Stoker Type

The most common type of boiler configuration to bum hog-fuel is the spreader stoker type, although some overfeed stokers also exist. Spreader stoker boilers can bum fuel with high moisture content, are relatively easy to operate, and have relatively high thermal efficiency. Overfeed stoked boilers have lower particulate emissions relative to spreader stoker boilers because less combustion occurs in suspension.13... 

Fort Howard Corporation Croon Hay, Ul Currant 2 2 and 1 xl" 30 tons tlre/IOOO tons coal par day No Nona required plant has 0 boilers totals 3 underfeed type that use 2 s2 TDF 2 spreader-stoker type that use 1> 1 TDF 1 cyclone fed with no IDF use now, but use planned. Produce recycled paper coal other base load fuel. References 3 and 4... 

Varied boiler firing configurations are found in hog fuel boiler applications, including dutch oven, fuel cell, spreader stoker with traveling or vibrating grates, and cyclone stoker types. As stated previously, the spreader stoker is the most widely used of these configurations. Spreader/stoker boilers in the pulp and paper industry often have an air swept spout added to the front of the boiler to feed bark down on top of the coal.14 Wood is puffed at one-... 

Most boilers in China are of the stoker type, which consume about one-third of total coal production, at an average efficiency of about 60% with high pollutant emissions. To raise efficiency and to lower pollutant emissions, recent R D efforts have been focused on CFFBs with low steam capacity, possessing the following features ... 

The emissions of two different commercially available types of wood chip combustion systems were analysed one boiler with a power output of 70 kW with a stoker type burner, the other boiler with a power output of 600 kW and a moving grate burner. Both systems had a computer controlled feed rate and combustion air supply. 

Densified waste can be burned in stoker-type boilers designed for coal or the simplest types of PTGL systems (i,e., packed bed)... 

The ignition weight loss figures, which show the percentages of uncombusted materials, for both the Japanese and the U.S. refuse are substantially lower than the standard Japanese values obtained with the conventional stoker type incinerator, which are below 10 wt.% for a furnace of less than 200 Mg/d and below 7% for a furnace of more than 200 Mg/d. 

The combustor off-gas corresponds to the throughput to the gas cooler (e.g., waste heat boiler) of a commercial plant. The gas analysis is given in Table VII, The values for the conventional stoker type incinerator are those in the case of large cities in Japan. They are average values with the exception of HC1, which is slightly higher. The amounts of particulate, SOx and HC1 contained in the off-gas of the Dry Process PUROX System are much less than those of the stoker incinerator. The reason is considered to be that the Cl", SO , etc. combine with alkali metals and shift into the slag in the converter. 

In comparison with the conventional stoker type incinerator,... 

It is also apparent that this slag is superior to that from the stoker-type incinerator in ignition loss and volumetric reduction ratio. 

The ash removed from the pyrolysis furnace (before melting), however, contains char, hence its ignition loss is slightly greater than that of the ash from the stoker-type incinerator. 

NOx and HC1 Contents of Exhaust Gas. Examples of analyses data showing the N0X and HC1 contents of the exhaust gas from this system are given in Figure A and 5 These figures show that the N0X content of the exhaust gas from this system is approx, one half that of the stoker-type incinerator. This is due to the fact that although the temperature in the pyrolysis furnace can be as high as approx. 1,100°C, the supply of air to... 

Now, the economical facets of this system will be compared with a conventional incinerator of the stoker-type. 

The results of a comparison of this system with its capacity of 150 t/d x 2 units, with a conventional stoker type incinerator... 

TYPE OF SYSTEM STOKER TYPE INCINERATING PLANT PYROLYSIS-INCINERATING PLANT... 

Research-Cottrell realized that the industrial and utility markets required different types of sulfur dioxide removal equipment. Therefore, it contracted with Ab Bahco Ventilation of Sweden to market their sulfur dioxide removal technology in the U.S. and Canada. Bahco technology is particularly applicable to industrial boiler and process applications (7, 8, 9). The first U.S. Bahco installation will handle seven stoker-type boilers at the Rickenbacker Air Force Base in Columbus, Ohio. 

The block flow diagram in Figure 5 indicates the principal functional sections of the citrate process, corresponding to the unit now operating in Terre Haute. A brief tour through these sections helps in gaining a perspective on the process. The 2000-SCFM gas stream being treated in the unit comes from a coal-fired spreader stoker-type boiler at 700°F with 25,000 lb/hr steam-rated capacity. 

Wastes containing PAHs may be effectively destroyed by various incineration processes as mentioned briefly in the above section. Weber et al. (2001) have studied the mechanisms of formation of polychlorinated diben-zofurans (PCDF), polychlorinated biphenyls (PCB), polychlorinated naphthalenes (PCN) and polychlorinated benzenes (PCBz) from the degradation of PAHs in two types of incinerators, the stoker type- and the fluidized bed incinerators. Their studies have revealed the occurrence of a sequence of steps, such as the cleavage of C-C bond in the PAHs, chlorination at these cleaved positions, further chlorination or oxygen insertion at the ortho positions to the chlorine atoms in the intermediate chlorinated species. A perylene structure in soot is proposed as the basis for the observed PCDF pattern in the fluidized bed incinerators. Polychlorinated dibenzo-dioxins (PCDD) and the polychlorinated... 

There are two main types of incineration system for municipal solid waste, the stoker-type and the fluidized bed systems. 

In the stoker-type furnace, municipal solid waste is fed on to grates by a hopper and burnt by the air which is usually blown from the bottom. The resulting ash which drops from the grates is collected at the bottom and carried away by a riddling conveyor. There are mainly three zones drying, combustion and burn-out. First the waste is dried... 

Mechanical stokers are designed to feed fuel onto a grate within the furnace and to remove the ash residue. The grate area required for a stoker of given type and capacity is determined from allowable rates established by experience. Table 6.13 lists typical fuel-burning rates for various types of stokers, based on using coals suited to the stoker type in each case. The prac-... 

Stoker type Grate type Fuel Typical release rate, 1000 Btu/h ft (MW/m ) Steam capacity, 1000 Ib/h (kg/s) ... 

To derive the least-square value of these constants, nonlinear regression analysis was performed using a statistical analysis program. A total of 185 field test data were used for the regression analysis. Air-cooled probes consisting of various alloys were exposed at three actual stoker-type WTE boilers for 700, 3000 and 6000 hours. Test conditions are summarized in Table 19.4. The metal temperature of the probes was controlled at 450 and 550°C. The obtained and derived regression equations for and are shown below ... 

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