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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
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Preface
Contents
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Sulphuric Acid Decolourization
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Process Engineering Data Sheets - PEDS
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Introduction

Bibliography of Sulphuric Acid Technology
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Preface
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Sulphuric Acid Plant Specifications
 

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Maintenance and Inspection - Plate Heat Exchanger
September 12, 2003

Introduction
Cleaning
Opening the Unit
Closing the Unit
Re-Gasketing
Associated Links

Strong Acid Coolers

Weak Acid Coolers

Introduction

Plate heat exchangers are found in both the gas cleaning and strong acid section of an acid plant.  The maintenance and care required for either of the units is identical.

Cleaning

Fouling of the plate exchange can occur on both the cooling water and sulphuric acid sides of the exchanger although fouling on the cooling water side is most common.  Cleaning-In-Place (CIP) allows the exchanger to be cleaned without the need to open and dismantle the entire unit which can be very time consuming. 

Packaged CIP system may be available from the vendor but can be easily made up if none is available.    A typical CIP will consist of a reservoir for holding the cleaning solution or chemical, a circulating pump, valves, piping and flexible hose.  The vendors recommendations for cleaning the unit should be followed.

If the deposits and buildup in the exchanger are severe, the unit may need to be dismantled for manual cleaning of each plate.  In some cases the plates can be left hanging from the carrying bar while each plates is scrubbed with a soft brush and running water.  The plates are then rinsed with a high pressure hose.

If a cleaning solution is required to clean the plates, the plates should be removed from the frame and scrubbed with a soft brush and cleaning solution and then rinsed with water.

Care should be taken not to damage the gaskets.

Cleaning Agents

Deposit Cleaning Agent Concentration
(Maximum)
Temperature
(Maximum)
Calcium Carbonate Nitric Acid 4 wt% 60°C
Calcium Sulphate Sulfamic Acid 4 wt% 60°C
Silicates – Silt Citric Acid 4 wt% 60°C
Silicates – Alumina Phosphoric Acid 4 wt% 60°C
Silicates – Diatomic Organisms Complexing Agents (EDTA, NTA)Sodium Polyphophates 4 wt% 80°C
Bacteria Growth/Slime Sodium Hydroxide 4 wt% 80°C

Hydrochloric acid should never be used on stainless steel plates.  As well, water used for the preparation of cleaning solutions should contain no more than 300 ppm chlorides.

The following chemicals are not recommended for use: Ketones, Esters, Halogenated Hydrocarbons and Aromatics.

Opening the Unit

Dismantling a plate heat exchanger for inspection, cleaning or maintenance should be done according to the manufacturers instructions.  Most manufacturers recommend the following:

Closing the Unit

Reassembling the plate heat exchanger should be done according to the manufacturuer’s instructions.  The following are general guidelines common to most manufacturers:

Re-Gasketing

Re-gasketing of the plate pack may be required if leaks occur in the unit.  Most manufacturers offer re-gasketing service but this requires that the entire plate pack be sent back to the factory.  On-site re-gasketing can be done if time or costs are a factor.

By far the easiest type of gasket to replace are the clip-on type gaskets.  The old gasket is simply removed, the sealing service cleaned and the new gasket installed.

Glue on gaskets are more difficult to replace.  Gluing and replacement procedures will be provided by the manufacturer if this method if required.