Development Of Blast Furnace Gas Spray Cooling System

The liquid atomization is widely used in energy and power, chemical, agricultural and environmental projects. The research on spray cooling focuses on the effect of cooling in field of fire in the field or "room temperature" condition of agriculture. But the study on the cooling effect of the water mist at high temperature is rare. The research of atomization nozzles focuses on that used for fuel atomization in internal-combustion engines and aerospace. But there are little studies on the two-fluid nozzles used water as the atomization media.This paper introduces the mechanism of liquid atomization and use a single droplet as the object to study its fragmentation pattern in a stable flow. We established the mass diffusion mathematical expression of single droplet evaporation according to Fick Law and derived the basic equation of mass diffusion rate when droplet evaporates. The process of the heat and mass transfer between the droplets and air is divided into two stages due to the characteristics shown during the droplet evaporation process:the non-steady-state phase and the steady-state phase. The analysis shows that the quality changes of droplets in non-steady-state phase can be ignored, only the sensible heat exchanges between droplets and the air need to be considered. The temperature will not change any more in the steady-state phase, and the droplet evaporation is achieved by the heat absorbed from the air. We also get the time required for droplet evaporation from the theoretical analysis. We analysis the vaporization of droplets in a relatively static media according to the molecular diffusion theory and analysis its energy changes by using a spherically symmetric model. The heat and mass transfer during droplet's vaporization in the medium of forced convection is analyzed by using effective film theory. And on this basis, we make the theoretical analysis of energy transform when during the droplets vaporization.After studying the mechanism of liquid refrigerant atomization and principles of several kinds of liquid refrigerant atomizer, based on the key indicators and influencing factors to measure the quality of atomization, numerical analysis method is used to study the effect of the structure of the nozzle and the running parameters on atomization and flow characteristics of nozzles. According to nozzle design principles and practical design experience, the calculation of mixed pneumatic atomizers is given. By analyzing the structure of the core within the nozzle, different effects to atomization effect by different core structure are given.The numerical simulation calculation to the spray two-phase field is done by software with the method of numerical analysis and the following conclusions are obtained:the main factors which effect the temperature distributing in the gas pipeline are flux and temperature of high-temperature gas, spray volume and spatial position of nozzles. Empirical formula of temperature at any spatial location point in the cooling pipe and independent variables mentioned above is fitted based on a large number of simulations. Combined with the empirical formula and the actual situation, the control system of spray cooling system is designed to achieve the goal of controlling the cooling water accurately to the temperature.The achievement of this paper can provide the important theoretical basis of studying and developing the spray cooling system of blast furnace gas and designing the mixing nozzle. Also it can provide theoretical guidance of accurate controlling on the cooling water.