A brief introduction to odor and odor reduction.

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A brief introduction to odor and odor reduction.

Since most people not dealing with odor and odor reduction on a professional base have limited knowledge about this highly specialized field of knowledge, SEID often senses a need to inform our potential customers “what it’s all about”.

This because it is in the interest of both our customer and to us that our customers know what they get when they purchase an odor reduction system from SEID. Clients often understand the implications of requirements from legislating authorities regarding odor and odor emissions. We have therefore put together this little introduction to odor and odor reduction, hoping that it will help our customers to better understand the different terms used in future discussions. If necessary, SEID will gladly provide a curious reader with more information about all topics dealt with in this introduction.

1.0 Odor terminology.

Odor Units (OUE).

The standard unit used throughout Europe when dealing with odor and odor reduction.

1 OUE/m³ is defined as the odor concentration in 40 ppb 1-butanol or 0,6 ppb hydrogen sulphide. It is a small unit.
Levels below 1.000 OUE/m³ is normally not considered to have a strong smell/odor.

Odor concentration / odor emission.

Odor concentration determines how saturated an emission is with odor. It’s defined in OUE/m³. Odor emission is a function of odor concentration in emission and the emission volume flow and is defined as OUE/sec.

OML-calculation.

Computerized simulation to show how an emission affects the surrounding area. Based on factors like meteorological statistics and data, the topography of the area surrounding the emission point, odor emission and location of emission point (height above ground level where an emission leave the source). An OML-calculation normally covers the conditions expected within 98 or 99% of the hours within a year based on available meteorological data. In other words, during a small percentage of the hours within a year, the meteorological conditions are not within the limitations used in the calculation, and for this period of time, the results from the calculation are not valid.

2.0 Measuring odor.

In order to determine the odor concentration in an emission, samples of the emission are collected in bags and sent to an authorized laboratory for odor panel testing. The first thing a laboratory does after receiving such bags is to dilute the samples with a neutral gas (normally N2 which is considered odor-free) to different concentrations. The degree of dilution normally varies in steps with a factor of 3, within a range of 450x up to 110.000x. These diluted samples are then presented to an odor panel, which is a group of 6-10 trained people, starting with the most diluted ones. The testing of samples continues until a dilution-level from which more than 50% of the panel can detect odor is reached. Based on which dilution-level different panel-participants detected odor a calculation is done, giving the odor concentration in the undiluted emission. The accuracy of such an odor panel test is ±30%.

3.0 Odor legislation.

The legislative framework described here regulating odor and odor emissions are most in us in Europe, but more and more countries are adopting these stringent rules. Densely populated countries were the first ones in Europe to establish guidelines for how to regulate a business’ odour-emissions. The way it’s done is actually very simple – A maximum level for how many OUE/m³ possible to trace back to one source (a factory with several emission-points is regarded as one source) in the surrounding area is defined. These maximum levels are as of today 5 OUE/m³ in residential areas and 10 OUE/m³ in commerce areas. OML-calculations based on figures for a factory’s odor emissions will reveal whether the factory complies with the requirements or not. This does not mean the same as a guarantee that no neighbor will ever detect any kind of odor from the factory. The uncertainties involved when dealing with odor are too many in order to give such a guarantee. But the chance for any neighbour detecting any odor from the factory is reduced to a minimum, and should it happen on some rare occasion it will not lead to “a situation”. The possible odor nuisance coming from a factory that is able to prove that it is not violating the regulations described here is considered acceptable.

4.0 Dealing with odor – an example.

To summon the information given in this introduction and put it into a context, we will here describe how the odor situation is handled when a new fish feed factory is to be built here in Norway.

* Conducting a survey of the future emission situation.

Here we look upon emission volumes, which parts of the production process the emissions origins from, the principle for ventilation of the factory, the loading- and unloading facilities, etc, and we calculate assumed future odor emission from the new factory based on figures from previous surveys of similar emissions.

Example:

  • Source Emission volume Odor concentration Odor emission
  • Extruder 10.000 m³/h 135.000 OUE/m³ 375.000 OUE/sec
  • Dryer 20.000 m³/h 42.000 OUE/m³ 233.000 OUE/sec
  • Cooler 20.000 m³/h 7.000 OUE/m³ 39.000 OUE/sec
  • Hammer mill 8.000 m³/h 10.000 OUE/m³ 22.000 OUE/sec
  • Total 58.000 m³/h 41.550 OUE/m³ 669.000 OUE/sec

* Conducting necessary OML-calculations.

In order to establish what implications the requirements from the authorities regarding odor will have for the project, the demand for odor reduction technology required height on chimneys/stack, it’s vital that such a calculation is carried out in an early phase of the project. The effect of assumed odor reduction technology is taken into account, and calculations will reveal necessary height on chimney/stack where emissions leave the factory in order to comply with the requirements.

For a SEID-installation dimensioned according to normal criteria, a guarantee of 90% reduction of the odor concentration is given. In this case, assumed odor emission used in the OML-calculation would, therefore, be approx. 70.000 OUE/sec. Based on the results from the OML-calculations one can see what effect different levels of odor concentration and odor emission has for the demand to height on chimney/stack.

Design- and install odor reduction technology according to demands. Build a stack with a height in accordance with demand revealed in OML-calculation – Preferably with some “safety-margin”. (Results from odor panel tests can vary very much. Though results from previous and similar tests are of great help in a project like this, there is no guarantee that results from new tests at a new factory will be quite like previous ones)

* Verifying the odor situation after completion of factory.

As soon as possible after regular production has started in the new factory, odor samples from the emission point will be collected and sent to an authorized, independent, laboratory for odor panel testing. With the results from these tests, and results from OML-calculations conducted earlier in the project, SEID and the customer should be able to provide the authorities with documentation that the factory complies with the authorities’ requirements to odor.

SEID will in this phase advice a customer about:

In order to establish what implications the requirements from the authorities regarding odor will have for the project, the demand for odor reduction technology required height on chimneys/stack, it’s vital that such a calculation is carried out in an early phase of the project. The effect of assumed odor reduction technology is taken into account, and calculations will reveal necessary height on chimney/stack where emissions leave the factory in order to comply with the requirements.

For a SEID -installation dimensioned according to normal criteria, a guarantee of 90% reduction of the odor concentration is given. In this case, assumed odor emission used in the OML-calculation would, therefore, be approx. 70.000 OUE/sec. Based on the results from the OML-calculations one can see what effect different levels of odor concentration and odor emission has for the demand to height on chimney/stack.

Still, need to know more?
Please contact us for further information!

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