WO2018234615A1 - A method and a system for estimating residual liquid content after a liquid removal process - Google Patents

A method and a system for estimating residual liquid content after a liquid removal process Download PDF

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Publication number
WO2018234615A1
WO2018234615A1 PCT/FI2018/050269 FI2018050269W WO2018234615A1 WO 2018234615 A1 WO2018234615 A1 WO 2018234615A1 FI 2018050269 W FI2018050269 W FI 2018050269W WO 2018234615 A1 WO2018234615 A1 WO 2018234615A1
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WO
WIPO (PCT)
Prior art keywords
temperature
liquid
carrier
removal process
liquid removal
Prior art date
Application number
PCT/FI2018/050269
Other languages
French (fr)
Inventor
Teemu KINNARINEN
Manu HUTTUNEN
Lauri NYGREN
Tuomo Lindh
Jero Ahola
Antti HÄKKINEN
Vesa Karvonen
Bjarne Ekberg
Original Assignee
Lappeenrannan Teknillinen Yliopisto
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Publication of WO2018234615A1 publication Critical patent/WO2018234615A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/72—Investigating presence of flaws
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
    • F26B5/041—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum for drying flowable materials, e.g. suspensions, bulk goods, in a continuous operation, e.g. with locks or other air tight arrangements for charging/discharging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
    • B01D33/62—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D33/00—Filters with filtering elements which move during the filtering operation
    • B01D33/80—Accessories
    • B01D33/804—Accessories integrally combined with devices for controlling the filtration
    • B01D33/809—Accessories integrally combined with devices for controlling the filtration by temperature measuring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D37/00—Processes of filtration
    • B01D37/04—Controlling the filtration
    • B01D37/048—Controlling the filtration by temperature measuring
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/008—Control or steering systems not provided for elsewhere in subclass C02F
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/13—Treatment of sludge; Devices therefor by de-watering, drying or thickening by heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/22—Controlling the drying process in dependence on liquid content of solid materials or objects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • C02F11/123—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using belt or band filters
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • C02F11/126—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using drum filters
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/005—Processes using a programmable logic controller [PLC]
    • C02F2209/006—Processes using a programmable logic controller [PLC] comprising a software program or a logic diagram
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/02—Temperature
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/06—Pressure conditions
    • C02F2301/063—Underpressure, vacuum

Definitions

  • the disclosure relates generally to liquid removal, e.g. dewatering. More particularly, the disclosure relates to a method, to a system, and to a computer program for estimating residual liquid content of material, e.g. slurry, discharged from a liquid removal process. Furthermore, the disclosure relates to a method and to a liquid separation device for removing liquid from material. Furthermore, the disclosure relates to a computer program for controlling a liquid removal process.
  • the carrier is moving and material having a high liquid-content is supplied onto a surface of the carrier.
  • the above-mentioned pressure difference causes a gas flow which removes liquid from the material through the carrier when the material travels through a liquid removal area affected by the pressure difference.
  • Material from which at least a part of liquid has been removed in the above-described way is peeled off from the surface of the carrier and delivered to further processing and/or storing.
  • a liquid separation device can be for example a rotary vacuum drum-filter, a rotary vacuum disc-filter, or a vacuum belt-filter where the gas flow, e.g. an air flow, for removing liquid is based on vacuum. It is however also possible that the liquid-removing gas flow is based on gas pressure higher than the atmospheric pressure. Furthermore, it is also possible that the liquid-removing gas flow is based on gas pressure higher than the atmospheric pressure on one side of the carrier and on vacuum on the other side of the carrier.
  • the gas flow e.g. an air flow
  • the residual liquid content of material which is discharged from a liquid removal process of the kind described above can be controlled by changing the speed of the carrier, the supply rate of the material onto the carrier, and/or the pressure difference.
  • the residual liquid content can be reduced by increasing the pressure difference, by decreasing the speed of the carrier, and/or by reducing the supply rate of the material onto the carrier.
  • the residual liquid content can be increased by decreasing the pressure difference, by increasing the speed of the carrier, and/or by increasing the supply rate of the material onto the carrier.
  • a new estimator system for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process.
  • the material can be for example slurry from which liquid e.g. water is to be removed.
  • An estimator system according to the invention comprises:
  • - data processing equipment for producing the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to a cooling effect caused by evaporation of liquid from the material during the liquid removal process.
  • the above-described estimator system is based on the fact that evaporation of liquid from wet or moist solid material causes a cooling effect due to the evaporation-heat specific to the liquid.
  • the heat energy required for evaporation of liquid is provided mainly by the solid material, which in turn cools down, according to its physical properties. Therefore, there is the above-mentioned correlation between the temperature decrease and the residual liquid content of the material.
  • a liquid separation device for removing liquid from material e.g. slurry.
  • a liquid separation device comprises:
  • an estimator system for producing an estimate value indicative of residual liquid content of the material coming out from the liquid removal area
  • controller for controlling at least one of the following in accordance with the estimate value: the speed of the carrier, the supply rate of the material onto the carrier, the pressure difference.
  • An estimation method for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process.
