Waste heat restoration system is the process of utilizing waste material heat that has been stated in various heating techniques. There is great heat that is being wasted by companies which influences the efficiency of the industry to a larger extent than any other factors. So, there is an inevitable need to resolve this problem and make sure that the efficiency of the industry is increased.
High temperature warmth recovery potential is available in many industries. High temperature waste heating available can be employed for generating power, heating normal water & air, increasing process temps etc. Taking into consideration the acute scarcity of electric power, this ready source can show a benefit to the industry in more than one way.
This task is completed at Nava Bharat Projects Limited (NBVL), Paloncha, and Khammam District in utilization of waste high temperature available from Submerged Electric Arc Furnace (SEAF) petrol gases by setting up a Double forward heat exchanger (LPHX - Low Pressure High temperature Exchanger and HPHX - RUTHLESS Warmth Exchanger) in petrol gas avenue. Generally Main Condensate & Supply Water in Vitality Plant is warmed in LP & HP heaters of Turbine regeneration pattern by drawing steam from Vapor Turbine extractions.
In this project, Main Condensate & Feed Water will be warmed in installed high temperature exchanger by partially/completely bypassing LP & Horsepower heaters. Therefore, the vapor sketch from Turbine extractions will come down/zero. As a result, the specific heavy steam utilization of turbine will also come down and consequently the entire efficiency of the complete system is improved upon.
Chapter 1: INTRODUCTION
Waste warmth is heat which is produced in an activity by fuel combustion or substance response, and then "dumped" into the environment even though it could be reused for a few useful and economical purpose. The essential quality of temperature is not the amount but rather its "value". The strategy of how to recuperate this heat relies partly on the temp of the throw away heat gases and the economics involved.
Large level of hot energy gases is made from Boilers, Kilns, Ovens and Furnaces. If a few of this waste temperature can be retrieved, a considerable amount of primary energy can be kept. The energy lost in waste material gases can't be retrieved completely. However, much of heat could be recovered and loss minimized.
Heat Loss -Quality
Depending upon the sort of process, waste heating can be retrieved at nearly any heat from that of chilled chilling water to temperature waste material gases from an commercial furnace or kiln. Usually the higher the temperature, the higher the product quality and the more cost effective is the heat recovery. In virtually any study of waste materials heat recovery, it is completely necessary that there should be some use for the recovered warmth. Typical examples of use would be preheating of combustion air, space home heating, or pre-heating boiler give food to drinking water or process water. With high temperature heat restoration, a cascade system of throw away heat recovery may be practiced to ensure that the maximum amount of heating is recovered at the highest potential. An example of this system of waste high temperature recovery would be where the high temperature level was used for air pre-heating and the reduced temperature level used for process feed water heating or steam raising.
Heat Deficits - Quantity
In any heat recovery situation it is vital to know the quantity of temperature recoverable and also how it could be used.
The amount of heating recoverable can be computed as, Q = V x x Cp x ‹T
Where,
Q is heat content in kCal
V is the movement rate of the element in m3/hr
is density of the fuel gas in kg/m3
Cp is the precise high temperature of the element in kCal/kg oC
‹T is the heat range difference in oC
Development of the WHRS
Understanding the procedure is vital for development of Waste products Heat Recovery system. This is accomplished by reviewing the process movement sheets, layout diagrams, piping isometrics, electronic and instrumentation wire ducting etc. Detail overview of these documents can help in determining:
a) Options and uses of waste materials heat
b) Upset conditions taking place in the seed due to high temperature recovery
c) Option of space
d) Other constraint, such as dew point developing in an machines etc.
After identifying source of waste warmth and the possible use than it, the next thing is to select ideal heat restoration system and gadgets to recuperate and make use of the same. (Reay, 1979)
The basic strategy of the waste heat recovery is to fully capture the waste heating steams and, employing a heat exchanger, transfer that heat to some other medium to place back into the procedure. The features of waste heat recovery are it can reduce facility's annual fuel bills, reduce herb emissions and improve production. In process home heating, using waste heating will displace a portion of the fuel or electricity that could in any other case be purchased. Waste products heat recovery is actually a good idea when:
The heat of the waste products heat is hotter than the input requirements of the process.
