Atmospheric emissions

Description

Air quality is a major concern at the start of the 21st century. Controlling the sources of polluting emissions is a key part of pollution control, mainly in terms of compliance with emission standards and the development or monitoring of pollution control facilities.
Industrial companies are subject to regulations requiring them to carry out continuous monitoring (self-monitoring) and occasional analyses (by accredited laboratories) of their pollutant emissions.
ISSeP carries out measurements of stationary sources for both the public and private sectors.
The parameters studied are a function of both industrial conduct and the operating permits in force. Less common parameters for which there is no sampling standard are studied on a case-by-case basis.
As a Reference Laboratory for the Walloon Region, the Institute participates in the accreditation procedure (technical part) as well as in the definition and development of reference methods for both sampling and analysis.

1. General

Emissions represent the discharges emitted by a source. Atmospheric emissions are related to air quality (monitored by networks), which represents the concentration of a pollutant in the ambient air in a given area. The latter concentration represents local emissions plus background pollution.
The most important aspect of emission measurements is the care taken with on-site sampling. A representative sample of the gas composition must be taken from the industrial pipe. It is not possible to intercept the entire gas flow. Standards have been drawn up to ensure representative sampling.
Standards specify the position and distribution of sampling points in the duct, as well as the sampling flow rate. Others describe techniques for determining the concentration of a large number of analytes. Where no standard exists, the sampling technique is defined in collaboration with the analysis laboratory.

2. Sampling objectives

Emission measurements can be carried out not only for regulatory purposes, but also for the development of industrial techniques. These include :

Emissions checks, at the request of the relevant authorities (DPE, Walloon Region, etc.). The parameters to be measured and the frequency of measurements are determined by the operating permit.
Impact studies. When the operating permit has to be renewed, or when an important parameter of the operating conditions is modified, leading to a change in the pollutant content of the discharges, it is necessary to carry out a study of these.
Process studies, at the request of manufacturers. The development of industrial plants sometimes requires the measurement of specific parameters, and not necessarily at the stack.
Verification of purification systems (filters, afterburners, scrubbers, etc.), at the request of manufacturers. A simultaneous upstream and downstream measurement on a plant or prototype can be used to define the purification efficiency.

3. Parameters studied

The parameters to be monitored depend above all on the type of industrial plant being studied:

gas flow in the pipe is the first parameter that can be determined, along with the concentration of dust suspended in the gas.
major compounds: H2O, O2 and CO2 (range: %). These values are also used to calculate flow rates and therefore determine withdrawal rates.
minor compounds: CO, SO2, NO, NOx, N2O, CxHy (range: mg/m3).

Alongside these parameters, which could be defined as classic, there are a great many inorganic and organic compounds which are measured depending on the type of plant encountered:

Inorganic compounds: chlorides, fluorides, cyanides, heavy and volatile metals (Hg, Cd, Tl, As, Co, Pb, Cr, etc.).
Organic compounds: dioxins and furans, PCBs, PAHs, etc.

4. Types of installation

Emission measurements can be carried out on all types of industrial pipe, provided they are fitted with sampling flanges that meet the relevant standards.
By sector, for example: