A SYSTEM AND A METHOD FOR CLASSIFICATION OF MATERIALS

FIELD OF THE INVENTION

[001] The invention relates to a system and a method for classification of materials.

BACKGROUND OF THE INVENTION

[002] Classification is a process for separating particulate material into two or more products based on size, form or weight by the velocity with which they fall through usually air or water. It can be broadly based on their separation principles, i.e. dry classification and wet classification. Mostly, the construction, demolition and excavation wastes are handled/recycled in dry form and crushed. They are then screened to recover only aggregates. The fines thus generated are not utilized and are wasted which is also an environmental hazard as they are mostly disposed of in landfills without any recovery of materials.

[003] The recycled aggregates produced by dry processing (dry classification) are of poor quality due to adhering fines, cement dust, gypsum etc. on them and cannot be utilized efficiently for quality construction. It is used mostly as low value material in applications such as in road making as fillers and sometimes partially in concrete production. This leads to high cement consumption to achieve desired strength.

[004] Wet classification is a type of classification wherein water or any other liquid is used for the separation of coarse and fine particles. The lighter particles are carried away by the fluid whereas the heavier particles tend to settle. Wet classification has to be employed in order to separate and recover the fines. However, a large quantity of water is required for wet classification and recovery of the water is another area of concern. Traditional water recycling systems, such as settling ponds/dykes and water tanks are being used to recycle the water. These traditional water recycling systems generally consume large amount of time for recycling the water. Moreover they and are separately placed and are not an integral part of the plant/system.

[005] Most often, wet classification plant/system requires large space, heavy foundation, consume good amount of power and need frequent maintenance. Further, additional space, power and an additional setup is required for processing and recovering the water for re-use. Moreover, there is a significant demand globally for crushed sand and aggregates for construction related activities. This combined with the fact that the natural sand resources are getting depleted; there is therefore a need for utilisation of recycled sand and aggregates. Thus there is felt a need for an integrated system and a method for efficient sizing and classification of material and complete waste management and water recycling which allows extraction of graded quality products from different raw materials with maximum recovery of process water for reuse, thereby reducing the requirement of fresh water drastically.

SUMMARY OF THE INVENTION

[006] Accordingly, the present invention provides in one aspect provides a system for classification of materials. The system has a feeding means configured to feed the materials to a logwasher for surface scrubbing. Further a multiple deck rinsing screen is adapted to receive the scrubbed material from the logwasher and classify the materials into two or more products of different sizes. The classified products are stockpiled by respective product conveyors. A de- gritting trash screen adapted to receive water containing light weight particles from the logwasher and separate the water from fine materials. The fine materials are then stockpiled. A first sump is configured to receive slurry from the multiple deck rinsing screen and the de- gritting trash screen. Further, a first hydrocyclone is adapted to receive the slurry from the first sump by a respective slurry pump. The first hydrocyclone divides the slurry into an underflow and an overflow. A first grading and dewatering screen is adapted to receive the underflow from the first hydrocyclone thereby separating the particles based on size. The recovered water and the undersize particles are passed into a second sump and the oversize particles are discharged onto a respective conveyor as a classified product. Further, a second hydrocyclone is adapted to receive slurry from the second sump by a pump. The second hydrocyclone divides the slurry into an underflow and an overflow wherein the fine slime particles in the second hydrocyclone overflow are rejected. Also procided is a second grading and dewatering screen adapted to receive the second hydrocyclone underflow for separating the dewatered oversize particles as a further classified product via a respective conveyor for stockpiling.

