ITTO20130172A1 - MIXTURE WITH INSULATING PROPERTIES FOR REFRACTORY MATERIALS - Google Patents

Description

Blend with insulating properties for refractory materials

DESCRIPTION

The present invention relates to an innovative mixture made in liquid form with high insulating properties for application on refractory materials. This mixture can be used in all sectors in which it is necessary to isolate processes at high temperatures, such as in foundries, in the petrochemical and chemical industry in general, in the steel industry and in blast furnaces for the production of ceramics. Many of the sectors mentioned above use ceramic fibers as refractory materials. These fibers are special artificial vitreous fibers (silicates) which have a random orientation and a content of alkaline and alkaline earth oxides Na2O, K2O, CaO, MgO, BaO in quantities lower than 18% and are introduced in risk class 2 CE and labeled with the risk phase R49. As is known, in fact, the agent R49 is carcinogenic by inhalation. The toxicological classification of the fibers is obtained through the evaluation of some parameters that define the bio-solubility or bio-persistence in the respiratory system (durability criterion) and the inhalability of the fibers (dimensional criterion).

The main sectors of use of ceramic fibers are, as already mentioned, all the fields in which it is necessary to isolate processes at high temperatures, as they have greater efficiency and lower costs than traditional refractory materials. In this context, the use of ceramic fibers has the drawback of releasing dust and fibrous particles into the external environment, with a consequent risk for operators in the sector.

One of the purposes of the present invention is to improve the safety of man and the environment in the field of fibrous thermal insulation through a considerable reduction in the release of dust and fibrous particles (encapsulation of the fibers) in the environment.

This object is achieved by the optimal composition of the mixture of the present invention.

The mixture is presented in liquid and micronized form, the components that compose it are in hydrated form, to which a percentage of water is added from a minimum of 25% to a maximum of 35% with respect to the total of the mixture. This allows an easy application of the product from the refractory material either by brush or by spray. Once applied to the external surface of the insulating layer, it is absorbed by the ceramic fiber coating for a thickness varying between 3 mm and 5 mm.

This mixture is composed according to what is reported in Table 1:

Chemical analysis

after cooking 150 ° C-%

SiO2 10-20

SiC 55-90

ZrO2 5-30

Table 1

This mixture has a high density and purity, and has been designed to achieve very high levels of reflectance with consequent energy savings during the normal operating cycle. Thanks to its reflective power, it increases the thermal transfer by radiation to the load, improving thermal efficiency, reducing the rise times and consequently decreasing energy consumption. Further characteristics of the mixture are shown in Table 2:

Color Light gray Maximum working temperature 1700 ° C

Dry density - Kg / dm³ 2.35

Shrinkage after firing at 1050 ° C -% <1.2

Table 2

The mixture in question can be applied on ceramic fiber coatings, insulating bricks and concrete, reducing the porosity of refractory materials.

An advantage of the present mixture is that of optimizing the transfer of radiant heat in the chambers of industrial furnaces. This advantage is given not only by the characteristics of the composition but also by the typical "gray body" color that absorbs and radiates a percentage of energy close to that of a "black body" in the same conditions.

Some of the substrates (bricks and refractory concretes) show high emissivity values at room temperature but, as the temperature increases, these values decrease rapidly. The mixture object of the present invention, on the other hand, was specifically designed to maintain the emissivity at high temperature values and included in a range of 50 - 1600 ° C; furthermore, as the temperature increases, the irradiation potential increases with emissivity between 0.70-0.90.

When the mixture is applied on refractory linings, they absorb heat from the burners and hot gases, increasing the radiation and convection capacity up to three times compared to a traditional refractory. The heat absorbed by the coating is immediately radiated onto the charge inside the system. The temperature of the fumes decreases, the applied product protects the refractory substrate from devitrification and shrinkage of the ceramic fiber modules.

A further advantage given by the use of the mixture is represented by energy savings: the greater the entity of the process, the greater the fuel savings.

In addition to energy savings, the reduction of the energy absorbed by the coating will allow a faster heat-up and a more rapid temperature recovery, shortening cycle times, increasing and improving productivity.

A further advantage given by the application of the mixture on the refractory linings, is given by a greater uniformity of the radiant heating and by the better quality of the treated products. Laboratory tests have evaluated the encapsulation capacity of ceramic fiber surfaces used as insulating coating on industrial furnaces to establish whether the application of the product is able to prevent, or drastically reduce, the dispersion of ceramic fibers inside the workplaces.

The results obtained, relating to the quantity of fibers removed per unit of surface, on three specimens A, B and C (sintered at 1050 ° C) of the following dimensions: length 23 cm, height 7 cm, thickness 3 cm.

