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close this book BASIN - News No. 6 - July 1993 : Energy efficiency and environmental protection
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View the document The vertical shaft brick kiln (VSBK)
View the document Fuel-efficient brick kiln for Pakistan
View the document Coal fired, small-scale brickmaking in Zimbabwe
View the document Is commercial viability in small-scale brickmaking attainable or a far cry?

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Wall Building Advisory Services at GTZ/GATE, Section 4130, Dag-Hammarskjöld-Weg 1, D-6236 Eschborn 1, Germany

The vertical shaft brick kiln (VSBK)

This type of kiln was developed in China in the 1950's. China was then facing severe problems regarding sufficient energy supply for the large population and for industrial development, as is now the case with many countries in the Third World. The need for building materials is rising at the same time with the aspirations of the people for own shelter.

The vertical shaft brick kiln in China was developed with one objective in mind: To produce bumt clay bricks of a high standard, with a special view to energy- efficiency and environmental considerations. The experimentation stage resulted in some necessary modification. The kiln does not use any firewood at all, except for a minimal amount needed to start the first fire.It can even be fired with coal dust alone. By now, hundreds of this type of kiln have been put up and used effectively in China.

Its principle is as follows:

The vertical shaft brick kiln is a continous kiln. It is operated without interruption 24 hours a day. The smallest unit has two shafts, from which 200-240 bricks per shaft (depending on the size of the bricks) are extracted every 1,5 hours (total 270-320 per hour). One could compare it with a tunnel kiln, except that the bricks move from the top to the bottom of the vertical shaft (see Fig. 4). Bricks fired in the kiln can either be solid or hollow, formed and extruded by machine, or hand-made.


Vertical Shaft brick Kiln in Nepal

The vertical shaft brick kiln has in the meantime been successfully introduced by Chinese experts in Nepal, through a GTZ-project. At present, the kiln is being introduced in Pakistan. Both in Nepal and Pakistan brickfiring is commonly done in Bull's trench or Hoffmann kilns. From the experiences gained in China and now already in Nepal, it can be said that the vertical shaft brick kiln has the following advantages:

* As the coal is burned efficiently, it does not produce smoke;

* The kiln can also be operated during the rainy season;

* Compared to the Bull's trench and Hoffmann kiln, the operating costs (labour, etc.) are lower,

* After training, the kiln can be operated by semi-skilled labour, while higtdy skilled manpower is required to operate both the Bull's trench and Hoffmann kiln;

* Quality checks on the fired bricks can be made after 20 hours operation. To check the quality of fired bricks from the Hoffinann kiln, one has to wait for ten days, from the Bull's trench kiln as long as three weeks.

Since we have received a large number of enquiries about the vertical shaft brick kiln in the past months, we would like to offer the following points on supplementations and. experiments and on criteria and prerequisites for its tranferability. These were forwarded to us by Gerhard Merschmeyer, a brick engineer from MISEREOR, who has visited the vertical shaft brick kiln in Nepal.

Supplernentations and Experiments

A standard-version Chinese vertical shaft brick kiln offers adequate energy efficiency with normal masonry (bricks and cob mortar), insulation (comprising a mixture of clay and rice husks), an outer shell of conventional masonry, and a manually operated picker and elevator. If, however, a VSBK is expected to operate continuously on a year round basis, certain structural modifications and auxillary measures must be taken with regard to firing process monitoring, throughput and production flexibility.

No matter whether the kiln is a basic model or an expanded version, direct heat recovery for the dryer should always be ruled out in favour of a kiln-independ-

ent drying system, e.g. a simple solar-powered set-up with no extraction fans (basic version).

1.Regarding Structural Details

The firing-zone liner should be made of fired clay bricks and fireproof mortar.

Expansion joints should be provided between the three zones, in order to avoid extensive heat-cracking of masonry.

Inspection ports are required for monitoring the brick setting, firing temperature, temperature profile and the condition of the liner.

2.Regarding Technical Equipment

A manually operated winch is needed for lifting the green bricks.

