The Greenhouse Effect

The Greenhouse Effect CE 326 Principles of Environmental Engineering Prof. Tim Ellis January 26, 2009

Greenhouse Effect • Greenhouse effect: n_______ effect of the gases in earth’s atmosphere to trap incident solar radiation • earth is an average of ____ ̊C warmer than if no greenhouse effect • average earth temp would be ____ ̊C instead of current ____ ̊C

Global Warming • Global warming: t_______ that the accumulation of specific gaseous compounds is causing an uncontrollable increase in the earth’s temperature with potentially devastating g_______ effects

What is Known • naturally occurring greenhouse gases include w______ vapor, carbon dioxide, methane, nitrous oxide, and ozone • concentrations of most are increasing due to a______________ sources • water vapor is the most a__________ greenhouse gas, but its concentrations are closely related to global temperatures and are relatively constant • P_________ of high concentrations of CO2 in past history of the Earth have been accompanied by high temperatures at the Earth’s surface, and periods of low carbon dioxide had relatively low surface temperatures. http://www.meteor.iastate.edu/gccourse/model/co2/seedsci.html

What is known • sea level has risen 4-8 inches over the past century • global mean surface temperatures have increased 0.25-0.5 C since the late 19th century • Greenhouse gases have long lifetimes, ranging from ____ years for methane to about _____ for carbon dioxide to ______ years for nitrous oxide. • Anthropogenic increases in these gases could influence the earth’s climate for many centuries. • The climate system has high i_______, primarily due to the long time scales of ocean dynamical processes. http://www.meteor.iastate.edu/gccourse/model/co2/seedsci.html

What is known • S__________ particles that form from sulfur dioxide emitted primarily by the burning of coal contribute to local cooling although the magnitude is uncertain. • Decreases of ozone in the lower stratosphere have contributed to c_______ effects in that region. http://www.meteor.iastate.edu/gccourse/model/co2/seedsci.html

What we think will happen • the stratosphere will continue to c_____ as CO2 concentrations r____. Ozone depletion will add to the cooling. • water vapor in the lower troposphere (0-3 km) will increase about ____% for every 1oC of warming. Relative humidities will stay approximately the same. • The warming of the last c_______ is consistent with model projections of global warming due to CO2 modified by the regional cooling effect of sulfate particles. http://www.meteor.iastate.edu/gccourse/model/co2/seedsci.html

What we think will happen • D_________ of CO2 over pre-industrial levels (likely to occur in the later half of the 21st century unless emissions are significantly reduced) is projected to lead to a global warming of 1.5 to 4.5oC (2 - 8oF). • by 2100 we can expect temperature increase of _____oC to ____ oC. • Sea-level rise is most likely to be ___ (+/-25) cm by year 2100 with continued rise beyond that time highly likely. Continued high (quadrupled) CO2 could lead to ___+/- m rise in sea level. • Global mean precipitation will increase at ____ (+/-0.5)% per 1oC of warming. http://www.meteor.iastate.edu/gccourse/model/co2/seedsci.html

Is there a scientific debate over man-made global warming?

Water vapor constitutes Earth's most significant greenhouse gas, accounting for about 95% of Earth's greenhouse effect.

Melting the ice cap was a “solution”

Air Pollution Control Devices • A________ tower • B__________ • C____________ Separator • aD___________ Bed • E______________ precipitator • V___________ scrubber

Air Pollution Control Devices • Absorption Tower (Packed Bed, Spray Tower, Wet Scrubber) • D________ of the pollutant gas to the surface of the liquid • T_______ across the gas/liquid interface (dissolution) • D_______ of the dissolved gas away from the interface into the liquid • Henry’s law: P = HCl • where: P = equilibrium partial pressure of gas, kPa, H= Henry's law constant, kPa⋅m3/g and Cl = concentration of pollutant gas in liquid phase, g/m3 • want to maximize gas liquid contact by maximizing surface area • efficiency will be limited by the solubility of the pollutant

Baghouse • same principle as the h_____ v______ c_______ • bags are cleaned periodically as the p______ d___ across the bag becomes excessive (approximately every 2 hours) • cleaned by mechanical r_________ (used for shake-deflate design) • cleaned by h____ p_________ air jets (used for pulse jet design) • must be a d____ gas stream • potential f____ hazard • bag "r______" with time • develops a fine mat which helps to screen out particles • for p________ removal, or used in conjunction with F____ G____ D_____________ (FGD) applications

Cyclone Separator • used for particulates larger than ___ μm • gas stream is accelerated through a s___ m_____, centrifugal force moves heavier particles out and down • as the d_____ of the cyclone is reduced, the efficiency increases (as does the pressure drop) • use of m________ tubes in parallel (multiclones) improves efficiency

Adsorption Bed • surface p__________ • p______ or c________ bond with the surface • adsorbents: activated c_____, activated a_____, silica gel, and others • 1 ounce of activated carbon has a surface area of ______ acres • bed must be r________ prior to breakthrough

Electrostatic Precipitator • w____ in t____ or wire and p____ configurations • wet or dry, wet cleaned by w______ s____, dry by rapping, can be cleaned while in service • c_______ wire imparts an electrical charge (neg), particles are attracted to charged (pos) collecting plates • high p__________ removal efficiencies possible

Venturi Scrubber • velocity of gas is a_________ by a factor of four in the throat section where nozzles inject water or solution • high velocity causes a__________ of liquid • pressure drop following the t________ section creates a lot of turbulence resulting in good intermixing • requires s_________ (e.g., cyclone) following venturi to collect particles and liquid

T___________ Incineration

The Greenhouse Effect