Coke making process and its environmental impacts:

Coke making process and its environmental impacts:

Coke is a solid carbon fuel and carbon source used to melt and reduce iron ore. Coke and coke by-products, including coke oven gas, are produced by the pyrolysis (heating in the absence of air) of suitable grades of coal. The process also includes the processing of coke oven gas to remove tar, ammonia (usually recovered as ammonium sulfate), phenol, naphthalene, light oil, and sulfur before the gas is used as fuel for heating the ovens.

A. Coke making process: In the coke-making process, bituminous coal is fed (usually after processing operations to control the size and quality of the feed) into a series of ovens, which are sealed and heated at high temperatures in the absence of oxygen, typically in cycles lasting 14 to 36 hours. Volatile compounds that are driven off the coal are collected and processed to recover combustible gases and other by-products. The solid carbon remaining in the oven is coke. It is taken to the quench tower, where it is cooled with a water spray or by circulating an inert gas (nitrogen), a process known as dry quenching. The coke is screened and sent to a blast furnace or to storage. Coke oven gas is cooled, and by-products are recovered. Flushing liquor, formed from the cooling of coke oven gas, and liquor from primary coolers contain tar and are sent to a tar decanter. An electrostatic precipitator is used to remove more tar from coke oven gas. The tar is then sent to storage. Ammonia liquor is also separated from the tar decanter and sent to wastewater treatment after ammonia recovery. Coke oven gas is further cooled in a final cooler. Naphthalene is removed in the separator on the final cooler. Light oil is then removed from the coke oven gas and is fractionated to recover benzene, toluene, and xylene. During the coke quenching, handling, and screening operation, coke breeze is produced. It is either reused on site (e.g., in the sinter plant) or sold off site as a by-product.

B. Pollution during coke making process:

The coke oven is a major source of fugitive air emissions. The coking process emits particulate matter (PM); volatile organic compounds (VOCs); polynuclear aromatic hydrocarbons (PAHs); methane, at approximately 100 grams per metric ton (g/t) of coke; ammonia; carbon monoxide; hydrogen sulfide (50–80 g/t of coke from pushing operations); hydrogen cyanide; and sulfur oxides, SOx (releasing 30% of sulfur in the feed). Significant amount of VOCs may also be released in by- product recovery operations. For every ton of coke produced, approximately 0.7 to 7.4 kilograms (kg) of PM, 2.9 kg of SOx (ranging from 0.2 to 6.5 kg), 1.4 kg of nitrogen oxides (NOx), 0.1 kg of ammonia, and 3 kg of VOCs (including 2 kg of benzene) may be released into the atmosphere if there is no vapor recovery system. Coal-handling operations may account for about 10% of the particulate load. Coal charging, coke pushing, and quenching are major sources of dust emissions.

Wastewater is generated at an average rate ranging from 0.3 to 4 cubic meters (m3) per ton of coke processed. Major wastewater streams are generated from the cooling of the coke oven gas and the processing of ammonia, tar, naphthalene, phenol, and light oil. Process wastewater may contain 10 milligrams per liter (mg/l) of benzene, 1,000 mg/l of biochemical oxygen demand (BOD) (4 kg/t of coke), 1,500–6,000 mg/l of chemical oxygen demand (COD), 200 mg/l of total suspended solids, and 150–2,000 mg/l of phenols (0.3–12 kg/t of coke). Wastewaters also contain PAHs at significant concentrations (up to 30 mg/ l), ammonia (0.1–2 kg nitrogen/t of coke), and cyanides (0.1–0.6 kg/t of coke). Coke production facilities generate process solid wastes other than coke breeze (which averages 1 kg/t of product). Most of the solid wastes contain hazardous components such as benzene and PAHs. Waste streams of concern include residues from coal tar recovery (typically 0.1 kg/t of coke), the tar decanter (0.2 kg/t of coke), tar storage (0.4 kg/t of coke), light oil processing (0.2 kg/t of coke), wastewater treatment (0.1 kg/t of coke), naphthalene collection and recovery (0.02 kg/t of coke), tar distillation (0.01 kg/t of coke), and sludges from biological treatment of wastewaters.

