The Foster Wheeler

gasification technology for biofuels:

refuse-derived fuel (RDF) power generation

Juha Palonen Foster Wheeler Energia Oy

Finland

Timo Anttikoski Foster Wheeler Energia Oy

Timo Eriksson

Foster Wheeler Energia Oy

Abstract

Fluidized-bed gasification enables cheap, CO2-neutral and local low-grade fuels such as wood chips, wood waste, bark, demolition wood, straw and also waste such as REF (in-origin classified recycled fuel) and refuse-derived fuel (RDF) to be converted into combustible gas for replacing expensive and CO2-intensive oil, natural gas or coal. Foster Wheeler Energia Oy (FW) has continued to develop its gasification technology to meet the technical and legislative demands arising from using primarily waste-derived fuels. Cleaning the product gas of particles, alkalis, chlorides and heavy metals prior to combustion enables safe utilization of waste fuels in a new or existing high-efficiency boiler. It essentially eliminates the risks related to direct co-firing in boilers, e.g. fouling and corrosion of heat surfaces, deactivation of DeNOx catalyst and contamination of the boiler fly ash. The end target is that when the product gas has been cleaned and it is fired in a boiler together with other fuels, it should be considered as “normal” fuel, not a waste-based fuel. Such interpretation has already been validated for one case in Finland, the Lahti gasifier plant in Finland. Pilot plant tests and long-term testing with slipstream equipment at the Lahti gasifier plant proved the performance of this clean gas concept. The product gas can be cleaned sufficiently to be utilized to produce electricity at high efficiency. The efficiency of a gasification plant in electricity production can be higher than 35 %. Typically, in conventional waste incineration, it is lower than 25%, even in modern plants. This paper describes the status of the FW gasification technology for refuse-derived fuels, efforts to commercialize the clean gas concept for RDF fuels and the early stages of the recent development work targeted at bioliquids production. 1. Introduction The FW CFB gasification technology was developed in the early 1980s, the driver for development being very high oil prices. The first commercial-scale CFB gasifiers, using 17 to 35 MW of dry waste wood as feedstock, were delivered for the pulp and paper industry in the mid 1980s, enabling oil to be substituted in the lime kiln process. During the 1990s, a gasification process producing raw gas from a variety of biomass and recycled fuels to be co-combusted in a pulverized coal (PC) boiler was developed. Additionally, three commercial-scale atmospheric CFB/bubbling fluidized-bed (BFB) gasifiers with fuel inputs from 40 to 70 MW were supplied during the years 1997-2003. Based on these recent successes and evaluation of the future needs, FW has been developing a gasification concept for converting difficult-to-burn, mainly waste-derived solid fuels into clean gas either to be co-combusted in existing boilers or to be combusted all alone in a so-called stand-alone/greenfield concept. The first project using this concept, including a 160 MW gasification plant, hot gas cleaning equipment and combustion in a new gas fired boiler is currently at the negotiation and permitting phase.

