RU2277120C1 - Method of production of the water-method fuel and its composition - Google Patents

Abstract

FIELD: power industry; methods of production of the water-method fuel.

SUBSTANCE: the invention is pertaining to the field of the power industry, in particular, to development the composition and the method of production of the highly-concentrated water-coal fuel(WCF) derived from the coal slimes and intended for the mixture pumping-over or transportation by the hydraulic transportation means (coal-pipelines, rail tank cars, road tank cars) for the long distances. The water-coal slurry of 15-60 % concentration is stirred for 1-2 minutes, then add the black oil in the amount of 14-15 % of the coal mass and again it is stirred for 5-8 minutes with rate of n=1000-1500 rpm. At that the coal-black oil granules (CBOG) are formed with the coal ash value - A^d = 4.8-5.6 % and sulfur content value S^d = 0.2-0.3 %. Extraction of the coal from the slime makes 80-85 %. The waste rock remains in the water phase with the ash value of 78-84.5 %. The produced coal-black oil granules of 2-3 mm size are separated by the screen with the meshes size of 0.5 mm from the water and the waste rock. Then the granules are fed into the ball mill, where the water and the reactant-stabilizer are fed to. In the capacity of the reactant-stabilizer use the sodium humate stain amount of 1-2 mass % of the coal-black oil granules. The wet milling is exercised within 20-25 minutes till production of particles of the size less than 0.25 mm. The gained slurry from the milling device is fed into the bolter-classifier with the meshes of 0.25 mm. The production of the granules with the size less than 0.25 mm compounds 90.1 - 99.91 %. The water-coal fuel contains 60-64 % of the coal-black oil granules, 0.6-1.28 % - of sodium humate and the rest - water. Stability of the produced WCF is maintained within 30-40 days at the viscosity of 0.6-0.8 Pas.

EFFECT: the invention ensures, that stability of the produced water-coal fuel is maintained for 30-40 days at its viscosity of less than 1 Pas.

2 cl, 13 ex, 2 tbl

Description

The invention relates to the energy industry, and in particular to the production of time-stable water-coal fuel (HLF) in the form of a suspension supplied by means of hydraulic transport for combustion in boiler plants and other heat-generating systems operating on liquid fuel.

The known method [A.S. USSR No. 1151770 of 04.23.85, class F 23 K 1/02] preparing low-reaction coal for burning by grinding it in a mill with simultaneous treatment with an apolar reagent and mixing with water; separation of a large fraction on a sieve; heat treatment to partially remove the apolar reagent from the granules; with the addition of a plasticizer for the stability of a water-coal suspension (WCS).

The disadvantage of this method is the complexity of the process, multi-stage and the use of expensive reagents (plasticizers).

Also known is a method of preparing coal oil granules for burning in a furnace [A.S. USSR No. 1537964 from 01/23/90, class F 23 K 1/02], which consists in adding an apolar reagent to a high-ash WCS with the formation and dehydration of highly concentrated granules, with further mixing of the obtained granules with the original WCS in a turbine granulator, as a result of which the granules are destroyed to the required size, and the resulting slurry is fed to the combustion in the furnace.

The disadvantage of this method is the low stability of the WCS in time, which does not allow pumping it by hydrotransport over long distances.

The closest to the achieved effect is the prototype [Russian Patent No. 1489170 of 02.27.99, class C 10 L 1/32], which describes the composition and method of producing a water-carbon suspension used for transportation through a pipeline consisting of (in wt.%) coal - 58-60; humate - 0.5-0.7 and water up to 100.

To prepare a water-coal suspension, crushed coal (with an ash content of 15.8%) of the optimal particle size distribution, obtained by mixing in a 1: 1 ratio of two particle sizes of 0.2-0.1 mm and less than 0.04 mm, is used. To obtain a 60% water-carbon suspension, 0.21 g of humic acid was dissolved in 13.6 g of a 0.1 N NaOH solution, then 0.21 g of amine was added and mixed thoroughly. To the resulting solution was added 21 g of coal with an optimal particle size distribution and stirred for 30 minutes at a speed of 1500 rpm. The obtained WCS has a viscosity of 0.231-0.541 Pa · s and is resistant to delamination within 25-30 days. As an amine, tetraethylammonium hydroxide, urea, thiourea are used.

The disadvantages of the prototype is:

1. High ash content of the finished WCS (A ^d = 15.8 wt.%).

2. High sulfur content (S ^d = 0.67 wt.%).

3. Use as stabilizers of expensive chemicals (in particular, amino humic acids).

4. The relatively low stability of the obtained WCS (20-25 days).

5. The concentration of coal in the WCS 58-60 wt.%.

6. Preliminary grinding of coal and sieving to the optimum particle size distribution obtained by mixing in a ratio of 1: 1 two classes of fineness of 0.2-0.1 mm and less than 0.04 mm, which is obtained by ultrafine grinding in a vibration eraser.

