History, Construction, Types, and Working of Safety Valves in Steam Boilers
Steam boilers first came into light in the 17th century, wherein boilers were kettle-type that functioned by placing water above a firebox to generate steam. As the years progressed, the design and construction of steam boilers were enhanced and upgraded as they were used in industries and ships or locomotives. However, it also resulted in boiler explosions at an alarming rate that took place frequently, causing loss of lives and production. It led to the increasing need for safety measures to be taken while manufacturing a steam boiler. After years of work, safety valves were invented and installed in steam boilers in order to protect life and property during industrial process operations.
History of Safety Valves:
The first-ever safety valve was invented in 1707 by Denis Papin and was installed in his steam digester that seemed to be as a pressure cooker rather than a steam boiler. Safety valves in the early years were manufactured with great caution. After a hazardous explosion, Richard Trevithick started installing a pair of safety valves in the boilers by 1806. These safety valves were not adjustable, released high pressure, and would continuously leak the waste steam. With the passing years, engineers began to invent safety valves of different types that were highly efficient in safeguarding the process plant and the lives of operating staff. Presently, safety valves are essential in every steam boiler by most countries and organizations including ISO 4126, ASME, API, and various others. Most of the safety valves are manufactured with stainless steel, used in a boiler system for various industries such as pharmaceutical, food processing, chemicals, and many more.
Structure of Safety Valves:
Safety valves are generally located on the steam drum of the boiler and open automatically when the inlet-side pressure of the valves exceeds the predetermined pressure. There are three main components of a safety valve: disc, nozzle, and spring. The total capacity of the safety valve must be more than the maximum flow capacity (MFC) of the safety valve in case steam valves fail to open. Most steam boilers connect two safety valves in it, but it may require a third safety valve if it does not exceed the MFC.
Types of Safety Valves:
There are several types of safety valves that perform differently. In countries like India and America, spring-loaded safety valves are used extensively along with torsion bar safety valves. Let us have a look at different safety valves in detail.
Spring Loaded Safety Valves/Spring Loaded Pressure Relief Valves:
Spring-loaded safety valves, also known as pressure relief valves, are the most commonly used safety valves in most countries. It is designed in a way to compel the load of the steam to press the disc against the inlet pressure. Different boilers require different safety valves depending on the type of fluid.
Pilot Operated Pressure Relief Valves:
Pilot operated pressure relief valves consist of the main valve and pilot assy. In the case of spring-loaded pressure relief valves, it uses the force of the spring for the inlet pressure. However, in pilot-operated pressure relief valves, the reseating and reliving of pressure is performed by the pilot assy. Although there is a lack of adjusting facility, pilot-operated pressure relief valves have variations in a larger size suitable for high-pressure conditions.
Dead-weight Pressure Relief Valves:
The pressure vessel is set at very low pressure in the design pressure of dead-weight pressure relief valves. Such safety valves release pressure by adjusting the disc weight. These characteristics are also found in vacuum relief valves that extract the pressure as the pressure vessel falls into negative pressure.
Working of the Safety Valves:
The overpressure in boilers results in the nozzle receiving higher pressure from the inlet of the valves that begins to make boiling or simmering sounds. When the pressure exceeds the predetermined spring pressure, the disc starts lifting and releasing the steam with a popping sound. Once the steam is released, leading to a drop in steam and pressure, the spring closes the disc. It is vital to frequently check the steam valves to ensure it is undamaged and functions efficiently.
Boiler relief, however, functions in a slightly different manner than safety valves by opening gradually as the pressure increases rather than opening fully as in safety valves. Similar to its way of opening, boiler relief closes gradually after the pressure limit is reduced and is mostly used for liquid vapor.
On the other hand, safety relief valves have the quality of both safety valves and boiler relief and are mainly used for liquid and gaseous vapor.
Since its formation in 1983, Rakhoh Boilers strives to enhance and improve the safety of the boiler operations by manufacturing and installing boiler safety valves of the highest quality that ensure the safety of the process plants and prevent any fatal accidents or injuries to the staff working and operating the plant.
