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Category Archive: Heat Recovery Equipment

Tag Archive: Heat Recovery Equipment

  1. Condensing Economizers Can Help Operations Reclaim Latent Heat

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    Condensing economizers can help recover latent heat.
    Condensing economizers can help recover latent heat.

    Boilers involve a lot of energy and heat, much of which can be wasted if a system isn’t designed to prevent this. One way to capture and reuse lost heat is through installing a condensing economizer. This item captures water vapor and heat, turning it into usable energy.

    Condensing economizers have a place in virtually every industry. Food processing plants, greenhouses, pulp and paper mills, hospitals and even district heating systems all utilize boilers and have the potential to use economizers. Investing in one can reduce energy requirements and cut operational costs.

    However, condensing economizers typically don’t come in a one-size-fits-all format. They often require highly specialized design and are fabricated to meet the specific needs of one facility’s operations.

    How Condensing Economizers Work

    In most natural gas-fired boilers, it’s tough to cool flue gas much lower than 250 degrees Fahrenheit, according to the U.S. Department of Energy. Beyond this point, the gas can begin to condense, and the resulting vapor can become corrosive, posing a threat to the integrity of the stack or stack liner. However, for the flue gas to be captured and used as boiler feedwater, it needs to be cooled below its natural dew point of 135 degrees Fahrenheit.

    Condensing economizers collect flue gas and cool it to the appropriate temperature, allowing the economizer to reclaim sensible heat (in the form of flue gas) and latent heat (in the form of flue gas water vapor). The amount of latent heat that’s recoverable depends on the type of fuel used, the style of condensing economizer used and other factors.

    Types of Condensing Economizers

    There are two types of condensing economizers that plant managers or other decision makers can choose from: direct and indirect.

    A direct contact condensing economizer includes a vapor-conditioning chamber that’s connected to a countercurrent spray chamber, the Department of Energy explained. Inside the spray chamber, droplets of cool fluid come into contact with the hot gas to facilitate the heat exchange. The droplets cool the stack gas. This option provides a high heat transfer rate and allows for relatively easy water recovery, though this method can only heat water to about 140 degrees Fahrenheit. This style requires a mist eliminator, which prevents droplet carryover.

    An indirect contact condensing economizer utilizes a shell and tube heat exchanger to capture the flue gas. This style offers greater heating and cooling capacity; water can be heated to as much as 200 degrees Fahrenheit and cooled to as low as 75 degrees Fahrenheit.

    One example of an indirect contact condensing economizer successfully helping reduce costs and energy requirements was detailed by the Department of Energy. A food processing facility wanted to reduce its deaerator steam requirements, which were 5,000 lbs per hour. The company installed the economizer, which served to lower flue gas temperatures from 300 degrees Fahrenheit to 120 degrees Fahrenheit. The process allowed them to capture 2 million British Thermal Units per hour, and effectively cut its deaerator steam requirements down to 1,500 pounds per hour.

    Considerations for Condensing Economizers

    For both direct and indirect contact condensing economizers, the water exiting the system is usually very acidic and should be neutralized before being used as process water or directed to a sewage system. External heat exchangers, membranes or pH control systems are all viable options for this.

    Choosing the right materials of construction is an important aspect of designing a heat recovery system with an economizer. Because the water vapor can be highly acidic or otherwise corrosive, the fabrication materials should be resistant to wear. Stainless steel and similar alloys typically hold up well when exposed to water vapor that comes as a result of hydrocarbon fuel combustion, which is the case with natural gas-fueled boilers.

    The space in which the economizer will be used should also be carefully analyzed. For operations where most of the deaerator steam comes from blowdown heat recovery, there is limited potential for cost savings with an economizer. Additionally, operations where there isn’t much need for cold or low-temperature water, a direct contact condensing economizer won’t be especially helpful.

    Working with heat exchanger experts such as those at Enerquip can help you determine your needs and the potential for heat recovery at your facility. Enerquip’s engineers will help you design a shell and tube heat exchanger that suits your specific operation. Request a quote, today.

  2. Waste heat recovery systems reduce operational expenses in cement plants

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    Concrete is the most widely utilized construction material on the planet, and has been so for centuries. The advantages of including it in building projects are well-known and simple: It’s strong and highly durable, and the ingredients – gravel, sand and water – are found just about anywhere.

