Tips to Increase Steam Boiler Efficiency
Manufacturing and process industries require steam for various process operations. Therefore, boilers are imperative for generating high-quality steam to accomplish operational purposes in the processing facilities. One of the most important factors to consider before investing in a steam boiler is boiler efficiency. Boiler efficiency can be termed as the ratio of the useful heat output to the total energy input. The majority of heat lost in the steam boiler is in the boiler water or stack. The process plant can significantly increase its boiler efficiency by following some practices, consequently reducing excess costs.
15 Practices to Increase Boiler Efficiency:
- Regular Tuning of the Burner:
The right amount of air is one of the factors that impact boiler efficiency. A certain amount of oxygen is essential for the proper combustion of fuels. In case of air being too low, the carbon in the fuel starts to oxidize, leading to the formation of carbon monoxide. It results in the release of heat in a reduced amount as the fuel is not burned completely. Soot, smoke, and carbon monoxide are caused due to low air that causes harm to the boiler. Excess air also decreases boiler efficiency as it is transported to the stack hot that wastes heat.
An optimum amount of air ensures proper and complete combustion of the fuel. For proper combustion, the amount of air needs to be measured with an O2 probe. The probe is inserted in the stack while tuning the burner for optimal boiler efficiency. Tuning the burners regularly results in maximum savings of fuel.
- Reduce the Stack Temperature:
Reducing stack temperature is an easy process that decreases the operating pressure when the steam boiler is not in operation.
- Proper Insulation of Valves:
Insulation plays a crucial role in capturing heat and preventing its wastage. Neglecting the insulation after maintenance can cause tremendous heat loss. Insulating valves helps in avoiding heat loss, reducing accidents, and ensuring easy access for maintenance. Optimal use of heat, in turn, increases the boiler efficiency.
- Using an Economizer:
Economizers utilize the wasted hot flue gas and heat the feed water for combustion purposes in a steam boiler. Installing an economizer can significantly reduce the fuel consumption for heating the water, thereby increasing the boiler efficiency.
- Cleaning of Fireside:
As the boiler age advances, the soot layers start forming on the fireside of the boiler tubes that act as an insulator. Consequently, it reduces the heat transfer rate and increases fuel usage. Due to the low heat transfer rate, the hot gases pass without transmitting heat to the water. It resultantly increases the stack temperature and decreases the overall boiler efficiency. Therefore, it is necessary to inspect and clean the fireside of the steam boiler to prevent soot formation.
- Cleaning of Waterside:
It is pivotal to thoroughly check the waterside to ensure that there are no leakages or scale formation. Scaling forms on the heat transfer surfaces due to improper chemical treatment, high levels of water hardness, and irregular blowdown. It results in hindering the heat transfer that eventually reducing the boiler efficiency. If overlooked, scaling can cause overheating in boilers that lead to expensive boiler repairs.
- Boiler Blowdown:
Boiler efficiency can be increased by recovering heat from the blowdown process. The blowdown valve helps in releasing the boiler water containing soluble and insoluble solids. It reduces the number of dissolved solids that impede the heat transfer process.
- Controlling Blowdown Rate:
Although blowdown removes the impurities from the steam boiler, it also discharges heat from the boiler system. It is crucial to maintain the rate of heat drained through blowdown. The required amount of blowdown can be ensured by installing an automatic blowdown valve.
- Return Condensate to the Boiler:
Condensate is the result of steam transmitting its heat and condensing. The by-product is utilized with already heated water that requires less fuel to generate steam again. Reusing the condensate also reduces the amount of makeup water and chemical treatment required.
- Preheating Combustion Air:
If the air feed in the boiler for combustion is already heated, it requires less fuel to generate steam. A 40 °F increase in the air used for combustion can save up to 1% fuel costs.
- Retrofitting Burners:
Steam boilers require air for proper and complete combustion. Too little air or too much air affects the combustion process, thereby reducing the overall boiler efficiency. Retrofitting and upgrading to a high-efficiency burner is a better option compared to tuning the burners. Retrofitting is an ideal solution for burners that are more than 15 years old. Burner upgrading can save up to 20% of fuel costs.
