An Introduction to Reverse Osmosis in Steam Boilers with its Advantages and Disadvantages
Steam boilers and their operation are integral in the process and manufacturing industries. Boiler water is pivotal in ensuring the proper functioning of the boiler system. Reverse osmosis in steam boilers refers to a crucial process that ensures high-quality boiler water for steam generation. Boiler water includes two important resources, steam condensate return and makeup water. Earlier, there were few alternatives to increase the boiler water quality through softening or demineralizing the makeup water or increasing the condensate return. However, with recent advancements, the efficiency of Reverse Osmosis (RO) has tremendously improved in the quality of water produced, the quantity of water, and the cost of operating the system.
What is Reverse Osmosis in Steam Boilers?
Reverse osmosis in steam boilers is a process used for the extraction of mineral content and impurities from the boiler water. Reverse osmosis in steam boilers is usually performed to purify brackish water into freshwater or to make water consumable through the removal of minerals from the water. The bottled water in markets often promotes their brand as reverse osmosis (RO) purified water.
Role of Reverse Osmosis in Steam Boilers:
Reverse osmosis in the steam boiler is essential for the purification of boiler water and the performance of steam boiler systems. Reverse osmosis in steam boiler ensures two important factors:
- Purification of the boiler water for cooking purposes:
Steam boilers utilized for food or brewing process operation require reverse osmosis to ensure the hot water is consumable and would not negatively impact the taste of the processed product.
- Safeguarding the steam boiler from mineral buildup:
As boiler water boils, it turns to steam and releases into the air as a gas. Contrary to water, the salt and other minerals in the steam fail to evaporate. As a result, these minerals consequently build up as scales inside the steam boiler system, leading to the formation of hotspots and inefficiency in performance, and in severe cases, system failures. Reverse osmosis in the steam boiler eliminates the mineral content before the boiler water is fed to the feedwater tank, thus ensuring hassle-free operation of the steam boiler.
Working of Reverse Osmosis in Steam Boilers:
Reverse osmosis is an effective technique used for purifying boiler water. Reverse osmosis in a steam boiler operates by forcing a stream of pressurized water through a semi-penetrable membrane that eliminates bacteria, contaminants, and other small particles, thereby purifying the boiler water.
With the technical advancement in reverse osmosis, it now offers water flowing out of the membranes at almost 100% purity in some cases.
Advanced reverse osmosis in steam boilers uses a reduced pressure flow of water, resulting in low energy used in the pumps and, consequently, less cost.
Advantages of Reverse Osmosis in Steam Boiler:
- Considerable increase in the steam boiler cycles of concentration and reduced heat loss
- Reduced use of makeup water
- Over 98% removal of dissolved solids in the boiler water, including salts causing scale formation that reduces heat transfer
- Increased efficiency of the steam boiler with minimal boiler deposits
- Reduction of alkalinity in boiler water through the direct result of less neutralizing amine use
- Reduction in fuel cost and makeup water for heating as well as clean heat transfer surfaces
Disadvantages of Reverse Osmosis in Steam Boilers:
- Initial investment cost of the equipment
- Membranes of Reverse Osmosis need cleaning or replacement periodically, in approximately 3 years.
- Steam boilers operating with large loads may not result in optimal output from the Reverse Osmosis unit, hence affecting the quality.
- Water pre-treatment may be required, depending on the reverse osmosis boiler water quality. Highly chlorinated or waters with high scale-forming salts require pre-softening or treatment with sulfite or acid.
- Over 20-25% of Reverse Osmosis water is wasted in the drain if it cannot be used for another purpose.
Challenges Without Reverse Osmosis in Steam Boilers:
Regular maintenance of steam boilers can help to reduce operational costs by keeping low power consumption and avoiding downtime because of repairs. Reverse osmosis in steam boilers as pre-treatment significantly reduces costs due to poor maintenance of the steam boiler.
Reverse osmosis reduces the dissolved solids that result in scaling. Elimination of these contaminates enhances the steam boiler efficiency and increases its productivity. The pH level of boiler water is an essential factor for steam boiler efficiency.
Reverse Osmosis as Solution:
Placing reverse osmosis in the steam boiler before a demineralizer reduces the number of regeneration cycles that reduce the consumption of acid and caustic.
