FORM 2
THE PATENT ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION:
A process for preparing liquid poly aluminium chloride having high relative basicity and a system thereof.
APPLICANT:
Grasim Industries Limited, an Indian Company, having address at Aditya Birla Centre, B-Wing, 2nd Floor, S. K. Ahire Marg, Worli, Mumbai – 400030, Maharashtra, India.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION [001] The present invention relates to a process for preparing liquid poly aluminium chloride having high relative basicity and a system thereof. Specifically, the invention relates to a process for preparing liquid poly aluminium chloride (PAC) having 60%-70% relative basicity, 15%-17% of chloride content, 13%-14% of alumina content, and a solid concentration of 40%-50%, by weight of the PAC and a novel system thereof.
BACKGROUND OF THE INVENTION
[002] Poly Aluminium Chloride (PAC) can be divided into three groups namely, low-basicity PAC, medium-basicity PAC and high-basicity PAC. High-basicity PAC has a relative basicity between 50%-75% and is generally preferred in comparison to low-basicity products. Also, high-basicity PAC having a high Aluminium oxide (Al2O3) content is preferred in comparison to low Al2O3 content.
[003] In the prior art process, the basicity of PAC is increased by adding a base to it. In the prior art processes, the base added to PAC is sodium aluminate that increases the basicity from 40% to 65% (approx.). This reaction requires dilution of PAC solution to a great extent otherwise addition of sodium aluminate leads to precipitation of aluminium in the resulting solution which creates turbidity. This high-basicity PAC is produced both in liquid and powder forms. Usually, once the liquid PAC is produced, water is evaporated from it to obtain the solid powder. Therefore, in cases where the liquid PAC is further diluted with water to increase in basicity at higher dilution, the amount of solid content produced is less thereby decreasing the efficiency of the process. Usually, the amount of solid content produced is up to 35% in the produced high basicity PAC liquid.

[004] Moreover, the high basicity PAC produced from the prior art processes has a very low alumina content of 10%-11%.
[005] Hence, a strong need exists for a process of preparing high basicity PAC and a novel system thereof that solves some of the problems present in the prior art as mentioned above.
SUMMARY OF THE INVENTION
[006] According to an embodiment of the present invention, there is provided a process for preparing liquid poly aluminium chloride (PAC) having 60%-70% relative basicity, comprising the following steps of circulating dilute PAC having 15.0%-18.5% aluminium as alumina and 20%-23% chloride content in a tank through a pump at a flow rate of 20 to 100 m3/hour; and adding sodium hydroxide having 10%-48% concentration, at a rate of 10 to 50 kg per min per ton of PAC, at the inlet of the pump to react with PAC under high shear forming a solution in the tank, the solution being liquid PAC having 60-70% relative basicity, 15%-17% of chloride content, 13%-14% of alumina content, and a solid concentration of 40%-50%, by weight of the PAC, wherein the solution is agitated for 0.5 to 3 hours at a temperature ranging from ambient temperature up to 135°C, throughout the process.
[007] According to another embodiment of the present invention, there is provided a system for preparing liquid poly aluminium chloride (PAC) having 60%-70% relative basicity comprising a tank for preparing a solution of dilute PAC and sodium hydroxide; an agitating means, placed inside the tank, for agitating the solution; a pump connected to the tank through a pipe; a dissolution vessel containing sodium hydroxide, connected to the pipe through a tube such that the sodium hydroxide enters the pipe at the junction where the pipe is connected to the pump such that the pump receives sodium hydroxide at a fixed rate, wherein the tube comprises a nozzle which controls the flow at which sodium hydroxide enters the pipe, and a

