Research & Development Company TOREX
Eng
+7 (343) 211-06-53

Eco-friendly & Sustainable approach

 

  • TOREX eco-concept. Environmentally friendly approach and mindset.  Labor and health protection activities; Evaluation results of labor conditions;
  • Recycling and disposal solutions. Green technologies and developments (efficient engineering elaborations to reduce the emissions to the ambient); concrete filler technologies with an application of ash; Cutting edge straight grate technologies dedicated to reduction of greenhouse gases; Waste and by-product reclamation technologies. Desulfurization projects
  • Social and corporate development (special internships for bachelor and MA graduates)

 

 

     

 TOREX Eco-Concept

 

 A careful and environmentally friendly approach within the context of industrial sector is somewhat revitalized now in numerous countries around the world. This is not a simple trend, but an indispensable attribute of environmental protection policy for global multinational corporations operating in metallurgical, mining, oil, gas and other core industries. Furthermore, the rapidly revised environmental compliance standards with regard to major metallurgical plants in Russia lead to development of breakthrough and power efficient technologies. Those technologies are adaptable to hazardous emissions and impurities released to the ambient and ultimately safe for bio-environment adjacent to industrial area.

Starting from its inception and for decades further, NPVP TOREX has been extensively focused on eco-sustainability concept as an integral part of corporate policy, while developing and integrating pelletizing technologies at brownfield projects. Apart from technological solutions, our company is committed to the internal eco-principles, in particular: arrangement of designated containers and recycling procedure for various domestic by-products made of plastic/paper/aluminum, including invalid electric batteries. Afterwards, the named materials are transported to drop-off stations.  In addition, TOREX personnel is involved in in-house activities served to maintaining the green and healthy lifestyle. A tendency to eliminate a paper consumption in the document flow is one more accomplishment.  

Special assessment of the working conditions in TOREX 

A special assessment of the working conditions in TOREX company is being held once per 5 years. Such activities allow for collecting the data related to working places, number of employees, job characteristics, occupation, equipment and materials. The assessment might include the following criteria:

  • Determination of parameters for hazardous and harmful workplace factors (e.g. physical, biological and chemical)
  • Determination of business process factors (complexity and potential stress from working process)
  • Assessment of PPE availability

Upon completion of assessment, the reports are being submitted with an indication of the relevant values and results.  

In the period of seasonal disease risk and other vulnerabilities (including anti-flu and tick-borne encephalitis shots), TOREX management implements a vaccination process among the personnel in order to keep a working well-being.   

TOREX   TECHNOLOGIES

   

Waste reclamation and environment protection actions

        We have developed the technologies to recover the waste products as follows:

  •  DRI pellets and zinc concentrate;
  • organic and mineral fertilizers;
  • construction filler for concrete (spherical rubble);
  • metallurgical briquettes.

Technology 1. 

The mixed metallurgical slurry is being fed to thickeners 1 by slurry pipelines.  Slurry with moisture up to 40% is being mixed and averaged in intermediate collecting tanks 2, and then fed into drying drums 3, where the slimes are dried to moisture of 6-8%. Dry waste products (with moisture up to 1%) are being received into bins 4 equipped with dedusting units.  Undersized coke (coarseness 10-0 mm) is being fed to the screen 5 to separate the fractions 10-5 and 5-0 mm. The dried up slime and dry dust are being dosed to the collecting conveyor within the specified ratio along with coke of coarseness 5-0 and then fed to ball drum mill 6 for further grinding.  The ground and homogenized blend and bentonite powder are being fed to feed bins and thereafter are dosed to intensive screw mixer 7.
 The mixed blend is fed to the bin before pelletizing disk 8 in order to hold a bentonite.  The green pellets with coarseness 10-20 mm are generated inside of pelletizing disk.  Mixer and pelletizing disk are equipped with the water supply devices to ensure a moisture of the blend within 9.0-9.2%.  Green pellets are fed to roller feeder 9 which screens the off-spec pellets (-9 mm) A spillage from roller feeder is being conveyed back to the ball mill 6 by conveyor system.  The green pellets which loaded onto the grate 10 are exposed to heat treatment (drying to 350 ºC and preheating to  900 ºC). Stacking of the pellet bed with preheated and strengthened pellets is considered taking into account high thermal loads. The pellets are taken from discharge chute of the grate.  Grate hood is being heated up by natural gas.  Flue-gas is handled to the dust collecting system 12 and after cleaning discharged to the stack 14.

