Now the ‘FE Odyssey: “I Am a ButterFEly.”’, the final installation of the Blast Anatomy series, will follow the iron (FE) through its journey – all the way from its birthplace in mine to its final destinations, right around us. Better yet, the FE itself will walk us through the entire adventure!

Like a majestic butterfly who muddles through arduous stages – eggs, caterpillars then pupa – the journey of steel is just as rigorous: from iron ore buried deep in the mines until it finally presents its true self, as steel.

Join now to follow the FE Odyssey. POSCO Newsroom presents: “Blast Furnace Anatomy #3 – FE Odyssey: “I Am a ButterFEly.”

l Into the World – Like a Butterfly Fighting Its Way out of the Egg,
Iron Ore Makes Its Way out of the Mine

▲ Roy Hill Mine, Western Australia

I was born in Roy Hill mine in Western Australia, over 6,500 kilometers away from Pohang where one of POSCO steelworks is located. While buried deep in the ground of Roy Hill, I always dreamed of transforming into cool and chic steel products – a sturdy car, a slick home electronics, or a shiny stainless travel mug that offers people warm beverages.

Roy Hill mine has a total of 2.3 billion tons of iron ore deposits. POSCO started investing in Roy Hill mining project since 2010 now holding 12.5% of its shares. Roy Hill boasts the annual production of 55 million tons of iron ores. It’s huge! And that’s how so many of my siblings come from there. Besides Roy Hill, my other iron ore siblings also come from places like Canada and Brazil.

From the mine, do I travel straight to steelworks? Not exactly. I wish it were that simple. Before I get transported to the port in Australia, I make a stop at a laboratory for thorough testing – all my internal organs undergo rigorous testing. Using magnets, the lab technicians classify ores with high iron (FE) content. Fortunately, the iron ore that housed me passed the inspection, and I headed to the harbor so I can be sent to Korea.

My siblings and I boarded the transport ships to Korea. After 15 days of a long journey across the ocean, I can hardly forget the excitement I felt when we finally docked. Here we were, at the pier for POSCO’s raw materials, and I was stepping closer to my dream. Every year, 55 million tons of iron ores reach the POSCO docks – both Pohang and Gwangyang combined! These iron ores all share one dream and one dream only – the dream of becoming steel.

After we disembarked from the ship, we got stacked in raw materials yard. The raw material yards at POSCO steelworks measure to be 1.85 million m² – both Pohang and Gwangyang combined.* In that vast field of POSCO yard, I met some new friends – some were called ‘coal.’ Later on, when we reunited in front of the blast furnace, the coal friends would stand before me already transformed as ‘coke.’ Because coal could produce acidic dust, they would first travel to a place called ‘silo,’ an eco-friendly storage facility specifically designated for them.

*The Seoul World Cup Park: 2.1 million m².

When I looked closely, I noticed my iron ore siblings all had very different body types. We were all jagged and uneven. So we got separated, tossed and rolled around a lot, so our bodies can be shaped just right for the furnace. It was a lot of work, but I was so psyched – I knew I would soon get to travel into the blast furnace!

l Rites of Passage for Butterflies, So for the Iron Ores

As it turns out, I knew nothing of what it took to become steel. From the raw materials yard, I thought I would head straight into the blast furnace. Little did I know that I had to undergo one last stage – a process called ‘sintering.’ I also went through several other processes and entered a hot oven. As I got baked in it, I got more polished and solid. It was 1,300℃, so it was super hot, but I heard it’d be even hotter inside a blast furnace, so I got through it okay. After sintering, I transformed into sinter, a raw material for steelmaking, not an ugly and unpolished iron ore anymore!

As sinter, I passed through three filters, and right in front of the rotation chute, I reunited with the friends I’ve met earlier at POSCO yard. We would enter the blast furnace together. Through the rotation chute, we twirled and rolled around, a lot.

