FI93902C - Method and apparatus for determining the resin content of a pulp stock sample - Google Patents

Description

93902

METHOD AND APPARATUS FOR DETERMINING THE RESIN CONTENT OF A PULP SAMPLE

The invention relates to a method for determining the resin content of a pulp stock sample 5. The invention further relates to an apparatus for determining the resin content of a pulp stock sample.

The development of paper and cellulose processes to be more economical and environmentally friendly has brought new challenges. For example, increasing the degree of closure of the wet part of a paper machine and e.g. with the increasing use of recycled fiber, harmful substances enriched in circulating water are becoming an increasing problem. In general, the chemistry of the wet part is still poorly understood, making it difficult to control. This causes quality and productivity problems that are significant. Insufficient information on wet end variables has led to the abundant, uneconomical use of additive chemicals and has had a detrimental effect on the quality of the finished product. Thus, there is a need for selective measurement methods that describe the state of the pulping process. In particular, there is a need for selective on-line measurement methods to monitor the continuous shifts of various variables in the pulp stock process.

Dissolved and colloidal organic compounds, and especially resinous substances, have been identified as very important sites for monitoring in the circulating water measurement sites. - In this context, resin substances generally mean various resinous extracts from conifers and deciduous trees. - Resin materials can be problematic in papermaking, causing, for example, holes and stains in the paper, loss of the finished product, and can clog the blankets of the paper machine 35, which prolongs the downtime of the machine.

The major problems in determining the amount of resin have been their relatively small amount in 2 93902 circulating water and sample handling. Laboratory measurement methods have been developed for the determination of resin substances in the form of resin balls.

One common method of measuring the number of resin balls 5 from a sample taken from a process is a manual counting performed under a microscope, the so-called pihkapal-lolaskenta. However, with this method, only the largest resin balls can be detected due to the limit of the microscope's resolution, which just falls within the maximum range of resin ball sizes. Furthermore, the measurement results depend on the person performing the calculation. In addition, the method is laborious and it is difficult to achieve sufficient statistical accuracy with the calculation.

The number of resin beads has also been estimated indirectly by turbidity measurement (turbidity measurement) known under laboratory conditions after centrifugation or settling of the whole sample. Landing has been used to separate the resin balls from the process sample. However, there are 20 uncertainties in the measurement of turbidity. For example, pretreatment is difficult to perform because the particle size distribution of the sample must remain stable regardless of the process conditions. The shape of the size distribution (density function) of the resin balls is very steep in the range sensitive to turbidity measurement (0.3 - 0.6 μπι), 25 so the turbidity measurement is sensitive to changes in sphere size that occur throughout the process. The suitability of the measurement as an on-line measurement method has not been demonstrated.

Furthermore, 30 hemocytometers originally developed for medical applications have been used to count resin balls. But even this method is difficult to adapt to on-line measurements.

In one method, the sample is first centrifuged, the resulting sample is extracted into MTBE (methyl tert-35-butyl ether) solvent, and the amount of resin is measured by gas chromatography under laboratory conditions. However, gas chromatography is difficult to use

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3 93902 process conditions and is not easily suitable as an on-line measuring device.

In a new laboratory method, resin beads are stained with a specific fluorescent dye and the stained balls are determined using optical measurement based on the use of laser light (Lorenzak P., Kröhl T., and Horn D., Determination of the Effectiveness of Pitch Control Agents by Means of a New Laser -optical Particle Counting Method; Proceedings of the 10 4th International Conference: New Available Techniques and Current Trends, SPCI, pp. 334-347). This method is also inappropriate for on-line use.

As described above, direct continuous on-line measurement to determine the resin content of the sample has not been possible so far.

It is an object of the present invention to obviate the above drawbacks.

In particular, it is an object of the invention to provide a method by means of which the state of the pulp pulping process can be better monitored.

For aspects of the invention, reference is made to the claims.

