, many chemical pulp mills use pyrolytic chemical recovery systems to recycle at least a portion of the produced sodium carbonate (Na<NUM>CO<NUM>) and sodium sulfate (Na<NUM>SO<NUM>). Converting these products back into the commercially useful chemical reactants, sodium hydroxide (NaOH) and sodium sulfide (Na<NUM>S), allows mills to run economically.

New black liquor from a chemical digester is generally dilute and non-combustible. Therefore, to prepare black liquor for pyrolysis, operators generally funnel the black liquor through flash tanks or other evaporation steps to concentrate the solid particles in the black liquor. Operators then heat and inject the concentrated black liquor into a chemical recovery boiler. The recovery boiler evaporates the remaining water from the black liquor droplets and the solid compounds in the black liquor undergo partial pyrolysis. The remaining inorganic compounds fall to the bottom of the furnace and accumulate in a char bed. Some of the carbon and carbon monoxide in the char bed acts as a catalyst to convert most of the sodium sulfate (Na<NUM>SO<NUM>) into sodium sulfide (Na<NUM>S). The sodium sulfide (Na<NUM>S) then exits the recovery boiler with the sodium carbonate (Na<NUM>CO<NUM>) as liquid smelt.

This smelt flows through one or more smelt spouts at the bottom of the recovery boiler. Coolant, usually water, may cool the smelt spouts. Operators typically collect the green liquor and transport the green liquor to a causticizing plant to react the sodium carbonate (Na<NUM>CO<NUM>) with lime (CaO) to convert the sodium carbonate (Na<NUM>CO<NUM>) into sodium hydroxide (NaOH) and thereby reproduce the white liquor.

As the smelt contacts the green liquor in a dissolving tank, the smelt explodes and emits a series of audible sounds. This is generally known as "banging" by those in the industry. The smelt flowing from the spout is typically between <NUM> degrees Celsius (°C) to <NUM>, while the average temperature of the green liquor is about <NUM> to <NUM>. Without being bound by theory, it is believed that the large temperature difference may increase the reactivity of the smelt and green liquor and thereby cause or contribute to banging. If left unregulated, a sudden influx of smelt may cause an explosion in the dissolving tank and recovery boiler, which poses grave safety risks to nearby operating personnel.

To manage smelt dissolution and to avoid excessive noise and the possibility of catastrophic explosions, conventional dissolving tanks generally disrupt the smelt as the smelt falls from the spout. Disruptors may be one or more shatter jets. A shatter jet blasts the falling smelt with steam or other shattering fluid at high pressure to create smelt droplets. These droplets collectively have a greater surface area than an undisrupted smelt flow. The individual droplets also have a smaller volume than an overall undisrupted smelt flow. The increased surface area and smaller amounts of reactants allows for banging explosions that are generally less intense than the explosions would be if the smelt contacted the green liquor as a continuous, uninterrupted, undisrupted flow. Typically, the end of the spout is elevated above the liquid level of green liquor and the shatter jets disrupt falling smelt as the smelt falls from the spout end. The shatter jet nozzles typically cannot be adjusted remotely. When a smelt upset occurs, operators generally cannot safely adjust the discharge rate of disrupting fluid into the dissolving tank.

<CIT> relates to a method and assembly for disrupting the flow from the smelt spout of a recovery boiler.

Occasionally, smelt may cool prematurely in the recovery boiler or spout and decrease or eliminate the smelt flow rate. In this antediluvian state, liquid smelt tends to accumulate behind the obstruction. If the obstruction dislodges, the sudden smelt influx may overwhelm the shatter jet's ability to disrupt the smelt into sufficiently small droplets and an agitator's ability to mix the influx into the green liquor effectively. Moreover, if the deluge is particularly substantial, the smelt may flow over the sides of the spout and bypass the shatter jets entirely. In other scenarios, a shatter jet or agitator may fail. In these situations, the increased volume of smelt contacting the green liquor drastically increases the banging's explosive intensity and explosion risk.

