Method for monitoring and controlling filtration by means of filtrate measurement

Abstract

The present invention relates to a solution for monitoring, process control and supervision of solid filtration, in particular washing processes of said solids, in a filtration system, and in particular to a method for monitoring and controlling the process of filtration and washing of solids in a filter device for cake filtration, wherein at least one measuring device is applied in or on the filtrate outlet of the filter device, said measuring device measuring at least one parameter of the filtrate flow from the filter device for cake filtration at least during the washing process.

Description

Technical Field

[0001] The present application relates to solutions for monitoring, process control and supervision of solid filtration, especially washing operations of these solids, in filtration plants. The solids are free-flowing materials, usually the result of crystallization or precipitation in granular or powder form, and are also often referred to as solid bulk materials. Background Art

[0002] The conventional production methods for producing solid active ingredients starting from crystallization or precipitation are subdivided as follows:

[0003] 1. Crystallization / precipitation, also called solid formation: This step in the production process forms solids suspended in the mother liquor.

[0004] 2. Filtration: In a filtration device for pressure, vacuum or centrifugal filtration (hereinafter also collectively referred to as a filtration device), the solid is separated from the mother liquid.

[0005] Conventional filtering devices are, for example, suction filters, centrifuges, drum or disk filters, etc., but can also be porcelain or glass funnels with flat screens or frits, or another porous filter element. When using a suction filter, for example, the suspension to be filtered is transferred to the device, the filtrate is separated from the solids under pressure or vacuum, and discharged. Figure 1 A suction filter is shown in schematic form by way of example.

[0006] Typically, in step 3 of solid filtration, the filter cake is then washed in a displacement and / or resuspension washing operation to "clean the solids", i.e., to obtain the desired quality characteristics of the solids. In this step, a fixed amount of solvent (fresh or recycled) is usually evenly distributed over the filter cake over a fixed number of washing steps. The number of washes depends on the desired purity of the solids. Typically, the filtration apparatus is not opened between washing steps, and therefore, for this and other reasons, sampling of the filter cake is not possible.

[0007] The solid is dried in step 4. This is usually also done on a pressure suction filter (suction dryer) or in a separate drying step.

[0008] Between steps 3 and 4, there may be further formulation steps, such as adding plasticizers, stabilizers, etc.

[0009] Typically, filtering and washing operations are viewed as "black boxes" that are optimized by trial and error (Ruslim et al., Chemical Engineering Science 62 (2007) 3951-3961). Ruslim et al. addressed the problem of uneven distribution of the washing medium in filtering and washing operations. He studied the measurement of the filter cake online, but preferred offline measurement, and wrote that the measurement of the filter cake was better than the measurement of the filtrate flow. He used only the measurement of the filtrate flow to fully check for impurities.

[0010] Louhi-Kultanen et al. describe a method and a measuring device for controlling filtering and washing operations with a Raman spectrometer, wherein the measurement is also carried out in the filter cake. This is a local measurement (on the filter cake surface) or an invasive measurement method (immersion optics), which damages the filter cake. In addition, this method does not allow trace measurements, since the measurement limit of the Raman spectrometer is 1%. LOUHI-KULTANEN et al. do not give any indication of the measurement of the filtrate flow (LOUHI-KULTANEN et al.: "Filter cake washing: Partial dissolution of organic particles and real-time monitoring based on Raman spectroscopy", SEPARATION AND PURIFICATION TECHNOLOGY, ELSEVIER SCIENCE, AMSTERDAM, NL, vol. 59, no. 3, 4 February 2008 (2008-02-04), pp. 270-276, XP022453823, ISSN: 1383-5866, DOI: 10.1016 / J.SEPPUR.2007.06.017).