I heard some of my friends didn’t quite make it to the rotation chute. They didn’t pass through the filtering stages earlier. But I heard they were going to be reused as raw materials for the sintering instead.
I entered the furnace as sinter, but there were other raw materials like ‘sized lump’ and ‘pellet’. The sized lump came in just the perfect size right from the extraction. Relatively small iron ores became pellets through compressing and molding. Subsidiary materials like limestones also entered the furnace with me. Of course, the crucial fuel friends like coke, who help us melt, also joined us.

Facing the blast furnace, I got so nervous, so I took a deep breath to calm myself down. Because the temperature inside the furnace could reach as high as 2,300℃, it was rather hard to breathe, but my coke friend and I patiently took turns forming layers inside the furnace. As time went on, we traveled down. As we traveled down, we could feel the hot air flying up. Along with the hot air, I flew up in the middle of the furnace. I wasn’t quite sure where I would go next. Meanwhile, I heard my coke friend shouting, “hot air slapping!”

The coke hot aired by 1,200℃ air from the bottom, was oxidized producing carbon monoxide as a result. In turn, this carbon monoxide took oxygen away from me. These series of chemical reactions separated me from oxygen, and I became pure iron, FE! I finally transformed into molten iron and dropped to the floor. Along with my siblings, I roared in victory and exited the furnace through the tap hole.

l How Molten Iron Becomes Steel

I became molten iron, but the excitement was short-lived. To become steel, I have yet to face another set of journeys. As is, right out of the furnace, I was called ‘pig iron’ still containing several impurities like carbon, phosphorus, and sulfur. I still had to go through several processes inside the steelworks to reborn as a slick and beautiful steel product. The processes to come were: steelmaking, casting and rolling.

POSCO’s Pohang and Gwangyang Steelworks are integrated steelworks – because they have all the facilities to turn something like me, a piece of iron ore rock, into perfect and complete steel – all in one place. Let me walk you through each step.

Step 01. Steelmaking process – removing impurities from molten iron, molten iron becomes molten steel at this stage.
To become steel, I still had to shed impurities completely, and my carbon proportion had to be adjusted also. As pig iron, I exited the furnace through the tap hole and got loaded onto the ‘Torpedo Ladle Car’ and transported to the converter.

At this stage, the steelworks workers called me ‘molten iron,’ which meant pig iron made in the blast furnace. The torpedo ladle car is a specially designed car that transports molten iron. Each car, which can load up to 300 tons of molten iron, heads to the converter. Once I got to the converter, I saw scrap metals as well as pure oxygen. The carbon inside me became oxidized, and its proportion was reduced down to 0.3%. At this stage, I became independent from all the unnecessary impurities. Through this steelmaking process, I became molten steel – pure and optimized pre-steel. I wasn’t yet complete but was a ‘steel’ nonetheless, finally!

Step 02. Casting process – where the liquidated steel becomes solid.
As molten steel, I went into a mold, and through the continuous casting process, I got cooled and solidified to become intermediary materials like slab, bloom, and billet. It’s like shaping cookie dough with cookie cutters of various shapes and sizes. Slabs are used for plates or hot rolled coil; blooms for large steel bars or wire rods; and billets are made into small steel bars or wire rods.

Step 03. Rolling process – making steel into plates or wire rods.
After casting, slab, bloom, and billet pass through several rotating rolls taking a series of constant pressure. During this process, I either get thinned out or get stretched as per the client order – in whatever thickness or length. This is the stage where I can finally become wire rods, plates, or coils.

After the rolling process was complete, I underwent yet another rounds of check-ups to see if I had all the adequate qualifications as a steel product. At this stage, I even received an identification tag! I still remember myself waiting in the storage room excited to leave for the next destination. Some of my siblings got on a ship to the United States, and some of my big siblings got transported to the port in Ulsan in a specially designed truck.

l Like Butterflies Flying All Around the World, Steel Travels and Is Everywhere

To become an adult, butterflies must undergo long and arduous journey – first fighting its way out of the eggs, and going through caterpillar and chrysalis stages. Just like butterflies, I was merely a piece of rock at birth. Then, I became sinter, then a pure ‘FE,’ then finally, steel.

