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Treatment Technologies

Air emission control technologies for the removal of particulate matter include scrubbers (or semidry systems), baghouses, and electrostatic precipitators (ESPs). The latter two technologies can achieve 99.9% removal efficiencies for particulate matter and the associated toxic metals: chromium (0.8 milligrams per normal cubic meter), cadmium (0.08mg/Nm³), lead (0.02 mg/Nm³), and nickel (0.3 mg/Nm³). Sulfur oxides are removed in desulfurization plants, with a 90% or better removal efficiency. However, the use of low-sulfur fuels and ores may be more cost-effective. The acceptable levels of nitrogen oxides can be achieved by using low-NOx burners and other combustion modifications.

Wastewater treatment systems typically include sedimentation to remove suspended solids, physical or chemical treatment such as pH adjustment to precipitate heavy metals, and filtration.

Solid wastes containing heavy metals may have to be stabilized, using chemical agents, before disposal. Sludges should be disposed of in a secure landfill after stabilization of heavy metals to ensure that heavy metal concentration in the leachates do not exceed the levels presented for liquid effluents. Noise abatement measures should achieve a maximum increase in background levels of 3 decibels (measured on the A scale).

Emissions levels for the design and operation of each project must be established through the environmental assessment (EA) process on the basis of country legislation and the Pollution Prevention and Abatement Handbook, as applied to local conditions. The emissions levels selected must be justified in the EA and acceptable to the World Bank Group. Any deviations from these levels must be described in the World Bank Group project documentation. The established emissions levels can be consistently achieved by well-designed, well-operated, and well-maintained pollution control systems.

Air emissions should be monitored continuously after the air pollution control device for particulate matter (or alternatively an opacity level of less than 10%) and annually for sulfur oxides, nitrogen oxides (with regular monitoring of sulfur in the ores), and fluoride. Wastewater discharges should be monitored daily for the listed parameters, except for metals, which should be monitored at least on a quarterly basis. Frequent sampling may be required during start-up and upset conditions.

Monitoring data should be analyzed and reviewed at regular intervals and compared with the operating standards so that any necessary corrective actions can be taken. Baseline data on fugitive PM emissions should be collected and used for comparison with future emissions estimates, which should be performed every three years based on samples collected. Records of monitoring results should be kept in an acceptable format. The results should be reported to the responsible authorities and relevant parties, as required.

The key production and control practices that will lead to compliance with emissions guidelines are summarized here.

× Prefer the direct steel manufacturing process where technically and economically feasible.

× Use pelletized feed instead of sintered feed where appropriate.

× Replace a portion of the coke used in the blast furnace by injecting pulverized coal or by using natural gas or oil.

× Achieve high-energy efficiency by using blast furnace and basic oxygen furnace off-gas as fuels.

× Implement measures (such as encapsulation) to reduce the formation of dust, including iron oxide dust; where possible, recycle collected dust to a sintering plant.

× Recirculate wastewaters. Use dry air pollution control systems where feasible. Otherwise, treat wastewaters.

× Use slag in construction materials to the extent feasible.

sulfur oxides, sintering or pelletizing operations, nitrogen oxides, sintering and heating hydrocarbons, carbon monoxide, dioxins and hydrogen fluoride, major pollutants.

крупно масштабне виробництво, хімічне розкислення залізної руди, киснева піч, домна, традиційний процес виробництва, електрична дугова піч, чистий кисень, металолом, шлак, карбонові сталі, спікання, виробництво сталі, висівки, вторинна окалина, процес обдавання (обкатування), рециркуляція відходів, середня швидкість, основні забруднювачі, зібраний пил, мінеральна шерсть, перероблювати відходи, домна, виробництво чавуну.

The OxiCup process, based on a modified cupola furnace, converts iron-rich waste from steelworks, mixed with carbon, into hot metal. (Christian Bartels-von Varnbueler Kuttner GmbH & Co). Today, about 20-25 kg of fine iron oxide-rich dust per tonne of raw steel arises in the off-gas cleaning systems of integrated steelworks in Germany. Because of their zinc, lead and alkaline content these materials cannot be recycled back into the production process and have to be recycled externally or dumped at some expense. Limited landfill capacities, rising costs, tighter laws and governmental regulations, and the public environmental discussion, make it increasingly difficult to continue the current practice. Therefore, a new technology had to be developed to recycle these residuals back into the production process and prevent dumping, for environmental and cost reasons.

