GLOBAL DESCRIPTION OF THE PROCESS

PROCESSES

The production process of bricks and clay derivatives begins with the selection of the
land in the mines, analyzing the different types that meet physical properties and
appropriate chemicals for the manufacture of red ceramic and stoneware products.

Once the analysis is done, the soils are mixed and left to rest to achieve a better
homogenization, after which two options can be taken: a dry process or a process
humid. Once the raw material is in optimal conditions, the process begins
extrusion, where it is molded and cut according to the shape and size of the product to be obtained.

At the end of the extrusion, molding, and cutting process, the product moves to the drying stage.
which can be in two ways: natural, where the product is taken to the yards and placed in
in such a way that air circulates, with a time frame of between five and eight days; and artificial, process in the
It circulates hot air by mechanical means, with a time frame of 24 to 72 hours.

At the end of the drying process, the material goes to the stages of burning, quality control and
dispatch or storage.

Currently, the most important methods for making bricks can be divided into three.
groups, according to the state of the clay used.

Plastic cutting process using wires

Compact plastic process.
Semi-dry or semi-plastic process.

In Colombia, the most used process is the wire cutting plastic process, in which
uses a maximum plasticity clay, with a moisture content of 15 to 20%. This
method is especially adapted for forming bricks from the lowest quality clay.
the most important employment is for the production of ordinary red bricks, tiles, pipes and
accessories for construction. The clay used for this type of product is a clay
superficial, which is characterized by the presence of impurities such as stones and small
pebbles that may have been incorporated during the undermining.

The fundamental difference between the wire cutting plastic process and other processes
consists of the fact that in the first one no molds are used to shape the bricks, the principle of
this training method is the extrusion of a continuous column of plastic clay paste
through a press via a mold. The column is then cut into bricks
through the tensioned wires of a cutting machine. Unlike the plastic process of
cut by wires, in the compact plastic process and in the semi-dry process, the bricks are
molded in a press.

The compact plastic process is also used in Colombia but to a lesser extent than
the plastic cutting process using wires. In this process, the water content varies from
10 to 15%, depending on the clay used and the type of product that needs to be formed. The paste
plastic is pushed through a extruder into a closed mold (clot box), and
when the mold is full, the paste is discharged. This preformed piece of clay (clot) is
it then leads to the press. Modern presses usually consist of two eccentric presses
that press the bricks alternatively; while one press is unloading, the other is
exerting pressure. When pressing the compact plastic, it is advisable that the pressure is
keep on each brick for a considerable amount of time. When bricks are needed of
a high degree of finish (facade brick) is pressed in a press following
the first. The bricks that come out of the first press are lifted to a position from the
which, through a driving device, are placed precisely in the press mold
subsequent, which is driven at the same speed as the first press.
The semidry or semiplastic process uses clay with a consistency halfway between
dry and plastic. The material used is in the form of a wet powder that contains 5
at 9% water. The cohesion of the clay particles is produced by the making machine
bricks, applying a very high pressure (between 500 and 2000 lb/inch.2) about the pasta.
The drier it is, meaning the less plastic the material, the greater the pressure required.
to communicate the necessary cohesion to the particles. The semi-dry process is particularly
suitable for pressing clay bricks that contain bituminous materials. The latter
it acts as a lubricant, making the addition of oil to the clay powder unnecessary. In a
semi-dry brick making machine, the material, after having passed through the mill
grinder and through the sieve, falls by gravity in the form of powder, descending through a chute
from canvas, to the sliding cart. This cart moves forward, up to right on top
from the empty mold, into which the wet powder falls. The wet powder that has fallen inside the
The empty mold is pressed using two different pressings between the upper and lower plungers.
The pressed brick is pushed to the unloading table by the sliding cart when it
move forward again to fill the empty mold. For the re-pressing, a
additional mold (repressing mold) immediately after the first mold, the brick is
automatically taken to this additional mold and pressed again. One of the main
The advantages of semi-dry pressing is the fact that pressed bricks do not have to be
dried in special dryers, but can go directly to the oven.

PROCESSED PRODUCTS

The products obtained in the manufacturing process of bricks and clay derivatives
they are the following:

Bricks. They are artificial stones of parallelepiped shape, low in height, obtained through the
molding and firing of clays of suitable composition. The bricks must have
certain properties such as mechanical resistance to weathering and to changes in
temperature, to be homogeneous, not heavy or very porous.

The type of brick structure (laminar) decreases its strength, this can be avoided.
greasing the extruder nozzle, regulating the discharge speed, adding alkalis to
the paste to increase plasticity or by increasing the cooking temperature. The bricks
Machine-made fabrics are more porous, permeable, and less resistant to compression.
than those made by hand. The bricks must have reduced thermal conductivity and good
resistance to freezing.

Brick Classes

Ordinary or Construction. They have a compressive strength of 1500 lb/inch.2(105

kg/cm27000 lb/inch2(492 kg/cm2), water absorption greater than or equal to 8%. The bricks
common ones are made with more or less sandy and lean clays. If the clay is too
plastic, the bricks are exposed to deformations and cracks. The bricks must be
cooked at a rather high temperature to provide the required mechanical strength
an adequate resistance to atmospheric influences. It is also important that the bricks
do not present complete vitrification, since a certain degree of porosity is necessary and
that the thermal insulating properties of the brick improve.

