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HERB kraft recovery boilers

High Energy Recovery Boilers (HERB) for the kraft pulping process feature a unique vertical air system that minimizes emissions and ensures a high power-to-heat ratio from the recovery process.

The challenge

Rising energy costs and the security of supply are causing pulp producers to re-think their overall energy strategy. Critical to that strategy is the chemical recovery boiler. Thermal energy from kraft black liquor is regarded as CO2 neutral. The capability to produce surplus energy, which can be sold as green energy, is also enticing. A recovery boiler capable of maximizing the production of thermal energy and at the same time efficiently recovering the chemicals is required.

The solution

The ANDRITZ HERB kraft recovery boiler is designed to deliver the highest power-to-heat-ratios from the recovery process. The vertical air system enhances the combustion process so that recovery furnace operates more efficiently.

Vertical air system

The Vertical Air system mixes the air around the combustion process so that the recovery furnace operates more efficiently. The furnace can be operated with a smaller amount of excess air, which lowers the amount of flue gas and the power consumption of the fans. A reduced excess air amount, in combination with the correct staging of the air, contributes to a potentially significant reduction in NOx.

Heat recovery from flue gases

Part of the HERB design is the heat recovery from flue gases after the electrostatic precipitator. Additional cooling of the flue gases results in substantial savings in auxiliary fuel consumption. As an alternative, increased electricity production can be achieved.

Diluted non-condensable gases and dissolving tank vent gas burning in recovery boiler

All diluted non-condensable gases (DNCG) collected from the pulp mill, together with the dissolving tank vent gases, can be burned in the HERB unit in order to achieve an odourless mill with minimum emissions to the atmosphere.

Dynamic training simulator

The IDEAS dynamic simulator is ideal for design and training purposes. A virtual plant is easily created to checkout DCS configurations and train operators well before construction of the actual boiler is completed. Operators can become proficient in managing disturbances or making set point changes in a safe, virtual environment that is an exact duplicate of the view on the actual DCS.

Recovery boiler ACE

The ACE family of software tools optimizes the control and operation of any kraft recovery boiler. The optimization software helps achieving more uniform, stable operation. ACE products are based on a unified platform of software, hardware, and communication architecture.

HERB benefits

  • Designed for capacities up to 8,000 tds/d
  • Low NOx and other emissions to the atmosphere
  • More power from the same initial energy
  • Green energy (CO2 neutral) production

ANDRITZ High energy recovery boiler, HERB

ANDRITZ high energy recovery boiler (HERB)

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