TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
1.
SUBJECT OF THE SPECIFICATION
The subject of this technical specification is 45% aqueous urea solution which is commercially marketed as
®
PULNOX , obtained by the synthesis from ammonia and carbon dioxide.
®
PULNOX 45% is used for manufacturing of urea-formaldehyde resins and in flue gas treatment technology.
2.
REQUIREMENTS
2.1 GENERAL REQUIREMENTS
Urea solution is transparent or slightly turbid or turbid liquid with yellow coloration.
2.2. DETAILED REQUIREMENTS
Detailed requirements are shown in Table 1 (below).
Table 1
No
3.
Requirements
Unit
Limits
1.
Urea content, in the range
%
43 - 47
2.
Ammonia content, not more than
%
0.9
3.
Biuret content, not more than
%
0.6
LABELLING
Product label shall be located in conspicuous location and shall be permanently affixed to the packing. Label
text and information should be in a size of type large enough to be readily legible.
Labelling must include the following elements:
•
The commercial product name: PULNOX .
•
The chemical name: 45% urea solution
•
The name, address, logo and telephone number of the manufacturer
•
The nominal quantity of the product
•
Usage, storage and transport information
•
Manufacturing date
•
Handling symbols: “Keep dry”, “Keep away from heat”, “Stacking limit – by number”, “Temperature
limitations” and “This way up”.
4.
®
PACKING
45% technical urea solution is filled into the following containers:
•
Tank vehicles and tank wagons
•
Plastic (i.e. polyethylene, polypropylene, Vinton ) intermediate bulk containers
•
Containers made of alloy steel
•
Usage of other kinds of packagings is acceptable, provided they ensure quality of the product and
safety during transport, storage
Materials not recommended for use with 45% urea solution: copper, copper alloys, non-alloy steel and
galvanized (zinced) steel.
Additional precautions:
•
Before filling up, tanks and containers should be rinsed with demineralized water
•
In general avoid contamination of this product
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TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
5.
STORAGE
The 45% urea solution should be stored in non - pressure tanks or containers of any capacity. Store in cool, dry
and well – ventilated areas at temperatures between 10° and 30°C. Tanks and containers with urea solut ion
must be protected against exposure to strong sunlight. Storage temperature should be kept above ~10°C t o
prevent crystallization of urea from solution. Failure to comply with the above mentioned precautions may affect
product quality.
6.
TRANSPORT
45% technical urea solution should be shipped in tank vehicles, tank wagons or in a smaller containers (i.e.
drums, canisters). containers (i.e. drums, canisters). To avoid contamination, it is necessary to apply the
highest standards during transport. The product is not subject to RID and ADR.
7.
ANALYTICAL METHODS
7.1. TESTING SCHEDULE – see Table 2
Table 2
Test description
Limits as per:
Test description as per:
1. Test of general requirements
2.1.
7.4.
2. Determination of urea content
2.2.1.
7.5.
3. Determination of ammonia content
2.2.2.
7.6.
4. Determination of biuret content
2.2.3.
7.7.
7.2. BATCH SIZE
Product batches are released for further use by following the relevant procedures and when the results of
testing fully conform with the specification of the standard.
The meaning of product batch is considered as well defined and possible to determine amount.
7.3. SAMPLING
Bottles for sampling
Use 1000 ml wide-neck bottles. Proper materials for theses bottles are: high density polyethylene (HDPE), high
density polypropylene (HDPP), polyfluoroethylene (PFE),polyvinylidenedifluoride and tetrafluoroetyleneperfluoroalky vinyl ether copolymer (PFA)
Prior to the first use, the bottles should be washed and rinsed with deionized water and then filled up with 45%
urea solution.
Labelling of sampling bottles
Each sampling bottle should be provided with a label (dimension approx. 10 x 5 cm) or a tag. These labels
must be waterproof and resistant to 45% urea solution.
Sampling procedure
Open a sampling wide-neck bottle and place its cap upside down on the clean flat surface. After rinsing the
sampling pipe, fill up the bottle completely with the 45% urea solution from the tank. Then, empty the bottle,
refill it with the above mentioned solution and cap the bottle tightly. Attach a label/tag to the bottle.
During sampling particular care should be taken to prevent dusts and liquid pollutants from getting into the
bottle.
Upon sampling, the sample should be delivered to the analytical laboratory as soon as possible.
Sampling bottle should be provided with a label or a tag.
Volume of sample
The required volume of a sample is 1 liter.
Details on labelling
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TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
Labelling must mention:
•
The product name
•
The name of company which owns the sample product
•
The address of the place where the sample was taken
•
The manufacturer of the sample product*
•
The batch number or lot number
•
Designation of container from which the sample was taken
•
Determination of part of the container from which the sample was taken (sampling point)
•
The date and time of sampling
•
The shipping date
•
The name, surname and signature of person responsible for sampling
*
*
*
*
*
*
*
Required in dispute only.