Engineering or Vitrified. The compressive strength is greater than 7000.

lb/inch2(492 kg/cm2) and the average water absorption by weight is 4.5 to 7%. They are
of dark color, with high mechanical resistance, they are sewn at high temperatures, they are
weather-resistant and are used for street pavement.
Hollow Construction Bricks. They are blocks with one or more empty spaces that
It crosses through, the thickness of the wall is generally small compared to the
size of the holes, they are lightweight and structurally strong. The pastes
employees in the making of these bricks must be more plastic than that of the
other ceramic objects and the drying of these materials poses no difficulty, being
faster than that of solid bricks and less exposed to deformation.
Hollow bricks are subdivided into:

- For interior walls and partitions. Both sides prepared for plastering or finishing.
both sides smooth to use without plastering or rendering or one side for rendering.
For floors, ceilings, attics, and structural

The following table shows the specifications of hollow construction bricks.

Specifications for Hollow Construction Bricks

TYPE DIMENSIONS (cm)

H2 Hollows 35*18*13
H3 Gaps 35*23*9
H10 Gaps 45*20*10
H15 Gaps 40*25*15
H20 Hollows 40*25*20
H23 Gaps 35*23*18
Source: British Standard Specifications.

Facade Bricks or Cladding. Used inside buildings, the color stands out.
(red, yellow, gray), durability, weather resistance, uniformity of size and shape. The
the surface can be smooth or textured rough made before cooking

Tejas. The tiles are generally made through the plastic process, they are obtained white in
rough, made of compacted plastic clay extruded by a maxaladora through a die, and
are cut by wires in a manner similar to that used in the production of bricks. The tiles
The clay must be cooked to a degree such that it has a quite reduced porosity to be
practically waterproof, but should not be too glassy in order to
avoid "sweating", they must also be resistant to the elements and frosts, since
that must be continuously exposed to atmospheric action. The absorption of water must
be less than 10.5% and its flexural strength greater than 175 lb (79.45 kg).

Types of Tiles.

Reds, multicolored, blues, covered with sand, pavement slabs, tiles and shingles of
companies, subdivided into:

eaves tiles
Tiles and half tiles
Tiles of various slopes
Ridge tiles
Vertical angle tiles
Ridge tiles.

Tiles. They are called this way some pieces of various shapes, square, rectangular, triangular,
hexagonal tiles, which are used in the flooring of rooms. Their manufacturing is the same as that of the
bricks.

ENTRIES TO THE PROCESS

The inputs to the process are classified into

RAW MATERIALS
NATURAL RESOURCES
RAW MATERIALS

The material used in the manufacture of bricks and clay derivatives is chamotte.

Chamote. It is the breaking material produced in the brick manufacturing process and
clay derivatives, and it is incorporated into the process after being previously crushed in a
jaw crusher. The chamotte can be of two types depending on the origin: Raw chamotte is
the one generated in the drying process, and characterized by not undergoing chemical changes; and the
cooked chamote, which is produced during the cooking stage, this material has undergone changes
physical and chemical changes due to the high temperatures to which the material was subjected in the oven.
This material improves the product's durability.

NATURAL RESOURCES.

The natural resources used in the manufacturing of clay products are the following:

Clay. It is a product of the decomposition of feldspathic rocks. The constituents

mainly are hydrated aluminum silicates and can be divided, among others, into the
groups of kaolinite and montmorillonite. The main ceramic characteristic is its
plasticity (particle size); other properties are: suspending agent, resistance
mechanics after drying, variety of colors according to impurities, impact resistance
thermal and high temperatures, insulating properties, etc.

One of the classifications based on its properties is:

Calcined white clays

Residual kaolin
Brasas (ball clays)
Refractory clays
Sedimentary kaolins
Refractory flint clays
Clay with high alumina
Low plasticity clays
Clays and schists for bricks, pipes, and tiles
Clays for stoneware (plastic with fluxes)
Clays for bricks (with iron oxide)
Fusible clays (with more iron oxide)

For the production of bricks and tiles, calcareous clays (with less than 30% of
CO3Ca), ferruginous and low in fat so that they do not deform or break during drying.
and cooking, without being harmful a certain content of sand that acts as a degreaser and
it reduces the contraction, having to contain the least possible amount of pyrites, gypsum and
pebbles that produce stains, efflorescence, disintegration, and breakage during cooking of the
material for the swelling process caused by such substances. The composition of
The clays used for the manufacture of bricks and tiles must range between the following
limits: If0243-61%, AL20326-39%, MgO 0-1.5%, CaO 0-1%, Fe2030-2.5%, (Na20 + K20) 0-
2.5%, sulfates 0-2% (they become insoluble by adding Cl2Ba or C03loss by calcination
(humidity + C027.4-18%, with a density of 1.5, and a humidity between 5 and 10%. Other
raw materials that can be used are pure clays mixed with sand to avoid
the cracking during drying and cooking. The clay usually enters the process with a
humidity of 14%.

Water. The water used in the production of bricks is water that is added to the clay,
the stage of preparing the raw material, to give it the required moisture (15 to 20%), to
its subsequent treatment in the extrusion stage.

Air. It is basically used in the drying and cooking stages. In the first, it is used for
carry out the drying operation naturally (outdoors) or artificially
which heats the air flow by taking advantage of the heat generated in the oven. In the stage
of cooking in combustion reactions in the oven.

Coal. It is used as fuel for energy generation in the drying stages.

cooking in all the brick factories in the country. The coal is composed of organic parts and
minerals. Among them are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), the
sulfur (S) and the ashes.

The following figure shows the coal consumption as a percentage by type of company in
country.