- Reduce Carryover:
Carryover is caused by water leaving the boiler system along with steam. The wet steam carries impurities like dissolved solids with it. The impurities leave deposits in the boiler system that impacts boiler parts such as control valves and pressure regulators. It results in damage in steam boilers that affects their efficiency.
- Inspection of Steam Trap:
A broken or damaged steam trap allows steam to blow away into the condensate system. Therefore, it is important to regularly inspect the steam trap and replace it if broken to ensure maximum efficiency.
- Avoid Excessive Use of Steam:
Reducing steam usage can significantly increase boiler efficiency. Insulating the pipes and tanks heated by steam decreases steam utilization and consequently fuel usage. A high-pressure condensate system can reduce the steam used at the deaerator and fuel requirement in the boiler.
- Regular Maintenance of Boiler:
Despite following precaution and standard guidelines in operating steam boiler systems, issues like corrosion, scaling, foaming, etc., are inevitable in the boiler system. It is vital to conduct boiler maintenance regularly to obtain peak efficiency.
Rakhoh Boilers is a leading name in industrial steam boiler manufacturer and thermal solutions since 1983. We have successfully installed 3000+ boilers in 26 countries worldwide for over 20 process industries. We manufacture robust steam boilers and provide the best boiler services to enhance boiler efficiency and productivity.
To learn more about our products and services, visit www.rakhoh.com
- Published in Boiler
Feed Water Treatment for Steam Boilers
A boiler is an integral asset in the manufacturing and processing units to accomplish various operations. To ensure processing efficiency, the steam quality must be of the highest quality. Feedwater treatment is essential for high steam quality that aids in operational purposes. Proper treatment for feed water prevents scaling, corrosion, and fouling of the boiler system. As a result, it avoids expensive plant downtime and maintenance fees as well as boiler breakdown.
What is a Boiler Feed Water Treatment?
The boiler feedwater treatment system consists of various technologies that apply to the feedwater treatment requirements for steam boilers. Feedwater treatment is vital for both high-pressure and low-pressure boilers. Implementing proper boiler water treatment is important to avoid expensive retrofits or replacements in the long run.
Effective feed water treatment facilitates,
- Elimination of harmful impurities prior to feeding it to the steam boiler
- Enhance boiler chemistry control
- Increase use of condensate steam
- Control return-line corrosion
- Prevent downtime and boiler failure
- Longer equipment lifecycle
Boiler feedwater treatment components depend on the water quality being drawn from concerning the water makeup quality required for the boiler. Effective boiler feedwater treatment includes,
- Filtration and Ultrafiltration
- Membrane processes like reverse osmosis and nanofiltration
- Deaeration/Degasification
- Ion exchange/softening
- Coagulation/Chemical precipitation
The impurities present in feed water determine the combination required for the treatment.
Why is Boiler Feed Water Treatment Important for the Process Plant?
Boiler feedwater treatment is essential to eliminate dissolved solids, suspended solids, and organic material that includes the following,
Copper: Copper causes deposits to settle in high-pressure turbines that reduce its efficiency and requires expensive cleaning or equipment change-outs
Calcium: Calcium causes scaling in various forms depending on the boiler feed water chemistry
Iron: Both soluble and insoluble iron deposits on the boiler parts and tubes, causing harm to the downstream equipment and impacting the quality of the operational process.
Aluminum: Aluminum deposits as scale in the interior of boiler and reacts with silica that increases the scaling
Silica: Silica causes extreme hard scaling if not removed to low levels, particularly in high-pressure boilers
Magnesium: When magnesium combines with phosphate, it sticks to the interior of boiler and coat tubes that consequently attracts more solids and increases scaling
Hardness: Hardness contributes to the deposits and scaling on the boiler parts and piping
Dissolved Gases: Dissolved gases such as oxygen and carbon dioxide causes chemical reactions that lead to severe corrosion on boiler parts and pipes
Working of Boiler Feed Water Treatment System:
The treatment processes differ, depending on the boiler requirements and the quality of feedwater and makeup water. Generally, a boiler feedwater treatment system includes the following steps,
Makeup Water Intake:
The process involves extracting the makeup water or leaking water from the boiler from its source.
