Package boiler

Last updated
Typical gas-fired package boiler
The burner and centrifugal blower is at the left. Two vertical water level gauges can also be seen. History of lff2.jpg
Typical gas-fired package boiler
The burner and centrifugal blower is at the left. Two vertical water level gauges can also be seen.

A package boiler is a factory-made boiler. Package boilers are available in a range of standard designs. Package boilers are used for heating and act as a steam generator for small power purposes such as self-powered industrial plants. They cannot be used for large-scale power plants such as co-generation plants due to their size and lack of efficiency. Advantages of package boilers are that they can be brought in as a whole assembly, perfect for tight spaces, and easily installed. They require steam pipes, water pipes, fuel supply, electrical connections and can be made ready almost immediately. Because of their compact design, these boilers are cheaper to operate due to their automatic burner management system as well as maintenance cost. [1]

Steam generator (boiler)

A steam generator is a form of low water-content boiler, similar to a flash steam boiler. The usual construction is as a spiral coil of water-tube, arranged as a single, or monotube, coil. Circulation is once-through and pumped under pressure, as a forced-circulation boiler. The narrow-tube construction, without any large-diameter drums or tanks, means that they are safe from the effects of explosion, even if worked at high pressures. The pump flowrate is adjustable, according to the quantity of steam required at that time. The burner output is throttled to maintain a constant working temperature. The burner output required varies according to the quantity of water being evaporated: this can be either adjusted by open-loop control according to the pump throughput, or by a closed-loop control to maintain the measured temperature.

Cogeneration simultaneous generation of electricity, and/or heating, or cooling, or industrial chemicals

Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to generate electricity and useful heat at the same time. Trigeneration or combined cooling, heat and power (CCHP) refers to the simultaneous generation of electricity and useful heating and cooling from the combustion of a fuel or a solar heat collector. The terms cogeneration and trigeneration can be also applied to the power systems generating simultaneously electricity, heat, and industrial chemicals – e.g., syngas or pure hydrogen.

Efficiency is the ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without waste. In more mathematical or scientific terms, it is a measure of the extent to which input is well used for an intended task or function (output). It often specifically comprises the capability of a specific application of effort to produce a specific outcome with a minimum amount or quantity of waste, expense, or unnecessary effort. Efficiency refers to very different inputs and outputs in different fields and industries.

Contents

A great cost-saving for package boilers is their simple need for draughting. The chimney may either use an existing masonry chimney, or else a simple steel tube stack is provided, just sufficient to clear the nuisance of the exhaust fumes. As the burner provides its own draught from a fan, they do not require the tall brick chimneys needed to provide the draught for a coal-fired.

Internal arrangement

Internal layout of a three-pass fire-tube boiler Flammrohrrauchrohrkessel 7.jpg
Internal layout of a three-pass fire-tube boiler

Package boilers are commonly called water or fire tube Boilers. Water tube boilers use convection heating, which draws the heat from the fire source, and passes against the generating tubes of the boiler, causing water inside those tubes to boil off into steam. The fire tube boiler arrangement utilizes conduction heating which transfers heat from physical contact. Fire tube boilers are not commonly used due to their method of conduction heating because pipes in direct contact with fire and cold water could damage the pipes. The package boiler is usually a two or three-pass fire-tube boiler with an internal furnace tube. This is similar to the much earlier Scotch boiler.

Boiler closed vessel in which water or other fluid is heated

A boiler is a closed vessel in which fluid is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation.

Water-tube boiler type of boiler

A high pressure watertube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes. In smaller boilers, additional generating tubes are separate in the furnace, while larger utility boilers rely on the water-filled tubes that make up the walls of the furnace to generate steam.

Fire-tube boiler

A fire-tube boiler is a type of boiler in which hot gases pass from a fire through one or (many) more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating the water and ultimately creating steam.

Generating tubes filled with water are in direct contact with the heat source inside the boiler, causing damage to the pipes as well as scaling. These boilers however are great with steam production due to the large volume inside the boiler and the surface area of the steam output. In order for these boilers to operate properly, they require a long warm-up process, and are prone to thermal shock of the boiler. These boilers can be rated up to 500,000 lb/hr. [2] The wall membrane of the boiler are dual welded, (welded on either side of the wall membrane) to provide extra reinforcement for high loads.

Thermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. This differential expansion can be understood in terms of stress or of strain, equivalently. At some point, this stress can exceed the strength of the material, causing a crack to form. If nothing stops this crack from propagating through the material, it will cause the object's structure to fail.

A-type, D-type and O-type are all water tube package boilers.

