Traditional Kiln Research Articles

Effect of burning conditions on properties of artificial hydraulic lime mortar obtained from limestone and siliceous waste materials

The present study was carried out to produce an artificial hydraulic lime for repair and conservation of historic masonry. Lime mortar is preferred to cement based mortar for conservation work because it is more compatible with stone and ancient brickwork, as well as being a more sustainable material. The study focused on the effect of burning conditions on the properties of an artificial hydraulic lime mortar obtained by burning limestone and siliceous waste materials. The raw meals were prepared from five types of siliceous materials obtained as byproducts from industrial processes (pulverised fuel ash, glass cullet, silica sand, crushed rock and spent oil shale) with the amount of silica between 3 and 16%. The raw meal was burned in an electric furnace at 975°C for 3 h. The mortar was prepared by mixing hot slaked lime putty (water/lime ratio ∼1.6) and 'Gowrie' sand at a lime/sand ratio of 1 : 3 by weight. The limes and lime mortar were prepared and tested according to BS EN 459-2:2001. The investigations carried out on the products included free lime analysis, strength test and microstructural examination. The results show that the glass cullet lime is the most hydraulic product and can be classified as feebly hydraulic. It suggests that this hydraulic lime could be produced using a traditional kiln at a low cost.

Polycyclic aromatic hydrocarbons in smoked fish – a critical review

Among hundreds of components, wood smoke also contains at least 100 polycyclic aromatic hydrocarbons (PAH) and their alkylated derivatives. Many of them are carcinogenic. Benzo[α]pyrene (BaP) is regarded as a marker of the carcinogenic PAH in smoke and smoked fish, although in olive residual oil the maximum level of 2 μg/kg for each of the eight most carcinogenic PAHs, including BaP, has been set. Contemporary analytical procedures based on extraction of the hydrocarbons from the matrix, clean-up procedure, separation by gas chromatography (GC) or high performance liquid chromatography (HPLC), followed by detection and quantification by mass spectrometry (MS) or fluorescence detectors (FLD), respectively, make it possible to determine individual PAH in smoked foods at concentrations of the order of 0.1 μg/kg or even 0.01 μg/kg. Heavily smoked fish from traditional kilns, especially their outer parts, may contain up to about 50 μg BaP/kg wet weight, while the meat of mild hot-smoked fish, from smokehouses supplied with conditioned wood smoke from external generators, contains only about 0.1 μg/kg, or even less. Some older data on the contents of BaP in smoked fish should be treated with caution, if the analytical procedures used did not guarantee unequivocal separation and identification of the individual PAH.

Evaluation at industrial scale of electric-driven heat pump dryers (HPD)

Electric-driven heat pump drying is evaluated in lumber from different softwoods (Maritime, radiata and Scot pines) and hardwoods (Iroko, Beech). The evaluation was carried out at industrial scale being controlled by five different driers over a two-year period. Up to 235 different cycles of drying were evaluated. Specific energy consumption seems to be between 0.64 kWh/l to 0.73 kWh/l in softwoods and between 1.0 to 1.3 kWh/l in hardwoods. These values are much lower than those usually reported for the traditional kiln drying. In moderate permeable lumber, the overall duration of drying is very similar to traditional kiln drying, but is longer in the case of very permeable softwoods. This drying technology seems to be efficient when drying lumber, at least when medium temperatures (65–70°C) are involved.

