DESC:FIELD OF THE INVENTION

The present invention relates to Process for utilizing brine sludge of membrane cell plant for construction of compressed bricks. More particularly the present invention relates to construction of compressed bricks using brine sludge waste.

BACKGROUND OF THE INVENTION

The pure brine (salt solution) is used for electrolysis to produce caustic soda, Chlorine (Cl2) gas and Hydrogen (H2) gas. The brine (salt solution) have the impurities of Calcium (Ca), Magnesium (Mg), Sulfate (SO4), Sand & Silica etc. which are present in salt. The impurities of brine are precipitated in the form of insoluble compound by reaction of chemicals. Calcium (Ca) is precipitated as Calcium Carbonate (CaCO3) by reaction of soda Ash (Na2CO3), Magnesium (Mg) as Magnesium Hydroxide (Mg(OH)2) by reaction of caustic soda (NaOH), and Sulfate (SO4) as Barium Sulfate (BaSO4) by reaction of Barium Carbonate (BaCO3). All impurities settled down in a big size brine clarifier and the sludge slurry is drained from the bottom of the clarifier to a sludge slurry tank and pumped to filter press through a sludge slurry pump. The filtrate brine is reused and the cake of all these impurities (CaCO3+Mg(OH)2+BaSO4+sand &Silica etc) are the solid waste (Brine sludge) for the industry and chlor- alkali plant are bearing a huge cost for the Management, Handling and disposal of this brine sludge waste. The storage and disposal of this solid waste occupies land and creates soil pollution also. There was no any technology for the utilization of brine sludge.

Beside brine sludge there is another pollutant i.e. fly ash generated by burning of coal at power plants. It is the particulate matter i.e. fine particles removed from the smoke generated by coal based thermal power plants, before the smoke is emitted into the atmosphere. US. Europe, China and India burn most of the coal in the world, with China burning almost 50% of the coal as burned by rest of the world. India obtains nearly 75% of its power needs from coal based thermal power plants. In India alone 90mt of fly ash is generated per annum and is largely responsible of environment pollution along with CO2 emitted from such coal based thermal power plants. India ranks 4th in the world, in product of fly ash as by-product waste after USSR, USA and China. Approx. one third of the fly ash generated is used for purposes such as mixing with concrete as an additive, and using as part of the roadbed (underlay) of highways. The remaining two-thirds are unused, and they must be disposed of as a solid waste in landfills or slurry ponds, which is not only costly but also poses potential water pollution problems. Manas Ranjan Senapati’s article “Fly ash from thermal power plants – waste management and overview” indicates that Particulate matter (PM) considered as a source of air pollution constitutes fly ash. The fine particles of fly ash reach the pulmonary region of the lungs and remain there for long periods of time; they behave like cumulative poisons. The submicron particles enter deeper into the lungs and are deposited on the alveolar walls where the metals could be transferred to the blood plasma across the cell membrane. The residual particles being silica (40–73%) cause silicosis. All the heavy metals (Ni, Cd, Sb, As, Cr, Pb, etc.) generally found in fly ash are toxic in nature and cause no. of diseases. The Central Fuel Research Institute, Dhanbad has developed a technology for the utilization of fly ash for the manufacture of building bricks. Fly ash bricks have a number of advantages over the conventional burnt clay bricks. Unglazed tiles for use on footpaths can also be made from it. Awareness among the public is required and the Government has to provide special incentives for this purpose. Fly ash is suitable for use as pozzolana. In the presence of moisture, it reacts chemically with calcium hydroxideat room temperature to form compounds possessing cementitious properties. Fly ash has a high amount of silica and alumina in reactive form. These reactive elements complement the hydration chemistry of cement. On hydration, cement produces C–S–H gel and free lime, i.e. Ca(OH)2. The C–S–H gel binds the aggregates together and strengthens the concrete. Water, sulphates and CO2 present in the environment attack the free lime causing deterioration of the concrete. A cement technologists observed that the reactive elements present in fly ash convert the problematic free lime into durable concrete. The difference between fly ash and portland cement becomes apparent under a microscope. Fly ash particles are almost totally spherical in shape, allowing them to flow and blend freely in mixtures. This property makes fly ash a desirable admixture for concrete. Distemper manufactured with fly ash as a replacement for white cement has been used in several buildings in Neyveli, Tamil Nadu, in the interior surfaces and the performance is satisfactory. The cost of production will only be 50% that of commercial distemper. The National Metallurgical Laboratory, Jamshedpur has developed a process to produce ceramics from fly ash having superior resistance to abrasion. Fly ash provides the uptake of vital nutrients/minerals (Ca, Mg, Fe, Zn, Mo, S and Se) by crops and vegetation, and can be considered as a potential growth improver. It serves as a good fertilizer. The use of fly ash in large quantities making the road base and surfacing can result in low value–high volume utilization.