The fuel cost savings achieved are greater than the administrative centre and operational costs of the waste products heat recovery equipment.
The value of the waste heat steam is determined mostly by its temperatures. It is extensively placed that any waste products temperature stream (air or liquid) of at least 500oF (260oC) is a practicable source for recovery. Obviously, the bigger the temperature, the higher the quality or value of the waste materials steam. Relating to a recent Office of Energy (DOE) report, with stack heat of 1 1, 000oF (538oC), the heat carried away may very well be the sole biggest loss in the process. Above 1, 800oF (982oC), stack losses will ingest at least 50 percent of the total fuel source to the procedure.
Equipment used for waste heat restoration:
The variety of equipment designed for waste heat recovery includes recuperators, regenerators and throw away warmth and exhaust gas boilers/vapor generators. The heat healing process can be gas to gas or gas to water. The merchandise of waste heat recovery can be preheated combustion air, warm water and vapor. The hot water and vapor can be utilized for vegetable services or within the original process home heating. The steam may also be used to run heavy steam turbines for mechanical work or even to produce electricity.
A recuperator is a gas-to-gas heating exchanger placed on the stack of the oven or exhaust of any primary mover. Recuperator's transfer heat from the outgoing gas to inbound combustion air without allowing steams to combine. There are lots of designs for recuperators, but all rely on pipes or plates to copy heat. They will be the most widely used waste heat recovery devices.
A regenerator is basically a rechargeable storage space device for heating. They can work with gas-to-gas, gas-to-liquid or liquid-to-liquid waste products heat options and can be installed on ovens, perfect movers, chemical substance reactors and with heavy steam condensate. A regenerator can be an insulated container filled with material with the capacity of absorbing and keeping large amounts of thermal energy. Through the first part of the cycle, the waste materials stream moves through the regenerator, warming the storage medium. The second part of the cycle gets the un-heated stream flow through the regenerator, absorbing warmth from the medium before it gets into the process. The pattern then repeats itself. In constant procedures, two regenerators are required. As with recuperators, there are numerous designs for regenerators such as temperature wheels, passive, fin-tube and shell-and-tube.
Waste heating and exhaust gas boilers/steam generators are similar to standard boilers except they are simply heated by the waste materials heat heavy steam from the procedure or primary mover alternatively than off their own burner. Waste products high temperature boilers are of most value to process business that require huge amounts of heavy steam in their process. The steam generated from a waste material heat steam won't generally replace existing boilers but will supplement the steam that they produce, thus reducing the power cost to use the direct-fired boilers. As the heavy steam from a waste heat steam is offered only when the procedure is running, squander heat boilers are usually designed to operate with existing boilers or with steam generators in a blend system. (Kessler, 2004)
Chapter 2: Literature Review
Waste high temperature may or might not exactly be recovered from all the market sectors. This basically relies upon the quantity of waste heat available for the reason that particular industry and the economics involved with its extraction. The heat recovery that is done in a few of the market sectors in India is reviewed below.
Cement industry:
India, being the second largest cement designer in the world after China with a complete capacity of 151. 2 Million Lots (MT), has got a huge cement industry.
In cement crops practically 40 percent of the total heat insight is turned down as waste warmth from exit gases of preheated and grate much cooler. This waste temperature can be effectively applied for electric power technology. Cogeneration of electricity besides mitigating the challenge of power shortage also helps in energy saving as well as reducing garden greenhouse gas emissions.
