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Project results



1. Introduction


2. Odour emission balance measurements in pilot foundries

2.1 Odour emission balance measurements 2012


3. Cleaning efficiency measurements of the tested abatement systems

3.1 Biofiltration abatement system

3.2 Adsorption abatement system

3.3 Oxydation abatement system

3.3.1 Pre-test measurement of CTP pilot plant

3.3.2 RTO test at the aluminium foundry in Austria

3.3.3 Pilot tests at iron foundry in Finland in 2013

 


1. Introduction

In foundries, there are several odorous emission sources. Typically, emissions origin from the unit processes of melting, core making, flask cooling, die casting, shake out, and sand reclamation.

Foundry’s noxious and odorous emission gases are either inorganic or organic ones. Typical inorganic gases are sulphur oxides, carbon oxides, etc. Foundry processes use a large number of organic chemicals as binding, coating or surface treatment agents or additives that can be also regarded as odour compounds e.g. amines, xylenes, toluenes, furfuric alcohol, creosolene, formaldehydes, etc. The most common nuisance-causing and noxious compounds used in foundries are organic decomposition products e.g. tetrametyl-, ethyl-, propylbenzenes, naphthalenes (other PAHs), benzene, styrene, BTEX, cresolene, mesitylenes, etc.

Chemicals can be both irritating or even poisonous as well as being odorants. They may cause multiple health effects and some of the gases are also considered to be green house gases. This problem is a wide transnational environmental and health issue in Europe, especially in densely populated areas and among foundry industry employees. In fact, there are about 290.000 persons employed in the foundry industry across Europe who are affected by the problem.


Flow chart of the foundry processes:

In this project the odour emissions will be determined and measured from the main foundry processes such as core making, pouring and casting lines and sand reclamation. The tested cleaning systems will be also placed on these sites.


2. Odour emission balance measurements in pilot foundries


It is essential in odour abatement to recognise the chemical compounds causing odour effects in question. In the case of the foundry, there are several odour emission substances. Secondly, it is important to define the quantity of odour and the clean air level to be met. In this project, both the recognition and the olfactometric identification will be carried out.

 

The odour emission definition is called here “odour emission balance measurement” because it contains the mass flow calculations of all major exhaust flow definitions of the foundry. Odorous and hazardous emissions will be measured and defined from different foundry processes such as pouring, core making, sand reclamation processes.

The emissions of odour components will be studied in laboratory casting trials. Streaming air from the samples of various moulding materials containing hot iron and aluminium will be assessed by the human test panel and by a gas chromatograph-mass spectrometer. Identifying individual components and determining their respective contributions to the odour will be done by combining the panel assessments with gas chromatography-mass spectrometry (”GC-MS sniff test”). Measurements will be carried out according to the standart SFS-EN 13725:2003 - Air quality: determination of odour concentration by dynamic olfactometry.


2.1 Odour emission balance measurements 2012

In 2012 three odour emission balance measurements at pilot foundries were completed. Measurements were carried out by Institut für Gießereitechnik gGmbH and AX-LVI Consulting Ltd. Swerea SWECAST AB was responsible for the arrangements of odour emission measurements in two pilot foundries in Sweden.

The first pilot foundry was an iron foundry in Sweden that produces components mainly for heavy vehicle industry. Annual production is about 25.000 ton/year. The molds are produced in mechanical molding line using green sand. The cores are made with cold box method and they are coated with water based coating agent.

Measurements were carried out in September 2012 and the highest odour emissions (ouE/h) were measured at the beginning of the cooling line and at the filter of sand reclamation filter and pouring. The total odour emissions were 1 748 978 483 ouE/h. The total odour emission in 2012 was 86 305 ouE/h/produced ton.

Measurement results from the second pilot foundry will be released by Swerea SWECAST AB on project website in 2013. This was an aluminium foundry.

Odour emission measurements at the third pilot foundry were carried out in Germany by IfG. This pilot foundry was a steel foundry with the production of >20 t steel cast per day. The molds are produced in machine moulding shop, using bentonite-bonded quartz sand. Hand moulding shop produces molds by means of the resol ester process (alpha set method) with sand regeneration. Core-making shop produces furan resin bonded cores and they are coated with water-based agent. 