duct connected to the pump on one side for intake of the solution and to the reaction tank on the other side to discharge the solution.
BRIEF DESCRIPTION OF THE DRAWINGS:
[008] Figure 1 depicts a schematic representation of a process for preparing liquid poly aluminium chloride having high relative basicity, in accordance with an embodiment of the present invention;
[009] Figure 2 illustrates a chart showing an increased production of powder in accordance with an embodiment of the present invention; and
[010] Figure 3 shows the difference in turbidity in prior art process and present process, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[011] As set out in the claims, the present invention eliminates or reduces the aforementioned problems of the prior art by providing a process for increasing the basicity of PAC to 60%-70%. The present process is highly efficient as there is an increase in production of both liquid and solid PAC while avoiding the use of sodium aluminate as a base. The present invention also provides a simple system for carrying out said process.
[012] According to an embodiment of the invention, there is provided a process wherein PAC having 15.0%-18.5% aluminium as alumina and 20%-23% chloride content is taken and diluted with water. Thereafter, this dilute PAC is circulated in a reaction tank through a pump. Preferably, the dilute PAC is circulated at a flow rate of 20 to 100 m3/hour and preferably at 60 m3/hour.

[013] Thereafter, sodium hydroxide having 10%-48% concentration is added at the inlet of the pump to react with PAC under high shear forming a solution in the tank. Preferably, this solution is agitated for 0.5 to 3 hours at a temperature ranging from ambient temperature up to 135 °C, throughout the process. The solution formed is liquid PAC having 60%-70% relative basicity, 15%-17% of chloride content, 13%-14% of alumina content, and a solid concentration of 40%-50%, by weight of the PAC. In another embodiment, the solution is agitated at 20 to 200 rpm and preferably at 100 rpm, in the tank. In a preferred embodiment, sodium hydroxide having 30%-33% concentration is added at the inlet of the pump.
[014] In another embodiment of the present invention, there is provided a system for preparing liquid PAC. Figure 1 depicts a schematic representation of the system having a tank for preparing a solution of dilute PAC and sodium hydroxide. An agitating means is placed inside said tank for agitating the solution. There is a pump connected to the tank through a pipe. A dissolution vessel that contains sodium hydroxide is connected to the said pipe through a tube such that sodium hydroxide enters the pipe at the junction where the pipe is connected to the pump such that the pump receives sodium hydroxide at a fixed rate. Lastly, a duct is connected to the pump on one side for intake of the solution and to the reaction tank on the other side to discharge the solution. Preferably, said tube comprises a nozzle that controls the flow at which sodium hydroxide enters the pipe.
[015] In an embodiment, the agitation means is a stirrer. In another embodiment, the pump is a centrifugal pump and is operated at a speed of 1000 to 5000 rpm and preferably at 3000 rpm.
[016] In an embodiment, there is optionally a means to control temperature of the solution in the tank from ambient temperature up to 135°C and preferably at 120°C. Usage of all these alternatives of the means to control the temperature of the solution are considered to be within the scope of the present invention.

[017] In an embodiment, a powder PAC is prepared from the liquid PAC by evaporating the water from liquid PAC. Preferably, the liquid PAC obtained from the present process has a high solid content and therefore once the water is evaporated, a higher amount of powder PAC is obtained. This results in a high process efficiency and an increased production of high basicity PAC in a comparatively lesser time. The graph in Figure 2 illustrates the increased production of solid PAC from 20 tons per day to 36 tons per day by the present process. Additionally, as shown, the solid content in liquid PAC also increased from 32% to 45% which resulted in high production of PAC powder.
[018] In an embodiment, as shown in Figure 3, sodium hydroxide is added at a rate such that there is no turbidity in the resulting solution. In an embodiment, sodium hydroxide is added at a rate of 10 to 50 kg per min per ton of PAC and preferably at 30 kg per min per ton of PAC. Preferably, sodium hydroxide is added through a tube attached to the inlet of the pump such that the tube is placed perpendicular to the direction of flow of dilute PAC from the tank to the pump.
[019] Moreover, the present process is environment friendly as it does not use sodium aluminate that is used in the prior art processes thereby avoiding the huge sludge generation and handling issue of sodium aluminate due to solidification.
[020] In another embodiment, a liquid poly aluminium chloride having 60%-70% relative basicity, 15%-17% of chloride content, 13%-14% of alumina content, and a solid concentration of 40%-50%, by weight of the poly aluminium chloride is prepared using the process and system of the present invention.
[021] Advantages and benefits of the process of producing high solid PAC content containing liquid high basicity PAC according to the embodiments of the present invention would become

