The unit is a 330 MW boiler. It has 16 burners, tangential nozzles and maximum steam flow of 1010 t/h. The plant was using a slurry type additive that caused more problems than it solved.
The boiler cleaning downtime was 294 hours in six months between July and December.
This caused a production loss of 140 000 MWh during this period.
The unit was burning extremely poor quality fuel that was high in asphaltenes, carbon residue, vanadium, sulfur and water, resulting in severe corrosion and deposit problems.
The boiler has to be shut down every 3 months for cleaning and every 8 months the Ljungstrom air preheater had to be replaced.
Normal efficiency was less than 50%.
Heat value: 40 300 MJ/kg
API gravity at 60°: 11°_par
Viscosity at 80°: 450 cSt (max)
Sulfur content: 3,5% (max)
Water by distillation: 1,0%
Vanadium: 400ppm (max)
Bycosin’s organic magnesium based product, DP 94001 deposit inhibitor was proposed for the trial as it has been proved to be superior to other treatments used at the plant.
At this particular plant the treatment used was causing more problems than it was solving. It was important for the plant to get a quick reduction of deposits, which was another reason to use the Bycosin DP 94001.
DP 94001 deposit inhibitor has proven to be superior to other treatments by keeping tubes clean and reducing or eliminating slag deposits and making the remaining deposits soft, porous and easy to remove.
Using a high dosage (1:2000) allows rapid removal of a heavily slagged boiler.
DP 94001 also reduces stack solids.
Cleaning downtime has shown to be reduced by as much as 75%.
The organic Mg easily penetrates into the deposits and reduces the vanadium bond and allows the slag to fall off the tube and changes the consistency of the deposits that remain.
The treatment increases the melting temperature of the ash in the fuel, reducing additional deposits and preventing corrosion at both high and low temperatures.
This allows a better heat transfer and better boiler efficiency.
The trial was done in two steps over two years. The first step was to see what Bycosin could do when added into a very dirty boiler.
Then the boiler was mechanically cleaned and the plant was run with DP 94001 for a period of
23 months. Then the second phase was run as a new test both with and without Bycosin to get baseline readings.
The trial objectives was protecting the boiler against corrosion, to maintain its capacity and not loosing any production due to unscheduled stops.
The trial was initially run for twelve days and the data was collected and evaluated in several ways. The trial then continued for 23 months with the 94001 before the plant decided on a second phase to comparing both “With” and ”Without” the additive.
Note the effect on the super heater tube temperature when Bycosin DP94001 was used. The decrease in temperature is because the flame is shortened by the action of the catalyst from the additive.
The catalyst helped to burn the fuel more efficiently and the larger molecules in the oil were more completely burned.
The plume reduction at the stack was reduced from a huge black stream to a light haze and unburned carbon was substantially reduced.
A secondary effect was that the stack solid particle acted as precursors to deposits. If the amount of stack solids can be reduced, the deposits will also be reduced resulting in better heat transfer and higher efficiency.
Note the graph on next page that shows that power output increased and stabilized.
The main goal with the second phase was to get a comparative test with and without Bycosin additives. The trial period was 27 months long and started without dosage July 1 year one and was finished Jan 5 year two. The comparative trial with Bycosin additive was made between Oct 18 year two and March 22 year three.
Without additive, the plant had to wash the air pre heater twice, do a partial cleaning of the furnace and clean the superheater once. About three quarter into the reference run, the boiler had to be shutdown due to fouling and the loss of production was 139 861 MW.
When using Bycosin, the plant was able to complete the full second trial without stopping.
The fouling significantly diminished which allowed the boiler to stay clean and operate at a much higher capacity.
After the trial, a significant improvement in cleanliness was observed in the air preheater. The mechanical cleaning was carried out in a much shorter time and with longer cleaning intervals.
Improve Boiler Output:
During the trial the objective was to maintain boiler capacity of 330 MW and to keep the furnace from dropping in production power before a planned shutdown.
Also, during the entire trial, the metal surfaces of the tubing at the super heater would not overheat.
Long Term Benefit:
As a boiler starts to foul, the pressure in the furnace would rise to a critical level where the boiler had to be shut down. This happened after about 2/3 of the trial period when they were not using the DP94001.
When the oil was dosed with DP94001, the boiler went the entire trial period at a steady pressure and without any premature shutdowns.