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...

Recovery of Waste Heat Jan02

Recovery of Waste Heat...

Recovery of Waste Heat  Waste heat is the heat which is generated in a process due to the combustion of fuel or due to a chemical reaction and then discharged into the environment without being put to practical use. Sources of waste heat include hot combustion gases discharged into the atmosphere, process off  gases, conductive, convective and radiative losses from equipment and the heated products leaving various  industrial processes (hot coke, hot metal, liquid steel, and hot rolled product etc.), and heat transfer from hot equipment surfaces (heat transferred to cooling water). Waste heat recovery consists of the capture and reuse of the waste heat of the industrial processes for heating or for generating mechanical or electrical work. Typical uses include combustion air preheating, preheating of fuel gas, boiler feed water preheating, raw material preheating, generation of process steam, and production of steam for power generation etc. The basic idea behind the recovery of the waste heat is to try to recover maximum amounts of heat in the plant and to reuse it as much as possible, instead of just releasing it into the environment (air or a nearby river). Waste heat is intrinsic to all manufacturing processes. During the industrial manufacturing processes, around 20 % to 50 % of the energy consumed is ultimately lost via waste heat contained in streams of hot exhaust gases and liquids, as well as through heat conduction, convection, and radiation from the surface of the hot equipments as well as from the heated products. Waste heat recovery is a valuable alternative approach for improving overall energy efficiency improvements of the industrial furnaces. Energy efficiency  which can be achieved through waste heat recovery is normally in the range of 10 % to 50 %. The essential fact is...

Basics of Steam Boiler Feb22

Basics of Steam Boiler...

Basics of Steam Boiler A steam boiler is an enclosed container where water is heated under controlled conditions to convert it into steam. Boiler is basically a heat exchanger where heat is transferred to water. It is also sometimes referred to steam generator. Thermal energy for heating water is supplied either by fuel (Gas, liquid or solid) or by waste energy available from various industrial processes. Sometimes solar energy is also used for the production of steam. Steam produced in a boiler can be low pressure, medium pressure or high pressure.  In an industrial context, the steam produced is used as process steam in various industrial processes or for driving turbines for the production of electricity. Every boiler is designed to transfer as much thermal energy as possible to the water contained in the boiler. Heat energy is transferred by conduction, convection and radiation. The relative percentage of each is dependent upon the type of boiler, the designed heat transfer surface and the fuels that power the combustion. There are mainly two types of boilers. They are fire tube boiler and water tube boiler. Fire tube boiler consists of numbers of tubes through which hot gasses are passed. These hot gas tubes are immersed into water, in a closed vessel. In this boiler one closed vessel or shell contains water, through which hot gas tubes are passed. These hot gas tubes heat up the water and convert the water into steam and the steam remains in same vessel.  Fire tube boilers are generally used for relatively small steam capacities and low to medium steam pressures. These boilers are compact, of packaged construction and cheaper. Water tube boiler is a kind of boiler where the water is heated inside tubes and the hot gasses surround...