Admission of Bypass Steam Into a Water Cooled Condenser and Air Cooled Condenser: Similarities, Differences and Areas of Concern

2014 ◽  
Author(s):  
Ranga Nadig ◽  
Dave Sanderlin
Keyword(s):  
Steam Turbine ◽  
Large Diameter ◽  
Cooling Water ◽  
Ambient Air ◽  
Combined Cycle ◽  
Steam Flow ◽  
Normal Operation ◽  
Bypass Operation ◽  
Circulating Water ◽  
Turbine Exhaust

In power plant locations with adequate supply of cooling water the steam from the steam turbine is condensed in a water cooled condenser. In most instances circulating water from the cooling tower is used to condense the turbine exhaust steam. In other instances once through cooling is deployed wherein water from a lake, river or sea is used to condense the turbine exhaust steam. In water challenged locations or locations where wet cooling cannot be deployed due to permitting or regulatory issues, the steam from the steam turbine is condensed in an air cooled condenser (ACC) wherein ambient air is used to cool and condense the turbine exhaust steam. In a combined cycle plant, during normal operation, the water or air cooled condenser condenses the turbine exhaust steam. During bypass operation, when the steam turbine is out of service, the high-pressure steam from the HRSG is attemperated in a pressure reducing/desuperheating (PRD) valve and then admitted into the water cooled or air cooled condenser. The bypass steam flow is substantially higher than the design turbine exhaust steam flow and the duration of bypass operation can vary from a few hours to several weeks. The requirements for admission of bypass steam into a water cooled condenser are substantially different from that for an air cooled condenser. In a water cooled condenser the bypass steam is admitted in the steam dome. The bypass steam as well as the turbine exhaust steam is condensed outside the tubes. In an air cooled condenser the bypass steam is admitted in the large diameter steam duct. The bypass, as well as the turbine exhaust steam (normal operation), is condensed inside the tubes. There are similarities and differences in the requirements for admission of bypass steam into a water cooled and air cooled condenser. The differences must be identified and addressed to ensure safe and reliable performance of the condenser.

Improving Natural Draft Cooling Tower Performance With Heat Injection

2002 ◽  
Author(s):  
Eugene Grindle ◽  
John Cooper ◽  
Roger Lawson
Keyword(s):  
Water Temperature ◽  
Computer Model ◽  
Cooling Tower ◽  
Ambient Air ◽  
Combined Cycle ◽  
Steam Boiler ◽  
Natural Draft ◽  
Circulating Water ◽  
Vapor Stream ◽  
Heat Injection

This paper presents an assessment of heat injection as a means of improving natural draft cooling tower performance. The concept involves injecting heat into the cooling tower exit air/vapor stream immediately above the drift eliminators in order to increase the difference between the density of the exit air/vapor stream and the ambient air. The density difference between the air/vapor in the cooling tower stack and the ambient air is the engine that drives airflow through the cooling tower. The enhancement of the airflow through the cooling tower (the natural draft) results in more evaporation and thus lowers the circulating water temperature. Because the heat is injected above the drift eliminators, it does not heat the circulating water. To evaluate the cooling tower performance improvement as a function of heat injection rate, a thermal/aerodynamic computer model of Entergy’s White Bluff 1 & 2 and Independence 1 & 2 (approximately 840 MW each) natural draft cooling towers was developed. The computer model demonstrated that very substantial reductions in cold water temperature (up to 7°F) are obtainable by the injection of heat. This paper also discusses a number of possible heat sources. Sources of heat covered include extraction steam, auxiliary steam, boiler blow-down, and waste heat from a combustion turbine. The latter source of heat would create a combined cycle unit with the combination taking place in the condensing part of the cycle (bottom of the cycle) instead of the steam portion of the cycle (top of the cycle).

