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Energy Efficiency Guide for Industry in AsiaTraining Session on Energy Equipment Industry Sectors Presentation to Energy Efficiency Guide for Industry in Asia Chapter 15 Industry Sectors © UNEP GERIAP
Training Agenda: Industry Sectors1) Iron & Steel Sector description Process flow Energy conservation 2) Chemical 3) Cement Sector description Process flow Energy conservation 4) Pulp & Paper Industry Sectors We will look at four industry sectors including iron and steel, the chemical sector, cement industry and pulp and paper. We will start with iron and steel. © UNEP 2005
Iron & Steel Industry Sector Description Two categories:1. Primary steel production Manufactured right from the basic iron and steel ore to final product 2. Secondary steel production Conversion metal scrap, ignots and metal scraps manufactured through various routes Industry Sectors The iron and steel industry can be divided into two distinct categories, primary and secondary steel production. In primary steel production steel is manufactured right from the basic iron and steel ore to final product. The industries producing the primary steel are generally integrated steel plants which manufactures the final products in form of billets, angles, channels, rods etc. Secondary steel manufacturing involves conversion metal scrap to ingots and metal scrap and ingots manufactured through various routes to formed products. Induction furnaces are used for melting scrap arc. For conversion of ingots to products reheating or induction heating furnaces are used. In addition furnaces, electrical or thermal, are also used for heat treatment. GHG emissions due to carbon dioxide emissions occur due to the use of fossil fuels and electricity in furnaces. © UNEP 2005
Iron & Steel Industry Process Flow Basic primary steel processHigh grade iron ore is crushed for sizing and to produce both fine and lump ore Pelletizing is a process that mixes very fine ground particles of ore with limestone, dolomite etc Industry Sectors Among the elements composing the crust of the earth, iron exists in the largest quantity next to oxygen, silicon, and aluminum. Iron exists as natural ores in the form of oxides, and the estimated amount of ore deposits in the world is approximately 800 billion tons. Typical ores are hematite and magnetite High-grade iron ore is crushed for sizing, producing both fine ore as well as lump ore. The fine ore is processed into sintered ore by sintering. In the sintering process, fine ores 2-3mm in diameter are mixed with coke breeze as a fuel. Pulverized ore is processed into pellets by pelletizing. Pelletizing is a process that involves mixing very finely ground particles of ore with fluxing materials such as limestone and dolomite and then shaping them into balls of mm in diameter by a pelletizer. Thereafter the balls are hardened by firing with heavy oil or coal as a fuel. The figure illustrates the primary steel making process. Figure: Primary steel making process Source: JFE © UNEP 2005
Iron & Steel Industry Process Flow Basic secondary steel processRaw material Melting Refining Casting Rolling Re-rolling Re-heating furnace Rolling mill Cooling Shearing Inspection dispatch Industry Sectors The basic secondary steel process can be divided in several stages beginning with the raw material. In the iron and steel industry, raw materials are scrap, fluxes and ferro alloys. During the melting stage, scrap and sponge iron, fluxes, ferro alloys are melted in an electric arc furnace. Thereafter, the molten metal from electric arc furnace is taken in a ladle for refining. In casting, the liquid steel is cast into semi finished products such as billets, blooms, slabs etc. During rolling, these billets, blooms, slabs are heated at 1200°C to make the metal malleable and then rolled into finished products. The rolling stage can be followed by a re-rolling. Rolling mill means that the hot slab is rolled through a series of rolls to facilitate gradual reduction to required size. The rolled products are then cooled in ambient conditions before undergoing the next process step The ends are sheared to remove the cracked end portions and to meet the required customer needs. The products are inspected for metallurgical and physical defects through non destructive testing such as radiography. The finished and inspected products are then bundled and dispatched. © UNEP 2005
Iron & Steel Industry Process Flow Steel foundry Industry SectorsCan be classified into a) melting, b) moulding, c) fettling and d) heat treatment Arc furnace Melting of scrap by application of intense heat generated by the arc Induction furnace Transfers energy through a magnetic field and its intensity decides the amount of absorbed energy Industry Sectors The steel foundry operations can broadly be classified into four areas. They are melting, moulding, fettling and heat treatment. The operation starts with melting of the scrap in the arc or induction furnace. The molten metal is subjected to refining which basically involves adjusting the composition of the molten metal through carbon and alloy additions. The liquid metal is tapped in a ladle that is carried to the mould shop where the metal is poured in the mould boxes. The casting is removed from the mould boxes and taken for surface finish The arc furnace is connected to a transformer of a rating which is normally 400 to 500 KVA per tonne of metal. The process involves melting of scrap by application of intense heat generated by the arc. An induction furnace is shaped similar to a cylindrical ladle surrounded by an induction coil. Energy transfer is through a magnetic field which directly links the charge. The amount of energy that is absorbed depends on the magnetic field intensity, the electrical resistivity of the charge and the operating frequency. © UNEP 2005
Iron & Steel Industry Process Flow Energy flows Industry SectorsRolling Thermal energy Electrical energy Steel foundry Arc melting Induction melting Cutting Reheating Furnace Rolling Cooling Shearing Electricity Fuel Finished Product Raw material Industry Sectors When it comes to energy flows, the energy costs in rolling constitutes about 40 to 50% of the manufacturing cost in this industry. Fuel in terms of oil and coal accounts for about two third of the energy cost. Thermal energy is required for heating the steel before the rolling operation. Fuel oil is the most commonly used fuel in the reheating furnaces. Electrical energy is used by all the units to run their motive loads. Steel foundry is electrical energy intensive and energy costs per tonne could go up to as high as 40 %. Arc melting also require energy so does induction melting. (click once) This flow diagram illustrates the energy flow in rolling. (Let audience reflect over the diagram before continuing) Figure: Energy flow in rolling © UNEP 2005