[007] In another aspect of the present invention, disclosed is a method for classification of materials. The method involves feeding the materials and water to a logwasher by a feeding means followed by scrubbing to obtain a scrubbed material. The scrubbed material is then discharges from the logwasher onto a multiple deck rinsing screen for classification into two or more classified products. These products are then delivered into multiple stockpiles of different size range via integrated product conveyors. The water containing light weight particles from the logwasher is then discharged onto a trash screen whereby water is separated from fine materials followed by stockpiling of the fines. The recovered water with fines obtained from the logwasher is discharged onto a trash screen and water and undersize material from the multiple deck rinsing screen into a first sump in slurry form. This slurry is then pumped into a first hydrocyclone by a respective slurry pump. The first hydrocyclone divides the slurry into an underflow and an overflow. The fine slime particles are rejected through the first hydrocyclone overflow. The coarser particles obtained from the first hydrocyclone underflow in a slurry form are discharged to a first grading and dewatering screen followed by delivering the oversize material from the first grading and dewatering screen onto a respective conveyor to obtain a classified product. The recovered water and undersize particles are passed from the first grading and dewatering screen to a second sump in a slurry form. The recovered water and undersize particles are then pumped in the slurry form, from the second sump to a second hydrocyclone. The second hydrocyclone divides the slurry into an underflow and an overflow and rejecting the fine slime particles through the second hydrocyclone overflow. The second hydrocyclone underflow is fed to the second grading and dewatering screen wherein the oversize material is discharged from the second grading and dewatering screen onto a respective conveyor to obtain a further classified product. The waste slurry from first and/or second hydrocyclone overflows is then fed to a water recycling system having a blending chamber. In the water recycling system the clean water is discharged to a clean water collection tank. This clean water is re-circulated to the multi-deck grading screen, and/or first and second grading and dewatering screens and/or first and second sumps and/or logwasher via a re-circulating water pump.

BRIEF DESCRIPTION OF THE DRAWINGS

[008] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

Figure 1 illustrates the method flow of the materials for classification according to an embodiment of the present invention.

Figure 2 illustrates the method flow of the materials for classification according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[009] As shown in Figure 1, disclosed is a system 10 for wet classification. The system 10 has a feeding means 100 which is configured to receive materials for classification. The logwasher 101 is coupled with the feeding means 100 in order to receive the materials from the feeding means 100. The logwasher 101 scrubs the material to obtain coarse particles and water containing light weight particles. The system 10 further has a multiple deck rinsing screen 102 and a de-gritting trash screen 105. The multiple deck rinsing screen 102 is positioned such that it receives the coarse particles from the logwasher 101 and the de-gritting trash screen 105 is positioned such that it receives the water containing light weight particles. The multiple deck rinsing screen 102 classifies the materials into two or more products of different sizes and are stockpiled by respective product conveyor (103). The multiple deck rinsing screen 102 grades the coarse particles into two or more products of different size range. The system 10 further has product conveyors 103 and 104 positioned to stockpile the graded respective products received from the multiple deck rinsing screen 102. The de-gritting trash screen 105 which receives the water containing light weight particles separates the water from fine materials. These fine materials are stockpiled and the water gets collected in a first sump 106 in a slurry form. The first sump 106 is configured to receive the slurry from the multiple deck rinsing screen 102 and the de-gritting trash screen 105.

[010] The system 10 also has a pair of hydrocyclones; a first hydrocyclone 108 and a second hydrocyclone 112. The system 10 also has a slurry pump 107. The slurry pump 107 pumps/transfers the water containing light weight particles in a slurry form from the first sump (106) to the first hydrocyclone 108. The first hydrocyclone 108 divides the slurry into an underflow and an overflow. The system 10 further has a first grading and dewatering screen 109. The first grading and dewatering screen 109 is positioned to receive the underflow from the first hydrocyclone 108. The first grading and dewatering screen 109 separates the particles based on size to recover water and to obtain undersize particles and oversize particles. The recovered water and the undersize particles are passed into a second sump (110). The system 10 also has a product conveyor 113. The conveyor 113 is positioned to receive the oversize particles from the first grading and dewatering screen 109. These oversized particles are discharged by the conveyor 113 as a classified product. The slurry from the second sump 110 is pumped to the second hydrocyclone 112 by a pump 111. The second hydrocyclone 112 divides the slurry into an underflow and an overflow. The overflow of the second hydrocyclone 112 containing the fine slime is rejected. The system 10 further has a second grading and dewatering screen 109. The second grading and dewatering screen 109 is positioned such that it receives the underflow of the second hydrocyclone 112. The second grading and dewatering screen 109 separates the underflow from the second hydrocyclone 112 to obtain a further classified product. This product is stockpiled via a respective conveyor 114.

[011] The system 10 further has a water recycling system 117 having a blending chamber 115.