Coagulation and Chemical Precipitation:
Once the larger components are eliminated from the original water source, various chemicals are introduced in the reaction tank to remove the suspended solids and other contaminants. The process usually begins by mixing reactors with one or two reactors that add specific chemicals to extract the finer particles in the water by combining them into heavier particles. Aluminum-based coagulates such as alum and polyaluminum chloride are used extensively. Minor pH changes also aid in the coagulation of the particles.
Filtration and Ultrafiltration:
The next process includes a certain type of filtration to remove the suspended particles like sediment, turbidity, and specific organic matter. Removal of suspended solids upstream protects the membranes and ion exchange resins from the fouling in the pre-treatment process, if performed initially in the process.
Ion exchange softening:
While preheating boiler feed water, a softening resin is required if high hardness is present complexed with bicarbonates, sulfates, chlorides, or nitrates. The process utilizes a strong acid cation exchange process that charges resin with a sodium ion. As the hardness comes through, it has a higher affinity for calcium, magnesium, and iron to grab the molecule and release the sodium molecule in the water.
Dealkalization:
The boiler feedwater treatment system utilizes dealkalization to reduce alkalinity/pH after the softening process. Sodium chloride dealkalization follows a strong anion exchange resin for replacing bicarbonate, sulfate, and nitrate for chloride anions. Even though it does not eliminate alkalinity entirely, it removes the majority of it with an easy and economical process. Weak acid dealkalization merely removes cations bound to bicarbonate and converts it to carbon dioxide.
Reverse Osmosis and Nanofiltration:
Reverse Osmosis and Nanofiltration processes are often used to remove the most harmful impurities that can foul and clog the reverse osmosis and nanofiltration membranes. The process force pressurizes water through semipermeable membranes that trap contaminants such as bacteria, salts, organics, silica, and hardness. The filtration units are widely used for high-pressure boilers that require extremely low concentrations of suspended and dissolved solids.
Deaeration or degasification:
At this point, any condensate returned to the boiler system will mix with the treated makeup water and enter the deaeration or degasification process. Gases such as oxygen or carbon dioxide would be extremely corrosive to the boiler system and piping, causing oxide formation and rust. Therefore, it is imperative to remove these gases to ensure the safety and lifespan of the steam boiler.
Distribution:
After sufficiently treating the boiler feedwater, it is fed to the boiler system for heating and generating steam. Pure steam is used for operational purposes while the condensate return is administered back to the process with pre-treated makeup water for its pre-treatment process.
Rakhoh Boilers have been one of the leading steam boiler manufacturers for 38+ years. We have delivered efficient and reliable steam boilers and provided after-sales service for more than 20 process industries worldwide.
Learn more about our products and services at www.rakhoh.com
- Published in Boiler
Caustic Embrittlement in Steam Boilers | Causes and Prevention
Steam boilers are paramount for hassle-free process operations in manufacturing and process facilities. It is prudent for the operating personnel to ensure that the steam boilers are not facing any issues that would affect the operational purposes of the process plant. Regular maintenance and checking the machinery parts are important for optimal productivity of the steam boiler and safety of the processing unit. Boiler issues such as corrosion, scaling, water carryover, priming, framing, etc., are inevitable and require prompt action before it causes far-reaching loss and harm. One such issue that can severely impact the functioning of the steam boiler is caustic embrittlement.
What is Caustic Embrittlement?
Caustic embrittlement is a phenomenon that takes place in a steam boiler when the caustic substances gather in the materials of the boiler. It is also characterized by the cracking of riveted mild steel boilerplates. Caustic embrittlement takes place at the temperature range of 200°C to 250°C. It is caused due to the local deposition of concentrated hydroxide.
Caustic embrittlement mainly occurs on the stressed parts of the boiler, including cracks, joints, bends, and rivets. The residual sodium carbonate that is utilized for the softening process goes through hydrolysis. As a result, it forms sodium hydroxide at high pressure and temperature. Caustic embrittlement is also termed stress corrosion cracking.
Caustic Embrittlement in Steam Boilers:
Caustic embrittlement is a type of corrosion that is caused due to high concentration of sodium hydroxide (NaOH). It is caused by the formation of irregular cracks on the boiler metal, especially at high local bends such as joints and bends.