Source: UIS-IDEAM

The ashes of coal can quantitatively contain the following components: from 15-
21% of Al2O3; from 25-40%, SiO2; from 20-45% Fe2O3; from 1-5% CaO; from 0.5-1%, MgO and from 2-
8% SO3In some coals, the chloride content varies between 0.01 and 0.1% for
coals rich in ash, up to 0.5%. The fluoride content of the coals is
0.02% at most. The ashes of lignites contain 25-40% CaO; 3-10%
Al2O3between 0.5-5% of MgO and up to 40% of SO3Besides the mineral components, the
coal ashes contain salts (chlorides and sulfates), volatile components, such as
water of crystallization in clay minerals, in sulfates (gypsum) and in some salts;
Aside from it, there is also carbon dioxide in carbonates and sulfur gas in sulfates.

The combustible components are carbon, hydrogen, and sulfur; in combustion

These elements combine with the oxygen in the air and therefore generate heat. The greater
the proportion of these components in the fuel, the higher the heat of
combustion. When evaluating a fuel, only carbon and the
hydrogen that they contain.

The following table presents the elemental composition of coal and coke.

Elemental composition of coal and coke.

Components Hullas % Coke %

Carbon (C) 60-92 80-90
Hydrogen (H) 1-5 0.4-2
Oxygen (O) 2-14 -
Nitrogen (N) 0.3-2 -
Sulfur (S) 0.5-4 0.4-1
Ashes 5-15 8-14
 Humidity 2-15 1-1.5

Source: Manual of Chemical Engineering, Robert Perry. McGraw Hill Publishing, Mexico 1993.

Sulfur, although it burns, is not desired to be in the fuel, since when it burns
produces sulfurous anhydride, which, in the presence of water, yields sulfurous acid (H2SO3, which
it corrodes the metal parts of the installations and like Sox in the waste gases released to
the atmosphere acts in an extraordinarily annoying way on its organic environment.

Carbon does not immediately react with the oxygen in the air; the combustion to CO and to
CO2it occurs in chains, during which carbon reacts first with the radical
OH much more active. For the fuel to ignite, the presence of
small amounts of water vapor, because when theoretically the coal is dry it
inflames with difficulty. Because of that, the drying of the coal should not be extreme. A humidity
of the order of 1-1.5% boost combustion.

Natural Gas. Natural gas is the gaseous fuel most commonly used in the
ceramics industry, but not so much in the brick industry due to its high cost, in
function of the product that is obtained. The main components of natural gas are the
methane, CH4and ethane, C2H6The heavier hydrocarbons, such as propane, C3H8butane
C4H10, pentane C5H12and hexane, C6H14they are only present in natural gas in amounts
small. It is designated as "wet" if the natural gas contains pentane and hexane.

Heating Value. It is equal to the sum of the combustion heats of the fractions.
corresponding to each of the components. If the fuel is presented in the form of
chemical combination, then the heat of combustion of each of the elements minus the
thermal energy needed to dissociate that combination into its elements. In the gas
natural thermal energy for the dissociation of carbon and hydrogen from the molecules of the
hydrocarbons present in the form of chemical combination is approximately 9% of
total heat of combustion. Thus, the heat of combustion of methane:

CH4+ 2O2= CO2= 2H2O + 213,000 cal.

Volume of combustion gases. The components of natural gas combust.

according to the following equations:

Methane CH4+ 2O2CO2+ 2H2O; Ethane 2C2H6+ 7 O2= 4CO2+ 6H2O

Propane 2C3H8+ 10 O26CO2+ 8 H2O; Butane C4H10+ 6 ½ O2= 4CO2+ 5 H2O

Pentane C5H12+ 8O2= 5CO2 + 6 H2O; Hexane C6H14

With the help of these equations, the volumes of the products can be calculated.
combustion of natural gas if its composition is known.

Volume of combustion gases from coal, fuel oil, and natural gas. The combustion of
coal, fuel and natural gas, for the same amount of thermal units, provide different
volumes of combustion gases.

The summary provided below contains the volumes of the combustion gases (with
a 10% excess air generated in the production of 100 kcal obtained by combustion
of coal, fuel, and natural gas.

1000 kcal obtained from coal produce 1.24 m3Combustion gases 1000 kcal
obtained with natural gas produce 1.47 m3N of combustion gases.
From those values, it is deduced that the fuel produces approximately 6% more gases than the
coal; natural gas, 18.5% more than coal. 1000 kcal obtained from fuel produce
1.31 m3In combustion gases.

Castilian Crude. Like coal, it is a widely used fuel in the industry.

brick factory of the country. The main problem presented by this fuel is its high content of
sulfur, which according to ECOPETROL is 2.2%. It is a crude oil with characteristics
similar to that of heavy fuel oil which, once it comes out of the well, is subjected to dehydration for
remove the excess water and leave it in a condition to be used as fuel.

In the industry, it is used as fuel in furnaces, dryers, and boilers.

The most important characteristics of Castilla crude oil are shown in the following table.

Physical properties of Castilla crude oil

VALUE
CHARACTERISTICS UNITS
TYPICAL
Sulfur % mass 2.2
Ashes % mass 0.8
Water by distillation % volume 0.6
o
Flash point C 82.7
o 2
Viscosity at 40 C mm / s 1360
o 2
Viscosity at 40 C mm / s 668
Vanadium mg/Kg 320
Nickel mg/Kg 99
Iron mg/Kg 32
Sodium mg/Kg 2

Chemical Engineer's Handbook, Robert Perry. McGraw Hill Publishing, Mexico 1993.

The emissions produced by its incomplete combustion are significant amounts.

of NOXCOXand SOX.

