ＲＩＴＥ−ＮＩＳＨＩ-ＴＡＭＡ LABORATORY in Ishikawajima-Harima Heavy Industries Co.,Ltd.

NOx (nitrogen oxides), mainly produced from combustion processes, causes ozone layer destruction and air pollution. Heavy type fuels emit more NOx, therefore, it is important to develop low NOx combustion technology especially for these fuels. Heavy oil Type A (by Japanese classification) is a representative heavy oil which accounts for about 10% of the total amount of petroleum consumption in Japan. Generally it is consumed in small boilers and diesel engines and generates 1,000ppm level of NOx emissions. Our aim was to establish a combustion technology that greatly reduces the NOx emissions for heavy oil by adapting technology from the dry low NOx gas turbine combustor. The final goal was to reduce NOx below 90ppm (at 16% O2), more than a 10x reduction.

A dry low NOx combustor of lean premixed combustion type was developed.

Performance tests were conducted at the following conditions:

fuel: low sulfur heavy oil Type A,

inlet air temperature: 390℃,

outlet gas temperature: 1,160℃ (design point; full operating condition).

The results were as follows:

- NOx was under 30ppm (at 16% O2) with over 99.9% of combustion efficiency.

- Ignition range was wide enough for practical use.

- Part load tests confirmed normal combustion over the full load range.

- Carbon deposition occurred locally at the combustor wall.

NOx was greatly reduced below 1/3 of the final goal. Moreover, the basic performance as a practical gas turbine combustor was reached, except for the level of carbon deposition.

We are planning to conduct an engine test to verify the endurance and reliability of the combustor. Our appraisal is that a dry low NOx gas turbine for heavy oil can be practically realized in the near future.