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TABLE 1 GAS COMPOSITIONS AND PHYSICAL PROPERTIES OF TG AND LFG FIGURE 2 FLAMMABILITY PLOT OF SNG

FIGURE 3 MCP-WI CHART OF HONG KONG’S GAS APPLIANCES FIGURE 4 MCP-WI CHART OF HONG KONG’S GAS APPLIANCES (WITH SNG+TG)

FIGURE 5 RESULTS OF THE GAS APPLIANCE TEST FIGURE 7 DURING CONSTRUCTION OF THE PROCESSING FACILITY

is heavier than air. This means that, in Figure 3 was provided by HKCG to reformation) in order to inject it into the
during a gas leak, it will accumulate on predict whether the gas can be burnt mix. Needing a solution, we decided to
the ground instead of dispersing. If the properly and maps the maximum mix it with TG.
concentration of accumulated flammable combustion potential (MCP) against the
gases reaches the explosion limit, there Wobbe index (WI). Maximum mixing ratio of SNG and TG
is a risk of fire. In order to minimise this The WI and MCP of SNG are 17.82MJ/ As the production rate of SNG is small
risk, SG needs to remain below 0.95. Nm³ and 18.87cm/s respectively, compared to that of TG, it was feasible
Carbon dioxide is the heaviest which is far from the desired zone and to mix SNG into TG without causing
component in LFG with a SG of 1.52 (at probably will result in flame lift. the properties of the gas to fall outside
15°C). By reducing the CO₂ content, we SNG is not interchangeable with town the zone. The results can be seen in
can effectively control the SG of LFG. gas. One of the reasons for this is that Figure 4.
town gas consists of a large amount of Theoretically, the maximum ratio
Interchangeability of SNG and TG hydrogen gas (around 50 per cent) while of town gas to SNG can reach 13 per
As the SNG is designed to be used as a SNG has none. cent without causing any abnormal
fuel, it is necessary to check whether Due to LFG’s low levels of utilisation, burning. However, for safety reasons,
it can be burnt properly in the average it is not worth producing hydrogen the maximum ratio of town gas to SNG
Hong Kong gas appliance. The chart gas (which requires steam methane was kept to eight per cent.

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