Installing a Reverse Osmosis instead of a softener will reduce fuel costs due to higher operating cycles. It also reduces the steam purity issues due to the low quality of boiler water from the softener that increases the alkalinity in the boiler water, consequently increasing condensate corrosion levels.
Conclusion:
For efficient and reliable steam boilers and thermal solutions for your process plant, contact Rakhoh Boilers, one of the leading boiler manufacturers in Pune with 38+ years of expertise. We have successfully installed 3000+ boilers in over 26 countries worldwide.
For more details on our products and services, visit www.rakhoh.com
- Published in Boiler
A Guide to Causes and Prevention of Overheating in the Boilers
Steam Boilers are indispensable for the processing operations in industries and require proper handling and maintenance for safe and hassle-free functioning. Overheating in the boilers is a major concern that poses a threat to the safety of the process plant and operating personnel. Overheating takes place due to various reasons, ranging from limescale build-up and blockages to faults within the steam boiler itself. During overheating in the boilers, the unit discerns that heat is increasing to an unsafe level, thereby indicating a safety feature that causes it to shut down. Earlier, neglecting overheating in the boiler would have led to a boiler explosion, with extremely hazardous consequences. However, such occurrences have become rare, but overheating in the boiler should still be addressed immediately to avoid accidents.
How to Detect Overheating in Boilers?
In most cases, the major indication of overheating in the boiler is a shutdown. Usually, it occurs when the boiler has overheated and the pressure within the steam boiler has risen to a hazardous level. The steam boiler will stop working to stop pressure from increasing to the level that causes the unit to explode. When the steam boiler stops working and indicates overheating, it is necessary to stop the water supply that will resultantly stop water from flowing into the unit and reduce the risk of pressure building in the steam boiler eventually leading to the risk of boiler explosion. It is also prudent to seek guidance from an experienced engineer or boiler manufacturer to fix the issue under their expertise and skills.
Causes of Overheating in Boiler:
There are multiple reasons for overheating in boilers that are not immediately noticeable. Therefore, it is vital to examine every component of the steam boiler to detect the root cause of overheating. Some of the commonly found causes of overheating are:
- Limescale Build Up:
The limescale build-up is caused by the hard water that chokes the heat exchangers and leads to overheating in the boiler. It can also be detected through a whistling sound occurring in steam boilers. Excessive limescale on the heat exchanger hinders the flowing of water, eventually causing the risk of overheating in the boiler.
- Failed thermistor:
Boilers include a thermistor that is the piece of equipment to measure the temperature of the water in a steam boiler. When it gets faulty, the water temperature can increase to dangerous levels that may result in causing the entire steam boiler to overheat. In most cases, it is advisable to replace the thermistor or ask help from an engineer or boiler manufacturer in severe cases.
- System Blockage:
Although system blockage used to take place in old steam boilers, it can occur in any heating system. However, the blockages in the system can also result in overheating in the boiler. If the steam boiler makes a lot of noise, or some radiators are unable to heat up properly, it indicates the blockage in the steam boiler system.Clearing the blockages by flushing the system before the steam boiler overheats is the solution to prevent system blockage from causing more severe problems.
- Faulty Pump:
Issues within the steam boiler itself can cause overheating in boilers. One such issue is faulty pumps that circulate water around the system. Improper functioning of pumps results in hot water staying within the steam boiler. When such an occurrence continues for a long time, it leads to overheating in the boiler. However, damaged or faulty pumps are fixed by replacing them with new pumps to ensure proper operation of the steam boiler.
Prevention of Overheating in Boilers:
Steam boilers become over-pressurized due to the failure of the pressure relief valve and other controls. Although the steam boiler is connected with an open piping system with radiators, the air vents in radiators close at normal operating temperatures. As a result, excessive pressure builds up with the failure of the gas valve or safety controls. Overheating in the boiler is a serious issue that should not be neglected to ensure the safety and proper functioning of the process plant. The best way to prevent overheating in the boiler is to perform regular and proper steam boiler maintenance to assess any needed repairs to be done to steam boilers before any issue causes hazardous consequences like shut down or overheat. Outdated steam boilers should be replaced for all the advanced safety features to prevent the dangers of overheating in the boilers.
