Laboratory work №1 Theme lessons: Research of the properties of natural carbonate raw materials
The purpose of lessons: the study of the physical and mechanical, chemical and physical properties of natural carbonate raw materials, evaluation of the suitability of the raw material for magnesia lime technology, firing magnesite and magnesia binder receive.
The plan of lessons
Introduction to the procedure of GOST 22688-77 "Building lime. Test methods "- the definition of active MgO
Introduction to the method of GOST 1216-87 "Caustic magnesite powder. Specifications"
The study of the physical and mechanical, chemical and physical properties of natural carbonate raw materials
Evaluation of the suitability of the raw material for magnesia lime technology
Buring magnesite and magnesia binding material receive
Running time of work – 3 hours
Brief theoretical information
Magnesia astringent and based materials have high strength characteristics approaching on their values to natural materials. But more importantly, unlike natural materials, magnesia cement has an abnormally high rates of tensile strength and flexural strength (up to 20 MPa and above), which is associated with features of the hardened magnesite, which are present in the form of fibers crystallizing magnesium oxychlorides. Fibrous crystals not only increase the strength of the cement, but also function as reinforcing material.
Binders - building materials for the manufacture of concrete and mortar. There are inorganic (mineral) binders (cement, gypsum, lime, etc.). Mineral binders (usually powder) by mixing with water (sometimes with aqueous salt solutions) form a plastic mass and then acquires stone type condition. They are divided into hydraulic capable to harden and keep durability in the air and in the water (example., portland cement), and air, hardening and preserving the strength of only the air (gypsum, lime).
Lime (from the greek asbestos - unquenchable) - generic name calcine (and downstream processing) of limestone, chalk and other carbonate rocks. There are quicklime (CaO), slaked lime.
Burning - heating and holding at a high temperature (in kilns) of different materials to impart desired properties or remove impurities.
Equipment, tools and technical means: natural carbonate raw materials; jaw crusher; metal or porcelain mortar; technical and analytical balances; fireclay or porcelain crucible; muffle furnace.
The order of performance of works in the audience:
Master students familiarize with the procedure of GOST 22688-77 "Building lime. Test methods "- the definition of active MgO and GOST 1216-87" Caustic magnesite powder. Specifications"
After studying the necessary information master students studying the physic-mechanical and physic-chemical properties of natural carbonate raw materials
Then Master students evaluate the suitability of the raw material for magnesia lime technology and calcined magnesite to produce magnesia binding material
The main raw material used in the production of caustic magnesite is a carbonate rock. Requirements for carbonate rocks for magnesia lime are shown in Table 1.
Table 1 - Requirements for carbonate rocks for production of lime
Indicators |
Classes |
||||
A |
B |
C |
D |
E |
|
СаСО3, % no less |
93 |
90 |
85 |
47 |
72 |
MgСО3, % no less |
4 |
7 |
7 |
45 |
8 |
Clayey containing impurities SiO2, Al2O3, Fe2O3, % no more |
3 |
3 |
8 |
8 |
20 |
Elemental carbonate raw material mainly comprises mineral magnesite MgCO3 and impurities in small amounts of calcite, dolomite, clay minerals, quartz. The presence of impurities in the raw magnesite is reflected in the process of producing caustic magnesite, causing a change in firing temperature and furnace productivity, and also affects the properties of the finished product - a binder.
As a raw material for producing a magnesia binding material in vitro magnesite deposit was selected.
Physical and mechanical properties of raw materials used in the work are given in the report on form Table 2 and the reference data.
Table 2 – Physical and mechanical properties of magnesite raw
Type of raw materials |
True density, kg/m3 |
Bulk density, kg/m3 |
Porosity, % P=(1-ρbulk/ρtrue)100 |
Natural rock humidity, % |
Compressive strength, kgs/sm2 (MPa) |
||
loose |
ulotnennny |
loose |
ulotnennny |
||||
М |
|
|
|
|
|
|
|
Note: in Table M - magnesite
The chemical composition of magnesite is shown in Table 3.
Table 3 - The average chemical composition of magnesite, mas.%
Type of raw materials |
Insoluble residue (SiO2) |
Al2O3 |
Fe2O3 |
СаО |
MgО |
Δmпр |
Σ |
M |
16,50 |
1,53 |
2,38 |
2,00 |
37,17 |
39,80 |
99,38 |
Mineralogical basis of the formation of magnesite MgCO3 77.96% in an amount, as impurities accompany quartz, talc, calcite, chlorite, montmorillonite.
On differential thermal in the temperature curve magnesite 550-580°C is present deep endothermic effect corresponding to the dissociation of MgCO3, which allows to determine magnesite calcination temperature for binder - caustic magnesite - in the laboratory.
