Note: Descriptions are shown in the official language in which they were submitted.
CA 02800816 2012-12-21
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WATER INTEGRATION OF DOMESTIC EFFLUENT TREATMENT
AND COKER PROCESSING WATER
TECHNICAL FIELD
The present invention relates to the treatment of domestic effluent and coker
processing water.
BACKGROUND
Domestic effluent treatment systems may be designed to reduce the
concentration of various compounds before discharging the treated water.
Domestic effluent may be treated in a treatment system that includes one or
more
ponds, which may include a primary lagoon followed by a polishing pond.
Domestic effluent can be treated for reduction of organic compounds, inorganic
pollutants, as well as suspended and dissolved solids, to reduce biochemical
oxygen demand (BOD), chemical oxygen demand (COD), pathogens and total
suspended solids (TSS), for example. Domestic effluent treatment systems can
employ microbial, filtering and settling mechanisms to degrade or reduce the
concentration of certain compounds.
Bitumen or heavy hydrocarbon upgrading facilities often include coker units
that
enable delayed coking of feedstocks. Coker units require a relatively large
quantity of water for certain steps in the coking process, e.g., coke
quenching
water and coke cutting water. Coke quenching water is used to cool the coker
drums after the high temperature thermal cracking of hydrocarbon feedstock.
When the petroleum coke is at a suitable temperature after cooling, coke
cutting
water is used to remove petroleum coke that has deposited within the coker
drums from the thermal cracking.
Water for use in coker units has typically relied on nearby natural water
sources
such as rivers, which can have environmental and other drawbacks.
SUMMARY
Processes, systems, and techniques for integrating a domestic effluent
treatment
operation with a hydrocarbon coking operation are described.
There is provided a process for integrating a domestic effluent treatment
operation with a hydrocarbon coking operation. The process includes retrieving
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from the domestic effluent treatment operation a domestic effluent water
including
pathogens; pre-treating the domestic effluent water to reduce a concentration
of
pathogens therein, to produce a pre-treated water stream; and supplying the
pre-
treated water stream to a coker unit as coker quench water to quench the coker
unit and produce a pathogen depleted spent quench water.
The step of pre-treating may include ultraviolet (UV) treatment of the
domestic
effluent water.
The process may include, prior to the step of pre-treating, the step of
clarifying the
domestic effluent water to increase the ultraviolet transmittance (UVT)
thereof.
The step of clarifying may be performed so as to increase the UVT of the
domestic effluent water above 40%. The step of clarifying may be performed so
as to reduce a concentration of algae in the domestic effluent water. The step
of
clarifying may include covering at least part of the domestic effluent
treatment
operation in order to reduce or prevent exposure to sunlight and thereby
inhibit
algae growth.
The process may also include measuring the UVT of the domestic effluent water
prior to the step of pre-treating, and, in response to a UVT measurement
exceeding a pre-determined threshold, reducing energy input into the UV
treatment.
The step of clarifying may include filtering and/or chemical flocculation. The
filtering may include pressure-filtering and/or providing a plurality of
filters
arranged in series. The step of pre-treating may be performed proximate to the
domestic effluent treatment operation.
The domestic effluent treatment operation may include primary treatment of
source domestic effluent in a lagoon, to produce a primary effluent water, and
polishing treatment of the primary effluent water in a polishing pond, to
produce
the domestic effluent water.
The step of retrieving the domestic effluent water may include providing a
retrieval
assembly for retrieving the domestic effluent water from the polishing pond.
The step of retrieving the domestic effluent water may include periodically
pumping the domestic effluent water out of the polishing pond at a periodic
retrieval flowrate that is greater than an inflow rate of the primary effluent
water
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into the polishing pond, and periodically stopping the pumping for a shut-off
time
period.
The periodic retrieval flowrate and the shut-off time period may be provided
such
that an overall retrieval outflow from the domestic effluent water is
generally equal
to inflow of primary effluent water into the polishing pond. The periodic
retrieval
flowrate may be between 2 and 8 times greater than the inflow rate of the
primary
effluent water into the polishing pond. The process may include covering the
polishing pond with a floating ball cover to inhibit growth of algae therein.
The process may include controlling a level of the polishing pond around a pre-
determined value. The step of controlling the level of the polishing pond may
include measuring the level of the polishing pond. In response to a level
measurement being less than a first pre-determined threshold level, at least a
portion of the domestic effluent water that is retrieved from the polishing
pond
may be recycled back into the polishing pond, or retrieval of the domestic
effluent
water from the polishing pond may be stopped, or the retrieval of the domestic
effluent water from the polishing pond may be reduced. In response to the
level
measurement being greater than a second pre-determined threshold level,
retrieval of the domestic effluent water from the polishing pond may be
increased,
by increasing retrieval rate and/or retrieval duration, or recycled water back
into
the polishing pond may be reduced, by storing and/or discharging to
alternative
containment facilities.
The step of retrieving the domestic effluent water may further include
periodically
pumping the domestic effluent water out of the domestic effluent treatment
operation at a periodic retrieval flowrate that is greater than an inflow rate
into the
domestic effluent treatment operation, and periodically stopping the pumping
for a
shut-off time period.
The periodic retrieval flowrate and the shut-off time period may be provided
such
that an overall retrieval outflow from the domestic effluent treatment
operation is
generally equal to inflow into the domestic effluent treatment operation. The
periodic retrieval flowrate may be between 2 and 8 times greater than the
inflow
rate into the domestic effluent treatment operation.
The step of retrieving the domestic effluent water may further include
continuously
pumping the domestic effluent water out of the domestic effluent treatment
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operation at a generally constant retrieval flowrate, the generally constant
retrieval
flowrate being substantially similar to an inflow rate into the domestic
effluent
treatment operation.
The process may include exposing all of the pre-treated water stream to
temperatures of at least 70 C for at least 7 minutes in the coker unit,
thereby
destroying all pathogens present in the pre-treated water stream.
The process may include recycling at least a portion of the pathogen depleted
spent quench water as part of the coker quench water.
The hydrocarbon coking operation may receive oil sands bitumen as a feedstock.
The process may further include diverting excess pre-treated water stream from
the coker-unit upon detection that a flow rate of the pre-treated water stream
entering the coker unit exceeds a capacity of the coker unit.
There is also provided a system for integrating a domestic effluent treatment
operation with a hydrocarbon coking operation. The system includes a retrieval
assembly for retrieving from the domestic effluent treatment operation a
domestic
effluent water including pathogens, a pre-treatment unit in fluid
communication
with the retrieval assembly configured for receiving and pre-treating the
domestic
effluent water to reduce a concentration of pathogens therein, to produce a
pre-
treated water stream, and a supply assembly in fluid communication with the
pre-
treatment unit for receiving the pre-treated water stream and supplying the
same
to a coker unit as coker quench water to quench the coker unit.
