Refractory Materials for Biofuel Boilers

Abstract

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.

Analysis of the Structure and Durability of Refractory Castables Impregnated with Sodium Silicate Glass

“…These boilers utilize renewable energy sources such as wood, straw, mixed municipal waste, and other materials to reduce the reliance on fossil fuels in order to align with ambitious targets set by the European Union aiming for at least 27% renewable energy by 2030 [3]. The lining of these biomass boilers is constructed using various refractory materials, including castables, which are carefully selected for their ability to withstand high temperatures and to maintain structural integrity over extended periods [4,5]. For instance, in the demanding conditions of some species of biomass combustion where temperatures can range up to 1200 • C, it is advised to opt for chemically resistant refractory castables containing SiC, or alumina-chrome, engineered to withstand extreme operating conditions [4].…”

“…However, wood biofuel boilers predominantly operate at temperatures below 1100 • C, making them prime candidates for castables enriched with aluminosilicate aggregates like fireclay or mullite [5]. Regrettably, these castables exhibit limited resistance to alkali corrosion, which often leads to premature degradation attributed to the corrosive influence of alkalis present in the refractory materials and fuel [6].…”

Investigative Study of Effects of Gallus domesticus guano, Cucumeropsis mannii shell and Elaeis guineensis shell Additives on the Refractory Properties of Isiagu Clay

“…Until now, efforts have been made to address this imbalance, yet, there is a need for refractories with improved mechanical and thermal properties. This is important since chemical attacks and mechanical abrasions in the process of utilizing them, decrease their life span to as low as 1 to 2 years [7]. Some researchers have used local clays together with additives to improve the various properties of the refractory clay namely; thermal shock resistance, cold crushing strength, bulk density, porosity etc [8,9].…”

Analysis of the Formed Protective Layer Inhibiting Alkali Corrosion in Aluminosilicate Refractory Castables

“…This leads to a more intensive fouling of the boilers, deposition of fly ash on the heating surfaces, and alkali corrosion of materials used in the equipment [2,3]. Corrosion of refractory materials significantly reduces the durability of the lining [4,5] of the boilers and also causes failure [6].…”