HomeMy WebLinkAboutSP 144B; SDG&E Wastewater Facility; Specific Plan (SP) (11)STANFORD RESEARCH INSTITUTE
Menlo Park, California 94025 • U.S.A.
Phase II Report 23 March 1976
EXAMINATION OF STACK EMISSIONS FROM
ENCINA POWER PLANT AND DAMAGE SPOTS
IN TERRAMAR
Prepared by:
E. M. Liston
Prepared for:
San Diego Gas and Electric Company
San Diego, California
SRI Project 4783
Approved by:
R.T.H. Collis, Director
Atmospheric Sciences Laboratory
Ray L. Leadabrand, Executive Director
Electronics and Radio Sciences Division
CONTENTS
LIST OF ILLUSTRATIONS , ill
I INTRODUCTION 1
II SUMMARY 2
Sampling and Analytical Procedure 2
Characteristics of Stack Participates 2
Characteristics of Damage Spots in Terramar 3
Conclusions 3
III CHARACTERISTICS OF PARTICULATE MATTER FROM STACKS . 4
Sampling Procedures 4
Analytical Procedures • • • 5
Properties of the Majority of Particles 5
Properties of Large Particles ....... 6
Corrosive Nature of Large Particles 6
Fallout Velocity of Large Particles 7
IV CHARACTERISTICS OF MATERIAL FROM DAMAGE SPOTS . . 8
Sampling Procedure 8
Analytical Procedures 8
Results of Analyses 9
Interpretation of Results 10
11
LIST OF ILLUSTRATIONS
1. Scanning Electron Micrograph of
Particulate Matter from Encina Stack < 12
2. Automobile Paint — Example One 13
3. Chrome Plated Cover 15
4. Boat Deck 17
5. Paint on Garage Door--Example One 19
6. Paint on Garage Door--Example Two 21
7. Copper Water Pipe—Example One . 23
8. Copper Water Pipe--Example Two 25
9. Automobile Paint--Example Two 27
10. Cement Edge Around Swimming Pool . 29
11. Automobile Paint . . . . . 31
111
I INTRODUCTION
In December 1975 Stanford Research Institute performed a short-term
study for the San Diego Gas and Electric Company. The purpose of that
study was to assess the effects of their Encina Power Plant on the atmo-
spheric concentration of particulates and sulfates, and on any damage to
vegetation in the area.
Based on the data obtained during that study it was concluded that
the macroscale effects of the Encina Power Plant on the atmosphere and
vegetation in the vicinity of the plant are limited in extent and minimal
in significance.
The report on that study was issued on February 5, 1976.
Subsequent to that study of the macroscale effects of the power plant,
SRI was requested to perform an additional study to evaluate the possi-
bility that particles from the stacks were causing damage to paint and
other surfaces on a microscopic or very localized basis.
To perform this study we visited five different locations in the
Terramar area. At each of these locations we located, photographed, and
sampled material from damage spots. The data were analyzed to evaluate
the possibility that the damage was being caused by particles from the
stacks of the Encina Power Plant.
II SUMMARY
Sampling and Analytical Procedure
Four sets of particulate samples were taken and examined:
• Samples were collected on filters inserted into the
stacks. These filter samples collect a broad range
of particle sizes.
• Samples were taken from the stack using a special
probe sampler. This probe was designed to collect
the larger particles primarily.
• Samples of large fallout particles were collected
from employees' automobiles in the parking lot of
the power plant.
• Samples of material were collected from selected
damage spots in the Terramar area.
The collected materials were examined using a variety of techniques
including optical microscopes, a scanning electron microscope, an X-ray
fluorescence probe, neutron activation analysis, an X-ray diffraction
camera, and wet chemical techniques.
Characteristics of Stack Particulates
The vast majority of the particles emitted from the Encina Power
Plant are spherical, porous bodies less than 50 microns in diameter.
They are composed primarily of carbon with varying amounts of iron,
sulfur, and many other elements. The term "cenospheres" has been applied
to these particles.
