Washed PKS for Decarbonization of Iron and Steel Plants

The steel industry contributes 8% of global CO2 emissions, with each ton of steel produced producing an average of 1.85 tons of CO2 emissions. Compared to iron ore mining, iron and steel production contributes significantly more to CO2 emissions. Decarbonization efforts in the steel industry begin with the use of renewable energy for smelting. Biomass-based fuels, such as charcoal, which has a high carbon value, can replace the use of coke derived from coal. The use of hydrogen from renewable energy sources is the ultimate decarbonization target for the steel industry.

Currently, the steel industry largely uses coal as an energy source or reducing agent. This coal is processed into coke and used in blast furnaces. It is estimated that approximately 70% of global steel production uses the blast furnace or BF-BO process, and in China, over 90% of steel production uses the BF-BOF process. To reduce carbon intensity, natural gas is used as the fuel. The use of natural gas as a gaseous fuel also acts as a transition medium and, because it is derived from fossil fuels, is also a carbon-positive fuel.

Nearly all CO2 emissions in the steel production sector come from blast furnaces (BFs), which refine iron ore into crude iron or pig iron. The challenge is significant: there are approximately 1,850 steel mills worldwide, with approximately 1,000 using blast furnaces, producing approximately 1.5 billion tons of pig iron annually.

The use of charcoal in a blast furnace not only reduces carbon dioxide (CO2) emissions but also sulfur dioxide (SO2) emissions due to its very low sulfur content (approximately 100 times lower) than coke. Likewise, the use of limestone is reduced, thereby automatically reducing slag production. This also makes the blast furnace's operation acidic.

The use of biomass-based carbon fuel (biocarbon) in the form of charcoal has a better climate impact because it is carbon-neutral. Furthermore, technically, because it is a solid fuel, similar to coke derived from coal, it requires little or no changes or modifications to the smelting furnace. However, the availability of high-quality charcoal, large volumes, and a continuous supply remain major constraints.

This makes the use of charcoal to replace coal-based coke in blast furnaces crucial. Charcoal, derived from biomass, is a renewable, sustainable material used as a reducing agent or fuel in blast furnaces. The chemical reaction separates oxygen atoms from iron atoms, emitting CO2. This converts iron ore (Fe2O3) into crude (pig) iron.

However, the difference lies in the fact that the carbon source used as a reducing agent or fuel in a blast furnace comes from renewable and sustainable sources, making it a carbon-neutral process. Conversely, using coke from coal, as it comes from a fossil fuel, is a carbon-positive process. Similarly, using natural gas as a carbon source for reducing agents or fuel in a blast furnace, although it is said to have lower carbon intensity, is also considered a carbon-neutral process.

The use of charcoal or biocarbon materials for metallurgy or steelmaking has actually been commonplace for some time. In the early 1900s, global charcoal production reached its peak, exceeding 500,000 tons. In the 1940s, charcoal production declined to nearly half its early 1900s levels due to the replacement of other carbon materials, such as coke from coal, in the manufacture of steel and other metals.

Charcoal is a fuel and reducing agent derived from biomass that has significant potential for use during this transition phase. Palm kernel shells (PKS) are a potential biomass raw material for charcoal production. Palm kernel shells (PKS) are available in the millions of tons, ensuring a reliable supply. Charcoal, a product of biomass carbonization or pyrolysis, has a high calorific value, high fixed carbon content, and stability. However, another factor, ash chemistry, influences the quality of the resulting steel. This is somewhat similar to the ash chemistry of wood pellets from calliandra or gliricidia energy plantations.

When used as a reducing agent in blast furnaces, charcoal must have a low phosphorus content, while wood pellets from calliandra or gliricidia energy plantations must have low potassium, sodium, and chlorine content. The potassium, sodium, and chlorine content of wood pellets affects the quality of the wood pellets and their use in power generation. Pulverized combustion power plants, widely used worldwide, will reject wood pellets with this quality. Similarly, blast furnaces will reject charcoal with a high phosphorus content.

To achieve this quality, low-phosphorus content, the palm kernel shells (PKS) must first be washed. After washing, the phosphorus content decreases, and they are then dried and pyrolyzed, or carbonized, to produce palm kernel shell charcoal (PKSC). The same applies to wood pellets. The only difference is that wood pellet production doesn't involve pyrolysis or carbonization; instead, after drying and achieving the desired particle size, the pellets undergo biomass densification in a pelletizer.

