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Topsector Energy: “HeatMatrix reduces industrial heat loss substantially!”

  • HeatExchanger polymer Heatmatrix

Recovery of waste heat from industrial chimneys

In combustion processes, a significant amount of heat is lost through the chimney. Recovering this waste heat has proven to be extremely difficult using traditional metal heat exchangers. Main reason being that exhaust gas streams often are corrosive and/or contain fouling. As a consequence, a lot of waste heat is just blown into the atmosphere. However, a revolutionary polymer heat exchanger, developed by HeatMatrix, makes it feasible to recover and reuse 50% of this ‘problem’ waste heat. It enables the industry to save energy costs and significantly reduce CO2 emissions. It is a proven technology that has been successfully implemented in various industry segments already. The Early Adopter pilot project programme of the TKI Energy & Industry enabled HeatMatrix to test and validate the use of its technology in a new industrial sector (heavy clay production).

Enormous impact
The impact of large-scale use of heat exchangers to recover waste heat from flue gas could potentially be enormous. “We’ve calculated that if all chimneys in the Rotterdam harbour area were fitted with a HeatMatrix heat exchanger, the energy saved would be enough to provide 10% of all households in the city of Rotterdam each year with energy,” says Paul van Dillen, Director Global Sales and Marketing at HeatMatrix. “We’ve also calculated that the global market for corrosive and fouling waste heat represents a value of €2 billion. What’s more, for every euro invested, a HeatMatrix heat exchanger will deliver ten times more reusable energy than a solar park will in new energy. Imagine what would happen if all chimneys in the world were fitted with a heat exchanger.”

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Utilities “Polymere warmtewisselaar voorkomt corrosie”

(Text only available in Dutch)
Met rookgassen gaat letterlijk warmte de lucht in. En dat is zonde. Warmtewisselaars in schoorstenen kunnen die warmte terugwinnen, maar corroderen en vervuilen snel door de zure en organische stoffen in het rookgas. Een polymere warmtewisselaar heeft hier geen last van en zorgt daarmee voor een significante energiebesparing.

In verbrandings- en droogprocessen gaat een behoorlijk deel van de opgewekte warmte verloren. De gemiddelde temperatuur van de rook- of afgassen die de schoorstenen van stoomketels, raffinaderij fornuizen, stoomreformers, naverbranders en industriële drogers verlaten, heeft doorgaans nog een temperatuur van honderd tot tweehonderd graden Celsius.

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Het terugwinnen van deze warmte met metalen warmtewisselaars is redelijk uitdagend omdat het rookgas corrosief wordt zodra de temperatuur van het rookgas onder het zuurdauwpunt, rond de 130 tot 150 graden Celsius, zakt van gasstromen waar zwavel, fluor, chloor of andere corrosieve stoffen in zitten. Om die reden laten veel fabrikanten van dit soort systemen die warmtewisselaar maar zitten. En dat is jammer, want daardoor gaat gemiddeld tien procent van de warmte die ontstaat bij verbranding of wordt gebruikt in een droogproces verloren via de schoorsteen.

Polymeer
HeatMatrix heeft hiervoor een oplossing gevonden door een warmtewisselaar toe te passen die gemaakt is van een high-performance polymeer. De ontwikkelaars van de HeatMatrix LUVO technologie (air preheaters / APH’s) geven aan dat de helft van die tien procent verloren energie alsnog teruggewonnen kan worden. Hiermee kan de industrie weer een stapje verder zetten in het terugdringen van de CO2-emissies.
Het hart van de HeatMatrix technologie wordt gevormd door een rigide matrix structuur van aan elkaar verbonden plastic pijpjes. ‘Deze pijpjes kunnen worden gebundeld tot iedere gewenste grootte en dus iedere capaciteit van warmtewisselaar’, zegt directeur Paul van Dillen van HeatMatrix. ‘De warmtewisselaar die wij leveren is meer dan tien keer lichter en drie keer compacter dan de gebruikelijke metalen warmtewisselaars. Dit maakt ze gemakkelijker te installeren op lastiger te bereiken plekken.’

