Air cooled condenser (ACC) for thermal power plant

Generally, applying another type in an insufficient-water area needs to make a water reservoir to collect the water for serving cooling tower. Thus,  Air cooled condenser (ACC) will help reduce capital cost of such a water reservoir, save water consumption cost during operation. Also, it solves the problem of diverting water from the community.

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In the thermal power plants, exhaust steam from the steam turbine flow into the air cooled condenser (ACC) where the condensation occurs. Then the condensate-water returns to the boiler in a closed loop. Meanwhile the exhaust steam coming from the turbine is at a low pressure, the Air Cooled Condenser works at pressure as vacuum to avoid the pressure drop increase and impact to the efficiency of power generation, and then the non-condensable gases will be removed continuously by the air evacuation system.

Configuration and Scope of Shuangliang Air Cooled Condenser

Scope normally covers equipment and ducts from turbine exhaust to inlet of condensate pump, mainly including:

• Tube bundle
• Air supply system
• Air evacuation system
• Condensate system
• Cleaning system
• Exhaust steam ducting system
• Supporting structure
• Draining system
• Electric system
• Instrument & control system

Principle

 of Air cooled condenser

The working principle of Air Cooled Condenser is to distribute the exhaust steam from the steam turbine straightly to the stream condensers in several rows through ducting. At the same time, the large axial-flow fans intake air and sweep over the tube bundles externally to carry away heat. In tube bundles, the exhaust steam gradually changes to condensates and is accumulated in the condensate tank through the bottom headers. Moreover, the vacuum of the whole Air cooled condenser (ACC) covers by the air evacuation system. For this reason, the steam turbine can activate smoothly and confirm power generation efficiency. 

The steam condensers are consisted of two types of tube bundles: parallel- flow and counter-flow types.

In the parallel-flow tube bundles, most of the steam is condensed, meanwhile the non-condensing gas is extracted in counter-flow tube bundles which they are connected through the bottom headers.

Additionally, the advantages of the direct air cooled condenser system (ACC) is occupying less floor area, various anti-freezing methods and flexible arrangement.

Technical and Advantage of Shuangliang Air cooled condenser

Single-Row Tube

Shuangliang Single-Row Tube is one of the best selective innovations which is applied in Air Cooled Condenser (ACC), characteristics designed by welded large flat tube and aluminum snake-like fins, are rolled from single-sided aluminum cladded carbon steel strip. The flat tubes and fins are connected by brazing.

1. High heat transfer efficiency

The heat exchange at both sides of tube bundle is fully activating, mean to the exhaust steam has large size of flow area and very low-pressure loss, so the heat transfer efficiency is extremely high.

2. Strong resistance to corrosion

 

To have strong corrosion resistance, the external surface of base tube for the tube bundle is clad with aluminum alloy, the heat exchange fins of tube bundle also aluminum alloy spray coating, even after those materials are processed, aluminum oxide protective layer will still be formed thereon to achieve good corrosion resistance.

3. High strength and good cleaning ability

 

Welding several single-row fin tubes and tube-sheet was also applied in order to strengthen all the structures. Moreover, this process would apply for facilitate installation and transportation. Another distinctive characteristic, using straight-line type in single-row tube fins are easy to wash with high-pressure water without any deformation.

4. Good anti-freezing performance

 

In order that the condensate flows more smoothly, we create a large length-width ratio of the base tube. Furthermore, this specific characteristic is able to reduce the extent of sub-cooling and the risk of tube freezing in winter.

5. Weld seam position

The weld seam is on the arc of the base tube of the single-row tubes, The arc spray aluminum coating has the better welding strength.

Shuangliang no need to be worried about the leak occurring during the operation since it can be repaired immediately without removing the entire tube bundle or replacement. Above all, we do believe in Easy maintenance and low maintenance costs.

