Boiler fuel solid

Short contact time SRC can be upgraded via catalytic hydroprocessing into low sulfur boiler fuels. However, the solid SCT SRC feedstock requires solvent dilution to reduce its viscosity. Furthermore, even for a 50 wt % W. Kentucky SCR SRC blend, all pilot unit lines and valves have to be heat-traced above 350°F in order to achieve smooth mechanical operations. 

CFB boilers receive solid fuels in fairly coarse sizes, and only one or a few feed points are needed. 

Certain oilseed processors use byproducts of production as alternative fuels, which is particularly true in sunflower and peanut processing where hulls are burned as boiler fuel. This creates additional combustion challenges, but reduces solid waste. 

The simplest type of densification system consists of a shredder followed by an agricultural type "cubing machine. These machines were originally built to produce densified animal feeds, but can be modified easily to produce solid waste fuel cubes. One of the first systems of this type was operated during the early 1970 s in Fort Wayne, Indiana, to produce a solid waste fuel for the city power plant (4). A more recent application of densification was demonstrated by the Papakube Corporation of San Diego, California, which manufactures solid waste cubes as a boiler fuel (5). 

Flask, A.P. and J.A. Pryor. "SRC Solids Boiler Fuel and Building Block." The 6th Energy Technology Conference, Washington, D.C. (February 27, 1979). 

Palm oil industry is one of the biggest industries in Malaysia which contribute to a large amount of solid waste as an output. The palm ash is produced after burning the palm oil shells and fibres as boiler fuel for palm oil consumption. 

The primary product of the SRC-I process was a low-sulfur, low-ash, solid boiler fuel... 

There are, however, technological means available to burn incompletely desulfurized fuels at the same time minimizing SO2 emissions. In the auto-desulfurizing AUDE boiler developed by IFF, the effluent is treated in place by an absorbent based on lime and limestone calcium sulfate is obtained. This system enables a gas desulfurization of 80% it requires nevertheless a relatively large amount of solid material, on the order of 200 kg per ton of fuel. 

Incineration with Heat Recovery Heat contained in the gases produced from the incineration of solid wastes can be recovered as steam. The low-level heat remaining in the gases after heat recoveiy can also be used to preheat the combustion air, boiler makeup water, or solid-waste fuel. 

TABLE 27-19 Solid-Waste Fuels Burned in Industrial Boilers... 

It is possible to have boilers supplied to operate on liquid, gaseous and solid fuels, although there may be a time penalty of two or three days when converting from solid to liquid and gaseous fuels and vice versa. 

Figure 23.5 A stoker-fired watertube boiler of 36,300 kg/h steam capacity at 28 bar and 385°C (from British Coal Publication, Boiler House Design for Solid Fuel, 1980, and kind permission from College of Fuel Technology)...

The chamber is externally insulated and clad. Combustion equipment for solid fuel may be spreader or traveling-grate stokers or by pulverized fuel or fluid bed. Oil and gas burners may be fitted either as main or auxiliary firing equipment. The boilers will incorporate superheaters, economizers and, where necessary, air preheaters, grit arresters, and gas-cleaning equipment to meet clean air legislation. 

Having now established the space requirement for the boilers, we must consider the other items of plant to be housed in the same structure. These may include water-treatment plant, heat-recovery system, tanks and pump, instrument and controls. With oil- and gas-fired installations, there is little additional plant to consider within the boiler house. With solid fuel then the handling, distribution and perhaps storage could also form part of the building with provision for ash handling and removal. 

External to the boiler house, provision for the storage and handling of solid and liquid fuel is required with access for delivery vehicles. With some small boilers such as electrode or steam-coil generators, where the boiler only serves a single item of plant or process, it is practical to install them immediately adjacent to that process. The electrode boiler is eminently suitable here as no combustion gases are produced. 

Solids emissions from solid and liquid fuel fired plant are covered in the HMSO publication Grit and dust-The measurement of emissions from boiler and furnace chimneys. This states levels of emissions which should be achieved in existing plant and specified for new plant. Suitable sampling connections should be incorporated into the flue ducting for the use of test equipment if permanent monitoring is not included. 

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 ... 

Advantages of this type include an ability to burn all fuels including those containing solid particles, good turndown ratio (4 to 10 1 typically) and an insensitivity to oil conditions such as pressure and temperature. It is widely used in shell boilers, and the only real limitation is that the cup surface has to be cleaned daily. The most common atomizer layout is shown in Figure 24.7. Variants include direct driven cup and separate mounting of the primary air fan. 

Note The above sizes apply to boilers fired with solid fuel. For oil-and gas-fired boilers the relief valve should be one size larger. 

The ash deposits resulting from the combustion of solid and oil fuels often contain appreciable quantities of other corrodants in addition to vanadium pentoxide. One of the more important of these is sodium sulphate, and the effects of this constituent in producing sulphur attack have been mentioned. The contents of sodium sulphate and vanadium pentoxide present in fuel oil ash can vary markedly and the relative merits of different materials depend to a great extent upon the proportions of these constituents. Exposure of heat-resisting alloys of varying nickel, chromium and iron contents to ash deposition in the super-heater zones of oil-fired boilers indicated a behaviour pattern depending on the composition of the alloy and of the ash... 

Because of the furnace design, which incorporates a relatively large and unrestricted combustion zone, FB boilers are entirely suitable for coal and other solid fuel firing. 

They tend to be bottom-supported and can be supplied either as packaged or modular (field-erected) units. Industrial boilers may be designed to bum cmshed coal (PF), oil, gas, or a combination of oil and gas with a solid fuel. 

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