The resultant technology, named OxiCup, is based on a modified cupola furnace which turns cold-bonded carbon-containing agglomerates into hot metal. The main advantages of this process for a steel mill are:

• The process is very similar to a blast furnace, hence minimal operator training is necessary.

• It supplements BF-grade hot metal for the steel mill and achieves higher utilisation of iron units.

• Zinc-enriched sludge can be sold for further recovery.

• All kinds of metallic revert metals, like skulls, desulphurisation metals and metals from slag processing can also be treated.

The process consists of the physical combination of fine grained waste oxides with a coke breeze reducing agent into bricks (called C-bricks) which are charged to a shaft furnace, together with other iron-bearing by-products, coke and fluxes. While the charge is descending in the furnace material is heated, and at about 1,000°C the coke breeze inside the bricks is converted to CO-gas which directly reduces the iron oxide grains.

The high temperature and the high surface area of the fine waste material make the reaction rate very fast. In laboratory tests the samples were reduced and metallised within a few minutes, whereas in the shaft furnace the material spends about 20 minutes in the required temperature range between 1,000°C and 1,400°C. The brick turns to direct reduced iron (DRI), which further descends to the melting zone of the furnace where it melts together with other metallic by-products.

Carburisation of the hot metal takes place predominantly in the hearth of the cupola. Hot metal and slag are tapped continuously and are passed through an iron and slag separator; then the hot metal is sent for further treatment, and the slag is sent to a slag granulation system. The zinc content of the residues is volatilised and leaves the furnace with the top gas, and as strongly enriched shaft furnace dust.

After extensive laboratory testing the first industrial trial was made in a foundry cupola. The 10 t/h furnace was operated for more than 10 hours with up to 30 per cent of C-bricks. There were no major changes in the composition of hot metal and the production rate decreased, as expected, to 8.5 t/h. There was a slight increase of iron oxide in the slag from 1 per cent to 2.5 per cent, which equates to 1 kg Fe/t HM. The CO content in the top gas increased and there was also a rise in dust due to the relatively low strength of the bricks.

The main conclusion of the trial was that the Fe-oxides were reduced and converted to hot metal.

To prove the process over longer periods of time, ThyssenKrupp Stahl, together with Mannesmann, Kuttner, B.U.S and Messer Griesheim, decided to build a pilot shaft furnace in Duisburg as a feasibility demonstration plant for a hot metal production of 15 t/h at a cost of DM 15 million (€7.7 million). Peripheral equipment such as a recuperator and a wet disintegrator-gas-cleaning-system, were bought used from a foundry nearby in order to minimise costs.

The furnace itself was built in the supporting steel structure of former blast furnace No.3 in Hamborn. The inner diameter of the hearth is 2.4 m and of the shaft 2.6 m. A total of 17,000 m³/h of cold blast is heated in a recuperator up to 520°C and the furnace is equipped with six cast copper tuyeres and a system to inject oxygen via supersonic lances. The advantage of this technology, compared to oxygen-enrichment to the blast, is more effective penetration, which is very important for low coke and refractory consumption rates. The top gas leaves the furnace at about 300°C via a gas off-take to the disintegrator gas cleaning system. The furnace-shaft itself is more than 5 m longer and the charge material in this part of the shaft seals the process against the atmosphere. The top gas is cooled, washed and then burned, either in the recuperator for heating up the cold blast, or in a torch, because for this stage of the project there was no connection to the gas mains of the steel mill. The furnace is lined with cast refractory material and operates as a typical wet bottom cupola. Iron and slag flows continuously through the taphole. Slag and iron are separated in a conventional front spout and the process retains the normal cupola flexibility. It is possible to shut down the furnace in one minute.