[0011] According to the current prior art, during industrial filtration and washing operations, quality control of the solids while they are still in the filtration equipment (i.e. point 2 or 3) is not carried out. Usually, analysis is only performed after step 4 has been completed. Typically, a solid sample is extracted from the dried filter cake and analyzed, usually in a laboratory, by means of chromatography. It is often assumed in the professional world that the quality of the filter cake can only be determined by direct filter cake analysis. As a result, advances in online measurement technology have not so far affected the monitoring of filter cake quality during the filtration process. If the tested filter cake does not meet the specifications, the dried product must be reprocessed, discarded or cut. The amount of washing medium and the washing strategy (displacement, countercurrent or slurry washing) are usually determined experimentally once and verified by analysis of the filter cake.

[0012] If an early quality control of the solid is possible, it is possible to immediately proceed with the reaction in the case of poor quality, for example with additional washing (provided that the impurities can be washed out and are not contained in the crystals). In the case of very good quality, it is possible to dispense with washing or washing medium, and thus with solvent or water, as the case may be. Both variants will enable direct and considerable savings in costs and time.

[0013] Kopra et al. disclose a method and a measuring device for controlling filtering and washing operations of the paper industry in pulp washing with a refractometer. In the process, the refractive index of the washing medium introduced into and out of the filtering device is determined, with the aim of determining whether the washing medium can be reused. The measured values ​​are used to adjust the washing medium feeder to avoid unwanted washing losses. Kopra et al. do not give any indication of using these measured values ​​in order to draw conclusions about the progress of the washing operation or the quality of the filter cake. Considering the filtering device, this is in any case impossible because there are no measured values ​​that are distinguished from the corresponding washing. (Kopra et al. "Application of the refractometer in the measurement and monitoring of brown stock washing, doctoral dissertation", 1 January 2015 (2015-01-01), XP055374630, URL: https: / / aaltodoc.aalto.fi / bitstream / handle / 123456789 / 15451 / isbn9789526061344.pdf? sequence = l & isAllowed = y) .]. Summary of the invention

[0014] The problem addressed is therefore that of providing a solution for monitoring of filtration and washing processes which can be used for online monitoring, making it possible to draw conclusions about the progress of the process, in particular about the quality of the filter cake, without requiring any interruption of the washing process for quality control of the filter cake and without causing damage to the filter cake.

[0015] This object is achieved by measuring the filtrate flow from the filter device using a measurement technique, wherein parameter values ​​of the filtrate flow are measured during a period of filtering and washing operation, and the changes of these are analyzed during this period of time. It has been surprisingly found that such an analysis during filtration enables conclusions to be drawn about the progress and quality of the filtering and washing processes.

[0016] The present application first provides a method for monitoring and controlling the filtering and washing operations of solid bulk materials in a filtering device for cake filtration according to claim 1 and its dependent claims, wherein at least one measuring device is installed in or on the filtrate outlet of the filtering device, and the measuring device measures one or more parameters of the filtrate flow from the filtering device for cake filtration during the washing operation, and analyzes changes in the measured parameter values ​​within the time period.

[0017] In the context of the present application, suitable measurable parameters of the filtrate stream are in particular the refractive index, density, ultrasound transmission time, redox potential and spectral accumulation and / or substance-specific properties of at least one representative component (major and / or minor component) in the filtrate stream, such as absorption, impedance, color or fluorescence signal of the filtrate. For aqueous media, it is also possible to use pH and / or conductivity.

[0018] However, the choice of measuring method depends on the substances used in the process (especially one or more products and / or one or more by-products). Particularly preferably, the measurement of the refractive index and / or the density of the filtrate is used during filtering and washing. It is also possible to combine one or more of the above-mentioned methods. For quality control as well as pure measured values ​​(raw data), it is also possible to use a previously determined calibration function to determine the concentration of the (secondary) components.

[0019] In a preferred embodiment of the method, parallel recording of the refractive index and the measured values ​​of the filtrate quality customary in the art (according to VDI guideline 2762) is carried out.

[0020] The method is suitable for monitoring both continuous and batch processes. For application purposes, in a continuous washing process, the washing medium is continuously metered onto the filter cake so that the filter cake is evenly covered over its entire area. In a batch process, a predetermined amount of washing medium is applied to the filter cake for washing.

[0021] Preferably, the method comprises computer-implemented steps for analyzing the measurement data. Typically, these steps are performed by a suitably configured computer system.