7.4. GENERAL REQUIREMENTS CHECKING
Testing for compliance with general requirements is performed visually.
7.5. DETERMINATION OF UREA CONTENT BY REFRACTIVE INDEX
7.5.1.
Purpose of the method
This analytical method is suitable for liquids with refractive indexes values between 1.33 ÷ 1.41, measured at
temperature range of 20° ÷ 30°C. Based on the refrac tive index measurement it is possible to determine urea
content in aqueous solutions within the range of 40% ÷ 50% (w/w).
7.5.2.
Principle of the method
Measurement of refractive index must be carried out at a constant, specified temperature.
Urea content is specified with the use of the reference curve.
7.5.3.
Apparatus
a)
Refractometer, measuring range of 1.3300 to 1.4100;
b)
Analytical laboratory balance with precision of 0.0002 mg;
c)
Drying oven;
d)
Laboratory beaker about 150 ml of volume;
e)
Common laboratory glass.
7.5.4.
Reagents and solutions
a)
Demineralized water, conductivity: < 0,5 mS/m
b)
Urea, crystalline, analytical grade (biuret content less than 0.1% (w/w) ). Before preparing of reference
curve, urea should be dried for 2 hours at 105°C.
7.5.5.
a)
Determination procedure
General rules
Sample must be thoroughly dissolved in water and free of urea crystals. If needed, heat the sample carefully up
to 45°C to obtain homogenous solution.
Test must be performed in accordance with the respective operation manuals delivered with refractometer.
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TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
b)
Preparation of the reference curve and determination of the evaluation factor
Weigh crystalline urea into a glass beaker and add sufficient demineralized water to obtain urea solutions with
concentration respectively:
40% (w/w), 45% (w/w), 50% (w/w)
Further, perform refractive index measurements for previously prepared urea solutions at temperature 20°C.
Visualization of the refractive index and urea solutions concentration creates significant linear dependence.
Based on urea concentrations and measured refractive indexes calculate evaluation factor F needed for further
calculations using the following formula:
F=
∑ (w )
∑ (n − n )
U
U
W
where:
F - evaluation factor, (%);
∑ (w ) - sum of all reference urea solutions concentrations, [% (w/w)];
U
∑ (n
U
− nW )
- sum of subtractions between obtained refractive indexes for reference urea solutions
and refractive index for water.
Water refractive index is: nW = 1.3330 or use the calibration curve stored in the instrument memory.
c)
Check out of equipment function and reference curve
Refractometer performance shall be checked once a week with the use of water or a suitable reference
standard.
d)
Test sample preparation and measurements
Refractive index measurements must be performed for original sample without further preparation. These
measurements must be carried out at temperature 20°C. At least two measurement procedures should be
performed with different test portions. If the difference between the two measured values exceeds 0.0002 of
the unit, the measurements should be repeated.
7.5.6.
a)
Expression of the result
Calculations
Calculate the urea content as weigh percentage (w/w) using the following formula:
wU = (n p − n w ) x F − wBi
where:
wU
- is the urea content, [% (w/w)];
np
- is the refractive index of the urea solution sample;
nw
- is the refractive index of water;
F
- is the evaluation factor, (%);
wBi
- is the biuret content of the solution, [% (w/w)].
or based on reference curve calculate finally:
wU = w − wBi
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TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
where:
wU
- is the urea content, [% (w/w)];
w - value taken from the instrument;
wBi
b)
- is the biuret content of the solution, [% (w/w)].
Final result
The final result should be an arithmetic mean of the results of two consecutive tests. Round off result of the
refractive index to four decimal places. Round off the result of the urea content calculation to the nearest 0.1%
(w/w).
7.6. DETERMINATION OF ALKALINITY (calculation on NH3)
7.6.1.
Purpose of the method
This analytical method allows to determine alkalinity of tested 45% urea solution, calculated as ammonia.
7.6.2.
Principle of the method
The measurement is based on potentiometric titration of free ammonia with a standard hydrochloric acid
solution, in the presence Tashiro indicator (pH indicator).
7.6.3.
Apparatus
a)
Analytical balance with resolution of 0.01 mg or better
b)
Conical flask about 300 ml of volume
c)
Dosimat
7.6.4.
Reagents
a)
Hydrochloric acid, analytical grade; concentration: 0.5 mol/l;
b)
Tashiro indicator prepared as follows: mix 0.2% of methyl red alcohol solution with 0.1% of methylene
blue alcohol solution in a ratio 1:1 (v/v) under constant stirring.
7.6.5.