Corrosie
Het gebruik van een warmtewisselaar van polymeer heeft meerdere voordelen ten opzichte van metaal. ‘Het probleem van metaal is dat het niet bestand is tegen zuren en andere corrosieve elementen, maar ook vervuiling van de warmtewisselaars beïnvloedt de prestatie van de warmtewisselaars negatief’, zegt Van Dillen. ‘Een uit polymeren opgebouwde warmtewisselaar kent deze problemen niet. Polymeren kunnen niet corroderen en zijn bovendien eenvoudig schoon te houden omdat stof en andere vervuilende deeltjes niet aan het oppervlakte hechten. Het is zelfs mogelijk om de warmtewisselaar met een ingebouwd schoonmaaksysteem te leveren, waardoor de prestatie gewaarborgd blijft. Afhankelijk van de toepassing zorgt een plc-aangedreven reinigingssysteem ervoor dat de warmtewisselaar eens in de zoveel tijd in-line wordt doorgespoeld.’
Ook met de warmteoverdracht zit het wel goed: doordat de warme en koude lucht in tegenstroom langs de dunne wanden van de HeatMatrix worden geleid, leveren ze een betere prestatie dan metalen warmtewisselaars.

Besparing
Een ander interessant aspect van de inzet van polymeren in plaats van metaal is dat hiermee veelal een totaal nieuw product is ontstaan. Van Dillen: ‘Naast de vervangingsmarkt die we zien in de petrochemie, is het vaak zo dat we niet een bestaande warmtewisselaar vervangen maar onze innovatieve technologie juist toevoegen om bestaande en nieuwe systemen efficiënter te maken. Het beste zou zijn als de warmte van stoomketels of fornuizen helemaal niet meer wordt afgevoerd via de schoorsteen, maar tot dat mogelijk is, biedt onze technologie het beste alternatief. De IEA heeft uitgerekend dat zestig procent van de CO2-reductie van energie efficiency-maatregelen moet komen. Daar kunnen we een nadrukkelijke bijdrage aan leveren. Enige uitdaging is dat de zware industrie nog redelijk conservatief en terughoudend is met investeringen in nieuwe innovatieve technologieën zoals die van HeatMatrix. Nu leveren wij onze technologie al vanaf 2011 en hebben we inmiddels een behoorlijk aantal grote klanten in diverse industrie segmenten die de HeatMatrix warmtewisselaars gebruiken. Alle installaties draaien naar volle tevredenheid van onze klanten en dus kan met recht gezegd worden dat onze technologie zich inmiddels heeft bewezen. Gelukkig zien we dat ook de industrie maatschappelijk verantwoord ondernemen steeds meer hoog in het vaandel draagt. Bovendien dwingt de wetgever de industrie ook steeds meer om besparende maatregelen door te voeren.’

Terugverdientijd
Het potentieel van de inzet van warmtewisselaars is volgens Van Dillen groot. ‘We hebben berekend dat als alle schoorstenen in Rotterdamse haven zijn uitgerust met een HeatMatrix warmtewisselaar, we met de bespaarde energie tien procent van de Rotterdamse huishoudens kunnen bedienen. We hebben ook berekend dat de wereldmarkt voor corrosieve en vervuilingsgevoelige restwarmte een bedrag van twee miljard euro vertegenwoordigt. Misschien nog wel belangrijker: iedere euro die in de HeatMatrix-technologie wordt geïnvesteerd, levert tien keer meer energie op, in de vorm van besparing, dan een zonnepark in de vorm van elektriciteit. Het zou dus standaard moeten worden dat iedere schoorsteen wordt uitgerust met een warmtewisselaar.’
Uiteraard vergt een additionele technologie wel een hogere investering, maar volgens Van Dillen is deze binnen twee jaar terug te verdienen. ‘Tenminste, als een fabrikant de HeatMatrix direct in zijn ontwerp meeneemt. Helaas hebben we tot nog toe veel te maken met retrofits in bestaande installaties. Maar ook in die gevallen zijn terugverdientijden van ruim onder de vijf jaar mogelijk.’
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  • Nozzles cleaning unit HeatMatrix
  • Inline cleaning unit heat exchanger

HYDROCARBON ENGINEERING “Progressive Pre-Heating”

  • Inside industrial Air preheater HeatMatrix
  • Polymer bundles inside APH
  • Cross section of heat matrix APH

By Bart van den Berg

Many petrochemical companies are currently assessing opportunities to improve the efficiency of furnaces, fired heaters and boilers in order to optimize operational cost. Upgrading the air pre-heating section of these units with a polymer air pre-heater generates attractive additional savings and simultaneously eliminates corrosion problems. This article introduces an air pre-heater technology that enables waste heat recovery from corrosive flue gas over the full temperature range in order to maximize furnace efficiency.