Importance of Auxiliary Power Consumption for Combined Cycle Performance

2010 ◽  
Vol 133 (4) ◽  
Author(s):  
S. Can Gülen
Keyword(s):  
Power Plant ◽  
Power Consumption ◽  
Electric Power ◽  
Steam Turbine ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Combined Cycle Power Plant ◽  
Auxiliary Power ◽  
Definition Of ◽  
Turbine Exhaust

The key product of a combined cycle power plant is electric power generated for industrial, commercial, and residential customers. In that sense, the key performance metric that establishes the pecking order among thousands of existing, new, old, and planned power plants is the thermal efficiency. This is a ratio of net electric power generated by the plant to its rate of fuel consumption in the gas turbine combustors and, if applicable, heat recovery boiler duct burners. The term in the numerator of that simple ratio is subject to myriad ambiguities and/or misunderstandings resulting primarily from the lack of a standardized definition agreed upon by all major players. More precisely, it is the lack of a standardized definition of the plant auxiliary power consumption (or load) that must be subtracted from the generator output of all turbines in the plant, which then determines the net contribution of that power plant to the electric grid. For a combined cycle power plant, the key contributor to the plant’s auxiliary power load is the heat rejection system. In particular, any statement of combined cycle power plant thermal efficiency that does not specify the steam turbine exhaust pressure and the exhaust steam cooling system to achieve that pressure at the site ambient and loading conditions is subject to conjecture. Furthermore, for an assessment of the realism associated with the two in terms of economic and mechanical design feasibility, it is necessary to know the steam turbine exhaust end size and configuration. Using fundamental design principles, this paper provides a precise definition of the plant auxiliary load and quantifies its ramification on the plant’s net thermal efficiency. In addition, four standard auxiliary load levels are quantitatively defined based on a rigorous study of heat rejection system design considerations with a second-law perspective.

Tube Failure During Startup in a Steam Surface Condenser Installed in a Combined Cycle Plant Operating in Cold Climate

2004 ◽  
Author(s):  
Ranga Nadig
Keyword(s):  
Combined Cycle ◽  
Cold Climate ◽  
Steam Flow ◽  
Wet Steam ◽  
Flow Induced Vibration ◽  
Circulating Water ◽  
Plate Spacing ◽  
Surface Condenser ◽  
Combined Cycle Plant ◽  
Operating Points

Combined cycle plants in cold climates experience low circulating water inlet temperatures during winter months. Low circulating water inlet temperatures combined with partial bypass steam flow to the condenser results in extremely low condenser pressures and high steam velocities. Improper design, control & operation of desuperheating valve and improper drainage of bypass header lines can lead to pockets of wet steam in the bypass steam. High steam velocities combined with wet steam pockets of varying quality can cause flow-induced vibration and tube failures. This paper examines the performance of a condenser in bypass mode for varying condenser pressures, bypass steam flow rates, support plate spacing, and moisture pockets with varying quality. Actual and critical steam velocities are calculated. Condenser operating points prone to flow-induced vibration and associated tube failures are predicted. Recommendations on safeguards to eliminate flow induced vibration and resulting tube failures are discussed.

scholarly journals Design and Operating Experiences With Gas Turbine Combined Cycle Units

1971 ◽  
Author(s):  
R. W. Jones ◽  
A. C. Shoults
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Economic Factors ◽  
Chemical Company ◽  
Gas Turbine Exhaust ◽  
Selection Of ◽  
Turbine Exhaust

This paper presents details of three large gas turbine installations in the Freeport, Texas, power plants of the Dow Chemical Company. The general plant layout, integration of useful outputs, economic factors leading to the selection of these units, and experiences during startup and operation will be reviewed. All three units operate with supercharging fan, evaporative cooler, and static excitation. Two of the installations are nearly identical 32,000-kw gas turbines operating in a combined cycle with a supplementary fired 1,500,000-lb/hr boiler and a 50,000-kw noncondensing steam turbine. The other installation is a 43,000-kw gas turbine and a 20,000-kw starter-helper steam turbine on the same shaft. The gas turbine exhaust is used to supply heated feedwater for four existing boilers.

scholarly journals Multiple Evaporation Steam Bottoming Cycle

1997 ◽  
Author(s):  
H. Jericha ◽  
M. Fesharaki ◽  
A. Seyr
Keyword(s):  
Gas Turbine ◽  
Steam Line ◽  
Combined Cycle ◽  
Steam Flow ◽  
Feed Water ◽  
Exhaust Gas ◽  
Gas Cooling ◽  
Gas Turbine Exhaust ◽  
Cycle Efficiency ◽  
Turbine Exhaust

