There are many ways of accommodating high hydrogen fuel gases whilst still keeping the flame cool enough to minimise NOx formation. To read more from the series online, visit the series hub. We just have to control it. The rich zone may be as simple as a neat gas poker firing onto the edge of the lean gas flame. Modulation of 2, 3, or 4:1 may be suitable with a methane gas but not for pure hydrogen. (The Coanda effect results in a flow of gases, where these gases follow a curved surface because that curved surface has no gaseous molecules adhering to collide with – and therefore modify the direction of – the flow stream.). There is a further flame to consider - flameless combustion. Adiabatic flame temperature hydrogen, methane, propane and octane - in Kelvin . To achieve low NOx, one of the favourite procedures is to reduce the combustion air to all burners (making the flames sub-stoichiometric) and removing all the fuel lance internals from the last row of burners, thus supplying the “secondary” air at the end of the combustion chamber.

So wherever the gas and oxygen meet they will react and give off more heat. There are usually many burners, often several hundred, arranged in rows. Radiated heat energy incident on a surface is either absorbed or reflected. The higher flame speed increases the flame temperature locally, which generates NOx. But in your neighbourhood and your nation you should be morally obliged to prepare for hydrogen. The gas and air are injected into the chamber separately and are heated by the radiation within the chamber to well above the SIT before mixing occurs. So the burner manufacturer has to design a burner to give a flame which will minimise the production of NOx. But undoubtedly, hydrogen is our friend in the furnace. What effect does the hydrogen composition have on the furnace, the flame, and the exhaust? The secondary air is delivered outside the diffusion flame package, with low turbulence to minimise mixing. It is just a little bit more difficult if the composition changes excessively.

This review has looked at the development of burner design to take account of emission regulations, specifically NOx. Retrieved 2008-01-27. "Temperatures in flames and fires". Your plant is likely to be legally obliged to control the NOx emissions.

The hydrogen is usually made from natural gas, by steam methane reforming (SMR) without capturing the CO₂, and in sufficient quantity for the process. Fitting flame detection on all, say 500 burners, is likely to be blocked by financial considerations. Nozzle mix flat flame burners should not have any significant problem as the hydrogen content of the gas is increased, save for the choice of nozzle material.

Coke oven and blast furnace gases are common, but they do have a significant influence on the original design of the burner. However, hydrogen has a much higher maximum flame temperature, so that any fuel with hydrogen added will have a higher maximum temperature and hence a greater sensitivity to unmixedness in the flame. Hence this gas main composition changes from that of natural gas to include hydrogen, typically up to 30%. This design will need a further chamber for the final combustion (probably flameless combustion) before the exhaust gases pass into the convection section. Burners can be designed for any gas composition with hydrogen.

We had hydrogen in towns gas throughout the middle of the last century and the researchers are investigating replacing methane in the gas main with hydrogen, at least in part to begin with. This is the 11th article in a series discussing the challenges and opportunities of the hydrogen economy, developed in partnership with IChemE’s Clean Energy Special Interest Group.

So, because changing to low NOx will probably require new burners, it would make sound economic sense to choose a burner design which is also suitable for high hydrogen. In this case the gas and air are premixed and admitted into the combustion chamber, where they find a source of ignition.

Regenerators or recuperators are used to recover heat from high temperature furnace exhaust gases.

it, like methane is not poisonous, (just asphyxiating and explosive); it has quite a high spontaneous ignition temperature (SIT) of 650, it has very wide flammability limits (3–70% H, it burns to water vapour, thus eliminating CO. it burns with a much higher flame speed (300 cm/s) than methane (30 cm/s), thus stabilising the flame. Choosing one of the iron and nickel family of catalysts, together with heat, steam, methane and oxygen, a large proportion of hydrogen is made, together with CO2. (For these values, the initial temperature of air, gas, and oxygen is 20 °C.) View a wider selection of the archive from within the Magazine section of this site. Your plant is likely to be legally obliged to control the NOx emissions. So how does the hydrogen content affect the NOx emissions?

There are many ways of accommodating high hydrogen fuel gases whilst still keeping the flame cool enough to minimise NOx formation. There will then be free carbon which will burn with a yellow flame. It’s not unknown for a boiler burner to have five different fuels, though one or two of these fuels may merely be a method of disposing waste or vent gas from another process. The diffusion flame may well obtain sufficient temperature to crack the fuel before it is combusted. This calculation is very similar. We offer readers a flexible range of subscription options and you are certain to find one that suits your needs. Consultant in Combustion Engineering and Radiation Heat Transfer at Kinson Power, H2 and NH3 – the Perfect Marriage in a Carbon-free Society. Phasing over from pure methane to high hydrogen could be achieved with new jets/nozzles, but this procedure would be suited to a specific change of fuel and not just to gradual changes in fuel composition.

But in your neighbourhood and your nation you should be morally obliged to prepare for hydrogen.

The exhaust gases will, of course, take heat out of the high temperature furnace and so heat recovery devices such as regenerators or recuperators become a necessity. Catch up on the latest news, views and jobs from The Chemical Engineer. The general public is increasingly aware of global warming, and remedies such as Reduce, Reuse, Recycle.

The refractory has an emissivity near 1, so radiation to the product is achieved. Burner manufacturers have designs for both premix and nozzle mix flat flame burners, and for both induced draft and forced draft. Adiabatic Flame Temperatures - Adiabatic flame temperature hydrogen, methane, propane and octane - in Kelvin Butane - Dynamic and Kinematic Viscosity - Online calculators, figures and tables showing dynamic and kinematic viscosity of liquid and gaseous butane, C 4 H 10 , at varying temperarure and pressure, SI and Imperial units The radiation from the flame appears less because the flame is dissipated throughout the combustion chamber where the light intensity is high – white hot.

The heat of combustion from a flame at the centre of a pre-mixed cloud of gas and air produces a pressure wave which is sufficient to provide the source of ignition to the adjacent mixture (like a diesel engine) and so the combustion front proceeds at the speed of sound, or greater. All these fuels can be burned with low NO x if the fuel-and-air mixing is controlled and the above primary zone temperature conditions are adhered to. Process stability would suggest that modulation, even if it is only 2:1, would be beneficial.

In these power station burners there can be several other fuels. The flame which one hopes never to see in a furnace is a detonation flame. Hydrogen is well known in many large industries, but for production of other materials. Premix burners therefore have a limited turn-down range and are designed for a particular flame speed. During heatup after a shutdown, rather than trying to modulate the burners, gentle heat input is often achieved by lighting rows or individual burners on/off.