FIELD OF INVENTION

The present invention relates to an improved horizontal screw classifier. More particularly, the present invention relates to an improved horizontal screw classifier for refining of crude substances such as minerals or ores, including salt or gypsum in single pass by removing maximum superfluous and embedded impurities; which eliminates the risks of loss of substance being refined and requires considerably less amounts of utilities, power & wash-liquor thereby being efficient and cost-effective. Present improved horizontal screw classifier is portable.

BACKGROUND AND PRIOR ART

Various mineral or ores are available in crude or raw form which contains many impurities such as sand, dirt etc., which renders it difficult to use it directly for commercial purpose. Many industries such as Chlor-Alkali Industries, Soda Ash, Dyes-Paint Industries & Soap Industries, table salt, fortified salt, Cement industries, Plaster of Paris industries, chalk industries, Fertilizer industries, etc. prefer to use mineral resources which are free from impurities.

For example, raw salt or gypsum is mainly obtained in coarse or big lumps along with many soluble and insoluble impurities as calcium, magnesium compounds and dirt. Both salt and gypsum are soft & dense. Salt is composed of sodium chloride (NaCl) while Gypsum is a sulfate mineral which is composed of calcium sulfate dihydrate (CaSO ₄ .2H20). Salt and gypsum have many industrial applications and are used widely in food industry, fertilizers, plaster of Paris, blackboard chalk etc. Impurities in salt and gypsum render it difficult to use for industrial or other purposes. Quite often highly impure products are left unused and often discarded as a waste. Also, it leads to coastal congestion and pollutes fertile land and water. For commercial purpose, raw material is refined to obtain refined salt with purity above 99% is desirable and gypsum with purity above 70% is preferred. Said raw material consists of raw form of salt or gypsum along with other salts and impurities with moisture content and is obtained by drying seawater or bore well brine under sun in salterns. In order to attain industrial viability, impurities are separated from the raw salt or gypsum to achieve the preferred purity. This is done by washing raw material in classifiers. The primary objective of classifier is to remove superfluous and embedded impurities from raw material wherein, purification/ refinement/ up-gradation to remove soluble and insoluble impurities is done by mechanical/ physical method of wet slurry or by dry air processing a sparingly performed gravity separation of non-valuable substance from the valuable raw material.

Various classifiers have been developed and are available in the market to remove these impurities and refine raw material. These classifiers include:— a) Inclined Screw conveyor Classifiers: The said classifiers are assembly of open 'U' trough & screw having structural support at an inclination of about 10° to 40° with horizontal for refining raw material. Washing efficiency of any inclined screw is reduced particularly when slurry is required to be conveyed at an inclination. This is because the wash liquor flows downwards by gravity through a path of least resistance, forming channels beside salt conveyance. Downward flowing wash liquor cannot displace the air between the crystals crevices. And also when wash liquor does not flow counter-currently through the salt, but it bypasses the salt/gypsum. Thus, the washing efficiency of raw material is reduced due to reduction in conveying efficiency in inclined screw.

To counter act the above mentioned problem the wash liquor spraying practice is employed on screw. There are also inclined twin-screw classifiers in use. While processing gypsum there may be inclined open screw with overflowing effluent arrangement. In order to remove more impurity multiple devices like repeated inclined screw conveyor is used. Similarly combination of hydro-cyclone, bend screen and disperse column are also employed. However, this approach requires more wash liquor and energy which is not only expensive, but cumbersome and results in higher loss of useful product. Moreover variation in raw impurities reflects on product impurities. These factors reduce overall efficiency of inclined screw classifiers. b) Wire mesh drip-off conveyor belt: This is an additional measure to fulfill the limitations of inclined, open screw classifier. The discharge of it becomes feed of inclined metallic belt conveyor. The layer of salt/gypsum is running on porous metallic wired belt or vibrating screen wherein wash liquor is sprayed on it from top to remove soluble/ insoluble impurities pushing out from pores. However, spray on wired belt conveyor has disadvantages of loosing useful finer value- product in effluent. In addition, it is unsafe for the workforce. c) Disperse column in classifier: This works on simple principle of floating and settling of heavy and light particles & separation by regulating upward flow of wash liquor in a vertical column. It is also called elutriator. Lighter particles are rejected out from the top and heavier are allowed to settle down and discharged from bottom using solenoid controlled timer valve. The product discharged from bottom is always with soluble impurities of wash liquor. d) Hydrocyclone: Said hydrocyclone works on the principle of particle's weight based inertia loss and separation of lighter particles from heavier ones. Said hydrocyclone equipment is stationary and the slurry revolves fast inside creating vortex in the center of a conical apparatus. However, both the coarse and fine particles of the raw material with soluble impurities of wash liquor and finer value-product also goes out through vortex. Thus, it fails to remove the impurities from the raw material efficiently. e) Sieve screen: Inclined flat or bend type sieve screens are used for size separation. Here screen is stationary and slurry runs over it. The finer value-products are rejected through screen openings and in effluent. f) Jet pump for sprinkling of wash liquor on big stacks of raw gypsum/ salt:

Raw/ washed products are arranged in big stacks and wash liquor is sprinkled like rain on it using jet pump to remove impurities. However, it consumes excessive wash liquor and washes only external surface of stack without removing internal impurities.

Thus, none of the said classifications are able to remove impurities from raw material efficiently with minimum loss.

DISADVANTAGES OF THE PRIOR ARTS:

The existing classifiers suffer from at least one of the following disadvantages:

1. Most of them require multiple devices to refine raw.

2. Most of them have low washing efficiency and consume more energy.

3. Most of them use high amount of wash liquor and costly. 4. Most of them have cumbersome operations.

5. Many of them are complex with huge structure.

6. Most of them produce product with high moisture.

7. Most of them do not adopt stray & poor/ crude raw for washing.

8. Most of them need attendants standing for impurities removal.

9. Most of the plants are beyond reach of small salt farm owners.

10. Most of them have high loss of value-product.

1 1. Most of them are not portable.

12. Most of them use high utilities.

13. Most of them need repetitive passes to get refinement.

14. Most of them are unsafe for work force.

15. Most of them are unfit for processing different raw minerals.

16. Most of them are unfit to accommodate temperature/ chemical conditions.

17. Most of them wash or refine the material by counter current of washing liquor or by co-current of washing liquor.

18. Most of them employ single type of washing liquor.

19. Most of them are inefficient or less efficient in removal of impurities.

20. Most of them cannot process finer particle sizes.

Thus, there is a need to develop simple cost effective, portable & safe versatile classifier with improved refining efficiency in single pass using justified wash liquor at negligible particle loss of value-product.

OBJECTIVES OF THE INVENTION:

The primary object of the present invention is to provide an improved horizontal screw classifier for refining of crude minerals, salt or gypsum in single pass. Another object of the present invention is to provide an improved horizontal screw classifier for removing maximum superfluous and embedded impurities of a crude substance while refining them.

Yet another object of the present invention is to provide an improved horizontal screw classifier which eliminates the risks of loss of fine substance being refined.

Yet another object of the present invention is to provide an improved horizontal screw classifier which requires considerably less amounts of utilities, power & wash-liquor thereby being efficient and cost-effective. Yet another object of the present invention is to provide an improved horizontal screw classifier which is simple single device and portable.

Yet another object of the present invention is to provide an improved horizontal screw classifier for refined product which has considerably reduced amounts of moisture. Yet another object of the present invention is to provide an improved horizontal screw classifier that eliminates need of persistently standing attendants in classification improvement.

Yet another object of the present invention is to provide an improved horizontal screw classifier which is economical. Yet another object of the present invention is to provide an improved horizontal screw classifier which is easy and safe to handle.

Yet another object of the present invention is to provide an improved horizontal screw classifier which facilitates the use of co-current, counter current and mixed current of wash liquors with material to be washed thereby ensuring maximum removal of impurities. Yet another object of the present invention is to provide an improved horizontal screw classifier which facilitates the use of multiple types of washing liquors thereby ensuring removal of all types of impurities.

Yet another object of the present invention is to provide an improved horizontal screw classifier which is efficient.