Approximately one part in 10,000 of the total particulate emissions
from the stack are of particles larger than 100 microns (0.1 mm or
0.004 in). These particles have settling velocities great enough to
make them a potential problem in the Terramar area. For example, a 0.5 mm
(0.02 in) particle would be expected to contact the ground within about
1000 feet of the stack with a 10 mph wind.
It was found that some of these large particles contain iron and
sulfur and are corrosive to steel surfaces under conditions of high
humidity. The corrosion has the same physical appearance as some of the
damage spots in the Terramar area.
Characteristics of Damage Spots in Terramar
Nine different damage spots were selected for examination. These
spots all had the same general appearance, a dark central core surrounded
by a brownish-yellow ring. They were selected because it was suspected
that they might be caused by fallout of large particles from the stacks.
They were found on garage door paint, chrome plating, a plastic boat deck,
automobile paint, a copper water pipe, and cement. In some cases the
damage had penetrated into the material on which the spot was found. In
other cases the damage spot could be completely rubbed off with a finger.
Analysis of the material collected from these spots showed the
presence of cenospheres. The core material was, in general, composed of
iron oxide particles with some sulfur present.
Conclusions
It was concluded that the Encina Power Plant stacks are emitting
some particles that are large enough to impact in the Terramar area.
Some of these particles are corrosive and are probably the cause of some
of the damage spots reported in Terramar.
Ill CHARACTERISTICS OF PARTICULATE MATTER FROM STACKS
Sampling Procedures
Two sets of samples were taken, filter samples and probe samples.
The filter samples were taken by pulling stack gas through a filter paper
supported in a Gooch crucible. This method of sampling captures primarily
the finer particles (less than 50 microns). It is used to obtain large
amounts of material for analytical purposes.
Probe samples were obtained by inserting a one-inch outside-diameter
aluminum tube into the gas stream in the stack. This tube was positioned
so that it was perpendicular to the gas flow and extended about four feet
into the inside of the stack. The surface of the tube was coated with a
layer of heavy silicone grease (Dow Corning High Vacuum Grease). This
grease is very sticky and has a melting point much higher than the
temperature in the stack. Therefore, any particles hitting the grease
will tend to stick to the probe.
The aerodynamics of the probe are such that it captures primarily the
larger particles. The small particles stay entrained in the air stream
as it blows around the tube and do not come in contact with the grease.
Theoretically, a one-inch diameter tube will not collect particles less
than about 10 microns under the conditions in the Encina stacks.
This type of impact sampler should capture all large particles that
come in contact with it. However, during the sampling program it was
noted that there were occasional gouges in the grease. It was also noted
that there were no very-large particles. We believe that any very-large
particles would bounce off of the surface of the tube and not be captured.
Analytical Procedures
Several different analytical procedures were used to determine the
size, shape, physical structures, and chemical composition of the various
particles that were collected:
• A scanning electron microscope (SEM) was used to
determine the shape, size, and physical structure
of the particulate matter.
• An X-ray probe on the SEM was used to determine
the major elements in either single particles or
in clusters of particles.
• An X-ray diffraction camera was used to determine
the crystal structure of one sample.
• Neutron activation analysis was used to perform
elemental analyses of large samples.
• Wet chemical techniques were used to perform total
sulfate analyses of large samples.
Properties of the Majority of Particles
Most of the particles from the stacks were similar to those shown in
Figure 1. They were spherical, porous, and generally under 50 microns
in diameter. They were primarily composed of carbon, plus varying amounts
of iron (4-14%), zinc (0.5-14%), sulfate (20-25%), calcium,. vanadium,
nickel, potassium, sodium, aluminum, silicon, and others. The exact
composition of the particles depends on the source and processing history
of the oil being burned.
The term "cenosphere" is sometimes applied to these particles.
All figures are at the end of this report.
Properties of Large Particles
The data obtained from the probe sampling of the stack and from fall-
out samples indicated that about one part in 10,000 of the total particu-
late matter was present as particles larger than about 0.1 mm (0.004 in).
A few particles were recovered as large as 3 mm (1/8 in). These were
mostly irregular agglomerates of cenospheres.