In many mills, operators commonly move in and amongst the processing equipment to monitor process conditions and output. An explosion in the dissolving tank or recovery boiler poses a serious safety risk to personnel in the immediate vicinity, and the resulting fire poses a serious risk to personnel in the rest of the mill. Such explosions also cause an unregulated amount of pollutants to enter the air and groundwater and predicate significant production loss. Explosions of this scale can inactivate a mill for weeks to months.

Previous attempts to address this problem can be seen in the apparatus and method described in <CIT>, entitled, "Cooled Smelt Restrictor at Cooled Smelt Spout for Disrupting Smelt Flow from the Boiler". This apparatus comprises a door that is configured to partially or substantially restrict smelt flow in a closed position. However, this device is a single-use solution that relies on precise timing to prevent an explosion. Because it is a single-use device, operators must shut down the recovery boiler and shut down or re-direct ancillary processes to replace a used "smelt restrictor. " The recovery boiler shutdown interrupts production, often for days or weeks.

<CIT>, entitled, "Acoustic Emission System and Method for Predicting Explosions in a Dissolving Tank", describes a system configured to measure and evaluate banging in order to predict smelt explosions. While these systems have been generally effective at reducing explosions, both systems are reactive and generally trigger a failsafe just moments before an explosion might otherwise occur. Therefore, a failure of one of these systems at a critical moment could result in the same explosions that plagued conventional recovery boilers and dissolving tanks.

Furthermore, undissolved smelt may accumulate at the dissolving tank's floor, which can reduce the quality of the green liquor and increase scaling inside the dissolving tank. Scaling on the primary agitator's propeller increases the mass of the propeller, thereby requiring the motor to expend additional energy to maintain a desired rotational velocity and in extreme cases, reduce the mixing in the dissolving tank increasing the potential for an explosion. Neither of the devices disclosed in <CIT> or <CIT> address this issue.

<CIT> discloses a method and device for emptying the floor of a soda recovery boiler.

From <CIT>, a method of processing a wood fibre fraction to form a gellike pulp is known.

The present invention provides a system as recited in claim <NUM>, and a method for monitoring and adjusting a rate of smelt dissolving in a dissolving tank as recited in claim <NUM>.

The problem of runaway smelt explosions due to heavy smelt flows in a dissolving tank and the problem of scaling of the primary agitator in the dissolving tank is mitigated by a system comprising an ultrasonic transducer having a transducing end disposed in the dissolving tank, wherein the ultrasonic transducer emits ultrasonic waves above <NUM> kilohertz ("KHz").

Without being bound by theory, it is contemplated that the ultrasonic waves may destabilize a protective layer of vapor that can form around a smelt droplet in a dissolving tank. A collapsed vapor layer may accelerate the molten smelt droplet's contact with the green liquor, thereby accelerating the rate of the smelt's banging and decelerating the smelt's rate of dissolving into the green liquor for a given set of process conditions. Without ultrasonic waves, it is contemplated that the protective layer of vapor may form a barrier between the molten smelt droplet and the green liquor, thereby permitting the potential accumulation or amalgamation of smelt droplets in the dissolving tank to explosive levels. Such an amalgamation would effectively undermine the disruptor's intended function.

It is further contemplated that the ultrasonic waves may create an energetic environment that prevents pirssonite (Na<NUM>CO<NUM> · CaCO<NUM> · <NUM><NUM>O), calcite (CaCO<NUM>), and other precipitates from accumulating on the agitators. Accordingly, another exemplary embodiment may comprise placing an ultrasonic transducer in a green liquor or white liquor conduit or a white liquor holding tank to mitigate scaling.

In certain exemplary embodiments, sensors may be disposed in or around the dissolving tank to monitor the rate of smelt flow into the dissolving tank. These sensors may transduce signals from the dissolving tank and transmit said signals to a data processor such as a computer, a programmable logic controller ("PLC"), a field programmable gate array ("FPGA"), an application-specific integrated circuit ("ASIC"), or other processor. The data processor may modulate the intensity of the ultrasonic waves emitted by the ultrasonic transducer to accommodate changes in smelt flow. In other exemplary embodiments, the data processor may adjust the power or frequency of the ultrasonic transducer in response to changes in process conditions. For example, when the sensors detect an upset condition, the data processor may increase the intensity or the frequency of the ultrasonic waves emitted toward the falling smelt. In certain exemplary embodiments, the data processor may regulate both the intensity and the frequency of the ultrasonic waves.

