White liquid oxidation device and method

Abstract

A white liquor oxidation apparatus (1) comprising: a detector (2) disposed inside an oxidized white liquor process flow configured to measure at least one characteristic of the process flow by spectroscopy; and a controller (3) connected to the detector to receive measurement data from the detector. The controller (3) is configured to determine the amount of at least one substance in the process flow according to the measured data and control the white liquid oxidation process according to the determined amount of at least one substance.

Description

Background Art

[0001] The present disclosure relates to the oxidation of white liquor in the wood processing industry, and more particularly, to a white liquor oxidation apparatus and method.

[0002] Since the commercialization of oxygen delignification (also known as oxygen bleaching), the oxidation of white liquor (WL) has been used in the wood processing industry. Using white liquor as an alkali source in oxygen bleaching requires oxidizing various sulfur forms into sulfates in an external container. This is done because if unoxidized sulfur is introduced into the bleaching reactor, the oxygen atmosphere in the reactor will react to oxidize the unoxidized sulfur, which will consume oxygen and cause unnecessary reactions and release heat, making it difficult to control the temperature inside the reactor.

[0003] It is well known that poorly oxidized white liquor (OWL) cannot be used in the bleaching stage using oxygen or peroxide because partially oxidized sulfur compounds will consume additional bleaching chemicals in a specific stage or subsequent stages, so it is not economical to use oxidized white liquor in such applications. In addition, the amount of thiosulfate in oxidized white liquor (OWL) should be as low as possible because thiosulfate is known to cause cellulose degradation and also corrode many bleaching reactor materials.

[0004] Typically, laboratory measurements such as sulfide titration or ion chromatography (IC) of oxidized white liquor are carried out after this process. However, sulfide titration is not a good enough method for evaluating this process, and the IC analysis of OWL is very time-consuming. In addition, generally speaking, laboratory analysis requires sampling from the process flow, and the feedback loop is very slow. Summary of the Invention

[0005] The object of the present disclosure is to provide a novel apparatus and method for white liquor oxidation.

[0006] The object of the present disclosure is achieved by a method and an apparatus, the features of which are as described in the independent claims. Some embodiments of the present disclosure are disclosed in the dependent claims.

[0007] The present disclosure is based on the idea of using spectrometry to determine the amount of at least one substance in the process flow and using it to control the white liquor oxidation process. In other words, spectrometry is used to make measurements from the process flow in an online manner without sampling and taking the sample to the laboratory for detailed analysis.

[0008] The advantages of the present disclosure are accurate and real-time measurement. The feedback time can be significantly shortened, and process control can be improved. Brief Description of the Drawings

[0009] The following will describe the present disclosure in more detail with reference to the drawings through preferred embodiments, where:

[0010] Figure 1 Schematically shows some features related to the white liquor oxidation process according to an embodiment;

[0011] Figure 2 shows the apparatus in white liquor oxidation; and

[0012] Figure 3 shows the method of white liquor oxidation. DETAILED DESCRIPTION

[0013] The present disclosure relates to white liquor oxidation apparatuses and methods.

[0014] Figure 1 Schematically shows some features related to the white liquor oxidation process 100 according to an embodiment. There are known to be various different methods of implementing the white liquor oxidation process, and the related apparatuses and details may vary. Therefore, these different examples are not discussed in detail here, and only an arbitrary example is disclosed in Figure 1 to illustrate some features and concepts.

[0015] In the wood processing industry, white liquor oxidation is widely used in oxygen delignification (also known as oxygen bleaching). Using white liquor as an alkali source in oxygen bleaching can prevent various sulfur forms (usually mainly sodium sulfide) from being oxidized to sulfates in the external vessel 110. This is important because if unoxidized sodium sulfide is introduced into the bleaching reactor, the oxygen atmosphere in the reactor will oxidize Na 2 2S, thereby releasing heat, making it difficult to control the temperature in the reactor.

[0016] Moreover, white liquor with poor oxidation degree cannot be used in the bleaching stage using oxygen or peroxide because partially oxidized sulfur compounds will consume additional bleaching chemicals in a specific stage or subsequent stages. Therefore, it is not economical to use oxidized white liquor in such applications.

[0017] In addition, it is well known that thiosulfate can cause cellulose degradation and can also corrode many bleaching reactor materials. Therefore, the amount of thiosulfate in oxidized white liquor (OWL) should be kept as low as possible.

[0018] Figure 2 shows the apparatus in white liquor oxidation.

[0019] The apparatus 1 in white liquor oxidation, in other words, the apparatus related to white liquor oxidation, such as Figure 2Device 1 in the oxidation of white liquor, including a detector 2, which is arranged inside the white liquor oxidation process flow (in other words, inside the white liquor oxidation process), and is configured to measure at least one characteristic in the process flow by spectroscopy. This enables online measurement, in other words, measurement directly from the process flow through the detector 2 arranged in the process flow, which is a real-time measurement compared to measuring samples taken to the laboratory.

