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Tag Archive: Interchangers

  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. Further, Enerquip’s engineers will help you design a shell and tube heat exchanger that suits your specific operation.

    Request a quote, today.

  2. 4 industries that can benefit from waste heat recovery systems

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    Food and beverage facilities
    Food and beverage facilities often have waste heat they can recover to reduce costs.

    In an age of fluctuating oil costs and increased demands for sustainable practices, waste heat recovery has proven to be a win-win situation for plants and processes in a wide range of industries.

    Waste heat recovery is the process of collecting heat that would have otherwise dissipated into the air inside or outside of a facility, and using it elsewhere in an area of the plant that requires heat generation. This can reduce operational expenses because it decreases the need to pay for heating.

    While virtually any large-scale facility can benefit from waste heat recovery, there are a few industries identified as the fastest-growing end-users of waste heat recovery systems. Here are four sectors where facility managers may find that installing waste heat recovery systems could cut costs and make their processes more efficient:

    “The cement industry is the fastest growing adopter of waste heat recovery systems.”

    1. Fuel refining

    Petroleum refining takes the top spot for industries using waste heat recovery systems. Producing fuel is incredibly energy-intensive, with processes like distillation, thermal cracking and treatment all requiring high temperatures.

    2. Cement production

    The cement industry is the fastest growing adopter of waste heat recovery systems, perhaps in part because of the highly energy-intensive process required to make clinker, the product of a chemical reaction that results in small rocks that are eventually ground into cement.

    Much of the heat lost during this process comes from the kiln, which is heated to 200 to 400 degrees Celsius and is where the chemical reaction takes place. According to a Waste Heat Recovery Technology Analysis drafted by the Department of Energy, systems to recover lost heat from these kilns are widely available but rarely utilized.

    3. Food and beverage

    The food and beverage industry also produces plenty of heat that can be recovered for use elsewhere throughout a facility. Gatorade’s Wytheville, Virginia, plant is one example that worked hard to become as sustainable an operation as possible – it was the first food and beverage site of its size to earn the LEED Gold distinction, according to Food Engineering.

    One of the many adaptations Gatorade made to the facility was its waste heat recovery system.

    “We heat and cool many things around here,” Arnie Wodtke, Gatorade’s director, noted to Food Engineering.

    The facility installed Enerquip shell and tube heat exchangers, which routed cold water – used to cool bottles after filling – to two boilers. Economizers attached to the boilers improved the rate at which that water is heated. When the water reaches 180 degrees Fahrenheit, it’s sent back to the boiler.

    “It’s easy to measure the direct savings from an energy-efficient motor,” explained Rich Schutzenhofer, vice president of engineering, technology development and resource conservation at the Chicago headquarters of Pepsico’s Quaker/Tropicana/Gatorade group, according to Food Engineering.

    “People don’t take into consideration what a 1 percent increase in productivity means across the entire workforce,” he continued. “That’s real; it’s not bells and whistles.”

    4. Higher education

    It’s not just industrial facilities that can benefit from waste heat recovery systems. The University of Illinois-Chicago invested in a heat exchanger and other equipment of its own to reduce operational expenses by $8,000 annually.

    The system is expected to save 15,900 therms of natural gas and 3,100 kilowatt hours of electricity each year. A heat exchanger, combined with repairs to fix leaking pipes, will save the university 2.5 million gallons of water every year.

    “We’re saving energy and the environment at the same time,” Waleed D’Kidek, superintendent of utilities, told UIC Today.

    Have you determined areas of your process where usable heat is going to waste? Reach out to the knowledgeable engineers at Enerquip. We know how to evaluate your operation and determine the best shell and tube heat exchanger for your waste heat recovery needs.

  3. Shell and tube heat exchangers used for waste heat recovery

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    Waste heat recovery has been a topic of concern for large-scale industrial companies for several decades. Not only does recovering waste heat make an operation more environmentally friendly, but it also helps to cut costs. Additionally, it can reduce the amount of resources needed to power a facility.

    Many industries and facilities have implemented different methods of waste heat recovery. One popular choice is using a shell and tube heat exchanger. According to the Energy Efficiency Guide for Industry in Asia, these exchangers are best suited for recovery methods dealing with warming liquids with heat recovered from:

    1. Condensates from process steam, distillation processes or refrigeration, or air-conditioning systems
    2. Coolants from engines, lubricants, bearings, air compressors, furnace doors, pipes or grates
    3. Flue gas streams and exhaust streams from furnaces, dryers and exhaust stacks

    The waste heat usually flows shell side, while the liquid is positioned tube side. This is because the higher-pressure liquid or vapor should be in the tube, because the shell is the weaker container. Utility fluids and products being heated can also be kept cleaner on the tube side of a heat exchanger. Waste heat typically produces condensation. Allowing condensates to form on the inside of the tube will typically cause flow irregularities and could lead to problems with the exchanger.

    Vegetable oil processing plant

    One example of a shell and tube heat exchanger put into practice for recovering waste heat is outlined in Energy Mines and Resources Canada’s Energy Management Series for Industry Commerce and Institutions. The paper explained a vegetable oil processing plant hoped to reduce its use of a steam heater in the refining process. The semi-processed oil needs to be heated from 30 degrees Celsius to 80 degrees before heading to the final stage of processing and then storage.

    “A shell and tube heat exchanger for waste heat recovery saved a processing plant $29,570 a year.”

    When the oil is transferred to storage, some heat is expelled that the company wanted to recover. This heat would then be used to warm the oil before going to the steam heater, reducing the amount of energy needed to bring the oil to its optimum temperature. By sending the oil through the heat exchanger prior to going into the steam heater, the oil can be heated to 70 degrees Celsius, requiring the steam heater to only raise the temperature by 10 degrees instead of 50.

    By implementing this practice, it was predicted the processing plant could save $29,570 annually. Taking into consideration the cost of the exchanger and its installation, it would take slightly more than half a year to see financial benefits.

    Diesel engines

    Research done by Saiful Bari, a senior lecturer, and Shekh N. Hossain, a research student at the Barbara Hardy Institute, a division of the School of Engineering at the University of South Australia, showed shell and tube heat exchangers could also provide beneficial heat recovery methods for diesel engines.

    Bari and Hossain explained the exhaust from diesel engines contains 38 percent usable energy. Heat exchangers were fitted to connect to the engine’s exhaust and arranged in parallel and series configurations. The two exchangers had different purposes. One, called the super heater, was used to superheat steam coming from the exhaust, which normally expands in the truck’s turbines. The second, named the vapor generator, was used to generate vapor from a liquid put into the exchanger.

    The researchers found in initial testing that 16 percent of additional power was recovered. Knowing that the heat exchangers used were not built specifically for this application, they decided to customize them to more efficiently recover the heat. After optimization, 23.7 percent additional power was generated. They also found that maximum heat recovery could be achieved with both the series and parallel arrangements when the engine’s pressure is higher, specifically at 30-bar working pressure. With this pressure, up to 9.85 kilowatts of energy could be retrieved. With lower-pressure engines, the parallel configuration is more efficient than the series configuration because it produced a higher mass of steam.

    Bari and Hossain attributed the success of their research partially to the fact that they customized the design of the heat exchangers to the particular engine used. They noted that, by using these shell and tube heat exchangers for heat recovering, the efficiency of the engine rose from 30 percent to 41 percent.

    Both of these examples show that waste heat recovery can be used to save money and resources, as well as make processes more energy efficient. Many different industries can benefit from using shell and tube heat exchangers in this way.