Waste Heat Recovery Devices...

Waste Heat Recovery Devices  Industrial furnaces are used for carrying out certain processes which requires heat. Heat in the furnace is provided by (i) fuel energy, (ii) chemical energy, (iii) electrical energy or (iv) a combination of these energies. Gases which are generated during the process leaves the furnace at a temperature which is the inside temperature of the furnace and hence have a high sensible heat content. Sometimes the exhaust gases carries some chemical energy, which raises the temperature of exhaust gases further due to post combustion because of this chemical energy. The heat energy contained in the exhaust gases is the waste energy since it gets dumped in the environment. However, it is possible to recover some part of this energy if investments are made in waste heat recovery devices (WHRDs). Methods for waste heat recovery include (i) transferring heat between exhaust gases and combustion air for its preheating, (ii) transferring heat to the load entering furnaces, (iii) generation of steam and electrical power, or (iv) using waste heat with a heat pump for heating or cooling facilities. WHRDs work on the principle of heat exchange. During heat exchange the heat energy of the exhaust gases gets transferred to some other fluid medium. This exchange of heat reduces the temperature of the exhaust gases and simultaneously increases the temperature of the fluid medium. The heated fluid medium is either recycled back to the process or utilized in the production of some utilities such as steam or power etc. The benefits of WHRDs devices are multiple namely (i) economic, (ii) resource (fuel) saving, and (iii) environmental. The benefits of these devices include (i) saving of fuel, (ii) generation of electricity and mechanical work, (iii) reducing cooling needs, (iv) reducing capital investment costs in...

Water Management in a Steel Plant...

Water Management in a Steel Plant  Water is used in every shop of a steel plant and practically all the functions of water are utilized in the steel plant. Water is used in steel plant for process and heat transfer purposes; whereas water losses in the process are unavoidable (evaporation, drift), there is margin for further improving water use for the sake of the environment, energy efficiency, improvement of operations and for economic reasons. Use of water in a steel plant varied widely and is dependent on the availability of water, technologies employed, age and condition of the plants and equipment, kinds of the processes, and the plant operating procedures. Recycling of water also varies in a wide range in integrated steel plants.  Availability of water is one of the major factors in determining the rate of recycling. Water consumption in steel plant is mainly by evaporation, by spray from cooling towers, or by incorporation into a product. Various terms used in steel industry for water are as follows. Process water – It is the water that comes into contact with an end product or with materials incorporated into an end product. Cooling water – It is the water used exclusively for cooling purpose. Boiler feed water – It is the water introduced into boilers for conversion to steam Sanitary and service water – It is the water used for drinking, showers, general cleaning, and flushing of wastes. Intake water – It is the water which is pumped to the steel plant from water source. Make up water – It is the water added to the water system to compensate for the water losses. Recycle water – It is the water which is reused in a closed loop inside a water system often after...