Fa c t s h e e t : Vertical Shaft Brick Kiln, South Africa

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V E R T I C A L S H A F T B R I C K K I L N T E C H N O L O G Y ( V S B K )4I N T R O D U C T I O N A N D HISTO R Y

Vertical shaft brick kiln (VSBK ) is acontinuous, updraft, moving ware kiln inwhich the fire remains stationary while thereis counter current heat exchange betweenair (moving upward) and bricks (movingdownward).

T he VSBK technology has evolved from the traditional up-draught kilns in rural China

during late 1950s; however, the widespreaddissemination of the technology took place afterthe economic reforms. At its peak during mid1990s, thousands of VSBKs were reported to beoperating in China.

Since 1990, under different technology transferprojects the technology has been transferred toseveral developing countries including India,

Nepal, Vietnam and since 2010 in South Africa.Sou th Af r i c an brick makers and service providers have been able to innovate and haveadded new features to the technology, and inthe process have transformed a ruraltechnology into an industrial technologysuitable for large scale production.

A B O U T T H E K I L N E N T E R P R I S E S USING T H I S T E C H N O LO G Y

Kiln Nature of enterprise Level of mechanization Brick produced Production capacity Operational season

CONTINUOUSMOVING WARE INDUSTR I AL SEMI MECHANIZED SOLID AND

PERFORATED

SMALL & MEDIUMBetween

0 .5-6.0 million bricksper month

PERENNIAL

Number of VSBK’s in SA

Operations Shafts

Operational 31 75

Under Development 2 30

1 Includes one plant with 27 shafts utilising adifferent construction methodology, constructedprior to the VSBK project

Economic Sustainabil ity• Improved Profit Margin• Reduced Firing Fuel Required & Emissions Tax• Lower Fired Waste & Improved Yield• Improved Productivity• Higher Quality• Greater Product Flexibility• Favourable Production Cycle

Environmental Sustainabil ity• Reduced GHG Emissions• Contributes to Resource efficiency• Reduced operational footprint

Social Responsibil ity• Improved working conditions• Reduced exposure to particulates• Skills Development & Improved Job Security

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1: KilnThe vertical shaft brick kiln is a continuous, moving ware kiln inwhich bricks are fired in a vertical shaft of rectangular crosssection. T he height of the shaft is around 6 – 8 m and nominalcross-section of the shaft 1.90 x 1.40 m. The kiln consists ofbanks of multiple shafts. T he shafts are enveloped by an outerwall made up of bricks and the gap between the shaft andouter kiln wall i s filled with insulating material.

2: ExhaustThe shafts have their exhaust gas ducting connected to acommon exhaust.

5: Counter Current Principle

Air for combustion enters the shaft from the bottom (5.1). Itgets preheated by the hot fired bricks in the lower sectionof shaft (brick cooling zone) before reaching thecombustion zone. After combustion, the hot flue gasespreheat the green bricks in the preheating zone beforeexiting the kiln through the exhaust flue. (5.2).

The kiln works as a very efficient counter current heatexchanger where the heat transfer takes place betweenthe air moving up (continuous flow) and the bricks movingdown (intermittent movement) in the shaft.

6: UnloadingT he brick setting in the shaft is supported on removablebars (6.1) provided at the bottom of the shaft. Brickunloading is carried out in batches from the bottomwith the help of a trolley (6.2). Generally, in every 2-3hours, one batch is unloaded at the bottom and a batchof green bricks is loaded at the top. At any given time,there are typically 12 - 14 batches in the kiln.

4: Firing ZonesGreen bricks loaded from the top, gradually movedown the shaft. The peak firing temperature is at themiddle of the shaft, where combustion of fuel is takingplace. Fired bricks after cooling are unloaded at thebottom. There are 3 distinct zones in an operating VSBK:

4.1 Brick preheating zone: It is in the upper section ofthe shaft where the green bricks get preheated bythe hot flue gases on their way to the exhaust flue.

4.2 Brick firing zone: It is located in the middle of theshaft where fuel combustion and vitrification of thebricks is taking place.

4.3 Brick cooling zone: It is in the lower section of theshaft where the hot fired bricks are cooled down bythe ambient air entering into the shaft.

3: LoadingGreen bricks are loaded from the top of the shaft inbatches. T he fuel, in the form of coal (small nuts), is laidalong with the green bricks. Common practice is thatinternal fuel in the form of coal fines within the clay body issupplemented by a small quantity of external fuel.

