Ashing process

The basic Solvay process remains the dominant production route for soda ash. Its continued success is based on the raw matedals, salt and limestone, being more readily available than natural alkaU. AH soda ash processes are based on the manipulation of saline phase chemistry (6,7) an understanding of which is important both to improving current processes and to the economic development of new alkaU resources. 

There are two main processes for conversion of celestite, ie, strontium sulfate, to strontium carbonate. The principal process is the black ash process. Strontium nitrate is produced by dissolving celestite in nitric acid and purifying it. Most other strontium compounds are produced from strontium nitrate. To service this market, NOAH Technologies Corporation (San Antonio, Texas) has estabUshed a plant in Mexico to manufacture most commercial- and reagent-grade strontium compounds except strontium carbonate. 

Strontium carbonate also precipitates from strontium sulfide solution with carbon dioxide. Hydrogen sulfide is generated as a by-product of this reaction and reacts with sodium hydroxide to produce sodium hydrosulfide, which is sold as by-product. The abiUty of the black ash process to produce a product exceeding 95% strontium carbonate, from ores containing <85% strontium sulfate, has led to its predorninance. 

Most barium compounds are prepared from reactions of barium carbonate [513-77-9] BaCO, which is commercially manufactured by the "black ash" process from barite and coke ki a process identical to that for strontium carbonate production. Depending on the co-product, soda ash and/or carbon dioxide are also consumed. 

Manufacture. An outline of the black ash process for BaCO manufacture is shown ki Figure 1. It is from the appearance of the product exiting the thermal reduction step that the process derives its name. 

Sulfide Solution Concentration. Tire by-product of the black ash process has considerable bearing on the ultimate economic viabiUty of barium production. It is desirable to be able to vary by-products to rnaxiaiize earnings. Sodium sulfide [1313-82-2 Na2S, sold as 60% flake, and sodium bisulfide [16721-80-5] NaHS, sold as 45% solution or as 70% flake, are t)-q)ically co-produced. 

This is usually prepared by either a base-exchange method using sodium zeolite, by a lime-soda ash process, or by the addition of sodium hexametaphosphate. In addition to the bacteria derived from fhe mains water, additional flora of Bacillus spp. and Staphylococcus aureus may be introduced into systems which use brine for regeneration and from the chemical filter beds which, unless treated, can act as a reservoir for bacteria. 

Cleaning SCF s such as CO2 can be used to clean and degrease quartz rods utihzed to produce optical fibers, products employed in the fabrication of printed-circuit boards, oily chips from machining operations, precision bearings in military applications, and so on. Research is in progress for removing residues in etch/ash processes in m icroelectronics. 

In the second stage, the black ash process, the sodium sulfate was reduced to sodium sulfide and then converted to sodium carbonate by calcining with limestone and coal in a rotating kiln known as a black ash furnace or revolver ... 

Lurgi dry ash process Coal (bitumi- nous, lignites) LHV Fuels, chemicals, ammonia (several pants 100 MW plus 361 MW) 18,000... 

BHEL pilot plant Lurgi dry ash process Schwarze Pumpe... 

In the soda ash process, solid or dissolved sodium carbonate is added to bari-... 

Density separation is also applicable to wet bottom ash processing and can be required in... 

Air classification is perhaps the simplest fly ash processing option and is normally employed to improve the fineness of the ash (i.e., remove coarse particles). A typical cyclone classifier uses centrifugal force to separate fine particles from an air stream. The particles enter tangentially into a cylindrical chamber dispersed in an air stream and centrifugal force forces the coarser particles to the wall of the cylinder while the air stream and finer particles spiral to an inner vortex. The air exits from the inner core via an outlet port while the particles slide down the chamber walls and exit the bottom. 

Perhaps the most significant advantage of using froth flotation to beneficiate fly ash is the ability to process ash that has been impounded in disposal ponds and landfills. This is advantageous for several reasons. First, it effectively de-couples ash beneficiation from ash production. There is no need for the utility to alter disposal practices or install additional ash handling equipment in order to accommodate ash processing since the feed to the processing plant... 

The major reactions are complicated by a number of minor or secondary reactions, and by impurities in the raw materials. As a result the black ash may contain 1 to 2 per cent, of sodium silicate to If per cent, of sodium aluminate 1 per cent, of sodium ferrous sulphide small proportions of sodium cyanide and thiocyanate derived from the nitrogen of the coal a relatively small amount of ultramarine etc. Proposals to use barium carbonate, etc., in place of limestone in the black-ash process are indicated in connection with the preparation of sodium carbonate from sodium sulphide. 

Black ash process -for barium carbonate [BARIUM COMPOUNDS] (Vol 3)... 

Solvay and Company was formed as a family enterprise in 1863. Numerous difficulties were encountered at first until Solvay s ammonium process of manufacture was perfected, replacing the old Leblanc black ash process. ... 

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