Applications of steam and hot water is widely observed in the society. Those applications range from domestic uses such cooking, indoor heating to industrial uses such as boiler based power generation. The primary use of a boiler is not to boil a liquid or fluid, but to produce the heat required for various applications. Initially the heat generation of the boiler was achieved by combustion of biomass. Biomass is natural material obtained from living creatures, for example, plants. To produce heat from biomass it can either be directly combusted or else I can be used to produce bio fuels such as methane gas, ethanol and bio diesel. Due to the factors such as availability of bio mass at a large scale, ability to obtain required material at a lower cost boiler which were run on bio mass became popular. But with time users recognized its disadvantages such as high space allocation, high initial investment, high maintenance cost. users turned themselves in to boilers which run on other type of fuels. With this introduction of,
Diesel Fired Boiler
Electric Fired Boiler
Gas Fired Boiler
Oil Fired Boiler
Under these several boilers were introduced which were manufactured to meet the requirement of the customer. They range from basic fire tube boiler, water tube boiler to more advanced steam and condensate boiler.
In the selection of this boiler following factors are essential to be considered. They are CITATION Jun99 l 1033 (Junaidi, 1999),
Reviewing boiler types
Comparing features and benefits
Determining the maintenance requirements
Determining the fuel consumptions and also boiler efficiency
But considering these factors it was concluded that a Diesel fired boiler system which will be the most suitable to produce steam in a varying quantity. Since the desired boiler is to be installed in to factory following factors were furthermore considered.
Total Cost on fuel: fuel cost amounts to the cost spent on boiler plus the additional machinery required for the operation.
Emissions: combustion of fuel oil results emission of gasses such as carbon (CO2), sulfur (SO2) .Maintence and operation: Due to the combustion of fuel inside the boiler , byproducts such as solidified carbon particles(soot) gets accumulated inside the boiler. This may lead an obstruction to the operating and moving parts thereby constant maintance and cleaning will be required to make sure the boiler is run without a breakdown or loss of its efficiency.
Boiler Capacity: fuel oil as a liquid has a higher density therefore a larger storage tank will be essential to store the amount of fuel required for the boiler to function upon the expected duty cycle .Use of a diesel boiler is said to more productive according to Rezeau, A*.; Díaz where is it mentioned as “Its size and easier assembly allows a quicker and easier installation in the boiler-room, which is often located in the basement of the building and does not have too much free space of easy access” CITATION Rez07 l 1033 (Rezeau, et al., 2007).Since the desired boiler is to be used in a factory area much of the space spent to place the boiler can be saved by using a diesel boiler.
It is also mentioned as “Its simplicity (thanks to fewer elements required compared to a steel boiler) facilitates the implementation of an automatic maintenance system” CITATION Rez07 l 1033 (Rezeau, et al., 2007).Which proves the fact by using diesel boiler automation can be done much more efficiently and easily.
The requirement of this boiler is produce steam for the manufacturing of the pharmaceuticals. thereby boiler is required to maintain maximum steam generation efficiency throughout the process, simplicity of operation, and compliance to both stringent air emission and safety regulations. It is expected to automate the whole process of operation. This will make sure the production of pharmaceuticals tablets occurs without any error.
The focus of this article to optimize the boiler according to the composition of the flue gas. As mentioned above it is expected to use a boiler which operates upon diesel as the fuel. By combustion of diesel. According to Anil W. Date “Petroleum-derived diesel is composed of about 75%saturated hydrocarbons and 25% aromatic hydrocarbons including naphthalene and alkylbenzenes. The average chemical formula for common diesel fuel is C12H24, ranging approximately from C10H20 to C15H28 ” CITATION Ani11 l 1033 (W.Date, 2011). Only CO2 and water vapor is produced in the ideal combustion of the diesel but at the practical scenarios combustion of diesel may lead to the formation of carbon monoxide-CO, hydrocarbons-HC, particulate matter-PM and nitrogen oxides-NOx CITATION ?br14 l 1033 (?brahim Aslan Re?ito?lu, 2014).This flue gas analysis is carried out to ensure and improve safety of the burning equipment’s , improve fuel economy to make sure the boiler is running at the energy saving mode at all times and finally to minimize the pollution by reducing undesired exhaust emissions.
In Practical scenarios fluctuations in fuel flow ,lack of perfect mixing between fuel and air in the combustion zone would lead to excess air ( ? Lambda ) intake in order to achieve more complete combustion. Without the presence of extra air, the formation by-products such as carbon monoxide and soot may occur. However a perfect balance between the excess air fuel is required to achieve the maximum combustion efficiency of a boiler.
