GAS QUALITY ADJUSTMENT


ADJUSTMENT OF GAS QUALITY

To ensure that the gas does not interfere with the integrity (corrode or damage) of the pipeline or other appliances and also meet gas quality regulations such as
      a.  Gas Safety (Management) Regulations, 1996
    b. European Association for the Streamlining of Energy Exchange – gas, (EASEE-gas)
For gas, that does not meet the specified gas quality regulation or specifications; I recommend any of the following measures should be accepted to assure the integrity of pipelines or other appliances.
(1) Blending
Gas quality adjustment within the network, known as gas mixing or blending. Gas blending is the process of mixing gases for a specific purpose where the composition of the resulting mixture is specified and controlled.
a.   Within networks not possible if risk of off-specification gas to customers
b.   At beach sub-terminal possible-availability/security of supply
(2) Gas treatment
a.   Derichment of high Wobbe index gas (ie. lowering the Wobbe index)
                             i.        Natural Gas Liquids (NGL) removal possibly with reforming
o   Sidestream reforming: catalytic conversion of sidestream into lower CV gas. Moderate complexity. previously used in Italy
                            ii.        Cryogenic distillation: removal of heavier hydrocarbons from LNG. Moderate complexity, previously used in Spain, needs LPG sales capability.
                           iii.        Ballasting with inert gas
o   Nitrogen (N2) injection: ballasting of high Wobbe index gas with nitrogen to reduce calorific value (CV). Large volumes of nitrogen (N2) are required. It is a simple technology, widespread use, and can be outsourced.
o   Most LNG too rich for the market. Ballasting with nitrogen brings within specification
b.   Enrichment of low Wobbe index gas
                             i.        LPG injection
                            ii.        Inerts removal
(3) Change of specification
(4) Curtailment or cessation of flows of gas with characteristics outside of Gas quality specification

Note:
Wobbe index/number widely regarded as the best single measure of the interchangeability of fuel gas

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