Working process
Carbonate raw materials are ground in two stages: in a jaw and roller crusher (Figures 1a and b) and then in a laboratory roll mill MLR-15 (Figure 2a) or metal (porcelain) mortar by hand into pieces of 5 mm size 3- (or less) . After each grinding sampling for analysis and screening on sieves for fractions №5000 was held, 3150, 2000, 1000, 500, 315, 100 μm using a vibrating screen Fritsch Analysette 3 PRO (Figure 2b).
|
|
a) |
b) |
a) – Jaw, inlet 150-100 mm, 20-50 mm output
b) – roller, inlet 20-50 mm, 10-15 mm output
Figure 1 - Laboratory Crushers
|
|
a) |
b) |
a) – Laboratory roller mill MLR-15;
b) – Circular Vibrating Screen Fritsch Analysette 3 PRO
Figure 2 - The Mill and crashing the laboratory
On the technical balance is weighed weighed particulate material in an amount of 25-100 g (on the instructions of the teacher), is placed in a porcelain or fireclay crucible and fired in an electric laboratory muffle furnace (Figure 3).
Figure 3 – Electric muffle furnace
Oven heated by the free mode to the firing temperature selected previously. Holding at the final temperature is 0.5-1 (2) hour. After firing, calcining magnesite crucible with product placed in a desiccator to cool. The cooled calcine (magnesia astringent) weighed on technology (analytical) weights and calculated mass loss during firing sample according to the formula. Storage magnesia astringent - caustic magnesite produced in the laboratory, carried out in a closed plastic bag placed in a desiccator.
According to the results of laboratory work provides data on the properties of the investigated carbonate raw materials, raw materials weight loss during firing and concludes as firing on the following process parameters: theoretical and practical values of flow coefficients of magnesite raw materials; theoretical and practical values of the output coefficients of the finished product - magnesia binder.
Technological calculations
Magnesite
is decomposed at lower temperatures (beginning decomposition of
possibly 400°C). Decarbonization magnesite continues as long as the
partial pressure of carbon dioxide in the environment is lower than
the pressure (elastic) MgCO3 dissociation. Typically, in industrial
firing conditions, the degree of decarbonization of raw materials
reaches 90-98%. The material balance of the carbonate rocks of the
dissociation process can be characterized by the theoretical raw
material consumption ratio:
and the theoretical output
of the finished product ratio - magnesia astringent - Кt(escape).
When full decomposition is formed of 1 kg of MgCO3 and MgO 0.476 kg 0.524 kg CO2. Consequently, to obtain 1 kg of MgO require pure magnesium carbonate:
K consumption = 1 * 1 / 0,476 = 2,10
where: - MgCO3 pure theoretical flow rate to produce 1 kg of magnesium lime, kg;
0,476 - theoretical output ratio of magnesium lime.
The theoretical flow rate of magnesite raw materials will be:
Кt(output) = 1 / (1 – 0,524 * τMgCO3)
where: Кt(consumption) – theoretical coefficient of discharge of raw magnesite, 1 kg of raw material per 1 kg of lime;
1 - raw material consumption - 1 kg;
0,524 — theoretical LOI raw magnesite caused by removing CO2 from magnesium carbonate;
τMgCO3 - the proportion of magnesium carbonate in the rock.
The theoretical output of the finished product ratio (1 kg magnesia binder of 1 kg of raw material) - magnesia binder amount:
Кt(output) = 1 - 0,524 * τMgCO3
Practical finished product output ratios (1 kg magnesia binder of 1 kg of raw material) and the consumption of raw materials (1 kg of raw material per 1 kg of magnesia astringent) are calculated according to the formulas:
Кpr(output) = (m-Δmпр) / m
Кpr(output) = m / (m - Δmпр)
where: m - consumption of raw materials (in the assumed rate equal to the mass of rock sample before firing), g;
Δmпр - loss during firing (calcination), sample investigated breed, g.
The weight loss during firing rock sample is calculated according to the formula:
Δmпр = М1 / М * 100
where: Δmпр - weight loss, %;
М1 - differences in sample weight before and after firing, g;
М - the original linkage material, g
The order of registration reports and their protection:
The report is issued in the following order:
To familiarize with the procedures of GOST 22688-77 "Building lime. Test methods "- the definition of active MgO and GOST 1216-87 "Caustic magnesite powder. Specifications"
To study the physical, mechanical and physic-chemical properties of natural carbonate raw materials
To assess the suitability of the raw material for magnesia lime technology
Perform firing magnesite and magnesia binding agent receive
Control questions
To characterize the natural carbonate raw materials?
To characterize magnesia lime?
To characterize magnesia astringent substance?
Task on the house:
To familiarize with the procedures of GOST 22688-77 "Building lime. Test methods "- the definition of active MgO and GOST 1216-87 "Caustic magnesite powder. Specifications"
Perform an analytical review of natural carbonate raw materials for the South Kazakhstan region
To study the physical and mechanical, physical and chemical properties of natural carbonate raw materials
Perform an analytical review of the market of construction materials of the Republic of Kazakhstan
Tasks to MIW