WO2016193766A1

WO2016193766A1 - Manufacturing of silicoaluminate fire brick with portland cement without drying and without sintering

Info

Publication number: WO2016193766A1
Application number: PCT/GR2015/000041
Authority: WO
Inventors: Georgios ROKOS
Original assignee: Rokos Georgios
Priority date: 2015-05-29
Filing date: 2015-07-31
Publication date: 2016-12-08
Also published as: GR1008802B

Abstract

The present patent refers to the manufacturing of silicoaluminate firebrick without drying and without sintering, for the production of which silicoaluminate minerals and Portland cement and silica fume are used, without effect on its end thermal properties. The present patent refers to silicoaluminate firebricks with low content in alumina oxide (low duty fire bricks), which find application in constructions for wood burning. The production of silicoaluminate firebricks with the method of this particular patent that does not necessitate sintering brings about the following advantages: - Effacement of cost of fuel, provided that the latter is associated with the sintering of the bricks. - Reduction of C02 emissions. - Increase in production capacity, as a result of the elimination of the production output constraints posed by the volume of the kiln.

Description

DESCRIPTION

Manufacturing of silicoaluminate fire brick with Portland cement without drying and without sintering. The present patent refers to the production of silicoaluminate fire brick, without the drying and firing process, for the production of which silicoaluminate minerals and Portland cement are used, without effect on its final thermal properties.

The fire brick or refractory brick is a brick of refractory ceramic material that is used in industrial ovens, fireplaces, wood burning ovens and generally applications that develop high temperatures. Its main characteristic is the high resistance to temperature (>1000°C).

Depending on their precise end properties, fire bricks differentiate as per:

» Their composition (the compounds such as silica, alumina, magnesium, zircon, etc)

• The bonding nature (ceramic or chemical)

® The specifications of raw materials (physical or synthetic, fired or unfired, etc).

• Their intended application. Each category entails some certain physical or chemical properties.

Silicoaluminate firebricks are classified depending on the ratio of alumina oxide to silica dioxide. Generally, the higher this ratio, the higher is the temperature resistance.

The present patent refers to silicoaluminate firebricks of low content in alumina oxide (low duty fire bricks), which are applied in constructions for wood burning.

For the production of silicoaluminate firebricks with low content in alumina oxide, the production process stages are as follow: a) Mining

This process consists of mining clay which contains significant quantity of silicoaluminate minerals (also known as fireclay). The silicoaluminate minerals in question are rich in content of alumina oxide and silica dioxide, which cumulatively will have to run into at least 75%. Coinstantaneously the content in alkalis (potassium and sodium), iron and calcium will have to be low as their presence dramatically restrains the refractoriness of raw material. The main argillaceous minerals of fireclay are kaolinite and illite. b) Grinding, Milling and Sieving

Post to its mining, the above described clay is subject to grinding process with crushers or milling in mills, since in its initial situation it might have the form of stratum. The grinding or milling serves the next stage, that of grain size segregation. lisuaiiy, the silicoaluminate minerals are segregated, through sieving, in various grain size classes since each combination yields different properties.

c) Weighting

For the production of the mixture, each grain size class is weighted so that it is introduced at the proper dosage.

d) Mixing

The weighted dosages of different grain size classes are mixed for the production of a homogenous mixture. At this point it is probable to add a percentage of water that will facilitate the next stage.

e) Forming

The mixture of components is transferred to hydraulic presses, or to extruder, or to a casting line, so that a particular brick form is given.

f) Drying and Heat Treatment

The bricks produced in stage e) are subject to drying process in driers, so as to reduce to minimum possible the humidity rate before arriving at the sintering process in kiln. This happens because the presence of high humidity may bring about cracking(s) in the mass because of fierce production of steam from the temperature increase. The formed item

(brick) is, at this stage, mechanically very weak and easy to disintegrate, g) Sintering

The sintering process begets what is called "vitrification" or "ceramization". Sintering takes place in industrial kilns which develop a minimum temperature of 1000°C.

The required duration of stay of the items (bricks) at the highest sintering temperature so that they acquire the necessary mechanical properties derives from the level of this temperature and the composition of the item. A significant factor is the content of the mixture in alumina oxide, the high presence of which calls for higher end temperatures.

