Centrifuge with automatic sampling and control and method thereof

A centrifuge including a bowl, a bowl drive motor, a screw conveyor, a screw conveyor drive motor, a pump, a pump motor, a bowl VFD to drive the bowl drive motor, a conveyor VFD to drive the screw conveyor drive motor, a pump VFD to drive the pump drive motor, an analysis assembly and a computer electrically connected to the bowl VFD, the conveyor VFD, the pump VFD, and the analysis assembly. The analysis assembly is configured to automatically sample slurry pumped into the bowl and automatically transmit data, characterizing the slurry, to the computer. The computer is configured to calculate control schemes for the bowl VFD, the conveyor VFD, and the pump VFD using the data and, transmit control signals to the bowl VFD, the conveyor VFD and the pump VFD to operate the bowl VFD, the conveyor VFD and the pump VFD according to the control schemes.

FIELD OF THE INVENTION

The present disclosure relates to a centrifuge with automatic sampling and analysis of a slurry pumped to the centrifuge and a liquid effluent discharged from the centrifuge, and automatic control of bowl, conveyor and pump motors.

BACKGROUND OF THE INVENTION

It is known to measure properties of a feed slurry and a liquid effluent stream for a centrifuge by analyzing samples taken by hand by an operator of the centrifuge. The analysis is then used to determine control parameters for operation of a centrifuge. For example, the operator obtains and analyzes the data to determine set points for the various motors in the centrifuge and then manually enters the set points into a control system for the centrifuge.

The known method of manual sampling and control input is not responsive to current conditions in the centrifuge, since there is a time delay between obtaining samples and manually inputting set points due to the necessity for the operator to analyze the samples and determine proper control set points. Further, to most accurately control the centrifuge to respond to real time conditions, given the above drawbacks, would require almost continuous manual sampling by the operator. That is, the operator would be virtually dedicated to the sampling, analysis, and set point calculation noted above, which would greatly increase operating costs, since further personnel may be necessary to address operational needs that the operator cannot attend to. Also, manually obtaining samples requires the operator to be in the immediate proximity of the centrifuge. Given the size, mass, and speeds associated with operation of the centrifuge and to prevent injury to the operator, it is desirable to limit the amount of time an operator must spend in the immediate vicinity of the centrifuge.

SUMMARY OF THE INVENTION

According to aspects illustrated herein, there is provided a centrifuge for centrifuging a slurry, including: a bowl driven by a bowl drive motor; a screw conveyor driven by a screw conveyor drive motor; a pump driven by a pump motor; a bowl variable frequency drive unit (VFD) operatively arranged to drive the bowl drive motor; a conveyor VFD operatively arranged to drive the screw conveyor drive motor; a pump VFD operatively arranged to drive the pump drive motor; a first analysis assembly connected to a first section of pipe connecting the pump and the bowl; and at least one computer electrically connected to the bowl VFD, the conveyor VFD, the pump VFD, and the first analysis assembly. The first analysis assembly is configured to automatically sample a slurry pumped through the first section of pipe and automatically transmit first data, characterizing the slurry, to the at least one computer. The at least one computer is configured to calculate respective control schemes for the bowl VFD, the conveyor VFD and the pump VFD using the first data and transmit respective control signals to the bowl VFD, the conveyor VFD and the pump VFD to operate the bowl VFD, the conveyor VFD and the pump VFD according to the respective control schemes.

According to aspects illustrated herein, there is provided a centrifuge for centrifuging a slurry, including: a bowl driven by a bowl drive motor; a screw conveyor driven by a screw conveyor drive motor; a pump driven by a pump motor; a bowl variable frequency drive unit (VFD) operatively arranged to drive the bowl drive motor; a conveyor VFD operatively arranged to drive the screw conveyor drive motor; a pump VFD operatively arranged to drive the pump drive motor; a first analysis assembly; and at least one computer electrically connected to the bowl VFD, the conveyor VFD, the pump VFD, and the first analysis assembly. The first analysis assembly is configured to automatically sample a liquid effluent discharged from the centrifuge and automatically transmit first data, characterizing the liquid effluent, to the at least one computer. The at least one computer is configured to calculate respective control schemes for the bowl VFD, the conveyor VFD and the pump VFD using the first data and transmit respective control signals to the bowl VFD, the conveyor VFD and the pump VFD to operate the bowl VFD, the conveyor VFD and the pump VFD according to the respective control schemes.