My dream came true. I became advanced high-strength steel (AHSS) and got used in a car, in hydrogen batteries – also in refrigerators and washing machines! Some of me became a bridge that crosses over an ocean. I was reborn as indispensable products in people’s lives.

And I don’t just mean me in contemporary society. Even my ancestors played crucial roles in sparking Industrial Revolution and in accelerating modernization. It’s a well-known fact the Industrial Revolution kicked off right around when the steam engine started being used as the main energy source. Simultaneously, the advanced smelting technique during the eighteenth century helped replace wood railways with iron railways. Together with the steam engine, trains became another momentum pushing the Industrial Revolution forward. Even after the Industrial Revolution, I was used everywhere as construction materials, in the machinery, for ships, cars, and home electronics. I was present all throughout human history.

I go on quietly carrying out my duties whether people notice me or not. I am hiding in guitar and piano strings creating beautiful melodies – and even in ticking clocks and car tires. Have you ever noticed my presence?

Like a caterpillar who turned into beautiful butterflies, I, who was once an unpolished piece of rock is now traveling all around the world in different shapes and sizes. Look around! You will notice I’m everywhere – and right next to you, at this moment.

l POSCO’s ‘Deep Learning’ Blast Furnace

POSCO embarked on the journey of smart technology back in 2016, the year when a super AI AlphaGo beat Se-Dol Lee, human champion of the game Go.

As disheartening as it was, Lee’s defeat became an awakening moment for Korea and an opportunity for POSCO to start digging deep on the relatively new concept, artificial intelligence. From that moment on, POSCO accelerated its research into AI and deep learning collaborating with top university researchers across the country to develop smart blast furnace.

The core of smart blast furnace technology is, ‘Deep Learning.’ Deep learning discovers patterns amongst countless random data utilizing it to predict the possible outcome just as human intelligence categorizes random items.

Let’s say there are thousands of random pictures – pictures of cats and dogs. A computer reads, analyzes, and categorizes the data from each picture, so the next time it ‘sees’ similar photos, it will recognize, determine and predict the correct pattern, thus identifying the picture as either cat or dog. Lots of companies are already utilizing this technology to analyze massive volumes of audio-visual data.

l What Is a ‘Smart’ Blast Furnace?

A blast furnace is a gigantic structure of 110 meters in height, taller than an average 40-story building – it makes molten iron. Inside the blast furnace flows a mixture of solids and liquids whose temperature rises as high as 2300℃. Since blast furnaces operate 24/7 non-stop, it’s difficult to ‘look’ inside a furnace.

However, the No.2 blast furnace of Pohang Steelworks is changing the game of steelmaking business. The ‘smart’ Pohang No. 2 furnace utilizes deep learning with an automotive system that monitors and auto-controls the inside conditions of the furnace.

POSCO started by defining the five variables that affect the conditions of a furnace. Then, countless random data was digitized for standardization. All the major data which used to be controlled heuristically is now measured live and become digital data paving a new path so the furnace can start learning deeply.

After the digitization completed, POSCO took on smartization process to establish a system to predict and automate the condition of the blast furnace. The key distinction between digitization and smartization is that smartization allows prediction. Because the data is so massive – over 1,000 types – the smartization process assigns algorithm appropriate for each data and perform analysis-prediction-control. Based on the rendered result, the system determines whether the inside conditions are good or bad – or can cause problems.

To put it simply, a smart blast 1) learns countless live-collected cases and data; 2) self-assesses the conditions of inputs (i.e. raw materials and fuels) and the furnace condition; 3) predicts the result of furnace operation; 4) automatically pre-controls the operating conditions; 5) yields the best combination result with minimum error.

l AI Furnace, Smarter than Humans

Every day, the visual data generated from the smart blast furnace daily reach up to hundreds of gigabytes. The smart furnace learns this massive amount of data and is getting smarter every day. What are the potential implications of this vast learning?

Before the smartization, the field employees used to personally measure the blast temperature every two hours, but now the bottom sensor of the furnace live-records the molten iron temperature. Not only does it live-record the current temperature, it also predicts the temperatures inside the furnace an hour ahead auto-adjusting the temperature of hot metal accordingly.

