MERIMMAXIMIZED EMISSION REDUCTION AND
ENERGY RECOVERY IN IRONMAKING

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ADVANCED TOP GAS CLEANING FOR
BLAST FURNACES, FINEX AND COREXADVANTAGES OF MERIM:• No sludge and waste water
treatment necessary• Clean gas concentration of< 3 mg/Nm³ achievable

YOUR CHALLENGEOUR SOLUTION

Demands placed on availability,
product quality and productivity ofironmaking plants are continuously
increasing, and these can only be
met with advanced solutions suitable
for the rugged iron- and steelmaking
environment. At the same time, stricter
environmental regulations necessitate
extensive investments, and these arehaving a direct impact on ironmaking
plants with their high quantity ofenvironmental emissions.

A fully satisfactory, environmentallycompatible solution for the treatmentof top gas from the ironmaking
process has not existed until now. In
response to this challenge, Primetals
Technologies recently developed
the MERIM process, which stands for
Maximized Emission Reduction andenergy recovery in IronMaking. In aseries of successive treatment steps
the dust in the offgas is removed
to levels previously unattained withconventional wet-type top gastreatment techniques.

As plant designers, our job is tooffer the best possible solutions thatsimultaneously satisfy environmental
requirements and economicalnecessity. While there is significant
market potential for new investmentsin the growing markets of eastern
Europe, Asia and India, industrial
nations are focusing more on plantmodernizations and reducing theenvironmental impact.
Conventional wet-type top gas
cleaning technologies have a highwater demand and require expensive
sludge and waste water treatment.
In addition, wet cleaning leads tosubstantial pressure and temperaturedrops which result in reduced
efficiency of the downstream top gas
recovery turbine.

The MERIM is mainly designed forblast furnace top gas cleaning but canalso be successfully applied for Corexand Finex. The new system includes a
cyclone for coarse dust separation anda high-performance fabric filter forfine dust removal. In order to solve theproblem of temperature fluctuationsin the top gas, Primetals Technologies
developed a gas conditioning concept
which allows for safe operation evenat extreme low and high temperatures.
This system consists of a burden
burner and an advanced burden spraysystem.

High energy recovery potential in
combination with low investment andoperating costs compared to wettype solutions for blast furnace top
gas cleaning.

• 20 to 30% higher energy
output from top gas recovery
turbine due to higher processtemperatures and lower
pressure losses• Easy reutilization and handlingof by-products• Lower operating andinvestment costs compared towet solutions (e.g. electricity,water)• Less maintenance andincreased availability• Less space requirements(about 40 to 60% lesscompared to a complete wettype installation)• Advanced emission control(e.g. HCl, H2S) is possible due
to additive injection and dust
recirculation

Using this green solution, energy
consumption and land filling can be
reduced to currently unachieved levels.
The cleaned gas meets both current
and future emission regulations andthe CO2 footprint can be significantlyreduced.
THE LIFECYCLE PARTNER
Primetals Technologies is oneof the world´s leading lifecycle
partners for metals industry. We
offer a comprehensive technology,modernization, product and service
portfolio as well as integrated
automation and environmentalsolutions covering the entire life
cycle of plants to improve ourcustomers´competitveness.

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MERIMTOP GAS CLEANING PROCESS WITHHIGHEST ENERGY RECOVERY
MERIM

Temperature
control

Pulse jetpressuse filter

Recirculate (optional)

Typical MERIM process

PROCESS DESCRIPTIONIn the first step of the MERIM process, optimized coarse
dust separation takes place in a cyclone. Thanks to thedesign of the cyclone, the recyclable fraction is enriched
and the fraction for waste that contains zinc is minimized.
The heart of the process is the set of pulse jet pressure
filters where fine dedusting takes place. In this step, thegas enters several pressure-resistant filter vessels where
the dust is collected on high-performance filter media. The
removed dust is discharged through the bottom of the filter
and transported via a pneumatic conveying system to a
storage silo.
The cleaned top gas then enters the top gas recovery
turbine. The dry solution has a 20% to 30% higher energy
output compared to common wet-type dedusting systems
due to higher process temperatures and lower pressurelosses. Depressurization valves (Septum Valves) are also
installed to control the furnace pressure when the top gas
recovery turbine is not in operation.
The temperature control unit consists of a burden burnerand burden spray system that ensures that a specifictemperature range (usually 100-250°C) is maintained. This
prevents damages to the fabric filter and gas ducts.

4

Optionally, an additive dosing station and a recirculation
system can be installed. A mixture of recirculated dust andadditives can be injected into the raw gas stream in frontof the fabric filter for the removal of other harmful gas
components (e.g., HCl, H2S).
Blast furnace top gas cleaning is normally carried out ina two-stage dedusting process that comprises of a dust
catcher or cyclone (first stage) and a scrubber. Waste watermust then be treated in a dedicated water treatment plant.
With MERIM the whole waste water treatment can beavoided, operating costs and space requirements arereduced and the dust and harmful components present in
the offgas are removed to very high levels.

3-inlet cyclone

Pulse jet pressure filter

CYCLONEPULSE JET FILTERIn this step, the offgas passes through a cyclone designed
to ensure an optimized separation into recyclable dust
and fine dust with a high zinc fraction. This maximizes thedust collecting efficiency and thus reduce the dust loadat the filter. Thanks to the new three-inlet cyclone design,
the downcomer can be supported centrally through thecyclone vessel and maintenance is made significantly easier.