Corrosive flue gas
The corrosiveness of flue gas is the main reason that energy efficiency of furnaces, fired heaters and steam boilers remains poor. Flue gas originating from sulphur containing fuel becomes corrosive below a temperature of approximately 150 °C (acid dew point corrosion). Local cold spots in metal air preheaters will lead to rapid corrosion and break down of plates and tubes. Break down goes unnoticed for a while, but the shortcut between combustion air and flue gas leads to energy loss, more power to the combustion air fan and limited throughput because of maxed out combustion air fan. These cold spots already occur when the flue gas bulk temperature is as high as 250 °C because of cold ambient air at the other side of the heat exchanging surface, which results in a flue gas side surface temperature below the acid dew point.

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Existing technologies
In order to lower flue gas outlet temperatures and improve energy efficiency several techniques have been applied with mixed success. When cooling down flue gas to approximately 170 °C, recycling of heated combustion air to the inlet of the forced draft fan will lift the air temperature and subsequent local cold spot temperature. Frequently, also an air preheater driven by steam is applied for additional heating during the winter. These measures cost energy!

For the highest energy efficiency flue gas has to be cooled below the acid dew point for which metal exchangers are not suitable anymore or become very expensive. Alternatives, such as glass tube and polymer tube have been applied but are sensitive for flow induced vibrations and temperature shocks, which leads to tube breakage or rupture. The subsequent shortcut between combustion air and flue gas leads to consequences as described above.

Polymer heat exchanging tube bundles
The HeatMatrix polymer air preheater consists of multiple corrosion resistant tube bundles contained in a single metal shell or housing, which is made corrosion resistant by applying a coating or polymer liner (see figure 1 and 2). The proprietary polymer bundle design consists of multiple tubes that are connected to each other over almost the full length of the tube. This structure creates a strong rigid matrix grid that is able to resist high gas velocities and thermo shocks. The connector between the individual tubes creates simultaneously a counter current flow configuration between the two gas streams. This configuration improves heat transfer by up to 20% compared to cross flow type exchangers (see figure 3). Flue gas flows from top to bottom through the tubes (red arrow) and combustion air flows in opposite direction around the tubes (blue arrow).

The inlets and outlets of the exchanger are located at the side of the heat exchanger in order to allow easy access to the polymer tube bundles. These lightweight bundles are retractable from the top and can be cleaned or replaced without demounting the complete exchanger. In the case of fouling flue gas each bundle can be equipped with an in-line spraying nozzle, which thoroughly cleans each bundle in an alternating cleaning sequence during operation.

Hybrid air preheater design
For applications with a flue gas temperature below 200 °C integration of the polymer air preheater is straightforward. For applications with a flue gas temperature above 200 °C a combination between a metal air preheater and polymer air preheater in series is required (see figure 4). The polymer part protects the metal part against low air temperatures that lead to cold spot corrosion problems and the metal part protects the polymer part against high temperatures. This combination is available as an integrated exchanger with only one single shell or as a compact assembly containing a separate metal air preheater and a separate polymer air preheater. A small flue gas and air by-pass around the air pre-heater assembly provides full control over the acid dew point for all operating cases (see figure 5).

Case study air preheating
The following example is of a typical furnace at a refinery. A flue gas flow of 105,000 kg/hr at 330 °C is used to preheat combustion air in a hybrid configuration of a metal and polymer air preheater. The realized efficiency improvement is 9,9 %, which corresponds to 6,6 MW in this specific case. Flue gas is cooled to 180 °C in the metal exchanger and subsequently to 125 °C in the polymer exchanger. The combustion air is first preheated to 120 °C before it enters the metal exchanger and is further heated to a final temperature of 256 °C.

Waste heat to liquid
Not all combustion processes can benefit from preheated combustion air as outlet for waste heat from corrosive flue gas. For example the electrical efficiency of gas turbines will reduce dramatically when combustion air is preheated. Furthermore, some installations have limit space for large ducting and/or air preheater assemblies. For these applications a liquid outlet for waste heat can be utilised if available (e.g. preheating condensate, city heating grid, other process streams). Such a recovery system consists of a polymer gas-gas exchanger and a standard finned tube gas-liquid exchanger separated by a circulating air loop in order to separate corrosive flue gas from higher-pressure liquid. This failsafe and robust design prevents any upsets in either of the independent connected systems (see figure 5).

Concluding remarks
In order to improve energy efficiency in the petrochemical industry flue gas is the most interesting waste heat source to look at. During the conversion of primary energy approximately 5 to 10 % of the energy used is lost via hot flue gas. There is no need to emphasize that significant savings are within reach when 50 to 70 % of refining operational cost consists of energy cost. Cooling flue gas beyond the acid dew point is unconventional but with a robust exchanger for the corrosive part significant savings can be realized in a reliable way.

