FIELD OF INVENTION
The present invention relates to a plant for preparing Synthetic gypsum.
BACKGROUND OF THE INVENTION
Gypsum is used in cement to control the setting properties of cement paste, which also contributes to its strength. Main source of gypsum in cement is Mineral gypsum or Chemical gypsum which is byproduct of Chemical Industry. Naturally occurring gypsum has limited deposits and of low and inconsistent quality. Generally chemical gypsum is acidic in nature and having many impurities which cause to increase in setting time, loss of strength and affect durability. However, chemical gypsum byproduct is used as partial replacement in cement by washing or neutralization with the help of lime.
Further, it detonates the quality of cement. Hence, acid free high purity gypsum is required to be developed.
OBJECTS OF THE INVENTION
A primary object of the present invention is to provide a plant for preparing Synthetic gypsum which provides improved quality and natural high purity synthetic gypsum.
Another object of the invention is to provide a plant for preparing Synthetic gypsum which produces cost effective synthetic gypsum.

Still another object of the invention is to provide a plant for preparing Synthetic gypsum which is simple in construction.
SUMMARY OF THE INVENTION
This invention provides a plant for preparing Synthetic Gypsum comprising of Limestone hopper, Acid tank, Screw conveyor, Premixing chamber, Mixing chamber, Den and Gas Cleaning System comprising of ejector, ventury and scrubbing tower connected to each other, wherein a skewed paddle is mounted on shaft in combination of advancer and retarder paddle.
The provision of skewed paddle, advancer and retarder make mixing of limestone, sulfuric acid and water more homogeneous as compared to the known art. Hence, it requires lesser time to complete the reaction. Further, free moisture in the gypsum of the present invention is lower, which makes it usable within a day in cement mill.
The present invention causes increase in production with hardly any wastage of acid mist due to better control and introduction of ventury.
Process of manufacturing of Synthetic Gypsum comprising of steps as follows:
• Limestone powder and sulfuric acid are accurately measured by weigh feeder and flow meter respectively.
• This limestone powder is transported to Pre-mixer at constant rate through screw conveyor where premixing of water, acid and limestone is carried out by cyclonic motion. This is followed by

introduction of mixed raw materials into mixing chamber where breaking of sulfate layer is carried out by to and fro motion of paddle for uniform reaction. Thereafter, homogenized material is subjected to curing in Den. It takes 30-50 minutes which leads to growth of gypsum crystals.
The waste gases exhausted from mixer through 3 stage Gases Cleaning System comprising of ejector, ventury and scrubbing tower, wherein water is sprayed. So that, any sort of dust or acidic mist are collected 85 the water from the scrubbing system is recycled in the process. The same is reused in preparing Synthetic Gypsum. Finally the synthetic Gypsum is discharged as product.
STATEMENT OF INVENTION
According to this invention, there is provided a plant for preparing synthetic gypsum comprising of a hopper introduced with limestone powder for supply of the same to a buffer hopper, in which the powder is further advanced to premixer connected with mixer and den wherein the premixer is supplied with sulphuric acid and water for reaction with the limestone powder to obtain gypsum.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawing and wherein:
Fig. 1 shows: plant of the present invention for preparing synthetic gypsum.

DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWING;
The present invention discloses a plant for preparing synthetic gypsum. The limestone used as a raw material for clinkerization is procured from the mines, which is crushed and grinded with minor percentage of iron source in a grinding machine. Said grinded raw material is subjected to homogenization in silo, which is also used for storage of fine powder. The homogenized powder of limestone is forwarded to preheater, calciner and kiln supplied with cross current of air. There is some return of fine dust from feeding point of preheater which is collected in ESP and followed by processing in the plant of the present invention. However, instead of the fine dust, fine powder from the silo can be processed in the plant.
Now, reference may be made to fig. 1 wherein the lime stone powder is introduced into a hopper for discharging onto a screw conveyor to avoid contact with air, which is supplied to a buffer hopper through a bucket elevator. The fine dust particles of the limestone from the hopper is collected into bag filter connected to the hopper, wherein said bag filter is provided in connection with exhaust fan. Again, the limestone powder is advanced from the buffer hopper to screw conveyor through belt conveyor with belt weigher. The belt conveyor conveys the powder and also indicates weight. The provision of belt conveyor and screw conveyor is done for controlled supply of the limestone powder to premixer. The premixer is supplied with water and sulphuric acid as shown in the figure for mixing of limestone powder, water and sulphuric acid with the cyclonic motion. This gives rise to slurry with the dissipation of CO2 due to reaction between the reactants. The slurry is further supplied to a mixer for homogeneous mixing by complete reaction resulting in a homogeneous slurry with the dissipation of acid mist, dust particles of limestone and carbon dioxide.