Cogeneration systems have been successfully operating in concrete plant life in India, China and South-east Asian countries. In existing ideas cogeneration technologies based on bottoming cycles have potential to create up to 25-30 percent of the power requirement of a place. However, the Indian cement industry is yet to make strong attempts in this direction due to living of various technological and financial constraints. (Gulf Seacoast Clean Energy Application center, 2008)
Sulphuric acid Herb:
Sulphuric acid required for a sulphonation response is produced in-house using elemental sulphur as the starting uncooked material. The process technology used for the purpose is Two times Contact Twin Absorption (DCDA) process. DCDA is considered to be the most effective process technology (resulting in nearly almost zero atmospheric emission of sulphur bearing gases) for producing sulphuric acid. Along the way of development of sulphuric acid using elemental sulphur as the starting material hot gas and hot acid streams get generated during various periods of the procedure. As a part of the process, traditionally the heat contained in the hot gas channels is recovered in the form of steam in throw away heat boiler. The waste materials high temperature in the hot acid steams is low grade heating (temperatures being low) which is not recovered in all the traditional sulphuric acid vegetation. The magnitude of recovery of waste warmth from the hot fluid steams, and the quantum of heavy steam generated is determined by the technical top features of the process plant, the capital cost mixed up in process of temperature restoration and the chance to use the recovered temperature. (Prakash, 2008)
Waste heat has been bigger than solar energy:
The typical professional power plant in the U. S. is merely about half as energy efficient as those found in 1910, relating to Sean Casten, CEO of Recycled Energy Development (RED)
In fact, those people Thomas Edison designed were more efficient. Edison's crops weren't actually very productive as making energy, Casten mentioned, but he sold heat generated during procedures, which boosted the entire. A complete two-thirds of the gas burned to create power in the current power plants - which generally were built-in the middle-1960s with 1850s technology - gets lost he asserts.
Although it can be challenging and expensive to harness, waste heat is getting increased concentration as a source of power in both U. S. and China, mostly as a result of quantities of heating out there. A report conducted by Lawrence Berkeley National Labs estimated in 2005 that the U. S. alone has 100 gig watts of untapped electrical capacity by means of waste high temperature that on a yearly basis could produce 742 terawatt hours of electricity. That's bigger than the solar fleet, which gets assessed in megawatts. UC Berkeley's Arun Majumdar quotes that the U. S. consumes 100 quads (100 quadrillion BTUs) of energy annually and 55 to 60 percent of it gets dissipated as waste products heat.
Generating that warmth, naturally, also means surplus greenhouse gases. Roughly 42 percent of carbon dioxide emissions come from power plant life, said Casten. If electricity plants are truly only 33 percent reliable, which means that 28 percent of the carbon dioxide output in the U. S. could be removed without crimping the nationwide lifestyle. Vehicles only take into account 19 percent.
Some companies, such as Cypress Semiconductor and GMZ Energy, want to develop thermoelectric materials. These are semiconductors that, covered around a steam pipe, could convert ambient temperature to electricity.
Companies like Israel's Ormat and Westmont Sick. -established RED - which increased a $1. 5 billion fund with Denham Capital Management to take on waste heat assignments - are largely focusing on a lot more traditional techniques. Particularly, exploit excess vapor pressure and heat to turn a turbine, electric power heating system systems or boil more normal water. It all depends on the circumstances on the ground. Waste fuels may also be harvested.
While the bulk of waste heat is generated in large crops, there's also smaller pockets. Gas pipelines are equipped with booster stations which keep up with the pressure inside the pipeline as the gas journeys from one indicate another. Each one on average requires 10 megawatts of electricity but gives off about 3 megawatts well worth of waste warmth.
"You will find opportunities all over the place - silicon manufacturers, concrete, metal, " he said. "They may have high amounts of pretty high quality misuse heat. "
One of the business's more dramatic assignments will go online this year 2010. Western world Virginia Alloys, a silicon supplier, will install a waste heat recovery system that will generate 45 megawatts of electrical power. The business only uses 120 megawatts right now. (Put yet another way, the business only really needs 75 megawatts because of its operations and is currently burning off 45 megawatts. )
To date, the top obstacle has been cost. Most industrial-scale waste materials heat jobs cost between $5 and $50 million. That's too high for most to pay out of capital finances and too low for a general population financing job.
"There's an enormous Goldilocks problem, " he said. To bypass this, RED will pay for any waste temperature recovery system it installs and then gets payed for energy personal savings under long-term deals. Goldilocks problem is only locating the appropriate solution for the challenge. (Kanellos, 2009)
Hence having looked at lot of cases and the past and today's of waste warmth recovery, we can access that waste warmth is not retrieved in every the business. It depends on the many factors as the quantity of temperature, the economics involved and the feasibility of the misuse heating to convert into useful warmth in that particular vegetable. The plant that I have looked at has that possibility to convert waste heating into useful high temperature in every the perspectives.