6. Single-Row Tube Bundle Fatigue test

Evacuated by vacuum pumping, the tube bundle will be reached to vacuum condition and then returned to normal pressure. After that, cycle tests will evaluate the number of cycles (fatigue life) in which the change occurs abruptly in the single-row tube.

To ensure reliance of Shuangliang Air cooled condenser (ACC), the qualified value of the product fatigue life should be more than 1,000 times and more than ten times the actual fatigue times. Due to qualified value, our customers can assure that our product&#;s safety lasts the 30-year design life.

THREE MAJOR TEST DEVICES

 

1. Performance testing device on tube bundles of

Air cooled condenser (ACC)

 

The Performance testing device on tube bundle as applies for experimenting heat exchange performance of various types of fined tube bundle structure and online random test of finished products.

After pressure and temperature of the steam are gradually reducing, the testing device will simulate several operating backpressures of the steam turbine, measure the heat exchange performance and resistance loss of the tube bundle. It also obtains the heat exchange coefficient and air resistance of tube bundle at different air speed and internal flow resistance of tube bundle at different steam flow speed.

Furthermore, to evaluate actual performance of tube bundle, the testing device is also utilized for examining thermal performance of tube bundle.

2. The unique environmental test 

laboratory 

: 1×4 

Air cooled condenser (ACC)

environmental test device

Shuangliang Air cooled condenser is available for worldwide. It can simulate the summer operating conditions and winter operating conditions of Air cooled condenser (ACC), the unique environmental test laboratory will imitate ambient temperature of 50°C~-25°C. Therefore, there are two operating conditions to test in different situations.

One is the summer operating condition. It&#;s for testing the heat transfer performance of the tube bundles of the Air cooled condenser (ACC) which provides the basis for the design of the actual Air cooled condenser (ACC).

The other is the winter operating condition. It is for evaluating whether the control program of Air cooled condenser (ACC) is valid for antifreeze protection measures during operating conditions such as the machine functional of start, stop and low load operating conditions. Finally, it could test the minimum antifreeze steam flow under different temperature conditions.

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3. The unique large full-performance test bed: Hot-state test device for one unit of MW

For more air cooled condensing units manufacturerinformation, please contact us. We will provide professional answers.

Additional reading:
What Are the Best Chillers Systems?

Air-cooled condenser (ACC)

The unique large full-performance test device can simulate the main operating conditions of power station for the performance test, heat exchange performance, system reliability, stability, and economy of Shuangliang Air Cooled Condenser (ACC). Particularly ensure the ACC can operate capacity at summer full load and winter anti-freezing running reliability.

Shuangliang Air cooled Research and Development

Achieving the great leap of Air cooled condenser (ACC) for power plants from theoretical R&D to engineering application isn&#;t an easy thing. To solve several errors in our industry, we conduct nine fundamental research to provide design support for Air cooled condenser (ACC) for power station. Therefore, It&#;s more suitable for Global market.

1. Experimental Research on heat exchange performance of heat exchange component
2. Experimental Research on resistance characteristic on air side of heat exchange component
3. Investigation on resistance characteristic on steam side inside the tube of heat exchange component
4. Experimental Research on atmospheric corrosion resistance of fins
5. Fouling performance test of tube bundle
6. Cleaning test of fins of tube bundle
7. Experimental Research on freezing protection of tube bundle
8. Experimental Research on computer numerical simulation of Air cooled condenser (ACC)
9. Experimental research on fatiguing test of tube bundle

Shuangliang Air Cooled Condenser Reference in Power Plant

Shuangliang has received the letter of award (LOA) from Singapore ST Marine. It&#;s about the award of bidding for air-cooled condenser in TUAS IWMF garbage power plant project. It is planned for two phases, each phase to generate 2 X 65 MW power with waste treatment capacity to be 2,900 tons/day. In conclusion, when the project is completed, it will be the largest garbage incineration power plant in Singapore and even in whole Southeast Asia.