The pre-treatment unit may include an ultraviolet (UV) treatment unit. The UV
treatment unit may include multiple UV reactors.
The system may include a clarifying device for clarifying the domestic
effluent
water to increase the ultraviolet transmittance (UVT) thereof prior to
introduction
into the UV treatment unit. The clarifying device may be configured to
increase
the UVT of the domestic effluent water above 40%. The clarifying device may be
configured to reduce a concentration of algae in the domestic effluent water.
The
clarifying device may include a covering deployed over at least part of the
domestic effluent treatment operation in order to reduce or prevent exposure
to
sunlight and thereby inhibit algae growth. The covering may include a floating
ball
covering.
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The system may further include a UVT measurement device for measuring the
UVT of the domestic effluent water prior to the UV treatment unit, wherein the
UV
treatment unit is configured such that, in response to a UVT measurement
exceeding a pre-determined threshold, energy input is reduced.
5 The clarifying device may include a filtering unit. The filtering unit
may include a
pressure-filtering device and/or a multi-filter device having a plurality of
filters
arranged in series. The clarifying device may include a chemical flocculation
unit.
The pre-treatment unit may be located proximate to the domestic effluent
treatment operation. The domestic effluent treatment operation may include a
primary treatment lagoon for treating source domestic effluent, to produce a
primary effluent water, and a polishing pond for further treating the primary
effluent water, to produce the domestic effluent water.
The retrieval assembly may include an inlet that is configured and located in
fluid
communication with the polishing pond.
The retrieval assembly may further include a retrieval controller for
controlling
flowrates therein.
The retrieval controller may be configured so as to enable periodic pumping of
the
domestic effluent water out of the polishing pond at a periodic retrieval
flowrate
that is greater than an inflow rate of the primary effluent water into the
polishing
pond, and periodical stopping of the pumping for a shut-off time period.
The retrieval controller may be configured to provide the periodic retrieval
flowrate
and the shut-off time period such that an overall retrieval outflow of the
domestic
effluent water is generally equal to inflow of primary effluent water into the
polishing pond.
The retrieval controller may be configured such that the periodic retrieval
flowrate
is between 2 and 8 times greater than the inflow rate of the primary effluent
water
into the polishing pond.
The system may further include a floating ball covering provided on a surface
of
the polishing pond to inhibit growth of algae therein.
The system may further include a level controller for controlling a level of
the
polishing pond around a pre-determined value.
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A level measurement device may be provided in the polishing pond for measuring
the level of the polishing pond. The level controller may be configured to: in
response to a level measurement being less than a first pre-determined
threshold
level, recycle at least a portion of the domestic effluent water that is
retrieved from
the polishing pond back into the polishing pond; or stop retrieval of the
domestic
effluent water from the polishing pond; or reduce the retrieval of the
domestic
effluent water from the polishing pond. In response to the level measurement
being greater than a second pre-determined threshold level, the level
controller
may be configured to: increase retrieval of the domestic effluent water from
the
polishing pond, by increasing retrieval rate and/or retrieval duration; or
reduce
recycled water back into the polishing pond, by storing and/or discharging to
alternative containment facilities.
The supply assembly and the hydrocarbon coking operation may be configured
and operated for exposing all of the pre-treated water stream to temperatures
of
at least 70 C for at least 7 minutes in the coker unit, thereby destroying all
pathogens present in the pre-treated water stream.
The system may further include a quench water recycle line for recycling at
least
a portion of the pathogen depleted spent quench water as part of the coker
quench water.
The system may further include a bypass system for diverting excess pre-
treated
water stream from the coker-unit upon detection that a flow rate of the pre-
treated
water stream entering the coker unit exceeds a capacity of the coker unit,
There is also provided a process for integrating a domestic effluent treatment
operation with a hydrocarbon coking operation. The process includes:
retrieving
water from a pond in a domestic effluent treatment operation, the pond
receiving
an inflow of effluent for treatment, wherein the retrieving comprises
cyclically
pumping an outflow of the water from the pond, wherein each pumping cycle
provides a flowrate that is greater than the inflow rate of the effluent into
the pond;
and providing at least a portion of the outflow of the water retrieved from
the pond
as coker quench water to a hydrocarbon coking operation and using the coker
quench water in a quenching cycle.
There is also provided a process for integrating a domestic effluent treatment
operation with a hydrocarbon coking operation. The process includes retrieving
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domestic effluent water from the domestic effluent treatment operation. The
domestic effluent treatment operation includes treating domestic effluent in a
primary lagoon to produce a primary effluent water; and treating the primary
effluent water in a polishing pond to produce the domestic effluent water. The
retrieving includes cyclically pumping an outflow of the domestic effluent
water.
Each pumping cycle provides: a pumping stage providing a retrieval flowrate
that
is greater than an inflow rate of the primary effluent water into the
polishing pond;
and a downtime stage providing sufficient time so that each pumping cycle
retrieves an outflow of the domestic effluent water that is generally
equivalent with
the inflow of the primary effluent water. The process also includes providing
at
least a portion of the domestic effluent water retrieved from the polishing
pond as
coker quench water to a hydrocarbon coking operation and using the coker
quench water in a quenching cycle.
BRIEF DESCRIPTION OF DRAWINGS
Fig 1 is a block flow diagram including a domestic effluent treatment
operation
and a hydrocarbon coking operation with water integration.
Fig 2 is another block flow diagram with water integration.
Fig 3 is a graph of quench water flow versus time.
Fig 4 is a process flowchart.
Fig 5 is another block flow diagram including a hydrocarbon coking operation.
DETAILED DESCRIPTION
Techniques described herein provide water integration between a domestic
effluent treatment operation and a hydrocarbon coking operation.
The water integration techniques include the use of domestic effluent water as
a
source of coker processing water, e.g., quench water and/or cutting water, in
a
hydrocarbon coking operation. Such techniques may facilitate leveraging the
water requirements of coker quench cycles to reduce the need for increasing
capacity at a domestic effluent treatment operation. For example, coker
quenching requires water in high quantity but of lower quality than other
hydrocarbon extraction or processing operations, and water derived from a
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domestic effluent treatment operation can be efficiently used to meet coker
quenching requirements.
Referring to Fig 1, a water integration system 10 includes a domestic effluent
treatment operation 12 and a hydrocarbon coking operation 14. In the
implementation shown and discussed, domestic effluent water is obtained from
the domestic effluent treatment operation 12 and provided to the hydrocarbon
coking operation 14 for use as coker quench water. It should be understood
that
in other implementations, the domestic effluent treatment water can be used as
coker cutting water.