According to aspects illustrated herein, there is provided a centrifuge for centrifuging a slurry, including: a bowl driven by a bowl drive motor; a screw conveyor driven by a screw conveyor drive motor; a pump driven by a pump motor; a bowl variable frequency drive unit (VFD) operatively arranged to drive the bowl drive motor; a conveyor VFD operatively arranged to drive the screw conveyor drive motor; a pump VFD operatively arranged to drive the pump drive motor; a first analysis assembly connected to a section of pipe connecting the pump and the bowl; a second analysis assembly; and at least one computer electrically connected to the bowl VFD, the conveyor VFD, the pump VFD, and the first and second analysis assemblies. The first analysis assembly is configured to automatically sample a slurry pumped through the first section of pipe and automatically transmit first data, characterizing the slurry, to the at least one computer. The second analysis assembly is configured to automatically sample a liquid effluent discharged from the centrifuge and automatically transmit first data, characterizing the liquid effluent, to the at least one computer. The at least one computer is configured to calculate respective control schemes for the bowl VFD, the conveyor VFD and the pump VFD using the first and second data and transmit respective control signals to the bowl VFD, the conveyor VFD and the pump VFD to operate the bowl VFD, the conveyor VFD and the pump VFD according to the respective control schemes.

According to aspects illustrated herein, there is provided a method for centrifuging a slurry using a centrifuge including a bowl driven by a bowl drive motor, a screw conveyor driven by a screw conveyor drive motor, a pump driven by a pump motor, a bowl variable frequency drive unit (VFD) operatively arranged to drive the bowl drive motor, a conveyor VFD operatively arranged to drive the screw conveyor drive motor, a pump VFD operatively arranged to drive the pump drive motor, a first analysis assembly connected to a first section of pipe connecting the pump and the bowl, a second analysis assembly, and at least one computer electrically connected to the bowl VFD, the conveyor VFD, the pump VFD, and the first and second analysis assemblies, the method including: automatically sampling, using the first analysis assembly, a slurry pumped through the first section of pipe; automatically transmitting, using the first analysis assembly, first data, characterizing the slurry, to the at least one computer; automatically sampling, using the second analysis assembly, a liquid effluent discharged from the centrifuge; automatically transmitting, using the second analysis assembly, second data, characterizing the liquid effluent, to the at least one computer; calculating, using the at least one computer, respective control schemes for the bowl VFD, the conveyor VFD and the pump VFD using the first and second data; transmitting, using the at least one computer, respective control signals to the bowl VFD, the conveyor VFD and the pump VFD; and operating the bowl VFD, the conveyor VFD and the pump VFD according to the respective control schemes.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a schematic representation of centrifuge10with automatic sampling and control. Centrifuge10, for example a decanter style centrifuge, includes bowl11, screw conveyor12, pump15, bowl drive motor19, conveyor drive motor21, and pump motor35. Centrifuge10includes: bowl variable frequency drive unit (VFD)32operatively arranged to drive the bowl drive motor; conveyor VFD31operatively arranged to drive the screw conveyor drive motor; pump VFD34operatively arranged to drive the pump drive motor; and at least one computer30(hereinafter referred to as “computer30”) electrically connected to the bowl VFD, the conveyor VFD, and the pump VFD. In an example embodiment, centrifuge10includes analysis assembly50A connected to pipe, or conduit,17connecting pump15and bowl11. Assembly50A is electrically connected to computer30.

