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Trends for the energetic use of biomass

Prof. Dr. Herbert Spindler

Germany

Fördergemeinschaft Ökologische Stoffverwertung e.V., Halle/Saale (FOEST)

www.FOEST-Halle.de

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Content

0. Introduction

1. Use of biomass

2. Parameters of utilization

3. Importance of gasification

4. Future Fuels

5. Outlook

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Background

Against the background of the shortage of fossil fuels, which becomes ever more visible, the climate change, and the demand for sustainable development, the possibilities and limits of an energetic use of biomass are discussed. Because of the rapid increase of energy prices the bio-energy will become competitive in a short time. The gasification of biomass is to be seen as especially profitable, because the gasification technology is considered the basis of extremely pure liquid fuels, which are able to fulfil all waste gas norms. Therefore the biomass industry is an important support for the agriculture and the forestry.

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Energetic Use of Renewable Raw Material

Classification by technical state

Primary process Primary product Utilization

combustion steam, heat electricity, heating

gasification combustion gas electricity, syntheses

fermentation biogas electricity, useable gas

liquefaction bio-alcohol, motor drive

(chemical & mechanical) bio-diesel, oils chemistry

pyrolysis gases, liquids, coke wide range

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Evaluation

Combustion processes ( λ> 1 ) are controlled best. Large plants available. Efficiency factors relatively low due to thermodynamical reasons, limits reached.

Gasification processes (thermal ,0 < λ< 1) not yet marketable even after long period of research, but high efficiency factors foreseeable (2-3 times higher compared to combustion), therefore prospectively increasing importance. Problems of gas purification largely solved. In small to average power range (up to 2 MW) fixed-bed gasifiers are advantageous, in average to high power range (>10 MW) fluid bed gasifiers are of advantage. High utilization potential.

Fermentation (methane fermentation, microbial) is only partially an energetic utilization process (biogas), which originally served disinfection. Remarkable technical state, but compared to gasification small speed of reaction, low efficiency factor, great reactor volume required, and after-care of fermented liquid manure necessary.

Liquefaction (alcoholic fermentation, extraction, compression) to bio-fuels (ethanol, RME) is facing technical and economical difficulties, but is funded by the EU. Mixing the products with conventional fuels is also tested.

Pyrolysis (λ = 0) to a mixture of gas, liquid and low-temperature coke in very differently designed procedures as „slow“, „fast” and „flash“ pyrolysis. The varying products are processed in very different ways.

Energetic Use of Renewable Raw Material

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Process and Configuration Energy

(External effects will not be taken into account)

The expenditure of energy E for a target energy ET is

  E = ET + EW + EO+ Δ EC = EP + Δ EC

ET = Target energy: is the desired energy that is obtained from the energy input.

EW = Lost energy, which is used up in addition

EO = Operation energy, which has to be added for the flow of operation

EP = ET + EW, Process energy: total energy that is needed so that the process can

actually run at a given configuration.

ηs = ET/EP, specific efficiency factor, with which the conversion of process energy

into target energy takes place (plant efficiency factor).

If the process runs in stages 1 to n, then η = η1*η2... ηn < 1.

EC = Configuration Energy: cumulative energy needed to set the material frame for

the energetic process and to run this process.

ΔEC = Proportion of EC, that corresponds with the time in which ET is obtained.

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Down draft fixed-bed gasifier plant for 560 kWel

in „Civitas Nova“, Wiener Neustadt, Austria

Betreiber: Energieversorgung NiederösterreichErrichtung und Planung: IUT GmbH, HarrisleeWissenschaftliche Begleitung (RENET AUSTRIA):TU-Wien, Prof. Dr.-Ing. HofbauerWiss. Kooperationspartner: GNS GmbH,Halle/S.

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Parameters for the Economy of Gasification

Model for an electricity-based gasification of biomass

Following parameters are introduced:CE = specific energy production costs in Euro/kWh

Ce = specific electricity production costs in Euro/kWh

It is Ce = CE /ηpl , with ηpl = electrical plant efficiency factor = ηGηmot

ηG = efficiency factor of gasification

ηG = HuG vG/HuB mB = HuG a/HuB a = vG/mB = gas yield

ηmot = motor-generator efficiency factor

CP = CE/hr = specific costs of power in Euro/kW per operating hour

= BC/FP = basic costs / fuel power BC= CC + OC + MC = costs of capital+ operating costs+ costs of materialsFP = HuB mB = Heat value of fuel in MJ/kg by flow rate in kg/h

MC contain costs forfuels (natural wood, wood waste, stalk materials straw dung, sewage sludge), auxiliary materials (catalysts, absorbents, solvents, filters),waste materials (ashes, waste water, waste gas)

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Ce small conventional Ce = ca. 2 Ct/kWh (coal, nuclear electricity)

At present time gasification Ce = 10 – 20 Ct/kWh (Fichtner)

BC minimal MC small, 0 if possible mB high

FP high (at a given CC, OC, hence a given plant)