    Cement and concrete’s carbon emissions

    Despite the obvious benefits of using concrete in construction projects, there’s one major downside to the concrete and cement industries: Their carbon footprint is enormous. In fact, cement production is thought to contribute as much as 5 percent of global CO2 emissions, according to the Cement Sustainability Initiative.

    A large part of these emissions is unavoidable. When limestone – a critical component of cement – is heated up, it converts to calcium oxide and releases carbon dioxide. This transformation accounts for about half of the CO2 emissions released during cement production, according to the Cement Industry Federation. Another 35 percent of the emissions created is a byproduct of burning fuels to keep the cement plant operable. The remaining 15 percent is due to electricity used throughout the plant.

    Although cement creation contributes to global pollution in a major way, the need for concrete outweighs any notions that production should be cut back. Relying on alternative construction materials has not yet proven to be more environmentally friendly, according to Cement Science. Additionally, transporting alternative materials to certain construction sites is far more complicated than logistics to do with concrete.

    Compared to the production of steel and other materials, cement and concrete use relatively low levels of energy, Cement Science pointed out. The biggest reason the cement industry contributes such a large portion of CO2 emissions is its popularity. In 2016, 4,200 million metric tons of cement was produced globally, with 85.9 million metric tons being made in the U.S., according to Statista.

    Waste heat recovery systems market increases

    Growing concerns about climate change and the negative impact of carbon emissions have encouraged many companies to develop ways to lower their carbon footprints. Various governments’ dedication to green production practices have led to tighter regulations. And more consumers voicing their support for companies that make an effort to lower their own emissions has motivated production plants to explore new ways to make their operations more environmentally friendly.

    These trends have fuelled the growth of the waste heat recovery system market, which is expected to grow 6.9 percent annually between 2016 and 2021, according to a report from MarketsandMarkets. By 2021 the market is expected to be valued at $65.87 billion.

    MarketsandMarkets found that the largest driver of this growth is the cement sector. The global cement industry is projected to grow 9 percent a year until 2021. Massive construction efforts around the world, particularly in Indonesia, India and China, are some of the biggest reason for this.

    As the need to reduce carbon emissions becomes more pertinent to the cement industry, and as the need for cement in global construction projects continues to be at a high level, it’ll become more important for manufacturers to invest in waste heat recovery systems.

    Waste heat recovery in the cement making process

    The first time a cement producer employed a heat recovery system to reduce operation costs was Japan’s Kawasaki Heavy Industries, which outfitted its Sumitomo Osaka Cement plant with a waste heat recovery system in 1980, according to a report from the International Finance Corporation. Since that time, more cement companies have enjoyed the benefits of waste heat recovery. “Up to 30 percent of a cement plant’s electricity needs can be generated using waste heat recovery systems.”

    The typical process by which cement is made includes raw materials (usually limestone, sand, shale or chalk) being collected in a rotary kiln, which heats the materials to around 2,640 degrees Fahrenheit. At this temperature, the materials undergo chemical reactions that result in a product called clinker, which looks like small dark rocks. After the clinker is cooled, it’s ground to a fine powder along with additives like gypsum. This powder is the final product – cement.

    Reaching 2,640 degrees requires a lot of energy. Kilns are powered by heat sources like coal or natural gas. Rock and sand can be preheated prior to moving into the kiln, which cuts down on the energy required to heat up the materials. The hotter the shale, chalk and other materials can get prior to entering the kiln, the faster the cement-making process will be and the more energy efficient the plant runs.

    Preheaters in cement operations are typically systems of large cyclones that utilize exhaust gas leaving the kiln. Some systems have as many as six cyclones. Materials successively pass through each one, getting hotter as they go before finally reaching the kiln. Each cyclone takes advantage of heat escaping the kiln.

    Using heat from the kiln to prepare raw materials for production is an excellent way to increase energy efficiency, but it’s not the only method of utilizing waste heat in a cement operation. Aside from the kiln, heat escapes from the preheating cyclones as well as the system used to cool the clinker before it’s ground into cement. These sources of heat can be directed to other parts of the plant where heat is needed, including the general HVAC system. It can also be used to generate electricity to decrease the plant’s reliance on the grid and lower utility costs. Nearly one-third of a plant’s electricity needs can be generated using waste heat recovery systems, the IFC explained.

