Influence on the Atmosphere of Production of Raw Materials for Metallurgy

The concept of end-to-end energy-ecological assessment of the entire sequence of processes in the production of a product is known. A similar estimate was introduced for greenhouse gas emissions in the iron and steel industry. However, the contribution of the processes of extraction, enrichment and transportation of raw materials in the above estimates is given approximately. In this work, an attempt is made to clarify this contribution by determining emissions of harmful substances and greenhouse gases for a generalized technological scheme of an open pit. The calculations used the data of the main units on the assumption of their operation at maximum power. For this reason, auxiliary units were not considered.


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In [1], an end-to-end energy-ecological assessment of the entire sequence of processes in the production of a product is proposed. A similar estimate is given for greenhouse gas emissions in ferrous metallurgy [2,3]. The contribution of the processes of extraction, enrichment, transportation of raw materials in the above estimates is taken at 10-20% of the parameters of the main technological processes. In this paper, an attempt is made to clarify this contribution by numerical assessment of emissions of harmful gases (WG) and Greenhouse Gases (GHG) for a generalized technological scheme of an open pit and a mining and processing plant (GOK).
The production of raw materials here includes the processes of ore mining, transportation, transshipment, and beneficiation. The features of these processes depend on the type of output product (ferrous or non-ferrous metals), however, general technological schemes can be distinguished. Crushing of the massif by drilling and blasting operations, loading and transporting from the bottom by road transport to the transshipment site, loading trains (turntables) with traction units (TA) and delivery of ore to the GOK, crushing and grinding ore, beneficiation, concentrate pelletizing, transportation of concentrate or pellets to a metallurgical plant (MK) -this is a possible general technological scheme for the production of raw materials. In specific conditions, there may be no transport by turntables, for example, vehicles deliver ore directly to the GOK. The calculations were made on the assumption that all units operate at full capacity for 24 hours. This will make it possible to indirectly estimate the emissions of auxiliary units, for example, the formation of roads by bulldozers, rearrangement of railway tracks in technological dead ends, etc. All of these processes generate emissions of dust, harmful gases, greenhouse gases into the atmosphere. Dust formation is not covered here. An attempt has been made to estimate emissions of harmful and greenhouse gases.
The method for estimating emissions (emissions) is based on the following formulas: . .