STAGES AND TEAMS OF THE PROCESS

Adjustment of Raw Materials

Raw materials in the state of division and purity in which they are found in nature
they cannot enter the process directly, which is why the clays are air-dried on
surfaces in sandy to produce disaggregation and purification if the preparation process
it is by dry way; if the preparation is by wet way, the clay is used as it comes out
deposit to form a ductile and homogeneous paste. When it is desired to increase the
plasticity of a clay, this is accumulated by wetting it abruptly for a period
of a determined time depending on the type of clay, which is called maturation
or maceration. Once the clay is ready, it is transported by means of conveyor belts to the
feeding hoppers, responsible for dosing the clay to the crushing equipment and
grinding.

Feeders. The feeders with metal scale beds or rubber belts are
basically intended to collect and dose the material along the lines of
preparation and molding of clays. They come in various widths and lengths, as well as in
different heights and types of hoppers, adapting to the needs of the installation of which
part. They are powered by a geared motor that moves the bed or bottom and another
which activates the distributor shaft. These feeders are called type (E) and in type (C),
an integral reducer and a single motor drives both mechanisms. With the feeders, it
also obtain the appropriate proportions for the components of the mixtures
of clay, as well as, gathering material and making the lines of the installations independent where
needs to frequently change qualities or types of products to be manufactured, not being
It is therefore convenient to store large quantities of product.

The different types of feeders are described below.

 Vibrating Hoppers. Considered among the most important and versatile. They are used
to enlarge the opening of the storage tanks and cause the flow to
breaking the bridges formed by the material. Two basic types of hoppers are common
vibratory: the rotary type, in which the vibration is applied perpendicularly to the channel
of flow and the type of vortex, which provides an elevation and an oscillation
combined with the material, causes the bridges that are formed to break.
Screw feeders or helical feeders. It is used to help unload.
deposits and produce a uniform diet. In this case, it is important the
need for a variable pitch screw to produce a uniform drive
of the material through the full opening of the hopper. For there to be uniform flow, the
The numerical relationship of the screw feeder opening to the diameter should not
exceeding six.
Star feeders. With a screw conveyor or spiral conveyor collector.
they provide a very uniform output across the slotted opening. It should
add a vertical section of at least one outlet above the feeder
to ensure uniform output through the opening.

Conveyor Belts. Conveyor belts are used almost universally.

They can cover distances at speeds of up to 5.08 m/s and handle up to 4539 tm/h (5000
ton/h). They can also operate at short distances at sufficiently slow speeds.
for manual collection, with a capacity of only a few kilometers per hour.

The slopes of the conveyor belts are limited to a maximum of approximately 30

degrees, and the most common ones are found in the range of 18 to 20 degrees. It can only be
produce directional changes in the vertical plane of the belt's trajectory and must
carefully design as vertical curves or relatively flat bends.

Conveyors can be made of steel sheet, rubber, or scales. The belt

steel sheets are used in horizontal and straight sections, over long distances, they are
more expensive but better withstand impacts. Rubber bands are used in straight sections and
of medium inclination, they are cheaper and faster. The scale tapes, of lower
speed that rubber ones are used for transporting heavy loads, in curves or
elevated earrings.

It is essential to clean the belts after loading. The stuck clay dries and does not
it detaches. Very plastic and excessively wet clays can present
adhesion problems in the tapes.

GRINDING AND SIEVING

The grinding and sieving stage is carried out in order to obtain a particle size.
suitable for use in the manufacture of bricks and clay derivatives. The grinding in
the manufacturing of bricks should be gradual and generally in two stages: the first one a
preliminary crushing, which is carried out to reduce the size of the material and achieve better
results in subsequent grinding. In the preliminary grinding, the material is reduced to a
approximately 8 cm in diameter at most; the second stage called
pulverization or grinding is carried out in order to achieve a higher degree of fineness of the
particles, milling can be done dry or wet.

The equipment used in preliminary or primary crushing is as follows:

Crushers.. The fragmentation is carried out between two or three rollers with blades.
incorporated, rotating one upside down from the other along their axes arranged horizontally in
parallel. The product to be shredded enters the machine and passes between the rollers and the
blades, being reduced to the size of the aforementioned cylinders, through the actions of
shearing and compression. Reduction ratio (Hard 3:1; Soft 10:1).
Disintegrators: The fragmentation is carried out between two rollers, one of which has knives.
incorporated, rotating one upside down from the other on their axes arranged horizontally in
parallel. The disintegrated product enters the machine passing between the rollers, being
reduced by the blades, through shearing and pressure actions. Reduction ratio
(Hard 5:1; Soft 10:1).

Other equipment used in preliminary crushing includes:

Jaw Breakers
Ball Mills
Jaw Crushers
Gyratory Crushers
Roller Crusher
Impact Breakers
Tray Shredder
Launcher mill
Centrifugal and bell mills

The equipment used in secondary spraying or crushing is:

Rollers. Rollers are machines closely related in the processes of

preparation, in the machinery facilities for the ceramic industry, structural, bricks,
Tejas, etc. They are mainly applied in installations via semi-wet and especially
In specific cases where allowed, dry means are sufficient. They are used as secondary machines.
(5 to 3 mm) or tertiary (1 to 0.5 mm) refining, the product fragmentation is carried out by
compression, friction between the rollers, rotating in opposite directions towards the gauge or
separation between them. The production of the gauge depends on the size of the input material,
from humidity and plasticity, becoming limited the smaller the gauge, of the speeds
peripherals and the width of the rollers. The maximum size of the product to be crushed depends on the
friction coefficient between the product to be ground and the rolls of the mill, size or
diameter of the grinding cylinders and the speed of the rolling mill. Reduction ratio
(Hard 5:1; Soft 10:1).

