FI20225979A1 - Arrangement and method for treatment of bleaching chemical residues - Google Patents

Arrangement and method for treatment of bleaching chemical residues Download PDF

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Publication number
FI20225979A1
FI20225979A1 FI20225979A FI20225979A FI20225979A1 FI 20225979 A1 FI20225979 A1 FI 20225979A1 FI 20225979 A FI20225979 A FI 20225979A FI 20225979 A FI20225979 A FI 20225979A FI 20225979 A1 FI20225979 A1 FI 20225979A1
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FI
Finland
Prior art keywords
detector
bleaching
sodium bisulphite
process flow
treatment
Prior art date
Application number
FI20225979A
Other languages
Finnish (fi)
Swedish (sv)
Inventor
Esa Hassinen
Tom Hultholm
Original Assignee
Upm Kymmene Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Upm Kymmene Corp filed Critical Upm Kymmene Corp
Priority to FI20225979A priority Critical patent/FI20225979A1/en
Priority to PCT/FI2023/050600 priority patent/WO2024094923A1/en
Publication of FI20225979A1 publication Critical patent/FI20225979A1/en

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1052—Controlling the process
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0021—Introduction of various effluents, e.g. waste waters, into the pulping, recovery and regeneration cycle (closed-cycle)
    • D21C11/0028—Effluents derived from the washing or bleaching plants
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/001—Modification of pulp properties
    • D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
    • D21C9/004—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives inorganic compounds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes
    • D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/12—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds
    • D21C9/123—Bleaching ; Apparatus therefor with halogens or halogen-containing compounds with Cl2O
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/10—Arrangements of light sources specially adapted for spectrometry or colorimetry
    • G01J3/108—Arrangements of light sources specially adapted for spectrometry or colorimetry for measurement in the infrared range
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3577—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing liquids, e.g. polluted water

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  • Life Sciences & Earth Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Treatment Of Fiber Materials (AREA)
  • Treating Waste Gases (AREA)

Abstract

An arrangement (1) for treatment of bleaching chemical residues arrangement comprises a detector (2) arranged inside a process flow and configured to measure an amount of sulphite in the process flow by means of spectroscopy. The arrangement (1) further comprises a controller (3) connected to the detector (2) to receive measurement data from the detector (2) and configured to determine an amount of sodium bisulphite in the process flow based on the measurement data, and to control a process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow.

