Renata Boris

Action of the Products of Biofuel Combustion on the Phase Composition and Structure of Refractory Material

The changes occurring in the phase composition and microstructure of aluminum-silicate refractory material which disintegrated during operation in a solid-biofuel combustion unit were investigated. The main reasons for the disintegration of the material were determined on the basis of investigations performed by using modern methods and analyzing the results in comparison with published data on the chemical composition of volatile products of biofuel combustion and their physical-chemical properties.

Study of Alkali Resistance of Refractory Materials Used in Boilers Operating on Wood Fuel

Using the ASTM C 454–83 method alkali resistance is studied for various refractories (chamotte brick, traditional and medium-cement chamotte concrete) used most often in power generation boilers operating on wood fuel. Resistance to alkali of medium-cement concrete developed by the authors with a filler prepared from sinter grade Gorkal-50 (produced by the Gorka Plant, Poland) is also studied. It is established that use of milled quartz sand additive improves resistance of the test cement significantly towards the action of alkaline salt (K2CO3 is used in the work) at 1100°C. It is shown that the test additive during action of alkali facilitates formation of a protective layer that prevents penetration of K2CO3 decomposition products into the material structure.

Refractory Materials for Biofuel Boilers

The energy equipment usable for solid biofuel incineration usually operates upon aggressive conditions. The internal structures (lining) of the equipment are made of refractory materials that are affected by combined loads: thermal, mechanical and chemical (i.e. high temperature–up to 1200°C, chemical impact of alkaline compounds and slag, repeating thermal shocks, abrasive effect caused by solid particles and so on). A majority of traditional refractories usable for lining in such equipment are not durable. Upon certain conditions of use (such as high local temperatures, influence of alkaline biofuel combustion products and so on), durability of the traditional materials is 1–2 years only. The opportunities of new refractory materials application should be set upon taking into account the conditions of operation for biofuel boilers of specific types. In this section the data on the peculiarities of using refractory materials in biofuel boilers are reviewed, and the impact of aggressive operating conditions of such thermal equipment on the properties of refractory materials is discussed. In addition, the investigations results of refractory castables alkali resistance and its explosive spalling are discussed. The recommendations for use of refractory materials in biofuel boilers are also presented.

The effect of carbon and polypropylene fibers on thermal shock resistance of the refractory castable

AbstractThis work investigates medium cement refractory castable with additives of carbon and polypropylene fibers. The peculiarities of microstructure changes in the fiber and castable matrix contact zone, channel formation, and changes of cold crushing strength of fiber additives, which have a refractory castable matrix under temperature treatment, were investigated. The investigation results allowed to predict that using a mix of fibers more effective than using them individually. The influence of fiber additives on the mechanical characteristics and thermal shock resistance of the refractory castable with fiber additives was tested. It was found that the addition of carbon fiber has a positive impact on the thermal shock resistance of the investigated castable, which is confirmed by the results obtained by thermal cycling, as well as by the values calculated for thermal shock resistance R4 and Rst. In addition, the results of the investigation of thermal cycling show that the value of the thermal shoc...

Influence of temperature on the effect of plastification in concrete mixtures

Abstract Demand for plasticisers used in concrete industry is growing in Lithuania and other countries. The paper examines a plasticising admixture based on carboxylate and the influence of temperature on the properties of concrete mixtures. Two types of Portland cement – limestone CEM II/A – LL 42.5R and slag CEM II/A – S 42.5N – have been investigated. To determine the effect of plasticising admixtures on the rheological properties of a concrete mixture, the slump, spread and density of the mixture, along with the depth of cone penetration, were examined. Then, with reference to the obtained data, yield stress was calculated. The research results illustrate the effects specific to certain combinations of plasticising admixtures with different types of cement. A plasticised concrete mixture with limestone Portland cement retains its slump better and remains almost unchanged for 90 min. The slump of the plasticised concrete mixture with slug Portland cement, however, is decreasing gradually for the full p...