Regarding future renewable energy applications, biomass is recognized in many countries as the energy source with the largest potential. Gasification is an attractive conversion process due to its high efficiency and the numerous potential uses of the product gas. FW is actively participating in R&D programs and projects targeting at future syngas applications. VTT (Technical Research Centre of Finland) together with FW, Neste Oil and other industrial partners, is developing the gasification process and especially the gas treatment, in order to be able to produce ultra-clean product gas. The process is based on pressurized oxygen-steam fluidized-bed gasification, followed by novel catalytic gas reforming technology. The gasification process is designed for a wide range of biomass feedstocks including different woody biofuels, straw and other agrobiomasses, as well as various waste-derived fuels. The novel gas cleaning technology eliminates the tar problem, maximizes the syngas yield and makes it possible to adjust the H2/CO ratio of syngas. The ultra-clean syngas is suitable for producing end products such as Fisher-Tropsch liquids, methanol, synthetic natural gas (SNG) and hydrogen. 2. Gasification Advantages With fluidized-bed gasification, cheap and potentially CO2-neutral solid fuels can be converted into combustible gas for replacing expensive oil, natural gas or coal. Locally available low-grade fuels such as wood chips, wood waste, bark, demolition wood, straw and wastes such as REF (in-origin classified recycled fuel) and refuse-derived fuel (RDF) have been successfully gasified. A CFB gasifier is a true multifuel unit with good fuel flexibility, i.e. the above-mentioned fuels can be used in the same unit - though the heat output varies with the heat value of the fuel. In Europe, typically about 30-150 MWth of biofuel energy is available within a 50 km radius of a power plant. By connecting a gasifier for instance to a mid- or large-size coal-fired boiler with a high efficiency steam cycle, local biomass sources can be converted to CO2-neutral power and heat at very high efficiency, compared with stand-alone boilers with the same fuel input. The gasifier-PC boiler process connection also offers low investment and operating costs, utilization of existing power plant capacity with small modifications to the main boiler, high plant availability and reduction of the boiler emissions. The clean gas concept with pre-combustion cleaning of the product gas makes it possible to safely utilize difficult-to-burn, waste-based fuels in a high efficiency PC boiler without the risks associated with direct co-firing, such as fouling, high temperature chlorine corrosion and poisoning of the DeNOx catalyst. A stand-alone power plant can also be based on the clean gas gasification technology. In such a concept, clean gas is fired alone in a new gas-fired boiler, which can be designed for clearly higher steam data than normal boilers utilizing waste-based fuels, resulting in high efficiency in electricity production. This concept is presented in more detail in Chapters 8 - 9.

3. Foster Wheeler Atmospheric CFB Gasification The atmospheric CFB gasification system developed by FW is relatively simple. It consists of a gasification reactor, a cyclone to separate the circulating-bed material from the gas, and a return pipe to return the circulating material to the bottom part of the gasifier. All these components are entirely refractory-lined. From the cyclone, the hot product gas flows into an air preheater located below the cyclone. Gasification air is blown with a high-pressure air fan through an air distribution grid at the bottom of the reactor, below a bed of particles. The air velocity is high enough to fluidize the bed particles and convey some of them out of the reactor and into the cyclone, where most of the solids are separated from the gas and returned to the lower part of the gasifier. Both the gas and solids are extracted from the bottom of the cyclone. The circulating solids contain char that is combusted with the fluidizing air, generating the heat required for the pyrolysis process and subsequent, mostly endothermic, gasification reactions. The circulating material also serves as a heat carrier and stabilizes the process temperatures. Coarse ash accumulates in the gasifier and is removed from the bottom with a water-cooled screw. The following Figure 1 shows the main components of a CFB gasifier and Table 1 shows the reference list. Figure 1. The Foster Wheeler Gasifier.

850 °C

900 °C

BOTTOM ASH COOLING SCREW

HOT LOW CALORIFICGAS (750 - 650 °C)

UNIFLOW CYCLONE

BIOFUEL FEED

REACTOR

BOTTOM ASH

GASIFICATION AIR FAN

COOLING WATER

AIR PREHEATER

RET

UR

N L

EG

850 °C

900 °C

BOTTOM ASH COOLING SCREW

HOT LOW CALORIFICGAS (750 - 650 °C)

UNIFLOW CYCLONE

BIOFUEL FEED

REACTOR

BOTTOM ASH

GASIFICATION AIR FAN850 °C

900 °C

BOTTOM ASH COOLING SCREW

HOT LOW CALORIFICGAS (750 - 650 °C)

UNIFLOW CYCLONE

BIOFUEL FEED

REACTOR

BOTTOM ASH

GASIFICATION AIR FAN

COOLING WATER

AIR PREHEATER

RET

UR

N L

EG

Table 1. Foster Wheeler atmospheric gasifier references.