The following reaction takes place in the mixer
CaCo3+H2SO4+H2O -> CaSO4.2H2O+CO2
The slurry from the mixer is discharged into den preparing cake, outlet of which is provided with a cutter for cutting the cake into lumps to be dumped in gypsum yard.
For disposal of acid mist, CO2 and dust particles from the mixer, premixer and den, said den is connected to ejector, ventury, cyclone, RCC tower and stack provided in series. Thus, the gases evolved in the process of Gypsum production are scrubbed with the help of three stage scrubbing system.
Pollution Control System
The gases evolved from Mixer and Den during the chemical reactions are scrubbed with water in three-stage process
1. Injector and Ventury scrubber.
2. Wet cyclonic separator.
3. Water spray tower
Injector and Ventury Scrubber
The gases are formed during chemical reactions in the Mixer and Den collected through blower is firstly scrubbed with water in Injector. Water

circulation is through high volume pump. The undissolved gases are further go to the ventury scrubber.
The un-dissolved gases come from Injector are scrubbed in the ventury scrubber, wherein Continuous water spray absorbs the gases.
Wet Cyclone Separator
The air containing un-dissolved gases and particles are scrubber in the wet cyclone. The Spraying Water Contains Solution of NaOH.
Scrubbing Tower
In scrubbing tower the counter current contacts between the water and undissolved gases. Out of atleast five towers four towers are operated on the wet basis with continuous water spray from high pressure nozzles, fifth tower is operated on the dry basis to protect water carry over to scrubbing fan. These gases move to the Chimney via Blower.
All re-circulation water is collected in pits with zig jack flow to settle the silica particles. Silica, water Precipitate of CaC03 or Na2C03 slurry separated with filter press & silica cake is used in Gypsum as filter.
Thus, inlet of said den is connected to an ejector for processing of acid mist with CO2 and dust particles of lime stone, which is sprayed with water for absorption of acid mist and dust. The spray is provided with said ejector. Remaining acid mist with CO2 and limestone dust is processed through the ventury for absorption of limestone and acid mist.

The provision of spray is also made with said ventury. Similarly, cyclone with a water spray is used for processing of the same with water and cyclonic motion. Further, the RCC tower is utilized for absorption of remaining limestone particles and acid mist and last chamber of the RCC tower with a dryer dries CO2. The dry CO2 is exhausted to atmosphere though a stack in connection with a fan.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM;
1. A plant for preparing synthetic gypsum comprising of a hopper introduced with limestone powder for supply of the same to a buffer hopper, in which the powder is further advanced to premixer connected with mixer and den wherein the premixer is supplied with sulphuric acid and water for reaction with the limestone powder to obtain gypsum.
2. A plant as claimed in claim 1, wherein the hopper is connected to said buffer hopper through a screw conveyor and bucket elevator.
3. A plant as claimed in claim 1 or 2, wherein the buffer hopper supplies the limestone powder to said premixer through belt conveyor with belt weigher and screw conveyor.
4. A plant as claimed in any of the preceding claims, wherein the premixer mixes the limestone powder, H2SO4 and water with the cyclonic motion.
5. A plant as claimed in any of the preceding claims, wherein the
mixer mixes the slurry from said premixer homogeneously.
6. A plant as claimed in any of the preceding claims, wherein the
mixer discharges its slurry to the den for preparing cake, outlet
of which is provided with a cutter for cutting the cake into
lumps.

7. A plant as claimed in claim 6, wherein the den, inlet of which is
connected to three stage scrubbing system such as herein
described for scrubbing acid mist, C02 and limestone dust
particles from the mixer and den.
8. A plant for preparing synthetic gypsum substantially as herein described with reference to the accompanying drawing.