Composition of limestone

The chemical composition of pure limestones is close to calcite, where CaO is 56% and CO 2 is 44%. Limestone in some cases includes impurities clay minerals , dolomite , quartz, less often gypsum , pyrite and organic remains that determine the name of the limestones. Dolomitized limestone contains from 4 to 17% MgO, marl limestone - from 6 to 21% SiO 2 +R 2 O 3. Limestone sandy and silicified has impurities of quartz, opal and chalcedony. It is customary to reflect in the name of limestones the predominant presence of organogenic remains (bryozoan, algal), or its structure (crystalline, clotted, detritus), or the shape of rock-forming particles (oolitic, brecciated).

Description and types

According to the structure, limestones are crystalline, organogenic-detrital, detrital-crystalline (mixed structure) and sinter (travertine). Among crystalline limestones, coarse-grained, fine-grained, and cryptocrystalline (aphanitic) are distinguished by grain size, and recrystallized (marble-like) and cavernous (travertine) by brilliance at a fracture. Crystalline limestone is massive and dense, slightly porous; travertine - cavernous and highly porous. Among organogenic detrital limestone, depending on the composition and size of the particles, the following are distinguished: reef limestone; shell limestone (), consisting mainly of whole or crushed shells, bonded with carbonate, clay or other natural cement; detritus limestone composed of shell fragments and other organogenic fragments cemented with calcite cement; algal limestone. White (so-called writing) also belongs to organogenic-clastic limestones. Organogenic-detrital limestones are characterized by a large, low volumetric mass and are easily processed (sawed and polished). Detrital-crystalline limestone consists of carbonate different shapes and size (lumps, clots and nodules of fine-grained calcite), with the inclusion of individual grains and fragments various breeds and minerals , lenses flints. Sometimes limestone is composed of oolitic grains, the cores of which are represented by fragments of quartz and flint. They are characterized by small pores of various shapes, variable volumetric mass, low strength and big water absorption. Sintered limestone (travertine, calcareous tuff) consists of sintered calcite. It is characterized by cellularity, low bulk density, easy processing and sawing.

According to the macrotexture and conditions of occurrence among limestones, there are massive, horizontally and obliquely layered, thick and thin platy, cavernous, fissured, spotty, lumpy, reef, fungal, stylolite, underwater landslide, etc. Organogenic (biogenic), chemogenic, clastic and mixed limestones are distinguished by origin. Organogenic (biogenic) limestones are accumulations of carbonate remains or entire skeletal forms of marine, less often freshwater organisms, with a small admixture of predominantly carbonate cement. Chemogenic limestones arise as a result of lime precipitation followed by recrystallization of the carbonate mass of sediments, mainly from sea ​​water(crystalline limestone) or from deposits from mineralized (travertine). Clastic limestones are formed as a result of fragmentation, washout and redeposition of angularly rounded fragments of carbonate and other rocks and skeletal remains, mainly in marine basins and on the coasts. Limestones of mixed origin are a complex of deposits resulting from the successive or parallel superposition of various carbonate sedimentation processes.

The color of limestones is predominantly white, light gray, yellowish; the presence of organic, ferruginous, manganese and other impurities causes a dark gray, black, brown, reddish and greenish color.

Limestone is one of the most widespread sedimentary rocks; she composes various forms relief Earth. Limestone deposits are found among deposits of all geological systems - from Precambrian to Quaternary; the most intensive formation of limestones occurred in the Silurian, Carboniferous, Jurassic and Upper Cretaceous; make up 19-22% of the total mass of sedimentary rocks. The thickness of limestone strata is extremely variable: from a few centimeters (in separate layers of sediments) to 5000 m.

Limestone properties

The physical and mechanical properties of limestones are extremely heterogeneous, but are directly dependent on their structure and texture. The density of limestones is 2700-2900 kg/m 3 and varies depending on the content of impurities of dolomite, quartz and other minerals. The bulk mass of limestones varies from 800 kg/m 3 (for shell rocks and travertine) to 2800 kg/m 3 (for crystalline limestones). The compressive strength of limestones ranges from 0.4 MPa (for shell rock) to 300 MPa (for crystalline and aphanitic limestone). In wet condition, the strength of limestones often decreases. Most of the deposits are characterized by the presence of limestone, not uniform in strength. Losses wear, abrasion and crushability increase, as a rule, with a decrease in the volumetric mass of limestones. Frost resistance for crystalline limestones reaches 300-400 cycles, but it changes dramatically for limestones of a different structure and depends on the shape and connection of pores and cracks in it. The workability of limestones is directly related to their structure and texture. Shell rock and porous limestones are easily sawn and hewn; crystalline limestones are well polished.

