This standard specifies the method for determining the chlorine consumption (delignification degree) of pulp. This method is applicable to all kinds of pulp. GB/T 2678.3-1995 Determination of chlorine consumption (delignification degree) of pulp GB/T2678.3-1995 Standard download decompression password: www.bzxz.net

GB/T 2678.3-1995
This standard is equivalent to the international standard ISO3260-1982 "Determination of chlorine consumption (delignification degree) of pulp". This standard is basically the same as ISO3260 in terms of technical content, and only some editorial modifications have been made to ISO3260. This standard has made the following changes to the technical content of the previous version: the concentration of each solution in the fifth item of the reagent of this standard is expressed in accordance with the expression method specified in GB1.4-88; - the two terms of chlorine consumption and chlorine value are unified as chlorine value, and the constant term in the formula of chlorine consumption X is merged; the concentration symbol N in the chlorine consumption formula is changed to c, and the correction factor symbol C is changed to K. This standard will replace GB2678.3-81 from the date of entry into force. This standard is proposed by the China Light Industry General Association.
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. The drafting unit of this standard: China Pulp and Paper Industry Research Institute. The main drafters of this standard: Chen Qizhao, Zhu. 232
GB/T 2678.3—1995
ISOForeword
ISO (International Organization for Standardization) is a worldwide federation of national standards research institutes (ISO members). International standards are proposed by ISO technical committees, and each member country interested in the topic of an established technical committee has the right to participate in the committee. International organizations, whether governmental or non-governmental, participate in its work by collaborating with ISO. Draft international standards adopted by technical committees must be tried out in member countries that agree before the ISO Council accepts them as international standards.
International standard ISO3260 was proposed by ISO/TC6 Technical Committee for Paper, Board and Pulp. The second edition was proposed directly to the ISO Council in accordance with the first part of ISO technical work guide 6.11.2. It replaces the first edition (i.e. ISO 3260-1975) and has been approved by the following member states: Austria, Germany, Poland, Belgium, Hungary, Romania, Bulgaria, India, South Africa, Canada, Iran, Spain, Czechoslovakia, Israel, Sweden, Egypt, Netherlands, Switzerland, Finland, New Zealand, Turkey, France, Norway, Soviet Union. No member state expressed objection.
1 Scope
National Standard of the People's Republic of China
Pulp-Determination of chlorine consumption (Degree of delignification)
This standard specifies the method for determining the chlorine consumption (degree of delignification) of pulp. This method is applicable to all kinds of pulp.
2 Reference standards
GB/T 2678.3-1995
eqv IS0 3260:1982
Replace GB2678.3-81
The following standards contain provisions that constitute the provisions of this standard through reference in this standard. At the time of publication of this standard, the versions shown are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T2677.2-93 Determination of moisture content of papermaking raw materials 3 Principle
The chlorine consumption of pulp is determined by making the pulp react with a certain amount of hypochlorite solution in a strong acid medium for a certain period of time, and then determining its residual chlorine by indirect iodine method. This standard requires that the amount of residual chlorine is not less than 50% of the amount of added chlorine. There is a linear relationship between the chlorine consumption of pulp and the residual lignin in the pulp. As long as the chlorine consumption of pulp is measured, its residual lignin can be calculated. 4 Instruments
4.1 Dry pulp crusher.
4.2 Electric stirrer.
4.3 Chlorine consumption tester, composed as follows, see Figure 1. 4.3.1 Thick-walled conical flask: 1000mL.
4.3.2 Simple separatory funnel: 50m, connected to the ground mouth of the conical flask (4.3.1). 4.4 Vacuum pump (or water pump).
4.5 Constant temperature water bath (maintained at 25±1℃). 4.6 Electromagnetic stirrer.
4.7 Stopwatch.
Approved by the State Administration of Technical Supervision on July 6, 1995 234
Implemented on April 1, 1996
5 Reagents
GB/T2678.3—1995
Figure 1 Pulp chlorine and fluorine consumption tester
5.1 Hypochlorite solution: chlorine content 0.564 mol/L or 0.282 mol/L. 5.2 Hydrochloric acid (GB62289): 12% (m/m) aqueous solution. 5.3 Potassium iodide (GB1272-88) solution [c(KI)=1 mol/L]. 5.4 Sodium thiosulfate (GB 637-—88) standard titration solution [c(NazS,O.)=0.1 mol/LJ or [c(NazS2O.)=0.2 mol/L]. 5.5 Starch: 0.5% (m/V) aqueous solution.