In a next step, precleaned gas from the cyclone is carried tothe pulse jet filter. This system consists of several pressureresistant vessels which contain a number of filter bags. Thedust particles remain on the outside surface of the filter
cloth and the filter cake is built up at the surface of themembrane. The design of the filter media and its membrane
ensure a high separation efficiency.

Approximately 85% of the dust is removed in the highly
efficient cyclone and thus optimize iron recovery. The
generated dust can be easily reused in the sinter plants.
However, not all top gas dusts are suitable for recyclingin the ironmaking process. High concentrations of heavy
metals in the burden, especially zinc, can potentially affectblast furnace operation. Therefore, this optimized dust
separation device in the first stage of top gas treatment isimportant from an operational and cost perspective.

When a certain pressure drop is reached over the filter, theN2 pulse jet system is activated and the filter cake falls off
the cloth surface. The separated dust is collected in thefilter hoppers and further transported to the residue silo via
pneumatic or mechanical dust conveying systems.

MAIN BENEFITS• Separation efficiency of approx. 85%• Minimization of landfill costs• Adjustable separation efficiency for optimal zincseparation

The cleaned top gas from the filter vessels is collected in amain duct which guides the gas stream directly into a topgas recovery turbine where the high energy content of theclean gas is converted into electricity.
The pressure drop at the fabric filter is lower than 20 mbar
(average 15 mbar), which is for less than the pressure drop
at a scrubber. Together with a lower temperature loss at thefabric filter, this leads to a 20 to 30% higher energy output
at the top gas recovery turbine.

5MERIM
STEP BY STEP TO HIGHERENERGY OUTPUTREFERENCES
MERIM PLANTS

Temperature control unit

Additive dosing station

Filter vessel

Pilot plant for COREX

Pilot plant for FINEXTEMPERATURE CONTROLADDITIVE DOSING AND INJECTION (OPTION)

MERIM PLANT FOR JSW

PILOT PLANT MERIM FOR FINEXSpecial attention must be paid to the top gas temperature,as the filter bags can only work properly in a temperature
range of 100°C to 250°C. Primetals Technologies hasdeveloped a top gas conditioning concept which allows forhigh and low temperatures. This concept comprises of aburden burner and an advanced burden spray system.

In the additive dosing station, additives and recycled dust
can be mixed. The mixture is then injected into the raw gas
stream in front of the fine dedusting fabric filter. Dependingon the gas cleaning requirements, different additives canbe used.

MERIM PLANT FOR KARDEMIR A.S.,
TURKEYA pilot installation at an ironmaking
plant designed to treat 6,000 Nm³/hof offgas was installed to better
investigate the dry dedusting filtersystem.

BURDEN BURNER• Gas components such as HCl or H2S can be removed

High-pressure gas cleaning for Corex
gas based direct reduction plant
The top gas from the Corex plant iscleaned by three filter vessels in orderto achieve very low clean gas dust
concentrations to reduce abrasion atthe gas compressors. The cleaned gas
is subsequently used at the Midrex
plant to produce hot DRI.

• Prevents condensation at the filter cloth - avoids clogging• Corrosion protection of gas ducts and gas cleaning
equipment• High velocity burners achieve optimized temperature
distribution in the top gas
BURDEN SPRAY• Fast temperature control due to fine water droplet
distribution• Protects gas ducts and gas cleaning equipment againsthigh temperature impact during slips• Less water required compared to common burden sprays• No wetting of the burden due to fast and effective
evaporation of the water droplets

MAIN BENEFITS• Dust recirculation allows for higher exploitation of theadditives• Longer filter bag lifetime due to fast filter cakegeneration

In the year 2012 Kardemir A.S. ordereda MERIM plant including top gas
conditioning system for their new
Blast Furnace #5. The furnace ishaving a working volume of 1650 m3
and is producing around 1,2 mio tonsof Hot Metal per year. The dry top gas
cleaning plant is designed for a gas
volume of max. 400.000 Nm3/h and
top gas pressure of max. 2,5 bar(g).
Primetals Technologies was
responsible for the whole plantengineering as well as supplyof critical key components andsupervision services during erection
and commissioning.
The clean gas content is max. 5 mg/
Nm3 and due to the dry gas cleaning
technology approx. 27% more
electrical energy can be recoveredat the downstream installed Top Gas
Recovery Turbine (TRT).

Technical Data:• Volume: 600,000 Nm³/h; 1 bar(g)• Clean gas dust concentration <5.0mg/Nm³

HANDLING OF EXTREMESITUATIONS• Temperature permanently >220°C• Dust load of 20 to 40 g/Nm³• High content of (sticky)hydrocarbons >250 ppm• Fine particles of D(v,0.90) 20 μm
and D(v,0.5) 8 μm
During testing, a clean gas dust
concentration of <1 mg/Nm³ wasachieved, which shows that the fabricfilter system is capable of meeting topgas cleaning requirements.

The plant went into operation onJan. 2015.

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Primetals Technologies Austria GmbHA joint venture of Mitsubishi Heavy Industries and partners

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