[0022] In order to analyze the measurement data, these are sent from one or more measuring devices, for example via a data interface (OPC, SQL, fieldbus, such as profibus, modbus, Ethernet, analog signals, etc.); the imported measurement data are stored in an archiving module, such as a database module, in which the measurement data and a time stamp t and preferably all information for clearly identifying a production batch are recorded.

[0023] The database module is connected to an evaluation system.An evaluation system in the context of the present application is a measurement control system or a computer configured for executing the method steps.

[0024] Therefore, the present application further provides a computer system for controlling filtering and washing operations on solid bulk material in a filtration apparatus for cake filtration, wherein the computer system comprises:

[0025] an archiving module configured for storing, during a period of filtering and washing operation, parameter values ​​of the filtrate flow with a time stamp t transmitted from at least one measuring device in or on the filtrate outlet of the filtration device, and for transferring these to an evaluation system,

[0026] an evaluation system connected to said archiving module and configured to analyse the variation of said parameter values ​​during said period of time and to use this variation analysis to determine the end of said filtering and washing operation and / or the effectiveness of said washing operation,

[0027] - a display element for the end of the filtering and washing operation and / or the effectiveness of the washing operation, and / or

[0028] - Elements for issuing a command to end said filtering and washing operations.

[0029] Typically, the evaluation system is connected to a system for controlling the washing medium feeder and is configured to be able to issue a command for continuing or ending the washing medium feeder.

[0030] More preferably, the feeding of washing medium is started and stopped with the help of the evaluation system, or a new washing operation is carried out by means of the evaluation system (e.g. a valve) issuing corresponding commands to a controllable washing medium feeder. Typically, the washing medium feeder can be controlled via one or more control elements (e.g. a process control system) for controlling the washing medium feeder.

[0031] In a specific embodiment of the method, a limit value evaluation and / or a variation analysis is performed.

[0032] In the evaluation of limit values ​​of the raw data or of the concentration values ​​calculated therefrom, the analysis of the measured data generally comprises the following steps:

[0033] 1. Transferring the measured values ​​of the monitored parameters of the filtrate flow to the evaluation system over a predefined period of time during the filtration and washing process, at least until a predefined parameter value determined beforehand experimentally or empirically and corresponding to the desired quality of the filter cake is reached. If this value is reached, it can be assumed that the filter cake has been washed according to the specifications; the washing operation can be ended.

[0034] 1.1. In a continuous process, when the parameter value from 1 is reached, the feed of the washing medium ends; the filter cake is further processed.

[0035] 1.2. In the batch process, the end of the washing process will be communicated. For the next batch washing of further filter cakes, the amount of washing medium may optionally be adjusted (usually reduced) according to the predefined parameters from 1. The method of adjusting the amount of washing medium is described in further detail below.

[0036] 2. If the predefined parameter values ​​are not reached (see 1.), it can be assumed that the filter cake is not optimally washed; the washing operation is continued as follows

[0037] 2.1. In a continuous process, extend the wash medium feed.

[0038] 2.2. In a batch process, an already washed cake can be subjected to additional washing. In the next batch with new filter cake, the amount of washing medium can be increased.

[0039] If, despite the described measures (see 2.1 or 2.2), the predefined parameter values ​​are not reached, purification by displacement of the mother liquor alone is not sufficient. Typically, the washing strategy is changed; for example, slurry washing (suspension washing) or a combination of displacement and slurry washing may be performed.

[0040] As an alternative or in addition to the limit value evaluation, the method comprises a step for performing a variation analysis on the raw data or on the concentration values ​​determined from the raw data.

[0041] In the analysis of changes in the raw data or in the concentration values ​​calculated therefrom, the measurement data analysis usually comprises the following steps:

[0042] 3. Transfer the measured values ​​of the monitored parameters of the filtrate flow to the evaluation system within a predefined time period during the filtration and washing process. Calculation of the first derivative of the curve is generated from the measured values. If the first derivative (= slope) of the measured curve stops changing or falls below a predefined value, the following measures can be taken:

[0043] 3.1. In the continuous process, the feed of the washing medium is ended. Depending on the limit value evaluation from 1. (reached / not reached), further measures are optionally taken, for example a change in the washing strategy.

