Sustainable Mining and Metallurgy

Abstract:In the process of domestic waste incineration, a large number of off-gas containing pollutants is produced. Aiming at the requirements of ultra-low emission of waste incineration off-gas pollutants in the future, this paper combined the deep desulfurization technology and the deep denitrification technology, introduced process, principles, advantages and disadvantages of the whole process of SCR denitrification combined with wet deacidification and eliminating white mist, the whole process of efficient SNCR denitrification combined with wet deacidification with acoustic temperature measurement system and the whole process of PNCR denitrification combined with wet deacidification. By comparing the above off-gas cleaning process solutions, three recommended technical routes of the whole process were given.

Abstract:This paper studied the impact of a series of new policies affecting domestic waste incineration power generation price subsidies jointly issued by the Ministry of Finance and Treasury, the National Development and Reform Commission and the National Energy Administration in 2020 on waste incineration power generation enterprises. Under these new policies, the subsidy is given following the principle of Payment According to Revenue. There are four subsidy methods: the current benchmark power generation electricity price of 0.65 yuan KW-h is maintained for the stock projects, the new projects connected to the grid in 2020 contend for the 1.5 billion yuan quota, the subsidy for the new added projects started up in 2020 is apportioned by the central and local governments, and the new projects that have not yet been started in 2020 are to be connected to the grid by competitive price bid. In addition, these new policies also prescribed the upper limit for the quantity of generated power to be subsidized, 15 years after the project is connected to the grid, it no longer enjoys the subsidy funds from the central government, the green certificate is issued and the green certificate transaction is allowed. Finally, the domestic waster to power plant project in Hebei Province was taken as an example to calculate the subsidy amount according the new policies.

Abstract:This paper briefly introduced the development status of increasing anode height, and compared the electrolytic cells of the heights of 650mm and 710mm in terms of increased power consumption by increasing voltage drop, anode conduction velocity, electrolytic cell stability, etc. It can be known that after the anode height is increased, the increase of voltage drop will lead to the increase of power consumption, the anode current distribution tendency of the two type electrolytic cells is uniform, and the conduction velocity has no obvious difference; the stability of the cell with 710mm high anode is better than that with 650mm high anode. The increase of anode height reduces material consumption, electricity, direct labour and transportaiton costs, which can generate an annual revenue of about 18.65 million yuan and can achieve good environmental effect.

Abstract:In order to improve the efficiency of off-gas collection of electrolytic cell and reduce the fugitive emission of off-gas, the off-gas flow field inside the two NEUI 600kA electrolytic cells was measured. It was found by analyzing the testing data that in the direction of X, the off-gas temperature distribution inside the hood of the two cells had the tendency of being high in the middle and low on both sides, and the position of the highest temperature was not fixed; for all the two cells, the off-gas temperature was higher in the aluminum end than that in the off-gas end; the overall negative pressure inside one of the two cells was relatively uniform, but some specific positions had large negative pressure fluctuations, some positions were even in positive pressure status; the negative pressure of the other cell had the tendency of being large in the middle and being small in the off-gas duct end and the aluminum outlet end. The data of off-gas temperature and pressure showed that the internal off-gas flow field was basically in agreement with the design; the off-gas volume and negative pressure at the electrolytic cell outlet were also consistent with the design values.

Abstract:The precipitation in the furnace bottom of electrolytic cell will increase the energy consumption per ton of aluminum, and disturb the stability of magnetic field distribution, as to make the inner shape of the hearth irregular and impose bad influence on the electrolytic cell production. This paper summarized the effect of magnetic field distribution, molecular ratio, electrolyte level, aluminum level, covering material, anode effect and other production conditions on the formation and elimination of bottom precipitation. It is shown by analysis that the precipitation at the bottom of the furnace can be effectively eliminated by appropriate measures such as raising the electrolytic cell voltage and the molecular ratio of electrolyte, adjusting the aluminum level and strengthening the thermal insulation at the top of the electrolytic cell, etc.

Abstract:The amount of carbon dross is an important index of the performance of reactive pre-baked anode in aluminum electrolysis. The generation of carbon dross and quality fluctuation of anode are related to the non-standard operation of aluminum electrolysis. There are many factors affecting the quality of anode, including the quality of raw material, the formula of raw materials, the production process and so on. This paper introduced the practice of the carbon-dross-free anode production technology in the aspects of anode production raw material preparation, forming process improvement, roasting process operation. Processing aggregate calcined coke is prepared by mixing technology ; the storage temperature of binder coal tar pitch should be controlled, and the content of components and trace elements should be homogenized by mixing different quality asphalt, and the residual anode should be treated by advanced residual anode cleaning technology; the anode block forming process and the roasting process were optimized；the anode surface was treated. Finally, the anode quality was gradually improved and the amount of carbon slag was continuously reduced.