References in biomass power plant and solid waste power plant                              

Reference in Thermal Power Plant

1. Air -cooled condenser

    Project for Siemens 4×MW New Capital CCPP in Egypt   ( ACC for the largest CCPP in the world)
2. Botswana project (4×150MW)
3. Guohua Dingzhou Power Plant in Hebei Province (2×660MW)
4. Hulunbeier Power Plant (2×600MW)
5. Wison Cathay Power plant for 1 × 60,000 ASU of Wison Cathay

6. Air -cooled condenser

    unit for 4×60,000 ASU of Zhongmei Yulin Energy Chemical Co., Ltd.

7. Air- cooled condenser

    for 4× ASU for coal-to-alkene project of Shenhua Baotou Energy Co., Ltd.
8. China Coal Tuke Energy Chemical Project for 2×40,000 ASU of China Coal Tuke Energy Chemical Co., Ltd.

9. Air- cooled condenser

    for 4 × 48,000 ASU of Datang Keqi Coal-to-Gas Co., Ltd.

10. Air cooled condenser

     unit for 1 × 35,000 ASU of Shenhua Yulin Energy Co., Ltd.

11. Zero Water Consumption CHP System (ZWCCHP) in LATAM market

Shuangliang&#;s team

Our Team in Germany

In October , Shuangliang Clyde Bergemann Co., Ltd. was established in Germany and is the research and development center of Shuangliang Eco-Energy in Europe. The air cooling team of Shuangliang Clyde Bergemann Co., Ltd. is composed of senior industry experts, and the core personnel industry experience is more than 30 years. Moreover, Two of them are the most authoritative German VGB air-cooled island performance test standards drafters in the world air-cooling industry. German VGB guide is the most authoritative air-cooled island performance test standard recognized by the world air-cooling industry.

Our Team in Hungary

In , Shuangliang established a joint venture with Hungarian Bihong Engineering Co., Ltd. to establish Jiangyin Shuangliang Bihong Steel Structure Engineering Technology Co., Ltd. Therefore, our company can enhance the design and engineering capabilities of Shuangliang air-cooled steel structure.

Shuangliang&#;s Awards

&#;China Grand Award for Industry&#;  for the first time

It is known as the &#;Oscar&#; award of Chinese industry. We are the only enterprise winning the award in the industry of energy-saving and environmental protection

China Grand Award for Industry for the 2nd time

Above all, we are the only private enterprise to win both the Enterprise Award and the Project Award.

In this article a specific type of condenser, naming AIR COOLED CONDENSER, is investigated. Before describing the Air Cooled Condensers (ACC), few subjects shall be in brief discussed. It shall be mentioned now that in my experience, I used ACC with condensate steam turbines, which described in following chapter. But ACC usage is not limited to steam turbines only, as they can be used in refrigerant cycles as well.

Condensate steam turbines

In steam turbines, inlet pressure (and temperature) of steam, rotates the impellers resulting in work. The pressure and temperature of a steam forms a parameter called Enthalpy. I do not want to go over thermodynamic course. There are really good sources if one wants to study in this field. Work that is done in a steam turbines is equal to differential between Inlet and Exhaust steam&#;s enthalpy. By reducing the temperature and pressure, enthalpy will reduce. With a same inlet condition, we try to reduce exhaust enthalpy as much as possible to extract more work out of steam stream. However if we reduce the temperature below DEW POINT, the steam will condense into water that will damage the impellers. In this case turbines requires another equipment called condenser.

What is condenser?

Condensers are equipment that reduce the temperature of a stream of steam, result in complete condensation outside turbine casing. In this process, vacuum will be induced. The vacuum will drive the steam and small droplets of water into condenser. Condensers can be used downstream of condensate steam turbines or in the refrigeration cycle. Condensers, based on cooling media, divided into two groups:

• Water Cooled Condenser (WCC) or Surface condenser
• Air Cooled Condenser (ACC)

Figure 1- Surface condenser- Courtesy of DongHwa

Figure 2- Air Cooled condenser- Courtesy of CONCOSYSTEMS

Working Principal of condensers

In a condenser the temperature of steam stream is reduced below dew point by using other medium such as cooling water or air. As the temperature goes below the dew point, droplets of water will form.

