U.S. patent number 3,854,881 [Application Number 05/179,964] was granted by the patent office on 1974-12-17 for apparatus for determining organic carbon content of polluted liquids.
Invention is credited to Alfred Cohen.
United States Patent |
3,854,881 |
Cohen |
December 17, 1974 |
APPARATUS FOR DETERMINING ORGANIC CARBON CONTENT OF POLLUTED
LIQUIDS
Abstract
Apparatus for determining the organic carbon content of a liquid
sample whereby the sample is acidified and scrubbed to remove its
inorganic carbon content, and then vaporized in a reaction chamber
having an air atmosphere which oxidizes to carbon dioxide the total
organic carbon content of the sample. Measurement of the amount of
carbon dioxide formed from the organic carbon is effected by an
infrared analyzer.
Inventors: |
Cohen; Alfred (Woodbury,
NY) |
Family
ID: |
22658725 |
Appl.
No.: |
05/179,964 |
Filed: |
September 13, 1971 |
Current U.S.
Class: |
422/79;
436/146 |
Current CPC
Class: |
G01N
31/005 (20130101); G01N 33/1846 (20130101); Y10T
436/235 (20150115); B01J 2208/00407 (20130101); B01J
2208/0053 (20130101) |
Current International
Class: |
G01N
33/18 (20060101); G01N 31/00 (20060101); B01j
009/02 (); G01n 031/12 (); G01n 033/18 () |
Field of
Search: |
;23/23PG,253PC,284,277R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reese; Robert M.
Claims
What is claimed is:
1. In an analytical apparatus for determining the total quantity of
organic carbon as a pollutant in an aqueous stream by vaporizing a
sample taken from the stream and oxidizing to carbon dioxide the
total organic carbon in the sample, the determination being on the
basis of the measure of carbon dioxide formed per unit measure of
the sample, the improvement which comprises a mixing chamber, a
first metering pump disposed to deliver into said mixing chamber a
continuous flow sample taken from the stream, a second metering
pump disposed to deliver into said mixing chamber a continuous flow
of liquid reagent for reaction therein with the sample to remove
the inorganic carbron content thereof as carbon dioxide; a reaction
chamber, means connected to said mixing chamber and to said
reaction chamber to deliver from said mixing chamber into said
reaction chamber a continuous flow aqueous sample to be analyzed
and which is substantially free of inorganic carbon and carbon
dioxide, said reaction chamber having an inlet for introducing the
aqueous sample to be analyzed and an outlet for the exit of gaseous
and vapor products formed from such sample, means for introducing
air into said reaction chamber to establish an oxidizing atmosphere
therein, a packing material disposed within said reaction chamber
for heating the sample introduced, and means for heating said
packing material to a temperature at which the organic carbon in
the sample is oxidized to carbon dioxide by said atmosphere, said
packing material being disposed to define within the reaction
chamber an inlet plenum zone communicating with said inlet to
accommodate preheating of the sample by the packing material
without contact therewith, and an outlet plenum zone separated from
said inlet plenum zone and communicating with the outlet to collect
and deliver thereto the gaseous and vapor products from the sample,
said outlet plenum zone being communicated with said outlet by a
conduit extending through said packing material.
2. The improvement according to claim 1 including a conduit
extending outside the reaction chamber and communicating with an
air supply means and said inlet for introducing air therethrough
along with the sample.
3. The improvement according to claim 1 wherein the means for
heating said packing material is disposed outside the reaction
chamber.
4. The improvement according to claim 1 wherein said packing
material is crushed quartz and occupies at least 50 percent of the
reaction chamber volume.
5. The improvement according to claim 1 wherein said inlet plenum
zone is at one end of the reaction chamber and said outlet plenum
zone is at the opposite end of the reaction chamber, and said
packing material contains voids accommodating the flow therethrough
to the outlet plenum zone of the gaseous and vapor products of the
sample.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
In the measurement of pollution levels in aqueous systems, the
amount of organic carbon in a sample taken from the liquid source
to be monitored is an important index of the existing pollution
level.
Accordingly, there is a need for equipment and methods that enable
rapid and accurate determination of the organic carbon content of a
liquid on a continuous or quasi-continuous sampling basis. One
rather elaborate apparatus for total carbon analysis is described
in U.S. Pat. No. 3,296,435 issued on Jan. 3, 1967 to J. L. Teal et
al.
