Effects of deposition and fouling on thermal behaviour of glass furnace regenerators

A model is presented to predict the decrease of the thermal performance of glass furnace regenerators due to fouling by flue gas condensates. The model consists of 4 parts: a description of the thermal performance (heat transfer) of regenerator checkers; a description of chem. reactions in and deposition from flue gases in the regenerator; a description of the heat transfer in the furnace combustion chamber; and detn. of volatilization of S, chloride, and Na components from the melt. The aging and the redn. of the thermal efficiency due to fouling has been predicted for different checker-work constructions, as a function of the pull rate, as a function of glass melt temps., and as a function of the applied cullet fraction in the batch. Depending on the different conditions, the predicted increase in energy consumption is a few percent per yr, mainly due to fouling. Cruciform and chimney block checkers seem to be less sensitive to this fouling than pigeonhole and basket-weave packings. As glass melt temps. increase, dust emissions and fouling rates increase. The model is in quite good agreement with practical observations in industrial furnaces. [on SciFinder (R)

Comparative study on energy-saving technologies for glass furnaces

A review, with 57 refs., compares various new technols. for increasing the efficiency of glass-melting furnaces. The most important technols. are: batch and cullet preheating, using a fluidized bed for batch preheating and dust filtration; thermochem. recuperators using a reformer; O2 burners; advanced air preheat systems like ceramic recuperators; twin-bed burners; and new combustion technologies. The energy savings of these different measures for an industrial glass furnace was calcd. by an energy-balance model. A soda-lime glass furnace with a prodn. rate of 250 metric tons glass per day was chosen as an example for making these comparisons. Melting of batches with up to 100% cullet may have addnl. advantages for the energy consumption because of the possible lower melting temps. needed to remelt pure cullet without other raw materials. Batch and cullet preheaters are the most important systems for the near future. Besides the improvement of the energy efficiency, the impact of some of the mentioned energy-saving technologies on the redn. of the emission of pollutants like dust, NOx, SOx, chlorides, and fluorides seems to be promising. [on SciFinder (R)

Effects of deposition and fouling on thermal behaviour of glass furnace regenerators

A model is presented to predict the decrease of the thermal performance of glass furnace regenerators due to fouling by flue gas condensates. The model consists of 4 parts: a description of the thermal performance (heat transfer) of regenerator checkers; a description of chem. reactions in and deposition from flue gases in the regenerator; a description of the heat transfer in the furnace combustion chamber; and detn. of volatilization of S, chloride, and Na components from the melt. The aging and the redn. of the thermal efficiency due to fouling has been predicted for different checker-work constructions, as a function of the pull rate, as a function of glass melt temps., and as a function of the applied cullet fraction in the batch. Depending on the different conditions, the predicted increase in energy consumption is a few percent per yr, mainly due to fouling. Cruciform and chimney block checkers seem to be less sensitive to this fouling than pigeonhole and basket-weave packings. As glass melt temps. increase, dust emissions and fouling rates increase. The model is in quite good agreement with practical observations in industrial furnaces. [on SciFinder (R)

Modeling of sand grain dissolution in industrial glass melting tanks

A combination of a microscale and a macroscale model, describing dissoln. of sand grains in batch blankets or in the molten glass, is presented. The macroscale model is based on a 3-dimensional calcn. procedure to det. the temp. distributions and the flows in industrial glass-melting tanks. With microscale models, using mass transfer relations for diffusional transport, the dissoln. rate of single sand grains can be calcd. The dissoln. of the sand is detd. by following a large no. of single grains during their trajectories through the batch blanket and the molten glass in the glass melting tanks. The dissoln. rate of a sand grain is calcd. for the temps. and flow conditions in every vol. element in the tank through which the grain proceeds. The dissoln. rate in the batch blanket depends strongly on temp. and the stage of the dissoln. process. Initially the very fast shrinkage rate of the grain as temps. exceed 1200 Deg results within 10 min in the dissoln. of more than 50% of the sand in the blanket. Forced and free convection in the glass melt leads to increase in the dissoln. rate, up to a factor 5 compared to motion-free conditions. Forced bubbling for instance results locally in extremely high mass transfer rates and often improves the melting performance of industrial glass furnaces. [on SciFinder (R)

Modeling of the aging of glass furnace regenerators

A model was developed to predict the decrease of the thermal performance of glass furnace regenerators due to fouling by flue gas condensates. The model consists of 4 parts: a) description of the thermal performance (heat transfer) of regenerator checkers; b) description of the heat transfer in the furnace combustion chamber; c) detn. of volatilization of S, Cl, and Na components from the melt; and d) modeling of chem. reactions in the deposition from flue gases in the regenerator. The aging and the redn. of the thermal efficiency due to fouling was predicted: for different checkerwork constructions or refractory types; as a function of pull rate; as a function of glass melt temps.; and as a function of applied cullet fraction. Depending on the different conditions, the predicted increase in energy consumption is .apprx.1 up to >3% per yr, mainly due to fouling. Cruciform and chimney block checkers seem to be less sensitive for this fouling than basketweave packings. As molten glass temps. increase, dust emissions and fouling rates are going up. According to the model calcns., a higher cullet fraction in the batch will lead to reduced aging rates of the regenerators. The model is in quite good agreement with practical observations in industrial furnaces. [on SciFinder (R)

Modeling of sand grain dissolution in industrial glass melting tanks

A combination of a microscale and a macroscale model, describing dissoln. of sand grains in batch blankets or in the molten glass, is presented. The macroscale model is based on a 3-dimensional calcn. procedure to det. the temp. distributions and the flows in industrial glass-melting tanks. With microscale models, using mass transfer relations for diffusional transport, the dissoln. rate of single sand grains can be calcd. The dissoln. of the sand is detd. by following a large no. of single grains during their trajectories through the batch blanket and the molten glass in the glass melting tanks. The dissoln. rate of a sand grain is calcd. for the temps. and flow conditions in every vol. element in the tank through which the grain proceeds. The dissoln. rate in the batch blanket depends strongly on temp. and the stage of the dissoln. process. Initially the very fast shrinkage rate of the grain as temps. exceed 1200 Deg results within 10 min in the dissoln. of more than 50% of the sand in the blanket. Forced and free convection in the glass melt leads to increase in the dissoln. rate, up to a factor 5 compared to motion-free conditions. Forced bubbling for instance results locally in extremely high mass transfer rates and often improves the melting performance of industrial glass furnaces. [on SciFinder (R)