In still other exemplary embodiments, the data processor may adjust the rate of agitation based upon inputs from the sensors and ultrasonic transducer. In still other exemplary embodiments, the data processor may adjust a discharge rate of the disruptor in response to input from the sensors and ultrasonic transducer. By way of example, the sensors and control system may include the sensors and control system described in <CIT>.

In other exemplary embodiments, the sensors may include but are not limited to accelerometers, strain sensors, acoustic sensors, temperature sensors, density analyzers (including for example Baumé hydrometers), and density chemical analyzers such as total titratable alkali ("TTA") analyzers, cameras, and combinations thereof.

In an exemplary embodiment, an ultrasonic transducer may be used in conjunction with a disruptor such as a shatter jet nozzle. In such an embodiment, it is believed that the use of an ultrasonic transducer in conjunction with a shatter jet may reduce or eliminate the amount of disrupting fluid (e.g. steam) used to disrupt the smelt into smelt droplets. Furthermore, it is contemplated that that the use of the ultrasonic transducer system described herein can agitate the dissolving liquid and facilitate the circulation and dissolution of smelt droplets in the dissolving liquid (e.g. green liquor). As a result, a primary agitator (e.g. a main dissolving tank or "MDT" agitator) may be operated to use less energy to circulate the dissolving liquid in the dissolving tank.

The exemplary systems described herein may further increase personnel safety by eliminating the need for operating personnel to adjust manually the flow of fluid through the shatter jets during normal, upset, or transient conditions.

The foregoing will be apparent from the following more particular description of exemplary embodiments of the disclosure, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, with emphasis instead being placed upon illustrating the disclosed embodiments.

<FIG> is a schematic representation of an exemplary ultrasonic smelt dissolving and shattering system <NUM>. <FIG> depicts a recovery boiler <NUM> having a spout <NUM> adjacent to a dissolving tank <NUM>. The spout <NUM> directs a volume of smelt <NUM> into the dissolving tank <NUM>. As seen in the cutaway, the dissolving tank <NUM> contains a dissolving liquid <NUM>. The dissolving liquid <NUM> is commonly green liquor. The liquid level <NUM> of the dissolving liquid <NUM> is generally below the top <NUM> of the dissolving tank <NUM>. A primary agitator <NUM> driven by a motor M agitates the dissolving liquid <NUM> and helps equalize the dissolving liquid's temperature. The motor M may be a variable speed drive motor. Although the primary agitator <NUM> depicted in <FIG> is a propeller <NUM> connected to a driveshaft <NUM>, it will be understood by those having ordinary skill in the art that an "agitator" is a device configured to move dissolving liquid <NUM> through the dissolving tank <NUM>. Other agitators may include for example, fluid jets <NUM>, devices that undulate the dissolving liquid <NUM>, and other rotating bodies.

Primary agitators <NUM> typically comprise a propeller <NUM> or other mechanical implement extending into the dissolving liquid <NUM>. Secondary agitators (see <NUM>) may be fluid jets <NUM> that inject air or other fluid into the dissolving liquid <NUM> to agitate the dissolving liquid <NUM>. While it is possible to use secondary agitators (see <NUM>) simultaneously with primary agitators <NUM>, operators more commonly activate secondary agitators (see <NUM>) when primary agitators <NUM> fail or underperform. As the volume of smelt <NUM> falls from the spout <NUM>, a disruptor <NUM>, for example, a "shatter jet," directs a pressurized disrupting fluid <NUM> (commonly in the form of steam) toward the falling smelt <NUM>. The disrupting fluid <NUM> interrupts the continuous smelt stream <NUM> and thereby creates smelt droplets <NUM>. While shatter jets are common types of disruptors <NUM>, it will be understood that other devices that break up or dropletize the smelt stream <NUM> falling form the spout <NUM> is a "disruptor" <NUM>.

