Production Practice of Benefited Ingredients in Oxygen-enriched Bottom Blowing Process

1 Introduction:

A lead-zinc smelter currently has three lead-smelting lines that use an oxygen-enriched bottom blowing process. It produces about 250,000 tons of crude lead, 236,000 tons of 98% sulfuric acid, and 20,000 tons of zinc oxide. Subsequent deep-processing and recycling processes will produce 3,300,kg of gold, 510 tons of silver, 1,900 tons of white and 340 tons of fine enamel.

The plant handles about 510,000 tons of lead-containing materials each year, including a large amount of high-concentrated lead containing ZnO, Au, Ag, Cu, Sb, Bi and other valuable elements. In recent years, the plant has been making efforts to develop a recycling economy and expanding the lead recycling industry. At present, it can stably recycle 150,000 tons of lead paste in lead-acid batteries every year. In addition, the plant's zinc smelting system and lead smelting deep processing system return to the raw material process every month to participate in the re-equipment of various types of intermediate materials in more than 3000t, which is rich in Pb, Au, Ag, Sb and other valuable elements. Material structure and elemental composition of raw materials processed by the lead smelting system of the plant.

1. With a stable bottom furnace throughput, the higher the Pb, ZnO, and S grades in the pellets, the greater the yield of crude lead, sub-zinc oxide, and 98% sulfuric acid produced directly by the bottom-blowing system. .

2. The greater the investment amount of high-silver lead or gold ore, the greater the output of gold and silver recovered by subsequent deep-processing operations;

3, high-grade lead paste containing Pb grade, if a large number of investment can effectively increase the production of crude lead;

4. Intermediate slag contains lower Pb grades, but its high grade is rich. If it can be used in time, it can increase the output of by-products.

In the production practice, it is necessary to comprehensively consider various types of material inventory, operation conditions of furnace and kiln equipment, and market conditions, and adjust the mix structure in a timely manner so that the company will have the greatest economic benefits. For Pb-rich materials rich in associated elements, it is called profitable minerals.

In the industry, the self-sufficiency rate of ore fines has continued to decline, and high-quality ore sources have been gradually depleted. It is no longer competitive to rely solely on the output scale to obtain benefits.[1] As the largest electrolytic lead and silver producer in China, this plant has actively explored a clean and efficient green and sustainable smelting road in recent years. The implementation of benefit-based ingredients is one of the important components.

2, the existing ingredients process problems :

In order to ensure the production of crude lead, sulphuric acid, and sub-zinc oxide in the production process of the bottom-blowing furnace, the high-Pb, high-ZnO, and high-S materials are prioritized before the benefit-based batching work. The mineral powder that is partially rich in Cu, Sb, Bi and other deep processing and recovery elements cannot be put into use in a timely manner, and the output of the recovery process products fluctuates greatly, which affects the recovery efficiency.

In addition, a large number of high-grade ore fines have been put into use, which has led to an extension of the inventory cycle of some low-grade ore fines and also caused difficulties in the management of the material inventory yard.

2.2 Long time inventory of gold mines and high silver mines

In the oxygen-enriched bottom-blown lead process, gold and silver are trapped in crude lead, and after electrolysis, they are recovered in the anode slime of the residual anode. The anode mud is then subjected to pyrometallurgical refining and electrolysis yields gold and silver. It can reach 10d or more.

Due to the low Pb content in the gold ore, the grade of Pb in the mixture will be decreased during the application, which will affect the crude lead production. At the same time, since the Pb content in the high-silver ore is generally less than 50%, the amount of Pb used in the blending is lower, so the inventory period of gold and silver mines Can reach 20d or more, gold and silver from the mineral powder into products, processing cycle can reach more than 30d.

2.3 Less investment in lead paste and intermediate slag, taking up large amounts of funds

Because of the large amount of sulfate and lead oxides contained in the lead paste, the melting process in the oxygen-enriched bottom-blowing furnace can cause high smoke and dust rates and low lead deposition rate. [1] Therefore, in the past, the factory produced its own regenerated lead paste. It cannot be dealt with promptly and completely, causing a backlog of inventory.

In addition, the intermediate slag Pb, Fe, S and other elements of low grade, will result in Pb, S grade drops in the mix, affect the furnace heat balance and the FeO-SiO2-CaO slagging system balance, it has not been timely Investment, resulting in increased inventory.

It can be seen from the above that under the circumstance of pursuing output alone, gold and silver materials, self-produced lead paste, and intermediate slag cannot be put into use in a timely manner, resulting in a large backlog, resulting in excessively high proportion of the company’s funds, seriously affecting the company’s capital turnover, and increasing Company operational risk. It is imperative to reduce intermediate stocks by making profitable ingredient explorations.

3, efficiency of ingredients and its effects :

3.1 Increase the proportion of lead paste investment

The oxygen-enriched bottom-blowing lead process has the characteristics of strong material applicability, low energy consumption and high metal recovery rate [3]. The plant decided to change the proportioning structure of the material in response to the serious backlog of lead paste. In April 2014, an experimental group was set up to improve the proportion of lead paste. Through the experimental process of nearly four months, it was found that in the case of 40% of lead paste, 25% of gold ore, and 35% of lead concentrate in the mixture, the conditions of the bottom-blowing furnace were stable, and the process indicators were normal. At this point, the average grade of the ball into the furnace is as follows:

By increasing the proportion of lead used, experiments were conducted to further understand the ingredients model that maintains the heat balance in the oxygen-enriched bottom-blowing furnace and the balance of slag-forming elements, laying the foundation for the next experiment. After a year of experimental exploration, the plant has reached the point where the self-produced lead paste is put into use, and inventory is reduced to less than 10 days, which greatly reduces the middle occupancy of funds.

3.2 The single-use of gold and silver mines and the increase of slag consumption

In view of the strong adaptability of materials to oxygen-enriched bottom-blown lead furnaces, short furnace time, and easy-to-adjust furnace conditions, the plant decided to separate stocks of gold and silver ore, not to participate in mixed ingredients, and to directly use batching belts to reduce Its investment cycle.

In the process of investment in gold and silver mines, the following problems have arisen:

1. When the investment amount of gold and silver deposits is large, the furnace temperature rises significantly and the SO2 gas concentration increases significantly;

2. The grade of pellets Pb has decreased, and the production of crude lead has decreased;

3. The ZnO grade in high lead slag decreased, and the output of secondary zinc oxide decreased.

Later, after many studies, based on the experiment of increasing the proportion of SO2 and increasing the production of crude lead, the proportion of lead paste was increased. Further testing of different material ratios to finalize the lead concentrate mixture: gold ore: silver ore: lead paste is around 4:1:1:4, which can ensure that the ball grade Pb grade is above 48% and the S grade is 16%- 18%, after the use of the furnace, the furnace conditions are stable and the indicators are normal.

The intermediate slag accumulation in the plant is mainly the silver slag produced by the silver flotation section of the zinc system leaching process. From Table 1, it can be seen that the ZnO-containing grade also reaches a relatively high level, and the high-lead slag after the single lower gold and silver mine is used. In the case of decreasing ZnO grade, the proportion of slag in the lead mixture was continuously increased. The proportion of slag in the mixed ore was increased from 10% to less than 15%. The ZnO grade in the mixture increased from 6% to 7%. To 9%, zinc oxide production returned to normal.

After the above measures, the use of gold and silver deposits is guaranteed within 10 days after entering the factory, shortening the processing cycle. At the same time, the amount of miscellaneous materials in stocks has also dropped significantly.

3.3 Reasonable use of high-enriched ore fines

The three oxygen-enriched bottom-blown furnace smelting systems of this plant differ from each other by several years in terms of production time. Because the design production capacity, equipment performance, and production capacity improvement space are all different, the composition requirements of the materials vary.