Tests were carried out on these specimens both in correspondence with

surfaces not exposed to the work environment (M1, M2, M3) and of

consequently not treated, both on the surface exposed to the environment

work M4 treated with the encapsulating product under consideration. Tables 3,

4 and 5 report the results obtained:

,

Sample A (fibers / surface)

M1 7.4 mg / cm2

M2 7.7 mg / cm2

M3 4.8 mg / cm2

M4 (surface treated) 0.1 mg / cm2

Table 3

Sample B (fibers / surface)

M1 5.9 mg / cm2

M2 6.3 mg / cm2

M3 4.2 mg / cm2

M4 (surface treated) 0.7 mg / cm2

Table 4

Sample C (fibers / surface)

M1 5.0 mg / cm2

M2 7.5 mg / cm2

M3 4.1 mg / cm2

M4 (surface treated) 0.2 mg / cm2

Table 5

Based on the results obtained from the tests carried out on the specimens

delivered to the laboratory, it is observed that the surface treated with the

compared to the untreated ones, the mixture reduces, on the average of the three samples by 93.9% the quantity of fibers removed compared to the untreated surfaces.

On the basis of the foregoing, it is possible to state that the treatment with the encapsulating product is able to drastically reduce the possibility of formation of airborne fibers in the work environment, effectively contributing to a better protection of exposed workers.

Further tests were performed in the laboratory to evaluate the adhesion capacity of the product. Heating tests in kiln of sample elements obtained from ceramic and â € œecologicalâ € fiber mats, insulating and refractory bricks and dense concrete on which cold applications of the material have been carried out. The quantity of product applied has been adjusted following the different characteristics of the refractories used and consequently their different absorption capacity.

After the heat treatment at 1000 ° C, the product is sintered and well anchored on all the treated refractory samples.

A further application test of this mixture was carried out on a continuous oven for firing industrial ceramic tiles.

The technical data of the system are shown below:

- temp. max use 1280 ° C;

- combustion plant in an oxidizing atmosphere;

- strong chemical aggressions concentrated in the preheating area due to the condensates released by the clays (engobe);

- production of about 27,000 square meters of tiles per week;

- about 650/670 thousand kg of cooked material per week;

- average consumption around 45/47 thousand cubic meters of methane per week. The application was performed with the system stopped and cold. Considering the delicacy of the system, the product was applied only on the side walls for about 25 m (from the pre-heating area to the end of the heating area).

An application test of the product on the vault was also carried out for about 2 m at the start of preheating.

In order to avoid spraying of the product, the application was carried out with a brush.

Once the application of the product was completed, the customer inserted the ceramic tubes and closed the inspection doors. At the end of the scheduled maintenance, the customer switched the system back on for the new production campaign.

A check after three months of operation of this plant revealed the following:

- average energy saving of 5.07% - Î ”mc / kg;

- better thermal uniformity;

- better uniformity of energy consumption;

- the partial test carried out in the vault did not cause any release of material on the tiles;

- the product adhered perfectly to the existing refractory; - economic saving;

- decrease in CO2 emissions, taking into consideration the last four weeks of production Î ”m3 / m2 of approximately 38,166 tons.

On the basis of the tests carried out, it can be stated that the suitability of the product in reducing energy consumption and improving plant performance during the production process is optimal.

Claims (8)

R I V E N D I C A Z I O N I 1) Insulating mixture for lining refractory materials characterized in that said mixture after drying at 150 ° C comprises the following compounds in a weight percentage with respect to the total mass of the mixture of: - SiO2 from 10% to 20%; - SiC from 55% to 90%. - ZrO2 from 5% to 30%. 2) Mixture according to claim 1 characterized in that it is in liquid and micronized form, in which said compounds are present in hydrated form. 3) Mixture according to claim 2 characterized in that it contains a percentage of water from a minimum of 25% to a maximum of 35% with respect to the total of the mixture. 4) Mixture according to one of claims 1 to 3, characterized in that it has an emissivity value between 0.70-0.90 for a temperature range between 50 - 1600 ° C. 5) Mixture according to one of the claims from 1 to 4 characterized in that it has a shrinkage lower than 1.2%, after baking at 1050 ° C. 6) Mixture according to one of claims 1 to 5 characterized in that it has a maximum operating temperature of 1700 ° C. 7) Mixture according to one of the claims from 1 to 6 characterized in that it has a dry density equal to 2.35 Kg / dm³. 8) Use of the mixture according to one of the claims from 1 to 7 for application on ceramic fiber coatings, insulating bricks and concretes, reducing their porosity.