Should We Try Liquid Fuel or Embrace Darkness?
Abdul Wadud ponders the country's gas crisis and its implications for power generation
A H Arif/Driknews
Of late there has been a huge hue and cry about the scarcity of gas in the country. According to Petrobangla, the present demand for gas in the country is about 2,000 million cubic feet per day (mmcfd) as against a supply of about 1,800 mmcfd, thus leaving a gap of 200 million.
As a result, other than the adverse impact on industry and other sectors, power generation has been affected very adversely. Many power plants have been shut down. The gap between demand and supply is increasing every day without any substantial planning effort to reduce it.
We have been left to the whims of nature. The policy makers are expressing their helplessness to avoid this disaster that is in the offing due to the paucity of gas. Investment has slowed down.
There has been panic with the investors, businessmen, industrialists, and common users as to what is going to happen in the face of shortfall in the supply of gas, which is increasing with the passage of time.
It is a general feeling among stakeholders that Petrobangla is responsible for this state of affairs in the sector because they are basically entrusted with the responsibility for exploration, production, and transmission and distribution of gas among the consumers.
Petrobangla has not diligently and constantly performed their responsibility. However, it is very unkind to blame Petrobangla alone for this situation in the country. It is to be borne in mind that there has been unprecedented growth in the demand for natural gas in the country over the past ten years at a rate which was far beyond the conception of experts working in the field.
In 2000, the overall demand for gas in the country was about 1,200 million cubic feet per day. It is interesting to note that the demand for gas over the last fifty years (the first gas supply to CHATAK Cement Plant in 1955) has grown on an average equal to about 250 million cubic feet per day for every ten years whereas even in the last 8 years alone since 2000 the gas demand has grown by 800 million. Even if we consider demand data of the last 20 years it would be found that growth in gas demand over the 10 years has surpassed all records.
This high growth rate remained unnoticed by the policy-makers. The record shows that there has been development in the industrial sector particularly with SMEs. The GDP contribution by industry during the nineties was 15 percent whereas in 2008 the GDP contribution by industry is 32 percent. This growth in industrialisation, particularly with SMEs, has put a tremendous demand on the energy sector, particularly the gas sector, which is responsible for the high demand of gas.
The industrialisation pressure has pushed the demand of gas to an unprecedented level for which Petrobangla was obviously not prepared at all. Even the present infrastructure of transmission and distribution, not to speak of production capacity, is not prepared to meet the present requirement of the country.
The energy sector in the country heavily depends on natural gas. Currently, natural gas accounts for about 72% of the commercial energy consumption compared to 35% in 1980. The history of gas industry dates back to the early years of the 20th century when the first exploration well was drilled in 1950. The exploration activity in oil and gas sector in the country picked up pace in the 1950s. The first commercial gas discovery was made in 1955. Since then exploration efforts resulted in the discovery of 22 gas fields of which 16 are currently in production, 4 are in non-producing mode, and 2 are suspended as practically depleted. The 22 gas fields of Bangladesh have a total estimated proven plus probable reserves of 13.2 trillion cubic feet and possible recoverable reserve of 7.7 trillion cubic feet as of June 2008.
The major driving force behind the growth of gas consumption is the power plants both in public and private including IPP and captive generation, totaling about 56% of total generation.
Due to the incorrect assumption that Bangladesh is floating on gas, most of the power plants have been built on gas without thinking of any alternative fuel. For instance, coal was never thought of as alternative fuel until the Barapukuria Coal Mining Project was taken in hand about 10 years back.
Later on, several coal deposits have been struck but due to long dispute over the method of extraction the future of any coal-based power plants remains uncertain. Liquid fuel like furnace oil was never thought of except in limited area where gas grid is not available. The low price of gas compared to liquid fuel is also responsible for the plants being built on gas alone
Generation-wise, the power plants in Bangladesh may be divided into two categories: Hydro and Thermal. In the eastern zone, five hydro-power plants are operating, having installed capacity of 250 MW. Excepting these units, the rest of generation is on thermal source.
The thermal power stations include steam turbine compression turbine and combined cycle comprising of steam turbine and compression turbine. All of the thermal power plants are operating on gas. All of the power plants in the western region except Baghabari are operating on liquid fuel including furnace oil, SKO, HSD, and LDO, because of non-availability of gas in that area.
Based on the type of fuel being used, either gas (85%), liquid fuel (10%) or hydro (5%), the Power Plants can be divided into the following:
The installed generating capacity including public and IPO is about 5,000MW. The IPO has been excluded from the exercise, which means the generating capacity in the public sector is 3,500-4,000. As already spelled out, the thermal power plants running on gas use three modes of generation: Compression Turbine (CT) Steam Turbine (ST), Combined Cycle (CT+ST).
