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In power generation field, one of the aspect concerns is about energy consumption. For thermal power station, the main prime mover is steam which operates in a cycle known as Rankine Cycle. The steam is produce from water in a boiler by combustion process and then condensed in a condenser.
Thermal power station use the same concept as other power station, but the different is on the type of the fuel used. Most Power Station in the world use fossil fuel as the main source of energy, and some use nuclear power, but there is an increasing use of cleaner renewable source such as solar, wind and hydroelectric.
Coal Fire Power Plant is type of power station that used solid fuel as their main source of energy. The coal will combusted in boiler to heated the water to produce steam. During the combustion process, the soot formation will occur within the boiler tube and hence reduce the heat transfer. Using partial of the steam produce, the soot was removed by blowing the steam into the boiler tube.
The soot blowing system will help to keep the performance of the furnace and hence reduce energy consumption. On the opposite effect, by doing soot blowing regularly, the steam will be wasted.
Basically, the presence of soot in coal power plant must happen. How much the soot accumulate in the boiler depend on the coal that been used. The buildup of soot in the boiler will reduce the efficiency of the boiler because of reducing the heat transfer area that is boiler tube. To maintain the boiler efficiency, the boiler tube should be periodically been blow by the steam against the surface upon where the deposits have been accumulate.
To maintain the boiler efficiency the tube cleanliness must be maintain. To maintaining this cleanliness level, it required continuous cleaning at the tube. Although it need continuous cleaning, it would not be efficient in practical condition. This is because cleaning is costly and wear and tear can occur in the boiler. This is costly because it needs to do extra maintenance and steam in the boiler to clean the boiler. Cleaning cost and boiler cleanliness must be reasonable because it relate to the efficiency of the plant itself.
In order to verify problem statement as stated, it has to develop specific objectives as follows:
To measure the effect of soot formation over time on boiler efficiency.
To identify for the optimal sequence of sootblower operations.
1.4 Scope of Project
This project is limited to analyze furnace performance from soot blowing activities and regarding to energy sustainability and environmental conservation.
1.5 Significant of Project
The outcome of this project can be used to optimize boiler efficiency. By determining the optimum frequency of the soot blowing, cost saving operation can be obtained. Hence, help to reduce energy consumption for the power plant.
2.1 Energy conservation, Energy sustainability and Environmental conservation
Kapar Power Plant generates electricity by using solid fossil fuel, coal. As we know, fossil fuel is very limited amount of energy sources in the earth, and it is also non-renewable energy that cannot be replenished. Combustion of fossil fuels also will release conventional pollutant such as SOx, NOx,CO and particulates which will adverse effect on 'greenhouse' and more accurately to the environment and human life. During the combustion, carbon is converted to carbon dioxide, which is then released into the atmosphere. Emission of large amount of carbon dioxide will contribute to the global warming. Depending on the method of burning, other emission may be produced as well. Ozone, sulphur dioxide, NO2 and other gases are often released, as well as particulate matter. Sulphur and nitrogen oxides contribute to smog and acid rain. Considering the high potential of energy conservation and benefits of energy sustainability, the level of efficiency should be improved so that fuel consumption can be used in the long term and reducing harmful emission.
2.2 Introduction of steam power plant
In Malaysia most of the power plant is using steam power plant or also known as thermal power plant. Steam power plant also famous not only in Malaysia, but in other country also using it as to generating electricity. Steam power plant is driven by the water that been heated. The steam power plant varies in the type of fuel that uses coal, oil or even natural gases to heat up the water to be steam.
2.2.1 Function of steam power plant
In steam power plant, water that been heated in the boiler will become superheated steam. The superheated steam that been heat up by the fuel will turn the turbine which is connected to the generator. When the turbine turn at certain speed it will generate electron or that commonly call electricity as the product.
2.2.2 Coal fired power plant
Generating electricity need a fuel source. Coal is one type of fossil fuel in solid state that been use in the coal fired power plant. Since the main source of coal fired power plant is coal it will emit some sulphur to atmosphere that is not good to health. Even though people know that by using coal will course a bad effect to greenhouse, it still popular to use it because it cheaper compare to oil and natural gases and the price quite stable.
2.3 Introduction to boiler
Boiler is defined as a closed container in which contains the water is heated by combustion of a fuel type, regardless of the type of fuels coal, oil and gas to produce high-pressure steam.
Figure 2.1: Boiler System
2.3.1 Process of power generating in a coal fired power plant
The conversions of high pressure hot water from the feed water line to superheated and reheat steam supplied to the turbine takes place in the following steps:
Water from the feed water line enters the economizer and flows upwards, counter current to the flue gas which is flowing downwards, absorbing heat from the flue gas. Water from the outlet header of the economizer enters the steam drum through economizer outlet pipes.
From the boiler drum, water is supplied to the waterwall inlet headers, located in the lower portion of the boiler, through eleven downcomers, and their feeder tubes. The downcomers are located outside the furnace and do not absorb any heat. The waterwall inlet headers supply the front, rear and side waterwalls with boiler water. Boiler water rises through the waterwall tubes from the inlet headers, absorbing radiant heat from combustion in the furnace. This heat absorption converts water partly to steam. The water and steam mixture are collected in waterwall outlet header s and enters the drum through riser tubes.
The higher density water in the downcomer tubes compare to the lower density steam and water mixture in the waterwall tubes causes a natural circulation to take place from the drum through the downcomers and then through the waterwalls back to the drum. A column of water has circulate several times through the downcomer and wateralls before it is fully converted to steam. Maximum circulation occurs when the firing rate is minimum.