Caustic embrittlement is a commonly occurring issue taking place when a component is operating in a caustic environment. It is counted as one of the many environmental cracking mechanisms, generally taking place in carbon steel equipment as well as low alloy and austenitic stainless steel equipment.
Caustic environments consist of high concentrations of NaOH and KOH that lead to cracking, usually in welding because of high residual stress. It also affects the base metal with high residual stress.
Caustic embrittlement is an intercrystalline fracture that is caused by the high concentration of caustic soda and the material under stress. The stress corrosion cracks follow the grain or crystal boundaries of the material. Caustic embrittlement is mainly found in the areas of the steam boiler that are highly stressed, such as tube and tube plate connection, riveted head, seam, and boiler mountings.
Causes of Caustic Embrittlement:
Various reasons lead to caustic embrittlement, including the action of the following three components,
- Susceptible materials such as carbon steel
- Particular chemical species like concentrated hydroxide
- Tensile stress around the riveted holes
As the water evaporates in the steam boiler, the concentration of sodium carbonate in the boiler starts increasing. Sodium carbonate is usually used for the softening of lime soda water in high-pressure boilers. If the concentration of sodium carbonate accelerates, it undergoes hydrolysis that leads to the formation of sodium hydroxide.
Scaling is prevented when sodium hydroxide is administered to the boiler water. Cracking in the steam boiler shell and tube plates are caused by the alkali present around the rivet heads, crevices, and hot spots, along with fabrication stress around the rivet holes. As the alkaline water enters the minute holes and cracks on the boiler interior, the water starts dispensing out of the cracks. It results in the accumulation of hydroxide salts left behind as the water evaporates. The hydroxide impacts the material of the boiler and dissolves iron as sodium ferrite.
Corrosion occurring at high pH levels leads to producing hydrogen that affects the crystal structure of iron, making it brittle and hard. It may prove hazardous as the tube can fail at the boiler’s normal operating temperature.
Prevention of Caustic Embrittlement:
Caustic embrittlement can be prevented through several measures such as,
- Managing the temperature and potential
- Managing the Hardness and stress level- residual or load
- Avoiding the use of alkalis
- Utilizing material that does not crack when used in a caustic environment
- Using sodium phosphate instead of sodium bicarbonate as a softening agent for boiler water
- Introducing tannin and lignin in the boiler water assists in blocking the hairline cracks, consequently preventing the accumulation of sodium hydroxide
- Introducing Na2SO4 in boiler water helps in blocking hairline cracks
Conclusion:
Rakhoh Boilers have emerged as a leading steam boiler manufacturer in Pune since its inception in 1983. With extensive knowledge and expertise in industrial boiler manufacturing and thermal solutions, we have successfully installed 3000+ boilers in over 26 countries worldwide. We have catered to 20 process industries by providing an efficient and reliable range of steam boilers, waste heat recovery systems, thermic fluid heaters, and boiler accessories. As a trusted boiler manufacturer, we provide the best boiler services like steam trap assessment, boiler automation, energy audit, annual maintenance contract, management, and training, etc.
To know more about our products and services, visit www.rakhoh.com
- Published in Boiler
An Overview of Types of Steam Boilers and Its Applications
Steam boilers play an integral part in most of the process and manufacturing industries in today’s world. Steam boilers are ideal for process operations as steam has a higher energy holding capacity and is safe and convenient to use. Depending on various factors such as industrial requirements, applications, fuel availability, steam pressure, volume, etc., steam boilers can be simple or complex. The two primary types of steam boilers used are Fire Tube Boilers and Water Tube Boilers. Over the last years, boiler manufacturers have expanded the options in the two basic types, offering extensive options to the customers. Let us dive deep into the details of both types of boilers.
Fire Tube Boilers:
As the name suggests, fire tube boilers function with the fire (combustion gases) inside the tubes. Fire-tube boilers have been prominent for over the century. Fire tube boilers are preferred by industries requiring high-pressure steam.