FIG. 2is a schematic block diagram of centrifuge10ofFIG. 1. In an example embodiment, computer30implements the functions and operations described above and below by using processor40to execute computer readable instructions43stored in memory element44. Computer30, processor40and memory element44can be any computer, processor, and memory element, respectively, known in the art.

Analysis assembly50A is configured to automatically sample a slurry pumped through pipe17to the bowl and automatically transmit data52A, characterizing the slurry, to computer30. Computer30is configured to: calculate control schemes54,56, and58for the bowl VFD, the conveyor VFD and the pump VFD, respectively, using data52A; and transmit control signals60,62, and64to the bowl VFD, the conveyor VFD and the pump VFD, respectively, to operate the bowl VFD, the conveyor VFD and the pump VFD according to control schemes54,56, and58, respectively.

In an example embodiment, assembly50A is configured to measure at least one parameter66of the slurry selected from the group consisting of feed density, viscosity, turbidity, solids content, particle distribution and flow rate, and transmit data52A including measurement68of the at least one parameter66. For example, assembly50A includes any sensors or other apparatus70known in the art for sampling the slurry and measuring one, some, or all of parameters66. It should be understood that assembly50A is not limited to measuring the parameters noted above and that assembly50A can measure any parameter known in the art using any sensors or apparatus known in the art.

In an example embodiment, as part of calculating control schemes54,56, and58, computer30is configured to calculate speeds72,74, and76for the bowl drive motor, the screw conveyor drive motor and the pump motor, respectively, and transmit control signals60,62, and64including transmitting speeds72,74, and76. In an example embodiment, computer30also calculates differential speed94between speeds72and74.

Computer30and assembly50A are configured to sample the slurry without intervention by an operator and to automatically transmit data52A without intervention by an operator. That is, computer30and assembly50A execute the operations necessary for sampling the slurry and transmitting data52A independent of actions by an operator and without the necessity of intervention by the operator. Further, computer30generates and transmits control schemes54,56, and58without intervention by the operator, and VFDs32,31, and34control bowl drive motor19, conveyor drive motor21, and pump motor35, respectively, without intervention by the operator. It should be understood that intervention by the operator is possible if desired.

In an example embodiment, computer30includes display device78and is configured to analyze data52A to determine recommended level80for liquid in the bowl (pond level) and transmit signal82, for display on display device78, including recommended level80.

In an example embodiment, computer30is configured receive input84identifying speeds51and53for the bowl and conveyor motors, respectively, desired torque load86for the conveyor motor, and maximum flow rate88for the pump. Computer30is configured to regulate pump speed55/slurry flow rate57to maintain actual torque load90for the conveyor motor at desired torque load86; or when unable to maintain actual torque load90for the conveyor motor at desired torque load86, regulate pump speed55/slurry flow rate57to maintain maximum flow rate88. Input84can be generated by any means known in the art, for example, by an operator of centrifuge10.

In an example embodiment, computer30is configured to: determine that actual torque load90is greater than desired torque load86; and regulate pump speed55to control flow rate57of the slurry to reduce actual torque load90to be equal to or less than desired torque load86. As is known in the art, the quickest means of reducing an undesirably high torque90is by increasing flow rate57. However, as is also known in the art, the more effective, but slower, long term response to undesirably high torque90is manipulating differential speed94between the bowl and the conveyor as described below.

In an example embodiment, computer30is configured to: receive input92quantifying torque load90on the conveyor motor; vary differential speed94until, at differential speed94A, torque load90increases by predetermined degree, or amount,96; calculate differential speed94B based on differential speed94A, for example, slightly less than speed94A to prevent a spike of torque90; and, operate the bowl and conveyor motors to maintain differential speed94B. In an example embodiment, computer30is configured to determine that torque load90is greater than desired torque level86and operate the bowl and conveyor motors to increase differential speed94B to reduce torque load90.