Referring still to Fig 1, in some implementations the domestic effluent
treatment
operation 12 may include a primary lagoon 16 for receiving raw domestic
effluent
18 or a stream derived from raw domestic effluent. The primary lagoon may
operate as a continuous flow aerated lagoon system. The raw domestic effluent
18 supplied to the primary lagoon 16 may form a bottom layer including settled
solids, a top layer including lighter floating solids and a middle layer
including
mainly primary effluent water 20. The primary effluent water 20 in the lagoon
16
contains bacteria that biodegrade various pollutants, notably organic
material,
present in the domestic effluent. The primary effluent water 20 may thus be
subject to both anaerobic and aerobic water treatment. Under anaerobic
treatment, bacteria that are not oxygen dependent convert certain organic
pollutants in the water, as the bacteria can act under low oxygen conditions.
The
anaerobic treatment alone does not provide a complete conversion of the
organic
pollutants and is followed by an aerobic treatment. Under aerobic treatment,
bacteria that are oxygen dependent continue the conversion of certain organic
pollutants in the water. Thus, there are several types of micro-organisms that
are
active in the primary lagoon 16 for biodegrading different substrates
considered
as pollutants. Some of the micro-organisms are considered as pathogenic in the
sense that sufficient contact with flora, fauna and/or humans can cause
physiological problems. The primary effluent water 20 includes pathogens along
with other micro-organisms and other pollutants that may be subjected to
further
downstream treatment. One technique to measure the concentration of pathogens
in effluent water is to measure a concentration of coliform bacteria in the
water.
Coliform bacteria are not generally pathogenic. However, the presence of
coliform
bacteria is used as an indicator of the overall concentration of pathogens in
water
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effluent, as coliform bacteria are easy to culture from samples that are used
for
water quality analysis
The primary effluent water 20 may then be supplied to a subsequent treatment
system, which may include a polishing system 22. The polishing system 22 may
include one or more polishing ponds depending on the design of the domestic
effluent treatment operation 12. The polishing system 22 contributes to the
removal and degradation of additional pollutants, such as pathogens and some
solids, to produce domestic effluent water 24. The domestic effluent water 24
still
includes some remaining pollutants such as pathogens, suspended solids and
dissolved solids. If the effluent water is not recycled and is discharged into
the
environment as a discharge stream 25, such as an adjacent river or other body
of
water, a concentration of pollutants the domestic effluent water 24 is
controlled
according to local regulatory limits. One such regulatory limit is the
concentration
of coliform bacteria present in the effluent water. An example of a regulatory
limit
is to have coliform bacteria concentrations in the effluent water below 200
cfu/100
ml (colony-forming units per hundred milliliters).
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In certain scenarios, the above-described domestic effluent water treatment
systems, including the lagoon and polishing pond, are sufficient to reduce the
concentration of pathogens in the water within a target regulatory limit prior
to
discharge into the environment. One such scenario may occur during operation
of
the treatment systems in cold months, when the treatment systems allow a very
low level of pathogen survival. However, in warmer months, the levels of
pathogen survival are much higher. Therefore, water derived from the domestic
effluent treatment operation 12 is supplied to a pre-treatment unit 28 in
order to
further reduce a concentration of the pathogens in the effluent water, and
thus
control the level of pathogens in the effluent water across a more complete
range
of operational conditions. The pre-treatment unit 28 brings the pathogen
levels to
near or below local regulatory limits, either for use in coker unit operations
or for
discharge into public waterways.
In certain scenarios, if the cokers cannot handle the volume of domestic
wastewater within their normal operational cycles, some arrangement for
diversion of excess flow can be made. The liquid concentrations of coliform
bacteria in domestic effluent water that is routed to a by-pass of the coker
unit
may not be sufficiently low for direct release to a public waterway, if not
adequately disinfected by the pre-treatment unit. However, the stream from the
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pre-treatment unit can be sent to a storage lagoon and be diluted with water
from
other sources. This dilution the stream obtains from its progression into its
final
storage lagoon is designed such that the final concentration of colifornn
bacteria is
lowered to levels that are at least an order of magnitude lower than the exit
from
5 the pre-treatment unit. Thus, with any further dilution into the final
public
waterway, the coliform bacteria concentrations can be adequately below target
local regulatory limits.
Referring to Fig. 1, the water integration technique detailed below recycles
water
produced by domestic effluent treatment operations 12 for use as coker quench
10 water. Recycling as coker quench water can reduce diverting domestic
effluent
water to other effluent or tailings containment systems, or direct discharge
to
public waterways. Recycling can also replace river water or other cold process
water as a quenching medium in the coker unit. Recycling can also reduce the
use of API-recycle water, also used for coker unit quenching.
Referring to Fig 2, in some implementations, the domestic effluent water 24
may
be retrieved from the polishing system 22 using one or more retrieval pumps 26
for supplying water toward the hydrocarbon coking operation.
Referring back to Fig 1, pre-treatment of the water prior to transferring to
the
hydrocarbon coking operation 14 reduces the concentration of pathogens. At
least
a portion of water derived from the domestic effluent treatment operation 12
is
supplied to a pre-treatment unit 28 as a feed water stream 30. The feed water
stream 30, thus includes the domestic effluent water 24 retrieved from the
polishing system 22. The pre-treatment unit 28 is configured and operated to
reduce the pathogen concentration in the feed water stream 30.
In certain scenarios, the pre-treatment reduces exposures of coker unit
operators
to potentially hazardous elements, such as pathogens, in proximity of coking
operations, e.g., if a leak were to occur. However, at the installations
housing the
coker units, access to the various coker decks is restricted during the
introduction
of quenching water and de-heading of the cokers. Such operations lead to
potential exposures to elevated levels of hydrogen sulphide or other hazardous
vapours during the de-heading process. Therefore, workers on the affected
coker
deck areas typically employ personal protection equipment to prevent any
excessive exposures. Although not specifically designed for biological
aerosols or
pathogens, the particle sizes relevant to these aerosols or pathogens are very
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similar to the other dusts that are filtered by respirators. Moreover, the
effluent
from the pre-treatment system can be totally enclosed in a pipeline, as it
proceeds
through the pre-treatment unit, and then piped onward until it reaches the
inlets of
the coker units. Thus, exposure to pathogens in either the pre-treated
effluent
water or the air above it (or dissolved within) for coker unit workers during
this
transfer process can be minimized.