Nowadays, instead of clay brick, fly ash bricks are used. The conventional fly ash brick last for more than 100 freeze-thaw cycles and has high concentration of calcium oxide and is described as "self-cementing". Its manufacturing saves energy, reduces mercury pollution, and costs 20% less than traditional clay brick manufacturing. Its main ingredients include 55% fly ash, 30% sand and 15% hydrated lime with 14% gypsum. Gypsum acts as a long term strength gainer. The finished product is a lighter Block - while providing the similar strengths. By using these blocks in structural buildings, the builder saves around 30 to 35 % of structural steel, and concrete, as these blocks reduce the dead load on the building significantly. It has high fire insulation, high strength, have low seepage and require less water. However, there is disadvantage of fly ash brick as it has low Mechanical strength and limitation of size (large size has more breakages).

Alike fly ash, the brine sludge is a solid waste and burden to the industry for its management handling and disposal. It is a soil pollutant also. Brine sludge can be used in cement plant but the huge transportation cost is involved to transport the waste to cement plant. Further the cement plants require processing charges for the utilization of same, which is not economical to the industry. The disposal, management and proper utilization of waste products has become a concern for the scientists and environmentalists. Proper management of brine sludge and fly ash is necessary to safeguard our environment. Because of high cost involved in road transportation for dumping of brine sludge and fly ash, it is required to explore all their possible applications. It is highly desirable to find more beneficial use of brine sludge as well as fly ash, so that in the future less brine sludge and fly ash needs to be disposed of as a solid waste. Therefore, there is need for gainful utilization of brine sludge as well as fly ash such as use in compressed brick manufacturing, cement and ceramics. Furthermore, therefore is also need for use of such non-vitrified (non-fired) products that reduces the dependency upon fossil fuel and in turn reduces air pollution and carbon dioxide that causes greenhouse effect and global warming.

Therefore. there is also need for compressed bricks having higher strength comparative to clay bricks or fly Ash bricks alone. There is also need to improve strength to conventional fly ash bricks. There is also need for non-vitrified (non-fired) masonry products.
These and other features, aspects and advantages of the present invention will become better understood with reference to the appending description and drawing.

SUMMARY OF INVENTION

The present invention provides for novel utilization of brine sludge for construction of compressed masonry units such as bricks, tiles, blocks etc.

One of the object of the present invention is to re-use solid waste such as brine sludge and stop them from polluting the soil.

One another object to present invention is to gainfully use the brine sludge having Calcium Carbonate that has binding property and Barium Sulfate that has the properties like gypsum to make compressed bricks having higher strength comparative to clay or fly Ash masonry units.

One another object of the present invention is to re-use the fly ash along with brine sludge to make compressed masonry units such as bricks, tiles, blocks etc. having higher strength comparative to clay or fly Ash masonry units.

DESCRIPTION OF THE DRAWING

Fig. 1 is flow chart of process for utilizing brine sludge of membrane cell plant for construction of compressed masonry units such as bricks, tiles, blocks etc.

DESCRIPTION OF INVENTION
In response to aforementioned, the present invention herein provides for a process for utilizing brine sludge of membrane cell plant for construction of compressed masonry units such as bricks, tiles, blocks etc. The present invention comprises the following steps (A) precipitating the impurities in brine solution in form of insoluble compounds by reaction of chemicals; (B) removing solid impurities being deposited by sedimentation from the brine clarifier; (C) draining the sludge slurry from the bottom of the clarifier to a sludge slurry tank and pumping to filter press through a sludge slurry pump; (D) mixing brine sludge with fly ash in Pan mixture; (E) adding 5% of lime (by weight) to the mixture; (F) adding 10% of stone dust to the mixture; (G) adding 5% of cement to the mixture (H) placing or injecting the mixture into one or more shaping devices:; (I) vibrating the mold; (J) applying pressure to the mixture to densify it and form desired shapes and individual units through processes such as compaction or extrusion i.e. compacting the mixture in the mold using an appropriate pressure; and dislodging the compacted product (masonry unit) from the mold; (K) conveying or transporting the completed units to a curing room or curing chamber containing moist air, and allowing the units to cure and gain strength. Upon completion of the foregoing eleven steps, the cured masonry products will be ready for storage and transportation to the market place for use. The eleven steps are described in detail below:

