The search for cleaner brick production technologies has led to the identification of Vertical Shaft Brick Kiln (VSBK) technology. The Vertical Shaft Brick Kiln technology originally developed in China is an energy efficient, environment-friendly and economically viable means to produce quality bricks.

(The progress and development of  the project has been periodically reported earlier - in the DA Newsletters of September 1996, November 1996, April 1997 and December 1997.)

The VSBK consists of one or more shafts located inside a rectangular brick structure. The shafts are around 1 metre wide with nominal lengths of 1 m, 1.5m, 1.75m or 2.0m. The inside surface is a brick wall, sometimes lined with refractory bricks. The gap between the shaft wall and outer kiln wall is filled with insulating materials - clay, rice husk, fly ash etc.

The shaft is loaded from the top with a number of "batches" of bricks for firing. Each "batch" normally contains four layers of bricks set in a predetermined pattern. The stack of bricks rests on square support bars (which can be removed or inserted) resting on a pair of horizontal beams across the arches in the unloading tunnel.

During its operation, one batch of dried green bricks is loaded at the top at a time. A weighed quantity of powdered coal,
(about 10 mm in size) is spread on each layer uniformly to fill the gaps. Brick unloading is done from the bottom using an unloading trolley which runs on rails along the length of the unloading tunnel. Lifting and lowering of the trolley is done using chain pulley block sys-tem or, as of late, using single-screw unloading mechanism. For unloading, the trolley is lifted so that the whole stack of bricks in the shaft rests on it. The support bars are then removed. The stack is then lowered till the layer with openings appears, through which the support bars are then re-inserted. On further lowering, the load of the stack is taken by the support bars except for the batch being unloaded which comes down along with the trolley which finally rests on a pair of rails. The trolley is later pulled out along the rails and the bricks subsequently unloaded and sorted out for despatch. The next batch is loaded at the top from the green bricks, lifted upto the loading platform. The frequency of unloading - loading varies from 90 to 150 minutes.

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 in the cooling zone and itself gets heated. Maximum temperatures of upto 1000 degree Centigrade are attained in the central firing zone. The hot gases moving upwards dry and heat up the green bricks in the preheating zone. This recovery of sensible heat accounts for the high energy efficiency of the VSBK technology.

• It represents a very energy-efficient, low-cost method of firing bricks. The fired quality is high with very low wastage.

• The kilns require very little maintenance, once constructed, and are not complicated to build.

• The kiln is very compact, not requiring a large area of land, and could be built near to the clay source. In China, the kilns are demolished and rebuilt using the same materials, as the clay source is depleted.

• The construction cost is low.

• The kiln is not affected by variations in the weather as long as dry green bricks are available.

• More than one shaft allows for firing flexibility to cope with the seasonal and economical variations in brick production and demand.

• The kiln is highly suitable for use where fuel is incorporated into the brick.

Environmental Performance

The original design of VSBK introduced by the Chinese experts incorporated aspects of cost-effective construction methods to achieve energy efficiency and economy of operation. Features to ensure better environmental performance and operational health and safety were not given priority.

The Environmental Systems Branch (ESB) of Development Alternatives has conducted the environmental assessment of the three VSBKs - Datia, Kankia and Palghat. The assessment was carried out to estimate the emissions of Particulate Matter (PM), Sulphur Dioxide (SO2) and Nitrogen Oxides (NOx) at loading and unloading platforms and also at stack. The monitoring was carried out based on Bureau of Indian Standards (BIS) and Environment Protection Agency (EPA) codes. The dust measurements were carried out using the gravimetric analysis and NOx were analysed using the spectrophotometric method. The ambient and work place concentrations were measured using the High Volume Sampler (HVS) and Respirable Dust Sampler (RDAs). The stack emission measurements were carried out with the stack monitoring kit.

Following the initial environmental assessment of the VSBK at Datia during the first phase of its operation, the results were carefully scrutinized. Though the results of energy audit conducted by TERI showed much lower specific energy consumption compared to clamps and BTKs the environmental results showed that there was scope for improvement of the environmental conditions at the work place, which anyhow was better than in BTKs. A review workshop was held in June 1996 where the project team identified the desirable modifications such as:

1. Opening out the walls of the loading platform.

2. Increasing the number of inlet flues to the chimney.

3. Increase in monitor height in the roof of the kiln.

4. Providing lid covers for the shafts.

5. Increase in the height of the kiln shaft.

These modifications were implemented in October-November 1996. During the next phases of operation in 1997 and 1998, environmental monitoring was conducted at intervals. The results have shown much improvement in the environmental conditions at the work place. The representative results are given in Tables 1 and 2 along with the results of the second kiln at Kankia.

