Continuous parameter and air emissions monitoring Description Description

2.5.5 Monitoring in iron and steel plants

Table 2.16: Examples for continuously measured air emissions at Voestalpine Stahl, Linz, Austria Relevant pollutants

Dust NO_x SO₂ CO H₂S HF Plant Potential emissions source

mg/Nm³

Reference O₂

H₂S in coke oven gas X(¹)

Coke oven

Sulphuric acid plant X

Sinter strand X X X X

Sinter plant

(²) Dedusting of building X

Cast house dedusting BF 5 & 6 X Blast

furnaces Cast house dedusting BF A X

Dedusting unit 1 X X(³)

Secondary dedusting 2.1 X

BOF plant

Secondary dedusting 2.2 X

Unit 3 X X X 3 %

Unit 4 X X X 3 %

Unit 5 X X X 3 %

Gas and steam turbine X X X 15 %

Power plant

Unit 6 X X 3 %

(¹) Hourly average value.

(²) According to the permit, Hg has to be monitored continuously at the reference plant due to local considerations (high content of Hg in the ore). Trials are still ongoing.

(³) As of 06/2007, the current emission limit value was under revision. Continuous measurements should be performed for SO2emissions.

NB: — Status 06/2007. Emissions which are measured discontinuously are not included in the table. Permit conditions might change in the course of the actual environmental impact assessment ‘Voestalpine L6’.

— Where limit values have been set up, they are marked with an X (based on half-hourly average values).

In the UK, the coke ovens for dust emissions from under firing are monitored continuously by obscuration meters and in sinter plants the dust emissions are monitored continuously. In blast furnaces, the monitoring of the cooling water flow is of relevance. SOX, NOX, dust and CO are monitored on hot stove releases. Releases of dust from cast houses are monitored.

Reference literature

[ 26, Oberösterreichische Landesregierung 2004 ] [ 242, Caughlin 2007 ] [ 277, Wiesenberger 2007 ]

2.5.5.2 Examples of continuous monitoring of ducted air emissions 2.5.5.2.1 Continuous measurement of dust emissions from secondary dedusting

systems in basic oxygen furnaces Description

The monitoring system at SSAB Oxelösund AB, Sweden allows for a continuous control of the bag filter performance. The measurement results are reported daily, weekly and monthly. The BOF operations (charging, blowing, tapping) are very closely controlled.

A continuous dust measurement system is installed in the exhaust gas system after the secondary dedusting filter. There are two instruments for measuring dust emissions in the channels following the secondary dedusting filter and another two in the roof openings. The

external company. The collected data are saved in SSAB’s own database. The control of the bag filter function is done by SSAB’s own operators. Revision is made once per year. The fluorescence method is used to detect leakage.

Dust emissions from the LD furnace (BOF) (excluding primary off-gas) are also closely monitored. The emissions are reported during three separate process phases: charging, blowing and at other times.

Achieved environmental benefits

In the case of poor performances of the secondary dedusting system, prompt action can be taken. Overall emissions can be reduced. Figure 2.17 shows the weekly averages which have been achieved with the aforementioned monitoring system over a period of one year.

0 0,5 1 1,5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Week 1 – 26 Limit value <10 mg/Nm³

mgdust/Nm3

0 0,5 1 1,5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Week 1 – 26 Limit value <10 mg/Nm³

mgdust/Nm3

0 0,5 1 1,5 2 2,5 3

27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53

Week 27 – 53 Limit value <10 mg/Nm³

mgdust/Nm3

0 0,5 1 1,5 2 2,5 3

27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53

Week 27 – 53 Limit value <10 mg/Nm³

mgdust/Nm3

Source: [ 208, Lindfors et al. 2006 ]

Figure 2.17: Dust quantities from secondary dedusting systems presented as weekly averages

Cross-media effects No data submitted.

Operational data

The system calibration according to the measured values happens once a year. The calibration period takes two days.

Applicability

The technique is applicable for both new and existing steel plants.

Economics No data submitted.

Driving force for implementation No data submitted.

Example plants

SSAB Oxelösund AB, Sweden.

Reference literature [ 208, Lindfors et al. 2006 ]

2.5.5.2.2 Continuous monitoring of downstream bag filters in EAF plants [ 208, Lindfors et al. 2006 ]

Description

The EAF steelworks at Ovako Imatra, Finland consists of a whole building evacuation and a separate dust suction from the EAF itself. The filter plant installation is equipped with efficient spark arresting and cyclones, from which the dust (>5 micron, 30 % of the total amount) is charged back to the EAF together with the scrap. The main fans (average 620000 Nm³/h) have a rotation speed control. The bag house has a conservative (large) dimensioning (9400 m²) and the filter bags are a normal needle felt type with PTFE coating. The filter bags are cleaned with a pulse-jet system.

Continuous monitoring and a careful service of the bag house works in the ways given below:

• it monitors dust emissions, without any real calibration. It is important to detect any change of emissions level (leakage in one bag can immediately be detected)

• it continuously monitors via two separate instruments:

a tribometric measuring system – SINTROL^®

an optical measuring system – SICK^®[ 360, Sick-Maihak 2006 ]

• it visually checks all bags for spark holes and intensity: every second week, one worker for three hours. The clean side of the bags should be kept totally clean. Holes of 1 mm diameter can be detected without difficulty so no fluorescence method is needed.

Achieved environmental benefits

In the case of poor performances of the bag filter system, prompt action can be taken. Overall emissions can be reduced.

Cross-media effects

This measure also provides clean surroundings inside and outside the steel plant.

Operational data No data submitted.

Applicability

The monitoring system is well applicable to both new and existing plants and should be applied to large EAF plants. To determine the definition of ‘large EAF’ as a relevant emission source,

Economics No data submitted.

Driving force for implementation

The driving forces for implementation are the environmental benefits associated with the technique.

Example plants Ovako Imatra, Finland.

Reference literature

[ 208, Lindfors et al. 2006 ] [ 242, Caughlin 2007 ]

2.5.5.3 Monitoring of process gases