Abstract:Aiming at the problem of large off-gas flow of 180kA electrolysis series in an electrolytic aluminum plant, measures were taken to adjust the opening of off-gas valve and clean up the accumulated material in the gas collecting system. The statistical data showed that after the regulation, the off-gas flow under standard conditions dropped from 8075Nm ³/h of before regulation to 5086Nm ³/h, the heat dissipation of the off-gas dropped from 0.617V of before regulation to 0.529V; the DC power consumption has been lowered by 92kW·h/t-Al, and the power consumption for cleaning was reduced by 30kW·h/t-Al. In conclusion, the off-gas flow regulation and control have achieved ideal effect.

Abstract:A large amount of waste mineral oil is produced in industrial production, which has high use value. The traditional waste mineral oil regeneration processes includes distillation-acidic-white clay process, distillation-hydrogenation process and distillation-solvent rectification process. These processes have the disadvantages of poor product quality, poor production continuity and being easy to generate large quantity of secondary hazardous waste. In this paper, based on the traditional processes, the process of Rectification under vacuum+Centrifugal extraction+Solvent refining was adopted to handle the waste mineral oil. After being treated by such processes as pre-treatment, normal pressure dewatering, centrifugal extraction, solvent refining, product refining, etc., the base oil product can be obtained to realize the resource recovery of waste mineral oil. Moreover, the impact of extractant use amount, operating temperature of rectification under vacuum and reflux ratio on the process recovery, product quality and economic results was also analyzed. In production, appropriate solvent-oil ratio, operating temperature and reflux ratio should be selected.

Abstract:In order to understand the changes of soil acidification and nutrient distribution at different slope positions of extremely acidified waste dump,taking three typical waste dumps as the research object in Xinshan Area of Dabaoshan Mine in Guangdong Province, the changes of soil pH and net acid generation test, and the distribution differences of soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available nitrogen (AN), available phosphorus (AP) and available potassium (AK) at different slope positions were analyzed. The results showed that:(1) The pH value range of 0~100cm layer at the slope toe of the waste dump was 1.96~3.76, which meant the soil was strongly acidic. The acid production capacity of soil was medium or high in 0~20cm layer, which had the trend of slope middle ＜ slope top ＜ slope toe;(2) The average content of SOM in 0~20cm soil layer had the trend of slope toe ＞ slope middle ＞ slope top, and the variation ranges were 0.24~2.32g/kg, 0.53~1.83g/kg and 1.28~1.55g/kg, respectively;the average content of TN had the trend of slope toe ＞ slope top ＞ slope middle, the higher slope toe was 0.25g/kg; the average contents of TP and TK were high, which were 1.00g/kg, 1.02g/kg, 0.94g/kg and 44.74g/kg, 48.59g/kg and 47.81g/kg at the slope top, slope middle and slope toe, respectively;the average content of AN had the trend of slope toe ＞ slope top ＞ slope middle, which were 54.37mg/kg, 34.53mg/kg and 26.60mg/kg, respectively; The average contents of AP and AK at the at the slope top, slope middle and slope toe were 3.52mg/kg, 2.52mg/kg and 2.15mg/kg and 36.67mg/kg, 36.67mg/kg and 38.33mg/kg, respectively; (3) The soil fertility index (SFI) in 0~20cm soil layer along different slope positions was 0.28~0.52, which had the trend of slope toe ＞ slope top ＞ slope middle.

Abstract:By taking a copper smelter project in northwest China as the research object, based on the hydrogeological investigation, the groundwater flow model and solute transport coupling model were established by using Visual MODFLOW to analyze the transport law in the groundwater environment of the characteristic contaminants under the condition that waste acid leaks from the copper refining plant under abnormal working conditions. The prediction results showed that during the whole simulation period, SO^2-₄ pollution halo migrated with groundwater flow, and its concentration and pollution range increased first and then decreased gradually. The monitoring results of two downstream virtual observation wells showed that the pollutant concentration was lower than the standard requirements. The prediction simulation helps enterprises to reduce the risk of groundwater pollution and ensure the quality and safety of production.

Abstract:By combining with the production practice of copper smelting slag beneficiation of different stages in a certain company, analysis was made of the rationality of different beneficiation process flows for treating electric furnace slag, converter slag and mixed slag. As was shown in the analysis results, it was beneficial to the improvement of slag beneficiation indexes that the two-stage continuous milling and flotation process was adopted for electric furnace slag with low copper grade and fine copper mineral particle size, and the staged milling and flotation process for converter slag and mixed slag with high copper grade and uneven copper mineral particle size. At the same time, the relevant data in the current mixed slag beneficiation was analyzed. In view of the existing analysis of low recovery rate of the second roughing operation, large circulation of middlings, low enrichment ratio and recovery rate of concentrate operation, and suggestions were made on the specific measures such as strengthening on-site fine milling, high concentration flotation, etc.

