Unit 2: Conventional Energy System PDF

1/28/2024 UNIT 2: IK YANKEY ENERGY SYSTEMS ENGINEERING Finite energy resource stocks includes: Coal Shale Oil Petroleum N...

1/28/2024 UNIT 2: IK YANKEY ENERGY SYSTEMS ENGINEERING Finite energy resource stocks includes: Coal Shale Oil Petroleum Natural gas These are accumulated concentrated solar energy for millions of years that are available to us IKYANKEY These finite resources are sort of closed to coming to an end. Others also doubt because new once are always been discovered. The ordinary man do not know who to believe any more. Hence need to know exactly the status of the resources. Primary energy fall into two main categories: 1. primary fuels and 2. primary energy flows. Primary Fuels like coal, natural gas, and uranium are dense stores of energy that are consumed when used. Primary flows are natural processes that have IKYANKEY energy associated with movement. (solar radiation and water flowing) A fuel is a substance that stores energy while an energy flow is a natural process that has energy which can be extracted from the process. 1  1/28/2024 Fuels are dense repositories of energy that are consumed to provide energy service such as heating, transportation and electrical generation. Most of the primary energy used in the world, 90- 95% comes from fuels as illustrated in figure 2. Fuels like coal and natural gas are used in power IKYANKEY plants. Crude oil is processed into secondary fuels such as gasoline, diesel and kerosene for cars and other applications. Coal, natural gas, diesel, gasoline etc. store discrete amount of energy and once is used up it is gone. Fuels can be solids, liquids or gases. Examples: Gases: Natural gas, acetylene, hydrogen, IKYANKEY Compressed Natural Gas (CNG). Liquids: gasoline, diesel, kerosene, liquefied natural gas (LNG), liquefied petroleum gas (LPG), ethanol, methanol, butanol. Solids: Wood, wax, coal, char, peat, charcoal, bagasse, biomass Flash point: Lowest temperature at which fuel can form an ignitable mix with air Fire point: Temperature at which the vapor continues to burn after being ignited Cloud point: Temperature at which a sample has visible cloudiness such as wax or paraffin. Pour point: Temperature at which the fuel will no IKYANKEY longer pour hence resistant to flow. Gum content: Quantity of remaining solid residue after a sample has been heated and evaporated for a prescribed period of time in air Trace metal content: Va, Cu Aromatic content: Percentage of aromatic hydrocarbon content 2  1/28/2024 Assignment 1 1) Freezing point 2) Viscosity 3) Ash content 4) Sulfur content IKYANKEY 5) Thermal stability i. Define the above mention fuel properties. ii. For a specific fuel draw a table of the fuel properties and the values associated with it. Power sources like hydroelectricity, tidal power, wind power, and solar power take advantage of primary energy flows, where energy is harnessed from natural energy sources. Once the energy is extracted from a fuel, it's gone, IKYANKEY but natural processes put energy back into primary flows over time making them renewable. Primary energy flows like wind, sunlight and tidal power are non-dispatchable and intermittent. Meaning that there is little to no control over when the energy is available. Until the advert of internal combustion engines, oil had no or very few uses. As technology improved the use increased and this is shown theoretically below. The area under the IKYANKEY curve gives the total amount of petroleum exploitable. Fig 2.2a The rate use of fossil fuel 3  1/28/2024 It is normally not convenient to use the rate to draw the curve because there are many factors that affect the rate. These factors are: Local conditions Temporary perturbations Prices Q∞= total amount of recoverable petroleum Market structures IKYANKEY The curve is therefore drawn using the cumulative use. The curve for the use of finite resources Fig 2.2. Cumulative consumption of petroleum is shown in fig 2.2 The cumulative discoveries and production saturates at a point as shown in fig 2.3. The cumulative discovery is always greater than the cumulative production. The cumulative reserve