A ramp is preferable to an elevator.

A brickwork flue with damper is needed for diverting the flue gases while the kiln is being loaded.

Transfer cars at the exit points (cooling zone) facilitate and accelerate transferof the picking equipment from one shaft to the next.


Figure 2: Loading of the kiln


Figure 3: Isometric view of kiln and fig 4, shematic sketch

3. Regarding Kiln Operation

The combustion air volume must be controllable in order to retard and accelerate the combustion process as necessary, in case of power outage (no lift), lack of green bricks for firing, temperature-sensitive brick clay, and changeover to cored bricks. A buffer store is required for 4 to 6 hours worth of green bricks for nighttime loading.

4. Regarding Fuels/Combustibles Other than Coal

Devices are needed to allow fueling of the kiln with coconut shells, the husks of rice or coffee, etc.

Contrivances must be devised for determining the calorific value of the coal.

Directions must be drawn up onthe use of fuels, such as peacoal or sawdust- also as combustible opening materials for the clay composition (less work for

loading the kiln, higher porosity and less shrinkage).

 

Criteria and Prerequisites for the transferability of the VSBK

Attention to the following factors will detennine the extent to which an energy-conserving vertical shaft brick kiln can be integrated into a given production sequence. Otherwise, it would either not be possible to achieve the desired fuel efficiency and perfonnance, or the kiln-waste quota would be much higher than in another existing kiln.

1.Regarding Brickyard Expertise

Pertinent experience in the selection of raw materials and in the preparation and firing of bricks is indispensable for comprehending the details of the overall production process. Othcrwise, it would not be possible to properly diagnose subsequent "teething troubles" and other problems.

2.Regarding the Design Basis

The kiln must be built by experienced artisans working in accordance with valid building regulations governing the construction of firing systems.

A lack of theoretical know-how must be compensated for by practical experience. If need be, prior experience can be derived from an ongoing kiln

construction project.

3.Regarding Operational Characteristics

The ceramic properties of the raw material with regard to firng temperature, firing time and firing behaviour must be known and applicable to the VSBK.

High-quality preparation, shaping and drying are indispensable for the production of true-to-form bricks, with particular regard to the smooth loading

and unloading of the kiln.

4.Regarding Personnel

The personnel, particularly those responsible for operating the kiln, must be willing to accommodate themselves to the new technology and, hence, to the altered production sequence.

The fact that a VSBK must be tended around the clock, including weekends and holidays - loading green bricks and extracting the fired ones - will necessitate total restructuring of the production sequence and personnel assignments.

Shaft kilns are especially wefi-suited for use in medium-size brickworks with mechanical shaping capabilities and a year-round operating mode. Nonetheless,

a VSBK could also be a good solution for smaller, seasonal facilities producing hand-moulded bricks to close tolerances.

Fuel-efficient brick kiln for Pakistan

In Pakistan, the brick industry is presently the largest industrial energy consumer. Bricks are fired in Bull's trench kilns with coal, firewood and also old tyres.

in order to examine possible ways of reduction in energy input in Pakistan, the GTZ has started a demonstration project by putting up a fuel-efficient brick kiln.

This vertical shaft brick kiln from China, as described in the preceding article, has recently been introduced in Nepal by the GTZ-Ceramics Promotion Project. A short report about this project appeared in the GATE- Joumal No. 4/91. In Nepal it was found, after the kiln had been in operation for a while, that the potential fuel saving may be as high as 50%. Furthennore, since the kiln uses only coal, the saving in firewood, which is currently being used as fuel for the local brick kilns, will be tremendous.

The project in Pakistan is carried out for the GTZ by the German consulting firm INTEGRATION, in cooperation with the Fuel Saving Technologies Project (FECT) of the GTZ in Peshawar. The project objective is to test the efficiency of the kiln and its appropriateness for Pakistan with regard to construction techniques, type of fuel used, the quality of bumt clay products (bricks and tiles) and economic viability. After a four months' testing period there will be an evaluation and appraisal.