According to eurotron
“During combustion with an excess of air ?=1.1 it develops 11.5 m3 of flue gases ( for each m3 of burned gas) as :
(CO2) 1.0m3 + (O2) 0.2m3 + (N2) 8.3m3 + (H2O) 2.0m3 = 11.5 m3” CITATION Com06 l 1033 (Anon., 2006).
This analysis can be carried down in mainly 2 methods,
Analysis on Dry basis
Analysis on Wet basis
Analysis on Dry basis
This is conducted by
removing water content fully from the flue gases
condensation of the flue gas.
This will result the analyser to measure oxygen content as O2 = 0.2 : 9.5 = 2.1%.
under this procedure we refer to the oxygen content to the volume of dry gases (9.5m3) with an excess air amount ?=1.1.
Analysis on Wet basis
In this anaylsis water content will not be removed which provides a measure Oxygen as O2 = 0.2 : 11.5 = 1.7% .here the Oxygen contents to the volume of dry flu gases is 11.5 m3 with excess of air ?=1.1
In the analysis of the flue gas Electrochemical sensors will be used . these sensors require dry gas to measure its composition there for dry basis in the analysis is used to measure the composition of the flue gas generated by the boiler. International units will be considered in taking the measurements , hence the gas concentration will be measured in the means of PPm (parts per millions).Pollutants in the emissions can also be measured in terms of mg/Nm3 (milligrams per cubic meter).But since we need to address the factor of efficiency of the boiler mg/Kwh will also be considered. Thereby a through this energy related unit a wide understanding about the efficiency of the boiler can be obtained. This converstion can be directly obtained as follow,
Value in Mg/Kwh= value in ppm *1074 CITATION Nak98 l 1033 (.M, 1998).
One of the key Priorities of flue gas analysis is run the boiler a Energy saving manner.It is required by the requaltions to measure for efficiency of all the heat generating boilers.the Efficency of the boiler is measured as follow CITATION Eng03 l 1033 (ToolBox, 2003),
Boiler Efficiency related to the boilers energy output to the boilers energy input can be expressed as:
Boiler efficiency (%) = 100 (heat exported by the fluid (water, steam ..) / heat provided by the fuel)
This is also recognized as the ratio between the “Useful output” and the “Gross heat input”. For a Boiler operating at an ideal condition it is considered that 1Kcal is the heat quantity required to grow the temperature of 1 Liter of water by 1celcious. But this amount varies in the practical applications. In automation of the boiler the objective is to change the variable parameters in the boiler to bring close to this ideal condition.
Combustion efficiency in relation to the emission of the flue gas is measured as follow CITATION Ami17 l 1033 (Hajari, 2017),
Efficency = 100-Qs Stack Flue loss
Where ,Qs = k * (Tg – Ta) / CO2
Qs- Stack Flue Loss
K- Factor related to fuel
Tg -Flue Gas Temperature
Ta -Supplied Combustion Air Temperature
CO2 -% of Carbon Dioxide
It is to be noted that certain regulations need to be followed to make sure that the operation of the boiler is conducted in an environmental friendly, safe manner while it is operating at the optimum efficiency CITATION DrI08 l 1033 (Rogers, 2008). They are ,A. NFPA 85 Boiler and Combustion Control Systems Hazards code.
B. API 556 Instrumentation and Controls for Fire Heaters and Steam Generators
C. AS 3814 Industrial and Commercial Gas-Fired Appliances
D. AS 61508 /AS 61511 Standard for Safety Instrumented Systems.
Compliance to these regulations will make sure the boiler is function according to the laid down rules and regulations.
In order to perform the flue gas analysis following steps are expected to be followed,
Boiler has to work under the maximum power in the stable condition for a desired period of time.
Probe is to be inserted in to the tube of the boiler at a height which is 2 times the diameter.
If a Type C boiler is in use remote combustion air probe is to be inserted.
Perform the draft Measurement
Obtain the correct factor for the calculations
Perform the flue gas Analysis.
Importance of the boiler featured in this article is that the above mentioned process will be conducted automatically without any involvement of a human. In this manner it is expected to avoid errors caused due to human mistakes .This will provide information to the Control system to function without any errors. But it is expected to run periodic maintenance on the measuring equipment to make sure the reading taken are without errors.