 

1 – thickeners, 2 – interim collectors, 3 – drying drums, 4 – silos, 5 – screen, 6 – ball mill, 7 – screw mixer, 8 – pelletizing disk, 9 – roller feeder, 10 – grate, 11 – fan, 12 – battery cyclones, 13 – process fan, 14 – stack, 15 – rotary kiln, 16 – fan, 17 –interim collector, 18 – cyclone furnace, 19 – fan, 20 – waste heat boiler, 21 – bag filter, 22 – bin, 23 – packing line, 24 – process fan, 25 – drum cooler, 26 – magnetic separator, 27 – screen.

The hardened pellets are loaded into discharge head of rotary kiln 15, whereinto the undersized coke of 10-5 mm is fed.  In the rotary kiln heated up by natural gas, a reduction of zinc oxides occurs, along with iron and associated elements found in the hardened pellets.  Reducing atmosphere in the floating pellet bed is ensured by a solid fuel presented both inside of the pellets and additionally charged in the furnace.   Zinc reduced under the high temperature (up to 1150 ºC)  is evaporated and taken off with a flue gas through the charging head of furnace.  Flue gas is being handled to the cyclone furnace 18, where afterburning occurs along with capture of the solid fractions removed from the furnace.  The dust captured in the cyclone furnace and battery cyclones of grate along with a spillage under grate removed by underwashing and then fed to interim collector 17 with onward transfer to thickeners.  Upon completion of after-burning a flue gas goes through the waste heat boiler 20, where its temperature drops down to 200-250 ºC and steam formation of supplied water occurs.  A condensation of vapor-like zink to the solid aggregative state occurs at the same time.  Cooling gas is being fed to the bag filter 21.  Captured dust with coarseness 0,03-100 microns represents ZnO concentrate which collected in the bin 22 equipped with dedusting units.  ZnO concentrate is fed to packing line 23 from bin and discharged to the concentrate stockyard with transportation to the consumers.   Reduced pellets with a metallization degree of ~40 % are recharged from a rotary kiln to the drum cooler with water cooling 25. Temperature of pellets in the drum cooler is decreased to 100ºС. To prevent an oxidation of DRI pellets, the drive station is designed in  a leak-tight way and working space of cooler is filled with nitrogen.  The cooled pellets are being fed to drum magnetic separator 26 where a coke ash extraction occurs in the material flow.  Separated pellets are fed to screen 27, where an on-spec fraction 8-18 mm is generated and transported to the blast furnace.   Off-spec fines (-8 mm) is conveyed to sintering machine. The envisaged scheme have the following advantages.  First off, besides environmental issues, this scheme would help to get two types of product: commercial concentrate of zinc oxide and pre-reduced iron bearing pellets for the further blast furnace production.  Secondly, this scheme is commercially viable in terms of capital and operating costs.  Thirdly, a relatively cheap and feasible equipment is used. 

 Technology 2. 

Waste products from burning of organic fuels (ash) and silt slurry, recovered during operation of dredge ships on the fairway sections of water basins, are account for a vast volume of solid mineral waste in numerous regions of Russia, for instance in Leningrad oblast.  Presently, these materials are being stored in landfills, which affects a sanitary situation of surroundings and occupies the major areas of land. As a result, the land itself is not suitable for further economic turnover.   A comprehensive recycling of generated waste with separation of commercial products (for instance, mineral fertilizers) might be a solution to this problem.  Ash is chemically inert raw material which improves a drainability of soils and silt contains a complex of substances which easily recycled by microorganisms into humus.  Therefore, addition of these materials along with a nitrogen compounds fixated by plants, phosphorus and kalium to the top soil could improve a fertility of soils, while tackling the waste reclamation issues and remediation of landscapes affected by storage. 