  • An estimation method according to the invention comprises:
  • the method comprises:
  • the computer program comprises computer executable instructions for controlling a programmable processor to:
  • a new computer program for controlling a liquid removal process that comprises conveying, with carrier, material through a liquid removal area affected by a pressure difference so that there is a gas flow through the carrier and the material carried by the carrier, wherein the computer program comprises:
  • the computer program product comprises a non-volatile computer readable medium, e.g. a compact disc "CD”, encoded with a computer program according to the invention.
  • figure 1 illustrates a liquid separation device according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material e.g. slurry
  • figure 2 shows a flowchart of an estimation method according to an exemplifying and non-limiting embodiment of the invention for estimating residual liquid content of material discharged from a liquid removal process
  • figure 3 shows a flowchart of a method according to an exemplifying and non-limiting embodiment of the invention for removing liquid from material e.g.
  • figure 4 illustrates a liquid separation device according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material e.g. slurry
  • figure 5 illustrates a liquid separation device according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material e.g. slurry.
  • Figure 1 illustrates a liquid separation device according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material 1 10 that can be for example slurry.
  • the liquid separation device is a vacuum belt-filter that comprises a carrier 107 configured to convey the material 1 10, e.g. a cake of slurry, in the positive x-direction of a coordinate system 199.
  • a liquid separation device is a rotary vacuum drum-filter, a rotary vacuum disc-filter, or another liquid separation device that is based on gas flow through material from which liquid is removed.
  • the liquid separation device comprises a pump 106, a piping system, and other structures configured to maintain a pressure difference ⁇ over the carrier 107 and the material 1 10 carried by the carrier.
  • the material 1 10 is supplied on the carrier 107 so that the carrier 107 conveys the material through a liquid removal area 109 affected by the pressure difference ⁇ .
  • the pressure difference ⁇ maintains a gas flow through the carrier 107 and the material 1 10 carried by the carrier, and thereby the pressure difference ⁇ sucks liquid from the material 1 10 through the carrier 107.
  • some of the pores of the material 1 10 become empty of liquid due to the influence of the gas low maintained by the pressure difference ⁇ .
  • the process of emptying the pores is called desaturation or deliquoring.
  • the liquid being removed from the material 1 10 can be for example water.
  • the liquid separation device further comprises an estimator system according to an exemplifying and non-limiting embodiment of the invention for producing an estimate value LC e which is indicative of residual liquid content of the material 1 10 coming out from the liquid removal area 109.
  • the estimator system comprises temperature sensor equipment 101 for obtaining temperature data which expresses how much the temperature of the material 1 10 changes during the liquid removal process, i.e. when the material is transferred through the liquid removal area 109.
  • the temperature sensor equipment 101 may comprise for example a first temperature sensor for measuring a first temperature value Ti at a first area where the material 1 10 arrives at the liquid removal process and a second temperature sensor for measuring a second temperature value T2 at a second area where the material is discharged from the liquid removal process.
  • the difference between the second and first temperature values T2 - Ti expresses the temperature change occurred during the liquid removal process.
  • the temperature sensor equipment 101 comprises a first thermographic camera for obtaining a first temperature profile over the width of the cake of the material 1 10 at the first area where the material arrives at the liquid removal process and a second thermographic camera for obtaining a second temperature profile over the width of the cake of the material at the second area where the material is discharged from the liquid removal process.
  • the difference between the first and second temperature profiles is indicative of the temperature change occurred during the liquid removal process.
  • the T in a circle denoted with a reference 103 represents the one or more temperature sensors or the first thermographic camera at the first area and, correspondingly, the T in a circle denoted with a reference 104 represents the one or more temperature sensors or the second thermographic camera at the second area.
  • the temperature data is obtained with a single thermographic camera which produces data indicative of the spatial temperature distribution over the width and the length of the cake of the material. In this exemplifying case, the spatial temperature distribution is indicative of the temperature change occurred during the liquid removal process.
  • the above-mentioned estimator system further comprises data processing equipment 102 for forming the estimate value LC e indicative of the residual liquid content based on the above-mentioned temperature data and on pre-stored data expressing the correlation between a decrease of the liquid content of the material 1 10 and the change of the temperature of the material due to the cooling effect caused by evaporation of liquid from the material during the liquid removal process.
  • the heat energy required for evaporation of liquid is provided mainly by the solid portion of the material 1 10, which in turn cools down, according to its physical properties. Therefore, there is the above-mentioned correlation between the temperature decrease and the residual liquid content of the material 1 10.
  • the above-mentioned pre-stored data expressing the above-mentioned correlation can be obtained for example with a procedure comprising the following actions:
  • the liquid separation device further comprises a controller 108 for controlling the operation of the liquid separation device at least partly in accordance with the above- mentioned estimate value LC e so as to keep the residual liquid content within desired limits.
  • the controller can be configured to control for example the pressure difference ⁇ , the speed v of the carrier 107, and /or the supply rate s of the material 1 10 onto the carrier.
  • the residual liquid content of the material 1 10 coming out from the liquid removal area 109 can be reduced by increasing the pressure difference ⁇ , by decreasing the speed v of the carrier, and/or by reducing the supply rate s of the material onto the carrier.
