Pulverized Lignite Firing Heaters (BKS)
Power range: 3 MW to 20 MW
Availablity
Pulverized lignite is an easily available source of energy, for which a good supply infrastructure exists.
The delivery is made by special tank trucks of the supplier and filled into the vertical fuel silo.
Typical suppliers are RWE Rheinbraun, Vattenfall and MIBRAG.
An overview can be found on DEBRIV Bundesverband Braunkohle.
Cost benefits
Pulverized lignite is significantly cheaper than natural gas or fuel oil.
The prices of pulverized lignite are just a third of the prices for natural gas or fuel oil.
With the slightly higher operating costs of the system a cost benefit half as much compared to natural gas or fuel oil occurs.
With these cost savings, the higher investing costs will be amortized in a short time.
Good controllability of the power - also with BKS
One of the advantages of the oil and gas heaters is their quick controllability and their large control range from small to major fire. This is important in particular at thermal oil systems in heating processes. It makes the difference between the conventional lignite or wood firing on grates.
Pulverized lignite firing is as fast and as far adjustable as oil firing or natural gas firing.
The dust is blown into the combustion chamber with the BKS burner and burns with a flame which is similar to the flame of fuel oil.
Flue gas cleaning
With the burning of BKS more ashes are produced than with the burning of fuel oil or natural gas.
Therefore, dust is removed from the flue gas before entering the smokestack. For this, cyclone air filters, fabric filters, electrostatic filters or a combination of filters are used.
By using these filters, the requirements to the air pollution control according to German TA-Luft can be kept or undercut.
Power ranges and temperatures
The thermal oil systems with BKS firing start with 3 MW. Usually smaller systems are not economic.
The maximum size with one burner is approx. 20 MW.
The reachable temperatures of the thermal oil are identical to the fuel oil and gas. With mineral oil a temperature of approx. 280°C up to 290°C can be reached, above 350°C are possible with special synthetic oils.
System Components
Heater:
The position of the heater is vertical, the flame is burning from top to bottom and blasts on the round heating surface. The combustion chamber is large, the flame can burn out perfectly.
With small powers, the convection heating surfaces are attached directly to the burner room (three pass heater). With large heaters they are in a downstream device, either as concentric tube coil or as plain tube bundles.
Burner:
The burner is always a multi-fuel type burner, i.e. besides BKS it can also burn fuel oil and/or natural gas. Therewith the system can be started and the fuel BKS can be ignited. If a failure appears in the BKS fuel supply the system can be run with surrogate fuel.
Combustion air preheater:
The hot flue gas are cooled down after the burner. With this heat the combustion air is preheated.
Therewith a higher degree of efficiency can be reached, at the same time the dust removal becomes easier.
The position of the combustion air preheater is vertical. The heating surfaces are either plain tube bundles with the flue gas inside the pipes for easy cleaning or resp. plate fins. Dust can also be refined at the bottom of the air preheater.
Dust removal:
The most most frequently used dust removal system exists of a multi-cyclone and an electrostatic filter. Within the multi-cyclone the largest amount of dust and especially the rough particles are refined. Within the electrostatic filter the fine particles are refined.