WO2018141434A1

WO2018141434A1 - System and method for operating reactor units in a process plant

Info

Publication number: WO2018141434A1
Application number: PCT/EP2017/080300
Authority: WO
Inventors: Harshad NERURKAR
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-01-31
Filing date: 2017-11-24
Publication date: 2018-08-09

Abstract

The present invention provides method and system for operating reactor units (102) in a process plant. In one embodiment, the process control system (100) comprises a reactor unit (102) provided with an enclosure (104) capable of producing a solute (126) and a residue (130), and automatic control valves (106, 108). The system (100) comprises a first sensor (116) disposed in the enclosure (104) and a second sensor (118) positioned in the discharge pipe (112). The system (100) comprises a control unit (120) which determines formation of a phase (128) between the layer of the solute (126) and the layer of the residue (130) based on process status inputs from the first sensor (116). The control unit (120, 602) operates the automatic control valves (106, 108) based on process status inputs from the second sensor (118) such that the solute (126) and the residue (130) are separately discharged.

Description

System and Method for Operating Reactor Units in a Process Plant Description The present invention relates to a field of process control systems, and more particularly relates to process control systems for operating reactor units in a process plant.

In chemical and pharmaceutical industry, a reactor unit is used to perform liquid-liquid extraction and washing operation. In the liquid-liquid extraction and washing operation, feed and solvent of pre-determined quantity are added in the reactor unit. An agitator provided in the reactor unit is turned on to mix the feed and the solvent. The agitation process is carried out with heating/cooling process which involves varying temperature inside the reactor unit using fluids in coils internal to the reactor unit or ackets /coils external to the reactor unit. Alternatively, the agitation process is carried out without the heating/cooling process. Addition of the solvent creates a thermodynamic instability in the reactor unit. This causes transfer of desired component from the feed to the solvent till thermodynamic stability is achieved. The thermodynamic stability is represented by partition coefficient or ratio of solubility of desired component in the feed and the solvent at standard conditions .

After pre-determined time as per standard operating procedure (SOP) is elapsed, the agitator is turned off. The mixture of feed and solvent in the reactor unit are allowed to settle down for a pre-determined time as per the SOP. During the settling process, desired component (hereinafter referred as solute) in the feed is separated from other components containing impurities (hereinafter referred as residue) . Consequently, two separate layers, i.e., the solute (rich extract layer) and the residue (rich raffinate layer) , are formed at the end of settling process. The solute and the residue may have hydrophilic or hydrophobic characteristics.

Once the pre-determined time is elapsed, an operator operates a manual control valve to discharge the residue. During discharging of the residue, the operator sees in a sight glass located in the discharge pipe of the reactor unit to determine presence of an interface layer following the residue. The presence of the interface layer indicates that the discharging of the residue is near completion. If the interface layer is seen through the sight glass, the operator takes a decision to close the manual control valve discharging the residue and opens another manual control valve to discharge the solute. In this manner, the solute and the residue are separately discharged from the reactor unit. The efficiency of the liquid-liquid separation and washing operation lies in effectively recovering the solute (in terms of percentage yield) by isolating the residue in minimum number of cycles, leading to optimum batch cycle time.

To achieve desired percentage yield with minimum impurities, which are consistent critical quality attributes (CQA) desired for a batch to qualify from the regulatory authorities, it is important that process point and time of formation of phase, and initiation and end of separation of layers of the solute and the residue in the reactor unit is accurately determined, and the solute and residue are separately discharged via the discharge pipe of the reactor unit. Currently, an operator may not know exact process point and time of formation of phase, and separation of the layer of the solute and the layer of the residue in the reactor unit. Also, the operator does not know when to initiate discharge of the solute. This is because, the operator manually determines the process point and time of formation of phase and separation of the layer of the solute and the layer of the residue based on several factors such as standard operating procedure (SOP) time, interface ring as seen through a sight glass provided in the discharge pipe of the reactor unit, etc. Accordingly, the operator operates manual automatic control valves to discharge the solute and the residue separately. However, this is difficult and error prone tasks considering changing process conditions (i.e., emulsion, color difference between the both layers, temperature, and velocity at discharge pipe) , characteristics and different volumes of feed and solvent, especially when the reactor unit is used to produce different products. This becomes even more complex and error prone when different cycle times are required for different products. Due to this, it is more likely that the solute gets transferred into undesired fluid, or impurities are transferred in desired fluid, leading to loss of percentage yield of solute and/or increase in impurities in the desired fluid. This may further lead to recycling or rejection of the desired fluid. Also, this may require additional washing cycles to recover solute from the undesired fluid or isolate impurities from the desired fluid, leading to more batch time to achieve Critical Quality Attributes (CQA) . In some pharmaceutical plants, given high value of the product, the operator needs to precisely monitor and control the reactor unit. In such cases, the operator may have to fine-tune the process for each product or use most conservative approach when cycle time is longest. The manual attendance of the operator is time consuming and also hazardous to the operator due to harmful solvent vapors from the reactor unit. This is makes it difficult to monitor and control reactor unit through human intervention.

None of the known systems seem to address the above problems. For example, JPS5678604 (A) discloses a system for automatically separating two liquids in a receiver tank. The system detects an interface of said two liquids with a reflection type ultrasonic wave detector and changes over a valve provided in the discharge pipe of the receiver tank based on the detected signal. However, the system does not address the problem of automatically determining process point and time of phase formation, and accordingly discharge of the residue and the solute respectively. Moreover, the system does not relate to automatically operating a reactor unit, such as a chemical reactor, for producing higher percentage yield of solute (e.g., active pharmaceutical ingredient) in optimum batch cycle time.

