Fuels black liquor

In the operation of a recovery boiler, the inorganic fraction of the fuel (black liquor) ends up as a molten mixture of inorganic salts (smelt) with some unbumed carbon. The presence of this molten salt in the boiler results in a hazardous situation if it were to be contacted with water or a dilute black liquor. Essentially all boUer explosions have, therefore, resulted from an accident wherein water did contact the smelt. About one-third of the explosions can be traced to an operational situation where the fuel (black) liquor was very dilute (or even pure water) and this fluid fell to the furnace floor to contact smelt. In another one-third of the cases, a water tube failed and allowed direct ingress of water into the boiler. The remaining third were assigned to miscellaneous events—all of which allowed water to enter. 

Jet fuel Gasoline Diesel fuel Black liquor... 

The term waste heat boiler is also widely used to cover heat recovery boilers (HR boilers), which tend to be direct-fired steam generators, albeit employing low-grade by-product fuels such as bagasse, wood bark, com cobs, peanut shells, blast furnace gas, black liquor, and the like. 

Demirbas, A., Karshoglu, S., and Ayas, A. (1996). Hydrogen Resources Conversion of Black Liquor to Hydrogen Rich Gaseous Products, Fuel Science and Technology International 14(3). pp. 451-463. 

Mtyor TaUoil spent acid system Spend acid from talloil operation was added directly to fiimace separately from black liquor fuel... 

Black liquor - [OXYGEN] (Vol 17) -from paper mills for fuel [STEAM] (Vol 22)... 

The process is conducted at the high pH in the presence of sodium sulfide, sodium hydrosulfide, and sodium hydroxide at 150-180°C for about 2 hours (Fig. 33.26). Along with the primary cellulose product, the process generates a solution containing dissolved lignin, most of the wood s hemicellu-loses, and spent pulping chemicals ( black liquor ). This solution is used in the kraft recovery boiler as a source of power for the mill and fuel for chemical recovery operations crucial to economic operation. The chemistry of pulping reactions has been the subject of much study, and summaries are available the literature.425 127... 

Dayton, D. C. and Frederick, W. J., Direct observation of alkali vapor release during biomass combustion and gasification.2. Black liquor combustion at 1100 degrees C. Energy Fuels 1996, 10 (2), 284-292. 

Liquors from Neutral Semichemical Pulping and from Kraft Pulping. In making neutral sulfite semichemical pulp, the black liquors may have about 10 parts of water to 1 part of total solids, of which about one-third is sodium acetate and sodium formate. After evaporation to about 1 part solids to 1 part water, sulfuric acid is added to the concentrate to free the acetic and formic acids. When the concentrate is extracted with acetone, the mixed acids are obtained, the acetone is separated for recycle, and the acids are concentrated and refined. The raffinate is stripped and is passed to the usual furnace to be burned for recovery of the inorganic salt values. This process gives a smelt of sodium sulfate, which may be used in the kraft process as chemical makeup. The loss of the fuel value of the acetic and formic acids is practically negligible. 

The energy potential of black liquor, 1.05 EJ/year, is used commercially and is not potential in the sense that it has not been realized yet. If use of the kraft process increases, production of black liquor and its use as a boiler fuel will also increase. 

Historically, a classic example of an evaporation process is the production of table salt. Maple syrup has traditionally been produced by evaporation of sap. Concentration of black liquor from pulp and paper processing constitutes a large-volume present application. Evaporators are also employed in such disparate uses as desalination of seawater, nuclear fuel reprocessing, radioactive waste treatment,preparation of boiler feed waters, and production of sodium hydroxide. They are used to concentrate stillage waste in fermentation processes, waste brines, inorganic salts in fertilizer production, and rinse liquids used in metal finishing, as well as in the production of sugar, vitamin C, caustic soda, dyes, and juice concentrates, and for solvent recovery in pharmaceutical processes. 

As far as possible, the costs are quoted om data valid for today s activities in Sweden. Some 20 wood pellet plants produce three hundred thousand tons of biofuel for commercial use mainly in utility cortqianies. The reason for this is the CO2 tax in Sweden laid on all fossil fuels, The total use of wood fuel in Sweden is about 1 million tons or 5 TWh, excluding the use of black liquor in the pulp industry and other similar utilisations. The issue about CO2 taxation on fossil fuels in Sweden is here left out of the discussion although that, of course, forms the basis for the situation. 

Black liquor is not an ideal fuel, partly because of its moisture and partly because of the very high ash content, i.e. the inorganic elements. It has been difficult to achieve steam temperatures above 480°C, compared to 540°C with coal. The ability to generate electricity can be achieved only with higher combustion temperatures by burning at a higher solids content (80%). Newer steels and designs can limit corrosion from small amounts of chlorides and potassium. New recovery furnaces can have rated capacities of over 2500 tonnes of dry solids per day. 

Power Production. Steam cycles for generation of electric power use various types of boilers, steam generators, and nuclear reactors operate at subcritical or supercritical pressures and use makeup and often also condensate water purification systems as well as chemical additives for feedwater and boiler-water treatment. These cycles are designed to maximize cycle efficiency and reliability. The fuel distribution of sources installed in the United States from 1990—1995 are as follow coal, 45% combined cycle, 27% miscellaneous, 14% nuclear, 11% solar, oil, and geothermal, 1% each and natural gas, 0.3%. The 1995 summer peak generation in the United States was 620 GW (26). The combined cycle plants are predominantly fired by natural gas. The miscellaneous sources include bagasse, black liquor from paper mills, landfill gas, and refuse (see Fuels frombiomass Fuels fromwaste). 

This instrument has been used to determine the water contents of many substances, included among them are polymers (131-137) pharmaceutical products such as penicillin, vitamins (138) effervescent tablets (139). Nuclear fuels, pulping black liquor, minerals (141) and coal (140) have also been studied. 

This paper presents some of the opportunities CFD offers when applied to analyse different combustion systems. Practical examples presented are ash deposition predictions on heat exchanger surfaces and walls in a bubbling fluidised bed furnace and detailed nitrogen oxide emission predictions for the same furnace type. Furthermore, the extension of a standard model using process specific data is presented for the fuel conversion process in a black liquor recovery furnace. 

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