After the smelt droplets <NUM> contact the dissolving liquid <NUM>, the smelt droplets <NUM> emit an audible bang and eventually dissolve into the dissolving liquid <NUM>. In an upset condition, the amount of undissolved smelt in the dissolving tank <NUM> increases. When the amount of undissolved smelt increases in the dissolving tank <NUM> due to an increased flow rate, the incoming smelt stream <NUM> can overwhelm a disruptor's ability to shatter the smelt stream <NUM> into sufficiently small smelt droplets <NUM>. Without being bound by theory, it is believed that the vast differences in temperatures between the volume of smelt <NUM> and the dissolving liquid <NUM> causes the smelt droplets <NUM> to explode soon after contacting the dissolving liquid <NUM>.

It was believed that an increased rate of smelt flow into the dissolving tank <NUM> was the only cause of upset conditions. However, Applicant discovered that a layer of vapor <NUM> (<FIG>) forms around the smelt droplet <NUM> (<FIG>) when the smelt droplet <NUM> has a temperature in the range of about <NUM> to about <NUM> and the dissolving liquid <NUM> (<FIG>) has a temperature in the range of about <NUM> to about <NUM>. This vapor layer <NUM> may insulate the smelt droplet <NUM> from the dissolving liquid <NUM> and thereby allow the smelt droplets <NUM>, <NUM> to accumulate and remain undissolved in the dissolving tank <NUM> even at nominal smelt flow rates.

To mitigate this problem, Applicant developed a system comprising an ultrasonic transducer <NUM> disposed within the dissolving tank <NUM>. The ultrasonic transducer <NUM> has a transducer end <NUM> that directs ultrasonic waves <NUM> having a frequency above <NUM> into the dissolving liquid <NUM>. The ultrasonic transducer <NUM> may be, by way of example, a piezoelectric transducer or a magnetostrictive transducer. If the ultrasonic transducer <NUM> is a piezoelectric transducer, the piezoelectric crystal may be barium titanate, lead zirconate titanate ("PZT"), or other piezoelectric crystal.

In operation, a piezoelectric ultrasonic transducer <NUM> vibrates rapidly in concert with an electrical signal oscillating an ultrasonic frequency. The electrical signal may originate from a power supply or other power source. The resulting movement of the ultrasonic transducer creates a series of compression waves (see <NUM>) that create millions of microscopic voids in the dissolving liquid <NUM>. These "voids" or "cavitation bubbles" collapse and release significant energy. For example, a collapsing cavitation bubble may reach temperatures above <NUM>,<NUM> and pressures above <NUM> megapascals ("MPa"). For comparison, the surface of the sun averages about <NUM>,<NUM>. Magnetostrictive ultrasonic transducers <NUM> operate similarly to the piezoelectric ultrasonic transducer <NUM> except that a magnetic field is used to vibrate the megnetostrictive transducer instead of an electrical signal.

Without being bound by theory, it is believed that the ultrasonic waves <NUM> and resulting cavitation may cause the vapor layer <NUM> to collapse faster than in dissolving tanks <NUM> lacking such an ultrasonic transducer <NUM>. The ultrasonic transducer <NUM> therefore reduces the delay of the smelt droplets <NUM> dissolving in the dissolving liquid <NUM>.

<FIG> depicts several exemplary placements of ultrasonic transducers <NUM> disposed in a dissolving tank <NUM>. It will be understood that different exemplary embodiments may have a subset of the depicted ultrasonic transducer <NUM> placements (e.g. ultrasonic transducers <NUM>a disposed at the dissolving tank floor <NUM>) or a combination of subsets (e.g. ultrasonic transducers <NUM>a disposed at the dissolving tank's floor <NUM> and ultrasonic transducers <NUM>b, <NUM>c disposed at a side <NUM> of the dissolving tank <NUM>). Furthermore, in other exemplary embodiments, one or more ultrasonic transducers <NUM> can be engaged to the dissolving tank <NUM>, for example, being engaged to the side <NUM> of the dissolving tank <NUM>, being engaged to the top <NUM> of the dissolving tank <NUM>, or being engaged to the floor <NUM> of the dissolving tank <NUM>.