Customer SizeMW

Fuel Applica tion Year

Hans Ahlstrom Laboratory, Finland 3 Misc. Test unit 1981

Oy W. Schauman Ab, Finland 35 Bark,sawdust Lime kiln fuel 1983

Norrsundet Bruks Ab, Sweden 25 Bark Lime kiln fuel 1984

ASSI Karlsborg, Sweden 27 Bark Lime kiln fuel 1984

Portucel, Rodao, Portugal 15 Bark Lime kiln fuel 1985

Kemira Oy, Vuorikemia, Finland 4 1986

Lahden Lämpövoima Oy, Finland 40-70 Biofuels Hot raw gas to boiler

1997

Coal, peat

Test unit, clean gas

Corenso United Ltd., Finland 40 2000Aluminiousplastic waste

Cyclone cleaned gas to boiler

Electrabel, Belgium 50 Biofuels Hot raw gas to boiler

2002

4. The Lahti Gasifier, a Showcase for the Technology The first CFB gasifier connected to a PC boiler was constructed in 1997 at the Kymijärvi power plant of Lahden Lämpövoima Oy. The Kymijärvi power plant produces electric power (167 MWe) and district heat (240 MW) for the city of Lahti, Finland. The Lahti gasifier was connected to a 20-year-old Benson-type once-through boiler, the steam data of which are 125 kg/s, 540 °C/170 bar/540 °C/40 bar. The boiler was converted from heavy-oil-firing to coal-firing in 1982, and typically it operates about 7,000 h/a, depending on the heat demand and electricity prices. The Lahti gasifier started commercial operation in 1998 and initially used biofuels such as bark, wood chips, sawdust and uncontaminated wood waste. Other fuels have also been tested subsequently, including in-origin classified waste fuel (REF), railway sleepers and shredded tyres. As a result of availability and price changes, the share of REF fuel has gradually increased at the expense of cleaner biofuels. The gasifier has operated well with varying fuel mixes, with availabilities of 96 % or higher. Figure 2 shows the fuels used and energy produced in 1998–2005 and Table 2 the annual availabilities 1998-2001 (not calculated since 2001).

Figure 2. The fuels used and energy produced in the Lahti Gasifier 1998 – 2005.

6348 49 39

2514 22 25

9

9 1515

3136 30 30

1523

2934 31 38 38 40

57 11 11 11 8 5

14

0 %

20 %

40 %

60 %

80 %

100 %

225GWh

342GWh

295GWh

445GWh

407GWh

415GWh

427GWh

297GWh

1998 1999 2000 2001 2002 2003 2004 2005

OthersPeatPaperPlasticsREFGluelamWood

Table 2. Annual operating availabilities of the Lahti Gasifier 1998 – 2001.

1998 1999 2000 2001 Availability % 99.3* 98.9 97.1 96.1 * Second half of the year. The effects of the gasifier on the main boiler were studied with comprehensive measurements during a one-year monitoring program. The changes in the boiler emissions are presented in Table 3. Table 3. Summary of the gasifier effect to the main boiler emissions. Emission Change caused by gasifier CO2 Decrease by ~ 100 000 ton/a NOx Decrease by 10 mg/MJ (5 - 10 %) SOx Decrease by 20 – 25 mg/MJ HCl Increase by 5 mg/MJ * CO No change Particulates Decrease by 15 mg/m3n

Heavy metals Slight increase in some elements, base level low

Dioxins, Furans, PAH, Benzenes, and Phenols No change

5. The Ruien Gasification Project Following the success in Lahti, a gasification plant based on the same concept was constructed at the Electrabel Ruien power plant, which is the largest fossil fuel-fired power plant in Belgium. The gasifier was connected to the tangentially-fired once-through boiler (steam values 180 bar / 540 °C) of Unit 5, which has a power output of 190 MWe. The new plant increases the use of renewable energy, thus reducing CO2 emissions. The Flemish legislation includes a system of green certificates to encourage the use of renewable energy. Figure 3 illustrates the gasifier connection to the boiler. Figure 3. Layout of the Ruien Gasification Plant connected to the PC boiler.