However, there were a few particles that had distinctly different
characteristics. Under an optical microscope they appeared to be either
an amorphous or a polycrystaline mass of inorganic matter that could have
various colors such as white, yellow, brown, or grey. One sample of this
material, which had a crystalline structure that was observed on several
occasions, was analyzed using an X-ray diffraction camera. It was tenta-
tively identified as (K,Na,Fe)xFe3(S04)3(OH)2'9H20 (Metavoltine). We
believe that, in general, this type of material is a complex mixture of
chemicals containing iron, sulfur, and oxygen. The X-ray probe on the
SEM cannot detect oxygen, so it is very difficult to establish definitely
the composition of the particles.
A second general type of material that was sometimes seen during
optical examination of the particle was a porous mass that had a red-brown
color. X-ray analysis of these samples showed a large amount of iron,
and it is believed that these particles contain some iron oxides.
Corrosive Nature of Large Particles
A few of the unusually large particles discussed in the last section
were placed on a piece of clean cold-rolled steel. This piece of metal
was suspended in a covered glass dish. A small amount of water was placed
in the bottom of the dish to maintain a high humidity atmosphere around
the steel and the particles.
In less than 12 hours a number of the particles had absorbed enough
water to form small puddles around the central particles. In all cases
these deliquescent particles caused corrosion of the steel within the
12-hour period. This corrosion had the appearance of a central black
core surrounded by a ring of yellow. The liquid surrounding the core was
very acid (pH < 3).
Fallout Velocity of Large Particles
The speed with which large particles fall through the air depends on
both their density and their size. We estimate that for particles 0.1 mm
(0.004 in) in diameter the settling velocity is about 0.25 meters/sec
(3/4 ft/sec). For 3 mm (0.12 in) particles the settling velocity is
about 5 meters/sec (15 ft/sec).
A crude estimate of the impact area for these particles can be made
by assuming an effective stack height of 60 meters (200 ft) with a 10-mph
wind (ignoring all aerodynamic effects of the building). A 0.5 mm (0.02 in)
particle carried out of the stack will reach the ground in 40-60 seconds.
This will place it about 600-900 feet from the plant.
IV CHARACTERISTICS OF MATERIAL FROM DAMAGE SPOTS
Sampling Procedure
The damage spots examined in the field were located visually with
the help of a ten-power magnifier. A typical spot had a small black core
surrounded by a brownish-yellow ring. Photographs were taken of the spots
using 1:1 magnification so that the image on the film was the same size as
the spots. The central core was removed with a dental probe and trans-
ferred to a sample holder for the SEM. In some cases, the yellow ring or
the material under the core were also scraped away and transferred to a
sample holder.
Analytical Procedures
Three different analytical procedures were used to analyze these
materials:
• The X-ray probe on the SEM was used to determine the
major elements in the recovered material.
• The SEM was used to determine the shape, size, and
physical structure of the materials.
• Optical microscopes were used to measure the size
of the large particles, to determine the color of
the particles, and to look for cenospheres in the
recovered materials.
Neither neutron activation analysis nor wet chemical analysis were
used on these materials because not enough material was available for
these techniques.
Results of Analyses
Figures 2 through 10 show nine different damage spots. These photo-
graphs show the spots approximately ten times actual size. The cover
sheets for each of these figures give a detailed analysis of the recovered
material.
It should be stressed that these photographs represent a highly
selective sample of damage. These spots were all picked because of their
distinctive dark core surrounded by a brownish-yellow ring. It was
suspected that damage with these characteristics could be caused by
particulate matter from the Encina plant.
In general, the analyses of the damage spots showed the following:
• The X-ray analysis showed that most core materials
were primarily iron with some samples showing
varying amounts of sulfur and other trace elements.
• The SEM showed that most of the core samples were
amorphous with some polycrystaline material. It
was not possible to identify any special crystaline
structure that was useful in identifying the
residual material.
The process of examining a sample with the SEM is
time consuming, so it was only used to search for
cenospheres in the largest pieces of residual
material. In some cases cenospheres could be seen
embedded in the amorphous mass of the main cores.
