RU2743951C1 - Method for anti-freezing of wet iron ore concentrate - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to prophylactic agents for preventing freezing of bulk materials, their adhesion and freezing to the walls of vehicles in winter, in particular when unloading wet iron ore concentrate from railway cars. The method includes mixing wet iron ore concentrate of wet magnetic separation with antifreeze additive, wherein a polymer liquid and / or dry reagent in the form of water-soluble surfactants based on sodium formate and pentaerythritol is used as an antifreeze additive. Polymer antifreeze additive is mixed with wet iron ore concentrate in the amount of 2.5-12.0 kg / t of wet concentrate when it is loaded into wagons or when stored in a stack. At the same time, when using a liquid reagent, the consumption of the polymeric antifreeze additive is 2.5-12.0 kg / ton of wet concentrate, and when using a dry reagent, the consumption of the polymer antifreeze additive is 2.5-8.0 kg / ton of wet concentrate.EFFECT: creation of conditions allowing loading, transportation and unloading of wet iron ore concentrate in winter, while maintaining the physical and chemical properties of the concentrate.1 cl, 2 tbl, 3 ex

Description

The invention relates to prophylactic agents for preventing freezing of bulk materials, their adhesion and freezing to the walls of vehicles in winter, in particular when unloading wet iron ore concentrate from railway cars of Russian Railways.

It is known that processing plants widely use processes carried out in aqueous media (concentration in heavy suspensions, flotation, wet magnetic separation, etc.), during which a significant amount of ballast - water gets into the iron ore concentrate.

Therefore, the final operations in the beneficiation processes are mechanical and thermal dehydration of the beneficiation products, primarily iron ore concentrates. It is known that wet iron ore concentrate is very problematic when unloading it from railway cars in winter.

To remove moisture from iron ore concentrate, there are known methods for drying sinter concentrate in rotating drums, including feeding the concentrate into a rotating bed through a uniform stream of hot gases. (AS No. 1179073, CL F27B 7/36, 1984).

Also known is a method of operating a drum-type furnace for drying fine concentrate, in which the air-fuel mixture is fed for combustion with an excess air ratio of 0.60-0.95. (Inventory certificate No. 1679162, class F27B 7/36, publ. 09.23.91, bull. No. 35).

The main and common disadvantage of all known methods of drying concentrates is the need to build bulky and expensive drum-type drying plants.

In the absence of drying plants, both the supplier and the consumer of the MMS concentrate face great difficulties with the delivery and unloading of this product from railway cars in winter.

There is a known method of unloading dead coal from a car, in which, before loading, the inner walls of the car are covered with a layer of wetted snow. Then the car is exposed to low temperatures until the snow is completely frozen, which facilitates the unloading of the unloading of coal and reduces its time. In the process of unloading the car by overturning, the low-strength snow layer is easily destroyed and the car is completely emptied. (P-2137698, B65G 69/20, publ. 09/20/1999).

A similar solution is proposed in A.S. No. 86215, publ. in bul. No. 10, 1950. It is proposed to freeze a layer of ice on the walls of the vehicle, which allows you to safely unload bulk material.

In A.S. No. 1527113, B65G 67/04, 69/20, publ. 12/07/1989, bul. No. 45, it is proposed to apply a layer of molten nitrogen fertilizers, such as ammonium nitrate or urea, to the surface of the vehicle body, after which bulk material is loaded. In this case, moisture is absorbed by nitrogen fertilizer and an anti-freeze layer is formed, which separates the bulk material from the walls of the body.

However, the known technical solutions can be used when loading and unloading single wagons in small volumes of transported bulk material.

When loading an entire railroad train of Russian Railways (40-50 wagons and more), these technological solutions are definitely not acceptable. In addition, the known proposals only partially solve this problem. By creating a layer on the sides and bottom of the vehicle, the issue of free-flowing material in the total volume of a loaded wagon or other vehicle is not completely resolved. When unloading the submerged bulk material, large bottles (large monolithic pieces) are often formed, which have to be broken by various means.