Transition from traditional brick manufacturing to more sustainable practices

Brick manufacturing in many Asian countries is predominantly a cottage industry and employs traditional kilns, which are energy-inefficient and polluting. In Bangladesh, about 4500 brick kilns are in operation, producing about 9 billion bricks per year. Of the 4500 kilns, more than 4000 are of the Bull's trench kiln (BTK) type. The BTK employs an extremely crude technology to fire bricks. There are also about 400 fixed chimney kilns, 15 zigzag kilns, 25 Hoffman kilns and 5 modern tunnel-type kilns currently in operation in the country. Other than the Hoffman kiln, which uses natural gas, the other three types of kiln use low-grade coal and firewood as fuel. The pollution from these kilns has reached alarming proportions. There is an urgent need to make a transition from these polluting technologies to more environment-friendly technologies. The two such technologies that can readily be employed are the Hoffman kiln and the vertical shaft brick kiln (VSBK). The replacement of the existing technologies will result in significant reductions in greenhouse gas emission, especially if the coal-based technologies can be replaced by natural gas-based technologies. Calculations show that these technologies are able to reduce GHG emissions by 42 and 29 % respectively compared to the existing BTK technology. The existing technologies are simple, require low capital investment, yield very good returns and employ a large number of people. As a result they are enormously popular with small-time entrepreneurs. The alternative technologies are complicated and expensive. The governments in the countries where traditional brick-making is employed face an uphill task in trying to bring about a transition because all alternatives require higher initial investments, and existing brick industryowners cannot afford them. Loan schemes administered through banks are also not working out because BTK owners have no creditworthiness. A solution that preserves the good points of the existing industry and addresses the pollution problem is proving difficult to achieve through regulatory control alone. A rapid transition, if it introduces modern brick-making, will wipe out the numerous existing brick kiln-owners and replace them with a much smaller number of wealthier entrepreneurs. Further, consumers will have to buy costlier bricks and greater pressure will be exerted on the country's balance of payments. The brick industry in Bangladesh brings out quite poignantly the sustainable development challenges facing a developing country. Preserving the ecosystem and reducing unsustainable use of natural resources while preserving jobs and alleviating poverty can indeed prove insurmountable in some cases.

New Timber Kiln Designs for Promoting Uniform Airflows Within the Wood Stack

Two geometrically innovative timber kilns have been designed, constructed, and subsequently tested for airflow uniformity within the stacked wood. The roofs of both kiln configurations were barrel-shaped rather than the traditional peak or flat-top shaped. The first configuration employed outward-swinging overhead baffles, which is the arrangement found within most commercial kilns. The second configuration had inward-swinging overhead baffles and contoured right-angled bends to the plenum chambers from the ceiling space, where the fans were located. Velocity measurements down the height of the timber stack showed that the uppermost packs in the kiln with outward-swinging baffles were starved of airflow. Flow visualizations indicated that the blocking action of a recirculation zone or a boundary-layer separation zone in the inlet plenum chamber was responsible for the reduction in flow through these packs. A similar phenomenon was shown to occur in a traditional kiln with a peak-shaped roof and outward-swinging baffles. The velocity range in the contoured kiln with inward-swinging baffles was reduced by a factor of three, and no recirculation zones appeared in the plenum chambers. Thus, the shape of the roof has very little influence on the uniformity of flow within the timber stack, although significant savings in pressure losses through the kiln are possible by employing a barrel-shaped roof. Airflow uniformity is improved by contouring of the inward edges of the right-angled bends from the ceiling space to the plenum chambers. The contoured configuration is currently operating commercially at a number of sites in New Zealand.

The Structure and Identity of Folkcraft Pottery Traditions in Onta, Kyushu Island

