Outlet Flue Research Articles

New experience in field of application of corrosion resistance protection in flue gas desulphurisation plant absorbers

AbstractAbsorbers form the main part of the flue gas desulphurisation plants for 360 MW units at the Belchatow Power Station in Poland. The plant working cycle and service life are dependent on the grades of the corrosion resistance, protection materials used as an absorber lining in individual zones. The objective of manufacturers activities in this field has been to extend the service life of the flue gas desulphurisation plant. This has been implemented by testing 'wallpapering' technology in the absorber cylindrical part, using plate sheets of Hastelloy nickel alloys, 0·5 to 1·6 mm in diameter. Experiments involving Hastelloy nickel alloys, grades C-22 and C-2000, among others, were used to evaluation the resistance of the base material, 'wallpaper' plate sheet, welded joints and heat affected zones (HAZ) towards corrosion. The corrosion tests were executed for three different conditions of corrosive environment: (a) actual boiler outlet environment: chemical composition of boiler outlet flue gases, w...

Preparation and characterization of activated carbon from oil palm wood and its evaluation on Methylene blue adsorption

Activated carbons were prepared from the biomass of oil palm wood (OPW) via two stages, pyrolysis and physical activation, using an environmentally friendly pyrolysis pilot plant, and an activation pilot plant was studied. The latter uses the outlet flue gases from limestone calcination process as activating agents. Experimental results showed that pyrolysis and activation conditions leading to various final average temperatures had significant effect on the properties of activated carbons prepared. Suitable pyrolysis operating conditions of 7 m 3 h −1 airflow rate for 4 h until final average pyrolysis temperature 390 °C and activation conditions of 7.45 kg limestone calcined with airflow rate 202.4 ml s −1 for 3.5 h until final average activation temperature of 806 °C produced an activated carbon yield of 13.7%, 68.3% fixed carbon, 16.9% volatile matters, 4.3% ash, and 10.6% moisture, and 1084 m 2 g −1 BET surface area, and a micropore surface area of 931.6 m 2 g −1 was obtained. Methylene blue adsorption was tested and 90.9 mg g −1 maximum adsorption capacity was found. The high micropore fraction, N 2 adsorption isotherm and SEM showed that these activated carbons possessed intricate pore network comprising micropores and narrow mesopores. FTIR characterization indicated that pyrolysis and activation temperatures affected the surface functional groups and maximum Methylene blue adsorption was dependent on BET surface area.

A Versatile Computer Simulation Model for Rotary Regenerative Heat Exchangers

A simulation technique for predicting the thermal performance of rotary regenerative heat exchangers, in particular those used for heating the intake air to power station boilers, has been developed and verified by means of site measurements. Various geometries of both rotating-hood and rotating-matrix types of air heaters can be accommodated in the simulation model, including packings of corrugated steel plates of various specified profiles and any given thicknesses and lengths in the flow direction. Rotational speed, leakage, blockage, and non-uniform inlet flow distribution may be taken into account as input variables. The heat transfer and pressure drop correlations for the various plates considered, which also form part of the input data, were determined experimentally using a single-blow transient test facility, constructed as part of this research program. The effect of erosion of the plates by fly ash particles carried in the outlet flue gas on heat transfer performance is also considered, and experimental results show that erosion has little effect on the thermal performance (up to the point that structural integrity is about to be compromised), but also that the pressure drop is reduced.

Alternative arrangement of unit for thermal processing of wastes from polluted air

New efficient equipment for the thermal treatment of gas wastes from polluted air (incineration of volatile organic compounds and carbon monoxide) has been developed recently. This equipment can be used in various branches of industry (for the treatment of polluted air from paint shops, chemical cleaning systems, degreasing processes, printing machines, gas wastes from various chemical processes, for the thermal treatment of off-gases originating in refineries, in the production of plastic, the pharmaceutical industry, the food industry, laboratories, etc.). A principal idea of this equipment is based on placing the cylindrical combustion chamber inside a heat exchanger–polluted air preheater. Main advantages of this equipment are as follow: compactness and utilizing heat losses from the combustion chamber for additional preheating the polluted gas. Modified equipment for catalytic treatment can be used as an alternative unit. Various options of arrangement can be applied in industrial practice. This unit can be used as a compact one (minimization of space requirement owing to a convenient arrangement of fans), over pressure (only air fan), under pressure (only flue gas fan — recommended especially in cases where the polluted air is supplied by pressure). Waste to energy arrangement is that in the case of an excessive concentration of pollutants–combustibles. Then the energy of the outlet flue gas can be utilized not only for the polluted air preheating but also for steam generation, water heating or other purposes.