  • the residual liquid content can be increased by decreasing the pressure difference ⁇ , by increasing the speed v of the carrier, and/or by increasing the supply rate s of the material onto the carrier.
  • the estimate value LC e used for controlling the liquid separation device can be for example the above-mentioned temperature difference T2 - Ti .
  • the temperature difference T2 - Ti can be assumed to be directly proportional to the residual liquid content, i.e. the ratio '(T2 - Ti) / residual liquid content' is assumed to be constant.
  • the gain of the control loop can be tuned to be in harmony with the ratio: '(T2 - Ti) / residual liquid content'.
  • the implementation of the data processing equipment 102 can be based on one or more analogue circuits, one or more digital processing circuits, or a combination thereof.
  • Each digital processing circuit can be a programmable processor circuit provided with appropriate software, a dedicated hardware processor such as for example an application specific integrated circuit "ASIC", or a configurable hardware processor such as for example a field programmable gate array "FPGA".
  • the data processing equipment 102 may comprise one or more memory circuits each of which can be for example a Random-Access Memory "RAM" circuit.
  • the implementation of the controller 108 can be based on one or more analogue circuits, one or more digital processing circuits, or a combination thereof.
  • the controller 108 may comprise one or more memory circuits.
  • Figure 2 shows a flowchart of an estimation method according to an exemplifying and non-limiting embodiment of the invention for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process.
  • the estimation method comprises the following actions:
  • - action 201 obtaining temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and
  • An estimation method comprises:
  • thermographic camera obtaining, with a second thermographic camera, a second temperature profile over the width of the cake of the material at a second area where the material is discharged from the liquid removal process, a difference between the first and second temperature profiles being indicative of the change of the temperature occurred during the liquid removal process.
  • Figure 3 shows a flowchart of a method according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material e.g. slurry.
  • the method comprises the following actions:
  • - action 302 conveying, with a carrier, the material through a liquid removal area affected by the pressure difference so that there is a gas flow through the carrier and the material carried by the carrier
  • action 303 producing an estimate value indicative of residual liquid content of the material coming out from the liquid removal area by carrying out an estimation method according to an embodiment of the invention
  • - action 304 controlling at least one of the following in accordance with the estimate of the residual liquid content: the speed of the carrier, the supply rate of the material onto the carrier, the pressure difference.
  • the pressure difference is increased in response to a situation in which the estimate value is greater than a target value and the pressure difference is decreased in response to a situation in which the estimate value is less than the target value.
  • the speed of the carrier is decreased in response to a situation in which the estimate value is greater than a target value and the speed of the carrier is increased in response to a situation in which the estimate value is less than the target value.
  • the supply rate of the material onto the carrier is decreased in response to a situation in which the estimate value is greater than a target value and the supply rate of the material onto the carrier is increased in response to a situation in which the estimate value is less than a target value.
  • a computer program according to an exemplifying and non-limiting embodiment of the invention comprises computer executable instructions for controlling a programmable processing system to carry out actions related to a method according to any of the above-described exemplifying embodiments of the invention.
  • a computer program comprises software modules for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process.
  • the software modules comprise computer executable instructions for controlling a programmable processor to: receive temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and - produce the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to the cooling effect caused by evaporation of liquid from the material during the liquid removal process.
  • a computer program comprises software modules for controlling a liquid removal process that comprises conveying, with carrier, material through a liquid removal area affected by a pressure difference so that there is a gas flow through the carrier and the material carried by the carrier.
  • the software modules comprise:
  • the above-mentioned software modules can be e.g. subroutines or functions implemented with a suitable programming language.
  • a signal according to an exemplifying and non-limiting embodiment of the invention is encoded to carry information defining a computer program according to an exemplifying embodiment of invention.
  • Figure 4 shows a schematic top-view of a liquid separation device according to an exemplifying and non-limiting embodiment of the invention for removing liquid from material 410 that can be for example slurry.
  • the liquid separation device is a rotary vacuum disc-filter.
  • the liquid separation device comprises an estimator system according to an exemplifying embodiment of the invention for producing an estimate value indicative of the residual liquid content of the material 410 after the liquid removal process.
  • the estimator system can be similar to that explained with reference to figure 1 .
  • Figure 5 shows a schematic side-view of a liquid separation device according to an exemplifying and non-limiting embodiment of the invention for removing liquid from material 510 that can be for example slurry.
  • the liquid separation device is a rotary vacuum drum-filter.
  • the liquid separation device comprises an estimator system according to an exemplifying embodiment of the invention for producing an estimate value indicative of the residual liquid content of the material 510 after the liquid removal process.
  • the estimator system can be similar to that explained with reference to figure 1 .
  • the above-presented examples relate to continuous liquid removal processes where material under liquid removal is transferred as a continuous flow through an area affected by a pressure difference.
  • the above- described principle for estimating the residual liquid content is applicable also on a batch process where a batch of material is subject to liquid removal so that the liquid removal starts at a first moment of time for the whole batch and, correspondingly, the liquid removal ends for the whole batch at a second moment of time.