<FIG> shows multiple ultrasonic transducers <NUM>a disposed at the dissolving tank's floor <NUM>. The depicted embodiment further illustrates an ultrasonic transducer <NUM>b disposed on the side <NUM> of the dissolving tank <NUM> under the liquid level <NUM>. A further ultrasonic transducer <NUM>c is placed on the side <NUM> of the dissolving tank <NUM> at the liquid level <NUM>. <FIG> also depicts an ultrasonic transducer <NUM>d extending from the top <NUM> of the dissolving tank <NUM> down into the dissolving liquid <NUM>. Ultrasonic transducer <NUM>f also extends from the top <NUM> of the dissolving tank <NUM>, but does not extend into the dissolving liquid <NUM>. Ultrasonic transducers <NUM>e have transducer ends <NUM>e disposed in the dissolving liquid <NUM> substantially away from the floor <NUM>, top <NUM>, and sides <NUM> of the dissolving tank <NUM>. A conduit ultrasonic transducer <NUM>g is disposed in an outlet conduit <NUM> fluidly communicating with the dissolving tank <NUM>. Exiting green liquor <NUM> flows downstream to the next recausticizing step, which is usually a green liquor clarifier configured to allow particles to settle out of the green liquor over several hours.

Placement of the ultrasonic transducers <NUM> may vary among exemplary embodiments depending in part upon the expected ultrasonic wave intensity and expected propagation. Propagation depends in part upon the power consumed by the ultrasonic transducer <NUM>. Wave propagation is also a function of the dissolving liquid's density and the distance and the medium through which the ultrasonic wave <NUM> travels.

For example, selecting an ultrasonic transducer <NUM> that has the power to transmit ultrasonic waves <NUM> though the depth D of the dissolving liquid <NUM> and placing the ultrasonic transducers <NUM>a at the dissolving tank's floor <NUM> may be preferable to placing a similarly configured ultrasonic transducer <NUM>b on the side <NUM> of the dissolving tank <NUM>. Ultrasonic waves <NUM> from a vertically disposed ultrasonic transducer <NUM>b on a side <NUM> of the dissolving tank <NUM> may reflect off the opposing sidewall and interfere with oncoming ultrasonic waves <NUM>.

The insulating vapor layer <NUM> is asymmetrically disposed around each smelt droplet <NUM>. As <FIG> depicts, buoyancy causes a majority of the vapor layer <NUM> to be disposed above the downward falling smelt droplet <NUM>. The top <NUM> of the smelt droplet <NUM> is generally hotter than the bottom <NUM> of the smelt droplet <NUM> and this temperature differential further contributes to the vapor layer's asymmetric distribution. Ultrasonic waves <NUM> coming from the dissolving tanks' floor <NUM> may therefore interact with the thinner portion of the vapor layer <NUM> thereby facilitating the vapor layer's collapse.

To reduce the power needed to transmit ultrasonic waves <NUM> from the floor <NUM> of the dissolving tank <NUM> to the liquid level <NUM>, it can be desirable to place the transducer end <NUM>e of an ultrasonic transducer <NUM>e under the smelt droplets <NUM> but substantially above the dissolving tank's floor <NUM>. "Substantially above" the dissolving tank's floor <NUM> may be about halfway from the liquid level <NUM>, less than one third the depth D from the liquid level <NUM>, or other distance sufficient to allow the ultrasonic waves <NUM> to travel from the transducer end <NUM>e upward to the liquid level <NUM> while maintaining a frequency above <NUM>. In other exemplary embodiments, an ultrasonic transducer <NUM> can be disposed at the midpoint of the depth D of the dissolving liquid <NUM> in the dissolving tank <NUM>. An ultrasonic transducer <NUM> disposed closer to the bottoms <NUM> of the smelt droplets <NUM> than the dissolving tank floor <NUM> will reduce the distance the ultrasonic wave <NUM> will travel and therefore the power needed to generate the ultrasonic wave <NUM>.

By reducing the delay between smelt droplet <NUM> contact with the dissolving liquid <NUM> and the dissolving of the smelt droplets <NUM> under nominal operating conditions, it is contemplated that mill operators may be able to reduce the amount of disrupting fluid <NUM> needed to dropletize the smelt stream <NUM>. The reduced disrupting fluid <NUM> may result in energy savings while improving safety. For this reason, it is contemplated that a disruptor <NUM> may be omitted in certain exemplary embodiments.