BRIEF DESCRIPTION OF DRAWINGS

SUMMARY OF THE INVENTION Present improved horizontal screw classifier mainly comprises of-

• Inlet assembly;

• Washing assembly;

• Outlet assembly;

• Joining Assembly;

· Structural Assembly. Wherein:

Inlet assembly is provided to introduce the raw material to be refined using present improved horizontal screw classifier. The Washing Assembly is provided for refining of the raw material by washing with crushing and churning enabling removal of maximum superfluous and embedded impurities. Said washing assembly is comprised of plurality of segments further comprising of washing components for washing and refining of the raw material. Said Joining Assembly is provided for joining of said plurality of segments of the Washing Assembly. The Outlet Assembly is provided for retrieval of washed and refined material from the present improved horizontal screw classifier. The Structural Assembly provides structural support to the components of the present improved horizontal screw classifier.

Different types of washing liquids or washing liquors; including wash liquor, clean liquor and drain liquor are used which serve as solvents for impurities and aid in refining of the material being washed in the present improved horizontal screw classifier. Said washing liquids are introduced in the present improved horizontal screw classifier through respective inlets and are removed from it through respective outlets along with impurities after washing.

DESCRIPTION OF THE INVENTION:

The embodiment of the present invention is to provide an improved horizontal screw classifier for refining of crude substances such as minerals or ores, including salt or gypsum in single pass in a single unit by removing maximum superfluous and embedded impurities of a crude substance by crushing and gravity separation; which eliminates the risks of loss of fine substance being refined and requires considerably less amounts of utilities, power & wash-liquor thereby being efficient and cost- effective. Present improved horizontal screw classifier is portable.

Present improved horizontal screw classifier mainly comprises of :

• Inlet assembly;

• Washing assembly;

• Outlet assembly;

• Joining Assembly;

• Support Assembly.

Wherein: Meaning of Reference numerals of said component parts of present invention:

1 Present improved horizontal screw classifier

2 Inlet Assembly

2A : Feed Inlet Spout

2B : Wash liquor inlet

3 Washing Assembly

3A : Segments titled includes following

3A1 First segment

3A2 Second segment

3A3 Intermediate segment

3A4 Last segment

3Aa Tubular Trough

3Ab Rotating Staggered Flight Screw

3Ac Screw Shaft

3Ad Staggered Screw Blade

3B Stationary Baffles 3B 1 Primary Perforations

3B2 Secondary perforations

3B3 Hanger Bushing

3C Clean Liquor inlet

3D Wash Effluent Outlet

3E Clean Effluent outlet

3F Sweeper Window

4 Outlet Assembly

4A Drain liquor inlet

4B Inclined Outlet Trough

4C Product Discharge Outlet

5 Joining Assembly

5A Shaft coupling

5B Flanges

5C Lugs to centralize baffles

6 Structural Assembly

6A Support structure

6B Thrust bearing housing

6C Hanger bearing

Referring to Fig. 1 and Fig. 2, the Inlet assembly (2) is provided to feed the raw material to be refined in the present improved horizontal screw classifier ( 1). Said Inlet Assembly further comprises of:

• Feed Inlet Spout (2A)

• Wash liquor inlet (2B) Said Feed Inlet Spout (2A) is provided to introduce the raw material into the present improved horizontal screw classifier ( 1). Said raw material includes mineral or ore such as salt or gypsum. A Wash Liquor inlet (2B) is provided to feed wash liquor in the Inlet Assembly (2) for washing the raw material. Said wash liquor which is fed in the Inlet Assembly (2) is a highly saturated liquid with concentration of 15° to 30° Be' brine preferably 20° to 25° Be'; which includes brine which is highly saturated salt water and thus enables washing of the raw material without getting value-product dissolved in the wash liquor ensuring that there is no loss of material in dissolved form.

