Field of Invention

[001] The invention predominantly refers to building materials, namely, loose-fill thermal insulation materials and methods for the production thereof.

Background Art

[002] Thermal insulation materials are used in the building sector to protect premises against loss of heat. The use of thermal insulation materials allows one to reduce the thickness of building structures, the weight thereof, as well as the amount and costs of materials. The most commonly used insulation materials include rockwool, polystyrene foam, polyurethane foam, fibrolith and bulk cellulose. There are different types of thermal insulation materials: flexible, non-flexible, organic (woodchip and cork boards, wood fibre boards, felt, cardboard, reed boards, peat products, fibrolith, porous plastic), inorganic (rockwool, rubbercork, glass wool, foam glass, various asbestos materials), bulk (for instance, grainy, powdery, fibrous), sprayable (for instance, two-component polyurethane foam).

[003] It is known that widely used mineral thermal insulation materials are relatively high energy-intensive, with high production costs or a negative effect on the environment. Therefore, the use of environmentally friendly thermal insulation materials from renewable resources and with low production costs is especially topical.

[004] Thermal insulation materials are mainly characterised by thermal conductivity coefficient A, which is the amount of heat (energy) that, under the influence oftemperature gradient, which, within a unit of time, flows through a unit of area of the material crosssection, if the difference of temperatures between them is 1 degree. It is measured in watts per metre and per one Kelvin [W-m^-K ¹ ]. To ensure that the material complies with the characteristics ofthermal insulation material, coefficient A must be lower than 0.07 [1, 2], [005] There are known methods of lignocellulose processing [3, 4], which provide for the treatment of ground biomass containing lignocellulose with saturated steam within the temperature range from 180 °C to 240 °C to ensure the more efficient separation of biomass components.

[006] A loose-fill lignocellulose thermal insulation material and the method of obtaining thereof is known [5], which includes the following successive steps: crushing of lignocellulose raw materials, fractioning there of, drying to a certain relative moisture level and subjecting to steam explosion treatmentto obtain a mass of fibrous bundles. The main drawbacks of the known method include the need to adapt treatment conditions individually for each raw material of lignocellulose. Furthermore, during the processing of the raw material, by means of the known method a non-homogeneous mass of fibrous bundles is obtained - from partially split fibre to individual fibres. As a result, it is difficult to achieve homogeneous and low density, when installing the loose-fill material, which can deteriorate thermal insulation properties.

Objective and nature of the invention

[007] The objective of this invention is to prevent the aforementioned drawbacks, namely, to develop a method for the production of lignocellulose bulk material, which would be simple, universal and could be used for the processing of different lignocellulose materials. [008] The offered method for the production of bulk lignocellulose material includes the following steps: (i) mechanical crushing of raw lignocellulose containing material that is free from metals and mineral foreign bodies (except for hemp shives); (ii) fractioning of lignocellulose raw material by using a sieving system and retaining the 3-13 mm fraction for further use; (hi) drying or moisturising of the lignocellulose raw material to reach the relative moisture content of 45-50%; (iv) processing of the fractioned lignocellulose raw material with steam explosion; (v) drying of the lignocellulose fibre mass obtained during the previous step to a relative moisture content of 10-15%. In accordance with the preferable embodiment of the invention, the steam explosion treatment in step (iv) is performed over a time interval of 5-40 seconds at a temperature of 230-240 °C and pressure of 30-33 bar. [009] In accordance with another preferable embodiment of the invention, prior or after the step (v), the step (ivb) or (vi) of mixing the lignocellulose with antipyrenes and antiseptic substances is carried out.

Brief description of drawings

[010] Lignocellulose loose-fill thermal insulation material and the block scheme of one manifestation of the used steam explosion device are schematically reflected in Fig. 1-3. Fig. 1. non-fractionedhemp shives before and after steam explosion treatment, where Fig.

1.A- hemp shives before steam explosion treatment and Fig. l.B - hemp shive fibre mass after steam explosion treatment;

Fig. 2. fractioned grey alder chips before and after steam explosion treatment, where Fig.

2.A- grey alder chips before steam explosion treatment and Fig. 2.B - grey alder chip mass after steam explosion treatment;

Fig. 3. - block scheme of one manifestation of steam explosion equipment used within the framework of the offered method.

[Oil] Lignocellulose material (grey alder wood, wheat, rye, oat straw) is mechanically ground and fractioned in a column of sieves by obtaining the useful fraction of 3-13 mm. Relative moisture of fractioned raw materials is ensured within the limits of 45-50%, by performing drying or moisturising of the raw material as required. The prepared raw lignocellulose material is subjected to steam explosion treatment in a sealed reactor from 5-40 seconds at the temperature of 230-240 °C and the pressure of 30-33 bar (Figure 1- 2).

