Method of producing lightweight ceramic sand particulates from coal pond ash and use thereof

Abstract

The present invention relates to fabricating lightweight ceramic sand as a building and construction material. More specifically it relates to a novel process of manufacturing sintered synthetic lightweight ceramic sand particulates directly from pond ash and fly ash as a secondary raw material. The said synthetic lightweight ceramic sand can be used as a building material. The novel feature of the invention is to manufacture low cost lightweight sand at high throughput to compete against the fast depleting natural sand and crushed stones.

Claims

1. A process of manufacturing sintered synthetic lightweight ceramic sand particulates from coal pond ash as a primary raw material comprising the following steps: (a) mixing pond ash between 50-95 wt %, fly ash between 40-5 wt %, bentonite between 5-0 wt %, silica between 10-0 wt %, and natural additive between 0-1 wt % to transform to granules; (b) drying said granules to obtain dried granules; (c) high temperature sintering of said dried granules thereby obtaining said lightweight ceramic sand, characterised in that, bulk density of said lightweight ceramic sand produced is between 750 kg/m.sup.3 to 1180 kg/m.sup.3, and thermal conductivity of hardened mortar produced from said lightweight ceramic sand is less than 0.70 W/(m*K) using a Hot Disk device that meets ISO standard 22007-2.

2. The process of manufacturing the sintered synthetic light weight ceramic sand particulates as claimed in claim 1 wherein, the pond ash comprises of 50 wt % to 70 wt % of combination of SiO.sub.2, Al.sub.2O.sub.3 and Fe.sub.2O.sub.3.

3. The process of manufacturing the sintered synthetic light weight ceramic sand particulates as claimed in claim 1 wherein, said natural additives is selected from pentasodium triphosphate and sulphonated salts of melamine formaldehyde; between 0-1 wt %.

4. The process of manufacturing the sintered synthetic light weight ceramic sand particulates as claimed in claim 1 wherein, the granules are formed using high intensity shear-mixer and dried between 150-300 Deg C.

5. The process of manufacturing the sintered synthetic light weight ceramic sand particulates as claimed in claim 1 wherein the granules are dried using a dryer in the range of about 150-300° C. and air feed between 750-1,500 m.sup.3/h and drying duration 4-8 minutes.

6. The process of manufacturing the sintered synthetic light weight ceramic sand particulates as claimed in claim 1 wherein, the dried granules are sintered at high temperature in the range of about 975-1300° C.

7. The process of manufacturing the sintered synthetic light weight ceramic sand particulates as claimed in claim 1 wherein, the size of lightweight sand particles produced is between 0.063 to 4 mm.

8. The process of manufacturing the sintered synthetic light weight ceramic sand particulates as claimed in claim 1 wherein, pond ash and fly ash samples were received from coal fired power plants.

9. The process of manufacturing the sintered synthetic lightweight ceramic sand particulates as claimed in claim 1 wherein, said lightweight ceramic sand offers an alternative to natural sand, crushed stones from natural resources or lightweight line aggregates to produce concrete, plasters, mortars, renders and roof tiles.

10. The process of manufacturing the sintered synthetic light weight ceramic sand particulates as claimed in claim 1 wherein the coal pond ash is not dried before granulation.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention may be understood more readily by reference to the following detailed description of the invention taken in connection with the accompanying drawing figures, which forms a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein and that the terminology used herein is for the example only and is not intended to be limiting of the claimed invention. Also, as used in the specification including the appended claims, the singular forms ‘a’, ‘an’, and ‘the’ include the plural, and references to a particular numerical value includes at least that particular value unless the content clearly directs otherwise. Ranges may be expressed herein as from ‘about’ or ‘approximately’ another particular value. when such a range is expressed another embodiment. Also, it will be understood that unless otherwise indicated, dimensions and material characteristics stated herein are by way of example rather than limitation, and are for better understanding of sample embodiment of suitable utility, and variations outside of the stated values may also be within the scope of the invention depending upon the particular application.

(2) Embodiments will now be described in detail with reference to the accompanying drawings. To avoid unnecessarily obscuring the present disclosure, well-known features may not be described or substantially the same elements may not be redundantly described, for example. This is for ease of understanding.

(3) The drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure and are in no way intended to limit the scope of the present disclosure as set forth in the appended claims.

(4) In order to achieve a better understanding of the nature of the present invention a preferred embodiment of a method of fabricating lightweight ceramic sand will now be explained.

(5) In one embodiment, the present invention discloses a novel process of granules formation from pond ash and fly ash. The said process allows mixing of pond ash in the range of 50-95 wt % and fly ash in the range of 50-5 wt %. Granules are formed using highly intensity shear-mixer and dried between 150-300 Deg C. Dried granules are sintered at high temperature in the range of about 975-1300° C. The resultant product conforms size gradation as per harmonized DIN 13139 (sand for mortars) and DIN 12620 (fine aggregates for concrete). Simultaneously, the product also conform DIN 13055 (lightweight aggregates for concrete and mortars).