Steel production requires an average of 6,000 MJ of energy per ton (equivalent to 50 kg of hydrogen) or 200 kg of charcoal, and requires approximately 600-800 kg of woody biomass as raw material. With a calorific value nearly identical to woody biomass, this is equivalent to using palm oil mills (PKS), which are plantation or agro-industrial waste.

Meanwhile, demand for low-carbon steel is growing rapidly as steel industries and governments worldwide commit to reducing carbon emissions from fossil fuels. The use of charcoal or biocarbon in blast furnaces is a key component of low-carbon steel production, as 100% of the steel is not yet produced using renewable energy. 

Maximizing Palm Oil Mill Profits with Cogeneration Utilization of EFB (Empty Fruit Bunch) and Export of PKS (Palm Kernel Shells)

As a profit-oriented company, maximizing profits is a natural and ongoing endeavor. Besides increasing efficiency, innovation can also be pursued, creating or developing new businesses. This is especially true if the innovations involved in creating new businesses also address environmental issues, such as utilizing palm oil mill biomass waste. In palm oil mills, empty fruit bunch (EFB) waste is generally underutilized, or if utilized, it is still suboptimal or inadequate, such as composting empty fruit bunches (EFB).

Empty fruit bunches (EFB) are a significant biomass waste product from palm oil mills, accounting for approximately 22% of the total production, but are generally underutilized and pollute the environment. Utilizing EFB through cogeneration will not only address the problem of EFB, but also generate heat or energy to replace the use of palm kernel shells (PKS) as boiler fuel, and also produce high-quality organic potassium ash fertilizer.

If the PKS used for boiler fuel reaches 50%, then using this technology means that 50% of the PKS can be recovered, or 100% of the PKS can be sold or exported. For example, a palm oil mill normally sells 3,000 tons of PKS per month. With this technology, the mill can sell 6,000 tons of PKS per month. This would certainly increase the supply of PKS significantly.

Even if applied on a larger/macro scale, namely in Indonesia with CPO production of around 50 million tons/year, the actual production of PKS is around 12.5 million tons/year. However, with the current practice of utilizing PKS as boiler fuel, say reaching 50% of PKS production, the actual amount of PKS that can be sold/exported by palm oil mills is 6.25 million tons/year. Now, with the use of this technology or the installation of equipment (EFB furnace cogeneration), the amount of PKS that can be sold/exported will be close to or equal to the PKS production in the mass balance or diagram above (not subtracting the amount burned in the palm oil mill boiler).

The demand for palm kernel shells (PKS) is increasing in line with the global decarbonization trend. In fact, PKS is a major competitor for wood pellets in the global biomass fuel market. Large PKS users come from Japan and Europe. PKS exports to Japan typically reach around 10,000 tons per shipment, while those to Europe typically reach a minimum of 30,000 tons per shipment due to the longer distances and the use of handymax or even panamax vessels. Cogeneration of empty fruit bunch (EFB) furnaces with palm oil mill boilers will increase the volume of PKS that can be sold or exported. Implementing this technological innovation, besides being the fastest and most practical, also offers multiple benefits, making it worthy of consideration. It could even become a trend and even a standard operating procedure in Indonesia's approximately 1,000 palm oil mills.

Water Related Problems in Cooling Towers

The constant trickle of water can hollow out rocks. Furthermore, a continuous flow of water will gradually erode everything in its path. A more dramatic and spectacular example is the Grand Canyon in Arizona, United States. Furthermore, if the flowing water is hot, it will erode or dissolve the solids it passes through (leaching) more quickly than cold water. By the time the hot water returns to the cooling tower, it is already full of suspended solids. The cooling tower, as a means of dissipating heat, flows hot water from the top of the tower, and cool air from the surrounding environment that comes into contact with the warm water absorbs the heat. As a result, the water becomes cooler and the air becomes warmer.

Hot water also tends to be corrosive and form deposits. This is why the materials used to construct cooling towers must be durable and able to withstand large temperature differences. Certain types of wood and plastic can be used for cooling tower construction. If the materials are of poor quality, the cooling tower construction will be short-lived and even dangerous. When hot water enters the cooling tower and mixes with suspended solids, some of the water evaporates, leaving the suspended solids behind. This suspended solids-rich liquid concentrates in the sump at the bottom of the cooling tower. Over time, the concentration of these suspended solids increases until it reaches a level that must be controlled by removing it from the system, known as blowdown.