Combustion

Package boilers are fired from fuel oil in the form of liquid or gas. Fuel is ignited in the burners which creates an explosion within the boiler. Such package boiler do not require purifiers (filters) because they burn consistently removing all contaminants within the fuel. To create constant combustion within the boiler, the forced draft fan forces air into the burner, causing a tornado effect creating turbulence to keep the flame ignited and the furnace pressurized. Other essentials such as Burner electronics provide auto-ignition and on-demand lighting feature that monitors the flame and pressure within the boiler. tube boiler Package boilers are commonly called water or fire tube Boilers. Water tube boilers use convection heating, which draws the heat from the fire source, and passes against the generating tubes of the boiler, causing water inside those tubes to boil off into steam. The fire tube boiler arrangement utilizes conduction heating which transfers heat from physical contact. Fire tube boilers are not commonly used due to their method of conduction heating because pipes in direct contact with fire and cold water could damage the pipes. The package boiler is usually a two or three-pass fire-tube boiler with an internal furnace tube. This is similar to the much earlier Scotch boiler.

Pros and Cons

Pros [1]

The difference between atmospheric pressure and the pressure existing in the furnace or flue gas passage of a boiler is termed as draft. Draft can also be referred to the difference in pressure in the combustion chamber area which results in the motion of the flue gases and the air flow.

Cons

Types of Package Boilers

The D-type Package Boiler

The D-type boiler has a water drum, steam drum, and generating tubes. Water flows into the steam drum, flows down the downcomers and into the water drum. Water is then sent from the water drum through the generating tubes, where the fire is located around causing water molecules to boil off into steam. Steam rises up more generating tubes and finally back into the steam drum where the dry pipe is located then into the plant. This configuration shaped the package boiler into a D-shape, hence the name D-type package boiler. These boilers are mostly used for plants that allow greater clearances.

The A-type Package Boiler

The A-type package boiler has two water drums and one steam drum compared to the D-type package boiler. Water boils off in the water drums shared by a common header, then sent up the generating tubes, into the steam drum and up the dry pipe. Just like the D-type package boiler, fire heats the tubes surroundings causing the tubes to increase in temperature thus boiling off water molecules to steam. A-type package boilers were designed to improve package boiler reliability and reduce tube replacements. A-type package boilers are smaller than D-type therefore will fit smaller plants, but does not have the same power output as D-type package boilers.

The O-type Package Boiler

O-Type Package boiler. The boiler has two drums, one water drum and one steam drum. The combustion chamber is in the middle surrounded by downcomers and generating tubes. Boiler Type O.jpg
O-Type Package boiler. The boiler has two drums, one water drum and one steam drum. The combustion chamber is in the middle surrounded by downcomers and generating tubes.

The O-type boilers are a little simpler compared to D-type and A-type. They consist of one water drum and one steam drum. Generating tubes are lined up from either sides of the steam and water drums. When water boils due to convection heating, steam rises up through the tubes and into the steam drum. This is a symmetrical design for restrictive plant layouts. O-type boilers are mainly used for their fast steam production and reduced maintenance cost. [3]

Related Research Articles

Furnace device used for heating in industry

A furnace is a device used for high-temperature heating. The name derives from Latin word fornax, which means oven. The heat energy to fuel a furnace may be supplied directly by fuel combustion, by electricity such as the electric arc furnace, or through induction heating in induction furnaces.

Steam explosion violent boiling or flashing of water into steam

A steam explosion is an explosion caused by violent boiling or flashing of water into steam, occurring when water is either superheated, rapidly heated by fine hot debris produced within it, or heated by the interaction of molten metals. Pressure vessels, such as pressurized water (nuclear) reactors, that operate above atmospheric pressure can also provide the conditions for a steam explosion. The water changes from a liquid to a gas with extreme speed, increasing dramatically in volume. A steam explosion sprays steam and boiling-hot water and the hot medium that heated it in all directions, creating a danger of scalding and burning.

Heat recovery steam generator energy recovery heat exchanger that recovers heat from a hot gas stream

A heat recovery steam generator (HRSG) is an energy recovery heat exchanger that recovers heat from a hot gas stream. It produces steam that can be used in a process (cogeneration) or used to drive a steam turbine.

Pilot light

A pilot light is a small gas flame, usually natural gas or liquefied petroleum gas, which serves as an ignition source for a more powerful gas burner. Originally, a pilot light was kept permanently alight; however, this is wasteful of gas. Now it is more common to light a burner electrically, but gas pilot lights are still used when a high energy ignition source is necessary, as in when lighting a large burner.