Iron & Steel Industry Process Flow Material & energy balanceIndustry Sectors This figure illustrates the energy balance in a reheating furnace. As the furnaces operate at high temperatures, the exhaust gases leave at high temperatures and this results in poor efficiency. Therefore a heat recovery device such as air preheater should be part of the system. The lower the exhaust temperature, the maximum is the furnace efficiency. This concept is applicable for a heat treatment furnace as well.. Figure: Energy balance in reheating furnace © UNEP 2005
Energy Conservation OpportunitiesIron & Steel Industry Energy Conservation Opportunities CP-EE measures: Industry Sectors CP-EE approach to minimize energy in reheating furnaces is given in the following fish bone diagram. Basically it involves rationalization of combustion, rationalization of heating and cooling, prevention of heat losses and waste heat recovery. Figure: Reheating furnace © UNEP 2005
Energy Conservation OpportunitiesIron & Steel Industry Energy Conservation Opportunities CP-EE measures in reheating: Table: CP-EE measures in reheating and heat treatment furnaces Industry Sectors Improvement Area Energy-Saving Measure Energy Saving Potential Efficient Combustion Maintain minimum required free oxygen in combustion products. 2% to 10% Efficient Combustion (burners) Eliminate formation of excessive amount of CO or unburned hydrocarbons. Also eliminate or minimize air leak-age. Flue Gas Heat Recovery Preheat and/or dry combustion air and the charge/load. After-burn the combustibles and cascade the exhaust gas heat. 5% to 25% Heat Loss Reduction Use optimum insulation for equipment and maintain it regularly. Employ furnace pressure control. 1% to 5% This table lists the cleaner production and energy efficiency measures available in reheating and heat treatment furnaces. Improvement areas include efficient combustion through maintaining a minimum rof required free oxygen in combustion products. The formation of excessive carbon monoxides can also be eliminated. Another improvement area is to recover flue gases. The heat loss can also be reduced by using optimum insulation. (Let audience reflect over table before continuing) © UNEP 2005
Energy Conservation OpportunitiesIron & Steel Industry Energy Conservation Opportunities CP-EE measures in reheating: Table: CP-EE measures in reheating and heat treatment furnaces Industry Sectors Improvement Area Energy-Saving Measure Energy Saving Potential Design of Furnaces and Heating Select proper burner and furnace design to enhance heat transfer to the load. 5% to 10% Furnace Operation Clean heat transfer surfaces frequently. Furnace and Heating System Heat Transfer Replace indirect heat systems with direct heat systems where possible. Improved Scheduling and Load Management Operate with full load; minimize idle time, shutdowns, and start-up cycles. 2% to 5% Use of Process Simulation Use models to optimize temperature settings to avoid long "soak" times or overheating. Equipment Design Materials Use advanced and improved materials. Other measures include selecting proper burner and furnace designs. The heat transfer surfaces should also be regularly cleaned. Indirect heating systems should furthermore be replaced by direct heat systems where possible. Another improvement area is load management where one should seek to operate on full load and avoid shut downs and start ups. Process simulation and equipment design materials also provide opportunities to save energy. © UNEP 2005
Energy Conservation OpportunitiesIron & Steel Industry Energy Conservation Opportunities CP-EE measures in arc furnace melting: Scrap preparation Scrap segregation Use of oxygen lancing Temperature control CP-EE measures in induction melting: Idling periods Charge metals Optimizing heel Radiation losses Industry Sectors The arc furnace steel-making method effectively utilizes a waste resource by using scrap as its raw material. Thus, this method saves energy by itself as it requires less energy than the blast furnace-converter method to produce one ton of crude steel. CP-EE measures in arc furnace melting are listed here. Increasing the bulk density of the scrap reduces the number of chargings. Scrap should be segregated as per the carbon content and charged accordingly. Use of oxygen during the melting stage results in reduction in meltdown time because of exothermic reaction of oxygen with iron and other combsutible elements present in the scrap. Finally, monitoring the tapping temperature and narrowing the gap between tapping and pouring temperature will increase the lining life, productivity and decrease energy consumption. Here, the CP-EE measures for induction melting are listed. First, minimizing the periods of idling provides an energy saving measure. In addition, the cleanliness of charge, charge density and charge size are also important factors affecting the energy consumption. Optimising the heel percentage versus specific energy consumption and minimizing radiation losses are also important energy saving measures. © UNEP 2005
Energy Conservation OpportunitiesIron & Steel Industry Energy Conservation Opportunities Energy efficient technologies: Melting Ceramic recuperator Ceramic fiber Ceramic coatings Regenerator Industry Sectors For melting, major methods that are currently used to accelerate the melting process and to save electric power required for the process include the use of an oil burner for auxiliary melting of the material in the furnace, oxygen lancing and the use of a heavy weight to compress bulky feed material in the furnace. A ceramic recuperator uses a unique ceramic material to coat and protect a custom made radiant tube metallic recuperator. In this concept, the flue gases from the furnace pass through a n inconel tube with the ceramic coating. Thus the flue gases heat the combustion air and this can result in energy savings of 33%. Ceramic fibre insulation can be applied on the hot face refractory to help the furnace heat up and cool down at a rapid rates. This reduces cycle time, improves productivity and decreases energy consumption. Furthermore, the emissivity can be improved by the application of high emissivity ceramic coatings. This will increase heat transfer, reduce wall losses and thereby save energy. Regenerative burners are operated in pairs. While one is used to burn the fuel, another burner uses a porous ceramic bed to store heat. After a short period the process is reversed and the heat stored in the ceramic bed is used to pre-heat the combustion air. © UNEP 2005