The ultrasonic waves <NUM> may further create an energetic environment in the dissolving tank <NUM> that vibrates the primary agitators <NUM>, sides <NUM>, and other metal components in the dissolving tank <NUM>. Without being bound by theory, the vibration of these metal components may prevent pirssonite (Na<NUM>CO<NUM> · CaCO<NUM> · <NUM><NUM>O), calcite (CaCO<NUM>), and other precipitates from accumulating on the primary agitators <NUM>, sides <NUM>, and other metal components in the dissolving tank <NUM> and in the outlet conduit <NUM>. To delay scaling in the past, operators increased the rate of speed of the primary agitators <NUM>. With the adoption of an exemplary system described herein, it is contemplated that operators may be able to reduce the speed of the primary agitators <NUM>, thereby saving energy and cleaning costs while increasing reliability and mixing efficiency.

Sensors <NUM> may be disposed in or around the dissolving tank <NUM> to monitor smelt flow conditions. The sensors <NUM> or the data processor <NUM> may be configured to adjust the intensity of the ultrasonic waves <NUM> based on the rate of smelt flow into the dissolving tank <NUM> or based on other process conditions. Other "process conditions" may include, for example, temperature, acoustic emissions from the banging, and the density of the dissolving liquid <NUM>.

Sensors <NUM> used in an exemplary ultrasonic smelt dissolving and shattering system <NUM> may be selected from the group consisting of: accelerometers, strain sensors, acoustic sensors, temperature sensors, cameras, and density analyzers (including, for example, Baumé hydrometers, or TTA analyzers), or combinations thereof. The ultrasonic smelt dissolving and shattering system <NUM> may comprise a data processor <NUM> configured to evaluate process conditions and to adjust a wave condition of the ultrasonic transducer <NUM> based upon the process conditions. In certain exemplary embodiments, the wave condition may be a wave frequency. In other exemplary embodiments, the wave condition may be a wave intensity. In still other exemplary embodiments, the wave condition may be both a wave frequency and a wave intensity (i.e. power transferred per unit area).

In certain exemplary embodiments, the data processor may be selected from the group consisting of a computer, a programmable logic controller ("PLC"), a field programmable gate array ("FPGA"), an application-specific integrated circuit ("ASIC"), or other processor.

In the depicted exemplary embodiment, the data processor <NUM> is in signal communication with the ultrasonic transducers <NUM>, the sensors <NUM>, the disruptor <NUM>, and the primary agitator <NUM>. Signal communication may be achieved through wires or wirelessly. It is further contemplated that "signal communication" may comprise the use of one or more intermediate signal processors (e.g. amplifiers, analog to digital converters, relays, filters, etc.) configured to modify and/or transmit the signals between the data processor <NUM> and the ultrasonic transducers <NUM>, the sensors <NUM>, the disruptor <NUM>, and the primary agitator <NUM>. It will be understood that other exemplary ultrasonic smelt dissolving and shattering systems <NUM> may not have a data processor <NUM> in signal communication with each of the ultrasonic transducers <NUM>, the sensors <NUM>, the disruptor <NUM>, and the primary agitator <NUM>.

Although not depicted, it is contemplated that the ultrasonic transducer <NUM>f extending from the top <NUM> of the dissolving tank <NUM>, the ultrasonic transducers <NUM>c suspended in the dissolving liquid <NUM>, and the conduit ultrasonic transducer <NUM>g can be in signal communication with the data processor <NUM> in a way substantially similar to the other depicted ultrasonic transducers <NUM>a, <NUM>b, <NUM>c, <NUM>d. In other exemplary embodiments, the secondary agitator (see <NUM>) may be in signal communication with the data processor <NUM>. Combinations of any of the disclosed embodiments are within the scope of this disclosure.

