Boiler efficiency may sound high-brow but it’s a simple cost effective method that saves money, fuels more production and aims to rev up local industries.

A simple question: in times like these, can we afford to lose energy worth millions of Taka just because of negligence? Obviously, the answer would be a resounding NO! Yet that is exactly what is happening in thousands of Bangladeshi factories where boilers are used. Owing to inefficient usage of these machineries, valuable heat energy is being wasted every day resulting in much higher energy expenses. Boiler Efficiency, therefore, is an issue that requires immediate attention. This article, part of a series of four articles on Cleaner Production, attempts to shed some light on this issue.

Boilers are some of the major and most widely used components in industries requiring generation of heat. They are also responsible for a considerable portion of a factory’s total energy consumption. Even small improvements in their performance can, bring down the cost significantly. To give a simple example, a mere increase of 60 Celsius temperature of Boiler Feed Water (water that is flown through the boilers) can reduce fuel costs by 1%. This means an increase of 300 C in feedwater temperature (which is quite possible to achieve), can cut down fuel costs by a staggering 5%. In today’s ultra competitive world of business where margins are being continually squeezed, factory owners would be more than willing to find new ways to become more cost competitive. One such advantage clearly lies in boiler performance improvement.

Additionally, the amount of energy that can be saved through running boilers optimally can be overwhelming. If the numerous factories using boilers can diminish their fuel consumption even by 5% through efficiency measures, the energy saved could be enough to produce hundreds of additional megawatts of electricity. In an energy-starved country like Bangladesh, this piece of information should give the policy makers in the government something to think about, and the private sector enterprise a way forward to not just reduce direct cost but also to help reduce hours of power cuts.

Those who might  think that such measures will require huge investment and are beyond smaller companies; are in for a pleasent surprise. Improvement of boiler efficiency, like other components of Cleaner Production, can bring in wonderful results at insignificant costs. For instance, installing an Automatic TDS Controller machine for a 3.5 ton boiler would cost around BDT 2-3 lakh, and the yearly saving would be BDT 3-3.5 lakh. This means payback period would be less than even a year, while savings continue for years. Financing in investments to upgrade boilers thus bears little risk and is almost certain to result in profits.

Before discussing possible ways of making boilers more efficient, it would be helpful to know how exactly they work. The task of a boiler is to provide steam and hot water for varying purposes. Basic structure of a boiler is made up of a closed cylindrical vessel, usually made of steel. Inside the boiler there are tubes bundled closely, known as fire tubes. There is a burner at the mouth of the boiler, which burns fuel (generally natural gas) with oxygen from air to produce very hot gas. This gas is then directed along the fire tubes. Inside the boiler vessel, water is inserted from a tank called the Boiler Feed Water Tank. This water comes in contact with the fire tubes, heats up and soon turns into steam which is collected in the steam dome at the upper portion of the boiler. The steam is then transmitted through pipelines to other machineries where it is utilized.

So where is the energy lost? In a number of areas in fact, the first of which is the loss of heat through flue gas. The hot gas that comes out of the boiler after running through the fire tubes is known as flue. When flue is emitted from the boiler, it usually has a temperature of 2000-2700 Celsius, and its whole heat energy is lost if it is released in the environment. To solve this problem, Boiler Economizers are used. These are essentially waste heat recovery devices. When water is supplied to the boiler from the feed water tank, its temperature is around 250 Celsius. This water is heated and converted into steam, and then heated again to temperatures of 1800 Celsius. Now if the feed water is preheated before entering the boiler, it requires less time and energy to transform into steam. A boiler economizer uses the heat remaining in the flue gas to preheat the water in the feed water tank thereby saving energy.

Another possible area of energy loss in boilers is excessive boiler blow-down. Blow-down is the process of releasing water from the boiler when excessive solid content is present there. These solid particles, if not removed, deposit on the boiler’s internal surface and cause serious obstruction to heat transfer. So blow-down is undertaken to reduce the amount of solid present in the water. However, when water is released, valuable heat energy is lost with it as well. Therefore, it must be ensured that blow-down is done only when the Total Dissolved Solid (TDS) content exceeds the acceptable range, or 3500 ppm (parts per million). In Bangladesh, operators conduct blow-down based on their judgment often when TDS is as low as 1800 ppm or at no risk of exceeding the acceptable level. This results in unnecessary heat loss. To tackle this problem, Automatic TDS Controllers could be excellent instruments. These devices regularly provide readings of TDS and automatically conduct blow-down when the level of solids exceeds the acceptable level.

In addition, information regarding the usage of fuel and rate of production has to be known first in order to reduce resource consumption. In most factories of Bangladesh, there are no mechanisms in place to monitor the amount of natural gas needed and steam produced. The scopes for improvement, therefore, remain unexplored. Introduction of steam, water, and gas flow meters may bring positive results in this aspect. These inexpensive devices can help factories pinpoint areas where things need to be examined.

Cleaner Production is not about drastic improvements: rather it deals with seemingly small changes that eventually have a considerable impact on the performance and efficiency of the enterprise. Improving Combustion Efficiency of a boiler can be an example. Simply put, this term is a percentage of heat input that does not get lost through the flue gas. In a pilot program conducted in Bangladesh by IFC in collaboration with Solidaridad, the boiler initially ran at a combustion efficiency of 80.6%, which was later increased to 83%. This was possible by regularly taking readings from a flue gas analyzer. Only proper monitoring can make the industries save up large sum of money by enhancing the combustion efficiency.

When the financial assessment of the above are considered, it becomes apparent how profitable they can be for the enterprises. For example, Economizers can save a substantial amount of money every month. In the pilot study in Bangladesh, it was seen that in a 3.5 ton boiler with flue gas temperature of 2000 Celsius, installing an economizer can save BDT 61,500 every month, and over BDT 7 lakh every year. An economizer costs around BDT 15 lakh, so the payback period is 2 years. Importantly, economizers last for the lifetime of the boiler. Similarly, an Automatic TDS Controller in a boiler of the same size can save around BDT 12,000 worth water and BDT 17,000 of fuel costs every month. Savings will be much higher for larger boilers. Installation cost is around 2 to 3 lakhs, meaning the payback period is not more than 1 year. Metering and monitoring can also bring in large amount of monetary savings for the factories. A mere increase of 2% combustion efficiency, as mentioned in the paragraph above, allowed the factory where the pilot was conducted to save BDT 1,47,000 per month. Incremental cost for monitoring would hardly be more than BD 25,000 per month. In total, deligeboiler efficiency can save upto 28 lakh taka annually, with an investment of 21 lakh taka.

It can be truly shocking to realize how improvident we really are with the scarce resources available, and how big an opportunity awaits to reduce costs by just becoming more efficient. In the adoption of Cleaner Production, achieving efficiency in terms of boiler usage can truly bring about a revolutionary change in a number of industries of Bangladesh. With lower energy costs, higher production and reduced carbon footprint, this could give companies an edge over others to sustain in the increasingly competitive scenarios.