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Image by Bernard Hermant


(Appropriate for Madurai)

Note: This Project Profile relates to our project commissioned at Madurai (Tamil Nadu) in 2011.  For evaluating project viability at any other location in South India, this profile may be used as a general guideline, and it may be modified by incorporating the actual input costs and prevalent manufacturing practice at that location.

1.0  Details of manufacturing process to be adopted:


a. Clay winning (or excavation) is done manually using spades, shovels and baskets. Care is taken to expose the entire vertical clay profile reaching up to the maximum depth to which clay occurs. Clay is dug vertically from top to bottom of the exposed face so that material in all intermediate strata gets mixed in the process. The excavated clay is transported in trucks or tractor trolleys to the plant. Plastic clay and lean clay are stocked one above the other in thin layers in such a way that thickness of each layer is proportionate to its desired proportion in the raw-mix. This ‘stockpile’ is then kept soaked in water for at least a week in advance. This improves homogeneity of the material by allowing sufficient time for the water to penetrate evenly into the raw-mix.


b. Shaping:


The soaked raw-mix is then dug vertically from top to bottom by using a JCB/Backhoe Loader and is fed to Box Feeder. The raw-mix then falls on to the belt conveyor fitted below the Box Feeder and is carried to Roller Crusher-Cum-Stone Separator.  Its output is carried to hopper of ‘Ishtika’ Mixerpress (IMP) by another belt conveyor. The machine consists of a mixer, a press block, a mould chain, a mould washing station and a mould sander.  Final adjustment of water content in the raw-mix can be done by adding 5 to 7 % water in the mixer.  The Ishtika Mixerpress requires about 88.95 KW (120 HP) connected load.  8 bricks are shaped every stroke on a metal pallet. The mixerpress operates at a speed of up to 15 strokes per minute. Thus, capacity of the Ishtika Mixerpress is 7,200 bricks (of 230 x 110 x 70 mm fired size) per hour.


c.  Drying:


Loaded pallets coming out of the Ishtika Mixerpress on its Chain Conveyor are then transferred manually to hand carts which are carried inside Drying Shed.  Pallets are unloaded manually from the hand carts and placed on bricks set on edge and kept in regular rows on ground. This ensures at least a few inches air gap below the pallets for air circulation.   

After 2 or 3 days, bricks are manually turned on their edges for faster drying.  Thereafter, bricks dry inside the shed on edge for another 1 or 2 days.  They are then arranged on shed floor in 10-layer ‘walls’ or arranged in the open on pallets till such time they become ‘reasonably’ dry (i.e. till their moisture content is reduced from about 27 per cent to below 7 per cent).  Dry bricks / pallets are then carried manually/by forklift inside the setting area of Fixed Chimney Bull’s Trench Kiln (FCBTK) through its wickets (or doors). 

d. Firing:


Dry bricks are manually set in a pre-determined pattern with trace holes, fuel shafts, flues, etc. kept in accordance with set practice.  FCBTK is a continuous kiln working on natural draught created by a chimney.  Crushed 'B' or 'C' grade steam coal or imported coal is used as main fuel for firing bricks.  Wood/saw dust may be used as additional fuel.  Fuel is fed through feed holes provided in the kiln-top.  Firing temperature ranges between 8500 C and 9500 C.  Fully fired and cooled bricks are manually unloaded and carried to the Open Brick Yard or are directly loaded into trucks and dispatched. 

  1. Unlike ‘hand-moulding’ operation, soft mud machine moulding provides much better occupational health and safety conditions to workers.  It also reduces labour intensity of the traditional shaping and drying operations by a factor of 8 and eliminates dependence on skilled ‘moulders’ by delinking quality of green bricks from human skill. 

  2. Machine-moulded bricks are uniform in size and shape and have perpendicular faces and sharp edges.  Therefore, use of these bricks in walling saves up to 15 % mortar and plastering expenses.

  3. Thorough mixing of raw-mix components in the mixer results into uniform firing, better crushing strength and lower breakages during handling. 

  4. Unlike extruder, the mixerpress exerts only the bare minimum pressure required for proper shaping of green bricks thereby ensuring a reasonably ‘open’ brick body which in some cases, offers the possibility of drying freshly shaped bricks directly under sun without fear of cracking.  Also, soft mud machine molded bricks have frogs which extruded bricks cannot have.  This offers a huge advantage over extruded bricks as traditional markets always prefer frogs for better ‘keying’.

  5. Soft mud machine moulding process can incorporate much higher percentage of 'non-plastic' wastes, fuels and / or soils as compared to extrusion.   The wastes could be from agriculture, urban waste treatment plants and industries like coal processing, textile, tanning, sugar, liquor, petroleum, paper, wood-processing, agro / food processing, etc.

    This solves the disposal problem of the waste generating agencies; minimizes the requirement of primarily extracted clays and fossil fuels; increases the porosity of fired bricks making them lighter and thermally / acoustically more insulating and  improves the enterprise profitability by saving costly external fuel, which forms 25- 40 % of cost of production of bricks.  Lightweight bricks also require less transportation energy and can be handled easily by laborers thereby improving their comfort level and speed of work.   

    We are now developing a technique on pilot-scale which - like extrusion - can introduce circular holes in the soft mud moulded bricks.  When introduced commercially in the near future, this feature will also make the soft mud moulded bricks lightweight, less energy and resource intensive and less costly. 

  6. Ishtika Mixerpress is an ideal machine for manufacturing terrace tiles and pavers with chamfered edges. Chamfering is made possible in the softmud molding process by making special provision in each mould cavity. Chamfering operation is very difficult in the extrusion process.  Terracetiles and pavers add much better value than ordinary fired clay bricks.

2.0 Advantages of the soft mud moulding process:

 It is assumed that the promoter owns about 5 acres of land required for the project on which he already has an operating Fixed Chimney Bull’s Trench Kiln (FCBTK) of about 30,000 bricks / day capacity (including appropriate facilities for water pumping / storage and coal crushing).  Therefore, these costs have not been included in the Project Cost.

3.0 Project Feasibility:

3.1 Production:

a) Green bricks moulded / hour = 8 bricks / stroke x 15 strokes / minute x 60 minutes / hour = 7,200 nos. 
Assuming about 60 % working efficiency of the plant, green bricks moulded  / shift / day = 7,200 x 8 x 0.60 = 35,000 nos. 

​b) Assuming 3 % production loss during drying and 3 % during firing; 280  firing days / season (i.e. 40 weeks x 7 days / year) and 240 moulding days / season (i.e. 40 weeks x 6 days / year),

Green bricks moulded / season = 35,000 x 240 = 84,00,000;
Production of saleable fired bricks / season = 84,00,000 x 0.97 x 0.97 
 ≈ 79,00,000 nos.      

Production of saleable fired bricks / day = 79,00,000 / 280 
 ≈ 28,000 nos. 

3.2  Estimated Additional Investment:

3.3 Cost of production @ 100% capacity utilization (i.e. @                    79,00,000 bricks / year or 28,000 bricks / day):

 (Cost Rs. /1000 Bricks)

* 7 KW Box Feeder + 4.40 KW Conveyors (2 nos.) + 18.50 KW Roller Crusher + 88.95 KW Ishtika Mixerpress + 7.50 KW
Coal Crusher + 3.75 KW Raw Water Pump

Minimum selling price expected (ex-kiln) = Rs. 10,000/- per 1,000 bricks

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