is IKYANKEY the difference between the the cumulative discovery Fig 2.3 Cumulative curves for petroleum discoveries, and the cumulative production. production and reserves This is given as: 𝑸𝑹 = 𝑸𝑫 − 𝑸𝑷 2.2 IKYANKEY Fig 2.6. The Hubbert theory of the exploitation of a finite resource 4  1/28/2024 The formation of coal began about 200–300 millions of years ago when organic materials were buried under sediment. Throughout this time it was exposed to: high temperatures and pressures, IKYANKEY which forced moisture out, material became high in carbon, low in hydrogen and oxygen. The resulting material is coal. Different types of coal were formed under different conditions. 1. Lignite Lignite is the lowest rank of coal. It is soft and brown-blackish in color. It usually occurs close to the surface. It has: high moisture (up to 66%) and ash content (6–19%), low energy density, and high volatile matter. IKYANKEY It is easy to convert into gas and liquid petroleum. Lignite is used to: generate electricity (79%), generate synthetic natural gas (13.5%), and produce fertilizer products (7.5%). 2. Sub-bituminous coal Sub-bituminous coal is intermediate between lignite and bituminous coal. As lignite is more deeply buried it becomes sub- bituminous coal. It is dull dark-brown to black in color, and harder than lignite. It has IKYANKEY 20–30% moisture content, Primarily used for steam-electric power generation. 3. Bituminous coal Bituminous coal is formed at higher pressure and temperature which remove more impurities. It is black with bands of dull and bright material. 5  1/28/2024 It has little moisture content and harder than sub-bituminous but still fairly soft. Used for: steam-electric power generation, heating and cooking. 4. Anthracite Anthracite is the highest ranked coal. It is IKYANKEY metamorphosed by heat and pressure. It is: black, glossy appearance, moisture content less than 15%. Its principal use: residential and commercial heating fine particle is filters and used as charcoal briquettes. Fossil fuel Non-renewable energy source Umbrella category that includes Gasoline heating oil IKYANKEY diesel fuel jet fuel many others Often called “crude oil” Mostly comes from oil drilling Petroleum is formed from the remains of marine plankton that has been buried under layers of sand and silt. Heat and pressure cause chemical reaction, and IKYANKEY converts to waxy substance known as kerogen. This process take millions of years. Catagenesis then produces natural gas and oil. 6  1/28/2024 1. Upstream Industry Locating Oil present in pores of rock Located using seismic surveys Gravimeters and magnetometers are also used. IKYANKEY Fig 2.7 Oil present in pores and seismic detection of oil fields Drilling Hole is drilled using oil rig, steel pipe inserted for support Oil wells have valves called “Christmas Tree,” that regulates: pressure and flow, Fig.2.8 oil well and a “Christmas tree. connects the well to IKYANKEY pipes for storage. There are 3 recovery procedures. 1. Primary 2. Secondary 3. Tertiary Primary - Secondary - Fluids pumped into reservoir to increase reservoir pressure. water, natural gas, air raises recovery rate to 35-45 % of reserves Tertiary (Enhanced Recovery) - increases mobility of petroleum thermally enhanced IKYANKEY recovery, carbon dioxide flooding recovers additional 5-15% of the petroleum reserve. Fig.2.9 Secondary and Tertiary recovery Process. 7  1/28/2024 RAIL PIPELINE IKYANKEY OIL TANKER BARGE Fig 2.10 Overview of the Midstream Industry Energy Production Process includes: Refining: crude oil into products Separation: distillation IKYANKEY process Conversion: hydrocarbons are changed gasoline, crude oil, etc. Treatment: adds specialized properties Current Usage Gasoline - most common use Agriculture – fertilizer Plastics - many plastics are petroleum-based Tires - synthetic rubber Pharmaceuticals - many of creams are petroleum- based PROs CONs IKYANKEY Ease of access to Non-renewable petroleum High energy density Air pollution Relatively cheap to Acid rain extract Produces constant Potentials for spills supply of energy 8  1/28/2024 Natural gas consists of gaseous hydrocarbons which are compounds of hydrogen and carbon. It is primarily: Met hane CH 4 70-90% Et hane C2 H 6 0-20% methane (CH4), Propane C3 H 8 0-20% But ane C4 H10 0-20% propane (C3H8) Carbon dioxide CO2 0-8% butane (C4 H10). Oxygen O2 0-0.2% IKYANKEY Nit rogen N2 0-5% ethane (C2H6), Hydrogen sulfide H2 S 0-5 % Natural gas is colorless and tasteless. The typical composition of unrefined natural gas is shown in the table. 