the gas turbine - power & compression systems inc. · web viewthe affects of the environment on...

Power & Compression Systems

THE GAS TURBINE

and

THE ENVIRONMENT

AboutThe Instructor:Tony Giampaolo, P.E. is president of Power & Compression Systems, an engineering company providing custom designed control systems, design audits, feasibility studies, field test, and forensic engineering for engines, turbines, compressors, and control systems in simple and cogeneration cycle applications. Giampaolo has written a book "The Gas Turbine Handbook: Principles and Practices" and articles for Oil & Gas Journal, Diesel & Gas Turbine Worldwide, and Western Energy Magazines. He is a registered professional engineer in California, Florida, and Ohio, holding both Bachelor and Master of Science Degrees in Mechanical Engineering. He has been a part-time faculty member at California State University.

P.O. Box 3028, Mission Viejo, CA 92690 Phone (949)582-8545 Fax (949)582-8992

PO Box 3028, Mission Viejo, CA 92690 Phone (949)582-8545 Fax (949)582-89921


CONTENTS

Introduction

Define Environment

Define Gas Turbine

Large, Medium, & Small (Micro-Turbine <100kw)

Gas Turbine's Impact On The Environment

Air Pollution

Noise Pollution

Environment's Impact On The Gas Turbine

Compressor Fouling

Turbine Erosion & Corrosion

Gas Turbine Applications Under Deregulation



IntroductionThe affects of the environment on the gas turbine and the efforts to reduce the gas turbine's impact on the environment have a major impact on the expense of operating and maintaining a gas turbine.

This presentation addresses the impact gas turbines have on the environment and conversely the impact the environment has on gas turbines. Emissions will be discussed relative to natural sources of airborne contaminants, firing temperature, and fuel choice. Also, techniques to reduce emissions in the combustor and turbine exhaust will be examined. The impact of the environment on the gas turbine will focus on monitoring and controlling the quality, temperature, and relative humidity of the inlet air. How these affect unit performance, efficiency and fuel consumption will be weighed.

Both large and small-scale gas turbines will be important power sources throughout the next 100-to-200 years. To ensure continued acceptance, emissions must be eliminated or significantly reduced, component life must be increased, and operating cost must be reduced. Some of the techniques to achieve these goals will be addressed.

The information discussed in this presentation is excerpted from my book "The Gas Turbine Handbook: Principles & Practices", available through The Fairmont Press, Inc.



EnvironmentThe Environment is all of the external factors, such as water, soil, climate, light, and oxygen affecting an organism. Specifically, in our case, it is the atmosphere or the ocean of air we live in.

Atmosphere is defined as a mixture of gases surrounding any celestial object that has a gravitational field strong enough to prevent the gases from escaping. The principal constituents of our atmosphere on earth are nitrogen (78 percent) and oxygen (21 percent). The atmospheric gases in the remaining 1 percent are argon (0.9 percent), carbon dioxide (0.03 percent), varying amounts of water vapor, and trace amounts of hydrogen, ozone, methane, carbon monoxide, helium, neon, krypton, and xenon.

Greenhouse Effect describes the role the atmosphere plays in insulating and warming the earth's surface. The atmosphere is largely transparent to incoming short-wave solar radiation, which is absorbed by the earth's surface. Much of this radiation is then reemitted from the earth at infrared wavelengths, but it is reflected back to the earth by gases such as carbon dioxide, methane, nitrous oxide, and ozone in the atmosphere. The reflected radiation maintains the temperature of the earth in a range that is hospitable to life. This heating effect is the basis of the theories concerning global warming.

The amount of carbon dioxide in the atmosphere has been increasing by 0.4 percent a year1 because of the use of fossil fuels such as oil, gas, and coal. The clearing of tropical forests has also been a contributing factor. Other gases that contribute to the greenhouse effect, such as methane and chlorofluorocarbons, are increasing even faster. The net effect of these increases could be a worldwide rise in average global temperature of 1.0° to 3.5° C (1.8° to 6.3° F), with a best estimate of 2.0° C (3.6° F), by 2100. Warming of this magnitude would alter climates throughout the world, affect crop production, and cause sea levels to rise significantly. If this happened, millions of people would be adversely affected by major flooding.2

Note:

1 cubic meter = 35.3 cubic feet1 milligram (1mg) = 0.00004 oz. (0.4x10-4)1 microgram (1g) = 0.00000004 oz (0.4x10-7)

1 Note: 0.4% of 0.03% = 0.00012% increase per year2"Greenhouse Effect," Microsoft® Encarta® 97 Encyclopedia. © 1993-1996 Microsoft Corporation. All rights reserved.



