Study On The Application Of A New Decoppering Technique In Refining Of Lead Bullion

Nowadays, most factories decopper by adding S directly in refining lead bullion. The principle of this conventional process is that PbS is obtained through the reaction of S and Pb firstly, and then Cu₂S exist because of the reaction between PbS and Cu, the Cu₂S slag was drown off through the process of skims for the the density of Cu₂S is smaller than that of lead. However, there is a big problem with this method. The temperature of this refining process is so high that the chemical reaction process is difficult to be controlled and a lot of S will be wasted , because S can be burnt at 248-261 ℃. So, many problems such as air pollution resulted from SO₂, much waste of S and high production cost will exist associated with the combustion of S.In order to resolve this problem, we divide the decoppering process to two steps and invent a new method to decopper from lead billion. Firtsly, we stabilize the element S by changing S to PbS;secodly, we add PbS in decoppering.so the way which S is used become the key to this problem,and it just is the creatation of this experiment.Therefore, according to the theory of PbS can be dissolved in lead and the density of PbS is much higher than S, we invented a new craftwork , it is adding PbS take the place of S in decoppering. Before the experiment, the thermodynamics and kinetics analysis on the preparement of PbS and decoppering reaction was carried out, which provides the academic support for the experiment.In this paper, the preparation of PbS and decoppering by adding PbS are our main work. To stand out the superiority of the new craftwork ,we study the impact of percent overcharge of sulphur, heating temperature and heating time on percent formation of PbS was investigated, and the percent overcharge of PbS and agitation time for decoppering from lead bullion were taken into account too.According to the experimental results of PbS preparement, we can draw three conclusions. Firstly, the percent formation of PbS is over 92% when the percent overcharge of S ranges from 22% to 33%, and the supreme value 95.5% was achieved when the percent overcharge of S is 25%;secondly, the percent formation of PbS is over93% when the heating time ranges from 6.5h to 8.5h , which comes up to largest when the heating time is about 8h;thirdly, the percent formation of PbS is over 96% when the heating temperature ranges from 340 °C to 400°C, and the maximal value 98.7% is obtained when the heating temperature is 380°C. Therefore,we believe that the experimental conditions when percent overcharge of S is 20%, heating temperature is about 35O°C and heating time is 8 are suitable.Moreover, in terms of the experimental results of decoppering, we can make another two conclusions. The first is that Cu content in decopperized lead bullion is about 0.01% when the percent overcharge of PbS ranges from 20% to 25%;the Cu content in decopperized lead bullion is lowest when the agitation time is about 0.5h. From the result of the experiment, we can see, the use factor of S comes up to 92% and which is much higher that of traditional method, furthermore, the content of the lead bullion dropped from 0.814% to 0.01 l%,and the decoopering rate can arrive to 98.65%.In a word, the result of decoppering is good and the use factor of S is ideal, the use factor of S is very high. This new decoopering technique has a good application prospect and is worthy to lucubrate.