Selected Mitigation Measures

Emissions from Operation of Fuel-Consuming Vehicles and Equipment Construction

The overall potential for significant adverse impacts from construction-generated dust is considered to be unlikely due to the following reasons:

Project construction activities will mostly involve native soils as per the Soil Baseline Assessment conducted at the project site;

Dust and fugitive emissions are controlled through the application of the following measures:

 Regular inspection and dust suppression (misting) of stockpiles where necessary (including wind shielding, storage away from site boundaries, and restricted height of stockpiles);

 Provisions for wheel washing and wet suppression during loading of wagons / vehicles in instances of potential high dust environments;

 Covering vehicles carrying dry spoils and other wastes;

 Restricting vehicle speeds on access roads and other unpaved areas of the site. A maximum speed of 20 km per hour will be strictly enforced over all unimproved surfaces within the construction zones;

 Equipment exhausts will be directed vertically upwards where possible and stationery equipment will be sited as far from sensitive receptors and inhabited buildings as is feasible;

 Wherever possible plant and equipment engines will not operate for long periods if the equipment is not in use. When feasible, electrically powered equipment will be used instead of petrol or diesel, including welding machines, pressure washers, air compressors, etc.;

 Unpaved roads will be routinely misted with water during dry periods and according to weather conditions; and

 No onsite burning or incineration of waste materials will be allowed within the construction zones.

Operations

The steam boiler and the flaking unit will include low NOx burners to effectively reduce NOx emissions to meet EAD permissible limit of 55 mg/N^m3. The SOx emissions will be below the MoE’s permissible limit of 500 mg/N^m3.

Entire chlorine gas from the electrolysis section will be will be sent to the main chlorine

scrubber to produce sodium hypochlorite. The chlorine absorption unit will be designed with a treatment capacity sufficient to absorb the full cell-room production in the event of emergencies.

The chlorine absorption unit will lower the chlorine content in the emitted gas during operation to less than 1.72 ppmv (5 mg/N^m3) in the worst-case scenario compared to 20 ppmv of USEPA’s permissible limits - Maximum Achievable Control Technology (MACT).

In addition, the emitted HCl vapour will be less than 6.70 ppmv (10 mg/N^m3) in the worst-case scenario compared to 12 ppmv of USEPA’s permissible limits (MACT).

All of the hydrogen gas produced during electrolysis of salt in the production will be used onsite as chemical feedstock for production of HCl in the HCl synthesis unit. The hydrogen gas will be safely handled in the production of HCl by providing an emergency vent in the process line. The entire vent system will be designed to include a flame sensor and a steam and nitrogen purging mechanisms. In addition, the process safety relief valves will be connected to vent system, and during process upset, these safety relief valves will be activated for venting the hydrogen gas to avoid unsafe conditions. The Chlor-Alkali Plant will also install hydrogen gas holder in the system to minimize the process upsets and to reduce venting.

During loading of caustic and NaOCl, fugitive emissions are not anticipated. However, fugitive emissions are likely during HCl loading. A small scrubbing unit with an efficiency of 95% will be provided to control these fugitive emissions during HCl loading.

Expected HCl concentration at the loading area will be less than 0.033ppm (0.05 mg/m³) and the HCl concentration in the scrubber outlet during loading operation will be approximately 0.17 ppm (0.25 mg/m³).

In summary, the air emissions under normal operations for the Al Ghaith Chlor-Alkali project are not expected to have any significant impact.

Decommissioning

Same as for the Construction phase above.

Emissions of Greenhouse Gases

Construction, Operation and Decommissioning

The EPC Site Environmental Manager and/or EPC Maintenance Manager will encourage implementation of good construction practices with respect to handling GHG containing materials such as refrigerants, as mentioned in Section Error: Reference source not found. This will be to ensure that fugitive emissions from improperly closed storage containers are prevented.