Determination procedure
Into a 300 ml conical flask containing approximately 100 ml of distilled water, weigh 50 g of urea solution with
precision of 0.01g. Add one or two drops of Tashiro indicator and titrate the solution with standard hydrochloric
acid solution until the color changes form green to pink – violet.
7.6.6.
a)
Expression of the result
Calculation
Calculate the alkalinity (X) expressed as a percentage by mass of ammonia (w/w) using the following formula:
X =
V • 0,0085 • 100
m
where:
V
- is the volume of the hydrochloric acid used for the titration (ml);
0.0085 - is the quantity of NH3 equivalent to 1 ml of hydrochloric acid solution (c=0.5 mol/l), (g/ml);
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TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
m s - mass of the urea solution test sample (g).
b)
Final result
The final result should be an arithmetic mean of the results of two consecutive tests. Round off the result to the
nearest 0.002% (w/w).
7.7. DETERMINATION OF BIURET CONTENT
7.7.1.
Purpose of the method
This analytical method allows to determine biuret content in 45% urea solution by photometric method. The
method applies to urea solutions with biuret content from 0.1% to 0.5% (w/w).
7.7.2.
Principle of the method
In an alkaline medium in the presence of potassium sodium tartrate, biuret and bivalent copper forms a colored
violet cupric compound. The absorbance of this solution is measured at a wavelength of 550 nm. The value of
absorption at this wavelength is a measure of biuret concentration in the sample.
7.7.3.
Apparatus
a)
Laboratory balance, resolution in reading 0.0002 g and 0.01 g
b)
Vacuum filtration set with a diaphragm filter, pore size 0.45 µm
c)
Spectrophotometer, relevant for measurements at 550 nm wavelength
d)
Cell, d = 5cm
e)
Volumetric flasks: 1000 ml, 250 ml, 100 ml, 50 ml; class A- compatible
f)
Pipettes; class AS-compatible
g)
Rotary evaporator
h)
Constant–temperature bath
7.7.4.
Reagents and solutions
Unless otherwise stated, during the analysis, use only chemicals of analytical grade and deionized and boiled
out water (to remove carbon dioxide).
a)
Potassium carbonate solution (saturated at ambient temperature)
b)
Standard aqueous solution of copper sulphate pentahydrate. Transfer 15 g of copper sulphate
pentahydrate (CuSO4 x 5H2O) into 1000 ml volumetric flask. Dissolve in water and dilute to volume
with the same solvent.
c)
Standard alkaline solution of potassium sodium tartrate. Transfer 45 g of sodium hydroxide into 1000
ml volumetric flask and dissolve in 500 ml of water. After cooling, add 50 g of potassium sodium
tartrate (KNaC4H4O6 x 4H2O) and make up to the mark with water. Leave standing for 24 hours before
use.
d)
Biuret standard solution of 0.8 mg biuret/ml. Transfer 800 mg of pure biuret into 1000 ml volumetric
flask. Dissolve in water and dilute to volume with the same solvent. Prior to that, biuret must be dried
for 3 hours at 105°C.
If biuret of relevant purity is not available, then the commercial product should be purified prior to making
calibration curve.
Proceed as follows:
•
To the beaker containing 500 ml of 25% ammonia water add approx. 50 g of biuret and stir for 15
minutes;
•
Then filter off the biuret, wash with ammonia-free water and dry;
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TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
•
Dissolve in ethanol (1g of biuret/100ml of EtOH), filter and evaporate to ¼ of volume;
•
Cool to 5°C and filter;
•
Dry the biuret in vacuum oven at 80°C
•
Check biuret purity by spectrophotometric measurements as per item 7.8.5 d)
The re-crystallization step from ethanol should be repeated until purity reaches constant level.
7.7.5.
a)
Determination procedure
Interferences
Use only optically transparent solutions for spectrophotometric measurements. Any materials causing turbidity
should be removed with the use of vacuum filtration with a diaphragm filter of pore size 0.45 µm. Free
ammonia or ammonium ions create with bivalent copper a colored complex, which absorbs light energy at
550nm. The method is applicable only if the NH3 or NH4 content in the sample does not exceed 500 mg/kg.
If ammonia content is higher than above mentioned then remove the excess by the following way:
Weigh 50 g of sample with precision 0.001 g and transfer into 1000 ml flask of a rotary vacuum evaporator; add
15 ml of potassium carbonate solution prepared as per item 7.8.4 a). Further, evaporate ammonia for 1 hour in
a warm water bath at 45°C, under a vacuum of 2 kPa t o 3kPa with rotating speed of 60r/min. After this
operation approximately 20 ml of the solution should remain in the flask. This volume should be poured to a
250 ml volumetric flask and further treatment as specified below should be performed.
b)
Preparation of the calibration curve
Transfer 2 ml, 5 ml, 10 ml, 15 ml, 20 ml and 25 ml of aliquots of biuret standard solution (prepared as shown in
7.8.4 d)) into a series of six graduated 50-ml flasks. Add water to obtain total mixture volume of about 25 ml.