(A) Precipitating the impurities in brine solution in form of insoluble compounds by reaction of chemicals: The pure brine (salt solution) is used for electrolysis to produce caustic soda, Chlorine (Cl2) gas and Hydrogen (H2) gas. The brine (salt solution) have the impurities of Calcium (Ca), Magnesium (Mg), Sulfate (SO4), Sand & Silica etc. which are present in salt. The impurities of brine are precipitated in the form of insoluble compound by reaction of chemicals. Calcium (Ca) is precipitated as Calcium Carbonate (CaCO3) by reaction of soda Ash (Na2CO3), Magnesium (Mg) as Magnesium Hydroxide (Mg(OH)2) by reaction of caustic soda (NaOH), and Sulfate (SO4) as Barium Sulfate (BaSO4) by reaction of Barium Carbonate (BaCO3).

(B) Removing solid impurities being deposited by sedimentation from the brine clarifier: A big size brine clarifier is used as settling tank built with mechanical means for continuous removal of solid impurities being deposited by sedimentation.

(C) Draining the sludge slurry from the bottom of the clarifier to a sludge slurry tank and pumping to filter press through a sludge slurry pump: All impurities settled down in brine clarifier and the sludge slurry is drained from the bottom of the clarifier to a sludge slurry tank and pumped to filter press through a sludge slurry pump. The filtrate brine is reused and the cake of all these impurities (CaCO3+Mg(OH)2+BaSO4+sand &Silica etc) are the solid waste (Brine sludge).

As the brine sludge is a waste product and soil pollutant, therefore it is necessary to use the brine sludge so that it does not gets dump to the soil and pollutes it. The brine sludge waste was analyzed for its components and property, it was noticed that brine sludge has Calcium Carbonate which has binding property and Barium Sulfate which has the properties like gypsum. It was further noticed that when Brine sludge is processed and mixed in a particular ratio with fly ash, sand etc. the compressed bricks manufactured have slightly higher strength comparative to fly Ash bricks.

(D) Mixing brine sludge with fly ash in Pan mixture: The property of the component is utilized in different ratio with other materials to find out optimal ratio for manufacturing of the compressed masonry units such as bricks, tiles, blocks etc. of required strength. The following experiments were carried out to find out the optimum amount or ratio of brine sludge and fly ash.

First Experiment:
In the first experiment, 50% of brine sludge was mixed with 35% of fly ash, 10% stone dust and 5% lime but the bricks formed at this ratio were not hard after giving more than 30 days curing time.

Second Experiment:
In the second experiment, the ratio of brine sludge was decreased and ratio of fly ash was increased. The ratio of sand and lime was kept same. 45% of brine sludge was mixed with 40% of fly ash, 10% stone dust and 5% lime but still after giving more than 30 days curing time the bricks formed at this ratio were not hard and easily breakable by hand.

Third Experiment:
In the Third experiment, the ratio of brine sludge was further decreased and ratio of fly ash was increased. The ratio of sand and lime was kept same. 40% of brine sludge was mixed with 45% of fly ash, 10% stone dust and 5% lime but still after giving more than 30 days curing time the bricks formed at this ratio were not hard and breakable by hand.

Fourth Experiment:
In the fourth experiment, the ratio of brine sludge was further decreased and ratio of fly ash was increased. The ratio of sand and lime was kept same. 30% of brine sludge was mixed with 55% of fly ash, 10% stone dust and 5% lime but still after giving more than 30 days curing time the bricks formed at this ratio were not hard and breakable by hand.

Fifth Experiment:
In the fifth experiment, the ratio of brine sludge was further decreased and ratio of fly ash was increased. The ratio of sand and lime was kept same. 20 % of brine sludge was mixed with 65% of fly ash, 10% stone dust and 5% lime. Bricks formed at this ratio were comparatively harder and were not breakable by hand (strength 55 kilo Newton) and took lesser curing time (25 days).

Sixth Experiment:
In the sixth experiment, the ratio of brine sludge was kept 20% and ratio of fly ash was kept 60%. The ratio of stone dust and lime was kept same. This time 5% cement was added to this mixture. The Bricks formed at this ratio were also dry and hard and took same curing time (25 days) and had better strength (70+ kilo Newton) comparative to fly ash bricks.

Seventh Experiment:
In the seventh experiment, the ratio of brine sludge was increased to 25% with fly ash ratio reduced to 55%. The ratio of stone dust, lime and cement was kept same. The Bricks formed at this ratio were also dry and hard and took same curing time (25 days) and have better strength (80+ kilo Newton) comparative to fly ash bricks.

