PROJECT PROFILE OF SOFT MUD BRICK PLANT
BASED ON DE BOER DAMLE “ISHTIKA MIXERPRESS”
Note: This Project Profile relates to our project installed at Madurai (Tamil Nadu). For evaluating project viability at any other location, this profile should be used as a general guideline only 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:
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. The raw-mix is then kept soaked in water for at least a week in advance. This improves homogeneity of the mix by allowing sufficient time for the water to penetrate evenly into the material.
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 mould chain, a press block, a mould washing station and a mould sanding conveyor. 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 80.50 KW (108 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 size 230 x 110 x 70 mm) per hour.
Drying: Loaded pallets coming out of the Ishtika Mixerpress on its Wet 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 kept on ground in regular rows. This ensures at least a few inches of 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 in 10-layer ‘walls’ 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 are then carried manually inside the setting area of Bull’s Trench Kiln (BTK) through its wickets (or doors).
Firing: Dry bricks are manually set in a pre-determined pattern with trace holes, fuel shafts, flues, etc. kept in accordance with set practice. BTK 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. Saw dust may be used as additional fuel. Fuel is fed through feed holes provided in the kiln-top. Firing temperature ranges between 10000 C and 10500 C. Fully fired and cooled bricks are manually unloaded and carried to the Open Brick Yard or are directly loaded into trucks and dispatched.
2.0 Basis for material balance and machinery sizing:
3.0 Advantages of the process:
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.
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.
Thorough mixing of raw-mix components in the mixer results into uniform firing, better crushing strength and lower breakages during handling.
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’.
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 lightweight 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. De Boer (Wijchen, The Netherlands) has recently developed 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.
Ishtika Mixerpress is ideal for manufacturing paving blocks with chamfered edges – which are very difficult to be made by extrusion and which give much better value addition than ordinary fired clay bricks.
4.0 Project Feasibility:
It is assumed that the promoter owns about 5 acres of land required for the project on which he already has an operating Bull’s Trench Kiln (BTK) 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.
Green bricks moulded / hour = 8 bricks / stroke x 20 strokes / minute x 60 minutes / hour x 75 % working efficiency = 7,200 nos. Assuming 5-hour (or single shift) working of the Ishtika Mixerpress / day, green bricks moulded / day = 7,200 x 5 = 36,000 nos.
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 = 36,000 x 240 = 86,40,000; Production of saleable fired bricks / season = 86,40,000 x 0.97 x 0.97 = 81,30,000 nos. Production of saleable fired bricks / day = 81,30,000 / 280 ≈ 29,000 nos.
4.2 Estimated Additional Investment:
4.3 Cost of production @ 100% capacity utilization (i.e. @ 81,30,000 bricks / year or 29,000 bricks / day):
(Cost Rs. /1000 Bricks)
* 13 HP Box Feeder + 6 HP Conveyors (2 nos.) + 30 HP Roller Crusher + 108 HP Ishtika Mixerpress + 10 HP Coal Crusher + 5 HP Raw Water Pump