Energy Conservation OpportunitiesIron & Steel Industry Energy Conservation Opportunities Energy efficient technologies: Industry Sectors This figure illustrates the operating principle of the regenerative burner system. (Let audience reflect before continuing) Figure: Regenerative burner system operating principle © UNEP 2005
Training Agenda: Industry Sectors1) Iron & Steel Sector description Process flow Energy conservation 2) Chemical 3) Cement Sector description Process flow Energy conservation 4) Pulp & Paper Industry Sectors © UNEP 2005
Chemical Industry Sector Description Industry SectorsProduction of graphite for brake linings and lubricants, chemical catalysts for plastics, elastomers and pharmaceuticals and more Most chemical applications require spray drying or milling why particle size is important Most milling processes comprise a grinder, a classifier, a cyclone and a blower The formed material size needs to be measured Industry Sectors Hello © UNEP 2005
Chemical Industry Process Flows Fertilizer industry Industry Sectors85% of the world’s ammonia production is used for making chemical fertilizer Fertilize production accounts for 2% of total global energy consumption Fertilize production accounts for 1% of global carbon dioxide emissions Ammonia manufacture is expensive and is about % of the production costs Natural gas is the most commonly used hydro- carbon feedstock for new fertilizer plants Industry Sectors The fertilizer sector is one of the largest and energy intensive energy industries why we will focus on this sector while looking at the chemical industry. (click once) Ammonia is the most important raw material for making fertilizer and 85 per cent of the world’s ammonia production is used for making chemical fertilizer. It has also been estimated that the production of fertilizers currently accounts for about 2 per cent of total global energy consumption. Furthermore, fertilize production accounts for 1 per cent of global carbon dioxide emissions. Ammonia manufacture is an energy intensive process and energy cost is about per cent of the production cost. Recovery of small quantities of heat can accumulate to become sizable energy savings. Natural gas is the most commonly used hydrocarbon feedstock for new plants and preferred over other raw material from an environmental perspective. © UNEP 2005
Chemical Industry Process Flows Primary reforming Industry SectorsThe natural gas that leaves the desulphurization tank is mixed with process steam It is preheated in the primary reformer Secondary reforming Only 30-40% of the hydrocarbon feed is reformed in the primary reformer In a secondary, the temperature is increased to increase conversion Industry Sectors In primary reforming, the natural gas that leaves the desulfurization tank is mixed with process steam and preheated to °C in the convection section of primary reformer. The mixture of steam and gas enters the gas fired primary reformer filled with a nickel catalyst. The temperature is raised to °C. In secondary reforming only per cent of the hydrocarbon feed is reformed in the primary reformer. The temperature must be increased to increase the conversion. This is done in secondary reformer where process gas is mixed with preheated compressed air and then passed over nickel catalyst. The reformer outlet temperature is about 1000°C, and up to 99 per cent of the hydrocarbon feed to primary reformer is converted. © UNEP 2005
Chemical Industry Process Flows Energy balance Industry SectorsCompared to natural gas, ammonia manufacturing with heavy oil is 30-40% more energy intensive and with coal route 80% more Steam reforming ammonia plants have surplus heat available for steam production and modern plants can be energy self sufficient The theoretical minimum energy consumption for ammonia manufacture through steam reforming is ~21.6 GJ/t of ammonia (HHV) Industry Sectors Hello © UNEP 2005
Carbon dioxide RemovalChemical Industry Process Flows Natural gas Ammonia synthesis Compression Methanation Carbon dioxide Removal Shift conversion Reformer (Secondary) Reformer (Primary) Sulphur Removal NH3 Condensate CO2 Heat ZnS Power Heat, Power Air, Power H2O, Fuel Material balance Emissions from ammonia plants include SO2, NOx, CO, CO2, VOCs, particles, hydrogen sulfide, methane, hydrogen cyanide and ammonia Industry Sectors Emissions to the atmosphere from ammonia plant include sulphur dioxide, nitrogen oxides, carbon monoxide, carbon dioxide, hydrogen sulfide, volatile organic carbons, particulates, methane, hydrogen cyanide and ammonia. A typical material balance for ammonia plant is shown in this figure. Figure: Material balance for an ammonia plant © UNEP 2005
Energy Conservation OpportunitiesChemical Industry Energy Conservation Opportunities Areas for CP-EE measures in ammonia plants: Primary reformer Excess air reforming Heat exchange auto terminal reforming Reformer catalyst Reformer tubes Furnace design Shift conversion Carbon dioxide removal section Leakage of CO2 from compressors Flue gas from the furnace Cogeneration Industry Sectors This is a list of some of the areas and sections where Cleaner Production measures can be made. For example, in the primary reformer, the preheating process air in the secondary reformer can come from waste heat in the primary. Also, fired furnaces can be replaced with gas heated. This gives energy savings. Another opportunity is excess air reforming where gains such as reduced primary reformer size and reduced energy demand can be obtained. Another example is to use a superior catalyst with high activity that has a better geometrical shape and packing. This achieves lower shift temperature and gives higher conversion of hydrocarbon feed as well as lower tube wall temperature. Looking over the furnace design can improve the efficiency thanks to uniform heating and easier control of heat input. In terms of cogeneration there can be simultaneous production of heat and power which gives substantial energy savings. © UNEP 2005
