Technology - SUPRACID^®
March 1, 2003

Introduction

The SUPRACID^® process is a combination of the SULFACID^® process and an upstream acid concentrator.  The combined process can be used when the incoming gas is above 100°C and the water content is well below its saturation point.

The basic principle is to contact the gas with a stream of acid causing water to evaporate from acid thereby concentrating the acid in the process.  This concentration is achieved in a one or two stage concentrator comprising acid sprays and multi-venturi nozzle trays.

Hot gas entering the bottom of the concentrator is contacted by a circulating stream of 60 to 70% sulphuric acid (acid concentrations will vary with the application).   Weaker acid (20 to 30% H₂SO₄) from the second stage concentrator is fed to the first stage.  The hot gas is cooled by evaporation of water into the gas while the weaker acid is effectively concentrated from 20-30% to 60-70%.  The gas then passes into the second stage of the concentrator which is located directly above the first stage.

In the second stage, the gas is cooled further, again by evaporation of the water into the gas stream.  Acid at a concentration of 20 to 30% sulphuric acid is circulated to cool the gas further by evaporation of water from the acid.  In the second stage, weaker acid (approximately 14% H₂SO₄) from the downstream SULFACID® reactor is mixed with the circulating acid.  The overall effect is top cool the gas and concentrate acid from 14% to 20-30% sulphuric acid.

The cooled gas leaves the concentrator and enters the SULFACID® reactor where the sulphur dioxide is converted to sulphuric acid by wet catalysis in the presence of oxygen, water and carbon-bearing catalyst located in the fixed bed reactor.

Product acid is drawn from the first stage of the concentrator on level control.   The acid is cooled and filtered (if required) before delivery to storage.