Feasibility Study of Bio-Sludge Hydrochar as Blast Furnace Injectant

Abstract

Hydrothermal treatment can convert paper mill biological (bio-) sludge waste into more energy-dense hydrochar, which can achieve energy savings and fossil CO2 emissions reduction when used for metallurgical applications. This study assesses the basic, combustion and safety performance of bio-sludge hydrochar (BSHC) to evaluate its feasibility of use in blast furnace injection processes. When compared to bituminous and anthracite coals, BSHC has high volatile matter and ash content, and low fixed carbon content, calorific value and ignition point. The Ti and Tf values of BSHC are lower and the combustion time longer compared to coal. The R0.5 value of BSHC is 5.27 × 10−4, indicating a better combustion performance than coal. A mixture of BSHC and anthracite reduces the ignition point and improves the ignition and combustion performance of anthracite: an equal mixture of BSHC and anthracite has a R0.5 of 3.35 × 10−4. The explosiveness of BSHC and bituminous coal is 800 mm, while the explosiveness of anthracite is 0. A mixture of 30% BSHC in anthracite results in a maximum explosiveness value of 10, contributing to safer use of BSHC. Mixing BSHC and anthracite is promising for improving combustion performance in a blast furnace while maintaining safe conditions.

Exploring Hydrochars from Lignocellulosic Wastes as Secondary Carbon Fuels for Sustainable Steel Production

“…So, it is recommended to mix the studied hydrochar from paper mill biological sludge with anthracite, not exceeding 30% hydrochar addition. This strategy reduced the ignition point of anthracite and improved its ignition and combustion performance [21]. It was also found that hydrochars from different biogenic sources, like maize and wheat straw, in co-combustion with anthracite, decrease the ignition and burn-out temperatures by increasing the hydrochar blending ratio [23].…”

“…Under these conditions, this technology allows for saving energy costs. Along with the solid product with a typical yield of 45-70% by weight of the initial wet biomass, an aqueous stream accounting for 5-25% is also generated, while the gases released are limited to 2-5% [21]. Depending on the severity of the treatment, hydrochars are like peat and lignite and, in more extreme cases, like sub-bituminous coal or hard lignite.…”

“…Due to the high explosiveness, several studies have reported that hydrochar alone is unsuitable for direct injection in the blast furnace [20][21][22][23]. Combining hydrochar with charcoals or coals may decrease CO 2 emissions and reduce coal consumption.…”

Development of a Continuous Hydrothermal Treatment Process for Efficient Dewatering of Industrial Wastewater Sludge

“…The increase in the HHV and the removal of most of the water (99.2% of the initial feedstock) could make this a suitable process to produce solid fuel. Further investigation to see if the press cake can be used directly as a solid fuel (e.g., in the steelmaking industry) should be performed [40], whereas the effluent could be used for nutrient recovery [41] and biogas formation via anaerobic digestion [42]. The effect of the high ash content of the hydrochar obtained from this specific feedstock should be carefully evaluated as this will exclude the use as, e.g., soil remediation.…”

Continuous Hydrothermal Carbonization of Olive Pomace and Orange Peels for the Production of Pellets as an Intermediate Energy Carrier

“…Other applications that are commonly reported for hydrochar are the use as an adsorbent (e.g., CO 2 ), for pollutant removal (like metals and dyes), as a soil amendment and as a carbon sequestration medium [13,[32][33][34]. Recently, some more dedicated papers have focused on its use as a metallurgic reducing agent [35][36][37], as a source for nutrient recovery [38,39] and in the recovery of valuable compounds like fatty acids and phenols from the HTC products [40,41]. Additional research in these areas would be valuable, especially at a pilot scale, as recovery of valuable compounds can further improve the business case and feasibility of HTC processes in industry.…”