[0044] 3.2. In the batch process, the end of the washing process is communicated. For the next washing step, the amount of washing medium is optionally adjusted (reduced or increased) depending on the limit value evaluation from 1.

[0045] In a specific embodiment of the method, the quality of the washing is determined from the measured data by means of one or more further data analyses. For this purpose, the slope of the measurement curve is preferably calculated in a period C (between two measurements, for example between the measurements of the time stamps t-1 and t). For slopes that have been predefined as approved, the calculated slope is compared with a range of values ​​(working range); this has usually been determined from previous washings with satisfactory quality. When the slope leaves the working range during washing, there may be differences in the washing operation or the effectiveness of the washing, and therefore there may be a malfunction.

[0046] A fault may exist when:

[0047] a) The slope is too flat, e.g. caused by cracks in the filter cake.

[0048] b) The slope is not uniform, for example caused by pores or channels in the filter cake.

[0049] Evaluation of the slope enables the process to be understood or monitored so that suitable countermeasures can be initiated. These could be, for example: note the (un)saturation of the filter cake, check the filter medium for malfunctions, smooth the filter cake, etc.

[0050] Typically, the slope is equal to wash speed Δ concentration / Δ time, or alternatively Δ measurement signal / Δ time, where Δ = change. This enables, for example, process optimization, e.g.

[0051] a) An increasing slope means an increasing wash speed, which can be achieved, for example, by increasing pressure. This results in a shorter wash time, which shortens the cycle time.

[0052] b) A decreased slope means an increased washing time. This increases the diffusion time of the washing medium into the solid pore system, which can increase the washing effectiveness.

[0053] If a malfunction is identified, the system issues a warning; the system optionally ends the washing operation.

[0054] -Effectiveness of washing

[0055] In a specific embodiment of the method, the effectiveness of the washing operation is determined by the following steps:

[0056] a) determining a time period C from a measurement curve, wherein the measurement curve varies with a slope that is at least or equal to a predefined value X (see Figure 2 ),

[0057] b) Calculate the slope value from a) as the average slope over time period C,

[0058] c) Calculate the variability of the slope in part C from a),

[0059] d) if the slope value is within the predefined working range and the variability of the slope is less than X, the washing operation is effectively performed; the washing operation is continued until the slope value reaches a predetermined value to achieve sufficient washing quality,

[0060] e) If the slope value is ≤ a predefined minimum value (flat slope) and / or the variability of the slope value is high, then a gradient formation or discontinuity in the cake is suspected. Issue a warning and / or increase the filtration pressure.

[0061] The optimum wash ratio is analyzed by wash curve analysis of subsequent batches (measured by wash ratio, Figure 3 or 5) determine. If there is no further change in the measured value, the optimum wash ratio, ie the optimum amount of wash medium, has been exceeded.

[0062] In a specific embodiment of the method of the invention, the amount of washing medium consumed for a washing operation until the calculated end of the washing operation is determined and fixed as the optimal amount of washing medium for the next washing operation. In the case of a batch washing operation, a new amount of washing medium is added for washing the filter cake. In a continuous process, the amount of washing medium is calculated online and a warning is issued, for example, in the event of exceeding the optimal amount of washing medium.

[0063] The measured values ​​can be considered / interpreted online or subsequently in their entirety (process optimization).

[0064] More specifically, measurements in the filtrate stream from a filtration device for cake filtration and subsequent analysis of the obtained measurements can enable product-specific verification of the quality of the filter cake in relation to the concentration of secondary components in the filtrate stream or to a measurable cumulative parameter of the filtrate stream.

[0065] The method of the invention provides, inter alia, the following information about the progress of the process:

[0066] the progress of the evaluation process,

[0067] Identification of stop / end point criteria

[0068] Identify process faults, such as irregular filter cake structure

[0069] Process stability

[0070] Instructions for optimizing the amount of washing medium

[0071] This information is used to perform indirect filter cake analysis.