Other equipment used in the spraying stage includes:

Disintegrator
Launcher Mill
Roller Mill
Hammer Mill
Pendulum mill
Cylinder Mills (smooth or grooved)

Once the product is ground, it is classified by sieving, using sieves of

rotary drum or oscillating drum; in both cases, the machines are arranged
so that they can serve at the same time to transport the ground and sifted product to the silos or
respective readings. The iron particles and magnetic oxides are removed by passing through the
ground material by a magnetic separator or purifier, formed by bundles of soft iron
what they do as poles of an electromagnet.

The following are the most commonly used types of sieves.

Rotary Screens. In most screens that provide defined size fractions, there are
first separate the coarse material and, at the end, the fine ones. These machines contain several series
of sieves, one on top of the other, fitted into a box or casing. The largest sieve is
top and the finest at the bottom, and all are equipped with suitable drainage conduits
to separate the different fractions. The mixture of particles is introduced into the upper sieve.
The sieves and the casing move to allow particles to pass through the openings of the
same. The rotation takes place in a vertical plane around a horizontal axis, through a
eccentric placed at the bottom of the casing halfway between the point of
feeding and discharge. The sieves are rectangular and quite long, from 0.5 by
1.5 m to 2 by 5 m. The rotational speed and the stroke amplitude are adjustable, just like
that the angle of inclination. The rotation speed is from 600 to 1800 r.p.m. and the motor from 1 to 3
CV.

Vibrating Screens. Vibrations can be generated mechanically or electrically.

Mechanical vibrations are normally transmitted from high-speed eccentrics to the
case of the device and from there to the strongly inclined sieves. The vibrations
electric currents produced with powerful solenoids are transmitted to the casing or directly to the
screens. Generally, no more than three platforms are used in vibrating screens. They are
usual about 1800 to 3000 vibrations per minute. A sieve 30 cm wide by 60 cm
large requires approximately 1/3 of a horsepower; one that is 1.20 m by 3 m, requires 4 horsepower.

Kneaded or mixed.

Kneading consists of intimately mixing the previously prepared clay with water, and it is
the more perfect it is, the more uniform the mixture. Variables such as the following affect the kneading:

Clays. The clays must fall at the beginning of the mixer, that is, in the first
kneading blades. The use of clay regulators and dosers is recommended for
that this does not flow into the mixer with different intensity or intermittency, in addition
it facilitates the process of stopping feeding due to clay buildup.
Water. The water must be brought into contact with the mud at the beginning of the process, it is
to say, from the moment the clay falls into the mixer. The water that falls more
forward, it equates to losing kneading length, time, and greater effort of the
machine, causing breakage of shafts and bearings. The level of must be maintained
humidity, to avoid variations in the molding of the clay; the distribution of water must
to be uniform, so that every clay particle is moistened; the hot water,
which is almost vapor, easily penetrates and comes into contact with all the particles of
the clay, leaving no dry spots; the clay must be well moistened to avoid
greater efforts of the machine, especially heating the outlet mouth.
the mouth is hot, it transfers the heat to the clay that is in contact with it and the
central falls to normal temperature, causing parts to clear easily
due to the different contractions and expansions.

Mixer. The mixer should be long, but greater length results in higher consumption of
force, greater weakness of the axes and bearing breakage due to high stress. The useful length
recommended is 2 to 2.5m (for bricks and products scale 1:1), the length and time of
kneading depends on the length of the machine, the tilt of the blades, and the revolutions
of work.

The factor that affects production is the width of the mixer, which must be suitable.
to the production of pieces. The side blades cut the clay between the same blades of
kneading, it also prevents the transport of more or less wet clay and facilitates the intimate
link between wet clay parts, providing uniformity to the clay.

The kneading paddles are angled and some have on the outer cutting surface
steel segments, to replace them when they wear out. The segments are joined with
screws to the base, but these oxidize when in contact with water and are difficult to change

The quality of the clays obtained with extruder mixers and filter mixers is
superior to that achieved with traditional mixers.

Existing mixers in the market:

Double Shaft Mixer. The most common mixer used for mixing work.
from clay. The paddles are inserted in the center of the mixing tank.
 Counter-Current Mixer. Especially for fine work, it consists of a
closed on both sides, the discharge is carried out in the center of the mixer,
where at its bottom there is a round or square opening through which the clay falls already
dampened. Requires more power and a higher installation cost.
Compression Mixer. Achieves a greater union of water and clay, causing it to exit.
the mixture in the form of macaroni in every sense, through the grates arranged to
final. It removes hard and foreign bodies because there are fins at the beginning of the axis.
and then propellers that drive the mass in a single direction, at the end of which,
the foreign bodies will stop and can only exit through the side grilles
clay in the shape of macaroni. An automatic device periodically ejects
waste to the outside, without interrupting the operation of the machine, extending its life
useful. This machine performs the functions of rolling cylinders after kneading,
when compressing the clay to be able to go outside. The exit grilles are
interchangeable. The mixer does not require much force because the outlet area
The airflow around the grilles is superior to that of a normal cookie tin at the outlet.
Extruder Mixers. They are especially suitable when adding to the
degreasing clays or chamotte that mix poorly and tend to produce
segregations. They are also very useful when working with plastic and compact clays.
that become wet with difficulty.
Filter Mixer. It is an extruder mixer equipped with filtering screens.
from which the clay passes. They are very suitable for retaining roots and stones that
contain some types of clay, which are difficult to remove in the preparation for
wet route that causes frequent stops at the biscuit factory due to obstruction of
molds and nozzles.

