This document provides recommendations for safely mixing concentrated sulfuric acid in large diameter pipelines. It notes that prediluting the acid in a two-stage process has advantages over direct mixing. Specifically, it recommends first diluting the concentrated acid (93-98%) to a safer 10% or 5% concentration using an inexpensive "premixer." This reduces corrosion risks and allows for less costly mixer materials. It also improves acid distribution across the pipe diameter when injected. Direct mixing of low volumes of concentrated acid can result in uneven distribution and risks of high temperatures damaging piping.

1. Recommendation for Mixing
Concentrated Acid in Large
Diameter Pipelines -- Predilution
Application Data - Bulletin 317
Abstract: coming in contact with mixer
Mixing concentrated sulfuric acid (93%- components that are not fully compatible
98%) to water or a wastewater pipeline with the acid.
is a common and cost effective method
for managing the pH of the stream.
When injecting sulfuric acid in a large
diameter pipe, Komax has found that
prediluting and mixing this acid in two
stages provides many advantages over
directly mixing the concentrated acid in
the pipe.
Background:
Concentrated Sulfuric Acid has a Solution: Pre-diluting concentrated
specific gravity of 1.8 so it tends to Sulfuric Acid
migrate to the bottom of the mixer By prediluting the concentrated acid
housing particularly at lower fluid through the use of an inexpensive
velocities (i.e., less than 2 feet per “premixer” down to a safer 10% or 5%
second) which compounds the problem. concentration, the mixer can be
Sulfuric acid has a viscosity similar to constructed of less costly material, and
honey, and requires vigorous mixing to the life of the mixer will be extended for
fully dissolve the acid in water. years.
Additionally, there is a strong heat An additional advantage is the larger
producing exothermic reaction that volume of diluted acid solution will
occurs during this dilution process. If provide equal flow rates through each
water and concentrated acid are allowed discharge orifice of the acid injector
to stagnate, high temperatures (over 350 resulting in improved acid distribution.
ºF) will occur, which can result in When injecting one to two gallons per
damage to the piping and injection hour of concentrated Sulfuric Acid the
system. Concentrated acid is not resultant flow exiting the injector is only
particularly corrosive. However, as the 2 to 4 ounces per minute. At this flow
concentration decreases to 30%-50%, rate all of the acid will exit the first
the acid becomes very reactive and will injector orifice precluding uniform
damage mixers that are constructed of dispersion of acid across the mixer
Ductile Iron, Carbon Steel, or 316 housing diameter. When the flow is
Stainless Steel Static Mixer. The key to a measured in gallons per minute, even
long mixer life is to eliminate acid in the distribution across the diameter of the
30-50% strength concentration from mixer is easy to maintain.
www.komax.com
04/29/06

2. www.komax.com
04/29/06