d5.1 compatibility of burner components with fpbo...burner such as oil filters, oil pump, oil...

06.07.2017 / D5 1_COMPATIBILITY_OF_BURNER_COMPONENTS_WITH_FPBO_1.1_OWI_20170706 1/13

Project title: Renewable residential heating with fast pyrolysis bio-oil

Grant Agreement: 654650 Start of the project: 01.01.2016 (48 months)

Deliverable number: D5.1

Deliverable title: Compatibility of burner components with FPBO

Work package: WP5 Delivery due date: 31/12/2016 Actual submission date: 06/07/2017 Responsible organisation: OWI Oel-Waerme-Institut gGmbH Authors: Sebastian Feldhoff, Roy Hermanns Version: 1 Revision: 1

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Type: R R - Report DEM - Demonstrator, pilot, prototype DEC - Websites, patent fillings, videos etc. Level: PU PU - Public CO - Confidential, only for members of the Consortium*) Cl - Classified*)

DISCLAIMER

This document contains information which is the proprietary to the Residue2Heat Consortium. Neither this document nor the information contained herein shall be used, duplicated or communicated by any means to any third party, in whole or in parts, except with prior written consent of the Residue2Heat Coordinator. Contents of this document are not intended to replace consultation of any applicable legal sources or the necessary advice of a legal expert, where appropriate. All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose. The user, therefore, uses the information at its sole risk and liability. For the avoidance of all doubts, the European Commission has no liability in respect of this document, which is merely representing the authors' view.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 654650


Executive summary All fuel leading parts of a residential heating system have to be compatible with Fast Pyrolysis Bio-oil (FPBO). In scope of Task 5.1 standard burner components used in residential heating appliances have been tested in terms of long term operability with FPBO. For this report oil burner pumps are in the main focus of the investigation using a dedicated test setup.

Due to physical and chemical properties of FPBO, deposit formation in fuel leading parts is probably unavoidable. Deposit formation has been observed in several setups, in order to minimize the negative effects of deposit formation, (particle) filters were removed from the fuel supply line. For future fuel optimization it is therefore suggested to lower the concentration of solid particles and additionally limit particle size diameters to make the fuel filters more or less superfluous. Additional tests will be promoted in order to identify not only specific fuel components (or group of substances), which cause filter coating, but also burner components which ensure a long-term operability of FPBO.

Intermittent operation as it is typical in domestic heating applications using standard fuel pumps will be difficult to realize. During turn-off time sticky deposits settle at inner parts of the pump (e.g. gears) and can prevent a restart. The longer the turn-off time the less likely the pump will be able to restart. Alternative solutions should be investigated.

As observed during the test procedures wear and corrosion occur. However, these effects appear to be of minor concern at the present state of development. Nevertheless, reduction of acid and water content in the fuel would be beneficiary with respect to pump life time.

The present investigations have shown that special measures have to be taken for the domestic use of FPBO in residential heating systems, with respect to combustion appliances. This expectable fact requires a corresponding further development of the system components for FPBO combustion boilers.


Table of Contents

Executive summary............................................................................................................................................ 2

Table of Contents .............................................................................................................................................. 3

1 Introduction ............................................................................................................................................... 4

1.1 Scope ................................................................................................................................................. 4

1.2 Objectives .......................................................................................................................................... 4

2 Fuels ........................................................................................................................................................... 4

3 Experimental setup .................................................................................................................................... 5

3.1 Dedicated setup ................................................................................................................................. 5

3.2 Lab scale burner setup ...................................................................................................................... 6

4 Results ....................................................................................................................................................... 7

4.1 Dedicated setup ................................................................................................................................. 7

4.2 Lab scale burner setup .................................................................................................................... 10

5 Conclusions / Final remarks ..................................................................................................................... 12

List of abbreviations ........................................................................................................................................ 13


1 Introduction

1.1 Scope All fuel leading parts of the burner have to be compatible with Fast Pyrolysis Bio-oil (FPBO), especially regarding choice of materials due to chemical properties of FPBO (corrosion). In scope of Task 5.1 standard burner components used in residential heating appliances are to be tested in terms of principle functionality as well as in terms of long term operability with FPBO. For this report oil burner pumps are in the main focus of the investigation. In addition, different nozzle designs have been tested during Task 5.2.

This report sums up the outcome of extensive test conducted at OWI concerning hardware tests in a simplified, dedicated test setup on the one hand and during development of the lab scale demonstrator on the other hand.