Functioning of Fire Tube Boilers:
The burner ignites in tubes immersed in water, which is included in the main vessel of the boiler. With several fire tubes, the heat from the gases passes to the water and heats it to the boiling point. The generated steam is captured in a space above the water and exits from the steam outlet for operational purposes. Since both the steam and water share the same vessel, the steam pressure is restricted. It is important to note that exceeding the vessel pressure beyond its capacity would lead to a hazardous consequence.
Fire-tube boilers can be classified based on the location of their furnace. They are termed external furnaces and internal furnaces.
External furnaces are further divided, into 3 types:
- Horizontal-return tubular fire tube boiler
- Short firebox fire tube boiler
- Compact fire tube boiler
On the other hand, internal furnaces are divided, into 2 types:
- Horizontal tubular fire tube boiler
- Vertical tubular fire tube boiler
Advantages of Fire Tube Boilers:
- Simple design and low maintenance
- Easy to operate for efficient performance
- Feedwater treatment is not necessary
- Economical as compared to Water Tube Boilers
- Ideal for Small Industries
Disadvantages of Fire Tube Boilers:
- Maximum working pressure up to 20 bar
- Overall efficiency up to 75%
- Difficult to handle load fluctuations
- Possibility of Drum Failures and Explosions if Neglected
- Steam generation and steam quality is low as compared to Water Tube Boilers
Water Tube Boilers:
As the name implies, water tube boilers function with the water inside the tubes. The gases from the furnace enter a large containment area, in which it bounces off the rear wall, passing the heat to the water tubes uniformly and efficiently. Water tube boilers reduce fuel costs and are significantly safe to use as the possibility of steam explosion due to failure is less because of less water.
Functioning of Water Tube Boilers:
The water tube boiler consists of multiple water tubes in a chamber. These tubes are sealed and can tolerate pressure individually without impacting the adjacent tube. The heat is passed to the water through the metallic tubes. The water heated rises to the top of the boiler in the steam drum. The steam is produced at a high rate in water tube boilers.
Contrary to fire tube boilers, the heat source surrounds the water in water tube boilers. It results in reduced stress on the boiler. Water-tube boilers are widely used for generating steam at high pressure and volume.
Components of Water Tube Boilers:
Water-tube boilers generally include the following:
Boiler Shell: external cylindrical unit of the pressure vessel
Burner: source of ignition to heat the water
Mud Drum: located at the bottom of the water container that accumulates the impurities from the water. It also facilitates blowdown operations.
Strainer: filter to strain out the solid elements
Sight Glass: monitoring the water levels
Advantages of Water Tube Boilers:
- Requires less floor area
- Direction of water circulation is well defined
- Easily handles load fluctuations
- Rate of steam generation and steam quality are high
- Overall efficiency up to 90% with an economizer
- Ideal for large industries and power plants
Disadvantages of Water Tube Boilers:
- Complex in design and high maintenance cost
- Requires trained operator for efficient operation
- Uneconomical for small industries
- Feedwater treatment is essential to prevent overheating and bursting
Efficiency in Steam Boilers:
Boiler manufacturers generally rate the boiler efficiency higher than its actual efficiency. However, by complying with few factors, industries can derive maximum efficiency from steam boilers. Some of the factors that impact boiler efficiency include:
- Regular Maintenance of steam boilers enhances the boiler efficiency. In fact, lack of maintenance can reduce the boiler efficiency up to 10%
- Boiler accessories like economizers can add up the efficiency level of the steam boiler
- Proper boiler size and the frequent on-off cycle can significantly impact the steam boiler efficiency
Rakhoh Boilers manufactures an extensive range of steam boilers for more than 20 process industry sectors in India and overseas. We are reputed to provide high-quality steam boilers such as Membrane Boilers, Bi-Drum Boilers, Husk Fired Boilers, Oil fired Boilers, Waste Heat Recovery Boilers, Thermic Fluid Heaters, etc. Apart from boilers, we provide the best boiler accessories and boiler services that boost the efficiency and performance of the steam boiler system.
