Abstract

During oil and gas operation, water is used for many operation processes, which make water contain various contaminants depending on the sources and processes. Sour water strippers (SWS) are critical units to remove ammonia (NH3) and hydrogen sulfide (H2S) from sour water streams to condition the waters for the discharge or reuse. Different streams from various sources may induce different scale issues to cause operation productivity reduction and even equipment failure. The most common scales in sour water strippers are calcite, iron sulfite, silicates, etc. depending on the water chemistry of source streams.

This paper presents case histories of scale issues and treatment of sour water strippers with various source waters. For each case history, the specific inorganic scale problems and treatment strategies are discussed. Based on the lab testing and field application results, scale inhibitor treatment or even cleaning-up program are evaluated.

This paper provides valuable information on potential scale problems and treatment for sour water strippers with various water sources, and gives references or guideline for similar scale treatment.

Introduction

Sour water stripping is used to remove ammonia (NH3) and hydrogen sulfide (H2S) from sour water streams coming from many operation units to condition it for discharge or reuse.1-3 In a complex refinery, most of the sour water comes from distillation, fluid catalytic cracking, catalytic reforming, coker and acid gas removal units, with many other operations contributing to the balance. The different streams are usually collected in a surge tank for centralized processing via a heat exchanger and a single stripper column, or two in series.

A combination of pH control and heat, from direct injection steam or reboiler drives off the ammonia and hydrogen sulfide. The presence of solids and hydrocarbons (‘oils’) are major contaminants in the units of heat exchanger, stripper column, and reboiler fouling. These fouling will cause the loss of SWS capacity and may bottleneck refinery production rates, drive the need for unscheduled SWS shutdowns and cleanouts leading to additional production losses, high maintenance costs and increased worker safety issues from exposure to the highly volatile H2S in the sour water system.

Keywords:
paraffin remediation, wax inhibition, corrosion inhibition, hydrate remediation, hydrate inhibition, asphaltene remediation, h2s management, downstream oil & gas, wax remediation, oilfield chemistry
Subjects:
Production Chemistry, Metallurgy and Biology, Environment, Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene, Corrosion inhibition and management (including H2S and CO2)
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