The initial dosing rate was set up as 1 liter/50 tons of coal.
During this period, coal for combustion was delivered mainly from mine with low ash melting temperature
Partial self-cleaning of heating surfaces of the boiler was noticed (especially evident as periodic collapsing of slag buildups from the heating surfaces).
Before using Pentomag 2550, inside the firebox liquid slag was flowing down the boiler water walls.
This slag, after collapsing from the walls, created a very difficult to be crushed/crumbled glassy structure.
After using the antislagging additive, slag buildups inside the firebox changed its character.
A trial from using PENTOMAG 2550 at coal fired power plant proved a positive impact of the additive on boilers operation, especially when burning slagging coal i.e. coal with low ash melting temperature.
The additive effectively prevents creating of the deposits inside the boiler
also when co-combustion of coal with over 5% share of biomass, in relation to high amount of chlorine in biomass.
The use of the additive significantly protects the heating surfaces via preventing of deposit formation.
Thanks to this, the following negative aspects can be avoided:
- significant increase of metal temperature, which causes the necessity of full spray water injection to the boiler;
- improper heat exchange between flue gas and heat exchangers, which causes increase of flue gas temperature at the inlet of catalyst above acceptable value and forces the boiler operator to lower the power unit load;
- excessive heat load of the radiant superheaters III0 and V0 which causes increase of primary and secondary steam temperatures as well as decrease of boiler power due to protection measures;
- necessity of mechanical cleaning (or even hammering) of sintered slag inside the firebox.
The additive prevented excessive formation of slag material which causes the above described effects inside the boiler.
Undoubtedly, the additive has to be used when:
- slagging coal is burned;
- co-combustion with more than 5% of biomass takes place;
- coal (from stockyard) of unknown origin is burned;
- when first symptoms of slagging occur.
When it comes to the principle of continuous dosing of coal additive, it would need further investigation with and without using the additive when non-slagging coal is continuously burned and while co-combustion with biomass share below 5%.
The amount of additive and specifics of coal delivery did not allow to perform such analyze in this special case.