Energy Conservation OpportunitiesChemical Industry Energy Conservation Opportunities Areas for CP-EE measures in ammonia plants: Ammonia converter Carbon dioxide removal section Leakage of CO2 from compressors Compressors Better purification techniques Pre-reformer Ammonia synthesis converter Absorption refrigeration system Cooling of synthesis gas Desulphurization Industry Sectors Furthermore, by using the exit waste gas from the ammonia converter to produce steam, energy savings can be obtained. The purification techniques can be improved by inserting gases separated from the ammonia reactor feed gas. This eliminates the need for purging in the synthesis loop and gives an increased conversion reaction as well as decreases the operating cost of synthesis loop. For compressors, those with high efficiency can be used as well as integrally geared compressors. Also, high performance vane diffusers can be installed. These measures improves the efficiency and lowers energy consumption. In addition to the mentioned, the other areas with energy conservation opportunities are presented further in the text book. © UNEP 2005
Energy Conservation OpportunitiesChemical Industry Energy Conservation Opportunities Energy efficiency technologies: Gas heated reformers Selectoxo unit Lower syngas inert level Heat exchange auto terminal reforming Purge gas recovery unit Industry Sectors We will now look at the energy efficiency technologies. Gas heated reformers are tubular gas-gas exchangers in which the secondary reformer outlet gases supply the reforming heat. Gas heated reformers has several advantages over fired furnaces such as reduced energy consumption, smaller volumes, lower maintenance costs, nil stack loss, longer tube life and reduced downtime. Selectoxo is a technology. Plants can use a combination of High Temperature Shift/Low Temperature Shift/Selectoxo Technology in place of conventional HTS/LTS. The major advantages with this are low pressure drop and efficient heat recovery from the process gas. Conventionally purification of syngas takes place during methanation step. Alternatively, if the impurities especially inerts like argon are removed from make up gases, higher conversion per pass and reduced purging can be achieved. The end result is a more efficient process. Excess heat available in secondary reformer can be utilized in primary reforme and emissions to the atmosphere significantly reduced. Purge gas recovery unit is installed to recover hydrogen from the loop purge. The recovered hydrogen is circulated back for ammonia production. © UNEP 2005
Energy Conservation OpportunitiesChemical Industry Energy Conservation Opportunities Energy efficiency technologies: Pre-reformer Improved catalyst Carbon dioxide removal processes Industry Sectors Other energy efficiency technologies include the installation of a pre-reformer. This is now gaining popularity among the modern plants. A pre-reformer converts the naptha to a mixture of methane, carbon monoxide and hydrogen. The other benefits are that it can handle natural gas as feed stock, and it can operate as pure natural gas reformer. It also provides sulphur protection for catalyst in primary reformer and extends the life of primary reformer catalyst, as well as stables the operating conditions in the primary reformer. The catalyst can also be improved. The latest catalyst has copper content and improved activity. It has a high resistance to poisoning, low by-product formation and longer life. Present trend for carbon dioxide removal is to replace the ammine solution for carbon dioxide scrubbing with more energy efficient practices such as benfied process, benfield low-heat process, benfield pressure swing process, giammarco-vetrocoke process with single and double activations etc. © UNEP 2005
Training Agenda: Industry Sectors1) Iron & Steel Sector description Process flow Energy conservation 2) Chemical 3) Cement Sector description Process flow Energy conservation 4) Pulp & Paper Industry Sectors © UNEP 2005
Cement Industry Sector Description Industry SectorsCement is produced by grinding, blending and burning limestone, sand, clay, bauxite or laterite These contain a suitable mixture of calcium oxides, silicon oxides, aluminum oxides and iron oxides Two types of CO2 emissions occur: From the energy consumption As a by product from the calcination process The global cement industry contributes to ~20% of all man made CO2 emissions The energy consumption in the cement industry is about 2% of the global primary energy consumption Industry Sectors Cement is produced by grinding, blending and burning either limestone, sand, clay, bauxite or laterite as they contain a suitable mixture of calcium oxides, silicon oxides, aluminum oxides and iron oxides. Two types of CO2 emissions occur from the cement industry. First from the energy consumption and secondly as a by product from the calcination process. The global cement industry contributes to ~20% of all man made CO2 emissions and has an energy consumption about 2% of the global primary energy consumption © UNEP 2005
Cement Industry Process Flows Production processes Industry SectorsMining surface mining is more eco-friendly Crushing size is reduced to 25 mm Raw material preparation roller mills for grinding and separators or classifiers for separating ground particles Coal milling provides dried pulverized coal to the kiln and precalciner Industry Sectors These are the different production processes in a cement industry (click once): The key raw material for cement production is limestone, this is mined and transported to the plant. Surface mining is gradually gaining ground because of its eco friendliness. To begin with, the limestone is fed to a primary and secondary crusher, where the size is reduced to 25 mm. Raw material preparation use roller mills for grinding and separators or classifiers for separating ground particles. These are the two key energy-consuming pieces of equipment at this process stage. In those plants that use coal, coal mills are part of the system to provide dried pulverized coal to the kiln and precalciner. The raw coal from the stock yard is crushed in a hammer crusher and fed to the coal mill. © UNEP 2005