The strategy is to generate an interest among local brickworks operators and concerned agencies and organisations in Pakistan for this type of kiln, with the aim of starting a nationwide dissemination of this kiln technology, on completion of the demonstration project.

A team of Chinese experts from the Henan province has commenced with the actual construction of the kiln in Peshawar in March this year. Test firing is scheduled tostart in the first week of May. Local artisans and brick kiln operators will be trained in construction techniques and in operating the kiln. Since the kiln has been put up at an existing local brickworks, its operation will be carried out as nonnal business. During test firing, other local brickworks owners and Govemment officials will be invited to see the kiln and to judge its performance.

Based on the experience with this type of kiln in Nepal, one can foresee that its obvious advantages in energy-saving will make a dissemination of this kiln technology in Pakistan easy.

Henrik Norsker

for INTERGRATION GmbH, Frankfurt a/M.

Coal fired, small-scale brickmaking in Zimbabwe

Zimbabwe, like many other countries, faces a critical shortage of building materials. Demand has far outstripped supply, especially for "conventional" materials such as bumt clay bricks and cement. A combination of circumstances has excacerbated the situation. Outdated plant and equipment; tardy re-investment; transport constraints and over-centralised production.

The nation also faces the problems of high unemployment, particularly among school leavers, and a scarcity of foreign exchange for capital investment.

If we consider these problems together, then it is evident that one solution is to employ labour intensive methods for the production of building materials. These production methods do not call for large scale investment or machinery that requires foreign exchange.

The small-scale manufacture of bumt clay bricks can compete in an economically effective way with large capital intensive plants. Furthermore, the quality of the bricks produced is just as good.

By siting these small brickworks near to the centres of highest demand, that is in the areas around towns and cities, it is possible to reduce the burden on the transport infrastructure and use the pool of labour, which will certainly be locally available.

Choosing simple effective brick making technologies means that the production of hardware can more easily be transferred to the small manufacturing sector in Zimbabwe.This means a spin-off in local production of equipment, which will further benefit the economy, creating or sustaining jobs and income.

The use of coal for filing bricks is appropriate in Zimbabwe. Coal is produced in this country and is readily available at competitive prices around urban centres. In addition, the use of coal, rather than wood, avoids the problem of deforestation and subsequent soil degradation.

To give an example of the scale of technologies involved:

A brickworks employing 56 staff could be expected to make more than 2 million bricks per year (enough for over 126 quite large single storey houses). An approximate guide to profitability can be obtained: If we consider the manufacturing cost per brick to be around Z$ 0.24 and the selling price to be Z$ 0.29, then the annual profit will be over Z$ 122,000. The pay-back time on initial investment will be under 2 years. In fact the selling price of such bricks is likely to be well in excess of Z$ 0.40! (NB:These figures are based on costs for April 1992)


At the Kuwirirana Co-operative, Zimbabwe: Figure 5: Brick production with a hand mould Figure 6: Brick production with a manual press (Photos:H. Schreckenbach)

For further infonnation contact:

ITDG, Building Materials and Shelter Programme,

PO Box 1744, Harare, Zimbabwe.

Tel:+ 263 - 796420, Fax: + 263 - 796409.

Is commercial viability in small-scale brickmaking attainable or a far cry?

A Case Study From Zimbabwe

A stone's throw away west of the hectic modem capital city of Zimbabwe, Harare, lies a small brick and concrete block making co-operative by the name KUWIRIRANA CO-OPERATIVE SOCIETY.The cooperative, which today is trudging along the tortuous road of success, is a good example of what it takes to be in commercial small scale brick making business in this fast changing economic climate here in Zimbabwe.

The humble beginnings of Kuwirirana date back to the mid-eighties, a period one might term the flower of co-operative movement thinking in Zimbabwe. Thus, spurred by the tide of the day, four members of what is now Kuwiiirana formed a car maintenance business, which unfortunately quickly folded up due to teething problems, related to lack of premises to operate from.

After this initial set back, only two founder members found themselves still with the energy to try out other business activities, whichculminated in the current clay brick and block making operations.

