We are in the business of designing, making, and installing steam generators for industrial and electric utility applications. We feel that we are obliged to respond to the invitations for ”Save the Planet” to avoid “Global Warming” by specifying the common issues from a professional point of view. Steam generators derive their heat requirements from the combustion of fossil fuels – gas, oil, coal, etc. There are a number of environmental concerns connected with this process that we would like to address.
The Combustion Process
When a pure hydrocarbon burns, there are two products of this combustion. Water (H2O) is produced from the combustion (oxidation) of the hydrogen components. Carbon dioxide (CO2) is produced from the combustion of the carbon components. These two products are inescapable results of burning hydrocarbons. This oxidation releases heat, which is used in industrial processes, as well as in the home.
There is a continuing discussion on the effects of the increase of the carbon dioxide levels in the earth’s atmosphere. It is one factor blamed for the so called “greenhouse” effect, which predicts a warming of the earth’s atmosphere.
Carbon dioxide is a vital component of the earth’s atmosphere. From it the trees, and all green plants, derive the carbon they need to build leaves, roots, branches, and trunks. In this process they take in carbon dioxide, absorb the carbon, and release oxygen. In the burning of fossil fuels we are releasing the carbon stored up by the plants thousands or millions of years ago.
Fossil-fueled boilers for electric utilities and industry are one contributor to the carbon dioxide in the atmosphere. Another major factor in the increase of carbon dioxide levels is the destruction of the world’s great forests. This is doubly damaging.
Not only are the trees – that take the carbon dioxide from the air and return oxygen to it – being destroyed, but the process by which so much of them are being destroyed – by burning – is adding significant levels of carbon dioxide to the atmosphere.
Automobiles, and other transportation users of petrochemical fuels, are also a significant factor in contributing carbon dioxide to the atmosphere.
It should be the policy of all boiler industry to design and supply boilers having the highest possible efficiency in the conversion of fuel to useful heat. In this way the addition of carbon dioxide to the atmosphere is reduced to the lowest possible level for a given amount of heat produced. There are designs of boiler that are less efficient in this process, and they are less expensive to produce. We should not supply such steam generators/ boilers.
Other Combustion Products
As well as the two major products of fossil fuel combustion, there is a range of other products of combustion that are released into the atmosphere. What these are depends mainly on the fuel used.
When coal or oil has sulphur as one of their constituents, then the products of their combustion will include oxides of sulphur. Unless removed from the flue gases before release into the atmosphere, these sulphur oxides can combine with moisture in the atmosphere to produce sulphuric acid and other undesirable sulphur compounds. Equipment is available to remove these oxides of sulphur from the flue gases. Companies supply such equipment at the request of the customer, where the sulphur level of the fuel calls for it.
Another undesirable group of potential combustion products are the oxides of nitrogen (NOx). If released into the atmosphere these may combine with moisture to form nitric and nitrous acids, thus contributing to “acid rain”. Designs of oil and gas burners are available which minimize the formation of these oxides, and these burners are supplied only when specified by the customer.
Fluidized Bed Combustors, Atmospheric/ Circular
In the specific case of coal, there is a combustion process known as the fluidized bed combustor, in which the fuel is mixed with limestone (calcium carbonate) and then burned. During the combustion process the sulphur combines with the calcium carbonate to form sulphates, which are then removed with the ash rather than being released to the atmosphere.
Many companies are in the development of fluidized bed combustors, either in “Atmospheric Bubbling, AFBC for short” or “Circular Fluidized Bed, CFB”. This technology is available in many international companies, who are managing a research programme to adapt this process to the specific lignite fuels.
Another advantage of this technology is that the combustion temperatures in the fluidized bed combustor are such that negligible amounts of the oxides of nitrogen are produced.
Integrated Gasification combined cycle/ IGCC
IGCC firing technology may be employed. Here in this technology you build a sort of refinery next to the future power plant to generate “Synthetic gas” from poor lignite then you fire this synthetic gas which comprises mainly H2 and CO, in the combined cycle power plants similar to natural firing.
We need to make extensive research if this technology would be applicable for our own indigenous low LHV lignite with high ash and high moisture content.
Municipal Refuse disposal and Other Wastes
Another environmental concern is with the growing volume of solid waste material from our cities and industries.
With a greater sensitivity for our environment, and an increasing scarcity of land, the practice of dumping such wastes in landfills is becoming less acceptable.
Techniques exist for the combustion of such waste material in the local thermal power plants in an efficient and environmentally viable manner.
This municipality refuse disposal process not only minimizes the landfill problem, but also produces heat which may be used in district heating schemes or for the production of electricity.
Municipalities are to solve their solid waste disposal problems through thermal power plants industry, which are ready to work with forward thinking municipalities in its application.
One major source of electric utility power generation produces no carbon dioxide release into the atmosphere. This source derives its heat from the controlled disintegration of nuclear fuel in a nuclear reactor. This heat is then transferred to water to produce steam to drive turbines.
Although there are waste products of the nuclear reaction that require considerable care in their handling, storage, and disposal, many logically thinking people agree that nuclear power offers the best solution for long term thermal power production, with the minimum effect on our environment.
In the 4th generation plants there is maximized security and minimized waste. Local engineering capability is to be employed at the highest level in order to absorb the technology for best use in national advantage.
The combustion processes used in these boilers involve high volumetric heat release rates and intense flames. Careful design and meticulous attention to detail are required to operate this equipment safely. Accurate and continuous measurement, monitoring and control are essential to operate within the design parameters.
Utilities should use only the most up to date, microprocessor controls and instrumentation for these tasks. There are suppliers for the equipment which will operate on a continuous basis completely automatically, with a minimum of operator monitoring, thus ensuring maximum efficiency and safety in its operation.
All steam generating boilers contain steam at high pressure. The integrity of the pressure bearing components is of vital importance to the safety of operating personnel.
All boilers should be designed, built, and tested in accordance with the stringent requirements of the Boiler and Pressure Vessel Codes of European Union, as well as the American Society of Mechanical Engineers. ASME application has advantage to work overseas.
The world has a lot of coal, but right now carbon capture and sequestration is not commercially viable, and no guarantee it will be in the future. Solar and wind plants have long term availability problem. Natural gas has national security implications and does emit CO2 which creates global warming.
The primary energy sources for new capacity and energy efficiency measures need to be chosen using some kind of quantitative risk-assessment scheme that most likely will result in a diverse energy mix that includes nuclear.
We are really not sure how to get around/adapt to the global climate change problem without some drastic changes, even if nuclear energy is implemented.
Although every action we take, every time we move or speak, has some effect on the environment, it is the major effects that must be addressed if we are to act as responsible citizens of an all-too-fragile world.
We should design and supply which does have an appreciable effect on the environment around us. It should be our policy and our concern that any impact on the environment be minimized as best we know how.
We should continue to apply the best technical solutions to these concerns, with maximized local engineering capability and make best use of our local fuel resources. We will not compromise our designs with inefficient solutions when we know a better way. We should work with our customers and the community to provide the cleanest, safest, most up to date technology in the equipment that we supply. We are citizens of this world and intend to act responsibly in it.
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