BACKGROUND OF THE INVENTION
Dewatering is an essential aspect of mineral and coal processing industry to handle the separated products after beneficiation. Filtration is a process in the dewatering to reduce the moisture to obtain a solid/particulate cake. There are different types of filtration being used in the mineral industry for the dewatering based on the physical and surface properties of the material. Vacuum filtration is a widely accepted and low-cost dewatering system for mineral/coal filtration system. Vacuum belt filtration is one of the widely used dewatering systems in mineral and coal processing industry due to its capacity to handle high capacity, easy operability and lower operating cost. The design of these filters at plant scale require a higher volume of slurry to test at laboratory, or transportation of pilot scale unit to the mine site. However, the design is purely on empirical natures established by the filter manufacturers which are not in the public domain. These above processes of carrying out test work for the accurate scale up and predicting the performance have various limitations. For example, the processing of large quantities of slurry in larger scale at plant site requires the installation of higher capacity machines which is cost ineffective solution. Also, for performing filtration in the laboratory set up, since a large volume of slurry has to be transported to the laboratory , the process becomes cumbersome. Further, the existing laboratory procedure by using Buchner filtration set up misled the design as well as the kinetics of filtration data. In this regard, it is

necessary to design a portable vacuum filtration set up which can be used for the accurate prediction of filtration of the slurry.
Patent 1980/ US 966706 discusses a method of lowering the residual moisture of the filter cake by employing a dewatering aid with a combination of hydrophobic alcohol and a non-ionic surfactant. The process involves filtration of the mineral slurry by adding a designated chemical. This method is in generic on the enhancement of the filtration efficiency of the concentrated mineral slurry.
Patent 2005/ US 6855260B1 discusses a method of enhancing the dewatering of particulate materials by adding hydrophobizing reagent along with low hydrophile- lipophile balance (HLB) number surfactant. This is a method relevant to particularly filtration of the particulate slurry. The moisture reduction can be further improved by using suitable electrolytes in conjunction with the low HLB Surfactants, spraying surface tension lowering reagents onto the filter cake, subjecting the cake to a suitable vibratory means and by using combinations thereof. The reagents used in this invention is primarily to alter the surface tension of a particle to enhance the hydrophobicity and then remove the surface moisture easily by using filtration.
Patent 1993/ WO1993003812 A1 discusses a method of dewatering of coal slurries. The process involves adding an anionic flocculant to the slurry and subsequently adding a dewatering aid to the slurry at or just before the formation of a filter cake during a filtration step. This patent also emphasises on the optimum dosage of an anionic flocculant along with a dewatering aid to filter cake for efficient removal of moisture from the coal slurry. This method is in general on the enhancement of the filtration efficiency of the mineral slurry.
Patent 1981/ US4257879 discusses a method for optimisation of the coal slurry dewatering process by regulating the content based on the particle size. According to this patent, the slurry is separated into a relatively fine grain fraction and coarse grain fraction, with the division point being between about 0.03 and 0.15 mm, and the process is carried out, with a formation

of a coal agglomerate from the fine grain fraction. Further, a dehydration process is employed to both the coarse grain fraction and the coal agglomerate from the fine grain fraction. This is also relevant to the efficient dewatering system for the coal slurry.
Patent 1990/ US4892663 discloses a method for dewatering of a coal slurry by adding a dewatering aid before filtration. This patent was discussed for the application of surfactant while filtering the coal slurry by using vacuum filtration. Also, selected quaternary ammonium dewatering aids of the specific structure are disclosed for coal slurry filtration. In the literature, there is no such comprehensive method disclosed on such portable vacuum filtration experimental set up for dewatering the ultrafine mineral or coal slurry.
OBJECTS OF THE INVENTION
An object of the present invention is to propose a dewatering system for filtration of mineral and coal ultra-fines.
Another object of the invention is to propose a dewatering system for filtration of mineral and coal ultra-fines, for the accurate prediction of filtration kinetics of the mineral/coal ultrafine slurry at a given vacuum pressure.
Another object of this invention is to propose a dewatering system for filtration of mineral and coal ultra-fines, for online data capturing on the filtration kinetics as well as pressure drop in the dewatering system.
A further object of this invention is to propose a dewatering system for filtration of mineral and coal ultra-fines in particular, a portable vacuum test dewatering device, in which different parts removable as well as connected to each other.
These and further objects and advantages of the invention will be apparent to a person skilled in the art on reading the description in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
This invention relates to a dewatering system for filtration of mineral and coal ultra-fines, more particularly to portable type vacuum filtration system for performing filtration of mineral and coal ultra-fines. The test device includes a vacuum outflow system, a vacuum pump of high capacity, a slurry holding column chamber with specially designed filter media supporting base, cover plate for purging gas/reagent, and a capturing data system for cake moisture as well as pressure gradient during the process. This invention describes the advanced dewatering portable system for the slurry to obtain the cake from the mineral/coal slurry with pressure and filterability data.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: A diagram illustrating a portable vacuum filtration test device for mineral/coal fine and ultrafine slurry.
Figure 2: Diagram illustrating the details of the slurry holding chamber along with all the features.
Figure 3: Particle size distribution of chromite fines
Figure 4: Zeta potential of chromite ore fines
Figure 5: Results of filtration for chromite slurry
Figure 6: Filtration kinetics (in terms of moisture) for chromite slurry.
The accompanying drawings, which are in and constitute a part of this invention, illustrate exemplary embodiments and, together with the description, explain the disclosed principles.
DETAILED DESCRIPTION OF THE INVENTION
Thus according to this invention is provided a dewatering system for filtration of mineral and coal ultra-fines.In accordance with this invention is provided an advanced portable dewatering

