Boilers

Boiler systems are used anywhere heat/steam are needed, including power generation, central heating for residential and commercial buildings, manufacturing, and pulp/paper processing. ESi is routinely called upon to investigate and remediate different types of boiler issues and can provide specific recommendations to help improve operational efficiencies and reduce risk, maintenance and downtime, often resulting in significant cost savings.

Boilers Used for Central Heating

For centuries now, boilers have been used to provide central heating for homes, businesses, commercial office buildings, manufacturing facilities, hospitals, and more. These low pressure boilers (100~150 psig) produce saturated steam and are commonly referred to as “fire tube” boilers, in contrast to high pressure boilers, which are much larger and are often called “water wall” boilers.

Today’s boilers are considerably more energy efficient than in years past, often require less maintenance and are at less risk of failure. However, to ensure reliable operation with minimal repair and downtime, it is important to understand the age/life expectancy, condition and efficiency of the boilers used in the building heating system.

Power Generation

For power generation, super-heated steam is needed to run the steam turbine efficiently, and boilers are generally larger in size and operate at higher pressures and temperatures. These boilers are known as supercritical boilers. Recent developments in high temperature materials and coatings have enabled higher gas turbine inlet temperatures, significantly increasing operating efficiency. Additionally, cogeneration plants are now able to recover the thermal energy generated by the combustion of the fuels used to heat the gas that is run through the gas turbines.

A cogeneration plant adds a heat recovery boiler -- a simple “water wall”  boiler which takes the thermal energy from the hot gases in the gas turbine and applies additional heat to produce superheated steam, which can then be run through a steam turbine. In some plants, a small portion of the steam is then reinjected into the combustion chamber of the gas turbine to increase the mass flow, enabling higher power output and improved control of NOx emissions.

• Boiler Materials - Because the efficiency of conventional boiler/steam turbine power plants is a strong function of the steam temperature and pressure, the materials used to build the pressure vessel of a boiler can be critically important. Newer plants are constantly looking at new alloys that can operate safely at higher temperatures. Boilers that burn biofuels and black liquor boilers also require special alloys to protect the outside of the boiler tubes from the corrosive attack of the combustion products.

• Boiler Feedwater - Proper chemical treatment and control of the boiler feedwater is also important in order to control corrosion and minimize formation of internal deposits inside the boiler tubes that can result in hydrogen damage (when corrosion occurs under these deposits).

• Fuels– Many different solid, liquid and gas fuels are used in boilers, including natural gas/propane, diesel/fuel oil, wood chips, and black liquor, which is used to run the “black liquor recovery boilers” used in paper pulp plants.