Challenges
Alumina producers face ongoing challenges to reduce costs and increase production. Today, the investment needed for a modern greenfield refinery is typically in the range of several billion dollars. But to gain economies of scale, larger, more complex refineries are constructed.
Key considerations are to minimize energy and raw material consumption; minimize heater cleaning and maintenance needs in a sustained, high-temperature environment; and reduce overall environmental impact.
During operational upsets, high transient pressures through a tube digestion unit can potentially expose plant, equipment, and personnel to operational safety risks.
Solutions
The use of innovative high-capacity, single-stream tube digestion technology reduces refinery complexity and improves energy efficiency.
Tube digestion replaces the conventional shell-and-tube heat exchangers with jacketed pipe heaters. And, for some bauxites, it can also replace conventional digester vessels with pipe reactors. This simplifies the digestion plant and allows a single-stream flow sheet to be employed.
A semi-automatic valve design avoids heat stress and dehydration while providing operational security.
With technology partner Outotec, our patented tube digestion technology is a high-capacity solution that can reduce a facility’s energy consumption by up to 15% and cut greenfield capital costs by up to 7%.
Integrated tube digestion and evaporation solutions use single-stream heating in jacketed pipe technology. This allows for the efficient use of the heat, which translates into high thermal efficiency and minimal maintenance.
Benefits
Energy efficiency is improved over conventional shell-and-tube heat exchangers or autoclaves.
Jacketed pipe heating can be fabricated and constructed from readily available standard piping materials, allowing greater ease of chemical and mechanical cleaning.
The simplified design eliminates complex interconnecting pipework and manifolds, reducing the risk of loss in production and operating capacity.
This is a robust system with lower operation and maintenance requirements, which in turn reduces capital, maintenance, and operating costs over the life of the system.
The integrated flash-cooling design allows the system to balance process conditions and prevent excessive two-phase flows, reducing flash tank scaling and significantly improving vapor quality.