Application of limestone

Limestone has universal application in industry, agriculture and construction. In metallurgy, limestone serves as a flux. In the production of lime and cement, limestone is main component. Limestone is used in chemical and Food Industry: how auxiliary material in the production of soda, carbide calcium , mineral fertilizers, glass, sugar, paper. It is used in the purification of petroleum products, dry distillation of coal, in the manufacture of paints, putties, rubber, plastics, soaps, medicines, mineral wool, for cleaning fabrics and processing leather, liming soils.

Limestone is the most important construction material, from which facing

MUNICIPAL EDUCATIONAL INSTITUTION SECONDARY EDUCATIONAL SCHOOL with. OCTOBER

STERLITAMAK DISTRICT OF THE REPUBLIC OF BASHKORTOSTAN

Section: World of Chemistry

Category: The world around us

Performed:Zaidullina Alsu, a 7th grade student of the MOBU secondary school with. October

Scientific adviser: Iskhakova R.U., teacher of chemistry, MOBU secondary school s. October

2015

Introduction

study the literature on this issue;

explore physical properties limestone;

explore Chemical properties limestone;

get limestone on your own;

to conclude.

LITERATURE STUDY. What is limestone?

Limestone -sedimentary rock organic origin, consisting mainly of calcium carbonate ( CaCO3 ) in the form of calcite crystals of various sizes.

Limestone, consisting mainly of the shells of marine animals and their fragments, is called shell rock. In addition, there are nummulite, bryozoan and marble-like limestones - massively layered and thinly layered.

According to the structure, limestones are crystalline, organogenic-detrital, detrital-crystalline (mixed structure) and sinter (travertine). Among crystalline limestones, coarse-grained, fine-crystalline and cryptocrystalline (aphanite) are distinguished by grain size, recrystallized (marble-like) and cavernous (travertine) by brilliance at a fracture. Crystalline limestone - massive and dense, slightly porous; travertine - cavernous and highly porous.

Among organogenic detrital limestone, depending on the composition and size of the particles, the following are distinguished: reef limestone; shell limestone (shell rock), consisting mainly of whole or crushed shells, bonded with carbonate, clay or other natural cement; detritus limestone composed of shell fragments and other organogenic fragments cemented with calcite cement; algal limestone. White (so-called writing) chalk also belongs to organogenic-detrital limestones.

Organogenic-clastic limestones are characterized by large porosity and mass and are easily processed (sawn and polished). Detrital-crystalline limestone consists of carbonate detritus of various shapes and sizes (lumps, clots and nodules of fine-grained calcite), with the inclusion of individual grains and fragments of various rocks and minerals, flint lenses. Sometimes limestone is composed of oolitic grains, the cores of which are represented by fragments of quartz and flint. They are characterized by small pores of various shapes, variable bulk density, low strength and high water absorption. Sintered limestone (travertine, calcareous tuff) consists of sintered calcite. It is characterized by cellularity, low bulk density, easy processing and sawing.

Limestone has a universal application in industry, agriculture and construction:

In metallurgy, limestone serves as a flux.

In the production of lime and cement, limestone is the main ingredient.

Limestone is used in the chemical and food industries: as an auxiliary material in the production of soda, calcium carbide, mineral fertilizers, glass, sugar, paper.

It is used in the purification of petroleum products, dry distillation of coal, in the manufacture of paints, putties, rubber, plastics, soaps, medicines, mineral wool, for cleaning fabrics and leather, liming soils.

Limestone has been used since ancient times as a building material; and at first it was rather “simple-hearted”: they found a cave and settled it, in accordance with the existing requests.

2. STUDY OF PHYSICAL PROPERTIES.

(Appendix 2).

Each mineral has its own characteristics, inherent only to it, I considered the following signs:

Shine

matte

Hardness

average

Color

white-grey

Density

2000-2800kg / m 3

Electrical conductivity

10~5 to 10~~4

Thermal conductivity

0.470 m*K

Solubility. (Annex 3)

Solubility in water

Limestone does not dissolve in water

Solubility in acetone (organic solvent)

Limestone does not dissolve in acetone

STUDY OF CHEMICAL PROPERTIES

(Annex 4)

Experience number 1. Interaction of limestone with acids (hydrochloric, acetic, nitric).