MOLDING

At this stage, obtaining the molded shapes is conditioned by the consistency of the
dough and the shape and size of the objects that are going to be obtained, it is generally done
by extrusion. In this process, to obtain good extruded products, it is
it is essential that the clay has the corresponding plasticity. The behavior of a
clay during molding is determined by its plasticity, precisely obtaining the
better results with medium plasticity clays. Both high plasticity clays,
Rich in colloids, such as low plasticity clays, often cause problems in extrusion.

With lean clays or low plasticity clays, it is difficult to maintain the molding moisture inside.
of some correct limits, since the variants it allows are very limited (soft extrusion
with hollow materials of European type). If worked with a slight excess of moisture, the
pieces that are extruded deform as they advance over the rollers, forming "paw"
elephant", and if, on the contrary, there is a lack of moisture in the clay, notches appear on the pieces
Hollow and the cutter crumbles the walls.

In clays with high plasticity and especially colloid-rich clays, with molding moisture
ranging from 25 - 40%, the machine's performance may be reduced by up to 10.
and 20% of its nominal value when the material adheres to the blades, significantly reducing its
capacity.

The extrusion process takes place in horizontal or vertical presses where the clay
through the push provided to the vacuum by a piston or by a screw, it is forced to
pass through a nozzle that shows variations according to the finished product (block, tile,
tube, stick, etc.

Bricks, tiles, cobbles, blocks, and other masonry pieces are obtained through
a horizontal extruder. The clay tubes are manufactured using vertical extruders or
horizontal where the nozzles vary for obtaining tubes of different diameters.

Extruder. An extruder is basically a machine composed of a set of

components or mechanisms that allow for the compaction of clay mass, through the
removal of air occlusions or degassing and the pressure to which the clay is subjected
between the body of the machine's screws and the funnel or mold.

The pressure cylinder is the component of the extruder that is next to the
vacuum chambers, and that also contains the blades at two diameters with a transition
constant through a conical helix. Once the clay has passed through the axes of the
mixer, is placed in the input area and suitably homogenized and
crumbled by the stars is introduced into the vacuum chamber and led towards the
core of the transport helix by the feed blades. From the transport area, the
Clay moves to the pre-compression area where the actual compression begins.
at the same time it is homogenized, starting the formation of the texture, to move on
following the pressure zone, where the material, upon varying the section of the conical screw,
it suffers a transverse slip and better grip on the outer cylinder as it increases the
speed of displacement, moving on to the pressure zone, where it is
maximum and subsequently to the exit zone or funnel with mold.

In the exit area or funnel together with the mold, where a correct maintenance must be kept.
geometry so that the flow or output bar is not altered, losing its laminar structure,
without internal slips of the material that generate internal stresses in the
pieces and subsequently possible breakages during drying or baking.

DRYING.

The drying stage is primarily carried out to remove part of the water that the piece brings.
extruded and that was incorporated mainly during the kneading stage. The pieces in the
drying goes through three phases: a first of loss of water contained in the pores; another of
new water removal until maximum contraction is reached and a third consisting of
the loss of the remaining water, allowing the appearance of pores.

Drying is a simultaneous operation of heat and mass, which is of vital importance in the
brick industry, because it is at this stage of the process where the greatest
percentage of production losses due to cracks, contractions, delays
production, deformations, obstructions of roads. It can be said that the production of a
brick industry depends on drying, as the extraction capacity, production and
The oven is generally high.

In general terms, it can be said that one must know the chemical characteristics and
physical properties of clays, to determine the drying speed. The drying speed is more
adequate, is the one that is achieved in the shortest time, without causing breakages due to
contraction.

The drying used in the brick industry and clay derivatives can be natural or artificial.
In natural drying, ceramic products are left in large areas, under cover or in the open air.
free. Structural masonry products are dried by the action of the wind, therefore
the drying time depends on atmospheric conditions such as air speed,
temperature and relative humidity. This type of drying prevents a high production rate in
medium or highly technified plants (continuous furnaces).

When a wet brick is introduced into an artificial dryer, in which hot air circulates,
a heat flow is established to the interior of it, forcing the moisture out of the solid.
The dry air, when in contact with the damp material, transfers heat to its surface,
evaporating its free moisture. If the temperature and air speed remain constant,
the water is eliminated at a constant rate, until the solid reaches its critical moisture, moment
in which the first dry spots appear. If the drying is abrupt, a
abnormal humidity removal gradient, which is accompanied by cracking,
deformations and contractions of the material.
In a dryer, the temperature of the hot air can be high while the bricks
they maintain a high level of humidity (10-15%). For a certain temperature of
the air, the heat consumption will be lower, the higher the final degree of
outgoing air humidity, if hot gases are used, it is advisable that they come from
clean sulfur fuels to prevent discoloration of bricks.

Artificial Dryers. The installation of artificial dryers entails supplementary costs.

high, another unfavorable economic reason lies in the fact that they are equally needed.
number of calories to dry it, as to cook it. However, in order to increase the
production and reduce breakage losses, a proper drying calculation can reach
guarantee fairly reduced coal consumption, based on the recovered heat in
the evacuation of the oven fumes. The artificial dryers are classified as intermittent
or continuing.

Intermittent Dryers. In the intermittent dryers, the pre-dried material in

environmental conditions, is introduced into one of the adjacent chambers of the
dryers, which must have humidity and temperature controllers. The
cameras are of different dimensions and gases can be used in them
chimney of the furnaces or the combustion gases from a neighboring home. These gases
are introduced through the floor and redistributed by a fan, to exit humid through the
lower part with the help of an extractor. The circuits can be connected or
independents.
Continuous Dryer (Tunnel Type). The tunnel type continuous dryer consists of a
gallery of 60 to 80 meters, in which hot air penetrates at one of its ends
against the flow of the material, which is transported through the
tunnel in wagons or shelves. The temperature ranges from extremely cold to hot at 30
At 120 degrees Celsius, the drying lasts 20 to 24 hours. Generally, this
Drying is used when there is a tunnel oven in the process.