Conclusion:
Rakhoh Boilers are a leading name for steam boiler manufacturers since its inception in 1983. To date, we have manufactured and successfully installed more than 3000 efficient steam boilers in over 26 countries globally. We also provide a waste heat recovery system, thermic fluid heaters, boiler accessories, and the best boiler services to ensure the efficiency and performance of the steam boilers.
To learn more about our products and services, visit our website www.rakhoh.com
- Published in Boiler
Causes and Prevention of Boiler Explosion in Industries
Steam boilers are an integral asset in any manufacturing and processing unit. While investing in steam boilers, plant managers ensure that the boiler promises efficiency, reliability, optimal combustion, and steam quality. It is essential to regularly check and maintain the wear and tear of boilers, failing which, may lead to a boiler explosion. Steam boilers, if left unchecked, are potential bomb that cause severe damage to the process plant and operating team. Although the boiler explosion rate is rare compared to boiler installations annually worldwide, it does not entirely eliminate the possibility of boiler explosion.
What is Boiler Explosion?
Boiler explosions are destructive failures of steam boilers. There are two primary reasons that commonly cause boiler explosions. One of them is the failure of pressure parts of the steam and waterside. Such failures are caused by corrosion of vital parts, failure of safety valves, or low water levels. The second-most common cause of boiler explosion is caused due to fuel/air explosion that takes place in the furnace. It is also sometimes termed a firebox explosion. Such explosions in solid-fuel boilers are rare; however, an explosion in oil-fired boilers and gas-fired boilers lead to damaging consequences.
Causes of Boiler Explosions:
As discussed above, boiler explosions mainly occur due to either pressure vessel failure or fuel combustion explosion. Let us understand some of the causes of explosion in detail:
Failure of Pressure Vessel:
Pressure vessel failure is usually caused by rusting or overheating of metal by low water levels or excess scale formation. The vessel is also impacted by damaged safety valves or water hammer. It occurs when the pressure range of the vessel is affected. To understand it better, the pressure change in the steam boiler operating at 100 PSIG can expand the water 1500 times than its original volume. Consequently, it leads to a substantial force that causes hazardous boiler explosions.
Fuel Combustion Explosion:
Fuel combustion explosions often take place due to failure in burners. Ignition failure, improper gas lines, or loose valves leads to combustion gas buildup in the high-temperature vessel. It results in boiler explosion along with leakage of gases throughout the process plant. An initial explosion can cause rupturing of pressure vessels, resulting in a second explosion that is tremendously hazardous.
Steam Pressure:
Usually, in a steam boiler, water is heated to produce steam that is stored in the boiler chamber. The steam is under immense pressure that requires precise operating methods to prevent boiler explosion. Operating personnel neglecting the proper guidelines and regular maintenance cause the risk of boiler explosion. As steam pressure exceeds the boiler design, it results in a hazardous explosion that severely harms the vicinity and the safety of the operating team.
Scaling or Corrosion:
The presence of oxygen in feedwater or hot water leads to scale formation and corrosion in steam boilers. It results in damaging the metal of the boiler and eventually boiler explosion if left overlooked. If neglected, corrosion and scaling cause weakening of boiler metal and the welds that seal the tank.
Precautions to Prevent Boiler Explosion:
Negligence in management is the primary cause of boiler explosion that can be prevented by following some safety guidelines mentioned below:
- Inspection of pump inlets and loose connections
- Installation of ash removal system to avoid ash accumulation in the furnace or other equipment
- Pump priming
- Regular checking of safety valves
- The boiler should be operated as per its design pressure
- Treatment of water before feeding it to boiler
- Ensure that the boiler vents function properly
- Regular inspection for leakages of water, gases, steam, and air
- Ensure proper insulation of heated parts of boilers
- Maintenance of Forced Draft Fan and Induced Draft Fan
- Regular checking of Pressure Gauge
- Regular cleaning of accessible boiler parts
- Cleaning of boiler tubes to prevent ash accumulation or scale formation
- Maintaining the primary and secondary air ratio as per fuel feeding
- Scheduled checking of burner operation, back pressure, and line pressure to avoid thermal stress
- Follow boiler manual and standard guidelines for safety
- Periodic maintenance of steam boiler and boiler accessories
- Proper training of operating personnel on appropriate methods of operation
- In serious issues, ask for the guidance of the boiler manufacturer
Boiler explosions, though undoubtedly hazardous, can be avoided by proper operation practices and regular maintenance of steam boilers. Rakhoh Boilers, with their expertise and experience in thermal engineering for over 38+ years, offer a comprehensive solution for industrial steam boilers. We manufacture a range of world-class quality products such as steam boilers, waste heat recovery boilers, thermic fluid heaters, and boiler accessories. We also provide excellent boiler services like energy audit, steam trap assessment, boiler automation, annual maintenance contract, etc.