Chapter 3: Methodology
Nava Bharat Endeavors Limited has Electrical power arc furnaces for production of Ferro alloys (Manganese, Silicon and Chromium alloys), which are essential inputs for make of metal. Manganese and Silicon alloys impart power and hardness and become powerful deoxidizing agencies, Chromium alloys make material corrosion resistant and heat resistant.
The fume from the furnace is diluted with ambient air and cleansed by the gas cleaning plant before tired to atmosphere. One of the furnaces is equipped with radiant gas cooler. It is designed to save the heat, which is dissipated from the radiant cooler. It really is proposed to install a double go away warmth exchanger (LPHX-low pressure heat exchanger and HPHX-high pressure heating exchanger), that copy the waste temperature to Main condensate and feed water before the primary condensate and give food to water are preheated in the LP & HP heaters of 32MW Captive Vitality Plant.
Chapter 4: Findings
Ferro Alloy Flower arrangement:
The plant includes the Submerged Electric Arc Furnace (SEAF), Tote filtration system, Radiant Gas Chiller, ID lover and Stack.
The submerged arc furnace is a semi available furnace with a capacity of 27. 6 MVA, where the ores are melted. The off gas is emitted from the furnace. The amount of the gas varies depending on the raw material. The dilution air is drawn from the openings across the furnace by your time and effort from ID fan, which is situated at the downstream of the glowing gas chiller.
There are two chimneys directly connected to water-cooled furnace hood. Both of these chimneys are provided with butter travel dampers, which are usually kept under closed condition. Each chimney will get the branch connection to radiant gas chiller below the butter take a flight dampers. Under normal circumstances the gas goes through the radiant gas much cooler.
Radiant gas cool is an design of gas holding pipes. The heat from the gas is cooled by the natural rays and convection to ambient air.
The gas after chilling is attracted by the ID fan and sent to the bag house to remove the particles in the gas stream. The handbag house is provided with reverse air fan to clean the dusty carriers. The bag house is with eight compartments out which one compartment will be under cleaning at any time. The bag materials is fiberglass.
Manufacturing Process:
The above alloys, known as bulk Ferro alloys, are manufactured by charging pre-determined levels of raw materials consisting of ores, reductants and fluxes into submerged electric arc furnaces. The mixture of raw materials depends upon the specs of Ferro alloy to be produced.
High currents at low voltage are transferred through the three electrodes of the furnace and the fee of raw materials. The resistance provided by the recycleables to the circulation of electricity creates tremendous heat, leading to smelting of the recycleables charged into the furnace and the consequent metallurgical reactions takes place.
Carbon in the reductant reacts with the oxides in the ores. The metallic content of the ore forms a Ferro alloy as the other gangue materials become slag. Both Ferro alloy and the slag are in liquid form as a result of high temperature in the furnace bath. Because of difference in densities the alloy and slag are segregated. The density of slag is lower than the liquid metal, slag floats to the most notable.
At regular intervals, the molten metal and slag are tapped out from the furnace bath by having a tap hole. The liquid slag is granulated by impingement against a jet of water in case of Ferro stainless and Silico Manganese. The Ferro Manganese slag is reused for the production of Silico Manganese due to its high Manganese and low Phosphorous content.
The granulated slag is utilized for make of travel ash bricks and concrete jewelry.
The liquid material (i. e. , the Ferro alloy produced) is accumulated in a ladle and cast into moulds in a continuing casting machine or powder bedrooms as a cake. These cakes, after air conditioning, are broken down to the scale specified by the client, depending on the metallurgical practices accompanied by the client. The sized material is crammed in hand bags of 50 kilograms for home marketplaces and one firmness or loose for export markets generally speaking and dispatched to the clients.