  • the temperature values indicative of the temperature change occurred during the liquid removal process can be measured at a same place but at different moments of time - one at the beginning of the liquid removal process and the other at the end of the liquid removal process.

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Abstract

The invention relates to an estimator system for estimating residual liquid content of material discharged from a liquid removal process. The estimator system comprises temperature sensor equipment (101) for obtaining temperature data indicative of a change of temperature of the material, where the change of the temperature has occurred during the liquid removal process. The estimator system comprises data processing equipment (102) for estimating the residual liquid content based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to a cooling effect caused by evaporation of liquid from the material during the liquid removal process. Thus, the estimator system utilizes the fact that evaporation of liquid from a wet or moist solid material causes a cooling effect due to the evaporation-heat specific to the liquid.

Description

A method and a system for estimating residual liquid content after a liquid removal process
Field of the disclosure The disclosure relates generally to liquid removal, e.g. dewatering. More particularly, the disclosure relates to a method, to a system, and to a computer program for estimating residual liquid content of material, e.g. slurry, discharged from a liquid removal process. Furthermore, the disclosure relates to a method and to a liquid separation device for removing liquid from material. Furthermore, the disclosure relates to a computer program for controlling a liquid removal process.
Background
In many cases, a liquid separation device for removing liquid from material such as e.g. slurry comprises a carrier for carrying the material and a pump system for effecting a pressure difference over the carrier and the material carried by the carrier. In many implementations, the carrier is moving and material having a high liquid-content is supplied onto a surface of the carrier. The above-mentioned pressure difference causes a gas flow which removes liquid from the material through the carrier when the material travels through a liquid removal area affected by the pressure difference. Material from which at least a part of liquid has been removed in the above-described way is peeled off from the surface of the carrier and delivered to further processing and/or storing. A liquid separation device can be for example a rotary vacuum drum-filter, a rotary vacuum disc-filter, or a vacuum belt-filter where the gas flow, e.g. an air flow, for removing liquid is based on vacuum. It is however also possible that the liquid-removing gas flow is based on gas pressure higher than the atmospheric pressure. Furthermore, it is also possible that the liquid-removing gas flow is based on gas pressure higher than the atmospheric pressure on one side of the carrier and on vacuum on the other side of the carrier.
The residual liquid content of material which is discharged from a liquid removal process of the kind described above can be controlled by changing the speed of the carrier, the supply rate of the material onto the carrier, and/or the pressure difference. The residual liquid content can be reduced by increasing the pressure difference, by decreasing the speed of the carrier, and/or by reducing the supply rate of the material onto the carrier. Correspondingly, the residual liquid content can be increased by decreasing the pressure difference, by increasing the speed of the carrier, and/or by increasing the supply rate of the material onto the carrier. Concerning the control of a liquid removal process of the kind mentioned above, it is advantageous to have an estimate of the residual liquid content of material that is discharged from the liquid removal process. Thus, there is a need for technical solutions for estimating the residual liquid content with a sufficient accuracy and with a sufficiently small estimation delay, too.
Summary
The following presents a simplified summary in order to provide a basic understanding of some embodiments of the invention. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.
In accordance with the invention, there is provided a new estimator system for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process. The material can be for example slurry from which liquid e.g. water is to be removed. An estimator system according to the invention comprises:
- temperature sensor equipment for obtaining temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and
- data processing equipment for producing the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to a cooling effect caused by evaporation of liquid from the material during the liquid removal process.
The above-described estimator system is based on the fact that evaporation of liquid from wet or moist solid material causes a cooling effect due to the evaporation-heat specific to the liquid. In other words, the heat energy required for evaporation of liquid is provided mainly by the solid material, which in turn cools down, according to its physical properties. Therefore, there is the above-mentioned correlation between the temperature decrease and the residual liquid content of the material.
In accordance with the invention, there is provided also a new liquid separation device for removing liquid from material e.g. slurry. A liquid separation device according to the invention comprises:
- a pump for generating a pressure difference,
- a carrier for conveying the material through a liquid removal area affected by the pressure difference so that there is a gas-flow through the carrier and the material carried by the carrier,
- an estimator system according to the invention for producing an estimate value indicative of residual liquid content of the material coming out from the liquid removal area, and
- a controller for controlling at least one of the following in accordance with the estimate value: the speed of the carrier, the supply rate of the material onto the carrier, the pressure difference.
In accordance with the invention, there is provided also a new estimation method for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process. An estimation method according to the invention comprises:
- obtaining temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and - producing the estimate value based on the temperature data and on pre- stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to a cooling effect caused by evaporation of liquid from the material during the liquid removal process.
In accordance with the invention, there is provided also a new method for removing liquid from material. The method comprises:
- generating a pressure difference,
- conveying, with a carrier, the material through a liquid removal area affected by the pressure difference so that there is a gas-flow through the carrier and the material carried by the carrier,
- producing an estimate value indicative of residual liquid content of the material coming out from the liquid removal area by carrying out an estimation method according to the invention, and - controlling at least one of the following in accordance with the estimate value: the speed of the carrier, the supply rate of the material onto the carrier, the pressure difference.
