What are the methods for determining total water in coal?

The moisture of coal directly affects the use, transportation and storage of coal. The increase of moisture in coal decreases the useful components in coal, and the moisture becomes steam to absorb heat during combustion, thus reducing the calorific value of coal. The increased moisture content of the coal also increased ineffective transportation and created difficulties for unloading.

It is characterized by cold areas in winter, and frozen cars often occur, which affects unloading, production, and wagon turnover, which aggravates the tension of transportation.

Let's take a look at the method of determining total water:

Method 1 (two-step method).

Method 1a: Drying in a stream of nitrogen.

A certain amount of coal sample with a particle size of <13mm is dried to a constant mass in an environment with a temperature not higher than 40, and then the coal sample is crushed to a particle size of <3mm, and dried to a constant mass in a nitrogen gas stream under (105 110). The total moisture is calculated based on the mass loss of the coal sample after two steps of drying.

B: Drying in an air stream.

A certain amount of coal sample with a particle size of <13mm is dried to a constant mass in an environment with a temperature not higher than 40, and then the coal sample is crushed to a particle size of <3mm, and dried to a constant mass in a nitrogen gas stream under (105 110). The total moisture is calculated based on the mass loss of the coal sample after two steps of drying.

Method 2 (one-step method).

Method 2a: Dry in a stream of nitrogen.

A certain amount of coal sample with a particle size of <6mm was weighed and dried in a nitrogen stream under (105 110) until the quality was constant. The total moisture is calculated based on the mass loss of the coal sample after drying.

B: Drying in an air stream.

A certain amount of coal samples with a particle size of < 13mm (or <6mm) are weighed, and the quality is constant after drying in the air stream under (105 110). The total moisture is calculated based on the mass loss of the coal sample after drying.

Method 3 (microwave drying method).

Weigh a certain amount of coal sample with a particle size of <6mm and place it in a microwave oven. Under the action of the alternating electric field of the microwave generator, the water molecules in the coal vibrate at high speed to produce frictional heat, which causes the water to evaporate rapidly. The total moisture is calculated based on the mass loss of the coal sample after drying.

1. The meaning of internal water, external water, and total water of coal 1. The intrinsic moisture of coal is the water adsorbed in the internal pores of coal particles. The internal moisture needs to be at a temperature of more than 100C for a certain amount of time to evaporate. 2. The external moisture of coal is the moisture attached to the surface of coal particles.

External moisture easily evaporates in dry air at room temperature, and when the water vapor pressure evaporating to the surface of the coal particles balances with the humidity of the air, it no longer evaporates. 3. The total moisture of coal is the sum of the external moisture and internal moisture of coal, and is an auxiliary index of coal according to ash addition. It must be pointed out that the external and internal moisture of the coal measured when the total moisture of the coal is tested in the laboratory is completely different from the external and internal moisture of the coal in different structural states mentioned above.

The external moisture measured in the laboratory refers to the moisture lost by the coal sample in the air and when the air humidity reaches equilibrium (this is the internal moisture adsorbed in the coal capillary pores, and the amount increases with the decrease of air humidity and the increase of temperature at that time), and the moisture remaining in the coal is the internal moisture. Obviously, the external and internal moisture tested in the laboratory are not only related to the external moisture and internal moisture in different structural states in the coal, but also to the humidity and temperature of the air that are tested. 2. Detection method 1, the water content determination method of coal and its proportioned raw materials on the belt without steel wire In the production process of briquette, the fuel value, volatility, moisture and adhesion of coal are the main factors affecting its quality.

Among them, the proportion of moisture is one of the important factors of its quality. Therefore, in the briquette production process, it is necessary to test the moisture of pulverized coal and coal particles at the inlet and outlet of the dryer. MS-580 Pulverized Coal Near-infrared Moisture Meter and MS-590 Pulverized Coal and Raw Coal Microwave Moisture Meter, specially tailored for briquette ratio moisture detection in briquette plants, especially suitable for measuring the moisture content of coal and its proportioned raw materials on the belt without steel wire.

2. In the silo, at the discharge port, and in the hopper, the analysis of pulverized coal quality includes: ash, moisture, calorific value and other important indicators. In order to eliminate the influence of moisture on the ash measurement results.

1% moisture is approximately equivalent to an ash determination deviation. Assuming that the moisture content of the coal is between 5% and 10%, the ash determination deviation caused by the change of moisture is . The combination of moisture and ash meter, because the microwave moisture meter measurement accuracy can reach, the ash measurement error caused by moisture is negligible, which can greatly improve the ash measurement accuracy.

