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Sulphuric Acid on the WebTM Technical Manual DKL Engineering, Inc.

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Sulphuric Acid on the Web

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DKL Engineering, Inc.

Handbook of Sulphuric Acid Manufacturing
Order Form
Preface
Contents
Feedback

Sulphuric Acid Decolourization
Order Form
Preface
Table of Contents

Process Engineering Data Sheets - PEDS
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Table of Contents

Introduction

Bibliography of Sulphuric Acid Technology
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Preface
Contents

Sulphuric Acid Plant Specifications
 

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Properties - Sulphuric Acid - Colour
December 20, 2001

Introduction
Measurement
Treatment
Associated Links

 


Introduction

Pure sulphuric acid is colourless or "water white". However, the presence of small amounts of organic material, will discolour the acid. These may be present in the incoming gas and are not totally removed in the gas cleaning section of the plant.

The degree of discolourization varies from a light brown to black depending on the quantity of organic matter.  This colour would make an otherwise good quality acid sell at a discounted price or not at all.

Measurement

An arbitrary standard scale is used as a means for matching of colour intensity.  A colour of 5 units means that the intensity of the colour of this sample is equal to the intensity of the colour of a sample of sulphuric acid 50% in water, containing 5 milligrams of platinum (as potassium chloroplatinate) per liter.

Treatment

Blending of acid is of limited effectiveness in improving the colour of the acid due to the large amount of colourless acid required to achieve an acceptable product quality.

Hydrogen peroxide (H2O2) is effective in removing colour from the acid and the rate at which hydrogen peroxide clears up the acid varies with the acid temperature, the quantity of SO2 dissolved in the acid and the strength of H2O2.

Bench scale test should be performed to determine the amount of hydrogen peroxide to be added, the temperature and residence required to produce a product acid of acceptable quality.  

Based on the results of the testing, bleaching system can be designed based on conservative design parameters.

One acid producer found that to reduce the product acid colour to acceptable levels required between 0.5 to 1.4 kg of 50% H2O2 per metric tonne of 98% H2SO4 at an operating temperature of 80ºC.  The residence time required for the reaction to take place was 2 hours.  A conservative design of a bleaching system based on these test results would be for double the dosing rate and a residence time of 4 to 5 hours.