[0072] In a first embodiment of the method according to the invention, the determination of the refractive index is used as a cumulative signal relative to the secondary component.

[0073] The measuring instrument located in the filter device accordingly serves to determine the measured values ​​online, for example the refractive index in the filtrate flow. The measuring instrument is preferably installed in the filtrate outlet 5 - either in a non-pressurized manner or optionally in a pressure conduit ( Figure 1 ).

[0074] The measured values ​​and their changes over time can be used as characteristics for quality control. Typically, the values ​​measured online are compared with a pre-determined calibration function between the measured values ​​and the quality of the secondary component / product ( Figure 2 ).

[0075] The present application also provides a filtering device, which includes a washing medium feeder, a filter element, a filtrate outlet and a measuring device for measuring in the filtrate flow, wherein the measuring device is selected to measure one or more parameters of the filtrate flow, such as refractive index, density, ultrasonic transmission time, pH, conductivity, redox potential and / or spectral characteristics. According to the present invention, the measuring device is installed in or on the filtrate outlet. Typically, the measuring device is installed in the filtrate conduit of the filtering device.

[0076] Preferably, the filtration device further comprises a measuring device for measuring the mass of the filtrate. Typically, the mass of the filtrate in the filtrate collection container is determined / recorded by means of a balance. Alternatively, the mass of the filtrate is determined / recorded from the volume flow rate / mass flow rate by means of a flow meter.

[0077] Preferably, the measurements of the invention are combined with measurements of the filtrate quality.

[0078] Suitable filtering apparatuses are, but are not limited to, suction filters, centrifuges, Buchner funnels, frit funnels, filter crucibles, drum filters, disk filters, belt filters and filter presses. DETAILED DESCRIPTION

[0079] Example A for qualitative evaluation of solids washing:

[0080] In a first set of experiments, the examination of the wash filtrate was examined by means of the refractive index in a displacement wash and was illustrated by way of example using the Sivanto product.

[0081] For this purpose, samples were taken from the filtrate stream in several portions at defined junctions during filtration / washing. The refractive index was measured offline using a refractometer (Abbemat 300 from Anton Paar) and compared with the refractive index of the wash solution ( Figure 3). Taking into account the regular progression of the process, the measurement will be close to the refractive index of the washing solution. First, the filtrate consists of the mother liquor, and therefore a plateau is observed in the course of the refractive index. If the mother liquor is gradually replaced by the washing medium in the displacement washing, the refractive index decreases until a constant value is reached. This value optimally reaches the value of the washing medium used.

[0082] It has thus been shown that the refractive index is suitable as a cumulative signal for detecting a decrease in the concentration in the filtrate; deviations of the concentration and the filtration rate per unit time from the expected values ​​can be displayed and identified.

[0083] The correlation with the filter cake quality was checked in individual cases and this was possible with Sivanto. In each case, after the washing was complete (each experiment was carried out with a different amount of washing medium), samples from the filtrate flow and the filter cake during the washing were analyzed by HPLC.

[0084] In further experiments, a process refractometer was integrated into the filtrate outlet of a laboratory test bed for filtration as an online measurement technique. For this purpose, a process refractometer of the type PR-43 from K Patents was used, which has a measuring range of nD 1.32-1.53. A flow adapter was used for laboratory experiments.

[0085] Example B for qualitative and quantitative evaluation of solid washing of model particles:

[0086] i. Experimental Procedure:

[0087] According to VDI Guideline 2762, at 100 cm 2 The filtration and washing experiments were carried out in a laboratory pressure filter at 0.2 bar gauge and room temperature. A process refractometer (Abbemat 300 from Anton) was integrated into the filtrate conduit. The refractive index and quality of the filtrate were recorded in a time-resolved manner. After the experiment, the height and quality of the filter cake were determined.

[0088] The filtration was terminated at a saturation S of the filter cake of S=1, ultrapure water was carefully spread on the filter cake, and then washing and mechanical dehumidification were carried out. After the experiment, the refractive index of the mother liquor filtrate and the washing filtrate was determined at 23° C. using an Abbemat 300 from Anton Paar.

