Energy & Power

Cover Report

Clean Coal Future of Coal in Bangladesh
Khondkar Abdus Saleque

Sooner or later Bangladesh will commence coal exploration. Dire necessity and economics will drive Bangladesh to adopt the most appropriate method of mining. The developing economy can even achieve a double digit growth for a few years if only the present chronic energy generation and supply situation can be appropriately addressed. The caretaker government has managed to increase the power generation level to some extent through better management of load, better operation and maintenance of existing plants. The national production capacity, which reduced to 3200MW in December 2006 has now increased to about 4000 MW. But still there is 1000-1200 MW shortage to meet the peak demand and hence significant load shedding still persists. Many of the planned initiatives for augmenting power generation cannot progress due to gas supply uncertainties. There is no crisis in gas production. But there are constraints in transmission and supply. This is the problem with our predominantly mono fuel based power generation.

We must not continue to rely for 90% of power generation on natural gas leaving substantial high quality coal underground for years disputing over mining methods and other related issues. We must diversify the energy basket bringing in new options including coal, Hydro, solar, bio diesel, nuclear, geothermal etc. CTG is taking several initiatives, finalizing the coal policy, going for third round bidding in the deep sea for gas & oil exploration, exploring nuclear options, planning for setting up of coal fired plants in the northern region. For our long term energy security government is also planning for importing gas and electricity from Myanmar. A certain section of our civil society in the name of protecting gas, oil, electricity and port is opposing a particular coal mining method. This situation among others may be causing some confusion and delay in concluding the coal policy.

There may be strong logic against export of gas considering the huge domestic demand and our mono fuel based energy scenario, the logic against export of coal is also reasonable to some extent but their stand against surface mining to recover 90% coal from shallow coal seam can not be supported from technical as well as economic point of view. In the backdrop of above, if the coal mining goes ahead and coal based power plants are set up there is every likelihood that another section of environmentalist may start campaigning against global warming emanating from greenhouse gas emissions due to burning of coal. We must start addressing the situation now. For a thickly populated country like Bangladesh and having affected by severe natural calamities we cannot irrationally introduce another new element which may worsen the environment. Burning of coal must follow proper technology to keep Green House Gas emission to a minimum level. Bangladesh has to be very careful in selecting the correct technology and ensuring that the coal plant does not cause major environmental pollution.

The author is involved in dealing with Tarong Energy in connection with the construction of about 3km of Recycled Water Pipeline inside their Traong Power plant area. We are taking several actions for safe and environment friendly pipeline construction within the power plant area. This plant uses coal from the adjacent surface mine. It has given the author opportunity to discuss various aspects related to coal fired gas generation with power plant engineers and their safety and management professionals. They have shared the literature and given web link to access the other documents.

Coal is an extremely important fossil fuel and will continue to remain so. About 23% of the primary energy needs are catered by coal. 39% of the world’s electricity is generated from coal. It also accounts for 70% of worlds steel production. It is the world’s most abundant and widely distributed fuel source. IEA predicts a 43% increase of coal use from now till 2020.

Burning coal produces about 9 billion tones of carbon dioxide each year which pollutes of environment and contributes to climatic change.70% of this emission comes from coal based power plants. This is alarming. USA, China, Australia, Brazil are the biggest polluters. We have seen the impact of the greenhouse gas emission in the climatic changes of these countries and regions. USA suffered from repeated Typhoons, floods, Austraia has prolonged draughts, north and south America is repeatedly devastated by cyclones and floods, Asian countries are being devastated by recent visits of tsunami.

Research and development are continuing aggressively to develop clean coal technology. This technology will address the problem of the world’s enormous resources of coal and can be utilized for future power generations without contributing to global warming. Much of the challenges are in commercializing the technology so as to ensure that coal use remains economically competitive despite the cost of achieving (“zero emission). In many countries people are leaning towards power generation from renewable sources and nuclear power options. Well, Bangladesh must also think of restrict the power generation from coal to logical limit as the clean coal technology is still some years to come. We are in a desperate situation .We having to have some coal plants in any case to meet our immediate and mid term power demand but we must be very careful that it does not cause more harm than good. We may limit coal fired generation for the time being to a maximum of 2000MW up to 2020.In the meantime if clean coal becomes economically viable we may go ahead with further coal plants.

Low-emission or clean coal technologies reduce the level of greenhouse gas emissions generated from coal-fired power stations. The clean coal technology that is being explored in Queensland Australia include the capture and permanent storage of CO2 in deep underground rock formations (geo-sequestration), and technology to modify the way electricity is produced to allow the capture of CO2 emissions.

Before we proceed further it is consider prudent to be acquainted with some common terms, which are referred to in this write up.

Carbon capture and Storage:

Carbon capture and storage or geo- sequestration is the process of capturing the CO2 released from combustion or burning of fossil fuels, including coal. Once captured, this gas is compressed and transported through pipelines to locations with suitable geological (rock) formations for the gas to be injected into and stored long term.

Integrated Gasification Combined Cycle:

Integrated gasification combined cycle combines the coal gasification process and gas fired combined cycle power generation to produce electricity. Coal is finely ground and through a chemical process turned into synthetic gas (syngas) and CO2.The CO2 can then be captured for storage. The syngas is burned, driving a turbine that powers a generator, producing electricity. The exhaust heat from the turbine is recovered to produce steam, powering steam turbine – producing more electricity.