Cooking

The cooking process is the most important and delicate phase of the manufacturing process. In this
the stage confers the desired properties to the piece, while also putting into
manifest if the preceding stages, preparation, molding, and drying have been completed
correctly or not. The materials that are subjected to cooking go through this process.
through various states, complex reactions occur, governed by their composition
mineralogical, chemical and granulometric.

When the clay mineral has reached temperatures between 150 and 2000C, the bound water
totally disappears, beginning the decomposition of the iron silicate hydrates, at
similar to alumina silicates. When clay reaches a temperature between 450 and
5500C begins to lose combined water, the clay decomposes and the organic matter
it burns; between 700 and 8000A paste is formed (a mixture of silica, alumina, iron oxides,
calcium and magnesium). Since the 8000C up to 1000 - 11000The cooking actually takes place
happiness.

The phases of oven baking are three: Heating, cooking, and cooling. In the first phase...
it gradually eliminates hygroscopic water, the water is continuously removed by air
renovated and constantly increasing the temperature. The heating is considered finished.
when the whole mass reaches 1000C. In all tunnel kilns and in some Hoffman kilns, the
Heating is carried out with the air from the cooling zone that passes to the heating zone without going through
fire, through special conduits.

During cooking, the chemical reactions are completed, and the materials undergo a slight
contraction and acquire a characteristic structure that gives strength to the finished material. The
cooking temperature ranges between 1000 and 11000C.

In the cooling stage, the temperature must drop from cooking to normal.
which must be carried out gradually in the area of 500 to 6000C, since the
The conversion from beta to alpha quartz in the bricks can cause contractions or cracks in the
bricks. In addition, a gradual decrease (especially in closed kilns) is important
in the hardness, toughness, and coloring of the vitrified pieces.

The cooling of the pieces is defined by their size; the larger the size of the
Bricks, with so much greater slowness the temperature will rise and cool those.
products whose cooling has been done slowly are tough and very resistant to
mechanical actions and on the contrary, rapid cooling makes them brittle, to the point
that if they have been cooled too hastily, they sometimes break spontaneously, without the
intervention of external mechanical agents.

After cooking, the materials take on a color that is very variable, depending
the components of the clay and type of atmosphere, whether oxidizing or reducing.
Generally, the reddish colors characteristic of oxides prevail in structural materials.
ferric.

Vitrification is referred to as the ceramic process by which silicoaluminous materials are

they sinter forming a hard, shiny, and generally transparent surface layer. The
vitreous products (tubes) are impermeable, scratch-resistant, chemically inert and
In general, they are products that are more pleasant to the touch and sight. Sintering is the reaction
among solid particles, to produce a less porous product. Many oxides are forming
made of glass, the most common are the B2O3SiO2y P2O5that often vitrify due to
cooling. The crystalline structure of SiO4 tends to be present in the liquid, in which
a temporary polymerization results in irregular groups that make it very viscous. When these
cooling do not regroup in the regular crystalline structure, but remain as
irregular polymers that will subsequently form the vitreous layer. Boric oxide has high
tendency to form the vitreous state, the incorporation of B2O3to the silica, is accompanied by
a decrease in the melting point and a stabilization of the glassy state. Vitrification is
produce by adding salt and borax to the furnace, when it has reached a temperature of (10500C ).
This type of coating is specifically applicable to pipes.

Among the types of kilns used in the manufacture of bricks, tiles, and clay roof tiles
we have:

Sleeping Fire Oven. It is a handmade oven, built in a circular shape, generating

a circular vault. It has a side door through which the material is loaded. In these kilns
a layer of coal is placed, followed by a layer of bricks and consecutively a layer of
charcoal and another of bricks, until the top of the oven is reached. Once it has been finished the
the bricked (location of the bricks inside the oven) is lit. The firing lasts 30 days and the
The production of bricks is 15 to 20 thousand bricks per batch. The coal consumption is 15.
20 tons per batch. This type of oven is used in artisanal brick kilns.

They are intermittent furnaces with low production and high pollution. Due to a burn not
homogeneous, the material produced is of low quality. That is to say, some bricks are left
well done, while others remain raw.

Arab Oven. It is a rectangular-shaped oven that has eight burners in the areas.
lateral and lower for coal supply. It has no roof or chimney. They are ovens of
fast cooking (7 days), high production and high pollution. Consumes between 8 and 10 tons
about a ton of coal per batch. The flue of the furnace should start with about
corner bricks, already baked to cover a square of 10 to 15 meters long, on this
Another series is placed and so on, trying to maintain an equal separation between rows.
As height is gained, an inclination is given to the walls of the furnace.
When everything is ready, it is turned on in the lower burners. This type of oven is used in
the artisanal brickmakers

Trunk Type Oven. It has the same design as the Arabic one, but it expels the combustion gases through
natural shot, through a chimney located in nearby areas. In this furnace, it is reduced
significantly the emission of smoke and particulate matter, in relation to the Arabic oven.
Consume between 9 and 12 tons of coal per batch, depending on the size of the oven.