The design fuel for the gasifier is fresh wood chips, but the gasifier can also utilize other types of fuel, such as bark, hard and soft board residues and dry, recycled wood chips, and the fuel moisture may vary between 20 and 60%. Depending on the fuel mix, the heat input to the boiler is normally 45 – 70 MW. The plant has been in commercial operation since May 2003. 6. The Corenso Gasification Project In Europe, about a million tons of liquid carton board is consumed annually. The majority of this still ends up in landfills due to the lack of collecting systems. Additionally, until now, there have been difficulties in utilizing the remaining mixture of plastics and aluminum in energy production. A new concept was developed based on BFB gasification technology capable of generating power from plastics and recovering aluminum and the world’s first plant was built in Varkaus, Finland. Originally, the liquid packaging board recycling plant was opened at the end of 1995 at Corenso United Oy Ltd’s coreboard mill in Varkaus. The mill’s fiber recycling plant (in Figure 4) separates used liquid packages and wrappings into their components: separated wood fiber is used for coreboard production and, formerly, the remaining mixture of polyethylene plastics and aluminum would be incinerated in a boiler. However, incineration of this mixture in a normal boiler proved to be very problematic due to the aluminum forming deposits on the heat transfer surfaces and on the grid of the boiler. These layers had to be removed at regular intervals, which caused interruptions in the power production and decreased the availability.

In order to overcome the problems, a new concept based on BFB gasification technology was developed by Corenso United Oy Ltd with FW and VTT. The process development work started at VTT’s test laboratory in 1997, followed by a 15 MW demonstration-scale gasification plant built by FW at StoraEnso’s (SE) Varkaus mill. During the tests this demonstration plant was operated for a total of 1,400 hours. Figure 4. Recycling of multi-material packaging.

The development work resulted in construction of a full-scale gasification plant at the SE Varkaus mill by FW, the plant having an output of 40 MW, generating 165 GWh of syngas energy and recovering and recycling more than 2,100 ton/a of metallic, non-oxidized aluminum. The gasification plant shown in Figure 5 has been in operation approx. 23000 hours (December 2005).

Figure 5. Corenso gasification plant at Varkaus paper mill.

7. Gasification of Straw Straw gasification technology, including gas cooling and cleaning, was developed further and found technically feasible by Foster Wheeler and Energi E2 (Denmark) in 1999 - 2001. The work also included development of the straw feeder technology of TK-Energy (Denmark). 7.1 Tests Carried Out The alkaline and chlorine contents of straw may vary significantly, but the following values are typical for Danish straw: sodium (Na) 0.03 %, potassium (K) 1.8 % and chlorine (Cl) 0.6 %, all in d.s. Straw gasification test runs were carried out at the FW 3-MWth ACFBG pilot plant. 7.2 Test Results During the three test campaigns, more than 220 tons of pelletized and loose straw were gasified, with over 400 total operating hours. Based on the pilot test program, the following conclusions could be drawn:

− Gasification of loose straw is technically feasible. − Smooth, stable operation with high-alkaline fuel was achieved. − Wood and straw may be gasified together with trouble-free operation. − Carbon conversion was in the 95 - 97 % range. − Both soot blowing and spring hammering kept the gas cooler clean. − The hot gas filter operated well without blinding by tars and it also removed

alkalis and chlorides at 350 - 370 °C. − In the gasification conditions, PAH were formed but dioxins and furans were

not formed. − The optimal gasification conditions were validated in the project.