NPVP TOREX has developed the technology for recovery of organomineral fertilizers from ash waste left from wastewater sludge.  To ensure a strength of granules the binding additives were used, such as cement M400 and powder lignosulphonate. In addition, potash chloride, carbamide, potassium phosphate have been applied as the mineral additives.  The size of granules was 1-5 mm. Strength testing according to GOST 21560.2-82 revealed a granule strength within 0,7-1,0 MPa.   Process flow diagram of fertilizer production shall comprise the raw material preparation stages (for silt - drying and removal of coarse fractions, debris; for ash - removal of coarse fractions), blending of components, granulation, strengthening (drying, steam treatment) and packing. 

Technology 3.

Pelletization could be used as a method to produce artificial aggregates for concrete.  Production of non-indurated pellets based on the cement binder allows for recovering an artificial gravel with the strength  5,6..6 MPa.  

As part of the studies, the possibilities evaluated as to recovery of artificial filler for concrete using an ash with cement (sample 1 and sample 2), as well as cement with reinforcement of pellets by mineral fiber (sample 3 and sample 4). Besides, pellets with a blend of ash and bentonite were produced (proportion of bentonite 0,6 and 1,0 for the samples No 5-6 and No 7 accordingly) with subsequent thermal treatment (max temperature of firing was 1200°С).  Density was determined as per GOST R EN 1602-2008; compression strength as per GOST 24765-81 (N/pellet) and GOST 9757-90 (MPa).

Item No.

Fraction, mm

Strength, N/pellet

Bulk weight, kg/m3

Density, kg/m3

1

10-12

579,6

872

1620

2

12-15

617,3

862

1599

3

10-12

473,7

838

1620

4

12-15

507,0

818

1529

5

10-12

692,3

675

1250

6

12-15

1348,4

725

1342

7

10-12

1126,3

678

1256

 

All samples were represented by round-shaped grains, with a dense structure and the presence of small pores. Moisture for the samples No. 1-4  is equal to 6,1…8,0% and 0.1% for the samples No. 5-7.  Water absorption of gravel is 22,3…23,2%. As it can be seen from the results of studies undertaken, an ash might be a source of round-shaped fractionated gravel with the compression strength up to 11 MPa and bulk weight less than 700 kg/m3. 

This type of gravel can be used as a concrete filler.  In addition, a gravel produced using an induration technology is exemplified by higher strength and lower density which makes this material as a promising option to produce the specific types of concrete. 

Technology 4.

One of the important trend of contemporary metallurgy is increase of pellet proportion which is related to a growing demand in the global pelletizing market and high commercial value of the product.  Increase of pellet proportion in the burden of blast furnaces specifies both an alteration of cast iron production technology and balance of iron bearing waste in case of sinter production decline.  An extra option for increase of pellet proportion is total removal of a sinter from burden and waste supply in the briquette composition.  The representative samples of various composition were prepared in order to analyze an utilization of briquettes with iron bearing waste. 

The briquettes from waste product were selected for a study. Component composition is given in the table 1 and chemical composition is in table 2.  Selection of briquette composition is determined by the following conditions: disposal (recycling) of the specified quantity of iron bearing waste; attainment of briquette basicity from natural to 5,5 units; application of cement as a binder and hydrated lime as as fluxing agent. 

Properties of briquettes

B2

Fe

SiO2

CaO

Al2O3

MgO

LOI

Consumption thous. t/annum

1

5,03

32,34

6,25

31,40

0,93

1.65

14,68

831,50

2

5,51

31,74

5,94

32,70

0.86

1,70

14,18

846,50

3

4,47

35,35

6,31

28,18

0,90

1,56

14,37

759,00

4

3,32

39,91

6,78

22,48

0.94

1,38

14,60

671,50

5

2,77

42,76

6,94

19,20

0,94

1,29

14,50

626,00

6

1,28

50,52

7,62

9,75

0,99

0,99

14,69

529,00

 The size of briquettes is selected in such a way to test them as per ISO 13930 without additional activities (cutting, grinding).  The base materials were dried up, dosed and homogenized by unified grinding to attain a constant mass.  Homogenized mass was getting moisturized  and pressurized under 40 Mpa on the universal hydraulic machine BT1-FR050THW/A1K.  In average, a mass of samples was within 8-10%.  Geometrical dimensions of briquette are as follows: d= 40 mm, h = 40 mm.  Briquettes were held during 28 days in air and dry conditions with determination of grade strength and softening ratio (atmospheric resistance).  

