US 5,924,794 AGranted

Chemical blending system with titrator control

AssigneeFSI International, Inc.

InventorsKevin T. O'Dougherty, Travis A. Lemke, Donald C. Grant

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Abstract

A chemical blending system for blending two or more constituent chemicals to a desired concentration. One embodiment of the system includes a mix tank, a recirculation line having an inlet and an outlet in the tank, and a pump in the recirculation line for recirculating and mixing the blended chemical. A source of diluent is fluidly coupled to the mix tank through a diluent inlet and supply line. A source of concentrated chemical is fluidly coupled to the recirculation line through a concentrated chemical inlet, supply line, and an adding valve located in the recirculation line between the inlet and pump. A conductivity-type sensor in the recirculation line provides continuous measurements of the blended chemical concentration. A titration analyzer is coupled to the recirculation line to provide periodic blended chemical concentration measurements. A programmable logic control system including a processor and associated memory is coupled to the adding valve, conductivity-type sensor and titration analyzer. A blending control program and process control values are stored in the memory. The processor executes the blending control program and controls the concentrate adding valve as a function of the concentration measurements provided by the conductivity-type sensor and titration analyzer to blend the chemical to the desired concentration.

Claims40

Dependent claims

A chemical blending system for blending at least first and second chemical constituents to obtain blended chemical having a desired chemical concentration, including:

a first constituent inlet for receiving a first chemical constituent;
a second constituent inlet for receiving a second chemical constituent;
a blending tank fluidly coupled to the first and second constituent inlets, for receiving the chemical constituents and holding the blended chemical;
a recirculation line having an inlet and an outlet in the blending tank;
pump means having a suction end and a pressure end in the recirculation line, for recirculating blended chemical from the blending tank through the recirculation line to blend the chemical constituents;
at least a first regulating mechanism coupling the first constituent inlet to the recirculation line between the recirculation line inlet and the suction end of the pump means, for regulating the amount of at least the first chemical constituent supplied to the recirculation line;
a first concentration measuring instrument having first operating characteristics, for measuring concentration of the blended chemical in the blending tank;
a second concentration measuring instrument having second operating characteristics different than the first operating characteristics, for measuring concentration of the blended chemical in the blending tank;
memory for storing digital data representative of:
a blending control program;
and
a concentration qualification range representative of chemical concentrations within a qualification range of the desired chemical concentration;
and
a digital processor coupled to the memory, first and second concentration measuring instruments and to the first regulating mechanism, for executing the blending control program and controlling at least the first regulating mechanism as a function of the concentration measurements provided by the first and second concentration measuring instruments to blend the first and second chemical constituents to a concentration within the qualification range.

11 more elements

A chemical blending system for blending at least first and second chemical constituents to produce blended chemical having a desired chemical concentration within a qualification range, including:

a first constituent inlet for receiving the first chemical constituent;
a second constituent inlet for receiving the second chemical constituent;
blending apparatus fluidly coupled to the first and second constituent inlets, for receiving and blending the first and second chemical constituents to produce the blended chemical;
a first regulating mechanism for regulating the amount of at least one of the chemical constituents received by the blending apparatus;
a first concentration measuring instrument having first operating characteristics, for measuring concentration of the blended chemical in the blending apparatus;
a second concentration measuring instrument having second operating characteristics different than the first operating characteristics, for measuring concentration of the blended chemical in the blending apparatus;
and
a control system coupled to the first and second concentration measuring instruments for controlling the first regulating mechanism, including:
first control means for actuating the first regulating mechanism to control chemical blending as a function of concentration measurements from the first concentration measuring instrument when the measured concentration is less than a first blend concentration set point which is less than the qualification range;
second control means for actuating the first regulating mechanism to control chemical blending as a function of concentration measurements from the second concentration measuring instrument when the measured concentration is greater than the first blend concentration setpoint and less than a lower qualification range setpoint of the qualification range;
and
third control means for qualifying the blended chemical by causing the first regulating mechanism to discontinue the receipt of the chemical constituents when the concentration measurements from the second concentration measuring instrument are within the qualification range.

9 more elements

A chemical blending system for blending concentrated chemical with a diluent to obtain blended chemical having a desired chemical concentration within a qualification range, including:

a concentrated chemical inlet for receiving concentrated chemical;
a diluent inlet for receiving diluent;
a blending tank fluidly coupled to the concentrated chemical inlet and the diluent inlet, for receiving and blending the concentrated chemical and diluent to produce the blended chemical;
a concentrate flow regulating mechanism responsive to concentrate control signals, for controlling the flow of concentrated chemical from the concentrated chemical inlet into the blending tank;
a first concentration measuring instrument having first operating characteristics, for measuring concentration of the blended chemical in the blending tank and providing first instrument readings as a function of the measurements;
a second concentration measuring instrument having second operating characteristics different than the first operating characteristics, for measuring concentration of the blended chemical in the blending tank and providing second instrument readings as a function of the measurements;
memory for storing data representative of:
concentrate injection information representative of the relationship between the concentrate control signals and blended chemical concentration changes induced by actuation of the concentrate flow regulating mechanism;
a fine blend setpoint concentration which is less than the qualification range;
and
qualification range setpoint concentrations representative of chemical concentrations within a qualification range of the desired chemical concentration;
and
a digital processor coupled to the memory, first and second concentration measuring instruments and the concentrate flow regulating mechanism, and including means for:
(a) monitoring first instrument readings of blended chemical concentration measurements provided by the first concentration measuring instrument;
(b) generating concentrate control signals as a function of the concentrate injection information and the first instrument readings, to actuate the concentrate flow regulating mechanism and add a finite quantity of the chemical concentrate in an attempt to increase the blended chemical concentration to the desired concentration if the monitored first instrument reading is less than or equal to the fine blend setpoint concentration;
(c) monitoring second instrument readings of blended chemical concentration measurements provided by the second concentration measuring instrument if the monitored first instrument reading is greater than the fine blend setpoint concentration;
(d) generating concentrate control signals as a function of the concentrate injection information and the second instrument readings, to actuate the concentrate flow regulating mechanism and add a finite quantity of the chemical concentrate in an attempt to increase the blended chemical concentration to the desired concentration if the monitored second instrument reading is greater than the fine blend setpoint concentration and less than the qualification range setpoint concentrations;
(e) repeating functions (a)-(d) until the second instrument reading is within the qualification range setpoint concentrations.

15 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/395,374Filed 21 Feb 1995
Granted: 20 Jul 1999
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G05D 11/138
By sensing at least one property of the mixture: by sensing the concentration of the mixture, e.g. measuring pH value
B01F 35/2133
Measuring: electrical conductivity or dielectric constant of the mixture
B01F 35/82
Forming a predetermined ratio of the substances to be mixed: by adding a material to be mixed to a mixture in response to a detected feature, e.g.…
Y10T 137/2509
Mixture condition maintaining or sensing: by optical or chemical property