BIOFACT case study: corn cobs

BIOFACT – Biomass Fuels Advisory Characterization Tool – is a recently developed fuel characterization tool which aims at rapidly detecting operational risks due to the use of biomass in energy plants. It is build to support engineers to have a better idea about non-conventional fuels and buyers to safely expand the fuels portfolio.

It does not substitute CFD analyses and pilot experimental testing. It is built to minimize the use of such time- and budget-consuming methods to the most interesting fuels. After filling in the fuel data (biofact.eu/analyze), it is possible to download a report with the results. Here a case study for corn cobs.

In the report, four sections are present: the Input section (with the data submitted), the BIOFACT-C (Combustion) section, the BIOFACT-T (Technology coupling) section and a short wrap up.

 

[pdf-embedder url=”http://www.biofact.eu/wp-content/uploads/2017/07/Example-1.3.pdf”]

The BIOFACT-C section is a quick assessment of operational risks during combustion of the specific fuel, namely the risks of/for: fouling, agglomeration and slagging, corrosion (high temperature), HCl emissions, particulate matter (PM10), SOx emissions, fuel NOx emissions, handling and storage. Each risk is computed with models based on the input data. As a complementary information, a suggestion of

The BIOFACT-T section is build to suggest the most suitable energy conversion Technologies for the specific fuel analyzed. The major combustion technologies are here considered: Bubbling Fluidized Bed combustion, Circulating Fluidized Bed combustion, Fixed Bed combustion (industrial or residential), Pulverized Fuel combustion, Thermal and material recovery (incineration). Fuel characteristics (at the moment 10 properties) and technologies requirements are matched on a matrix (which is kept updated with Best Available Technologies data). The results are the list of suitable (green) / borderline (orange) / inadequate (red) properties. For this corn cobs sample, because of agglomeration is a major risk, the tool evidences that fluidized beds might not be the most suited solution. However, such risk is not problematic for applications in fixed-bed, industrial scale units (e.g. due to fine bed temperature control). Grate furnaces might be more suitable to handle molten slag – agglomerated ash particles than fluidized beds. Beside complementary information such as the computed LHV are indicated.

The wrap up is a summary of the brief comments reported above.

Would you use such tool to screen unconventional fuels? Would this be an effective help for the preliminary fuel characterization?

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Operational excellence in biomass energy plants

Operations costs, in biomass energy plants, depend on input feedstock quality. To optimize operations and find economic optima, three preliminary steps could be considered.

1) Fuel costs [€/MWth], how do they vary depending on the fuel quality?

Fuel Such as Cost variation (average)
Easy Sawdust, whole tree chips 100%
Average Bark, stumps, forest residues 67%
Challenging Demolition wood, plywood residues 56%
Very challenging Agrofuels, SRF 44%

Note: figures, averaged for solid fuels (Europe).

2) O&M costs [€/y]: chemicals (~20%), electricity (~20%), maintenance (~60%), how do they vary depending on the fuel quality?

Fuel Such as Cost variation (average)
Easy Sawdust, whole tree chips 100%
Average Bark, stumps, forest residues 124%
Challenging Demolition wood, plywood residues 154%
Very challenging Agrofuels, SRF 194%

Note: Values averaged for thermal energy generation (50-500 MWth, fluidized beds boilers), including data from virtual.vtt.fi/virtual/combust.

3) Evaluate the economic feasibility balance including the reduction of fuel costs and the increased O&M costs for the specific installation.


As a summary, first, it is necessary to classify fuels according to operational risks (not a trivial task: even the same fuel type could be Easy/Average/Challenging/Very challenging depending on its origin and properties). It might be smart to use predictive analyses (e.g. BIOFACT-C) and previous return of experience.

Second, based on such 3-step preliminary analysis (and the technical constraint of the specific installation with its components), it is possible to assess with which new fuels it would be possible to operate the energy plant.

How do you perform your operational excellence analyses? Are you expanding the capabilities of your technologies? Any considerations is welcomed.

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Bioenergy technologies role in the 2°C Scenario: how the market could change in the next 15 years?

The Energy Technology Perspectives (ETP) is the International Energy Agency’s publication which estimates how technologies impact the objective of limiting the global temperature rise to 2°C.

The 2°C Scenario (2DS) of the ETP 2016 lays out an energy system deployment and an emissions trajectory consistent with what at least a 50% chance of limiting the average global temperature increase to 2°C, up to 2050. The 2DS sets the target of cutting CO2 emissions by almost 60% by 2050, compared with 2013.