Improvements to the steam bottoming cycles hold the promise of raising the combined cycle thermal efficiency to values near and above 60%. Up to now, steam bottoming cycles with three pressure levels of steam evaporation have been realised. A further advantage seems possible by the use of double fluids, such as mixtures of steam and ammonia. In the cycle proposed here, the authors limit Themselves to the use of steam and water only, in order to avoid all the difficulties, that may arise from such mixtures. The solution given here, relies on multiple evaporation levels, more than three up to five and even more. They should be to be achieved with the help of newly developed steam turbochargers, which allow the unification of the steam flow from three different neighbouring pressure levels, into one steam flow to be transmitted via the live steam line to the main turbine. This large number of evaporation levels, together with the required economisers for feed water heating and the ensuing superheaters arranged in the proper way, gives a steam water heat acceptance curve, which can be closely matched to the exhaust gas cooling line, so that the heat transfer from the gas turbine exhaust to the steam bottoming cycle can be effected with a minimum of temperature differences. It should be pointed out that the steam pressures are selected in the undercritical region, and that a total combined cycle efficiency very near to 60% can be achieved. Using most modern gas turbine models together with this novel bottoming cycle will even allow to exceed the value of 60%. Examples given have been calculated for standard gas turbine models.

Importance of Auxiliary Power Consumption on Combined Cycle Performance

2010 ◽  
Author(s):  
S. Can Gu¨len
Keyword(s):  
Power Plant ◽  
Power Consumption ◽  
Electric Power ◽  
Steam Turbine ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Combined Cycle Power Plant ◽  
Auxiliary Power ◽  
Definition Of ◽  
Turbine Exhaust

The key product of a combined cycle power plant is electric power generated for industrial, commercial and residential customers. In that sense, the key performance metric that establishes the pecking order among thousands of existing, new, old, and planned power plants is the thermal efficiency. This is a ratio of net electric power generated by the plant to its rate of fuel consumption in the gas turbine combustors and, if applicable, heat recovery boiler duct burners. The term in the numerator of that simple ratio is subject to myriad ambiguities and/or misunderstandings, resulting primarily from the lack of a standardized definition agreed upon by all major players. More precisely, it is the lack of a standardized definition of the plant auxiliary power consumption (or load) that must be substracted from the generator output of all turbines in the plant, which then determines the net contribution of that power plant to the electric grid. For a combined cycle power plant, the key contributor to the plant’s auxiliary power load is the heat rejection system. In particular, any statement of combined cycle power plant thermal efficiency that does not specify (i) the steam turbine exhaust pressure, and (ii) the exhaust steam cooling system to achieve that pressure at the site ambient and loading conditions is subject to conjecture. Furthermore, for an assessment of the realism associated with the two in terms of economic and mechanical design feasibility, it is necessary to know the steam turbine exhaust end size and configuration. Using fundamental design principles, this paper provides a precise definition of the plant auxiliary load and quantifies its ramification on the plant’s net thermal efficiency. In addition, four standard auxiliary load levels are quantitatively defined based on a rigorous study of heat rejection system design considerations with a second-law perspective.

Combined Steam-Turbine Power Producing Concept With Recirculating Steam Compressor

2007 ◽  
Author(s):  
Branko Stankovic
Keyword(s):  
High Temperature ◽  
Steam Turbine ◽  
Waste Heat ◽  
Combined Cycle ◽  
Steam Flow ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
High Temperature Steam

This concept shows that an efficient combined cycle, comprising topping & bottoming cycle, does not have to be privilege of gas turbine plants only, but could also be achieved with steam turbine plants. An efficient power-producing concept of a combined steam-turbine cycle with addition of a recirculating steam compressor is disclosed. Topping part of such a combined steam-turbine cycle operates at elevated steam turbine inlet temperature and pressure, while its “waste heat” is recovered by the bottoming part of the combined cycle in a heat-recovery boiler (steam heat exchanger). The recirculating steam compressor pumps the cooled majority of the entire steam flow to the maximum cycle pressure, while smaller steam flow fraction continues its full expansion to some low pressure in a condenser. The cycle waste heat could be transferred to the bottoming part of the combined cycle in a variety of modalities, depending on the chosen main high-temperature steam-turbine inlet temperature and inlet pressure (supercritical/subcritical). At an assumed constant steam-turbine inlet temperature of 900°C (∼300 bar), a very high gross cycle thermal efficiency could potentially be achieved, ranging from 56 to 62% with the high-temperature steam-turbine pressure ranging from subcritical (30 bar) to supercritical (300 bar). Such a combined steam-turbine cycle seems to be a suitable energy conversion concept that could be applied in classic thermal power plants powered by coal, but also seems as an ideal option for application in the new generation of gas-cooled nuclear rectors, where the gaseous reactor coolant, heated up to 1000°C, would indirectly transfer its heat content to working fluid (superheated steam) of the topping part of the combined steam-turbine cycle. Alternatively, the proposed concept may be combined with renewable energy sources of a sufficient temperature level.