Chemicals and equipment:

Strong acids: HCI (salt), HNO 3 (nitrogen).

Weak CH 3 COOH (acetic).

Stand with test tubes, spirit lamp, holder.

Reagent

Observations

Conclusion

HCI(salt),

The reaction is violent

Interacts well with hydrochloric acid

HNO 3 (nitrogen)

Water droplets appeared on the walls of the test tube and carbon dioxide was released.

The reaction is violent

It interacts well with nitric acid. Better with salt.

CH 3 COOH(vinegar)

Water droplets appeared on the walls of the test tube and carbon dioxide was released.

The reaction is slow, but when heated, the reaction rate increased.

Does not interact well with acetic acid. Because weak acid.

CaCO 3 +2HCl=CO 2  +H 2 O+CaCI 2

CaCO 3 +2CH 3 COOH=(CH 3 COO) 2 Ca + H 2 O+ CO 2 

CaCO 3 + 2HNO 3 =Ca(NO 3 ) 2 + CO 2 +H 2 O

Conclusion: Limestone reacts with acids to release carbon dioxide and water. With strong acids, the reaction was violent, and with weak acid the reaction started only after heating.

Experience number 2. Interaction with alkalis (water-soluble bases).

(Annex 4)

Chemicals and equipment:

Sodium hydroxide - NaOH , rack with test tubes, spirit lamp, holder.

Experience Description : A certain amount of limestone was added to the test tube and sodium hydroxide was added. There was no reaction, after 15 minutes another reagent was added and heated. No reaction was observed.

Conclusion: Limestone does not react with alkalis.

Experience number 3. The decomposition of limestone.

(Appendix No. 5).

Chemicals and equipment: limestone, tripod, vent tube, flask, torch, spirit lamp.

Experience Description : Limestone was placed in a test tube and closed with a gas outlet tube, the end of which was lowered into the flask. They lit the stove and started to heat it up. The presence of carbon dioxide was determined using a burning splinter.

Observations: Limestone is decomposing. The color turned white. Water droplets appeared on the walls of the test tube and carbon dioxide was released.

CaCO3 CaO+CO2

Conclusion: When heated, limestone decomposes to form calcium oxide and water.

Experience number 4. Getting limestone at home.

To complete the experience you will need:

plastic bucket

plastic cups

dry plaster

gypsum mixture

Time for the experiment: 15 minutes to prepare for the experience and 5 days to get limestone.

To get limestone:

1. 1. 1. Pour the resulting mixture into plastic cups.

         I placed the cups in a warm place. Left alone for 5 days.

         On the 5th day, the resulting limestone was removed.

Note:

Shells can be any size, but use smaller shells for best quality limestone.

Observation: Does the resulting limestone look like natural?

Result:

Limestone is one of the types of sedimentary rocks. When microscopic marine animals die, they fall to the bottom of the ocean, where they are collected by barnacles. This is how shells collect these particles over time, and limestone is formed..

1.1. Sampling and preparation of samples for chemical analysis and determining the moisture content of flux limestones is carried out according to this regulatory document.

1.2. Limestone sampling is carried out during the loading and unloading of transport vessels, during the formation of stacks, filling bunkers and warehouses, or emptying stacks and warehouses.

1.3. Quality control of flux limestones is carried out according to the results of chemical analysis of the combined sample taken from the batch.

1.4. Sampling and preparation of samples for chemical analysis is carried out from each batch of limestone.

1.5. The minimum number of pooled samples to be taken from a batch of limestone is equal to the quotient of the mass of the batch divided by the mass of limestone from which one pooled sample is taken. The mass of limestone from which one combined sample is taken - according to OST 14 63-80 and OST 14 64-80. If the resulting number turns out to be a fraction, it is rounded up to a larger whole number.

1.6. The maximum allowable moisture content in limestone and the frequency of its determination are set in accordance with OST 14 63-80 and OST 14 64-80, by agreement between the manufacturer and the consumer.