Cement Industry Process Flows Production processes Industry SectorsPyro processing transform the raw material mix into gray clinkers in the form of spherically shaped nodules Pre heater and pre calciner from the preheater/precalciner process 60 % of flue go to the raw mill and 40 % to the conditioning tower Clinker cooler heat recovery from the hot clinker and temperature reduction of the clinker Finish milling grinding of clinker to produce a fine grey powder Industry Sectors Pyro processing is to transform the raw material mix into gray clinkers in the form of spherically shaped nodules. Thus, the function of the kiln in the cement industry is to first convert CaCO3 into CaO and then form clinker compounds through quite complex chemical reactions and physical processes. In the preheater vessels hot exhaust gases from the rotary kiln pass counter currently through the downward-moving raw materials. Compared with the simple rotary kiln, the heat transfer is improved. Additional thermal efficiencies and productivity gains have been achieved by diverting some fuel to a calciner vessel at the base of the preheater tower. This system is called the preheater/precalciner process and from here 60 per cent of flue go to the raw mill and 40 per cent to the conditioning tower. The clinker cooler has two tasks: 1) to recover as much heat as possible from hot clinker so as to return it to the process; and 2) to reduce the clinker temperature to a level suitable for the equipment downstream. Once the clinker leaves the kiln it must be cooled rapidly to ensure maximum yield for the compound that contributes to the hardening properties of cement. The main cooling technologies are the reciprocating grate cooler and the tube or planetary cooler. Finally, the cooled clinker is mixed with additives to make cement and ground. These materials are then sent through mills which perform the remaining grinding. Finish milling is the grinding of clinker to produce a fine grey powder. Gypsum is blended with the ground clinker, along with other materials, to produce finished cement. Gypsum controls the rate of hydration of the cement in the cement-setting process The energy used for cement grinding depends on the type of materials added to the clinker and on the desired fineness of the final product. © UNEP 2005
Cement Industry Process Flows Industry Sectors Energy flowsLimestone Mining Crushing Raw Milling Pyro Processing Clinker Cooling Cement Grinding Packing & Dispatch Coal Milling Transport Diesel for loaders, dozers and compressors Diesel for dumpers and trucks/ Electrical energy for ropeway Electrical Energy for crushers Electrical Energy for Mill drive and fans Heat Energy from kiln off gases fuel input for fans, drive and clinker breaker Bauxite, Ferrite Gypsum Pre calcination Kiln drive, fans and ESP for mill drive and fans fuel input/waste heat from clinker cooler Figure: Energy flows in a cement plant Process Flows Energy flows Industry Sectors Energy consumption nearly 40-40% of production costs Mill drives, fans and conveying systems are major energy consumers The cement making process is highly energy intensive and energy consumption accounts for nearly 40 – 50 per cent of the production costs. The major electrical energy consumption areas are mill drives, fans and conveying systems. This figure illustrates the energy flows in a cement plant. © UNEP 2005
Cement Industry Process Flows Electrical energy flows Industry SectorsClinker burning: ~30% Finish grinding: ~30% Raw mill circuit: ~24% Thermal energy flows 50% of the energy costs The kiln and precalciner are major users Industry Sectors About 30 per cent of electric power is consumed for finish grinding, and a little under 30 per cent each is consumed by the clinker burning process. Raw mill circuit is another major consumer that accounts for 24 per cent of the energy. The raw mill circuit and finish grinding process mainly consumes electric power for the mill, and the clinker burning process mainly for the fan. Thermal energy accounts for almost half the energy costs that incurre in cement manufacture. A variety of fuels such as coal, pet coke, gas and oil in addition to unconventional fuels such as used tires, incinerable hazardous wastes, agro residues etc are used in the cement plant. The major use of thermal energy is in the kiln and precalciner. © UNEP 2005
Cement Industry Process Flows Material & energy balanceImportant for optimized operation of the cement kiln, diagnosing operational problems, increasing production and improving energy consumption In a cement plant processes involve gas, liquid and solid flows with heat and mass transfer, the combustion of fuel, reactions of clinker compounds and any undesired chemical reactions Parameters to consider include velocity, static pressure, dust concentration, surface temperature and power Industry Sectors An understanding about the material and energy balance in a cement plant is is important in order to optimize the operation of the cement kiln, diagnose operational problems, increase production, improve energy consumption, lower emissions, and increase refractory life The cement process involves gas, liquid and solid flows with heat and mass transfer, combustion of fuel, reactions of clinker compounds and undesired chemical reactions that include sulphur, chlorine, and Alkalies. It is important to understand these processes to optimize the operation of the cement kiln, diagnose operational problems, increase production, improve energy consumption, lower emissions, and increase refractory life. When measuring the mass balance, the parameters to consider include velocity, static pressure, dust concentration, surface temperature and power © UNEP 2005
Energy Efficiency OpportunitiesCement Industry Energy Efficiency Opportunities CO2 reductions involves a two pronged strategy: Industry Sectors Improving energy efficiency Promoting blended cements that can decrease the clinker percentage in the cement The reduction of CO2 emissions from a cement plant involves a two pronged strategy. First, the energy efficiency must be improved. Second, blended cements that can decrease the clinker percentage should be promoted as this reduces the process CO2 emissions. © UNEP 2005