When steam changes into water, the volume of steam will drops significantly. This reduction in volume will cause a vacuum.

A reminder of Physic course: In the standard condition, one mole of ideal gas has a volume of 2.24m^-2 (22.4 Litre), one mole of liquid water is 18 gr that is equal to 1.8e-5 m^3 (18Ml). Although in this case we are far away from ideal gas conditions but still this volume change is huge resulting in huge vacuum induction when water vapor changes to liquid water.

Different cooling medium are used based on plant condition. First choice is normally water. Next choice is Air.

Cooling medium: Water vs. Air

Both Air and water can be used as cooling media. The amount of heat that the cooling medium take from steam is calculated by following formula:

Q=mCΔθ

Q is total transferred heat, m is the mass, C is heat capacity and last term (Δθ) is the temperature difference. For condensing the same amount of steam, Q is fixed.

C is different for water and air, which is 4.16 kJ/kg.K for Water and 0.718 kJ/kg.K for air. Δθ has a limit also. When cooling water is used, the limit is tighter for example maximum 10°C. Even if sea/ocean water is used (which is normally won&#;t be used because of corrosion and heavy treatment requirements) this temperature difference is limited by Environmental condition. For air is this amount is limited. As the air temperature goes up, Q will reduce, thus we limit the temperature rise.

In my experience for water cooled condenser the maximum allowable temperature rise is 10C while for Air Cooled condenser this amount is 30°C

Figure 3- Water Cooled Condenser

Figure 4- Air Cooled Condenser

Above clarifications shows that we require less mass amount of water comparing to Air.

This results in smaller water cooled condenser versus air cooled condenser.

Condensers in figure 3 and figure 4 are both for a SAME service. The difference in size is absolutely visible. While the WCC is cylinder with diameter of 1.5m and length of 8m, the ACC is a box with the size of 10m x 15m x 50m.

Pros and Cons

Back to the topic, in this section I want to discuss the pros and cons of air cooled condenser. Whenever it is possible, I compare these points with water cooled condenser. But in general they are totally opposite.

Pros

• Long term cost: Air is free. On the other hand one shall pay for water or the treatments on the water. In long run ACC cost less than WCC.
• Availability: Air is always available while the water is not always present. In addition air requires almost no treatment while water requires sufficient treatment to avoid corrosion and erosion in condensers.
• Maintenance: ACC requires less maintenance since they do not require pumped cooling water.
• Cost of other facilities : Although the cost for ACC unit is greater than WCC, but if the condenser is the only consumer of cooling water, ACC saves a lot of money while the cooling tower/cooling pumps and cooling water treatment facilities can be omitted. It shall be mentioned again this is the case ONLY when condenser is the only consumer of cooling water.

Cons

• Size: as mentioned in previous chapter, for a same duty much more air is required. Thus the size of Air cooled condenser are much bigger than water cooled condenser. An example is showed in figure 3 and figure 4. The duty for both condensers are around 70 T/Hr. Air cooled condenser is much bigger than water condenser with a same duty.
• Higher capital cost: With a same capacity, ACC costs more comparing to WCC to purchase and install.
• Uncontrolled heat transfer: In water cooled condenser coolant inlet and outlet temperature is fixed, thus it is easy to calculate heat exchange rate. In the Aircooled condenser it is totally difference. Heat transfer can be limited by environmental conditions such as dust or temperature variation. Thus with a same working condition ACC can produce different cooling capacity.
• New technology: this point is not a con, nor a pro. Air cooled condensers are newer technology comparing to water cooled condenser. There are lots of research going on in order to optimize the design. Naturally less manufacturers can make these comparing to water cooled condensers.