Description

ARRANGEMENT AND METHOD FOR TREATMENT OF BLEACHING CHEMICAL
RESIDUES
BACKGROUND
The present disclosure relates to treatment of bleaching chemical residues, and more particularly to an arrangement and method for treatment of bleaching chemical residues.
Sodium bisulphite may be used in industrial processes, such as in wood processing industry, for treating harmful oxidising compounds, such as chlorine dioxide. Especially bleaching chemical residues tend to weaken colour and strength of fibres and cause problems for paper gluing and dyeing. Sodium bisulphite may be bought from commercial producers or sodium bisulphite formed as a by-product in flue-gas desulfurization, may be used in such processes instead.
In known solutions, samples are taken from the process for laboratory analysis of the amount of sodium bisulphite by density measurement. This is, however, uncertain and time consuming and the feedback loop is slow.
BRIEF DESCRIPTION OF THE DISCLOSURE
An object of the present disclosure is to provide a new arrangement and method for treatment of bleaching chemical residues.
The object of the disclosure is achieved by a method and an arrangement which are characterized by what is stated in the independent claims. Some embodiments of the disclosure are disclosed in the dependent claims.
The disclosure is based on the idea of determining an amount of sodium bisulphite in process by means of spectroscopy and use it in pulping process. In other words, the measurement is made using spectroscopy and online from the process flow without a need
N for taking samples and taking samples to a laboratory for detailed analysis.
N
I 25 An advantage of the disclosure is that the measurements can be accurate and real time.
W The feedback time may be reduced considerably, and the process control improved by © providing a continuous, real time process control with a considerably decreased
E measurement uncertainty compared to conventional methods. o 5 BRIEF DESCRIPTION OF THE DRAWINGS
N 30 In the following the disclosure will be described in greater detail by means of preferred
Q embodiments with reference to the accompanying drawings, in which
Figure 1 illustrates schematically some features related to a process for treatment for bleaching chemical vapours according to an example;
Figure 2 illustrates schematically flue-gas desulfurization according to an example;
Figure 3 illustrates an arrangement for treatment of bleaching chemical residues; and
Figure 4 illustrates a method for treatment of bleaching chemical residues.
DETAILED DESCRIPTION OF THE DISCLOSURE
The disclosure relates to an arrangement and method for treatment of bleaching chemical residues, preferably in connection with wood processing industry.
According to an embodiment, treatment of bleaching chemical residues may comprise at least one of treatment of bleaching chemical vapours and treatment of bleaching chemicals. The bleaching chemical residues treated in such a process may, thus, be for instance in a vapour form, in a solution form, in a solid form, in a slurry form and/or in a pulp form. According to an embodiment, treatment of bleaching chemical residues may comprise reducing and/or inactivating chlorine containing bleaching chemical residues.
According to an embodiment, treatment of bleaching chemical residues may comprise treating chlorine containing vapours or chlorine comprising bleaching chemicals in another form with sulphur compounds, such as sodium bisulphite.
Figure 1 illustrates schematically some features related to a process for treatment for bleaching chemical vapours according to an example, and Figure 2 illustrates schematically flue-gas desulfurization.
Sodium bisulphite may, thus, be used in industrial processes, such as in wood processing industry, for treating harmful oxidising compounds, such as chlorine containing chemicals, like chlorine dioxide. Especially bleaching chemical residues tend to weaken colour and strength of fibres and cause problems for paper gluing and dyeing. Sodium bisulphite may
N also be used in bleaching process scrubbers to treat bleaching chemical vapours, such as
N chlorine dioxide vapours, an example of which is illustrated in Figure 1 and explained in
DN 25 more detail below.
W According to an embodiment, sodium bisulphite may be used in a fibre line bleaching 7 process for treatment of bleaching chemical residues, more particularly bleaching a chemicals. Different kinds of fibre line bleaching processes are known in the art, and such 2 a process is, thus, not shown in detail. According to an embodiment, a line connected to 8 30 such a fibre line bleaching may comprise a line 32 connected to a process for treatment of
N bleaching chemicals as illustrated in Figure 2. According to another embodiment, sodium
N bisulphite may be used in connection with a bleaching process gas scrubber 4, such as in the embodiment of Figure 1, for treatment of bleaching chemical residues, more particularly bleaching chemical vapours. According to an embodiment, a line connected to such a bleaching process gas scrubber 4 may comprise a line 31 connected to process for treatment of bleaching chemical vapours as illustrated in Figure 2. According to an embodiment, the fibre line bleaching process and/or the bleaching process gas scrubber 4 may be used in connection with wood processing industry.