It is known to use a prophylactic agent to prevent the freezing of wet rocks, their adhesion to the walls of the rolling stock. A prophylactic agent is a mixture of a solvent and a petroleum based thickening agent. Vat residues of by-product coke production and / or by-products of production of butadiene, isoprene, ethylene are used as a solvent. Mineral and synthetic oils of all types are used as a thickening additive.

A prophylactic agent in the form of an easily movable oily liquid is applied to the processed bulk material, while a thin film is formed on its surface, which prevents freezing of the material (P-2272061, S09K 3 / 18.3 / 22, publ. 03/20/2006, bull. No. 8 ). In this invention, the components of the production waste of various products of oil refining and petrochemicals are used.

In RF patents 2111228, 2132350, 2155201, a prophylactic agent is obtained on the basis of such refined products as kerosene-gas oil fractions of catholic and thermal cracking and tar.

The main disadvantage of these technical solutions is the limited resources of petroleum raw materials and the shortage of components included in the prophylactic agent, as well as an insufficiently low pour point.

As the closest analogue, the method of drying finely ground iron ore concentrate was taken (P-2425155, class C22 V 1/00, publ. 07/27/2011, bull. No. 21).

The method of drying finely ground iron ore concentrate includes mixing a moist concentrate with a moisture content of 8-12% with quicklime with a particle size of up to 10 mm in a drum or rotary mixer. Quicklime is fed into the mixer in the amount of 40-70 kg / t of wetted concentrate. The resulting mixture is subsequently dried in wagons during transportation or in a stack during storage until a moisture content of 2.8% is achieved when 65 kg / t of moist concentrate is fed into the mixer, 3.0% - when lime is supplied 50% of a moist concentrate, 3.5% - when feeding 40 kg / t of wetted concentrate. The size of particles of class 0-0.074 mm in the wetted concentrate is not less than 70%.

However, the liming of the concentrate is not satisfactory to all consumers, therefore, reducing the moisture content of the concentrate remains a very important point for both the supplier and the consumer of raw materials.

The technical result of the proposed invention is to create conditions that allow loading, transportation and unloading of iron ore concentrate MMS in winter while maintaining the physical and chemical properties of the concentrate.

The technical result is achieved by using a polymeric antifreeze additive. As an antifreeze additive, a polymeric liquid and / or dry reagent is used in the form of water-soluble surfactants based on sodium formate and pentaerythritol, while the polymeric antifreeze additive is mixed with the MMC concentrate in an amount of 2.5-12.0 kg / t of wet concentrate at loading into wagons or stacking, and when using a liquid reagent, the consumption of polymer antifreeze additive is 2.5-12.0 kg / t of wet MMC concentrate, and when using a dry reagent, the consumption of polymer antifreeze additive is 2.5-8.0 kg / t wet concentrate.

The option of mixed use of liquid and dry reagents is also possible.

It is known that the MMC concentrate has a developed surface (specific surface up to 5500 cm ² / g) and contains a lot of intragranular moisture, for example, after filtration, the concentrate has a moisture content of 7.0 to 10%.

This concentrate is not suitable for transportation and bunkering in winter.

In the patented invention, the applicant proposes to use a polymeric antifreeze additive based on the components sodium formate and technical pentaerythritol to prevent freezing of wet iron ore concentrate. Polymer antifreeze additive is made in the form of liquid and dry reagents.

In order to trace the effect of the polymer antifreeze additive on the quality of the iron ore concentrate, let us consider the physicochemical parameters and the structure of the reagent produced by Polyplast UralSib LLC.

Polymer antifreeze additive or Polyplast reagent - products of low hazard in terms of impact on the human body (4 hazard classes) in terms of toxicometry parameters - are manufactured in accordance with TU 5745-054-58042865-2010.

The polymer antifreeze additive is available as a dark brown aqueous solution or as a brown powder.

In terms of physical and chemical indicators and consumer properties, the polymeric antifreeze additive must comply with the requirements and standards given in table 1.