6 Sampling and processing
6.1 Dry pulp board
Take an appropriate amount of dry pulp board and place it in a dry pulp crusher to crush it (if there is no dry pulp crusher, you can also use a blade to scrape the pulp board into fluff), store it in a sealable sample bottle, balance the moisture for analysis. 6.2 Wet pulp
Take an appropriate amount of wet pulp sample, separate the undigested components and pulp blocks through screening, wring it dry and tear it into small pieces, store it in a sealable sample bottle after proper air drying, balance the moisture for analysis. 7 Test steps
Accurately weigh 0.5g of the prepared sample, accurate to 0.0001g. If it is straw pulp, weigh more sample appropriately. At the same time, weigh another sample to determine the moisture content according to GB/T2677.2. Place the sample in an electric stirrer (4.2) and add 250mL of 25-26℃ steamed stuffing water. Wait until the sample is completely 235
GB/T 2678.3—1995
After wetting, start the electric stirrer to disperse the sample into single fibers, then transfer all the dispersed samples to the reaction bottle (4.3.1) of the chlorine consumption tester, rinse the stirrer with 135mL of distilled water several times, and pour the rinse liquid into the reaction bottle, place the reaction bottle in a constant temperature water bath (4.5) at 25±1℃, and stir it with an electromagnetic stirrer (4.6), install the separatory funnel (4.3.2) of the chlorine consumption tester and open the piston at the bottom of the separatory funnel, connect the vacuum pump (4.4) to the upper part of the separatory funnel, and slowly evacuate the reaction bottle, close the piston at the bottom of the separatory funnel, add 10mL of 12% hydrochloric acid solution (5.2) to the separatory funnel, and put the acid into the reaction bottle, and start the stopwatch (4.7) to count (be careful not to let air into the reaction bottle). Rinse the separatory funnel with 10 mL of distilled water, and place the rinse water in the reaction bottle. Use a pipette to add 15 mL of hypochlorite solution (5.1) to the separatory funnel, put it into the reaction bottle when the stopwatch counts 2 min (do not stop the stopwatch at this time), rinse the separatory funnel with 5 mL of distilled water, and place it in the reaction bottle. Add 20 mL of potassium iodide solution (5.3) to the separatory funnel, when the stopwatch shows 17 min, put the potassium iodide solution into the reaction bottle, rinse the separatory funnel with 50 mL of distilled water and place it in the reaction bottle. Shake the reaction bottle vigorously for about 4 min to dissolve all the chlorine in the bottle into the solution, remove the separatory funnel, and rinse the reaction bottle wall and the interface between the separatory funnel and the reaction bottle with distilled water. Then use sodium thiosulfate standard titration solution (5.4) (Note: 0.1mol/L and 0.2mol/L sodium thiosulfate standard titration solution should be used for titration of bleached pulp and unbleached pulp respectively.) When the solution turns light yellow, add 5mL 0.5% starch solution (5.5) and continue titrating until the blue color disappears. Take another 400mL of distilled water for blank test.
8 Result calculation
The chlorine consumption X is calculated according to formula 1):
Where: Xi—
Chlorine consumption, %;
X - 3. 546 ×KXc(V.- V)
The amount of sodium thiosulfate standard titration solution consumed in the blank test, mL; V.
V is the amount of sodium thiosulfate standard titration solution consumed when measuring the sample, mL; c is the concentration of sodium thiosulfate standard titration solution, mol/L; m is the mass of the absolutely dry sample, g;
is the correction factor, which is obtained by calculating the residual chlorine content according to formula (2) and looking up table (1). K
is the residual chlorine content (%) =
Table 1 Relationship between residual chlorine content and correction factor K value Residual chlorine content
Lignin content X: converted according to formula (3):
Where: X2——lignin content, %,
0.9——conversion coefficient;
Chlorine consumption.
X, = 0. 9Xl
(1)
(2)
(3)
Two determinations are carried out at the same time, and the arithmetic mean is taken as the determination result, and the figures are rounded to the second decimal place. The error between two measured values ​​should not exceed 0.2%.
Test report
The test report shall include the following contents:
This national standard number;
Related description of the sample;wwW.bzxz.Net
Test results and necessary explanations;
GB/T 2678.3—1995
Any abnormal phenomenon observed during the test; Any operation that is not specified in this national standard or reference and may affect the results. 237
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