Electricity + Control July 2019

ENERGY MANAGEMENT + ENVIRONMENTAL ENGINEERING

Natural gas as an energy source for industry

Laetitia Jansen van Vuuren, Technologies Product Engineer, Energas Technologies

There is a natural gas pipeline network in most of the industrial areas in Gauteng, but why are so many of the large energy users still not making use of gas? Especially when there is a national and global drive is to reduce carbon emissions and move away from coal.

Take Note!

1. A big advantage of piped natural gas is its afford- ability, compared to liquid petroleum gas and elec- tricity. 2. Natural gas also has a much cleaner carbon foot- print compared to coal as a fuel for power generation. 1 2

I n the USA natural gas accounts for about 31% of the industrial sector’s total energy consumption and 26% of the electrical power sector’s energy consumption, whereas, in South Africa, less than 4% of total energy is sourced from gas. Costs and other advantages In South Africa, electricity from the grid used to be cheap and dependable, but times have changed. In today’s tough economic environment, industries cannot afford the downtime caused by power outages stopping production. Costs have also escalated and the rate per kWh is even higher when the demand and network charge is added to the overall consumption cost, in effect doubling the R/kWh charges. Let’s look at an example. If a medium-sized food manufacturing company uses 60 500 kWh over a month and the tariff is R1.26/kWh, the total consumed cost is R76 230. However, once the demand and network charge is added to the energy cost, the total bill amounts to R135 500.When these additional costs are factored in, the effective rate for power consumed is almost doubled to R2.24/kWh. The rate of R2.24/kWh is equivalent to R622.22/GJ, where a gigajoule (GJ) is assumed as a common energy unit. Looking at these figures, natural gas as an alternative energy source becomes much more attractive. A big advantage of piped natural gas is its affordability, compared to liquid petroleum gas (LPG) and electricity. It ranges between R150 and R320/GJ compared to LPG at R400 to R520/GJ (R20/kg to R26/kg) or electricity at R350 to R622/ GJ (R1.26 – R2.24/kWh). It also has the advantage

of relative price stability in that it is not prone to the constant price fluctuations seen in crude oil products. It has a much cleaner carbon footprint compared to coal as a fuel for power generation and, when compared to renewable energy sources, natural gas remains reliable even when the sun is not shining or the wind is not blowing. Another advantage of natural gas is the safety aspect: it is lighter than air and will evaporate into the atmosphere if a leak occurs, whereas LPG, which is heavier, is more likely to accumulate at ground level and ignite. Natural gas has the potential to replace electricity as a primary energy source for industrial users. Heating (hot water, air or steam) is often the highest energy requirement in processes and, if natural gas is used for such applications, it can reduce the power required significantly. The balance of power needed can then be supplied by a gas generator to ensure there are no power interruptions or associated production losses. Converting to natural gas With Eskom’s currently unreliable supply and the predicted load shedding reality, the conversion to gas will become a serious consideration for industries. Where the gas supply network is not close enough to Sasol’s natural gas pipeline, CNG (compressed natural gas) offers a good alternative – if the facility is within a 200 km radius of a CNG supply station or makes use of a virtual gas network. Conversion stations, trailers and equipment required can be leased or purchased from the CNG supplier.

A filter and metering skid as installed for an industrial gas user connected to the gas supply pipeline.

18 Electricity + Control

JULY 2019