Mathematical Model for Prediction of Biomass Ash Melting Temperature using Additives

Abstract

Some types of biomass ash have low ash melting temperature which can result in various problems in combustion processes. Ash slags and sinters can avoid heat transfer in heat exchangers, which can also cause corrosion of heat transfer surfaces. One of the ways of burning fuels with low ash melting temperature is to use additives. Ash melting temperature can be determined in a laboratory on the basis of standard STN ISO 540. Meltability of ash is characterized by the physical state of ash occurring during the heating process under well-defined conditions in the furnace. Experimental determination of ash melting temperature is quite expensive. In this work a prediction method of ash melting temperature is described. The mathematical model uses multiple linear regression where input parameters are the known chemical composition of fuel ash and used additive converted to an amount of SiO2, CaO, K2O, MgO and Al2O3. The mathematical model is relatively accurate with real ash melting temperatures and reaches accuracy about of 90 % compared with ash melting temperatures obtained by STN ISO 540 method in a laboratory.

Chemical Looping Combustion and Gasification: A Review and a Focus on European Research Projects

“…In order to optimize the behavior of biomass and wastes due to their composition, the study of solid fuel pretreatments constitutes a relevant branch of research about thermochemical conversions, for example, by torrefaction, ,− washing/leaching, ,,,,− or the addition of chemical additives (which can reduce the ash concentration, increase the ash melting point, and/or change the chemical properties of ashes). , …”

Analysis of paper sludge pellets for energy utilization

“…The meltability of ash is characterized by the physical state of the ash, which occurs during the heating process under well-defined conditions in a furnace. During the melting of ash, the following four temperatures were monitored (Holubcik 2013):…”

The Increase of Silver Grass Ash Melting Temperature Using Additives

“…From the chemical point of view, biomass ash consists mostly of a mixture of oxides of inorganic elements K2O, Na2O, CaO, MgO, Fe2O3, Al2O3, SiO2, P2O5, while their distribution in biomass is very variable (Fig. 1) [4]. Fuel quantity depends on conditions under which the combustion process takes place [5].…”

“…Due to low values of the deformation temperature or ash melting temperature of some types of biomass, in the case of imperfect control in the combustion unit, the combustion temperature can exceed the critical value and, consequently ash sinters and sticks are formed on the heat exchanger surface and other components of the combustion unit, which reduces thermal efficiency of the device. Sinters, slags and sticks heat the combustion chamber with radiation, which results in the temperature increase of released exhaust gases [4]. Large pieces of sintered ash can mechanically damage parts of the combustion unit.…”

“…Table 1. Phytomass ash melting temperatures in a dry state [4] Ash can cause various problems in the combustion devices, e.g. it can prevent from heat transfer in heat exchangers, cause corrosion, preclude cleaning and ash removing, throttle the supply of fuel and combustion air and many others.…”