Hatch alumina tube digestion technology reduces costs and increases production

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.

Canada's Hatch, a six-decade old business boasting technical experience in the mining, energy, and infrastructure sectors, says the use of innovative high-capacity, single-stream tube digestion technology can reduce refinery complexity and improve energy efficiency sigificantly.

Hatch explains, 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, Hatch has come up with its patented tube digestion technology that can reduce a facility’s energy consumption by up to 15 per cent and cut greenfield capital costs by up to 7 per cent.

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.
• Jacketed pipe heating can be fabricated and constructed from readily available standard piping materials.
• The simplified design eliminates complex interconnecting pipework and manifolds, reducing the risk of loss in production and operating capacity.
• The integrated flash-cooling design allows the system to balance process conditions and prevent excessive two-phase flows.

This is a robust system with lower operation and maintenance requirements.