The direct lead-smelting production line put into production in 2010 is the first oxygen-enriched bottom-blowing oxidation-liquid high-lead slag directly reduced in China—a liquid lead-free copper-cast anode production line. The dust collection system of the production line has a large amount of redundant design, and has a good dust collection effect. It can also ensure a good dust collection effect in the case of increased smoke and dust in the furnace. Therefore, the ore fines with higher ZnO grades will be used in the direct-smelting system. Because the high ZnO content in the ore fines will result in a large amount of soot in the reduction furnace, the soot tends to be sticky, and the dust collection system of the direct lead smelting production line can be well resolved. The above problem.

At the same time, the Sb and Bi containing higher slag and slag are also used in the direct smelting system to adjust the content of Sb and Bi in the liquid crude lead. After the copper is removed, the anode plate contains 0.5% of Sb. 1.2% to ensure that the anode mud has enough strength not to fall off in the electrolytic cell. Therefore, the Sb grade of the mixture in the direct-coupled system is more than 0.8%, and the yield of crude lead containing Sb is in the range of 0.8%-1%. It is not necessary to add high Sb crude lead in the electrolytic system to reduce the processing cost.

In addition, for mines with high Cu content, they are mainly used in two other production lines. The final output is coarse lead containing more than 0.1% Cu. The lead is pulled to the electrolysis plant and recycled lead is used in addition to the copper cast anode to ensure that the anode plate contains Cu is below 0.05%. Targeted blending with high-enriched ore fines has reduced the recycling process for valuable metals, reducing return refining losses and increasing recovery.

3.4 CRT lead glass instead of quartz sand

In the oxygen-enriched bottom-blown process, quartz sand and limestone are used as fluxes to adjust the slag type in the furnace. After investigation, the technicians of the plant found that the glass scrapped and recovered from cathode ray tube television sets contains lead, namely CRT lead glass. Such glass contains Pb20% and SiO2 60%-70%. At present, China has entered the peak period of CRT TV retirement. According to statistics, the amount of lead metal in abandoned CRT glass has reached about 20,000t/d each year [4]. The price of Pb elements in CRT lead glass is lower than the market price by 5,000 yuan/t or so. If it can be completely replaced by quartz sand, it can create better economic benefits under the conditions of sufficient market supply.

In May 2015, the plant started experimenting with CRT lead glass instead of quartz as a fluxing agent. After adjustment of the batch ratio, the Fe:SiO2 in the furnace reaches a stable state of 1.5-2 when Fe is added to the single gold deposit. The dosage of lead glass can reach 16t/d, the slag in the furnace has good fluidity, and the experiment has been successful.

The plant has now completely used CRT glass instead of quartz sand, and it is estimated that about 900 tons of lead metal will be recovered in a year, generating more than 4.5 million yuan in profit.

3.5 Using Effective Budget Software to Guide Ingredients

In order to further develop benefit-based ingredients, the plant organizes information, science and technology, and raw materials department personnel to develop ingredient benefit budgeting software. For each type of ore fines, the purchaser of raw materials fills in the pricing formula for each element according to the contract, and then the production department supplements the test results of the specific types of elements. During the batching, only the amount of pre-dosage is input behind the corresponding types of mineral powder. The software can calculate the unit weighted processing benefit (yuan/t) for the batch of materials. The technicians can adjust the bill of material according to the calculation results to achieve Optimal ratio.

6. Conclusion :

Through more than one year of efficiency-based batching practices, the plant has effectively reduced self-produced lead paste and intermediate slag inventory and reduced the backlog of funds. Through the rational allocation of investment methods, the investment of gold and silver materials into the plant within 10 days has been completed, the recovery process of high-rich ore fines has been shortened, and the valuable elements have been promptly output to the finished product. Through the use of efficiency budgeting software, the ingredients are digitized and refined, providing data support for raw material procurement.

With the development of non-ferrous industry technology, it has become an inevitable trend to develop profitable ingredients and increase the metal recovery rate. According to its own process conditions and material structure, the plant has actively explored beneficial ingredients and has achieved beneficial results. The goal of double-growth in output and efficiency has taken a solid step. It also has positive promotion value in the industry.