Residue disposal

Additional operations essential to commercial bauxite processing are steam and power generation, heat recovery to minimise energy consumption, process liquor evaporation to maintain a water balance, impurity removal from process liquor streams, classification and washing of ttihydrate, lime caustication of sodium carbonate [497-19-8] to sodium hydroxide [1310-73-2] repair and maintenance of equipment, rehabiUtation of mine and residue disposal sites, and quaUty and process control. Each operation in the process can be carried out in a variety of ways depending upon bauxite properties and optimum economic tradeoffs. 

Residue Disposal. The major environmental problem in the Bayer process is disposal of bauxite residue which is effected by marine disposal, lagooning, use of underdrain lakes, or semidry disposal. Marine disposal in oceans or rivers, diluting the alkaline residue by large quantities of water, is environmentally unacceptable. Lagooning behind retaining dikes built around clay-sealed ground is commonly used, but there have been isolated leaks into aquifers. This has motivated installation of underdrains between the residue and clay-sealed, plastic-lined, lake bottom. This design removes the hydraulic head from the lake bottom and improves consoHdation of the residue. 

Once the candidate corrective measure alternatives have been identified, a more detailed evaluation of each alternative needs to be undertaken. From an engineering perspective, the first step in the evaluation process would include the development of a conceptual design for each alternative. The conceptual design would consist of a process description, a process flow diagram and a layout drawing. Preliminary sizing of equipment and utility and land requirements would be developed. In addition, chemical requirements and residuals produced can be estimated. From the conceptual design, permitability and residuals disposal issues can be identified and addressed. 

It is not currently feasible to achieve a zero discharge of chemical pollutants from metal finishing operations. However, substantial reductions in the type and volume of hazardous chemicals wasted from most metal finishing operations are possible.8 Because end-of-pipe waste detoxification is costly for small- and medium-sized metal finishers, and the cost and liability of residuals disposal have increased for all metal finishers, management and production personnel may be more willing to consider production process modifications to reduce the amount of chemicals lost to waste. 

Waste pesticides and container residues disposed of by farmers on their own land. 

Phytoextraction 15- 40 18-60 Time/land commitment Residue disposal... 

Soil extraction and leaching 250- 500 8-12 5,000-m minimum chemical recycle Residue disposal... 

The cost to operate a full-scale BCD system is estimated to be about 245 per ton. The major savings in the BCD over incineration treatments is in the lack of residuals disposal costs because no toxic substances such as dioxins and furans are created at the relatively low temperamres used in the BCD process. Since treated soil normally meets the requirements for on-site disposal, the costs of transport and off-site disposal are also eliminated (D15525J, pp. 11, 12). 

The vendor estimates costs for operating labor, utilities, maintenance and repair, treated residue disposal, and disposal of waste items excluded from the current system to be between 0.05 and 0.14/lb, depending on the size of the machine. This estimate is based on 60 hr per week operation, and utilities costing 0.06/kWh of electricity, 0.096/gal of water, and 0.048/gal of sewer discharge (D14408B, p. 4). The vendor estimates the price of an IDS unit to be from 450,000 to 5,000,000, with capacity ranges from 100 to 6000 Ib/hr (personal communication, Brian Bateson, Vance IDS, 12/3/97). 

As in the other members of the superfamily, the heme pocket of ligninolytic peroxidases includes two conserved histidine residues disposed above and below the heme plane (Fig. 3.4a). The second histidine acts as the fifth ligand of the heme iron, occupying a proximal position, while the first one is at a higher distance being, therefore, called distal histidine (by extension, the regions located below and above the heme plane are also called proximal and distal regions). 

Thus forests are made more conducive to the production of commercial timber, and a residue disposal problem is solved by generating electricity. As energy prices continue to escalate, increasing uses may be found for regional biomass resources. 

Basis for Plant Design. The composition of municipal refuse is assumed as shown in Table III. The municipal refuse has the lower calorific value of ca. 1,500 Kcal/Kg. Plant size of 600 T/D is assumed. The capital investment costs, utilities, etc. were calculated using contacts with equipment vendors. Cost for repairs are assumed to be two percent of the plant construction cost per year. Unit costs of utilities and unit prices of recovered energy and material are assumed, based on the actual prices in 1979. Ash and other residues disposal cost is assumed to be 2,450 Yen/T, taking note of the representative cost data of large cities in Japan, The grant available to a municipality is assumed to pay up to fifty percent of the capital investment. The remaining investment cost must be amortized in fifteen years with the interest rate of six percent. 

Operation costs for the plant excluding cost of residue disposal, in calender year 1977, is roughly estimated to be about 22.36 per ton as indicated below ... 

Alkali- terf-butoxide, in particular the potassium compound, is frequently used in this book, in combination with -butyllithium. In many cases the 1 1 molar mixture of -BuLi and r-BuOK can be used instead of the dangerous and (much more) expensive fm-butyllithium. To maintain a good quality, the powder should be stored under indert gas in flasks which are closed by rubber stoppers. Glass stoppers should not be used, as there is the possibility that they may become stuck due to alkali residues. Disposal of bad-quality material can best be carried out by cautiously adding it (in small portions) to a sufficient amount of 96 % ethanol followed by water. 

Farmer JG, Thomas RP, Graham MC, Geelhoed JS, Lumsdon DG and Paterson E (2002) Chromium speciation and fractionation in ground and surface waters in the vicinity of chromite ore processing residue disposal sites. J Environ Monit 4 235-243. 

Reutilization of residues by linking of production processes is not another form of residue disposal, but enables resources to be used as economically as possible. However. this does lead to additional interdependencies, which may decrease flexibility. 

The quality and profitability of a product must be ensured under given market conditions. In principle, a new production process can be put into practice only if the costs, including the costs of residue disposal, are less than those of the existing process [69]-[71], For any investment decision [72],... 

A. J. Poll, Recovery Rates Achieved by Kerbside Collection Schemes and their Impact on Residue Disposal in proceedings of Waste Handling, Processing and Recycling, London, Institution of mechanical Engineers, pp. 53-61 (1W3). 

Residue disposal. Whether the recovery operation is for the removal of water from a solvent, removal of residue or separation of two or more solvents there will always be some waste material to get rid of. Mode 4 plays a valuable role in getting rid of the residue or distillate streams at low costs or even small credits to the process. The disposal of the water phase is always a charge to the job and the capability of activated carbon to remove solvents from water is important here. Like transport this is an extra which must be taken into accoimt for each job. 

An operating cost break down at current prices in Spain is depicted in Table II in US dollars at the prevalent exchange rate, 170 PTA per USD. A 10% contingency factor has been allowed. As a worst case scenario, a residue disposal cost has been included, assuming that the gypsum was not sold. 

Aqueous solutions containing uranyl or thorium compounds can be evaporated to dryness and the residues disposed of as radioactive waste. Because of their toxicity, solidification may be necessary prior to burial at a low-level radioactive waste site. 

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