Sulfuric Acid Systems
Sulfuric acid has an array of uses throughout the chemical processing, steel, refining, and battery industries among a variety of other.
A properly designed dilution system, with attention to materials of construction and control is critical to the obtaining the desired end result. The concentrated acid is introduced to the feed water in a mixing tee. Substantial heat is generated in the process, therefore the ratios and rate of dilution must be carefully controlled and monitored.
CG Thermal is your partner in process design. We provide skid mounted sulfuric acid dilution systems custom designed for your process requirements. If you are not looking for a skid mounted system, we can provide a menu of engineering services to sync with your in house capabilities, or just the components per your specifications.
Although our Impervite graphite is an option, we generally recommend our Umax Advanced Ceramic heat exchangers for most sulfuric acid dilution systems. The Umax tube will not corrode at any concentration. Since it is 50% harder than tungsten carbide, the Umax tube can be used at higher velocities without concern of erosion. The ability to operate at higher velocities coupled with it’s high thermal conductivity, make it the most thermally efficient choice. The tubesheet design allows for easy access to all tubes for cleaning and in-house repair.
As an optional upgrade, we will include a recirculating loop to ensure thorough mixing and reduce the temperature seen by system components. If your plant would benefit from redundancy, we will design with (2) heat exchangers in series.
The system will be supplied with a batch controller receiving temperature, flow, pressure and concentration inputs and generating outputs to control valves and pumps to maintain the desired outlet temperature and concentration. An HDMI can either be skid or remotely mounted.
We can provide a proposal with as little information as the batch size (tons/day or lbs/hr), inlet concentration and the desired diluted concentration. Each system can be customized to meet your layout, material preferences, and specific needs.
Regeneration of the spent Sulfuric Acid is equally important in many cases for economic and environmental reasons.
Commonly supplied at 93% concentration but diluted as a reactant or for its end purpose, its corrosivity and material compatibility will vary greatly with concentration and temperature. Although Impervite graphite is a suitable choice in many instances, the Umax Advanced Ceramic heat exchanger is becoming the design of choice.
There are two choices for handling the spent acid – either neutralize the spent acid and dispose of it or, regenerate it to remove the impurities so the acid can be reused. With the current high demand, sulfuric acid regeneration is quickly becoming the preferred method for both economic and environmental reasons.
Common Processes that Require the Regeneration of Sulfuric Acid:
- The alkylation process, H2SO4 catalyst is used to react isobutane with a light olefin to produce the alkylate component used in high octane gasoline.
- The viscose-rayon process uses H2SO4 spin baths in the production of rayon fibers and cellulose films.
- Because of its affinity for water, a common use of H2SO4 is as a drying agent.
Material and Design Considerations:
For heat transfer applications involving sulfuric acid, materials of construction vary depending on the temperature, concentration, impurities, required service life and cost effectiveness. Common cost-effective materials include SiC ceramic, graphite, and polyphenylene sulfide (PPS-GR).
Because of its resistance to corrosion in H2SO4 at all concentrations and most temperatures incurred in regeneration processes, PTFE lined steel is a commonly used for the construction of towers, separation drums, and other vessels utilized in regeneration, especially in positive pressure systems. PTFE can be bonded for use under vacuum using specialized adhesives. However, most adhesives are rated for temperatures less than that of the PTFE lining.
Several of sulfuric acid’s thermal properties require particular attention when considering heat and mass transfer systems involved in regeneration.
The viscosity of sulfuric acid varies significantly with temperature and concentration. With increased concentration and a decrease in temperature, viscosity will rapidly increase.
Vacuum conditions are frequently required when reconcentrating sulfuric acid because it has a low vapor pressure. At lower concentrations, the vapor pressure is mostly governed by the water. However, at higher concentrations, the degree of vacuum will have a more significant effect on the process temperature, which will in turn affect the energy input for the separation. This could result in higher process temperatures, reduced efficiency, and limited material options.
Electrical conductivity varies with concentration as a parabolic function, resulting in two concentrations described by the same value. This condition needs to be considered in choosing measurement and control devices. Several approaches can be taken depending on the precision required.
Learn more by downloading this white paper, Important Considerations in the Regeneration of Sulfuric Acid, or watch CG Thermal’s presentation from CRU-Sulphur + Sulphuric Acid 2021.
Turnkey System Includes:
- Custom design to achieve your specified criteria ( dilution rate, concentration and temperature)
- A quoted option includes a glycol chiller to use as cooling water. This will reduce operating costs significantly and reduce size of HX needed.
- Conductivity sensors are located after the heat exchanger with flow control valves on acid feed will control product acid concentration.
- Flow sensors on the acid feed will achieve consistent product and production rate
- Level sensors and switches can be provided on tanks to prevent overfilling or running pumps dry
- Flow sensor and switches are used on the cooling water to ensure safe and sufficient flow.
- Temperature sensors on acid streams will ensure safe temperatures.
- Instrument display, PID controllers, and pump controls are located for easy access.
Please provide us with your requirements. We look forward to using our expertise to assist you.