PROCESS MONITORING AND CONTROL OF FILTRATION BY MEANS OF FILTRATE MEASUREMENTS

Abstract

The invention relates to solutions for the monitoring, process control and supervision of a solid filtration, particularly the washing process of said solid in a filtration system, and particularly to a method for monitoring and controlling a process for filtering and washing a solid in a filtration device for cake filtration, wherein at least one measuring device is applied in or to the filtrate outlet of the filtration device, which measures the at least one parameter value of a filtrate flow from the filtration device for cake filtration at least during the washing process.

Claims

1. A method of monitoring a filtration and washing operation on a solid-state bulk material in a filter apparatus for cake filtration, comprising: separating a solid-state bulk material in a suspension medium using a filter element for cake filtration; leading off the suspension medium in the form of a filtrate stream into a filtrate outlet; measuring at least one parameter value of the filtrate stream over a period of a filtration and washing operation; and conducting a change analysis of the at least one parameter value over the period of the filtration and washing operation to ascertain at least one of the end of the filtration and washing operation or the effectiveness of the filtration and washing operation.

2. The method of claim 1, wherein the at least one parameter value is selected from the group comprising refractive index, density, ultrasound transit time, redox potential and cumulative spectroscopic properties and substance-specific properties of one or more main or secondary components.

3. The method of claim 2, wherein at least one of the refractive index or the density of the filtrate stream is measured.

4. The method of claim 1, wherein the at least one parameter value over the period are transmitted as measurement data to an archiving module for storage of the measurement data and stored with a timestamp t.

5. The method of claim 1, wherein the change analysis is computer-implemented.

6. The method of claim 5, wherein the end of the filtration and washing operation is ascertained by the following steps: a) providing the at least one parameter value measured to an evaluation system, b) calculating the first derivative of a measurement curve between the measurement data at the times t-1 and t, c) if the first derivative from b) is more than zero or more than a predefined value for the derivative of the measurement curve at which the method is considered to have ended, the filtration and washing operation is continued; step b) is repeated for a further measurement curve, d) if the first derivative from b) is zero, if it is less than or equal to the predefined value, the filtration and washing operation is ended and the end of the filtration and washing process is communicated via a user interface.

7. The method of claim 6, wherein the filter apparatus comprises a wash medium feed, and the amount of wash medium consumed for the filtration and washing operation until the end of the filtration and washing operation is ascertained and fixed as the optimal amount of wash medium for the next filtration and washing operation.

8. The method of claim 4, whereby the effectiveness of the filtration and washing operation is ascertained by the following steps: a) transferring measurement values of the measurement data to an evaluation system over a predefined period of time in the filtration and washing operation, b) calculating a first derivative of a measurement curve between the measurement data at the times t-1 and t, c) comparing the first derivative with an approved predefined range of values for the first derivative in which the filtration and washing operation is considered to be effective, d) ending the filtration and washing operation and giving notice of the variance via a user interface if the first derivative is outside the predefined range of values from c), alternatively or additionally to step d) e) calculating a period C in which the first derivative is within the predefined range of values from c), f) calculating a slope value as the average slope over the period C from e), g) calculating a variability of the slope value over the period C from e), h) if the slope value from f) is within a predefined working range for the slope value and the variability of the slope from g) is less than or equal to a predefined tolerance limit for the variability at which the washing operation is considered to be effective, the washing operation is continued, i) if the slope value from f) is outside the predefined range of values for the slope value or the variability of the slope value from g) is above the predefined tolerance limit for the variability, a warning is issued or the filtration and washing operation is ended.

9. The method of claim 5, wherein the method is used for online monitoring of the filtration and washing operation.

10. The method of claim 5, wherein at least one concentration of at least one component in the filtrate stream or at least one measurable cumulative parameter of the filtrate stream is ascertained.

11. A system for monitoring a filtration and washing operation on a solid-state bulk material in a filter apparatus for cake filtration, wherein the system comprises: an archiving module configured for the storage of parameter values of a filtrate stream with a timestamp t transmitted from at least one measurement apparatus in or on a filtrate outlet of the filter apparatus over a period of the filtration and washing operation and for transfer of the measurement values to an evaluation system, the evaluation system connected to the archiving module and configured to analyze changes in the parameter values over the period of the filtration and washing operation, and to use this analysis to ascertain at least one of the end of the filtration and washing operation or the effectiveness of the filtration and washing operation, an element for issuing a control command for ending of the filtration and washing operation, and a display element for at least one of the end of the filtration and washing operation or the effectiveness of the filtration and washing operation.

12. A filter apparatus comprising: a wash medium feed, a filter element for cake filtration and a filtrate outlet, at least one measurement apparatus for measurement of parameter values in the filtrate stream, installed in or on the filtrate outlet, and the system of claim 11.

13. The filter apparatus of claim 12, wherein the at least one measurement apparatus can measure one or more parameters selected from the group consisting of refractive index, density, ultrasound transit time, pH, conductivity, redox potential and spectroscopic properties of the filtrate stream as cumulative parameters, or alternatively of at least one representative constituent, in the filtrate stream.

14. The filter apparatus of claim 12, selected from the group consisting of suction filters, centrifuges, Büchner funnels, frits, filter crucible, drum filter, disk filter, belt filter and filter press.

15. The filter apparatus of claim 12, wherein the filter apparatus has a controllable wash medium feed that can receive commands for opening or closing of the wash medium feed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0108] FIG. 1: Schematic diagram of a pressure suction filter

[0109] 1 pressure suction filter, 2 filtercake, 3 measuring unit (e.g. example RI)

[0110] FIG. 2: Representation of trend of the measured value (RI) against time, divided into process phases:

[0111] A—displacement of the mother liquor, B—intermediate region, C—approved region, D—diffusion region, E—end of the wash effect.

[0112] FIG. 3: Comparison of refractive index (□) and sum total of the secondary components (○) for the product Sivanto. The refractive index of pure butanol at 20° C. is 1.39932. (Example A).

[0113] FIG. 4: Mass of filtrate M (○) and refractive index RI (.square-solid.) as a function of time t. Region 1: filtration; region 2: wash.

[0114] FIG. 5: NaCl concentration (.square-solid.) and refractive index RI (○) as a function of the wash ratio.

[0115] FIG. 6A: Filtercake with channels, removal of moisture after mother liquor filtration.

[0116] FIG. 6B: Filtercake after mechanical removal of moisture after wash.

[0117] FIG. 7: □ mass (M) and .circle-solid. refractive index (RI) as a function of time (t).

[0118] FIG. 8: Block diagram of the method for control of the washing operation

[0119] 1—Input of measurement data [0120] 2—Calculation of the first derivative [0121] 3—First derivative >0 or greater than a predefined value? [0122] 4—End of the washing operation [0123] 5—Error message [0124] 6—First derivative within a predefined range C? [0125] 7—Calculation of the average slope and variability (steps e-g) [0126] 8—Average slope and variability within the predefined ranges?