white quartz sand making production plants

silica sand processing & sand washing plant equipment

silica sand processing & sand washing plant equipment

Silica sand low in iron is much in demand for glass, ceramic and pottery use, and for many of these applications clean, white sand is desired. Impurities such as clay slime, iron stain, and heavy minerals including iron oxides, garnet, chromite, zircon, and other accessory minerals must not be present. Chromium, for example, must not be present, even in extremely small amounts, in order for the sand to be acceptable to certain markets. Feldspars and mica are also objectionable. Generally, iron content must be reduced to 0.030% Fe2O3 or less.

Silica sand for making glass, pottery and ceramics must meet rigid specifications and generally standard washing schemes are inadequate for meeting these requirements. Sand for the glass industry must contain not more than 0.03% Fe2O3. Concentrating tables will remove free iron particles but iron stained and middling particles escape gravity methods. Flotation has been very successfully applied in the industry for making very low iron glass sand suitable even for optical requirements.Sub-A Flotation Machines are extensively used in this industry for they give the selectivity desired and are constructed to withstand the corrosive pulp conditions normally encountered (acid circuits) and also the abrasive action of the coarse, granular, slime free washed sand.

The flowsheet illustrates the more common methods of sand beneficiation. Silica may be obtained from sandstone, dry sand deposits and wet sand deposits. Special materials handling methods are applicable in each case.

The silica bearing sandstone must be mined or quarried much in the manner for handling hard rock. The mined ore is reduced by a Jaw Crusher to about 1 size for the average small tonnage operation. For larger scale operations two-stage crushing is advisable.

The crushed ore is reduced to natural sand grain size by Rod Milling. Generally, one pass treatment through the Rod Mill is sufficient. Grinding is done wet at dilutions in excess of normal grinding practice. A Spiral Screen fitted to the mill discharge removes the plus 20 mesh oversize which either goes to waste or is conveyed back to the mill feed for retreatment.

Sand from such deposits is generally loaded into trucks and transported dry to the mill receiving bin. It is then fed on to a vibrating screen with sufficient water to wash the sand through the 20 mesh stainless screen cloth. Water sprays further wash the oversize which goes to waste or for other use. The minus 20 mesh is the product going to further treatment.

The sand and water slurry for one of the three fore-mentioned methods is classified or dewatered. This may be conveniently done by cyclones or by mechanical dewatering classifiers such as the drag, screw, or rake classifiers.

From classification the sand, at 70 to 75% solids, is introduced into a Attrition Scrubber for removal of surface stain from the sand grains. This is done by actual rubbing of the wet sand grains, one against another, in an intensely agitated high density pulp. Most of the work is done among the sand grains not against the rotating propellers.

For this service rubber covered turbine type propellers of special design and pitch are used. Peripheral speed is relatively low, but it is necessary to introduce sufficient power to keep the entire mass in violent movement without any lost motion or splash. The degree of surface filming and iron oxide stain will determine the retention time required in the Scrubber.

The scrubbed sand from the Attrition Machine is diluted with water to 25-30% solids and pumped to a second set of cyclones for further desliming and removal of slimes released in the scrubber. In some cases the sand at this point is down to the required iron oxide specifications by scrubbing only. In this case, the cyclone or classifier sand product becomes final product.

Deslimed sand containing mica, feldspar, and iron bearing heavy minerals can be successfully cleaned to specifications by Sub-A Flotation. Generally this is done in an acid pulp circuit. Conditioning with H2SO4 and iron promoting reagents is most effective at high density, 70-75% solids. To minimize conditioning and assure proper reagentizing a two-stage Heavy Duty Open Conditioner with Rubber Covered Turbine Propellers is used. This unit has two tanks and mechanisms driven from one motor.

The conditioned pulp is diluted with water to 25-30% solids and fed to a Sub-A Flotation Machine especially designed for handling the abrasive, slime free sand. Acid proof construction in most cases is necessary as the pulps may be corrosive from the presence of sulfuric acid. A pH of 2.5-3.0 is common. Wood construction with molded rubber and 304 or 316 stainless steel are the usual materials of construction. In the flotation step the impurity minerals are floated off in a froth product which is diverted to waste. The clean, contaminent-free silica sand discharges from the end of the machine.