In light of the above, there exists a need for accurately determining process point and time of phase formation, as well as discharging the solute and the residue from reactor units. Therefore, it is the object of the present invention to provide a method and system for automatically operating reactor units in a process plant to accurately determine process point and time of phase formation, and discharge the solute and the residue separately in such a manner that higher percentage yield of solute can be achieved in optimum batch cycle time. The object of the present invention is achieved by a process control system for operating reactor units in a process plant. The process control system comprises one or more reactor units. Each reactor unit may be metal, lined and glass constructed of varying volumetric capacity. In an exemplary implementation, the reactor unit may be a chemical reactor. Each reactor unit comprises an enclosure capable of producing a solute and a residue from chemical mass transfer of a feed and a solvent, an agitator for mixing the feed and the solvent in the enclosure, heating/cooling unit, and automatic control valves for individually discharging the solute and the residue. The enclosure may produce solute such as aqueous solution and residue such as organic solution by mixing solvent and feed or vice versa. The solute is active pharmaceutical ingredient (API) . The automatic control valves comprise a first automatic control valve and a second automatic control valve positioned following the first automatic control valve provided in the discharge pipe of the reactor unit. The second automatic control valve is a diverter valve having a first outlet for discharging the residue and a second outlet for discharging the solute.

The process control system also comprises a first sensor disposed in the enclosure, a second sensor positioned in the discharge pipe of said each reactor unit, and a control unit coupled to the automatic control valves, the first sensor and the second sensor of the respective reactor units. The control unit may include a Programmable Logic Controller (PLC) or a server of a process control system in a process plant. The first sensor and the second sensor are inverse frequency shift capacitance level sensors. The inverse frequency shift capacitance level sensors may be analog or digital sensors. An inverse frequency shift capacitance level sensor is a device capable of detecting interface layer with or without emulsion. The inverse frequency shift capacitance level sensor can respond to any material with low dielectric constant by detecting a change in oscillating frequency. This is because the inverse frequency shift capacitance level sensor can record large change in oscillating frequency with small change in dielectric constant. Based on the change in oscillating frequency, capacitive reactance value is computed. The capacitive reactance value indicates formation, presence, or absence of the interface layer. Advantageously, the inverse frequency shift capacitance level sensor has good resolution, repeatability and accuracy compared to other types of sensors. Thus, the inverse frequency shift capacitance level sensor are suitable for detect presence of the interface layer separating solute and residue in the enclosure.

The first sensor and the second sensor provide the process status inputs to the control unit. The control unit is capable of continuously monitoring formation of the phase between the layer of the solute and the layer of the residue. The control unit is capable of determining that the phase is formed between the layer of the solute and the layer of the residue in the enclosure based on first process status inputs from the first sensor. In an embodiment, the control unit is capable of receiving the first process status inputs from the first sensor, and determining whether the phase is formed based on the first process status inputs. The phase is an interface layer (with or without emulsion) formed between the layer of the solute and the layer of the residue in the enclosure. The interface layer separates the layer of the solute from the layer of the residue. The phase is said to be formed at process point and time when thermodynamic equilibrium is attained between the feed and the solvent, settling of the solute and the residue is complete, and clear separation between the layer of the solute and the layer of the residue is achieved. The thermodynamic equilibrium is attained when transfer of a desired component from the feed to the solvent is complete, i.e., thermodynamic stability is achieved. The control unit is capable of determining exact process point and time when the thermodynamic equilibrium is attained, settling of the solute and the residue is complete, and clear separation between the layer of solute and the layer of residue is achieved based on the first process status inputs from the first sensor.

The control unit is capable of automatically operating the first automatic control valve and the second automatic control valve upon formation of the phase in such a manner that the solute and the residue are separately discharged via the discharge pipe of the reactor unit. In an embodiment, the control unit is capable of opening the first automatic control valve to discharge the residue through the first outlet of the second automatic control valve after the phase is formed. The control unit is capable of gradually reducing flow rate of the first automatic control valve with decrease in level of the residue in the enclosure.

Furthermore, the control unit is capable of receiving a first set of the second process status inputs from the second sensor, and determining whether presence of the phase is detected in the discharge pipe based on the first set of the second process status inputs. The control unit is capable of closing the first automatic control valve to prevent discharge of the solute through the first outlet of the second automatic control valve if the phase is detected in the discharge pipe. Furthermore, the control unit is capable of opening the second outlet of the second automatic control valve, and opening the first automatic control valve to discharge the solute through the second outlet of the second automatic control valve. Moreover, the control unit is capable of receiving a second set of process status inputs from the second sensor, and determining whether the solute is completely discharged through the second outlet of the second automatic control valve based on the second set of the second process status inputs. If the solute is completely discharged, the control unit is capable of closing the first automatic control valve and closing the second outlet of the second automatic control valve.