To learn more about our products and services, visit www.rakhoh.com
- Published in Boiler
A Brief on Importance of Boiler Water Treatment
Steam Boilers are the heart of the process and manufacturing sector. Boilers are crucial for providing steam and hot water for process operation purposes. As we are aware, steam boilers generate steam by heating water through fuel combustion that implies the pivotal role of water in steam production. Therefore, boiler water treatment is imperative to ensure that the steam boiler provides high-quality steam without damaging the system. Additionally, boiler water treatment prevents various steam boiler issues such as corrosion, scaling, carryover, and even boiler failure. Maintaining proper boiler water treatment is necessary to ensure that the steam boiler operates properly.
What is Boiler Water Treatment?
Boiler water treatment refers to purifying the water and improving the quality used by a boiler system. The combustion process in the steam boiler depends tremendously on the purity and quality of the water to perform the operations of producing high-quality steam. It also safeguards the steam boiler against corrosion and ensures continuous heat exchange. If the boiler water is not treated, it can lead to the entire system facing poor efficiency and permanent damage to equipment that reduces the steam boiler’s life and may even result in a hazardous situation with boiler explosion due to superheating.
Importance of Boiler Water Treatment:
Boiler water treatment is crucial to ensure that the steam boiler is properly operating. As the impurities enter the boiler water, it fouls the steam boiler and leads to damaging the boiler system, reducing its lifespan and efficiency. It results in excessive bills for the same operation. Dissolved salts in the boiler water causes scaling, while the other contaminants in the boiler water impact the machinery if not removed by external or internal boiler treatment.
Prevents Decomposing Of Boiler Tubes:
The dissolved salts in boiler water accumulate on the surfaces with the evaporation of water as part of the regular operation of the steam boiler. The salt hinders the transfer of heat from the steam boiler, which reduces the overall efficiency of the steam boiler system. Additionally, boiler tubes with scaling narrows, resulting in reduced flow and contributing to pressure drops. Tubes accumulated with scaling require replacement that costs both time and money.
Steam boiler with low pH water or dissolved oxygen will directly impact any steel equipment included in the steam boiler. Eventually, it results in pits or holes as well as thinning formation in the steam boiler tubes that may cause rupture and impact the entire steam boiler.
- Decreases Overheating:
As the impure water turns into steam, the impurities are passed throughout the steam boiler surfaces. It generates scale and other deposits that restrict the effective passing of heat in the steam boiler system. As the heat needs to enter the layer of deposits before transferring out of the boiler, a steam boiler without proper water treatment tends to face an increase in overheating. Utilizing pure water in steam boilers ensures that deposits or scaling are not formed, and the steam boiler can operate with its regular heat exchange.
- Maintaining Turbine Efficiency:
As steam is used to operate equipment such as turbines, the impurities present in the boiler water can be carried by steam to the turbine blades. As a result, it forms deposits that reduce efficiency and cause loud and jarring vibrations. It also leads to turbine failure over time. The erosion of turbine blades impacts its performance, leading to a further reduction in efficiency.
- Steam Boiler Corrosion:
Boiler water containing oxygen will eventually lead to the thinning and pitting of the metal pipes. It can hinder the heat transferring abilities of the steam boiler and causes contamination of the boiler water. Appropriate boiler water treatments eliminate the oxygen from the boiler water and prevent corrosion.
- Foaming or Carry-over:
A high concentration of solids in the water leads to frothing or foaming on the surface of the boiler water. The evaporation of water as steam causes deposits in valves, heat exchangers, turbines, and superheaters. It causes corrosion and reduces the function of the steam boiler system. Boiler water treatment reduces the foaming and prevents such steam boiler issues.