With the assistance of the local City Council's Social Sevices department, Kuwiiirana were permitted to use part of the former s premises to manufacture concrete blocks and were later on allocated a piece of land to diversify into clay brick production. At last, a ray of hope had shone down on the budding cooperative.

Kuwirirana Co-operative comprises twelve share-holding members, lead by Constantine Chikwanda, one of the founder members and chairman of the co-operative. The co-op currently employs a total of twenty-two people. It is managed by the Chairman, a Vice Chairman, Treasurer and three Production Managers. In an economy beset by a host of problems, which include a high unemployment rate of over 30 percent, any business venture which leads to employment creation, no matter how small, is seen as contributing to economic viability. Kuwirirana Cooperative is no exception.

Apart form providing employment for its members and other workers, the co-operative strives hard to improve the standard of living and the morale of its employees, by constantly reviewing and adjusting salaries and wages based on the dedication of members to hard and honest work.

For a period of four years after the co-op's founding, financial monitoring took a back seat in the co-op's affairs and this was not by design, but a genuine problem that the cooperative did not know how to go about establishing one. In early 1991, Intermediate Technology Development Group (ITDG) made its first

contacts with Kuwirirana Co-operative Society and, after acquainting itself with the co-op's state of affairs, intervened, using a two pronged strategy to give technical as well as financial advisory services to the co-operative.

Thus one of the early tasks of ITDG was to prepare a business plan and to establish a financial monitoring system for the cooperative. This task was executed in tandem with doses of technical advice on better brick production methods, which included the use of appropriate and affordable moulding tables, designed by ITDG and manufactured by local suppliers using indigenous materials at eighteen percent of the landed cost of imported similarequipment. In addition, ITDG took the co-operative through a tour of "production clinics", which in the main, covered soil testing, quarrying crushing, seiving, moulding, drying, staking and firing. When the product was sent for quality assurance tests,the report card was good.

After a period of six months of good data capturing, technical advice and close monitoring, a review was done. The results were fascinating. It was noted that during the period rewiewed, both turnover and the co- operative's profit margin had almost doubled. The main reasons for this were that with better data capturing methods, good business planning, sound technical advice on better production and firing methods, as well as professional advice on better marketing strategies, the business was able to unleash a greater part of its hidden energy. To put it simply, the assistance rendered by ITDG led to improved efficiency in production, cornpetifive pricing and tamed some of the operating expenses, such as depreciation costs.

Not all is well, though, for Kuwirirana Co-operative Society. Of late, the co-operative has been served with an eviction order to vacate the site where they were commercially making clay bricks for sale. Ironically, the order to move the flourishing business from its present premises comes from the City Council - the same organisation which initially allocated that land to the co-operative. The land happens to fall in an area long zoned for residential development. The eviction threats from council employees have had detrimental effects on the co-operative members, whose morale plummeted to the lowest ebb and has resulted in a temporary hiatus of the clay brick making operations. The co-op is, however, seeking legal aid and clarifica tion of the issues involved. It is presently actively producing concrete blocks and is also building houses on a supply and fix basis.

Transport has been listed as one of the problems faced by Kuwirirana, as the contractors are often very expen sive. This, coupled with marketing problems owing to high inflation rate, high interest rates and the drought which have affected buyers' disposable income, have had negative impact on the co-operative's progress.

However, due to determination from the realisation that being a new group their voyage is inevitably fraught with many unforseen dangers, and with managerial and technical support from donor agencies, such as Collective Self-Finance Scheme, Intermediate Technology Development Group, Zimbabwe Christian Council, etc, Kuwirirana have managed to keep afloat and are certainly on the road to commercial viability.

Compiled by

Farai Mutsambiwa - Socio Economist

Mineral Industries and Shelter Sector

ITDG -Zimbabwe

Note: If y ou have any questions or want further information on the articles in the WAS-section, kindly write to :

Mrs. Hannah Schreckenbach,

BASIN at GATEIG7Z,

PO Box 5180

D-6236 Eschborn - I / Germany