The object of the present invention is achieved by a control unit which comprises a processor, and a memory coupled to the processor, wherein the memory comprises a process control module stored in the form of machine-readable instructions and executable by the processor. The process control module is capable of receiving first process status inputs from a first sensor disposed in an enclosure of a reactor unit, and continuously monitoring formation of a phase between a layer of a solute and a layer of a residue in the enclosure based on the first process status inputs from the first sensor. The process control module is capable of determining that the phase is formed between the layer of the solute and the layer of the residue. The process control module is capable of receiving a second process status inputs from a second sensor, and generating control signals capable of operating automatic control valves of the reactor unit upon formation of the phase to separately discharge the solute and the residue from a discharge pipe of the reactor unit. The process control module is capable of generating a first control signal to open a first automatic control valve of the automatic control valves for discharging the residue through a first outlet of a second automatic control valve of the automatic control valves after the phase is formed. The process control module is capable of generating a second control signal to gradually reduce flow rate of the first automatic control valve with decrease in level of the residue in the enclosure. The process control module is capable of receiving a first second set of the second process status inputs from the second sensor, and determining whether presence of the phase is detected in the discharge pipe based on the first set of the second process status inputs. The process control module is capable of generating a third control signal to close the first automatic control valve if the phase is detected in the discharge pipe such that discharge of the solute through the first outlet of the second automatic control valve is prevented. The process control module is capable of generating a fourth control signal to open the second outlet of the second automatic control valve, and generating a fifth control signal to open the first automatic control valve to discharge the solute through the second outlet of the second automatic control valve. The process control module is capable of receiving a second set of process status inputs from the second sensor, and determining whether the solute is completely discharged through the second outlet of the second automatic control valve based on the second set of process status inputs. Accordingly, the process control module is capable of generating a sixth control signal to close the first automatic control valve if the solute is completely discharged, and generating a seventh control signal to close the second outlet of the second valve.

The object of the present invention is achieved by a method of controlling reactor units in a process plant. The method comprises receiving first process status inputs from a first sensor disposed in an enclosure of a reactor unit by a control unit, and continuously monitoring formation of a phase between a layer of a solute and a layer of a residue in the enclosure based on the first process status inputs from the first sensor. The method comprises determining that the phase is formed between the layer of the solute and the layer of the residue.

The method comprises receiving a second process status inputs from a second sensor, and generating control signals capable of operating automatic control valves based on the second process status inputs upon formation of the phase to separately discharge the solute and the residue from a discharge pipe of the reactor unit. Therein, the method comprises generating a first control signal to open a first automatic control valve of the automatic control valves for discharging the residue through a first outlet of a second automatic control valve of the automatic control valves after the phase is formed. The method comprises generating a second control signal to gradually reduce flow rate of the first automatic control valve with decrease in level of the residue in the enclosure.

Furthermore, the method comprises receiving a first set of the second process status inputs from the sensors, and determining whether presence of the phase is detected in the discharge pipe based on the first set of the second process status inputs. Moreover, the method comprises generating a third control signal to close the first automatic control valve if the phase is detected in the discharge pipe such that discharge the solute through the first outlet of the second automatic control valve is prevented. The method comprises generating a fourth control signal to open the second outlet of the second automatic control valve, and generating a fifth control signal to open the first automatic control valve to discharge the solute through the second outlet of the second automatic control valve. Additionally, the method comprises receiving a second set of the second process status inputs from the second sensor, and determining whether the solute is completely discharged through the second outlet of the second automatic control valve based on the second set of the second process status inputs. The method comprises generating a sixth control signal to close the first automatic control valve if the solute is completely discharged, and generating a seventh control signal to close the second outlet of the second automatic control valve. The above-mentioned and other features of the invention will now be addressed with reference to the accompanying drawings of the present invention. The illustrated embodiments are intended to illustrate, but not limit the invention. The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings, in which:

FIG 1 is a block diagram of a process control system of a process plant, according to an embodiment of the present invention. is a block diagram of a programmable logic controller as shown in FIG 1, according to an embodiment of the present invention. is a process flowchart illustrating an exemplary method of operating a reactor unit of the process plant, according to an embodiment of the present invention . is a process flowchart illustrating a detailed method of operating the reactor unit of the process plant, according to an embodiment of the present invention. is a block diagram of a process control system of a process plant, according to another embodiment of the present invention. is a block diagram of a process control system of a process plant, according to yet another embodiment of the present invention. is a schematic representation depicting an exemplary batch cycle for liquid-liquid extraction and separation operation. is a schematic representation depicting another exemplary batch cycle for liquid-liquid extraction and separation operation. is a schematic representation depicting yet another exemplary batch cycle for liquid-liquid extraction and separation operation. Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide thorough understanding of one or more embodiments. It may be evident that such embodiments may be practiced without these specific details.

The terms 'phase' , and 'interface layer' are interchangeably used throughout the document.

FIG 1 is a block diagram of a process control system 100 of a process plant, according to an embodiment of the present invention. The process control system 100 comprises reactor unit 102 and a control unit 120 such as Programmable Logic Controller (PLC) for operating the reactor units 102. The reactor unit 102 comprises an enclosure 104, an inlet 110 provided at the top of the enclosure 104 and a discharge pipe 112 provided at bottom of the enclosure 104. The reactor unit 102 also includes an agitator unit 114. The reactor unit 102 comprises an automatic control valve 106 and an automatic control valve 108 provided along the discharge pipe 112. The automatic control valve 106 is provided for controlling outflow of fluid (e.g., aqueous solution and organic solution) from the reactor unit 102. The automatic control valve 108 is a diverter automatic control valve having an outlet 132 connected to an organic solution receiver and an outlet 134 connected to an aqueous solution receiver. Although not illustrated in FIG 1, the reactor unit 102 may also comprise heating/cooling system. The process control system 100 comprises a sensor 116 disposed in the enclosure 104 and a sensor 118 positioned in the discharge pipe 112. As shown, the sensor 118 is arranged prior to the automatic control valve 106 in the discharge pipe 112. In one embodiment, the sensor 116 and the sensor 118 are inverse frequency shift capacitance level sensors. In an exemplary implementation, the first sensor 116 is inverse frequency shift capacitance level transmitter and the second sensor 118 is inverse frequency shift capacitance level switch.

