Vertical Shaft Brick Kiln

Vertical Shaft Brick Kiln, VSBK in Chambo, Ecuador - Horno Vertical Continuo HVC

About

• This is an updraft kiln for firing clay bricks. Updraft = heat is reused (cold air entering below cools down the descending bricks, is then used for firing, then warms up the still-cold bricks on top of the stack).
• Developed in China in the late 1960s during the cultural revolution. In some ways, its development parallels that of the Chinese Greenhouse: a rural, medium-scale technology that was eventually strongly supported by government and academia, leading to many small technical improvements and massive roll-out.
• Combines low cost of updraft firing with high fuel economy.
• Usually fired with low-grade coal fines, but may be adapted to other fuels
• Said to be twice to three times as energy efficient as Hoffmann kiln
• energy consumption figures (China): 0.103 kg coal per brick or 975 MJ/kg per 1000 bricks.
• Firing shaft is very well insulated on all four sides, minimizing heat loss.
• Bricks are loaded at the top and removed at ground level in a continuous process (see animation below for details)
• Each batch of bricks is made up of four layers, making a total of 320 bricks per batch.
• Many kilns put out 10,000-15,000 bricks per day (this figure may refer to a 2-shaft kiln)
• Brick wastage is very low when compared to other kilns, being only 2-5% in China.
• Operating principle is similar to that of a vertical shaft lime kiln.
• The firing process is completed in about 24-30h as the bricks move from top to bottom.
• Versatile: hand-molded bricks or extruded bricks; even non-standard shapes as long as the stability of the stack is assured

Related Pages On This Wiki

• Kiln
• Biochar/Brick Co-production System
• Biochar-Lime Co-production System
• Compressed Earth Blocks

Pros and Cons vs. Compressed Earth Blocks

Pro:

• no liquid fuel (e.g. diesel, gasoline, ethanol) or electricity needed that would otherwise be required for the CEB press; energy savings due to lower-grade fuel, no need for liquid fuel distillation
• uses low-cost / low-quality fuel such as coal fines or charcoal fines, possibly pyrolysis gas from other processes (see development proposal below)
• carbon negativity more easily achieved (if part of a Biochar/Brick Co-production System)
• possibility to re-used waste heat (space heating for applications such as greenhouses, fish tanks, etc.)
• no stabilizer needed (e.g. cement, lime, flyash, etc.), leading to energy savings.
• reduced wear and tear on the infrastructure per brick (volume is large)
• possibly more stable and more weather-resistant bricks (this requires comparisons, lab testing)
• CEBs may not be suitable for all applications anyway (e.g. where they are exposed to a lot of water), so an alternative is needed. Fired bricks are a good, proven alternative.
• bricks are of consistently high quality (in fact, they HAVE to be, because of the compressive force that they have to withstand for the stacking)
• likely less work needed per brick for handling (one of the links below describes the labor requirements thusly: "Labour requirements are low, requiring one man to load and two men to unload, during an 8 or 12 hour shift. The labourers are not working continuously, as there are 3 or 4 hours between each loading/unloading session.")
• less need to monitor bricks over weeks (e.g. curing of CEBs with moisture monitoring etc.)

Con:

• possibly increased fuel use per brick. This is not certain, as the VSBK is very energy efficient, and the fuel use for CEBs is not zero either. Calculations are difficult because of very different fuel types.
• a larger installation means less flexibility (this facility is not easy to move, in contrast to CEB press, although moving the kiln has actually been done in China)
• potential air pollution problems (this is largely a factor of higher volume/concentration of production)
• requirement for continuous operation on nights/weekends (there are breaks though - see labor requirements under "Pro")
• VSBK is only for the production of bricks. Tiles would have to be fired in some other way.
• need for a well-trained, skilled "brickmaster" who is able to keep the fire at the right level and intensity
• possibly more stringent requirements for suitability of clay

Income Potential

• At a realistic market price of $0.5/brick, 10k bricks per day can provide $5000/day gross revenue (minus labor costs, minus fuel costs, minus amortization, etc.)
• construction cost for one such facility (standard, coal-fired) in India was mentioned as $50,000 (reference year unclear).
• amortization cost is negligible, considering an expected operational lifetime of 15 years
• output of 3 million bricks/year = ~$1.5M
• fuel costs may be minimal if waste biomass is used (wood, straw, other biomass)

Development Proposal

(also see: Biochar/Brick_Co-production_System) The typical VSBK is coal-fired, mostly using low-quality coal fines. As shown in the (Vimeo) animation above, pieces of coal are scattered onto the bricks from the top. Since coal is a polluting and often unavailable fuel, the proposal here is to develop a (carbon-negativ)e VSBK fired with pyrolysis gas (with biochar as a co-product). Some reports exist suggesting that wood chips and crop waste can be used as fuel instead of coal fines, but it is not clear how that affects the whole process.

• The brick kiln could be re-designed as part of a pyrolysis system to run on the pyro-gas (see also: Biochar/Brick Co-production System). In such a system, the pyrolysis gas would be blown into the kiln from the front and back, through the 5 or so holes in the bottom layer of each brick stack.
• This gas-fired kiln would have cleaner emissions than the coal-fired one (less: soot, heavy metals, organic pollutants, etc.). The off-gas could conceivably be used for CO2 enrichment in a greenhouse or garden/field (this may require a biofilter step first).
• Co-products in addition to bricks: biochar, heat, CO2-rich gas for greenhouses.
• higher expected cost: A pyrolysis gas fired facility will likely be somewhat more complicated and expensive than a coal-fired one.

Further Information (links)

• TERI: VSBK (short overview)
• Swisscontact is an agency that has done a lot of work trying to facilitate knowledge transfer about this technology
• paper from Swisscontact: "VSBK - An effective South-South Technology Transfer for climate change mitigation in the Clay Brick sector" (internal copy: here)
• Fastonline: VSBK (internal copy: here)
• internal .pdf copy of: "Lessons in technology transfer: a case study of the vertical shaft brick kiln" BASIN - News No. 14 - August 1997 : Bridging Gaps through Cooperation (BASIN-GTZ-SKAT, 1997, 35 p.)"
• Devalt.org: "The Vertical Shaft Brick Kiln : a technology for the masses" (internal copy here)
• Article from GATE - 4/91 - Environmental NGOs Humanity Development Library - The Chinese vertical Brick Kiln
• VSBK India(has FAQs)