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Fuel Quality Affecting Combustion and Boiler Efficiency
Efficiency is the most important requirement for any and every process industry. Efficiency ensures that the process plants are operating smoothly and effectively. However, there are numerous factors to ensure that the efficiency of the steam boilers is attained as warranted by the boiler manufacturers. It is well-known that investing in the steam boiler is merely a fraction of the total cost covered by the process industry. In fact, the primary cost incurred by the industries is that of fuels. In most cases, boiler efficiency is lesser than the rated efficiency from the boiler manufacturers. Various components are responsible for contributing to the overall efficiency of the boilers. Two main factors that affect boiler efficiency are Combustion efficiency and Thermal efficiency.
Types of Fuels Used in Steam Boilers:
Different process plants use different fuels depending on their availability, requirements, and costs. Fuels are mainly classified as solids, liquids, and gaseous forms that have unique chemical properties that may function only with a certain type of steam boiler. Some of the different types of fuels are:
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Solid:
- Coal
- Wood
- Briquettes
- Wood Chips
- Wood Logs
- Bailed Bagasse
- Sawdust
- Rice Husk
- Coffee Husk
- Palm Shell
- Groundnut Shell
- Coconut Shell and many more
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Liquid:
- Light Diesel Oil
- High-Speed Diesel
- Furnace Oil
- Low Sulfur Heavy Stock
- Industrial Diesel Oil
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Gaseous:
- Natural Gas
- Liquefied Petroleum Gas
- Biogas
What is Combustion in Steam Boilers?
Combustion is a chemical process wherein the oxygen from the air is reacted with fuel at high temperature to release the stored energy, better known as thermal energy in the form of flue gases at high temperature. Fuels and fuel quality do indeed play an imperative role in combustion. Fuel combustion in the oxidizing atmosphere takes place when the fuel reaches a certain temperature called ‘flash point’ in the case of liquid fuels and ‘fire point’ in the case of solid fuels.
In combustion, partial energy released by the fuel is utilized in converting the moisture content in fuel into water vapor. Therefore, it can be concluded that the process of combustion also generates water vapor. However, in most cases, the water vapor produced is not used for any applications that lead to the wastage of heat energy contained in it. As the moisture or water content of the fuel increases, a larger part of the energy released by fuel is utilized in converting the moisture into vapor. Consequently, it will reduce the overall energy transferred to the boiler drum for the purpose of steam generation.
Therefore, it is important to pay due attention to the quality of fuels while buying them. Secondly, it is essential to be careful in fuel handling and storage, and must not be stored in open spaces where the chances of getting wet from rain are high.
Optimal fuel consumption is ensured with complete and proper combustion with minimal heat loss. To determine the quality of combustion in a steam boiler, one can check the color of smoke. Emission of white smoke indicates high air to fuel ratio that means that although the combustion was complete, a high amount of air carried excess heat energy. On the other hand, black smoke indicates a low air-to-fuel ratio with oxygen deficiency which means incomplete combustion and high unburnt losses. Grey smoke is an indication for optimum air to fuel combustion with optimal fuel combustion and minimum loss.
Correlation between Fuels and Efficiency in Boilers:
Solid fuels have a tendency of fouling that foul the tubes in the course of time with the flue gases generated. It results in a reduction in heat transfer area and an increase in fuel consumption. It is noteworthy that any changes in the fuel quality would, directly and indirectly, affect the boiler efficiency. Although, boiler manufacturers suggest aiming to bridge the gap between direct and indirect boiler efficiency.
Fuel to steam efficiency is an essential measure for boiler efficiency, but calculating it in an actual situation is difficult. It can be considered as the amount of energy converted into steam. Fuel to steam efficiency depends on conditions such as complete load and specified air and feedwater temperature.