In accordance with the invention, there is provided also a new computer program for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process. The computer program comprises computer executable instructions for controlling a programmable processor to:
- receive temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and - produce the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to a cooling effect caused by evaporation of liquid from the material during the liquid removal process.
In accordance with the invention, there is provided also a new computer program for controlling a liquid removal process that comprises conveying, with carrier, material through a liquid removal area affected by a pressure difference so that there is a gas flow through the carrier and the material carried by the carrier, wherein the computer program comprises:
- computer executable instructions according to the invention for controlling a programmable processor system to produce an estimate value indicative of residual liquid content of the material coming out from the liquid removal area, and
- computer executable instructions for controlling the programmable processor system to control at least one of the following in accordance with the estimate value: speed of the carrier, supply rate of the material onto the carrier, the pressure difference.
In accordance with the invention, there is provided also a new computer program product. The computer program product comprises a non-volatile computer readable medium, e.g. a compact disc "CD", encoded with a computer program according to the invention. Exemplifying and non-limiting embodiments of the invention are described in accompanied dependent claims.
Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings.
The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in the accompanied dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does as such not exclude a plurality.
Brief description of the figures Exemplifying and non-limiting embodiments of the invention and their advantages are explained in greater details below in the sense of examples and with reference to the accompanying drawings, in which: figure 1 illustrates a liquid separation device according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material e.g. slurry, figure 2 shows a flowchart of an estimation method according to an exemplifying and non-limiting embodiment of the invention for estimating residual liquid content of material discharged from a liquid removal process, figure 3 shows a flowchart of a method according to an exemplifying and non-limiting embodiment of the invention for removing liquid from material e.g. slurry, figure 4 illustrates a liquid separation device according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material e.g. slurry, and figure 5 illustrates a liquid separation device according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material e.g. slurry. Description of exemplifying embodiments
The specific examples provided in the description below should not be construed as limiting the scope and/or the applicability of the accompanied claims. Lists and groups of examples provided in the description are not exhaustive unless otherwise explicitly stated. Figure 1 illustrates a liquid separation device according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material 1 10 that can be for example slurry. In this exemplifying case, the liquid separation device is a vacuum belt-filter that comprises a carrier 107 configured to convey the material 1 10, e.g. a cake of slurry, in the positive x-direction of a coordinate system 199. It is also possible that a liquid separation device according to an exemplifying and non- limiting embodiment of the invention is a rotary vacuum drum-filter, a rotary vacuum disc-filter, or another liquid separation device that is based on gas flow through material from which liquid is removed.
The liquid separation device comprises a pump 106, a piping system, and other structures configured to maintain a pressure difference Δρ over the carrier 107 and the material 1 10 carried by the carrier. The material 1 10 is supplied on the carrier 107 so that the carrier 107 conveys the material through a liquid removal area 109 affected by the pressure difference Δρ. The pressure difference Δρ maintains a gas flow through the carrier 107 and the material 1 10 carried by the carrier, and thereby the pressure difference Δρ sucks liquid from the material 1 10 through the carrier 107. In typical cases where the material 1 10 is porous, some of the pores of the material 1 10 become empty of liquid due to the influence of the gas low maintained by the pressure difference Δρ. The process of emptying the pores is called desaturation or deliquoring. The liquid being removed from the material 1 10 can be for example water.
The liquid separation device further comprises an estimator system according to an exemplifying and non-limiting embodiment of the invention for producing an estimate value LCe which is indicative of residual liquid content of the material 1 10 coming out from the liquid removal area 109. The estimator system comprises temperature sensor equipment 101 for obtaining temperature data which expresses how much the temperature of the material 1 10 changes during the liquid removal process, i.e. when the material is transferred through the liquid removal area 109. The temperature sensor equipment 101 may comprise for example a first temperature sensor for measuring a first temperature value Ti at a first area where the material 1 10 arrives at the liquid removal process and a second temperature sensor for measuring a second temperature value T2 at a second area where the material is discharged from the liquid removal process. In this exemplifying case, the difference between the second and first temperature values T2 - Ti expresses the temperature change occurred during the liquid removal process. In order to improve the accuracy of the temperature data, it is possible to install more than one temperature sensor on the above-mentioned first area where the material 1 10 arrives at the liquid removal process and more than one temperature sensor on the above-mentioned second area where the material 1 10 is discharged from the liquid removal process. It is also possible that the temperature sensor equipment 101 comprises a first thermographic camera for obtaining a first temperature profile over the width of the cake of the material 1 10 at the first area where the material arrives at the liquid removal process and a second thermographic camera for obtaining a second temperature profile over the width of the cake of the material at the second area where the material is discharged from the liquid removal process. In this exemplifying case, the difference between the first and second temperature profiles is indicative of the temperature change occurred during the liquid removal process. In figure 1 , the T in a circle denoted with a reference 103 represents the one or more temperature sensors or the first thermographic camera at the first area and, correspondingly, the T in a circle denoted with a reference 104 represents the one or more temperature sensors or the second thermographic camera at the second area. Furthermore, it is also possible that the temperature data is obtained with a single thermographic camera which produces data indicative of the spatial temperature distribution over the width and the length of the cake of the material. In this exemplifying case, the spatial temperature distribution is indicative of the temperature change occurred during the liquid removal process.