Referring to Fig 2, in some implementations, there is a domestic effluent
water
return stream 32 for returning a portion or all of the domestic effluent water
24 that
is obtained from the polishing system 22. The return stream 32 is sent back
into
the polishing system 22 in order to bypass the pre-treatment unit 28
temporarily,
e.g., during downtime or turndown operations. The return stream 32 may
configured and operated to facilitate diversion of domestic effluent water
back to
the polishing pond 22 in certain instances, e.g., in case the UV treatment
unit 28
experiences an operational upset. The return stream 32 can also provide an
alternate sample point for domestic effluent water that is more readily
accessible
to operations and maintenance personnel.
In some implementations, there is a bypass stream 36 for bypassing a portion
or
all of the feed water stream 30 around the pre-treatment unit 28.
The pre-treatment unit 28 is configured and operated to decrease a
concentration
of pathogens in the effluent water. More regarding the pre-treatment unit 28
and
related operations will be discussed further below.
A coker quench water stream 38 derived from the domestic effluent treatment
facility 12 is supplied to the hydrocarbon coking facility 14. In some
implementations, water sources may be combined with this coker quench water
stream 38, such as industrial effluent streams 40 that may include API
separator
water, and/or various water recycle streams, such as a treated spent coker
water
stream 42. The combined streams, which include the stream 38 derived from the
domestic effluent treatment facility 12, are provided as coker quench water 44
to a
coker unit 46.
Fig 3 provides an example of flowrate versus time of the coker quench water 44
introduced into a coker drum of the coker unit 46 for a given quench cycle.
Fig. 4 shows a process for utilizing water from a domestic effluent treatment
operation which includes retrieving water derived from the domestic effluent
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treatment operation, the water including pathogens, indicated by reference
numeral 100. The water is pre-treated to reduce the pathogen content and
produce a pathogen reduced water for use a coker quench water, indicated by
reference numeral 102. The coker quench water is transferred to a hydrocarbon
coking operation and using the coker quench water in a quenching cycle,
indicated by reference numeral 104.
In some implementations, a process integrating water between a domestic
effluent treatment operation and a hydrocarbon coking operation includes
retrieving water from a pond in a domestic effluent treatment operation, the
pond
receiving an inflow of effluent for treatment. The retrieving can include
cyclically
pumping an outflow of the water from the pond, wherein each pumping cycle
provides a flowrate that is greater than the inflow rate of the effluent into
the pond.
At least a portion of the outflow of the water retrieved from the pond is
provided as
coker quench water to a hydrocarbon coking operation and using the coker
quench water in a quenching cycle.
In some implementations, a process integrating water between a domestic
effluent treatment operation and a hydrocarbon coking operation includes
retrieving domestic effluent water from the domestic effluent treatment
operation.
The domestic effluent treatment operation includes treating domestic effluent
in a
primary lagoon to produce a primary effluent water, and treating the primary
effluent water in a polishing pond to produce the domestic effluent water. The
retrieving can include cyclically pumping an oufflow of the domestic effluent
water.
Each pumping cycle provides a pumping stage providing a retrieval flowrate
that
is greater than an inflow rate of the primary effluent water into the
polishing pond;
and a downtime stage providing sufficient time so that each pumping cycle
retrieves an oufflow of the domestic effluent water that is generally
equivalent with
the inflow of the primary effluent water. At least a portion of the domestic
effluent
water retrieved from the polishing pond is provided as coker quench water to a
hydrocarbon coking operation and using the coker quench water in a quenching
cycle.
Various techniques and implementations will be described in more detail below,
in
relation to particular parts of the system.
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Domestic effluent treatment operation and water retrieval
The domestic effluent treatment operation 12 may be implemented in a variety
of
ways. The incoming effluent 18 may be from a sewage system associated with a
hydrocarbon processing facility, such as a bitumen mining, extraction and
upgrading plant. The domestic effluent 18 may come from working personnel at
the bitumen extraction and upgrading facility, camps or domiciles for the
working
personnel and/or household sewage from communities.
In some implementations, the domestic effluent treatment operation 12 may be
proximate to the coking operation 14, thus reducing transportation
infrastructure
and energy for supplying the domestic effluent water 24 as coker quench water.
Alternatively, the domestic effluent treatment operation 12 may be relatively
remote from the coking operation 14, thus requiring additional fluid
transportation
configurations. Of course, the domestic effluent water used as coker quench
water may be a mixture of multiple streams from different domestic effluent
water
sources that may be proximate or remote from the coking operation 14.
As will be discussed further below, if the domestic effluent treatment
operation 12
is relatively remote with respect to the coking operation 14, the water may be
handled and subjected to certain pre-treatment steps. For example, in some
implementations the domestic effluent treatment operation 12 and the coking
operation 14 may be located in different locations within a bitumen mining,
extraction and upgrading operation, with a given terrain separating the two
operations. The separating terrain may be occupied by various installations,
infrastructure and working personnel associated with the bitumen mining,
extraction and upgrading operation. In such scenarios, a fluid transportation
assembly 48 may be provided to retrieve the water, transport the water across
the
terrain, and supply the water to the coking operation.
Referring to Fig 1, domestic effluent water 24 retrieved from a polishing pond
22
typically has a concentration of pathogens. In some implementations, the pre-
treatment system 28 is provided relatively near to the polishing pond 22 to
reduce
the pathogen concentration proximate the domestic effluent treatment operation
12 such that the resulting fluid can be transported across various terrains or
distances in the bitumen mining, extraction and upgrading plant, which can
cover
a large area. Pre-treatment proximate the domestic effluent treatment
operation
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,
12 can enhance protection of the environment and personnel, for example around
the fluid transportation assembly and near any operator sites prior to
quenching.
Referring to Fig 1, in some implementations, a lagoon outlet flow meter 50 may
be
provided when water fed to the polishing pond comes from a primary lagoon 16.
The flow meter may be provided so as to monitor and totalize fluid flow from
the
lagoon 16 to the polishing pond 22. The flow can be monitored on a regular
basis
(e.g. daily) to track re-use water demand, for example. The flow can be
monitored
to assess whether excess effluent water 20 from the lagoon 16 is being fed to
the
polishing pond 22, for example to determine whether additional flowrate of
water
should be retrieved from the domestic effluent treatment operation 12 for use
as
coker quench water in order to reduce or maintain the discharge of domestic
effluent water 24 to effluent containment systems, tailings containment
systems
and/or back into a natural water source.
Referring to Fig 1, in some implementations, the polishing pond 22 may be
maintained at a minimum level to prevent excessive odours from developing.