C. Pollution Prevention and Control: Pollution prevention in coke making is focused on reducing coke oven emissions and developing coke-less iron & steel-making techniques. The following pollution prevention and control measures should be considered.

1. General -

(a) Use cokeless iron- and steel-making processes, (b) such as the direct reduction process, to eliminate the need to manufacture coke. (c) Use beneficiation (preferably at the coal mine) and blending processes that improve the quality of coal feed to produce coke of desired quality and reduce emissions of sulfur oxides and other pollutants. (d) Use enclosed conveyors and sieves for coal and coke handling. Use sprinklers and plastic emulsions to suppress dust formation. Provide windbreaks where feasible. Store materials in bunkers or warehouses. Reduce drop distances. (e) Use and preheat high-grade coal to reduce coking time, increase throughput, reduce fuel consumption, and minimize thermal shock to refractory bricks.

2. Coke Oven Emissions –

(a) Charging: dust particles from coal charging should be evacuated by the use of jumper-pipe systems and steam injection into the ascension pipe or controlled by fabric filters.

(b) Coking: use large ovens to increase batch size and reduce the number of chargings and pushings, thereby reducing the associated emissions. Reduce fluctuations in coking conditions, including temperature. Clean and seal coke oven openings to minimize emissions. Use mechanical cleaning devices (preferably automatic) for cleaning doors, door frames, and hole lids. Seal lids, using a slurry. Use low-leakage door construction, preferably with gas sealing.

(c) Pushing: emissions from coke pushing can be reduced by maintaining a sufficient coking time, thus avoiding “green push.” Use sheds and enclosed cars, or consider use of traveling hoods. The gases released should be removed and passed through fabric filters.

(d) Quenching: where feasible, use dry instead of wet quenching. Filter all gases extracted from the dry quenching unit. If wet quenching, is used, provide interceptors (baffles) to remove coarse dust. When wastewater is used for quenching, the process transfers pollutants from the wastewater to the air, requiring subsequent removal. Reuse quench water.

(e) Conveying and sieving: enclose potential dust sources, and filter evacuated gases.

3. By-Product Recovery –

(a) Use vapor recovery systems to prevent air emissions from light oil processing, tar processing naphthalene processing, and phenol and ammonia recovery processes.

(b) Segregate process water from cooling water.

(c) Reduce fixed ammonia content in ammonia liquor by using caustic soda and steam stripping.

(d) Recycle all process solid wastes, including tar decanter sludge, to the coke oven.

(e) Recover sulfur from coke oven gas. Recycle Claus tail gas into the coke oven gas system.

Measures taken to mitigate environmental impacts while concreting for construction

Measures taken to mitigate environmental impacts while concreting for construction

With the large scale construction activities going on everywhere, the potential environmental impact in cement works for concreting are to taken care of. Air quality, noise nuisance, water quality and visual impact induced by concrete batching plant operated for construction working.

A. Fresh concrete and cement-related mortars are toxic to marine life. Therefore, Concrete run-off from washing or leaking equipment or from disposing of these materials to the street gutters and stormwater drains eventually finds its way into waterways, which has the potential to cause pollution. It not only does serious environmental degradation, but also against law.

Concrete run-off blocks stormwater drains, pollutes our creeks, lakes and rivers and has a major impact on water quality, aquatic plants and animals. Appropriate measures must be taken to control concrete run-off.

Understanding few environmental best management practices should significantly reduce the likelihood of pollution from typical day-to-day concreting activities; some of these are:

(a) Establishing a concrete wash-down area on-site. (b) The wash-down area must be located with appropriate sediment controls. These should be inspected and maintained regularly and be repaired or replaced as necessary; (c) minimize the amount of wash-down water generated, scrape excess concrete off the equipment before it is washed; (d) Place excess concrete into a site receptacle designated for concrete and masonry; (e) A high pressure, low volume water spray nozzle conserves water and reduces maintenance of sediment controls; (f) Wash-down water is best managed by draining it into a container, allowing the water to stand until the solid particles settle at the bottom. After adjusting the pH of the water to neutral, it can then be siphoned off and reused, and the residue in the bottom can be allowed to set, then recycled with other excess concrete and masonry material; (g) No wash-down water may be disposed of to the sewerage system without prior agreement of the local water authority; (h) Do not allow equipment wash-down water to flow directly into a stormwater drain or system.

