System load is measured in either BTUs or tons of steam (at a specific pressure and temperature). It would be nearly impossible to size and select a boiler(s) without knowing the system load requirements. Knowing the requirements leads to the following information:
The boiler(s) capacity, taken from the maximum system load requirement.
The boiler(s) turndown, taken from the minimum system load requirement.
Conditions for maximum efficiency, taken from the average system load requirement.
Determining the total system load requires an understanding of the type(s) of load in the system. There are three types of loads: heating, process, and combination.
Excess air provides safe operation above stoichiometric conditions. A burner is typically set up with 15% to 20% excess air in higher firing ranges. Higher excess air levels result in fuel being used to heat the air instead of transferring it to usable energy, increasing stack losses and significantly decreasing efficiency. Boilers with lower excess air throughout the operating range have higher efficiencies.
Emissions standards for boilers have become very stringent in many areas because of the new Clean Air regulations. The ability of the boiler to meet emissions regulations depends on the type of boiler and burner options. ZOZEN has options to meet 5ppm NOx regulations, as well as 1 ppm CO regulation at 30 ppm NOx out of the box. We can also custom-engineer Selective Catalytic Reduction (SCR) for more rigorous emissions controls.
Condensing boilers can achieve up to 98% thermal efficiency, compared to 70%-80% with conventional designs (based on the higher heating value of fuels). Typical models offer efficiencies over 90% when the return water temperature is at 110 ºF or less; the lower the return water temperature, the higher the efficiency gain.
This is because, under normal circumstances, the exhaust temperature of the boiler cannot completely condense the water in the flue gas, and the difference between the low calorific value and the high calorific value is mainly in the part of the latent heat of vaporization, so the low heat is used. The value is calculated to reflect the true efficiency of the boiler. However, there will be some special circumstances. For example, if the boiler is a condensing boiler, the calculation of the condensed water portion should be calculated using the high calorific value.
Package boiler is a boiler that had been fabricated and available as a complete package. The entire pressure parts have been assembled in the workshop and ready to be sent to the field or site where power plant is located. On the field/site requires only connection and integration of course work in electrical connections, water pipes, steam pipes and fuel piping system to operate. Package boiler is one of classification of boiler based on erection. Design package boilers in general are the type of Fire Tube Boiler and have made up shell and tubes. This type has high heat transfer both radiation and convection.
The combustion air preheater is definitely one of heat exchanger applications. Based on Figure 1 below, flue gas simply leaves steam boiler and passes via air preheater. The combustion air is passed through this equipment too to increase its temperature before being combined with boiler fuel.
Because the temperature of combustion air is lower than the temperature of flue gas, combustion air receive heat transfer from flue gas through combustion air preheater in the process of convection heat transfer. The heat transfer make temperature of flue gas lower and consequently minimizes its heat loss and also decreases the air temperature to stack.
ASME code – also known by its longer name: ASME Boiler & Pressure Vessel Code – regulates the design, development, and manufacturing of boilers used in a variety of industries and applications.
This code was developed by the American Society of Mechanical Engineers, an organization that has been around for well over 100 years and is focused on establishing safety codes and standards for mechanical equipment.
Within the industrial heating industry, ASME code is the established standard that many pieces of equipment are built to.
Heating systems that adhere to the specifications set forth by ASME code have been constructed according to guidelines intended to promote safety and quality. As such, heating equipment that is ASME code compliant has been thoroughly inspected to assure that it meets high safety and quality standards.
