Dry Coolers in Steam Turbine Systems in Thermal Power Plants
Dry Coolers in Steam Turbine Systems in Thermal Power Plants
Thermal power plants are one of the most important areas where dry coolers are used. In the traditional coal-fired, oil-fired or gas-fired steam turbine power generation system, dry cooler is used to cool the high temperature and high pressure steam discharged from the turbine, so that it can condense into water, realize the recycling of steam, and improve the efficiency of power generation. At the same time, the dry cooler can also cool the lubricating oil and sealing oil of the turbine to ensure the normal operation of the equipment.
Steam Cooling and Recycling
Working Principle: In the steam turbine system of a thermal power plant, steam is discharged in a high temperature and high pressure gaseous form after doing work in the turbine. The dry cooler cools and condenses the steam by means of air cooling as it flows through the tubes. Steam flows inside the cooling tube bundle of the dry cooler, while cold air flows outside the bundle driven by a fan. Through heat exchange, the heat of the steam is transferred to the cold air, and the temperature of the steam is lowered, ultimately condensing into liquid water.
Improving power generation efficiency: This recycling of steam is critical to improving power generation efficiency. In a typical Rankine cycle, for example, after steam expands and does work in the turbine, if it is not efficiently cooled and condensed, it cannot be returned to the boiler in liquid form for the next round of the heating cycle. The dry cooler enables the steam to be quickly converted into liquid water, thus ensuring the continuity of the steam cycle, reducing energy loss and improving the efficiency of the entire thermal cycle. For example, effective cooling by a dry cooler can increase the thermal efficiency of power generation by several percentage points.
Reduction of work mass loss: the dry cooler can effectively recover the water in the steam and realize the recycling of work mass. In thermal power generation, reducing mass loss not only reduces operating costs, but also reduces the impact on the environment. Without the effective condensation of steam by the dry cooler, a large amount of steam would be lost to the environment and would need to be constantly replenished with new workmass, which would increase water consumption and the cost of chemical water treatment.
Lube and Seal Oil Cooling
Importance of lubricant oil cooling: Critical parts of the turbine, such as bearings, require lubricant oil for lubrication and cooling during operation. The lubricating oil absorbs the heat generated by bearing friction during circulation, resulting in an increase in temperature. If the temperature of lubricating oil is too high, its viscosity will be reduced and its lubricating performance will become poor, which will easily cause bearing wear or even damage. The dry cooler can cool the lubricating oil to keep it in the proper working temperature range. Generally speaking, the temperature of the lubricating oil should be controlled at about 40 - 50℃, which can ensure the stable performance of the lubricating oil and prolong the service life of the equipment.
Role of sealing oil cooling: For the shaft sealing system of the turbine, the sealing oil plays a role in preventing steam leakage and air from entering the inside of the turbine. The sealing oil will also absorb heat and increase in temperature during the working process. The dry cooler cools the sealing oil to ensure the sealing performance of the sealing oil and prevent steam leakage or air ingress due to the decline of sealing oil performance caused by high temperature, so as to ensure the safe and stable operation of the turbine.