Following much laboratory testing, the optimised C-brick was a cement-bonded 110 mm hexagonal brick. Together with the waste oxides, the bricks contain LD-fine dust, BF-sludge and mill scale, 15 per cent of coke breeze and cement, which is intensively mixed in a special mixer. The bricks were then formed in a vibrating press and cured by storing for five days before they were handled as a bulky material. The Fe-content of the bricks is about 50%.

In the first six weeks after start up of the furnace only common scrap was used. From then on the charged materials consisted of 100 per cent skulls from the steelplant and the magnetic fraction of desulphurisation slag. Material in the size range of 10-600 mm can be treated without any problems, but larger pieces have to be charged in a limited amount. The Fe-content of these metallic revent materials is about 70-80 per cent because of adherent slag.

After solving the common technical start up problems, the focus of optimisation was on refractory campaign life. Due to the slag rate of about 350-450 kg/t hot metal, which is very high compared to a foundry cupola (60 kg/t HM), the tap hole wore very quickly. By redesigning the geometry of the front spout and making a change in the composition of the refractory material, the taphole campaign life was extended to 14 days: the same value as for scrapbased cupolas. It was possible to tap up to 10,000 t of hot metal and 4,000 t of slag per campaign.

The proportion of C-bricks was gradually increased to a maximum 70%. The production of hot metal decreased as expected due to the lower Fe-input. In the pilot stage the plant produced almost 50,000 t of hot metal and processed more than 5,000 t of C-bricks. The amount of bricks in the charge had no major effect on the hot metal composition, whereas the use of metals from desulphurisation slag results in fairly high sulphur contents. The influence of sulphur on the solubility of carbon in hot metal can also be seen. The carbon content decreases to 4 per cent as the sulphur content rises to 0.3 per cent, at Si-levels of about 1.5 per cent. The variation of the Fe-content in slag is only a matter of refractory wear at the slag notch. In contrast to a foundry operation Si was reduced from the slag.

More significant is the correlation of the percentage of C-bricks in the charge materials and the permeability of the furnace, measured as back pressure in the bustle pipe. The increase of back pressure is caused by the increase of shaft gas and there is no indication of a quasi-cohesive zone and no clogging or hang-ups were observed.

The void-factor rises with increasing amounts of C-bricks because the bricks have all the same size, and the conditions in the packed bed move in the direction of the ideal mono-grain structure which decreases the back pressure. The increase of the rate of C-bricks from 55% to 70% of the charge material showed no further increase of the back pressure. It can be assumed that both effects eliminate each other.

The furnace conditions were stable in every stage of the trials, and even one hour off-blast caused no problem when returning to normal operation. Unfortunately, the second­hand blowers and the off-gas cleaning system were at the limit of their capacity and so a further increase of the C-bricks content was not possible.

The main conclusion of the operation of the demonstration plant is that the process to reduce Fe-oxide agglomerates (C-bricks) to hot metal in a shaft furnace is stable and reliable. A total of 22.5 t/h of C-bricks were charged, in addition to 9 t/h of skulls. The use of skulls up to 600 mm in size in the shaft furnace instead of in the converter, increases the performance of the BOF plant, allows higher direct tapping rates and lowers the cost for desulphurisation.

Clean Zn coated scrap can now be used in the BOF shop in large quantities. The Zn rich sludge of the OxiCup furnace can be sold for further recovery. Undesirable fine materials can be taken out of the sinter plant, which increases performance and lowers stack emissions.

The highlights of the achieved results are:

• 740 t/d maximum production - 100 per cent skulls;

• 70 per cent maximum portion of bricks in charge;

• 22.5 t/h maximum consumption of C-bricks;

• 450 t/d maximum production in 70 per cent bricks - 30 per cent skulls mode;

• 14 day taphole refractory campaign life;

• 6 week hearth refractory campaign life;

• Use of China-coke without problems;

• Use of 20 per cent blast furnace coke.

The results of the 70 per cent brick trials are equivalent to a specific productivity per m³ of working volume of about 11 t/m³ per 24 h, and more than 110 t/m² per 24 h per m² of hearth area. The plant is now rebuilt as a commercial operation installation while a brick-making facility is to be built in the area of the furnace.