The above-mentioned estimator system further comprises data processing equipment 102 for forming the estimate value LCe indicative of the residual liquid content based on the above-mentioned temperature data and on pre-stored data expressing the correlation between a decrease of the liquid content of the material 1 10 and the change of the temperature of the material due to the cooling effect caused by evaporation of liquid from the material during the liquid removal process. The heat energy required for evaporation of liquid is provided mainly by the solid portion of the material 1 10, which in turn cools down, according to its physical properties. Therefore, there is the above-mentioned correlation between the temperature decrease and the residual liquid content of the material 1 10. The above-mentioned pre-stored data expressing the above-mentioned correlation can be obtained for example with a procedure comprising the following actions:
1 ) Measurement of changes of temperature within a range of conditions, such as e.g. different solid loadings per filtration area, kgSoiids/m2, and different pressure differences Δρ, and taking corresponding samples of material discharged from the liquid removal process. The aim is to produce material samples with different residual liquid contents to cover the whole range from saturated material samples to material samples from which more liquid cannot be removed mechanically by a gas flow. 2) Determination of the residual liquid contents of the samples e.g. by drying them to obtain the equilibrium dryness, and by calculating the mass fraction of liquid in them. The standard temperature of 105 °C is applicable for most inorganic materials, and the applied temperature can be higher or lower than 105 °C if the material requires this. 3) Forming the correlation between the change of the temperature and the residual liquid content for example by presenting corresponding values of the residual liquid content and of the change of the temperature as points on a coordinate plane and fitting a curve, typically a straight line, to the data by an adequate mathematical method. The liquid separation device further comprises a controller 108 for controlling the operation of the liquid separation device at least partly in accordance with the above- mentioned estimate value LCe so as to keep the residual liquid content within desired limits. The controller can be configured to control for example the pressure difference Δρ, the speed v of the carrier 107, and /or the supply rate s of the material 1 10 onto the carrier. The residual liquid content of the material 1 10 coming out from the liquid removal area 109 can be reduced by increasing the pressure difference Δρ, by decreasing the speed v of the carrier, and/or by reducing the supply rate s of the material onto the carrier. Correspondingly, the residual liquid content can be increased by decreasing the pressure difference Δρ, by increasing the speed v of the carrier, and/or by increasing the supply rate s of the material onto the carrier. It is worth noting that the estimate value LCe used for controlling the liquid separation device can be for example the above-mentioned temperature difference T2 - Ti . In cases where the above-discussed correlation is assumed to be linear, the temperature difference T2 - Ti can be assumed to be directly proportional to the residual liquid content, i.e. the ratio '(T2 - Ti) / residual liquid content' is assumed to be constant. The gain of the control loop can be tuned to be in harmony with the ratio: '(T2 - Ti) / residual liquid content'.
The implementation of the data processing equipment 102 can be based on one or more analogue circuits, one or more digital processing circuits, or a combination thereof. Each digital processing circuit can be a programmable processor circuit provided with appropriate software, a dedicated hardware processor such as for example an application specific integrated circuit "ASIC", or a configurable hardware processor such as for example a field programmable gate array "FPGA". Furthermore, the data processing equipment 102 may comprise one or more memory circuits each of which can be for example a Random-Access Memory "RAM" circuit. Correspondingly, the implementation of the controller 108 can be based on one or more analogue circuits, one or more digital processing circuits, or a combination thereof. Furthermore, the controller 108 may comprise one or more memory circuits. Figure 2 shows a flowchart of an estimation method according to an exemplifying and non-limiting embodiment of the invention for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process. The estimation method comprises the following actions:
- action 201 : obtaining temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and
- action 203: producing the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to the cooling effect caused by evaporation of liquid from the material during the liquid removal process. An estimation method according to an exemplifying and non-limiting embodiment of the invention comprises:
- measuring at least one first temperature value at a first area where the material arrives at the liquid removal process, and - measuring at least one second temperature value at a second area where the material is discharged from the liquid removal process, a difference between the first and second temperature values being indicative of the change of the temperature occurred during the liquid removal process.
An estimation method according to an exemplifying and non-limiting embodiment of the invention comprises:
- obtaining, with a first thermographic camera, a first temperature profile over the width of a cake of the material at a first area where the material arrives at the liquid removal process, and
- obtaining, with a second thermographic camera, a second temperature profile over the width of the cake of the material at a second area where the material is discharged from the liquid removal process, a difference between the first and second temperature profiles being indicative of the change of the temperature occurred during the liquid removal process.
Figure 3 shows a flowchart of a method according to an exemplifying and non- limiting embodiment of the invention for removing liquid from material e.g. slurry. The method comprises the following actions:
- action 301 : generating a pressure difference,
- action 302: conveying, with a carrier, the material through a liquid removal area affected by the pressure difference so that there is a gas flow through the carrier and the material carried by the carrier, action 303: producing an estimate value indicative of residual liquid content of the material coming out from the liquid removal area by carrying out an estimation method according to an embodiment of the invention, and - action 304: controlling at least one of the following in accordance with the estimate of the residual liquid content: the speed of the carrier, the supply rate of the material onto the carrier, the pressure difference.
