硝酸钙溶液自然循环低温预浓缩实验研究

Experimental Study on the Preconcentration of Calcium Nitrate Solution in Natural Circulation Under Low Temperature

针对我国磷矿品位下降给硝酸磷肥的生产带来的困难,磷矿酸解液的结晶除钙面临巨大的挑战,采用低温热源实现酸解液的预浓缩是冷冻法结晶除钙应对磷矿品位不断下降并实现低位热能利用的有效举措。将自然循环系统应用于硝酸钙溶液的预浓缩,采用低温余热作为热源,维持进料在20℃～25℃之间蒸发浓缩,浓度在45%～55%之间变化,蒸发管内传热Nusselt数仍然可以保持在28.4～36.7,易于实现低温浓缩操作的连续化,适用于低温热源的利用,具有较大的工业开发价值。

With the continuous decline in phosphate rock grade, the production of nitric-acid phosphate becomes diffi- cult and the removal of calcium from nitric acid hydrolysis solution is faced with huge challenges. In response to the above and in order to make good use of low temperature heat energy, the pre-eoncentration of solution through low temperature heat source is an effective way to remove calcium. Applying the natural circulation system to the pre-coneentration of calcium nitrate solution, using the low temperature waste heat as heat source, with the evaporation concentration of the feed being conducted under the temperature of 20℃ - 25 ℃ and the concentration being 45% -55%, （wt%） the inside tube＇s Nusselt number for evaporation can keep from 28.4 to 36.7. In this way, the continuous operation could be obtained and the low temperature waste heat can be made full use of. therefore it is of great value in industrial development.