XX
where is the specific fuel consumption, g / kWh; -engine power, kW; -exhaust gas temperature, ° С; t -engine running time, s. The greenhouse gas CO2 is contained in waste gases up to 12% by volume [5,6]. Thus, the highest CO2 gas emission from nPP units at a known volume Vog is determined where ρDU = 1.977 kg / m 3 is the density of carbon dioxide.
The quarries have auxiliary vehicles with gasoline engines, but their share in emissions is much less than dump trucks and diesel locomotives. Specific emissions will be calculated by dividing total emissions by the mass of MPP products delivered to the consumer, kg/t. Drilling of the wells. Well drilling is performed by drilling rigs, for example, a rotary drilling machine SBSh-250 MNA-32, equipped with an electric motor QB = 500 kW. The depth of the wells is 10-20 m, the diameter is 250 mm [7]. We will neglect other electricity consumers of the drilling rig since our calculations are of an estimate nature. A well with a depth of 15m, such a drilling rig will, according to approximate calculations, be drilled for 2 hours, which will take 1000 kWh. From rough calculations it is necessary to drill nBR = 72 wells (3 rows of 24). The distance between the wells in a row, between their rows and between the first row of wells and the edge will be taken as 8 m. Thus, the blasted block will be 83,000 m 3 , and chipping -124,500m 3 , the total mass of the MDBM chipping = 166000 t [8]. For these data, we will choose more equipment that can process the breakout in 24 hours.
The machine tool with an electric drive does not have its own emissions of harmful substances and greenhouse gases, but such emissions do occur in the production of electricity. Let's call these emissions transit. Energy from coal-fired power plants has the highest emissions of HH and GHG and for rough calculations is suitable for determining the upper limit. A coal-fired Thermal Power Plant (TPP) has specific gas emissions in kg / kWh: [9]. From (2) at t = 2 hours and nBR = 72 we obtain, kg:  Other harmful gases listed in (Table 1), are not considered due to the insignificance of their emissions and the approximations of the estimated calculations in this work. The diesel engine of the calculated excavator has a specific fuel consumption = 210 g / kWh [13,14], power = 800, kW, exhaust gas temperature = 500 °C. For these data, the volume of exhaust gases for t = 86400 s from (3) will be 62497 m 3 . Consequently, from (4), the emission of three diesel excavators will be, kg = 44480. Let's say the excavator cycle is 0.5 minutes. Then, three excavators will load 28,800 tons of rock per day. Transportation from the face.
Excavators load crushed ore into dump trucks. For example, in the body "BelAZ-7517", which can transport MTZ = 160 tons [15] and has an engine with a capacity of QTZ = 1400 kW. In 24 trips a day, a dump truck will take out 3840 tons of bumps from the quarry. The total weight of the chipping 166,000 tons per day can be removed by 43 dump trucks. From (2) we will determine that 43 dump trucks for t = 24 h form VG, kg: . Let us assume the cycle time of loading-unloading of a dump truck is 30 minutes. In 24 hours, it will complete 44 cycles and transport  Table 2 shows the parameters of such crushers selected for analysis [21]. The capacities are selected from the ranges given in [21]. With this choice, one KKD requires two KSD and ten KMD. If at the inlet of KKD 1500 m 3 , then at the outlet of all KMD 1500 m 3 is formed (we neglect losses). In this case, 400 + 2 · 500 + 10 · 250 = 3900 kWh of electricity is consumed. The specific consumption will be 3900/1500 = 2.6 kWh / m 3 . The same result can be found by adding the numbers in the last column of the ( Table 2). The density of ores of different metals has different meanings. If we take an average density of 2.0 t / m 3 , then for all crushing operations, the specific power consumption will be QДР = 1.3 kWh / t. There is no intrinsic emission from the crushing process. Transit specific emission during crushing . Flotation It is difficult to collect data on this process for some middle process. For this reason, the emissions of this process are assumed to be zero. This process is characterized by large masses of crushed rock and small masses of the resulting concentrate.  Consequently, from (4) the emission of the locomotive will be, kg: In our calculations, the rock / concentrate ratio is assumed to be 166000/4080 = 40.686. In this case, the summary data of the . From (3) at = 210 g / kWh, = 4412, kW, = 500 °C for t = 259200 seconds, we find the volume of exhaust gases -1034012 m 3 .
Therefore, from (4), the CO 2 emission will be, kg = 245309.  (Tables 4 & 5). Data in the line "Previous processes" in (Table 5) are obtained from the same line of ( Table 4) by multiplying its data by the quotient 4080/166000, i.e., assuming that a ton of ore is mined per ton of concentrate.  Example. In work [3] the values of own emissions of CO are given, kg: sintering machine (AM) -14; coke oven battery (KB) -5.5; blast furnace (BF) -5. Given the resource consumption, t: pellets from GOK to AM -0.9; from a coal mine to KB -1.4; from KB to AM -0.3; from AM to DP -1.3; from KB to DP -0.5. Through emission of cast iron is determined by the formula from [3] on the assumption that the data obtained for ore materials are valid for coal mines The emission of CO resources is equal to 1.057 + 1.057 = 2.114 kg, i.e., about 10% of the through emission of pig iron. For nonferrous metallurgy, the contribution of resources to the emission of products will be more than 10-20%.

Conclusion
The assessment of end-to-end emissions of harmful and greenhouse gases in the processes: 1.
Open pit ore mining 2. Enrichment

Transport
Ancillary processes, such as the formation of quarry roads, the transfer of the rail track, the transfer of the contact network, charging and stemming, etc. were not considered. However, for the main equipment, parameters were chosen without considering their use at small capacities. This circumstance to some extent compensates for the exclusion from the consideration of emissions of auxiliary equipment. End-to-end emissions of harmful and greenhouse gases generated during open-pit mining, crushing and delivery of poor ores (non-ferrous metals) make a significant contribution to the total end-to-end emissions of the main products.