Factors Affecting Fuel Quality:
Fuel specification has a tremendous effect on efficiency. With gaseous fuels, high hydrogen content contributes to increased water vapor in combustion in which the water vapor utilizes energy to change its phase. A high water vapor loss while igniting the fuel leads to lower efficiency.
Accelerated TDS level in feedwater tanks results in water carryover that leads to increased fuel consumption. In a steam generation, dissolved solids become more concentrated, which results in failure in the bursting of steam bubbles formed to reach the water surface, forming foam carried over to steam mains. It eventually results in wastage of fuel because of increased moisture content in steam.
Conclusion:
Since its establishment in 1983, Rakhoh Boilers have strived to deliver world-class quality products to their clients by manufacturing efficient and reliable industrial steam boilers that ensure enhanced productivity and sustainability. Rakhoh manufactures numerous products of ranging product capacity and pressure range for effective combustion with various fuels.
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Wet Scrubbers for Boilers | Types, Working, Applications, and Industries Using It
One of the major concerns of process plant managers and engineers is waste treatment and greenhouse emission control. Industrial wastes, as we know, are one of the major contributors to the increasing pollution in the climate. The wastes released from industrial processes are harmful to both the environment and the people living nearby. It has become prudent for industries to utilize pollution control equipment to aid them in monitoring and properly disposing of the harmful waste release. Wet scrubbers are one of the most efficient pollution control devices used in manufacturing plants among various boiler accessories.
In industrial processes, the combustion of fuel takes place on a large scale. These fuels mainly consist of Carbon (C), Hydrogen (H), Sulfur (S), Nitrogen (N), and Oxygen (O), along with other components. During combustion, fuel, and air ignite and produce flue gases that include Carbon Dioxide (CO2), Sulfur Dioxide (SO2), Water (H2O), and Ash particulates. Among these, Sulfur Dioxide or SO2 and Ash are the most released pollutants in the environment.
What are Wet Scrubbers?
Wet scrubbers are a type of pollution control equipment located in the flue gas path that absorbs Sulfur compounds and oxides from Ash waste and Sulfur Dioxide (SO2). As the name suggests, wet scrubbers involve scrubbing the gases with water for dispensing the dirty pollutants or gases that may lead to harmful emissions and pollution. Wet scrubbers have high efficiency of up to 99.99% in disposing of fine dust particulates from the flue gases in boilers.
Types of Scrubbers:
Scrubbers are classified into two types viz. Dry Scrubbers and Wet Scrubbers. Dry scrubbers are not that widely used compared to wet scrubbers as they do not deliver the same dust removal efficiency as wet scrubbers. Dry Scrubbers perform the procedure of dry reaction, termed as ‘sorbent’ in which components like alkaline slurry are utilized in removing the acid from the flue gases by passing it through the sorbent.
Whereas in wet scrubbers, flue gas is passed through it and administered with a liquid (mostly water) that removes the dust pollutants from gases. Wet scrubbers are preferred by many industries as it is efficient and cost-effective pollution control equipment that removes around 99% of air pollutants from the flue gases.
Working of Wet Scrubbers:
Wet scrubbers function with a parallel flow or counter flow contact of flue gases containing Sulphur Dioxide (SO2) and Ash particulates with water which is diluted with Calcium Carbonate (CaCO3). The sulfur dioxide produces acid in the water, while the calcium carbonate creates alkalinity that destroys the acidic properties of sulfur dioxide.
Water is an ideal choice for the removal of pollutants from flue gases. In wet scrubbers, water is enclosed in a metal container through which the polluted gas is passed. These gases are cleaned and disposed of contaminates with water, and the clean gas is released from the scrubber. Apart from water, there are other liquids as well that effectively removes the pollutants from flue gases. The caustic solution that includes NaOH and Sodium Hydroxide is the preferred liquid for controlling acidic gas. Sodium Carbonate (Na2CO3) and Calcium Hydroxide are also widely used liquids in wet scrubbers.
