本发明提供了一种钢铁厂低品质余热利用系统及其使用方法，所述系统包括：一级换热装置，用于在第一流体与第二流体之间传热，所述第一流体为除盐水，所述第二流体为高炉冲渣水；二级换热装置，用于在第三流体与第四流体之间传热，所述第三流体为从所述一级换热装置流出的除盐水，所述第四流体为高温烟气；闪蒸装置，与所述二级换热装置连通，从所述二级换热装置出来的除盐水进入闪蒸装置中转化为蒸汽用作海水淡化装置的热源以蒸发得到海水蒸馏水。本发明采用钢铁厂的高炉冲渣水、烟气余热等低品质热源来替代低温多效海水淡化的热源，有效利用了余热，并且降低了低温多效海水淡化生产的成本。

The present invention provides a low-quality waste heat utilization system of a steel plant and a use method thereof. The system includes: a primary heat exchange device for transferring heat between a first fluid and a second fluid, the first fluid being Demineralized water, the second fluid is blast furnace slag flushing water; the secondary heat exchange device is used to transfer heat between the third fluid and the fourth fluid, and the third fluid flows out of the primary heat exchange device The demineralized water, the fourth fluid is high-temperature flue gas; the flash vaporization device is connected to the secondary heat exchange device, and the demineralized water from the secondary heat exchange device enters the flash vaporization device to be converted into steam for use The heat source of the seawater desalination device evaporates to obtain distilled seawater. The invention uses low-quality heat sources such as blast furnace slag flushing water and flue gas waste heat of steel plants to replace the heat source of low-temperature multi-effect seawater desalination, effectively utilizes the waste heat, and reduces the production cost of low-temperature multi-effect seawater desalination.