7. The relatively low heat of combustion of the WCS.

Around the coal-mining and coal-processing enterprises in hydraulic dumps, external sedimentation tanks and sludge collectors, a large amount of coal is accumulated, presented in the form of fine coal high-ash sludges. Utilization of coal sludge will simultaneously solve two problems, on the one hand, to increase the yield of commercial coal and obtain clean recycled water, and, on the other hand, to carry out environmental measures, i.e. eliminate sludge collectors and hydraulic dumps. In addition, high-ash coal sludge is not suitable for direct use in the technology of VUT.

The task is to develop a composition and method for producing highly concentrated low-ash fuel, designed for pumping or transportation by hydrotransport (coal pipes, railway tanks, tank trucks) over long distances over 100 km.

For coal-fired fuel pumped through a pipeline or transported over long distances in road and rail tanks, certain requirements are imposed:

1. Coal particles should not be more than 0.3 mm, since during transportation they are precipitated by gravity, which leads to blockage of the pipes.

2. The resulting suspension should be stable for at least 30 days.

3. The viscosity of the suspension should be not more than 0.8 Pa · s when pumping through the pipeline and not more than 1.6 Pa · s when transported by road and rail.

4. The suspension should be highly concentrated 55 <C _m <75 wt.%.

5. VUT should be low ash, as this:

- increases the calorific value of the fuel-efficient compound;

- reduces harmful emissions into the atmosphere;

- reduces ash and sludge removal;

- reduces wear and increases the service life of boilers.

The problem is achieved in that the coal-water suspension from hydraulic dumps with ash content A ^d = 14.5-20% (wt.), Sulfur content S ^d = 0.58-0.6% (wt.), Solid phase concentration of 15-60% ( wt.) and a particle size of coal sludge of less than 1 mm is subjected to enrichment by oil sintering to separate waste rock.

A coal-water suspension with a coal concentration of 15-60% (wt.) Is mixed for 1-2 minutes, then fuel oil is added in an amount of 14-15% (wt.) Of the mass of coal and again mixed for 5-8 minutes at a speed of n = 1000- 1500 rpm In this case, coal-oil granules (UMG) are formed with ash content A ^d = 4.8-5.6% and sulfur content S ^d = 0.2-0.3%. The extraction of coal from sludge is 80-85%. The waste rock with an ash content of 78-84.5% remains in the aqueous phase. The resulting coal-oil granules 2-3 mm in size are separated on a sieve with cells of 0.5 mm from water and gangue. Then the granules enter a ball mill, where water and a stabilizing reagent are supplied, i.e. carry out wet grinding, which is an explosion, fireproof and environmentally sound process.

As a stabilizing reagent, sodium humate is used in an amount of 1-2% by weight of coal-oil granules. Wet grinding is carried out for 20-25 minutes to obtain particles less than 0.25 mm in size.

The resulting suspension from the mill enters a sieve-classifier with 0.25 mm cells. The output of granules less than 0.25 mm is 90.1-99.91%. The sublattice product is hydrofuel ready for hydrotransport, containing% (wt.):

coal-oil granules 60-64 sodium humate 0.6-1.28 water rest

The stability of the obtained HFL is maintained for 30–40 days at a viscosity of 0.6–0.8 Pa · s.

At the stage of enrichment of high-ash coal sludge, the optimal time for mixing the suspension with fuel oil is 5-8 minutes. Stirring for less than 5 minutes leads to a reduction in coal recovery from sludge to 79%, an increase in sulfur content in coal to 0.33% and, accordingly, a reduction in ash content of waste to 75%. This is because the apolar liquid (fuel oil) does not have time to completely wet the surface of the coal particles. An increase in the mixing time of more than 8 minutes does not lead to an increase in the degree of extraction and ash content of the waste, therefore it is impractical to carry out mixing for a longer time, since additional energy is consumed.

The mixing speed of the suspension is 1000-1500 rpm With an increase in the number of revolutions of more than 1500 rpm, especially at low concentrations of the suspension, granules break up to sizes of 1-2 mm. A decrease in the number of revolutions of less than 1000 rpm contributes to an increase in the size of coal-oil granules to 3-4 mm, which is undesirable, since they must still be crushed to sizes less than 0.25 mm in the second stage of preparation of water-coal fuel.

