TT-GGJ type crucible coke swelling index tester
I. Equipment Introduction
The cruciblecoke swelling index testeris amethod for determining the caking property by measuring the swelling property of coal.
The magnitude of the crucible swelling number depends on the melting characteristics of the coal, the gas evolution during the formation of the plastic layer, and the impermeability of the plastic layer. Since the test result is determined based on the shape of the coke residue, subjectivity is often unavoidable, and it is even possible to judge coal with poor caking property as having good caking property, which is a disadvantage of this method. However, this test method is quick and simple, and the test result can reflect the caking property of coal to a certain extent. Therefore, it is listed as one of the international classification indicators for hard coal. The International Organization for Standardization (ISO) and countries such as the UK, USA, France, Japan, Russia, and Poland have national standards for this method. In 1985, China established the national standard for the determination of the crucible swelling number of bituminous coal.
There are two heating methods for determining the crucible swelling number: one is the traditional gas lamp heating; the other is electric furnace heating. The standards of ISO and the USA, Russia, France, Poland and other countries allow both heating methods to be used simultaneously. China currently specifies the use of electric heating method.
II. Scope
This standard specifies the method summary, instruments and equipment, test preparation, test procedures, result expression, method precision, and test report for determining the crucible swelling number (CSN). This standard applies to bituminous coal.
III. Key Points of Determination Method
Place a certain mass of coal sample in a special crucible, and heat it to (820±5)℃ according to the specified procedure. Compare the obtained coke button with a set of standard coke button profile diagrams with sequence numbers, and take the closest coke type sequence number as the crucible swelling number.
IV. Instruments and Equipment
(1) Electric heating furnace (Fig. 1)
Wind a coil of nickel-chromium wire with a power of 1000W on a grooved refractory plate 1 with a diameter of 100mm and a thickness of 13mm. The refractory plate is placed on a plate 2 of the same size. A quartz dish 3 with a wall thickness of 1mm, height of 10mm, and outer diameter of 85mm is placed on plate 1 to hold the crucible.
The above heating part is placed in a refractory brick 4 with a diameter of about 140mm. The brick has a groove with a depth of 60mm and a diameter of 105mm. The top is covered with a 20mm thick refractory plate 5. There is a hole with a diameter of 50mm in the center of the plate for placing the crucible. The entire refractory brick is placed on an asbestos board 6 of 3mm to 5mm thickness, and then placed together with the asbestos board in the furnace shell 7. Fill the space between the brick and the furnace shell with aluminum silicate fiber or asbestos fiber and light alumina as thermal insulation material. There is a refractory cover 8 on the top of the furnace. A hole is opened at the bottom of the furnace. Insert the temperature measuring thermocouple 9 from the hole so that its hot junction just contacts the inner surface of the quartz dish. The electric heating furnace is equipped with suitable temperature measurement and control devices.
(2) Crucible and lid (Fig. 2)
Made of porcelain or quartz that is resistant to high temperature (greater than 1000 ℃).
Specifications: Total height of crucible: (26±0.5)mm; Top outer diameter: (41±0.75)mm; Bottom inner diameter: 11mm~14mm; Mass: 11g~12.75g; Volume: 16mL~17.5mL; Crucible lid (without hole): inner diameter 44mm, height 5mm.
(3) Crucible lid with hole (Fig. 3)
Made of porcelain or quartz resistant to high temperature (>1000℃). Same dimensions as the crucible lid without hole in (2), with a round hole of diameter 6mm for inserting thermocouple.
(4) Crucible tongs.
(5) Balance: minimum graduation value 0.01 g.
(6) Stopwatch: accurate to second (s).
(7) Weight: (500±10)g flat bottom weight.
(8) Thermocouple: sheathed nickel-chromium thermocouple, 2 pieces.
(9) Coke button observation tube (Fig. 4): The coke button observation tube shall comply with the provisions in Fig. 4.
Fig. 1 Electric heating furnace
Description: 1, 2, 5- Refractory plate; 3- Quartz dish; 4- Refractory brick; 6- Asbestos board; 7- Furnace shell; 8- Refractory top cover; 9- Thermocouple.
Fig. 2 Crucible with lid (unit: mm)
Description: 1- Flat top; 2- Lid; 3- Crucible.
Fig. 3 Crucible lid with hole (unit: mm)
Fig. 4 Coke button observation tube
V. Sample Preparation
Prepare air-dried coal sample with particle size below 0.2 mm according to GB 474. Prevent the coal sample from being ground too finely during preparation. Test as soon as possible after sample preparation; otherwise, seal and refrigerate, and the test period shall not exceed 3 days. Before weighing, fully mix the coal sample for at least 1 min.