Clinker burning processCement Industry Energy Efficiency Opportunities Table: Classification of CP-EE measures in three steps Raw material process Clinker burning process Finish process First step 1) Selection of raw material 2) Management of fineness 3) Management of optimum grinding media 1) Prevention of stoppages 2) Selection of fuel 3) Prevention of leak 1) Management of fineness 2) Management of optimum grinding media Second step 1) Use of industrial waste material 2) Replacement of fan rotor 3) Improvement of temperature and pressure control system 4) Improvement of mixing & homogenizing system 2) Recovery of preheater exhaust gas 3) Recovery of cooler exhaust gas 4) Replacement of cooler dust collector 1) Installation of closed circuit dynamic separator 2) Installation of feed control system Third step 1) From wet process to dry process 2) From ball and tube mills to roller mill 2) Conversion of fuel 3)From SP to NSP 4)Use of industrial waste 5)From planetary and under coolers to grate cooler Industry Sectors Cleaner production and energy efficiency in cement plants starts from the software that includes the operation and process control, and extends into the field of hardware including equipment improvement and process improvement. (click once) Generally, CP-EE measures can be classified into the following three steps where you address the raw material process, the clinker burning process and the finish process. This is illustrated in the table. For raw material, the material shall first be selected and optimum grinding media managed. Secondly, thje use of industrial waste, replacement of fan rotor, temperature improvement etc can be considered. The third step for raw material includes converting from wet to dry process, and from ball and tube mills to roller mills. For the clinker burning process, the first step includes preventing stoppages and fuel selection. The second step includes recovery pf preheater exhaust gas an replacement of cooler dust collector. The third step involves the conversion of fuel, and converting from planetary and under coolers to grate coolers. The finish process involves the management of fineness and optimum grinding media. The second step deals with the installation of closed circuit dynamic separator and a feed control system. © UNEP 2005
Energy Efficiency OpportunitiesCement Industry Energy Efficiency Opportunities CP-EE measures: Raw meal mix design change Elimination of run-on equipment Finish Mill Optimization Avoidance of air supply leakage Installation of more efficient fan motors Employees’ awareness Power monitoring and targeting Process Replacement Measures % electrical energy reductions have been achieved in a cement plant by: Industry Sectors This is an example of how electrical energy reductions can be achieved in a cement plant. These measures inlcude: raw meal mix design change; elimination of run-on equipment; finish mill optimization; avoidance of air supply leakage; installation of more efficient fan motors; employees’ awareness; power monitoring and targeting; and process replacement measures. © UNEP 2005
Energy Efficiency OpportunitiesCement Industry Energy Efficiency Opportunities CP-EE measures: Capacity utilization Essential for energy efficiency Brings down the fixed energy loss component At least 90% required to achieve low specific energy consumption Fine tuning equipment Only requires marginal investment Can yield 3-10% energy savings if efficiently performed Technology upgrades Industry Sectors High capacity utilization is very essential for achieving energy efficiency. This brings down the fixed energy loss component of the specific energy consumption. At least 90 per cent capacity utilization is to be ensured for achieving low specific energy consumption. Also achieving high capacity utilization is under the control of plant personnel. For example, a survey of excellent energy efficient companies shows that 80 per cent of the companies attribute capacity utilization as one of the foremost reason for a major drop in specific energy consumption. Therefore, the first and foremost step for an aspiring energy efficient unit should be on increasing capacity utilization and reduce the specific energy consumption. Fine tuning of equipment is another opportunity for saving energy. On achieving high capacity utilization, the fine tuning of equipment should be taken up by the energy efficient plants. Various energy audit studies reveal that when fine tuning is efficiently done, this can yield 3 to 10 per cent of energy saving. The greatest incentive for resorting to fine tuning is that it requires only marginal investment. Quantum jumps in energy saving can be only achieved through technology upgrades or by applying new technologies. We will go through these next. © UNEP 2005
Energy Efficiency OpportunitiesCement Industry Energy Efficiency Opportunities Energy efficient technologies: Process control and management systems Raw meal homogenizing systems Conversion from wet to dry process Conversion from dry to multi stage pre-heater kiln Conversion from dry to pre-calciner kiln Conversion from cooler to grate cooler Optimization of heat recovery in clinker cooler Industry Sectors This is a list of various available energy efficient techniques. Process control and management systems is automated computer control that can help to optimize the combustion process and conditions. Raw meal homogenizing systems is the use of a gravity type homogenizing silos. The conversion from wet to dry process is a complex operation that only leaves the structural parts intact. The conversion from dry to multi stage pre-heater kiln is a four or five stage pre-heating that reduces heat losses. The conversion from dry to pre-calciner kiln increases capacity and lowers the specific fuel consumption. The conversion from cooler to grate cooler gives an efficient heat recovery. The optimization of heat recovery in clinker cooler improves the heat recovery by reducing the excess air volume as well as control of the clinker bed depth and new grates. © UNEP 2005
Energy Efficiency OpportunitiesCement Industry Energy Efficiency Opportunities Energy efficient technologies: High efficiency motors and drives Adjustable speed drives Efficient grinding technologies High-efficiency classifiers Fluidized bed kiln Advance comminution technologies Mineral polymers Industry Sectors Furthermore, high efficiency motors and drives enable variable speed drives and improved control strategies. Adjustable speed drives reduces throttling and coupling losses. Efficient grinding technologies can improve the grinding characteristics. High efficiency classifiers means that material stays longer in the separator and this leads to sharper separation and reduces over grinding. A fluidized bed kiln leads to lower capital costs and lower energy use. Advance comminuition technologies are non-mechanical milling technologies such as ultra sound. This is however not yet commercially viable. Finally, mineral polymers that are made from alumino-silicates laves calcium oxides as the binding agent and this lowers energy usage too. © UNEP 2005