[0089] In order to convert the determined refractive index (online) into NaCl concentration and mass, a calibration line was recorded with an off-line refractometer.

[0090] The model particles used were SiLibeads S type 0-50 μm glass beads (from Sigmund Lindner GmbH). The solid concentration was 400 g / kg. The impurity used was NaCl at a concentration of 200 g / kg. The amount of suspension applied was about 1000 g, i.e. 120 g of NaCl were introduced into the system as dissolved impurities. For washing, 1192 g of ultrapure water (corresponding to a washing ratio of 4.3 l water / l dry filter cake) was used to obtain a very clean filter cake.

[0091] The dried filter cake is resuspended in ultrapure water and the extraction is stirred. After centrifugation, the refractive index of the supernatant is determined. This corresponds to the value of water. In addition, the free Cl in the supernatant is determined with the aid of a cuvette test. - is 0. This means that the washed filter cake in this example does not contain any NaCl.

[0092] iii. Experimental evaluation:

[0093] Online analysis: qualitative assessment

[0094] In parallel recording of filtrate quality and refractive index, according to Figure 4 The following observations were made during the experiments:

[0095] -During filtration and washing, the mass of the filtrate increases and then remains constant at the end of the experiment during the removal of water from the filter cake. Since only the mother liquor leaves the filter cake, the refractive index remains constant during filtration. In the subsequent washing, the refractive index decreases from the value of the mother liquor to the value of the pure washing medium.

[0096] If a plateau value of almost pure washing medium is reached, it can be assumed that no further washing of the filter cake will be possible by displacement washing. In other words, for further purification it is necessary to examine another washing strategy, such as slurry washing. If there is no further change in the value of the refractive index, the washing can be ended.

[0097] If the above data are based on the wash ratio, the necessary amount of wash medium can be determined directly (see description below).

[0098] Figure 5 The variation of the refractive index (RI) against the wash ratio is shown. It is obvious that with increasing amount of water the constant measured value of the mother liquor filtrate decreases. At the end of the wash a plateau value is reached.

[0099] The decrease in RI and its retention at a constant value indicate that no further washing effect can be achieved. In other words, even with a greater washing ratio, the washing effect of the filter cake does not improve further. This purely qualitative assessment can be used to end the washing at a washing ratio of 1.5 in this example. This directly saves time and costs for the washing medium. Recording such data in operation can generate a sufficient data basis for the optimization of the washing time and washing medium consumption.

[0100] Quantitative assessments can be achieved with a higher degree of complexity for real products. For model projects this is outlined below.

[0101] Online analysis: quantitative evaluation

[0102] For quantitative evaluation of the online measurement data, a plot of RI and mass of the filtrate versus the filtration and washing time was selected (see Figure 5 ). For each time period, the mass of the filtrate and the mass of NaCl can be calculated from the data recorded by the NaCl concentration-refractive index calibration line.

[0103] m NaCl =(m 滤液,1 -m 滤液,0 )*c NaCl,1

[0104] Alternatively, the curve can be integrated as follows:

[0105] The area under the curve can be determined by the trapezoidal rule, so that the area covered in s*g / kg can be determined for each time period:

[0106] Area within the time period: A1 = 0.5*(t1-t0)*(c NaCl，1 -c NaCl，0 )

[0107] By means of a reference time interval and the mass of the filtrate recorded in this time interval, it is possible to determine the mass of NaCl in this time interval (see Tables 1 and 2).

[0108]

[0109]

[0110] Total NaCl filtration volume: 83g

[0111] Table 1: Integration of filtered measurement data

[0112]

[0113] Total NaCl washing amount: 33g

[0114] Table 2: Integration of measurement data for washing

[0115] If all masses of NaCl from the individual time periods are added up - ie the measurement curve is integrated - the result is the mass of NaCl washed out in the entire experiment. In the present example, this amounts to 116 g NaCl, corresponding to a difference of about 3% in the amount of NaCl used.