[0020] Device 1 in the oxidation of white liquor (for example Figure 2 Device 1) also includes a controller 3 connected to the detector 2 to receive measurement data from the detector 2. The controller 3 is further configured to determine the amount of at least one substance in the process flow based on the measurement data. The controller 3 is also configured to control the white liquor oxidation process based on the determined amount of at least one substance. According to one embodiment, the controller 3 may include the control system of device 1 or a part of the control system of device 1. According to one embodiment, the controller 3 may include a control unit and / or a regulator.

[0021] According to one embodiment, the detector 2 may include an infrared spectrometer. More specifically, the infrared spectrometer can be used to measure the concentration of compounds, for example, at one or more measurement points in the process, using infrared spectroscopy for measurement. According to one embodiment, the detector 2 may more specifically include a Fourier transform infrared (FTIR) spectrometer. Fourier transform infrared spectroscopy (FTIR) is a technique for obtaining infrared spectra absorbed or emitted by solids, liquids, or gases. One advantage of such embodiments is that the FTIR spectrometer can simultaneously collect high-resolution spectral data over a wide spectral range. The FTIR spectrometer itself is known and will not be elaborated here.

[0022] The detector 2 based on spectroscopy generally has a wavelength range within which the detector 2 can be used and / or is configured to be used. In the device 1 and method disclosed in this specification, when performing the measurements disclosed in this specification, the appended claims, and the drawings, the detector 2 can be configured to use the entire wavelength range of the detector 2.

[0023] According to one embodiment, the detector 2 may be a spectrometer configured to use the mid-infrared wavelength range in the measurement. According to one embodiment, the detector 2 may be a spectrometer configured to use a wavelength range of 400 - 4000 cm -1 According to one embodiment, the detector 2 may be a spectrometer configured to use a wavelength range of 648–4000 cm -1 According to one embodiment, the detector 2 may be a spectrometer configured to use a wavelength range of 800–1220 cm -1A spectrometer within a wavelength range, and according to another embodiment, the detector 2 can be configured to use a wavelength range of 1000–1168 cm -1 A spectrometer within a wavelength range. In some embodiments, it may be beneficial to use a wider wavelength range. For example, this may be the case in embodiments where multiple characteristics of a process flow are measured (such as the amounts of multiple substances, such as concentrations). In other embodiments, especially in embodiments where only one or a few substances are measured, it may be beneficial to select a narrower range within which the correlation between the infrared spectroscopy measurement results and the amount of the target substance (such as concentration) is the strongest. For example, in embodiments of the present disclosure, the wavelength ranges with the strongest correlation for sulfur forms such as sulfite, sulfate, and thiosulfate are 800–1220 cm -1 or 1000–1168 cm -1 , so it may be beneficial to use one of these ranges, for example.

[0024] According to one embodiment, the detector 2 can be arranged inside the oxidized white liquor process by mounting the detector to a pipeline and / or a container of the process flow. According to one embodiment, the detector 2 can be directly mounted to the pipeline or the container through a mounting flange and / or arranged to the pipeline and / or the container of the process flow in other ways suitable for the type of the detector 2. The container can include any type of vessel, container, receiver, or the like suitable for receiving the material or the process flow.

[0025] According to one embodiment, the amount of at least one substance in the process flow can include at least one of the following: the amount of sulfite in the process flow material, the amount of sulfate in the process flow material, and the amount of thiosulfate in the process flow material. According to one embodiment, the amount of at least one substance in the process flow can include the amounts of sulfite, sulfate, and thiosulfate in the process flow material measured by spectroscopy.

[0026] According to one embodiment, the controller 3 can be configured to adjust at least one of the white liquor and the oxygen process stream in the white liquor oxidation process according to the determined amount of at least one substance in the process flow to ensure that the oxidized white liquor is fully oxidized for the purpose of oxygen bleaching. According to another embodiment, the oxidized white liquor can include at least one of the following: partially oxidized white liquor and fully oxidized white liquor (TOWL).

[0027] According to one embodiment, the process flow for measuring the amount of at least one substance includes oxidized white liquor, more specifically fully oxidized or partially oxidized white liquor.

[0028] According to one embodiment, the controller 3 may be further configured to adjust the process temperature in the white liquor oxidation process to an optimal reaction temperature according to a determined amount of at least one substance in the process flow, so as to ensure sufficient oxidation of the white liquor, thereby achieving oxygen bleaching. According to one embodiment, the process temperature may be adjusted to increase the oxygen solubility and optimize the oxygen consumption to achieve the desired reaction. The oxidation reaction is an exothermic reaction, so reducing the temperature may enhance at least part of the oxidation reaction. The process temperature may also affect the delay of the oxidation reaction.

[0029] Figure 3 A method for white liquor oxidation is shown.

[0030] A method for white liquor oxidation, for example Figure 3 The method shown may include the following steps: measuring at least one characteristic of the process flow 31 by spectrometry using a detector 2 disposed inside the white liquor oxidation process flow; receiving 33 measurement data from the detector 2 in a controller 3 connected to the detector 2; determining 35 the amount of at least one substance in the process flow by the controller 3 based on the measurement data received from the detector; and controlling 37 the white liquor oxidation process based on the determined amount of at least one substance.