Xcel Energy Riverside Repowering Project

2010 ◽  
Author(s):  
Paul Eiden ◽  
Tim Rathsam ◽  
Darin Schottler
Keyword(s):  
Natural Gas ◽  
Steam Turbine ◽  
Mississippi River ◽  
Catalytic Reduction ◽  
Water System ◽  
Combined Cycle ◽  
Concrete Walls ◽  
Circulating Water ◽  
Generating Capacity ◽  
Circulating Water System

Xcel Energy’s Riverside Repowering Project was a voluntary emissions reduction project with the goals of improving air quality in Minnesota while, at the same time, increasing the amount of electricity produced. The Riverside Plant was converted from being a coal-fired facility to a combined-cycle facility firing natural gas. The fuel switch resulted in significant plant emission benefits, with emissions of sulfur dioxide decreasing by 99%, nitrogen oxides (NOx) decreasing by 96%, and mercury being eliminated entirely. Plant output increased from a nominal generating capacity of 386 MW to a summer day net output of 472 MW. The three existing coal-boilers were retired. Two F-technology combustion turbine generators (CTGs) and two heat recovery steam generators (HRSGs) were installed. Each CTG fires natural gas with dry low-NOx combustors. Each HRSG includes a selective catalytic reduction (SCR) section supplied with aqueous ammonia. Steam generated from the HRSGs is fed to an existing steam turbine. The low-pressure steam from the HRSG is admitted into the steam turbine through a new connection. The steam turbine extraction lines for feedwater heating are capped. To accommodate the resulting increased flow through the turbine, two rows of blades were replaced. A new full-flow steam turbine bypass system operates during plant startup and shutdown. An auxiliary boiler was added to provide warming and sealing steam to the steam turbine. A new distributed control system (DCS) operates the facility, with workstations located in the plant’s existing control room. The existing once-through circulating water system on the Mississippi River was modified with the addition of wedgewire screens to comply with the Clean Water Act Section 316(b). The CTGs and HRSGs are fully enclosed in a new building that is integrated with the structure for the steam turbine. Due to the proximity of residential housing, sound attenuation is critical. Space for the new building was created by demolishing formerly retired units. Reclaiming this area resulted in a unique layout. The HRSGs are constructed over wood piles installed in 1914–22. The HRSG foundation consists of an elevated slab supported on concrete walls distributing load to the original pile caps. Between the HRSGs and the CTGs are retired concrete coal hoppers that divide the site. The CTGs sit approximately 20 feet higher than the base of the HRSGs. The combined cycle achieved commercial operation on May 1, 2009.

Performance Entitlement of Supercritical Steam Bottoming Cycle

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
S. Can Gülen
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Performance Enhancement ◽  
Combined Cycle ◽  
Cycle Systems ◽  
Steam Boilers ◽  
Potential Impact ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

A supercritical steam bottoming cycle has been proposed as a performance enhancement option for gas turbine combined cycle power plants. The technology has been widely used in coal-fired steam turbine power plants since the 1950s and can be considered a mature technology. Its application to the gas-fired combined cycle systems presents unique design challenges due to the much lower gas temperatures (i.e., 650 °C at the gas turbine exhaust vis-à-vis 2000 °C in fossil fuel-fired steam boilers). Thus, the potential impact of the supercritical steam conditions is hampered to the point of economic infeasibility. This technical brief draws upon the second-law based exergy concept to rigorously quantify the performance entitlement of a supercritical high-pressure boiler section in a heat recovery steam generator utilizing the exhaust of a gas turbine to generate steam for power generation in a steam turbine.

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