Because of its instability, hydrogen is “blended” with natural gas and used as a “green” fuel, usually in large industrial applications that have excess Hydrogen on hand or are making a targeted move toward lowering of emissions and meeting environmental regulations. The blending process is delicate and yet is essential in keeping steady combustion and avoiding expensive outages.

Many end-users are considering switching to hydrogen firing for their steam generation needs; therefore, it is essential to highlight some of the challenges they would be facing when planning to make the fuel conversion or addition. Most end-users have their boiler/burners plant systems suited for natural gas firing; if we compare the natural gas and hydrogen combustion characteristics, the hydrogen firing speed is significantly higher (~5 times) than natural gas. This requires the burner and gas nozzles to be designed for the new fuel velocity. Hydrogen has a higher stoichiometric adiabatic flame temperature (~450 F degrees higher) than natural gas, making necessary the upgrade of internal burner components to higher grade steel or alloys suited for the elevated temperatures.

Emissions play another curveball into the firing of hydrogen, as hydrogen burns “hotter” than natural gas and have a faster combustion rate than natural gas; hydrogen is prone to thermal NOx generation. Considering few techniques to lower the NOx, such as flue gas recirculation (FGR), steam injection, and Ultra-low NOx burners can effectively reduce the emissions to the required levels.

Hydrogen, like other “free fuels” such as bio-gas or digester gas, can be a waste/ bi-product of process plants that can be recycled to power the plant.

A simplistic approach to satisfying plant output demand is to run multiple units with some burning only “free” fuel, and some burning only Purchased fuel. Besides the higher capital cost for multiple units, this can also result in units running at lower loads and thus lower efficiencies. Even worse, it can result in units with low turndown capability to continuously cycle on/off –further lowering efficiency, and potentially upsetting the Process Plant operations. A better approach is to provide a control system and burner that allows multiple fuels to be fired simultaneously in a single unit with a variable Fuel Ratio (“free” fuel versus Purchased fuel). The control logic is designed to burn as much “free” fuel as possible while simultaneously meeting the Plant demand for Steam, Hot Water, or Electrical Output.

Our Preferred Special Combustion Engineering (PSCE) division has considered all the above. It has developed and installed our Hydrogen burner system on multiple sites successfully, keeping the end-user boiler systems operating safely, environmentally sound, and economically improved.

Solution

Made in the U.S.A., this project demonstrated a a sustainable, safe reclamation of waste hydrogen with high efficiency and carbon foot print reduction.

An American based chemical manufacturer decided to make use of their waste/bi-product hydrogen which significantly reduced their use of fossil fuel for their process steam requirements. But the customer needed the right company to deliver a controls, burner, boiler, fuel handling, blending, and a balance of plant integrated combustion package. They came to Preferred Utilities Manufacturing for a total combustion design solution which included a custom (IBEW / UL 508) PLC flame safe guard system with integrated combustion control, fuel ratio control, boiler water control and balance of plant interface. A 10″ touch screen operator interface with plant wide SCADA communications provides easy process / efficiency monitoring and trouble shooting operations.

For single source responsibility, significant energy savings, and unsurpassed combustion engineering expertise, choose Preferred.