Wet scrubbers capture the waste particles in their droplets that extracts the pollutants from the gases. The droplets from the released gas are separated with a mist eliminator. The liquid solution used must be properly treated before discharging it in the climate. Wet scrubbers are the only pollution control equipment that can separate both the gas and particulates from a gas stream.
Application of Wet Scrubbers with Different Pollutants:
Wet scrubbers are efficient pollution control equipment that aids in the removal of various pollutants such as:
Volatile Organic Components:
Wet scrubbers are utilized for the removal of volatile organic compounds. The removal efficiency varies depending on the components. However, the average efficiency range is between 70% and 99% and an average of 90% efficiency in most cases.
Vapors and Gases:
Inorganic fumes and gases are the primary contaminants that are removed with wet scrubbers. Pollutants such as hydrogen sulfide, fluorides, chromic acid, chlorides, ammonia, and SO2 mostly achieves removal efficiency ranged between 95% and 99%
Hazardous Pollutants and Particulate Matters:
The efficiency of hazardous dust particles and pollutants is relatively low, ranging between 50% and 95% and depending on the nature and components of the particulates.
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Advantages of Wet Scrubbers:
- Less Space Requirement
- Low Capital Costs
- Ideal for Optimizing Boiler Operation
- Reduced Fuel Consumption
- Recycle and Reuse of WasteWater
- Manages High-temperature and High-humidity gas streams
- High Efficiency and Easy to Operate
- Collects both Gases and Particulate Matter
- Reduction in Pollution and Greenhouse Emission
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Industries Using Wet Scrubbers:
- Iron
- Steel
- Stainless Steel
- Zinc
- Copper
- Food
- Dairy
- Distillery
- Cement
- Pharmaceutical
- Paper and Packaging
- Chemicals
- Refinery and Petrochemicals
- Plywood
- Textile
- Power Generation
Wet scrubbers are preferred by many different industries, some of them including:
Rakhoh Boilers has always worked towards the advancement and sustainability of industries and provides highly efficient and customized wet scrubbers that are ideal for handling high gas volumes and high-pressure drops and capable of collecting fine dust particulates. It is easy to install and ensures uniform distribution of water and avoids the possibility of scaling.
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Waste Heat Recovery Boilers in Industries | Structure, Benefits, and Industries Using It
Process Industries these days are growing extensively and rapidly. While it is indeed advantageous for the growth and progress of an economy, it is undeniable that industries are one of the major contributors to the ever-increasing pollution and environmental harm. With the increasing industrial operations, there has been a resultant increase in the pollutants and greenhouse emissions from the industries that are harmful to the climate and people. Therefore, to reduce the negative consequences caused by industrial waste, process plants opt for Waste Heat Recovery Boilers for manufacturing operations.
As the name suggests, Waste Heat Recovery Boilers are systems that recover or extract excess heat and convert it to useful thermal energy for utilizing it in other operations. The type and extent of wastes released depend on the industry. Therefore, Waste Heat Recovery Boilers must be resilient enough to absorb heat from different types of emissions. Rakhoh Boilers manufactures Waste Heat Recovery Boilers that are customized as both fire tube and water tube construction depending on the industrial requirements.
Structure of Waste Heat Recovery Boilers:
Waste Heat Recovery Boilers are in most cases, designed as per the factors concerning the waste emission from the industries. However, the amount of steam generation or heat transfer depends on the amount of heat available in the flue gas. Industries must determine the capacity and steam pressure required for the processing operations. Some of the primary factors to consider while deciding the type Waste Heat Recovery Boiler are:
1. Fuels Used and Its Properties
2. Flue Gas Temperature in ℃
3. Flue gases generating exhaust in kg/hr. or Nm3/hr.
4. The operation or stage where the system is utilized
Benefits of Installing Waste Heat Recovery Boilers:
Waste Heat Recovery Boilers are preferred by many industries and for good reasons. It helps in both extracting and recycling the excess heat that can be used for other purposes and reducing the amount of harmful emissions in the environment. Some of the noteworthy advantages of Waste Heat Recovery Boilers are:
Higher Efficiency:
Installing a Waste Heat Recovery System in Industries leads to a profound outcome of accelerated efficiency. It is natural to conclude that extracting the excess heat, reduces the amount of fuel and the operational cycle that generally takes place for processing.