Inverted Flame Oven. They are intermittent closed furnaces where it is possible to regulate
better the shot, which can be natural or forced. The feeding of the dry structural material
It is carried out through a side door. The coal feeding can be done through some grates.
(3 - 4) placed on the wall of the ovens or by means of a stoker. The flame rises against the wall and
it is attracted by the shot towards the base, where the combustion gases are collected, to
subsequently evacuate them through the chimney. It consumes between 15 to 30 tons of coal per
batch, depending on the capacity of the oven. They are mainly used in the cooking of
special materials, such as tiles, vitrified tiles, and stoneware pipes, that require a
high cooking temperature.

The hive oven is a replica of the inverted flame, although with a smaller diameter and smaller
capacity, they are hemispherical furnaces, which evacuate combustion gases through
ascending shot. They are low-capacity furnaces, consuming around 5 to 10 tons of
carbon per batch.

In the inverted flame kilns and in the beehive kilns, vitrified products are manufactured, which
they are produced by adding salt and borax when the material is at high temperature, the
The fuel generally used is coal. The level of pollution generated by this
Ovens can be reduced by using stoker or burners. These types of ovens are used in
the mechanized Chircales and in the small brick factories.

The burning cycle includes the following stages:

Oven load
Proper cooking
Cooling
Download

Hoffman kiln. It consists of two parallel galleries, formed by contiguous chambers.

whose ends are joined by a firewall. They are continuous high-production furnaces, where
Vitrified materials cannot be produced. In these furnaces, the fire moves through the
oven in the opposite direction of the clock hands, allowing for high efficiency
thermal and production, since the heat obtained in the combustion chamber is used in the
preheating of the preceding chambers. In about a week (7 days) we
the burning cycle ends.

Each gallery is made up of several chambers, each with its respective door.
for the loading and unloading of the furnace and a discharge channel that goes to the main collector that
leads to the chimney. Each chamber connects to the collector through a flue.
which are hermetically sealed with valves. To maintain the horizontal circulation of the
gases through the chambers, it is necessary to allow the charge to leave 1/3 of the section free
transversal.

The fuel feeding is done at the top of the furnace, using

manual feeding or with the help of carbojet (pneumatic feeding), which must
to take place in a dispersed manner, avoiding jets that cause incomplete combustion.
Consume about 25 to 30 tons of coal per oven turn or per burning cycle.
This type of oven is used in medium brick plants.

One of the most well-known varieties of the Hoffman kiln is the Zig Zag and the chamber kilns.
parallel, which are continuous furnaces of lower production, and can have from 10 to 16
cameras. They are ovens similar to Hoffman type, from which they differ by the
movement of fire through the chambers.
Tunnel Oven. They are continuous ovens, with low levels of pollution, where the material is
mobilizes through wagons that move through the gallery. The conception of this
an oven responds to the idea of setting a fire zone and passing products to be baked,
following the heating curve of the oven. This implies the advantage of calorie savings in
the cooling and preheating of the furnace, in addition to labor cost savings in
loading and unloading of the bricks and greater speed in the firing stage.

The length of the furnace fluctuates between 80 to 120 meters long. The fuel is supplied by the
upper part by means of a pneumatic transport system, which completely reduces the
pollution at this stage. This furnace is used by highly technified industries and
with high levels of production. It consumes nearly 500 tons of coal per month.

The temperature curve of the furnace indicates the heat treatment to which a piece is subjected.
shaped and dried when passing through the oven, this curve can be modified taking into account
that time is a function of the mass to be treated and that heat cannot penetrate it
speed in a mass of ten tons that of five.

The reasons that have justified the implementation of these kilns in the ceramic industry
respond to the following.

The air and combustion gases circulate in the opposite direction to that of the bricks.
The air that enters through the discharge mouth of the furnace gradually heats up in
contact with the fired pieces in their cooling phase.
The air reaches the combustion zone at a high temperature, favoring the
combustion.
The flames and combustion gases pass through the heating zone transferring their
energy before escaping into the atmosphere.

Roller kilns are a modification of tunnel kilns, they are continuous kilns where the
ceramic material is not transported in carts, but through a successive series of
ceramic rollers, from where their name derives. These furnaces generally have two or three
flow lines through which the material to be cooked circulates. The fuel used in these furnaces is
gas and its use foresee a fuel economy. These types of ovens are used
mainly due to the large brick factories, whose production exceeds 300 tons/month.

SELECTION AND PACKAGING.

After the products are manufactured, they undergo a classification process by attributes.
and by variables, generally carried out at the oven door at the moment of exit to
patios. At this stage, according to the previous classification, it is possible to obtain materials from
first, second, third, and fired breakage material, the latter is incorporated.
again to the production line as chamote.

Mass and Energy Balance

For the production of one ton of bricks and clay derivatives in the industrial activity
the manufacturing of clay bricks, tiles, and roof tiles C.I.I.U. 369102, is recorded the
following inputs and outputs. The presented data is calculated by the GROUP OF
RESEARCH ON THE UIS-IDEAM AGREEMENT, based on bibliographic information.

The following table presents the inflows and outflows of raw materials,
inputs and natural resources used in the production of one ton of brick or some
derived from clay (tiles or shingles).

Entradas y salidas del Proceso

 TICKETS TO OUTPUTS TO THE PROCESS
PROCESS
Clay 1161 Kg Product 1 Ton
Chamote 155 Kg Evaporated Water 238 Kg
Water 77Kg Cooking Losses 77Kg
Carbon 72.5 Kg Breaks 20 Kg
Air 1916.74 Kg Air 952 Kg
Combustion Gases
1037.31 Kg

Source: UIS-IDEAM Agreement Working Group

In the followingfigurethe mass balance is presented to obtain one ton of bricks or

any clay derivative (tiles or shingles).

The video to show

The provided text is a URL and does not contain translatable content.