Various units may be put in place to maintain the level of the pond relatively
constant. For example, a continuous level indicator may be provided in the
polishing pond 22. The indicator may include a pressure sensor for hydrostatic
level measurement, which may be placed on the bottom of the polishing pond to
measure its level. Instrument cables can be run through a protective sleeve to
guard against ice breakage. The polishing pond level may rise or fall due to
higher
or lower than average inflow, storm water ingress, pond seepage and/or
evaporation. Operators can manually cycle a pump to reset the level or change
the time sequence to increase or decrease the batch flow of effluent water 24
out
of the polishing pond 22. This can provide flexibility to operators to
maintain the
polishing pond level as needed. When the domestic effluent water flow is
turned
down or off, a corresponding portion of the coker quench water may come from
other sources, such as existing API separator pond water 40 and/or other water
sources.
Referring to Fig 2, in some implementations, should the polishing pond level
reach its maximum when there is no active quenching process, retrieval pumps
26 can be provided with a piping connection 52 to allow the pond to be drained
to
static or mobile units, e.g. trucks, as a temporary measure. Fluid captured in
mobile units may be transported to an effluent treatment plant, for example.
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,
Referring to Fig 1, in some implementations, the domestic effluent treatment
operation 12 may also include a sump (not illustrated), which may be located
at a
side of the polishing pond, to recover overflow water from the polishing pond
22.
The level of water in the sump may be monitored (e.g. through a wireless
5 network) and may be controlled by starting and stopping a sump pump (not
illustrated) automatically. A pressure sensor for hydrostatic level
measurement
may be set on the bottom of the sump to measure the level and send an output
to
a pump controller, which operates the pump start or stop to maintain a maximum
predetermined level that should not be exceeded. Operators can monitor the
level
10 and locally adjust set-points for pump start or stop on the controller.
Pre-treatment unit and related operations
Referring to Fig 1, the domestic effluent water 24 that is retrieved from the
domestic effluent water treatment operation 12 may be provided to a pre-
treatment unit 28.
15 As described above, the domestic effluent water 24 may contain a certain
concentration of pathogens. For example, the domestic effluent water 24
retrieved
from the polishing pond 22 may have reduced levels of certain pollutants such
as
organic compounds and solids, but may still benefit from further reduction of
pathogen concentration. In addition, according to testing of an example of
domestic effluent water 24 retrieved from a polishing pond 22, concentrations
of
certain pollutants may vary depending on weather, season or other factors.
In some implementations, the pre-treatment unit includes an ultraviolet (UV)
treatment unit, which may include one or more UV reactors. The UV treatment
unit is configured to receive the feed water stream 30, which may be composed
of
various streams including at least one from the domestic effluent treatment
operation 12. The UV treatment unit have lamps that provide a dose of UV light
in
order to deactivate pathogens in the feed water stream 30. In some scenarios,
the
feed water stream 30 has a UV transmittance (UVT) of at least a pre-determined
UVT threshold to facilitate pathogen inactivation. UVT is a measure of the
amount
of light that can pass through a sample. The pre-determined UVT threshold may
be 30%, 35%, 40% or 45%, for example. The pre-determined UVT threshold may
be determined based on the adequate UVT to achieve effective deactivation
level
of pathogens.
CA 02800816 2012-12-21
16
In some implementations, the pre-treatment unit may alternately include any
other
system capable of decreasing a concentration of pathogens in the effluent
water.
For example, water from the polishing pond may be subsequently treated in a
long-term storage lagoon, in order to allow bacteria to further biodegrade any
pathogens in the effluent water over a longer period of time and thus bring a
concentration of pathogens within a target threshold.
In some implementations, the UV treatment unit includes a UV control panel
having outputs to indicate status for the following: Remote lamp on-off
control;
Flow interlock; Remote signals; Re-transmission of UV intensity; and Number of
Off-On lamp cycles for each reactor. Control of the UV treatment system may be
done locally, but the UV reactors can remain powered full-time, which may be
facilitated by low-pressure, high output (LPHO) UV bulbs that can typically
only be
started and stopped 4 times per day, and take 4 minutes to warm up. Excessive
start cycles limit lamp life. Operating the UV reactors prior to warm-up can
result
in a low applied UV dose.
In addition, referring to Fig 2, on the suction side of the retrieval pumps
26, an on-
line UVT meter 54 may be installed. Data from this UVT meter is brought back
to
a programmable logic controller (PLC), to allow operators to determine whether
any of the three operating UV reactors can be switched off should UVT of the
domestic effluent is higher than a pre-determined UVT threshold.
Referring to Fig 2, in some implementations, the UV treatment unit 28 may also
include a high temperature sensor and/or alarm. In case of an alarm, an
effluent
pump 26 would turn on for a time period (e.g. 5-10 seconds) to send fresh
water
into the UV reactors. The control panel may include a high temperature alarm,
which may provide a local alarm. If high temperatures persist, the UV system
may
be shut down.
In some implementations, the UV treatment reactors may be based on LPHO
lamps. In a particular illustrative example, each reactor has 20 lamps, and
based
on polishing pond sample data, three reactors can be used to treat 300 USGPM,
with a fourth reactor included as a spare. The LPHO lamps cycle on and off
four
times per day to prevent premature lamp failure. Because of the intermittent
nature of coker quenching operations, the UV reactors can be powered at all
times. The lamps may operate at about 90 C and can operate without flowing
water for cooling. Each UV reactor may include double-block and bleed valving.
A
CA 02800816 2012-12-21
17
temperature sensor may also be provided. Upon detection of high reactor
temperature, the effluent pumps may be run briefly to exchange the water in
the
UV reactors for fresh, colder water. Of course, various other types and
configurations of UV reactors can be used.
In some implementations, UV transmittance levels may rise due to algae
mitigation, e.g. by use of the floating ball cover, and the UV reactors can
consequently treat higher flow rates of domestic effluent water 24, or the
same
flow rate could be treated to achieve greater coliform count reductions after
treatment. Conversely, a provision can be made in the fluid transportation
assembly 48 for installation of an additional clarifying treatment (e.g.
filtration) to
compensate for UVT values lower than expected. As mentioned above, there may
be an on-line UVT sensor 54 to provide water monitoring capabilities so as to
adjust flow accordingly.
In the event that the domestic effluent water 24 used to provide the feed
water
stream 30 has a UVT below the pre-determined threshold, a clarifying treatment
may be performed prior to supplying the stream to the UV treatment unit.
The clarifying treatment may include various methods. For example, the
clarifying
treatment may be configured for reducing algae content from the domestic
effluent water 24. Increases in UVT can be due to the presence of algae.