Inorder to have a clear idea about the condition of the flue gas following types of sensors are to used. These sensors will be connected to the exhaust of the boiler. The type of sensors which will be used are,
CO2 SensorO2 Sensor
The output signal generated by these sensors is a physical quantity thereby to convert this to useful form Analog to digital converter will be used. Through ADC sensors will be connected to the microcontroller. Where the collected data from the sensors will be used to automate the boiler. Continuous Monitoring of the collected data will occur through the microcontroller since the accumulated data is stored in the microcontroller’s memory. It is expected to collect data from the boiler for a time period of 2 weeks where the condition of the flue gas is recognized when the boiler is running at its optimum level. By using this data various threshold levels will be assigned for each sensor. If the data acquired by any of the sensor exceeds or goes below its preset threshold level which is setup according to the boiler specification to obtain efficiency of the boiler, it will be indicated automictically to the maintenance technicians through a display device(HMI) of PC in work place or through Web base application to the supervisors and engineers to their smart phone to monitor boiler condition and to make correct decision. It is expected to automate the boiler to make the corrective measures by itself by using the training data. Thereby the boiler will always be running under the optimum conditions.
The diesel boiler operates as follow. initially it is required to filter the water which is used to produce steam. For which a physical barrier is used, it is also regarded that chemicals and biological processes can be used to remove impurities in water. In this matter water is filtered before being directed to the softeners. The filtered water is then fed into the softeners. The boiler plant mentioned in the article is consist of 2 such softeners. Consistency of minerals in water determines whether it belongs to the category of hard water. The basic function of the softeners is to break down this hard water and soften it . Basically, the removal of Calcium, Magnesium and some other metal cations will soften the hard water. ” Hard water can cause a number of problems with your plumbing system and appliances using water, including your boiler. The minerals in the hard water can lead to scale building up within your boiler” CITATION Tho16 l 1033 (Evans, 2016). This shows the importance of converting hard water in to soft water before processing it through the boiler.
Water filtered through the softeners are then sent in to Chemical feed pump where required chemicals are added to the water. The direct output of the filtered water, which is the makeup water line is directed to the boiler 1 drain line. The output which originates from the softners are directed to the Hot water tank.Meanwhile from the high pressure header, a line is fed to the condensation pump which is then connected with the hot well tank. This line provides condensed material.
The outlet of this hot well tank is connected to high pressure pumps and is also fed with manual chemical feed. Under the supervision of flow meters, thermometers and pressure gauges, this line is fed to boilers through safety valves. The power for these boilers are given using diesel fuel. A diesel storage tank is providing service to these mentioned boilers above. From the diesel storage tank, a line is fed to the service tank. This is fed to the service tank through a duplex strainer. Duplex strainer or twin basket strainer is a kind of channel incorporated with a fuel, oil or water funneling framework and it is utilized to expel huge particles of soil and flotsam and jetsam. The duplex strainer framework as a rule comprises of two separate strainer bins lodgings. The framework additionally contains a valve handle put between the two baskets to occupy the stream of fluid to one strainer while the other is being cleaned. On a few strainers, the valve will work alone, and the strainer will play out a self-cleaning task. These kinds of strainers are introduced in pipeline frameworks where stream can’t be ceased. Contingent on their NB size they are fit for filtration up to 40 µm. Basket strainers discover use in businesses where wastage is mostly parts of solids. The maintenance is easy and efficient for duplex strainers, when compared to other kinds of strainers. Duplex strainers are primarily utilized as a part in various kinds of enterprises. Process industry, oil and gas industry, chemical industry, pulp and paper industry, power industry, in refineries and petrochemical plants, pharmaceutical industry, in water and wastage management, metals and mining industry, fire fighting industry etc. are some of the examples where duplex strainers are used. Strainers are utilized to expel perilous components that may cause incomplete or finish breakdown of activities in the event that they get into the framework. From the service tank, the boilers are powered up. Oil strainers, flow meters, gear pumps are present on the line to strain oil, to calculate, and read the flow rate, flow speed and to pump fuel along the line to the feed of the fuel in the boiler. 3 main valves are present in feeding the diesel fuel to the boilers. The main valve, which is the feed line. If main valve is closed, then there will be no supply line of diesel to the two boilers. Each boiler has 2 of these main valves on them. In addition to the main valve, there are 2 other solenoid valves to control the inlet of the boiler diesel fuel. These two solenoid valves are named as solenoid valve no. 1 and solenoid valve no. 2 for each of the boilers. In addition to the fuel pump, there is an air blower, which feeds air into the boilers respectively. The level indicator of the pressure gauge is monitored at all times. If a necessity arises, the excess water is sent to the drain using the drain line along the pressure gauge. In addition to that, water is intentionally poured out of the boiler system to maintain the concentration of impurities and minerals within the system. This process is done while the steam is evaporated. Water is blown out from the boiler with a certain amount of pressure by steam within the boiler. There are 2 main methods of blowdown. Bottom blowdown, which was utilized with early boilers caused sudden descending change of evaporator water level. And was generally removed descending to keep away from nearby living beings, because hot water showers may damage property and living beings underneath and around nearby.