The Washing Assembly (3) is provided for refining of the raw material by washing with crushing and churning enabling removal of maximum superfluous and embedded impurities. Said Washing Assembly (3) is comprised of:

• Plurality of Segments (3 A) titled include:

o First segment (3A1)

o Second segment (3A2)

o Intermediate segments (3A3)

o Last segment (3A4)

Each segment (3A) has washing components placed in it. Said washing components include:

^■ Tubular Trough (3Aa)

^■ Rotating Staggered Flight Screw (3Ab)

^■ Screw Shaft (3Ac)

^■ Screw Blade (3Ad)

■ Stationary Baffles (3B) with:

■ Primary Perforations (3B 1)

^■ Secondary perforations (3B2)

■ Hanger Bushing (3B3)

■ Clean Liquor inlet (3C) Wash Effluent Outlet (3D)

Clean Effluent Outlet (3E)

Sweeper Window (3F)

Wherein, each of the said plurality of segments (3A) is a washing unit and further comprising of washing components for washing and refining of the raw material. Said plurality of segments include First Segment (3A1) which is attached to the Inlet Assembly (2) to receive the raw material and the wash liquor for washing. Same is clearly shown in Fig. 1 and Fig. 2. The segment placed next to the First Segment (3A1) is the Second segment (3A2) and receives the raw material mixed with the wash liquor. The second segment is followed by plurality of intermediate segments (3A3) and a last segment (3A4) towards the outlet of the present improved horizontal screw classifier ( 1). Said segments (3 A) are interconnected by Joining Assembly (5) as explained later and shown in Fig. 2 and Fig. 3. Each of the said segments further comprises of a tubular trough (3Aa) wherein washing components are placed. The washing components includes a Rotating Staggered Flight Screw (3Ab) with a Screw Shaft (3Ac) and rotating Screw Blade (3Ad) which enables mixing and churning of the material being washed in present improved horizontal screw classifier ( 1). Stationary Baffles (3B) are placed between every two adjacent segments (3A) and within the segments (3A) in its tubular trough (3Aa) which facilitates in crushing and selective grinding of the raw material while passing through the perforations provided in said Stationary Baffles (3B). Said selective crushing is achieved by rupturing of the particles of raw along the planes where they are weakest wherein said rupturing takes place while the compressive thrust of the rotating screw facilitates forward movement of material being washed, towards the Baffles (3B). The particles of the material being washed are weak where the impurities disturb the crystal structure and therefore resulting in selective rupturing or selective wet crushing. Each Stationary Baffle (3B) as shown in Fig. 1 and Fig. 4 has Primary Perforations (3B 1) for crushing of raw material and Secondary perforations (3B2) for passing of wash liquor. A Hanger Bushing (3B3) is placed at the center of said Stationary Baffles (3B) for facilitating rotational motion of the Rotating Staggered Flight Screw (3Ab) in with its Screw Shaft (3Ac) through it. Further, each intermediate segment(s) (3A3) is provided with Clean Liquor inlet(s) (3C) for introducing clean liquor to the material being washed and refined in the present improved horizontal screw classifier ( 1). Said clean liquor is a liquid with medium saturation preferably 10°Be' to 15°Be' saturated liquid including sea water wherein said clean liquor functions in removal of left out insoluble while absorbing soluble impurities. Said Clean Liquor inlet(s) (3C) being in plurality provides the provision of introducing clean liquor from any point of operation or washing thereby facilitating efficient washing of the material being washed in the present improved horizontal screw classifier ( 1). Thus, the selection of Clean Liquor Inlet (3C) to be used while washing is dependent on the material to be washed. The parameters for deciding the same is discussed herein after in this specification. Further, a Wash Effluent Outlet (3D) is provided on said second segment (3A2) or on any intermediate segment (3A3) to eliminate the effluent of the material being washed in the Segments (3A) prior to it. The factors determining the distance of the Wash Liquor Inlet (2A) and Wash Effluent Outlet (3D) to determine whether the Wash Effluent Outlet is to be placed on the said Second Segment (2A2) or on intermediate segments (3A3) are discussed herein after in this specification. Clean Effluent Outlets (3E) are provided on said plurality of intermediate segments (3A3) for elimination of clean liquor effluent after washing from the Washing Assembly (3). Further, sweeper windows (3F) are provided to remove the settled substance as and when required. The Outlet Assembly (4) is for the discharge of the refined material from the present improved horizontal screw classifier ( 1) which is in turn received from the Washing Assembly (3).

