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Absorberende middelen inhoud

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Absorberende middelen inhoud



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Datum22.05.2018
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BIJLAGE 5


The European Norm EN 13432, titled "Requirements for packaging recoverable through composting and biodegradation. Test scheme and evaluation criteria for the final acceptance of packaging," describes a standard set of criteria for determining whether a material can be considered "compostable".

It was established by The European Committee for Normalisation (CEN) and is also published by (and can be ordered from) the British Standards Institution.

This norm is a reference point for all European producers, authorities, facility managers and consumers.

EN 13432 is the most strict of all of the standards for evaluating biodegradability and compostability. Other related standards include ASTM D6400, DIN CERTCO 7P-0199, DIN V49000, DIN V54900, ISO 14855 and OECD 207, and many of others that describe tests that are included in the EN 13432 standard.



Summary

Nowadays, the terms "biodegradation", "biodegradable materials", "compostability" etc. are very common but frequently misused and a source of misunderstanding. The European Norm EN 13432 resolves this problem by defining the characteristics a material must own in order to be claimed as "compostable" and, therefore, recycled through composting of organic solid waste. The definition of the compostability criteria is very important because materials not compatible with composting (traditional plastics, glass, materials contaminated with heavy metals, etc.) can decrease the final quality of compost and make it not suitable for agriculture and, therefore, commercially not acceptable. This norm is a reference point for the producers, the public authorities, the composting plant managers, and the consumers.

According to the EN 13432, the characteristics a compostable material must show are:

Biodegradability, namely the capability of the compostable material to be converted into CO2 under the action of micro-organisms. This property is measured with a laboratory standard test method: the EN 14046 (also published as ISO 14855: biodegradability under controlled composting conditions). In order to show complete biodegradability, a biodegradation level of at least 90% must be reached in less than 6 months.

Disintegrability, namely fragmentation and loss of visibility in the final compost (absence of visible pollution), measured in a pilot scale composting test (EN 14045). Specimens of the test material are composted with biowaste for 3 months. The final compost is then screened with a 2 mm sieve. The mass of test material residues with dimensions >2 mm shall be less than 10% of the original mass.

Absence of negative effects on the composting process. Verified with the pilot scale composting test.

Low levels of heavy metals (below given max values) and absence of negative effects on the final compost (i.e. reduction of the agronomic value and presence of ecotoxicological effects on the plant growth). A plant growth test (modified OECD 208) and other physical-chemical analysis are applied on compost where degradation of test material has happened.

Each of these points is needed for the definition of compostability, but alone it is not sufficient. For example, a biodegradable material is not necessarily compostable, because it must also disintegrate during the composting cycle. On the other hand, a material that breaks during composting into microscopic pieces which are then not fully biodegradable is also not compostable.

The norm EN 13432 is a harmonized norm. That is, it has been quoted in the Official Journal of the European Communities, it has been implemented in Europe at a national level, and it provides the presumption of conformity with the European Directive 94/62 EC on packaging and packaging waste.

BIJLAGE 6: Heat of combustion, calorific values, etc


The heat of combustion (ΔHc0) is the energy released as heat when a compound undergoes complete combustion with oxygen under standard conditions. The chemical reaction is typically a hydrocarbon reacting with oxygen to form carbon dioxide, water and heat. It may be expressed with the quantities:

  • energy/mole of fuel (J/mol)

  • energy/mass of fuel

  • energy/volume of fuel

The heat of combustion is traditionally measured with a bomb calorimeter. It may also be calculated as the difference between the heat of formation (ΔfH0) of the products and reactants.

Heating value

The heating value or calorific value of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The calorific value is a characteristic for each substance. It is measured in units of energy per unit of the substance, usually mass, such as: kcal/kg, kJ/kg, J/mol, Btu/m³. Heating value is commonly determined by use of a bomb calorimeter.


The heat of combustion for fuels is expressed as the HHV, LHV, or GHV (Higher-, Lower- and Gross- Heating Values)

Higher heating value

The quantity known as higher heating value (HHV) (or gross calorific value or gross energy or upper heating value) is determined by bringing all the products of combustion back to the original pre-combustion temperature, and in particular condensing any vapor produced. Such measurements often use a temperature of 25 °C. This is the same as the thermodynamic heat of combustion since the enthalpy change for the reaction assumes a common temperature of the compounds before and after combustion, in which case the water produced by combustion is liquid.


The higher heating value takes into account the latent heat of vaporization of water in the combustion products, and is useful in calculating heating values for fuels where condensation of the reaction products is practical (e.g., in a gas-fired boiler used for space heat). In other words, HHV assumes all the water component is in liquid state at the end of combustion (in product of combustion).