system for filtration of mineral and coal ultra-fines, to obtain the cake from the mineral/coal slurry with pressure and filterability data.
In accordance with this invention , the dewatering system, more particularly a portable type vacuum filtration system includes a vacuum outflow system, a vacuum pump of high capacity, a slurry holding column chamber with specially designed filter media supporting base, and a capturing data system for cake moisture as well as pressure gradient during the process.
Figure 1 shows the inventive dewatering system according to the invention, more particularly the portable type vacuum filtration for performing filtration of mineral and coal ultra-fines. The test device includes a slurry holding column chamber (1) with specially designed filter media supporting base (lb), a vacuum outflow system with a moisture trap system (5), a vacuum pump of high capacity (7), and a data capturing system (6) for cake moisture as well as pressure gradient during the process. The vacuum pump is connected to the slurry holding column (1) through the filter media supporting base (lb) on which filter cake (la) will be formed. The control of the vacuum system connects to the digital pressure gauge (2) to control and understand the filterability of the slurry in a given filtration media. The filtrate solution is collected in a collection chamber (3) which is placed above a digital weightometer (4) for auto-collecting the filterability kinetics data. The components of the portable test dewatering device are removably connected to each other.
As depicted in Figure 1, a method is provided to design a portable type vacuum filtration for performing filtration of mineral and coal ultrafine. Typically, for performing vacuum filtration experimentation, a considerable amount of samples of slurry are collected, and brought to the testing site where the sample is homogenized to make it representative, and further for performing experiments. However, the process of sample collection, transportation and homogenization of the sample is time-consuming as well as cost ineffective. Also, conducting vacuum filtration experiments on commercial scale belt filters may not be advisable due to consumption of large volume of slurry in the testing stage itself, thereby increasing the overall costs associated with the experiment.

Further, the slurry holding chamber (1) has been explained in Figure 2. The slurry holding chamber design depends on various factor such as characteristics of the slurry including particle size distribution, slurry density, viscosity, filter medium resistance, etc. Based on the application and slurry properties, holding chamber parameters are crucial for determining the design parameters of a scale up in such filtration system. The height of the cylindrical section (lc) of the slurry holding chamber (1) can be varied in between 50 mm to 150 mm for the efficient sludge holding as well as for maintaining the required filtrate cake thickness. Similarly, the supporting base for filter media (lb) has been designed to enhance and maintain an uniform pressure gradient across the cross-section and should support the high resistance filter cloth which can be replicated in the industry. The cylindrical section (lc) and supporting base is designed in such a way that it can be detached and joined easily without much drop in the vacuum pressure. There is a gradient of the wall profile to fix these two bodies, and the joining portion (8) can be visualised as shown in Figure 2. Also, the design of the filter media supporting base is to support the high resistance cake and efficient draining of the filtrate solution while filtering. For the efficient separation and flow of the filtrate solution, the base has been uniquely designed. The filter media supporting base (lb) is detachable from the base of said said slurry holding column chamber (1) and is provided with discontinuous concentric elevated profiles (9) alternating with ridges (10). The elevated profiles (9) have a uniform tapered gradient towards the centre of said media supporting base (lb) to enhance flowability of the filtrate towards the central aperture (11) of said supporting base (lb) .The elevated profile (9) with a uniform tapered gradient in the cross section also enhances the filterability and reproducibility in the scale-up process. This elevated profile is designed in a tapered way towards the centre so that the filtrate solution can flow towards the centre and is collected through a central aperture (11) over the base (12). The top cover plate (1d) is also designed as a detachable component and can be used for the purging of different gases as well as surfactants/chemicals during filtration with an option to allow the vacuum pressure inside the chamber.
Various embodiments disclosed herein provide a portable device to conduct vacuum filtration experiments in a manner that overcomes limitations of existing methods and devices used for