However, in Figures 9 and 10(b) the cenospheres
could be definitely identified. The samples
showing the cenospheres were actually taken from
different spots than are shown in the color photo-
graphs. However, the SEM photograph in Figure 9
was taken from a damage spot similar to that shown
in the other photographs in Figure 9. The SEM
photograph in Figure 10(b) was taken from the same
swimming pool and in a similar damage spot as that
shown in the photomicrograph in Figure 10(a).
The optical microscope showed that in most cases the
central core was not black; in thick pieces it was
reddish-brown and in thin pieces it was reddish-yellow.
It was found that some of the residual material was
very hard and other material was soft and powder-like.
It was possible to optically identify cenospheres in
all of the samples of material from the damage spots.
Interpretation of Results
We believe that when corrosive, deliquescent particles from the
stacks land on a surface they begin undergoing a daily cycle in which
they absorb water at night and dry out during the day. During this daily
cycle the original iron-containing compounds from the stack slowly oxidize
to form a soluble oxide or hydroxide. When the droplet dries out it
becomes super-saturated with iron oxide which then deposits on the original
core material. This deposition leads to the amorphous appearance of the
residual core material and to the X-ray analysis showing primarily iron.
The X-ray beam can only penetrate about one micron so it cannot show the
composition of any material inside the outer layer of oxide on the core.
This iron oxide will also deposit on the material on which the core landed
and form a circular ring with the characteristic reddish-yellow color of
iron oxide.
If the material on which the particle lands can be attacked by the
corrosive solution from the particle (for example, paint or steel) the
corrosion will occur whenever the particle is wet. In some cases the
corrosion will continue after the original particle is removed. For
example, Figure 11 shows the paint on an automobile. In this case there
was evidence that particles had landed on the paint because there was a
residual yellow stain. However, when the photograph was taken the
original core material was gone. In this case, it appeared that the
corrosion was started by the core particle and continued under the action
of salt spray long after the original core was removed.
10
It is not possible to identify with certainty the origin of any
specific corrosive particle because the nature of the corrosion process
changes the chemical and physical characteristics of the particle.
11
Figure 1
SCANNING ELECTRON MICROGRAPH (x 1000)
OF PARTICULATE MATTER FROM ENCINA STACKS
Figure 2
SURFACE: Automobile Paint
CORE SIZE: 0.25 x 0.6 mm (0.01 x 0.024 in)
X-RAY ANALYSIS: Iron (probably oxide)
SEM ANALYSIS: Polycrystaline (non-specific) and
amorphous
OPTICAL ANALYSIS: Massive dark red-brown. Thin sections
are reddish-yellow. Cenospheres present,
COMMENTS: Paint soft underneath.
13
Try^TJ
A' ' ' * «• *»' ' •* '• *^ • »
.
ORIGINAL
•
•
.* „
^W*$$bvw'*
CORES REMOVED
Figure 2
AUTOMOBILE PAINT
Figure 3
SURFACE: Chrome plated anchor chain cover on boat
CORE SIZE: 0.5 mm (0.02 in)
X-RAY ANALYSIS: Cores lost
SEM ANALYSIS: Cores lost
OPTICAL ANALYSIS: Cores lost
COMMENTS: Note the slight discoloration remaining at the
original sites after the cores were removed
and the surface was rubbed.
15
ORIGINAL
DAMAGE SPOTS REMOVED
Figure 3
CHROME PLATED SURFACE
Figure 4
SURFACE:
CORE SIZE:
X-RAY ANALYSIS:
SEM ANALYSIS:
OPTICAL ANALYSIS;
COMMENTS:
Boat deck (dimpled plastic)
0.6 mm (0.024 in)
Iron (probably oxide) with a little
aluminum silicate.
Amorphous, possibly some cubic crystals,
Possible cenospheres.
Massive dark red-brown, thin sections
reddish-yellow. Embedded cenospheres.
This core was firmly attached. It was
in a depression that could have caught
and held water or dew.
17
**£*»ORIGINAL
r •
-
...