The flotation tailing product at 25 to 30% solids contains the clean silica sand. A SRL Pump delivers it to a Dewatering Classifier for final dewatering. A mechanical classifier is generally preferable for this step as the sand can be dewatered down to 15 to 20% moisture content for belt conveying to stock pile or drainage bins. In some cases the sand is pumped directly to drainage bins but in such cases it would be preferable to place a cyclone in the circuit to eliminate the bulk of the water. Sand filters of top feed or horizontal pan design may also be used for more complete water removal on a continuous basis.

Dry grinding to minus 100 or minus 200 mesh is done in Mills with silica or ceramic lining and using flint pebbles or high density ceramic or porcelain balls. This avoids any iron contamination from the grinding media.

In some cases it may be necessary to place high intensity magnetic separators in the circuit ahead of the grinding mill to remove last traces of iron which may escape removal in the wet treatment scrubbing and flotation steps. Iron scale and foreign iron particles are also removed by the magnetic separator.

In general most silica sands can be beneficiated to acceptable specifications by the flowsheet illustrated. Reagent cost for flotation is low, being in the order of 5 to 10 cents per ton of sand treated. If feldspars and mica must also be removed, reagent costs may approach a maximum of 50 cents per ton.

Laboratory test work is advisable to determine the exact treatment steps necessary. Often, attrition scrubbing and desliming will produce very low iron silica sand suitable for the glass trade. Complete batch and pilot plant test facilities are available to test your sand and determine the exact size of equipment required and the most economical reagent combinations.

Silica sand for making glass, pottery and ceramics must meet rigid specifications and generally standard washing schemes are inadequate for meeting these requirements. Sand for the glass industry must contain not more than 0.03% Fe2O3. Concentrating tables will remove free iron particles but iron stained and middling particles escape gravity methods. Flotation has been very successfully applied in the industry for making very low iron glass sand suitable even for optical requirements.

Sub-A Flotation Machines are extensively used in this industry for they give the selectivity desired and are constructed to withstand the corrosive pulp conditions normally encountered (acid circuits) and also the abrasive action of the coarse, granular, slime free washed sand.

The flowsheet illustrated is typical for production of glasssand by flotation. Generally large tonnages are treated, forexample, 30 to 60 tons per hour. Most sand deposits can be handled by means of a dredge and the sand pumped to the treatment plant. Sandstone deposits are also being treated and may require elaborate mining methods, aerial tramways, crushers, and wet grinding. Rod Mills with grate discharges serve for wet grinding to reduce the crushed sandstone to the particle size before the sand grains were cementedtogether in the deposit. Rod milling is replacing the older conventional grinding systems such as edge runner wet mills or Chilean type mills.

Silica sand pumped from the pit is passed over a screen, either stationary, revolving or vibrating type, to remove tramp oversize. The screen undersize is washed and dewatered generally in a spiral type classifier. Sometimes cone, centrifugal and rake type classifiers may also be used for this service. To clean the sand grains it may be necessary to thoroughly scrub the sand in a heavy-duty sand scrubber similar to the Heavy-duty Agitator used for foundry sand scrubbing. This unit is placed ahead of the washing and dewatering step when required. The overflow from the classifier containing the excess water and slimes is considered a waste product. Thickening of the wastes for water reclamation and tailings disposal in some areas may be necessary.

The washed and dewatered sand from the spiral-type classifier is conveyed to a storage bin ahead of the flotation section. It is very important to provide a steady feed to flotation as dilution, reagents and time control determines the efficiency of the process.

Feeding wet sand out of a storage bin at a uniform rate presents a materials handling problem. In some cases the sand can be uniformly fed by means of a belt or vibrating-type feeder. Vibrators on the storage bin may also be necessary to insure uniform movement of the sand to the feeder. In some cases the wet sand is removed from the bin by hydraulic means and pumped to a spiral-type classifier for further dewatering before being conveyed to the next step in the flowsheet.

Conditioning of the sand with reagents is the most critical step in the process. Generally, for greater efficiency, it is necessary to condition at maximum density. It is for this reason the sand must be delivered to the agitators or conditioners with a minimum amount of moisture. High density conditioning at 70 to 75% solids is usually necessary for efficient reagentizing of the impurity minerals so they will float readily when introduced into the flotation machine.