VI. Preparation before Test
Power on the electric heating furnace, heat to about 850 ℃ and maintain constant temperature. Then open the furnace cover, place a cold empty crucible into the center of the quartz dish in the furnace chamber (start the stopwatch at the same time), quickly cover with the holed crucible lid, insert the hot junction of the thermocouple through the lid hole into the crucible, and press the hot junction tightly against the inner surface of the crucible bottom. Observe the temperature rise without covering the furnace lid. Adjust voltage, current, and furnace temperature. If the temperature at the bottom of the crucible can reach (800±10)℃ within 1.5 min after placing the cold crucible, and reach (820±5)℃ within 2.5 min, record the furnace temperature and current-voltage adjustment method, and control according to this method during the test. If the above requirements cannot be met, adjust the voltage, current, and furnace temperature, and repeat the test until the above requirements are met.
VII. Test Procedure
(1) Weigh (1.00±0.01)g of air-dried coal sample with particle size of 0.2mm, place it in the crucible and level the coal sample. Then, on a rubber plate with a thickness not less than 5mm, hold the crucible containing the coal sample with the five fingers of the hand facing downward, lift it to a height of about 15mm, then release it to fall freely. Drop it 12 times in this manner (rotate the crucible by an angle after each drop).
(2) When the furnace temperature reaches the predetermined temperature, use crucible tongs to open the furnace cover, place the crucible containing the coal sample into the center of the quartz dish in the furnace, immediately cover with the crucible lid without hole, and start the stopwatch at the same time. Wait until all volatile matter has escaped, the escape time shall not be less than 2.5 min. Then take out the crucible. Do not cover the electric furnace lid during this process.
(3) Perform 3 consecutive tests for each coal sample. After the 3 tests, carefully pour out the coke residue from the crucible, let it cool to room temperature, and then determine the coke type. If the range of the three determinations exceeds 1/2, add two more individual tests. If the range of the five determinations exceeds 1, check the instruments and equipment and perform five determinations again.
Note: During the interval between two tests, cover the electric heating furnace lid to allow the furnace temperature to return to the preset temperature as soon as possible.
(4) After the test, burn off the residues on the crucible and crucible lid, and wipe clean.
VIII. Expression and Reporting of Results
(1) Crucible Swelling Number of Coal Sample
The crucible swelling number of the coal sample is determined and expressed as follows:
a) Swelling number 0: Coke residue non-cohesive or powdery;
b) Swelling number 1/2: Coke residue sinters into a coke button without swelling. When placed on a flat hard plate and carefully loaded with 500g weight, it crumbles or breaks into more than 2 pieces;
c) Swelling number 1: Coke residue sinters into a coke button without swelling. After loading with 500g weight, it does not crumble or breaks into no more than 2 hard pieces;
d) Swelling number 11/2~9: Coke residue sinters into a coke button and swells. Place the coke button under the coke button observation tube, rotate it to find its maximum profile, then compare with a set of standard coke button profiles with sequence numbers (Fig. 5), and take the sequence number of the closest standard profile as the swelling number;
e) Swelling number greater than 9: Coke residue sinters into a coke button and swells. Place the coke button under the coke button observation tube, rotate it. If the maximum profile exceeds that of standard coke button profile 9 (Fig. 5), record as ">9" or "9".
(2) Reporting of Results
Take the arithmetic mean of three determination results for the same coal sample whose range is not greater than 1/2, round to 1/2 unit according to GB/T 483 and report. Digits after decimal point: 2 is rounded to 0, 3 is rounded to 5. If five determinations are performed, take the arithmetic mean of the five results, round to 1/2 unit and report. If the results are out of tolerance, repeat the experiment.
(3) Method Precision
The repeatability limit of the crucible swelling number of bituminous coal is: the range of three repeated determination results is not greater than 1/2; the range of five repeated determination results is not greater than 1. The critical difference for reproducibility is: the difference between the arithmetic means of repeated determinations performed by different laboratories on representative portions taken from the same coal sample at the final stage of sample reduction is not greater than 11/2. Sometimes no standard pattern close to the coke button profile can be found; the cut-and-fill method (cut-and-fill method: by visual observation, imagine comparing with standard coke button, cut off the protruding parts and fill them into the concave parts to obtain a complete coke button corresponding to the standard coke type pattern, thereby determining its swelling number) can be used to observe which standard coke type pattern the coke button is similar to.
Alternatively, the projection of the coke button can be sketched on millimeter graph paper, and then the area of the coke button projection (square millimeters) can be obtained from the graph paper, and the swelling number can be found from the projection area—crucible swelling number relationship curve. The swelling number can also be determined by a photoelectric projector.
Fig. 5 Standard coke button profile diagram and corresponding crucible swelling number