The PLC 120 is connected to the sensors 116 and 118 and the automatic control valves 106 and 108 via an input/output unit 124. The PLC 120 comprises a process control module 122 for operating the reactor unit 102. The sensors 116 and 118 periodically measures and provides process status inputs to the PLC 120 during operation of the reactor unit 102. The process control module 122 automatically operates the reactor unit 102 based on the process status inputs from the sensors 116 and 118. In the process plant, the PLC 120 and the I/O modules 124 are located in a safe area or in the same hazardous zone where the reactor unit 120 are located.

In an exemplary operation, the reactor unit 102 is used for producing aqueous solution 126 from a solvent and a feed which are allowed undergo a chemical mass transfer in the enclosure 104. Once batch cycle is started, the feed and the solvent in desired quantity are added in the enclosure 104. Then, the agitator unit 114 is started to perform agitation of the feed and the solvent with or without heating or cooling process. After a pre-determined time period, the agitator 114 is turned off and the aqueous solution 126 and the organic solution 130 are allowed to settle in the enclosure 104. During the setting process, the sensors 116 provide first process status inputs indicating status of formation of interface layer 128 between the aqueous solution 126 and the organic solution 130. The interface layer 128 separates the aqueous solution 126 from the organic solution 130.

The process control module 122 determines whether the interface layer 128 is formed between the aqueous solution 126 and the organic solution 130 based on the first process status inputs. At a process point and time, the process control module 122 determines that the interface layer 128 is formed based on the first process status inputs. The process control module 122 determines that the interface layer 128 is formed at a process point and time when thermodynamic equilibrium between the feed and the solvent is attained, the settling of the aqueous solution 126 and the organic solution 130 is complete, and clear separation between the aqueous solution 126 and the organic solution 130 in the enclosure is achieved. Accordingly, the process control module 122 generates controls signals capable of operating the automatic control valves 106 and 108 in a desired sequence to discharge the organic solution 130 and the interface layer 128 via the outlet 132 of the automatic control valve 108.

During discharge of the organic solution 130, the sensor 118 provides second process status inputs to the PLC 120 indicating whether presence of the interface layer 128 is detected in the discharge pipe 112. The presence of the interface layer 128 in the discharge pipe 112 indicates that the organic solution 130 is about to completely discharge from the outlet 132. If the second process status inputs indicate presence of the interface layer 128 in the discharge pipe 112, the process control module 122 generates control signals to operate the automatic control valves 106 and 108 in a desired sequence to discharge the aqueous solution 134 via the outlet 134 of the automatic control valve 108. In this manner, the reactor unit 102 is controlled by the PLC 120 such that the aqueous solution 126 and the organic solution 130 is accurately separated and discharged via the discharge pipe 112 of the reactor unit 112.

Although FIG 1 illustrates the process control system 100 with a single reactor unit 102 connected to the PLC 120, one can envision that multiple such reactor units can be coupled to the PLC 120 in a process plant via the Input/Output modules 124, and the PLC 120 can operate multiple such reactor units simultaneously . FIG 2 is a block diagram of the Programmable Logic Controller (PLC) 120 of FIG 1, according to an embodiment of the present invention. Particularly, the PLC 120 comprises a processor 202, a memory 204, a communication interface 206, and an input/output module 208. The PLC 120 is capable of monitoring and controlling the reactor unit 102 of FIG 1. Specifically, the PLC 120 is capable of receiving process status inputs from the sensors 116 and 118 and generating control signals for operating the automatic control valves 106 and 108 such that the aqueous solution 126 and the organic solution 130 are accurately separated in the enclosure 104 and discharged through the automatic control valve 108.

The processor 202, as used herein, means any type of computational circuit, such as, but not limited to, a microprocessor, a microcontroller, a complex instruction set computing microprocessor, a reduced instruction set computing microprocessor, a very long instruction word microprocessor, an explicitly parallel instruction computing microprocessor, a graphics processor, a digital signal processor, or any other type of processing circuit. The processor 102 may also include embedded controllers, such as generic or programmable logic devices or arrays, application specific integrated circuits, single-chip computers, and the like.

The memory 204 may be volatile memory and non-volatile memory. A variety of computer-readable storage media may be stored in and accessed from the memory 104. The memory 104 may include any suitable elements for storing data and machine-readable instructions, such as read only memory, random access memory, erasable programmable read only memory, electrically erasable programmable read only memory, hard drive, removable media drive for handling compact disks, digital video disks, diskettes, magnetic tape cartridges, memory cards, and the like. As depicted, the memory 204 includes a process control module 210. The process control module 210 is stored in the form of machine- readable instructions on any of the above-mentioned storage media and may be executed by the processor 202. When executed by the processor 202, the process control module 210 is capable of determining formation of the phase 128 between the aqueous solution 126 and the organic solution 130 and generating control signals to operate the automatic control valves 106 and 108 based on the process status inputs from the sensors 116 and 118, resulting in separately discharging the aqueous solution 126 and the organic solution 130. The detailed steps performed by the processor 102 to control the reactor unit 102 are described below with reference to FIG 3 and FIG 4 in the description that follows . The communication module 206 may enable communication of the PLC 120 with the sensors 116 and 118, and the automatic control valves 106 and 108 via Input/Output modules 124. For example, the communication module 206 may periodically receive inputs from the sensors 116 and 118. The inputs may indicate formation of an interface between the aqueous solution 126 and the organic solution 130. Also, the inputs may indicate whether the organic solution 130, the interface 128 and the aqueous solution 126 is completely discharged from the enclosure 104. The communication module 206 may enable transmit control signals to the automatic control valves 106 and 108 for operating the automatic control valves 106 and 108.