If jumping to the conclusions of the study, current clean energy technologies deployment is still behind what is required to meet the 2DS Scenario, even though recent progress on electric vehicles, solar PV and onshore wind is promising. But what shall be the role of bioenergy in order to pursue this 2DS scenario?

  • Firstly, biomass becomes the largest energy source in 2050 in the 2DS (the share of fossil fuels in primary energy is in the 2DS, 45%, almost halved by 2050 compared to today, 81%).
  • Secondly, according to the authors and referring to Fig. 1, if looking at the primary energy consumptions (for production of secondary carriers such as biofuels and electricity), a rapid increase in the total supply of energy from biomass sources is required. The sectors which will be consuming the most are refineries (sharply increasing demand) and, to less extent, power plants. On the contrary, direct consumption of biomass energy is expected to remain constant.
  • Thirdly, if focussing on the final energy consumption, even if the total use is kept constant (see direct consumption), the industrial and residential sectors will behave differently. A decrease in residential use of biomass energy, mainly driven by the further decrease of traditional biomass used for cooking, is expected. Hot water production shall become the most important application for residential direct use. An increase of the industrial deployment of bioenergy is expected, mainly in relation to the direct production of chemicals and its use in the cement industry.

Fig. 1 – Author’s elaboration of Energy Technology Perspectives 2016 bioenergy technologies data.

To conclude, the report suggests that bioenergy technologies shall contribute to the developments to limit the average global temperature increase to 2°C, with the use of biomass in refineries, power plants and industry (cement, chemicals), cutting CO2 emissions and improving the sustainability of our energy system. All data of the study, including the ones to produce the Fig. 1 can be downloaded and explored dynamically at www.iea.org/etp/explore.
Lucio De Fusco, PhD

 

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Torrefaction of biomass: does it reduce the risks of fuel ash slagging, fouling and corrosion in combustion?

Introduction

The torrefaction of biomass is a thermal process performed at 240-300°C to upgrade a raw material to an output solid with increased energy density (MJ/kg), more homogenous and less vulnerable to biodegradation. The fuel obtained after torrefaction has properties which allow an easier handling and improved thermal performances in combustion. Beside physical properties, the fuel chemical composition is changed. Such changes influence the inorganic matter content, composition, association, and therefore the operational risks in combustion due to inorganic matter.

Methodology

With this brief work, the potential of torrefaction to reduce the risks of fuel slagging, fouling and corrosion in combustion (due to the changes in the inorganic matter), by using a fuel characterization tool called BIOFACT, is verified. The analysis only refers to fuel composition. Specifically, the module to characterize the fuel for combustion BIOFACT-C is used. This module considers (v. 1.2): fouling, agglomeration/slagging, corrosion (high temperature), HCl emissions, particulate matter (PM10), SOx emissions. For each of such risks considered, the tool computes a semi-quantitative evaluation from 0 (lowest risk) to 100 (highest risk).

Two fuel samples are analyzed, considering the properties of the fuels before and after torrefaction, at different temperatures:

  • Eucalyptus wood, raw and torrefied at 220, 250, and 280°C
  • Birch wood, raw and torrefied at 240 and 280°C
Results

The results are presented below.


Depending on the fuel, torrefaction could influence the risk of operational issues related to the fuel ash. Emissions (SOx, HCl) and high temperature corrosion might be reduced, depending on Cl and the other ash constituents. Nevertheless, based on the preliminary analysis – valid for those specific fuels – fouling and agglomeration/slagging are not reduced. PM10 emission risk could increase, due to the higher relative concentration of some PM forming inorganic matter in the fuel (on weight).

This preliminary analysis shall be confirmed by experimental results. The interested reader could look at the related working paper (which includes references), accessible here.

 

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MWh from solid biomass in Europe (2000-2016): who produced the most?

According to the Renewable Electricity Capacity and Generation Statistics 2016 by the IRENA [1], in brief:

  • (2014) Germany, UK, Sweden, Poland and Italy are the first 5 countries ranked in terms of energy produced from solid renewable fuels
  • (2014) Sweden, Denmark, Estonia, Austria and Belgium are the first 5 countries ranked in terms of energy produced from solid renewable fuels per million inhabitants
  • (2000-2015) In the last 15 years, Poland, Estonia, Hungary and UK invested the most in new capacity from solid renewable fuels (evidenced also in the variation in the total energy produced) with respect to the year 2000 (>10 times)
  • (2012-2015) At country level, in the last three years, a relative reduction in new capacity built is registered (according to the IRENA [1]) for Belgium, the Netherlands and Austria


All data available in [1], elaborated by the author.
[1] International Renewable Energy Agency (IRENA), ‘Renewable Electricity Capacity and Generation Statistics 2016‘, data available at http://resourceirena.irena.org/, accessed 8/04/2017.