The water recycling system 117 is positioned such that it receives the overflow from the first and second hydrocyclones 108 and 112 via the blending chamber 115. A flocculent dosing system 116 adds a predetermined amount of the flocculent to the blending chamber 115 to obtain a dosed sludge. The dosed sludge travels under a fabricated baffle promoting laminar flow in the transfer pipe to the centre of the water recycling system 117. Clean water overflows from a fabricated peripheral channel (not shown in the figure) on the outside of the water recycling system 117 and discharges into a clean water collection tank 118. The water is discharged into the clean water collection tank 118 via a sieve bend 124. The sieve bend 124 arrests the fine trash floating in the water upstream of the clean water collection tank 118.

[012] The system 10 also has at least one recycle water pump 119. The at least one recycle water pump 119 recirculates the clean water from clean water collection tank 118 to the multiple deck rinsing screen 102, and/or first and second grading and dewatering screens 109 and/or first and second sumps and/or logwasher 101. Moreover, the overflow from the first and second hydrocyclones 108 and 112 is passed to a settling tank of a water recycling system 117. The system 10 further has a sludge discharge mechanism positioned at the bottom of the settling tank for discharging deposited sludge. The deposited sludge is extracted from the settling tank by an evacuation pump 120 and control valves.

[013] In an embodiment of the invention, as shown in Figure 2, a pre-screen 130 is positioned upstream of the logwasher 101. The pre-screen 130 is placed such that it receives the material from the feeding means 100. The pre-screen 130 removes finer material of a predetermined size from the material. The overflow from the pre-screen 130 is discharged to the logwasher 101 and the underflow from the pre-screen is discharged to said first sump 106 via a chute 135.

[014] In another embodiment of the present invention, disclosed is the system 10 for classification of materials based upon their size and extraction of fine graded particles. The system 10 has a feeding means 100 which is configured to receive materials for classification. The feeding means 100 has a grizzly feeder, feed hopper, feeder and a belt conveyor wherein the feeding means 100 is coupled with the logwasher 101.

[015] The logwasher 101 is coupled such that it receives the materials from the feeding means 100. The logwasher 101 receives additional water for surface scrubbing of the material to obtain a scrubbed material. The scrubbed material is separated into coarse particles and water containing light weight particles by the logwasher 101. The system 10 further has a multiple deck rinsing screen 102 and a de-gritting trash screen 105. The multiple deck rinsing screen 102 is adapted to receive the coarse particles from the logwasher 101 and the de-gritting trash screen 105 is positioned such that it receives the water containing light weight particles. The multiple deck rinsing screen 102 classifies the coarse particles into two or more classified products of different size range. The system 10 further has product conveyors 103 and 104 positioned to stockpile the respective classified products received from the multiple deck rinsing screen 102. The de-gritting trash screen 105 which receives the water containing light weight particles, separates the water from fine materials. These fine materials are stockpiled and the water gets collected in a first sump 106 in a slurry form. The first sump 106 receives water from the pre screen 130, the logwasher 101 and multiple deck rinsing screen 102.

[016] The system 10 also has a pair of hydrocyclones; a first hydrocyclone 108 and a second hydrocyclone 112. The system 10 also has a slurry pump 107. Under predetermined pressure, the slurry pump 107 pumps the water containing light weight particles in a slurry form from the first sump (106) to the first hydrocyclone 108. The first hydrocyclone 108 divides the slurry into an underflow and an overflow. The ultra-fine slime particles are discarded as tailings in the hydrocyclone overflow. The system 10 further has a first grading and dewatering screen 109. The first and second grading and dewatering screen 109 has respective sides of a split screen grading and dewatering screen incorporating the second sump 110. The first grading and dewatering screen 109 is positioned to receive the underflow from the first hydrocyclone 108. The first grading and dewatering screen 109 separates the particles based on size to recover water and to obtain undersize particles and oversize particles. The recovered water and the undersize particles are passed into a second sump 110 for recirculation. The system 10 also has a product conveyor 113. The conveyor 113 is positioned to receive the oversize particles from the first grading and dewatering screen 109. These oversized particles are discharged by the conveyor 113 as a classified product. The recovered water from the second sump 110 is pumped to the second hydrocyclone 112 by a pump 111. The second hydrocyclone 112 divides the slurry into an underflow and an overflow. The overflow of the second hydrocyclone 112 containing the fine slime is rejected. The system 10 further has a second grading and dewatering screen 109. The second grading and dewatering screen 109 is positioned such that it receives the underflow of the second hydrocyclone 112. The second grading and dewatering screen 109 separates the underflow from the second hydrocyclone 112 to obtain a further classified product. This product is stockpiled via a respective conveyor 114. [017] The system 10 further also has a water recycling system 117 having a blending chamber 115. The water recycling system 117 is positioned such that it receives the overflow from the first and second hydrocyclones 108 and 112 via the blending chamber 115. The blending chamber 115 is preferably located adjacent to the water recycling system 117. A predetermined amount of flocculent is added into the blending chamber 115 for quick settling of slurry in the water recycling system 117 to obtain a dosed sludge. A flocculent dosing system 116 adds the predetermined amount of the flocculent to the blending chamber 115. The dosed sludge travels under a fabricated baffle promoting laminar flow in the transfer pipe to the centre of the water recycling system 117. The flow of dosed sludge further slows and promotes laminar flow for downward settlement of sludge. Clean water overflows from a fabricated peripheral channel (not shown in the figure) on the outside of the water recycling system 117 and discharges into a clean water collection tank 118. The water is discharged into the clean water collection tank 118 via a sieve bend 124, located in an overflow water pipe of the settling tank. The sieve bend 124 arrests the fine trash floating in the water upstream of the clean water collection tank 118.

