Modern boiler plants are increasingly focused on energy efficiency, reducing their physical footprint, as well as minimizing capital and installation costs. Companies are striving to keep their total cost of operation as low as possible to remain competitive in the global economy. One of the challenges is having a steam supply that can handle large variations in demand. If the boiler is too small to handle peak demands, the plant cannot operate as designed. If the boiler is sized to handle short bursts of steam, the boiler may be oversized and have higher energy input versus output due to lower efficiencies at lower loads.
Boilers and steam production are essential to our modern lives. Boilers are used in almost every industry from generating electricity to heating buildings and everything in between. Due to the diverse demands for steam production, boilers come in various types and sizes.
Steam quality and steam purity are topics which often get confused with each other. Distinguishing the difference between the two will help you understand the unique impacts they have upon a steam system.
Understanding steam quality requires understanding vapor-liquid equilibrium in water. As heat is added to subcooled liquid water, it proceeds to the saturated liquid curve and becomes a saturated liquid (moving from incoming city water to point A). At the saturation point, any heat added to the water will form a vapor and the temperature will remain the same because all additional enthalpy (heat energy) being added to the system is being used to change the phase of the water from liquid to vapor.
The More You Know
Carryover is any contaminant that leaves the boiler with steam. It can be in a solid, liquid, or vapor form. The most common form of carryover is boiler water droplets that contain dissolved and suspended solids.
Boiler water carryover can cause deposits to form in valves, heat exchangers, turbines, and superheaters. If deposits are significant, heat transfer and/or turbine efficiency may be reduced. Additionally, carryover can strip away the protective magnetite layer on steam lines, remove the film formed by filming amine programs, cause erosion-induced corrosion, and result in product quality problems in processes using live steam.
Basic Boiler Functions
Boilers are specialized mechanical devices designed to generate pressurized steam. Steam is an essential raw material that drives industry and commerce worldwide. From the electricity used to power our homes and run our plants, to the plastic and vinyl in our automobiles, the paints and wood in on our homes, and the preparation of the food we eat, steam is used to make our lives more comfortable and convenient.