DIVISIONS OF THE ATMOSPHERE



MAJOR AIR POLLUTANTS

Major Air PollutantsSources of major air pollutants include individual actions, such as driving a car, and industrial activities, such as manufacturing products or generating electricity. Note: 1 cubic meter (1m3) is equal to 35.3 cu ft; 1 milligram (1 mg) is equal to 0.00004 oz; 1 microgram (1µg) is equal to 0.00000004 oz.



Define Gas Turbine

Gas Turbine is an engine that employs gas flow as the working medium by which heat energy is transformed into mechanical energy. Therefore, all gas turbines are gas generators. Gas turbines are often classified by their physical size, by the amount of power they produce, by their design criteria, or by their originally intended or modified use. Therefore, we have aircraft or jet engines and aero-derivatives describing engines originally built for flight applications and modified for stationary, land based applications; and we have industrial engine designs that are similar to steam turbines - these are often identified as "heavy industrial" gas turbines. This was the design that existed in the first quarter of this century. It was this gas turbine design that Dr. W.J. Stern, then Director of the South Kensington Laboratory declared "unworkable" as a power source for British fighter aircraft. Several years later Frank Whittle demonstrated a workable lightweight gas turbine and became the Father of the modern jet engine (he shares this honor with Hans Pabst von Ohain who developed a similar engine for Germany at approximately the same time).

Large, Medium, & Small (Micro Turbine <100kW)



Gas Turbine's Impact on the Environment

Air pollutionNOx, CO, NMHC

Noise pollution



AIR POLLUTION

CONTAMINATION OF THE AIR

IN LARGE ENOUGH CONCENTRATION,

FOR A SUFFICIENTLY LONG TIE,

TO CAUSE DAMAGE OR UNREASONABLE

INTERFERENCE WITH LIFE AND PROPERTY



NATURAL & MAN-MADE SOURCES OFATMOSPHERIC CONTAMINANTS

Emission Natural - kg/yr Man-Made - kg/yr Ratio Natural/Man Made

Reference

Hydrocarbons

Carbon Monoxide

Sulfur Oxides

Nitrogen Oxides

159x109

3.2x1012

415x109

45x1010

24x109

0.24x1012

139x109

4.5x1010

6

13

3

10

5

7

5,9,10

6,3

RESIDENCE TIME OF ATMOSPHERIC

TRACE ELEMENTS

Emissions Life Reference

CO 1-3 years 4

NO 1/2 - 1 day 6

NO2 3-5 days 6

HC (AS CH4) 1.5 years 4

SOX 3 - 4 days 6

P-M hours to days (troposphere)

days to years (stratosphere)

8

References:

(3) Abatement of Nitrogen Oxides Emissions for Stationary Sources”, National academy of Engineers (1972)(4) “Carbon Monoxide: Natural Sources Dwarf Man’s Output”, T.N. Maugh II (1972)(5) “Atmospheric Chemistry: Trace Gases and Particulates”, W.H. Fisher (1972)(6) “Emissions, Concentrations, and Fate of Gaseous Pollutants”, R. Robinson, R.C.

Robbins(1971)(7) The Sulfur Cycle”, W.W. Kellogg (1972)(8) “Physical Climatology”, W.D. Sellers (1965)(9) Ground Level Concentrations of Gas turbine Emissions”, H.L. Hamilton, E.W.

