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MEDITERRANEAN BIOMASS SUITABILITY AS DOMESTIC SOLID BIOFUEL. PHYSICOCHEMICAL CHARACTERIZATION AND REAL TEST COMBUSTION IN HEATING APPLIANCES.

LABORATORIES SYNERGY.

Pedro Delgado Plana, José A. Pérez Jiménez*, Manuel J. Díaz Villanueva Biomass Department - Advanced Technological Centre for Renewable Energies - CTAER

Geolit, A-44. P.K. 22,5. C/ Sierra Morena 12b, 23630 Mengíbar, Jaén. SPAIN Phone: +34 672 091 045, *E-mail: joseantonio.perez@ctaer.com

ABSTRACT: The characterization of solid biofuels for energy use, is one of the main researches, done by the Biomass Department as a division of the Advanced Technological Centre for Renewable Energies (CTAER). To achieve this objective, the study of solid biofuels is executed in two steps, both performed in different laboratories (such Physicochemical Characterization Laboratory and Real Combustion Test Laboratory). The main scientific innovation of this project is the useful synergy created between both laboratories named before. Due to this fact, a lot of great valuable information about mediterranean zone biomass for domestic use will be obtained in a near future. In addition, as results of this study, it is obtained a comparison between the values declared by the heating appliance manufacturer for a standard biofuel with those calculated by us in the real combustion test laboratory using an alternative mediterranean solid biofuel. In the real combustion test laboratory, a lot of problems such as slagging, excessive ash production, corrosion, unacceptable emissions,... can be detected too. The conclusions obtained from the two stages study of the mediterranean solid biofuel are utilized for a big amount of purposes. Among many others: improvements design in heating appliances, focusing of biomass valorization and so on.

Keywords: Synergy, Characterization, Combustion, Real Test, Improvements.

1 INTRODUCTION

During these last few years, in the heating appliances field, the use of solid biofuels, which are greener, has been increased in comparison with the use of fossil fuels, thus, replacing them in most cases. In the Biomass Department from the Advanced Technological centre for Renewable Energies, biomass characterization for energetic use is one of the main lines of work, particularly, domestic use biofuel option.

The work methodology can be resumed as

follows: Biomass is analyzed by official methods and, if the results are appropriate for a domestic thermal use, this biomass can be called solid biofuel. After that, biofuel is tested in a heating appliance and more results about biofuel behavior are obtained. Important researches can be realized with all the information collected.

In this sense, the mediterranean biomass

characterization is developed in two main stages realized in different installations: Physicochemical Characterization Laboratory and Real Test Combustion Laboratory.

At the first one, main parameters that define

solid biofuels, as particle size, moisture, ash, heating value, inorganic elements and so on are determined and studied. These analysis are performed in the Physicochemical Characterization laboratory.

If a domestic thermal use is intended, solid

biofuels, must meet minimum requirements. If they don’t, a different way of valorization might be researched. When it is concluded that a biofuel is suitable for combustion in domestic appliances, Second stage which is realized in the Real Test Combustion Laboratory begins.

At this laboratory different heating appliances are available and specially equipped to be used to investigate biofuel behavior in real conditions. In these studies, during testing time, a lot of parameters such as efficiency, water heating output, emissions, ash production (real conditions) are determined.

Finally, all the information generated can be used

for different purposes. Among many others,  some of them that can be highlighted are the design of technological improvements in heating equipment, advising for customers and manufacturers in different issues and looking for a way to adapt the appliances to each and every biofuel in order to get the best efficiency in every occasion. In addition a better and more exhaustive biofuel characterization is achieved. 2 MATERIALS AND METHODS. 2.1 Stage 1. Physicochemical characterization laboratory.

Characterization process begins with biomass reception. A minimum of 40 kilograms are required for a comprehensive characterization, including physicochemical analysis and real test combustion. The exact amount will depend of the number of test repetitions and the heating appliance consumption.

First of all, a biomass representative aliquot is taken into the first stage, Physicochemical Characterization. Secondly, sample is partially dried at 35 ºC for 24 hours. After that, samples are ground below 0.25 mm. In order to obtain constant moisture, a 24 hours stabilization process is realized.

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In this stage Samples are analyzed by official methods (table 1).

PARAMETERS STANDARD

MOISTURE UNE-EN 14774-3 ASH UNE-EN 14775

VOLATILE MATTER UNE-EN 15148 GROSS CALORIFIC

VALUE UNE-EN 14918

NET CALORIFIC VALUE UNE-EN 14918

TOTAL CARBON UNE-EN 15104 TOTAL HYDROGEN UNE-EN 15104 TOTAL NITROGEN UNE-EN 15104 TOTAL SULPHUR UNE-EN 15289

TOTAL CHLORINE UNE-EN 15289 BULK DENSITY UNE-EN 15103

Table 1.Parameters determined in solid biofuels and concerned normative.

With the aim of getting the most repetitive, exact and reliable determinations, a top quality measurement equipment are available in CTAER installations (table 2).

