Plants boiler

M. J. Hobson, Review ofBaghouse Systemsfor Boiler Plants, pp. 74—84, ref. 190a. 

M. Bashar and T. S. C2amecki, "Design and Operation of a Lignite-Fired CFB Boiler Plant," Proceedings of the Tenth International Conference on Fluidi d Bed Combustion, San Francisco, May 1—4,1989. 

Other burners are used for low capacity operations. A cascade or checker burner, ia which molten sulfur flows down through brick checkerwork countercurrent to a flow of air, is used ia small units with a sulfur trioxide converter to condition gases entering electrostatic precipitators at boiler plants operating on low sulfur coal. A small pan burner, which is fed with soHd, low carbon sulfur, is used to produce sulfur dioxide for solution ia irrigation water to control the pH and maintain porosity ia the soil. The same type of burner is used to disiafect wastewater ia this case sulfur dioxide is used iastead of chlorine. 

Utilities and yard services (boiler plant, refrigeration, compressed air, water supply and treatment, effluents, fire protection, yard piping, yard electrical, yard materials handling, raw and finished-product storage)... 

For a high-pressure boiler plant with a high evaporation rate, demineralized feedwater is classified as having an electrical conductivity of less than... 

Dampfkessel, m. steam boiler, -anlage, /. steam boiler plant, steam plant, -beklei-dung, /. boiler covering or casing, -blech, n. boiler plate, -kohle, /. steam coal, -spei-stmg, /. steam boiler feed. 

Exhibition of 1851 marked one of the positive turning points, with a separate boiler plant providing steam to power exhibits in the enormous Crystal Palace, a 600-meter-long glass structure. A similar exliibition, complete with separate boiler house, was held in New York two years later. 

Where joints are unavoidable, they should be welded. Steam coils should drain freely from inlet to outlet. Steam traps, usually of the bucket type, should also be provided. Condensate from steam coils should be drained to waste, unless adequate provision is made to drain trace quantities before return to the hotwell. Where hot-water coils are used, the water supply should be heated through a calorifier. These recommendations will avoid any risk of oil reaching the boiler plant. 

This legislation was formally adopted on 26 November 1988. It applies to plant for the production of energy (effectively, boiler plant and similar) and specifically excludes heating furnaces, drying plant, etc. The Directive applies to plant of thermal input 50 MW and over. If two or more separate plants are in close proximity such that... 

Process or heating plant may have controls ranging from manual operation with some processes supervised by interlocks to semi-automatic and fully automatic operation. Deciding factors will include temperature of operation, frequency of ignition, degree of operator supervision, and rating of the plant. For example, boiler plant, both steam and water, will invariably have automatic control whereas tunnel kilns operated continuously at high temperature are unlikely to require it. 

Condensate from the low-pressure coil together with that from the flash vessel will then drain to a collecting tank, or direct to a condensate pump, for return to the boiler plant. If the pressure of the flash steam is left to find its own level it will often be sub-atmospheric. As the condensate must then drain by gravity through the steam traps these also must be sufficiently below the condensate drain points to provide an appropriate hydraulic head, and a vacuum breaker fitted above the coil. The alternatives are to allow the condensate to drain directly to a condensate pump, or to supply additional low-pressure steam through a pressure-reducing valve, to maintain a positive pressure in the coil and flash vessel. 

Originally, the height of the chimney was designed to produce a draft sufficient to produce induced-draft air for combustion. With modern boiler plant, forced-draft and/or induced-draft fans are used. This allows for the greater degree of control of the air to be designed into the combustion appliance. The chimney is therefore only required to disperse the gases. 

On medium-sized boiler plant where gas is to be the main fuel, it may have oil as a secondary standby fuel. In this case, the chimney height must be based on the grade of fuel oil capable of being burned. 

Most boiler plants can be installed using one or more boilers, which can accommodate minimum to maximum loads. Occasionally, heavy peak loads occur for only relatively short periods, and here there may be an advantage on economic running grounds to install boilers whose firing rate will not meet these peaks. In these cases, there are two methods which may be used one is thermal storage and the other is with an accumulator. 

Whether the boiler is fired on oil, gas or solid fuel, it may be expected that it will operate automatically. When boiler plant is not run continuously initial start-up may be manual, time clock or through an energy-management system. Manual attendance may be limited to maintenance functions dictated by the type and size of plant. Automatic controls will cover three areas ... 