вагранка, дрібнозернисте залізо, необроблена сталь, очисні системи, кислотний, вміст, відходи, що містять залізо, агломерати, що містять карбон, шлам, загрузочний матеріал, коксові висівки, поступово випускати метал, швидкість виробництва, склад гарячого металу, гарнісаж, завод з повним металургійним циклом, под, колошниковий газ, шлаковідокремлювач, відновлювач, пил, відносно низька міцність.

modified cupola furnace, to convert iron-rich waste from steelworks, mixed with, oxide-rich dust, integrated steelworks, be recycled, limited landfill capacities, tighter laws, governmental regulations, public environmental discussion, residuals, to prevent dumping, carbon-containing agglomerates, the main advantages, blast furnace, zinc-enriched sludge, skulls, fine grained waste, reducing agent, to charge to a shaft furnace, iron-bearing by-products, coke and flux, to reduce the iron oxide grains, samples, to descend, metallic by-products, hearth of the cupola, to tap, recuperator, wet disintegrator-gas-cleaning-system, to minimize costs.

environmental, hot, breeze, landfill, cupola, waste,

integrated, costs, reducing, mill, recovery, grained

1. The basis of the OxiCup is modified cupola furnaces which _____ cold-bonded carbon-containing agglomerates into hot metal.

2. _____ the carburisation of the hot metal in the hearth of the cupola.

3. The furnace _____ with cast refractory material and works as a typical wet bottom cupola.

4. It is needed about 20 minutes for the material in the shaft furnace _____ the required temperature range between 1,000°C and 1,400°C.

5. In the first six weeks after start up of the furnace only common scrap _____.

6. The recuperator and a wet disintegrator-gas-cleaning-system _____ in order to minimise costs.

7. The reaction rate _____ up by high temperature and the high surface area of the fine waste material.

8. Previously to foundry cupola, the first industrial trial _____ of hearth of the cupola.

1. The high temperature and the high surface area of the fine waste material make the reaction rate very fast.

To make the reaction ….

2. In laboratory tests the samples were reduced and metallised within a few minutes.

To reduce ….

3. A new technology had to be developed to recycle these residuals back into the production process and prevent dumping.

To recycle….

1) The name of the technology.

2) Why has the technology been developed?

3) What is the technology based upon?

4) What are the advantages of the technology?

Zaporizhstal JSC is an Integrated Iron and Steel Works specializing in the production of hot- and cold-rolled sheets, tin-plates and consumer goods. Throughout the world these technological processes are connected with pollutant emission into atmosphere, water basin and the formation of industrial waste.

Zaporizhstal JSC accomplishes nature protection activity in the line of:

· Improvement of processing equipment operation (modernization).

· Commissioning of new, less power-consuming metallurgical equipment, with obligatory installation of corresponding nature preservation systems on the newly commissioned equipment.

· Modernization of the existing nature preservation equipment.

In 2000 a programme on retooling and modernization of the main equipment with maximum introduction of resource saving technologies has been made out at Zaporizhstal JSC. A significant place in this programme is dedicated to nature preservation measures.

The implementation of nature preservation measures in the last 6 years has enabled reduction of emissions into atmosphere by 41%, reduction of waste water disposal by 10%, secondary use of industrial water by 86%.

In 2000 reconstruction of blast furnace No.3 was accomplished. For the first time in Ukraine an aspiration unit together with a bag filter was assembled. It catches 99.5% of dust emissions during production of pig iron.

The fulfillment of this measure enabled to reduce dust emission into atmosphere by 4200 t/year.

The usage of units for nitrogen suppression of dust in the interbell space of all the blast furnaces enabled reduction of emissions by 11800t/year.

In November 2004 the reconstructed blast furnace No.2 was put into operation. Reconstruction costs amounted to 346 million UAH. Neither in Ukraine nor in the CIS countries can a similar furnace be found. The fulfilled complex of measures on blast furnace No.2 enabled to reduce emission of noxious agents into atmosphere by 8200 t/year.

Taking into consideration the reconstruction experience of these two furnaces technical retooling and modernization of the whole blast furnace production will continue.

In September 2007 an aspiration unit (2 electrofilters) for cleaning emissions from the tail parts of the sintering machines was put into operation. Approximately 2500 tons of sintering dust is caught and returned to production.