Because it is contemplated that the use of ultrasonic transducers <NUM> may allow operators to reduce the disruption rate and the agitation rate, it is further contemplated that the data processor <NUM> can be configured to adjust the rate of disruption and/or agitation based upon the signal output from the sensors <NUM> and ultrasonic transducers <NUM>. As an example of an exemplary method, the data processor <NUM> may receive a transducer output signal <NUM> from an ultrasonic transducer <NUM> and a sensor output signal <NUM> from a sensor <NUM>. The transducer output signal <NUM> may indicate that the ultrasonic transducers <NUM> are emitting ultrasonic waves <NUM> at maximum power. The sensor output signal <NUM> may indicate that the density of the dissolving liquid <NUM> is above the desirable range. The data processor <NUM> may analyze the signals <NUM>, <NUM> and send an agitator input signal <NUM> to the agitator (see <NUM>, <NUM>) to increase the rate of agitation. A desirable or "nominal" range for the density of the dissolving liquid <NUM> is typically between <NUM>,<NUM> kilograms per meter cubed ("kg/m<NUM>") and <NUM>,<NUM>/m<NUM>. If the sensor <NUM> is a temperature sensor, the desirable or "nominal" temperature range for the dissolving liquid <NUM> if the dissolving liquid <NUM> is green liquor is about <NUM> to <NUM>.

By way of another example, the data processor <NUM> may receive a transducer output signal <NUM> indicating that the ultrasonic transducers <NUM> are emitting ultrasonic waves <NUM> at maximum power. The sensor output signal <NUM> may indicate that the temperature of the dissolving liquid <NUM> is above the desirable range. An agitator output signal <NUM> may indicate that the agitator (see <NUM>, <NUM>) is outputting at maximum capacity. If the agitator is a primary agitator <NUM>, the agitator <NUM> could be rotating at maximum capacity. If the agitator is a secondary agitator (see <NUM>), the secondary agitator (see <NUM>) outputting at maximum capacity could be a fluid jet <NUM> injecting fluid into the dissolving tank <NUM> at a maximum rate. The data processor <NUM> can analyze the signals <NUM>, <NUM>, <NUM> and send a disruptor input signal <NUM> to the disruptor <NUM> to increase the rate of disrupting fluid <NUM> output, thereby increasing the disruption rate.

In other exemplary embodiments, the data processor <NUM> may send a transducer input signal <NUM> to the transducers to adjust the power output of the transducers, change a physical property of the ultrasonic waves <NUM> or otherwise adjust the ultrasonic transducers' emissions. In still other exemplary embodiments, the data processor <NUM> may receive a disruptor output signal <NUM> indicating the amount of disrupting fluid <NUM> the disruptor <NUM> emits per unit of time.

The data processor <NUM> may be further configured to adjust a discharge rate at which disrupting fluid <NUM> exits the disruptor <NUM> based on the process condition by sending a disruptor input signal <NUM> to the disruptor <NUM>. In still other exemplary embodiments, the data processor <NUM> is further configured to adjust the power of the agitator (see <NUM>, <NUM>) based on a process condition by sending an agitator input signal <NUM> to the agitator (see <NUM>, <NUM>) and thereby adjust an agitation rate.

In certain exemplary embodiments, a method for monitoring and adjusting a rate of smelt dissolving in a dissolving tank <NUM> comprises: receiving a sensor output signal <NUM> from an sensor <NUM>, the sensor output signal <NUM> indicating a process condition at a measured time, receiving a transducer output signal <NUM> from an ultrasonic transducer <NUM>, receiving an agitator output signal <NUM> from an agitator (see <NUM>, <NUM>), receiving a disruptor output signal <NUM> from a disruptor <NUM>, and comparing the sensor output signal <NUM>, transducer output signal <NUM>, agitator output signal <NUM>, and disruptor output signal <NUM> to preprogrammed acceptable operating conditions to determine whether the smelt <NUM> is dissolving at an acceptable rate.

An exemplary method further comprises sending a transducer input signal <NUM> to the transducer <NUM> to adjust the power output of the transducer <NUM>, intensity, or frequency of the ultrasonic wave <NUM>. An exemplary method may further comprise sending an agitator input signal <NUM> to the agitator (see <NUM>, <NUM>) to adjust the rate of agitation to return the dissolving tank <NUM> to desirable dissolving conditions. An exemplary method may further comprise sending a disruptor input signal <NUM> to the disruptor <NUM> to adjust the volume of disrupting fluid <NUM> exiting the disruptor <NUM> to return the dissolving tank <NUM> to desirable dissolving conditions. Yet another exemplary method may further comprise sending a sensor input signal <NUM> to the sensor <NUM> to adjust the sensitivity of the sensor <NUM>.