In the method of the present invention for determining the resin content of a pulp stock sample, which sample contains wood fiber, resin, any other solids, dissolved organic and inorganic substances, and water; (a) wood fibers and any other solids, with the exception of resins I, are separated from a part of the pulp sample by means of a separation device based on specific gravity 30 in order to obtain the actual sample; (b) separating the resins and any wood fibers and other solids present from a portion of the pulp sample with a particle size separator to obtain a reference sample; and c) the resin content of the sample is determined by measuring 93902 4 from the actual sample obtained using a reference sample as a reference.

In the preparation of the actual sample, a centrifuge or a separator can be used as a separation device based on specific gravity. In this case, wood fibers, any other solids such as wood-based fines, fillers and pigments are separated from a part of the pulp sample, but no separation is made between the above-mentioned solids and water lighter resins in the form of resin balls and solutes which may be dissolved. substances or inorganic solutes.

In the preparation of the reference sample, a filter, e.g. a mechanical filter such as a ceramic or paper filter, can be used as the particle size-15 separation device. The hole size of the filter is selected according to the resin ball size distribution. The size distribution of the resin balls is for the most part in the size range 0.2 to 2 μm (Allen, L. H., Pitch in Wood Pulps, Pulp & Paper Canada, May 1975, pp. 70-77), so the hole size of the filter is preferably selected to be about 0.1 to 0.2 μm. In this case, in addition to any solid components mentioned above, any colloidal resin spheres are separated from a part of the pulp sample, whereby dissolved organic and inorganic substances remain in the reference sample.

In determining the resin content of the sample, the measurement is performed using the actual sample and the reference sample. The reference sample eliminates the possible interfering effect of the dissolved organic substances, such as carbohydrates and lignins, present in the pulp stock on the measurement results. In this case, a measuring device utilizing the structure of organic substances, e.g. a device measuring the absorption, emission or scattering of electromagnetic radiation, can be used to determine the resin content. Still

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5 93902 RAMAN spectroscopy can be used in the assay.

Preferably, an IR spectrophotometer is used with which the resin content can be quantified on the basis of an absorption spectrum typical of the resins present. Based on the absorption spectrum of the resins, a preferred wavelength range or optionally a fixed wavelength is selected. One preferred wavelength range is about 2400 to 3000 cm -1. When a control sample prepared according to the invention is used in the measurement, a specific resin content measurement can be performed. In addition, the measurement can be performed quickly and continuously.

The process according to the invention is very well suited as a continuous on-line process in connection with any pulping process, such as a pulp, cellulose or papermaking process. By papermaking in this context is meant the production of the actual paper, board or other web-like non-woven product 20 made from lignocellulosic fiber.

According to a continuous embodiment of the method, the preparation of the actual sample and the reference sample is arranged in parallel, the pulp sample from the process being divided into two parts by: (a) centrifuging or separating the second part with a continuous centrifuge or separator to produce the actual sample; and (b) filtering the second portion through a continuous filter to prepare a reference sample.

According to another continuous embodiment of the method, the preparation of the actual sample and the control sample is arranged sequentially by centrifuging or separating the pulp sample 35 (a) with a continuous centrifuge or separator. to obtain the actual sample; 6 93902 (b) A portion of the solution sample obtained from step (a) is filtered through a continuous filter to obtain a reference sample.

The present invention thus provides a method by which the total amount of resin in a sample can be specifically determined and which can be adapted to pulp pulping processes as an on-line measurement method. The present invention further provides an apparatus for carrying out the method.

Thanks to the invention, the resin content of the pulping process can now be monitored continuously for the first time in connection with the pulping process.

Furthermore, the reference sample prepared by the method of the invention allows the use of continuous, high-speed measuring devices, such as IR analyzers, to determine the resin content online in connection with any paper or pulp process.