Optimal Utilization of Resources:
Natural resources are decreasing at an alarming rate with their large-scale applications in the industries. Therefore, it has become necessary for industries to control and manage the use of natural resources carefully. The excess heat is used for other heating purposes, which in turn, require a lesser amount of fuel.
Reduction in Waste:
Production of Waste is inevitable in the process industries. While a certain amount of waste is unavoidable, a major amount of waste heat is recycled with Waste Heat Recovery Boilers, which are later used for other operations. It leads to reducing the amount of waste released into the atmosphere by the process plant.
Reduction in Operating Costs:
With the consistent development in technologies, plant managers are always looking for better and effective methods to increase productivity and decrease the waste produced in a plant. Waste Heat Recovery Boilers are the ideal solution for sustainability and efficiency.
Reduction in Energy Consumption:
As mentioned earlier, Waste Heat Recovery Systems helps significantly in reducing harmful emissions and increasing efficiency. Hence, it is easy to conclude that it considerably reduces the energy consumption in the manufacturing facilities that lead to growth in annual turnover.
Manages the Harmful Emission in Environment:
Waste Heat Recovery Systems not only helps in decreasing the amount of waste released in the environment, but it also aids in recycling and reusing the harmful and dangerous emission that needs to be treated before releasing it in the environment. That is still not enough to prevent causing harm to the climate and people living nearby. Rather than disposing of these gases, Waste Heat Recovery Boilers redirect them for other industrial applications that reduce the amount of dangerous pollutants in the climate.
Industries Using Waste Heat Recovery Boilers:
Waste Heat Recovery Boilers are used by several industries such as:
1. Steel
2. Non-ferrous metals
3. Chemicals
4. Cement
5. Petrochemical
6. Distilleries
7. Power Generation
8. Rubber
9. Pharmaceutical
10. Textile
11. Paper and Packaging
Rakhoh Waste Heat Recovery Boilers:
Since its inception in 1983, Rakhoh has consistently strived for advancement and sustainability for the betterment and progressive future. Rakhoh manufactures highly efficient Waste Heat Recovery Boilers that are compact and customized in design. It processes gas turbine, and biogas gensets exhaust, enabling fully automated operation. Its construction is customized as a fire tube and water tube, depending on the clients’ requirements.
Frequently Asked Questions:
How Does Waste Heat Recovery Boilers affect overall efficiency?
Waste Heat Recovery Boilers extract waste heat from the flue gases that can be reused for other process applications. It leads to a reduction of fuel usage and power consumption that contributes to increasing the overall efficiency of the process plant.
Are there any disadvantages of installing Waste Heat Recovery Boilers?
The only main disadvantage of installing Waste Heat Recovery Boilers is that it can be slightly expensive for small industries. Although investing in Waste Heat Recovery Unit can save up to 30% of the industrial costs, it depends on the size and productivity of the industry to decide whether it is worth investing.
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Process Stages in Brewing and Use of Steam Boiler in Distillery Industry
Distilleries are one of the important as well as most polluting industries. India alone has 300 distilleries that annually produce over 2 billion liters of ethanol. Alcohol is an essential ingredient in many process industries such as chemical, pharmaceutical, plastic, beverage, perfume, and food. Due to its increasing demand, distilleries are growing at a fast pace as an industry. For a successful distillery to function, one of the important pieces of equipment required is the steam boiler.
Distilleries these days rely mostly on cereals, molasses, potatoes, and other agro products in producing alcohol. Let us have a look at the various stages of processes carried in the distillery industry.