The input/output unit 208 may be a human-machine interface which enables operator to view process data associated with the reactor unit 102 and control process associated with the reactor unit 102. It can be noted that, the PLC 120 may have integrated human-machine interface or a human-machine interface externally coupled to the PLC 120.

FIG 3 is a process flowchart 300 illustrating an exemplary method of operating the reactor unit 102 of a process plant, according to an embodiment of the present invention. At step 302, first process status inputs are received from the sensor 116 disposed in the enclosure 104 of the reactor unit 102 by the PLC 120. For example, the PLC 120 may continuously receive the process status inputs from the sensor 116 during a separation and extraction process. The first process status inputs may indicate whether a phase 128 is formed between the aqueous solution 126 and the organic solution 130. In other words, the first process status inputs may indicate whether thermodynamic equilibrium between a feed and a solvent is attained, settling of the aqueous solution 126 and the organic solution 130 is complete, and clear separation of the aqueous solution 126 and the organic solution 130 is achieved. At step 304, formation of the phase 128 between the aqueous solution 126 and the organic solution 130 is monitored by the PLC 120. Typically, after the agitator 114 is turned off, the aqueous solution 126 and the organic solution 130 is allowed to settle in the enclosure 104. During the settling process, the phase 126 is formed between the aqueous solution 126 and the organic solution 130 which separates the aqueous solution 126 and the organic solution 130. Post mass transfer process, the PLC 120 continuously monitors formation of the phase 128 between the aqueous solution 126 and the organic solution 130 based on the first process status inputs.

At step 306, it is determined that the phase 128 between the aqueous solution 126 and the organic solution 130 is formed based on the first status process inputs from the sensor 116. At step 308, the automatic control valve 106 and the automatic control valve 118 are operated such that the organic solution 130 and the aqueous solution 126 is discharged separately upon formation of the phase 128. In an exemplary implementation, the automatic control valve 116 and the automatic control valve 118 are operated using control signals to discharge the aqueous solution 126 and the organic solution 130.

FIG 4 is a process flowchart 400 illustrating a detailed method of operating the reactor unit 102 of a process plant, according to an embodiment of the present invention. At step 402, a first process status inputs are received from the sensor 116. For example, the first process status inputs may indicate whether a phase 128 is formed between an aqueous solution 126 and an organic solution 130. The sensor 116 start sending the first process status inputs to the PLC 120 after agitator 114 is turned off. The formation of the phase 128 starts when the agitator 114 is turned off. At step 404, it is determined whether the phase 128 is formed between the aqueous solution 126 and the organic solution 130.

If it is determined that the phase 128 is not formed, then the process 400 goes to the step 402. The sensor 116 periodically sends the first process status inputs to the PLC 120. Based on which, the PLC 120 checks whether the phase 128 is formed. In an exemplary implementation, the PLC 120 checks whether a process point and time is reached where thermodynamic equilibrium between the feed and the solvent is attained, settling of the aqueous solution 126 and the organic solution 130 is complete and clear separation of the aqueous solution 126 and the organic solution 130 is achieved. If it is determined that the phase 128 is formed, at step 406, a first control signal is generated by the PLC 120. In one embodiment, the first control signal is generated immediately after the phase 128 is formed. In another embodiment, the first control signal is generated after a pre-set delay from the formation of the phase 128. The first control signal is configured to operate the automatic control valve 106 to an open position. The automatic control valve 108, which is a diverter automatic control valve with either the outlet 132 or the outlet 134 open at a particular instance, is in a first position. The outlet 132 is provided for discharging the organic solution 130 and the outlet 134 is provided for discharging the aqueous solution 126. When the automatic control valve 108 is in the first position, the outlet 132 is open and the outlet 134 is closed. Thus, the opening of the automatic control valve 106 causes the organic solution 130 in the enclosure 104 to pass through the outlet 132 of the automatic control valve 108. The organic solution 130 passing through the outlet 132 of the automatic control valve 108 is received by the organic solution receiver .

At step 408, a second control signal is generated to gradually reduce flow rate of the automatic control valve 106 during discharge of the organic solution 130 through the outlet 132. Accordingly, the flow rate of the automatic control valve 106 is gradually reduced with decrease in level of the organic solution 130 in the enclosure 104 such that no turbulence is created at discharge point, thereby maintaining Reynold's number. This helps in ensuring that the interface layer 128 smoothly passes over from the outlet 132 and the automatic control valve 106 is gradually closed subsequent to discharge of the interface layer 128. This helps to prevent aqueous solution 126 from discharging through the outlet 132 due to delay in closing the automatic control valve 108.

