Oil Fired Hot Water Boiler
Oil Fired Hot Water Boiler
1. Oil Fired Hot Water Boiler Preface
A oil fired hot water boiler is defined as "a closed vessel in which water or other liquid is heated, steam or vapor is generated, steam is superheated, or any combination thereof, under pressure or vacuum, for use external to itself, by the direct application of energy from the combustion of fuels, from electricity or nuclear energy."
Also included are fired units for heating or vaporizing liquids other than water where these units are separate from processing systems and are complete within themselves. This definition includes water heaters that exceed 200,000 Btu/hr heat input, 200 degrees Fahrenheit at the outlet, or 120 gallons nominal water containing capacity.
Boilers are one of the essential equipments onboard ships. It's purpose is to provide heating to the main diesel propulsion engine, to the bunker F.O. tanks (to make it less viscous for transfer purposes as well as easy ignition). The steam generated by the boiler can also be use for cleaning, and heating of the seawater in the freshwater generator thus evaporating it to make it potable water.
2. Working Process of Oil Fired Hot Water Boiler
A basic boiler is a machine with the simplest arrangement of the internal parts. The main job of a boiler is to make high pressure steam. The feed water supplied to the boiler drum utilizes the heat of the energy released by burning the fuel. This energy of the burning fuel is stored in the form of steam with high temperature and pressure. The fuel is burnt in a combustion chamber inside the boiler.
To attain high efficiency and complete combustion, air is supplied to this combustion chamber through a separate arrangement. The heat generated in this combustion chamber is transferred to the water from the boiler drum through a large surface area, which enables the highest rate of energy transfer.
3. Steam Generation of Oil Fired Hot Water Boiler
The process of steam generation starts when the feed water enters the steam drum through both internal tubes and the tubes that surround the furnace. The system of tubes that surrounds the furnace is known as waterwall or floor tubes. The feed water gets heated when passed through these tubes. Addition to this, there are Large-bore downcomer tubes that passes outside of the furnace and are used to circulate water between the drums, to which the tubes are attached from outside of the furnace.
The steam produced in the steam drum is known as wet or saturated steam. This steam cannot be used directly as it contains high amounts of moisture. To make this steam usable, it is first dried and heated with the help of a superheater located within the boiler. Once all the moisture content is removed from the steam, the superheated steam can be supplied to other systems. It is utmostly important to monitor and control the temperature of the superheated steam, or else it can cause damage to the systems to which it is supplied. For this reason, an implement known as an attemperator is used. The attemperator is a kind of cooler which is used to cool down the superheated steam to the right temperature. Thus, all the steam used in various system is taken out from the main steam drum of the boiler.
The energy from the fuel burning are used for various other purposes, the main two are as follows:
For heating feed water to produce steam
For superheating the steam from the boiler drum
To increase the efficiency of the boiler, the feed water that enters the boiler is pre-heated with the help of an economizer through which the feed water passes before entering the boiler. The exhaust gas of the boiler is also put to use by making it pass over an air heater, which heats up the combustion air entering the furnace. Thus, even the energy exhausted from the boiler is not allowed to go waste, which increases the overall efficiency of the system.
All these boilers are fitted with various safety fittings and control systems to monitor and control various aspects such as fuel oil flow rate, flow of combustion air, and feed water supply. All these systems should work in co-ordination to supply the amount of steam required by various system. The boiler is also provided with various mountings to ensure safe operation of the boiler.