the said experiment. For example, the embodiments disclose method and device for conducting vacuum filtration experimentation in a cost-effective and time-efficient manner. The disclosed system can be implemented in the form of a test device such that the test device easy to carry to places such as mineral and coal beneficiation plants. Research laboratories, and so on to perform experiments. Moreover, the disclosed system reduces the space required for the filtration set up.
As depicted in Figure 1, a method is provided to design a portable type vacuum filtration for performing filtration of mineral and coal ultrafines. The process handles the ultrafine particle size in between below 1 mm to 0.01 mm. The slurry of these particles is varied in the pulp density in the range of 5% solids (by weight) to 70% solids (by weight). Further, the filtration media can be altered based on the requirement by the application. There is a provision to accommodate the filter media over the specially designed media (1b) supporting base which can withstand the high resistance pressure created over it. The filter media (below la) can be directly used as the cloth used by the plant scale filters manufacturer by using polyurethane or polyester, etc.. The filter media supporting base has specially designed to create the uniform pressure gradient below the filter media. The aperture size of the filter cloth can be used as below as 8-micron size aperture in the mentioned system. The supporting base (1b) for the filtration media is specially designed to drain the filtrate water to the collection chamber (3). The base is designed in such a way that the draining of the filtrate solution should not disturb the pressure gradient below the filtration media. The supporting base (1b) is designed specially to detach from the slurry holding column (1c) which enables further study on the properties of the filter cake (1a). At the top of the slurry holding column (1c), there is cover plate along with a valve to facilitate the required vacuum as well as purging of any gas or spraying any reagent or surfactant over the cake surface to enhance the filtration efficiency. The cover plate is also detachable and can be used based on the requirement. Further below the slurry holding chamber (1) and before filtrate collection chamber (3), there is a pressure gradient sensor or digital pressure gauge (2) to measure the actual vacuum pressure developed on a dynamic basis during the experimentation. The dynamic pressure change below the filter cake (1a) has been collected online along with time a through a capturing data system (6). Similarly, the filtrate

solution collection chamber (3) is placed above a digital scientific weightometer (7) to understand and collect the filterability data during experimentation. The kinetics of the filtration data is collected through a capturing data system (6). The data collected on kinetics can be used for the design of vacuum filtration system as well as well as generating scientific data for the research purpose. There is also a moisture entrapment system (5) designed with silica placed in between filtrate collection chamber (3) and vacuum pump to entrap or absorb the moisture carrying the vacuum air.
It will be noted that the portable vacuum filtration set up is a batch scale process and from which filtration process can be designed for a commercial/plant scale. The main parameters such as particle size distribution, slurry density, filter cake thickness, vacuum pressure are to be to be tested for understanding the filtration kinetics, which involves consumption of a huge amount of slurry. It is difficult to carry to carry such large volume of slurry samples that may be required for the experiments. However, the disclosed device is designed to be a portable system that can help in conducting vacuum filtration experiments and mimic the actual separation, irrespective of the scale. It will be appreciated that the disclosed slurry filtration system described concerning Fig. 1 provides a portable filtration test device that can be utilised for performing filtration experiments under vacuum condition. The disclosed test-device enables in varying parameters such as slurry density, particle size distribution, slurry viscosity, pH, surfactant addition, gas purging, cake thickness and perform the experiments to determine optimal conditions for the to obtain the filtration kinetics for a given material. In an embodiment, the cake thickness can be varied from few mm to 50 mm. The test device involves process simplicity and is easy to scale up to achieve low moisture filter cake for a given material. A table illustrating values about an example of filtration conditions for the chromite fines along with slurry characteristics are described below.