Calorific value of gas HuG so far 4...5 MJ/Nm³; aim: HuG > 10 MJ/Nm

HuB in MJ/kg (TS) = 18,5 wood , 16...17 stalk materials, 7...10 sewage sludge

ηel 0,4 so far ηel = 0,15....0,2; ηV= 0,5...0.7; ηmot = 0,25...0,3

hr(max.) = 8766 h/a (calendar year) hr (norm.)< 7500 h/a

 Final aim: Ce < 5 Ct/kWh

Parameters for the Economy of Gasification

Aims:

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Parameters for the Economy of Gasification

specific electricity production costs Ce =spec. energy production costs (CE)

electr. plant efficiency factor (ηpl)

Approach:

aim: CE => small ηG ηmot = ηpl => high

CE [€/kWh] =spec. costs of power Cp [€/kW]

operating hours [h]

capital, operating, and material costs [€]

fuel power [kW] ( = HuBmB)Cp [€/kW] =

ηmot = motor-generator eff. factor

(efficient engines, high demands on quality of producer gas)

ηG = efficiency factor of

gasification

(high gas yield, high calorific value, air number λ minimal

actual costs: Ce = 0,1 to 0,2 €/kWh (Fichtner)

Final aim : Ce = 0,05 €/kWh

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Electricity Production Costs

The specific electricity production costs Ce are defined as the sum of the costs (costs

of capital + operating costs + costs of materials), which has to be expended to generate one kWh of electricity.

  Way of Generation Ce in EuroCent/kWh

Renewable photo-voltaic 50 – 60

biomass 10 – 12

wind 5 – 6

water 3 – 5

 

Conventional nuclear energy 2 – 3

coal 2 – 3

gas 2 – 3

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Utilization of the Product Gas from Thermal Gasification

Origin: lean gas with Hu = 4 – 12 (biogas 20, natural gas 30) MJ/Nm³

Way 1: Generation of electricity from fuel gas by means of BTPS (block-type thermal power stations) or gas turbines

Cold gas efficiency up to 90% achieved, electrical plant efficiency up to 30% with engine efficiency up to 40%.

 Way 2: Generation of electricity by means of fuel cells, high efficiency is to be anticipated, requires conversion of the deployment components into hydrogen within or outside of the cell, efficiency of the generation of electricity up to 60%, prospectively up to 90%

 Way 3: Hydrogen economy, e.g. gas driven cars, problem: low energy density of hydrogen.

 Way 4: modern FT synthesis, requires H2:CO = 2 : 1, for basic reaction CO + 2 H2 =

-CH2- + H2O , highly purified synthesis gases and modern catalysts necessary.

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Future Fuels

1. Generation:RME (bio-diesel), ethanol (alcohol additions)MtG (Methanol to Gasoline)

2. Generation:CtL (Coal to Liquid)GtL (Gas to Liquid)BtL (Biomass to Liquid)

Reanimation of the Fischer-Tropsch method to produce synthetic fuel („Synfuel“)

Steps: Production of synthesis gas (2 H2, CO)

Gas cleanup (dust removal, desulfurization) catalytic high-pressure synthesis (C20+-paraffins)

Hydroprocessing (naphtha, kerosine, diesel, benzine) 

Properties of Synfuel:Very clean, high cetane number, non-polluting,but expensive 

Implementation is dictated by environmental standards/regulations:Only Synfuel will be able to fulfill future EU exhaust gas regulations in terms of emission of particulates, freedom from sulphur, NOx, CO, HC content

Development trends for fuels in EUsince 2000: based on mineral oil

50 ppm S

about 2008: based on mineral oil < 10 ppm S

as of about 2010: based on natural gasSynfuel (virtually S-free)

as of about 2015: based on biomassSynfuel („Sunfuel“)

as of about 2020: Hydrogenregenerative

FÖSTBiokraftstoffe – stoffwirtschaftlicher Verbund

Ölpflanzen

Ölgewinnung

Öletechn.

Feinreinigung

Kohlehydrat-pflanzen

Rest-stoffe

BiomassenHolzStroh

Vergasung

StadtgasBiogas

Mischgas

BHKW

DüngerDüngerDampfDampfE-

energie

E-energie

Fermentation

Ablauf-aufbereitung

Ammon-sulfat

Ammon-sulfatÖle

reinst

Ölereinst ÖlesterÖlester Glyce-

rin

Glyce-rin

Ethanolreinst

Ethanolreinst

Verzuckerung

Fermentation

Destillation

Ethanoltechn.

UmesterungFein-

destillation

Rückstände

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Outlook

The importance of biomass for energetic utilisation will increase. The fuel supply in the future will result at least partly from the utilization of biomass.

Biomass will also play an important role as raw material in chemistry. We have already got concepts for bio-refineries.

Promising is the connection of biomass with the use of coal

The use of biomass will become economical with increasing costs for oil

But is remains doubtful whether the main part of the future energy supply will be made up of renewable energy. Therefore, the most important line of future energy supply will be the saving of energy.

Already W. Ostwald has postulated the „Energetic imperative“: Do not waste energy, but use it“ (1912)

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Many thanks

for your attention