7.3 A Full-Scale 100 MWth Straw Gasification Plant A design study was carried out for a full-scale straw gasification plant integrated with an existing large combined heat and power (CHP) plant. Practical solutions for all unit operations were developed. The budget for a complete plant was calculated and consequently the overall project economics were assessed. The results of the process validation and design study offered a technical and economic basis upon which to base a decision regarding a demonstration plant. The design study indicated that the economics of a 100 MWth gasifier integrated with an existing large CHP plant are sensitive to the fuel and energy prices. At the price level of 2001 (e.g., straw price 5.6 €/GJ or 83.1 €/ton; market price of electricity 21.4 €/MWh), a biomass fuel slightly cheaper than straw would have been required to make the investment profitable in Denmark. Technical and economical evaluations have been continued for straw and other biofuels with high alkali and chlorine contents, but so far no plants based on this concept have been built. However, the economics appear to favor the lowest-cost waste-based fuels that can be converted to power and heat with nearly identical systems.

8. Energy Production from Recycled Fuels through Gasification 8.1 Background Energy recovery from industrial and municipal wastes has become an important option for waste management and power production. The Kyoto protocol and the EU’s target to increase the share of renewable energy favor this trend. In the future, landfilling will not be possible for materials that can be composted or contain combustible fractions. In addition, requirements for more efficient recycling and energy recovery favor technologies utilizing combustible fractions at the highest efficiency. Building on the successful demonstration of CFB gasification and co-combustion in Lahti, FW has been developing gasification-based solutions for turning waste fuels into electricity and district heat energy. Besides pilot plant tests performed at FW’s Karhula R&D center with gas cleaning, long-term testing has been carried out with slipstream equipment at the Lahti gasification plant. This slipstream unit was provided with a FW gas cooler and a commercial hot gas filtration system. During the tests the slipstream unit was operated for more than 3300 hours. This development project led by FW has been co-funded by TEKES (National Technology Agency of Finland), and the other partners were Lahti Energia Oy and Energi E2 from Denmark. 8.2 Karhula Pilot Tests Karhula pilot plant tests have been one essential part of the development path. Operation at pilot-scale enables testing and optimization of different process components and process conditions at relatively low cost before moving on to a commercial-scale plant. The pilot plant is a complete gasification plant comprising an adjustable fuel feeding system, CFB gasifier, gas cooler, product gas filter and gas combustion either in a separate combustor unit (enables emission measurements) or in flare. Different types of fuels have been tested: wood chips, coal, straw, plastic-paper-aluminum pellets and RDF with chlorine content up to 2%. Other tests included different types of gasifier bed materials, gas cooler arrangements and cleaning methods. In summary it can be stated that, according to the gasification test runs performed at the pilot-scale CFB gasifier, syngas cooling and filtration in a hot gas filter are feasible. However, the operating hours of the pilot test runs were not adequate to reliably evaluate the long-term performance of the syngas cooler and filter elements. Thus, it was vital to continue the testing on long term basis in Lahti as described in the following chapter.

8.3 Lahti Slipstream Tests A slipstream process was constructed at the Lahti CFB gasifier for long-term testing of the gas cooler and product gas filter in realistic conditions, with product gas generated in normal operation of a commercial-scale gasifier running on waste- and wood-based fuels. The objectives of this project were to test the pieces of equipment in a commercial-type operating environment and generate data on the availability and performance of the system. The process conditions were fully representative of those which would be expected in “normal” operating conditions. Generally, the gasifier fuel was a mixture of wood and waste (REF), typically about 40% waste and 60% wood-based fuel. Additionally, tests with up to 100% waste were carried out to study syngas combustion and the emissions formed in the combustion of waste derived syngas. 8.3.1 Slipstream Pilot Plant Figure 6 shows an outline of the slipstream test unit consisting of the following equipment: Syngas cooler including ash removal system , hot gas filter with ash removal/recycling system, syngas fan, syngas combustor and auxiliary equipment (nitrogen system, additive feeders). Typically about 5% of the total syngas flowing from the 40-70 MWth CFB-gasifier to the main boiler was extracted to the slipstream unit. In the gas cooler, syngas temperature was decreased to the filtration temperature. After the hot filter, a fan provided with frequency converter for flow-rate control increased syngas pressure, and the gas was led back to the main gas line or to syngas combustion. Figure 6. Outline of the Lahti slip steam unit.

