Biomass boilers and gasification

BFB/CFB boilers

Bubbling fluidized bed boilers

ANDRITZ innovative fluidized bed combustion technologies for generating power from biomass incorporate decades of experience and have been implemented in all areas of the pulp and paper industry as well as for utility or municipal power plants.

Combustion in a fluidized bed boiler is characterized by thorough mixing and intensive movement of fuel in a dense cloud of heated solid particles under controlled temperature conditions. This excellent mixing leads to improved heat and material transfer during combustion, allowing various fuels to be fired simultaneously in the same boiler.

ANDRITZ offers a wide range of fluidized bed technologies, distinguished by capacity, fuel, and industrial application.

• EcoFluid bubbling fluidized bed (BFB) boilers utilize solid fuels, from clean biomass to alternative fuels and wastes. This efficient combustion technology ensures clean combustion with low environmental impact.
• The bubbling fluidized bed (BFB) is the best technology for combustion of a wide range of biomass and alternative fuels for steam and power generation. The high heat capacity of the fluidized bed evens out the fluctuations caused by fuel quality variation and effectively maintains combustion.
• The EcoFluid BFB boiler is pre-designed with standardized solutions and processes, with the additional flexibility of strongly customer-tailored features. All EcoFluid boilers are designed as natural circulation, high-pressure steam boilers, equipped with auxiliaries and emission reduction technologies as required.

Benefits of the EcoFluid bubbling fluidized bed boiler EcoFilter

• Fuel flexibility
  • Large variations in fuel moisture
  • Large particle size variations
• High combustion and boiler efficiency
• Low emissions
  • Low CO
  • Low NOx with air staging (SNCR and SCR available)
  • Low HCl and SO2 with sorbent injection and bag filter (if needed)
• Low maintenance costs
  • Simple, reliable construction
  • No moving parts
• High availability and long lifetime
  • Conservative design, effective soot blowing, high-quality components

Circulating fluidized bed boilers (CFB)

PowerFluid circulating fluidized bed (CFB) boilers are used for steam and power generation. They are characterized by their unmatched fuel flexibility and cover nearly all solid fuels from coal and biomass to alternative fuels and wastes. The clean combustion technology delivers high efficiency and reliability with lowest emissions.

Circulating fluidized bed (CFB) technology is the best technology for multi-fuel combustion –  the ability to use diverse fuels of differing quality. The diversity of fuels ranges from conventional (coal, oil) and biomass to alternative (biogenous residues, sludge, rejects, and refuse-derived waste fractions with high calorific value). The high heat capacity of the fluidized bed evens out the fluctuations caused by fuel quality variations and effectively maintains combustion.

PowerFluid CFB technology utilizes standard features and processes with strongly custom-tailored features for optimum performance.

Benefits of the PowerFluid circulating fluidized bed boiler

• ANDRITZ’ circulating fluidized bed technologies are characterized by unmatched fuel flexibility, high efficiency, and the ability to burn a wide range of fuels, including fuels which are difficult to burn. PowerFluid boilers maintain almost complete combustion with lowest emissions of nitric and sulfur oxides and high efficiency.
• Highest fuel flexibility
  • Multi-fuel combustion
  • Wide range of heating values, fuel types, and properties
  • Tolerates fuel fluctuations and other disturbances
• Almost complete combustion with lowest emissions
  • Low CO, TOC emissions
  • Low unburned carbon in ash
  • Low SOx with direct desulphurization by adding limestone
  • Low NOx with controlled temperature and air staging
• High efficiency
  • Low amount of excess air
  • High burnout rate
• Excellent load following capabilities and part load behavior
• Reliable design, high availability, and long lifetime

Kraft, sulfite, sodium recovery boiler

HERB kraft recovery boilers

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 the recovery furnace operates more efficiently.

• Vertical air system: The vertical air system mixes the air in 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 correct staging of the air, contributes to a potentially significant reduction in NOx.
• Heat recovery from flue gases: A 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 odorless 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 created easily to check out 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 of 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 achieve 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

Soda liquor boilers (SodEx)

SodEx soda liquor boilers are used for the combustion of chemical and pulp industry wastewater containing sodium, potassium, or biogenous impurities.

The SodEx liquor boiler is a customized solution for the cost-effective discharge and efficient combustion of wastewater from a bleach plant or other chemical process. The high-pressure steam produced can be used for electricity generation or as process steam. Odorous gases can be collected and incinerated in the boiler. An inorganic alkaline solution is produced by an incineration residue processing plant, which can be used to neutralize wastewater.