Oxy-Fuel:

Oxy-fuel involves the combustion of coal using the re-circulated exhaust flue gas combined with oxygen. The process produces a highly concentrated stream of CO2 gas, which can be more easily captured for transport and storage.

Burning coal for power also create other undesirable wastes which also needs to be accounted for. Some of actions the coal power plants deal these and planning to do in future are;

Coal is cleaned by washing. It reduces emissions of ash and SO2 during burning.
Electrostatic precipitators and fabric filters can remove 99% of fly ash from the flue gases.
Flue gas desulphurization reduces SO2 production and emission to atmosphere up to 97%.It is widely used. The viewed such a power plant of Tarong Energy in North Queensland.
Low –Nox burners allow coal –fired plants to reduce nitrogen oxide emissions by about 40%. Reburning techniques can reduce it to 70% and selective catalytic reduction can clean up to 90% of NOx emissions.
Increased efficiency of plants upto45% thermal efficiency will create situation for less emission per kWh generation than the existing less efficient plants.
Integrated Gasification Combined Cycle (IGCC) and Pressurized Fluidized Bed Combustion (PFBC) will enable thermal efficiency up to 50% in not too distant future.
Ultra –clean coal from new processing techniques may reduce ash below 0.25% and sulfur to very low levels. This means that pulverized coal may be directly fed into gas turbines with combined cycle and burned at high thermal efficiency.

These obviously change the economics of Coal power plants. The external costs will almost certainly be increasingly factored in through carbon taxes for burning coal.

Some of the waste products can be used productively .Fly ash and bottom ash can be used as building materials. Western Pipeline Alliance where the author is working now has been approached by Tarong Power energy to use the bottom ash as bedding material for our pipeline. We are waiting for approval of authority. It will be economic as it will be issued to us free. We are otherwise buying sand for use as bedding material for our 1500 mm O.D Cement Lined Mild Steel Pipeline.

However, the major focus is the emission of CO2, as it implicates global warming. KYOTO protocol requires that emission decline, notwithstanding increasing energy demand. The real challenges of Coal plants are to limit CO2 emission.

Several proven methods are in practice to capture and separate CO2 from gas streams but there has no such proven technique for doing the same in case of coal burning plants.The Integrated Gasification Combined Cycle (IGCC) plant is a means of using coal and steam to produce hydrogen and CO which are burned in a gas turbine with secondary steam turbine (Combined Cycle ) to generate electricity. The IGCC gasifier is fed with O2. The flue gas contains highly concentrated cO2 which can be readily captured by amine scrubbing. IGCC gasifier is fed with O2. These kinds of plants are in operation in USA. Development of this oxygen –fed IGCC process will add a shift reactor to oxidize CO with water so that gas stream is basically just hydrogen and CO2.These are separated before combustion and hydrogen alone becomes the fuel for electricity generation while concentrated pressurized CO2 is readily disposed of.

Oxy-fuel technology has potential for retrofit to existing pulverized coal plants, which are the backbone of electricity generation in many countries.

Injecting the captured CO2 into deep unmineable coal seams where it is absorbed to displace methane is a potential use or disposal strategy, which Bangladesh can ponder over. Research on geosequestration is ongoing in different parts of the world. The main potential appears to be deep saline aquifers and depleted oil and gas fields. In both, the CO2 is expected to remain as supercritical gas for thousands of years, with some dissolving.

The clean coal technology field is moving very rapidly in the direction of coal gasification with a second stage so as to produce a concentrated and pressurized carbon dioxide stream followed by its separation and geological storage. This technology has the potential to provide what may be called “Zero emission” – in reality , extremely low emissions of the conventional coal pollutants, and as low- as- engineered CO2 emissions.

In Australia Prime Minister, John Howard, and the opposition leader, Kevin Rudd, are strong supporters of clean coal technology as a long term solution of green house gas emissions. However, the former BHP head has different view. Paul Anderson thinks long term storage of carbon waste may be as difficult as dealing with nuclear waste. He said in an interview with Herald “People can’t believe you are safe putting nuclear waste five miles under the when it’s petrified in glass. How are they going to feel safe putting pressurized gas under the ground?” However, some debates will always be there. Clean coal technology will take some more years to come out of R& D stage but world must move on. We must utilize coal in the most efficient way utilizing the best available technology.

Bangladesh is on the threshold of embarking into coal age and coal power generation. All the associated impacts of the activity, current and evolving technologies must be carefully examined by relevant experts before selecting the most appropriate technology. We better not do something, which may cause more harm than good. We must be very careful in burning of coal. We must not go for lot of coal-based power plants. We have to see how we can deal with wastes of coal, how can we separate and recover CO2 and store them in geological reservoir. Some of us are thinking coal is required for 50 years energy security. This means they want to utilize most of it for power generation. Have they considered what will happen to Bangladesh if several coal plants following the present day coal plant technology are set up? The eventual greenhouse gas emission may make our very existence very critical. We have to embrace Clean Coal technology when this becomes a proven technology. Till that time we have to limit coal use in power plants as far as practicable.