The Heavy-duty Duplex Open-type Conditioner previously developed for phosphate, feldspar, ilmenite, and other non-metallic mineral flotation is ideal for this application. A duplex unit is necessary to provide the proper contact time. Circular wood tanks are used to withstand the acid pulp conditions and the conditioner shafts and propellers are rubber covered for both the abrasive and corrosive action of the sand and reagents.

Reagents are added to the conditioners, part to the first and the balance to the second tank of the duplex unit, generally for flotation of impurities from silica sand. These reagents are fuel oil, sulphuric acid, pine oil, and a petroleum sulfonate. This is on the basis that the impurities are primarily oxides. If iron is present in sulphide form, then a xanthate reagent is necessary to properly activate and float it. The pulp is usually regulated with sulfuric acid to give a pH of 2.5-3.0 for best results through flotation.

A low reagent cost is necessary because of the low value of the clean sand product. It is also necessary to select a combination of reagents which will float a minimum amount of sand in the impurity product. It is desirable to keep the weight recovery in the clean sand product over 95%. Fatty acid reagents and some of the amines have a tendency to float too much of the sand along with the impurities and are therefore usually avoided.

After proper reagentizing at 70 to 75% solids the pulp is diluted to 25 to 30% solids and introduced into the flotation machine for removal of impurities in the froth product. Thepulp is acid, pH 2 .5 to 3.0 and the sand, being granular and slime free, is rapid settling so a definite handling problem is encountered through flotation.

The Sub-A Flotation Machine has been very successful for silica sand flotation because it will efficiently handle the fast settling sand and move it along from cell to cell positively. Aeration, agitation and selectivity due to the quiet upper zone can be carefully regulated to produce the desired separation. The machine is constructed with a wood tank and molded rubber wearing parts to withstand the corrosive action of the acid pulp. Molded rubber conical-type impellers are preferred for this service when handling a coarse, granular, abrasive sand.

Flotation contact time for removal of impurities is usually short. A 4, and preferably a 6 cell, machine is advisable. Cell to cell pulp level control is also desirable. A 6 cell No. 24 (43 x 43) Sub-A Flotation Machine in most cases is adequate for handling 25 to 30 tons of sand per hour. If the impurities are in sulphide form a standard machine with steel tank and molded rubber parts is adequate provided the pulp is not acid. Otherwise acid proof construction is essential.

The flotation tailing product is the clean sand discharging from the end of the flotation machine at 25 to 30% solids and must be dewatered before further processing. Dewatering can be accomplished in a dewatering classifier and then sent to storage or drying. Top feed or horizontal vacuum filters are often used to remove moisture ahead of the dryer. Dry grinding of the sand to meet market requirements for ceramic and pottery use is also a part of the flowsheet in certain cases.

This particular sand was all minus 20 mesh with only a trace minus 200 mesh and 70% plus 65 mesh. Iron impurity was present as oxide and stained silica grains. The plant which was installed as a result of this test work is consistently making over a 95% weight recovery and a product with not over 0.02% Fe2O3 which at times goes as low as 0.01% Fe2O3.

Si02, minimum..99.8 per cent Al2O3, maximum..0.1 percent Fe2O3, maximum..0.02 per cent CaO + MgO, maximum.0.1 percent For certain markets, a maximum of 0.030 per cent Fe2O3 is acceptable.

Natural silica-sand deposits generally contain impurityminerals such as clay, mica, and iron oxide and heavy iron minerals which are not sufficiently removed by washing and gravity concentration. Flotation is often used to remove these impurity minerals to meet market specifications.

Anionic-type reagents, such as fatty acids, are used to float some impurities in alkaline pulp. Cationic-type reagents such as amines or amine acetates are also used with inhibitors such as sulphuric or hydrofluoric acids to float certain impurity minerals and depress the silica.

quartz aggregate crusher machine production line - best stone crusher plant solution from henan dewo

quartz aggregate crusher machine production line - best stone crusher plant solution from henan dewo

Dewo machinery can provides complete set of crushing and screening line, including Hydraulic Cone Crusher, Jaw Crusher, Impact Crusher, Vertical Shaft Impact Crusher (Sand Making Machine), fixed and movable rock crushing line, but also provides turnkey project for cement production line, ore beneficiation production line and drying production line. Dewo Machinery can provide high quality products, as well as customized optimized technical proposal and one station after- sales service.