Thermal Power Vegetable arrangement:
Thermal Power Place mainly involves Boiler, ESP (electrostatic precipitator), Vapor Turbine, Generator, Condenser, LP heater, HP heating unit, Boiler Give food to Pump, Condensate Removal Pump, Deaerator, Cooling Tower, CW (clockwise) & ACW (anticlockwise) pumps, Normal water treatment plant, Coal and ash handling flower.
Process of Electricity Generation:
The Thermal Power Plant employs steam turbine based ability generation, which is the hottest method for creation of electricity from coal. In this system, water can be used as a working fluid and is also heated up in a Boiler by using up coal, to produce steam, which, on further home heating, becomes superheated steam having a high temperature of 530OC and a high pressure of 93 kg/cm2. This superheated heavy steam runs the turbine, which turns high temperature energy into mechanised energy and drives a power generator combined to it. The generator turns the mechanical energy into electric power.
The auxiliary system includes circulating normal water system, ash collection and ash handling system, coal handling system, electric switchgear, transformers, etc.
The required coal is smashed and screened in the Coal Handling Seed by making use of crushers & screens. This smashed coal is carried to boiler bunkers through conveyors. From bunkers, the coal is fed into the boiler furnace.
Necessary air for combustion is pumped into the furnace by Primary and extra air fans. Principal and Secondary air are heated in Air Pre-Heater by utilizing waste heat in gasoline gases before fed to furnace for increasing the Boiler efficiency and the gasoline gases are tired to atmosphere through ESP & Chimney.
Ash collected after combustion of coal in two different locations. One is under foundation and the other reaches ESP. Ash gathered under bed is called as lower part ash or bed ash, which is conveyed to ash fish pond through slurry system and Take a flight ash at ESP is conveyed pneumatically to ash storage area silo.
Required feed normal water in Boiler for heavy steam generation is pumped from water treatment plant by using Boiler Supply Pump.
The steam turbine is a totally condensing type. After transferring through the turbine, the vapor is condensed to water in the condenser and pumped back again to the boiler. This circuit is repeated. You can find no discharges out of this system except a very minor level of steam blown from the steam circuit to keep the complex quality of boiler supply water.
The vapor Turbine has three extractions, you are for HP heating unit to heat up the feed normal water, second is designed for Deaerator to deaeration process and third is ideal for LP water heater to heat the key condensate.
The cooling drinking water system for condensing the vapor is of circulating type. In the cooling down tower sump, cool water is pumped to the turbine condenser where it picks up heat while condensing the heavy steam and is also pumped back again to the chilling tower for air conditioning.
Waste Heat Recovery System
The company (NBV) has installed a temperature exchanger to work with the heat available in the furnace gasoline gases, for home heating the boiler give food to normal water and main condensate of 32 MW Captive Vitality Plant found in the same premises. The heat exchanger is of combination circulation type with two passes. The first go away is called as HPHX and the next pass is named as LPHX. The petrol gases are passed vertically downwards over bundles of horizontal drinking water pipes in HPHX and upwards in LPHX. Feed water and main condensate are heated up in HPHX and LPHX respectively. The flue gas coming from the furnace moves over HPHX first, later over LPHX and lastly enters Gas Cleaning Plant (GCP) through an ID lover.
WHRS is intended for using the waste heat available in Submerged Electric Arc Furnace (SEAF) gas gases. It really is installed in the down heavy steam of furnace. This system contains Low Pressure Warmth Exchanger (LPHX) and High Pressure Heat Exchanger (HPHX) to heat up the main
Condensate and nourish water.
Constructional Features:
WHRS mainly includes ducting from SEA furnace to heat exchanger, double forward High temperature exchanger, Ducting from Temperature exchanger to GCP Identification fan, Feed water & Main condensate lines from Electricity Plant.
Ducting from furnace to Warmth exchanger: Submerged Electric Arc Furnace (SEAF) is having two chimneys of diameter 2000mm each with 65Mtrs elevation. A faucet off (size 2000mm) diameter from each chimney is considered horizontally at (+) 26. 50Mtr elevation and made a common duct. After tapings, pneumatic operated isolation dampers are given in two chimneys. The other end of common duct is linked to inlet of High temperature exchanger. The diameter of common duct is 3000mm. One dilution damper of size 800mm is established in keeping duct to dilute the flue gas with oxygen.