Indicatively, for a firebrick with low content in alumina oxide (around 20%) the temperature resistance reaches 1200°C, while sintering takes place at 1 150°C for six hours. The basic novelty of the present patent is the addition of Portland cement during stage d) of the production process above, which brings about the necessary initial mechanical properties without need to apply stages f and g and without affecting the end thermal properties of the bricks. Namely, a mixture of fireclay with the addition of Portland cement and water (if necessary) can attain strong mechanical properties. The specific mixture is pressed at high pressure to acquire specific form (shape). Thereafter, the formed item (brick) is stored at ambient conditions for short term so that chemical- hydraulic bonds are developed between the components of cement and clay. The development of certain bonds permits strong initial mechanical properties, and as a result the formed item may be used in a construction for wood burning. Moreover, the formed item is "ceramized" and attains its end properties at use, ie when it is exposed to high temperatures where it is used (e.g. fireplace). It is worth mentioning that the end product, with the same raw material, meaning fireclay with 20% content in alumina oxide, has similar resistance to temperature either produced with the classic style, or produced with the production method of this particular patent.

In fact, the manufacturing of silicoaluminate firebricks with the method of this patent, which does not require sintering, brings about the following advantages:

- Effacement of cost of fuel, provided that the latter is associated with the sintering of the bricks.

- Reduction of C02 emissions.

- Increase in production capacity, as a result of the elimination of the production output constraints posed by the volume of the kiln.

The examples that follow are given with a view to further explicate the present patent.

EXAMPLE 1

Stage 1) Mining of silicoaluminate clay A from quarry. Figure 1 comprises an XRD analysis of clay A and Table 1 contains the chemical analysis of silicoaluminate clay A.

Table 1

Stage 2) Grinding of silicoaluminate clay A in crusher and grain size segregation. Stage 3) Mixing of silicoaluminate clay A with Ordinary Portland Cement (OPC) and concurrent water addition proportional to the weight of the mixture.

Stage 4) Pressing part of the mixture in hydraulic press at high pressure so that bricks are shaped.

Stage 5) Storage of shaped bricks in ambient conditions for a short time (28 days). Measurements / Properties post to the above time-lapse:

® Refractoriness: >1200°C

• Flexural strength: 1 ,80 MPa

* Thermal Conductivity at 300 °C: 0,89 W/m ^χ K

· Heat Capacity: 0,77 J/g ^χ K

EXAMPLE 2

Stage 1 ) Mining of silicoaluminate clay B from quarry.

Figure 2 contains XRD analysis of clay B and Table 2 comprises the chemical analysis of silicoaluminate clay B.

Table 2

Percentage

Compounds (%) by weight

WKBSSSSSSSk

Na₂0

MgO

AI2O3 19 6

Stage 2) Grinding of silicoaluminate clay B in crusher and grain size segregation. Stage 3) Mixing of silicoaluminate clay B with Ordinary Portland Cement (OPC) and concurrent water addition proportional to the weight of the mixture.

Stage 4) Pressing of part of the mixture in hydraulic press at high pressure so that bricks are shaped.

Stage S) Storage of shaped bricks in ambient conditions for a short time (28 days).

Measurements / Properties after 28 days:

Refractoriness: >1200°C

Compressive strength: 33,80 MPa

• Flexural strength: 1 ,29 MPa

• Thermal Conductivity at 300 °C: 0,75 W/m * K

• Heat Capacity: 0,79 J/g χ K

Example 3

Stage 1) Mining of silicoaluminate clay A from quarry. The XRD analysis, the microscopic depiction and the chemical analysis of this clay are presented in example 1.

Stage 2) Grinding of silicoaluminate clay A in crusher and grain size segregation. Stage 3) Mixing of silicoaluminate clay A with White Portland Cement type 52,5 R and concurrent water addition proportional to the weight of the mixture. Stage 4) Pressing of part of the mixture in hydraulic press at high pressure so that bricks are shaped.

Stage 5) Storage of shaped bricks in ambient conditions for a short time.

Measurements / Properties post to time-iapse above:

Refractoriness: >1200°C

Compressive strength: 54,066 MPa

Flexural strength: 2,038 MPa

Thermal Conductivity at 300 °C: 0,88 W/m K

Heat Capacity: 0,69 J/g * K

Claims

1. Manufacturing of silicoaluminate firebrick without drying and without sintering, for the production of which silicoaluminate minerals and Portland cement and silica fume are used, without effect on its end thermal properties.