MT/T 747-1997Technical condition for sodium humate used as boiler scale inhibitor (English PDF)

4.1 Moisture determination

Press ZB

G21

005-87 Determination of the provisions of 2.4.

4.2 Determination of Humic Acid Yield

4.2.1 Method summary

Extract sodium humate from the sample with water. In a strongly acidic solution, oxidize the carbon in humic acid to carbon dioxide with potassium dichromate.

The consumption of potassium dichromate and the carbon coefficient of humic acid were used to calculate the yield of humic acid.

4.2.2 Reagents

4.2.2.1 Sulfuric acid (GB

625). Relative density 1.84.

4.2.2.2 Potassium dichromate solution. c 16K2Cr2O7 = 0.8 mol/L. Weigh 40 g of potassium dichromate (GB 642) in 1000 mL of water Medium, stored in small-mouth bottles for later use.

4.2.2.3 Standard solution of potassium dichromate. c 16K2Cr2O7 = 0,1 mol/L. Dry potassium dichromate (GB 642) at 130 °C for about 3 hours, Place in a desiccator to cool to room temperature, then accurately weigh 4.9036 g in a beaker, dissolve in water, then transfer to 1000 mL volumetric flask, Dilute to the mark with water and shake well.

4.2.2.4 Phenanthroline indicator. Weigh 1.5

g-phenanthroline (GB

1293) and 1

g Ammonium ferrous sulfate (GB

661) Dissolved in 100 mL of water Medium, stored in brown bottles.

4.2.2.5 Ammonium ferrous sulfate standard solution. c (Fe2) = 0.1

mol/L. Weigh 40

g Ammonium ferrous sulfate hexahydrate (GB

661) Dissolve in moderate amount Water, add 20 mL of sulfuric acid (4.2.2.1), diluted to 1000 with water mL, shake well and put into a brown bottle. The concentration of ferrous ammonium sulfate is not Stable, need calibration before use. Can put two clean aluminum sheets or cable aluminum wires in the bottle to keep the solution concentration stable for a long time Calibration. The concentration of the solution is calibrated as follows.

Accurately draw

mL of potassium dichromate standard solution at 250 in a conical flask, add 70 mL ~ 80 mL of water and 10 mL sulfuric acid (4.2.2.1), add 3 drops of phenanthroline indicator after cooling, titrate with the ammonium ferrous sulfate solution to be calibrated, the solution changes from orange red to brick red Color is the end.

The concentration of ferrous ammonium sulfate standard solution is calculated according to formula (1).

c (Fe2) =

V × 0.1

Where.

c (Fe2) --- the concentration of ferrous ammonium sulfate standard solution, mol/L;

V --- Volume of ammonium ferrous sulfate solution consumed in titration, mL.

4.2.3 Measurement steps

Weigh about 0.2

g (accurate to 0.0002

g) Sample at 250

In a conical flask, add 70 mL of water, insert a small glass funnel at the mouth, and set Heat extraction in boiling water bath 30 min, and often shake, take out the Erlenmeyer flask, after cooling, transfer all the solution and residue to 100 mL volumetric flask Medium, make up to volume with water, shake well, dry filter with medium speed filter paper, discard the first 10 mL filtrate, continue filtering to filtrate 30 mL ~ 50 for mL, accurately transfer 5.0 with a pipette mL of filtrate at 250 mL conical flask, add 5.0 with a pipette mL of potassium dichromate Liquid, slowly add 15 mL of sulfuric acid (4.2.2.1), shake and place in a boiling water bath and heat for 30 min, and shake frequently, remove the Erlenmeyer flask and cool to at room temperature, add 80 mL of water and 3 drops of phenanthroline indicator, titrated with ammonium ferrous sulfate standard solution, the solution changed from orange to green with brick Red is the end. At the same time, a blank test is performed according to the above steps.

4.2.4 Expression of results

The yield of humic acid is calculated according to formulas (2) and (3).

HAar =

0.003 (V0-V1) · c (Fe2) 0.64 × m × b × 100 (2) HAd = HAar × 100-Mar (3) where.

HAar --- the received humic acid yield of the sample,%;

HAd --- dry humic acid yield of the sample,%;

V1 --- Volume of ammonium ferrous sulfate standard solution consumed by the sample, mL;

V0 --- volume of ammonium ferrous sulfate standard solution consumed in blank test, mL;

c (Fe2) --- the concentration of ferrous ammonium sulfate standard solution, mol/L;

0.003 --- with 1.00

mL, c (Fe2) = 1.000

mol/L equivalent carbon mass of ferrous ammonium sulfate solution, g;

0.64 --- carbon coefficient of weathered coal humic acid;

a --- the total volume of the sample solution, mL;

b --- the volume of the sample solution taken during the measurement, mL;

m --- the mass of the sample, g;

Mar --- received moisture of the sample,%.

During the calculation process, one digit after the decimal point is taken, and the calculation result is rounded to the nearest digit.

4.2.5 Tolerance

The absolute difference between the results of the parallel measurement of the same test chamber of the sample shall meet the requirements of Table 2.

Table 2

Humic acid yield range,% 20 ~ 50 >=50 Absolute difference,% <=2 <=3

4.3 Determination of calcium oxide and magnesium oxide

Press GB/T

1574-1995 Determination of 6.5 and 6.6 or 7.3 and 7.4.

4.4 Determination of water insoluble matter

Press ZB

G21

005-87 Determination of the provisions of 2.7.

4.5 PH measurement

Press ZB

G21

Determination of the provisions of 2.5 in 005-87.

5.3 Preparation of sampling and analysis samples

5.3.1 The products shall be sampled according to the regulations in Table 3.

table 3

Total number of bags 1 ~ 10 total number of bags 11 ~ 49 11 50 ~ 64 12 65 ~ 81 13 Sampling probe (GB/T

6679 Appendix A) Insert diagonally from one side of the mouth of the bag to the opposite side of the bag Sampling, the total number of samples taken must not be Less than 2 kg, and then use a divider or heap cone quarter method to reduce the sample to 500 g, divided into two clean, dry in the mouth bottle or plastic bottle, stick a label indicating the name of the manufacturer, product name, batch number, sampling location, sampling date, and name of the sampling person. A bottle for product quality analysis, the other bottle is stored in a sealed 60 d, for reference.

5.3.2 Take 100

g scale down, grind until all pass 0.2 mm sieve standard sieve, mix well, place in a clean, dry bottle for for analysis.

5.4 Decision rules

5.4.1 If there is an important indicator that does not meet this standard, it should be resampled from twice the number of sampling bags.

When the requirements of this standard are not met, the product is judged to be unqualified.

5.4.2 If there are two general items that do not meet this standard, re-sampling shall be carried out again from twice the number of sampling bags.

When it does not meet this standard, it is judged that the product is unqualified.

6.1 Products are packed in woven bags lined with plastic bags. Net weight 25

kg ± 0.25

6.2 The following signs should be marked on the packaging bag. product name, trademark, net weight, and factory name.

6.3 During transportation, it should be put into a covered transportation tool to prevent rain and snow.

6.4 Store the product in a dry place.