PARAMETERS MEASUREMENT EQUIPMENT

MOISTURE Stove Memmert UFE 700 ASH Muffle Furnace

NABERTHERM LVT 15/11 VOLATILE MATTER

GROSS CALORIFIC VALUE Calorimeter Parr 6300 NET CALORIFIC VALUE

TOTAL CARBON Analyzer LECO TruSpec CHN 620-100-400 TOTAL HYDROGEN

TOTAL NITROGEN

TOTAL SULPHUR Analyzer LECO TruSpec S 630-100-700

TOTAL CHLORINE Titrator Mettler Toledo G20

ADDITIONAL EQUIPMENT

Magnetic Stirrer P. Selecta, Mill ZM 200, Mill Retsch SM 2000,

Precision balance Mettler Toledo New Classic MF,

MS 2045,… Table 2. Measurement equipment used.

Once this quality parameters are determined and to conclude this first stage, a study and discussion of the results obtained is carried out with the objective to focus an appropriate energetic valorization for the biomass analyzed.

In case of results obtained suggest combustion process may be an acceptable choice for the sample analyzed valorization that biomass is carried to the Real Test Combustion Laboratory (second stage) to keep studying it. The data obtained from the analysis executed in the first stage will be useful in regard to characterize the biofuel combustion process. In this sense, a database with real problems observed in heating appliances and their probable cause based in laboratory results is being made.

However, parameters calculated can sometimes suggest residential space combustion is not an appropriate use for this biomass. On this occasion, an alternative use can always be looked for. Anyway, the information obtained value is unquestionable and offers the choice of keeping investigating the best wise of residue’s valorization. 2.1 Stage 2. Real combustion test laboratory.

In this laboratory, The solid biofuel is burned in a domestic heating appliance where interesting parameters are measured and registered in order to develop a thermodynamical characterization of machine operation with this alternative solid biofuel.

An special infrastructure, including a water circuit

and a flue gas characterization and evacuation system has been built taking into account related normative. Both of this elements configuration is represented in the Figure 1.

A. Appliance with boiler, B. Flowmeter, C. Regulating valve, D. Pressure reduction vessel, E. Valve (cut off), F. Platform scale, G. Circulation pump, H. Steel-box insulated with 120 mm mineral wool or filled with scraps of cork, J. Safety equipment, K. Thermal discharge control, L. Safety valve, M. Pressure extension vessel, N, O. Flexible connections (not represented), P. Drain A. Pressure measurement point. B. Temperature measurement point. C. Extraction point for flue gas analyze. Figure 1.Example of test installation for appliances with water circuit (not necessary ours) and dimensions of measurement section of flue gas evacuation system.

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Possible configurations and examples of heating appliances characterization infrastructure are available in European standards.

In this case, normative to apply depends of the kind of heating appliance used in combustion process as can be observed in Table 3.

HEATING APPLIANCES NORMATIVE

UNE-EN 12809:2002

Residential independent boilers fired by solid fuel. Nominal heat output up to 50

kW. Requirements and test methods.

UNE-EN 12815:2002

Residential cookers fired by solid fuel. Requirements and test methods.

UNE-EN 13229:2002

Inset appliances including open fires fired by solid fuels. Requirements and

test methods.

UNE-EN 13240:2002

Roomheaters fired by solid fuel. Requirements and test methods.

UNE-EN 14785:2007

Residential space heating appliances fired by wood pellets - Requirements and

test methods Table 3.Normative related to different kinds of heating appliances.

Due to the fact there isn’t a standard heating appliance for solid biofuels combustion test, an arbitrary choice must be made.

In this sense, the combustion process characterization is realized referring to a concrete heating appliance and some results cannot be extrapolated to other machines. At our laboratory, A Hargassner Classic 15 heating appliance is available and especially equipped for the characterization of combustion process.

Nonetheless, If somebody is interested in characterize the combustion of an alternative mediterranean solid biofuel in a specific appliance of his property it doesn’t present any problem for us. On the contrary, characterize the biofuel behavior in different devices is an exciting experience which can generate a huge amount of knowledge.

The inverse process is also possible. Heating

appliances manufacturers are often interested in knowing if his machine can works with some kind of mediterranean biomass (for instance, olive stone) and how well it does. By this way, if a heating appliance good operation is guaranteed for an alternative mediterranean biofuel, sales will probably be increased.

Therefore, important benefits for all of heating

appliances manufacturers and mediterranean biomass owners, distributors and end users are obtained of the day to day work in Real Combustion Test Laboratory.

Returning to parameters measured, A distinction can be made between values quantified referring flue gas (Composition) and those measured in the water circuit and process environment (water flow).

The next two tables show a relation of parameters measured and equipment used and those calculated using the first ones in order to characterize the combustion process; table 4 and 5 respectively.