The invention provides an improved apparatus and a method for
performing total organic carbon analyses more efficiently and
rapidly than can be done with either the standard laboratory
five-day biochemical oxygen demand test ( B O D ), or the two-hour
chemical oxygen demand test, ( C O D ).
In the analytical apparatus of the invention, a sample stream from
the aqueous liquid source to be monitored is continuously fed into
a mixing chamber together with sufficient acid to react with and
remove as carbon dioxide all of the inorganic carbon content of the
sample, i.e. the carbonates in the sample. The acidified sample is
scrubbed to remove all carbon dioxide produced by the
carbonate-acid reaction, and the carbonate-free sample is metered
into a reaction chamber. The reaction chamber has an inlet through
which the sample and air for oxidizing the organic carbon of the
sample are introduced; an outlet for the exit of gaseous and vapor
products formed from the sample; and a granular packing material
inside that is heated by electric resistor elements disposed
outside the chamber in surrounding relation thereto. This packing
material is chemically inert, as for example, crushed quartz, and
is heated to a temperature at which the organic carbon in the
sample is oxidized to carbon dioxide by the air atmosphere in the
chamber.
Clogging of the reaction chamber by solids deposited upon the
packing material is minimized through a special arrangement of the
packing material with respect to the chamber boundaries. In
accordance with the invention, the packing material is disposed to
define within the reaction chamber an inlet plenum zone
communicating with the inlet to accommodate preheating of the
sample by the packing material without contact therewith; and an
outlet plenum zone. The outlet plenum zone is separated from the
inlet plenum zone and communicates with the outlet to collect and
deliver thereto the gaseous and vapor products of the sample.
The size of the chamber, its inlet plenum zone and the thermal mass
of the packing material are such that the sample is vaporized
within the inlet plenum zone, before contact with the packing
material itself.
Carbonaceous matter in the sample is quickly oxidized by the hot
air atmosphere of the chamber so that the effluent therefrom is a
mixture of water vapor and other gaseous products including carbon
dioxide, the amount of carbon dioxide corresponding to the amount
of organic carbon originally present in the sample. The water vapor
portion of the reaction chamber effluent is expediently removed by
a conventional gas-liquid separator before delivery to an infrared
analyzer for measurement thereby of the carbon dioxide
component.
For a better understanding of the invention and its various
advantages, reference should be had to the following detailed
description and accompanying drawing which together exemplify a
preferred embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing:
FIG. 1 is a schematic diagram of an organic carbon content analyzer
apparatus according to a preferred embodiment of the invention.
FIG. 2 is an elevation view, partly in section, of the reaction
chamber used in the apparatus represented by FIG. 1, as seen in a
typical installation arranged for external heating of the reaction
chamber and packing material therein.
FIG. 3 is a plan view of the reaction chamber and heating
installation shown in FIG. 2.
DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
In FIG. 1 there is schematically exemplified an analyzer apparatus
10 constructed in accordance with the invention and which is
operable to measure, on a continuous flow basis, the total organic
carbon content in a sample stream taken from an aqueous liquid
source 11, such as a body of water to be monitored for pollution
level.
A continuous sample stream from source 11 is delivered by a
metering pump 12 into a mixing chamber 13. Another metering pump 14
delivers hydrochloric acid from a reservoir 15 into mixing chamber
13 for the purpose of acidifying the liquid sample therein to a pH
of approximately 2.0. The inorganic carbon present in the sample as
carbonates is converted to carbon dioxide by reaction with the
acid, and the organic carbon content of the sample is substantially
unchanged.
The acidified sample stream is expediently fed into a conventional
gas scrubber 16 that is supplied with air from a pump 17 to purge
from the sample whatever carbon dioxide was formed by the
acidification reaction. This carbon dioxide, which corresponds
quantitatively to the amount of carbonates in the sample, is by
choice vented to a waste zone, but could be delivered to a
measuring means (not shown ) should it be desired to measure the
amount of inorganic carbon in the sample.
The carbonate-free sample is fed by a metering pump 18 from
scrubber 16 into a heated reaction chamber 19, which is also
supplied with air from pump 17 to establish an oxidizing atmosphere
within chamber 19. This hot oxidizing atmosphere rapidly vaporizes
the sample and oxidizes the organic carbon content thereof to
carbon dioxide.
The vapor and gaseous mixture effluent of reaction chamber 19 is
delivered to a conventional gas-liquid separator 20 that removes by
condensation the vapor component of the mixture and passes the
gaseous portion containing the carbon dioxide to an infrared
analyzer 21.