Training Agenda: Industry Sectors1) Iron & Steel Sector description Process flow Energy conservation 2) Chemical 3) Cement Sector description Process flow Energy conservation 4) Pulp & Paper Industry Sectors © UNEP 2005
Pulp & Paper Industry Sector Description Industry SectorsWorld production of paper and paperboard is about 323 million tons (year 2000) World pulp and paper devours over 4 billion trees annually The industry produces the net addition of 450 million tones of CO2 per year (IIIED) The fuels within the sector are coal, oil, gas and bio fuels There are significant opportunities for reduction of CO2 gas emissions Industry Sectors The world’s production of paper and paperboard is about 323 million tons. By one estimate, personal computers alone account for 115 billion sheets of paper per year worldwide The number of paper mills in operation is 10,000 worldwide. Furthermore, the world's consumption is increasing by about three percent every year. The pulp and paper industry sector is high-energy intensive and high investment oriented. World pulp and paper production devours over four billion trees annually and the industry produces the net addition of 450 million tones of CO2 per year. An important factor for CO2 emission in this sector is the fuel combustion. The fuels used in the pulp industry are coal, oil, gas and bio fuels. Whilst older mills caused severe air pollution, mitigating technology now exists to eliminate most harmful gas and particulate emissions. However there is a significant scope for reduction of CO2 emission in this sector by energy efficient and cleaner production measures. © UNEP 2005
Pulp & Paper Industry Process Flows Manufacturing processWood preparation Pulping Washing Bleaching Stock preparation Paper making Chemical recovery Industry Sectors The pulp and paper industry converts fibrous raw materials into pulp, paper, and paperboard. The processes involved in papermaking include raw materials preparation, pulping, bleaching, chemical recovery, pulp drying, and papermaking. We begin with wood preparation. This includes preparation of the main raw materials such as debarking, chipping, and conveying. Next is the pulping. The purpose of pulping is to free the fibers from the lignin that binds the fibers together in wood, and then to suspend the fibers in water. This is followed by washing which frees the pulp of soluble impurities and, at the same time, removes the black liquor and allows recovery of the maximum amount of chemicals for reuse. The washed pulp is sent for bleaching; the black liquor is sent to evaporators for thickening. During bleaching, remaining lignin that is still closely bonded to the is removed through a series of bleaching stages. Bleaching is used for different types of paper, varying from unbleached pulps, to brightened newsprint, to highly white printing paper. After bleeching the treated pulp is sent to stock preparation. During stock preparation pulps and additives are blended to form a uniform and continuous slurry. Refining imparts the desired qualities to the paper to be manufactured in accordance with its end use. Thereafter, the pulp suspension is fed to paper machines where it is converted into paper. During this paper making stage, the fibers are deposited in a sheet on a screen, drained and pressed to remove the bulk of water and then dried. After the paper has been slit into required widths, cut into sheets, trimmed and packaged, it is ready for the final step. This is the chemical pulping that evaporates any remaining water and smelts the remaining inorganic chemicals. © UNEP 2005
Pulp & Paper Industry Process Flows Industry SectorsBarking Chipping Chemical Pulping Mechanical Pulping Waste Paper Kneading Bleach Plant Liquor concentration Energy Recovery Recausticization Refiner Bark ( fuel) Electricity Steam Trees Used Paper Fuel Wood Preparation Bleaching Chemical Recovery Paper making Process Flows Industry Sectors Papermaking is a high energy consuming process. The intensity of the energy consumption depends on various factors such as product mix, raw materials, capacity utilization, types of equipment, degree of integration, size and age of the mill, design and imbalances of the equipment etc. This flow diagram illustrates a typical process flow with electrical and thermal energy for integrated and waste paper based mills. The processes for trees (click once), pulping (click once), bleeching (click once) and chemical recovery (click once) is illustrated. (Let audience reflect before continuing). The diagram continues further to the paper making process (click once) (change slide). Figure: Process flow diagram of the pulp and paper industry © UNEP 2005
Pulp & Paper Industry Process Flows Industry SectorsStock Preparation Forming Pressing Drying Steam Electricity Paper making Paper Industry Sectors This is a continuation of previous flow chart diagram of the paper making process. Figure: Process flow diagram of the pulp and paper industry © UNEP 2005
Pulp & Paper Industry Process FlowsEnergy flows in the paper industry: Thermal energy mainly consumed in the drier some mills use steam for drying the after coating Electrical energy used to power the rotor or impeller also used as rotary power for the cylinder, transportation, motive power and lighting loads Water flow water consumption is significant both in terms of consumed quantities as well as environmental aspects Industry Sectors (click once) Almost all of the thermal energy is consumed in the drier except in the pulp manufacturing section and digesters. Occasionally, some paper mills use steam for the purpose of drying after coating in the continuous papermaking and coating unit, and for the pulper to promote defiberizing and to accelerate beating and fibrillation caused by the swelling of the fiber. (click once) Electric energy is used as power for the rotor or the impeller. These directly act on the fiber in the defiberizing, beating, circulating, stirring and cleaning of raw materials. Electrical energy is also used as rotary power for the cylinder for the washing filter, drier, etc. Furthermore, it is used as transportation power for water and raw materials, motive power and lighting loads. (click once) The consumption of water in paper industry is significant both in terms of quantities and the possible damage on the adjacent environment. Problems associated with water use include increased sedimentation and turbidity, increased water temperature, loss of habitat diversity, possible concentration of toxic material and lowering of water tables. © UNEP 2005