Domestic effluent ponds typically have an abundance of nitrogen and
phosphorus. High hydraulic retention times and sloped sides (e.g. 3:1 slope)
of a
pond can result in a high surface area to volume ratio and provide an optimal
environment for the growth of algae. Algae may thrive during summer months
resulting in lower UVT in the domestic effluent water 24, although as the
algae
begin to die off in colder seasons the algae would absorb less UV light,
therefore
increasing the UVT of the water 24. For example, several water samples taken
from the pond during a summer to late fall period showed low UVT. The samples
also showed a sudden increase in total suspended solids (TSS) in the early
fall
period, which is likely from algae dying off due to a drop in ambient
temperature
and settling in the polishing pond. Thus, the clarifying treatment may be
conducted to remove algae, particularly in the summer season when algae are
more abundant.
It was also observed in an experiment that lower ambient temperature resulted
in
lower TSS, further indicating the effect of algae in the polishing pond water.
This
CA 02800816 2012-12-21
18
temperature impact on TSS is somewhat counterintuitive as TSS would typically
increase with lower temperature due to reduced biological activity. After a
certain
period, a decrease in TSS and an increase in UVT were evident. The presence of
fecal coliform in the effluent also had a similar counterintuitive behavior in
that
fecal conform counts did not have a similar decrease due to lower temperatures
until early October.
Due to the low UVT of certain domestic effluent water, UV treatment may be
enhanced by subjecting the water to the clarifying treatment to increase the
UVT
above the pre-determined threshold.
In some implementations, the clarifying treatment may include covering the
polishing pond 22 for algae control. This may be done by providing a floating
ball
cover deployed on the polishing pond 22 for algae control. The floating ball
cover
can be formed from black coloured floating balls formed from about 6" diameter
hollow polymer (e.g. HDPE) spheres and each having an orientation tab. The
floating balls may be dispersed over the surface of the polishing pond 22,
where
they arrange themselves evenly with the orientation tabs pointing down. The
tabs
also help prevent rolling and bunching of the balls. Three sides of the
polishing
pond may have a slope to retain the balls within the pond, e.g. if moved by
wind.
Extremities of the pond may be lined with a fence structure to provide further
retention as balls that are blown out of the pond can hit the fence and roll
back
into the pond. An additional amount of balls may be added to the initial
requirement of floating balls as replacement stock. The replacement stock can
be
placed in inventory and added to the polishing pond if wind forces balls over
the
extremities of the pond and they fail to return. In one example, approximately
100,000 to 150,000 of 6" outer diameter (OD) floating balls may be provided to
cover the entire surface area of a polishing pond.
In some implementations, the clarifying treatment may include filtration to
capture
solids and restrict large particles (e.g. over 30-40 micron) that can shade
light and
thus reduce effectiveness of the UV treatment. Various different types of
filters
may be used upstream of the UV treatment unit. The filtration treatment
produces
a filtered stream and a waste stream. In the case of disposable filters, the
waste
stream would include a solid waste stream. Other filtration options could
require
handling and monitoring of backwash water. For some backwash water systems,
a buried backwash tank may be provided and may have internal baffles to
facilitate solids removal. The backwash tank can be configured to allow
settlement
CA 02800816 2012-12-21
19
of larger solids that would be removed by a vacuum truck. Decant water may be
allowed to drain back to the front end of lagoon treatment.
In some implementations, a sidestream filtration system, such as the
VortisandTM
filter system may be used to provide pressure filtration with removal of
solids in
the 1-2 micron range. This sidestream filtration system uses centrifugal force
(vortex effect) to whirl the untreated water above media (multi layers) and
directs
larger suspended solids on a side wall of the tank. The particles above the
filter
bed develop a filter cake that then traps the smaller particles. This
increases the
effective filter surface within the tank when compared to a conventional sand
filter.
Turbulence may produce a sustained cleaning action (or cross flow filtration)
that
forces the suspended solids to accumulate. Contaminants trapped above the
sand are removed using an automatic backwash cycle which requires less water
and a shorter operating time than traditional sand filters. The turbulence
allows for
use of a finer filtration media that in turn allows for a smaller capture.
Conventional down flow depth filter technology can filter down to 10-15
microns in
particle size whereas the sidestream filtration system can filter to 0.45
microns.
Removal down to 2 micros, consistent with removal for green algae, can be used
in certain scenarios. In one example, a plurality, e.g. more than then, 36"
diameter
vessels may be used. This can provide redundancy whereby one tank can stop
for backwash while the other one remains in filtration mode. The size of the
system could be reduced by increasing the number of backwashes per day.
In some implementations, a cartridge and disc based system can be used for
filtration. One example of such a system uses 3 stages (2 disc stages and 1
cartridge stage). The process may include a roughing filter to remove large
solids
followed by a 20 micron filter stage. Pre-filtration stages may provide
improved
protection to the microfiber filters.
In one example, 2 x 3 micron microfiber filtering units are provided. These
self-
cleaning filters have an integral cleaning system to backwash captured solids.
The microfiber filter requires filtrate storage for flushing (1300 USG) the
unit. Such
a filtration device offers automated filtration and a lower level of operator
intervention.
In some implementations, the clarifying treatment may include chemical
treatment. For example, chemical flocculation may be used to improve UVT.
Chemical flocculation may also be used in combination with other separation
CA 02800816 2012-12-21
,
steps such as filtration as flocculation generates larger particles that are
more
easily removed by filtering. Chemical injection can be used to precipitate
chlorophyll dissolved in the domestic effluent water, in the event that algae
or
chlorophyll by-products affect the UVT.
5 Turning back to the UV treatment unit 28, in some experiments the effect of
applied UV dose (measured in mJ/cm2) on various pathogens was studied. There
appears to be a limited increase in coliform reduction above doses of 100
MJ/cm2.
The same dose shows a 4-log reduction of MS2, a virus which is easily
cultivated
in laboratories and used to measure viral reduction efficacy of treatment
systems,
10 which is above the reduction typical in water treatment systems.
Hydrocarbon coking operation
Referring to Fig 1, the hydrocarbon coking operation 14 may include a delayed
coking process, which includes an operating scheme that is generally
alternating.
15 The hydrocarbon coking operation 14 may be for heavy oil or
bitumen feedstocks,
such as those produced in the northern Alberta oil sands.
Referring to Fig 5, the hydrocarbon coking operation 14 may have a coker unit
46
including one or more pairs of coker drums 48a, 48b. In general, while one of
the
coking drums is in thermal coking operation mode, the other coking drum
20 undergoes quenching and cutting for coke cooling and removal followed by
preparation for its coking stage. A first coker drum 48a may be initially
heated by
an adjacent drum 48b that is already in its coking stage. When the coking drum
48a reaches an adequate or pre-selected temperature (which may be nominally
900 F), it may be ready to receive a bitumen charge from the coker furnace In
the
operating drum 48b, the bitumen undergoes thermal cracking which yields light
hydrocarbons in the form of a coking product vapour 50 and petroleum coke that
remains in the coker drum. The coking product vapour 50 is sent to a
fractionator
(not illustrated), which can fractionates out various different hydrocarbon
product
streams. At this point, the operating drum 48b contains some porous bitumen
and
coke.