This deliverable is to be updated by Month 25 and Month 37, as component tests will be conducted with conditioned FPBO during the subsequent course of Residue2Heat.

1.2 Objectives The introduction of new fuels like Fatty Acid Methyl Ester (FAME) based on new plant oils or FPBO into the household heating market involves new challenges which have to be solved before market introduction. Typically the physical and chemical properties of FPBO differ completely from DHO or diesel fuels. This affects the operability of appliances and makes standardization of FPBO and selection of FPBO suitable burner components necessary.

To ensure applicability of FPBO in residential heating applications it is necessary to guarantee its compatibility with important components of the burner, especially regarding choice of materials due to corrosion and reliability effects. Also seals must be tested for usage of alternative fuels in domestic heating systems.

In specifically designed component testing setups the influence of FPBO on the operability of the investigated component is being analysed. Performance of burner components will be identified by determining the time before break down, corrosion effects, stability of flow rates, changes in pressure over time, etc.

In recent years OWI has developed various component testing methods to investigate the sensitivity of typical residential heating system components. Aspects like fuel degradation or the change of physical and chemical fuel properties potentially lead to problems in technical applications. An existing test unit for heating oil has been adapted to be used with FPBO as a fuel. The performance of core components of the burner such as oil filters, oil pump, oil preheater and nozzle has been investigated by using different FPBO qualities. The aim was not only to select FPBO suitable components but also support VTT and BTG to improve the FPBO performance in residential heating systems, which will be done subsequently in the Residue2Heat project.

2 Fuels The development of the burner within Residue2Heat starts with the utilization of FPBO-ethanol-blends, whereas ethanol provides essential evaporation characteristics to the fuel, ensures better ignition and has a keep-clean effect on burner components. In addition, ethanol lowers significantly the viscosity of the blend and improves spray quality. The ethanol content will be reduced stepwise from 80% to 20% during this stage of development. Similarly the burner component tests presented within this report were conducted initially with FPBO-EtOH-blends and finally with pure FPBO.


Table 1: Fuel testing matrix

Fuel name Share of FPBO [% by volume]

Share of Ethanol [% by volume]

FPBO_20 20 80

FPBO_80 80 20

FPBO 100 0

3 Experimental setup A typical oil based residential heating system consists of components depicted in Figure 1. Each component will performs differently on alternative fuels and therefore influences the operability of the complete residential heating system.

Figure 1: Typical components in an oil fired boiler

In order to investigate the performance of the core components of a burner such as oil filter and oil pump, OWI adapted existing test units for heating oil to FPBO. The unit is described in detail in section 3.1. Furthermore, during the development of the lab scale demonstrator additional knowledge was gained especially regarding fuel nozzle design.

From the literature it is well known, that polymerization of FPBO can take place in supply lines, pumps or filters of a burner system when exposed even to moderate heat over a long period of time. This effectively means that the temperature must be regulated to lower temperatures and no direct heating should be applied. It is not intended to implement a standard oil pre-heater in the fuel supply line as these preheating systems operate at relatively high temperatures, ranging from 90 – 120 °C. A dedicated pre-heater needs to be used with pre-heating temperatures below 65 °C. It is well known that above 65 °C FPBO fuel degradation is significantly enhanced.

3.1 Dedicated setup For the purpose of testing oil pump performance a test rig as shown in Figure 2 was set up. The fuel is pumped in a loop without combustion for a significant amount of time. An intermittent operation of 10 minutes on and 5 minutes off was set. The off-the-shelf available oil burner pump is mounted in accordance to a typical household heating system. A 90 Watts induction motor is used. For this kind of long term operability test a 1 litre glass bottle serves as a simplified fuel reservoir. With this test setup it is possible to test long term operability of standard oil burner pumps over a few hundred hours of operation. Maximum test time was set to 200 h (intermittent operation).


P

pump

motor

1 l glass

bottle

T

Scale

AC

Figure 2: Dedicated pump test rig, left schematic diagram of the pump test rig, right top experimental setup, right bottom picture of the applied standard oil pump

After completion of the test procedure (or component failure) the pumps are disassembled. The inner parts such as gears, pressure channels and the internal particle filter are photographed. Furthermore, parts made from mild steel are cleaned with a suitable solvent and checked for corrosion effects.

3.2 Lab scale burner setup In the course of the development of the lab scale demonstrator (see Figure 3), numerous standard burner components have been utilized and also tested at the same time. Here, the description of the test setup is limited only to the fuel supply line of the burner. The overall concept of the lab scale burner design can be found in deliverable D5.3.