1. Biogenic process This is the anaerobic decay of non-fossilized biomass: biogas (methane and CO2), in landfills, for instance. Other production means are anaerobic digesters for manure or enteric fermentation from cattle. 2. Thermogenic process In thermogenic processes natural gas was formed over an extended period of time from organic material under IKYANKEY extreme pressure beneath the earth, especially at high temperatures. This happened in oil fields and coalbeds. 3. Abiogenic process Hydrogen gas and carbon molecules bond deep within the earth forming methane. High pressures cause the reaction to form methane rather than a different compound. Usage Most natural gas is used in heating, generating electricity and fuel for vehicles. Storage This can be as Compressed Natural Gas (CNG) or Liquefied Natural Gas (LNG). Transportation Transportation of natural gas was not technologically feasible before the 1940s. IKYANKEY The common practice was to flare or vent natural gas LNG carriers in the shipping industry. Piping and trucking (CNG) are other means of transportation. Environmental effects Natural gas is the cleanest fossil fuel. Natural gas vehicles (NGV) emit 20% less greenhouse gas than conventional vehicles. CO2 is released during drilling and burning of natural gas. 9  1/28/2024 The cumulative consumption of a resource from any initial time to any time t can be calculated by summing the consumption per year. If the magnitude of the resource is known or estimated, then the end time when the resource is used up can be estimated for growth, constant, or declining consumption using the relationship: IKYANKEY 𝒓 = 𝒓𝒐 𝒆𝒌𝒕 2.4 Where: r = future rate of consumption, ro= present rate of consumption, k = growth per year and t = time The present consumption of Ghana oil reserves is estimated at 100 units/yr and at a growth rate of 7%. i. What is the consumption after 100 years? Solution 2.1 Using eqn 2.4 𝒓 = 𝟏𝟎𝟎𝒆𝟎.𝟎𝟕∗𝟏𝟎𝟎 = 𝟏𝟎𝟎 ∗ 𝒆𝟕 IKYANKEY = 100*1097 = 1 x 105 so after 100 yrs the consumption is 1000 times greater. If the magnitude of the resource S is known or can be estimated, then the time TE when that resource is used up can be calculated or estimated for different growth rates k. If the estimated size of the resource is S then: 𝒓𝒐 IKYANKEY 𝑺= 𝒆𝒌𝑻𝑬 − 𝟏 2.5 𝒌 𝟏 𝑺 𝑻𝑬 = 𝒌 𝐥𝐧 (𝒌 𝒓 + 𝟏) 2.6 𝒐 10  1/28/2024 Table 2.2 shows estimated resources or reserves in 2008 and at a present rate of consumption of 31 Gbbl/yr IKYANKEY All calculations made about the future are just estimations, and possible solutions to our energy dilemma are as follows: Conservation and more efficient use of energy. It is much cheaper to save a barrel of oil than to discover new oil. IKYANKEY Decrease demand, transition to zero population growth, and begin an equilibrium society. Because the Earth is finite for population and our use of the Earth’s resources is also limited: a change to a sustainable society, which depends primarily on renewable energy, becomes imperative on a long timescale. For the world, we will have to do the following in the transition period (next 25 years), in order of priority: 1. Implement conservation and efficiency. 2. Increase substantially the use of renewable energy. 3. Reduce dependence on oil and natural gas. IKYANKEY 4. Use clean coal, which has to include all social costs (externalities). 5. Make use of nuclear energy. 6. Reduce environmental impact, especially greenhouse gases. 7. Implement policies (incentives and penalties) that emphasize items 1 and 2. 