Combustion efficiencies, improvement

High combustion efficiency—improved combustion efficiency is attained through the use of a circulating fluidization-mode combustion mechanism. 

Another furnace that does not require fuel preparation is the stoker boiler, which was used by New York State Electric Gas Corporation (NYSEG) in its TDE tests. At NYSEG, the stoker boiler, which has a 1649°C (3000°E) flame temperature (as does the cyclone boiler), has routinely blended low quaUty coal, and more recently, wood chips with its standard coal to reduce fuel costs and improve combustion efficiency. In the tire-chip tests, NYSEG burned approximately 1100 t of tire chips (smaller than 5x5 cm) mixed with coal and monitored the emissions. The company determined that the emissions were similar to those from burning coal alone. In a second test-bum of 1900 t of TDE, magnetic separation equipment removed metal from the resulting ash, so that it could be recycled as a winter traction agent for roadways. 

The compressor can be driven by electric motors, gas or steam turbiaes, or internal combustion (usually diesel) engines. The compressor can also be a steam-driven ejector (Fig. 7b), which improves plant reUabiUty because of its simplicity and absence of moving parts, but also reduces its efficiency because an ejector is less efficient than a mechanical compressor. In all of the therm ally driven devices, turbiaes, engines, and the ejector mentioned hereia, the exhaust heat can be used for process efficiency improvement, or for desalination by an additional distillation plant. Figure 8 shows a flow diagram of the vertical-tube vapor compression process. 

In AFBC units, heat is removed from the flue gas by a convection-pass tube bank. The particulates leaving the boiler with the flue gas consist of unreacted and spent sorbent, unburned carbon, and ash. Multiclones after the convection pass remove much of the particulate matter and recvcle it to the combustor, increasing the in-furnace residence time an improving combustion efficiency and sulfur retention performance. Bubbling PFBC units do not have convection-pass tube banks and do not recycle solids to the boiler. 

Give an example of how opacity monitoring of a coal-fired boiler could be used to improve combustion efficiency. 

Measures such as improved process design, operation, maintenance, housekeeping, and other management practices can reduce emissions. By improving combustion efficiency, the amount of products of incomplete combustion (PlCs), a component of particulate matter, can be significantly reduced. Proper fuel-firing practices and... 

Typically, online cleaning must be carried out fairly slowly and carefully, so that the programs may take 3 to 6 months, perhaps longer, before particularly satisfactory results are achieved. If the boiler is particularly dirty before an online clean is considered necessary, then the combustion efficiency will be lower than desirable. It consequently will take some time before this reduced efficiency improves significantly, and therefore there is an additional fuel cost that must be considered, as well as the cost of the online cleaning program. 

Fuel treatments have been used for very many years as an aid to improving the combustion efficiency process. Old formulations often used saw dust, wood flour, common salt, zinc sludge, ground oyster shell, and similar crude ingredients, but could still provide a dramatic effect when thrown into a fire. The metallic salts present (sodium in salt, zinc in sludge, and calcium in shell) acted as catalysts that dramatically lowered the ignition temperature of soot deposits from around 1100 °F/590 °C to only 600 °C/315 °C the fire burned vigorously and the soot disappeared. 

NOTE Where the primary problem is to improve combustion efficiency, the product typically is added to the fuel handling system via an automatic feeder and used continuously at a rate of 0.5 and 1.5 lb per ton of fuel. 

An intrinsic, exothermic water-gas shift reaction occurs in the steam reformer reactor. The combined reaction, steam reforming and water gas shift, is endothermic. As such, an indirect high temperature heat source is needed to operate the reactor. This heat source usually takes the shape of an immediately adjacent high temperature furnace that combusts a small portion of the raw fuel or the fuel effluent from the fuel cell. Efficiency improves by using rejected heat from other parts of the system. Note that the intrinsic water-gas shift in the reactor may not lower the... 

In future work the method will be improved so that measurements of combustion efficiency can be carried out. Other types of conversion concepts will be studied by the method. 

When A1 particles are added to GAP-AN pyrolants, agglomerated A1 fragments are formed on the burning surface. However, when A1 particles are mixed with pyrolants composed of GAP, AN, and AP, numerous flame streams are formed in the gas phase. The A1 particles are oxidized by the gaseous decomposition products evolved by the AP particles. The combustion efficiency of the A1 particles is improved significantly by the addition of the AP particles. 

The control of carbon monoxide emissions is based on the principle that less of the gas is produced when the efficiency of combustion is improved. One device to achieve this objective is the catalytic converter, now required on all motor vehicles sold in the United States. A catalytic converter provides a second stage of combustion in motor vehicles, allowing carbon monoxide and other unburned components of a fuel to be oxidized before release into the atmosphere. (The operation of a catalytic converter is described later in this chapter.)... 

Fluidized-bed combustion systems use a heated bed of sandlike material suspended (fluidized) within a rising column of turbulent air to burn many types and classes of waste fuels. The vendor claims that this technique results in improved combustion efficiency of high moisture content fuels and is adaptable to a variety of waste -type fuels. The scrubbing action of the bed material on the fuel particle is said to enhance the combustion process by stripping away the carbon dioxide and char layers that normally form around the fuel particle. This allows oxygen to reach the combustible material much more readily and increases the rate and efficiency of the combustion process. 

The patent literature on jet fuels is very extensive. Some examples of patents granted on jet fuels are as follows Fox Britton (Ref 2) claim the incorporation of viscosity-index improvers in jet fuels to improve engine start-up combustion efficiency over a wide range of temps. Materials claimed to be effective are ethyl glycol, Acryloid Sanotex... 

Since realization of the expected performance depends on rate of combustion and combustion efficiency, many studies have been made on catalysis. The studies of iron oxide have been particularly fruitful. The activity, amount and particle size of the iron additive can be an important tool in adjusting the performance of a propellant formulation. In many propellant formulations, performance can be improved by using soluble catalysis. 

Tnjector design determines combustion efficiency, engine stability, heat transfer, and performance reproducibility (4). The injector, in turn, is described by orifice construction and location and by the injector feed passage and supply system. Baffles may help to improve engine stability. 

Exhaust emissions of HC, CO, and NOx—the products of incomplete combustion—are controlled primarily by a catalytic converter, in conjunction with exhaust gas recirculation and increasingly sophisticated technology for improving combustion efficiency, including electronic emission controls. See emissions (stationary source),... 

In addition to the two combustors introduced briefly above, researches and development on the application of gas-continuous impinging streams to combustion has been carried out since the 1970s, e.g., the investigations made by Goldberg and Essenhigh [ 146], Ziv etal. [12], Goldman [147-149] and Liu et al. [150]. Mostly, these works involve experimental studies and model analyses, and mainly aimed at the improvements of combustor structure and the arrangement of burners in order to increase combustion efficiency. Most of the experimental combustors employed were very small and their application seems far from practical. 

The widespread use of combustion turbines in industry and by electric utilities, as well as the generating efficiency improvement offered by new combined cycle plants in conjunction with combustion turbines, represents an attractive market opportunity for SRC-II distillate coal liquids. 

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