Study On Large Scale Limestone-gypsum Spraying Desulphurization Technology And Project Application

With the national SO₂ emission standard being stricter and the development of domestic desulphurization market, the limestone-gypsum spraying wet flue gas desulphurization (WFGD) technology was applied extensively with its high efficiency and high reliability. Based on the WFGD projects which were undertaken, studies of basic parameters selection and mass balance calculation of the spraying WFGD technology, gas-liquid flow field simulation and resistance characteristics in spraying tower, design and operation optimization, process model and its numerical calculation of spraying tower were taken. Based on the application of the projects and research findings of spraying WFGD, typical operating mode design and operation schemes of spraying tower of 300MW unit had been studied in this dissertation by fuzzy evaluation.The rules of selection of basic parameters in limestone-gypsum spraying WFGD technology were discussed in this dissertation. The calculation principles of heat balance, water balance and solid balance in mass balance was analyzed. Calculation results of projects showed that the results of heat balance were in good agreement with those of foreign WFGD technology provider while results of water balance and solid balance were not because of the influence of device characteristics. But all the calculation results of mass balance can be satisfied in the WFGD engineering.It can be indicated that CFD technology can be applied in the engineering design, operation and optimization of spraying WFGD in this dissertation. By the use of structuralized/non-structuralized hybrid grid technology, the standard κ-ε turbulent model which describe the flue gas turbulent motion in the tower, the Discrete Phase Models which trace the movement of droplets, Discrete Random Walk model which describe the turbulent motion influence to the movement of droplets, the Rosin-Rammler model which describe droplets distribution, the gas-liquid fluid flow field and resistance characteristics of different design and operation condition in spraying tower of 300MW unit were simulated with the SIMPLE calculation method. Simulation results showed: slurry spraying can bring integration to flue gas flow field in spray tower. Spray zone and the inlet/outlet zone made the main pressure drop in spraying tower. The pressure drop in spraying tower of 300MW unit WFGD system with 4 spray levels which flue gas flow is 120×10⁴Nm³/h and tower diameter is 13m and levels spacing is 1.7m was 950Pa, which was in good agreement with the data of actual project. The diameter and number of spray levels of spraying tower contribute greatly to the pressure drop, while the levels spacing contribute little. Operation parameters - load and liquid to gas rate (L/G) affected pressure drop greatly.The design principles of spraying tower and its internal equipments in WFGD system were analyzed in this dissertation. The CFD technology was used to take the study of numerical simulation of the influence of geometry change of spray tower and its internal equipments to the gas-liquid flow field. Results showed that the diameter of spray tower should be 12m for typical 300MW unit. The flue gas entrance should incline and inclination angle should take 13° - 15° in engineering design because the inclined entrance was advantageous to the flow field uniformity. The height to breadth rate (H/B) tend to be small in the projects design of the flue gas entrance of spraying tower and the value should be 0.4 - 0.5. The breadth of plate above the entrance region should be 0.5m - 1.0m because the plate could not only prevent the slurry droplet from entering the entrance but also be advantageous to the flow field uniformity. The coverage fraction changed with the change of spray angle of nozzles and the coverage effect changed little with the change of the level spacing, the pressure drop of nozzle, the spray angle.The unsteady mass transfer penetration theory was applied to establish the...