[012] The provided steam explosion equipment (Fig. 3) includes a water preparation container (1), water tank (2), steam generator (3), steam explosion reactor (4), reactor opening valve (5), tank (6) for the receipt of material after steam explosion. The container (1) is hydraulically connected to the water tank (2), which is hydraulically connected to the steam generator (3), meanwhile, the steam generator is hydraulically connected to the steam explosion reactor (4). The steam explosion reactor (4) is adapted for the insertion of lignocellulose raw material and processing thereof with steam, which is followed by the transfer of processed material into the tank (6) through the valve (5), which is done automatically as a result of rapid decompression.

[013] The principal parameters of steam explosion treatment include time of treatment (t), pressure (p) and temperature (T), which taken together determine the mode of processing. The more severe the mode of treatment (severity factor Ro^-e^- ¹⁰⁰ ^ ¹⁴ - ⁷⁵ ), the lower the yield of the obtained material, which means higher material losses. In the event of the selected mode of steam explosion, the losses of raw materials only amount to 0.4- 3.9% of absolutely dry mass.

[014] The bulk density of the raw material transformed by means of steam explosion reduces by almost two times.

[015] After steam explosion treatment, the mass of the material is hot, moist and has changed colour from light to light brown. To ensure that the material is loose, as well as to prevent the formation of mould on the obtained material and to ensure optimal thermal conductivity of the material, the material should be dried until it reaches the relative moisture of 10-15%.

[016] To ensure biological and fire protection of the obtained material, antipyrenes and antiseptic substances, for instance, boron and tetraborate salt or graphite are added to the material. The produced thermal insulation material is packed into sacks and placed into the warehouse.

[017] The improved parameters of the material (bulk density and thermal conductivity) make it competitive in comparison with thermal insulation materials that are already present on the market. There is no need to shape the material obtained in this manner in the form of boards or carpets, which will make the end product more expensive and generate residues, while, in bulk form it can be easily incorporated in the constructions of the building, thus providing them with the required thermal insulation.

[018] The offered method is not technologically complicated and it allows to use biomass residues, for instance, generated by hemp shives. The method is suitable for the processing of different lignocellulose materials, for instance, hemp shives and grey alder chips. The method is characterised by comparatively low energy and water consumption in the production process, by obtaining natural, residue-free thermal insulation material. As a result of the use of the method the obtained material has a bulk density ranging from 46.6 to 55.2 kg/m ³ and thermal conductivity coefficient of A = 0.043-0.045 W-rn ^K ¹ . The heat capacity Cp (at the temperature of 10-20 °C) of the loose-fill thermal insulation material obtained from grey alder is 1400-1500 J/kg/K, but from hemp shives - 1700-1800 J/kg/K.

Examples of the Implementation of the Invention

[019] Example 1.

During the implementation of the invention, hemp shives (Fig. 1.A) are delivered, soaked in a bath to reach 45-50% relative moisture saturation. The moist hemp shives are placed into a tightly sealed reactor and processed in a saturated steam environment with the following technological parameters: temperature in the reactor T=230°C, steam pressure p=33 bar, processing time in the reactor t=5s. After the determined time of processing, the reactor valve (Fig. 3, 5) shall be immediately opened, as a result of which the material, under the influence of sudden drop in pressure is shot through the nozzle into the receiver (Fig. 3, 6), and, due to this rapid pressure drop, the decomposition of material into fibre occurs (Fig. l.B). Then the selected antipyrenes and antiseptic substances are added to the obtained material and dried to 10-15% of moisture. The dried material can be stored in warehouses or delivered immediately to the construction object and incorporated in horizontal, vertical, sloping and closed constructions by using the dry spraying method.

[020] Example 2.

During the implementation of the invention, the grey alder wood is ground in a wood chipper, fractionated through a set ofsieves, and a 3-13 mm fraction is obtained as aresult (Fig. 2.A); as required, the mass is soaked with water, thus ensuring the relative moisture of 45-50%. The prepared woodchips are placed into tightly sealed reactor and processed in a saturated steam environment with the following technological parameters: temperature in the reactor T=240 °C, steam pressure p=30 bar, processing time in the reactor t=40 s. After the determined time of processing, the reactor valve shall be immediately opened, as a result of which the material, under the influence of the sudden drop in pressure, is shot through the nozzle into the receiver, and, due to this rapid drop in pressure, the decomposition of the material into fibre occurs (Fig. 2.B). Then antipyrenes and antiseptic substances are added, and the mass is dried to the moisture of 10-15%. The dried material can be stored in warehouses or delivered immediately to the construction object and incorporated in horizontal, vertical, sloping and closed constructions by using the dry spraying method.

References

1. Dikmen, N., and Ozkan, S.T E. (2016). "Unconventional Insulation Materials”, In: Insulation Materials in Context of Sustainability, Intech. Chapter 1, 3-23.

2. Asdrubali, F., D'Alessandro, F., and Schiavoni, S. (2015). "A review of unconventional sustainable building insulation materials”. Sustainable Materials and Technologies, 4, 1- 17.

3. CA 1163058.

4. US 6419788B1.

5. LV15328.

6. DE19541626A1.