The quartz sand production line needs the help of various crushing machines, such as: sand making mchine, jaw crusher, vibrating screen and so on. The appearance of quartz sand production line is of multi-prism, spherical, pure white, with high mechanical strength, interception capability, acid resistance is good.

Quartz Sand Production Line Quartz Sand Production Line. Quartz crushers are mainly needed for crushing quartz raw meterial and obtaining the standard size of quartz product. Varieties of quartz are rock crystal, citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others. They are gained after crushing the quartz stone.

Quartz sand is coming from natural quartz ore after the crushing, screening, washing and other techniques. The quartz sand production line needs the help of various crushing machines, such as: sand making mchine, jaw crusher, vibrating screen and so on.

Sand production line is now mining machinery industry term, mainly due to the construction of the new urbanization spawned a huge demand for sand and gravel. However, BAICHY machine reminded, depending on the particle size of the gravel crushing, in fact, can be subdivided into gravel and sand making production line.

quartz sand production line. quartz sand is coming from natural quartz ore by crushing, screening, washing and other techniques. its appearance is of multi-prism sea sand mining equipment for sale,sea sand mining production

Aggregate Crusher Plant - DM Factory. Since its establishment in the year of 1979 in Izmir, TURKEY, DM has been serving to industry with over 200 people of staff, on production areas of 15000 m2 in Yazibasi /Izmir, 10.000 m2 in Ayrancilar / Izmir and 2.000 m2 in Ankara Showroom for more than 30 years.

Sand making machine is widely used in a variety of rock, abrasives, refractories, cement clinker, quartz, iron ore, concrete aggregate and other hard, brittle materials. HX series impact crusher (sand making machine) is especially suitable for construction sand making.

Aggregate production line has been widely used for producing gravel and sand finished product with different particle size in highway, high railway, hydroelectric dam construction, mechanism sandstone, construction fields and so on. We can provide high performance stationary and mobile aggregate crushing plant with various capacity.

artificial quartz stone tile slab production plant - mining & construction solutions from henan dewo machinery

artificial quartz stone tile slab production plant - mining & construction solutions from henan dewo machinery

Dewo machinery can provides complete set of crushing and screening line, including Hydraulic Cone Crusher, Jaw Crusher, Impact Crusher, Vertical Shaft Impact Crusher (Sand Making Machine), fixed and movable rock crushing line, but also provides turnkey project for cement production line, ore beneficiation production line and drying production line. Dewo Machinery can provide high quality products, as well as customized optimized technical proposal and one station after- sales service.

quartz slab production line design advantages: artificial quartz slab production line is a special equipment production line for making quartz slabs, utand stone machinery reasonable design, high efficient real fast vibration suppression equipment combination, which makes the product qualified rate of more than 99%.

Macostone is a manufacturer and trading combo enterprise. MACOSTONE is a leading manufacturer of artificial quartz stone slab with more than 10 years experience, and also has tile production line and countertops fabrication plant.MACOSOTNE is The Best Cost Performance Manufacturer in China at the moment.

Xiamen Shunshun Stone Co., Ltd has specialised in providing high grade quartz stone products for countertops, vanities and other remodeling projects since 1996. Our plant area in Quanzhou covers nearly 50000 square meters with five mature production lines.

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Xiamen Shunshun Stone Co., Ltd has specialised in providing high grade quartz stone products for countertops, vanities and other remodeling projects since 1996. Our plant area in Quanzhou covers nearly 50000 square meters with five mature production lines.

Dewo machinery can provides complete set of crushing and screening line, including Hydraulic Cone Crusher, Jaw Crusher, Impact Crusher, Vertical Shaft Impact Crusher (Sand Making Machine), fixed and movable rock crushing line, but also provides turnkey project for cement production line, ore beneficiation production line and drying production line.

4-120 mesh horizontal silica quartz sand making machine line - best stone crusher plant solution from henan dewo

4-120 mesh horizontal silica quartz sand making machine line - best stone crusher plant solution from henan dewo

Dewo machinery can provides complete set of crushing and screening line, including Hydraulic Cone Crusher, Jaw Crusher, Impact Crusher, Vertical Shaft Impact Crusher (Sand Making Machine), fixed and movable rock crushing line, but also provides turnkey project for cement production line, ore beneficiation production line and drying production line. Dewo Machinery can provide high quality products, as well as customized optimized technical proposal and one station after- sales service.