11  1/28/2024 Produce electricity from a heat source. Most efficient way to get electricity from a heat source and the most essential components in this process are: Boiler, IKYANKEY Turbine, Condenser, Pump, Super heater Economizer. Fig. 2.11 Layout of a simple Rankine cycle power plant Thermal power cycles take many forms, but the majority are: fossil steam, nuclear, simple cycle gas turbine, and combined cycle. Of those listed, conventional coal-fired steam IKYANKEY power is predominant. A block diagram of a thermal power plant is shown in figure 2.12 This diagram represent the basic point of what is known as the Rankine cycle in thermodynamics which you might have studied in detail some where in your programme. The ideal cycle comprises the processes from state 1: 1–2: Saturated liquid from Figure: Basic Rankine Cycle the condenser at state 1 is pumped isentropically (i.e.,S1=S2) to state 2 and into the boiler. IKYANKEY 2–3: Liquid is heated at constant pressure in the boiler to state 3 (saturated steam). 12  1/28/2024 3–4: Steam expands isentropically (i.e.,S3=S4) through the turbine to state 4 where it enters the condenser as a wet vapor. 4–1: Constant-pressure transfer of heat in the condenser to return the steam back to state 1 IKYANKEY (saturated liquid). 2.7 Coal: To get the heat you have to burn coal, but in chunks and may cause incomplete combustion. Hence the surface area is reduced by breaking it down to powdered form called pulverized coal and blown IKYANKEY with air which enters the boiler for complete combustion. Boiler: the fuel air-mixture enters the boiler to create a vortex. The numerous tubes (Water walls) on the boiler walls carry water which the boiler flame sees. IKYANKEY 13  1/28/2024 Turbine: Converts the pressure into kinetic energy of the steam when impinges on the blades. The entry point of steam at the turbine is small because steam enters at high pressure and as it expands the volume increase hence bigger space for the expanding steam at low pressure at the exit point. Because of the high pressure in the turbine in real IKYANKEY situation at power plant there are about three turbines: 1. High Pressure Turbine 2. Intermediate Pressure Turbine 3. Low pressure Turbine Fig 2.15 Three series turbine in a power plant In small power plants there are usually two turbines: 1. High Pressure turbine 2. Low pressure turbine IKYANKEY Condenser: cools the steam down to condensate and the water that cools the steam is also cooled before releasing to the environment. IKYANKEY Fig2.16a showing a condenser and cooling towers 14  1/28/2024 Cooling Towers: Cools the condensate before releasing to the natural water. The towers spray cold water and that is what you see at power plants. IKYANKEY Fig 2.17 Cooling tower in TPP The ideal thermodynamic efficiency of this plant is given as: T2  ideal  1  2.8 T1 Assuming that T2=200oc and T1=600oc, where T2 IKYANKEY is the exit temperature (temperature inside condense) and T1 is the inlet temperature. Calculate the ideal thermodynamic efficiency. The ideal efficiency is given by: T2  ideal  1  T1 35  273 IKYANKEY ideal  1  400  273 = 0.5 The practical efficiency of a power plant is between 28-36 percent. 15  1/28/2024 In thermal power Plant a huge quantity of heat has to be release into the atmosphere and this is a great deal of thermal pollution. Environmental pollution is of serious concern to governments and society in general. For a Power Plant the following are the main IKYANKEY environmental effects: Thermal Pollution Air Pollution: Ash CO NOx SOx CO2 Waste heat is heat which is generated in a process but then "dumped” to the environment even though it could still be reused for economic purpose. Sources of Waste Heat Sources of waste heat can be divided according to IKYANKEY three temperature ranges: 1. High Temperature range: Above 1200oF 2. Medium Temperature range: Between 450oF-1200oF 3. Low temperature range: Below 450oF For each of the temperature ranges mentioned in the previous slide state five (3) types of industrial process which serves as the source of waste heat and their temperature ranges. IKYANKEY 16  1/28/2024 To use waste heat from sources such as those above, one often wishes to transfer the heat in one fluid stream to another. Example from flue gas to feed water or combustion air. The device which accomplishes the transfer is IKYANKEY called a heat exchanger. The equipment that is used to recover waste heat can range from something as simple as a pipe or duct to something as complex as a waste heat boiler. Some applications of waste heat includes: 1. Medium to high temperature exhaust gases can be used to preheat the combustion air for: Boilers using air preheaters. Furnaces using recuperators. Ovens using recuperators. IKYANKEY Gas turbines using regenerators. 