At step 410, a first set of the second process status inputs are received from the sensor 118. The first set of the second process status inputs may indicate whether presence of the interface layer 128 is detected in the discharge pipe 112. The presence of the interface layer 128 in the discharge pipe indicates that the organic solution 130 is about to completely discharged through the automatic control valve 106. At step 412, it is determined whether the interface layer 128 is detected in the discharge pipe 112 based on the first set of the second process status inputs. If it is determined that the interface layer 128 is detected in the discharge pipe 112, then at step 414, a third control signal is generated by the PLC 120. The third control signal is configured to move the automatic control valve 106 to a closed position. At step 416, a fourth control signal is generated by the PLC 120. The fourth control signal is configured to move the automatic control valve 108 to a second position in which the outlet 132 is closed and the outlet 134 is open. At step 418, a fifth control signal is generated by the PLC 120. The fifth control signal is configured to move the automatic control valve 106 to an open position. When the automatic control valve 106 is moved to the open position, the aqueous solution 126 is discharged through the outlet 134 of the automatic control valve 108 to the aqueous solution receiver.

At step 420, a second set of the second process status inputs are received from the sensor 118. The second set of the second process status inputs indicates status of discharge of the aqueous solution 126 through the outlet 134 of the automatic control valve 108. At step 422, it is determined whether the aqueous solution is completely discharged from the automatic control valve 108 based on the second set of the second process status inputs. If it is determined that the aqueous solution 126 is not completely discharged, then the process 400 goes to step 420. The sensor 118 periodically sends the second set of the second process status inputs to the PLC 120 till the aqueous solution 126 is completely discharged. Accordingly, the PLC 120 determines whether the aqueous solution 126 is completely discharged each time the second set of the second process status inputs are received from the sensor 118. If it is determined that the aqueous solution 126 is completely discharged, then at step 424, a sixth control signal is generated by the PLC 120. The sixth control signal is configured to move the automatic control valve 106 to a closed position. At step 426, a seventh control signal is generated by the PLC 120. The seventh control signal is configured to move the automatic control valve 108 to the first position which results in closing the outlet 134 and opening the outlet 132. FIG 5 is a block diagram of a process control system 500 of a process plant, according to another embodiment of the present invention. The process control system 500 is same as the process control system 100 of FIG 1 except that the process control system 500 comprises a portable human-machine interface device 502 wirelessly connected to the PLC 120. In an exemplary implementation, the human-machine interface device 502 is connected to the PLC 120 via communication network such as Industrial Wireless LAN (WLAN) . The portable human-machine interface device 502 may be a smart phone, tablet, portable digital assistant (PDA), and the like. The portable human- machine interface device 502 enables operator to view process data associated with the reactor unit 102 and input commands for operating the reactor unit 102. The portable human-machine interface device 502 also enables operator to configure a batch process for producing aqueous solution using the reactor unit 102.

FIG 6 is a block diagram of a process control system 600 of a process plant, according to yet another embodiment of the present invention. The process control system 600 comprises a server 602, a portable human-machine interface device 606, and a Programmable Logic Controllers (PLCs) 608A-N. The portable human-machine interface device 606 and the PLCs 608A-N are connected to the server 602 via a network 604. The PLCs 608A-N are coupled to the sensors 116 and 118 and the automatic control valves 106 and 108 of the reactor units (e.g., the reactor unit 102) via Input/Output (I/O) module 124.

The server 602 comprises the process control module 122 for operating the reactor units 102. The server 602 acquires process status inputs received from the sensors 116 and 118 from the PLCs 608A-N. The process control module 122 determines formation of a phase 128 between an aqueous solution 126 and an organic solution 130 in the reactor units 102 and provides instructions to the PLCs 608A-N to control the reactor units 102. Accordingly, the PLCs 608A-N generates control signals to operate the automatic control valves 106 and 108 in a desired sequence to discharge the aqueous solution 126 and the organic solution 130 separately.

The portable human-machine interface device 606 may access process data (e.g., process status) from the server 602 and issue commands for operating the reactor units 102 from a remote location. The portable human-machine interface device 606 may configure a batch process in any of the reactor units 102. One can envision that the process control module 122 may reside in an industrial cloud environment, wherein the PLCs 608A-N may provide the inputs from the sensors 116 and 118 and receive control signals for operating the reactor units 102 from a cloud server in the industrial cloud environment.

FIG 7A is a schematic representation 700A depicting an exemplary batch cycle for liquid-liquid extraction and separation operation. As depicted in FIG 7A, X-axis represents time ^At' during which process steps are performed whereas Y-axis represents volume ^Λν' . The batch cycle for producing solute from a feed and a solvent starts at time ^At0' . At time ^At2', the feed of desired quantity is added into the enclosure 104. At time ^At4', agitation of the feed and the solvent in the enclosure 104 is initiated using the agitator 114. At time ^At6' , the agitation of the feed and the solvent is stopped. At time ^At6' , desired component from the feed starts transferring into the solvent. In other words, at time ^At6' , thermodynamic equilibrium of the feed and the solvent starts.