In Figure 1, a process for treatment for bleaching chemical vapours according to an example is illustrated in a simplified manner. Thus, not all the material flows and components, such as pumps, valves, and similar equipment, are shown, as the process specifics may vary and are as such known in the art. In the embodiment of Figure 1, bleaching chemical residues in the form of bleaching chemical vapours are treated in a bleaching chemical scrubber 4. The figure illustrates lines configured to feed alkalic vent gas 11, acidic vent gas 12, cold water 13, and sodium hydroxide 14, and a line for acidic sewer 15. According to an embodiment of this disclosure, a line 10 configured to guide process flow to the bleaching process gas scrubber 4, wherein the process flow comprises sodium bisulphite, may be connected to bleaching chemical scrubber 4. In other words, in the embodiment, sodium bisulphite provided to the bleaching chemical scrubber 4 via line 10 configured to guide process flow to the bleaching process gas scrubber 4 may be used for treatment of bleaching chemical vapours. According to an embodiment, a detector 2 may be provided in the line 10 configured to measure process flow to the bleaching process gas scrubber 4, such as to measure a concentration of a substance or compound in the process flow.
Sodium bisulphite may be bought from commercial producers, also called outsourced sodium bisulphite in this disclosure, or sodium bisulphite formed as a by-product in flue- gas desulfurization 7, such as illustrated in Figure 2, may be used in such processes
N 25 instead. Especially, when sodium bisulphite formed as a by-product in flue-gas
S desulfurization (FGD) 7 is used in pulping processes, the concentration of sodium = bisulphite in the process flow may depend on many variables. However, a sufficient
N amount, such as concentration, of sodium bisulphite is important for a desired efficiency 7 of the treatment of bleaching chemical residues. If, on the other hand, the concentration of i. 30 sodium bisulphite in the process flow varies, flow rate of the process flow may be
O controlled, in addition to or instead of controlling the concentration of sodium bisulphite, to 8 control the amount of sodium bisulphite fed to the processes related to for instance fibre
S line bleaching and or bleaching process gas scrubbers. Therefore, it is important to know the concentration of sodium bisulphite in the process flow to be able to properly control the processes.
In Figure 2, a flue-gas desulfurization 7 process according to an example is illustrated in a simplified manner. Thus, not all the material flows and components, such as pumps, valves, and similar equipment, are shown, as the process specifics may vary and are as such known in the art. Figure 2 illustrates a line 20 configured to feed flue gas to flue-gas desulfurization 7. Figure 2 also illustrates a line 30 configured to guide process flow from the flue-gas desulfurization 7 back to the flue-gas desulfurization 7 for further processing and/or to a sodium bisulphite vessel 8, which may be used for controlling the concentration of sodium bisulphite provided in a sodium bisulphite vessel 8, for instance by guiding process flow back to the flue-gas desulfurization 7 until a predetermined concentration of sodium bisulphite to be fed to the sodium bisulphite vessel 8 is achieved. Figure 2 further illustrates lines 31 and 32 for guiding sodium bisulphite from the sodium bisulphite vessel 8 to processes involved with treatment of bleaching chemical residues, namely a line 31 configured to guide process flow from the sodium bisulphite vessel 8 to a process comprising treatment of bleaching chemical vapours for instance in the bleaching process gas scrubber 4 and a line 32 configured to guide process flow from the sodium bisulphite vessel 8 to a process comprising treatment of bleaching chemicals for instance in a fibre line bleaching process. Depending on the embodiment, the sodium bisulphite vessel 8 may be connected to one or both of lines 31 and 32. Figure 2 additionally illustrates an optional line 21 for providing outsourced sodium bisulphite to the sodium bisulphite vessel.
Figure 3 illustrates an arrangement for treatment of bleaching chemical residues.
An arrangement 1 for treatment of bleaching chemical residues, such as the arrangement of Figure 3, comprises a detector 2 arranged inside a process flow. The detector 2 is configured to measure an amount of a substance or compound in the process flow by means of spectroscopy. Preferably, the detector 2 is configured to measure an amount of
N 25 sulphite in the process flow by means of spectroscopy.
N The arrangement 1 for treatment of bleaching chemical residues, later called the - arrangement 1, also comprises a controller 3 connected to the detector 2 to receive
S measurement data from the detector. The controller 3 is configured to determine an
E amount of sodium bisulphite in the process flow based on the measurement data, namely + 30 the measurement data from the detector 2, and to control a process related to treatment
NS of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow.
N According to an embodiment, the detector 2 may comprise an infrared spectrometer. More particularly, infrared spectrometer may be used to measure an amount of one or more substances and/or compounds, such as the concentration of one or more substances and/or compounds, for instance in one or more measurement points of the process, using infrared spectroscopy. According to an embodiment, the detector 2 more particularly may comprise a Fourier Transform Infrared (FTIR) Spectroscopy spectrometer. Fourier- transform infrared spectroscopy (FTIR) is a technique used to obtain an infrared spectrum 5 of absorption or emission of a solid, liquid or gas. An advantage of such embodiments is that an FTIR spectrometer can simultaneously collect high-resolution spectral data over a wide spectral range. FTIR spectrometers are known as such and are, thus, not explained here in more detail.