Thermal power station power plant in which heat energy is converted to electric power

A thermal power station is a power station in which heat energy is converted to electric power. In most of the places in the world the turbine is steam-driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different heat sources; fossil fuel dominates here, although nuclear heat energy and solar heat energy are also used. Some prefer to use the term energy center because such facilities convert forms of heat energy into electrical energy. Certain thermal power stations are also designed to produce heat energy for industrial purposes, or district heating, or desalination of water, in addition to generating electrical power.

Cockenzie power station

Cockenzie power station was a coal-fired power station in East Lothian, Scotland. It was situated on the south shore of the Firth of Forth, near the town of Cockenzie and Port Seton, 8 mi (13 km) east of the Scottish capital of Edinburgh. The station dominated the local coastline with its distinctive twin chimneys from 1967 until the chimneys' demolition in September 2015. Initially operated by the nationalised South of Scotland Electricity Board, it was operated by Scottish Power following the privatisation of the industry in 1991. In 2005 a WWF report named Cockenzie as the UK's least carbon-efficient power station, in terms of carbon dioxide released per unit of energy generated. The 1,200 megawatt power station ceased generating energy on 15 March 2013 around 8.30am. As of May 2014 the main station is being dismantled by Brown and Mason Ltd, a UK-based demolition company. There are plans to replace the station with a Combined Cycle Gas Turbine (CCGT) power station. The removal of the power station was done in stages with the twin chimneys and turbine hall being demolished in a controlled explosion on 26 September 2015, the front section of the boiler house on 4 November 2015 and the rest of the boiler house on 17 December 2015. This was the last remaining major structure to be removed.

Steam-electric power station power plant, wherein the thermal energy is exploited by steam in a steam turbine

The steam-electric power station is a power station in which the electric generator is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser. The greatest variation in the design of steam-electric power plants is due to the different fuel sources.

Boiler (power generation) device used to create steam by applying heat energy to water

A boiler or steam generator is a device used to create steam by applying heat energy to water. Although the definitions are somewhat flexible, it can be said that older steam generators were commonly termed boilers and worked at low to medium pressure but, at pressures above this, it is more usual to speak of a steam generator.

Flued boiler

A shell or flued boiler is an early and relatively simple form of boiler used to make steam, usually for the purpose of driving a steam engine. The design marked a transitional stage in boiler development, between the early haystack boilers and the later multi-tube fire-tube boilers. A flued boiler is characterized by a large cylindrical boiler shell forming a tank of water, traversed by one or more large flues containing the furnace. These boilers appeared around the start of the 19th century and some forms remain in service today. Although mostly used for static steam plants, some were used in early steam vehicles, railway locomotives and ships.

Yarrow boiler Obsolete class of high-pressure water-tube boilers widely used on ships

Yarrow boilers are an important class of high-pressure water-tube boilers. They were developed by Yarrow & Co. (London), Shipbuilders and Engineers and were widely used on ships, particularly warships.

Boilers for generating steam or hot water have been designed in countless shapes, sizes and configurations. An extensive terminology has evolved to describe their common features. This glossary provides definitions for these terms.

Three-drum boiler class of water-tube boiler used to generate steam, typically to power ships

Three-drum boilers are a class of water-tube boiler used to generate steam, typically to power ships. They are compact and of high evaporative power, factors that encourage this use. Other boiler designs may be more efficient, although bulkier, and so the three-drum pattern was rare as a land-based stationary boiler.

Johnson boiler

The Johnson boiler is a water-tube boiler used for ship propulsion.

Computational fluid dynamics (CFD) are used to understand complex thermal flow regimes in power plants. The thermal power plant may be divided into different subsectors and the CFD analysis applied to critical equipment/components - mainly different types of heat exchangers - which are of crucial significance for efficient and trouble free long-term operation of the plant.

Fairbairn-Beeley boiler

The Fairbairn-Beeley boiler was a design of fire-tube stationary boiler developed in the late 19th century. It takes its name from its two developers, Sir William Fairbairn and Thomas Beeley

O-type boiler

An O-type boiler is a form of water-tube boiler. It is named, like the D-type and A-type boilers, from the approximate shape of its tubes.

Industrial furnace

The purpose of an industrial furnace is to attain a higher processing temperature in comparison to open-air systems, as well as the efficiency gains of a closed system. Industrial furnaces typically deal with temperatures higher than 400 degrees Celsius.

References

  1. 1 2 Punte, S. "Type of boilers". www.energyefficiencyasia.org. Retrieved 2016-04-14.
  2. Funk, Jason R. "Boilers Basics" (PDF). dol.ks. Hughes Machinery. Retrieved 14 April 2016.
  3. Bases, G. "Techs & Specs - National Insulation Association". www.insulation.org. Retrieved 2016-04-14.