FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention
A PROCESS OF PREPARING A BUILDING MATERIAL FROM FLY ASH AND EFFLUENT FROM A SODA ASH
PLANT AND A BUILDING MATERIAL THEREOF.
2. Applicants
Name
TATA CHEMICALS LIMITED

Nationality
INDIA

Address
BOMBAY HOUSE, 24 HOMI MODI STREET, MUMBAI-400001

3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it is
to be performed.

The invention relates to the manufacture of fly ash bricks. More particularly, the invention relates to the manufacture of fly ash bricks using soda ash effluent.
DESCRIPTION OF RELATED ART
Fly ash is one of the residues generated in the combustion of coal and is usually captured in the chimneys of power generation units or boilers on account of environmental concerns and regulations. Depending upon the source and makeup of the coal being burned, the components of the fly ash produced vary considerably, but all fly ash includes substantial amounts of silica and lime.
Most fly ash produced industrially is disposed in landfills. Estimates indicate that the area of land occupied by landfill in India is in the region of 160 square kilometers. The recycling of fly ash has become an increasing concern in recent years due to an increasing cost of landfill and the present movement towards sustainable development.
There have been various uses suggested for the use of fly ash including in the manufacture of concrete and as a replacement of cement, raw feed for cement clinkers, soil stabilization and creating embankments, and as a material for a road sub-base. However, superior quality fly ash is required for manufacturing building materials, and fly ash containing high free lime content is considered unsuitable. Building material such as bricks and concrete manufactured using fly ash containing free lime content tend to crack easily and have unsightly pop ups. The situation is aggravated when the source of the fly ash is pet coke that is now largely used in power plants and boilers.
A similar problem exists in the effluent disposal of a soda ash plant, in that the effluent is typically filtered and dumped in a landfill. The quantity of land thus required in a soda ash plant

to accommodate the fly ash and effluent is significant and adversely affects the overall cost and efficiency of the plant.
There is therefore a need to address the issue of fly ash and soda ash effluent disposal.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The accompanying drawings illustrate the preferred embodiments of the invention and together with the following detailed description serve to explain the principles of the invention.
FIG. 1 is a schematic illustration of a system for the production of fly ash bricks in accordance with an embodiment of the invention.
SUMMARY
The invention relates to a process of preparing a building material from fly ash and effluent from a soda ash plant comprising mixing in a mixer the fly ash with effluent from the soda ash plant and water for a predetermined period of time, transferring the mixture so obtained into a mould to obtain the building material
The invention relates to a process of preparing a building material from fly ash and effluent from a soda ash plant comprising mixing in a mixer the fly ash with effluent from the soda ash ammonia recovery plant and water for a predetermined period of time, transferring the mixture so obtained into a mould, and curing the mixture to obtain the building material
The invention relates to a building material obtained from fly ash and soda ash effluent comprising mixing the fly ash with the soda ash effluent and water for a predetermined period, transferring the mixture to a mould and curing the mixture to obtain a building material.

DESCRIPTION OF PREFERRED EMBODIMENTS
To promote an understanding of the principles of the invention, reference will be made to the embodiment illustrated in the drawing and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
The invention provides for a process to develop building materials using soda ash effluent and fly ash and building materials so produced. In particular, the process relates to producing building materials such as bricks using soda ash effluent and fly ash containing free lime.
Though the following description describes the features of the invention in respect of fly ash bricks, the teachings of the document may be applied to prepare any building construction material of any shape or size, including but not limited to tiles or paving blocks. Similarly, though the invention describes fly ash as obtained from the combustion operation of a power plant or boiler, the teachings of the document are equally applicable to all sources of fly ash.
The process provides for mixing fly ash with soda ash effluent to prepare building materials such as bricks. The fly ash from power plants or boilers has significant levels of lime and sulphate and is mixed with the soda ash effluent that has significant levels of chloride. The contents are well mixed in a mixer along with water. The slurry so formed after mixing is taken and filled in the moulds of the required size to prepare the building material.
The period of mixing should be sufficient to ensure that the fly ash and soda ash effluent along with water are mixed well with each other.