- Decreases suspended solids:
Scaling, corrosion, and impurities in the boiler water accumulate solids that cause various problems within the steam boiler. Hard water can develop in the steam boiler, causing a build-up of scale deposits and eventually, impurities in the boiler water. Water softening treatment is an essential factor of boiler water treatment.
- Impurities in Boiler Water:
Water quality is crucial for the proper functionality of the steam boiler. A steam boiler with excessive impurities will eventually break down. Proper boiler water treatment will break down impurities and restore its functioning capacity.
Impact of Poor Boiler Water Treatment:
Neglecting boiler water treatment may cause,
- Presence of impurities from steam feed and condensate return systems
- Impurities like hardness from improper makeup water treatment system performance
- Condensate return system corrosion, damaging the piping and equipment and transferring iron oxide corrosion to the boiler, that deposits and reduces effective heat transfer
Conclusion:
Determining the proper boiler water treatment relies on various factors like boiler design and pressure, makeup water treatment system, amount of impurity present, and iron oxide carryover from condensate return. Rakhoh Boilers is one of the trusted names in steam boiler manufacturers in India with over 38+ years of expertise in thermal solutions. We manufacture efficient and reliable steam boilers, waste heat recovery systems, thermic fluid heaters, and boiler accessories. We also provide excellent boiler services like annual boiler maintenance, energy audit, steam trap assessment, boiler automation, fuel conversion, etc.
For more details on our products and services, visit www.rakhoh.com
- Published in Boiler
An Overview of Boiler Emission and Methods to Control It
Steam Boilers are paramount in process and manufacturing for many decades for their efficiency and high energy holding capacity for processing and heating purposes. However, on the flip side, steam boilers lead to boiler emissions, which are hazardous for the environment and the people in the vicinity. Therefore, various laws are implemented to control the emission level and ensure a balance of industrial advancement and environmental protection. Boiler manufacturers have incorporated various practices to minimize harmful emissions. Let us now understand the primary types of boiler emission and methods to control it.
What is Boiler Emission?
Boiler Combustion is caused primarily by standard fossil fuels (natural gas and ASTM Grade Oil) in commercial and industrial boilers that lead to the following nine emissions;
- Carbon dioxide
- Nitrogen
- Oxygen
- Water
- Carbon monoxide
- Nitrogen oxide
- Sulfur oxides
- Volatile organic compounds and
- Particulate matters.
The latter five combustion by-products are pollutants known to either cause harmful impacts on humans and the environment directly or indirectly. Let us learn about these emissions in detail,
Carbon Monoxide Emission (CO):
Carbon monoxide is caused due to incomplete combustion. Boiler manufacturers design burner/steam boilers to ensure complete combustion, releasing all of the energy present in the fuel. However, when some carbon molecules do not find oxygen molecules, it converts to carbon monoxide (CO) rather than carbon dioxide (CO2). Therefore, burners/steam boilers are designed to allow excess air to reduce the amount of carbon monoxide.
In the gaseous state, carbon monoxide is a poisonous substance whereas, in solid form, it is termed soot which is an unhealthy and dirty substance. Carbon Monoxide is one of the primary contributors to global climate change. High flame temperatures and appropriate air/fuel mixing are vital for low CO emissions. Industrial steam boilers incorporate low CO emission techniques like reducing flame temperatures by modifying air/fuel mixing patterns.
An induced flue gas recirculation can reduce NOx levels by lowering the flame temperature without increasing CO levels. As the flue gas is introduced into the flame in the initial stages of combustion and the air-fuel mixing intensifies, the CO levels remain consistent or reduced.
Nitrogen Oxide (NOx):
Nitrogen Oxide (NOx) is a chemical compound made of nitrogen and oxygen. As we are aware, the air we breathe consists of 20.9% oxygen (O2), 79% nitrogen, and .1% other. During the combustion process, some of the nitrogen and oxygen in the air combines and results in Nitrogen Oxide (NOx). High temperature leads to an excess amount of NOx, and that is why oil firing results in more NOx because it includes trace amounts of nitrogen and burns hotter than natural gas.
NOx, when combined with sunlight, leads to the formation of ozone (O3) and nitrogen. Although ozone is vital at the highest altitudes of our atmosphere to reflect away some sunlight from the earth, ozone at ground level is an unhealthy substance commonly referred to as smog.