This paper is an investigation of the development and maintenance of tradition in a small pottery village, Onta Sarayama, in Kyushu, Japan. Onta pottery gained broad recognition when it was discovered by non-locals in the early part of the twentieth century, and these have been influential in fixing the image of traditional pottery from Onta since that time. However, potters in Onta have not always given in to external pressures with regard to their work, but rather subjectively select those aspects of tradition which they feel will be beneficial to them in the long-term. As a result, the contemporary pottery tradition of Onta is an amalgamation of influences from both internal and external sources. Using Onta as an example, I describe the processes through which local people subjectively insert images from outsiders into their own traditions and especially focus on how they regard authenticity.In the early 1930s, a member of the Japanese Folk Craft Movement visited Onta for the first time. Since then, the great value of its traditional potters and their works has been widely recognized and Onta has became one of the most famous folk craft pottery villages in Japan. The Onta pottery tradition has four important characteristics: 1. The number of pottery households within the community is fixed. 2. Potters produce clay themselves from raw materials. 3. Pots are made on kick wheels and fired in traditional kilns which use wood for fuel. Electric kilns, wheels, and clay processing mills are not used. 4. Work is done collectively, not by individual artists. Today, Onta is the only pottery village maintaining such a community-wide traditional production system in Japan.However, during the Mingei boom of 1960-70s, Onta experienced a period of transition. The popularity of the village and the demand for the pottery made there became very high. At that time, potters in Onta considered introducing electric machines, and some sought their own way as individual artists. However, in the end, they decided to continue with the traditional method outlined by the Folk Craft Movement above. At that time, in many Japanese potteries, the production system was changing and machines were introduced. I consider why only Onta maintained the traditional method.In the paper, I argue that the potters of Onta recognized the value of the external folkcraft ideals and employed them positively for their own purposes. This is one example of how local people act in such a situation, specifically the interaction between potters and members of the folk craft movement.In summary, this interaction helped potters recognize the images which outsiders have of them and their work and influenced them in shaping the direction their work has taken. Clearly, the tradition of Onta pottery has been produced and maintained through the interaction between outsiders and the local people.

70%Ag 30%Pd Coated BaTiO3 Powder for Internal Electrode Applications

Recent trends in the electronic passive component manufacturing industry have been to eliminate or reduce reliance of pure Pd and high palladium contained Ag/Pd electrodes by substituting nickel or significantly lowers palladium content in Ag/Pd alloys. The conversion to base metal technology represents a substantial capital expense; the resistance to replace traditional air‐fired kilns to nitrogen or reducing atmosphere kilns has created the need for new low cost air fired electrode technology. This paper presents a new electrode technology incorporating a uniform, continually coated AgPd over engineered dielectric particles. The resulting powder greatly reduces the consumption of precious metal, and provides superior thermal mechanical properties. This is achieved by matching the core ceramic structure of the powder to the manufacturer′s dielectric, thereby controlling shrinkage while maintaining desired electrical properties.

Determination of polycyclic aromatic hydrocarbons in smoked fishery products from different smoking kilns.

The levels of 13 polycyclic aromatic hydrocarbons (PAH) were determined by an HPLC method with fluorescence and UV detection and by a GC/MS technique in smoked fishery products from modern smoking kilns with external smoke generation and from traditional smoking kilns. The average benzo(a)pyrene (BaP) concentration of all 35 samples from commercial smoking kilns with external smoke generation was 0.1 microgram/kg (wet weight) and the sum of the carcinogenic compounds determined in the study, i.e. benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenz(a,h)anthracene and indeno(1,2,3-c,d)pyrene did not exceed 4.5 micrograms/kg (wet weight). The BaP levels of the 27 smoked fish samples from traditional kilns ranged from 0.2 microgram/kg to 4.1 micrograms/kg, with a mean value of 1.2 micrograms BaP/kg. The average concentration of the sum of the carcinogenic compounds was 9.0 micrograms/kg. Large variations were found in the content of the non-carcinogenic PAHs phenanthrene, anthracene, fluoranthene and pyrene in all samples from both types of smoking kilns.

THE PRODUCTION AND PROPERTIES OF COCONUT STEM CHARCOAL IN THAILAND

A programme of experimentation and training on the production of charcoal from coconut stems in transportable metal k.ilns was carried out. Comparisons were made between different timber densities, preparation methods and kiln loading systems. Other timber sources and traditional kilns were used. The highest density coconut wood produced the best charcoal and extensive preparation was found to be necessary. Local clay kilns produced excellent charcoal, but were slow and needed considerable fuel. Coconut stem charcoal. production was markedly different from carbonisation of wood from dicotyledonous trees.
 
 The charcoal produced was found to have similar calorific value to that from other woods, but was faster‑burning and easier to ignite. Content of volatile matter was low and little ash was produced. The charcoal was often rather wet. A sample of consurners found that the charcoal was better than they had expected. The main complaint was the speed of burning.