1.7. Sampling is carried out uniformly from the entire mass of the batch by mechanized or manual methods.

1.8. Ordinary and averaged dolomitic limestones are classified by this document as homogeneous in terms of the content of useful and ballast components (standard deviation of the content of these components? ? 1.3%), and non-averaged dolomitic limestones - as heterogeneous in terms of the content of magnesium oxide (? > 1.3%) .

Calculation of standard deviation (?) - according to GOST 15054-80

where x i- mass fraction of the component in i-th sample taken from a batch of limestone ( i= 1, 2, ..., n), %;

Arithmetic mean mass fraction component in the limestone batch, %.

The frequency of the control determination of the heterogeneity of flux limestones in a batch in terms of the content of useful and ballast components is at least once a year.

1.9. The maximum error limit for testing homogeneous limestones is equal to the maximum error limit for the chemical analysis technique specified in OST 14 63-80 and OST 14 64-80; when testing heterogeneous limestones, it is equal to twice the value of this indicator.

b- width of the slot of the sample-cutting device, m;

V- speed of movement of the sample-cutting device, m/s.

2.2 The minimum mass of an increment sample taken from the surface of a stopped conveyor ( m 2) by mechanized method, calculated by the formula

(2)

where h- height of the limestone layer in the middle part of the belt, m;

2.4. Point sampling by mechanized or manual method from the assembly line is produced at regular intervals ( t) or after passing a certain mass of limestone ( m 3)

where M

Q- limestone flow rate, t/h;

n- the number of incremental samples that make up the combined sample.

2.5. The minimum number of point samples taken by mechanized or manual methods from the conveyor is given in Table. 2

table 2

Note. By agreement between the manufacturer and the consumer, an increase in the mass of limestone is allowed, from which one combined sample is taken, i.e. the mass of the combined sample can be taken from a batch weighing more than 1500 tons. In this case, the number of incremental samples for ordinary and dolomitic limestone increases by 1 and 4 samples, respectively, for every 600 tons over 1500 tons.

2.6. With the manual method of sampling from railway cars, one point sample is taken:

from ordinary limestone - from every third car;

from dolomitic averaged and non-averaged limestone - from each car.

With the manual sampling method, when loading limestone into a bunker or forming a stack, at least two point samples are taken per shift at the points provided for by the product quality control scheme.

2.7. In the case when ordinary limestone is heterogeneous in terms of the content of useful and ballast components (? > 1.3%), the number of point samples taken from the conveyor is doubled, and one point sample is taken from each car.

2.8. The combined sample from the bunker or stack must be at least 0.003% of the mass of limestone being tested. With a homogeneous material composition it is allowed to reduce the mass of the combined sample to a value of at least 0.02%.

2.9. The minimum number and mass of increments may be increased, but may not be reduced.

2.10. Sampling by manual method from the conveyor is carried out on a drop with the conveyor moving or from a stopped one.

2.11. Sampling by manual method from railway cars is carried out at a distance of at least 0.5 m from the side of the car in a certain order, shown in the diagram.

Scheme of spot sampling by manual method from wagons

Location of point sampling points from ordinary limestone located in wagons in the form of cones

Location of point sampling points from ordinary limestone, located in wagons in an even layer

Location of spot sampling points from dolomitic limestone located in wagons in the form of cones

Location of spot sampling points from dolomitic limestone, located in wagons in an even layer

2.12. When limestone is arranged in wagons in the form of cones, point samples are taken from the surface of the protruding part of the cone. In this case, the sampling points are, if possible, located along the generatrix of the cone, shifted by approximately (40 ± 10) ° relative to the long axis of the car at a height not exceeding 2/3 of the height.

2.13. When sampling limestone during reloading by cyclically operating mechanisms (buckets, grabs, etc.), point samples should be taken manually from the places where limestone was taken or poured without digging holes, with periods ( H) through the set number of working cycles of the loading mechanism, which is calculated by the formula

where H- the number of cycles of the loading mechanism, after which one point sample is taken, pcs;

M- mass of limestone, from which one combined sample is taken, t;

n- the number of incremental samples that make up one combined sample, pcs;

m h- the mass of limestone moved in one cycle of the loading mechanism, i.e.

2.14. Sampling from piles (they include limestone in warehouses and in river vessels) is carried out if it is impossible to test during the reloading process.

The stack is divided into squares, each of which should contain limestone weighing no more than specified in OST 14 63-80 and OST 14 64-80.