    A high-quality heat exchanger is the key to an effective waste heat recovery system in a cement plant. If you’re seeking out new ways to reduce your operational expenses, investing in a shell and tube heat exchanger to begin recovering otherwise wasted heat is an excellent place to start. To learn about the best way to incorporate a waste heat recovery system in your plant, reach out to the engineers at Enerquip.

  3. Maple syrup producers use shell and tube heat exchangers and membranes to improve production

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    Maple syrup is a beloved topping many people reach for when diving into a plate of pancakes or waffles. Though you’d be hard-pressed to find a person who doesn’t love this sticky-sweet condiment, syrup makers only have a short window of opportunity every year to produce this favorite flavor.

    The fleeting sugaring season

    Sugaring season begins with winter waning into spring, when the days get warm, but the nights still sink below freezing. The daily freeze-thaw cycle is what pushes sweet sap out of the trees from which the syrup is made. As soon as nighttime temperatures rise above freezing and buds begin to grow on the trees, the sap becomes bitter and unusable, thus ending sugaring season as swiftly as it began.

    Typically, sugaring season only lasts a few weeks or months, according to Discover New England. Every year is different, though. If winter should recede early, the season may begin early; if the weather warms up quickly, the season is cut short, Farming Magazine reported.

    “We’re hoping for another good season [in 2017] where we get 3 weeks or a month of good cool sugar weather,” explained Burr Morse of Morse Farm Maple Sugarworks in Montpelier, Vermont, to Farming Magazine. “We had a season back in 2012 where we had a great week of sugaring around the first part of March. Then it turned to summer for 10 days and we lost our sugaring right there. That can happen and it’s nothing anyone can predict.”

    Speeding up the sap production process

    Given the unpredictability of springtime weather, it’s crucial that maple syrup producers make every moment count during sugaring season. Different producers approach this dilemma differently. One Vermont company, The Maple Guild, invented a steam-craft system that allows the company to produce 55 gallons of syrup in just three minutes using indirect heat, as opposed to the industry standard of an hour using direct heat, according to FoodNavigator-USA.

    “Essentially, we pre-boil the syrup before it hits the main evaporators, and we do that with steam that was generated at the bottom evaporator – and we shoot air in to the top evaporator which makes the concentrate float in the steam,” explained Mike Argyelan, the CEO of The Maple Guild.

    Other companies use sanitary shell and tube heat exchangers to both pasteurize the syrup and make it less viscous and easier to bottle. Putting the product through this process also removes any insects or other contaminants that have a way of getting stuck in the sticky sap.

    Another technique is reverse osmosis, a process by which maple sap is concentrated before entering the evaporator where it becomes syrup. A research paper detailing experiments with RO on maple sap conducted at the University of Vermont Proctor Maple Research Center stated that this method can decrease the amount of time syrup spends in the evaporator, increasing both productivity and energy efficiency. Researchers compared the effects of concentrating the sap to 2, 8, 12, 15 and 21.5 percent sugar concentration and found that flavor, color and other characteristics were generally consistent across the board. ONMapleSyrup noted that by using RO, producers can reduce the number of taps needed to manufacture their syrup.

    In addition to saving time and taps, RO also reduces the need for fuel, making the syrup production process more environmentally friendly.

    Saving energy during syrup production

    Since syrup production is consolidated into a several-week-long sprint, condensed operations demand high energy spend. While more syrup producers are utilizing RO technology, there are other ways producers can save energy.

    A large amount of water needs to be removed from sap to make syrup. Because of this, the syrup-making process gives off incredible amounts of steam. The steam released provides a convenient and free heat source that producers are beginning to take advantage of.

    “Syrup manufacturers can capture the heat lost to rising steam.”

    A Forest Service Research Paper explained that by installing a shell and tube heat exchanger syrup manufacturers can capture the heat lost to rising steam and use it to preheat the sap before it reaches the evaporator. Like RO, this process will reduce the amount of time the sap needs to spend in the evaporator before it reaches the desired consistency.

    This mechanism was perfected in 1974 by George Raithby of the University of Waterloo in Ontario. Prior to Raithby’s development, the use of any equipment above the evaporator would compromise the final product because rising steam would condense on the metal surface and drip back into the open pans of syrup. Raithby used a shell and tube heat exchanger with a drip pan installed beneath it to collect the condensate. Inside the tubes, the sap could be heated from a starting temperature of about 40 degrees Fahrenheit to around 190 degrees Fahrenheit before it reaches the evaporator.

