How Boilers Keep the Plants RunningOctober 28, 2013
Boilers are one of the most fundamental systems of a refinery or plant. They are literally the pieces of equipment that keep the plant up and running. However, they are one of the least discussed aspects of the plants because the focus is typically on the quantity and quality of their actual product output, or about the cost of the fuel and raw materials that are coming in. This article will briefly examine some of the specifics about what boilers are, what you need to know about them, and how they keep plants running.
What Is a Boiler?A boiler is a piece of equipment which acts as a closed vessel to convert the water inside into steam. In order for this to happen chemical energy from a fuel source such as oil or gas is converted into heat by combustion. The heat is then transferred to the contained water, thereby increasing the pressure and eventually converting the liquid form into steam. The boiler should be designed to transfer the maximum amount of heat possible from the combustion into the water using processes such as radiation, conduction, and convection. The efficiency of the heat transfer is very important so that the fuel being burned yields the maximum, most cost effective results. In addition the boiler should also be designed to generate high quality steam that can be effectively utilized by the plant.
What Function Do Boilers Serve?Now that we’ve discussed what a boiler is, you may be wondering why one is needed and what the plants actually do with the steam that is produced by boilers. It will vary somewhat depending on the plant, but for the most part the steam produced by the boilers will serve one of the following functions:
- Fuel - Often the steam will be used to power turbines for electric generating equipment, blowers, and pumps.
- Production - The steam may also play a role in the actual production of the product by sterilization, or to achieve the processing temperatures needed for an aspect of production.
- Climate - The steam may also be used to power the plant’s heating and air conditioning units. This might be done for personal worker comfort, to keep equipment at proper operating temperatures, or both.
What Types of Boilers Are Common?Most industrial boilers fall into two broad categories of boiler types. However, within these types...specific designs and capacities abound. Boiler models may be chosen by different refineries depending on the technology and units available when the boilers were purchased, the budgeting, maintenance, efficiency concerns of the plant, and other factors specific to the requirements of the plant. The two main categories of boilers are:
- Fire Tube Boilers - Fire tube boilers utilize a system of tubes through which the heat source, or "fire", passes. The tubes are surrounded by water and the water is heated as the tubes also rise in temperature. Eventually steam is released for use.
- Water Tube Boilers - In contrast to fire tube boilers; a water tube boiler uses the water rather than the heat which is contained inside of a system of interconnected tubes. The heat moves around the tubes, thereby heating the water within the tubes and gradually transforming it into steam.
Additional Boiler ConsiderationsIn order for a boiler to continue functioning safely and effectively there are several additional considerations to keep in mind.
- Water Level - It is very important that the boiler’s normal operating water level (NOWL) be carefully maintained. If the water level drops too low it can cause boiler failure.
- Startup - The startup of a boiler is one of the most dangerous stages in its operation and is one of the most frequent times for furnace explosions. It is important to follow all manufacturer guidelines when starting up a boiler.
- Shutdown - Different shutdown procedures exist for different boilers, but in general this is also a sensitive time in the boiler’s operation cycle and it is once again important to follow recommended guidelines for the particular boiler.
- Maintenance - All boilers will require periodic maintenance and inspection. In addition, with age many boilers begin to operate less efficiently and as such may require a considerable overhaul such as a retrofit or retubing.