The outside air that comes into contact with the water from the cooling tower contains dust or small particles, as well as microorganisms such as various bacteria, fungal spores, and algae. These dust or small particles become suspended and accumulate/concentrate, forming deposits in the form of mud or crust. In the presence of sunlight, these microorganisms, such as bacteria and algae, photosynthesize, multiplying and increasing in number. Pathogenic bacteria like Legionella can even cause Legionnaires' disease. This mud and algae contaminate and clog heat exchanger tubes, accelerating their corrosion.

In the heat exchanger, if the scale thickness is 0.3 mm, it is estimated that there will be a heat/energy loss of 10% and if the scale thickness is 0.6 mm, it is estimated that there will be a heat/energy loss of 23%. And in general, fouling causes an annual energy/heat loss of around 15%, so it requires maintenance and pipe replacement every 3–5 years. If not handled properly, heat/energy loss due to fouling can reach up to 70% after five years. Fungi and bacteria will cause wood to rot/decompose, making it brittle and destroyed. Likewise, oxidation reactions on metal surfaces, because these metals release electrons or capture oxygen, causing corrosion on the metal. Corrosion on metal causes the metal to become increasingly eroded, brittle and damaged.

Maintaining water quality from various contaminants in a cooling tower, which volume thousands of tons per hour and operates 24 hours a day, is certainly not simple. Only by maintaining this water quality can the cooling tower's performance and lifespan meet its design targets. Using effective, efficient, and environmentally friendly technology is the best option. Advanced Oxidation Process (AOP) technology is an innovation to address these issues. This technological approach effectively, efficiently, and environmentally friendly addresses various water issues in cooling towers. For example, in algae cells, ions from the Advanced Oxidation Process (AOP) attack the sulfide groups contained in amino acids in the remaining proteins involved in photosynthesis. As a result, photosynthesis is inhibited, and the cells dissolve or disintegrate. If algae and microbial cells remain, their regrowth is inhibited by the AOP ions in the water, thus preventing algae growth. During this process, bacteria are also killed or rendered inactive.

The second example is the rust prevention mechanism of pipes. Iron (Fe) loses electrons according to the oxidation reaction and forms rust. However, when the AOP material participates in this reaction and releases electrons first, the iron is prevented from releasing electrons, thus suppressing rust formation. The rusted iron is converted to black rust through the AOP reaction, forming a dense oxide film that prevents further corrosion and protects the pipe and structure.

And the third example is the scale prevention mechanism. When water passes through the AOP system, calcium (Ca) and magnesium (Mg) ions—the components that cause hardness—are removed through crystallization in the liquid phase, thus softening the water. The resulting calcium carbonate particles cannot adhere to pipes. In hard water containing calcium (Ca) and magnesium (Mg) ions, needle-like scale structures typically form and adhere to pipe walls. Through AOP treatment, scale-forming ions undergo particle growth in the liquid phase, forming spherical particles ranging in size from a few micrometers to tens of micrometers.

According to the Gibbs–Kelvin formula, the volumetric free energy is reduced and the adhesive force is lost, thus preventing it from sticking to the pipe walls. Scale will accumulate at the bottom of the basin and be removed by a blowdown mechanism. In addition, this AOP technology will also remove scale that has already stuck to the pipes (scale removal existing pipes) and also the sterilization effect which is also very important for the quality of the cooling tower water such as preventing wood rot/decaying and killing pathogenic bacteria, both of these aspects will be explained on another occasion, Insha Allah.

To measure cooling tower performance based on the problems encountered and the solutions implemented, several parameters are used. These parameters include:
• Water pH
• Total dissolved solids (TDS)
• Tower equipment checklist
• Filters and strainers
• Wet bulb temperature and humidity

Meanwhile, safety in cooling towers is also important and needs to be considered. These include:
• Chemical additives (if used and not yet using AOP technology)
• Rotating equipment
• Dangers of hot water
• Working at heights
• Working safely on the cooling tower.
• Equipment failures
• Metal corrosion and wood rot/decay

The use of cooling towers can be said to be an important and fundamental equipment for industrial operations in general. Starting from power plants that still use fossil energy, cofiring or biomass power plants to geothermal power plants, data centers, chemical industries, biorefinery industries, petrochemical industries, iron and steel industries, food industries, pharmaceutical industries, textile industries, pulp and paper industries and so on. Related to the era of decarbonization and sustainability / sustainability of the use of renewable energy such as biomass including wood pellets and palm kernel shells / PKS as part of carbon neutral fuels or carbon negative such as carbon capture and storage (CCS) to biochar, of course environmentally friendly technology, especially easy to operate, affordable investment costs to repair-maintenance, will be an option for these industries, such as AOP technology for water conditioning in cooling towers so as to provide significant savings.