Further, add 10 ml of standard alkaline solution of potassium sodium tartrate prepared according to item 7.8.4
c) and stir it carefully. After obtaining homogeneous solution add 10 ml of copper sulphate solution according to
7.8.4 b) and stir it again. Immerse the flasks in water bath at temperature 30°C ± 1°C and leave them for 15
minutes until color appears. Cool down the flasks to ambient temperature, dilute to volume with water and mix.
Measure the absorption using a 5 cm cell at 550 nm wavelength against water as the reference.
Perform a blank test in parallel with the calibration curve determination, by applying the following procedure:
add to a 50 ml volumetric flask 10 ml of standard solution of potassium sodium tartrate prepared according to
item 7.8.4 c), 10 ml of copper sulphate solution according to item 7.8.4 b) and dilute to volume with water.
Measure the absorption using a 5 cm cell at 550 nm wavelength against water as the reference.
Subtract the absorbance of the blank test from the absorbance of the measured values and set up the
calibration curve. On the basis of the obtained results draw the curve (with water as reference). In the
measured range of concentration the curve must be strictly linear.
c)
Determination of the calibration factor F
Calculate the calibration factor F using absorption values of the reference solutions specified in item 7.8.5 b)
according to the following formula:
F=
∑ (m ) = 61,6
∑ ( E ) ∑ (E )
Bi
where:
F
- is the calibration factor (mg);
m Bi
- is the mass of biuret (mg);
E
- is the relevant absorbance.
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TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
Calibration curve and corresponding calibration factor are determined once a year.
d)
Check out of the calibration factor
Calibration factor must be tested once a week with using single-point calibration method. Perform
measurement as described in item 7.8.5 b) of 10 ml of the biuret standard solution (= 8 mg of biuret) (double
marking).
Further, calculate day-factor (FD) as shown below:
FD =
8
E1 − E 2
where:
FD
- is the day-factor (mg);
E1
- is the absorbance of biuret standard solution (average calculated from two measurements);
E2
- is the absorbance of the blank test.
The day-factor should differ max. ± 5% from the calibration factor specified as per 7.8.5.c). The day-factor
should be always used for test sample measurements.
e)
Test sample preparation and measurement
Into 250 ml volumetric flask, weigh 100 g of the test sample to the nearest 0.01 g precision. Dissolve in water
and dilute to volume with the same solvent. Pipette 10 ml of such prepared solution and transfer it in 50 ml
volumetric flask. Further, add 10 ml of standard alkaline solution of potassium sodium tartrate prepared
according to item 7.8.4 c)and stir it carefully. After obtaining homogeneous solution add 10 ml of copper
sulphate solution according to item 7.8.4 b) and stir it again. Immerse the flasks in water bath at temperature
30°C ± 1°C and leave them for 15 minutes until col or appears. Cool down the flask to ambient temperature,
dilute to volume with water and mix. Measure the absorption using a 5 cm cell at 550 nm wavelength against
water as the reference.
Perform a reagent blank test in parallel with the test determination, by applying the procedure described in item
7.8.5 b).
To determine any possible self-absorption transfer another 10 ml of the test sample into 50 ml volumetric flask.
Dilute to volume with water and measure the absorption of such prepared solution.
Duplicate measurements should be performed.
Blank value of reagents and the sample should be deducted from the measured value.
7.7.6.
a)
Expression of the result
Calculations
Calculate the biuret content as percentage by mass (w/w) using the following formula:
wBi =
(E S − E B ) × FD × 250
m S × 10 × 1000
× 100
where:
wBi
- is the biuret content [% (w/w)];
ES
- is the absorbance of the test sample;
EB
- is the absorbance of the blank test (reagent blank + sample blank);
mS
- is the mass of the test sample (g);
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TECHNICAL SPECIFICATION
PULNOX®
WT-2013/ZA-15
45% UREA SOLUTION
FD
b)
- is the day-factor (mg).
Final result
Round off the result to the nearest 0.01 % (w/w).
7.8. DATA ASSESMENT AND TEST CERTIFICATE
A batch of urea solution shall be considered to meet the requirements of this Technical Specification if test
results conform with the requirements indicated in Table 1.
8.
REFERENCES
•
9.
PN-C-06501:1981 – Chemical analysis. Preparation of indicators solutions.
ADDITIONAL INFORMATION
WT-2013/ZA-15 supersedes WT-2012/ZA-15
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