What Is a Steam Boiler?
Steam boilers are machines that boil water and supply it as high-temperature steam.
Most steam boilers are used as heat sources. They are used in a wide range of fields, from indoor heating to food sterilization. The steam was water originally, so the chemical hazard is low compared to many other heat sources.
Uses of Steam Boilers
Steam boilers are used for both industrial and residential purposes. However, they are most often used for industrial purposes. Specific uses of steam boilers are listed below.
- Sterilization of food in the food industry
- Generation of steam for power generation
- Product drying in chemical and paper plants
- Drying of laundry in the laundry
- Heat retention in hot springs and bathing facilities
- The heat retention of the electrolytic solution in electrolytic smelting
- For indoor heating and hot water supply
Steam locomotives are another example of uses of steam boilers, as they also have a built-in steam boiler to obtain engine power. However, they have become increasingly rare in recent years.
Principle of Steam Boilers
Steam boilers generate steam in most cases by evaporating water through fuel combustion. The boiler consists of a drum, combustion equipment, flue, water supply equipment, etc.
1. Drum
The drum stores pure water, which is mixed with steam during operation. The pure water inside the drum is designed to flow back to the combustion unit. Water heated by the combustion unit is separated into steam and pure water inside the drum.
2. Combustion Device
The combustion device burns fuel, and the fuel is supplied at regular intervals and mixed with air for combustion. It also has the function to stop fuel supply automatically in the event of abnormalities such as poor combustion or low water level in the drum.
3. Flue
The flue is a pipe for exhausting air after combustion. A ventilator is installed in the flue to adjust the airflow rate according to the fuel supply. If there is a lot of dust or oxides in the flue gas, a dust collector or desulfurization/denitrification equipment is installed in the flue.
4. Water Supply System
The water supply system supplies water to the drum, and in most cases, the water is pumped by a water supply pump. Since a large amount of metal ions in the water can deteriorate a boiler, a water purification device may be attached to the boiler.
Other Information on Steam Boilers
1. Steam Boilers for Business Use in the Past
Steam is necessary for all manufacturing industries, but it is not suitable for transportation over long distances. Therefore, steam boilers are almost always installed adjacent to demand facilities.
Since paper mills and petrochemical plants consume large amounts of steam, fossil-fueled steam boilers were installed in these plants around 1970. In many cases, power generation was combined with steam generation to make effective use of excess steam.
Since 2000, the use of steam boilers has been on the decline due to soaring crude oil prices and increasing social pressure to reduce greenhouse gas emissions. However, petrochemical plants still make effective use of steam boilers and power generation facilities because of the oil and gas generated as byproducts.
2. The Future of Commercial Steam Boilers
Water is a very effective heat transfer medium and indispensable to industry. Since steam returns to water after leakage, it tends to have less impact on the human body and the environment compared to chemicals and toxic substances. Furthermore, it is a natural raw material that is in inexhaustible supply.
Recent news reports indicate that some major manufacturers are withdrawing from the business of manufacturing large boilers for commercial use. This is because there are not many companies newly constructing large boilers. Steam boilers for power generation that use fossil fuels will likely continue to decrease in the future for the sake of reducing greenhouse gas emissions. However, it is difficult to imagine that steam will disappear in the future because of its excellent properties as a heat-transfer medium.