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

m g dus t/ N m 3 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

m g dus t/ N m 3 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

m g du s t/ N m 3 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

m g du s t/ N m 3

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 Description

At Voestalpine Stahl GmbH, Linz, Austria, the monitoring of process gases is required according to the permit of the environmental impact assessment. Table 2.17 presents the conditions of the permit. Data are regularly transferred to the local authorities.

Table 2.17: Example of permit conditions for the monitoring of process gases at Voestalpine Stahl, Linz, Austria

Blast furnace gas(1) Coke oven gas(1) BOF gas(1)

Measurement Continuous (2) Discont. Continuous (2) Discont. Continuous (2) Discont. H2 x x x CO x x x CO2 x x x Hydrocarbons x(3) N (chem. bond) x (3) Cl (total) x(3) S (total) x(3) x (3) x (3) Hg x (4) x (4) Pb x (4) x (4) x (4) Cr x (4) x (4) x (4) Cd x (4) x (4) x (4) Ni x (4) x (4) x (4) F (total) x (4) Dust (total) x (1) (5) x (4) x (4)

(1) No limit values are set (status 06/2007).

(2) Continuous measurements should be performed under the condition that approved instruments are available on the market (status 06/2007) [ 26, Oberösterreichische Landesregierung 2004 ].

(3

) As of 06/2007, no instruments for continuous measurements were available for Cl (total) and N (chem. bond). As regards hydrocarbons, CH4and higher hydrocarbons were measured discontinuously. Methods for

the continuous measurements of S (total) are still under evaluation. For discontinuous measurements, intervals are set depending on the parameter, typically monthly; Voestalpine Stahl GmbH, Linz, Austria [ 26, Oberösterreichische Landesregierung 2004 ]

(4) Contents of heavy metals (Hg, Pb, Cr, Cd, Ni), dust and fluorides have to be measured discontinuously, typically four times per year (status 06/2007).

(5) In the case of plastic injection which is performed at one BF, dust has to be measured continuously. Trials on this are still ongoing.

Source: [ 26, Oberösterreichische Landesregierung 2004 ] [ 277, Wiesenberger 2007 ].

Achieved environmental benefits

The monitoring of process gases provides information about the composition of process gases and about indirect emissions from the combustion of process gases, such as emissions of dust, heavy metals and SO2.

Cross-media effects No data submitted. Operational data

The quality (calorific value and cleanliness) and volume of the different process gases varies significantly and these factors have an impact on where the fuels can be usefully applied. To optimise energy efficiency, each type of fuel gas must be consumed at the most appropriate plant. For this reason, gases should be analysed continuously.

Applicability

This technique is considered to be generally applicable. Economics

No data submitted.

Driving force for implementation No data submitted.

Example plants

Voestalpine Stahl GmbH, Linz, Austria. Reference literature

[ 277, Wiesenberger 2007 ]

2.5.5.4 Discontinuous monitoring of ducted air emissions