The project has approached the officials of the Central Pollution Control Board and appraised them of the environmental performance, for eliciting their views. On their advice, the state pollution control agencies have been contacted. An independent monitoring agency recommended by CPCB has already conducted monitoring of the kiln at Datia.

The results of their analysis and evaluation can be gleaned by the concluding remarks of their report "Overall, it can be said the VSBK technology for brick production is less polluting as emissions of SPM and gaseous pollutants are insignificant in comparison to the conventional technologies and far below the prescribed limits for conventional technologies".

During discussions and interaction with brickmakers, including officials of the All India Brick and Tile Manufacturers Federation, it was felt that the production capacity of the VSBK needs upscaling to move towards the scales of volume of production prevalent in the BTK areas. With this purpose in mind the capacity of a two shaft kiln have been successively upgraded from about 5000 bricks per day in VSBK - 1 at Datia to about 9500 bricks per day in the VSBK - 4 at Pune.

For setting up more demonstration kilns in India after VSBK 1 at Datia, it was decided to have partners added to the project team, with Development Alternatives providing the lead and coordination.

The second kiln was built in Kankia, near Mohuda village and Berhampur town in Ganjam District of Orissa in partnership with Gram Vikas, an organization with strong commitment to create livelihoods for the rural masses and provide them dwelling units.

The third kiln was set up at Palghat, Kerala in partnership with Comtrust, a commercial organization (headquarters at Calicut) with a long history of more than 150 years in production of high quality clay products.

The fourth kiln was constructed at Pune, Maharasthra in partnership with MITCON DAMLE, a professional combine of MITCON, a consultancy organization engaged in entrepreneur development based on energy efficient and eco-friendly technologies and Shri Anand Damle, a practicing technology expert with a long experience in bricks and heavy clay products.

The salient features of the four operating VSBKs set up in India up till now are given in Table 3 below.

Further to this, the controlled dissemination at enterprise level has already started. DA is supporting setting up of VSBK-5 by a second generation brick manufacturer in Gwalior in the entrepreneur mode on a business scale and thus started penetrating the established conventional brick manufacturing market. The ground breaking ceremony of this was held on February 15, 1999 and the construction is expected to be completed by April 1999. The kiln will initially have two shafts of 1m x 2m cross section with a production capacity of about 7500 bricks per day. Plans and design for the kiln provide scope for expansion to about 15000 bricks per day with the addition of two more shafts.

Energy Efficiency : From the energy audit conducted on VSBK-1, VSBK -2 and VSBK-3 by TERI at regular intervals, specific energy consumption per kg of fired brick have been calculated, Typical figures are given in comparison with BTKs and clamps in the Table 4.

Production and Quality : For the same soil, bricks produced in VSBK are of better and uniform quality compared to bricks produced in clamps. In other words, for the same green brick quality, VSBK produces bricks of same or better quality than clamps. For improving the green brick quality, some measures have been initiated such as the use of extruder.

Economic Viability : The projected economics of operation of VSBK show a reasonable margin for the entrepreneur.

A team of local and international consultants is leading the initiative for improving resource productivity and to widen the applicability of the VSBK technology to a wider variety of soils.

Energy and environment teams are engaged at all kiln sites to ensure the reliability of the VSBK technology in terms of high energy and environmental performance. There is particular emphasis on achieving operational health and safety conditions. A pool of practitioners are being trained in all aspects of design, construction, operation and maintenance.

The project has initiated plans to co-ordinate with national and state level regulatory bodies like the Central Pollution Control Board to validate the environmental performance of VSBK and with association of brick manufactures and specialised agencies of Government of India such as Building Material Technology Promotion Council (BMTPC) with a view to validate the technical claims and economic viability of brick production through the VSBK technology. These are visualised as crucial steps for large scale dissemination and for meeting the long term needs of brick kiln owners. The current objective of the project team is to guide the evolution of VSBK technology in India, leading to formulation of a strategy for large scale dissemination. q

1. "Vertical Shaft Brick Kiln " - A demonstration unit in India", by Development Alternatives, Bricks and Tiles News Annual Number 1996.

2. "Chinese Vertical Shaft Brick Kiln - A promising technology" by S Maithel, P.R.Sohanbabu & N. Vasudevan, TERI. Ibid Annual Number 1995.

3. "Lessons in Technology Transfer : A case study of the Vertical Shaft Brick Kiln." BASIN News. No. 14 August 1997