HeaterSim

Fired Heater Simulation & Modelling

Fired Heater Revamp Projects

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Many revamp projects will involve technical analysis in order to improve the fuel efficiency. The fuel efficiency of the fired heater is directly related to the running costs and fuel consumption, hence the overall efficiency is often a key area of focus for all site operators.


There are 3 main approaches to increasing fired heater fuel efficiency:

- Reduce the excess air

- Increase the heat transfer surface (additional convection rows)

- Add an Air Pre-heat system (APH System)

 

Increasing Heat Transfer Surface

By simply reducing the level of excess air during operation can improve the heater efficiency. Often fired heaters are inadvertenly operated with excess air levels over 40% for sustained periods. This is commonly due to the heater being fired significantly below their design capacity, whilst the air supply has not been adjusted accordingly.


API 560 has the following recommended excess air levels:

- 20% Excess Air (Gaseous fuels)

- 25% Excess Air (Liquid fuels)

API 560 has the following recommended excess air levels:

- 20% Excess Air (Gaseous fuels)

- 25% Excess Air (Liquid fuels)


Fired heaters with modulating forced draft fans offer the greatest flexibility with excess air adjustment. This is because the fan is able to modify the air flow in accordance with the fuel flow, thus providing just the right amount of excess air for all firing cases.

Our Heater560 software can simulate both natural and forced draft heaters. You are also able to dynamically assess different operation cases using the DCS interface to make direct adjustments to the combustion air flow. Datasheets are automatically produced for the fans in seconds, saving you a huge amount of time.

Increasing Heat Transfer Surface

Additional heat transfer surface area can significantly improve heater efficiency and this is usually achieved by adding additional tube rows in the convection section. Process engineers should be aware that these additional tube rows will further reduce the flue gas temperature entering the stack and in some cases may increase the likelihood of flue gas condensation, which can cause corrosion on the outside of the tubes.


Our Heater560 sofware calculates the minimum tube temperatures for all simulations and provides commentary notes to advise on the likelihood of flue gas condensation. Process engineers can use this tool to confirm the feasiblity of increasing efficiency by adding more convection rows without the possibility of flue gas condensation and corrosion issues.



Air Pre-heat System (APH System)

An APH System improves operational efficiency by increasing the temperature of the combustion air entering the heater. The most common APH configurations use hot flue gas exiting the convection section to warm cold combustion air before it enters the burners.

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An APH systems can provide fuel efficiencies of 90% or more and often quickly secure a significant return on the investment required for such upgrades.

Heater560 is able to dynamically model heaters with APH systems, providing data such as the exiting flue gas temperature of the heater, which is important for understanding and preventing flue gas condensation problems within the APH unit itself. Heater560 also automatically produces datasheets for the APH, FD Fan and ID Fans required, saving an incredibly amount of time and allows you to send your requisition to your APH and Fan vendors and clients more quickly than your competitors.

example:

Before heater revamp            After heater revamp

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