During accomplishment of water control measures aimed at saving and rational usage of water resources the Works has gained the following results in 2000-2007:

· Reduction of return water discharge into the Dnieper River by 12.630 million m³;

· Reduction of polluting agents discharge into the Dnieper River by 8390 t/year.

In 2006 a closed complex of installations to catch the drainage water of the slag dumps in gully Markusova was constructed and put into operation.

The Works is constructing a hydrochloric acid pickling line with an installation for regeneration of hydrochloric acid, which excludes discharge of neutralized pickled solution waste into the Dnieper River.

Directly at the Works more than 35% of the total quantity of formed solid waste is used once more. This is metallic and metal containing waste, refractory scrap, foundry production waste, wood, etc.

Constant monitory research in the areas of the industrial waste grounds and slime dump yards is carried out. For these purposes the Works spends more than 280000 UAH annually.

In the period from 2001 to 2007 Zaporizhstal JSC has spent more than 900 million UAH on construction and modernization of nature preservation installations.

To control the effect of the Works on the environment a nature preservation and radiation security department has been organized. It consists of a laboratory on environmental control and a radioisotope laboratory. The environmental control laboratory continuously accomplishes monitoring of the Works' effect on the condition of all the environmental components, sanitary and hygienic control of the places of work. The radioisotope laboratory is responsible for evaluation of the radiological condition at the Works and radioisotope control of all delivered raw materials.

The Health and Safety Executive have announced its inspectors will be visiting foundries, with the specific task of establishing compliance with the Noise at Work Regulations 1989. The visiting inspector may not be the inspector you normally deal with. If you are not fulfilling your obligation enforcement action may be taken against the company.

The inspector will be looking specifically for Noise Risk Assessments, plans to reduce noise at source, what the company has done that is reasonably practical to reduce noise, the supervision and enforcement of the wearing of personal protective equipment, systems employed to maintain the hearing protection provided and noise suppressing equipment. This campaign is currently underway.

This article is to help a company avoid enforcement action being taken against it. Excessive noise exposure to persons in the foundry industry is a problem that has been well known for many years. This can have adverse effects on the human being. These effects can be temporary or permanent and manifest themselves in a number of ways such as:

1. Temporary or permanent hearing loss. The level of hearing loss can vary due to the levels of noise exposed to and the duration of the noise exposure.

2. Tinnitus. This is similar to a ringing or booming noise in the ears which may occur intermittently or permanently. Noise induced deafness and tinnitus effect the individual gradually and are normally permanent.

3. Discomfort in the form of nausea or giddiness.

4. Stress.

Legislation was introduced during the late 1980's in the form of the Noise at Work Regulations 1989 which imposes requirements on employers and individuals. This established a legal requirement for employers to control noise in the workplace and their employees’ exposure to noise. The Noise at Work Regulations introduced three action levels where employers are required to take specific actions. The noise must be reduced to its lowest reasonably practical level.

Employers are required to assess the levels of noise to which they subject their employees. These assessments must be carried out by a competent person. Records of these noise assessments must be made. It is necessary to review the assessments periodically to confirm their validity (recommended every two years). A review is also necessary whenever significant changes in the workplace or process occur.

Employees’ exposure to noise must be reduced to the lowest reasonably practical level considering the following hierarchy:

1. Prevent employee exposure by eliminating excessive noise.

2. Controlling exposure of the individual by reducing the length of time working in excessive noise.

3. As a last resort, the use of personal protective equipment.

Noise is sound energy caused by vibrations in air pressure that the ear can detect. Measurements of noise can be divided into two aspects:

1. Sound intensity. This is normally measured in decibels. This is calculated as a ratio between the sound intensity and a reference sound intensity, usually set at the threshold of hearing. This is calculated on a logarithmic scale.

