Limestone power consumption

Fig. 39. Power consumption vs. rotational speed of a rotating horizontal cylindrical mixer. Limestone was mixed, particle size about 1.35 mm. Experimental conditions varied as shown (07). a — rotational speed corresponding to critical state b = rotational speed corresponding to equilibrium state c = rotational speed corresponding to the state when all particles tend to rotate with the inner wall of mixer D = diameter of mixer, m. 0 D = 0.25 D = 0.30 X-D — 0.35. N = rotational speed of mixer, rpm P = power consumption of the horizontal cylindrical mixer, kg.-m./sec. X = per cent of mixer volume occupied by batch.

Rao, D.B.N., "The Effect of Crystallinity of Limestone and Particle Size Distribution of Kiln Feed on the Dust Emission, Specific Power Consumption and Clinker Quality," Proceedings of the 10th International Conference on Cement Microscopy, International Cement Microscopy Association, San Antonio, Texas, 1988, pp. 152-176. 

A crusher is fed with limestone having particles of 2 cm median equivalent diameter and discharges a product consisting of particles of 0.5 cm median equivalent diameter. The equipment operates at a capacity of 1.2 x 10 kg/h consuming a power of 10 hp. If the requirements of the process demand a finer size of the product (0.4 cm of median equivalent diameter) decreasing the capacity to 1.0 x lO kg/h, determine the theoretical power consumption under the new conditions. 

Sources of CO2 associated with Portland cement manufacture include (i) the decarbonization of limestone (ii) the exhausts of kiln fuel combustion and (iii) the exhausts of the vehicles used in cement plants and distribution. Of these sources, the first produces a minimum of about 0.47 kg CO2 kg cement, whilst production via the second source varies with the plant efficiency. For example, an efficient precalciner plant will produce 0.24kg CO2 kg cement, while a low-efficiency wet process may produce up to 0.65 kg CO2 kg . The production of CO2 via the third source is almost insignificant (0.002-0.005 kg CO2 kg cement). Hence, the typical total CO2 footprint is around 0.80 kg CO2 kg finished cement This leaves aside the CO2 associated with electric power consumption, which varies according to the local generation type and efficiency. Typical electrical energy consumption is of the order of 90-150 kWh per metric ton of cement this is equivalent to 0.09-0.15 kg CO2 kg finished cement if the electricity is coalgenerated. All of this amounts to about 7% of the total CO2 generated worldwide (Malhotra, 1999). 

Other Uses. Other uses include intermediate chemical products. Overall, these uses account for 15—20% of sulfur consumption, largely in the form of sulfuric acid but also some elemental sulfur that is used directly, as in mbber vulcanization. Sulfur is also converted to sulfur trioxide and thiosulfate for use in improving the efficiency of electrostatic precipitators and limestone/lime wet flue-gas desulfurization systems at power stations (68). These miscellaneous uses, especially those involving sulfuric acid, are intimately associated with practically all elements of the industrial and chemical complexes worldwide. 

The calcium oxide is produced immediately prior to reduction from high purity limestone. This enthalpy of the reaction is +465.6kJ/mol and is provided by electric power and results in the consumption of Soderberg electrodes made from anthracite. The cell is tapped to release the molten carbide which is produced in 80% purity. The off-gas from the cell is typically 80% carbon monoxide and about 10% hydrogen. Following the production of calcium carbide, acetylene is produced by addition of water to the carbide ... 

The rice husk-based bioelectricity hfe cycle starts with the production of agricultural inputs such as rice seed, fertihzer, and pesticide, which then are used for rice farming. After the rough rice grains are harvested, rice husk is separated from brown rice [44]. While the brown rice is normally processed to obtain white rice for commercial purpose, the rice husk is directly transported to the power plant for generating electricity. The operation of rice husk-based power plants is similar to that of coal-based power plants. Nevertheless, as rice husk tends to contain less sulfur than coal, limestone consumption is omitted when considering the rice residue-based power plant. 

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