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Silica Quartz Sand Price - Select 2020 high quality Silica Quartz Sand Price products in best price from certified Chinese White Quartz Sand manufacturers, Natural Quartz Sand suppliers, wholesalers and factory on Made-in-China.com, page 5

the trouble with silicon pv magazine international

the trouble with silicon pv magazine international

Triple Green, part 2: Silicon may be made of sand, but it is far from harmless. By the time the quartz becomes a module, it has lost its innocence. Nuclear power is used to smelt it, and the manufacturing process involves toxic chemicals and leaded fluxes and films. Crystalline solar technology is neither green nor clean but that could change. Part 2 of our series Triple Green on green energy, green recycling and green manufacturing.

Hotter than a steelworks: the furnace is running at more than 2,000 degrees Celsius as glittering electric arcs heat up the quartz sand. In terms of chemistry, quartz is an oxide of silicon. When extreme heat forces the oxygen out of a molecule a process known as thermal reduction industrial raw silicon remains. To produce these electric arcs, cables as thick as arms carry electricity to the furnaces. The smelter is heated with electricity because oil and gas cannot produce the necessary temperatures. For some time now, silicon manufacturers have been following in the footsteps of the aluminum industry, long regarded as an electricity guzzler. Silicon was formerly used mainly as a raw material for microchips, and hardly anyone spoke up about sustainable manufacturing. Now, the solar industry is constantly increasing its production and processing of silicon. Smelting silicon needs to become greener, and not only for the good of the industrys image. Just to stay competitive, manufacturers are working feverishly on decreasing the use of energy and toxic chemicals.

Power for the metallurgic smelting processes comes from large-scale power plants. In the U.S., for example, aluminum smelters use nuclear reactors and large hydropower plants in the Midwest. In Germany, silicon manufacturers turn to the combination of fossil and nuclear electricity offered by utility companies. A kernel of uranium can therefore be found in every solar panel. Green electricity doesn't seem to be an alternative yet, for financial reasons and because of the large amounts of electricity required. About thirty percent of the cost of silicon in Europe comes from electricity expenses, says Robert Hartung, board spokesperson for Centrotherm Photovoltaics in Blaubeuren, Germany. Centrotherm is one of the largest factory outfitters for the manufacture of solar silicon and crystalline cells. Its similar to smelting aluminum. In the future, we believe that new silicon plants will be built where electricity is cheap. In other words, silicon production and cell manufacturing will migrate to other countries. In addition, because of pricing pressure for silicon, temptation and opportunity are closely related. Hartung describes an example: Asia Silicon is planning new capacities in a region where hydropower is cheaply available. This way, they have unbeatable costs and production is practically carbon-neutral. Until now, Chinese manufacturers have made mostly negative headlines, such as when one company disposed of toxic silicon tetrachloride by simply dumping it in the countryside. Norways solar corporation REC also uses hydropower. The Scandinavians are currently investing more than a billion dollars to expand their solar capacity in Canada. There, too, hydropower is the main energy source.

Besides electricity consumption, material yield is very important at each production stage. About eighty percent of solar silicon production is done with the Siemens process. The electric arc furnace smelts quartz sand into liquid silicon with a purity of 99 percent. A chemical process using hydrochloric acid, and trichlorosilane then further purifies the raw silicon. Trichlorosilane is extremely corrosive and harmful to the respiratory system. The required safety technology also makes it very expensive. For these reasons, engineers are looking for ways to increase the process chains effectiveness. The important factor here is the chemical reactions yield: about 82 percent of the raw silicon is absorbed into the process gas. Thats not bad, but it could be much better, especially since the gas is then distilled to remove impurities aluminum, iron and copper. With the help of hydrogen, trichlorosilane is then dissolved on electrically heated rods of high-purity silicon at a temperature of 1,000 to 1,200 degrees Celsius. The silicon expands along the rods. However, this process only utilizes 16 percent of the trichlorosilane, Hartung calculates. Centrotherm therefore offers a converter to use up to 83 percent of the unused trichlorosilane.

