US 8,956,424 B2Granted

Method and apparatus for sequencing-batch purification of potassium nitrate from solid waste produced by glass-strengthening process

AssigneeNational Formosa University

InventorMin-Hui Yang

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Abstract

Provided is a method and an apparatus for purifying potassium nitrate from the solid waste produced by a chemical glass-strengthening process. In the method, the solid waste is melted into a liquid waste at first. Potassium nitrate of various purity grades can be obtained by batch processing the liquid waste through stepwise cooling processes of cooling the liquid waste to a first temperature facilitating the potassium nitrate contained in the liquid waste to be crystallized at a first rate and then cooling the liquid waste to a second temperature close to the freezing point of the potassium nitrate at a second rate that is slower than the first rate. The recovered potassium nitrate from the solid waste can be recycled and reused.

Claims20

Dependent claims

A purification method for recovering potassium nitrate from a solid waste that is produced by a glass-strengthening process and contains potassium nitrate and sodium nitrate, the purification method comprising the steps of:

(a) heating the solid waste to a melting temperature to melt the solid waste into a liquid waste in a first purifying tank;
(b) cooling the liquid waste from the melting temperature to a first temperature for facilitating the potassium nitrate contained in the liquid waste to be crystallized as potassium nitrate crystal attached to a sidewall of the first purifying tank at a first rate;
(c) cooling the liquid waste from the first temperature to a second temperature that is substantially close to the freezing point of the potassium nitrate at a second rate that is slower than the first rate;
and
(d) collecting the potassium nitrate crystal.

2 more elements

Dependencies are inferred from the claim text.