Table 6. Energy consumption, material consumption, and environmental benefits comparison of the combined atmospheric acid leaching-chloride iron extraction and high-pressure acid leaching in laterite nickel ore processing.

Experimental method	Energy consumption characteristics		Material efficiency		Economic evaluation				Environmental benefits
	Reaction conditions	Comprehensive energy consumption	Acid consumption	Metal extraction features	Investment cost per ton of nickel	Acid consumption cost	Operating cost	Applicable ore types	Waste minimization	Pollution control
Atmospheric acid leaching – chloride iron extraction	80–150 °C (Normal pressure)	Low, no high-pressure equipment required, and equipment operation energy consumption is low	300–450 kg t−1 of ore	Cl− enhances nickel dissolution, reduces impurity co-dissolution	Approximately 1.5 times the cost of electric furnace process	Low (acid recycling possible)	Low due to minimal neutralization and iron removal requirements	Limonite-type (high iron, low magnesium)	Slag utilization rate >90%, nickel slag 0.5–1 ton	A closed-loop hydrochloric acid cycle avoids waste acid discharge; carbon emissions are 13.7 tons CO2 per ton of nickel, which is 70% lower than the blast furnace process
High-pressure acid leaching (HPAL)	245–260 °C; 4–5 MPa	High, requires high-pressure equipment and has high energy consumption for equipment operation and heating	600–900 kg t−1 of ore	Requires handling of large amounts of iron impurities, significant co-dissolution of impurities	More than three times the cost of electric furnace process	High (sulfuric acid cannot be recycled)	High due to the need for neutralization and iron removal	High-grade ore	Slag utilization rate <100%, nickel slag 120 tons	Potential heavy metal wastewater risk, high carbon footprint