Working principal of Air cooled Condenser

Following figure shows a typical diagram of ACC. A fan pushes air on the steam tube bundles causing the steam to condensate. Liquid water , due to its weight, flows into the bottom of tube. This condensate is then collected in HOTPOT(not showed in this picture) and pump to boiler cycle for further usage.

Figure 5- Typical A-Frame ACC -Courtesy of FANS

Air Cooled Condensers types

Aircooled condensers can be categorized based on their Structural format. Naming A-Frame (figure 5), W-Frame, V-Frame (Figure 7 and cover figure) and Δ-Frame. (Figure 8). On V and W frames, fans mounted on top. When the fans installed at bottom, they can push dust particles into ACC. The first impact is reduced heat transfer. Another drawback is corrosion, as the dust particles solved in moisture droplets such as rain, they can damage the tubes. on the other hand top installation can conduct rain and other airborne particles inside the ACC.

Each model has its pros and cons. The major constraints are capacity structural limitations. Although W-Frame is two V-Frames connected to each other but downstream equipment such as pumps are shared. Thus one set of downstream equipment is omitted. These models are used for higher capacities. On the other handin the W-Frame ACC the heat convection between two Vs, (where two V-Frame are joined together) are lower since both sides has high temperature. In general Single frame ACC such as V and Δ have higher efficiencies but in heavy duty cases they are not feasible to build.

Figure 6- W-Frame ACC-Courtesy of SPG

Figure 7- V-Frame ACC- Courtesy of B&W SPIG

Figure 8- V-Frame ACC- Courtesy of B&W SPIG

Air cooled condenser parts

Following are major part of an ACC:

• Tubes: These tubes contain steam. Air passes these pipes and cool down the steam.
• Fan: Fan are used to flow the air. Fan discharge capacity has a limited range. Fans discharge flow can be controlled by different methods such as Speed variations or changing the vane angle of attack.
• Hotpot: it is a container that installed below the ACC and collect the condensate water.
• Pump: this pump (one or more) send the condensate water back to cycle for further treatment and use.

Important factors for Air cooled condenser design

There are different factor that a designer shall consider while designing or purchasing Air Cooled Condensers

1. Area: ACC requires much bigger space than a WCC. Area limitations are not limited to the space that ACC occupy, but also the utilities and piping works that required for ACC. Thus it shall be economically consider the extra cost for buying additional land, especially in the area that lands are expensive. Sometime even if the client willing to pay for extra land, these lands are unavailable. These are the cases in crowded area called PETROCHEMICAL HUBs such as ASSALUYEH south of Iran.
2. Temperature Variation: The design temperature is utmost important. Consider a location that minimum temperature is -5°C and maximum temperature is 50°C. For which temperature ACC shall be designed? If ACC designed for maximum temperature, more air flow is required. Meaning that the fans shall be bigger. In this case in winters, excessive air flow cause more steam convert to water, inducing greater vacuum. This can be a problem when ACC installed downstream of a steam turbine for example. Excessive vacuum increases the turbine speed, as more steam passes the turbine to ACC, causing a unit trip. On the other hand if ACC designed for minimum temperature, in the summers less heat extracted from steam and condensation process will not completed. ACC are hard to use in the locations that temperature has a wide range.
3. Heat distribution: Due to low heat capacity, air temperature will rise rapidly, comparing to water. This means that if the design is not optimized, tubes are not cooled uniformly causing thermal shock to the tube and lower efficiency for ACC. Low efficiency means bigger facilities, that is normally avoided. Heat distribution can be modeled with CFD.
4. Material: Steam tube material shall be able to withstand both high temperature and pressure variation.

Related articles

References

• Cover Picture is Courtesy of LU-VE
• Heinz P. Bloch and Murari P. Singh, 2nd Edition. "Steam turbines: Design, Application and Re-Rating" Mc Graw Hill.

#Condenser #Aircooled #air #watercooled #turbine #steamturbine

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