Automating the Process
Above mentioned process is automate in a manner where a programming platform is selected. Key factors in selecting the mentioned platform is the cost, availability and ease of use. PIC controllers are used to automate the process explained above. Choosing PIC microcontroller platform is because it’s high availability in market, very low cost compared to other platforms and the large user base CITATION Mar11 l 1033 (Bates, 2011). The availability of free development tools, vast collection of codes, notes, and advices in the internet, availability of serial programming and the capability of reprogramming were the other factors considered of selecting a PIC microcontroller for the research. Even though PIC microcontrollers consist of only one accumulator, it was selected because of it’s ease of use and the availability of PIC microcontroller material. From codes, notes to additional electronic equipment, the availability in market is vast. To gain access for the entire RAM, register bank switching is required. Also, operations and registers are not orthogonal. Even under these limitations, PIC microcontroller is considered for the selection because of the availability of RISC architecture, the simple instruction set where the program is to be programmed, availability of the built in oscillator with selectable speeds, low cost, easy handling etc.
Basically, the controlling and manoeuvring of the lines connected to the boiler will be controlled using PIC microcontrollers. Using servo motors, a tap like structure helps the control of the inlet air and the inlet diesel pump into the boiler. PIC microcontroller used is made by Microchip Technology. These PIC microcontrollers are used in manufacturing embedded systems all around the world. In the initial stages of the PIC microcontrollers when they were manufactured, they only had a read only memory (ROM). Some had field programmable EPROM for program storage. But the PIC microcontroller used in the research topic, uses flash memory for storing programs. Available data memory of chips is of 8 bit, 16 bit and 32 bit PIC microcontrollers. The program instructions differ according to the family of PIC, which is either 12, 14, 16 or 24. The number indicates how long the bits are of instructions. The PIC microcontroller used to control the boiler inlets is an 8 pin PIC microcontroller.
At the inlet, the circuitry is connected to a PIC microcontroller. The measured values from the air flow meter at the air inlet line, and the electromagnetic flow meter at the diesel inlet line, and the values from the pressure gauge which is connected to the boiler and the values of temperature from the thermometer which is connected to the boiler is fed into the PIC microcontroller. This data is then analyzed within the microprocessor, to integrate and follow the inlets under the maximum optimum level. When programming normally it is practiced letting flow a bit more air, and a very little extra amount of diesel into the boiler feed. It is done because if by any chance, an incomplete combustion occurs due to lack of inlet materials, the produced CO and other impurities which deposits inside the boiler, results in the decay of the boiler reliability very frequently. So, to prevent that from happening, an extra amount of air, and diesel is let into the boiler feed. Then the optimum level is already achieved without much wastage, and also the boiler is protected from an incomplete combustion from occurring. The feeds are controlled using tap like structures, where servo motors are used in the control of opening and closing the valves. These valves open and close in accordance with the feedback obtained from the inlet measurements of the air flow meter, the electromagnetic flow meter, the pressure gauge, and the thermometer. Levels of these sensors are kept monitored, and within the optimum range, ensuring proper complete combustion inside the boiler. By implementing this control system, it is expected to reduce the wastage of diesel pumping and providing unnecessary air flow into the boiler. Also, complete combustion occurs inside the boiler of doing so. Then the efficiency of the boiler is expected to increase drastically than it was used to be when done manually. A feedback from the outlet is also fed into the PIC microcontroller. The programming is separately done for the outlet. Researcher only focuses on the inlet supplies of air and fuel and will only optimize the inlet of the boiler. By optimizing the inlet of the boiler, the boiler is expected to run at optimum. But the feedback from the outlet, and the feedback from the boiler combustion should also be considered when optimizing the boiler efficiency as a whole. Therefore, the occurrence of complete combustion, and the outlet feedback is programmed into the PIC microcontroller.
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