B. Ensure that concrete washed from trucks and mixer units on site is contained and does not leave the site or enter the stormwater system.

C. For modern commercial skyscraper building development projects, the works involved piling, concreting and eventually superstructure construction. Many, being in the heart of busiest commercial central district, noise arising from the concreting work were the major concern. Measures to be adopted: (a) Quieter Method - A purposely-built acoustic enclosure was built to screen the operation of concrete pump and the concrete lorry mixer. The mixer is a Specified Powered Mechanical Equipment which demands a more stringent acceptable noise level; (b) No concreting work was allowed beyond 11 p.m.; (c) Administration - To ensure good communication, the contractor was required to submit a 48-hour-advance notification before commencement of concreting work of those identified bore piles and diaphragm walls necessitating major concrete pour; (d) With the incorporation of the purpose-built acoustic enclosure, the construction noise from the subject site was reduced to a level below the relevant Acceptable Noise Level.

D. General precautions: All such rules and legislations relevant to reduction of impact of concreting are to be adhered to by all the personnel engaged at the job site. Proper training procedures are also to be followed in order to impart training for adoption of all the procedure laid down.

Guidelines for making City Green

As cities are keep on growing because of urbanization, more and more cities are becoming congested. To make cities livable for the citizen and to make their life beautiful, it has been the constant endevour of the Government to encourage for green building, keep city pollution within the limit and to create sufficient green belt.

A. Green Building is a philosophy of design and construction that integrates natural resources more effectively, preserves and restores the natural and human resource base while creating healthier, more efficient “high-performance” structures, homes and communities. This philosophy incorporates the following guiding principles:

• Using natural and manmade resources efficiently;

• Considering the impact of buildings and development projects on the local, regional and global environment;

• Reducing building footprint and development size;
  

• Allowing ecosystems to function naturally;

• Conserving and reusing water; treating storm water on-site;

• Maximizing the use of local materials;

• Optimizing energy performance by installing energy efficient equipment and systems;
  

• Optimizing climatic conditions through site orientation and design;
  

• Integrating natural day-lighting and ventilation;

• Minimizing the use of mined rare metals and persistent synthetic compounds and volatile organic compounds;
  

• Minimizing construction waste by reducing, reusing and recycling materials during all phases of construction and deconstruction.

Sustainability is the practice of using resources to provide for the needs of today’s citizens while preserving the use of those same resources for the needs of future generations. Generally, objectives of green buildings are: (a) Improve work and learning environments, thus increasing worker productivity and student performance; (b) Mitigate health risks such as asthma and childhood lead poisoning; (c) Create local green building jobs within every existing industrial sector; (d) Reduce energy consumption and costs; (e) Affirm the City’s commitment to environmental conservation.

B. The creation of green-space in cities is often spoken of as if it were the result of orderly planning or regulation. Most of the cities have a plan to conserve green-space on the urban fringe. Generally, planning for creation of city green zones includes:

• Greening Commercial Corridors – This focus on landscape enhancements along strategic streets that can serve as a neighborhood's economic lifeline.

• City Parks Revitalization – This focus on maintaining and beautification of existing parks in a city.

• Setting-up of New Community Gardens;
  

• Street Beautification Projects- creation of "Garden Blocks".

· Education and Training Opportunities - Courses and workshops help city dwellers beautify their communities through horticulture.

C. Apart from setting up green buildings, green covers, strategy for implementing proper solid waste management, restricting generation of air / water pollutants and strict implementation of local emission control codes. Thus, guidelines should include:

• Utilize sites to capture environmental benefits and preserve or create new open space;
  

• Develop programs and policy to conserve potable water use, improve stormwater management and “green” the city sewage waste water system;
  

• Address city and regional transportation issues by encouraging transit-oriented development, improve public transit services and reduce dependency on individual automobile use;

• Implement citywide energy conservation programs and incentives, encourage use of renewable, non-fossil fuel energy sources and improve city performance on meeting regional clean air standards;
  

• Promote the development of local, green manufacturing industries and the use of recycled content materials or renewable materials for building, operations, and supplies for city work. Also establish more extensive recycling program to include construction and demolition waste recycling;
  

• Maintain city’s sustainable development by integrating programs, such as in workforce development, economic redevelopment, and the public school system.