The fuel is stored in a small plastic container. As it is typical for household heating installations the suction line is made out of a copper pipe. The pump (an off-the-shelf oil burner pump) is mounted on an induction motor with a capacity of 150 Watts (nr. 2 in Figure 3). As states previously, no pre-heater is installed in the fuel supply line towards the fuel injection nozzle (nr. 1 in Figure 3).

As with the dedicated test setup the fuel pump and different types of fuel nozzles have been analysed according their suitability with FPBO / FPBO-EtOH-blends.

1


Figure 3: Lab scale demonstrator, 1: Nozzle mount; 2: Pump motor and standard off-the-shelf oil burner pump with pressure gauge; 3: Needle valve for adjusting fuel flow rate; 4: Air flow controlling unit for two-phase nozzle atomizer.

4 Results Different kind of fuel blends have been tested both in the dedicated test setup and the lab scale demonstrator. FPBO-EtOH-blends with different shares of ethanol have been tested as well as pure FPBO The FPBO used in the experiments was R2H.BTG.001e as defined in D2.3. Mainly, FPBO_20 (ethanol with 20 % FPBO), FPBO_80 (ethanol with 80 % FPBO) and pure FPBO have been used during the experiments. In a future update of deliverable FPBO based other feedstock will be used. Within the following sections 4.1 and 4.2 the results of the compatibility tests are shown.

4.1 Dedicated setup

4.1.1 FPBO_20 using the standard oil burner pump The standard oil burner pump has been operated with FPBO_20 for the maximum test time of 200 hours. Pump pressure was set to approx. 15 bar and stays constant during the test. In Figure 4 the pump is shown after disassembling. The formation of deposits could be clearly observed, as well as mild steel corrosion - especially in the high pressure channels (picture in the middle). Solid particles were found as well. However, the pump was running until the end of the test procedure (intermittent).

1

2

3

4


Figure 4: Oil pump; FPBO_20

Minor deposit formation could also be seen on the pump gears itself and the gear fit (Figure 5). The deposits could be wiped off easily with a paper towel.

Figure 5: Oil pump; internal parts: gears (left and middle), gear fit (right); FPBO_20

4.1.2 FPBO_80 using the standard oil burner pump In comparison to the pump utilized with FPBO_20 the appearance of deposits/residues inside the pump of FPBO_80 changes. The residues shown in Figure 6 are sticky, more viscous and also contain higher amounts of solid particles. They cannot be easily removed by wiping off with a paper towel and need to be cleaned with the use of a solvent, e.g. ethanol. The pump failed to complete the test procedure described above and blocked after approximately 120 hrs.

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Figure 6: Oil pump; FPBO_80


4.1.3 FPBO_100 using the standard off-the-shelf oil burner pump The pump supplied with pure FPBO failed the test after a remarkable short time of 26 hrs. The consistency of the residues was comparable to FPBO_80, however even more sticky (see Figure 7). Due to the intermittent operation of the pumps the residues inside the pump (especially inside the gears) are allowed to settle during the off-time and act like glue. Pump failure typically occurs at pump restart events when shearing forces are too high and break free moving parts. This effect could also be enforced by enlarging off-time and on the other hand continuous operation (power modulation) could possibly extend the maximum operation time.

Figure 7: Oil pump; pure FPBO

4.1.4 Internal filters of the standard oil burner pump The internal filter elements (mesh size of 200 µm) of the fuel pumps were removed from the pump and checked for deposits. As shown in Figure 8 the amount of deposits held back by the filter is increasing with the share of FPBO in the fuel. In case of pure FPBO the mesh filter is completely covered with a layer of sticky, high viscous residues, which reduces fuel flow rates significantly.

Figure 8: Oil pump; internal filter: use of FPBO_20 (left), FPBO_80 (middle) and FPBO (right)

4.1.5 Summarizing remarks Standard fuel pumps of residential heating systems are not suitable for FPBO. This was expected, at

least without any further fuel conditioning.

The applied filters in residential heating systems are not suitable for FPBO.

It is questionable, that this pump type can be used in residential heating systems Alternative technologies have to be investigated.


4.2 Lab scale burner setup As stated at the beginning of this chapter several burner components have been tested during development of the lab scale burner setup. In the following the test results regarding pump performance and nozzle design will be presented.