[0116] Mass balance from offline determination:

[0117] In order to verify the mass balance from online measurement, determine the refractive index in the mass of filtrate and the filtrate collected. This can be used to calculate mass balance. In the experiment described in detail, 120g NaCl is used. Collecting 414g concentration is the mother liquor filtrate of 200g / kg NaCl and 1347g concentration is the washing filtrate of 24g / kg NaCl. The result is that 83g NaCl is dissolved in the mother liquor filtrate, and 32g NaCl is dissolved in the washing filtrate. Owing to not detecting NaCl in filter cake, therefore may reclaim 115g NaCl in the filtrate by measurement technology.

[0118] Conclusions about the quality of the washing performed

[0119] During washing, the refractive index decreases from the (starting) value of the mother liquor to a lower (plateau) value at the end of washing. The curve therefore falls with a specific slope. If there is any change in this slope, it is possible to infer the quality of the washing from it.

[0120] The following examples are recorded using the above model system:

[0121] The rods are inserted into the applied suspension to artificially create channels in the filter cake. After the mother liquor is filtered, water is removed from the filter cake ( Fig. 6A ). Figure 7 shows a progression, especially an increase in the refractive index. This indicates that the washing front does not run uniformly throughout the filter cake, but that discontinuities - here channels - have formed. This is not obvious from visual inspection of the washed filter cake alone, e.g. Figure 6B Where technically possible, it should not be possible to see any cracks, channels etc. hidden within the filter cake when inspecting the filter cake from above. BRIEF DESCRIPTION OF THE DRAWINGS

[0122] Figure 1 : Schematic diagram of pressure suction filter

[0123] 1 Pressure filter, 2 Filter cake, 3 Measuring unit (e.g. RI)

[0124] Figure 2 : Trend representation of the measured value (RI) over time, divided into process phases:

[0125] A-displacement of mother liquor, B-intermediate zone, C-approval zone, D-diffusion zone, E-end of washing effect.

[0126] Figure 3 : Comparison of the refractive index of the product Sivanto (□) and the sum of the secondary components (○). The refractive index of pure butanol at 20° C. is 1.39932. (Example A).

[0127] Figure 4 : Filtrate mass M (○) and refractive index RI (■) as a function of time t. Zone 1: Filtration; Zone 2: Washing.

[0128] Figure 5 : NaCl concentration (■) and refractive index RI (○) as a function of the washing ratio.

[0129] Fig. 6A : A filter cake with channels to remove water after filtration of the mother liquor.

[0130] Figure 6B : Filter cake after mechanical removal of moisture after washing.

[0131] Figure 7 : □ mass (M) and ● refractive index (RI) as a function of time (t).

[0132] Figure 8 : Block diagram of a method for controlling a washing operation

[0133] 1- Input of measurement data

[0134] 2- Calculation of first-order derivatives

[0135] 3- Is the first derivative > 0 or greater than a predefined value?

[0136] 4- End of washing operation

[0137] 5- Error message

[0138] 6-First order derivative within a predefined range C?

[0139] 7-Calculation of average slope and variability (step eg)

[0140] 8-Average slope and variability within a predefined range?

