Chemical Recovery Boilers
A chemical recovery boiler combusts black liquor produced as a by product in the pulp manufacturing process at paper mills.
Black liquor, a fuel derived from wood chips, is regarded as renewable.
A chemical recovery boiler not only effectively uses the thermal energy gained by combusting black liquor, but also recovers sodium ingredients that are reused in the pulp manufacturing process, and thus plays an important role in a pulp manufacturing plant.
Since it delivered the first such chemical recovery boiler in 1951, Mitsubishi Power has delivered more than a hundred units in over a half-century and continues to be one of the leading companies in the field.
Overview
High-pressure, High-temperature Steam Conditions
In 1983, Mitsubishi Power was the first in the world to develop and deliver a high-pressure, high-temperature chemical recovery boiler that produced steam at 10 MPa and 500°C. The highest steam conditions we have delivered to date are a steam pressure of 13.3 MPa and steam temperature of 515°C. Even today, these levels persist as the highest steam conditions for a chemical recovery boiler.
Producing steam at higher pressures and temperatures helps to boost generating efficiency in turbine generating equipment.
Corrosion Protection
With a chemical recovery boiler, the furnace wall tubes and superheater tubes are exposed to a severe corrosion environment compared with other fossil fuel-firing boilers.
This severe corrosion environment is due to the chlorine, potassium, sodium and sulfur contained in the black liquor fired. Our recovery boilers employ the following anti-corrosion measures to improve the reliability and durability of boiler equipment.
- Furnace Wall Tubes
Covering with overlaying of 25Cr steel
- Superheater Tubes
Use of 25Cr steel tubing
Low NOx combustion
Low NOx combustion can be achieved by employing a multi-stage air input method that adds fourth-stage air to the conventional primary, secondary and tertiary air, and eliminating localized regions of excessive air inside the furnace.
Delivery Records
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Customer Marusumi Paper Co., Ltd. Oe Mill Steam Power Plant Plant Recovery Boiler No. 8 Maximum continuous rating 179 t/h Black liquor processing capacity 1,200 t/day (solid matter conversion) Steam conditions Steam temperature 515°C Steam pressure 10.79 MPa Main Fuels Black liquor, heavy oil Start of operation 2007