The benefits

In the course of four decades, ANDRITZ has completed numerous liquor boiler installations and gathered valuable experience in this area. The SodEx boiler is designed for additional combustion of biogases and odorous gases (HVLC).

Sulfite liquor boiler (SulfitePower)

SulfitePower sulfite liquor recovery boilers help to close the chemical loop in a pulp mill – enabling the environmentally safe recovery and reuse of cooking chemicals.

SulfitePower boilers burn the organic content of the concentrated liquor and close the chemical cycle during pulp cooking. The process includes raw acid preparation and combustion of odorous gases while adhering to even the strictest environmental regulations. As a result of the thermal conversion of pulping chemicals, pulp mills can be self-sufficient in meeting their internal energy demand.

A multi-stage chemical recovery system uses highly efficient systems for the separation of both water-soluble and insoluble materials. The scrubber system is uniquely designed for this purpose and guarantees excellent raw acid quality, which is the basis for achieving a high yield during sulfite pulp production.

The benefits of sulfite liquor boilers

ANDRITZ sulfite liquor boilers generate high-pressure steam while converting the main chemicals in the spent cooking liquor to cooking acid for re-use in the pulping process. This is accomplished at very high efficiencies and with low air emissions. The boiler is designed for additional integration and combustion of methanol, furfural, sludge (production waste), gases with high SO2 concentrations, biogases, and odorous gases (HVLC).

BFB/CFB gasifiers

ANDRITZ gasification systems with simple and proven technology substitute fossil fuels with renewable fuel sources. These gasification systems offer high process efficiency and improved  environmental performance.

Gasifiers technology: ANDRITZ gasifiers are based on circulating fluidized bed (CFB) and bubbling fluidized bed (BFB) technologies. Approximate capacity range 10-200 MW fuel per unit.

Bubbling fluidized bed gasification (BFB)

The bubbling fluidized bed (BFB) technology employed by ANDRITZ for biomass gasifiers can be operated at any reasonable pressure and is a valuable technology to mitigate climate change. The technology was originally licensed by the Gas Technology Institute (GTI) in the United States (U-gas and Renu-gas processes). Since then, it has been further developed by ANDRITZ to be used in numerous applications for heat, power, or synthesis gas generation.

The company has developed a low-pressure biomass gasifier and gas clean-up system for use in gas engine-based, combined heat and power (CHP) plants. The first plant (Skive, Denmark) produces 6 MWe and 12 MWth district heating.

The initial emphasis in the development of gasifiers was for high-pressure air gasification to be applied with a gas turbine combined cycle (IGCC) to produce power from biomass with the highest possible electrical efficiency. ANDRITZ is currently involved in development projects to implement the first IGCC plant.

Pressurized oxygen gasification for biomass-to-synthesis gas production and biomass-to-liquids (BTL) has been developed in R&D and pilot scale in collaboration with GTI. Due to the growing interest in producing synthesis gas from biomass for various environmentally friendly gaseous and liquid fuels, we have established several development programs with large industrial partners in order to remain at the forefront of this development. The highest potential use of biomass-based synthesis gas lies in production of liquid transportation fuels and synthetic natural gas (SNG) on a very large scale.

Circulating fluidized bed gasification (CFB)

The circulating fluidized (CFB) bed gasifier was developed in the 1980’s by the former Ahlstrom Oy and was utilized in connection with lime kilns. Gasifier gas from bark and wood residues replaced heavy oil or natural gas as fuel for the kiln. ANDRITZ is in the process of updating this gasifier technology and “re-commercializing” it for use with modern kilns and boilers.

The CFB gasifier is designed to produce 10-150 MWth combustible fuel gas. The gasification system is capable by itself of replacing 100% of the oil/gas consumption in a boiler or kiln with sustainable biomass fuels.

The design is based on high-quality, proven in-house commercial equipment: from biomass fuel receiving equipment to the fuel gas combustion system, including tuning of the entire system. The latest system was sold to Metsä-Botnia, Finland, in 2011.

Most large coal-fired power boilers can be converted at least partially to use gasifier gas from biomass. If biomass is first gasified and the gas incinerated in the boiler, the amount of biomass replacement can be considerably larger than repowering with direct biomass combustion.

Using existing power generation capacity for CO2 reduction would be an economically viable way to utilize local biomass in an amount that is available within reasonable transportation distances. Also, co-firing of biomass gas in large and efficient power plants enables biomass utilization with excellent efficiency compared to distributed generation in small plants.