2. Frequency is the speed of the vibration of the sound. This is normally measured in hertz (Hz). Most industrial noise consists of a mixture of frequencies and the method of control is dependent upon the dominant frequency present. (Example of frequency: compressor house - normally low frequency, high speed pneumatic grinding tool - high frequency)

As previously stated, noise exposure must be reduced to its lowest reasonably practical level. Firstly, noise must be looked at source. Wherever possible, engineering controls of reducing noise should be incorporated at the design stage. Existing equipment should be replaced by less noisy equipment, but this may not always be possible. It may be possible, however, to reduce noise by modifying equipment, by stiffening up panels, the use of anti-vibrant mountings, reducing air velocities in duct work and fitting silencers to pneumatic exhausts. These are just some examples.

If it is not possible to reduce noise at source, consideration must be given to total or partial enclosure of the equipment generating the noise, with specifically made sound insulating materials. It is important to ensure that joints, access doors, material access points and service ducts are adequate to prevent noise leakage. In fully automated plants, consideration should be given to the use of a control room which is insulated against noise to protect the persons employed in the area.

The third and the least desirable method of protecting employees from excessive noise is the provision of personal protective equipment. This is normally only acceptable as a temporary measure or where noise cannot be reduced significantly and exceeds the second action level as prescribed in the Noise at Work Regulations 1989.

Where employees are exposed to noise levels above the first action level in the noise at Work Regulations 1989, it is essential for employees to receive basic training in the Regulations. Employees must be informed of the levels of noise to which they are exposed, the method of control to reduce the risk, including suitable personal hearing protection, where to obtain and how to fit such hearing protection, their duties under the Regulations and the need to report any defects in the protection provided. It is important to record the content of any training provided and persons trained. The training must be presented in a manner which can be understood by the persons receiving it.

The Health and Safety Executive – Інспектор з охорони праці та техніки безпеки

The Noise at Work Regulations – Нормативи допустимого рівня шуму

відповідність, правозастосовчі дії, зменшувати шум, обладнання для зниження рівня шуму, шкідливий вплив, тимчасовий або постійний, втрата слуху, дзвін у вухах, запаморочення, тиск повітря, інтенсивність звуку, останній засіб, усувати надмірний шум, поріг слуху, захисне обладнання, обладнання для вловлювання шуму, компресорна, технічний контроль, глушник, антивібраційні установки, диспетчерська,

швидкість коливання.

1. As previously ______ (to state), noise exposure must be reduced to its lowest reasonably practical level.

2. Wherever possible, ______ (to engineer) controls of reducing noise should be ______ (incorporate) at the design stage.

3. Consideration should be ______ (to give) to the use of a control room which is insulated against noise to protect the persons employed in the area.

4. It is important to record the content of any training ______ (to provide) and persons trained.

Reasonably, currently, permanently, gradually, normally.

Tinnitus, temporary or permanent hearing loss, nausea, giddiness, stress.

1. Whom is this article designated for?

2. What must be done in the companies before the visit of the inspector?

3. Can you give the definition of noise?

4. How can noise be measured?

1. The adverse effects of excessive noise on the human being.

2. How can employees’ exposure to noise be reduced to the lowest level?

3. Methods of the noise prevention in industry.

4. The main idea of the text.

ABSTRACT Metal and sulphate contaminated wastewater, produced by acid mine drainage and mineral processing, occurs at an estimated seventy percent of the world’s mine sites, making it one of the mining industry’s most significant environmental and financial liabilities. Historically, resource companies have typically used lime treatment to reduce the concentrations of metals and sulphate in wastewater; however, lime treatment can require additional process steps to produce water that complies with regulations, and can create a metal-laden sludge that requires on-going storage and management, creating a long-term environmental liability for site owners. In recent years, sulphide-based process technologies for metal removal have been successfully implemented at mine sites in Canada, the US, Mexico, Australia, and China and new ionexchange technologies for reduction of sulphate have been extensively piloted in Canada and Chile. These technologies offer significant benefits compared to conventional alternatives as they remove metals and sulphate to very low levels, eliminate the production of contaminated sludge, produce clean water that meets regulatory standards for discharge or re-use, remove metals in a saleable form that can off-set the cost of water treatment, and deliver savings for both capital and operating costs. This unique approach provides a sustainable business model that generates revenues from waste, reduces corporate liability for customers and delivers overall improvements to the environment. This paper will profile these technologies, and provide case-study examples of their application at mining operations.