Cost pressure is rising. Producers of wafers made from silicon blocks are also pinching pennies. One focus is silicon loss at the saws. Although losses in the sawing of wafers have continuously dropped over the past few years, Hartung says, with a 140 to 160-micrometer-thick saw blade, and wafers of 160 to 200 micrometers, 40 percent of the silicon is still lost. Regardless of falling silicon prices, these losses are a thorn in the side of manufacturers, who put a lot of energy into the process only to throw away almost half of the silicon. Manufacturers of systems therefore spare no expense or effort. For example, Applied Materials introduced its HCT MaxEdge wire saw a year ago. The company says it can decrease production costs for crystalline solar cells by 14 euro-cents per watt and will not only reduce losses, but also enable greater sawing speeds. Some manufacturers want to stop cutting silicon altogether and instead draw the correct shape directly from the liquid silicon. In edge-defined film-fed growth (EFG), the pure silicon liquid is drawn from an electrically heated graphite tub in the shape of octagonal polycrystalline tubes. The tubes grow about one millimeter per second up to six or seven meters. Each edge is ten to 12.5 centimeters long, and the tubes are 280 microns thick. A laser cuts the sides into silicon plates to produce wafers. This process uses 80 percent of the raw material. Wacker Schott Solar used the EFG process until September 2009, when Wacker and Schott terminated their joint venture and announced that they would no longer use the technology. Evergreen Solar of the U.S. uses the string ribbon process, in which the wafers are pulled directly out of the melt between two wires. This process also leaves less waste than the conventional process using ingots and wire saws. Nevertheless, such alternative processes have yet to become standard in mass production, although the price war on the market for solar cells is forcing production to be more streamlined and organized in compliance with sustainability criteria. The example of Wacker Schott shows that the value chain will be even more starkly divided in the future. Specialized silicon producers supply cell manufacturers, who in turn deliver to module factories. Such conglomerates as Solarworld and REC survive only thanks to their size. The speed of the race is impressive. Schott Solar, for example, more than doubled its cell production in Alzenau within a year. In 2008, we produced 130 megawatts of crystalline cells, corporate spokesperson Lars Waldmann confirms. In 2009, it was about 300 megawatts. This required between 1,500 and 1,700 metric tons of chemical additives acids, bases, and salts. These are used after sawing to etch the wafers down to the processing thickness of 180 micrometers and to structure the upper surface.

One of our main focuses for cell production is minimizing the use of acids, explains Holger Hoppe, corporate representative for environmental management at Schott Solar. The company plans to achieve this goal with longer service lives for the etching baths and lower concentrations in the baths. This plan also decreases the time and money needed to neutralize waste, since the waste water can only be removed once the chemicals are no longer reactive. Polycrystalline wafers are etched with nitric acid and hydrofluoric acid. Alkaline corrosives such as sodium hydroxide and caustic potash are used for monocrystalline wafers. Isopropyl serves as a cleaning agent. Here, too, low yield is a problem: for example, only two percent of the toxic base is used to etch monocrystalline wafers. Meanwhile, 98 percent is used in the expensive follow-up treatment that is, neutralization and filtering. These figures are the same for all manufacturers. Despite the laborious process undertaken to purify the waste water, traces of potassium remain. In streams, rivers and lakes, this chemical acts as a fertilizer, nourishing algae and killing fish. The photovoltaics industry thus follows in the footsteps of industrial agriculture which brings us back to the green image.

These days, the largest plants for solar cells are being built in the Far East. Within a short time, Taiwan has become one of the leading manufacturing nations. Chemical supplier Linde is currently building a pilot plant there that will process the caustic potash waste so it can be immediately fed back into cell production. There is great value in recycling, says Dean OConnor, head of Lindes solar division. The greatest economic benefit comes from eliminating the expensive after-treatment of toxic waste water. Figures from real-world operation are not yet available, but are expected this summer. Linde is leading the way to where suppliers see their opportunities with sustainable process technology and intelligent solutions, they can fill the giant market niche opened by price competition and the solar industrys green reputation. After all, the solar industry still has to perform a number of tasks before it actually achieves a true revolution in energy use. Other points of contention include phosphoric acids and phosphoryl chloride, used to dope silicon wafers with phosphorus. Boric acid, dimethylboron and diborane are used when doping with boron. The antireflective layer made of silicon nitride is created by separating monosilane and ammonia in a vacuum or by sputtering silicon in an ammonia atmosphere. The metallization of front and rear contacts requires pastes made of silver and aluminum. Compared to electricity use in silicon production, trichlorosilane and caustic potash are lesser problems, simply because the demand for these materials is much lower. Nevertheless, every cent counts and could end up tipping the scales after all, the race for marketable prices has just begun.