MEASURED PARAMETERS EQUIPMENT

FLUE GAS

TEMPERATURE Temperature transmitter

TTF300 with K termocouple. ABB

PRESSURE Pressure transmitter

2600T with seal S26. ABB

COMPOSITION ABB analyze equipment. Advanced Optima. AO

2000 DUST

CONCENTRATION Durag D-R 300-40

Analyzer WATER CIRCUIT AND ENVIRONMENT

SURFACES AND HOPPER

TEMPERATURES Type K Termocouples

BIOFUEL CONSUMPTION

4 cells and display balance CELSA

FLOW AND RETURN TEMPERATURES

Temperature sensors Honeywell VF20T

WIND SPEED Anemometer. (not available specifications)

FLOW Static flow sensor Superstatic 440. Sontex.

ADJACENT WALLS TEMPERATURE Type K Termocouples.

Table 4. Parameters measured during combustion of solid biofuel and equipment used.

PARAMETERS CALCULATED

UNIT OF MEASUREMENT

EFFICIENCY %

NOMINAL HEAT OUTPUT kW

PARTIAL HEAT OUTPUT kW

WATER HEATING OUTPUT kW

SPACE HEATING OUTPUT kW

CARBON MONOXIDE EMISSIONS % v/v ; mg/m3

FLUE GAS TEMPERATURE ºC

REFUELLING INTERVALS Minutes

ASH REMOVAL INTERVALS Minutes

Table 5. Parameters calculated in order to characterize the heating appliance operation with an alternative mediterranean solid biofuel.

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Once second stage is finished, all results obtained of both of two characterization stages are met for their study. At this moment, mediterranean biomass has already been totally characterized and important conclusions are elaborated about the suitability of the mediterranean biomass studied as a domestic biofuel.

All biofuel physicochemical parameters determined

are incorporated to a complete report. In addition, a lot of data concerning heating appliance operation with this biofuel are included in this document. What is more, biofuel behavior, especially problems observed are rigorously documented. Possible reasons, based in determinations results, are enumerated too.

Beyond that, if a client demands it, technological

improvements can be suggested and even implanted in order to increase appliance efficiency during operation with mediterranean alternative biofuel. 3 RESULTS AND CONCLUSIONS.

For the time being, results from two studies have been obtained and can be discussed in order to make conclusions.

On the one hand, a sample of Mediterranean biomass

ashes with unburned matter from a domestic heating appliance has been collected. In order to quantify this parameter, ashes and moisture determinations are realized for the sample collected.

Domestic heating appliance where combustion solid

residue sample was collected and determination results are shown in figure and table below respectively.

Figure 2. Domestic heating appliance which operates

with Mediterranean solid biofuel (olive stone).

Table 6. Results of moisture and ashes content determinations for Mediterranean biomass combustion residue (oliv stone). Results suggest technological improvements are usually necessaries with the objective of increasing heating appliances energetic efficiency when non-conventional biomass are handled.

On the other hand, a six samples physicochemical

characterization summary is shown in the table below. In this case, determinations have been realized for different kinds of Mediterranean biomass in order to study their suitability as domestic biofuel.

ID Moisture*** Ash*

Gross calorific value**

Elementary Analysis* C H N O

S*

Cl*

1 53,43 4,70 1645 43,96 / 5,33

5,65 / 44,89 0,17 0,49

2 25,32 1,06 3299 51,58 / 6,02

0,20 / 41,08 0,02 0,04

3 9,91 23,11 2577 N.D.

4 27,55 4,24 2731 48,79 / 5,86

0,43 / 40,61 0,05 N.D.

5 5,80 1,30 4046 52,00 / 6,30

0,20 / 40,23 0,02 0,03

6 6,10 0,96 4216 51,09 / 6,21

0,17 / 42,51 0,02 0,03

1: Arundo donax; 2: Olive stone, before cleaning and drying process; 3: Tobacco stalks; 4: Vine branches; 5 and 6: Olive stone, after cleaning and drying process. N.D. “Not determined” Table 7. Physicochemical characterization results for six samples of typical mediterranean biomass.

After these physicochemical determinations, it is concluded samples 1, 2 and 4 are inappropriate for residential spaces heating appliances due to their elevated moisture. In addition, sample 3 has an inacceptable ashes content and is also unsuitable for small applications combustion. On the contrary, samples 5 and 6 do look suitable and a Real Test Combustion will be realized in order to check them.

An additional conclusion obtained is drying and

cleaning process is essential when olive stone is going to be used in domestic heating appliances. 4. REFERENCES Solid Biofuels for Energy. London, Dordrecht, Heidelberg, New York: Springer-VerlagGrammelis, Panagiotis; 2011:256. ISBN 978-1-84996-392-3 Thermal Output of Heating Appliances Operating with Hot Water. Werner Kast, Herbert Klan and (Revised by André Thess). VDI-Buch, 2010, VDI Heat Atlas, Part 6, Pages 685-690 Combustion control and sensors: a review. Nicolas Docquier, Sébastien Candel. Laboratoire EM2C, Ecole Centrale Paris — CNRS UPR 288, Grande Voie des Vignes, F-92295 Châtenay-Malabry Cedex, 5. ACKNOWLEDGEMENTS

6. LOGO SPACE