Sulzer Technical Review 2 / 2019

Pumps for bio-oil plant

April 28, 2019

The world’s first commercial-scale CHP-integrated bio-oil plant is equipped with Sulzer pumps. This bio-oil is generated with the help of pyrolysis technology and combined heat and power (CHP) integration. Bio-oils can be used as a replacement for heavy fuel oil, further refined as raw material for biochemical and biofuel production. The use of this type of bio-oil has a significantly positive environmental impact because it reduces green­house emissions by more than 70% compared to fossil fuels.

Wood pieces as source for pyrolysis
Author Jukka Vanhalla
Author: Jukka Vanhala, Kotka, Finland.

The bio-oil plant belongs to the company Fortum and is situated in Joensuu, Finland. It has been operating successfully since 2013. The average daily output of this bio-oil plant is 137 tons of oil production (equivalent to 30 MW) and the maximum annual production is 50’000 tons. This corresponds to the yearly heating energy consumption of more than 10’000 houses in the northern hemisphere. The produced bio-oil can replace heavy fuel-oil used in existing oil-burning boilers with minimum modifications.

Raw materials for pyrolysis

Pyrolysis is the basis of several methods for producing fuel from lignocellulosic biomass. Possible biomass feedstock for pyrolysis includes forest residues, sawdust, waste wood, nut shells, straw, cotton trash, rice hulls or prairie grasses. Animal waste including poultry litter, dairy manure and potentially other manures are also under evaluation. Some industrial by-products are also suitable feedstock including paper sludge and distillers grain.

Bio-oil is competitively priced and ideal for sites with logistics that are designed for liquid fuel. Our bio-oil originates from our forests, which is why we have named it Otso, meaning ‘bear’ in Finnish. Being virtually sulfur-free, the bio-oil is a cost-efficient alternative for meeting energy production emissions limits. The Global District Energy Climate Awards organization rewarded our investment into the bio-oil plant with an Innovation award in 2013. Kasperi Karhapää, Bio-oil Business Manager, Fortum Power and Heat, Finland
Play Video
See Pyrolysis video of VTT, the Technical Research Center of Finland.

Flash pyrolysis process

Fuel bio-oil production uses the principle of flash pyrolysis. In this process, a specific feedstock is heated for just a few seconds to temperatures between 350 and 500 °C (660 and 930 °F). The decomposition of the biomass under high temperatures in an oxygen-free environment results in thermal decomposition and new chemical substances. Pyrolysis oil can also be used as a raw material for biochemical and biodiesel production in the future.

Bio-oil from wood chips

At Fortum, the wood chips are transformed in the pyrolysis reactor into a condensable vapor gas at 500 °C. The reactor is heated with hot bed material (sand) from the fluidized bed boiler and the heat transfer sand delivers the remaining solid biochar to the combustor. The vapor from the reactor is captured and condensed into liquid form to bio-oil (Fig. 1). Because of the high viscosity, this bio-oil tends to retain gas while being pumped in the further processes. The gas eventually accumulates in the pump and could disturb the flow and pressure level. An included gas-separation is a must for these process pumps.

Principle of bio-oil production with flash pyrolysis
Fig. 1 The principle of flash pyrolysis for bio-oils (Source: VTT, Finland).
Valmet’s process technologies are used to convert renewable raw materials into pulp, paper and bioener­gy. Valmet has unique knowledge in utilizing renewable raw materials and is active in this field globally. For pyrolysis, Valmet cooperated with VTT, a Finnish research, development and innovation center supporting companies to make use of scientific knowledge and technological innovations. Joakim Autio, Product Manager, Valmet, Finland
Salomix mixer and CFD graphic
Fig. 2 CFD calculation done for SALOMIX SLF mixer (Source: Sulzer).

The pumping solution with gas-separation

The Fortrum bio-oil plant was developed, tested and installed by the company Valmet in Tampere, Finland. During the development phase, Sulzer Pumps Finland Oy was contacted by Valmet to suggest the right process pumps for the plant. The pumps were tested under real process conditions at the Valmet Research & Development center.

The AHLSTAR process pumps (Fig. 3) were equipped with special accessories, usually installed for explosive atmosphere (ATEX) areas. The outstanding feature of the installed pumps was the special gas separation equipment that is required for the pyrolysis process. Sulzer modified the condenser circulation pumps into gas removing A-LM pumps to achieve proper gas separation. Only Sulzer could deliver such pumps to Fortrum at that time. The low energy consumption was another reason to decide on the AHLSTAR pumps. Sulzer also delivered a storage tank and SALOMIX™ SLF side-mounted agitators to the bio-oil plant. The SALOMIX selection was based on computational fluid dynamics calculations (Fig. 2).

Sulzer degassing pumps
Fig. 3 AHLSTAR process pumps with gas separation for flash pyrolysis (Source: Sulzer).

Future developments

In the area of distillation and separation, Sulzer Chemtech offers also solutions for biofuels. “Special internals exist for the separation of fluids containing algae, yeasts and bacteria,” reports Thomas Raiser, Senior Technical Consultant for Bio-fuels at Sulzer Chemtech in Switzerland.

Sebastian Hirschberg, Product and Application Manager Mixing at Sulzer Chemtech, explains: “The uniform heating of biomass is an essential component of process reliability. For the tempera­ture equalization of air flows Sulzer offers air mixing solutions such as Contour™ mixers. These mixers are always adapted to the customer-specific requirements and designed by Sulzer’s experts with the help of computational fluid dynamics (CFD).”

Research is ongoing to identify which renewable biomass materials can be used as sources for biofuels. Sulzer has strong involvement in practically all the related processes. The biofuels business is developing very fast and by cooperating with the biggest players on the market and reacting fast, Sulzer is a cutting-edge supplier. Sulzer is thus supporting the move towards a new, greener era.

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