Stages of Processing Drinks/Spirits in Distilleries:
Beverages require ethyl alcohol for its production and for extracting aroma in the resultant drinks. Ethyl alcohol, in turn, needs the fermentation of molasses for its production. Molasses are, in fact, the outcome of sugar processing operations that are dark red and of acidic nature with a 6.8 to 8.5 pH range. The fermented molasses are further processed, in the distillation that requires steam on a large scale. The processing in distillery includes two stages: Fermentation and Distillation.
Fermentation:
The molasses collected are diluted with water in a tank and later on, proceed with yeast propagation and fermentation. The dilution ratio to maintain sugar levels, however, varies in different stages. It is 8% to 9% for yeast propagation and 16% to 18% for fermentation.
As the name suggests, yeast propagation utilizes yeast for the fermentation process. In this stage, yeast cultivates or expands itself by being fed to a pre-fermenter and administered with diluted molasses. Yeast propagation requires oxidative conditions and controlled temperature.
The fermentation process occurs in the fermenter under monitored conditions, wherein around 25% of the fermenter is filled with diluted molasses and pre-fermenters yeast. It is administered with various chemicals like enzymes, urea, biocide, and sulphuric acid, that are monitored and controlled at a preset level. Coldwater is added in the fermentation process that takes as long as 24 hours to accomplish. The yeast sludge, molasses, and solids accumulated in fermentation are separated as solids and liquids through a high-speed centrifuge machine, and the liquid is sent further for distillation.
Distillation:
The distillation process consists of several stages in which the fermented liquid is preheated in two stages to get rid of volatile properties and sent to the analyzer column. Analyzer column functions under vacuum to destroy any likely scaling. The resultant liquid, after vaporization, proceeds with a pre-rectifier, to further concentrate the alcohol and remove impurities. Alcohol is concentrated again in the second rectifier and eliminates sulphuric properties. Lastly, the alcohol/drinks are cooled in the condenser.
Role of Steam Boilers in Distilleries:
As mentioned, steam boilers are unarguably crucial for distillery industries to perform various operations. Let us take a detailed look at the uses of steam boilers for distilleries.
Requirement of Hot Water:
The distilling process depends on an ample amount of hot water. Distilleries need water to be heated at different temperatures as per the drink or spirits being processed. Therefore, it is important to ensure that the steam boilers used for processing are of superior quality that can be controlled and monitored with precision.
Flavor and Aroma in Drinks/Spirits:
The amount of steam generated from steam boilers must be exact to ensure that the flavors and aroma of the produced drinks and spirits are as intended.
Disinfection and Sterilization:
Distilleries must be sanitized regularly to ensure its safety. Steam plays a vital role in disinfecting the utensils and other equipment used for the distillation process before it is utilized for consequent operation.
Controlled Heating of Premises:
Distilleries need steam boilers that can heat the specific regions as required. There are certain areas in a distillery that need to be heated uniformly for the distillation process to take place.
What to look for in a steam boiler for the distillery industry?
The processing operations in distillery industries are of longer duration. Therefore, it is essential to ensure that the steam boilers used in distilleries include the following factors:
High Efficiency:
Since steam boilers are operated constantly in distilleries, it needs to be highly efficient and of world-class quality to provide the best results.
Reliable and Long-lasting:
Steam boilers that are reliable ensure the safety of the operating staff of the processing plant. Similarly, boilers must be long-lasting to endure the various operations for distillation.
Reduced Greenhouse Emission:
Distillery industries produce an abundant waste during processing, with slop being the major pollutant after distillation. 1 liter of ethanol produces around 10 to 15 liters of spent wash that is highly toxic for the environment. Therefore, while choosing a boiler manufacturer, ensure that the steam boiler chosen releases minimal greenhouse emissions.
Rakhoh Boilers:
Rakhoh is one of the leading boiler manufacturer in India, catering to more than 20 industries including distillery, for more than 38 years. Our steam boilers are highly efficient and reliable that ensure effective combustion with various types of fuels. Our Membrane X and Bi-Drum/D Type/Power X are the preferred models for distillery industries.
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