Figure 1: HeatMatrix polymer air pre-heater
Figure 2: Polymer tube bundles
Figure 3: Cross section of a HeatMatrix air preheater
Figure 4: Metal and polymer air preheater in series
Figure 5: Process diagram of a metal and polymer air preheater assembly

About the author: Bart van den Berg is a co-founder of HeatMatrix Group (www.heatmatrixgroup.com) and has spent 20 years in various positions throughout the petrochemical industry. He holds a master degree in chemical engineering of Twente University Netherlands.

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PTQ 2015 “Heat recovery from corrosive flue gas”

For improvements to energy efficiency in the petrochemical industry, waste heat recovery from corrosive flue gas is the most cost effective source to exploit

By Bart van den Berg

During the conversion of primary energy, approximately 5-10% of the energy used is lost via hot flue gas. There is no need to emphasise that significant savings are within reach when 60-70% of refining operational costs consist of energy costs. Nowadays, many petrochemical companies are focusing their efforts on improving energy efficiency in order to remain competitive. Waste heat recovery from flue gas is the most cost effective way to contribute to this target. This article ihttp://heatmatrixgroup.com/case-studies/#case2ntroduces an air preheater technology for reliable waste heat recovery from corrosive flue gas.

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Corrosive flue gas
The corrosiveness of flue gas is the main reason why the energy efficiency of furnaces, fired heaters and steam boilers remains poor. Flue gas originating from sulphur containing fuel becomes corrosive below a temperature of approximately 150°C (acid dew point corrosion). Local cold spots in metal air preheaters will lead to rapid corrosion and breakdown of plates and tubes. Breakdown goes unnoticed for a while, but the shortcut between combustion air and flue gas leads to energy loss (reduced flue gas temperature at flue gas inlet), more power to the combustion air fan and limited throughput because of a maxed- out combustion air fan. These cold spots already occur when the flue gas bulk temperature is as high as 250°C because of cold ambient air at the other side of the heat exchanging surface, which results in a flue gas side surface

Existing technologies
In order to lower flue gas outlet temperatures and improve energy efficiency, several techniques have been applied with mixed success. When cooling down flue gas to approximately 170°C, recycling of heated combustion air to the inlet of the forced draft fan will lift the air temperature and subsequent local cold spot temperature. Frequently, an air preheater driven by steam is also applied for additional heating during the winter. These measures cost energy and limit recovery to approximately 20°C above the acid dew point.
For the highest energy efficiency, flue gas has to be cooled below the acid dew point; for this, metal exchangers are not suitable any more, or they become very expensive. Alternatives, such as glass tube and polymer tube, have been applied but they are sensitive to flow induced vibrations and temperature shocks, which leads to tube breakage or rupture. The subsequent short cut between combustion air and flue gas leads to the consequences described above.

Polymer heat exchanging tube bundles
The HeatMatrix LUVO air preheater consists of multiple corrosion resistant tube bundles contained in a single metal shell or housing, which is made corrosion resistant by applying a coating or polymer liner. The proprietary polymer bundle design consists of multiple tubes that are connected to each other over almost the full length of the tube. This structure creates a strong rigid matrix grid that is able to resist high gas velocities and thermo shocks. The connector between the individual tubes creates simultaneously a counter current flow configuration between the two gas streams. This configuration improves the heat transfer by up to 20% compared to cross flow type exchangers. Flue gas flows from top to bottom through the tubes and combustion air flows in the opposite direction around the tubes. The top end of the polymer tube bundles is fixed to the upper tube sheet and the lower end is allowed to expand in a sealing system connected to the lower tube sheet. The extra tube sheet in the middle of the exchanger prevents bypassing and directs combustion air into the polymer tube bundles.

The inlets and outlets of the exchanger are located at the side of the heat exchanger in order to allow easy access to the polymer tube bundles. These lightweight bundles are retractable from the top and can be cleaned or replaced without demounting the complete exchanger. In the case of fouling flue gas, each bundle can be equipped with an in-line spray nozzle, which thoroughly cleans each bundle in an alternating cleaning sequence during operation.