    The Forest Service conducted experiments to determine whether using a shell and tube heat exchanger to preheat the product would have any effect on the quality of the final bottle of syrup. The researchers found it did not, but pondered whether utilizing copper tubing instead of stainless steel would leave behind remnants of copper in the syrup. The researchers determined it did not after analyzing the ultimate product, though if producers are concerned about this effect, investing in a stainless steel shell and tube heat exchanger may be a smart move. Not only will it lend to consistent materials being used throughout the process, but it is also highly durable and long lasting.

    Sugaring season, short and sweet though it may be, is an important time of year for maple syrup producers and, whether they realize it or not, breakfast lovers everywhere. If you’re wondering how a new shell and tube heat exchanger or a membrane can improve your operation, reach out to the engineers at Enerquip.

  4. The causes of overheating and how to avoid them

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    After leaks, overheating is the most common concern for people working with hydraulic equipment. An overheated system can reduce the effectiveness and life span of oils in the system, and can degrade important polymer elements, like hoses and seals, Hydraproducts explained.

    While most people who work with hydraulic systems know that overheating is bad, few fully understand the causes of this concern. It can be hard to find a solution to an overheating problem, and even more difficult to uncover the exact cause.

    Defining overheating

    Generally speaking, an overheated system is one that’s running at 180 degrees Fahrenheit or hotter, according to Machinery Lubrication Magazine. However, every system is unique. It’s important to monitor the viscosity of your oil as well as your equipment temperature to determine whether it’s overheating.

    “An overheated system is one that’s running at 180 degrees Fahrenheit or hotter.”

    The ability to identify overheating right away is a crucial skill, but it’s preferable to avoid the issue altogether. The only way to avoid overheating, by definition, is to ensure that the amount of heat your system is generating is less than the amount it’s dissipating.

    Determining your system’s limitations

    The first step in avoiding overheating is knowing your system’s capacity. Machinery Lubrication Magazine explained this can be done with a simple equation using the system’s continuous input power and its efficiency percentage.

    The example provided by the source used a system that has a continuous input power of 100 kilowatts and an efficiency of 80 percent. In this case, the system needs to be able to dissipate at least 20 kilowatts at any given time.

    Any time circumstances reduce the system’s ability to cool or dissipate heat, or increase the heat load above 20 kilowatts, overheating will occur. Given these facts, there are two ways to correct an overheating problem: Decrease the heat load, or increase the heat dissipation.

    Decreasing heat load

    If your system is overheating, there’s an underlying cause that may not always be immediately evident. The best way to avoid increasing heat loads is to ensure that every feature of your system – from the machines to the oil and seals within them – is in top condition.

    Change out parts and fluids when they begin to degrade or otherwise go bad. Perform routine inspections to make sure you catch issues before they become operations-halting problems. Keep a regular maintenance and cleaning schedule as well.

    Sometimes it’s not a buildup of debris or a skipped cleaning that causes overheating. Any leaks in your hydraulic system can have a negative effect on your operation as a whole.

    “If your system is overheating, there’s an underlying cause.”

    The main goal here is to ensure that your equipment is operating efficiently at all times. When your system is operating as it should, there are fewer chances for it to overheat.

    Increasing cooling capacity

    If everything seems to be consistently in order, but you’re still having trouble with overheating, it’s a sign that your system needs an adjustment. Your cooling system could be worn out. Be sure to regularly check all cooling system parts and their functionality so you know when to replace something.

    Sometimes, your cooling system may just not have the right capacity for your hydraulic machinery. Don’t let this problem persist. One way to increase the dissipation rate is to add another oil cooler, Engineering Made Easy pointed out. With an added cooler comes increased ability to cool the system down before the temperature swings too high.

    An overheated hydraulic system won’t do you, your business or your clients any favors. A major part of running an efficient operation is the ability to maintain the right temperature. Be sure you know the maximum heat your system can handle, and take steps to keep it in that range.

    Remember, one important part of maintaining an efficient system is knowing when to replace critical equipment and components. When you need to replace your shell and tube heat exchanger, or add an oil cooler, reach out to the experienced heat exchange engineers at Enerquip