From time ^At6', the mixture of the feed and the solvent is allowed to settle in the enclosure 102. During the settling process, two layers are formed from the mixture of the feed and the solvent. The two layers include one layer of aqueous solution 126 (solute) and another layer of organic solution 130 (residue) is formed. An interface layer 128 is also formed which separates the aqueous solution 126 from the organic solution 130. At time ^At8', thermodynamic equilibrium between the feed and the solvent is attained, settling of the organic solution 130 and the aqueous solution 126 is completed, and clear separation of the aqueous solution 126 from the organic solution 130 is achieved. This is the process point where formation of the interface layer 128 is detected by the control unit 120. At time ^At8', the automatic control valve 106 is opened to discharge the organic solution 130 through the outlet 132 of the automatic control valve 108. At time ^At9' , the interface layer 128 is detected in the discharge pipe 112. The presence of the interface layer 128 in the discharge pipe 112 indicates that the organic solution is completely discharged from the automatic control valve 106. Thus, at time ^At9', the automatic control valve 108 is changed from a first position to a second position and the aqueous solution 126 is discharged from the automatic control valve 106 via the outlet 134 of the automatic control valve 108. At time ^tlO', the aqueous solution 126 is completely discharged and the batch cycle ends .

FIG 7B is a schematic representation 700B depicting another exemplary batch cycle for liquid-liquid extraction and separation operation. The batch cycle depicted in FIG 7B is similar to the batch cycle depicted in FIG 7A, except in the batch cycle of FIG 7B, discharge of the organic solution 130 is started at time ^tll' instead of time ^At8' . Once the interface layer 128 is formed, the discharge of the organic solution 130 is started after a pre-set delay. That is, the automatic control valve 106 is opened after a pre-set delay at time ^tll' .

FIG 7C is a schematic representation 700C depicting yet another exemplary batch cycle for liquid-liquid extraction and separation operation. The batch cycle depicted in FIG 7C is similar to the batch cycle depicted in FIG 7A, except in the batch cycle of FIG 7C, an electrolyte is added at time ^Atl2' to the mixture of feed and solvent in the enclosure 104 if large amount of emulsion is present in the mixture during the settling process. The electrolyte helps to smoothen the emulsion present in the mixture of feed and solvent. Upon adding the electrolyte, the mixture of feed and solvent is agitated from time period ^Atl3' to ^Atl4' . At time ^Atl5', the mixture of feed and solvent is allowed to settle till the interface layer 228 is detected. As shown in FIG 7C, the interface layer 228 is detected at time ^At8' . In various embodiments, the process control systems 100, 500 and 600 can be part of a distributed control system employed in a process plant. The process control systems 100, 500, and 600 can be used for different combination of feed and solvent for different volumes at different times without performing re- calibration. Thus, same reactor unit can be used for multiple batches. The process control systems 100, 500, 600 are suitable for handling heavier or lighter solvents and not limited to specific aqueous solvents. Also, the process control systems 100, 500, and 600 can seamlessly operate one or more reactor units using a single control unit. Additionally, the process control systems 100, 500 and 600 can be validated to meet the requirements of active pharmaceutical ingredients. Advantageously, the process control systems 100, 500, and 600 significantly reduce washing cycle time, and batch time as well as reduce the loss of percentage yield of solute in an aqueous solution extracted from a reactor unit in a consistent manner. Consequently, the process control systems 100, 500 and 600 help achieve critical quality attributes from a unit operation. Also, the process control systems 100, 500, and 600 provide safe operating environment in a process plant.

While the present invention has been described in detail with reference to certain embodiments, it should be appreciated that the present invention is not limited to those embodiments. In view of the present disclosure, many modifications and variations would be present themselves, to those skilled in the art without departing from the scope of the various embodiments of the present invention, as described herein. The scope of the present invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope .

Claims

Patent Claims

1. A process control system (100, 500, 600) comprising:

at least one reactor unit (102) comprising:

an enclosure (104) capable of producing a solute (126) and a residue (130) from chemical mass transfer of a feed and a solvent;

one or more automatic control valves (106, 108) arranged along a discharge pipe (112) of the reactor unit (102); characterized by:

a first sensor (116) disposed in the enclosure (104);

a second sensor (118) positioned in the discharge pipe (112) ; and

a control unit (120, 602) coupled to the one or more automatic control valves (106, 108), and the one or more sensors (116, 118), the control unit (120, 608) is capable of:

determining formation of a phase (128) between the layer of the solute (126) and the layer of the residue (130) in the enclosure (104) based on first process status inputs from the first sensor (116); and

operating the one or more automatic control valves (106, 108) based on second process status inputs from the second sensor (118) such that the solute (126) and the residue (130) are separately discharged via the discharge pipe (112) of the reactor unit (102) .

2. The process control system (100, 500, 600) according to claim 1, wherein the first sensor (116) and the second sensor (118) are inverse frequency shift capacitance level sensors.

3. The process control system (100, 500, 600) according to claim 1, wherein the control unit (120, 602) is capable of monitoring formation of the phase (128) between the layer of the solute (126) and the layer of the residue (130) .

4. The process control system (100, 500, 600) according to claim 1, wherein the first sensor (116) and the second sensor (118) are capable of periodically providing the first process status inputs and the second process status inputs to the control unit (120, 602), respectively.

5. The process control system (100, 500, 600) according to claim 1, wherein the one or more automatic control valves (106, 108) comprises a first automatic control valve (106) and a second automatic control valve (108) positioned after the first automatic control valve, wherein the second automatic control valve (108) is a diverter valve having a first outlet (132) for discharging the residue (130) and a second outlet (134) for discharging the solute (126) .

6. The process control system (100, 500, 600) according to claim

5, wherein in determining the formation of the phase (128) between the layer of the solute (126) and the layer of the residue (130), the control unit (120, 602) is capable of:

receiving the first process status inputs from the first sensor (116) ; and

determining whether the phase (128) between the layer of the solute (126) and the layer of the residue (130) is formed based on the first process status inputs.