OPT Briquette and EFB Briquette for Medium Capacity Industrial Biomass Boiler Consumption

The growing utility business, specifically the provision of steam and electricity for renewable energy-based industries, particularly biomass, has led to a growing need for biomass fuel. This also applies to industries using their utility units to produce steam and electricity using biomass fuel. In addition to biomass fuel, water quality, the raw material for steam and electricity production (using steam turbines), is also crucial and must be considered. Good water quality will ensure optimum steam and electricity production performance, and the longevity of equipment (boilers, heat exchangers, steam turbines, and cooling towers), and vice versa. Good water quality is like healthy blood for our bodies, enabling all organs to function optimally.

Palm oil industry solid waste is a potential raw material for biomass fuel. This solid waste is empty fruit bunches (EFB) and oil palm trunks (OPT). EFB is produced from palm oil mill operations with a percentage of approximately 22% of fresh fruit bunches (FFB), while oil palm trunk waste is produced from replanting programs of oil palm plantations, which are also very abundant. For more details, read here. Utilizing both of these biomass wastes for the production of biomass fuel, especially biomass briquettes, would be very good. But why are they processed into briquettes?

The advantage of briquettes over pellets, aside from technical advantages, lies in their scale. Briquette production requires a looser particle size and lower moisture content. Energy consumption per ton of briquette production is also lower than that of pellet production. This makes EFB briquette and OPT briquette production more suitable for a palm oil mill serving medium-sized industries. A palm oil mill with a capacity of 45 tons/hour of FFB will produce approximately 10 tons/hour of EFB. With a 20-hour daily operation, approximately 200 tons will be produced per day. With a moisture content of approximately 60%, this means that after drying, approximately 100 tons/day (10% moisture content) will be produced, or 2,500 tons/month.

Likewise, when using oil palm trunk (OPT) waste as raw material, it depends on the ratio or percentage of land replanted each year. Replanting itself is an effort to continuously maintain the productivity of the oil palm plantation itself, in addition to the use of superior seeds and intensification. For more details, read here. For example, with a land area of ​​10,000 hectares and each year replanting 5% of the land, or 500 hectares. With an average of 125 trees per hectare of oil palm plantation and each tree having an average dry weight of 0.4 tons, then per hectare obtained 50 tons of dry weight of biomass. With an area of ​​500 hectares, this means 25,000 dry palm trunk biomass (10% moisture content) each year or can be processed into OPT briquettes with a capacity of around 2,000 tons/month.

Biomass boilers, used for producing biomass briquettes (EFB briquettes/OPT briquettes), can utilize various combustion technologies, such as moving grates, stokers, reciprocating grates, and so on. The choice depends on the cost or price of the boiler and its efficiency. In addition to biomass fuel, to align with decarbonization and sustainability programs, water for boiler operation, including boiler feedwater and cooling water for heat exchangers (heat exchangers/condensers), is crucial. This is likened to blood for the human body; healthy blood ensures optimal function. If impure blood circulates throughout the body, for example due to kidney failure, organs will automatically be damaged, and a person will soon die.

To maintain water quality for steam production through a boiler, boiler feedwater/demin water must strictly comply with the boiler's operational specifications. The higher the boiler pressure, the higher the water quality or purer the water required. If the steam is used for electricity production, after the steam drives the turbine, it needs to be condensed in a heat exchanger (condenser) so that it changes phase back to liquid and enters the boiler again. This heat exchanger requires cooling water that is continuously used repeatedly, thus requiring a cooling tower. Not only does the boiler feedwater/demin water need to meet the required technical specifications, but so does the cooling water for this condenser. With water volumes circulating up to thousands of tons per hour and operating 24 hours a day (the same as boiler operations) in the cooling tower, a number of water problems in the cooling tower need to be addressed effectively and efficiently. A number of water problems that occur in cooling towers can be read here.

In addition to electricity production, steam is also used for processes within a specific plant. If the steam is then condensed, then liquid, and returned to the boiler, this requires a cooling tower, just as in electricity production. Efficient and environmentally friendly water treatment technology, which eliminates secondary pollution and is easy to operate and maintain, aligns with the vision of decarbonization and sustainability. This vision of decarbonization and sustainability will be even more optimal or ideal for utility units, namely the use of biomass-based renewable energy and environmentally friendly water treatment technology.