Furthermore, highly consistent algorithm assesses the inside condition of the furnace utilizing the thousands of images collected from the cameras installed on the tuyere nozzles. Based on the assessment, the smart furnace auto-controls the charging actions of iron ores and coke.

What about the skull? It’s layers of adhesives that stick to the furnace wall. To a furnace, it’s a cancer-like lump. What the smart system does is to analyze the images collected through furnace thermometers, sketch the overall shape of the skull, subsequently auto-controlling the charging mode.

Image source: ‘Shipment standby’ – By Tae-Ha Woo (20th Korean National Steel Day photo contest)

Currently, the Pohang No.2 blast furnace is the testing ground for this cutting-edge technology – the smart furnace boosted the daily production of molten iron by 240 tons. Annually this amounts to 85,000 tons with which automakers can produce 85,000 more cars. It is also a huge energy saver reducing the energy per ton of molten iron production.

One of the biggest achievements of the smart blast furnace is having stabilized the furnace management process through AI auto-control.

For the last three years, POSCO completed developing the auto-control system for each component of the blast furnace. Now the company is focusing on comprehensive integration. Going forward, POSCO plans to expand the applications to the Pohang No.3 and No.4 furnaces – they both have bigger internal capacity (5,600 ㎥) than the current No.2 furnace (2,550 ㎥).

POSCO took a giant step by adopting the world’s first thinking blast furnace. With time, more data will be collected, which will improve the quality and efficiency of molten iron production. In the era of the Fourth Revolution, POSCO will continue leading the way towards the smartization of steelworks across the globe.

Blast furnace produces molten iron, and it is indispensable to steelworks operation. With 110 meters in height, its scale is enormous.

All the steel products we see in our everyday lives are made from the molten iron. However, other than this simple fact, there really isn’t much we know about the blast furnace as what’s visible is its colossal steel exterior, not the inside.

What’s inside the blast furnace and how does it operate, with what technology? To help understand the details of blast operation, POSCO Newsroom presents ‘Blast Furnace Anatomy #1 – To the Heart of Steelworks Operation.’

l Earth, Fire, and the Wind: The Three Elements of Molten Iron

What gives birth to molten iron? It’s Earth, fire and the wind — these three elements come together in a blast furnace to create molten iron. How exactly? Let’s find out.

First, the iron ore, the raw materials for steel, comes from the Earth. Most iron ores — hematite, magnetite, limonite — contain an average of 60% of iron (Fe). Before the iron ores enter a blast furnace, it undergoes ‘sintering’ which turns the pristine iron ore into more compact and appropriate sizes.

The sintered iron ores become ‘sinter.’ The iron ores that come in just the perfect size right from the extraction are called ‘sized lump.’ The ores in microscopic scales are pelletized, which are called ‘pellets.’ Steelmaking utilizes all three materials as raw materials. Subsidiary raw materials like limestones are also used.

<Blast Furnace: Fuels & Raw Materials>

Now, the blast furnace will melt all the raw materials and extract only the iron (Fe), where coke and pulverized coal fuel the raw materials.

Coke is a grey, hard, and porous fuel made by heating coal up to 1000℃. Inside the furnace, coke is the main heat source melting various materials. It also acts as a reducing agent deoxidizing iron ores. The pulverized coal is a lump of the coal smashed into small pieces — of 0.125mm in size or less. Of the two, pulverized coal makes for a more economical option.

The raw materials and fuels alone do not magically create molten iron, of course. They will need the hot air inside the blast furnace — the hot air about 1200 ℃ in temperature. Then, the fuels and raw materials layered inside the furnace literally fly up inside the furnace! To better grasp the process, let’s slice the blast furnace in half and look inside.

This is what a blast furnace looks like. What exactly happens inside the blast furnace?

Fuels and raw materials enter the furnace through the top opening. The rotating chute evenly distributes the materials, landing them precisely at the due location. Then, the fuels and raw material layer in rotation — a layer of fuel, a layer of raw material, etc. Together, they create more than 40 layers of fuels and raw materials.