Claims

1. A method for monitoring filtration and washing operations on solid bulk materials in a filtration device for cake filtration, wherein the filtration device has a wash medium feeder, a filter element for cake filtration, a filtrate outlet for removing a filtrate flow and at least one measuring device in or on the filtrate outlet for measuring one or more parameter values ​​of the filtrate flow, - during the filtering and washing operation, solid bulk material in the suspension medium is separated in the form of a cake from the suspension medium by means of a filter element for cake filtration, the suspension medium is guided into a filtrate outlet in the form of a filtrate flow, and the measuring device measures at least one or more parameter values ​​of the filtrate flow over a period of time of the washing operation, It is characterized in that performing a computer-implemented variation analysis of parameter values ​​measured over a period of time of the washing operation, the variation analysis being used to determine the end of the washing operation and / or the effectiveness of the washing operation, and using the variation analysis for ending the washing operation; wherein the parameters of the filtrate stream are selected from the group consisting of: refractive index, density, ultrasonic transit time, redox potential and cumulative spectral characteristics of one or more major or minor components; and The end of the washing operation is determined by the following steps: a) providing the measured parameter values ​​to the evaluation system, b) calculating the first derivative of the measurement curve between the measurement data at times t-1 and t, c) continuing the washing operation if the first derivative from b) is greater than zero or greater than a predefined value of the derivative of the measurement curve for which the method is considered to be terminated; repeating step b) for further measurement curves, d) if the first derivative from b) is zero, if it is less than or equal to a predefined value, ending the washing operation and / or communicating the end of the washing process via a user interface; and / or wherein the effectiveness of the washing operation is determined by: a. transmitting the measured values ​​of the measurement data to the evaluation system within a predefined time period in the washing operation, b. Calculate the first derivative of the measurement curve between the measurement data at time t-1 and t, c. comparing said first derivative with an approved predefined range of values ​​of the first derivative in which said washing operation is considered to be valid, d. if the first derivative is outside a predefined range of values ​​from c, ending the washing operation and / or giving a notification of the difference via a user interface, As an alternative or in addition to step d e. a calculation period C, wherein the first-order derivative is within a predefined range of values ​​from c, f. Calculate the slope value from e as the average slope of period C, g. Calculate the variability of the slope value within period C from e, h. continuing the washing process if the slope value from f is within the predefined working range of the slope values ​​and the variability of the slope from g is less than or equal to the predefined tolerance limit of the variability in which the washing operation is considered to be effective, i. If the slope value from f is outside the predefined value range of said slope values ​​and / or the variability of the slope value from g is above a predefined tolerance limit of the variability, a warning is issued and / or the washing operation is ended.

2. A method as claimed in claim 1, wherein the refractive index and / or density of the filtrate flow is measured.

3. The method as claimed in any one of claims 1 to 2, wherein the parameter value within the time period of the washing operation is transmitted as measurement data to an archiving module for storing the measurement data and stored together with the time t.

4. The method as claimed in claim 1, wherein an amount of washing medium consumed by a washing operation until the end of the washing operation is determined and fixed as an optimum amount of washing medium for a next washing operation.

5. A method as claimed in claim 1 or 2, wherein the method is used for on-line monitoring of the washing operation.

6. A method as claimed in claim 1, wherein at least one concentration of at least one component in the filtrate stream is determined.

7. A system for monitoring filtration and washing operations on solid bulk material in a filtration device for cake filtration, wherein the system comprises: an archiving module configured to store parameter values ​​of the filtrate flow with time t transmitted from at least one measuring device in or on the filtrate outlet of the filtration device during the period of the filtration and washing operation, and to transfer said parameter values ​​to an evaluation system, - an evaluation system connected to the archiving module and configured to analyze the variation of the parameter values ​​during the period of the filtering and washing operation and to use this variation analysis to determine the end of the washing operation and / or the effectiveness of the washing operation by implementing the method according to claim 1; - an element for issuing a control command to end said washing operation, and / or - a display element for the end of the washing operation and / or the effectiveness of the washing operation.

8. Filtration device comprising a wash medium feeder, a filter element for cake filtration and a filtrate outlet, at least one measuring device mounted in or on the filtrate outlet for measuring a parameter value in the filtrate flow and a system as claimed in claim 7.

9. A filtration device as claimed in claim 8, wherein the measuring device can measure one or more parameters of the filtrate flow or, alternatively, of at least one representative component of the filtrate flow, selected from the group consisting of: refractive index, density, ultrasound transmission time, pH, conductivity, redox potential and / or spectral properties, as a cumulative parameter.

10. A filtration device as claimed in claim 8 or 9, selected from the group consisting of suction filters, centrifuges, Buchner funnels, fritten funnels, filter crucibles, drum filters, disc filters, belt filters and filter presses.

11. The filter device as claimed in claim 8, wherein the filter device has a controllable washing medium feeder, which can receive a command for opening or closing the washing medium feeder.

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