D. Citywide ban on smoking in all enclosed public spaces and public vehicles, also to be imposed for long term benefit of its citizen.

Coal-fired power plants and pollution

Coal-fired power plants are the single largest stationary source of air pollution in any country. The toxins these coal fired power plants produce severely damage both human health and the environment and contribute to a reduced quality of life. Cleaning up these plants and finding cleaner, alternative energy sources is the overall objective to achieving clean, healthy air in every country.

Air pollution consists of a mixture of chemicals with various harmful effects on the human body, wildlife, plants, and climate. The main ingredients of air pollution are the following:

* Ozone Smog: Formed at ground level when sunlight mixes with nitrogen oxides and hydrocarbon vapors emitted by power plants, vehicles, and industry. It contributes to airway irritation, coughing, wheezing, asthma attacks, and immune suppression.

* Sulfur Dioxide (SO2): Gas emitted through burning coal and oil, that converts into acid gases (sulfuric acid) and sulfur particulate matter (pm). Health effects include: airway irritation, heart rhythm destabilization, and asthma attacks.

* Nitrogen Oxide (NOx): General term for NO/O2 hazes formed from burning coal, oil, natural gas, and gasoline. It is a main ingredient in acid rain and ozone smog.

* Particulate Matter (PM): Soil, soot, SO2, and NOx particles from power plants, cars, and factories that are tiny enough to penetrate indoor spaces and deep into the lungs. They can trigger premature death from heart attacks, lung diseases, and cancer in adults; and stunted lung growth, low birth weight, neurological impairment, and SIDS in children.

* Mercury (Hg): Toxic metal particles settle in water, contaminate fish, and move up the food chain. Mercury ingestion can result in premature birth, low birth weight, structural defects, learning disorders, heart and neurological defects.

It would be our prime objective, not only for the general public, but for govt. concerned to prepare effective means / legislations to control such hazards immediately.

Control of Air pollution by controlling Particulate Matters

Airborne Particulate Matters (PM) - Pollution Prevention and Control:

Airborne particulate matters (PM) emissions can be minimized by pollution prevention and emission control measures. Prevention, which is frequently more cost-effective than control, should be emphasized. Special attention should be given to mitigate the effects, where toxics associated with particulate emissions may pose a significant environmental risk.

Measures such as improved process design, operation, maintenance, housekeeping, and other management practices can reduce emissions. By improving combustion efficiency in Diesel engines, generation of particulate matters can be significantly reduced. Proper fuel-firing practices and
combustion zone configuration, along with an adequate amount of excess air, can achieve lower PICs (products of incomplete combustion). Few following steps should be adhered to control PM:

1. Choosing cleaner fuels - Natural gas used as fuel emits negligible amounts of particulate matter.

2. Low-ash fossil fuels contain less noncombustible, ash-forming mineral matter and thus generate lower levels of particulate emissions.

3. Reduction of ash by coal cleaning reduces the generation of Particulate Matter (PM) emissions.

4. The use of more efficient technologies or process changes can reduce PIC emissions.

5. Advanced coal combustion technologies such as coal gasification and fluidized-bed combustion are examples of cleaner processes that may lower PICs by approximately 10%.

6. A variety of particulate removal technologies, are available – these are (a) Inertial or impingement separators, (b) Electrostatic precipitators (ESPs) , (c) Filters and dust collectors (baghouses), (d) Wet scrubbers that rely on a liquid spray to remove dust particles from a gas stream.

The principal methods for controlling the release of particulate matter are summarized here.

• Identify measures for improving operating and management practices.

• Consider alternative fuels such as gas instead of coal.

• Consider fuel-cleaning options such as coal washing, which can reduce ash content by up to 40%.

• Consider alternative production processes and technologies, such as fluidized bed combustion, that result in reduced PM emissions.

• Select optimal particulate removal devices such as ESPs and Baghouses.