At the bottom of the blast furnace, the hot air of 1200℃ heats the materials and fuels. The hot air with a force of 4.0bar triggers such a force that the materials fly up in the air. Because of the heat, coke chemically dissolves the raw materials.

These processes produce molten iron, slag, and by-product gas at which stage, they are still mixed. Then, the by-product gas rises to the top while the molten iron and slag drop to the bottom. Once filtered through dust collectors, the gas transforms as a power source for steelworks. As for slag and molten iron, they are each separated for slag granulation and steelmaking. From the moment the raw materials enter the furnace, it takes about six and a half hours for the materials to transform into molten iron.

l And By-products? Recycle, Recycle, and Recycle

The by-product gases produced inside the blast furnace are released through the top pipe, mostly carbon monoxide, carbon dioxide, and nitrogen. For every ton of molten iron produced, the furnace emits about 1,600 cubic meters of gas. The gases go through primary and secondary dust collectors for purification. The purified gases are utilized to power different facilities at steelworks. This is how POSCO self-produces 74% of the electricity for its steelworks operation.

<Blast Furnace: The Journey of By-product Gases>

Other by-products from inside the furnace also include ingredients like silica (silicon dioxide) — not part of necessary ingredients to produce molten iron. To separate silica from iron ore, the subsidiary material limestone is added during sintering. Once inside the furnace, limestone combines with the silica and drops to the floor. The mixture is lighter than molten iron, so it layers above the molten iron. This mixture is another steelmaking by-product, slag.

Where does the slag end up? POSCO slag is recycled 100% as fertilizer and cement. Blast-furnace slag is rich in silicic acid, an excellent fertilizer for rice farming. Altogether 390,000 tons of POSCO slag was used for agricultural farming in 2018.

POSCO also developed POSMENT, an eco-friendly cement with a higher portion of slag which reduces CO2 emission up to 60%. Altogether 10.69 million tons of POSCO slag contributed to reducing 8.39 million tons of net greenhouse gas emissions.

l Is Blast Furnace Outdated?

Because blast furnaces have been around for so long, it could feel outdated. However, the furnace is full of sophisticated technology.

The sophistication starts from the very moment when the raw materials drop into the blast furnace. Landing them at the precise locations requires advanced technology. Precise calculation is crucial in all procedures — the order of insertion, in what sizes, how much, where, and at what timing. Based on these calculations, the rotation angle of the chute is adjusted, so that the raw materials and fuels distribute evenly inside the furnace.

Another part of the furnace technology involves the insertion of hot air into the furnace through over 40 holes. The timing must be steady. To boost productivity, pure oxygen is sometimes added to the hot air. There is also a facility that produces the hot air, which is called a hot stove. What powers the hot stove is the by-product gas produced in the blast furnace — recycled 100%. Such sustainable technology is at the core of POSCO’s competitiveness.

With the mixtures of solids, liquids, and gases creating many chemical reactions, it can be difficult to predict exactly what’s happening inside the furnace. With the 46 years experience of operating blast furnaces, POSCO has a reliable system to predict the condition of furnaces, however. At POSCO, the condition of blast furnaces can be monitored through live-data such as the temperature of the furnace, pressure, and the status of molten iron-making. Since the blast furnace operation is 24/7 nonstop, maintaining a stable condition has a critical bearing on the safe and economical operations of steelworks.

l Blast Furnace Shapes Korea’s Modern History

It’s no wonder the Pohang No.1 Blast Furnace was cited as Korea’s economic national treasure — for the immense contribution it sparked for Korea’s overall economic growth.

During the 1960s, when the whole country was still reeling from the wounds of the war, POSCO’s blast furnace provided an opportunity not only to lift the country off abject poverty but to continue — to hope.

Even at this moment, the Pohang No.1 Blast Furnace is making molten iron just the same — like the time when the golden molten iron poured out of the tap of the Pohang No. 1 blast furnace for the first time. The initial sentiment of the time might have faded, but the blast operation continues.