Thank you, NAPO and Rao Arsalan
This week, i visited the boiler site that are firing the low viscos oil.
According to your comments, i tried to find out the guidelines for DP. But, there was no manual or guidelines about it.
The local burner vendor has been trying to solve the problems, but they didn't make it.
Our boiler operating engineers thinks that the vendor doesn't have any solution and doesn't even know the right causes of the problems. And there are no good burner maker here.
The fuel is the blended fuel of light heavy fuel oil(like No.4 or No.5)and No.1(like gasoline).
The viscosity of them are 80cSt and 1.3 at 50 celcius degree(122 Fahrenheit), respectively.
The blending ratio of them is 4:6 or 5:5 or 6:4.
The viscosity of the blended fuel ranges from 3.5 to 8 cSt at 50 celcius degree.
The manual of burner vendor said the burner could cover those viscosity range. But, they don't suggest the operation condition like DP.
The flame envelop the nozzle tip. So, I couldn't see the end of the nozzle tip through the peeping hole.
The angle of the flame is over 150 dgree. The flame color is yellowish but a little hazy.
There are severe carbon deposits around burner tile. The swirler got damaged quickly.
To reduce the flame angle, the operators increased the primary air. But it caused higher NOx emission.
Some handbooks recommend to use air atomizing for light oil.
So the operators are thinking of chaing the atomizing media.
As you mentioned, they don't know how the change will effect on the boiler operation.
Thanks again for your comments.
And i hope you will give more comments how to solve my problems.