The invention will now be described in more detail by means of the following application examples with reference to the accompanying drawings, in which Figure 1 schematically shows an apparatus according to the invention, in which the separating devices are arranged side by side, Figure 2 schematically shows another apparatus according to the invention, in which the separating devices are arranged in series, Figure 3 shows the absorption spectra obtained with an IR spectrophotometer obtained using a reference sample prepared according to the invention and pure water as a reference sample, and Figure 4 shows the correlation of the IR measurement with the resin ball assays performed in the laboratory.

Example 1;

Figure 1 shows a continuous apparatus 35 according to the invention, in which the separating devices are arranged in parallel. The apparatus comprises a continuous centrifuge 1, a continuous ceramic filter 2 and a continuous IR spectrophotometer 3. The apparatus 5 is connected as an on-line measuring apparatus in connection with the wet part of the paper machine 4.

In this application, the pulp sample stream 5 taken from a paper machine 4, e.g. a headbox, is divided into two parts 6, 7. The centrifuge 1 is arranged to receive the second part 6 and the ceramic filter 2 is arranged to receive the divided second part 7.

The pulp pulp sample entering the centrifuge 1, which in this case is a continuous decanter centrifuge, does not need to be pre-filtered, although pre-filtration can be used if desired. The rotational speed of the centrifuge is adjusted to separate the solids contained in the sample, with the exception of light resins. In this example, the rotational speed was chosen to be 6000 rpm, which corresponds to an acceleration of the centrifugal force 20 of about 3000 g. The centrifuge produces a continuous flow of liquid 8 as well as rather high-density pulp balls 9 (consistency of the order of about 30-40%), which can be returned to the process.

The liquid stream 8 obtained from the centrifuge is passed. 25 as an actual sample for the IR spectrophotometer 3.

The hole size of the continuous ceramic filter 2 is chosen to be about 0.1 to 0.2 μm, whereby the filter 2 separates the wood fibers and other solids contained in the pulp pulp sample, as well as practically all the resin balls. Only the dissolved organic and inorganic substances contained in the sample remain in the obtained filtrate 10. The filtrate is passed to a continuous IR spectrophotometer 3 as a reference sample. The separated solid 11 can be returned to the process.

35 The assay uses a reference sample to minimize the effect of absorption peaks of dissolved organic substances, such as carbohydrates and ligands, which are abundant in the sample over a selected wavelength range favorable to the resins, resulting in a specific measurement of the resins.

The method according to the invention was carried out in a paper machine environment. First, the amount of resin contained in the liquid stream from the centrifuge was checked and found to be of the same order of magnitude as the sample deposited and analyzed in the laboratory.

A commercial Bo-10 mem MB 155 FTIR analyzer was used as the IR analyzer. A wavenumber range of about 2400 to 3000 cm -1 was selected for the analysis of the resin content of the samples. Calibration was performed by the PLS method. Comparative compensation was obtained with a control sample.

Example 2;

Figure 2 shows a continuous apparatus according to Example 1, but in which the separation devices are arranged in series.

In this embodiment, the continuous centrifuge 20 fugue 1 is arranged to receive a pulp sample stream 5 from the paper machine 4. The centrifuge 1 and its operation are as shown in Example 1. Part 12 * of the liquid stream 8 obtained from the centrifuge 1, which contains resins and dissolved organic and inorganic compounds as residual solids, is passed to the ceramic filter 2 and the remainder 13 is passed as an actual sample to the IR spectrophotometer 3. The solids separated by the centrifuge 1 can be return to process 4.

A continuous ceramic filter 2, as shown in Example 1, substantially separates the solids remaining therein from the sample 12 entering the filter, i. resin materials. Only the dissolved organic and inorganic substances contained in the sample remain in the obtained filtrate 14. The filtrate is passed to the IR spectrophotometer 3 as a background sample.

The resin content is determined as in

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9 93902 cats 1.

