What are good tips for boiler energy saving?

we can save more energy by the following

1- using the most hot flue gases in super heaters to increase the temperature of produced steam

2- using the the upper part of flue gases in economizers  to heat the feed water before boiler entrance

3- taking heat from flue gases to preheat the air going to furnace  

 

Use flue gases to preheat the water entering in water walls & we may use flue gases heat to preheat the air which is going into furnace.

Top tips for saving energy in steam boilers - The era of cheap fuel is over. Improved energy efficiency is the best way to mitigate rising prices, but it can be difficult to know where to start. This article offers advice on the best ways to optimise the efficiency of your steam boilers. Faced with steadily increasing energy bills, today's companies need to use a range of monitoring and targeting techniques to identify and implement energy saving measures. It is estimated that basic housekeeping enables many no- and low-cost savings, which can add up to five percent or more of an industrial energy bill, while more formal energy management schemes can achieve savings of20 to30 percent or more, depending on which industrial sector a company operates in. A site survey from a reputable manufacturer such as ABB is a recommended first step to manage energy use. It is a good way to identify wasteful processes that are easily rectified and offers advice and selection of products tailored for the particular application. Service and maintenance packages are also available to ensure the process is running at optimum efficiency. However sophisticated a company’s planned energy management strategy might be, it starts with one essential realisation – you can’t manage what you can’t measure. For example, steam provides a popular and efficient form of heating throughout industry, as well as in building services, but how can boiler operators be certain that their steam systems are working as efficiently as possible? Combustion efficiency Efforts must start in the boiler itself, where operators need to aim for the best possible combustion efficiency. Most waste heat is lost in the stack gases leaving the furnace. Creating conditions that generate the smallest quantity of flue gas at the lowest possible temperature will boost efficiency. This is because channeling extra air through the process simply carries more heat away in the flue gas. Obviously, hotter flue gas also “steals” more energy than cooler gas, so that a22oC drop in stack temperature can boost boiler efficiency by one percent. On the other hand, supplying insufficient air will result in incomplete combustion of the fuel. This leads to fouling of heat transfer surfaces and emissions of soot, smoke and carbon monoxide. So getting the air supply right is a fine balancing act. The optimum combustion process provides just enough excess air to completely burn the fuel. The right level of excess air depends on the fuel, but it ranges from between five and10 percent for gas and10-15 percent for fuel oil, all the way to20-30 percent for stoked coal. Using instruments such as an ABB zirconia oxygen system and a temperature probe in the flue stack can ensure the plant is burning fuel optimally. Furthermore, if the oxygen level rises in the stack-gas over time, it can also indicate the need for minor adjustments or repairs, while a rising stack-gas temperature can indicate the need for tube cleaning, since fouling may be hampering heat transfer. Rapid heat transfer Heat transfer surfaces must be clean in order to conduct heat efficiently, but fouling can also be a problem on the “wet” side of the boiler. Water quality is the key here, since any solid contaminants can cause a build up of scale, which effectively act as unwanted insulation. The two main sources of contamination are the feed make-up water and the returning condensate. Condensate returns to the boiler from the condenser, having been cooled using locally sourced, lower quality water. Condensers are notoriously prone to leaks however, so cross contamination is common. Feed water on the other hand, is normally de-ionised, pre-heated, deaerated and chemically treated before it makes it to the boiler. A failure in any one of these processes can lead to contamination problems. Regular boiler blowdown is the obvious way to control contamination, although dosing the feed with chemicals such as ammonia or hydrazine also stops some chemicals getting that far. Careful, continuous monitoring also plays a vital role in ensuring good long-term boiler chemistry. So what should you look for? Typical parameters include: conductivity, pH, dissolved oxygen, sodium, silica, hydrazine, phosphate, ammonia and chloride. Tracking consumption Steam metering throughout the entire distribution system is crucial for good energy management. Proper metering allows operators to see exactly what’s going on. For example, meters can track the consumption of individual user processes across a site. This enables energy managers to encourage efficiency by introducing separate billing, or target