Steam boilers play a crucial part in the manufacturing and processing sector. The safety of boilers and process plants is essential as ignoring them may be hazardous and led to life-threatening consequences. Steam boilers, if left without regular servicing and maintenance, have the potential of exploding like a bomb. Following standard guidelines ensures the safety of the process plant and the working staff. Yet, there are some of the boiler and combustion issues that are overlooked. It leads to boiler breakdown, accidents, or in extreme cases, loss of property and lives.
Listed below are some of the commonly neglected boiler and combustion issues that may pose a threat to the safety and health of process plant operators:
One of the primary reasons for boiler failures and explosions is the lack of maintenance of the combustion system of a steam boiler. Many process plants do not train their operating staff about the combustion equipment and its maintenance, start-up and shut-down procedures, and emergency shut-down of boilers. In such an unanticipated situation, the staff remains unaware and uncertain of the steps to take that inevitably result in boiler breakdown or accidents in the processing unit.
Regular Safety Inspections:
Many times, process plant managers believe that merely following the standard guidelines is enough to prevent mishaps. Although it is important to follow the guidelines, manufacturing facilities must also ensure regular servicing and maintenance programs for boiler safety and longer life. Boiler-related services such as energy audits, steam trap assessment, annual maintenance programs, etc., helps to assure a healthy and productive work environment of a process plant.
Outdated Equipment and Accessories:
Many industries assert operating and complying with safety codes and standard guidelines. However, if the equipment and accessories used in manufacturing units date back to 50 years ago, then following the rules and regulations does not contribute that much to assuring plant and boiler safety.
Regular Testing of Valves and Pipes:
Valves and pipes are essential to ascertain proper combustion in a steam boiler. Boiler problems such as carryover, foaming, corrosion, scaling, erosion, etc., tend to negatively impact the performance of safety valves and pipes and tubes of a steam boiler. Therefore, it is prudent to maintain a proper and periodic inspection schedule of the valves and tubes.
Despite every precaution and safety arrangement, steam boilers are at risk of failure or breakdown due to inevitable human errors. It has been found that most of the boiler accidents are caused due to improper handling of the steam boiler by the operating staff. With the advancement in technologies, many manufacturing and process industries are turning towards automation control systems in the boiler to minimize the possibility of manual errors in process operations.
Even with the automated control systems, operating staff needs to be trained on the appropriate handling of the various equipment in the manufacturing unit. It is undoubtedly necessary to train the plant operators about proper operational techniques for effective functioning of the boiler system and thereby, optimal productivity of the process plant.
Safety Equipment and Emergency Plan:
Regardless of complying with every precaution and maintenance schedule, the chances of boiler accidents cannot be eliminated. Therefore, it is necessary to equip the process plant with every safety requirement such as a first aid kit, proper safety gear like helmet, gloves, shoes, and coveralls, fire extinguisher, fire alarms, and so on. It is also advisable to allocate pre-determined and ample workspace for different operations, inform the operating team about fire exits, and prepare an evacuation plan for any emergencies.
Advantages of Inspecting Boiler Issues Frequently:
Timely maintenance and detailed inspection of the boiler and its equipment leads to prevent the issues that may hinder the combustion process and increase the requirement of resources. Leakages, sediment accumulation, dirty burners, corrosion, etc., are some of the causes that may reduce the thermal energy in a steam boiler.
Fewer Breakdowns or Failures:
With the regular evaluation of the boiler system and its accessories, any harmful issues are brought to the notice of the plant manager sooner and consequently fixed before it causes any loss or damage and prevents the failure or breakdown of the steam boiler.
Health and Safety of the Operating Personnel:
The operating team is vulnerable to injuries and long-lasting harm if the boiler system remains unchecked for a long time. Frequent maintenance and fixing any boiler issues as soon as possible ensures a safe and healthy work environment for the personnel.
Longer Lifespan of Boilers:
Proper and scheduled maintenance programs of the steam boiler ensure its longer lifecycle and higher efficiency and productivity. As a result, it increases the profit of the manufacturing industry.
With our 38+ years of experience, Rakhoh Boilers have a clear understanding of the potential issues faced by a process industry and the best remedy to enhance its efficiency. We have been manufacturing efficient steam boilers for more than 20 process industries as well as providing the best boiler services such as boiler automation, energy audit, steam trap assessment, annual maintenance contract, customer training program, etc.
Know more about our products and service on www.rakhoh.com
Paper plays a crucial role in our day-to-day lives. The paper industry in India contributes about 1.6% of the total global paper production with an approximate turnover of 250000 Million. The first-ever machine-made paper was manufactured in India in 1812 when there were only 15 paper mills. Presently, India has approximately 800 paper mills manufacturing paper bags, handmade paper boxes, paper albums, etc., exporting paper products worth 4000 million worldwide. As per a report by the Indian Paper Manufacturers Association (IPMA), the per-capita paper consumption in India is estimated to be 13 kg. The paper industry offers employment to a significant population, and the paper and paper products industry may grow to a market of $ 13.4 billion by 2024.