MS-101 (102) series contact pulverized coal microwave moisture meter is specially tailored for the detection of briquette ratio moisture in briquette plants, especially suitable for moisture measurement of pulverized coal in the silo, discharge port and hopper.

Hello! The determination of the total moisture content in coal must be carried out with the help of instruments and equipment, otherwise it is impossible to determine the moisture. The digital blast drying oven can measure the total moisture content in the coal, and the microcomputer automatic moisture analyzer can also determine the total moisture content in the coal.

Moisture analyzer.

Digital blast drying oven.

I hope Hebi Huanuo Electronic Technology can help you!

Summary. According to the provisions of GBT211-200, we use three determination methods, 1:two-step method.

A1 nitrogen stream, A2 air stream drying 2: one-step method. B1 sighs in the air flow, B2 in the air flow in the dry 3:

The microwave oven drying method is suitable for all coal types in the nitrogen gas stream, bituminous coal and anthracite in the air stream, and the C method is suitable for lignite bituminous coal in the A1 arbitration method.

According to the provisions of GBT211-200, we use three determination methods, 1:two-step method. A1 nitrogen gas flow, A2 air flow in front of the big touch dry 2:

One-step method. B1 sigh flow, B2 air flow dry imitation rock drying 3: microwave oven drying method C nitrogen gas flow is suitable for all coal types, air flow is suitable for bituminous coal and anthracite, C method is suitable for brown Hui talk coal bituminous coal A1 arbitration method.

According to the regulations of GBT211-2007, we use three measurement methods, 1: two-step method. A1 nitrogen stream, A2 air stream in dry 2:

One-step rule pickpocketing. B1 sigh flow, B2 drying in air flow 3: microwave oven drying method C nitrogen signal flow is suitable for all coal types, air flow is suitable for bituminous coal and anthracite, C method is suitable for lignite bituminous coal where A1 arbitration method.

May I ask the teacher, when baking samples, can the bottle cap be removed, or not.

The process diagram of the method for determining water in coal is shown above.

Please ask the teacher, when baking, the bottle cap of the sample cannot be removed.

When baking, the cap of the sample bottle should not be removed.

The process diagram of the method for the determination of coal-friendly internal water is in the ** above.

Teacher, I am asking if the cap is open or the cap is on when baking?

The cap is open when baking, and the cap is closed after a period of baking, or the cap is half opened.

This is conducive to the dissipation of moisture, and the bottle should be quickly capped and placed in the dryer when taken out after drying.

The huge impact of moisture in coal on the utilization of coal is not good. The moisture in coal will absorb additional heat in the process of coal combustion, gasification and coking, reducing the thermal efficiency of coal. The moisture in the coal wastes transportation power during coal transportation; high moisture in coal, coal prices drop; The right amount of moisture in coal can reduce the generation of coal dust and reduce the loss of coal in transportation and storage.

Coal is a solid combustible mineral. Due to the different biomass deposition environments, the properties and composition of coal also vary. The water in coal can be divided into free water and chemical water according to the binding state. Therefore, it is essential to check the moisture content of coal.

Coal quality testing methods and procedures.

Step 1: Sampling Five-point sampling method.

Essentials, take five points diagonally, do not use the surface, and take a bucket of shovels at each point.

The coal samples taken should be as representative as possible and taken randomly. The coal sample is stirred evenly, sorted, and finally left about one kilogram as each sample to be tested, if there is a lump of coal, please select the crusher.

Step 2: Test for total hydration.

The first step of mined coal needs to be water, that is, the total water of the coal.

Required utensils: large weighing flask electronic balance drying oven test methods and formulas are as follows:

Open the drying oven first, raise the temperature to 145 degrees, weigh the weighing flask on the scale, and write down the tare weight. Then weigh out 10-12 grams of coal and write down the weight of the coal. Bake in the drying oven for 30 minutes, take it out, close the lid and let it cool, and weigh it on the balance. The formula is as follows:

Tare weight + coal weight - weight after baking.

The third step of coal weight: drying and sample preparation.

Fill a stainless steel plate with about 200 grams of coal samples and dry them in a drying oven at 145 degrees for about 30 minutes. After drying, it is ground in a sample maker to make a coal sample, and all of the following items are coal after sample preparation.

Step 4: Analyze water (also known as internal water) practices.

First, open the drying oven, raise the temperature to 145 degrees, weigh the tare weight of the small weighing flask on the balance and write it down; Then weigh out a coal sample of about 1 gram and write down the weight of the coal; Put it in a drying oven at 145 degrees to write down the time, dry it for 10 minutes, take it out, cover it with a lid and let it cool, weigh it on the balance and write down the total weight after drying. The calculation formula is as follows:

Tare weight + coal weight - weight after baking.

