Fluorite- Saving Energy

7/17/2019 Fluorite- Saving Energy

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SAVING OF ENERGY IN CLINKERS MANUFACTURINGPROCESS OF CEMENT USING MINERAL FLUORITE, (CaF2)

ABSTRACT

Raw materials like limestones, travertinos, minerals silica and ¡ron were characterized; inaddition to the fluorite mineral (CaF22). The triedmeterings of fluorite were 0,2%, 0,4%,0,6%, 0,8%, 1,0% of the crude. The necessary finenesses were determined and the additionof fluorite that allows to complete the reactions of formation of silicates 3CaO, Si02 and2CaO. Si02, leaving the smaller amount of free CaO. Tests at level of laboratory like aindustrial level, were reductions in the temperature of pyroprocess, for a mínimum of freelime. Also one obtained increases in the compressive strenghts ofthe cement.

According to results of laboratory, profit reduction of 100°C in the pyroprocess reactions.In Later industrial test profit tobe reduced in 60°C thetemperature.

Keywords: cement, fluorite, energy, pyroprocess.

INTRODUCTION

Clinkerization process in the cement industry is the largest consumer of energy

both thermal and electrical, representing energy cost over 40% of the cost ofmanufacture. Clinkerization process on an industrial scale is carried out at temperatures of1450 ° C in rotary kilns, where the reactions are in slurry phase, formingmainly calcium silicates and aluminoferrites

The specific consumption of thermal energy in recent technology plants are

higher than 700 kcal / kg of clinker. Cement manufacturers are focusing their

efforts on thermal energy savings, seeking replacement or reduction of fuels.

The improvement in the reactivity of the raw flour mixtures to feed thefurnaces is one way to improve productivity and energy savings. Thedistribution of energy consumption in the clinkering, tells us that the greatestpotential is in reducing the 448 kcal / kg of clinker formation heat and reducethe 236 kcal / kg of clinker, radiation heat loss, among others.

Fluorite is defined a mineralizer which is capable of promoting the formation ofa particular phase altering the thermodynamic stability with respect to otherphases. Accelerates the rate of reaction in both the solid phase, liquid phase orin the solid-liquid interface, reduces the appearance temperature of the liquid

phase favoring the development of silicates.

The liquid phase can consist clinkering between 23 to 32%, depending on raw



materials and consists of aluminates and ferrites. The liquid phase creates ameans to transport liquid crystalline silica, calcium and other minor elementswhich are dissolved in it. When the liquid is saturated in silica and calciumprecipitate forming 2CaO.Si02, (C2S, belite), then if the liquid is saturated with

CaO and about 1400 ° C, the C2S absorb calcium and form 3CaO.Si021 (C3S,alite ).

The reaction of tricalcium silicate in the solid phase takes place very slowly and

is greatly accelerated by the presence of the fluxes.

Al203 Fe203 oxides act as fluxes and increasing the reaction rate withoutsignificantly altering the thermodynamic equilibrium of the reaction.

We assessed designs burnability raw meal as well as the addition of calcium

fluoride mineralizer to accelerate the reactions.

Cements with fluorite, increase their set times and improve their resistance.

Techniques were used XRF, XRD and microscopy.

EXPERIMENTAL

Initially determined burnability conditions of the raw meal, which is

lime saturations designed with employees in order to obtain the portland

cement

1, we determined the oil particle sizes and the times and temperatures

clinkering to levels of 0.0%, 0.2%, 0.4%, 0.6%, 0.8% and 1.0% of fluorite (Tables

1 and 2).

Clinker laboratory.

A paste was prepared with 26% of raw water, forming pellets inlay. Dried at

110 ° C for 6hrs. The elimination of CO2 (decarbonation), was 30 minutes at

950 ° C.



Table 1. Chemical composition of fluorite

oxides Composition

Si02 % 6,71

Al203 % 1,11Fe203 % 0,54

CaF 2 % 85,7SO3 % 0,45

Burning loss % 3,48

Total % 98,60Chlorides % 0,01

Table 2. Composition of raw flour in laboratory-scale test

Fluorite 1,00% 0,80% 0,60% 0,40% 0,20% 0,00%

Si02 12,32 12,42 12,42 12,62 12,62 13,82

Al203 4,34 4,40 4,41 4,44 4,45 2,67

Fe203 2,36 2,37 2,38 2,41 2,42 2,39

CaO 42,53 42,43 42,43 42,53 42,43 43,63

S03 1,05 1,04 1,04 1,05 1,05 1,11

Silica Module 1,84 1,83 1,83 1,84 1,84 2,73

Fluxes Module 1,84 1,86 1,85 1,84 1,84 1,12Lime Saturation 103,35 102,22 102,17 100,92 100,64 100,53

Once optimum conditions of use of fluorite were obtained, there were phased

industrial tests in a rotary kiln of 85 m length and 5.25 m diameter with two towers

6-stage preheater, calciner tertiary air. Was used coal and natural gas fuel (figure

1) and (Table 3).