Infrared analyzer 21 is of conventional construction and serves to
measure the amount of carbon dioxide formed by oxidation of the
organic carbon in the sample. The total quantity of organic carbon
originally present in the sample can be readily established by
applying a known proportionality factor to the carbon dioxide
measurement. Analyzer 21 is preferrably of a type which has an
electrical analog signal presentation of the carbon dioxide
measurement data. In such case, the carbon dioxide data signal is
applied to the input of a compatible moving chart recorder 22 for
direct display of the analysis results, either in terms of carbon
dioxide quantity or, in terms of equivalent organic carbon, which
can be done by suitable calibration of recorder 22 using techniques
well known to those skilled in the art.
For calibration purposes, the inlet of metering pump 12 can be
diverted temporarily from source 11 to another source, (not shown
), of liquid having a known concentration of organic carbon
sufficiently constant as to be useable as a standard. The gas
mixture output of separator 20 can be applied to an oxygen demand
analyzer, (not shown ), instead of to the infra-red analyzer 21
where it is desired to measure the oxygen demand level of the
sample.
While other means could be employed for effecting oxidation of the
organic carbon content to carbon dioxide, the reaction chamber 19,
shown in specific detail by FIGS. 2 and 3 offers definite
improvements and advantages over prior art counterparts. The
Chamber 19 has a peripheral wall 23 joined to a top cover 24 and a
bottom cover 25 so as to form a sealed enclosure. Within chamber 19
is an apertured plate 26 which serves to retain a quantity of
crushed quartz material 27.
Packing material 27 is so disposed as to define within chamber 19
an inlet plenum zone 28 and an outlet plenum zone 29 which is
separated from inlet plenum zone 28. Plenum zone 28 communicates
with an inlet opening 30 provided in cover 24 and a conduit 31
extending outside chamber 19. Conduit 31 in turn communicates with
both the air supply pump 17 and the outlet of metering pump 18 to
accommodate the introduction of oxidizing air and the sample into
chamber 19. The outlet of chamber 19 is defined by a conduit 32
that extends through cover 24, inlet plenum zone 28, packing 27 and
plate 26 to communicate with the outlet plenum zone 29. Plenum zone
29 thus serves to collect and deliver to outlet conduit 32 the
gaseous and vapor products from the sample for exit from chamber
19. Plenum zone 28 is used for preheating the sample by packing 27
without contact therewith.
Pump 17 is selected and operated so as to deliver into chamber 19
several times the stoichiometric volume of air required for
complete oxidation of the maximum anticipated carbon content of the
sample.
Disposed outside chamber 19 in surrounding spaced relation thereto
are a plurality of electric heater elements 33 that are used to
heat the chamber 19 and quartz packing 27 to a temperature of
approximately 850.degree.C. At such temperature, and with a mass of
packing 27 that occupies at least 50 percent of the volume of
chamber 19, the sample is preheated to vaporization almost
immediately upon entering plenum zone 28, for sample feed rates up
to about 2 percent per minute of the plenum zone 28 volume.
For example, at a packing 27 temperature of 850.degree.C, plenum
zone 28 vaporization of an aqueous sample was achieved at a sample
feed rate of 4cc/minute into chamber 19 having a plenum zone 28
volume of 500 cc and a total volume of 2,660 cc of which 1,660 cc
was occupied by quartz packing 27.
With the plenum zone vaporization afforded by the invention, there
is no cold liquid impingement upon the packing, and therefore the
packing is not subject to further pulverization by thermal stress
action. Consequently, the flow area presented by the voids between
the pieces of packing 27 stays relatively constant and is not
reduced significantly by clogging due to pulverization compaction
of the packing 27.
In plenum zone 28, the sample is converted to a mixture of vapor
and suspended solids which then pass the inert packing 27 in heat
exchange flow contact therewith, and the organic carbon content of
the mixture is completely oxidized to carbon dioxide before passing
through plate 26 into the outlet plenum zone 29 at the opposite end
of chamber 19.
To aid in controlling the temperature of the packing 27 there is
provided in chamber 19 a thermocouple well 34, into which can be
inserted a standard thermocouple, (not shown ).
From the foregoing description it will become apparent to the
artisan that the invention is adaptable to many specific
applications where the carbon content of liquids must be monitored,
and that obvious changes in the exemplified apparatus can be made
to satisfy particular requirements.
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