Detectors 2 based on spectroscopy typically have a wavelength range, within which the detector 2 can be used and/or is configured to be used. In arrangements 1 and methods disclosed in this description, the detector 2 may be configured to use the whole wavelength range of the detector 2, when making the measurements disclosed in this description and accompanying claims and figures.
According to an embodiment, the detector 2 may be a spectrometer configured to use mid- infrared wavelength range in the measurement. According to an embodiment, the detector 2 may be a spectrometer configured to use a wavelength range of 400-4000 cm".
According to an embodiment, the detector 2 may be a spectrometer configured to use a wavelength range of 648 — 4000 cm”. According to an embodiment, the detector 2 may be a spectrometer configured to use a wavelength range of 800 — 1220 cm", and according to a further embodiment, the detector 2 may be a spectrometer configured to use a wavelength range of 1000 — 1168 cm. In some embodiments, it may be beneficial to use a wider range of wavelengths. This may be true for instance in embodiments, in which multiple characteristics of the process flow, for instance amount, such as concentrations, of multiple substances a measured. In some other embodiments, especially in
N 25 embodiments, in which only one substance or only a few substances are measured, it may
S be beneficial to select a narrower range, within which the strongest correlation between = the infrared spectroscopy measurements and amounts, such as the concentrations, of the
N substances of interest are found. For instance, in the embodiments of this disclosure, the 7 strongest correlations for sulphite may be found within the wavelength range of 1000 — & 30 1168 cm", for example, whereby it may be beneficial to use this range or a range including 3 this range.
N According to an embodiment, the bleaching chemical residues may comprise oxidizing
S compound(s). According to an embodiment, the bleaching chemical residues may more particularly comprise chlorine dioxide.
According to an embodiment, the process flow, inside of which the detector 2 may be provided, may comprise a cellulose process by-product from flue-gas desulfurization 7.
According to an embodiment, the process flow may comprise a solution comprising at least sodium bisulphite and water.
According to an embodiment, the detector 2 may be arranged in at least one of the following: a line and/or a vessel downstream from flue-gas desulfurization 7, a line and/or a vessel downstream from sodium bisulphite vessel 8, a line and/or a vessel upstream from a bleaching process gas scrubber 4, and a line and/or a vessel upstream from a fibre line bleaching process. In other words, one or more detectors 2 may be provided at one or more of the listed points of the process. It is clear for a person skilled in the art that a same point and a same detector may be referred to by several of the listed alternatives.
For instance, a sodium bisulphite vessel 8 and, thus, a detector 2 provided in the sodium bisulphite vessel 8 may be provided both downstream from flue-gas desulfurization 7 and upstream from a bleaching process gas scrubber 4 and/or a fibre line bleaching process, as seen in the embodiment of Figure 2. A vessel may comprise any type of a vessel, container, or receptacle suitable for receiving and holding the respective material or process flow in question. A line may comprise a line, a pipe, a hose or similar suitable for feeding, in other words guiding or providing, the material or process flow forward in the process.
According to an embodiment, the detector 2 may be arranged in a line and/or a vessel downstream from flue-gas desulfurization 7. According to an embodiment, more particularly, the detector 2 may be provided in a line of an in-process cycle in connection with flue-gas desulfurization 7, in a line between the flue-gas desulfurization 7 and sodium bisulphite vessel 8, such as in the line 30 configured to guide process flow from the flue-
N 25 gas desulfurization 7 back to the flue-gas desulfurization 7 for further processing and/or to
S the sodium bisulphite vessel 8, in a sodium bisulphite vessel 8, and/or in a line downstream = from a sodium bisulphite vessel 8, such as a line 31 configured to guide process flow from
N the sodium bisulphite vessel 8 to a process comprising treatment of bleaching chemical 7 vapours for instance in the bleaching process gas scrubber 4 and/or a line 32 configured & 30 to guide process flow from the sodium bisulphite vessel 8 to a process comprising
O treatment of bleaching chemicals for instance in a fibre line bleaching process. According 8 to an embodiment, the sodium bisulphite vessel 8 comprises a container comprising a
S solution comprising at least sodium bisulphite and water. Embodiments, in which the detector 2 is provided in the sodium bisulphite vessel 8 or upstream from the sodium bisulphite vessel 8 may be beneficial in connection with applications, in connection with which a quick feedback loop is important. In other applications, it might be sufficient to provide the detector 2 in a line downstream from a sodium bisulphite vessel 8, as it can still provide an inline measurement, in other words a measurement directly from the process flow by a detector 2 provided in the process flow, which is a real time measurement, as compared to samples taken to a laboratory for measurements. A real time measurement, on the other hand, enables real time control of the process, such as a continuous, real time control of operation of flue-gas desulfurization and/or a real time control of a process related to treatment of bleaching chemical residues.