energy saving measures where they will have the most effect. Trend information also enables operators to spot malfunctioning equipment or other problems as they develop. Accurate metering is the key. Operators need to know the mass of steam moving around the plant, since this equates to the energy flow. Traditional differential pressure meters such as orifice plates require peripheral paraphernalia including differential pressure transmitters and a flow computer to produce mass readings for steam, all of which adds up to a high-maintenance headache. In contrast, swirl meters have lower maintenance requirements and deliver greater accuracy – especially in applications where the steam flow varies over a significant range. Rather than an accuracy of two percent of the upper flow range, which is best an orifice plate can provide, swirl meters offer better than one percent accuracy over the entire flow range. Furthermore, the turndown is up to five times greater than that of an orifice plate. Swirl meters rely on static veins at the entrance to the meter to force the fluid into rotation. The meter then measures the frequency of a helical secondary rotation that automatically develops within this pattern. The frequency of the secondary rotation is directly proportional to the volumetric flowrate of the fluid, without any need to compensate for changes in pressure, temperature or density. The meters only need to know the temperature of the steam to calculate the mass flow. Where companies are looking to retrofit meters on existing steam systems, swirl meters offer the added advantage of being able to fit almost anywhere. Most flow meters need to receive undisturbed flow to deliver accurate results. So they need to be positioned a good distance downstream from pipe bends, valves or other components that might interfere with the readings. Instead of requiring straight inlet and outlet runs of15 pipe diameters and5 pipe diameters respectively, which is typical of vortex meters, swirl meters need just three and two diameters in most applications. With rising fuel costs and changing environmental legislation, the pressure to optimise the operation of combustion plant can only increase. The right monitoring schemes can improve combustion efficiency, reduce pollution, extend the life of equipment and reduce the frequency of unplanned stoppages. In short, UK companies need to embrace energy monitoring and targeting schemes if they hope to remain competitive. Top tips checklist Make sure you are only generating what you need. Measure the demand and compare it with what the boiler is generating. This will ensure you’re not wasting steam heating up your factory instead of your process, for exampleOptimise the combustion process by monitoring the flue gases. Only careful monitoring allows operators to strike a balance between supplying too much air, which carries heat away up the flue, and insufficient air, resulting in incomplete combustionMake sure that boiler duty is at optimum efficiency. For example, don’t use two boilers at30 percent output if you can run one at60 to70 percent outputCheck your instrumentation is up to scratch. Modern instruments are typically more robust and more accurate. They are also easier to maintain, and are less prone to problems such as driftIf you measure steam or gas, measure the mass flow, not the volume flow. It takes ten times the energy to create1 m3of steam at10 bar than at1 bar, yet the volume is the same

The best way to have boiler energy saving is to conduct boiler energy audit.

1. Boiler combustion system. air fuel ratio, fuel preparation, balance draft, excess oxygen analysis. all of these lead to fuel savings.

2.Boiler water, check water condition if it is free from hardness, check boiler water preparation mechanical and chemical process. this is very important , scale free boiler tube contributes boiler efficiency. Blow down as required, check steam pipe leaks, deffective steam trap. etc.

3.Check boiler insulations, heat transfer from boiler to the sorounding reduce overall efficiency.

4.Check boiler instrumentaion and controls. good boiler instrument and control contibutes energy savings.

5. Heat transfer area. check from time to time if tubes surface is free from soot and non combustible materials. Heat from combustion is transfer through tubes surface to working medium.Having clean tubes contribute to energy savings.

Hope this will help you.

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Insulate water tank and pipes By insulating your hot water tank and pipes you can significantly reduce the amount of heat that escapes.
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Insulate your home By insulating your home it will warm up more quickly, cool down slower and hold heat better while your heating is on, all of these will save you money on your fuel bills.

Rase feeding water and fuel temperature by  collecting the flashes from your line.

Use steam trape and and condensate pumps to collect the condenste water  and send it to water feeding tank.

Use thermal insulation for your steam distribution line.