Heat recovery in thermoplastics production

An energy optimization of production of a thermoplastic material, polyamid-6, i.e. nylon-6, using boiler flue gases heat recovery is presented. Energy and environmental studies show an increase of process efficiency simultaneously with a decrease of thermal pollution. If the feed water is heated with flue gases, the fuel consumption is reduced by about 13%, while the boiler outlet flue gases temperature decreases from 232°C to 55°C. Using an air preheater for combustion air preheating, 7.9% of the fuel will be saved, and at the same time, the atmospheric thermal pollution is diminished because the exhaust flue gases temperature becomes 62°C instead of 232°C. The combination of feed water and air preheating shows fuel savings of 13.6%, and the outlet flue gases temperature is reduced to 29.7°C.

Stable Combustion in Sludge Melting Furnace by Fuzzy Logic Control

This paper discusses combustion control using fuzzy logic for a sewage sludge melting furnace. The sewage sludge melting process is gaining attention as an effective method for reducing sludge volume. The slag from molten sludge is stable, causes no pollution, and can be used as a by-product. However, the operation of a sludge melting plant requires expert operators who have to deal with complex phenomena that take place in a melting furnace. In an effort to facilitate the operation, the authors have employed a control system which features the use of fuzzy logic for automatic combustion control in a cyclone type sewage sludge melting furnace. Confirmation was made that this fuzzy logic combustion control system functioned effectively for controlling the furnace temperature, O2 concentration in the furnace outlet flue gas, and concentration of NOx.

Criteria for designing electrostatic precipitators

This paper discusses the concepts of effective migration velocity and specific collector area as derived from the Deutsch equation. These two factors are commonly used as a means of specifying plant size and comparing proposals by different suppliers. It is demonstrated that effective migration velocity is not a constant dependent only on the fuel, being subject to large variations according to various features of the design of the precipitator. It is also shown that specific collector area cannot be used without at the same time considering the contact time of the gases in the electrostatic field. The removal of dust by a precipitator is carried out in two stages. The dust is first deposited on the collecting electrode, and a layer of significant thickness must be allowed to form so that when, in the second stage, it is dislodged by rapping, the layer breaks into agglomerated masses sufficiently large to fall into the hoppers below the collecting electrodes before being carried by the moving gas stream into the outlet flue. This requires that the frequency of rapping of each field of the precipitator shall be set at the correct rate according to the concentration of dust entering the field. Currently much stress is being placed on the intensity of the rapping blow and there is a tendency to specify increasing values of this blow. Due to the necessity of allowing a layer of dust to form, no increase in rapping intensity can overcome the effect of highly resistive dust. While the rapping force must be enough to shear the dust layer, any increase above this level is likely to result in the breakdown of agglomerates with an increase in dust emission and may also cause metal fatigue problems.

Precipitator Gas Flow Distribution

An electrostatic precipitator, furnished on a 500-Mw tan-gentially-fired steam generator burning coal, was to collect 99.6% of the fly ash being generated in the furnace of this unit. Preliminary measurements indicated that the installation was not meeting its collection guarantee. Precipitator outlet flue dust distribution indicated that poor gas flow distribution might be one of the causes of the low performance. When observation ports were installed in the outlet flue to permit a direct visual evaluation of the problem, it was found that high velocity jets were present in the collecting electrodes, and that hopper sweepage was present. A model study along with velocity distribution measurements of the installation were authorized. Flow analysis indicated that the field and model correlated well. Extensive changes were made in the model, which eliminated or minimized the high velocity jets and hopper sweepage. After these changes were made in the field installation, it was able to achieve the required d...

A WASTE HEAT DRYING SYSTEM INVOLVING RECUPERATION1

In an attempt to eliminate the smoke nuisance created by operating a brick plant within the limits of a city, a successful smoke eliminator and a waste-heat drying system involving recuperation were developed after some experimenting on old and new methods. The construction and arrangement of the recuperator is described as follows: A complete double-deck duct system was built carrying the combustion gases in the lower half and the waste heat in the upper half. In this system a damper chamber is constructed a t each kiln where the outlet flue leaves the kiln. The kiln outlet flue enters this chamber on the one side and the gas and waste-heat ducts one above the other leave on the other side. Both of these ducts are fitted with dampers. The construction of these chambers and the main duct is described. The advantages, limitations, and cost of this system are discussed.