Said Outlet Assembly (4) further comprises of:

• Drain liquor inlet (4A)

• Inclined outlet trough (4B)

• Product Discharge Outlet (4C) Said Drain liquor inlet (4A) is provided to introduce drain liquor in the Outlet Assembly (4) thereby providing final wash to the washed material received by the Outlet Assembly (4) from the Washing Assembly (3). Said Drain liquor is preferably clean liquid or liquid with lower saturation such as 0°Be' to 5°Be' saturation including weak sea water or fresh water which facilitates to absorb final left out soluble and insoluble impurities. The washed and refined material from the last segment (3A4) of said Washing Assembly (3) is received by the inclined outlet trough (4B) through which it reaches the Product Discharge Outlet (4C). The Inclined outlet trough (4B) has the Drain liquor inlet (4A) and is inclined upwards providing an upward path to the washed and refined material towards the Product Discharge Outlet (4C) against the gravitational force thereby enabling removal of moisture from the material by removal of liquid in gravitational direction. Thus, the discharged washed material has considerably reduced moisture. The capillary movement of the liquor helps in further removal of moisture thus the obtained refined material reduces moisture.

The segments of the Washing Assembly (3) are joined by the Joining Assembly (5) which further comprises of:

• Shaft coupling (5A)

• Flanges (5B)

• Lugs (5C) As shown in Fig. 3, the Screw Shaft (3 Ac) of said Rotating Staggered Flight Screw (3Ab) of one segment (3A) is joined to another in the adjacent segment (3A) with the help of Shaft coupling (5A). Flanges (5B) facilitate the joining of two segments and Lugs (5C) to centralize baffles (3B). The Structural Assembly (6) provides structural support to the present improved horizontal screw classifier ( 1) and comprises of:

• Support structure (6A)

• Thrust bearing housing (6B)

• Hanger bearing (6C)

The supports structure (6A) provides support to support the entire length of present improved horizontal screw classifier ( 1), the Thrust bearing housing (6B) bears the axial load and prevents the Rotating Staggered Flight Screw (3Ab) in opposite direction during operation whereas Hanger bearing (6C) are rotational bearings for Rotating Staggered Flight Screw (3Ab).

Further, prime mover like electric motors and gears are provided to facilitate the rotational motion of the Rotating Staggered Flight Screw (3Ab) and a power source to operate the same is provided. Gear box stand and motive power stands are also provided structural support.

WORKING OF THE INVENTION Present improved horizontal screw classifier ( 1) is turned ON and the raw material to be refined is fed in the Inlet Assembly (2) through Feed Inlet Spout (2A) and Wash liquor is fed through Wash Liquor Inlet (2B). Said raw material and the wash liquor then enter the First Segment (3A1) of the Washing Assembly (3) wherein the Rotating Staggered Flight Screw (3Ab) with a Screw Shaft (3Ac) and rotating Screw Blade (3Ad) placed in the Tubular Trough (3Aa) enables mixing and churning of the material for washing of said material in present improved horizontal screw classifier ( 1) and facilitates the material to move forward with its rotation, towards the Second Segment (3A2) and then to the plurality of Intermediate Segments (3A3) and so on. While moving forward from one segment (3A) to the next, the raw material gets selective wet rupturing or crushed while passing through the Primary perforations (3B 1) of the Stationary Baffles (3B) being placed between and within the segments (3A) of the Washing Assembly (3) while the liquor present in the Tubular trough (3Aa) along with the material and liquor mixture passes through the primary and secondary perforations (3B 1) and (3B2) of said Stationary Baffles (3B). The wash liquor facilitating the washing of the raw material fed into the Feed Inlet Spout (2 A) is eliminated from the Wash Effluent Outlet (3D) placed in the Second Segment (3A2) or any of the intermediate segments (3A3). Similarly, the clean liquor which is being fed through the Clean Liquor Inlets (3C) placed at intermediate Second Segment (3A2) and the plurality of Intermediate Segments (3A3) get eliminated through Clean Effluent Outlets (3E) after washing the material in the Washing Assembly (3). Said effluent outlets (3D and 3E) are placed slight upwards at angle so as to ensure removal of only effluent liquids; eliminating chances of fine material loss. The material, after being washed in various segments (3A) of the Washing Assembly (3) by the wash liquor and the clean liquor, moves towards the Outlet Assembly (4) through the Last Segment (3A4) of the Washing Assembly (3) wherein a final wash to the material is given by Drain Liquor introduced through the Drain Liquor Inlet (4A) while the material moves towards the Product Discharge Outlet (4C) through the Inclined Outlet trough (4B) wherein, the material moves upwards i.e. opposite to the gravitational force and the liquid in the washed material is drained down due to the capillary action and gravitational force thereby resulting in refined and low moisture product from the Product Discharge Outlet (4C). Present improved horizontal screw classifier ( 1) efficiently refines the raw material providing uniform quality of product, irrespective of the quality of the input raw material. Above described components of said assemblies (2, 3, 4, 5, 6 ) play an important role in imparting these high efficiencies of the present improved horizontal screw classifier ( 1). The use of three different liquors for washing, introduced at different stages of operation of said improved horizontal screw classifier ( 1) is one of the key factors effects the efficient working of the present invention. As mentioned above, there are plurality of inlets placed on at various components of the improved horizontal screw classifier ( 1) for introducing said liquors for washing; wherein Wash liquor is fed through Wash Liquor Inlet (2B) and Drain Liquor introduced through the Drain Liquor Inlet (4A) whereas there are plurality of Clean Liquor Inlets (3C) placed on the intermediate segments (3A3). However, the Wash Effluent Outlet (3D) and the Clean Effluent Outlet (3E) are placed on intermediate segments (3A3). This facilitates the co-current movement of material to be washed with the wash liquor along with mixing and churning; counter current of clean liquor and material to be washed or refined and mixed current at the meeting point of both thereby forming a surge and ensuring maximum removal of impurities. Further, the plurality of Clean Liquor Inlets (3C) facilitates use of multiple types of liquors for washing. For example if there are certain impurities that are acid soluble, apart from wash liquor, clean liquor and drain liquor, it allows using of acidic solvent through one of the Clean Liquor Inlets (3C) facilitating the removal of acid soluble impurities. Thus, ensures removal of all types of impurities. Therefore, present improved horizontal screw classifier ( 1) ensures maximum removal of all types of impurities thereby imparting high efficiency.

