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What is Dry Low Emission?

Gas fired turbines release Nox Emissions that require dry low emission (DLE) technology to reduce. The amounts produced are dependent on the temperature of combustion. If the temperature of combustion is low, then you can expect lower emissions. Dry low emission technology was incorporated in gas turbines so as to produce lower emissions without the need for steam or water to bring down the temperature. These old method is known as WLE (Wet Low Emission) technology. It has several disadvantages as follows:

dry low emission

  • You need a lot of water for it to work efficiently
  • You need plenty more space
  • Installing it offshore can be something of a nightmare
  • It is heavy

The DLE combustor works off a principle known as lean premixed combustion. This is similar to what you would find with a SAC combustor except for several differences as follows:pics1-resize

  • The DLE requires more space than what is required with a SAC turbine.
  • If you change the turbine on the DLE, you are not able to connect it straight to the equipment you have without having to change the position of your equipment considerably.
  • Depending on the type of gas turbine, the DLE carries 2 or 3 rings holding pre-mixers while the SAC one has only 1 ring.
  • DLE combustors require that you have a control system that is advanced with multiple burners.
  • DLE gives of lower NOx emissions for the simple reason that the process uses up less air and fuel, it has lower temperature and even combustion occurs at lower temperatures.

Background Information

In the 1970’s, there was concern for environmental issues leading to more research and better gas turbines that used steam or water to cool off. By 1980, a reduction to 42ppm was available using these machines and later that amount came down to 25ppm. Later in the 90s, they tested catalysators and ammonium. DLE started being developed in the 80s and in the next decade, it was installed in a variety of places reducing NOx emissions to under 25ppm. Today, using DLE turbines, you can go as low as 9ppm. In order to achieve this, you need to have at least 6% air passing through your pre-mixer.

If you have the new generation burners, you will find that they come with an added injection causing them to have better control. If you want to reduce your emissions to under 2.5 ppm, you should consider adding a SCR (Selective Catalytic Reduction). And if you have just started to think about getting one, consult your plans to our experts and make us install it for you.