Extraction, cost

All ore mineral deposits lie in or on solid rocks of which the Earth s crust is predominantly composed. The geological processes which are responsible for the formation of rocks also form the ore bodies associated with them. For the formation of an ore body, the metal or metals concerned must be enriched to a considerably higher level than their normal crustal abundance. The degree of such enrichment below which the extraction cost makes the processing of the ore uneconomical is termed the concentration factor. Typical values of the concentration factor for some of the common metals are given in Table 1.5. 

Containment of the flushed contaminants and spent flushing solutions is essential to successful application of in situ flushing. This happens when the treatment zone is bounded geologically by materials with relative low hydraulic conductivity. Depth to the contaminated zone is a limiting factor because of the higher injection and extraction costs that are required compared with more shallow contaminated zones. Contaminants can be easily removed when the flushing solution follows the same channels as the pollutant. Also, possible mechanical disturbance of the surface layer of the contaminated area may render the contaminants inaccessible. 

The NEA/IAEA system splits resources into known resources and undiscovered resources . Known resources are further divided into Reasonably assured resources (RAR) and inferred resources (IR) . The categories are internally divided into various cost classes, according to suggested extraction costs as shown in Table 4.2. The definition of these classes also changed from time to time. The classes below 40/kg U , below 80/kg U and below 130/kg U are the most widely used. Undiscovered resources are further subdivided into two categories, namely prognosticated and speculative resources. Prognosticated resources are subdivided into... 

Resource category Extraction cost ranges ( /kg U) Uranium resources (kt) Individual Total Data reliability... 

A typical worldscale olefins plant producing a billion pounds a year of ethylene from heavy liquids can also yield up to 50 million pounds of styrene. Since the styrene is a coproduct, and the extraction costs are modest, the economics are very attractive compared to on-purpose styrene. 

For in situ steam-enhanced extraction, cost estimates range from about 50 to 300/yd depending on site characteristics, particularly the depth of contamination and soil permeability. The more wells required per unit area (a function of contaminant depth), the higher the cost of remediation (D12529B). For more specific cost estimates of in situ thermal desorption techniques, refer to the individual technologies in the RIMS 2000 library/database. 

There have been reported numerous advantages of SFE for the extraction of natural products including reduction of extraction cost and time, environmental acceptance, and lack of toxicity to human health compared with conventional organic solvent extraction. However, the high polarity of alkaloids due to salt formation in plant tissue has made it difficult to extract them using SFE. In order to develop a universally acceptable SFE method for alkaloids present in plant materials, a basified modifier has been introduced to the SFE of selected alkaloids. On the basis of these results, it is believed that SFE using basified modifiers can be used as an alternative to conventional solvent extraction for alkaloids from plant material. 

The refining of raw sugar by solvent extraction costs less in energy and materials and can be done in a plant that is much less expensive to operate than a conventional plant (2). 

Large gas plants often have the advantage that when the price of naphtha (oil) is low relative to the price of gas, ethane can be left in the gas stream and sold at the gas price thus saving the extraction cost. Conversely, in time of low gas price and high oil price, ethane can be extracted and profitably sold. 

Within the context of proteins as polymer materials the number is still further limited, since only very few are available in sufficient bulk at low extraction cost to consider post-processing them into useful materials. More particularly, the fibrous proteins, such as collagen, certain plant proteins such as gluten, the component of wheat responsible for giving the elastic properties to bread doughs, and proteins produced from soy have been exploited to a limited degree, as we shall see below. In recent years there has also been renewed interest in fibrous silk proteins, from silk worms, spiders (as web-silk) and also from bioengineering routes. 

It is technically feasible to extract uranium from seawater. There are, however, sufficient quantities of terrestrial uranium deposits, with extraction costs well below the extraction costs of uranium from seawater. 

All of these applications are usually characterized as being barely profitable and, therefore, do not justify the additional extraction costs during processing. In the last few years, however, numerous research studies have shown a relationship between (/-limonene and the prevention of some forms of cancer (Girard and Mazza, 1998 Braddock, 1999). This gives these essential oils functional characteristics and attracts great interest to the incorporation of these oils in food products. 

The extraction costs of solids depend on several factors. One is the specific solvent ratio, kg C02/kg raw material, which is required to achieve the intended extraction result under optimised process conditions. The usual aim is to separate 85-95% of the valuable extract components a more complete extraction might not be economic. The solvent ratio is determined by the amount and the solubility of the extract to be separated from the starting material. In most cases the solvent ratio used for extraction is between 5 and 50 kg C02/kg material. 

Using 16 L of acetone at a cost of 125, 32 Soxhlet extractions cost... 

The production cost of limestone depends on a number of factors. The nature of the deposit can be important massive deposits with little overburden, horizontal strata and consistent physical/chemical properties favour low extraction costs, particularly if linked with a large-scale operation. Selection of appropriate equipment to keep the combined costs of labour, capital charges and other operating costs to a minimum is important to ensure a strong competitive position (see chapters 4 and 5). 

Table 12.4 The EU share of the world s recoverable uranium resources (RAR+inferred) by extraction cost...

Instrument-based extraction techniques such as supercritical fluid extraction (SEE) and pressurized liquid extraction (PEE) offer advantages because of their potential for automation, more selective isolation of residues through tuning of parameters, and on-line clean-up of samples. Their applications have been slowed by the limited number of commercially available instruments, additional extraction costs, and instrumental downtime. Although several applications have been developed using SEE and PEE, these techniques are not widely used in routine laboratories. 

The multiple hearth performs a product fractionation function that could reduce extraction costs of high value chemicals. 

The sea is so vast that if the concentration of a substance in seawater is 1 part per billion (IX 10 g per kilogram of water), there is 1 x 10 kg of the substance in the world ocean. Nevertheless, because of high extracting costs, only three substances are obtained from seawater in commercially important amounts sodium chloride, bromine (from bromide salts), and magnesium (from its salts). 

Polysaccharide extraction Hot water extraction Cost-effective and simple Time consuming, requires high temperature which may affect bioactivities of polysaccharides [71]... 

Cp e is the extraction cost for product isolation and is the extraction running... 

Extraction costs [6]. In a pilot plant the engineer estimates the cost (MU) of a concentrated product obtained from roots. The model is expressed as a function of time through the following equation ... 

The hazardous impacts of solvents for operators and also the environment are considered as another problem related to their usage. This process is suitable for laboratory studies only with limited success in pilot-plant and large scale processing. Recently, Metabolix (USA) has been using organic solvents for PHA recovery, which could be a promising process for reducing PHA extraction costs. ... 

---