According to an embodiment, the detector 2 may be arranged in a line and/or a vessel upstream from the bleaching process gas scrubber 4. According to an embodiment, the line and/or the vessel upstream from a bleaching process gas scrubber 4 may be provided downstream from flue-gas desulfurization 7. In other words, the vessel may comprise the sodium bisulphite vessel 8 and/or the line may comprise the line 30 configured to guide process flow from the flue-gas desulfurization 7 back to the flue-gas desulfurization 7 for further processing and/or to the sodium bisulphite vessel 8 of the other embodiments.
According to an embodiment, the line and/or the vessel provided upstream from the bleaching process gas scrubber 4 may comprise, in addition to or instead of the sodium bisulphite vessel 8 and/or the line 30, 31 and/or 32, a line 10 configured to guide process flow to the bleaching process gas scrubber 4. According to an embodiment, the line 10 configured to guide process flow to the bleaching process gas scrubber 4 may comprise or be directly or indirectly connected to the line 31 configured to guide process flow from the sodium bisulphite vessel 8 to a process comprising treatment of bleaching chemical vapours.
According to an embodiment, the detector 2 may be arranged in a line and/or a vessel
N 25 downstream from sodium bisulphite vessel 8. According to an embodiment, sodium
S bisulphite provided in the sodium bisulphite vessel 8 may comprise sodium bisulphite from = flue-gas desulfurization 7 and/or outsourced sodium bisulphite. Thus, the sodium
N bisulphite vessel 8 according to this embodiment may or may not be provided downstream 7 from the flue-gas desulfurization 7. According to an embodiment, the sodium bisulphite i. 30 vessel 8 comprises a container comprising a solution comprising at least sodium bisulphite
O and water. Depending on the embodiment, the detector 2 provided downstream from the 8 sodium bisulphite vessel 8 may or may not also be provided upstream from the bleaching
S process gas scrubber 4 and/or a fibre line bleaching process. In Figure 2, it is illustrated that sodium bisulphite is fed to the sodium bisulphite vessel 8 from both the flue-gas desulfurization 7 and as outsourced sodium bisulphite via a separate outsourced sodium bisulphite line 21. In different embodiments, one or both sources may be used. In embodiments, where sodium bisulphite is provided to sodium bisulphite vessel 8 via outsourced sodium bisulphite line 21 only, and not from flue-gas desulfurization 7, the sodium bisulphite vessel 8 does not need to be connected to flue-gas desulfurization 7.
According to an embodiment, the control of the process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow may comprise controlling at least one of the concentration and flow rate of sodium bisulphite solution to be fed to the process in connection with at least one of the following: reduction of active chlorine in a fibre line bleaching process and reduction of chlorine dioxide in bleaching process gas scrubber 4.
According to an embodiment, the bleaching process gas scrubber 4 may comprise a scrubber downstream from an acidic bleaching phase. According to an embodiment, the process flow may comprise filtrate of such a scrubber downstream from an acidic bleaching phase. Measuring amount of sulphite in such a process flow by the detector 2 may be used to determine the amount of sodium bisulphite, such as the concentration of sodium bisulphite, in the process flow for controlling the amount of sodium bisulphite in the process. This may be beneficial, as this can be used to ensure the amount of sodium bisulphite in the process flow is sufficient for the purpose of the bleaching process gas scrubber 4.
According to an embodiment, the bleaching chemical residues may comprise vent gases, more particularly alkalic and/or acidic vent gases from wood processing, for instance from pulping process(es). Such vent gases may be treated in a bleaching process gas scrubber 4.
N According to an embodiment, the control of the process related to treatment of bleaching
N 25 chemical residues based on the determined amount of sodium bisulphite in the process
DN flow may comprise controlling the operation of flue-gas desulfurization. According to an
Tr embodiment, sodium bisulphite formed as a by-product in flue-gas desulfurization may be
S used for treatment of bleaching chemical residues in the bleaching process gas scrubber
E 4. According to an embodiment, concentration of sodium bisulphite formed as a by-product o 30 in flue-gas desulfurization may be determined by the arrangement 1 upstream from feeding 2 the sodium bisulphite to the bleaching process gas scrubber 4. 3 Figure 4 illustrates a method for treatment of bleaching chemical residues.
According to an embodiment, a method for treatment of bleaching chemical residues, such as the method of Figure 4, comprises the steps of measuring 41 by a detector 2 arranged inside the process flow amount of sulphite in the process flow by means of spectroscopy; receiving 43 in a controller 3 connected to the detector 2 measurement data from the detector 2; determining 45 by the controller an amount of sodium bisulphite in the process flow based on the measurement data received from the detector 2; and controlling 47 a process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow.
According to an embodiment, the controlling of the process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow may comprise controlling at least one of a concentration and a flow rate of sodium bisulphite solution to be fed to cellulose pulp in connection with reduction of active chlorine in a fibre line bleaching process.
According to an embodiment, the controlling of the process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow may comprise controlling at least one of a concentration and flow rate of sodium bisulphite solution to be fed to bleaching process gas scrubber 4 for reduction of chlorine dioxide in the bleaching process gas scrubber 4.
N
N
O
N
N oO
I oc o o
MN
(e
LO
N
N
O
N

