Eia 5o29

Environmental Engineering

Sumair Imtiaz 08023123-027 8th Semester

Environmental Impact Assessment(EIA) of Sulphuric Acid Plant

Environmental Impact Assessment (EIA) "Environmental Impact Assessment (EIA) is the process of assessing the likely environmental impacts of a proposal and identifying options to minimize environmental damage. The main purpose of EIA is to inform decision makers of the likely impacts of a proposal before a decision is made. EIA provides an opportunity to identify key issues and stakeholders early in the life of a proposal so that potentially adverse impacts can be addressed before final approval decisions are made."

EIA is not a way of allowing an environmental 'veto' on development proposals. Environmental considerations may be set aside in favour of other considerations including economic and other benefits of going ahead. The Commonwealth and each State and Territory has legislation relating to EIA

Objectives of EIA  Ensuring environmental factors are considered in the decision-making process  Ensuring that possible adverse environmental impacts are identified and avoided or minimized  Informing the public about the proposal

Environmental impact of sulphuric acid industry

Sulphuric acid is made from any one of the basic raw materials - sulphur, pyrites or tail gases from metallurgical industries. The production of 1 ton of sulphuric acid (of 100% concentration) requires 0.33 ton of sulphur and produces 1.8 tons of high pressure steam. The manufacture of sulphuric acid requires three qualities of water, namely, demineralized water for boiler feed, process water to absorb sulphur trioxide and cooling water.

(a) Wastes and emissions from sulphuric acid manufacture:

Sulphur dioxide and acid mist are released from waste gas from the final absorber tower. Apart from boiler blow downs and water treatment plant regeneration, aqueous effluent from sulphuric acid plant originates from spills, leakages from pumps and flanges. The vanadium catalyst used for the oxidation process is returned to the catalyst manufacturer for vanadium recovery or safe disposal. Small amounts of sulphur dust are produced when sulphur is stored in open air. Sulphur dioxide and acid mist released into the atmosphere may contribute to acid rain.

(b) Pollution prevention and control in the manufacture of sulphuric acid: Sulphur with low ash content reduces catalyst requirement and produces less solid waste. Yellow sulphur is preferred to other colors of sulphur that have organic impurities. The catalyst is recycled. Sulphuric acid of more than 96% can be stored in mild steel tanks. Plant areas have impermeable flooring with the surface drainages connected to a neutralization pit. Emission levels of sulphur dioxide and acid mist is reduced by using a double conversion / double absorption system. Fiber mist eliminators having low gas velocities are used to remove all particles with more than 9 microns and 99% of all the smaller sized particles. Electrostatic precipitators are effective. In specific cases, final tail-gases are scrubbed with ammonia or caustic soda solutions. The existing single absorption facilities are upgraded with one of the following options: (i) Conversion to double absorption. (ii) Switching to cesium type catalyst. (iii) Additional alkaline tail-gas scrubbing. These installations are costly and they generate liquid effluents that need to be disposed of.

(c) Safety issues and occupational health hazards in the sulphuric acid production process:

Any sulphur dioxide concentration in excess of 27 mg/Nm3 is known to be a strong irritant and the allowable maximum safe and industrially accepted concentration is half this value. The maximum safe concentration for sulphuric acid mist for a 24 hour period is 0.14ppmv. The acid should be handled by skilled workers with full safety protection appliances such as eye wash fountains at strategic points, detailed operation manuals and safety guidelines. Continuous monitoring of sulphur dioxide levels in the stack and of acid mist and sulphur trioxide concentration in the gas after ing through the final absorber must be measured weekly.