2. Low to medium temperature exhaust gases: can be used to preheat boiler feedwater or boiler makeup water using economizers, 3. Exhaust gases and cooling water from condensers: can be used to preheat liquid and/or solid feedstocks in industrial processes. 4. Exhaust gases: can be used to generate steam in waste heat boilers IKYANKEY to produce electrical power, mechanical power, process steam, and any combination of above. 17  1/28/2024 Industrial heat exchangers are sometimes called: Recuperators, Regenerators, Waste Heat Steam Generators (WHSG), Condensers, Heat wheels, Temperature and Moisture exchangers, etc. Heat exchangers are characterized as single or multipass. IKYANKEY The terms single or multipass refer to the heating or cooling media passing over the heat transfer surface once or a number of times. Examples includes: Evaporator, Condenser, Parallel flow, Counterflow, or Crossflow. The specification of an industrial heat exchanger must include the following: 1. the heat exchange capacity, IKYANKEY 2. the temperatures of the fluids, 3. the allowable pressure drop in each fluid path, 4. the properties and volumetric flow of the fluids entering the exchanger. The essential parameters which should be known in order to make an optimum choice of waste heat recovery devices are: 1. Temperature of waste heat fluid. 2. Flow rate of waste heat fluid. 3. Chemical composition of waste heat fluid. 4. Minimum allowable temperature of waste heat fluid. IKYANKEY 5. Temperature of heated fluid. 6. Chemical composition of heated fluid. 7. Maximum allowable temperature of heated fluid. 8. Control temperature, if control required. 18  1/28/2024 Instead of letting heat escape uselessly up cooling towers, why not simply pipe it as hot water to homes and offices instead? That's essentially the idea behind CHP: to capture the heat that would normally be wasted in electricity generation and supply it to local buildings. IKYANKEY A conventional power plant makes electricity and wastes the heat it makes as a byproduct. A CHP power plant makes both electricity and hot water and supplies both to consumers. 1. Fuel (coal, natural gas, oil, or biomass) is added at one end. 2. The engine (roughly the same size as a four- cylinder car engine) burns the fuel by ordinary combustion. IKYANKEY 3. An electricity generator is connected to and driven by the engine's driveshaft. 4. About 15kW of electricity is produced, which can be used for conventional power or as an emergency supply. 5. Exhaust gases from the engine flow through one or more heat exchangers, which remove most of their waste heat. 6. A catalytic converter (similar to the one in a car) removes some of the pollution from the gases. IKYANKEY 7. The (relatively clean) exhaust emerges through a tail pipe or chimney. 8. Cold water flowing into the heat exchanger picks up heat from the exhaust gas and exits at a much higher temperature. 19  1/28/2024 When discussing various prime movers for micro- CHP systems, a primary method of comparison is to examine the efficiency of each prime mover. The efficiency of a micro-CHP system is measured as the fraction of input fuel that can be IKYANKEY recovered as power and heat. The three primary efficiencies that are associated with micro-CHP systems are: 1. Electrical efficiency, 2. Thermal efficiency, and 3. Overall efficiency. These efficiencies are defined as: IKYANKEY 100% 91% 32% 31% ~30% IKYANKEY Natural Power End Uses Transmission Distribution Resource Plant Figure : Efficiency of Central Power Generation. 20  1/28/2024 100% 91% 50% ~48% IKYANKEY Natural Power End Uses Distribution Resource Plant Fig 2.19 Efficiency of Combined-Cycle Power Generation. IKYANKEY Fig 2.20 : Efficiency of micro-CHP System. Thank You. ? IKYANKEY 21