When one travels from New Delhi to Jhansi by the Shatabdi express, one trains his eyes to the features on the left after passing the Sonagiri station eager to have the views of the forts and palaces which from part of Datia's glorious past.  Suddenly you see a new red brick structure with a lofty building with beautiful arches, rising shafts and an impressive ramp.  The new fortress is the VSBK – which hopefully can be the precursor of many such units which may dot the landscape in the future.

What is VSBK?

The Vertical Shaft Brick Kiln is a continuous kiln for firing construction bricks whose technology was developed in China in the last three decades and has had an exponential  growth in that country.

The first prototype of the VSBK was built in China in 1958.  With some improvements, VSBK’s were used randomly in some provinces in the 70’s and early 80’s.  To give an impetus to the technology, a study project was started in 1985 at the Energy Research Institute of the Henan Academy of Sciences at Zhengzhou to study the operation and  efficiency  of  the  VSBK; Recommendations on the optimum height and firing shaft dimensions and also addition of chimney evolved out of the study. Based on these, an improved design of VSBK was finalized in 1988. When implemented, there was better brick quality and savings in fuel cost.

From then onwards, there has been wide dissemination of the technology and it is now reported that there are some 50000 VSBK's operating in China - 3000 in Funan county alone.   One can find as many as40VSBK's even in a small village.

Dissemination' of the technology outside China started in 1990. VSBK's have been erected in Nepal, Pakistan and Bangladesh but remain largely in the technology demonstration phase.

How Does VSBK Work?

The VSBK essentially consists of one or more shafts located inside a   rectangular brick structure. The shaft is square or rectangular in section - usually 1 meter in width and 1m, 1.5 m, l.gm and 2 m in length Its inside surface is a brick wall sometimes lined with one layer of firebricks in the hot firing zone. The gap between the shaft wall and the outer kiln wall is filled with insulating materials such as clay or rice husk mixed with clay.  The shaft is open at top and bottom.  During continuous operation of the kiln after stabilization, one batch of dried bricks (generally 4 layers) are loaded at the top with a predetermined pattern of

arrangement and gap between the bricks. A weighed quantity of powdered coal   is spread on each layer uniformly to fill the gaps.  The kiln has unloading tunnels (usually constructed with arches on  top) running across the width of the kiln in line with the shafts. These have facilities for inserting a number of square support bars which can be removed or inserted, to rest on a pair of beams across the arches. The bricks unloading is done using an unloading trolley on wheels, running on rails along the length of the unloading tunnel.  There are various means of lifting the unloading trolley and making its members rest against the bottom of the bricks and lift the stack of bricks. These mechanisms generally are:

i)	Double screw arrangement with two screws - one on each supporting beam operating which the unloading trolley can be raised or lowered.
ii)	Chain pulley blocks where the two ends of the trolley as lifted by a pair of chain pulley blocks hung from beams across the arches in the unloading tunnel.
iii)	Single screw mechanism where a central lifting screw and nut arrangement is operated by handling a large diameter hand wheel to lift the unloading trolley.

The last one is preferred largely due to its ease of operation and less breakage of bricks. The unloading trolleys are lifted by the mechanism so that the beams on the trolley rest against the bottom surface of the bricks, and on further lifting the whole stack of bricks moves up and when the load is taken off the square support bars, these can be taken out manually. The whole stack of bricks is then lowered till the spaces in the next batch are in level with the supporting beam. The square support bars are then re-inserted in position. On further lowering, the load of the stack minus the batch being unloaded is taken by the supporting bars.  On further lowering, the batch being unloaded separates from the stack and comes down with the trolley to rest on a pair of rails running across the shaft along the unloading tunnel. The trolley is then pulled out along the rails. The bricks on the trolley are subsequently sorted out and kept in the respective classified areas.

The green bricks after drying are lifted up to the loading platform by carrying them Manually or by donkeys moving up a suitably designed ramp. Other methods of lifting such as manual or electric operated hoists have also been used.  The skill in operation is to keep the firing zone in the middle of the shaft.  The draught of air moving up from the bottom cools the fired bricks and it self gets heated.  Maximum temperatures of the order of 960 to 990C are attained in the central firing zone.  The hot gases moving upwards dry and heat up the green bricks which move down the shaft batch by batch.  The energy efficiency of VSBK is essential due to this intensive use of heat values generated.

The firing temperature is controlled by the amount of coal added internally spread in the space between green bricks loaded in each batch.  VSBK in India A project was started by Development Alternatives with support from the Swiss Development Go-operation in 1994 to validate the energy efficiency of the VSBK and evaluate its environmental performance.

A quick survey of various possible sites was conducted by the Development Alternatives Jhansi team. It was decided to locate the first kiln at Datia in Madhya Pradesh, between Jhansi and Gwalior off the 69th km on the highway from Gwalior.  The construction of the kiln started on March i·lth, 1996 under the guidance of the Chinese team. As per schedule the firing of the first shaft was started on April 30th, 1996 and the second shaft was started on May 10, 1996.;The operation continued till  June 25,  1996  when  the  kiln  was shutdown for the rainy season.  The excellent performance of the project is attributed to thorough planning and team work during implementation.  With the operation of the kiln for less than two months, the following indications of the results have become evident:

1)	The quality of the bricks produced is better than that produced in nearby clamps in terms of colour and ring.
2)	The compressive strength of bricks is between 65 kg/cm2 and 110 kg/cm2.
3)	The technology is viable with reasonable margins for the entrepreneur.  The profitability can further be improved by reduction in cost of green bricks, reduction in capital cost and increasing the scale of operation.
4)	The energy consumption is much less than in BTK's and nearby clamps showing a saving of about 30 to 60% (See graph).
5)	The breakage of bricks is only about 2 to 4% and much less than that observed in VSBK's in Nepal and Pakistan.

It is further planned to erect one more VSBK in India in a location with a different socio-economic environment and a different climatic condition.

K.R. Lakshmikantan is Manager (Projects), Development Alternatives, New Delhi, and Naval Cars is Mechanical Ensineer, Development Alternatives, Jhansi.

 

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