Zeltman (1974)(10) Air Quality Standards National and International”, S. Yanagisawa, (1973)



GAS TURBINE EXHAUST PRODUCTS

FROM

HYDROCARBON FUEL COMBUSTION IN DRY AIR

CONSTITUENT % BY WEIGHT REMARKS

N2 - Nitrogen 74.16 Mostly inert, from atmosphere

O2 - Oxygen 16.47 From excess air

CO2 - Carbon Dioxide 5.47 Product of complete combustion

H2O - Water 2.34 Product of complete combustion

A - Argon 1.26 Inert, from atmosphere

UHC - Unburned Hydrocarbons trace Product of incomplete combustion

CO - Carbon Monoxide trace Product of incomplete combustion

NOx - Oxides of Nitrogen

Thermal

Organic

trace

From fixation of atmospheric N2

From fuel bound nitrogen

SOx - Oxides of Sulfur From Sulfur in fuel



SCAQMD Environmental Rules & Regulations

Rule 1110.2Owners/operators of stationary engines with an amended Rule 1110.1 Emission Control Plan submitted by July 1, 1991, or an Approved Emission Control Plan, designating the permanent removal of engines or the replacement of engines with electric motors, in accordance with subparagraph (d) (1)(A), shall do so by December 31, 1999, or reduce the emissions from the engines to the limits listed in Table VI in accordance with the following schedule:

(i) By January 1, 1999, submit applications for permit to construct and permit to operate the engines and control equipment; (ii) By September 30, 1999, initiate control equipment installation; and (iii) By December 31, 1999, have the engine under compliance.

TABLE VIALTERNATIVE TO ELECTRIFICATION

NOx VOC CO 0.15 g/bhp-hr 0.15 g/bhp-hr 0.6 g/bhp-hr



SCAQMD Environmental Rules & Regulations

Rule 1134

(c) Emissions Limitations 1. The operator of any stationary gas turbine unit shall not operate such unit under

load conditions, excluding the thermal stabilization period or other time period specified in the Permit to Construct or the Permit to Operate issued prior to August 4, 1989, which result in the discharge of oxides of nitrogen (NOx) emissions, directly or indirectly, into the atmosphere at concentrations in excess of the following as measured pursuant to subdivision (e):

Compliance Limit = Reference Limit x EFF/25%

Where: Compliance Limit =

allowable NOx emissions (ppm by volume).

Reference Limit = the NOx emission limit (ppm by volume) is corrected to 15 percent oxygen on a dry basis, and averaged over 15 consecutive minutes. These limits for various megawatt ratings (continuous rating by the manufacturer without power augmentation) are as follows:

REFERENCE NOx LIMITS, PPM Unit Size

Megawatt (MW) Rating Effective

12-31-950.3 to Less Than 2.9 MW 252.9 to Less Than 10.0 MW 92.9 to Less Than 10.0 MW No SCR 1510.0 MW and Over 910.0 MW and Over No SCR 1260 MW and Over Combined Cycle No SCR 1560 MW and Over Combined Cycle 9

Effective 4/11/972.9 to Less Than 10.0 MW Utilizing Fuel Containing a Minimum of 60% Sewage Digester Gas by Volume on a Daily Average

25



Oxides of Nitrogen Emissions:

Oxides of nitrogen are produces primarily as nitric oxide (NO) in the hotter regions in the combustion reaction zone of the combustor.

Nitrogen oxides (NOx), found in the exhaust, are the products of the combustion of hydrocarbon fuels in air.

In this process nitrogen oxides are formed by two mechanisms: a) Thermal NO, and b) Organic NO

The predominant mechanism in the formation of NOx in gas turbine combustors

depends on such conditions as

the reaction temperature,

the resident time at high temperature,

the fuel/air ratio in and after the combustion reaction zone,

the fuel composition (the fuel bound nitrogen {FBN} content),

the combustor geometry, and

the mixing pattern inside the combustor



Oxides of Nitrogen Emissions:

Thermal NO produced in the hottest regions of the combustor extremely temperature dependent

Organic NO formed during combustion by chemical combination of the nitrogen

atoms, which are part of the fuel molecule and the oxygen in the air

The amount of Organic NO produced is affected by

the nitrogen content of the fuel,

a yield factor (a measure of FBN),

the fuel/air ratio, and

abatement techniques such as water injection.



SELECTIVE CATALYTIC REDUCTION

NOx is removed from the exhaust gas stream by the injection of ammonia (NH3) into the stream and the subsequent chemical reaction in the presence of a catalyst.