7. The process control system (100, 500, 600) according to claim

6, wherein in operating the one or more automatic control valves (106, 108) based on the second process status inputs from the second sensors (118), the control unit (120, 602) is capable of: if the phase (128) is formed, opening the first automatic control valve (106) to discharge the residue (130) through the first outlet (132) of the second automatic control valve (108); reducing flow rate of the first automatic control valve (106) with decrease in level of the residue (130) in the enclosure (104) ;

receiving a first set of process status inputs from the second sensor ( 118 ) ;

determining whether presence of the interface layer (128) is detected in the discharge pipe (112) based on the first set of process status inputs;

if the interface layer (128) is detected in the discharge pipe (112), closing the first automatic control valve (106) to prevent discharge of the solute (126) through the first outlet (132) of the second automatic control valve (108);

opening the second outlet (134) of the second automatic control valve (108) ;

opening the first automatic control valve (106) to discharge the solute (126) through the second outlet (134) of the second automatic control valve (108);

receiving a second set of process status inputs from the second sensor (118) ;

determining whether the solute (126) is completely discharged through the second outlet (134) of the second automatic control valve (108) based on the second set of process status inputs; if the solute (126) is completely discharged, closing the first automatic control valve (106); and

closing the second outlet (134) of the second automatic control valve (108) .

8. A control unit (120, 602) comprising:

a processor (202); and a memory (204) coupled to the processor (202), wherein the memory (202) comprises a process control module (122) stored in the form of machine-readable instructions and executable by the processor (202), characterized in that the process control module (122) is capable of:

receiving first process status inputs from a first sensor (116) disposed in an enclosure (104) of the reactor unit (102); determining formation of a phase (128) between the layer of the solute (126) and the layer of the residue (130) in the enclosure (104) based on the first process status inputs from the first sensor (116) ;

receiving second process status inputs from a second sensor (118) positioned in the discharge pipe (112) of the reactor unit (102); and

generating control signals capable of operating one or more automatic control valves (106, 108) of the reactor unit (102) based on the second process status inputs from the second sensor (118) to separately discharge the solute (126) and the residue (128) from a discharge pipe (112) of the reactor unit (102) .

9. The control unit (120, 602) according to claim 8, wherein the process control module (122) is capable of monitoring the formation of the phase (128) between the layer of the solute (126) and the layer of the residue (130) .

10. The control unit (120, 602) according to claim 9, wherein the process control module (122) is capable of:

if the phase (128) is formed, generating a first control signal to open a first automatic control valve (106) of the one or more automatic control valves (106, 108) for discharging the residue (130) through a first outlet (132) of a second automatic control valve (108) of the one or more automatic control valves (106, 108);

generating a second control signal to gradually decrease flow rate of the first automatic control valve (106) with decrease in level of the residue (130) in the enclosure (104);

receiving a first set of the second process status inputs from the second sensor (118) ;

determining whether presence of the phase (128) is detected in the discharge pipe (112) based on the first set of the second process status inputs;

if the phase (128) is detected in the discharge pipe (112), generating a third control signal to close the first automatic control valve (106) such that discharge of the solute (126) through the first outlet (132) of the second automatic control valve (108) is prevented;

generating a fourth control signal to open the second outlet (134) of the second automatic control valve (108);

generating a fifth control signal to open the first automatic control valve (106) to discharge the solute (126) through the second outlet (134) of the second automatic control valve (108); receiving a second set of the second process status inputs from the second sensors (118);

determining whether the solute (126) is completely discharged through the second outlet (134) of the second automatic control valve (108) based on the second set of the second process status inputs ;

if the solute (126) is completely discharged, generating a sixth control signal to close the first automatic control valve (106) ; and

generating a seventh control signal to close the second outlet

11. A method of operating reactor units in a process plant, comprising :

receiving first process status inputs from first sensor (116) disposed in an enclosure (104) of a reactor unit (102) by a control unit (120, 602);

determining formation of a phase (128) between a layer of a solute (126) and a layer of a residue (130) in the enclosure (104) based on the first process status inputs from the first sensor (116) ;

receiving second process status inputs from a second sensor

(118) positioned in the discharge pipe of the reactor unit (102) by the control unit (120, 602); and

generating control signals capable of automatically operating one or more automatic control valves (106, 108) based on the second process status inputs from the second sensor (118) to separately discharge the solute (126) and the residue (130) from a discharge pipe (112) of the reactor unit (102) .

12. The method according to claim 11, further comprising:

monitoring the formation of the phase (128) between the layer of the solute (126) and the layer of the residue (130) .

13. The method according to claim 12, wherein generating the control signals capable of automatically operating the one or more automatic control valves (106, 108) comprises:

if the phase (128) is formed, generating a first control signal to open a first automatic control valve (106) of the one or more automatic control valves (106, 108) for discharging the residue (130) through a first outlet (132) of a second automatic control valve (108) of the one or more automatic control valves (106, 108); generating a second control signal to vary flow rate of the first automatic control valve (106) with decrease in level of the residue (130) in the enclosure (104);

receiving a first set of process status inputs from the second sensor ( 118 ) ;

generating a fifth control signal to open the first automatic control valve (106) to discharge the solute (126) through the second outlet (134) of the second automatic control valve (108); receiving a second set of the second process status inputs from the second sensor (118);

generating a seventh control signal to close the second outlet (134) of the second automatic control valve (108) .

14. The method according to claim 11, wherein the solute is an active pharmaceutical ingredient (API) .