In an example embodiment, centrifuge10includes analysis assembly50B configured to automatically sample liquid effluent LE discharged from the bowl through pipe, or conduit,25and automatically transmit data52B, characterizing liquid effluent LE, to computer30. Computer30is configured to calculate control schemes54,56, and58using data52B.

In an example embodiment, assembly50B is configured to measure at least one parameter66of effluent LE selected from the group consisting of feed density, viscosity, turbidity, solids content, particle distribution and flow rate, and transmit data52B including measurement68of the at least one parameter66. For example, assembly50B includes any sensors or other apparatus70known in the art for sampling the slurry and measuring one, some, or all of parameters66. It should be understood that assembly50B is not limited to measuring the parameters noted above and that assembly50B can measure any parameter known in the art using any sensors or apparatus known in the art.

In an example embodiment, conveyor drive motor21is coupled to conveyor12via gearbox23. Centrifuge10receives the slurry via conduit, or pipe,45connected to pump15. Pump15pumps the slurry to bowl11via conduit, or pipe17. Bowl11is driven by bowl motor19via pulley arrangement20, and screw conveyor12is driven by conveyor motor21via gear box23. High density solids, which are separated from the slurry, are discharged from centrifuge10through conduit, or pipe,24. The remaining portions of the slurry (liquid effluent LE) are ejected from the centrifuge via conduit25. Bowl11is supported by two bearings27and29. Conveyor motor speed and direction information are detected by encoder46and communicated to conveyor VFD31via line42. Bowl VFD32, conveyor VFD31, and pump VFD34communicate with computer30over a communication network. Any VFD and any communication network known in the art can be used.

In an example embodiment, the operator can select modes of operation for centrifuge10including, but not limited to: barite recovery, cleanest effluent, driest solids, finest cut point, effluent percent solids, target effluent density, or any combination of these modes of operation, for example, listed by priority. Centrifuge10is capable of regulating bowl speed51, conveyor speed53, differential speed94, and pump speed55/slurry flow rate57automatically while indicating proper target pond depth, or level, setting80based upon a user selected operating mode for the apparatus. For example, computer30may calculate different respective values for speeds72,74, and76depending on the mode selected. Once in a selected operating mode, computer30generates control schemes54,56, and58and operates assemblies50A and50B as needed to most efficiently and effectively implement the operating mode selected by the operator.

In an example embodiment, various operation set points59are set to respective default values61for each operation mode. In an example embodiment, the operator may modify default values61.

In an example embodiment, computer30has an economy mode in which computer30monitors power consumption98for the centrifuge and adjusts operating conditions for the centrifuge, for example, via control schemes54,56, and58, to limit the power consumption. This is useful in cases where there is not adequate power available to operate centrifuge10at maximum capacity or in cases where power consumption is of concern.

An operator can interface directly with computer30, via local operator control panel99, or via remote computer37with a remote internet or intranet connection to computer30. This enables an operator to monitor and control centrifuge10while on site or remotely from off site. Additional hardware allows for remote visual viewing of centrifuge10from offsite or onsite in cases where the apparatus may be difficult to access.

In an example embodiment remote computer37is linked to computer30by any means known in the art, including, but not limited to hardwire line39or wirelessly, so that troubleshooting or operation of centrifuge10can be monitored and controlled from a remote location, if desired.

In an example embodiment, computer30stores historical data63in memory element44. Data63can include data52A and52B, control schemes54,56, and58, speeds72,74, and76, and any other information associated with operation of centrifuge10. Data63can be used to record, identify, and track historical trends in the operation of centrifuge10. Data63also can be used in the creation of control schemes54,56, and58and/or in control of assemblies50A and50B. For example control schemes54,56, and58generated using data63can account for operational considerations9, derived from data63and not readily apparent from analysis of data52A and52B, and which impact optimal operation of centrifuge10. Based on considerations9, computer30can create control schemes54,56, and58to result in more efficient, effective, and/or safe operation of centrifuge10than would otherwise be possible. Based on considerations9, computer30can control sampling frequency and the type of sampling and analysis performed by assemblies50A and50B to optimize functioning of centrifuge10.