Water is then introduced into the drum 48b for quenching purposes. The
quenching may include an initial stage of quench-steaming following by quench-
soaking. The quench-steaming stage includes adding quench water into the coker
CA 02800816 2012-12-21
.
21
drum at a flowrate such that the high temperature of the coker drum causes
most
of the quench water to be converted to steam. The resultant steam may strip
additional hydrocarbons from the pores of the bitumen remaining in the coker
drum. During the quench-steaming stage, the mixture of steam and effluent
vapours may continue to be sent into the fractionator to continue recovering
as
much high value hydrocarbon products as possible. Afterwards, during the
quench-soaking stage, more quenching water may be added at higher flowrates
into the coker drum 48b to further reduce the temperature of the coker drum
48b
and prepare the drum for coke cutting and cleaning.
For example, referring to Fig 3, each coker quenching cycle may last
approximately 4 hours per coker drum. Depending on how many coker drum pairs
are used in a given coking operation, quenching may be done on multiple coker
drums at a time (e.g. one per pair). During the quench-steaming stage,
quenching
may be initiated with a flow of about 300 USGPM for about 55 minutes. Then,
the
quench water flow may be increased at a rate of about 7.5 USGPM/min for 85
minutes, reaching a final flow rate of about 3,200 USGPM, which may be held
for
an additional 50 minutes. During this time, the quench water is retained in
the
drum and exposed to high temperature for extended time. The retained quenching
water may be retained for sufficient time to reduce the temperature of the
coker
drum to a pre-determined level and then the water may be released as a spent
quench water stream 52. Draining spent quench water 52 from the coker drum
may take several hours.
In some implementations, the domestic effluent water 38 used as coker quench
water 44 may contain a concentration of pathogens. The quenching water
requirements are such that the domestic effluent water may be efficiently used
as
coker quench water. The residual pathogens do not impair the quenching
process; rather, residual pathogens may be consumed or deactivated by the
quenching. For example, residual pathogens are exposed to sufficiently high-
temperature conditions for sufficient time so as to deactivate the pathogens.
In a particular illustrative example, a flow of recycled domestic effluent can
replace an existing API source of cooling water for the first hour of a
quenching
cycle for a coker unit. In such a scenario, about 19,000-21,000 gal. of
domestic
effluent water is used and about 79% of this water is flashed to steam. After
a
complete quenching cycle, top and bottom heads of the coker drums are removed
to extract the coke residues. By that time, water that has not flashed during
the
CA 02800816 2012-12-21
22
first hour will be drained below and sent to a coker spent water containment
system (e,g, an API lagoon system) . About 29% of water (or - 36,000 gal.),
including domestic effluent and other sources, e.g. API recycle water, is
flashed
over the entire cycle with a 125,000 gal. average total volume use. That means
that only 21% of the 19,000-21,000 gal., or about 4200 gal., on average,
survives
in liquid form to be diluted with the other sources of cooling water that make
up
the remaining 107,000 gal.of water that is fed to the coker unit during the
quenching phase. Therefore, the domestic effluent water may contain no more
than about 4 % of its original concentration of any surviving pathogens.
However, based on the fact that the domestic effluent water is trapped in the
coker for the remainder of the quenching cycle, there is ample time for the
effluent
water to be sterilized by the elevated temperature in the coker drum. Even
after
the remainder of the cooling domestic effluent water enters into the coker
drum
after the initial flashing stage, the time at which the mixture remains high
enough
in temperature (70-80 deg. C) to kill any bacteria, is more than 2 hours,
which
exceeds required conditions for the sterilization of water for food use, e.g.
between 7 minutes at 70 deg. C., and 30 minutes at 65 deg. C, or 2 hours at 60
deg. C. Consequently, any domestic effluent water entering the coker drum as
quench water will be subject to complete pathogen destruction before being
drained.
Pathogens have thus been eradicated from the drained quench water 52 that is
released from the coker unit 46. Pathogen eradication can facilitate handling
of
the spent quench water 52 downstream of the quenching. Improved handling of
the spent quench water 52 may include enhanced flexibility for water
treatment,
transportation, and recycling options into various processes that may benefit
from
a pathogen-deactivated water source.
Referring to Figs 1 and 2, the spent quench water stream 52 may be fed to a
water treatment unit 54, which may include one or more setting basins and/or
other units for removing fine solids, to produce a treated water that may be
recycled as the treated spent coker water stream 42 combined with domestic
effluent water 38 and optionally make-up water (shown as stream 58 in Fig 2).
A
portion 60 of the treated spent coker water stream 42 may also be supplied to
other processes, holding or disposal within the bitumen mining, extraction and
upgrading plant. Another portion (shown as stream 62 in Fig 1) of the treated
CA 02800816 2012-12-21
23
spent coker water stream 42 may be used within the coker unit 46 for purposes
other than coker quenching.
In some implementations, the domestic effluent water 38 may be introduced into
the coker drums at any time during the quench cycle such that the water is
exposed to at least 70 C/158 F for at least 7 minutes.
Fluid retrieval, transfer and supply between units and operations
Referring to Fig 1, the fluid transportation assembly 48 may be provided,
configured and operated for integration between the domestic effluent
treatment
operation 12 and the hydrocarbon coking operation 14.
The fluid transportation assembly 48 may include a retrieval assembly for
retrieving the domestic effluent water 24 from domestic effluent treatment
operation 12. The retrieval assembly may include a pipeline having an inlet in
fluid
communication with the polishing pond 22 and an outlet in fluid communication
with the pre-treatment unit 28. The inlet of the pipeline may be located in
the
polishing pond at location and depth to ensure retrieval of water
substantially
without air or settled material. The level of the polishing pond may be
managed in
accordance with a minimum level for submersion of the inlet.
The retrieval assembly may also include one or more retrieval pumps (shown as
26 in Fig 2) that are operatively coupled to the pipeline to enable
transporting the
domestic effluent water 24.