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Innovations decreasing electricity generation costs: quantitative estimations till 2025 for solid fuel plants

Very recently InnoEnergy commissioned a study to BVG Associates to evaluate how innovation would impact the electricity generating cost, in Europe and till 2025, from new gas CHP (combined heat and power) plants and retrofitted coal plants.

The study [1] outlines that for a 500 kW gas CHP plant, the levelized cost of energy (LCOE) shall drop by about 17% between 2016 (the baseline) and 2025, while for a 225 MWe solid fuel power plant (coal retrofitted) such decrease is estimated to be about 27%.

For the solid fuel plant, according to the authors [1] and as evidenced in Fig. 1, over half of the LCOE savings arise from innovations in the modification, pre-treatment and combustion of new fuels.

Screen Shot 2017-02-21 at 19.23.00.png
Fig. 1. LCOE decrease between 2016 and 2025 for solid fuels energy plants. Adapted from [1].
The identified major innovations for the solid fuel plant are reported in the following [1]:

  • Topic 1 – Improvements in fuels through modification, switching; hybrid fuels (-10% LCOE). The use of low quality fuels is limited by operational challenges (e.g. slagging and fouling). Today, fuel additives are still limited to basic minerals (e.g. kaolinite) to reduce slagging and fouling and fuel blending is still limited to fuels that are not classified as waste. The use of advanced mineral or artificial additives to reduce ash challenges and influence emissions and the blending of low quality fuels/wastes shall be increased. According to the study, 80% of the benefit of these innovations is already realisable in 2016, with 100% realisable by 2020 onwards, however with an implementation limited to 40% of plants in 2025 because of local policy and regulations limitations.
  • Topic 2 –Introduction of thermal pre-treatment of solid fuels (-7% LCOE). As an example, torrefaction, by upgrading the properties of biomass and waste fuels, could reduce fuel transportation and handling costs (but might increase processing costs). According to the study, 40% of such benefit is already realisable in 2016, with 100% realisable by 2025 onwards, with an implementation limited to 30% of plants in 2025 because of local policy and regulations limitations.
  • Topic 3 –Improvements in preventive maintenance, power plant start-up system and boiler flexibility (-5% LCOE). Innovations cover advanced burners to reply heavy oil start up burners with liquid biofuel waste (70% of the benefit of these innovations is realisable in 2016) and the increase in boiler’s flexibility to enable plant operation at below 40% of maximum output (e.g. improving electronic/digital control and using high temperature heat accumulation systems). Moreover, modern preventative maintenance algorithms,  based on real operations, could provide information about failure in advance (e.g. material failures due to corrosion, especially when using biomass).
  • Among other 10 innovations (-5% LCOE): improvements in treatment of solid fuel combustion byproducts (today used by the cement industry, tomorrow to produce artificial zeolites, geopolymers and cenospheres, or vitrified), improvements in steam circuit design (optimal turbine blades, valves and condenser designs), introduction of superconducting technology in transformers/cables, integration of the main three pollution control systems (NOx, SOx, dust emissions), today in series, by using single sorbents and oxidisers in single wet scrubbers.

As a summary, reduced fuel OPEX in solid fuel plants by 2025 is achieved through innovations that enable the use of lower cost fuel and waste products (Topic 1), with thermal pre-treatment (Topic 2) and additives. Improvements in operations (Topic 3) also deliver significant savings, with preventative maintenance, operational flexibility and treatment of the byproducts of solid fuel combustion.

Topic 1 is addressed by many research projects (e.g. [2]) and now also with an operational, available tool called BIOFACT (BIOmass Fuel Advisory Characterization Tool) which wants to disclose a tool to characterize solid biomass for its utilization as a fuel in existing and new units, by estimating the impact of its utilization in terms of operational problems. In fact, fuel characterization tools are supposed to unlock the 8% reduction of the solid fuels generation costs already realisable today, with the final objective of providing flexible back-up plants for wind and solar energy technologies as well as renewable heat production.

References

[1] InnoEnergy, “Future Energy Costs: Coal and Gas Technologies“, BVG Associates, 2016, (accessed 21/02/2017).

[2] European Union’s Horizon 2020 research project: Biofficiency. Developing the next generation of CHP plants, (accessed 21/02/2017).

By Lucio De Fusco, InnoEnergy PhD School Fellow

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