There are different factors which determine the selection of Clean Liquor Inlets (3C) and for determining the distance between the Wash Liquor Inlet (2 A) and Wash Effluent Outlet (3D), contact time between the material being washed and the liquors, number of segments and inlets for clean liquors, flow rate etc. Said factors are as discussed below as illustrative cases:

Table 1: Shows the selection of parameters based on solubility and the purity of the material being washed.

The illustrative cases enlisted in the above table 1 are described herein below:

Case 1 and 2:

When the solubility of the material to be washed or refined is high, such as salt, then the distance between Wash Liquor Inlet (2A) and Wash Effluent Outlet (3D) is kept more i.e. Wash Effluent Outlet (3D) is placed on one of the intermediate segment (3A3) which is distant from the First segment (3A1). This is because the wash liquor is highly saturated and will not allow dissolution of the material being washed, in it; thereby eliminating the risk of material loss by dissolution. Thus, contact time of the material being washed with the wash liquor is kept higher compared to the contact time of the clean liquor. Further, when solubility of the material being washed is high and the overall contact time with the liquid is to be kept low, number of segments and number of clean liquor inlets used is also low. The flow rate of the wash liquor as well as the flow rate of the clean liquor is kept low so as to avoid material to get dissolved in the liquor.

In the above cases, when the dirt or the impurities in the material to be washed is high, the flow rate of the liquors is required to be kept more than the flow rate used when the impurities are less.

Case 3 and 4: When the solubility of the material to be washed or refined is low, such as gypsum, then the distance between Wash Liquor Inlet (2A) and Wash Effluent Outlet (3D) is kept less i.e. Wash Effluent Outlet (3D) is placed on second segment (3A2). And the clean liquor is introduced earlier compared to case 1 and 2. This is because the solubility of the material is less and thus the chance of material loss through dissolution in the clean liquor is less. Thus, contact time of the material being washed with the wash liquor is lower compared to the contact time of the material being washed and the clean liquor. Further, when solubility of the material being washed is low and the overall contact time with the liquid is to be kept high, number of segments and number of clean liquor inlets used is also high. The flow rate of the wash liquor as well as clean liquor is kept low or high as there is no risk of material to get dissolved in the liquor.