To determine a softening ratio, some of briquettes were placed in a vessel with water so as to maintain a water level in it above the upper part of briquettes - at least 20 mm.  The samples were held during 48 hours. Compression strength of water-saturated and dry briquettes were determined.
According to results of measurements a softening ratio was determined, which stands for an ultimate stress of water-saturated briquettes to ultimate stress of dry briquettes ratio.  The briquettes are considered as water resistant if softening ratio is min 0.8.  Reducibility tests were carried out as per GOST 17212-84, reduction strength as per ISO 13930. Determination of starting softening temperature and temperature interval of softening is implemented as per GOST 26517-85.

Test No

1

2

3

4

5

6

Compression strength limit, MPa, wet briquettes

2.9

AE

4.2

4.3

5.1

4.4

Compression strength limit of dry briquettes, MPa

2.5

3.5

10

4.2

4.3

4.4

Softening ratio (SR)

1,20

1.10

1,02

1,02

1,20

1.00

Yield of fraction +6,3 mm during the test as per ISO 13930 (LTD+6,3), %

1.6

1.3

5.8

2.7

3.3

13,6

Fraction yield -3,15 mm during the test according to ISO 13930 (LTD -3,15), %

97.5

95,8

91,4

67,53

After-Firing duration (down-draught)

82,2

Fraction yield -0,5 mm during the test according to ISO 13930 (LTD -0,5), %

84,8

54,9

73,1

76,4

73,6

65,0

Reduction degree ,%

68,6

48,5

71,1

%

57,3

92,1

Starting temperature of softening °С

1090

1000

920

1060

1180

1290

Melting point, °С

1290

1150

1080

1380

1400

1430

Softening and melting range

200

150

66,0

320

220

140

Compression strength, MPa

2.5

3.5

10

4,2

4.3

4.4

Calculations of blast furnace smelting indices while using the tested briquettes and pellets in the burden were performed to assess an efficiency of briquette utilization in combination with pellets. The obtained data show that use of briquettes based on a cement binder along with increase of a pellet proportion improves the technical and economic indices of blast furnace smelting.

Pelletizing as a method to recycle the technology-related waste products

The volumes of solid waste generated in a global scale account for 17.4 billion t/annum. There are more than 600 kg of sludge and slag generated per tonne of steel as the by-products of metallurgical production, and over 300 kg of coal ash per tonne of coal at the heat power plants. Only less than half of a total by-products to be recycled and the rest of material is stored in the landfills exacerbating an environmental status of industrial regions.  A major part of these by-products is represented by finely divided components which need to be sintered prior to reclamation in the smelters, extraction process or construction sphere.  The technologies which ensure a production of sintered product from finely divided waste, will extend a range of by-products produced with conversion of recycled materials from waste to resourceful.  The existing pelletizing technologies are represented by briquetting, pelletizing and high temperature processes (sintering or lumping out of liquid alloys).  Briquetting has a lot of advantages, including an easy application and low power costs.  At the same time, briquetting technologies are sensitive to properties of base raw material (grain-size composition, moisture etc.) and binder properties.  Application of extrusion eliminates those disadvantages and nowadays might be considered as a full-scale substitution of existing pelletizing methods . High temperature processes require a vast amount of energy (due to fuel or electricity). These processes could be effective if there are liquid alloys as the by-products (for instance, liquid slags of blast furnaces). Pelletizing allows for producing a lumpy product out of finely divided materials along  with fractionated material of a proper spherical shape.   Presently, this technology is used only for pelletizing in iron ore industry. 

 

 

 

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