Air pollution by Particulate matters (Fine and Coarse Dust particles):

Air pollution by Particulate matters (Fine and Coarse Dust particles):

‘Fine particles’ are less than 2.5 micron in size and require electron microscope for detection, however, they are much larger than the molecules of Ozone etc., and other gaseous pollutants, which are thousands times smaller and cannot be seen through even electron microscope.

Fine particles are formed by the condensation of molecules into solid or liquid droplets, whereas larger particles are mostly formed by mechanical breakdown of material or crushing of minerals. ‘Coarse particles’ are between 2.5 to 10 micron size, and cannot penetrate as readily as of Fine particle; however, it has been seen these are responsible for serious health hazards. The severity of the health hazards vary with the chemical nature of the particles.

The inhalation of particles has been linked with illness and deaths from heart and lung disease as a result of both short- and long-term exposures. People with heart and lung disease may experience chest pain, shortness of breath, fatigue etc., when exposed to particulate-matter pollutants. Inhalation of particulate matter can increase susceptibility to respiratory infections such as Asthma, Chronic Bronchitis. The general medical term given for such lung diseases is ‘Pneumoconiosis’.

Emissions from diesel-fuel combustion in vehicles / engines / equipments; Dusts from cement plants, power plants, chemical plants, mines are a special problem, specially for those individuals breathing in close proximity to such atmosphere. Cars, trucks and off-road engines emit more than half a million tones of diesel particulate matter per year.

WE SEEK YOUR HELP TO SAVE ENVIRONMENT

Your few following small steps and effective decisions in everyday life would be a big leap in helping us to improve global environment.

1. Make energy efficient and conservation wise decisions in every sphere of life.
2. While driving motor vehicle, turn off the engine if waiting is longer. More fuel is wasted when idling than restarting. Be alert in traffic. Try to take alternate routes which have few signals to eliminate idling.
3. Warm-up the motor vehicle for one minute before moving. Accelerate gently and evenly and use your cruise control to maintain a steady speed.
4. Use motor vehicle's flow through vents instead of air conditioning (which decreases fuel efficiency by 21%) or by opening window.
5. Keep car engine tuned. A poorly tuned car wastes 15% more fuel. More fuel, means more pollution and travel fewer miles.
6. Properly inflate & align tires to save fuel & to reduce wear on tires over time.
7. Reduce the amount of miles you drive. Fewer distance driven, fewer polluting emissions created. Walk or ride a bike!
8. Use fuel efficient automobiles. Follow state guidelines on emissions testing & maintain any pollution-control devices.
9. Use public transportation when available.
10. Conserve electricity, including turning off lights when not in use.
11. Participate in recycling programs. Recycling conserves energy and also conserves natural resources.

Air pollution by Industry

Air pollution by Industry:
Air pollution is the presence of high concentration of contaminations, dust, smokes etc., in the general body of air man breaths. Pollutants are mixture of solid particles and gases in the air. Some air pollutants are poisonous. Inhaling them can increase the chances of health problems. People with heart or lung disease, older adults and children are at greater risk from air pollution.

Prime sources of air pollution are the industrial activities or processes releasing large quantity of pollutants in the atmosphere. These pollutants are mainly: (a) Smoke comes out from various industries like, power plants, chemical plants, other manufacturing facilities, motor vehicles, etc.; (b) Burning of wood, coal in furnaces and incinerators; (c) gaseous pollutants from Oil refining industries; (d) dust generated and thrown to general atmosphere by various industries such as cement plants, ore / stone crushing units, mining industries due to rock drilling & movements of mining machineries & blasting etc.; (e) Waste deposition for landfills which generate methane; (f) Toxic / germ / noxious gasses and fumes generated from military activities and explosives blasting in mines.

Air pollution control devices / equipments for industries:
The commonly used equipments / process for control of dust in various industries are (a) Mechanical dust collectors in the form of dust cyclones; (b) Electrostatic precipitators – both dry and wet system; (c) particulate scrubbers; (d) Water sprayer at dust generation points; (e) proper ventilation system and (f) various monitoring devices to know the concentration of dust in general body of air.
The common equipments / process used for control of toxic / flue gases are the (a) process of desulphurisation; (b) process of denitrification; (c) Gas conditioning etc. and (d) various monitoring devices to know the efficacy of the systems used.