High Pressure Boilers

Classification of High-Pressure Boilers

Modern high-pressure boilers can be classified according to the numerous categories below.

Types of High-Pressure Boilers

• Lamont Boilers
• Benson Boilers
• Loeffler Boilers
• Schmidt-Hartmann Boilers
• Velox Boilers
• Super Critical Boilers
• Waste Heat Recovery Boilers

High-pressure boilers can be divided into natural, forced, and once-through boilers. We look at some of these high-pressure boiler types below.

Lamont Boilers

This boiler uses forced circulation to operate. The drum receives feed water, the water in the drum is pumped to the evaporator portion, and the water and vapor are then returned to the drum. After being transported to the superheater, the steam in the drum is fed to the prime mover. Compared to standard water tube boilers, La Mont's initial designs proved lighter, safer, and capable of higher heat transfer rates and evaporation per square foot. They also demonstrated that the circulation of vaporized water at a differential pressure of 2.5 bar was 8 to 10 times greater.

Benson Boilers

When operating at part-load below 60° MCR, a Benson boiler, a type of once-through boiler that Marc Benson invented and patented in Germany in 1923, incorporates recirculation features. Small diameter tubes with a bore of about 25 mm are typically used in Benson boilers to create the furnace envelope. High subcritical or supercritical pressure feed water enters the furnace's bottom and is evaporated to high quality in the spiral section.

Before the steam/water mixture is supplied to the open boiler pass, a balancing header is frequently placed near the top of the furnace to eliminate any changes in steam quality caused by variances in heat absorption in different parallel spiral circuits. It undergoes superheating in pendant tube banks after superheating in the furnace envelope's upper portions. The balancing header separates the extra liquid when the furnace flow rate exceeds the total boiler demand for steam at low loads. The flue gases are used in fossil fuel-fired boilers for reheating, economizing, and air-heating purposes.

Waste Heat Recovery Boilers

Waste heat recovery boilers convert heat from industrial furnaces, refuse incinerators, and industrial waste into usable and efficient thermal energy. As a result, the waste heat recovery boiler is improving thermal efficiency, saving energy, and protecting the environment in industrial civilization.

This waste heat is produced from steel, non-ferrous metal, chemicals, cement, and other materials. Waste heat recovery boilers are improving thermal efficiency, saving energy, and protecting the environment in industrial civilization.

Working Principle of High-Pressure Boilers

Water cycles repeatedly from the shell (water drum) to the water tubes and back to the shell before being converted to steam. The water warms up during circulation as it comes into indirect touch with flue gases that conduct heat through tubes.

Circulation ratio is a significant consideration while developing water tube boilers overall. There are two fundamental concepts for water tube boilers based on circulation: Forced circulation and natural circulation boilers.

Natural circulation boilers are the sort of boilers where water circulates spontaneously due to the difference in density. The variation in temperature between cold and hot water causes the density to differ. The circulation ratio is crucial when designing natural circulation boilers to avoid overheating or tube bursts.

In contrast, the water circulation in a forced circulation boiler depends on a secondary pump that is mounted after the feedwater pump (primary pump) and that, depending on the design and safety requirements, either forces up or forces down the circulation ratio.

Applications of High-Pressure Boilers

• The expansion of steam in a steam turbine or engine can produce mechanical or electrical power.
• Heating: In cold climates, steam can heat residential and commercial buildings and create hot water for domestic usage.
• Industrial processes: The sugar, cement, agriculture, and chemical sectors can utilize steam for industrial processes like sizing and bleaching in the textile industry.

Advantages of High-Pressure Boilers

• The utilization of several small-diameter tubes effectively utilizes the heat of combustion.
• Powertherm boilers have a parallel set of tubes to prevent significant resistance to water flow.
• Typically, the components of steam boilers are arranged horizontally for greater accessibility and operating comfort.
• The risk of warming is decreased because the elements are heated evenly. As a result, the thermal stress disadvantage is also minimized.
• The rapid water flow through the boiler tubes eliminates the propensity for scale formation.
• Boilers that operate at high pressures can run on liquid or gaseous fuels.

Disadvantages of High-Pressure Boilers

• The tubes may become overheated if there is not enough water flow.
• The interior surfaces of the tube are where bubbles form, slowing down the heat transfer rate.