The CT and CC modes of generation have been excluded from the exercise as the built-in system does not allow to use liquid fuel in place of gas in operating such plants. Only the ST mode of power plants can be changed to liquid fuel. According to the estimate the total installed capacity of generation on ST mode is about 2,000MW, which means 60% of the thermal generation is based on steam turbine alone.
The steam turbine operates on a simple thermo-dynamic cycle. Steam generated in the boiler is fed into a steam turbine where it expands and produces mechanical power, which is converted into electrical energy by the generator coupled with it. The steam after expansion in the turbine condenses into water in the condenser and recycled in to the boiler for generation of steam for further feed into steam turbine. For economy, some turbines have multiple extraction stages of descending order of steam pressure down from super-heated steam to saturated steam. The steam boilers have different kinds of heating sources for producing steam.
According to modern practice, boilers operate on four types of fuel--: Nuclear, Solid (coal), Liquid (furnace oil) and Gas.
The nuclear energy-based power plants have basically a reactor in which the chain reaction proceeds to provide means of using the released energy for heating a working substance (steam) in a heat engine (turbine) to produce power.
The traditional coal-based power plants are somewhat clumsy and dirty. They have moving chain grates, which are endless chains that move continuo usly during operation. A bed ofcoal of uniform thickness is fed to the grate at one end. The volatile matter is soon distilled and burning continues at such a rate that practically ash is left at the opposite end of the grate. Air for combustion enters opening the sides of the grates and passes up through the grates' bed of fuel.
The modern coal-fired boilers have been much cleaner and are free from such clumsiness. Presently pulverised coal is being used as fuel. The coal is ground into fine particles. The burners are designed in such a way that this powder is sprayed into the boiler furnace under controlled air fuel mixture and burns like a vaporised fuel.
The furnace oil-based power plants use a burner where furnace oil at a controlled air-fuel mixture burns and the burned gases heat the boiler tubes to produce steam for feeding the stem turbine at a controlled pressure and temperature where it expands to produce mechanical visa vis electrical power.
The gas-based power plants also use burners where the gas in conjunction with air at controlled rate burns and the burned gases produce steam and power in the same fashion. There is a close similarity with a gas-based power plants and furnace oil based power plants. The only difference is the type of the burners being used in the sys tem.
So, by replacement of the gas burner with oil burner, a gas-based power plant can be changed to furnace oil-based power plant. This will need no modification of the furnace or tubes of the boiler. For the gas-based power plants, no storage of fuel is required as the gas is fed from the grid line. In case of oil-based power plants, storage is to be built for storage of fuel. This needs extra investment.
Presently, about 800 mmcfd of gas is being consumed in the power plants. Of this, 50% is operating on ST mode which means the conversion of ST mode gas-based power plants into oil (furnace oil) will result in releasing of 400 mmcfd of gas to be used for other relatively more important purposes, say in industry. The time frame for this purpose is maximum 10 to 12 months. The investment in comparison to building power plants is insignificant.
Technologically and investment-wise, the conversion is simple and less time consuming. But the major resistance which will come is in the form of increased cost of generation with subsequent higher tariff to the consumers. But we will have to accept this as a reality.
If we want to utilise our sunken investment, and, more importantly, if we want electricity, we do not have any alternative at present other than this. The alternative left is to embrace darkness.
Now we will have to choose whether we want to keep our plants shut for want of gas or whether we will go immediately for liquid fuel to run these power plants to give us power, light, and other requirements of life.
Presently, Bangladesh is importing about 1.5 million metric tons of crude oil and about 3 million MT of diesel and other grades of liquid fuel including furnace oil. In all, about 4.5 million MT of liquid fuel is being imported every year. It is an undeniable fact that in doing so a huge amount of liquid fuel will need to be imported, laying extra burden on foreign exchange reserve. To ease things, the program may be phased in on a yearly basis.
This piece throws some light on the issue of using liquid fuel in place of gas to run the existing power plants, which are already shut for want of gas. It is a reality that there is a paucity of gas in the country, and presently many power plants are shut for want of gas. In future, more will be added to the queue.
Munir Uz Zaman/Driknews
Coal and nuclear energy are long-term possible solutions. The government has to draw up plans to use coal or nuclear energy as alternative source fuel in power generation. But even if it is done today, it will take another 7 to 8 years to put these into real operation. Gas production is unlikely to increase in the near future.
The only immediate solution is to switch over to liquid fuel, both for existing and future power plants, which will come online in another 2 to 3 years from now. This will also save the shut down power plants from ruination due to continued idleness of the machinery of the power plants. Many countries of the world do not have gas. But they are running power plants and producing power and supplying to the consumers. If they can -- then why can't we?
Abdul Wadud is former MD of RPGCL (Rupantarita Prakritik Gas Company Ltd) under Petrobangla.