The Manufacturing Process from Pulp to Paper:
Paper processing includes various operational stages before the paper is deemed ready to be exported to markets. Paper processing mainly requires water, chemicals, energy, and cellulose (extracted from softwood or wood chips). Debarking of the wood logs is essential before forming them into wood chips. The main stages of the paper processing are as follows:
- Pulp formation:
The wood chips are transferred in a high-pressure vessel termed a digester. Over here, the wood chips are cooked and boiled with a chemical solution that is eventually dissolved and formed into a pulp. The pulp is filtered, and if required, bleached before it sending it for further process.
Once the pulp is formed, the process of beating takes place. As the name suggests, the pulp is beat along with adding other filler materials and additives. It impacts the quality of the paper.
- Processing Pulp to Paper:
In this process stage, the pulp is squeezed through a series of rollers by feeding it to automated machines that form it as paper. The beating process is followed, by a press section that consists of pressing the paper between steam-heated cylinders that removes the excess water from the paper.
- Finishing Products:
The resultant paper is rolled in reels that would be moved for further processing depending on the paper product to be manufactured.
Why are Steam Boilers Important in the Paper Industry?
Steam is pivotal in the paper industry for the process of drying the paper, energy requirement, and the cooking of wood chips in the digester. Some of the essential requirements of steam in paper processing are,
The utilization of rolls in paper processing requires it to be heated internally with steam. Therefore, it is essential to maintain an even temperature across the surface of the rolls for uniformity and high-quality products. Steam is an ideal choice as it condenses and distributes heat evenly.
Steam Carries Ample Heat:
Most processing plants require a considerable amount of energy, and the paper industry is no different. One of the optimal ways to carry energy for processing operation is through latent heat in steam. For instance, 150 psig of saturated steam carries around 3.5 times heat content, and the energy is released as soon as the steam comes in contact with the internal surface of the roll.
Precision in Steam Temperature:
As temperature demand increases or the higher grade papers are manufactured, higher pressure and temperature are needed. The plant operators can control the pressure and set the steam temperature inside the roll. The saturated steam maintaining the same temperature at a given pressure allows the operators to control the pressure and steam temperature as required.
Efficient Process Operations:
Steam boilers are highly efficient for generating steam and power for processing purposes. The generated steam is operated in an insulated, closed-loop system. Hence, steam boilers are efficient and reliable for the process industry’s operations.
Challenges in Paper Industry:
Expensive Raw Materials:
The raw material for paper processing mainly includes wood fiber which is high in cost and difficult to procure.
High Power Demand:
Paper mills require a high amount of power to function efficiently. Nowadays, paper processing plants have switched to power generation boilers that aid them in generating both steam and electricity.
Deforestation and Environmental Harm:
The cutting down of trees to acquire wood for process operations results in deforestation. It disturbs the environmental cycle and accelerates the pollution level.
Boilers in Paper and Paper Products Industry:
Steam boilers in the paper industry are used for generating steam and power required in the processing plants. Steam is essential for operations such as heating of chemicals, heating rollers, etc. Because of the paper industry requiring a high amount of steam; it is important to choose efficient and durable steam boilers. Boilers with reciprocating grates are best suited for the effective combustion of fuels like wood chips, wood logs, sawdust, and agro-waste used in paper process plants.
Rakhoh Boilers have been manufacturing highly efficient and reliable steam boilers for more than 38 years. Rakhoh’s boiler models such as Combo X, Membrane X, and Solid Fuel Bi-Drum are preferred by some of the leading paper mills in India.
Combustion is a vital and one of the initial processes in the functioning of steam boilers. Various fuels are ignited in solid fuel boilers that require proper combustion to generate steam and avoid greenhouse emissions from unburned fuels. Fluidized bed combustion is a technique that effectively burns the fuels in solid fuel boilers. In the fluidization method, the combustion is performed by mixing fuel and air in a specific proportion. A fluidized bed can be defined as a bed of solid particles, passed through a pressurized fluid (gas or liquid) that causes the solid particles to act as a fluid in certain conditions.
In India, the coal majorly available is of low quality, low calorific value, and high ash content that hinders the conventional grate fuel firing system. Fluidized bed combustion is ideal for burning fuels such as coal, rice husk, bagasse, agro waste, etc. and offers various benefits as compared to traditional firing systems such as flexibility in fuel choice, compact design of solid fuel boiler, combustion efficiency, and reduced emission of pollutants like SOx and NOx.