In addition to a general assessment of the emissions situation, manufacturing processes with major odour and pollutant emissions were identified in particular. In conjunction with the tests undertaken by IfG as project partner, hazardous substances were also measured in various departments of steel foundry in Germany. These measurements served as controls and provided a quantitative overview of the odour levels and gaseous pollutant levels. A feature specific to this foundry was that only a few emissions are contained and the majority emitted diffusely. For this reason, many samples were taken locally in the direct vicinity of the manufacturing processes and not at the stacks as usual. 

Odour emissions varied between 130-320 OU/m3 in different foundry processes. Highest concentrations were measured at the start of the cooling line and at the hand moulding shop. The lowest concentrations were measured at the end of the cooling line and sand reclamation. 

Project measurement results indicate that many different variables affect the composite odour. Among the most important factors are the type and amount of binder chemicals, and the duration and temperature of the cooling stage. The results also indicate that many different substances (over 100) contribute to a composite odour, and that it is seldom the case that only a few of them predominate.



Odour panel in Sweden - panelists from AX Consulting Odour panel measurements

Pictures  1 and 2. Odour panel measurements (”GC-MS sniff test”) and odour sampling at a project pilot foundry in 2012 in Sweden.


Odour panel measurements

Picture 3. Odour panel measurements at a project pilot foundry in 2012 in Sweden.



3. Cleaning efficiency measurements of the tested abatement systems

 

The performance of individual pilot odour abatement plants is studied in the project. The feasibility studies of six highly developed and innovative odour emission abatement techniques such as oxidation (catalytic, thermal and concentration + oxidation), biofiltration, adsorption, and ignition systems will be carried out in six European foundries. In total, seven pilot tests will be carried out in 2012/2013 in Germany, Finland and Austria. Piloting will be made by using small-scale installations in order to gain experience for full size system design and dimensioning.

The six selected cleaning techniques, the necessary properties as well as accessories and automation will be specified to successfully optimise the operation system. This is necessary to ensure overall efficiency and reliability. The features of the abatement techniques, which enable the functioning of the system in foundry processes, will be defined and controlled. To facilitate fully the techno-economic assessment of the abatement techniques, a design and instruction guide will be provided that will include the total annual cost estimates for the full-scale technologies.

After the project, foundries will have information on how to choose and design an outlet air purification system for VOC, odour and hazardous emission abatement. We will also know what kind of cleaning system will abate these emissions. The technology will be ready for validation in the emission treatment of foundry processes. The feasibility and transferability of the piloted cleaning systems will be evaluated in different foundry processes. It will also be possible to apply the results in other industries such as the steel, chemical, pharmaceutical and brick and ceramics industries.

Three abatement systems were tested in 2012.
Two abatement pilot plants were constructed and tested at a steel foundry in Germany in October-December 2012. Biofiltration pilot plant was supplied by REINLUFT Umwelttechnik Ingenieurgesellschaft mbH and adsorption pilot plant by Nederman Filtration GmbH.

3.1 Biofiltration abatement system

Biofilters lend themselves to all waste gas cleaning applications involving air pollutants that are readily biodegradable. Biodegradation of the pollutants is accomplished by micro-organisms colonizing on solid support media. Typical support media employed are chopped wood and wood bark, composts, wood bark or other origins, fibrous peat and heather which may be combined with one another or other structure-giving materials. As the waste gas passes through the bed of media, the pollutants are sorbed onto the surface of the filter media where they are degraded by micro-organisms. For optimum growth and metabolic activity, the micro-organisms rely on defined environmental conditions (moisture, pH, oxygen content, temperature, nutrients, etc.) which must be controlled within narrow limits.

Reinluft pilot plant integrated a two-stage high-performance biofilter. The container itself had a size of 20 feet and consists of a filter area and the control room. The control room was equipped with a fan for max. 1500 Bm³/h, a quench, an air scrubber and a control system. Waste gas from the pouring and cooling line was conducted to biofilter pilot plant.