4.2.1 Pump The pump utilized was an off-the-shelf oil burner pump of the same type as used in the dedicated pump test setup. It was used during different stages of development with several different FPBO-EtOH-blends as well as pure FPBO. From time to time it was necessary to open the pump and clean the inner parts to ensure operability. For the burner tests the internal fuel filter of the pump was dismounted to prevent filter clogging (as described above). In Figure 9 the inner parts of the pump used are shown as they appeared after approximately 40 hrs of burner tests (and after several cleaning procedures).

Figure 9: Oil pump; internal parts: gears (left) and pressure channels (right)

In compliance with the tests performed with the dedicated test setup agglomeration of residues in pressure channels and gears could be observed. Although, the mild steel surfaces have been attacked chemically (FPBO contains acids and water) the pump remains functional as such within the test time.

4.2.2 Nozzle Typical nozzles in household heating applications are of type swirl pressure nozzle. These units consist of a metal sinter filter at the fuel inlet and extremely small channels at the outlet to create high momentum and swirl of the spray/droplets. In order to generate sufficient spray quality (mainly regarding droplet diameter) a fuel supply line pressure of at least 15 bar is needed. In the first tests of the lab scale burner standard nozzle design and operating conditions were used. After only a few minutes of testing the spray disintegrated. Dismounting the nozzle showed immediate clogging of the sinter filter (Figure 10 and Figure 11).


Figure 10: Swirl pressure nozzle; unused (left) and used with FPBO (right).

Figure 11: Metal sinter filter of the swirl pressure nozzle used with FPBO.

During the lab scale burner development phase the nozzle design was changed to a two-phase nozzle, in order to improve the atomization. For this setup no metal sinter filter is needed and the overall gap dimensions are supposedly larger. This ensures better reliability with respect to formation of sticky or char-like deposits inside the nozzle geometries. The two-phase nozzle after usage with various FPBO-EtOH-blends for approximately 30 hrs is shown in Figure 12.


Figure 12: Two-phase nozzle; used with different FPBO-EtOH blends

Deposit formation can clearly be seen on all parts being in contact with the fuel. Nevertheless, fuel flow rate was reasonably constant, considering the observed deposit formation. The consistency is described as sticky, but easy removable with the use of ethanol as solvent.

5 Conclusions / Final remarks The applicability of standard core components of typical household heating systems with FPBO-EtOH-blends and “pure” FPBO has been investigated. Oil burner pumps have been tested using a dedicated test setup with respect to long term operability. In addition, two different nozzle designs were assessed during development of the lab scale demonstrator.

Due to physical and chemical properties of FPBO deposit formation in fuel leading parts is probably unavoidable. Deposit formation has been observed both with the dedicated setup and the lab scale burner setup. In order to minimize the negative effects of deposit formation (particle) filters were removed from the fuel supply line. Even coarse filters were clogged within a short time. For future fuel optimization it is therefore suggested to restrict concentration of solid particles and additionally limit particle diameters to make fuel filters more or less superfluous. Additional tests are promoted in order to identify specific fuel components (or group of substances), which cause filter coating.

Intermittent operation of the fuel pump as it is typical in domestic heating applications will be difficult to realize. During turn-off time sticky deposits settle at inner parts of the pump (e.g. gears) and can prevent a restart. The longer the turn-off time the less likely the pump will be able to restart. Alternatives should be investigated.

As observed during the test procedures wear and corrosion occur. However, these effects appear to be of minor concern at the present state of development. Nevertheless, reduction of acid and water content in the fuel would be beneficiary with respect to pump life time.

In order to assess long term operability the residential heating systems alternative of oil burner components need to be taken into account, additional tests with conditioned FPBO are needed and foreseen within the course of Residue2Heat. This report will be updated accordingly.

The present investigations have shown that special measures have to be taken for the domestic use of FPBO in heating systems, with respect to combustion appliances. The increased technical complexity leads to an increase in pool of equipment compared to conventional oil firing systems. This expectable fact requires a corresponding further development of the system components for FPBO combustion boilers. Similarly as with modern wood pellet boilers which are likewise technically significantly more expensive than comparable oil boilers or gas boilers, and require an explicit higher maintenance expenditure than gas and oil boilers. It is, however, to be expected that FPBO combustion systems will require less technical effort and will be more service-friendly than modern wood pellet boilers.


List of abbreviations The following definitions of the key terms are used in this and related documents:

DHO Domestic Heating Oil FPBO Fast Pyrolysis Bio Oil EtOH Ethanol FAME Fatty Acid Methyl Ester (also called biodiesel)

d5.1 compatibility of burner components with fpbo...burner such as oil filters, oil pump, oil...

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