As it is mentioned in Table 1, the disclosed test device is a lab scale test rig where vacuum filtration experiments are performed by using chromite ultrafine slurry. The particle size distribution of the chromite fines are given in Figure 3 which depicts 80% of the particles are size below 48 microns and 50% of the particles are below the size of 27 microns. It can be assumed that the feed particles are ultrafine. Further zeta potential of the slurry is determined, and the result is given in Figure 4. It is found the IEP (isoelectric point) of the particles is at pH value of 3.6 which is in acidic. Similarly, contact angle and surface tension of the slurry was measured and given in Table 2.
Table 2: Contact angle and surface tension of chromite ultrafine slurry of at different pH value.


The filtration experiment was carried out with a solid concentration of 60% solids (by wt.) for the chromite ultra-fines. The slurry was placed in the slurry holding chamber over the filter cloth. The vacuum pressure of 720 mm Hg was applied to filter the slurry and data was captured simultaneously on the pressure gradient as well as filtration kinetics. The results of the filtration kinetics and pressure variation are given in Figure 5. The residual moisture content of the filter cake is found to be 6.79% which can also be generated from the data directly as shown in Figure 6.
As is clear from the above case study results, the disclosed test device is a lab scale test rig where vacuum filtration tests can be carried out for the ultrafine particles. The test device is implemented in the form of a compact device which is easy to carry to the place wherever experiments are to be conducted. When a large volume of slurry samples are required for investigations, the experimental set up can be taken to the place where the slurry is available or generated for experimentation instead of transporting such large volume of slurry to the lab. Herein it is pertinent to note that the test device can be dismantled into the different components and can be reconnected easily.
The current method of the invention discloses a test device of a lab scale test rig where vacuum filtration tests can be carried out for the ultrafine particles. Further, the invention opens up online data acquisition with a minimum error on filtration data for the design and scale-up studies which is very important and crucial. The invention, of cpurse, is useful from the testing perspective as it is a portable and compact device which can be dismantled easily and carried to a required location for testing. The process further envisages efficient laboratory set up for the vacuum filtration of ultrafine mineral and coal slurry which is essential for the water recirculation, conservation and environment protection point of view.

WE CLAIM :
1 A dewatering system for filtration of mineral and coal ultra-fines, comprising a slurry holding column chamber (1) for holding a filter cake (la) based on the cake thickness required,
said slurry holding column chamber (1) being removably connected to a vacuum outflow system,
said slurry holding column chamber (1) being provided with a filter media supporting base (lb) for generating uniform vacuum pressure across the diameter of said filter cake and channelising the filtrate solution to flow inward centrally for collection in a collection chamber (3), the bottom of said slurry holding column chamber (1) being being releasably connected to a digital pressure gauge (2) connected to an on-line data acquisition system (6), said filtrate solution collection chamber (3) being placed above a digital weightometer (4) connected to an on-line data acquisition system(6).
2. The dewatering system as claimed in claim 1, wherein said vacuum outflow system comprises a high capacity vacuum pump (7) connected to said slurry holding column chamber (1) through a moisture trap system (5).
3. The dewatering system as claimed in claim 1, wherein said filter media supporting base (lb) is detachable from the base of said said slurry holding column chamber (1) and is provided with discontinuous concentric elevated profiles (9) alternating with ridges (10).
4. The dewatering system as claimed in claim 3,, wherein said elevated profiles (9) have a
uniform tapered gradient towards the centre of said media supporting base (lb) to enhance
flowability of the filtrate towards the central aperture (11) of said supporting base (lb).
5. The dewatering system as claimed in claim 1, wherein the ultrafine particles of mineral and
coal with size ranging from below 0.01 mm to 1 mm can be filtered .

6. The dewatering system as claimed in claim 1 and 2, wherein the used slurry density can range from 5% to 70 solids by weight.
7. The test device as claimed in claim 1, 2 and 3, wherein said filter cake produced from the vacuum filtration has a moisture as low as below 5% by weight and the cake thickness varies from few mm to centimetres.
8. The test device as claimed in claim 1, where in the test results in terms of filterability, kinetics, pressure gradient and moisture level can be monitored on-line with the data-acquisition system on every second basis.
9. The test device as claimed in claim 1, wherein the slurry holding chamber (la) includes a detachable component (1d) to purge gas or surfactant over the cake top surface in a controlled manner.
10. The dewatering system as claimed in claim 1 particularly to portable type vacuum
filtration for performing filtration of mineral and coal ultra-fines.