[0031] According to one embodiment, the white liquor oxidation method may be implemented using a white liquor oxidation device according to one embodiment or a combination of one or more embodiments disclosed in the present specification and / or the appended claims and drawings, for example Figure 3 The method shown.

[0032] According to one embodiment, the detector 2 may be disposed inside the white liquor oxidation process flow by mounting the detector to a pipeline or a container of the process flow.

[0033] According to one embodiment, the amount of at least one substance in the process flow may include at least one of the following: the amount of sulfite in the process flow material, the amount of sulfate in the process flow material, and the amount of thiosulfate in the process flow material.

[0034] According to one embodiment, the method further includes adjusting at least one of the white liquor and the oxygen process stream in the white liquor oxidation process by the controller according to the determined amount of at least one substance in the process flow, so as to ensure sufficient oxidation of the white liquor, thereby achieving the purpose of oxygen bleaching.

[0035] The advantage of the present disclosure is that measuring and controlling the quality of oxidized white liquor using on-line spectrometry (preferably an FTIR measurement system) can meet the required quality aspects in a more economical way than known solutions. Therefore, measuring the quality of oxidized white liquor may include measuring the contents of sulfite, sulfate, and thiosulfate ions in the process flow. These measurements can also effectively and efficiently adjust the white liquor and oxygen process streams on-line.

Claims

1. A white liquor oxidation device, characterized in that, the device comprises: a detector, which is arranged inside the white liquor oxidation process flow and is configured to measure at least one characteristic of the process flow by spectroscopy; and a controller, which is connected to the detector to receive measurement data from the detector and is configured to determine the amount of at least one substance in the process flow according to the measurement data and control the white liquor oxidation process according to the determined amount of at least one substance.

2. The device according to claim 1, wherein, the detector comprises an infrared spectrometer.

3. The device according to claim 2, wherein, the detector comprises a Fourier transform infrared spectrometer.

4. The device according to claim 2 or 3, wherein, the detector is a spectrometer configured to use the mid-infrared wavelength range in the measurement.

5. The device according to claim 4, wherein, The detector is a spectrometer configured to use a wavelength range of 400 - 4000 cm -1 -1.

6. The device according to claim 5, wherein, The detector is a spectrometer configured to use a wavelength range of 648–4000 cm -1 –1.

7. The device according to claim 6, wherein, The detector is a spectrometer configured to use a wavelength range of 800–1220 cm -1 -1.

8. The device according to claim 7, wherein, The detector is a spectrometer configured to use a wavelength range of 1000–1168 cm -1 .

9. The device according to any one of claims 1 to 6, wherein, the detector is installed on the pipeline or container of the process flow through a mounting flange, so that the detector is arranged inside the white liquor oxidation process flow.

10. The device according to any one of claims 1 to 7, wherein, the amount of at least one substance in the process flow includes at least one of the following: the amount of sulfite in the process flow material, the amount of sulfate in the process flow material, and the amount of thiosulfate in the process flow material.

11. The device according to any one of claims 1 to 10, wherein, the controller is configured to adjust at least one of the white liquor and the oxygen process flow in the white liquor oxidation process according to the determined amount of at least one substance in the process flow to ensure that the white liquor is fully oxidized, so as to achieve the purpose of oxygen bleaching.

12. The device according to claim 11, wherein, the oxidized white liquor includes at least one of the following: partially oxidized white liquor and fully oxidized white liquor.

13. A white liquor oxidation method, characterized in that, the method comprises the following steps: measuring at least one characteristic of the process flow by spectroscopy through a detector arranged inside the white liquor oxidation process flow; receiving measurement data from the detector in a controller connected to the detector; determining the amount of at least one substance in the process flow through the controller based on the measurement data received from the detector; and controlling the white liquor oxidation process based on the determined amount of at least one substance.

14. The method according to claim 13, wherein, the detector is a spectrometer configured to use the mid-infrared wavelength range in the measurement.

15. The method according to claim 14, wherein, The detector is a spectrometer configured to use a wavelength range of 400 - 4000 cm -1 -1.

16. The method according to claim 15, wherein, The detector is a spectrometer configured to use a wavelength range of 640–4000 cm -1 –1.

17. The method according to claim 16, wherein, The detector is a spectrometer configured to use a wavelength range of 800–1220 cm -1 -1.

18. The method according to claim 17, wherein, The detector is a spectrometer configured to use a wavelength range of 1000–1168 cm -1 .

19. The method according to any one of claims 13 to 18, wherein, the detector is arranged inside the white liquor oxidation process flow by installing the detector on the pipeline or container of the process flow.

20. The method according to any one of claims 13 to 19, wherein, The amount of at least one substance in the process flow includes at least one of the following: the amount of sulfite in the process flow material, the amount of sulfate in the process flow material, and the amount of thiosulfate in the process flow material.

21. The method according to any one of claims 13 to 20, wherein, the method further includes: According to the determined amount of at least one substance in the process flow, at least one of the white liquor and the oxygen process stream in the white liquor oxidation process is adjusted by a controller to ensure that the oxidized white liquor is fully oxidized, so as to achieve the purpose of oxygen bleaching.

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