In an example embodiment, one or both of analysis assemblies50A and50B are configured to sample the slurry or liquid effluent LE, respectively, continuously. In an example embodiment, computer30is configured to analyze one or both of data52A and52B to generate one or both of analysis65A and65B, respectively, and to calculate one or both of sampling schedule67A and or67B, respectively, using one or both of analysis65A and65B, respectively. Computer30is then configured to switch one or both of assemblies50A and50B from sampling continuously to sampling according to schedule67A or67B, respectively. Note that one of assemblies50A and50B can be sampling according to a respective sampling schedule while the other analysis assembly is sampling continuously.

In an example embodiment, one or both of analysis assemblies50A and50B are configured to sample the slurry or liquid effluent LE, respectively, according to one or both of sampling schedule69A and or69B, respectively. In an example embodiment, computer30is configured to analyze one or both of data52A and52B to generate one or both of analysis71A and71B, respectively, and to switch one or both of assemblies50A and50B to continuous sampling based on one or both of analysis71A and71B, respectively. Schedules69A and/or69B can be calculated by computer30as noted above, or inputted to computer30by an operator. Note that one of assemblies50A and50B can be sampling according to a respective sampling schedule while the other analysis assembly is sampling continuously.

Thus, centrifuge10, in particular assemblies50A and50B, utilizes various sampling and analysis hardware to measure parameters of the slurry and effluent LE, such as feed density, viscosity, turbidity, solids content, particle distribution and flow rate automatically and without operator intervention. Based on the measurements taken on the fly (either periodically or continuously) of the feed and effluent streams, computer30automatically determines the most effective and efficient mode of operation by varying bowl speed51, conveyor speed53, pump speed55, differential speed94, and pump flow rate57without operator input or intervention.

The following should be viewed in light ofFIGS. 1 and 2. The following describes a method for centrifuging a slurry using a centrifuge. Although the method is presented as a sequence of steps for clarity, no order should be inferred from the sequence unless explicitly stated. The centrifuge includes bowl11, screw conveyor12, pump15, bowl drive motor19, conveyor drive motor21, pump motor35, bowl VFD32, conveyor VFD31, pump VFD34, at least one computer30electrically connected to VFDs32,31and34, analysis assembly50A connected to pipe17and electrically connected to computer30, and analysis assembly50B electrically connected to computer30. A first step automatically samples, using analysis assembly50A, a slurry pumped through pipe17. A second step automatically transmits, using analysis assembly50A, data52A, characterizing the slurry, to computer30. A third step automatically samples, using analysis assembly50B, liquid effluent LE discharged from the centrifuge. A fourth step automatically transmits, using analysis assembly50B, data52B characterizing liquid effluent LE, to computer30. A fifth step calculates, using the computer30, control schemes54,56, and58for the bowl VFD, the conveyor VFD and the pump VFD, respectively, using data52A and52B. A sixth step transmits, using computer30, control signals60,62, and64, to the bowl VFD, the conveyor VFD and the pump VFD, respectively. A seventh step operates the bowl VFD, the conveyor VFD and the pump VFD according to control schemes54,56, and58, respectively.

By way of introduction to the oil drilling application, barite, or heavy spar, is a sulfate of barium, BaSO4, found in nature as tabular crystals or in granular or massive form and has a high specific gravity. Most crude barite requires some upgrading to minimum purity or density. Most barite is ground to a small, uniform size before it is used as a weighting agent in petroleum well drilling mud specification barite. Barite is relatively expensive, and an important objective of a preferred embodiment of the present invention is to recover barite from the slurry in an oil drilling operation for re-use.

It should be understood that centrifuge10and a method using centrifuge10is suitable for use in any situation or application requiring a centrifuge, for example, for handling material generated by earth drilling operations, for example, associated with oil and/or gas wells. With respect to oil and/or gas well drilling application, centrifuge10is arranged to centrifuge drilling mud and tailings.