Date of Award

2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr Samir Abueishah

Second Advisor

Dr.Naif A Darwish

Third Advisor

Dr.Mohamed Younes

Abstract

The processing of sour gases within Abu Dhabi Gas Liquefaction Company (ADGAS) LNG Trains located in Das Island involves sulfur dioxide (SO2) emissions that mainly result from fuel gas usage to produce steam and electricity, and incomplete recovery of sulfur from acid gases. ADGAS SO2 emissions affect the ambient air quality in Das Island, and this has the potential to affect the health of the residents of the island. The aim of this work is to explore the feasible technologies to minimize SO2 emissions from ADGAS, and study the impact of such on the ambient air quality of Das Island.

To minimize SO2 emission, this work follows an approach at which most of the H2S in the fuel gas will be directed to the Sulfur Recovery Units (SRU), and will be converted to sulfur product. Unconverted H2S will be routed to the SRU incinerator where it will be oxidized to SO2 which will be directed to the Flue Gas Desulfurization (FGD) units where it will be scrubbed by desulfurization solution and converted into harmless products that will be disposed safely. To achieve this, this work proposes two SO2 emissions minimization schemes; fuel gas sweetening scheme and flue gas desulfurization scheme. The fuel gas sweetening scheme involves revamping Trains 1 and 2 Utility Gas Absorbers (UGAs) to produce a sweeter fuel gas. This will be achieved through enhancing its sweetening efficiency by revamping its internals through upgrading its current packing to a higher efficiency packing that have the characteristics of an improved sweetening efficiency. The flue gas desulfurization involves installation of a Seawater FGD Units downstream of the SRUs incinerators. In these units, the SO2 in the flue gas will be scrubbed by the plant spent seawater in a dedicated packed bed absorber where SO2 in the flue gas will be absorbed into the sweater and converted to sulfate ions which are a natural constituent of seawater. The SO2 ground level concentration (GLC) will be predicted for the current and modified conditions by BREEZE AERMOD Pro software.

Implementation of the SO2 minimization schemes result in reducing the total SO2 emissions by 77% from 27,532 to 6364 tons/yr. Fuel gas sweetening scheme results in reducing the H2S content in fuel gas by 94% from 1200 ppm to 72 ppm; this results in decreasing the total SO2 emissions due to fuel gas usage by 98% from 10,092 to 168 tons/yr. Flue gas desulfurization scheme results in decreasing the SO2 emissions due to incomplete sulfur recovery in ADGAS Sulfur Recovery Plants by 99.5% from 1 1,299 to 57 tons/yr. These proposed schemes will result in minimizing the SO2 emissions due to fuel gas usage and incomplete sulfur recovery.

BREEZE AERMOD results under current conditions showed the followings:

  • All locations in Das Island do not comply with the 1-hr SO2 GLC UAE-Federal Environmental Agency (UAE-FEA) standards (i.e., 350 µg/m3) most of Das Island area does not comply with the 24-hr UAE-FEA standards (i.e., 150 µg/m3) and most of Das Island area complies with the 1-yr UAE-FEA standards (i.e., 60 µg/m3).
  • The maximum 1-hr, 24-hr and 1-yr SO2 1evels are 1869,507 and 74 µg/m3, respectively.
  • The locations of the maximum SO2 level are more of residential areas and this represent a threat to the health of Das Island residents.

BREEZE AERMOD results under proposed conditions showed the followings:

  • Only north of Das Island exceeds the UAE-FEA 1-hr limits. However, the residential areas comply with the standards.
  • The implementation of the proposed SO2 minimization schemes is expected to have a greater area of Das Island to be within the 1-hr, 24-hr and 1-yr standards of UAE-FEA.
  • The maximum 1-hr, 24-hr and 1-yr SO2 levels under the proposed conditions were found to be 636.2, 157.6 and 37.2 µg/m3, respectively.
  • The maximum highest SO2 GLC will be shifted to the North-East part of Das Island (i.e., industrial area) rather than the residential area.

The implementation of the SO2 minimization schemes will result in all ADGAS SO2 emission sources to comply with the UAE-FEA limits (500 mg/Nm3) The ADGAS SO2 emission sources will have the potential to challenge any proposed stringent UAE-FEA limits with high level of confidence as the emission rates at the modified conditions are reduced to about 5% of the standard (i.e., 25 mg/Nm3).

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