Figure 3 compares the absorption spectra obtained by the method according to the invention, in which a reference sample prepared according to the invention (A) is used as a reference sample, and with a reference sample in which pure water (B) is used as a reference sample.

Figure 4 compares the amount of resin substance determined by the method according to the invention with the resin ball determinations made by calculating the pulp samples taken at the same time in the laboratory. IR-mit background results are relative.

Based on the above, the method according to the invention is excellently suitable for continuous resin material determinations of pulp pulping processes 15.

The examples are intended to illustrate the invention without limiting it.

Claims (13)

A method for determining the resin content of a pulp pulp sample, which sample comprises wood fiber, resin, possible other solids, dissolved organic and inorganic substances and water, characterized in that (a) a part of the pulp pulp sample is separated by a specific gravity separator 10 other solids other than resins to obtain the actual sample; (b) resinous material and any wood fibers and other solids that may be present are separated from a portion of the pulp sample by a particle size separator to obtain a reference sample; and c) the resin content of the sample is determined by measuring from the actual sample obtained using a reference sample as a reference. Method according to Claim 1, characterized in that the method is carried out continuously in connection with the pulp pulping process. A method according to claim 2, characterized in that a part of the pulp sample (a) is centrifuged or separated by a centrifuge 25 or a separator to obtain the actual sample; and (b) filtering the portion as a filter to obtain a reference sample. A method according to claim 2, characterized in that 30 (a) the pulp sample is centrifuged or separated by a centrifuge or separator to obtain the actual sample; and (b) filtering a portion of the sample from step (a) as a filter to obtain a reference sample. Method according to one of Claims 1 to 4, characterized in that a filter with a hole size of 0.1 to 0.2 μm is used in the filtration. li 11 93902 Method according to one of Claims 1 to 5, characterized in that a method based on the structure of organic matter is used to determine the resin content. Method according to one of Claims 1 to 6, characterized in that the determination of the resin content is carried out by means of a measuring device which measures the absorption, emission, scattering or scattering of the generated electromagnetic radiation caused by the samples. 8. Apparatus for determining the resin content of a pulp sample comprising wood fiber, resin, any other solids, dissolved organic and inorganic substances, and water, characterized in that the apparatus comprises: (a) a specific gravity separator for preparing the actual sample; , which separates wood fibers and any solids other than resins from a portion of the 20 pulp samples; (b) a particle size separator for preparing a reference sample, which separates resins and any wood fibers and solids present from a portion of the pulp pulp sample; (c) a measuring device for measuring the actual sample and the reference sample to determine the resin content of the sample. Apparatus according to claim 8, characterized in that the apparatus is arranged to determine the resin content continuously from the pulp sample. Apparatus according to claim 9, characterized in that the apparatus comprises: 35 (a) a continuous centrifuge or separator for producing a female sample, a centrifuge arranged to receive a sample stream from the pulp milling process; b) a continuous filter for preparing a reference sample, the filter being arranged to receive a sample stream from the pulping process; and 5 (c) a continuous measuring device for measuring the sample and the reference sample, which measuring device is arranged to measure the actual sample from the centrifuge or separator and the reference sample from the filter. RAMAN spectroscopy, preferably with an IR spectrophotometer. 10 93902 Apparatus according to claim 9, characterized in that the apparatus comprises: (a) a continuous centrifuge or separator for producing the actual sample, which is arranged to receive the sample stream from the pulping process; (b) a continuous filter for preparing a reference sample arranged to receive a portion of the sample stream from the centrifuge or separator; and (c) a continuous measuring device arranged to measure the actual sample from the centrifuge or separator and the reference sample from the filter. Apparatus according to one of Claims 8 to 11, characterized in that the hole size of the filter 25 is approximately 0.1 to 0.2 μπι. Apparatus according to one of Claims 8 to 12, characterized in that the continuous measuring device is a measuring device based on electromagnetic radiation absorption, emission or scattering, preferably an IR spectrophotometer. Il 13 93902