Vertical shaft brick kiln technology

Vertical shaft brick kiln technology

Energy-efficiency, brick-by-brick

The rich, clayey soil on the banks of rivers is raw material for a whopping 140 billion bricks a year. Produced in over 100 000 brick kilns in India, these are part of a large but unorganized, brick sector in the country. It is generally perceived that the Indian brick industry has missed the bus of technological development and the environmental consciousness that follows it. Well, not quite.

The right foundation

A single shaft VSBK

In this scenario, the Swiss Agency for Development and Cooperation, in conjunction with TERI and other agencies (Development Alternatives, Gram Vikas, MITCON, SKAT, and Sorane SA) proposed a systematic programme to influence and augment brick production while seeking to conserve energy and benefit the environment. The idea was to successfully transfer the VSBK (vertical shaft brick kiln) technology, devised in the early 1970s for burnt-clay brick manufacturers in rural China, to the Indian brick industry. The VSBK technology is one of the best available options for small brick manufacturers–it makes their otherwise-polluting operations environment-friendly.

With their backs to the wall

The increasing emissions from the brick industry made the regulatory authorities issue deadlines (the 1996 notification) to brick-kiln owners to either clean up their act or shut shop. Several thousand polluting movablechimney BTKs (Bull's Trench Kilns) converted to fixedchimney BTKs. However, even as the June 2001 deadline for the CPCB (Central Pollution Control Board) directive loomed large, many small BTKs prayed helplessly for deliverance, since they faced the threat of closure, in the absence of any viable options.

A VSBK demonstration unit in Malur, Karnataka

The need of the hour was a non-polluting technology with lower energy consumption. It was also imperative to improve the working conditions of 8 million labourers engaged in this industry who were not only subjected to unprecedented levels of pollution but also serious health hazards. In fact, it was surmised that even a modest reduction in specific consumption of fuel would have a significant positive impact on the national energy scenario.

The then-applied technologies in brick manufacture such as clamps, downdraught kilns, and BTKs require huge proportions of highly polluting coal (with an ash content as high as 40%), firewood, and biomass as fuel. In fact, the coal consumed by this industry was an astronomical 24 million tonnes.

The building blocks of success

A VSBK demonstration unit in east Uttar Pradesh

In 1996, the first pilot kiln was established under the project at Datia in Madhya Pradesh. VSBK essentially comprises one or more rectangular vertical shafts within a kiln structure. Dried green bricks and coal were carefully stacked into batches and loaded on to the top of the shaft. From the bottom of the shaft, batches of fired clay bricks were continuously removed. During the kiln operation, the green bricks were progressively moved from the pre-heating, firing, and cooling zones before reaching the shaft exit.

The VSBK technology brought with it two major advantages–less fuel consumption and lower SPM (suspended particulate matter) emissions. Moreover, the VSBK could be operated perennially as the kiln's roof protected it from the vagaries of weather. With minimal land usage, development of multiple-shaft production units actually enhanced the ratio of land used to production output, and even led to a considerable improvement in the quality of bricks.

Beneficiaries

Subsequent to the initial pilot unit at Datia, three more units were set up under the project in other regions of the country (Kerala, Maharashtra, and Orissa). All these demonstrations established the energy efficiency, strong environmental performance, and sustainable nature of the technology. In 2000, another three kilns were constructed in Madhya Pradesh. These successes consequently attracted several brick makers with the result that today there are more than 40 VSBKs operational in India. TERI is currently involved in the dissemination of VSBK technology in south India. It is also propagating the idea of small-scale brick manufacturing based on the VSBK technology and the involvement of the firemen community in eastern Uttar Pradesh.

Applications/benefits

The VSBK technology can be best applied to the medium-sized brick kilns. There are several site-specific factors–quality of raw materials (soil and fuel) used for brick making, skills, labour cost, quality and price of bricks, and so forth. The economic analysis of the VSBK technology, as compared with the BTK, shows that the former requires an investment of 2.1 million rupees as against 1.5 million rupees for the BTK technology . Also, the VSBK technology requires about 105 tonnes of coal per million bricks, while BTK requires 160 tonnes of coal per million bricks. The NPV (net present value) of VSBK is 41 million rupees as compared to 32 million rupees of the BTK technology. The incremental NPV goes up from 8.8 million rupees to 9.4 million rupees when carbon dioxide benefits are accounted for.

For a shaft size of 1 x 2 m, the VSBK has a production capacity of about 8000 bricks per day with a specific energy consumption of 0.8–0.9 MJ/kg (megajoules per kilogram) of fired bricks. This is a distinct drop of 20%–50% in energy consumption as compared to the conventional set-ups. The initial investment is not a patch on the huge benefits accrued from adopting an energy-efficient technology.