Lower heating value

The quantity known as lower heating value (LHV) (or net calorific value) is determined by subtracting the heat of vaporization of the water vapor from the higher heating value. This treats any H2O formed as a vapor. The energy required to vaporize the water therefore is not realized as heat.


LHV calculations assume that the water component of a combustion process is in vapor state at the end of combustion, as opposed to the higher heating value (HHV) (a.k.a. gross calorific value or gross CV) which that assumes all of the water in a combustion process is in a liquid state after a combustion process.
The LHV assumes that the latent heat of vaporization of water in the fuel and the reaction products is not recovered. It is useful in comparing fuels where condensation of the combustion products is impractical, or heat at a temperature below 150 °C cannot be put to use.

The above is but one definition of Lower heating value adopted by the American Petroleum Institute (API) and they used a reference temperature of 60 °F (15.56 °C).


Another definition [used by GPSA - Gas Processors Suppliers Association and originally used by API (data collected for API research project 44)] is that the lower heating value is the enthalpy of all combustion products; minus the enthalpy of the fuel at the reference temperature [API research project 44 used 25 °C. GPSA currently uses 60 °F], minus the enthalpy of the stoechiometric oxygen (O2) at the reference temperature, minus the heat of vaporization of the vapor content of the combustion products.

The distinction between the two is that this second definition assumes that the combustion products are all returned back down to the reference temperature but then the heat content from the condensing vapor is considered to be not useful. This is more easily calculated from the higher heating value than when using the previous definition and will in fact give a slightly different answer.



Gross heating value

It accounts for water in the exhaust leaving as vapor, and includes liquid water in the fuel prior to combustion. This value is important for fuels like wood or coal, which will usually contain some amount of water prior to burning.



Measuring heating values

The higher heating value is experimentally determined in a bomb calorimeter by concealing a stoechiometric mixture of fuel and oxidizer (e.g., two moles of hydrogen and one mole of oxygen) in a steel container at 25° is initiated by an ignition device and the combustion reactions completed. When hydrogen and oxygen react during combustion, water vapor emerges. Subsequently, the vessel and its content are cooled down to the original 25 °C and the higher heating value is determined as the heat released between identical initial and final temperatures.


When the lower heating value (LHV) is determined, cooling is stopped at 150 °C and the reaction heat is only partially recovered. The limit of 150 °C is an arbitrary choice.

Note:

Higher heating value (HHV) is calculated with the product of water being in liquid form while lower heating value (LHV) is calculated with the product of water being in vapor form.



Relation between heating values

The difference between the two heating values depends on the chemical composition of the fuel. In the case of pure carbon or carbon monoxide, both heating values are almost identical, the difference being the sensible heat content of carbon dioxide between 150°C and 25°C (sensible heat exchange causes a change of temperature. In contrast, latent heat is added or subtracted for phase changes at constant temperature. Examples: heat of vaporization or heat of fusion). For hydrogen the difference is much more significant as it includes the sensible heat of water vapor between 150°C and 100°C, the latent heat of condensation at 100°C and the sensible heat of the condensed water between 100°C and 25°C. All in all, the higher heating value of hydrogen is 18.2% above its lower heating value (142 MJ/kg vs. 120 MJ/kg). For hydrocarbons the difference depends on the hydrogen content of the fuel. For gasoline and diesel the higher heating value exceeds the lower heating value by about 10% and 7%, respectively, for natural gas about 11%.



A common method of relating HHV to LHV is:
HHV = LHV + hv x (nH2O,out/nfuel,in)
where hv is the heat of vaporization of water, nH2O,out is the moles of water vaporized and nfuel,in is the number of moles of fuel combusted.
Most applications which burn fuel produce water vapor which is not used and thus wasting its heat content. In such applications, the lower heating value is the applicable measure. This is particularly relevant for natural gas, whose high hydrogen content produces much water. The gross calorific value is relevant for gas burnt in condensing boilers and power plants with flue gas condensation which condense the water vapor produced by combustion, recovering heat which would otherwise be wasted.



Referenties

Meer voorbeelden over het verduurzamen van absorberende middelen kan u vinden op www.gidsvoorduurzaamaankopen.be



1 http://ec.europa.eu/growth/single-market/public-procurement_nl

2 Opmerking: “Absorberend materiaal” verwijst in feite naar “een sorberend materiaal” wat een adsorbeermiddel, een absorbeermiddel of beide tegelijkertijd kan zijn!Per definitie:

Adsorptie: retentie van de vloeistof op het oppervlak van de sorbentdeeltjes.

Absorptie: retentie van de vloeistof binnen de sorbent zelf (via capillairen de poriën van een poreuze stof in)

Datum: december 2010



Gereviseerd in juni 2016

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  • BIJLAGE 6: Heat of combustion, calorific values, etc

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