Polyplast's reagent is a water-soluble surfactant containing a mixture of sodium and pentaerythritol format.

Polyplast's reagent is a very low-toxic substance, does not form toxic compounds in the air and wastewater.

Surfactant molecules (surfactant) are oriented in the surface layer at the interface (aqueous solution - air - charge particle) in such a way that the polar group, which has a high affinity for the polar phase (water), is drawn into it, while the non-polar the radical is pushed out into the non-polar phase (air).

As a result of a certain orientation of surfactant molecules, the free surface energy decreases, due to the formation of a monomolecular adsorption layer, which creates a force field for the attraction of neighboring particles. In this case, hydrophobic particles, previously not participating in the process, in the presence of surfactants can increase in size and serve as stable nucleation centers for small particles, or be located on the surface of already formed granules of hydrophilic particles.

Surfactant molecules dissolved in water, under the action of excess pressure, move from convex surfaces to concave or flat ones and fill the pores, thereby contributing to the manifestation of the pulling force between the particles and the formation of adhesive contacts.

The presence of sodium formate and pentaerythritol in surfactant macromolecules improves their adhesion to the hydrophilic surface of iron ore concentrate particles.

Taking into account the expected positive effect of the polymer antifreeze additive on the freezing capacity of the MMS concentrate when using reagents manufactured by Polyplast UralSib LLC, the applicant conducted tests in laboratory and industrial conditions. First, laboratory tests were carried out on the use of a polymeric antifreeze additive, and the results were compared with the basic technology and the use of quicklime (prototype).

For testing, OJSC VGOK purchased 20 tons of reagent (dry and liquid) produced by Polyplast, the characteristics of which were given above. To supply the dry reagent to the MMC concentrate, a charge bunker with a capacity of 2 m ³ was allocated, in which a polymer antifreeze additive was placed. The unloading of the additive from the hopper was carried out by two axleless conveyors with screw conveyors, the drive of which had an adjustable rotation speed. Polymer antifreeze additive from under the hopper was poured onto the collecting conveyor, where it was mixed with the MMC concentrate.

When testing the method proposed for patenting, the applicant conducted laboratory experiments on a sample of concentrate of about 2 tons.

Several variants of reagents were tested: liquid - №131, 50; dry - No. 51; without reagents and according to the prototype.

Test samples and control samples were prepared from the MMC concentrate, while the samples and samples were kept outdoors at an average temperature of 10 ° C for 24 hours.

Then all samples after freezing are kept at a temperature of + 17 ° С for 75-85 minutes. (the conditions of holding the cars in the defrosting garages before unloading the MMS concentrate were simulated).

The diameter of the base of the sample was 120 mm, the height was 112 mm, the moisture content of the concentrate was 7.62%, and the sample volume was 100 ml.

The samples were subjected to a control load until complete destruction. Each of the options was duplicated, the average test results are shown in table. # 2.

Thanks to the experimental studies of the proposed technical solution, the applicant determined the optimal standard costs of the polymer antifreeze additive. The best results were obtained: for the liquid reagent, the consumption of 2.5-12.0 kg / t of the MMC concentrate (experiments No. 7-12); for dry reagent 2.5-8.0 kg / t of MMS concentrate (experiments No. 15-19).

The costs of the polymer antifreeze additive were obtained and confirmed by the quality of unloading of cars with MMS iron ore concentrate from the consumer.

In addition, the applicant does not exclude the positive effect of freezing of the wet concentrate and the combined use of reagents (liquid + dry).

When the content of liquid and dry polymer antifreeze additives is less than 2.5 kg / t of wet MMC concentrate, the required effect of freezing of the MMC concentrate was not achieved.

When the consumption of polymeric antifreeze additives is more than 8.0 kg / ton of wet concentrate when using a dry reagent and more than 12.0 kg / ton of wet concentrate when using a liquid reagent, approximately the same positive effect is obtained. However, an increase in the consumption of the reagent leads to an increase in the cost of the MMC iron ore concentrate (it is not economically viable due to the high cost of the reagent).

