Research And Analysis On Energy Consumption And Energy Saving Potential Of Metallurgical Sulfuric Acid Production Process

Metallurgical sulfuric acid production exists extensively in the non-ferrous industry. All the researches about this production are belong to the field of flue gas recycling, and none of them are related to the system energy saving. However, with the increasing of the industrial output and consuming of flue gas for the acid production, the research on energy saving for the metallurgical sulfuric acid production and the sulfuric acid industry has been increasing substantially in recent years. In this paper, the system energy saving of a sulfuric acid plant was investigated.Based on first law of thermodynamics, the thermal equilibrium model was established. The results showed that:The heat loss of system cooling water was 85816.66 MJ/h which accounts for 60.26% of the total. The total heat loss for finished products, waste acid and exhaust gas of evacuation was 13391.33 MJ/h which accounts for 15.01% of the total.The main reasons that the overall energy intensity of a sulfuric acid production plant were analyzed by e-p method. It was shown from the result that the actual energy intensity of final product was 32.33 kgce and the standard energy intensity of final product was 14.85 kgce, so the energy-saving potential for enterprise was 17.48 kgce. The increment due to the increment of unit process energy intensity and products ratio was 16.33 kgce and 1.15 kgce, which takes up 93 percent and 7 percent of the overall energy saving respectively.The practical material flow diagram and the standard materials flow diagram (SMFD) ware constructed accordingly. The influences of materials flow on energy intensity were analyzed quantitatively. The following results can be obtained from the analysis:1) Outputting sulfur-containing materials from an intermediate process to surroundings increases the energy intensity of this process and product ratios of upstream processes, hence increase the energy intensity of final product, the larger the ordinal number of the unit process, the greater will be the increase. The main materials flows are loss of flue gas project and waste acid project.2) Returning sulfur-containing from absorption section (precipitation process) to former process such as drying section increases not only precipitation process energy intensity but also the product ratios of processes between absorption and drying preparation, hence increase the energy intensity of final product, the longer the returning distance, the greater will be the increase.3) Inputting sulfur-containing materials from drying section to absorption section, although increases precipitation process energy intensity, reduces the product ratios of processes between absorption and drying preparation, hence increase the energy intensity of final product.A calculation software about energy consumption analysis was designed and developed according to the theoretical basis of SMFD methodology. The calculation software can be widely used in the energy consumption analysis of production processes.BP neural network prediction model was established, which was used to predict the energy consumption of sulfuric acid factory system. There was little error between predictive value and actual value.