Working Principle of Fluidized Bed Combustion:
Fluidized Bed Combustion occurs when a gas or air is evenly distributed and passed upwards through a bed of fine solid particles such as sand. Initially, at low velocity, the particles remain undisturbed. As the velocity gradually increases, the particles reach a stage when it is suspended in the air stream, and the bed is fluidized.
Fluidization highly depends on particle size and air velocity. The mean solid velocity increases at a slower rate as compared to gas velocity. The difference between both velocities is termed slip velocity. Maximum slip velocity assures good heat transfer. When sand particles in a fluidized state are heated to the combustion temperature of coal while the coal is administered steadily into the bed, it results in rapid burning of coal and uniform temperature of the bed. The fluidized bed combustion occurs at between 8400C and 9500C. The combustion process requires Time, Turbulence, and Temperature. Particle bed in FBC uses limestone that controls the emission of sulfur dioxide and nitrogen oxide without any pollution control equipment.
Types of Fluidized Bed Combustion in Solid Fuel Boilers:
There are three major types of fluidized bed combustion boilers that are:
Atmospheric Classic Fluidized Bed Combustion (AFBC)/ Bubbling Bed:
In AFBC, the coal is crushed to 1mm to 10 mm, depending on the quality of the coal and the type of fuel fed in the combustion chamber. The atmospheric air acts as fluidization air and combustion air that gets preheated by exhaust flue gas and flows through the bed with a velocity ranging from 1.2 m/sec. to 3.7 m/sec. The amount of fuel reacted depends on the rate at which air passes through the bed.
AFBC solid fuel boilers are generally 0.9 m to 1.5 m deep and consist of in-bed evaporator tubes in the limestone, sand, and fuel bed to extract heat and control the bed temperature. It operates with a determined temperature range of 800oC and 850oC. If the temperature exceeds 950oC, there may be a risk of clinker formation, and if it lowers than 800oC, it may result in loss of combustion efficiency.
Components of AFBC in solid fuel boiler:
- Fuel Feeding System
- Air Distributor
- The in-bed heat transfer surface
- Ash Handling System
Circulating Fluidized Bed Combustion (CFBC):
The CFBC technique performs by administering crushed fuel of 6 mm to 12 mm size and limestone into the combustor. The bottom of the furnace consists of air distribution nozzles that deliver upward flowing air in which the particles are suspended. The fluidizing velocity ranges between 3.7 m/sec. to 9 m/sec. and combustion takes place between 840oC and 900 o C. The CFBC comes without steam generation tubes, but some of them consist of external heat exchangers. The circulation of particles leads to sufficient heat transfer and residence time for the utilization of carbon and limestone.
For larger process plants, CFBC provides greater area, fuel particle, and sorbent residence time for effective combustion and to control SO2. It is more cost-effective than AFBC and an ideal choice for medium to large boiler capacity firing low-grade fuel that requires control on sulfur emission.
Features of Circulating Fluidized Bed Combustion System in Solid Fuel Boilers:
- High processing capacity due to high gas velocity
- Low combustion temperature leads to minimal NOX
- Better turndown ratio
- Reduced erosion of the heat transfer surface
- High combustion efficiency
Pressurized Fluid Bed Combustion:
Pressurized Fluid Bed Combustion (PFBC) is mainly used in cogeneration plants and large-scale coal combustion. The gas turbine is driven from the off-gas in fluidized bed combustion. Waste heat from the gas turbine is utilized for preheating the condensate from the steam turbine and used as feed water for generating steam. Combining gas and steam turbines leads to the efficient generation of electricity.
Advantages of Fluidized Bed Combustion in Solid Fuel Boilers:
- Higher Efficiency
- Flexibility in Fuel Choice
- Effective Combustion of Low-Quality Fuels
- Reduced Corrosion and Erosion
- Easy Ash Removal and No Clinker Formation
- Less Requirement of Excess Air
- Quick Startup
- Avoids Soot Blowing
- Highly Reliable
- Quick Response to Load Fluctuations
- Easy Maintenance
- High Efficiency for Power Generation
Rakhoh Boilers has been one of the leading boiler manufacturers since its inception in 1983. We manufacture a wide range of efficient and reliable solid fuel boilers, oil-fired and gas-fired boilers that assure effective combustion of the fuels for optimal productivity and efficiency. We also manufacture high-quality boiler accessories and provide excellent boiler services.
Know more about us at www.rakhoh.com
Steam boilers are imperative equipment in almost every process industry, be it pharmaceuticals or chemicals, or food processing. Boilers are undoubtedly a major asset in any industry that serves the facilities for many years. It can be concluded that the quality of the boiler represents the quality of the final product that is processed. It is necessary to ensure that the steam boiler is functioning properly and delivering the optimal outcome. Regular boiler maintenance is of utmost importance to ensure the active functioning and safety of the boiler. Following a maintenance schedule can make a huge difference in accelerating the boiler efficiency and lifecycle and preventing breakdowns and excess cost for the wear and tear of the boilers.