In some implementations, the retrieval pumps 26 can be sized for about 300
USGPM, TDH (total dynamic head) of 319 ft, and a suction pressure of about 102
PSIG. The effluent pumps 26 may include Variable Frequency Drives (VFDs) that
can serve as motor starters for the pumps, in addition to speed control of the
pumps. Speed control of the retrieval pumps 26 can facilitate operational
flexibility
in maintaining polishing pond levels or supplying water to the pre-treatment
unit
28 and/or coker unit 46. For example, variable speed pumps can allow
increasing
flow into UV reactors should UVT values be favourably high, or allow diverting
domestic effluent water through piping connection 52 to the trucks at a
greater
flow rate for polishing pond level control.
In some implementations, two or more retrieval pumps 26 may be installed to
draw domestic effluent water 24 from the polishing pond 22 for transfer to a
UV
CA 02800816 2012-12-21
24
treatment system. A controller 64, e.g. a programmable logic controller (PLC),
may be operated to start and stop the retrieval pumps 26. The controller 64
may
be configured such that the pumps do not start if the UV system is in shut-
down,
e.g. due to fault alarms. If the level of the polishing pond 22 reaches a
certain low
level, the controller 64 may be configured to wait for a certain time before
shutoff
of the retrieval pumps 26. The controller 64 may also be configured to receive
an
input signal (e.g. analog input signal) from a pressure transmitter 66
installed on
the common discharge piping from the retrieval pumps 26. The controller 64 may
be configured to shut off the two pumps if the pressure exceeds a pre-
determined
limit.
In some implementations, the retrieval pumps 26 may be FlowserveTM 2K3x1.5-
10ARV M3 S FPD DCI effluent pumps. Sizing may be based on using one
operating, and one spare pump. The pumps may include a 3" OD horizontal
suction and a 1.5" OD vertical discharge. Both suction and discharge
connections
may be 150# flat-faced, neoprene gaskets being provided for the pump
connections.
In some implementations, instead of having a VFD to operate the retrieval
pumps
26, a single speed motor starter may be used. Such a device allows operation
staff to modulate the pump flow to match lagoon inflow and quenching
operations.
The fluid transportation assembly 48 may include a supply assembly for
supplying
the water 38 to the hydrocarbon coking operation 14. The supply assembly may
include a pipeline having an inlet in fluid communication with the pre-
treatment
unit 28 for receiving the treated water, and an outlet in fluid communication
with
the coker unit 46. The outlet of the supply assembly may be coupled to an
existing quench water injection system associated with the coker drums. The
supply assembly may include various other units such as holding or surge tanks
(not illustrated), connections for combining the domestic effluent derived
water 38
with other sources of water, and recycle lines. For example, there may be a
recycle line 68 for returning a portion or all of the water exiting the pre-
treatment
unit back into the lagoon 16. The supply assembly may also include one or more
supply pumps (shown as 70 in Fig 2) that may be configured as one or more
booster pumps.
In some implementations, the supply pipeline may be substantially provided
buried underground. Such a buried supply pipeline can reduce lengths of piping
CA 02800816 2012-12-21
,
,
for which heating elements (e.g. electrical heat tracing) re installed,
reducing
electricity demands, and can also increase above-ground roadway space.
Alternatively, the supply pipeline may have above-ground routing between the
domestic effluent treatment operation 12 and the coking operation 14, which
may
5 facilitate maintenance and monitoring.
In one scenario, the fluid transportation assembly may be provided such that
retrieval flowrate of the water from the polishing pond substantially matches
the
inflow into the polishing pond. For an inflow into the polishing pond of about
70
USGPM, the retrieval flow would also be about 70 USGPM. In this case, a
treated
10 storage tank may be provided to balance the flow to the coking operation
and
provide storage capacity for interruption of re-use demand.
In some implementations, the fluid transportation assembly may be configured
and operated such that frequent fluid movement occurs in the water transport
components from the polishing pond until the coke quenching. For example, this
15 may be enabled by avoiding intermediate storage tanks along the fluid
transportation assembly 48. Storage tanks would require additional pumps
adding
to the overall cost and maintenance of the system, and may also be vulnerable
to
re-growth and associated drawbacks. The flowrate of domestic effluent water
retrieved and supplied as coker quench water may thus be coordinated with
20 transportation and pre-treatment constraints as well as inflow rates
into the
polishing pond.
In one scenario, the fluid transportation assembly may be provided such that
the
retrieval flowrate of the water from the polishing pond is between about 2 to
8
times greater than the inflow into the polishing pond 22 and retrieval of
water from
25 the polishing pond is performed intermittently such that the overall
retrieval rate is
balanced with the inflow rate. For example, for an inflow into the polishing
pond of
about 70 USGPM, the retrieval flow would be between about 140 USGPM to 560
USGPM for between about 30 minutes per hour and about 7 1/2 minutes per hour
(e.g. 300 USGPM for 14 minutes per hour). This relatively larger retrieval
flow can
facilitate the ability to use the polishing pond to store untreated domestic
effluent
and catch up on subsequent quenching cycles and/or transfer water to other
sources such as other lagoons or truck hauling.
CA 02800816 2012-12-21
26
Additional aspects of some implementations
In some implementations, the fluid transportation assembly 48 may be
configured
and controlled so as to coordinate water retrieval from the domestic effluent
treatment operation 12 with supply to the hydrocarbon coking operation 14. The
retrieval pumps 26, the pre-treatment unit 28 and the interaction with the
coker
drum quenching cycle can be accomplished by operating the fluid transportation
assembly 48 using timed pump cycles. The retrieval pumps 26 may be operated
cyclically in on or off mode to retrieve the water from the polishing pond 22,
operating for a pre-determined time to balance inflow of the primary effluent
water
20 fed into the polishing pond 22 with the outflow of domestic effluent water
24
from the polishing pond 22. For example, if the inflow into the polishing pond
22 is
about 70 USGPM, the retrieval pumps 26 may be operated for 14 minutes every
hour as a retrieval rate of 300 USGPM, thereby balancing the inflow and
outflow
on an hourly basis. Rather than using pond level for control, which may have
lower accuracy as the change of level over a cycle is minimal and false
signals
may occur with wind and storm water ingress, the control may be based on
inflow
readings into the polishing pond 22.
In some implementations, the controller 64 may have a wireless network
connection for monitoring and controlling various operating and measurement
devices.
In some implementations, use of domestic effluent water as an on-site dirty
water
resource for coker quenching reduces demands for other sources of cleaner
water, such as adjacent natural bodies of water.
In some implementations, if the volume of treated domestic effluent is
sufficient to
be accumulated as a source of coker cutting water, the treated domestic
effluent
may be alternately used for the cutting and removal of the coke that has
accumulated within a coker drum. In other implementations, all treated
domestic
effluent water may be pooled together in a tank and then drawn on for either
cutting or quenching operations according to operational needs.
Various modifications may be made to the disclosed implementations and still
be
within the scope of the following claims.