more apparent from the below experimental details to a person skilled in the art.
[022] Experimental Data:
16 MT Poly aluminium chloride solution containing 17.2% aluminium as alumina and 21.9% chloride was taken in HB reactor and agitator was started at 100 RPM. 1.5 MT of process water was added to PAC liquid. Circulation of PAC liquid was started using high speed shearing pump. 3.7 MT of caustic (32%) was taken in dosing tank and added to circulating PAC solution through high shear pump at 30 litre/ minute per MT of PAC solution. Material was circulated for 2-3 hours and kept under agitation for further half an hour. There was increase in temperature of solution by 17°C during reaction.

Parameters Old Recipe New Recipe
Solid, % 31-33 45-47
Al as Al2O3, % by mass, min 10.2 13.0
Basicity, % by mass, min 64.0 66.0
Chloride as Cl-, % by mass, max 10.5 16.0
Turbidity, NTU 100-1000 <100
Insolubles, % by mass, max 0.5 0.1
pH of 5% solution, w/v 2.5- 4.5 3.7
[023] The foregoing description of specific embodiments of the present invention has been presented for purposes of description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obvious modifications and variations are possible in light of the above teaching.

We Claim:
1. A process for preparing liquid poly aluminium chloride (PAC) having 60%-70%
relative basicity, comprising the following steps:
a) circulating dilute PAC having 15.0%-18.5% aluminium as alumina and 20%-23% chloride content in a tank through a pump at a flow rate of 20 to 100 m3/hour; and
b) adding sodium hydroxide having 10-48% concentration, at a rate of 10 to 50 kg per min per ton of PAC, at the inlet of the pump to react with PAC under high shear forming a solution in the tank, the solution being liquid PAC having 60%-70% relative basicity, 15%-17% of chloride content, 13%-14% of alumina content, and a solid concentration of 40%-50%, by weight of the PAC,
wherein the solution is agitated for 0.5 to 3 hours at a temperature ranging from ambient temperature up to 135°C, throughout the process.
2. The process as claimed in claim 1, wherein the pump is operated at a speed of 1000 to 5000 rpm.
3. The process as claimed in claim 1, wherein sodium hydroxide is added through a tube attached to the inlet of the pump such that the tube is placed perpendicular to the direction of flow of dilute PAC from the tank to the pump.
4. The process as claimed in claim 1, wherein the solution is agitated at 20 to 200 rpm in the tank.
5. A powder PAC prepared from the liquid PAC prepared according to the process of claim 1, wherein the liquid PAC is evaporated to remove water.
6. A system for preparing liquid poly aluminium chloride (PAC) having 60%-70% relative basicity comprising:

a) a tank for preparing a solution of dilute PAC and sodium hydroxide;
b) an agitating means, placed inside the tank, for agitating the solution;

c) a pump connected to the tank through a pipe;
d) a dissolution vessel containing sodium hydroxide, connected to the pipe through a tube such that the sodium hydroxide enters the pipe at the junction where the pipe is connected to the pump such that the pump receives sodium hydroxide at a fixed rate,
wherein the tube comprises a nozzle which controls the flow at which sodium hydroxide enters the pipe, and
e) a duct connected to the pump on one side for intake of the solution and to the
reaction tank on the other side to discharge the solution.
7. The system as claimed in claim 6, wherein the pump is operated at a speed of 1000 to 5000 rpm.
8. The system as claimed in claim 6, wherein there is optionally a means to control temperature of the solution in the tank from ambient temperature up to 135 °C.
9. A liquid poly aluminium chloride having 60%-70% relative basicity, 15%-17% of chloride content, 13%-14% of alumina content, and a solid concentration of 40%-50%, by weight of the poly aluminium chloride.