The slipstream unit was operated from March 14, 2003, to April 26, 2004, for a total of 3,346 hours. In general, the long-term testing was smooth and major problems did not occur. Most of the interruptions of the slipstream testing were caused by malfunction of auxiliary equipment. Problems in the main equipment, syngas cooler and hot filter, caused few interruptions. Generally, they worked reliably. In the filter unit, different filter elements were tested in parallel: 3M’s glass fiber bag filters with ceramic coating and rigid low-density candle filter elements supplied by Tenmat (calcium silicate) and Madison Filter (aluminum silicate). The filtration temperatures varied from 320°C to 400 oC during the tests. The separation efficiency of the filter was excellent, with dust contents below 10 mg/m3n measured downstream of the filter. None of the tested elements of any type failed in service, and also after the testing all the elements were found to be intact. During the long-term testing, the syngas cooler worked properly the majority of the time. The hampering tar condensation on the cooling water tubes can be avoided by adjusting the temperature of the cooling water to the right level. Only a thin tar layer condensed on the surfaces of the water tubes. The syngas cooler was kept clean with FW spring hammers and typically, the cooling water tubes were kept quite clean even with infrequent operation of the spring hammers. The excellent operation of the gas cooler and the spring hammering was confirmed in the inspection made after the testing was completed: Some ash deposit was found between the spaces of the cooling water tubes, but this was only in the first cooling element, which was known to be at too high temperature from the very beginning. In addition to the long-term testing, syngas combustion tests were carried out in order to study the emissions in filtered syngas combustion. Syngas was co-combusted in a separate boiler with natural gas in combustion tests done in October–November 2003. Four syngas combustion test runs were performed with three different gasifier fuel mixtures of biomass and REF: 60/40, 30/70, 0/100. The following summarizes the experiences:

− Most of the heavy metals were in solid phase at the syngas filtration temperature and thus they can be captured from syngas to the filter ash.

− Above 99.9% of the fuel heavy metals can be removed to ashes. Mercury is in gas phase and it cannot be removed by filtration. The mercury content of flue gas is thus dependent upon the fuel mercury content. An additional process step will be able to capture mercury.

− The limit values of heavy metals set by the EU’s Waste Incineration Directive (WID) were easily met.

− In clean syngas combustion PCDD/F compounds did not form. The total content of dioxins and furans was only 0.00002 – 0.0004 ng/m3n I-TEQ, while the WID emission limit is 0.1 ng/m3n I-TEQ.

− About 80% of chlorine retention to ashes was achieved by normal limestone addition to the gasifier and syngas filtration. With calcium hydroxide (Ca(OH)2) feeding before the filter, chlorine retention was increased to above 95%.

− Sulfur retention to ashes was moderate. Most of the fuel sulfur appears in flue gas in gaseous phase and complete sulfur retention would require separate flue gas cleaning, because calcium-based sulfur retention is equilibrium limited in gasification.

8.4 Ash-Related Issues Fly ash disposal-related costs represent a significant share of the overall operating cost of gasification-based energy production. It is also expected that landfilling cost will increase in near future. Due to the reasons above, FW has, during recent years, expended a great deal of effort in R&D work focused on gasification ash treatment systems. Both internal R&D work, literature and experimental, and work with different institutes have been performed. With regard to the fly ash upgrading, based on both the internal development work and work performed together with other institutes, fluidized-bed oxidation of fly ash has proven to be very efficient and feasible, and the final product was very similar to conventional combustion fly ash. Depending on the general layout and concept, a fly ash oxidation reactor can be a stand-alone plant or it can be integrated to the gasifier or boiler. Depending on the location, it is possible to avoid additional flue gas cleaning facilities and simultaneously overall carbon conversion is increased close to 100%. 9. Commercial Clean Gas Concept for RDF FW has, over recent years, been developing a gasification concept for converting difficult-to-burn, mainly waste-derived solid fuels into clean gas either to be co-combusted in existing boilers or to be combusted in a so-called stand-alone concept (see Figure 8). Compared to the traditional combustion processes, the key advantages of this process are:

− It enables gas firing also in oil- and gas-fired boilers, heat recovery steam generators, etc

− Gas converted from difficult solid fuels (such as waste-based fuels) can be used safely in high-efficiency steam cycles

− A stand-alone waste-to-energy (WTE) concept based on gasification technology offers clearly higher electric efficiencies compared to normal WTE plants, as illustrated in Figure 7.