Fuel flows to the furnace were aimed at:

Furnace burner with 100% carbon, 16.2 ton / h.

A preheater tower: natural gas, 2400 Nm3 / h.

Preheater tower B: 2.0 ton / h of coal 10400 Nm3 / h of natural gas.



The raw meal is designed fromlimestone, silica mineral and iron,

and the chemical composition wasdetermined by XRF.

Figure 1. Rotary kiln and clinkering zone

Table 3. Composition of raw meal in industry-wide test

Si02 Al203 Fe203 CaO SO, FluoriteLime

saturation

12,47 4,38 1,89 42,98 1,06 0,40 104,04

12,15 4,38 1,85 42,90 1,03 0,40 106,21

12,52 4,48 1,88 42,91 1,09 0,40 103,24

12,76 4,56 1,89 43,25 1,04 0,40 102,16

12 75 4 45 1 89 42 70 1 09 0 40 101 23



RESULTS AND DISCUSSION

Worked with 5% retained on 200 mesh (75 microns), in trials with addition of

fluorspar.Calcium oxide is considered free, as one who does not react in the oven, becauseexcess calcium or unsuitable conditions for reaction. Figure 2 shows the variationof C3S by action of the test temperature.

Effect of temperature on the formation of silicates

Test Temperature, C

Figure 2. Effect of temperature on the formation of C, S

The C, S formed from 1100 ° C, decrease with increase in temperature, change in F,S by reacting with free CaO. The addition of calcium fluorite free lime decreases tofacilitate the reactions (see figure 3).



Reduction of free lime with fluorite

Figure 3. CAE effect, in the reaction of CaO with C3S.

The addition of fluorite, promotes the reaction of CaO 2CaO. 3CaO.Si02 to formSi02 (C3S) up to 0.6% addition of CaF2. (Figure 4).

Effect of fluorspar in the formation of C3S

1250 1 300 1 350 1 400 1 450

TEMPERATURE,o

C

Figure 4. Effect of CaF2 and temperature in the C3S

ition of F2Ca



Cements assays, exhibit an increase in setting times (table 4), the compressivestrength will increase with the addition of CaF2, reaching a maximum and thendecreases.

At industrial level was obtained lower energy consumption, Figure 5 shows thetemperature changes and the secondary air kcal / kg clinker.

Specific consumption test heat in oven 2.

Figure 5: Test of the fluorite industry, reducing thermal energy.

Table 4. Chemical and physical characteristics of the cement industry with fluorite

TEST TO CEMENT RESULT

Retained 325 mesh,% 9,64

Blaine, cm 2 / g 2 810

Expansion autoclave,% 0,16

Fluency,% 97

Initial Setting Time, mm. 204

Final Setting Time, mm. 342

Compressive Strength

1 day 121

3 days 209

7 days 326

28 days 382



The microstructures shown fluoride grains compact Figures fig 7.

CONCLUSIONS

- With the addition of 0.4% of fluorite, thermal energy consumption during theindustrial trial fell 56.5 kcal / kg clinker.

- The cement setting time increased slightly, being within the specifications ofASTM standards, NTP and UNE.

- The compressive strength of cement made in laboratory fluorite was increased by15% with respect to cement without fluorite calcined at the same temperature of1400 ° C.

- A laboratory level addition of 0.4% of fluorite in the clinkering temperature rangeof 1300 ° C to 1350 ° C were most suitable conditions to implement industrially.

Ruben Gilvonio Alegria and Fernando Dominguez Linares

The authors wish to thank Cementos Lima SA, Plant Atocongo, by supporting thedevelopment of this research.

Figure 6. Microstructure pointing

clinker free lime without fluorite Figure 7. Clinker with added

colored fluorite with HNO3. With

crystals 22μm



REFERENCES

1. F. Soria, (1982), "Chemical Composition Mineralogica commodity and savingenergy in the cement industry ", Expominer-82 Spain.

2. Luguin, (1989), "Influence of calcium fluoride on the processes of synthesis andcement activity, "Chemical-Technological Institute Kazagia.3. M. Coll and J. Pont (1979), "The fluorspar and cement industry", CementConcrete, November 1979, No552, Spain.4. O. Restrepo, J. Ivan and J. Restrepo (2007), "Effects of some mineral additionsColombian manufacture of portland cement clinker I "Dyna No152,Medellín.5. Blanco-Varela, M, Palomo, A., Gates, F. and Vazquez, T. (1995) "Influence ofCaF2 joint incorporation and CaSO4 clinkerization. obtainingnew cements ". Construction materials. No. 239. Eduardo Torroja Institute.Madrid.

Fluorite- Saving Energy

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