The "Chinese Kiln" in Herat (First Generation VSBK)

The First (Chinese) generation VSBKs established in Herat had a relatively short shaft (5m) with a smaller cross sectional area. Shafts were built with normal bricks that were not resistant to high temperatures and therefore required regular cost intensive repair. Unloading was done with chain pulley system. Because of the rather primitive Chinese design, the upfront investment was very low but required higher maintenance capital and very disciplined operation to produce good quality bricks.

The VSBK Design from Nepal: (Second Generation)

The Second Generation VSBK had a longer shaft (7-8m) with a nominal cross section 1m x 2m, which improved the combustion and reduced the sensitivity of the firing process, and thus increased its productivity. Shafts were made with fire resistant refractory bricks. Further improvements were made on emission control (chimney) and working conditions (screw jack for unloading). To achieve the best possible brick quality a special focus was set on the green brick production by introducing pug mils (mixing device) for soil conditioning as standard procedure.

The Kabul VSBK Design (Third Generation)

The Third Generation VSBK established in Kabul was based on the Nepal model, but was extended by the addition of a cooling chamber, which reduced thermal shock during unloading. Furthermore a lifting device was developed for making the transportation of the green brick to the loading platform easier. The five kilns established were built with two shafts only, and will require an extension to four shafts to compete with the large scale BTKs. To make the best use of the inconsistent coal quality, coal powder was mixed into the clay as internal fuel.

The Mechanised VSBK (Fourth Generation)

The newest VSBKs built in Nepal consist of six shafts with bigger dimensions, 1.25m x 2m respectively. Shafts are equipped with hydraulic unloading devices. Furthermore the green brick making process is partly mechanised, and the energy efficiency of the kiln was increased further by mixing coal powder into the clay as internal fuel.

The South African-Design (Fourth Generation XXL)

The large scale brickyards in South Africa are equipped with heavy green brick-making machinery, mixing coal into clay and moulding the bricks with a vacuum extruder. The VSKS have more than 30 shafts and are equipped with mechanic brick lifting and hydraulic unloading devices. The firing process and emission control are further improved with a forced draught chimney mechanism.