Importance of Boiler Maintenance in Process Industry:
Although boiler maintenance contracts will be an excess cost to the industry, it is worth the outcomes and advantages ensured with such regular programs. One of its primary benefits is the prevention of boiler failure that may result in substantial loss. Some of the significant advantages of boiler maintenance are as follows:
- Higher Safety and Reliability of Boiler and its equipment
- Low Replacement Costs
- Anticipated Downtime for Maintenance
- Saving of Water and Fuel
- Higher Energy Efficiency
- Reduced Emission
Apart from these benefits, there are three crucial reasons to adopt a boiler maintenance program to enhance the overall efficiency and performance of the steam boiler.
Monitoring the Water Quality:
The water quality directly impacts the boiler efficiency. In other words, water containing impurities or oil can result in low-quality steam. It may also cause wet steam and an inadequate operational cycle leading to energy loss and high operating costs. The boiler maintenance program includes the chemical testing of water quality under expert guidance that indicates the quality of water to prevent corrosion, scaling, and other issues. It can affect the efficiency and the lifespan of the boiler.
Proper Boiler Blow Down:
Blowdown is the process of draining the water from the boiler in regular intervals to remove the sludge accumulated at the bottom of the boiler. The dissolved solids in water cause poor water quality that increases corrosion and scaling. Blowdown is essential in a boiler maintenance contract, and it is advisable to seek the measures of performing blow down as per the boiler requirement.
Insulation is essential to ensure efficient and safe boiler operations. The amount of required insulation, the material of the insulation, and the range of insulation depends on the pipe size and its operational temperature. The boiler maintenance program assesses insulation by inspecting the piping, boiler surfaces, and fittings.
Fiberglass, Cellular Glass, Mineral fiber, and Calcium Silicate are the most commonly used insulation materials in steam boilers.
Practices to Follow for Boiler Maintenance:
Periodic boiler maintenance ensures the smooth functioning of the boiler system. Here are some of the techniques that can be carried for the proper maintenance of steam boilers
Some basic activities can be performed daily by the operating staff for maintaining the quality of boiler performance. Such practices include:
- Maintaining a Boiler Log/Record to note daily operation activities and metrics like flue gas and operating temperature, water level, consumption of fuel, gas pressure, etc.
- Monitor the water level in the boiler and the steam pressure in the boiler
- Conduct a bottom blowdown
- Conduct a water column blowdown
- Inspect the pressure and temperature of the boiler to determine its capability to handle the load
- Assess the stack temperature to ensure the boiler efficiency
- Monitor pressure level and the downstream pressure
- Check through sight port for any soot accumulation
- Ensure the proper functioning of the other boiler equipment
Weekly maintenance of boiler is time-consuming yet important and involves inspection on one day of the week of the following practices:
- Check the burner positioning and the burner shut off
- Conduct an evaporation test to determine the control and burner shut off when the water reaches a low level
- Inspect the functioning of fuel supply valves
- Check the proper functioning of alarms
- Check the motors in the boiler to ensure their proper functioning without excess vibration and noise.
- Check the high-pressure and low-pressure switches
- Conduct a thorough checking of leakages of flue gas, water, steam, and fuel
Here are the few things that must be inspected once a month by a technician:
- Check the burner pilot assembly to ensure its positioning and cleaning
- Check the burner diffuser to determine deformation such as cracking or burning
- Inspect air dampers to prevent the accumulation of dirt
- Check the boiler exterior for any indication of any hot spot that can be dangerous
Annual maintenance is conducted yearly under the guidance of qualified experts that inspects the following:
- Inspection and cleaning of fireside surfaces and chimneys
- Assessment of burner refractory material and manhole gaskets
- Checking of system valves and safety valves
- Inspection of burners and fuel oil levels
- Gauging all operating controls
- Assessment of other boiler equipment
Tips to Ensure General Boiler Maintenance:
- Ensure that boiler, burner, and boiler room are clean
- Avoid closing vents that supply air to the boiler room
- Repair leakages immediately
- Prevent foaming and priming and contact the boiler manufacturer in case of serious issues
Since its inception in 1983, Rakhoh Boilers have achieved an excellent reputation as a world-class boiler manufacturer and boiler service provider. With the expertise and experience of more than 38 years, Rakhoh Boilers are the preferred brand for industrial steam boiler and boiler services such as Annual Maintenance Contract, Energy Audit, Steam Trap Assessment, Boiler Automation, and many more.