NOx is considered to be an environmental issue because it causes reactions that lead to the production of ozone and acid rain. Ozone and acid rain can damage fabric, crack rubber, reduce visibility, harm forests and lakes, and cause health problems. Nitric oxide (NO) and nitrogen dioxide (NO2) are the primary nitrogen pollutants generated by steam boilers, collectively termed Nitrogen Oxide. In steam boilers, NOx is formed in two ways; thermal NOx and fuel NOx.
Thermal NOx is generated with a combination of nitrogen and oxygen in the combustion air at high temperatures in a flame. It contributes the majority of NOx formed during the combustion of gases and light oils. Fuel NOx results from the reaction of nitrogen in the fuel with oxygen in the combustion air. It rarely occurs with gaseous fuels. However, as oils contain significant fuel-bound nitrogen, fuel NOx can contribute to 50% of the total NOx emissions.
NOx emissions are controlled through two methods: post-combustion methods and combustion control techniques. The post-combustion methods manage NOx emissions after formation. The combustion control techniques prevent the formation of NOx during the combustion process. Some of the post-combustion methods include,
- Selective Non-Catalytic Reduction
- Selective Catalytic Reduction
- Combustion control techniques include:
- Low Excess Air Firing
- Low Nitrogen Fuel Oil
- Burner Modifications
- Water/Steam Injection
- Flue Gas Recirculation
Sulfur Oxides (SOx):
Sulfur compounds, or SOx, react with water vapor (in the flue gas and atmosphere) and result in the formation of sulfuric acid mist. Airborne sulfuric acid is found in fog, smog, acid rain, snow, lakes, rivers, and soil. The acid is extremely corrosive and causes harm to the environment.
The combustion of fuels with sulfur (primarily oils and coals) results in pollutants in the forms of SO2 (sulfur dioxide) and SO3 (sulfur trioxide), commonly termed as SOx (sulfur oxides). Low sulfur fuel, desulfurization of the fuel, Flue gas desulfurization (FGD) system are some of the techniques to reduce SOx. Fuel desulfurization is best-suited to coal for removing sulfur from the fuel before burning. Flue gas desulfurization utilizes scrubbers to remove SOx emissions from the flue gases.
Flue gas desulfurization systems are further classified as non-regenerable or regenerable. Non-regenerable FGD systems lead to the waste product requiring proper disposal. Regenerable FGD converts the waste by-product into a useful product like sulfur or sulfuric acid. Using low sulfur fuels is the most cost-effective method of SOx reduction for steam boilers.
Volatile Organic Compounds (VOC):
Volatile organic compounds, or VOCs, consist of a combination of carbon, hydrogen, and sometimes oxygen. It vaporizes easily once emitted in the air and causes issues with ground-level ozone formation. In the case of boiler emissions, it is usually referred to as hydrocarbons and divided into two categories – methane and non-methane.
Volatile organic compounds in steam boilers result from poor or incomplete combustion due to improper burner set-up and adjustment. Maintenance of the burner/steam boiler with proper air/fuel ratio maintains the VOC emissions at a minimal.
Particulate Matters (PM):
Particulate matter refers to the microscopic particles caused by incomplete combustion and/or the combination of particles like dust in the air combined with carbon or oxygen during the combustion process. Particulate matter in boiler emissions is classified into two categories, PM and PM10 in which PM10 is a particulate matter with a diameter of less than 10 microns. PM emissions depend on the fuel-fired in the boiler. Usually, PM levels from natural gas are significantly lower than those of oils. Techniques of particulate control vary for different types and sizes of steam boilers including, electrostatic precipitators, scrubbers, and baghouses. Additionally, proper burner setup, adjustment, and maintenance can reduce boiler emissions. If overlooked, particulate matter can lodge in human lungs, leading to respiratory diseases.
Conclusion:
Rakhoh Boilers is the leading name in boiler manufacturers in India for 38+ years. We manufacture efficient and reliable steam boilers, boiler accessories, waste heat recovery systems, and thermic fluid heaters. With our expertise in thermal solutions, we provide the best boiler services like steam trap assessment, energy audit, boiler automation, annual boiler maintenance, etc.
To learn more, visit www.rakhoh.com
- Published in Boiler