Combustion Behavior Of Blends Research Articles

Co-combustion characteristics of lignite/woody biomass blends. Reactivity and fusibility assessment

ABSTRACT Present work aimed at investigating the combustion behavior of lignite/woody biomass blends, in terms of ignition, reactivity, burnout temperature and time and at evaluating any synergy effects, by carrying out thermogravimetric analysis tests. Furthermore, it aimed, by applying a simple method for removing problematic ash elements, to examine their role on the combustion behavior of blends, as well as on mitigation of deposition problems in boilers co-firing such fuels, through mineralogical and fusibility analyzes. Fuels ignition occurred between 205 and 215°C, whereas the thermochemical reactivity followed the order: wheat straw>acacia pruning>cotton residue>lignite. The combustion performance and fusibility behavior of lignite were improved by blending it with the woody fuels. Some synergistic interactions occurred between component fuels. Alkali minerals increased the reactivity of acacia pruning and wheat straw in air and corresponding mixtures with lignite, while acted as diluents in cotton residue combustion. The slagging/fouling propensity of lignite/leached biomass mixtures was reduced.

Non-isothermal thermogravimetric investigation on mutual effect between bituminite and anthracite in blends for blast furnace injection

In order to clarify the mutual effect between bituminite and anthracite in blends during industrial combustion, the influence of particle size and heating rate as well as oxygen concentration in atmosphere was analyzed. The results of non-isothermal thermogravimetric analysis indicated that the combustion behavior of blends was of great difference though blends were prepared with the same volatile content of 20%. The catalysis of bituminite to anthracite changed with the thermal and kinetic condition of combustion reaction, and consequently, blends with different collocations were suitable for various combustion environments. Superior combustion properties of some blends were achieved at high heating rates, while others might react faster under high oxygen-enriched atmosphere. Simultaneously, the volume model and unreacted core model as well as random pore model were introduced to fit the experimental data. The kinetic calculation results showed that the combustion of blends at different heating rates all agreed better with that of random pore model in comparison with the other two models, while the apparent activation energy of samples all decreased with the increase in heating rate. The similarity of functional group structure between bituminite and anthracite is closely related to the accordance in combustion stage of bituminite and anthracite in blends.

Characterisation of coal blends for pulverised fuel combustion

This study evaluates the effect of blending on the combustion characteristics of pulverised coal through the testing of six coals and fifteen coal blends in an isothermal plug flow reactor (IPFR). The aim of the test was to assess whether the combustion behaviour of blends could be predicted from that of the parent coals. For blends of bituminous coals, an additive behaviour was found for ash, volatile matter and calorific value. Other non-standard fuel properties such as the high volatile matter content determined using the IPFR, fuel-N release and char combustion, were found to be additive. The blends of bituminous coals and lignite demonstrated non-additive properties as far as volatile matter release is concerned. It was concluded that the inorganic coal phase is responsible for non-additive behaviour in blends, since the volatile components of the coal mineral matter may undergo reactions with the second blend partner.