Learn more about our products and services at www.rakhoh.com
- Published in Boiler
An Overview of Flash Steam in Steam Boilers
Steam boilers are integral in manufacturing and processing units to generate steam utilized for heating, drying, and sterilizing purposes. Steam is essential for process operations as it has high energy holding capacity, it is safe to use, easily transportable, and economical to generate. However, steam boilers face various phenomena that need to be addressed or prevented. One such occurrence is known as flash steam. The steam that is formed by the hot condensate with reduced pressure is termed flash steam. Flash steam is no different than ordinary steam except that it is produced as the stream is exiting the boiler system and there is a pressure drop at the boiler’s outlet, which is the exit of the steam trap.
What is Flash Steam?
Flash steam is generated when the high-pressure condensate is released to lower pressure. The term flash indicates the way it is formed. Water boils at 100°C at atmospheric pressure. Steam is usually utilized at a pressure above the atmospheric pressure inside the steam piping. As the steam loses its heat by transporting it for the process operations or radiation loses, it results in the condensate. The condensate formed is of the same pressure and temperature as that of the steam.
The pressurized condensate is introduced to the atmospheric pressure with more energy than it could be contained in atmospheric pressure. The excess energy is utilized for converting the condensate. The occurrence is known as flashing and the steam generated is known as flash steam.
Due to flash steam, steel and copper piping connected to the outlet or steam traps are more exposed to internal corrosion. The steam trap becoming clogged leads to high stresses at the internal piping system. It removes the internal corrosion resistance coating that results in the thinning of the internal metal surface. The steam carries the impurities and further damages the pipe.
The formula to calculate the flash steam generated is as follows,
Flash % = (Hf1-Hf2)/Hfg2
Where,
Hf1 = Sensible heat in the condensate at higher pressure
Hf2 = Sensible heat in the condensate at lower pressure
Hfg2 = Latent heat of the steam formed at lower pressure
The volume of Flash Steam Generated:
Steam is denser compared to water, resulting in a small increase in the percentage of flash steam generated to appear as a large volume increase of generated steam. To understand it in-depth, the condensate volume at 100°C (212°F) is 0.00104 m3/kg, and the volume of atmospheric steam is 1.67 m3/kg. As high-temperature condensate at 1.0 MPaG (145 psig) is released to lower pressure like atmosphere, 16.1% by mass of that condensate flashes into steam.
Utilizing Flash Steam:
The vapor cloud is formed by flash steam as the aftermath of condensate discharge. Since the quality of flash steam and live steam is the same, many process units utilize a considerable amount of flash steam whenever possible.
Reusing flash steam in a lower pressure system generated by the high-pressure system leads to significant energy savings, along with reducing vapor clouds. The waste heat management system assesses the condensate recovery system and the flash steam recovery system as pairs.
Flash Steam Recovery:
A Flash steam recovery system releases flash steam into a vessel instead of the atmosphere. It is reintroduced in the steam boiler system or for feeding low-pressure applications. Condensate that is flashing while leaving steam traps enters the flash vessel. It reaches halfway with the steam and condensate separating to the top and bottom of the vessel, respectively.
Effective flash steam recovery system requires various factors:
- It requires adequate high-pressure condensate for releasing sufficient flash steam to result in cost-effective recovery
- Appropriate low-pressure application for the recovered flash steam. It is necessary to ensure that the demand for the flash steam is in accordance with its availability
- The application for the flash steam should be approximate to the high-pressure condensate source
- The steam trap and equipment should properly function against the backpressure applied by the flash system
- The steam pressure reaching below the determined flash steam pressure reduces the overall amount of flash steam formed
Advantages of Flash Steam Recovery:
- Improvement of process operation by recovering heat energy from the condensate boosts the overall efficiency of the steam boiler.
- Increase in the steam boiler capacity by reducing lost steam as flash steam, which is utilized for other operational purposes
- Reduction in Carbon emission
Conclusion:
Flash steam is an effective method to reuse steam and save energy and production costs of the manufacturing facilities.
Since our inception in 1983 as a boiler manufacturer in Pune, Rakhoh Boilers have emerged as a leading steam boiler and thermal solution provider globally. With more than 3000 successful installations of boilers in over 26 countries, Rakhoh ensures efficiency and reliability with their steam boilers, waste heat recovery system, thermic fluid heaters, boiler accessories, and boiler services.
Visit www.rakhoh.com to learn more about our products and services.
- Published in Boiler