Another exemplary method for monitoring and adjusting a rate of smelt dissolving in a dissolving tank <NUM> comprises: receiving a sensor output signal <NUM> from a sensor <NUM> disposed within a dissolving tank <NUM>, the sensor output signal <NUM> indicating a process condition at a measured time, receiving a transducer output signal <NUM> from an ultrasonic transducer <NUM> disposed in a dissolving tank <NUM> indicating a transducer output (see <NUM>), comparing the sensor output signal <NUM> with a programmed desirable operation range for the process condition, comparing the transducer output signal <NUM> with a programmed desirable operation range for the transducer, sending a transducer input signal <NUM> to the transducer <NUM> to adjust the transducer output (see <NUM>) when the sensor output signal <NUM> is outside the desirable operation range for the process condition.

An exemplary method may further comprise: receiving an agitator output signal <NUM> from a primary agitator <NUM> indicating a rate of agitation, and sending an agitator input signal <NUM> to the agitator (see <NUM>, <NUM>) to adjust the rate of agitation when the transducer output (see <NUM>) is outside of the programmed desirable operation range for the transducer <NUM>.

Another exemplary method may further comprise: receiving a disruptor output signal <NUM> from a disruptor <NUM> indicating a rate of disruption, and sending a disruptor input signal <NUM> to the disruptor <NUM> to adjust the rate of disruption when the transducer output (see <NUM>) is outside of the programmed desirable operation range for the transducer <NUM>. A further exemplary method may comprise pulsing the ultrasonic transducers <NUM> between an on and an off position over a period to increase smelt dissolving and prevention of scaling. Pulsing may further comprise alternating between a first transducer output and a second transducer output wherein the first transducer output and the second transducer output comprise different power levels, wave intensity, wave frequency, or other wave condition.

Yet a further exemplary method may further comprise: receiving a conduit transducer output signal (see <NUM>) from a conduit ultrasonic transducer <NUM>g disposed in an outlet conduit <NUM> indicating a conduit transducer output, comparing the conduit transducer output signal (see <NUM>) with a programmed desirable operation range for the conduit ultrasonic transducer <NUM>g, sending a conduit transducer input signal (see <NUM>) to the conduit ultrasonic transducer <NUM>g to adjust the conduit transducer output when the sensor output signal <NUM> is outside the desirable operation range for the process condition.

An exemplary system <NUM> comprises: a dissolving tank <NUM>, a spout <NUM> adjacent to the dissolving tank <NUM>, wherein the spout <NUM> is configured to convey a volume of smelt <NUM> into the dissolving tank <NUM>, an agitator (see <NUM>, <NUM>) disposed in the dissolving tank <NUM>, wherein the agitator (see <NUM> , <NUM>) is configured to mix the volume of smelt <NUM> into a dissolving liquid <NUM> in the dissolving tank <NUM>, and an ultrasonic transducer <NUM>, wherein the ultrasonic transducer <NUM> is configured to emit ultrasonic waves <NUM> within the dissolving tank <NUM> at a frequency above <NUM> kilohertz.

Claim 1:
A system comprising:
a dissolving tank (<NUM>);
a spout (<NUM>) adjacent to the dissolving tank (<NUM>), wherein the spout (<NUM>) is configured to convey a volume of smelt (<NUM>) into the dissolving tank (<NUM>);
an agitator (<NUM>) disposed in the dissolving tank (<NUM>), wherein the agitator (<NUM>) is configured to mix the volume of smelt (<NUM>) into a dissolving liquid (<NUM>) in the dissolving tank (<NUM>); and
an ultrasonic transducer (<NUM>), wherein the ultrasonic transducer (<NUM>) is configured to emit ultrasonic waves (<NUM>) within the dissolving tank (<NUM>) at a frequency above <NUM> kilohertz.