For a given gas condition (temperature, gas composition, etc.) the performance of the SCR is a function of the catalyst type and geometry, the residence time of the gas in the reactor, and the amount of ammonia injected upstream of the reactor.

Selection of the catalyst is specific to the temperature in which it is expected to operate.

The ammonia utilized in the process may be either anhydrous or aqueous.



Noise PollutionGas turbines are inherently noisy machines. Air rushing into the front of the compressor and exhaust gases rushing out of the turbine generates some of the noise. Another source of noise is the interaction between each moving airfoil and each stationary airfoil and strut. Noise levels generated by a gas turbine exceed the safe levels and must be attenuated.



Environment's Impact On the Gas Turbine

Airborne Contamination (salts, sand, dust, etc)

These have a detrimental impact on the compressor and the turbine Compressor Fouling Turbine Erosion & Corrosion

Ambient Temperature

The gas turbine is very sensitive to temperature. As temperature increases above 60 degrees F, gas turbine power decreases.

In some cases this power loss can be recovered by employing inlet air cooling (either evaporative cooling or refrigerated inlet air).



ENVIRONMENTAL CONDITIONS

Desert - sand, salt, dust Coastal - salt Agricultural - dust, pollen, chemicals (fertilizers) Arctic - snow, ice.

CONTAMINATIONS LEVELS

>5.0um dust, rain, fog, chemicals, minerals & metals 1-2um dust, salts, fog, soot, chemicals, minerals &

metals 0.3-0.5um hydrocarbon emissions, smog.



FILTER TYPES

Inertial Separators with & without dust removal capability

Prefilters similar in purpose to the inertial separator

Intermediate Filters with & without viscous coating

High Efficiency Filters

Cannister Filters with & without self-clean feature, and with & without prefilters



FILTRATION PROBLEMS

The filter may not be properly installed,

The wrong type of filter media may have been installed,

The filter element may not be properly maintained,

The filter plenum may not be properly maintained,

The operating environment has changed since the unit was installed.



FACTORS AFFECTING FILTER PERFORMANCE

AIR VELOCITY THROUGH THE FILTER

FILTER MEDIA'S ABILITY TO TOLERATE MOISTURE

AIR LEAKS AROUND THE DOORS AND WINDOWS



HOW TO IMPROVE FILTER PERFORMANCE

SET A TARGET FOR DELTA-P

LOAD FILTER TO THE “-P” TARGET

USE PREFILTER WARP (AFTER “-P” IS REACHED)

TO

EXTEND TIME AT THIS LEVEL OF FILTER

EFFICIENCY.

ELIMINATE THE USE OF MANUAL

OPERATION OF SELF-CLEAN SYSTEM.



COMPRESSOR FOULING

2% DROP IN c = (CDP/Pinlet)K-1/K - 1(T2/TA)-1

2% DROP CDP AT CONSTANT SPEED AND LOAD

3~5% REDUCTION IN LOAD CAPACITY PLUS A ONEPSIG DECREASE IN CDP AT CONSTANT CIT

CARBO BLAST*

WATER WASH CLEANING AGENTS

SOAP SOLUTION



Gas Turbine Applications under Deregulation

Power Generation Electric Mechanical Drive (compressors, pumps, etc.)

Waste Heat RecoveryCogeneration

Heating and/or coolingCombined Cycle

Power GenerationWhere Applied:

Central Power Plant On-Site Power Production

"Up to 20% (or 1300megawatts) of California's power forecasted demand of 6500MW by the year 2005 is projected as being potentially met by distributed generation".3

"EPRI projects the distributed energy resources up to 5 megawatts in size will meet 20% to 30 % of the nations demand over the next 20 years."4

Over the next 10 years utilities will shutdown nearly 20 GW of nuclear capacity that will have reached the end of its life. Gas turbine based combined-cycle units will probably replace many of those retired nuclear units.5

85% of our electrical outages occur due to transmission and distribution network problems.6

The cost of new transmission is approximately $1,000,000 a mile.7

For on-site applications to be successful they must be less expensive to install and operate than the alternative of purchasing power (or heat).