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5.2

5.1

6.1

6.2

4.2

4 .1

V E R T I C A L S H A F T B R I C K K I L N T E C H N O L O G Y ( V S B K )

D E S C R I P T I O N A N D W O R K I N G

Fa c t s h e e t : Vertical Shaft Brick Kiln, South Africa

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V E R T I C A L S H A F T B R I C K K I L N T E C H N O L O G Y ( V S B K )

P R O D U C T Q UA L I T Y

Actual Results vs Statutory Limits (@25 ºC and 101.3 kPa) Source: Occupational Health Risk and Environmental Emissions

Assessment Report, March 2012

O C C U PAT I O N A L H E A LT H A N D S A F E T YF I N A N C I A L P E R F O R M A N C EF U E L S A N D E N E R G Y

C oalFly Ash

C OMMONLY U S E D F U E L S

Because of proper combustion of fuel,efficient heat transfer and minimal heatlosses, VSBK is one of the most energyefficient brick kiln firing technology.

A very efficient counter flow heat transferarrangement between air and bricks, uniformfuel distribution and sufficient insulationaround the kiln attribute to the efficiency of aVSBK.

Note: Measured at firing temperature of900-10500C

MAIN C A U S E S F O R H E AT L O S ST he main sources of heat loss in a VSBK arethe flue gases and fired bricks coming out ofthe kiln.

MJ/kg of fire d br ick

0

1

2

3

4

A I R EMISS I O N S A N D IMPA C T S

C OMMENTS O N EMISS I O N S

Low fuel consumption and better combustionresult in low emissions. Practice of usinginternal fuel further helps in reducing theemissions.

C O 2 R e d u c t i o nAverage: 400 ton CO2 emissions reduction per annum compared to clamp kilns

M E AS U R E D EMISS I O N

FA C T O R S

Types ofproduct thatcan b e fire din the kiln

Solid bricksPerforated bricks

Roof tiles

Floor tiles

Fast heating and cooling of the bricks and highload in the lower section of the brick stackingare the main factors which can cause cracksand product breakages in a VSBK. However,with extruded bricks, breakages and lossesare very low.

Capital c o st b reakd own

Capital c o st of kiln te c h n o l o g yF or a six-shaft VSBK with annual produc-tion capacity of 11 – 13 million bricks andincluding the building, but would be site specific.

R 6 0 0 0 0 0 0 ( 2 0 1 6 )$

L O S S E S / B R E A K A G E S ~ 4%

G O O D ~ 9 6 %

P roduct QualityAs per the production records

VSBK is well suited for firing solid bricks. It canalso be used to fire bricks with perforations.

S P E C I F I C E N E R G Y C ONSUM P T IO NEnergy consumed for firing 1kg of fired brick

Average: 0 .9 MJ/kg of fired bricks

Exposure to Respirable Suspended Particulate MatterThe VSBK has a permanent kiln structureand with the introduction of the exhauststacks in the kiln (the initial VSBKs of Chinadid not have chimneys), the air pollutantsconcentration in the working environmentis low and the exposure of workers to airpollution is reduced to within prescribedSouth African standards

Usual annual Occupational Hygiene Monitoring asper the South African regulations is conducted.

Exposure to Thermal StressBecause of the enclosed working areasaround the kiln, workers working on thekiln are protected from the directexposure to sun and exposure to heatstress is very low.

This reduces the thermal stress and consequentrisk of eye & skin diseases and dehydration amongworkers.

Worker SafetyProperly constructed VSBKs havingmechanised brick lifting and brickunloading processes potentially exposeworkers to accidents. However, theserisks are managed through the process ofrisk assessments, the application of safetymeasures and proper training.

Low risk of injuries

maximumClamp Kiln (2-3.5)

minimum VSBK (0.84-1.0)

Construction Material 60 %

Labour 20%

Equipment 20%

Production capacity

35 000 bricks per day per bank of 6 shafts

Brick size 222 mm x 110 mm x 73 mmNumber of Operators required

~ 17

Payback Period

Simple Payback

2.0 – 3.0years

Fa c t s h e e t : Vertical Shaft Brick Kiln, South Africa

Pollutant SANS 1929:2009 VSBK

SO2

1 Hour µg/Nm3

24 Hour, µg/Nm3

Predicted, µg/m3

350 125 7.8

NO21 Hour 1 Year

21.5200

PM10 24 Hour 1 Year 9.1 (total)

V E R T I C A L S H A F T B R I C K K I L N T E C H N O L O G Y

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( V S B K )

Further Contact Information

Factsheet prepared byEnergy Efficient Clay Brick ProjectSwisscontactOffice 80B107 Nicolson StreetBrooklynPretoria, 0181South Africa

Tel: +27 (0)12 346 5102

PhotographyShaula GreyvensteinJez Rowe

Original factsheet layout and graphics

Greentech Knowledge Solutions Pvt. Ltd., New Delhi

Design & IllustrationShoili Kanungo

August 2016

F O R M O R E IN FO R M ATION:

The VSBK support network of service providers, hosted by the EECB project offer their services independently of each other, supporting the clay brick manufacturer through the various processes required when acquiring the VSBK technology.

www.vsbk.co.zasouthafrica@swisscontact.org

Fa c t s h e e t : Vertical Shaft Brick Kiln, South Africa

Acknowledgements

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