RU2026741C1 - Method for coal preparation for hydrotransportation - Google Patents

Abstract

FIELD: hydrotransportation. SUBSTANCE: method for coal preparation for hydrotransportation includes grinding of 50-100% of starting material by coarse grinding mill, then, produced material together with remaining required material is directed to pulverizing mill. EFFECT: higher efficiency due to reduced power intensity of final product preparation. 1 dwg, 1 tbl

Description

 The invention relates to methods for preparing coal for hydrotransport and direct burning, used in the coal industry and heat power engineering.

 A known method of preparing coal for hydrotransportation, implemented on a pilot industrial coal pipeline Belovo - Novosibirsk under a contract with the Italian company Snamprogetti [1].

According to this method, 30-35% of the original coal cl. 0-3 (6) mm is fed to a ball mill (fine grinding). At the same time, water and a plasticizer reagent are supplied to the mill. Grinding in a ball mill is carried out with a mass fraction of solid 38-50% to a particle size of 0-40 microns (d _cf = 6-15 microns). The resulting water-coal suspension together with the rest (65-70%) of the 0-3 (6) mm source coal is fed to a core mill (coarse grinding). To obtain the necessary mass fraction of solid, water is added to the mill. The result is a highly concentrated water-coal suspension (VVUS), which, after active mixing, is sent to storage tanks and then transported by main pumps through a pipeline and fed to direct combustion in boiler units.

 The closest technical solution is the method of preparing coal for hydrotransport, by which the source coal is fed only to the coarse mill, and 32-35% of the finished product from the coarse mill is fed to the fine mill [2].

The disadvantages of these methods are their low productivity, high energy intensity and, as a consequence, the high cost of the finished product. These shortcomings are due to:
- high energy costs (120-190 kWh / t) for grinding coal in a fine grinding mill;
- intense vaporization in a fine grinding mill, requiring the installation of additional equipment for collecting and disposing of the gas mixture;
- high consumption of grinding media in a fine grinding mill (up to 2.3 kg / t);
- frequent shutdown of technological equipment for reloading the grinding medium;
- low efficiency of use of the reagent - plasticizer due to the high temperature in the mills.

 The purpose of the invention is to eliminate these disadvantages, namely increasing the productivity of the process of preparing a suspension, reducing the energy intensity of the process, reducing the cost of the finished product.

 This goal is achieved by the fact that grinding in a coarse mill with a mass fraction of solid 50-60% is subjected to 50-100% of the starting material, after which the resulting product, together with the remaining necessary amount of starting material, is sent to the fine grinding mill.

 The amount of the remaining source coal supplied to the fine grinding mill is calculated as follows.

=

+

+Q_В
Откуда при Q^l _т=50+100% Q_т получим
Q

=

Q

-

-Q

где Q^ll _т - подача сухого угля в мельницу тонкого помола;
W - влажность угля, мас.%;
Q_т - суммарная подача угля в мельницы;
C_т - массовая доля твердого в готовой суспензии, %;
С^l _т - массовая доля твердого в суспензии после мельницы грубого помола, %;
Q_в - подача воды в мельницу тонкого помола.According to the equation of material balance can be written

=

+

+ Q _B
Whence at Q ^l _t = 50 + 100% Q _t we get
Q

=

Q

-

-Q

where Q ^ll _t - the supply of dry coal to the mill fine grinding;
W is the moisture content of coal, wt.%;
Q _t - total supply of coal to the mills;
C _t - mass fraction of solid in the finished suspension,%;
With ^l _t - mass fraction of solid in suspension after the coarse mill,%;
Q _in - water supply to the mill fine grinding.

 Feed coal source cl. 0-3 (6) mm in a coarse grinding mill (core mill) allows for wet grinding to a minimum of energy consumption to class. 0-0.8 (1) mm with a mass fraction of solid 50-60%. The specific energy consumption is 10-15 kWh / t. The resulting suspension has good fluidity and is easily pumped in any way. This product can be sent for grading 0.8 or 1.0 mm. The under-sieve product is returned to the coarse mill, and the under-sieve product is pumped or by gravity enters the fine mill. The rest of the coal is also fed to the fine grinding mill. 0-3 (6) mm, the reagent is a plasticizer and, if necessary, achieve a given mass fraction of solid - water.

As a result of grinding and mixing, the finished VVUS comes out of the mill, the granulometric composition of coal and the rheological characteristics of which correspond to the required ones. At the same time, energy consumption is 2-3 times lower, and therefore, the process productivity is 2-3 times higher than the corresponding indicators of the compared technologies. During the grinding process in both mills, the temperature regime does not rise above 40-45 ^о С, which helps to preserve the properties of the reagent - plasticizer, does not cause vaporization.

 The drawing shows a flow chart that implements the proposed method.

 Pre-crushed to cl. 0-3 (6) mm of coal is loaded into the storage hopper 1, from which by a feeder 2 and a batcher 50-100% of the coal is fed into the coarse mill 3. Technical water is also supplied to the mill to obtain the necessary mass fraction of solid 50-60% in the suspension exiting the mill. The resulting suspension of cl. 0-0.8 (1) mm by gravity merges into sump 4, from which it is sent by pump 5 to classifier 6.

 The sieve of the classification is returned to the coarse mill, and the sieve enters the mill 7 fine grinding. It is possible to directly feed the suspension from the coarse mill to the fine mill (indicated by a dotted line).

 0-50% of the initial coal of cl. (0-3) (6) mm, the reagent is a plasticizer and, if necessary, achieve the desired value of the mass fraction of solid in the finished explosive, water. The finished VVUS with a mass fraction of solid 59-65% and a particle size of 0-350 (500) microns of coal from a fine grinding mill is discharged into a sump 8, from which it is pumped for homogenization 10 by a pump 9 and then to a storage tank. From the storage tank, the finished VVUS with main pumps is fed into the pipeline.

According to the proposed method with the energy cost 2-3 times lower than in the known processes, is obtained with VVUS necessary rheological properties (apparent viscosity at a shear rate of 10 s - 1 and temperature of 20 ^{° C} does not exceed 1500 mPa˙s and suspension stability than 30 days This is achieved by the fact that wet grinding in mills of coarse and fine grinding is carried out in optimal conditions, provided by supplying the appropriate quantities of initial coal and suspension of the required size. it is confirmed by the following examples of the inventive method (see. Table).

 As can be seen from the results obtained, upon preliminary grinding in the mill of coarse grinding (core) 50-100% of the initial coal and subsequent grinding of the obtained water-coal suspension in the mill of fine grinding (ball), a highly concentrated suspension is obtained, the rheological properties of which (effective viscosity) correspond to the design parameters ( viscosity does not exceed 1500 mPa˙s.). At the same time, increasing the initial coal content in the ball mill feed to 55% increases the viscosity of the finished product to 1699 mPa˙s.

 A comparison of the obtained results with the basic options shows that the use of the proposed method while maintaining the rheological characteristics of the suspension provides a reduction in the energy intensity of the preparation of VVUS by 2–3 times, an increase in productivity by 2 times, and an increase in the solid mass fraction.

Claims (1)

 METHOD FOR COAL PREPARATION FOR HYDROTRANSPORT, including grinding it in coarse and fine grinding mills, characterized in that, in order to increase productivity and reduce the energy consumption of obtaining the finished product, 50-100% of the starting material is subjected to grinding in the coarse grinding mill, after which the resulting product together with the remaining necessary amount of starting material is sent to a fine grinding mill.

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