Abstract:Aiming at the problems such as low off-gas temperature, low catalyst activity, unreasonable setting of ammonia injection grid and unreasonable setting of catalyst powder blowing system of the SCR denitration system for the alumina high temperature roasting kiln off-gas under pre-heating condition for a certain company in Shandong, the reconstruction was carried out by taking measures such as adding temperature-raising burner for pre-heating process, using low-temperature catalyst, optimizing and modifying ammonia injection grid and ammonia injection system, rearranging catalyst powder blowing system, etc. After the reconstruction, the off-gas NO_x emission concentration was reduced from 100mg/Nm ³ to below 35mg/Nm ³, and the ammonia injection system operated stably, which have harvested good economic and social benefits.

Abstract:In this paper, for the selection of process solutions of copper smelting off-gas desulphurization, from the aspects of principle, process flow, desulphurization efficiency, process maturity, by-product comprehensive utilization, capital cost, operative cost, etc., comprehensive comparison was made between limestone-gypsum process, double alkali process, sodium-alkali process, ammonia process, hydrogen peroxide process, organic amines process, sodium citrate process and other wet desulphurization process, spray drying method and circulating fluidized bed method and other semi-dry desulphurization process and active coke desulphurization method and other dry desulphurization technologies. It was considered that the wet desulphurization process was still the most widely used and reliable technology in the copper smelting industry, of which the hydrogen peroxide process, organic amines process and other technologies have good development prospect.

Abstract:The original glass fiber demister of the acid-making primary absorption tower of Yunnan Tin Group 100000t/a copper smelting project was easy to corrode due to the high fluorine content in the off-gas, resulting in a large amount of acid mist at the outlet of the primary absorption tower, which corroded the acid making device, affecting the normal production of acid making system and even smelting system. Aiming at this problem, the new type carbon fiber demister was used. The mass of carbon fiber is lighter than that of metal aluminum, but has a strength stronger than steel, which has the characteristics of high hardness and high strength, light weight, good chemical properties and high temperature resistance. After the demister of the primary absorption tower was replaced by the new type carbon fiber demister, the production has been operated for 3 years, no filter-broken by corrosion occured, which meant that this new type demister can meet the process requirements of off-gas acid making for copper smelting.

Abstract:The electrolysis workshop of a certain nonferrous smelter has a set of nickel sulfate cleaning production system, the long-term production results in many equipment problems, which has large room for optimization. On the basis of the existing production mode, the equipment modification was carried out for the concentration reactor repair process, vacuum pump of concentration system, inner jacket of cooling crystallization tank, brine circulating pump, concentration agitation system, etc., and management optimization was made for maintenance cycle, circulating system and pipeline filtration, high energy consumption equipment, among others. The equipment improvement and management optimization have lowered the equipment fault frequency, reduced the system shutdown and hidden troubles in production, which made the nickel sulfate system operate stably and significantly reduced the nickel sulfate energy consumption and spare parts costs.

Abstract:The proved copper reserves in Tibet account for more than half of the national copper reserves, which makes it an important strategic reserve base of copper resources of China.The copper resources in Tibet are concentrated in the Yulong copper metallogenic belt in eastern Tibet, the metallogenic belt in the eastern section of Kailas from Lhasa to Nikazi, and the Bangong Lake-Nujiang River copper metallogenic belt from Bangong Lake in Ngari area to Nujiang River Source in Nagqu area.Based on the analysis of industrial basis, development priorities, the construction conditions and transportation costs of resources in each metallogenic belt area, it was suggested that all the copper concentrate of Yulong Copper Mine be smelted and processed in Qamdo Industrial Park in East Tibet, the copper concentrate from Lhasa area and Ngari area be transported to Tibetan-Qing Industrial Park in Golmud for smelting and processing.And finally, planning was made in terms of plant scale, metallurgical process, use of by-product sulfur, pollution prevention and control, etc.It was suggested that a copper smelter with smelting scale of 350000 tons/a should be built in Qamdo, the smelting process should be oxygen-enriched bottom blowing and side blowing, and SO₂ in smelting flue gas should be used to prepare sulphuric acid.

Abstract:The technical characteristics and progress of typical nickel refining with carbonyl processes at home and abroad were compared and analyzed, the characteristics of carbonyl process under normal pressure, low pressure, medium pressure and high pressure, as well as the breakthrough of nickel refining technology with carbonyl process under medium pressure in Jinchuan Group were summarized, and the existing problems and improvement direction of nickel refining process with carbonyl process under medium pressure in Jinchuan Group were pointed out. The results showed that the carbonyl process under medium and low pressure is the best choice for nickel refining technology improvement.

Abstract:Based on the Chinese Patent Retrieval Database, this paper analyzed the current situation and development trend of the technical branch of smelting method through the statistics data of the patent application trend, applicant type and geographical distribution characteristics of nickel-based superalloy prepared by smelting method in China. The result of the analysis showed that, as basic production method, single smelting method had the most patents, which mainly focused on improving the purity of melt from two aspects namely smelting process and smelting equipment; in recent years, improving the purity of melt via adapting combined technical means become the major research direction; The nickel based high temperature alloy produced with double smelting method has shown a trend of industrialization and triple smelting method will be developed at high speed in China.