Coal-water fuel production
The task of our experiment was to regrind the coal of 10–15 mm fraction to the coal dust of 0–300 µm, and to mix it with water and a plasticizer for obtaining a coal-water fuel (CWF). We carried out this experiment using AVS-150 vortex layer device.
The main principle in preparing a coal-water fuel is to ensure the coal grinding stability with specified parameters and the precise maintenance of concentrations of auxiliary substances which results in improved rheological properties and combustion stability.
In order to carry out the experiment, we took 600 g of coal, 400 mL of pretreated water, and polyphosphate as a plasticizer.
For visual clarity, the experiment was carried out not in the stream, but in the reactor. We measured the optimum characteristics of magnetic induction for this process using a multiteslameter.
At the first stage, we ground “dry” the coal of 10–15 mm fraction. Grinding lasted for 2 minutes through the use of ferromagnetic particles of 2 mm in diameter and 20 mm in length.
We checked the grinding result by means of testing sieves of 316 µm, 160 µm, and 50 µm. 96% of the sample passed through a 316 µm sieve after which we ran the sifted sample through a 160 µm sieve sifting out 60%, and through a 50 µm sieve where only 10% of the sample was sifted out.
At the second stage, we ground the coal of 10–15 mm fraction by wet milling with a coal-water mixture obtained at the same time. Grinding and mixing lasted for 2 minutes. The grinding results were checked by means of sieves after drying the sample. 98% of the sample passed through a 316 μm sieve, 86% of the sample passed through a 160 μm sieve, and 35% of the sample passed through a 50 μm sieve.
At the third stage, we mixed up the coal previously ground for 2 minutes. Mixing lasted for 30 seconds. The stability of obtained fuel had been checked for 5 days. As a result, the water and coal were slightly stratified; it is possible to maintain the CWF stability through periodic recirculation in storage tanks. In this case, using a plasticizer is not necessary. The results of sample grinding were checked by means of sieves after drying the sample. 98% of the sample passed through a 316 µm sieve, 90% of the sample passed through a 160 µm sieve, and 63% of the sample passed through a 50 µm sieve.
Based on the experiment results, the following conclusions can be drawn:
- the approximate capacity of AVS-150 device in the stream will be 3 m3/h;
- the power consumption will be 9 kW/h;
- as a result of thorough mixing in our device, it is not necessary that a plasticizer be added to CWF;
• the stream operation of the device can be continuous, because as the particles wear out, the additional loading thereof occurs automatically by means of a batcher.