Hybrid air preheater design
For applications with a flue gas temperature below 200°C (such as steam boilers), integration of the polymer air preheater is straightforward. For applications with a flue gas temperature above 200°C a combination of a metal air preheater and polymer air preheater in series is required. The polymer part protects the metal part against low air temperatures that lead to cold spot corrosion problems and the metal part protects the polymer part against high temperatures. This combination is available as an integrated exchanger with only one single shell or as a compact assembly containing a separate metal air preheater and a separate polymer air preheater. The latter can be equipped with an extra induced draft fan between the metal and polymer air preheater for independent control of flue gas towards the air preheater assembly and to overcome the extra pressure drop of the exchangers.

Waste heat to liquid
Not all combustion process can benefit from preheated combustion air as the outlet for waste heat from corrosive flue gas. For example, the electrical efficiency of gas turbines will reduce dramatically when combustion air is preheated. Furthermore, some installations have limited space for large ducting and/or air preheater assemblies. For these applications a liquid outlet for waste heat can be utilised if available (for instance, preheating condensate, a city heating grid, or other process streams). Such a recovery system consists of a polymer gas-gas exchanger and a standard finned tube gas-liquid exchanger separated by a circulating air loop in order to separate corrosive flue gas from higher pressure liquid. This fail-safe and robust design prevents any upsets in either of the independent connected systems.

Case study air preheating
The following example involves a typical furnace at a refinery. A flue gas flow of 95 000 kg/hr at 290°C was used to preheat combustion air in a hybrid configuration of a metal and polymer air preheater. The realised efficiency improvement is 9.6%, which corresponds to 5.8 MW in this specific case. Flue gas is cooled to 180°C in the metal exchanger and subsequently to 91°C in the polymer exchanger. The combustion air is first preheated to 122°C before it enters the metal exchanger and is further heated to a final temperature of 247°C.

Conclusion
In order to improve energy efficiency in the petrochemical industry, waste heat recovery from corrosive flue gas is the most cost effective source to look at. Cooling flue gas beyond the acid dew point is unconventional but, with a robust exchanger for the corrosive duty, significant savings can be realized in a reliable way. Additionally, this extra efficiency step contributes to a low carbon emission strategy.

Bart van den Berg is a co-founder of HeatMatrix Group and has spent 20 years in various positions throughout the petrochemical industry. He holds a master’s degree in chemical engineering from Twente University, The Netherlands.
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  • Polymer bundles inside APH
  • Cross section of heat matrix APH

PTQ 2014 “Air pre-heater improves energy efficiency”

  • Example Acid Dew Point
  • Example H2SO4 concentration
  • Open LUVO
  • Polymer heat exchanger inside

A corrosion resistant air pre-heater enables valuable heat recovery from corrosive and fouling refinery flue gas streams

By Bart van den Berg

In the search for energy efficiency in the refining industry, waste heat recovery from flue gas is one of the most interesting sources of hidden energy to look at. There are three reasons why a stack should be one of the first locations to look at in the search for energy savings. The first reason is that at a ‘stack location’ significant amounts of primary energy are converted into heat at one single location. The second reason is that flue gas is discharged into the atmosphere at relatively high temperatures between 150°C and 250°C. And finally, the outlet for the recovered waste heat is nearby as combustion air with a sufficient low temperature to absorb the excess heat. Energy efficiency improvements by up to 5% can be realised at all kinds of industrial steam boilers, furnaces and fired heaters, even in the case when air pre-heating is already applied to some extent.

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The current metal air pre-heaters are designed for a minimum flue gas exit temperature of approximately 160°C in order to prevent corrosion and subsequent high maintenance cost. Flue gas originating from sulphur containing fuel (for instance, refinery gas, fuel) has an acid dew point at around 130°C. For this reason, many existing air pre-heater systems incorporate a steam heater in order to pre-heat ambient combustion air to a minimum temperature that prevents corrosion in the air pre-heater.

The Dutch company HeatMatrix Group recently developed a new generation air pre-heater that enables heat recovery from corrosive and/or fouling flue gas streams. This exchanger contains polymer tube bundles that are resistant to corrosion by concentrated sulphuric acid at elevated temperature. The characteristics of this exchanger and its case study based performance are outlined in this article.

Acid dew point related corrosion
During combustion, the sulphur component of sulphur contami-nated fuel is converted into sulphur dioxide and trioxide. The sulphur trioxide condenses in the presence of water vapour at a dew point temperature, which is a function of the partial pressure of sulphur trioxide and water (‘acid dew point’). At this dew point, a first small amount of highly concentrated sulphuric acid precipitates, for example on the air pre-heater surface. In an air pre-heater, the skin temperature of the heat exchanging surface at the flue gas side (‘wall temperature’) is leading in this process. The bulk temperature of the flue gas can still be significantly higher. Detailed information on acid dew point temperature calculations can be found elsewhere.