In the above cases, when the dirt or the impurities in the material to be washed is high, the flow rate of the liquors is required to be kept high whereas when the dirt or the impurities are low, the flow rate used is low to high as there is no risk of material loss.

Further, in any of the above cases, when the flow rate of the wash liquor is kept low and the wash liquor effluent is containing less dirt, the flow rate of the clean liquor is increased. When the impurities are high, more number of clean liquor inlets is used and flow rate is increased or decreased based on the impurities released in the effluent liquor.

In addition, the flow rate of the drain liquor is always kept low. This is because it has to percolate through the solid. Moreover, if the flow rate is kept high, it will add moisture to the output rather than aiding in the capillary action.

Apart from the solubility and level of impurities of the raw material to be refined, particle size is another factor which is to be considered while refining the material using the improved horizontal screw classifier ( 1). When the particle size is high, the discharge rate is high and the flow rate of the liquors used for washing is kept high. Whereas when the particle size of the material to be washed is small, the discharge rate as well as the flow rate of the liquors is kept low. This is done for efficient washing and to prevent fine material loss due to high flow rate with high effluent discharge respectively.

Moreover, the materials with fine particles size are also refined with high efficiency in the present improved horizontal screw classifier (1) because the fine particles, while mixing and churning of the material in the Washing Assembly (3) gets interlocked with the other particles and hence are not released with the effluent.

The present improved horizontal screw classifier ( 1) ensures maximum removal of all types of impurities thereby imparting high efficiency. The effluent released from present improved horizontal screw classifier ( 1) contains maximum dirt or impurity discharge because at the effluent outlet the Wash liquor and the clean liquor meet to form surge or wave from the opposite direction. This is because; the liquids of two different concentrations meet at effluent outlet point.

It is pertinent to note that the above cases and parameters are given for the illustrative explanation only and not to restrict the scope of the invention. Any obvious derivation of the present invention shall fall within the scope of the present invention.

EXAMPLES

The above parameters when kept in mind provide optimized output with high purity product output. Various experiments were conducted to optimize and establish the same. Examples of each of the above case are given as under: MATERIAL WASHED Salt Salt

Table 2: Shows the experimental values pertaining to case 1 and case 2 of table 1 establishing the parameters and thereby working of the present invention.

In the above table 2, Example 1 and Example 2 relate to the case 1 and case 2 as provided in table 1 and the explanation thereof.

It clearly establishes that when solubility of the material to be washed in present improved screw classifier ( 1) is high; the parameters as discussed in table 1 shall apply. MATERIAL WASHED Gypsum Gypsum

15 WS the experimental values pertaining to case 3 and case 4 of table 1 establishing the parameters and thereby working of the present invention.

In the above table 3, Example 3 and Example 4 relate to the case 3 and case 4 as provided in table 1 and the explanation thereof. It clearly establishes that when solubility of the material to be washed in present improved screw classifier ( 1) is low; the parameters as discussed in table 1 shall apply. OTHER EMBODIMENTS

Another embodiment of the present improved horizontal screw classifier ( 1) is to provide said classifier as a single unit wherein said segments (3 A) of the washing assembly (3) are permanently joined to form a single unit or is built as a single unit wherein the Tubular Trough (3Aa) of said Washing Assembly (3) is continuous with components of the washing assembly (3) being placed within it wherein further the Stationary Baffles (3B) are placed at fixed distances with the help of the Joining Assembly (4).