Pulp & Paper Industry Process Flows Industry SectorsPress Roll I, 52.5 Kw Press Roll I, 52.5 KwI Couch Roll, 96 Kw Vacuum Boxes Industry Sectors Material and energy balances make it possible to identify and quantify previously unknown losses and emissions. These balances are also useful for monitoring and identifying CP-EE measures with cost benefits. In order to establish an energy balance for a particular area a typical schematic diagram is drawn with all details of equipments specification, type of energy flow. This diagram illustrates such details of paper machine areas from head box to paper realer with electrical and steam interaction. (Let the audience reflect over the diagram before continuing). Figure: Energy balance in a paper machine © UNEP 2005
Energy Efficiency OpportunitiesPulp & Paper Industry Energy Efficiency Opportunities CP-EE measures: Raw material preparation Enzyme-assisted barker Chip conditioners Improved screening process Belt conveyers Mechanical pulping Refiner improvements Low consistency refining (LCR) Heat recovery in thermo mechanical pulping Industry Sectors For raw materials preparation there are four CP-EE measures listed. These include the enzyme-assisted debarker: which is based on enzyme pretreatment of logs for debarking that reduces energy consumption in the process; the improved screening processes that allow for a more even size distribution of wood chips entering the digester will reduce steam consumption in both the digester and the evaporator in chemical pulping; belt conveyers that are efficient bark and chip handling systems For mechanical pulping there are measures such as refiner improvements that can be to switch to conical refiners rather than disk refiners. In addition, installation of LCR is justified based on energy savings and an increase in production rate. Thirdly, as steam is produced as by-product of thermo-mechanical pulping, most of this energy can be recovered as low-pressure steam in an evaporator/reboiler system. © UNEP 2005
Energy Efficiency OpportunitiesPulp & Paper Industry Energy Efficiency Opportunities CP-EE measures: Chemical pulping Continuous digesters Continuous digester modification Batch digester modification Industry Sectors Chemical recovery Falling film black liquor evaporation Paper making High consistency forming Extended nip press (shoe press) Moving on to chemical pulping, here a continuous digester allows recovery of heat from one part of the process to heat another. Modifications of the continuous digesters focus on reducing the amount of material that must be heated and increasing the level of heat recovery. For smaller mills, it may not be operationally efficient to switch to larger batch digesters in the digesting operation. Chemical recovery can be made through falling film black liquor evaporation. Papermaking in terms of stock preparation and sheet formation includes two CP-EE measures. In high consistency forming, the forming speed in increased and in extended nip press as much water as possible is removed. © UNEP 2005
Energy Efficiency OpportunitiesPulp & Paper Industry Energy Efficiency Opportunities CP-EE measures: General measures Optimization of regular equipment Efficient motor systems Efficient steam production & distribution Boiler maintenance Improved process control Flue gas heat recovery Industry Sectors Other general measures includes optimizing the regular equipment and improving the motor systems. Ensuring efficient steam production and distribution through boiler maintenance, improved process control and flue gas heat recovery can also result in substantial savings. © UNEP 2005
Energy Efficiency OpportunitiesPulp & Paper Industry Energy Efficiency Opportunities EE technologies: Alcohol based solvent pumping Bio pulping Ozone bleaching Black liquor gasification Industry Sectors We will no look at the new energy-efficient unit operations and introduce the new energy technologies. Alcohol based solvent pulping can produce high yield high quality pulps in shorter cooking times. The process also produces a sulfur-free lignin that is extracted at a much faster rate than the Kraft process. A drawback is the high cost of solvents that can be cost prohibitive. Bio-pulping consists of pre-treating the wood chips with biological agents to degrade the lignin. Ozone bleaching is an alternative bleaching process that can produce pulp of equal brightness to either ECF or TCF. Ozone systems are likely to gain more interest as new extended cooking and oxygen delignification systems, which are prerequisites for successful ozone bleaching, come online. Ozone will also gain more interest as a low cost partial substitute for expensive chlorine dioxide. Black liquor gasification is used to produce gas from spent pulping liquor. There are two major types of black liquor gasification: low temperature/solid phase and high temperature/smelt phase. © UNEP 2005
Energy Efficiency OpportunitiesPulp & Paper Industry Energy Efficiency Opportunities EE-technologies: Impulse drying Infrared drying Press drying Industry Sectors Impulse drying involves pressing the paper between one very hot rotating roll and a static concave press with a very short contact time. Impulse drying tremendously increases the drying rate of paper although there may be problems with the paper delaminating or sticking to the roll. Short-wave infrared drying provides better heat transfer capabilities and compactness. In press drying, the sheet is pressed between two hot surfaces or pressing cylinders at a temperature of °C. In most cases these cylinders are installed in between the conventional pressing section and the drying section of the machine. The drying rate can be 2-10 times faster than conventional drying. This technology is near commercialization. © UNEP 2005
THANK YOU FOR YOUR ATTENTIONTraining Session on Energy Equipment Industry Sectors THANK YOU FOR YOUR ATTENTION Industry Sectors © UNEP GERIAP
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