Claims (18)

1. An arrangement for treatment of bleaching chemical residues, characterized in that the arrangement comprises: a detector arranged inside a process flow and configured to measure an amount of sulphite in the process flow by means of spectroscopy; and a controller connected to the detector to receive measurement data from the detector and configured to determine an amount of sodium bisulphite in the process flow based on the measurement data and to control a process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow.
2. An arrangement according to claim 1, wherein the detector comprises an infrared spectrometer.
3. An arrangement according to claim 2, wherein the detector comprises a Fourier Transform Infrared Spectroscopy spectrometer.
4. An arrangement according to claim 2 or 3, wherein the detector is a spectrometer configured to use mid-infrared wavelength range in the measurement.
5. An arrangement according to claim 4, wherein the detector is a spectrometer configured to use a wavelength range of 640 — 4000 cm”.
6. An arrangement according to claim 5, wherein the detector is a spectrometer configured to use a wavelength range of 800 — 1220 cm”.
N
7. An arrangement according to any one of claims 1 — 6, wherein the bleaching chemical N < residues comprise at least chlorine dioxide.
N
8. An arrangement according to any one of claims 1 — 7, wherein the detector is arranged N O inside process flow, wherein the process flow comprises a cellulose process by- E 25 product from flue-gas desulfurization.
o . .
5
9. An arrangement according to claim 8, wherein the process flow comprises a solution a comprising at least sodium bisulphite and water. S
10. An arrangement according to any one of claims 1 — 9, wherein the detector is arranged in at least one of the following: a line and/or a vessel downstream from flue-gas desulfurization, a line and/or a vessel downstream from sodium bisulphite vessel, a line and/or a vessel upstream from a bleaching process gas scrubber, and a line and/or a vessel upstream from a fibre line bleaching process.
11. An arrangement according to claim 1 — 10, wherein the control of the process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow comprises controlling at least one of the concentration and the flow rate of sodium bisulphite solution to be fed to the process in connection with at least one of the following: reduction of active chlorine in a fibre line bleaching process and reduction of chlorine dioxide in bleaching process gas scrubber.
12. An arrangement according to claim 1 — 11, wherein the control of the process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow comprises controlling the operation of flue-gas desulfurization.
13. A method for treatment of bleaching chemical residues, characterized in that the method comprises the steps of: measuring by a detector arranged inside the process flow amount of sulphite in the process flow by means of spectroscopy; receiving in a controller connected to the detector measurement data from the detector; determining by the controller an amount of sodium bisulphite in the process flow based on the measurement data received from the detector; and controlling a process related to treatment of bleaching chemical residues based on N the determined amount of sodium bisulphite in the process flow. N — 25
14. A method according to claim 13, wherein the detector is a spectrometer configured to W use mid-infrared wavelength range in the measurement. oO E
15. A method according to claim 14, wherein the detector is a spectrometer configured to o use a wavelength range of 640 — 4000 cm". MN D
16. A method according to anyone of claims 13 — 15, wherein the detector is arranged S 30 inside process flow, wherein the process flow comprises a cellulose process by- product from a flue-gas desulfurization.
17. A method according to anyone of claims 13 - 16, wherein the controlling of the process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow comprises controlling at least one of a concentration and a flow rate of sodium bisulphite solution to be fed to cellulose pulp in connection with reduction of active chlorine in a fibre line bleaching process.
18. A method according to anyone of claims 13 - 16, wherein the controlling of the process related to treatment of bleaching chemical residues based on the determined amount of sodium bisulphite in the process flow comprises controlling at least one of a concentration and a flow rate of sodium bisulphite solution to be fed to bleaching process gas scrubber for reduction of chlorine dioxide in the bleaching process gas scrubber. N N O N N oO I Za o o MN (e LO N N O N
FI20225979A 2022-11-02 2022-11-02 Arrangement and method for treatment of bleaching chemical residues FI20225979A1 (en)

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CA1277110C (en) * 1986-05-07 1990-12-04 Rudolf Patt Method for cooking control of lignocelluloses by ftir spectroscopy
US5282931A (en) * 1992-07-08 1994-02-01 Pulp And Paper Research Institute Of Canada Determination and control of effective alkali in kraft liquors by IR spectroscopy
DE19814385C1 (en) * 1998-03-31 1999-10-07 Siemens Ag Process and device for process control and process optimization of chemical recovery in the manufacture of pulp
US20020053640A1 (en) * 1998-11-12 2002-05-09 Michael Kester Determination of ionic species concentration by near infrared spectroscopy
ATE289415T1 (en) * 1999-12-23 2005-03-15 Pulp Paper Res Inst DETERMINATION OF KAPPA NUMBER IN CHEMICAL PULP BY RAMAN SPECTROSCOPY

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