Example 1.

The concentrate with a moisture content of 7.5% was mixed with a dry polymeric antifreeze additive in an amount of 4.5 kg / t of MMS concentrate according to the usual technology. At a load of 200 t / h, 8 wagons of the MMS concentrate prevented with the reagent were loaded. Then the cars were exposed to the open air at an average temperature of 12 ° C for 3 days. Before the start of unloading, a picking of the loaded cars was carried out - the presence of a frozen crust on the concentrate cone up to 10 cm. After that, the cars were put for warming up in the defrosting garage for 2 hours at a temperature of + 67 ° С. Then the wagons were handed over for unloading, all wagons were clean after unloading.

Example 2

The concentrate with a moisture content of 8% was mixed in a drum mixer with a dry polymer antifreeze additive in an amount of 6.0 kg / ton of wet concentrate. Then the processed concentrate was immediately loaded onto the railway by a system of conveyors. wagons and sent to the consumer. Vysokogorsky Mining and Processing Plant supplied an experimental batch of 25 thousand tons of iron ore concentrate to MMS. at JSC EVRAZ ZSMK, where the resulting concentrate is used in sinter production for sintering the agglomerate. Carriages delivered within 5 days were put on heating for 3 hours. in defrost garages. The carriages were unloaded at a car dumper. There was no freezing of iron ore concentrate, and unloading from Russian Railways cars took place without complications.

Example 3.

Similarly to the previous example, the concentrate with a moisture content of 8.5% was treated with a liquid reagent in the amount of 8.0 kg / t of MMC concentrate. The liquid reagent was fed into the concentrate on a conveyor belt between the weighing machines. The feeding method is a conventional pump NCH-1000 using compressed air for uniform distribution of the reagent. Submerged in the railway. wagons prevented by the reagent MMC concentrate in the amount of 12 thousand tons was sent to the Chelyabinsk Met. combine. Arrived (in cold weather) after 45 hours. iron ore concentrate MMS after 2.5 hours. warming up in the defrosting garage easily unloaded from the wagons.

It should also be noted that when unloading cars on car dumpers, there were practically no rubbles (large monolithic lumps of dead concentrate) on the bunker gratings. Small bottles up to 400 mm in size were easily broken.

The use of the proposed method for treating iron ore concentrate MMC with a polymeric antifreeze additive provides the following advantages:

- the possibility of reducing capital and operating costs for the preparation of the charge for sintering by eliminating the drying of over-wetted iron ore concentrate MMS;

- the possibility of reducing harmful emissions into the environment by eliminating dust emissions during the drying of the MMC concentrate in drum installations;

- freezing does not occur in the total volume of the wet concentrate loaded into the vehicle, while at the same time, when unloading bulk material on the car dumper, large rubble does not occur.

Thus, the proposed technical solution fully fulfills the task.

Comparative analysis of the proposed method for processing MMC concentrate with reagents of Polyplast-UralSib LLC and known methods to prevent freezing of wet concentrates shows the advantages of the proposed technical solution.

Thus, the claimed invention meets the "novelty" criterion.

Analysis of patents and scientific and technical information did not reveal the use of new essential features specified in the proposed solution, according to their functional purpose. Therefore, the proposed invention meets the criterion of "inventive step".

Claims (1)

A method of preventing freezing of wet iron ore concentrate of wet magnetic separation (MMC), including mixing wet iron ore concentrate MMC with antifreeze additive, characterized in that a polymer liquid and / or dry reagent in the form of water-soluble surfactants based on sodium formate is used as an antifreeze additive and pentaerythritol, while the polymeric antifreeze additive is mixed with the MMC concentrate in an amount of 2.5-12.0 kg / t of wet concentrate when it is loaded into wagons or when stacked, and when using a liquid reagent, the consumption of the polymeric antifreeze additive is 2.5 -12.0 kg / ton of wet concentrate, and when using a dry reagent, the consumption of polymer antifreeze additive is 2.5-8.0 kg / ton of wet concentrate.