Coal combustion wastes gases

Fuel switch. The choice of fuel used in furnaces and steam boilers has a major effect on the gaseous utility waste from products of combustion. For example, a switch from coal to natural gas in a steam boiler can lead to a reduction in carbon dioxide emissions of typically 40 percent for the same heat released. This results from the lower carbon content of natural gas. In addition, it is likely that a switch from coal to natural gas also will lead to a considerable reduction in both SO, and NO, emissions, as we shall discuss later. 

Figure 8.7 PCDD/F I-TEQ (pg/g) values of flue gas after the combustion of lignite coal, solid waste, and PVC in the samples without inhibitor and 19 different compounds used with a 10% inhibitor of the fuel. (From M. Pandelova et al.. Environ. Sci. Technol, 2005.)...

Anthropogenic sources of fluoride include fossil fuel combustion and industrial waste. Hydrogen fluoride is water soluble and emissions are readily controlled by acid gas scrubbers. HF emission from coal combustion, that is considered to be the main anthropogenic source of HF, was estimated to be 0.18 Tg annually emission of HF from the combustion of petroleum and natural gas is almost certainly negligible [24]. Apparently only limited data are available concerning total annual emissions of HF from industrial operations however, there is evidence that emissions of fluorides have been declining [24,25]. 

The addition of lime to control acid drainage from mining wastes typically produces calcium arsenates (Pichler, Hendry and Hall, 2001). Bothe and Brown (1999) further concluded that lime precipitates As(V) as a number of hydroxyl and hydrated calcium arsenates (Ca4(OH)2(AsC>4)2 4H2O, CaslAsCLLOH (arsenate apatite), and/or Ca3(AsC>4)2 3H2O) rather than anhydrous tricalcium orthoarsenate (Ca3(As04)2). Calcium arsenates also occur in coal combustion byproducts (Chapter 7). In the flue gas treatment systems of coal combustion facilities, volatile arsenic can readily react with calcium to form the arsenates on the surfaces of flyash and injected lime (Seames and Wendt, 2000 Yudovich and Ketris, 2005, 175). 

Gas/gas reaction in which solids are transformed Coal combustion Gasification Incineration of waste Catalyst regeneration... 

Radionuclides are also liberated by the burning of coal in thermal power stations. Depending on its origin, coal contains various amounts of U and Th, and these as well as the daughters are released by combustion. Volatile species, in particular Rn, are emitted with the waste gas, Pb and Po are emitted with the fly ash, and the rest, including U and Th, is found in the ash. The global release of Rn is of the order of 10 Bq per year. 

For fuels with a high content of volatile matter, the gas combustion downstream of the bed is crucial for emission control. The fuel bed is the Drst stage in the combustion process and generates the conditions for the latter part. A review of available literature on the experimental simulation of solid fuels confirms that the knowledge of coal combustion is more detailed than that of biomass and municipal solid waste. The knowledge of biomass gasification devices today is extensive however, sec for example La... 

ABSTRACT Calcium-enriched bio-oil (CEB) can be used for flue gas desulfurisation in coal and waste combustion chambers. It is produced by mixing biomass derived fast pyrolysis oil with calcium oxide. The aim of the proposed project is to develop a technology i) to produce calcium-enriched bio-oil with a calcium content of 13 wt,%, and ii) to test the CEB in a combustion chamber by co-firing it with a sufur-containing fuel. In this paper the production method of CEB will be elucidated, and small-scale experiments related to CEB spraying will be presented. Finally, co-combustion experiments of a sulfur-containing fuel with CEB in a small flame tunnel (20 kW, ) will be reported. 

Ideally, fuel sources for cooking and distilling fuel alcohol would come from solid fuels, such as coal, wood and crop residues. Such practice would minimize the amount of high-quality liquid and gaseous fuels consumed for heating and increase the total quantity of liquid fuels available. Alternative fuels include natural and LP gas and fuel oil alcohol product mined solid fuels (coal, peat, anthracite) crop and forest residues, farm and forest fuel crops and combustible wastes methane gas produced from animal wastes and biomass and solar radiation. 

The particulate matter carried forward in gas streams can also cover a wide range of materials including inorganic mineral matter, organic particles and "natural" materials like wood particles. Inorganic substances possibly with carbon particles, are common foulants in combustion systems where fossil ftiels like oil and coal or waste materials like domestic refuse are burnt. Even with "clean" fuels such as natural gas, problems of fouling may arise as a result of poor combustion... 

In general the combustion of natural gas does not give rise to problems of fouling provided that the equipment, particularly the burners, is well maintained and satisfactorily operated. The fuel is purchased as a relatively high priced commodity, the supplier having carried out any treatment that may be necessary, e.g. the removal of water and H. The result is a fuel of consistent properties that makes combustion management a straightforward matter, in contrast to problems that may accompany the use of solid fuels such as coal or waste material, where consistency may be variable. 

In this type of combustion facility pulverized coal is burned with air in a reactor in the form, for example, of a horizontal cyclone. In this reactor high temperatures of ca. 1600°C are achieved and the ash components of the coal are melted to form slag. The liquid slag collects on the reactor wall as a result of the fluid-flow characteristics in the reactor. It flows out of the reactor through the tap hole and is then granulated in a water bath. The waste gas is cooled in boilers, whereby high-pressure steam is produeed, which is used to drive steam turbines for power generation. 

The process involving the high-temperature combustion of coal at 1600 °C and subsequent cooling of the waste gas to 700 °C is calculated on the basis of... 

On cooling the gas phase some gas components condense and thus lead to the formation of deposits in the boiler. Table 7.9 shows the composition of the condensed phases and the residual waste gas. The change in concentration of the main gas components is low on rapid cooling from 1600 to 700 °C. The condensed phases mainly consist of compounds of K and Na with Cl, P, and S. The low-melting sulfates, phosphates, and chlorides form first a liquid layer where solid dust particles can be deposited by sticking. The composition of the input fuel (coal, and waste material) besides the temperature and O2 partial pressure in the combustion chamber, determine... 

Smog SO2.HCI, CO, Sulfuric acid mist Industrial waste gas Combustion of coal Smoke treatment... 

---