In the drum, the steam and water mixture is separated into dry saturated steam and water by the drum internals consisting of infernal baffles, horizontal separators and chevron dryers. Separated water mixes with water from economizer and again circulates through the downcomers and waterwalls.
From the boiler drum, saturated steam pipes carry the dry saturated steam to furnace roof wall inlet header. It is from where saturated steam passes through a series of superheaters, absorbing heat as follows:
From the roof wall superheater and HRA rear wall superheater header to the primary superheater inlet header. (Parallel flow)
From the primary superheater inlet header to the primary superheater outlet header through the primary superheater tubes (counter flow)
From primary superheated outlet header to the division walls superheater inlet header (through desuperheater-not heated, but cooled if required)
From the division walls superheater inlet headers through the division walls superheater outlet headers through the division walls superheater tubes in line arrangement.
From the division walls superheater outlet headers to the platen superheater inlet header (through desuperheater-not heated, but cooled if required)
From platen superheater inlet header to the platen superheater outlet header through platen superheater tubes.
From platen superheater outlet header to the final superheater outlet header through the final superheater tubes.
From the final superheater outlet header to the main steam line.
Figure 2.2: Boiler room schematic
2.3.2 Boiler efficiency calculations
The boiler efficiency can be calculated using two methods:
The heat loss method
ii) The input-output method
Heat loss method
Efficiency is defined as the useful energy out of a process divided by the energy into the process. The mathematical formula for boiler efficiency using the heat loss method is:
Boiler Efficiency = 100 - total percentage boiler heat loss
The percentage heat loss is obtained by dividing the loss in kilojoules per kilogram of fuel by the calorific value per kilogram of fuel. With the heat loss method, the useful energy out is calculated by estimating the total heat losses from the boiler and subtracting the sum of these losses from 100 percent. The boiler losses include the following heat losses:
Heat exiting the stack due to:
Heat in the flue gas
Heat in the moisture from the fuel
Heat in the moisture formed by combustion of hydrogen
Heat in moisture from the air
Formation of carbon monoxide
Radiation, heat lost to the boiler surroundings
The mathematical formula for boiler efficiency using this method is
Boiler Efficiency = x 100
The boiler outputs is the heat leaving the boiler in the main steam and hot reheat steam minus the heat entering with the feedwater, cold reheat steam and desuperheater spray water flows. The boiler input is the heating value of the fuel and the credits are heat carried into the boiler by the combustion air, fuel and atomizing steam when firing oil.
Formation of soot
Soot is carbon that builds up from the incomplete combustion. During most operation of boilers especially coal fired boiler soot build up at water wall tube and other component. This soot build up block efficient heat transfer and must be remove to make the efficient of the boiler to be maintain. With different type of fuel uses, it will produce different amount of soot that accumulate. To maintain efficiency of the boiler, soot blower been introduce to the boiler to blow the soot that accumulate at the water wall tube.
Soot blower remove soot by blowing of the tube with medium such as compress air or steam. A typical soot blower made of lance tube with nozzle, feed tube and a valve like in figure 2.3 below. When the valve is open, a blowing medium will go through feed tube under pressure and discharge through nozzle in the lance tube. To maintain the heat transfer in the boiler, soot blowing process with take part. Soot blower can manually or automatically operated
There are two general type of soot blower found in most boilers:
Long retractable soot blower
The different between the two soot blower is the distance that they can be inserted into the boiler Wall deslagger can be insert in sort distance in the boiler furnace to remove soot on the water wall. Long retractable soot blower can insert more than the half of the boiler. It remove soot that in superheater and reheater. Both sootblower are retractable so that the lance tube can be inserted into the boiler while sootblower in the progress and then remove when it's not needed to prevent any heat damage.
Figure2.3: Schematic of a retractable soot blower mounted on a boiler wall 2.6 Soot blowing process and boiler efficiencyC:\Users\soulxylem\Desktop\Capture5.PNG
Soot blowing process is related to the boiler performance. Over time, the formation of soot around the boiler tube will increase due to the unburned carbon from the coal. The heat transfer will decrease and overtime boiler efficiency is decrease too. By soot blowing process, performance of the boiler can be maintained at the maximum output. But by doing regularly, more steam will be wasted and the cost will increase since steam is more expensive than air. Hence, it's important to determine the optimum frequency of the soot blowing.
This chapter describe about the methodology involved in this research. The methodology is done in order to achieve the objective of this study which is to identify for the optimal sequence of sootblower operations in coal power plant. The research methodology of this work has been shown in the flow chart below.
Methodology is one of the important things to be considered to ensure that the research will run smoothly and achieved the objective. Research methodology will describe the details and flow of the research progress.
3.2 Methodology Chart
Gather all information regarding Power Plant and sootblowing
Data Collection and preparing using EXEL spread sheet
Calculation and Analysis
Interpretation of results analysis
3.3 Finding resource
In this study, the Kapar Energy Ventures, Stesen Janaelektrik Sultan Abdul Aziz, Selangor Darul Ehsan was chosen to be the analyse the sootblowing operation. In the power plant consist of 6 of electric generating unit. Only one of the generating unit will be analyze for the optimization sootblowing operation.
3.4 Mathematical Model
3.5 Data Collection and preparing using EXEL spread sheet
3.6 Calculation and Analysis
3.7 Interpretation of results analysis
After cal culation and analysis have been made, the optimum frequency of soot blowing and
In order to determine the optimum frequency of soot blowing and analyze the boiler performance, understanding the principle of heat exchanger and energy consumption are the most important regarding to thermodynamic principle. By determine the optimum frequency of soot blowing; the boiler performance can be increase without the need of excessive waste of steam. For the next session for final year project II, the data obtained will be analyze and give the suggestion how to improve boiler efficiency by soot blowing.