When the temperature of the flue gas is further reduced beyond the acid dew point the concentration of sulphuric acid is also reduced, as well as the corrosiveness. Below 90°C, the corrosiveness of the flue gas is significantly lower compared to the corrosiveness just below the acid dew point temperature. From a variety of exotic metals, only tantalum can withstand acid dew point corrosion at acid dew points higher than 150°C. The polymer that is applied for the HeatMatrix polymer tubes is resistant to acid dew point concentrations up to 150°C and has a design temperature of 200°C.

High temperature acidic flue gas crosses the acid dew point close to the tip of the stack as result of cooling by ambient air. This lost energy can be recovered when the right heat exchanger materials are applied leading to an improved energy efficiency.

Polymer heat exchanging tube bundles
The HeatMatrix air pre-heater consists of multiple corrosion resistant tube bundles contained in a single metal shell or housing, which is made corrosion resistant through a coating or polymer liner. The proprietary polymer bundle design consists of multiple tubes that are connected to each other over almost the full length of the tube. This structure creates a strong rigid matrix grid that is able to resist high gas velocities and thermo-shocks. As opposed to polymer hose or glass tube designs, the connected polymer tube bundles are not sensitive to breakage or rupture. The connector between the individual tubes creates simultaneously a counter-current flow configuration between the two fluids. This configuration improves the heat transfer by up to 20% compared to cross flow type exchangers.

Flue gas flows from top to bottom through the tubes (red arrow) and combustion air flows in the opposite direction around the tubes (blue arrow). The top end of the polymer tube bundles is fixed to the upper tube sheet and the lower end is allowed to expand in a sealing system connected to the lower
tube sheet. The extra tube sheet in the middle of the exchanger prevents bypassing and directs combustion air into the polymer tube bundles.

The inlets and outlets of the exchanger are located at the side of the heat exchanger in order to allow easy access to the polymer tube bundles. These lightweight bundles are retractable from the top and can be cleaned or replaced without demounting the complete exchanger. In the case of fouling flue gas, each bundle can be equipped with a spraying nozzle, which thoroughly cleans each bundle in an alternating cleaning sequence.

The capacity of the air pre-heater is fully scalable by placing several polymer bundles in parallel in a shell. The smaller size exchangers have a cylindrical shape and the larger size air pre-heaters have a container shape to accommodate flue gas flows up to 500 000 kg/hr.

Installation options
For grass roots installations with a flue gas temperature below 200°C, integration of the polymer air pre-heater is straightforward. For installations with a flue gas temperature above 200°C, a combination between a metal air pre-heater and polymer air pre-heater in series is required. This hybrid design has the following advantages:

  • Increased heat recovery over a wide temperature range
  • The polymer air pre-heater protects the metal air pre-heater against low air temperatures that lead to cold spot corrosion problems
  • The metal air pre-heater protects the polymer air pre-heater against high temperatures

A steam air pre-heater for raising the temperature of the combustion air is no longer necessary with this hybrid air pre-heater design.

Addition of a polymer air pre-heater to existing installations will be a profitable investment as well. Existing civil and steel structures frequently have sufficient over-design to accommodate an additional lightweight exchanger. Also, for boilers with a large distance between stack and combustion air induced draft fan solutions can be provided. For this case, a twin coil system comprising a polymer flue gas exchanger and a simple finned tube exchanger is recommended.

Case study
The following typical case is based on the performance of multiple projects that have been realised over the past years. A flue gas flow from a large steam boiler of 100000 kg/hr at a temperature of 170°C enters the polymer air pre-heater and is cooled to 85°C by 95000 kg/ hr combustion air at 15°C. The recovered energy is 2.6 MW, which is approximately 5% of the steam boiler duty.

Conclusion
Energy efficiency and carbon abatement are currently hot topics and energy efficiency is seen as a most important contributor in every governmental strategy to reduce fossil fuel consumption. In that light, flue gases should be seen as an important source of hidden energy because flue gas still contains 5 to 10% of the primary energy used to drive the combustion process. New technologies like this polymer air pre-heater can contribute to improve energy efficiency throughout the refining industry.

Bart van den Berg is a co-founder of HeatMatrix Group and has spent 18 years in various positions throughout the petrochemical industry. He holds a master’s degree in chemical engineering from Twente University, the Netherlands
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