Figure 7. Electric efficiency and electricity production (operated at condensing mode) of different applications fired with waste based fuels.

ηe = 36 % 57 MWe

Gasification 120 bar, 540 ºC

40 MWeηe = 25 %Grate firing 40 bar, 400 ºC

40 MWeηe = 25 %Grate firing 40 bar, 400 ºC

9.1 The Lahti Stand-Alone 160 MWth Gasification Power Plant Case The objective for this project is to build a completely new CHP plant in the Kymijärvi power plant area in Lahti. The heart of this new CHP plant is a CFB-based gasification process equipped with gas cooling and cleaning systems. The cleaned product gas is combusted in a gas-fired boiler and the flue gases are additionally cleaned in a bag-house-type filter before the stack. The major advantage of this concept is that the product gas is cleaned before combustion. By removing harmful components before combustion, it is possible to produce energy from waste-based fuels with high steam temperature and pressure values, resulting in higher electrical efficiency than in units based on direct combustion technology. The design fuel input of the plant is 160 MW, electricity production about 50 MW and district heat production, 96 MW. On an annual basis the maximum waste stream through the gasifiers will be 250.000-300.000 t/a. The fuel, or waste, is a mixture of industrial-based RDF and locally sourced and sorted waste from households. Figure 8. The Foster Wheeler gasifier concept for recycled fuels.

Main boiler feed water

Main boiler furnace

Recycled fuels

CFB Gasifier

Pulsing gas

Cooling water

Flare

LP Steam

Filters

Fly ash

Bed materials

Gas cooler boiler

Fuel feed system

Main boiler feed water

Main boiler furnace

Recycled fuels

CFB Gasifier

Pulsing gas

Cooling water

Flare

LP Steam

Filters

Fly ash

Bed materials

Gas cooler boiler

Fuel feed system

Figure 9. A side view of a stand alone gasification power plant using RDF / REF as a fuel. The plant concept includes a waste fuel (RDF) reception and storage station; two separate 80 MW gasifier lines, each consisting of a gasifier, product gas cooler and hot product gas filter (with sorbent feeding); one common gas-fired boiler and a new CHP turbine plant. A bag house filter equipped with sorbent feeding will be installed after the gas-fired boiler to ensure that emissions will meet the EU WID requirements. Other miscellaneous equipment such as ash and water handling equipment are naturally part of the project. The system outline is presented in Figure 9. Based on today’s calculations, the value of the 160 MWth project is roughly 100 M€. 10. Biomass to Liquids – Long-term Development

10.1 Europe The current biofuel options are not economically feasible without supporting measures from the authorities, like tax relief. The EU’s Biofuel Directive presents an indicative target share of 5.75% in 2010 for the exploitation of biomass-based road transportation fuels in the EU, which corresponds to a biofuel utilization of about 17-18 Mote/a. In 2004, about 2 million oil equivalent tons of bioethanol and biodiesel were produced in the EU. Wood- and waste-derived liquid or gaseous transportation fuels could be produced more cost-effectively than the current commercial ones. These also having much lower greenhouse gas emissions than current biofuels. New production technologies are under development in several countries, and the first demonstration plants are expected to start up in the near future. 10.2 Process Development Aiming at Ultra-Clean Synthesis Gas FW, together with Neste Oil and other Finnish-based industrial partners, is participating in a VTT-driven project targeting the development of an advanced process for producing multi-purpose synthesis gas from solid biofuels.

