Another Efficient Solution: Helping alumina refineries go greener
Sustainable scale control technology in alumina production
Without using scale inhibitors in the alumina production process, scale massively accumulates in manufacturing equipment. As a result, energy consumption rises, fresh water needs to be injected, and hazardous "labor-intensive" de-scaling operations become necessary. With MAX HT® eliminating scale directly at the source, Solvay has developed a sustainable best-in-class technology that reduces both energy and fresh water consumption and related costs, in addition to solving a legacy production challenge within the alumina industry. And for that reason, MAX HT® technology earned the World Alliance for Efficient Solutions label at the start of 2020 for its role in protecting people and the environment in a profitable way.
A less emissions-intensive Bayer Process
Alumina, or aluminum oxide, is made from a naturally occurring ore called bauxite. It is the primary raw material for aluminum, the world’s second most used base metal applied in a wide range of industries such as transportation, construction, machinery and consumer goods. Specialty and high-purity alumina can also be used in diverse segments ranging from ceramics and batteries to semiconductors and LED displays.
Today, most alumina is produced through the Bayer Process, which involves circulating caustic soda-enriched liquor to leach and separate alumina from bauxite ore at high temperatures and pressurized conditions. This is an energy- and emissions-intensive process that results in a large carbon footprint, as many large-scale heat exchangers are run to concentrate and heat the Bayer liquor to extract more alumina from bauxite ore.
A fundamental challenge with this process is that scale forms on heating surfaces as Bayer liquor is heated - such as on heat exchanger tubes. As a result, heat transfer efficiency diminishes, reducing throughput, or increasing energy consumption and, therefore, CO2 emissions.
This is where Solvay’s MAX HT® Sodalite Scale Inhibitor enters. It optimizes energy consumption and, therefore, reduces emissions in the alumina production process. It minimizes scaling (impurities and contaminants) from the evaporator and digester heaters during the century-old Bayer Process and maximizes heat transfer - hence its name, which stands for Maximum Heat Transfer.
MAX HT® is used in more than 40 Bayer process plants worldwide, resulting in reduced energy consumption and reduced acid waste from heater cleanings.
A sustainable AND profitable solution
“A rigorous methodology is used to evaluate products and technologies before they are awarded the Solar Impulse Foundation’s label as an ‘Efficient Solution’, ” explains Mechelle Engemann, Sustainability Leader for Solvay’s Technology Solutions Global Business Unit. “We were asked to demonstrate that MAX HT® has a direct positive impact on the environment over its lifecycle while delivering economic savings for customers.”
On both fronts, MAX HT® delivers. It facilitates improved heat transfer, evaporation and flow, significantly increasing energy efficiencies that result in reducing CO2 emissions equivalent to 13-92 kg per ton of alumina produced. It also supports lower production and maintenance costs associated with scale-induced downtime and cleaning, while avoiding 0.9-2.7 kg in acid waste. When these savings are applied to the total alumina production from 20 plants, it leads to an estimated reduction of 0.54-3.9 billion kg of CO2 emissions, and 38-116 million kg of acid waste reduction. To put this in perspective, 2Mt CO2 equivalent is about the same as 20% of Brussels’ emissions, or that of approximately 115,000 American citizens.
Mechelle adds, “Leveraging analysis from current customers’ refineries, we demonstrated both direct and indirect financial savings for customers, which reduced their total cost of ownership.” What’s more, MAX HT® benefits the safety of refinery workers who, in many cases, are no longer exposed to hazards associated with acid cleaning.
Alumina refineries in China now burn less coal because they don’t need as much energy thanks to our improved MAX HT®.
A scale solution just for Chinese alumina refineries
Solvay has developed a specific MAX HT® line for the Chinese market whose liquor is somewhat different than the rest of the world’s. “The Chinese market was using a lot more energy than necessary. Alumina refineries in China now burn less coal because they don’t need as much energy thanks to our improved MAX HT®,” explains Ryan Zheng, Global Marketing Manager for Alumina and Industrial Minerals, Mining Solutions.
And to think, the challenge of reducing scale in alumina refineries worldwide was unsolvable until just 15 years ago. Today, thanks to MAX HT®, alumina refineries can operate free of sodalite scale in their heat exchangers, while lowering their environmental impact and allowing for billions of liters of fresh water to be saved annually, enough water for approximately 2,400 households in the United States.
And Solvay continues to develop products that help optimize mining operations worldwide, enabling customers to improve productivity and reduce operating costs while meeting both economic and environmental challenges.