Initially the bricks are kept inside wet gunny bags. After approximately 3 days, the bricks are taken out of the mould. They are then sprayed with water and kept for a predetermined period, preferably for at least 15 to 20 days.
The soda ash effluent is essentially the effluent generated from the ammonia recovery section of the plant and includes amongst others, CaCO3, Ca (OH) 2, SiO2, A12O3 etc. The soda ash effluent from the ammonia recovery section is filtered and the solids so obtained are used for the production of fly ash bricks as described herein.
In accordance with an aspect, the effluent solids are finely crushed before mixing with the fly ash to enhance the binding nature.
In accordance with a preferred embodiment, the fly ash and soda ash effluent are preferably mixed in a ratio of 70: 30. However, the fly ash and soda ash may be mixed in a ratio ranging from 50:50 to 80:20.
In accordance with a preferred embodiment, the fly ash is hydrated to convert the free lime present to calcium hydroxide. The hydration of the fly ash is done prior to mixing with the effluent solids.
With reference to the accompanying figure a system for preparing building materials such as bricks using fly ash and soda ash effluent is illustrated. Fly ash from the boilers used in a soda ash plant is collected (1) and hydrated with water (2). The hydration step is important as it converts the free lime present in the fly ash in to calcium hydroxide. The hydrated fly ash from stage (2) is sent to a mixer (6). Effluent from the ammonia recovery section of the soda ash plant (3) is filtered (4) and is sent to a grinder (5). The grinding stage is preferred as it breaks down the effluent solid ensuring better mixing and bonding with the fly ash. The effluent obtained from the grinder is then added to the mixer (6). Water is added to the mixer such that a mixture of fly ash, effluent and

water is obtained. This mixture is mixed for a period sufficient to ensure adequate mixing of the compounds. Additional water may be added to the mixer if necessary. The mixture from the mixer is then poured into moulds (7) of any desired shape or size to prepare the building material. The moulds are kept for a predetermined period to ensure sufficient curing (8) of the building material. The building material obtained is then tested for strength (9).
The sticky nature of the effluent assists in the binding of effluent with fly ash. A particular advantage of the bricks so obtained is that unlike conventional bricks, it is not required to soak the bricks in water during initial curing. The bricks may be kept in wet gunny bags and taken for drying after a predetermined period of time.
The curing may be done in wet sacks or any material capable of holding water for a predetermined period.
The strength of the brick was monitored after every 7 days. The final strength of the brick after 28 days is 60-62 kg/cm2, which is higher than the normal brick.
This process is low energy and requires only water. Moreover, the process of preparing fly ash bricks provides a suitable use for the soda ash effluent as a raw material and also solves the effluent disposal problem of soda ash plant and fly ash disposal.
The process allows the conversion of a low value fly ash having high free lime content to a valuable product with long lasting strength.
It will readily be appreciated by those skilled in the art that the present invention is not limited to the specific embodiments herein shown. Thus variations may be made within the scope and spirit of the accompanying claims without sacrificing the principal advantages of the invention.

We claim:
1. A process of preparing a building material from fly ash and effluent from a soda ash plant comprising mixing in a mixer the fly ash with effluent from the soda ash plant and water for a predetermined period of time, transferring the mixture so obtained into a mould, and curing the mixture to obtain the building material.
2. A process of preparing a building material as claimed in claim 1 wherein the fly ash is hydrated prior to mixing with the soda ash effluent.
3. A process of preparing a building material as claimed in claim 1 wherein the soda ash effluent is effluent generated from the ammonia recovery section of the soda ash plant.
4. A process of preparing a building material as claimed in claim 1 wherein the effluent solids are finely crushed before mixing with the fly ash.
5. A process of preparing a building material as claimed in claim 1 wherein the curing includes placing the building material in wet sacks.

6. A process of preparing a building material as claimed in claim 1 wherein the fly ash and soda ash effluent are mixed in the ratio ranging from 50:50 to 80:20 and preferably in the ratio70:30.
7. A building material obtained from fly ash and soda ash effluent comprising mixing the fly ash with the soda ash effluent and water for a predetermined period, transferring the mixture to a mould and curing the mixture to obtain a building material.
8. A process of preparing a building material substantially as herein described with reference to and as illustrated by the accompanying drawing.
9. A building material substantially as herein described with reference to and as illustrated by the accompanying drawing.

ABSTRACT
The invention relates to a process of preparing a building material from fly ash and effluent from a soda ash plant comprising mixing in a mixer the fly ash with effluent from the soda ash plant and water for a predetermined period of time, transferring the mixture so obtained into a mould to obtain the building material.