[018] The system 10 also has at least one recycle water pump 119. The at least one recycle water pump 119 recirculates the clean water from clean water collection tank 118 to the multiple deck rinsing screen 102, and/or first and second grading and dewatering screens 109 and/or first and second sumps and/or logwasher 101. Moreover, the overflow from the first and second hydrocyclones 108 and 112 is passed to a settling tank of a water recycling system 117.

[019] The system 10 further has a sludge discharge mechanism positioned at the bottom of the settling tank for discharging deposited sludge. The deposited sludge is extracted from the settling tank by an evacuation pump 120 and control valves. These control valves are preferably pneumatically operated valves, actuated by Air Compressor to the desired sludge disposal area after further mixing with flocculants. [020] The system 10 further has a programmable logic controller for controlling the operation of the system (10).

[021] The present invention also discloses a method for classification of materials. The method initially involves feeding the materials and water to a logwasher 101 by a feeding means 100. This is followed by scrubbing the materials in the logwasher 101 to obtain the scrubbed materials. The scrubbed material is the discharged from the logwasher 101 onto a multiple deck rinsing screen 102. The multiple deck rinsing screen 102 classifies the scrubbed material into two or more classified products. These separated products are then delivered into multiple stockpiles, differentiated according to their sizes via integrated product conveyors 103 and 104. Simultaneously the light weight particles and water from the logwasher 101 are discharged onto a trash screen 105. The trash material is separats the water from the remaining fines by the trash screen 105. The remaining fines are stockpiled. Further, the water from the multiple deck rinsing screen 102 is released into a first sump 106 in slurry form.

[022] The next stage of the method involves pumping the slurry from the first sump 106 a first hydrocyclone 108. A slurry pump 107 pumps the slurry into the first hydrocyclone 108 with a predetermined pressure. The first hydrocyclone 108 divides the slurry into an underflow and an overflow. The fine slime particles are rejected through the first hydrocyclone overflow and the coarser particles are obtained from the first hydrocyclone underflow in a slurry form. These coarser particles in a slurry form are then discharged to a first grading and dewatering screen 109. From the first grading and dewatering screen 109 the oversize material are delivered onto a respective conveyor 113 to obtain a classified product. Simultaneously the recovered water is passed and undersize particles from the first grading and dewatering screen 109 to a second sump 110 in a slurry form. The next step involves pumping the recovered water and undersize particles from the second sump 110 in the slurry form to a second hydrocyclone 112 for further rejection of slimes. The second hydrocyclone 112 divides the slurry into an underflow and an overflow. The fine slime particles are rejected through the second hydrocyclone overflow and the second hydrocyclone underflow is fed to the second grading and dewatering screen 109. The oversize material, present in the second hydrocyclone underflow, is discharged from the second grading and dewatering screen 109 onto a respective conveyor 114 to obtain a further classified product. Further the waste slurry from first and/or second hydro-cyclone 108 and 112 overflows are released to a water recycling system 117 having a blending chamber 115.