Double pass Heating exchanger: It is a two - pass cross movement type heat exchanger. First forward is called RUTHLESS Heat Exchanger (HPHX) and the second pass is named Low Pressure Heat Exchanger (LPHX). HPHX & LPHX includes 3 modules each and having normal water pipe coils inside the casing. Gas gases are moving over the drinking water pipe coils during procedure. A by-pass duct (1000mm diameter) with regulating isolation damper is provided in between HPHX & LPHX. Insulation materials of 175 & 125mm dense is provided on HPHX & LPHX respectively.
Ducting from Warmth exchanger to GCP Identification Fan: It really is 2200mm diameter. LPHX bypass duct is connected to the outlet duct. Store duct is provided with one temperatures transmitter & one draft transmitter. The Identification lover inlet is having a multi lower damper for controlling the stream rate.
Feed Water line: A touch - off is extracted from Power Plant supply water collection after HP heater with a motor unit handled isolation valve (with bypass valve) and connected to HPHX. The wall plug from HPHX is connected before the control valve in Electricity Plant feed water brand with a engine handled isolation valve. One HPHX by-pass engine managed valve is provided near control valve. Insulation materials of 75mm thick is provided over the complete piping.
Main Condensate brand: A touch - off is taken from Main Condensate type of Power Flower after LP water heater with a motor run isolation valve (with bypass valve) and linked to LPHX. The wall plug from LPHX is linked prior to the control valve in Vitality Place Main Condensate collection with a motor unit run isolation valve. One LPHX bypass motor handled valve is provided near control valve. Insulation materials of 50mm heavy is provided over the complete piping.
Process:
Feed water from the Boiler Give food to Pump with a temperatures of 155OC is warmed in HPHX with 380OC of fuel gas coming out from SEA furnace, then the feed water temp rises to 225OC and the energy gas temperature comes down to 226OC. This feed water brand is linked to the Boiler for vapor generation.
Main Condensate coming from Condensate Removal Pump through Heavy steam Jet Ejector & Gland Heavy steam Condenser with a heat of 89OC is heated up in LPHX with a 226OC of energy gas, then the Main Condensate temps will rise to 123OC and the flue gas heat range will comes down to 160OC. This store of Main Condensate is connected to Deaerator inlet piping.
The flue gases are discharged to atmosphere, after utilizing the waste heating available in flue gases through chimney by making use of ID lover.
The extraction vapor for HP & LP heating units will be cut off from Turbine i. e. HP & LP heating units are bypassed, while Waste material Heat Recovery System is operating.
Chapter 5: CONCLUSIONS
The objective of the project was to design a Waste Heating Recovery System (WHRS) for Nava Bharat Ventures Limited. The prevailing system was examined and found 1. 25 x 107 kCal/hr of throw away energy is reject to the surroundings from Sub - merged Electric Arc Furnace (SEAF).
Different ways of heat restoration were examined to determine which are most possible with the NBVL. It is necessary to judge the selected waste materials heat restoration system on the basis of financial examination such as investment, depreciation, payback period, rate of come back etc. Furthermore the advice of experienced consultants and suppliers must be obtained for rational decision.
When calculating energy cost savings and payback times for heat restoration units, it is important to compare warmth recovery with the existing source of energy for generating thermal energy, which might be a low-price fossil gasoline such as gas.
The aim of installing a fresh energy recovery system at Nava Bharat Projects Ltd was to have the ability to reduce petrol cost and increase Steam Turbine heat rate induced by high temperature being lost to the environment. All together, the GDP Identification fan power consumption will reduce, life of GCP bags is increased by lowering the gas temperatures at GCP inlet and thermal pollution also will reduce.
A Double move Heating exchanger was chosen and designed to recover heat from exit gas gases of SEAF system and warmth the Feed Water and Main Condensate through the use of the waste materials energy available in petrol gas.
The main target of this task was to reduce the expense of energy bills by reducing the amount of gasoline used to heat the center.
