Introduction

Sulfuric acid is one of the world's most widely used chemicals and finds numerous applications in the fertilizer, chemicals, water, dye and iron and steel industries.

The principle method used for its manufacture - the Contact Process - typically produces acid of 98.5% w/w concentration or stronger in the form of oleums. However, many of the processes and applications utilizing sulfuric acid require weaker acid than this. As a result, dilution equipment is often necessary in order to meet the requirement for this weaker acid.

Process Description

The dilution chamber illustrated in figure 1 has the capability of diluting acid of any concentration to produce sulfuric acid of any desired concentration.

For example:

98% w/w H2SO4

30% H2SO4

20% oleum

98% H2SO4

Typically, the concentrated acid is fed down the inner of two concentric pipes while the dilution water is passed down the outer one. The acid and water mix at the outlet of these pipes and then slowly flow up through a packed bed - in order to ensure good mixing and the avoidance of local hot spots - and exit from the chamber via an overflow pipe.

During the mixing/dilution process, considerable heat can be liberated and it is normal practice for the hot dilute acid leaving the dilution chamber to be cooled. In some circumstances, the amount of heat liberated within the dilution chamber is sufficient to produce boiling of the acid and so, in order to avoid this, provision is made for the recirculation of a portion of the cooled dilute acid, thus ensuring the temperature of the acid leaving the chamber is below its boiling point.

Throughputs and sizes of the standard range of dilution chambers are shown in the table on the reverse side.

There are several distinct advantages to using glass dilution equipment:

• Product purity is guaranteed. The glass dilution equipment can be used in the production of high purity grades of sulfuric acid. For example, battery, reagent and electrolytic, product purity being dependent only on the purity of the acid and dilution water. For these grades, glass dilution equipment is often used in conjunction with a glass S0₃ absorber.
• The equipment is simple and easy to operate.
• The equipment is extremely versatile. Borosilicate glass is completely inert to all sulfuric acid concentrations and so can be used over wide concentration ranges.

This Process Profile supersedes all previous issues.

QVF Process Systems pursues a policy of continuous product improvement. We therefore reserve the right to alter any product or process as described and illustrated.