Eighth Experiment:
In the eight experiment, the ratio of brine sludge was increased to 30% with fly ash ratio reduced to 50%. The ratio of stone dust, lime and cement was kept same. The Bricks formed at this ratio were also dry and hard and took same curing time (25 days) and have better strength (110+ kilo Newton) comparative to fly ash bricks.

Ninth Experiment:
In the ninth experiment, the ratio of brine sludge increase to 35% and fly ash ratio is reduced 45%. The ratio of stone dust, lime and cement was kept same. The Bricks formed at this ratio were also dry and hard and took same curing time (25 days) and have better strength (150+ kilo Newton) comparative to fly ash bricks.

In preferred embodiment of the invention, 20% of brine sludge (by weight) is mixed with 60% of fly ash (by weight) in Pan mixture.

In yet another preferred embodiment of the invention, 25% of brine sludge (by weight) is mixed with 55% of fly ash (by weight) in a Pan mixture.

In yet another preferred embodiment of the invention, 30% brine sludge (by weight) is mixed with 50% fly ash (by weight) in a Pan mixture.

In yet another preferred embodiment of the invention, 35% brine sludge (by weight) is mixed with 45% fly ash (by weight) in a Pan mixture.

(E) Adding 5% of lime (by weight) to the mixture; 5% of lime (by weight) is added to the mixture,

(F) Adding 10% of stone dust to the mixture; 10% of stone dust (by weight) is added to mixture.
In a preferred embodiment of the invention, sand is used in place of stone dust.
In another preferred embodiment of the invention, a mixture of sand and stone dust is used.

(G) Adding 5% of cement (by weight) to the mixture: 5% of cement (by weight) is added to the mixture,

