Typical sources of spent acids are:
- Nitration processes such as production of MNT, DNT, TNT, NB, NCB, DNCB, NGL, DEGN, EGDN, NC, Picric Acid, etc.
- Chemical applications as production of MEK and sulfonation
- Production of certain dyes and pigment
- Chlorine drying
- Gas purification
- Organic synthesis such as ether production
PLINKE has experience and reference plants in these applications.
Pre-Concentration is used when the Sulfuric Acid stream is fairly diluted (20-60 wt%), to bring concentration up to 70-75 wt%. Pre-Concentration is either processed at atmospheric pressure or at vacuum conditions. Different evaporator types can be used. For larger water evaporation capacities, multistep evaporator systems are often used for energy saving purposes. The vapors of one step are used as heating agent for another process step.
This process is used to concentrate Sulfuric Acid from 70 wt% up to 85 wt%. The medium concentration of Sulfuric Acid is mainly operated at vacuum of about 80–150 mbar. At these conditions medium pressure steam can be used for heating and normal cooling water is used for condensation. In cases where higher temperatures are required, as for example for like decomposition of organic contaminants, atmospheric evaporation at operating temperature up to 250°C is possible.
The PLINKE Gmbh's SAVACO® Process is used to produce high concentration Sulfuric Acid, up to 98 wt%. PLINKE developed a special heat exchanger operated with thermal oil as heating media at temperatures of up to 250°C. At these conditions, the process runs very economically at a reasonable vacuum level and very pure Sulfuric Acid is produced. If such high temperatures or concentrations are not required, other vacuum processes with steam heated heat exchangers are available.