In a method according to an exemplifying and non-limiting embodiment of the invention, the pressure difference is increased in response to a situation in which the estimate value is greater than a target value and the pressure difference is decreased in response to a situation in which the estimate value is less than the target value.
In a method according to an exemplifying and non-limiting embodiment of the invention, the speed of the carrier is decreased in response to a situation in which the estimate value is greater than a target value and the speed of the carrier is increased in response to a situation in which the estimate value is less than the target value.
In a method according to an exemplifying and non-limiting embodiment of the invention, the supply rate of the material onto the carrier is decreased in response to a situation in which the estimate value is greater than a target value and the supply rate of the material onto the carrier is increased in response to a situation in which the estimate value is less than a target value.
A computer program according to an exemplifying and non-limiting embodiment of the invention comprises computer executable instructions for controlling a programmable processing system to carry out actions related to a method according to any of the above-described exemplifying embodiments of the invention.
A computer program according to an exemplifying and non-limiting embodiment of the invention comprises software modules for producing an estimate value indicative of residual liquid content of material discharged from a liquid removal process. The software modules comprise computer executable instructions for controlling a programmable processor to: receive temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and - produce the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to the cooling effect caused by evaporation of liquid from the material during the liquid removal process.
A computer program according to an exemplifying and non-limiting embodiment of the invention comprises software modules for controlling a liquid removal process that comprises conveying, with carrier, material through a liquid removal area affected by a pressure difference so that there is a gas flow through the carrier and the material carried by the carrier. The software modules comprise:
- computer executable instructions according to an exemplifying and non- limiting embodiment of the invention for controlling a programmable processor system to produce an estimate value indicative of residual liquid content of the material coming out from the liquid removal area, and - computer executable instructions for controlling the programmable processor system to control at least one of the following in accordance with the estimate value: the speed of the carrier, the supply rate of the material onto the carrier, the pressure difference.
The above-mentioned software modules can be e.g. subroutines or functions implemented with a suitable programming language.
A computer program product according to an exemplifying and non-limiting embodiment of the invention comprises a computer readable medium, e.g. a compact disc "CD", encoded with a computer program according to an exemplifying embodiment of invention. A signal according to an exemplifying and non-limiting embodiment of the invention is encoded to carry information defining a computer program according to an exemplifying embodiment of invention.
Figure 4 shows a schematic top-view of a liquid separation device according to an exemplifying and non-limiting embodiment of the invention for removing liquid from material 410 that can be for example slurry. In this exemplifying case, the liquid separation device is a rotary vacuum disc-filter. The liquid separation device comprises an estimator system according to an exemplifying embodiment of the invention for producing an estimate value indicative of the residual liquid content of the material 410 after the liquid removal process. The estimator system can be similar to that explained with reference to figure 1 .
Figure 5 shows a schematic side-view of a liquid separation device according to an exemplifying and non-limiting embodiment of the invention for removing liquid from material 510 that can be for example slurry. In this exemplifying case, the liquid separation device is a rotary vacuum drum-filter. The liquid separation device comprises an estimator system according to an exemplifying embodiment of the invention for producing an estimate value indicative of the residual liquid content of the material 510 after the liquid removal process. The estimator system can be similar to that explained with reference to figure 1 . The above-presented examples relate to continuous liquid removal processes where material under liquid removal is transferred as a continuous flow through an area affected by a pressure difference. It is, however, worth noting that the above- described principle for estimating the residual liquid content is applicable also on a batch process where a batch of material is subject to liquid removal so that the liquid removal starts at a first moment of time for the whole batch and, correspondingly, the liquid removal ends for the whole batch at a second moment of time. In this exemplifying case, the temperature values indicative of the temperature change occurred during the liquid removal process can be measured at a same place but at different moments of time - one at the beginning of the liquid removal process and the other at the end of the liquid removal process.
The specific examples provided in the description given above should not be construed as limiting. Therefore, the invention is not limited merely to the exemplifying and non-limiting embodiments described above. Lists and groups of examples provided in the description are not exhaustive unless otherwise explicitly stated.

Claims

What is claimed is:
1 . An estimator system for producing an estimate value indicative of liquid content of material discharged from a liquid removal process, characterized in that the estimator system comprises:
- temperature sensor equipment (101 ) for obtaining temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and
- data processing equipment (102) for producing the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to a cooling effect caused by evaporation of liquid from the material during the liquid removal process.
2. An estimator system according to claim 1 , wherein the temperature sensor equipment (101 ) comprises:
- at least one first temperature sensor (103) for measuring at least one first temperature value (Ti) at a first area where the material arrives at the liquid removal process, and
- at least one second temperature sensor (104) for measuring at least one second temperature value (T2) at a second area where the material is discharged from the liquid removal process, a difference between the first and second temperature values being indicative of the change of the temperature.
