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BoilersChemical Recovery Boilers

A chemical recovery boiler is a type of biomass boiler that combusts black liquor produced as a by product in the pulp manufacturing process at paper mills.

Black liquor is a fuel derived from wood chips that is regarded as renewable.

A chemical recovery boiler not only effectively uses the thermal energy gained by combusting black liquor, but also recovers sodium (carbonate) 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 Hitachi Power Systems (MHPS) 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, MHPS 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.

Producing steam at higher pressures and temperatures helps to boost generating efficiency in turbine generating equipment.

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.

Corrosion Protection

With a chemical recovery boiler, the furnace wall pipes and superheater tubes are exposed to a harsher corrosion environment compared with other fossil fuel-burning boilers.

This harsh corrosion environment is due to the chlorine, potassium, sodium and sulfur contained in the black liquor used as fuel. Our recovery boilers employ the following anti-corrosion measures to improve the reliability and durability of boiler equipment.

Furnace Wall Pipes
Covering with overlaying of 25Cr steel
Superheater Tubes
Use of 25Cr steel tubing

Low NOx combustion

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, low NOx combustion can be achieved.

Delivery Records

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 (superheater outlet)
Steam pressure
10.79 MPa
Steam temperature
515°C
Main Fuels
Black liquor, heavy oil
Start of operation
2007

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