This would typically involve ensuring that safety valves on refrigerant gas containing cylinders are only opened when they are in use and otherwise kept normally shut to reduce the potential for fugitive emissions.

However, the best form of mitigation would be to utilize alternate refrigerant gas that does not have a GHG impact.

Emissions from Accidental Events Construction

The EPC Site Environmental Manager will ensure that appropriate internal wiring is utilised in construction machinery and it is run according to the manufacturer’s specifications in order to reduce the potential for a fire occurring due to a short-circuit and therefore the resulting combustion emissions. Additionally, it will also be ensured that the machinery is regularly inspected and maintained in order to reduce the potential for non-design performance of the equipment and therefore resulting higher direct exhaust emissions.

The EPC Site Environmental Manager will also ensure that flammable chemicals on site are temporarily stored in accordance with the manufacturer’s and MSDS requirements, in order to reduce the potential for an accidental fire occurring.

As a further fire preventative measure, the EPC Site Environmental Manager will also enforce an indoor no-smoking policy within the site buildings (i.e. offices) to reduce the potential for human-induced fires occurring. Relevant employees will also be trained in the measures to be followed in case a fire breaks out so that it can be controlled soon after break-out and the risk to employees’ health reduced.

The EPC Site Environmental Manager will also prepare a project emergency response strategy/plan addressing appropriate emergency procedures to be followed in case of a fire occurring during construction works. Again, this will ensure that a fire can be controlled soon after it breaks out and the risk of deterioration of ambient air quality and employees’ health is reduced.

Operation

The potential for accidental release of chlorine gas poses a risk in chlor-alkali plants, and that can be addressed on several levels requiring mitigation/control measures and emergency response programs.

A quantitative risk assessment (QRA) will be performed at the Al Ghaith plant subsequent to commissioning of the plant to further assess the accidental chlorine release hazards.

The caustic scrubber, with an overall operating efficiency of at least 95%, will be the primary chlorine gas control device. As discussed earlier regarding the control measures, entire chlorine gas produced will be sent to the main chlorine gas header in the HCl synthesis unit. Moreover, chlorine-containing waste gas streams from the HCl synthesis unit will be diverted to the chlorine absorption unit (hypo unit) where the gas will be absorbed by diluted caustic in a double-staged scrubber to produce sodium hypochlorite.

The chlorine absorption unit will be designed with a treatment capacity sufficient to

Excess chlorine vented to the scrubber can deplete the active scrubbing material and cause over-chlorination of the scrubber. This will result in release of toxic chlorine gas.

Therefore, active safeguards will be incorporated within scrubbing mechanism to avoid over-chlorination.

Following active safeguards will be included in the scrubbers to prevent over-chlorination:

 Emergency and automatic shut-off of chlorine upon high Oxidation-Reduction Potential (ORP) alarms. ORP will track the concentration of caustic in the scrubber liquid;

 Automatic or remote caustic injection to interrupt decomposition reaction; and

 Use of contactors in the scrubbers to maintain slight vacuum on the chlorine vent lines to reduce leaks to atmosphere.

In addition, procedural safeguards such as operating procedures and training will be required as good management practices. Moreover, published guidance on scrubber should provide specific information on the composition, quantity and duration of emission expected during over-chlorination incidents.

The emergency response measures to be undertaken in an event of accidental chlorine gas release are included in the Plant Disaster Management Plan (DMP). As discussed in the plan, the initial isolation distance will extend equally in all directions from the release, even upwind. When the gas is released at the ground level, the gas may travel upwind due to natural turbulence created by the wind. Also, studies have shown, under windless, night time conditions, the toxic dense gas spread out in all directions from the source near the ground. As expected, the bulk of toxic gas or vapour plume will be carried downwind.

To assure that the plans are well organized for any contingency, the plant has adequate resources to plan for emergency response.

Decommissioning

Same as for Construction phase.

5.1.3.3. Mitigation Measures to Address Cumulative Impacts