Picture 4. Biofilter pilot plant by REINLUFT Umwelttechnik Ingenieurgesellschaft mbH.


Based on the measurement results it could be shown that many volatile organic components from the steel foundry and most odours can be degraded and removed biologically. The overall VOC elimination capacity of the biofilter shows an efficiency of > 70 % at an average filter space loading of about > 110 m³/(m³h). The odour reduction efficiency was calculated to > 85%.


3.2 Adsorption abatement system

The system works with the adsorption of the odours in surface active materials like active coal or other suitable additives. The powdery additive is fed with a variable dosing system continuously in the raw gas. The adsorption takes place during the flight of the additive in the raw gas up to the filter media. At the filter media, consisting of needle felt, there is a rising dust cake that is online cleaned off. The cleaning system is a pulse jet system that works online during the continuous filtration process. In the cleaned off dust layer there is also a further adsorption of odours. 

Based on the measurement results the odour level in the raw gas of 110 – 360 OU/m3 was reduced to 53 – 76 OU/m3 in the clean gas after the filter. The odour reduction efficiency is calculated to approximately 54% based on the measurements.

The odour reduction efficiency is regarded as low. The reason is considered to be the very low raw gas concentration. With higher concentration for removal the efficiency would increase significantly, because the clean gas values stay almost in the measured level independent of the raw gas. This effect is regarded as normal and has proven to be true many times in applications with dry sorption of waste gases.





Picture 5. Adsorption pilot plant  by Nederman Filtration GmbH.


3.3 Oxydation abatement system

As part of the EU Project Odorless Casting, Chemisch Thermische Prozesstechnik GmbH is performing three pilot tests in Finland and  a cleaning efficiency measurement at the existing full scale RTO built by CTP in 1996 at an aluminium foundry in Austria.

The regenerative catalytic oxidation (RCO), regenerative thermal oxidation (RTO) and concentrator + RTO pilot systems will be tested at the project pilot foundries to abate odorous and hazardous emissions. CTP is responsible for the design and construction work of a small-scale pilot plant.


3.3.1 Pre-test measurement of CTP pilot plant

The pre-test unit was tested at a steel foundry in Finland in 2012 in order to get valuable information of the odour compounds and the type of catalyst feasible for such foundry conditions. A catalytic pilot unit operated for one month connected to the production hall ventilation exhaust at a steel foundry to be able to extrapolate the catalyst lifetime and test for catalyst poisons. Beside this test in a parallel reactor filled with zeolite high boiling substances are collected. The amount and boiling range of high boilers decides about the applicability of an adsorber concentrator and what type (rotary concentrator or fixed bed) has to be chosen.

Because of the high amount of high-boiling substances a rotary concentrator cannot be used. Desorption with 200 °C would not be sufficient to maintain the necessary cleaning efficiency. High temperature cleaning for rotary concentrators is limited to 300 °C and few times per year. But it would be possible to use a zeolite fixed bed, designed for desorption at 400 °C.



Picture 6. Connection and start up             Picture 7. Pre pilot test installation


3.3.2 RTO test at the aluminium foundry in Austria

The cleaning efficiency of a full scale thermal oxidation system was measured at the aluminium foundry in Austria. The existing RTO was built by CTP in 1996. All pouring places are connected to the exhaust gas collection system to remove pouring gases formed by pyrolysis of the binders. The pouring waste gas as well as emissions from cooling and shake out are purified in the RTO (Regenerative Thermal Oxidation system) meeting highest emission standards. 

The possibility to measure at a full scale plant gives more accurate and realistic data than any pilot test. The measurements were carried out in September 2012 by CTP and IfG. The cleaning efficiency rate of the RTO plant was 95 %. The excellent cleaning efficiency as well as the low total energy consumption of the RTO combined with the heat recovery systems makes this waste gas treatment process to the “Best Available Technology” for foundries like this aluminium foundry.


3.3.3 Pilot tests at iron foundry in Finland in 2013

The CTP prototype has been designed and constructed in 2012. The prototype will be tested at an iron foundry in Finland in summer 2013. Results will be available in august in 2013.