Only a fourth to a fifth of a solar modules added value results from the back-end and the processes that follow cell production: soldering cell strings, lamination, framing and quality control. Some module manufacturers started to centralize environmental management at the highest corporate level and set uniform manufacturing standards years ago. They realized then what Franz Nieper of Aleo Solar now confirms: Theres a correlation between profitability and waste. Aleos factory in Prenzlau runs its environmental management according to the ISO 14001 standard, because our customers ask about certification and environmental criteria, Steve Pestel explains. He is the environmental manager at Aleo Solar and has plans for his company to be a role model outside of Germany, as well. We will hold ourselves to the same quality and environmental criteria for our Chinese joint venture as we do for our factory in Prenzlau.

Aleo has significantly expanded production in Prenzlau in the last few years. The company started with a module output of 15 megawatts in 2003. Now, some 190 to 200 megawatts a year comes from three production halls. There is hardly any dangerous waste, but there are many clever ways to save. The company minimizes costs for the disposal of operating and cleaning materials by means of recycling: In 2008, credits for recycling glass and packaging almost made up for expenses for disposing of other waste, such as cleaning cloths and waste oil, Pestel says. Aleo tracks every possibility to save pennies. Our goal is to use five percent less energy each year, taking into account production output. Steve Pestel describes an example: Costs for water and waste water are very important. In principle, water is used at Aleo only to wash glass and could be fed into the municipal waste water system without further processing. In washing glass, we use water in a circulation system that is cleaned again through an ion filter. We therefore use less water in production than our employees use to shower. In module manufacturing, packaging, cleaning agents, and films make a dent in pocketbooks. Other costs include solar glass, aluminum for frames, copper stringers and fluxes for soldering machines. In 2008, 40 percent of Aleo Solars production waste consisted of packaging material, such as paperboard and used paper. Clear and tinted foils made of polyethylene contributed another 18 percent. Together, adhesive remains and trimmings from the laminators came to about 15 percent. The share of white solar glass was about ten percent. Broken cells are returned to suppliers, who include Q-Cells and Bosch Solar. One of Aleos focal points is the fluxes for soldering machines, in which the cells are connected to stringers. The fluxes are often butyl acetate and isopropyl alcohol with three to four percent solid particles. The actual soldering metal is a combination of tin and lead. Replacing it with a lead-free flux made of copper, tin and silver is difficult, since soldering mistakes increase when there is no lead. Soldering connections are then also insufficiently stable. Berlins Solon is also researching this problem. We have a register of hazardous substances, for example for the flux in the stringer machines. It contains solvents that emit harmful vapors, confirms Constantin Gerloff, corporate environmental management officer at Solon. Our objective is to decrease harmful substances by five percent in volume and number every year. The plant in Berlin uses less than 25 liters of flux each day, about a thousand liters each year. We see a need for research to further decrease harmful substances in modules, says Lars Podlowski, representative for technology on Solons managing board. One example is backside foils, which contain halogen. We need to replace them in the long run.

Halogens are organic bonds that contain, for example, chlorine or fluorine. If they get loose in the environment, they can cause serious damage. Like hydrochlorofluorocarbons (HCFCs), which used to circulate in air conditioning systems and refrigerators as a cooling agent, solar films with fluorine or chlorine can release climate-damaging gases when being recycled or burned. Another problem is that the conventional Tedlar (polyvinyl fluoride) film contains lead. Lead-free back sheets made of heat-resistant polyvinyl butyral (PVB) are therefore increasingly being used. This is not the same as polyvinylchloride (PVC), which also has the problem of containing halogens. In the laminators, which shrink-wrap the modules, reducing energy consumption is essential. The modules stay there for up to twenty minutes in a vacuum at 150 to 200 degrees Celsius until the films turn to liquid and air bubbles are eliminated. Swiss Solar Systems now equips its laminators with hybrid heaters, in which an oil film evenly distributes heat from electrically heated loops across the entire module surface. This process improves the interlacing in the EVA film, which is a polymer of ethylene and vinyl acetate. The large laminators waste heat is also used to heat the plants, but this requires large heat exchangers and water-based heating systems that must be considered as early as during a factorys initial planning stage. String ribbon wafers are drawn directly from the hot liquid silicon, thereby saving material costs.

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