(H) Placing or injecting the mixture into one or more shaping devices: The mixture is placed or injected into one or more shaping devices such as mold or hopper to produce the brick, block or other product shapes. This could be automated in ways similar to conventional factories that manufacture concrete bricks (pavers) and blocks, such as direct pouring (by gravity), feeding by a screw conveyor, or injection molding. If required, it is also possible to manually do it.
(I) Vibrating the mold: As only small amount of water is used in the mixture, the fly ash remains relatively dry and can form small clumps that are not readily flowable by gravitational force alone. If mixture is not uniformly poured in to the mold, the masonry units such as bricks, tiles, blocks etc. produced may have non-uniform density distribution, which affects the quality of the brick, especially its durability (freeze/thaw resistance). Mold vibration causes the mixture to settle in the mold, producing a more uniform and denser mixture with a more leveled surface. This helps to improve the quality control of the masonry units such as bricks, tiles, blocks etc. produced.
Where mixture is uniformly poured in to the mold this step may not be required. Further where required quality of masonry units such as bricks, tiles, blocks etc. is not high, this step may be avoided. Therefore, this step is not mandatory but desirable.
(J) Applying Pressure To The Mixture To Densify It And Form Desired Shapes And Individual Units Through Processes Such As Compaction Or Extrusion
(i) Compacting the mixture in the mold using an appropriate pressure: A piston or plunger is used to compact the mixture in the mold using an appropriate pressure. Ideally the inner surface of the mold should be smooth to minimize contact friction between the mold and the piston and the piston should be made of a non-corroding material, such as stainless steel or aluminum. The head of the piston i.e. the part in contact with the mold should be smooth. The shape and size of the piston and the mold depend on the shape and size of the brick required. The piston is connected to a device or machine such as a hydraulic or a pneumatic press that can produce thrust i.e. large linear force and pressure needed to compact the mixture in the mold.
(ii) Extrusion/ Dislodging the compacted product from the mold: After compacting the mixture in the mold, the compacted product can be dislodged from the mold either by opening up the mold (where split mold design is used), or by pushing out the masonry units such as bricks, tiles, blocks etc. from the mold by using either a piston. The piston used for dislodging could be the same piston that was used to compact the brick or a different piston could be used.
(K) Conveying or transporting the completed units to a curing room or curing chamber containing moist air or steam, and allowing the units to cure and gain strength: Next step is to convey or transport the completed masonry units such as bricks, tiles, blocks etc. by means such as belt conveyors etc., to a curing room or curing chamber for curing. Curing is done by storing the masonry units such as bricks, tiles, blocks etc. in a moist room or chamber - called "curing room" or "curing chamber". The moisture can also be supplied by spraying water to generate a mist in the room or chamber, or by supplying steam. The water in the moist air reacts with the Calcium Oxide (CaO) and other ingredients in the mixture. It causing cementitious and pozzolanic reactions, which in turn cause the masonry units such as bricks, tiles, blocks etc. to harden and gain strength over time.
The masonry units typically gain strength rapidly during the first week of curing, followed by continued but slower growth of strength thereafter. Typically, the strength growth becomes insignificant after 60 days of such curing. Curing can be sped up either by using warm steam to cure, or by spraying water on initially cured masonry units (for at least 24-48 hours). Dipping in water before initial curing can damage or melt (dissolve) the masonry units such as bricks, tiles, blocks etc. Further it is not necessary that masonry units such as bricks, tiles, blocks etc. should be complete cured in the curing room. Continued air cure during storage and transportation may cause the masonry units such as bricks, tiles, blocks etc. to gain further strength. Once cured, the masonry units such as bricks, tiles, blocks etc. can be stored at practically any moisture and temperature - preferably in a moist place with air temperature above freezing, which will cause the masonry units such as bricks, tiles, blocks etc. to gain strength continuously as time progresses.
In one or other embodiment of the invention, the method optionally includes the step of determining the amount of water required for making said masonry units. Wherein such water is added to the mixture before being injected or placed in to the shaping devices.
In yet another embodiment of the invention, the method optionally includes the step of selecting and mixing an air-entrainment agent with the mixture.
In yet another embodiment of the invention, the method optionally includes the step of adding colored pigments for color alternation.
It is to be noted that the method steps described herein above can also be used for making similarly manufactured masonry units such as tiles, blocks etc., simply by using molds and pistons of different shapes and sizes. Therefore, the term "brick" or "unit" used herein also includes such other products made using the aforementioned method steps.
It should also be mentioned that although a step by step method (process) is described here, some of the steps may not be needed in special situations. Further two or more of the steps may be combined in a single step.
As on the main aim of the present intention was to use more and more of brine sludge, depending upon the time requirement and inventory, higher ratio of brine sludge i.e. between 20 to 35% can be mixed with 60 to 45% of fly ash along with lime (5%), cement (5%) and stone dust (10%) to make compressed masonry units such as bricks, tiles, blocks etc. Where it is possible to give more curing time, the brine sludge ratio can be further increased.
The description herein is one of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The present invention has been described with respect to particularly preferred embodiments. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention.
It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.
,CLAIMS:1. A method to manufacture durable non-vitrified masonry units such as brick made of brine sludge and fly ash, comprising the steps of: (a) precipitating the impurities in brine solution in form of insoluble compounds by reaction of chemicals; (b) removing solid impurities being deposited by sedimentation from the brine clarifier; (c) draining the sludge slurry from the bottom of the clarifier to a sludge slurry tank and pumping to filter press through a sludge slurry pump; (d) mixing brine sludge with fly ash in Pan mixture; (e) adding 5% of lime (by weight) to the mixture; (f) adding 10% of stone dust to the mixture; (g) adding 5% of cement (h) placing or injecting the mixture into one or more shaping devices; (i) applying pressure to the fly ash mixture in order for it to densify and form desired shapes and individual units through processes such as compaction or extrusion (k) conveying or transporting the completed units to a curing room or curing chamber containing moist air or steam, and allowing the units to cure and gain strength.
2. The method as claims in claim 1, wherein the shaping device/s containing the mixture in step (h) are subjected to step of vibration or shaking in order to distribute the mixture uniformly in the shaping device/s.
3. The method as claimed in claim 1, wherein the mixture is having 20% to 35% of brine sludge by weight.
4. The method as claimed in claim 3, wherein the mixture is having 35% of brine sludge by weight.
5. The method as claimed in claim 1, wherein the mixture is having 60% to 45% of fly ash by weight.
6. The method as claimed in claim 5, wherein the mixture is having 45% of fly ash by weight.
7. The method as claimed in claim 1, wherein sand is used instead of stone dust.
8. The method as claimed in claim 1, wherein a mixture of stone dust and sand is used instead of stone dust alone.
9. The method as claimed in claim 1, comprising the steps of determining the amount of water required for making said masonry units.
10. The method as claimed in claim 1, comprising the steps of selecting and mixing an air-entrainment agent with the mixture.
11. The method as claimed in claim 1, comprising the steps of adding colored pigments for color alternation.
12. A durable non-vitrified masonry unit as formed by the method of any one of claims 1 to 11.
13. The durable non-vitrified masonry unit as claimed in claim 12 wherein such durable non-vitrified masonry unit is a brick.
14. The durable non-vitrified masonry unit as claimed in claim 12 wherein such durable non-vitrified masonry unit is a tile.
15. The durable non-vitrified masonry unit as claimed in claim 12 wherein such durable non-vitrified masonry unit is a block.