Treatment of Industrial Wastewater Mar20

Treatment of Industrial Wastewater...

Treatment of Industrial Wastewater Water is used in the industry for process needs, for cooling, for steam generation, for dust suppression and many other uses. Industrial wastewater is the aqueous discard that results after the water is used for the above purposes. Industrial wastewater is the result of substances other than water having being dissolved or suspended in water. Treatment of industrial wastewater covers the mechanisms and processes used to treat waters that have been contaminated in some way or other due to use of the water in the above activities. The objective of treatment is to remove the dissolved and suspended substances of the wastewater so that treated water can be safely discharged into the environment or can be recycled back in the same process or can be used in a different process. Constituents of wastewater Industrial wastewater contains the following constituents that need proper treatment. Suspended solids – These are the contaminants that are visible to the naked eye and can generally be filtered out of the water using common filter paper. Although there is no hard and fast definition, suspended solids tend to be larger than 1 – 2 microns in size. If the water is left to stand without disturbing it, the suspended solids will settle to the bottom of the container over time. Dissolved solids – These are contaminants that are not visible to the naked eye and cannot be removed from the water by filtration. The dissolved solids are defined as the materials that are generally smaller than 0.45 microns in size. The dissolved solids are either normally soluble substances or inversely soluble substances. The normally soluble substances are those materials that become more soluble with increasing temperature. The inversely soluble substances normally referred to as ‘hardness’ ions and...

Properties of Steels

Properties of Steels When selecting a steel material for a particular application, user has to be confident that it will be suitable for the loading conditions and environmental challenges it will be subjected to while in service. Understanding and control of the properties of the steel material is therefore necessary. Further properties of steel can be controlled through different processes such as hot and cold working, heat treatment etc. There are many measurement systems used to define the properties of given steel. These measurement systems normally come under four categories. These are physical properties, chemical properties, microstructural properties and mechanical properties.  Physical properties of steels The physical properties of steel are related to the physics of the material, such as density, thermal conductivity, elastic modulus, Poison’s ratio etc. Typical physical properties of steels are given in Tab 1. Tab1 Physical properties of steels           Properties Carbon steels Alloy steels Stainless steels Tool steels Density (tons/Cum) 7.85 7.85 7.75-8.1 7.72-8.0 Elastic modulus (GPa) 190-210 190-210 190-210 190-210 Poisson’s ratio 0.27-0.3 0.27-0.3 0.27-0.3 0.27-0.3 Thermal expansion (10-6/K) 11-16.6 9.0-15 9.0-20.7 9.4-15.1 Melting point (deg C) 1371-1540 Thermal conductivity (W/m-K) 24.3-65.2 26-48.6 11.2-36.7 19.9-48.3 Specific heat (J/kg-K) 450-2081 452-1499 420-500   Electrical resistivity (10-9W-m) 130-1250 210-1251 75.7-1020   Chemical properties of steels Iron is the basic component of steel. When carbon (C), a nonmetal, is added to iron (Fe) in amounts up to 2.0 %, the result is an alloy known as steel. Composition of steel mainly consists of iron and other elements such as carbon, manganese, silicon, phosphorus, sulfur, and alloying elements. A large number of elements in wide ranging percentages are used for the purpose of alloying of steels. Variations in chemical composition of steels are responsible for a great variety...

Corporate Social Responsibility...

Corporate Social Responsibility The present century is characterized by unprecedented challenges and opportunities, arising from globalization, the desire for inclusive development and the imperatives of climate change. Globally it is being recognized now that integrating social, environmental and ethical responsibilities into the governance of businesses ensures long term success, competitiveness and sustainability. This approach also reaffirms the view that businesses are an integral part of society, and have a critical and active role to play in the sustenance and improvement of healthy ecosystems, in fostering social inclusiveness and equity, and in upholding the essentials of ethical practices and good governance. This also makes business sense as companies with effective corporate social responsibility (CSR), have image of socially responsible companies, achieve sustainable growth in their operations in the long run and their products and services are preferred by the customers. The idea of CSR first came up in 1953 when it became an academic topic in HR Bowen’s ‘Social Responsibilities of the Business’. The term “corporate social responsibility” became popular in the 1960s and has remained a term use since then. Definitions of CSR Although the idea of CSR has been around for more than half a century, still there is no single universally accepted definition of CSR. All the definitions which are prevalent these days underpin the impact that businesses have on society at large and the expectations of the society on them. Various definitions which are prevalent today are given below. The European Commission (EC) has previously defined CSR as ‘a concept whereby companies integrate social and environmental concerns in their business operations and in their interaction with their stakeholders on a voluntary basis’. In October 2011 the EC published a new policy on corporate social responsibility. The Commission defines corporate social responsibility...

Mining of Iron Ores Mar14

Mining of Iron Ores

Mining of Iron Ores Iron ore is a type of mineral and rock from which metallic iron is extracted economically. This ore is normally rich in iron oxides and vary in color from dark grey, bright yellow and deep purple to rusty red. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3). The process of mining consists of discovery of an iron ore deposit through extraction of iron ore and finally to returning the land to its natural state. It consists of several distinct steps. The first is discovery of the iron ore deposit which is carried out through prospecting or exploration to find and then define the extent, location and value of the ore body. This leads to a mathematical resource estimation of the size and grade of the deposit. Exploration and evaluation consist of identification and quantification of ore bodies by using a range of geological, geophysical and metallurgical techniques. In its simplest forms exploration involves drilling in remote areas to sample areas. The data from exploration activities is logged, mapped, analyzed and interpreted often by using models. After the ore body has been evaluated, a detailed plan for mining is developed. This detailed plan identifies which ore bodies are to be mined and in what sequence in order to deliver the required iron ore product at an appropriate cost. The process of mine planning is an important step before the start of mine development and it continues on day to day basis once the mine becomes operational. To gain access to the iron ore deposit within an area, it is often necessary to mine through or remove waste material (also known as overburden) which is not of an interest. The total movement...

Corrosion of Steel and Corrosion Protection...

Corrosion of Steel and Corrosion Protection Corrosion is a multifaceted phenomenon that adversely affects and causes deterioration of properties in metals through oxidation. According to DIN EN ISO 8044 corrosion is defined as ‘Physical interaction between a metal and its environment which results in changes of the metal’s properties and which may lead to significant functional impairment of the metal, the environment or the technical system of which they form a part.’ Steel, the most commonly used material, corrodes in many media including most outdoor environments.  When unalloyed or alloyed steel without corrosion protection is exposed to the atmosphere, the surface takes a reddish brown colour after a short time. This reddish brown colour indicates rust is forming and the steel is corroding. While corroding the steel is getting oxidized to produce rust, which occupies approximately 6 times the volume of the original material consumed in the process. The corrosion process begins when a corrosive medium acts on the steel. The corrosion can be either chemical corrosion or electrochemical corrosion. Corrosion of steel is an electrochemical reaction that requires the presence of water (H2O), oxygen (O2) and ions such as chloride ions (Cl¯), all of which exist in the atmosphere. Atmospheric chloride ions are in greatest abundance anywhere near the coastline. This electrochemical reaction starts when atmospheric oxygen oxidizes iron in the presence of water. In addition, the atmosphere also carries emissions from human activity, such as carbon dioxide (CO2), carbon monoxide (CO), sulfur dioxide (SO2), nitrous oxide (NO2) and many other chemicals, which can also be significant in the corrosion process. The schematics of general corrosion process are illustrated below in Fig 1 Fig 1 Schematics of general corrosion process Types of Corrosion Besides general corrosion, there are various types of localized corrosion...