[023] The overflow from the first and second hydrocyclones 108 and 112 are released via the blending chamber 115 to the water recycling system 117. In the blending chamber 115, predetermined amount of a flocculent is added to the overflow followed by blending to obtain a dosed sludge. A flocculent dosing system 116 adds the predetermined amount of the flocculent to the blending chamber 115. The dosed sludge then travels under a fabricated baffle promoting laminar flow in the transfer pipe to the centre of the water recycling system 117. The flow of dosed sludge further slows and promotes laminar flow for downward settlement of sludge. Clean water overflows from a fabricated peripheral channel (not shown in the figure) on the outside of the water recycling system 117 and discharges into a clean water collection tank 118. The water is discharged into the clean water collection tank 118 via a sieve bend 124. The sieve bend 124 arrests the fine trash floating in the water upstream of the clean water collection tank 118. The clean water from clean water collection tank 118 is recirculated by at least one recycle water pump 119. The clean water is recirculated to the multiple deck rinsing screen 102, and/or first and second grading and dewatering screens 109 and/or first and second sumps and/or logwasher 101. In a separate step, the overflow from the first and second hydrocyclones 108 and 112 is passed to a settling tank of a water recycling system 117. Lastly, the sludge discharge mechanism extracts the deposited sludge from the settling tank by an evacuation pump 120 and control valves. These control valves are preferably pneumatically operated valves, actuated by Air Compressor to the desired sludge disposal area after further mixing with flocculants. [024] The present invention is fully pre-assembled, electrically wired with extensive test carried out prior to dispatch from factory ensuring minimal intervention required by installation and commissioning engineers. It relates to production of classified and graded products by segregating various materials such as construction, demolition, and excavation waste, railway ballast, road sweepings, tunnel boring waste, quarry material, minerals and the like that contains certain quantity of deleterious material, both free and adhering, through an integrated continuous or batch process with high efficiency in order to recover/improve the end product for the customer and lower its cost of production for users in material and minerals industry.

[025] In an exemplary embodiment, the present invention is used in production of sized and enriched high quality sand and aggregate that is used on every day basis by the construction industry. Advantageously, the present invention considerably improves the end product quality such as concrete work and plastering. Another example is adding value and enhancing the productivity of industries such as iron & steel making plants where efficient removal of silica and alumina present in the ore as the deleterious material can result into lowering of cost of production of the metal significantly. Furthermore, processing of construction and demolition waste will lead to generation of quality recycled sand and recycled aggregates for the construction industry. This will mitigate to a great extent the issue of sand and aggregate shortage as well address the huge problem of environmental pollution caused by unplanned dumping of the wastes in landfills, rivers etc.

[026] The advantage of the present invention is that it provides a method for rejection of deleterious material from the feed and production of graded high-quality products at high efficiencies while re-circulating most of the water within the circuit for reuse, thereby reducing the requirement of fresh water drastically.

[027] The system, and the method of the present invention can be extensively used for processing of, but not limited to, construction, demolition and excavation waste, railway ballast, road sweeping, tunnel boring waste, quarry material, and minerals like iron ore, bauxite, manganese, coal, lignite, chromite and limestone.

[028] Some of the salient advantages of the invention are stated below:

• It requires phenomenally less space for installation compared to traditional systems of the same capacity that need very large area. The compact nature of the system will allow it to be conveniently used in urban areas, factories, waste management sites, mobile applications, hilly areas etc. It can be also easily attached with upstream processes.

• It yields a phenomenal reduction in power consumption again due to compact layout of the system requiring lesser movement of material.

• It can be completely built and assembled in the factory thus significantly lowering

installation time and eliminating the risks associated with site fabrication. Besides longer installation time, the high cost and risk of site fabrication are commonly associated with traditional system. These drawbacks are overcome by the present invention.

• It offers a modular design that can be dismantled easily and shipped worldwide in

containers. Most traditional equipment cannot be shipped efficiently. Also modularity helps when the user desires to relocate the plant to a different project site. Again this is not possible with traditional system.

• It requires considerably less time to manufacture as the conventional system are designed as per the requirements of the site and are hence non-standard, which results in longer lead time for manufacture.

• The present invention has low level civil foundation requirements due to its integrated steel chassis that allows better weight distribution of the components installed on the system. Traditional systems are installed on large civil pedestals that involve high cost and construction time. • The system is complete with all electrical cabling and programmable logic control panel requiring no site electrical work. This is a huge advantage when compared to traditional systems which must be electrically connected at the project site. [029] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.