The working of the said embodiment is similar to the main embodiment wherein the raw material to be washed is introduced to the present improved horizontal screw classifier ( 1) through Feed Inlet Spout (2 A) and Wash liquor is fed through Wash Liquor Inlet (2B). Said raw material and the wash liquor then enter the Tubular Trough (3Aa) of the Washing Assembly (3) wherein the Rotating Staggered Flight Screw (3Ab) with a Screw Shaft (3Ac) and rotating Screw Blade (3Ad) placed in the Tubular Trough (3Aa) enables mixing and churning of the material for washing of said material in present improved horizontal screw classifier ( 1) and facilitates the material to move forward with its rotation, towards the Outlet Assembly (4). While moving forward from Inlet Assembly (2) towards the Outlet Assembly (4), the raw material gets selective wet rupturing or crushed while passing through the Primary perforations (3B 1) of the Stationary Baffles (3B) being placed within the Tubular Trough (3Aa) of the Washing Assembly (3) while the liquor present in the Tubular trough (3Aa) along with the material and liquor mixture passes through the primary (3B 1) and secondary perforations (3B2) of said Stationary Baffles (3B). The wash liquor facilitating the washing of the raw material fed into the Feed Inlet Spout (2A) and is eliminated from the Wash Effluent Outlet (3D) placed in the Tubular trough (3Aa) at a distant from the Inlet as determined according to the raw material to be washed or refined. The selection of distance is as per the Table 1 provided above. Similarly, the clean liquor which is being fed through the Clean Liquor Inlets (3C) placed at intermediate places on Tubular Trough (3Aa) get eliminated through Clean Effluent Outlets (3E) after washing the material in the Washing Assembly (3). The material, after being washed in various segments (3A) of the Washing Assembly (3) by the wash liquor and the clean liquor, moves towards the Outlet Assembly (4) wherein a final wash to the material is given by Drain Liquor introduced through the Drain Liquor Inlet (4A) while the material moves towards the Product Discharge Outlet (4C) through the Inclined Outlet trough (4B) wherein, the material moves upwards i.e. opposite to the gravitational force and the liquid in the washed material is drained down due to the capillary action and gravitational force thereby resulting in refined and low moisture product from the Product Discharge Outlet (4C).

In a further embodiment, for classifying entire finer particle size of raw having low settling velocity in the liquor, a provision of required settling zone exists between washing segment and product discharge outlet.

Having described what is considered the best form presently contemplated for embodying the present invention, various alterations, modifications, and / or alternative applications of the invention will be promptly apparent to those skilled in the art. Therefore, it is to be understood that the present invention is not limited to the practical aspects of the actual preferred embodiments hereby described and that any such modifications and variations must be considered as being within the spirit and the scope of the invention, as described in the above description. ADVANTAGES OF PRESENT INVENTION:

1. Present improved horizontal screw classifier refines of crude minerals, salt or gypsum in single pass by removing maximum superfluous and imbedded impurities of a crude substance while refining them.

2. It eliminates the risks of loss of substance being refined. This is because, there is no screening involved. The refining is done by washing.

3. It requires considerably less amounts of utilities, power & wash- liquor thereby being efficient and cost-effective.

4. It provides refined substance which has considerably reduced amounts of moisture as it enables the product to get dewatered by gravity prior to its discharge from classifier.

5. It provides improved washing with specialized baffles and with suitability of selecting optimum contact time for soluble impurities to leave the crystals crevices by diffusion. Further, it promotes partial shear, collision, crushing, compression & biaxial compression resulting squeezing, rubbing & brushing action on raw particles in presence of wash liquor for better washing. The particles will break gently along the planes where it is weakest. It is weak where the impurities disturb the crystal structure becomes Selective Rupturing.

6. It accommodates processing of free flow salt and fortification of salt in an improved horizontal screw classifier.

7. It can adopt waste/ stray raw processing.

8. It can adopt chemical/ thermal treatment in the classifier.

9. It is easy and safe to handle and thus adoptable by even small salt farm owners.

10. Present improved horizontal screw classifier is portable. It provides uniform product quality irrespective of variation in raw quality.

It adopts washing with fine size mixed feed of raw material. There is no material loss of fine particles. This is because the fine particles get interlocked into mix size material while churning.

It facilitates the co-current movement of material to be washed with the wash liquor along with mixing and churning; counter current of clean liquor and material to be washed or refined and mixed current at the meeting point of both thereby forming a surge and ensuring maximum removal of impurities.

Further, the plurality of Clean Liquor Inlets (3C) facilitates use of multiple types of liquors for washing. For example if there are certain impurities that are acid soluble, apart from wash liquor, clean liquor and drain liquor, it allows using of acidic solvent through one of the Clean Liquor Inlets (3C) facilitating the removal of acid soluble impurities. Thus, ensuring removal of all types of impurities. Therefore, present improved horizontal screw classifier ( 1) ensures maximum removal of all types of impurities thereby imparting high efficiency.