Spot sampling from a pile of limestone is carried out by taking an excavator to the full height of the scoop. The selected limestone is deposited on a prepared site for taking the required mass of a point sample.

If necessary, it is allowed to take samples in each square of the stack in a checkerboard pattern at the level of 1/3 of the height of the stack without digging holes.

Sampling is allowed in accordance with clause 4.2.4. GOST 15054-80.

2.15. When taking point samples by hand, limestone with a particle size of over 100 mm is chipped off representative pieces (10 - 30) mm in size.

2.16. The Dokuchaev Flux-Dolomite Plant is allowed to take and prepare samples of flux limestones according to the instructions approved by the chief engineer of the plant and agreed with the main consumer.

2.17. Point sampling at input control at the consumer it is allowed to produce from wagons using a clamshell sampler. The mass of the incremental sample must be at least the values ​​indicated in Table. one.

A point sample is taken from the surface of a truncated cone, the height of which must be at least 1/3 of the height of the full cone. At least one spot sample is taken from each wagon.

3. EQUIPMENT

3.1. Mechanisms for sampling fluxed limestone must meet the following requirements:

the sampling device must completely, at a constant speed and at regular intervals, cross the entire flow of homogeneous (by grade, fineness) limestone or part of it, provided that the samplers are multiple dividers;

the capacity of the sampling device should be sufficient to take the entire mass of a point sample in one cut-off or with incomplete filling (optimally 3/4 of the volume), and the width of the gap between the cutting edges should be at least three diameters of the maximum piece of limestone;

The design of the sampler must be accessible for cleaning, inspection and adjustment.

3.2. For manual sampling, the following are used: scoop (Appendix 1 GOST 15054-80), hammer, probe (Appendix 2 GOST 15054-80), sampling frame.

3.3. When preparing samples, domestic and imported equipment is used:

crushers, mills and attritors appropriate to particle sizes and mechanical strength limestone;

a set of sieves with mesh opening sizes corresponding to the size of crushing and grinding;

mechanical and manual dividers;

a drying cabinet providing a drying temperature of at least (105 ± 5) °С;

scales that provide a random measurement error of not more than ± 0.5% of the mass of the weighed load.

3.4. Before sampling begins, all machinery and sampling devices must be prepared, cleaned and adjusted.

4. SAMPLE PREPARATION

4.1. The pooled sample, composed of an appropriate number of increments, is numbered according to the manufacturer's accounting system and taken to the sample preparation room, where it is processed immediately.

4.2. To determine the moisture content of the combined sample, a part weighing at least 0.3 kg is taken, crushed to a particle size not exceeding (10 - 20) mm, placed in a tightly closed vessel and then sent to the laboratory or quality control department. The storage time of this sample is no more than 8 hours.

4.3. The remainder of the pooled sample (after taking a portion of it to determine the moisture content) is prepared for chemical analysis.

Primary crushing of the sample is carried out to a fineness of (0 - 10) mm, then - averaging and reduction to obtain a cash register of at least 0.2 kg.

When reducing the sample manually the following methods should be used: taper and quartering, shortening and squaring.

After reduction, a sample weighing at least 0.2 kg is crushed to a final size for chemical analysis, which is not more than 0.2 mm. Then the crushed sample is sifted through a sieve with holes corresponding to the final fineness adopted at this flux mining enterprise, but not exceeding 0.2 mm.

Metal particles contaminating the sample are removed by a magnet.

Two samples are prepared from this mass, one is sent to the laboratory, the second is stored for at least 1 month in case of arbitration analysis.

4.4. If the sample sticks during crushing, grinding and reduction, then, after extracting a sample from it to determine the moisture content, it must be dried at a temperature not higher than (105 - 110) ° C or (150 ± 5) ° C to constant weight.

4.5. A detailed scheme for preparing samples for chemical analysis and determination of moisture content is given in the relevant instruction of the manufacturer of flux limestones, approved in the prescribed manner.

5. PACKAGING AND STORAGE OF SAMPLES

5.1. Each sample for chemical analysis placed in a bag or jar is recorded in a special journal. The label of the package or jar should indicate: the name of the material and the number of the sample, the place and time of sampling and sample preparation, the names of the samplers and samplers.

5.2. The sample log for chemical analysis must contain the following data:

name of limestone and sample number;

the number of the batch from which the sample was taken; place and time of sampling and sample preparation;

names of samplers and samplers;

number of these guidelines.