An increase in the concentration of coal in suspension over 60% (wt.) Leads to an increase in viscosity, and the system acquires a pasty state, which is difficult to mix. As a result, the ash content, sulfur content and granule size increase, and the degree of extraction decreases. It is economically unprofitable to carry out the process of enrichment of the suspension with a concentration of less than 15% (wt.), Since the suspension is low concentrated, moreover, the waste water-carbon suspensions after flotation and by-products of dehydration contain solid particles of at least 15% (wt.).

The optimal consumption of fuel oil per unit mass of coal is 14-15% (wt.). This limit is due to the ash content of the original sludge. The higher the ash content, the less pure coal in the sludge, the less fuel oil is needed to oil the particles of coal. And vice versa, the lower the ash content of the sludge, the more pure coal, and accordingly, the consumption of fuel oil increases. If fuel oil is taken to be less than 14% by weight of coal, the surface of the coal particles is not completely oiled with fuel oil, and the extraction of coal from sludge is reduced to 74% (wt.). An increase in fuel oil consumption per unit mass of coal over 15% (wt.) Leads to an excess of fuel oil, which contributes to the coalescence of small granules into large conglomerates, and part of the fuel oil remains in the aquatic environment, polluting it.

The addition of a stabilizer - sodium humate in an amount of 1-2% (wt.) By weight of coal-oil granules is due to the fact that at this flow rate, coal-water fuel has better stability. With a decrease in sodium humate to 0.75% (wt.) By weight of the UMG, the stability of the VUT is 24 days at a viscosity of 1.0 Pa · s and the content of particles less than 0.25 mm is 79%. An increase in the consumption of sodium humate to 2.5% (wt.) By weight of UMG does not lead to better results (stability - 40 days, viscosity - 0.7 Pa · s), while the consumption of sodium humate additionally increases.

The optimal concentration of UMG in the finished water-coal fuel is 60-64% (wt.). The decrease in concentration is impractical, since when transporting fuel by hydrotransport, it is economically feasible to increase the coal content in the suspension. An increase in the concentration of UMG in water to 65% (wt.) Leads to an increase in the viscosity of the resulting fuel to 1.25 Pa · s, which complicates the transportation of fuel through the pipeline.

The optimal grinding time of coal-oil granules in a ball mill is 20-25 minutes. Reducing the time to 18 minutes leads to insufficient grinding of the granules, and the yield of particles less than 0.25 mm is only 79%, which subsequently leads to the deposition of large particles in the pipeline under the influence of gravity. An increase in grinding time to 27 minutes does not lead to an increase in the yield of particles less than 0.25 mm in size.

EXAMPLE 1

Take 1 kg of the initial water-coal suspension with a concentration of 15% (wt.), Ash A ^d = 14.5% and sulfur content A ^d = 0.58% and mix for 1-2 minutes. Then add 15% (wt.) Fuel oil by weight of coal and mix for 5-8 minutes at a speed of n = 1000 rpm. In this case, coal-oil granules 2-3 mm in size are formed, which are separated on a sieve. The ash content of UMG is 4.8%. The ash content of the waste is 84.5%.

The resulting coal-oil granules are fed into a ball mill, where water is added at the rate of obtaining a 60% suspension and sodium humate in an amount of 1% (wt.) By weight of the granules. In a ball mill for 20 minutes the granules are crushed to a size of 0.25 mm and get a coal-water fuel with a viscosity of 0.6 Pa · s, stable for 30 days. After 30 days, VUT begins to lose its stability. If this suspension is again intensively mixed, then it will again remain stable for 30 days, i.e. this system is thixotropic and has a "jelly memory".

Examples of the limiting and transcendental values for the coal enrichment stage are summarized in Table 1, for the stage of production of coal-grade coal, are presented in Table 2.

The method of producing water-coal fuel and its composition

The method of producing water-coal fuel and its composition

Claims (2)

1. A method of producing a stable coal-water fuel, including stabilization of a coal-water suspension, characterized in that the water-coal suspension with a concentration of 15-60 wt.% Is mixed for 1-2 minutes, then fuel oil is added in an amount of 14-15% by weight of coal and again mixed in for 5-8 minutes at a speed of 1000-1500 rpm, the resulting coal-oil granules 2-3 mm in size are separated on a sieve from water and waste rock and ground by a wet method in a ball mill with the addition of sodium humate in an amount of 1-2 wt.% in relation to coal-oil granules in those reading 20-25 minutes 2. Hydrocarbon fuel containing coal, humate and water, characterized in that pre-enriched coal sludge is used as coal, sodium humate is used as humate in the following ratio of components, wt.%: Coal pellets 60-64 Humate sodium 0.6-1.28 Water Rest