How to control the quality of urea

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National standard of GB 2440-9 1 urea

1 Subject content and scope of application

This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of urea.

This standard applies to urea synthesized by ammonia and carbon dioxide. Its main uses are agricultural fertilizers, plastics, resins, coatings, medicines and other raw materials for industrial sectors.

Molecular formula: CO(NH2)2

Relative molecular mass: 60.055 (according to the International Table of Relative Atomic Mass 1987)

2 reference standard

GB/T 244 1 urea-determination of total nitrogen content-titrimetric method after distillation

Urea, determination of biuret content, spectrophotometric method

Determination of moisture in urea Karl Fischer method

Urea for industrial use, determination of iron content, phenanthrene? Forest spectrophotometry

Urea for industrial use, determination of alkalinity, volumetric method

Urea for industrial use, determination of water insoluble matter content, gravimetric method

GB/T 2448 determination of urea particle size-sieving method

GB 8569 solid fertilizer packaging

Urea for industrial use, determination of sulfate content, visual turbidimetric method

3 technical requirements

3. 1 Appearance: granular or crystalline.

3.2 Urea shall meet the requirements of Table 1:

Table 1 urea technical index%

Nominal name

Excellent industrial and agricultural products, first-class products, qualified products, first-class products, qualified products.

Color white or light color

Total nitrogen (N) content (calculated on dry basis) ≥ 46.3 46.3 46.3 46.3 46.3 46.3 46.3 46.3.

Biurea content ≤ 0.50.91.00.91.01.5.

Water (H2O) content ≤ 0.3 0.5 0.7 0.5 0.5 1.0

Iron content (calculated as Fe) ≤ 0.0005 0.0005 0.00 10

Alkalinity (calculated as NH3) ≤ 0.0 1.020.03

Sulfate content (calculated as SO4-2) ≤ 0.005 0.0 10 0.020

Water insoluble matter content ≤ 0.005 0.0 10 0.040

Particle size (φ 0.85 ~ 2.80mm) ≥ 90 90 90 90 90 90 90 90 90.

Note: Crystalline urea does not control the particle size index.

4 test method

4. 1 determination of total nitrogen content

According to GB/T 244 1.

4.2 Determination of biuret content

According to GB/T 2443.

4.3 Determination of moisture

According to GB/T 2444.

4.4 Determination of Iron Content

According to GB/T 2445.

4.5 Determination of alkalinity

According to GB/T 2446.

4.6 Determination of Sulfate Content

According to GB/T 13256.

4.7 Determination of Water Insoluble Matter Content

According to GB/T 2447.

4.8 Determination of Particle Size

According to GB/T 2448.

5 inspection rules

5. 1 urea shall be inspected by the quality inspection department of the manufacturer. The production enterprise shall ensure that each batch of urea leaves the factory in accordance with the requirements of this standard, and each batch of urea leaves the factory with a quality certificate in a certain format, which includes the following contents: the name of the production enterprise, product name, trademark, product grade, batch number, production date, product net weight and this standard number.

5.2 The user has the right to conduct quality inspection on the received urea according to the provisions of this standard, and verify whether its indicators meet the requirements of this standard.

5.3 Urea shall be inspected by batch. The weight of each batch shall not exceed1000t. Users regard products with uniform quality with quality certificates as a batch.

5.4 Sampling method: For packaged products, when the total number of packaging bags is less than 5 12, the number of sampling bags shall be selected as specified in Table 2; When it is greater than 5 12, it should be selected according to the provisions of 3× < > (n is the total number of packaging bags). When sampling, use a sampler to vertically insert 3/4 from the center of the bag and take a uniform sample. Or use an automatic sampler, spoon or other suitable tools to collect cross-sectional samples from the belt conveyor at certain intervals.

5.5 According to the different requirements of industrial and agricultural products, quickly divide the samples into 600 ~ 1200 g average samples by divider or quartering method, and pack them in two clean, dry jars with grinding plugs or other containers with sealing performance. The container shall be labeled with the manufacturer's name, product name, batch number, sampling date and the name of the sampler. One for testing; The other copy is kept as a sample for one month for inspection.

Table 2 Selection of sampling bags

Total number of packaging bags Minimum number of sampling bags Minimum number of sampling bags

1~10All 182 ~ 2 16 18

1 1~49 1 1 2 17~254 19

50~64 12 255~296 20

65~8 1 13 297~343 2 1

82~ 10 1 14 344~394 22

102~ 125 15 395~450 23

126~ 15 1 16 45 1~5 12 24

152~ 18 1 17

5.6 If one index in the inspection results does not meet the requirements of this standard, samples should be taken from twice as many bags for reinspection. If samples are taken on the belt conveyor, they shall be re-sampled according to the provisions of Article 5.4 on bagged sampling and re-inspected.

As a result of reinspection, as long as one index does not meet the requirements of this standard, the whole batch of urea is unqualified.

5.7 If the supplier and the buyer have any objection to the product quality, it shall be implemented according to the relevant regulations of the State Bureau of Technical Supervision. Arbitration shall be conducted in accordance with the provisions of this standard.

6 Packaging, marking, transportation and storage

6. 1 Urea is packed in plastic woven bags (polyethylene film bags are used as inner bags) and composite plastic woven bags.

The net weight of each bag is 25 0.1,40 0.2 or 50±0.2kg, and the average net weight of each batch of product bags reaches 25, 40 or 50kg.

The quality of urea packaging should comply with the relevant provisions of GB 8569.

6.2 The packaging bag of urea shall be clearly marked with: manufacturer's name, product name, trademark, net weight of product and number of this standard.

6.3 Urea can be transported by vehicles such as cars, trains and ships. Means of transport and loading and unloading tools should be clean, flat and free from protruding sharp objects, so as not to puncture or scratch the package.

6.4 Urea should be stored in a flat, cool, ventilated and dry warehouse. Packaging should be neatly stacked, and the stacking height should be less than 7m.