The most frequent cause of damage and even explosion in boilers is a low-water condition. This will expose the heating surfaces, which ultimately overheat and rupture under the operating pressure. Experience has shown that since the introduction of controls for unattended automatic operation of boilers the accident rate has increased. Investigation invariably shows that lack of maintenance has been the main contributing factor. It is therefore imperative that personnel responsible for the running of the boiler plant be fully trained and conversant with its safe operation. 

It is generally the case that small boiler plants will create less noise than large ones. Nevertheless, due to the practice of siting small boilers close to working areas, the matter of noise must not be overlooked. Noise sources within the boiler house will be from the following ... 

The boiler plant, regardless of its size, is an essential part of the plant otherwise it would not be there. Having established this, it should be covered by a planned... 

Internal personnel will normally undertake boiler plant operation. Maintenance work may be by either internal personnel or outside contractors. Service contracts will be available from equipment suppliers covering all items of the boiler plant. Recently, companies have started offering contract energy-management schemes. These may be designed to suit individual applications and will be tailored to customer requirements. They may take over the operation of an existing plant or, if necessary, include for a new replacement plant. They will usually operate over a 3-10-year contract period. Dependent upon the terms of contract, all fuels, electricity, repairs and replacements may be covered. 

Where it is available the source can be a separate boiler plant, but common practice is to employ purpose-made electrode boilers within or adjacent to the plant. The latter reduces sensible gains to the plant but, being essentially saturated steam, condensate return pipes are required. In addition to the rise in moisture content of the air (kg/kg) being dependent on airflow and steam-injection rates, there is a very small increase in dry bulb temperature by the cooling of the vapor to the air temperature. The rise in total heat is total heat of steam (kJ/kg) x quantity supplied per kg air. 

Boiler plants are a major user of energy. The combustion efficiency of a boiler plant can easily be set at the optimum, and Table 30.2 suggests the parameters for this for various fossil fuels ... 

Close control of the amount of excess air is possible by the use of oxygen trim control equipment. Such equipment will control the flue gas oxygen content within the range of 2.0-3.0 per cent as compared to the normal 3.0-5.0 per cent. The improvement in boiler plant efficiency is of the order of 1.0-2.0 per cent. 

Many boilers do operate at low load factors and consequent poor annual efficiencies. This can be avoided by providing boiler plant with little or no margin over the actual required capacity and by installing multi-boilers or two or three smaller boilers. Boilers of this modular type are available for low-pressure hot water (LPHW) purposes, but obviously cost more than a single boiler. This will also increase the maintenance, number of examinations and the labor costs. Such an increase should be more than offset by the reduction in fuel costs due to the much higher annual boiler plant efficiency, which should be of the order of 20-30 per cent. 

Condensing boilers are now available for both gas- and oil-fired plant, the advantage of these being that the flue gases are further cooled down to below 100°C so that the latent heat available in the flue gas water vapor is recovered. The condensate has to be removed and the boiler capital cost is higher than for conventional plant. However, the boiler plant efficiency is increased to the order of 90 per cent, based upon the fuel gross calorific value. Where the flue gas exit temperatures are in excess of 200° C a further economy can be obtained by the provision of a spray recuperator in the case of gas and flue gas economizers for oil and coal. 

Large fans are required for boiler plant, furnaces and large air-handling units. These fans can now be fitted with variable-speed motors to reduce electricity consumption and maximum power, albeit at additional cost. 

At times it may be desirable to chemically clean various parts of the boiler plant and its auxiliaries. The reason may be curative or preventative. With low-pressure boilers and heat-exchange equipment, cleaning is carried out to restore heat transfer, and, for boilers, to prevent overheating. With higher pressure boilers, the restoration of heat transfer is trivial and, whilst some overheating may be avoided, the main reason for chemical cleaning is to prevent corrosion. In nuclear plant, an additional reason for cleaning is to remove radioactive material and improve safety. 

Boilers Plants always experience corrosion problems with boilers, and monitoring of corrosion has always presented a challenge relating to both access and simulation of exact conditions, e.g. condensation conditions. Applications in the monitoring of condenser tubes have been reported ... 

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