(6) In another embodiment, the aforementioned method of manufacturing lightweight ceramic sand comprises the steps as follows: (a) mixture of pond ash and fly ash are transform to granules; (b) drying said granules to obtain dried granules (c) high temperature sintering of said dried granules thereby obtaining said lightweight ceramic sand.

(7) In another embodiment, the aforementioned method utilises pond ash is preferably between 50-95 wt % and fly ash between 50-5 wt %. Further, bentonite clay may be added to the fly ash or to the pond ash, before forming granules. In addition, the coal pond ash may range between 50-95 wt %, fly ash 45-5 wt % and bentonite between 5-0%.

(8) In another embodiment, the aforementioned method may further include the addition of fine silica to the fly ash or to the coal pond ash, before forming granules. The aforementioned pond ash may range between 50-95 wt %, fly ash between 40-5 wt % and fine silica between 10-0 wt %.

(9) In another embodiment, the aforementioned method comprises a drying step wherein said drying is fluidized bed drying between 150-300° C.

(10) In another embodiment, the aforementioned method may further involve a step of high temperature sintering wherein the temperature may range between 975-1300° C.

(11) In another embodiment, the aforementioned method involves light weight ceramic wherein the size of said lightweight ceramic sand may range between be not limited to 0.063 mm to 4 mm. Further, the size of said lightweight ceramic sand conforms to size gradation as per harmonized DIN 13139 (sand for plaster). Furthermore, the size of said lightweight ceramic sand conforms to size gradation as per harmonized DIN 12620 (fine aggregates for concrete). In addition, the size of said lightweight ceramic sand conforms to lightweight aggregates definition as per harmonized DIN 13055:2016.

(12) In another embodiment, the bulk density of said lightweight ceramic sand is between but not limited from 750 kg/m.sup.3 to 1,180 kg/m.sup.3.

EXPERIMENTAL DESCRIPTION

(13) The below experimental details are provided to illustrate the working of the invention, and it should not be construed to limit the scope of the invention in any way.

(14) Pond ash and fly ash samples were received from coal fired power plants. Before granulation process, water content of pond ash was determined which is typically in the range of 25-35 wt %. The resultant cake then transferred into high intensity shear mixture. Fly ash (dry form) and additives are added into the mixture as well.

(15) The ratio of the said combination for pond ash cake 50-95 wt %, for fly ash is 50-5 wt %, for fine silica 10-0 wt % and for bentonite is 5-0 wt %. The mixture improves green body strength. The formulations are prepared as indicated in Table 1, which is provided below:

(16) TABLE-US-00001 TABLE 1 Formulation - 1 Formulation - 2 Formulation - 3 Chemicals G Chemicals G Chemicals g Pond ash cake 50-95 Pond ash cake 50-95 Pond ash cake 50-95 Fly ash 50-5  Fly ash 45-5  Fly ash 40-5  Bentonite 5-0 Fine silica 10-0 Total 100 Total 100 Total 100 Additives & Additives & Additives & Water Water Water Pentasodium 0-1 Pentasodium 0-1 Pentasodium 0-1 triophosphate triphosphate triphosphate Sulphonated 0-1 Sulphonated 0-1 Sulphonated 0-1 salts of salts of salts of melamine melamine melamine formaldehyde formaldehyde formaldehyde Water  0-15 Water  0-15 Water  0-15 Total Total Total Additives & Additives & Additives & Water Water Water

(17) Pond ash cake disposed into the high intensity shear-mixer. Fly ash, bentonite, additives, and/or fine silica added to the cake both rotor and pan are rotating. The blending and mixing carried out for up to 60 seconds to ensure homogeneous mixing. If the mixture is dried due to high fly ash content, then water is added to the mixture. This addition of water is done under rotating condition of both rotor and pan. The rotation is carried out for 3-6 minutes. During the rotation procedure plurality of granules/spheres is formed. The granules thus obtained are herein referred to as sand precursor.

(18) The moistened sand precursors are then dried using fluidized bed dryer. The residence time of fine particulates in the dryer depends upon several factors such as dryer's length, drying temperature, drying duration and air flow. For the experiment temperature of the dryer used in the range of about 150-300° C. and air feed between 750-1,500 m.sup.3/h and drying duration 4-8 minutes.

(19) Dried sand precursors which has moisture between 1-5 wt % are fired in rotary kiln. The residence time of sand precursors in the kiln depends on several factors such as kiln length, temperature of the kiln which is in the range of about 975-1,300° C., chemical composition, particulate size, throughput and temperature of sand precursors. The size of lightweight sand particles produced are typically between 0.063 mm to 4 mm. The bulk density of these lightweight sand particulates are between 750 kg/m.sup.3 to 1,180 kg/m.sup.3 depending on the source of coal.

(20) The foregoing descriptions of specific embodiments of the present disclosure have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present disclosure to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present disclosure and its practical application, to thereby enable others skilled in the art to best utilize the present disclosure and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but as such are intended to cover the application or implementation thereof without departing from the spirit or scope of the invention.