Power plants – Combustion products used as motive fluid
Patent
1992-07-06
1993-12-28
Bertsch, Richard A.
Power plants
Combustion products used as motive fluid
60 39092, 60 39464, 110264, 554591, 55460, F02G 300, B01D 4512
Patent
active
052728668
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of treating process or flue gases issuing from a pressurized gasification or combustion plant immediately prior to leading such gases into an expansion turbine. Especially, it relates to a method of treating gases cleaned in one or more particle separators and of leading such gases into a turbine via a combustion chamber of the turbine.
By connecting a gas turbine to a solids gasification or combustion plant, it is possible to produce energy with a wide range of fuels. Besides coal, also peat, wood, bark as well as other waste material are applicable fuels. Also in view of emissions, connecting a gasification process to a gas turbine is an advantageous solution in comparison with conventional steam power plants.
In order to prevent fast wearing of the gas turbine vanes, all particles have to be carefully separated from the gases before the gases reach the turbine vanes. Even very small particles wear the vanes in a short time, causing disturbances to the drive of the turbine. Large particles may destroy the turbine altogether in no time. Therefore, the gases are carefully cleaned in particle separators prior to leading them into the combustion chamber of the gas turbine and further to the turbine vanes.
However, particle separators may sometimes function dissatisfactorily or they may abruptly be damaged so that particles escape and, entrained in clean gas, flow into the turbine. In e.g. ceramic filters, there may emerge cracks, wherethrough fine particulate material, entrained in clean gas, enters the turbine unnoticed.
If the gas duct is provided with refractory lining, fine particulate material or even larger particles of refractory material may become loose and be entrained into the gas flow. Large pieces of refractory material may destroy the turbine completely in no time.
Preventing and foreseeing of the aforesaid damages has been difficult These damages are disastrous for the turbine. Fine particles wear the outer edges of the turbine vanes and large particles may destroy the vanes completely as soon as they reach the vanes.
The gas duct leading to the turbine may be manufactured of steel resistant to hot gas, thereby avoiding the drawbacks caused by refractories Normal steel does not, however, endure hot flue gases without cooling. Cooling of gas before the turbine is, however, disadvantageous in terms of energy economy. The hotter the gases are when led into the turbine the better is the result.
Special, heat-resistant metals may naturally be used in the flue gas duct, but they raise the cost considerably. Cost aspects are important, especially, if flue gases have to be transported long distances.
This problem, namely ensuring the cleanliness of seemingly clean gas immediately before the combustion chamber of the turbine has neither been interfered nor solved so far.
Gases containing particulate material or ash have been cleaned prior to feeding them into the gas turbine. It has been suggested, for example, that the gas issuing from the gasifier should be burned right away in the combustion chamber of the turbine and that the flue gases should not be cleaned until immediately before the turbine in a super cyclone. However, this procedure sets high demands on the cyclone because the gases have to be completely cleaned in only one stage so that no wearing particles remain in the gas flowing into the turbine.
The temperature of the gas to be introduced into the gas turbine should be as even as possible and preferably >1000.degree. C. in order to receive a high yield from the combustion process. The quality of the gas, even from the process of the same plant may, however, vary greatly depending on, e.g. the loading of the plant.
The yield of the gas could be raised by topping combustion, i.e. additional combustion in the combustion chamber. However, in the combustion stage and thereafter, when introduced into the turbine, the very hot >1000.degree. C. gas requires equipment which is either of refractory material or cooled or manufactured of special metals
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A. Ahlstrom Corporation
Bertsch Richard A.
Richman Howard R.
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