These new gas turbines must be more efficient and produce less contaminants. More efficient units will burn less fuel, and generate less CO2 per unit of power produced.

3 California Manufacturer Article "What's In It For You" by Eric Wong, Spring 19974 California Manufacturer Article "What's In It For You" by Eric Wong, Spring 19975 "Combustion Turbines Move Markets", by Jonh C. Zink, PH.D., P.E., Power Engineering, March 19986 California Manufacturing Article "What's In It For California" by Tom Tanton, Spring 19977 "A Regulator's perspective on Distributed Resources", by Renz D. Jennings, CADER 1997 distributed Resources Conference September 15, 1997.



Gas Turbine ApplicationsGeneral

Power Generation Electric Mechanical Drive (compressors, pumps, etc.)

Waste Heat RecoveryCogeneration

Heating and/or coolingCombined Cycle

Power Generation

Gas Turbine Applications after Deregulation

On-Site Power Production up 20%-30%Provided by Units under 5 MW

SCAQMD Environmental Rules & RegulationsRule 1110.2Owners/operators of stationary engines with an amended Rule 1110.1 Emission Control Plan submitted by July 1, 1991, or an Approved Emission Control Plan, designating the permanent removal of engines or the replacement of engines with electric motors, in accordance with subparagraph (d) (1)(A), shall do so by December 31, 1999, or reduce the emissions from the engines to the limits listed in Table VI in accordance with the following schedule:

(i) By January 1, 1999, submit applications for permit to construct and permit to operate the engines and control equipment; (ii) By September 30, 1999, initiate control equipment installation; and (iii) By December 31, 1999, have the engine under compliance.




NOx VOC CO0.15 g/bhp-hr 0.15 g/bhp-hr 0.6 g/bhp-hr

SCAQMD Environmental Rules & Regulations, Rule 1110.2


NOx VOC CO0.15 g/bhp-hr 0.15 g/bhp-hr 0.6 g/bhp-hr

SCAQMD Environmental Rules & Regulations, Rule 1110.2

SCAQMD Environmental Rules & RegulationsRULE 1134(c) Emissions Limitations

2. The operator of any stationary gas turbine unit shall not operate such unit under load conditions, excluding the thermal stabilization period or other time period specified in the Permit to Construct or the Permit to Operate issued prior to August 4, 1989, which result in the discharge of oxides of nitrogen (NOx) emissions, directly or indirectly, into the atmosphere at concentrations in excess of the following as measured pursuant to subdivision (e):

Compliance Limit = Reference Limit x EFF/25%

Where: Compliance Limit = allowable NOx emissions (ppm by

volume).Reference Limit = the NOx emission limit (ppm by volume)

is corrected to 15 percent oxygen on a dry basis, and averaged over 15



consecutive minutes. These limits for various megawatt ratings (continuous rating by the manufacturer without power augmentation) are as follows:

REFERENCE NOx LIMITS, PPM Unit Size

Megawatt (MW) Rating Effective 12-31-95

0.3 to Less Than 2.9 MW 252.9 to Less Than 10.0 MW 92.9 to Less Than 10.0 MW No SCR 1510.0 MW and Over 910.0 MW and Over No SCR 1260 MW and Over Combined Cycle No SCR 1560 MW and Over Combined Cycle 9

Effective 4/11/97

2.9 to Less Than 10.0 MW Utilizing Fuel Containing a Minimum of 60% Sewage Digester Gas by Volume on a Daily Average

25

REFERENCE NOx LIMITS (PPM)

Unit Size Megawatt (MW) Rating

Effective 12-31-95

0.3 to Less Than 2.9 MW 252.9 to Less Than 10.0 MW 92.9 to Less Than 10.0 MW No SCR 1510.0 MW and Over 910.0 MW and Over No SCR 1260 MW and Over Combined Cycle No SCR 1560 MW and Over Combined Cycle 9

Effective 4/11/97

2.9 to Less Than 10.0 MW Utilizing Fuel Containing a Minimum of 60% Sewage Digester Gas by Volume on a Daily Average

25

SCAQMD Environmental Rules & Regulations, RULE 1134


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