The process is based on pressurized oxygen-steam blown fluidized-bed gasification followed by novel catalytic gas reforming technology. The new gasification process is designed for a wide range of biomass feedstocks including woody biofuels, straw and other agrobiomasses, as well as various waste-derived fuels. The novel gas cleaning technology eliminates the tar problem, maximizes the syngas yield and makes it possible to adjust the H2/CO ratio of the syngas. The synthesis gas can be raw material for various end products: Fisher-Tropsch liquids, methanol, synthetic natural gas (SNG) and hydrogen. Concentrating on the production of Fisher-Tropsch liquids seems to be the most promising option in the short and medium term [1]. The process is being developed on a 500 kW-scale process development unit during the period 2005-2007. Industrial demonstration is projected at the moment for 2008-2010. The Finnish development work is aimed at intermediate-size syngas plants that will be economically feasible at 200-300 MW fuel input, especially when integrated with energy-consuming plants of other industries. The development focus is on the front end of the process: biomass handling, gasification and ultra-cleaning of gas to meet the specifications of the production processes of the above-mentioned end products. Compared with the other transport bioliquid processes, this approach advantages, including:

− Range of feedstocks is wide: forest residues, bark, straw, agrobiomasses, recycled fuels, peat (as a reserve fuel).

− Synthesis gas can be used for the production of several end products: diesel fuels, methanol/dimethyl ether (DME), synthetic natural gas or hydrogen.

− Diesel fuel, which is produced via Fisher-Tropsch synthesis, can be used directly in diesel engines either on its won or mixed with conventional diesel fuel. No new distribution networks are needed.

− Gasification plants producing synthesis gas can be integrated to the energy-consuming pulp and paper industry resulting in high energy efficiency for the biomass used.

Figure 10. Synthesis gas plant producing bioliquids, integrated to pulp and paper plant [Source: VTT].

Wood, strawenergy crops,peat, RDF

FT-synthesis& upgrading

Gasification andgas treatment

Pulp andpaper mill

Biomasshandling

anddrying

powerplantProcess steam & power

Paper& pulp

WoodDiesel

Energyto drying

synthesis-gas

bark,forestresidues,otherbiomass

fuel gas+ steam

steam & oxygen

11. Conclusions Energy recovery from industrial and municipal wastes has become an important option for waste management and power production. In the future, materials that can be composted or contain combustible fractions can not be landfilled. Also the requirement for more efficient recycling and energy recovery favors technologies utilizing combustible fractions at the highest efficiency. Building on the successful demonstration of CFB gasification and co-combustion in Lahti, FW has been developing gasification-based solutions for transforming waste-based fuels into energy. Besides pilot plant tests with gas cleaning, long-term testing has been carried out with slipstream equipment at the Lahti gasification plant. This slipstream unit provided with a FW gas cooler and commercial hot gas filtration system logged more than 3,300 operation hours with product gas in real conditions. This development project led by FW has been co-funded by TEKES, and the other partners have been Lahti Energia Oy and Energi E2 from Denmark. Negotiations for the supply of a complete 160 MWth power plant based on gasification, gas cleaning and combustion of clean product gas alone in a gas fired boiler is ongoing with Lahti Energia Oy in Finland. With regard to the long-term development work in the field of gasification FW, together with Neste Oil and other Finnish-based industrial partners, is participating in a VTT- driven project targeting the development of an advanced process for producing multi-purpose synthesis gas from solid biofuels. The process is based on pressurized oxygen-steam fluidized-bed gasification followed by novel catalytic gas reforming technology. The new gasification process is designed for a wide range of biomass feedstocks. The synthesis gas can be raw material for various end products: Fisher-Tropsch liquids, methanol, SNG and hydrogen. References /1/ McKeough P, Kurkela E: Comparison of the performances and costs of alternative applications of biosyngas; Paper presented at 14th European Biomass Conference, Paris, 17-21 October, 2005