3. An estimator system according to claim 1 , wherein the temperature sensor equipment comprises:
- a first thermographic camera for obtaining a first temperature profile over a width of a cake of the material at a first area where the material arrives at the liquid removal process, and - a second thermographic camera for obtaining a second temperature profile over the width of the cake of the material at a second area where the material is discharged from the liquid removal process, a difference between the first and second temperature profiles being indicative of the change of the temperature.
4. A liquid separation device for removing liquid from material, the liquid separation device comprising:
- a pump (106) for generating a pressure difference (Δρ),
- a carrier (107) for conveying the material through a liquid removal area (109) affected by the pressure difference so that there is a gas flow through the carrier and the material carried by the carrier,
- a controller (108) for controlling at least one of the following in accordance with an estimate value indicative of liquid content of the material coming out from the liquid removal area: speed of the carrier, supply rate of the material onto the carrier, the pressure difference, and
- an estimator system according to any of claims 1 -3 for producing the estimate value.
5. A liquid separation device according to claim 4, wherein the controller is configured to increase the pressure difference in response to a situation in which the estimate value is greater than a target value and to decrease the pressure difference in response to a situation in which the estimate value is less than the target value.
6. A liquid separation device according to claim 4 or 5, wherein the controller is configured to decrease the speed of the carrier in response to a situation in which the estimate value is greater than a target value and to increase the speed of the carrier in response to a situation in which the estimate value is less than the target value.
7. A liquid separation device according to any of claims 4-6, wherein the controller is configured to decrease the supply rate of the material onto the carrier in response to a situation in which the estimate value is greater than a target value and to increase the supply rate of the material onto the carrier in response to a situation in which the estimate value is less than the target value.
8. A liquid separation device according to any of claims 4-7, wherein the liquid separation device is one of the following: a vacuum belt-filter, a rotary vacuum drum- filter, a rotary vacuum disc-filter.
9. An estimation method for producing an estimate value indicative of liquid content of material discharged from a liquid removal process, characterized in that the estimation method comprises:
- obtaining (201 ) temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and - producing (202) the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to a cooling effect caused by evaporation of liquid from the material during the liquid removal process.
10. An estimation method according to claim 9, wherein the method comprises:
- measuring at least one first temperature value at a first area where the material arrives at the liquid removal process, and
- measuring at least one second temperature value at a second area where the material is discharged from the liquid removal process, a difference between the first and second temperature values being indicative of the change of the temperature.
1 1 An estimation method according to claim 9, wherein the method comprises: - obtaining, with a first thermographic camera, a first temperature profile over a width of a cake of the material at a first area where the material arrives at the liquid removal process, and
- obtaining, with a second thermographic camera, a second temperature profile over the width of the cake of the material at a second area where the material is discharged from the liquid removal process, a difference between the first and second temperature profiles being indicative of the change of the temperature.
12. A method for removing liquid from material, the method comprising: - generating (301 ) a pressure difference,
- conveying (302), with a carrier, the material through a liquid removal area affected by the pressure difference so that there is a gas flow through the carrier and the material carried by the carrier,
- producing (303) an estimate value indicative of liquid content of the material coming out from the liquid removal area by carrying out an estimation method according to any of claims 9-1 1 , and
- controlling (304) at least one of the following in accordance with the estimate value: speed of the carrier, supply rate of the material onto the carrier, the pressure difference.
13. A method according to claim 12, wherein the pressure difference is increased in response to a situation in which the estimate value is greater than a target value and the pressure difference is decreased in response to a situation in which the estimate value is less than a target value.
14. A method according to claim 12 or 13, wherein the speed of the carrier is decreased in response to a situation in which the estimate value is greater than a target value and the speed of the carrier is increased in response to a situation in which the estimate value is less than the target value.
15. A method according to any of claims 12-14, wherein the supply rate of the material onto the carrier is decreased in response to a situation in which the estimate value is greater than a target value and the supply rate of the material onto the carrier is increased in response to a situation in which the estimate value is less than a target value.
16. A computer program for producing an estimate value indicative of liquid content of material discharged from a liquid removal process, characterized in that the computer program comprises computer executable instructions for controlling a programmable processor to:
- receive temperature data indicative of a change of temperature of the material, the change of the temperature having occurred during the liquid removal process, and
- produce the estimate value based on the temperature data and on pre-stored data expressing a correlation between a decrease of the liquid content of the material and the change of the temperature of the material due to a cooling effect caused by evaporation of liquid from the material during the liquid removal process.
17. A computer program for controlling a liquid removal process that comprises conveying, with carrier, material through a liquid removal area affected by a pressure difference so that there is a gas flow through the carrier and the material carried by the carrier, wherein the computer program comprises:
- computer executable instructions for controlling a programmable processor system to control at least one of the following in accordance with an estimate value indicative of liquid content of the material coming out from the liquid removal area: speed of the carrier, supply rate of the material onto the carrier, the pressure difference, and a computer program according to claim 16 for controlling the programmable processor system to produce the estimate value. A computer program product comprising a non-volatile computer readable ium encoded with a computer program according to claim 16 or 17.
PCT/FI2018/050269 2017-06-22 2018-04-17 A method and a system for estimating residual liquid content after a liquid removal process WO2018234615A1 (en)

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