Coal weight step 5: ash.

First, raise the furnace to 850 degrees, and the program control operates according to the instructions. Weigh the weight on the balance and write down the tare weight. Then weigh out the coal sample of about gram and write down the weight of the coal.

Open the door of the high-temperature furnace, slowly push the weighed coal sample into the furnace, and burn for no less than 40 minutes. Point 1: The pushing process should be slow, and the coal should not be deflagrated. Point 2: The burning time should be sufficient.

The formula is as follows: Burnt weight - tare weight.

The sixth step of coal weight: volatile matter.

First, raise the furnace to 900 degrees, and program control the operation according to the instructions. Weigh the crucible on the scale and note the tare weight. Then weigh out a coal sample of about 1 gram and write down the weight of the coal;

Open the furnace door and quickly place the weighed coals into the furnace. Look at the watch, take it out after 7 minutes, let it cool, and weigh out the burned.

Tare weight + coal weight - weight after burning.

- 100% - Analyze water.

Calculation formula for coal weight fixed carbon:

Fixed carbon = 100 - (analytical water + ash + volatile) expressed in units

The moisture in coal generally refers to the total moisture MT, which is composed of surface moisture MF and internal moisture Minh. Intrinsic moisture, also known as intrinsic moisture minh, is the moisture in the plants that produce coal and the water entering the coal generation process, which cannot be removed by natural air-drying and must be removed by heating. Its content is stable for a certain type of coal.

Surface moisture enters during mining, storage and transportation, also known as external moisture, which can be removed by natural air drying. The content of surface moisture is greatly affected by natural conditions, so its value varies greatly.

The moisture in coal can be divided into free water and chemical water according to the binding state of the preparation group. Free water is the water that is mechanically combined by adsorption and wetting on the surface of the coal and adsorbed and condensed in the internal pores of the coal; Synthetic water is the water that is still retained after removing the total water that is bound to minerals in coal, also known as crystalline water. According to the different structural states of coal, the moisture in coal is often further divided into external moisture and internal moisture in the analysis and study of coal quality, and the sum of the two is total moisture (m). The decomposition temperature of the combined water (crystal water) combined with the minerals in the coal is high, usually above 2000C, and it is generally not measured.

The moisture content of the coal determined by the industrial analysis of the coal is the moisture (MAD) of the air-dried coal sampleIt is to air dry a certain number of coal samples in advance to make air-dried coal samples for laboratory use, and bake them at a temperature of 102 105 to the weight of the constant imitation stove to achieve complete drying. Then, based on the mass lost by the coal sample, the moisture of the coal is calculated.

That is, the moisture of the air-dried coal sample (in the past, the symbols used successively were wa and wf).The moisture of air-dried coal samples is related to coal quality, which decreases with the increase of metamorphism, but increases slightly in the anthracite stage. Similarly, when coal is weathered, the moisture is increased.

Coal moisture analyzer: Guanya moisture meter.

The femtosecond detection is determined according to GB T211-2007, and the moisture in coal can be divided into free water and chemical water according to its existence state. 1Method a applies only to bituminous and anthracite and serves as an arbitration method for determining the total moisture of bituminous and anthracite. Weigh 500 grams of coal sample (up to 1 gram) in a dry, clean shallow pan of known weight, and spread the coal sample evenly in the pan.

Put the shallow tray containing the coal sample into the pre-blast (start the blast 3-5 minutes before putting the plate of the weighed coal sample into the drying oven) and heat it to 105-110 C in the drying oven, and dry the bituminous coal for an hour and the anthracite for 3-hour under the condition of continuous blasting. Remove the shallow tray from the drying oven and weigh while hot. Inspections are then carried out for half an hour each until the reduction of the coal sample does not exceed 1 gram or the weight increases.

In the latter case, the primary weight before the weight gain should be used as the basis for calculation.

2 Method B applies to lignite, bituminous coal and anthracite and serves as an arbitration method for total moisture in lignite. Weigh 500 grams of coal sample (up to 1 gram) in a dry, clean shallow pan of known weight, and spread the coal sample evenly in the pan. Put the shallow tray containing the coal sample into the pre-blast (3-5 minutes before the plate of the weighed coal sample is put into the drying oven to start the blast) and heat it to a drying oven of 150-160 C, and dry the bituminous coal for 1 hour, the anthracite for 1 hour, and the lignite for 1 hour under the condition of continuous blasting.

Remove the shallow tray from the drying oven and weigh while hot. Inspections are then carried out for 15 minutes each until the reduction of the coal sample does not exceed 1 gram or the weight increases. In the latter case, the primary weight before the weight gain should be used as the basis for calculation.