^£
CORE
REMOVED
'* V*
"'"'SUB-CORE
MATERIAL
PARTIALLY
SCRAPED AWAY
Figure 4
PLASTIC BOAT
DECK
Figure 5
SURFACE: Paint on garage door
CORE SIZE: 1.25 x 1.0 mm (0.05 x 0.04 in)
X-RAY ANALYSIS: Iron (probably oxide) with paint
remnants.
SEM ANALYSIS: Amorphous. Possibly some embedded
cenospheres.
OPTICAL ANALYSIS: Massive dark red-brown. A few
cenospheres visible on edges.
COMMENTS: Paint very soft beneath core.
Garage door often left open (up)
which presented a horizontal surface
to fall-out.
19
Kfi-frrs.• ,'-•
fr.+mtmz:&
ORIGINAL
CORE
REMOVED
SUB-CORE
MATERIAL
PARTIALLY
SCRAPED AWAY
Figure 5
GARAGE PAINT
Figure 6
SURFACE: Paint on garage door
CORE SIZE: 0.25 x 0.5 mm (0.01 x 0.02 in)
X-RAY ANALYSIS: Iron (probably oxide)
SEM ANALYSIS: Amorphous mass with some flakes
OPTICAL ANALYSIS: Massive dark red-brown. Particles
too dense to definitely identify
cenospheres.
COMMENTS: Paint very soft beneath core.
21
'-- -•' - - • -• '/,j
ORIGINAL
--.
CORE REMOVED
Figure 6
GARAGE PAINT
Figure 7
SURFACE:
CORE SIZE:
X-RAY ANALYSIS:
SEM ANALYSIS:
OPTICAL ANALYSIS:
COMMENTS:
Copper water pipe
0.6 mm (0.024 in)
Copper, chlorine, trace of iron
Amorphous
Large number of cenospheres.
Note yellow iron oxide stain
under cores.
Absence of iron in X-ray analysis
may be due to selection of analysis
location.
23
ORIGINAL
CORES REMOVED
Figure 7
COPPER WATER PIPE
Figure 8
SURFACE:
CORE SIZE:
X-RAY ANALYSIS:
SEM ANALYSIS:
OPTICAL ANALYSIS:
COMMENTS:
Copper water pipe
1.25 x 0.75 mm (0.05 x 0.03 in)
Core lost
Core lost
Core lost
Note yellow iron oxide stain
under core and red copper oxide (ous)
under black copper oxide surface
flake (ic).
25
ORIGINAL
CORE AND FLAKE REMOVED
Figure 8
COPPER WATER PIPE
Figure 9
SURFACE:
CORE SIZE:
X-RAY ANALYSIS:
SEM ANALYSIS:
OPTICAL ANALYSIS:
COMMENTS:
Automobile paint
Approximately 0.6 mm (0.024 in)
(On similar specimen) Sulfur,
with small amounts of iron, nickel.
(On similar specimen) Positive
identification of cenospheres.
Cenospheres present.
After spots were rubbed with a
finger some disappeared completely,
some left a dull spot on paint.
27
ORIGINAL
CORE
REMOVED
SCANNING
ELECTRON
MICROPHOTO-
GRAPH OF
CORE
MATERIAL
Figure 9
AUTOMOBILE
PAINT
Figure 10
SURFACE:
CORE SIZE:
X-RAY ANALYSIS:
SEM ANALYSIS:
OPTICAL ANALYSIS:
COMMENTS:
Cement edge around swimming pool
(Various) 0.5 mm (0.02 in)
Iron and sulfur with traces of
cement.
(On similar specimen) positive
identification of cenospheres.
(see Figure 10A)
Some cenospheres.
It is very difficult to remove
samples from this porous cement
surface without destroying the
fragile spheres.
29
Figure 10(a) '
CEMENT AROUND SWIMMING POOL
Figure 10(b)
SCANNING ELECTRON-PHOTOMICROGRAPH
OF CORE MATERIAL FROM SWIMMING POOL
Figure 11
SURFACE: Automobile paint
COMMENTS: Note the darker yellow stains
in the damage spots in the center
of the close-up photograph.
31
. ,'
Figure 11
AUTOMOBILE PAINT