Patent Application
20130264185
The invention relates generally to the cleaning and desalination of water, and in a particular though non-limiting embodiment to systems, methods and means for cleaning and desalinating production water obtained from an oil or gas well.
Oil pumped from a well is not produced in a pure form; rather, it is typically mixed with a brine solution. Accordingly, this solution is usually called production water. Subsequent treatment in a separation and storage tank unit separates the oil from the brine, primarily due to a difference in their respective densities. Consequently, oil is usually separated toward the top of the unit because it is lighter, whereas the brine tends to accumulates toward the bottom of the unit because it is heavier.
The oily brine disposal process is frequently a complicated and expensive operation. For example, the oily brine can only be disposed of at regulatory approved sites, which are sometimes located far from the well site. The cost of oily brine is therefore relative to the distance of the well site from the disposal site. An alternative approach, therefore, is to desalinate the brine water as much as possible, so that less waste product needs to be transported to storage sites.
Current desalination methods primary include reverse osmosis, and evaporation. Evaporation can be achieved in many different ways, for example, using multi steam flash units; multiple effect evaporators; vapor compression evaporators; and a combination of multiple effect evaporators and vapor compression evaporators of various arrangements. These approaches can, depending on system design and operation requirements, comprise a variety of either single stage evaporation effects and/or or multiple evaporation effects.
In multiple-effect evaporation, a single steam energy source is used to produce steam in a plurality of evaporators, applying a cascade of pressures and temperatures from one effect to the next. Feed flow is run in either a series concurrent flow or counter flow toward the steam flow. In either case, the concentration of the brine increases toward the direction of the flow.
Ordinarily skilled artisans will appreciate that the higher the salt concentration in the production water being desalinated, the higher the resulting viscosity of the fluid; thus, higher heat transfers resistance as well as a pressure drop through the heat exchanger. A selection of the specific type of desalination system will be dictated by the cost of operations, and especially the cost of fuel; in most cases, however, the use of evaporation technology is effectively negated by the prohibitive costs of fuel or energy.
There is, therefore, a longstanding but unmet need for a simple and efficient productions water desalination unit and methods of operating the same that overcome the inefficiencies and limitations of the existing prior art.
The present invention greatly reduces the cost of production water disposal by evaporating water from the brine, thereby significantly decreasing the volume. The product distillate can then be disposed of safely, and subsequently used for irrigation and other applications. The distillate can even be processed and converted into potable drinking water.
The instant application discloses a plurality of systems and means for the safe, effective and economical desalination of oily brine and brackish production water. Associated methods of operations and proposed systems and subsystems are also disclosed. The system also admits to waste heat recovery from internal combustion engine exhaust and jacket cooling water, thereby utilizing the heat energy of a fuel feed to maximize system efficiency. The system and method are useful for desalinating not only oily brine water, but also brackish water, sea water, waste treatment plant water, flood water, etc.
In one specific though non-limiting embodiment, the claimed invention includes means for brine preparation; means for pre-heating brine using process heat recovery; means for producing heat energy from electricity generated and heat recovery from exhaust of the engine for evaporation; means for producing a first steam in a first effect heat exchanger; means for producing a second steam and a first distillate in a second effect heat exchanger; means for producing a third steam and a second distillate in a third effect heat exchanger; means for producing a third distillate in a condenser; and means for recovering process heat in a product heat recovery heat exchanger.
In a specific though limiting example embodiment of a method appropriate for operating the claimed system, the method includes disposing a means for brine preparation in communication with a means for pre-heating brine using process heat recovery; disposing the means for pre-heating brine using process heat recovery in communication with a means for evaporation; disposing the means for evaporation and transfer of heat energy using high temperature heat transfer fluid in communication with a means for producing a first steam in a first effect heat exchanger; disposing the means for producing a first steam in a first effect heat exchanger in communication with a means for producing a second steam and a first distillate in a second effect heat exchanger; disposing the means for producing a second steam and a first distillate in a second effect heat exchanger in communication with a means for producing a third steam and a second distillate in a third effect heat exchanger; disposing the means for producing a third steam and a second distillate in a third effect heat exchanger in communication with a means for producing a third distillate in a condenser; and disposing the means for producing a third distillate in a condenser in communication with a means for recovering process heat in a product heat recovery heat exchanger.
The desalination process disclosed herein is essentially a thermal multiple effect evaporation process, which uses cascading steam pressures and temperatures to produce various effects. One unique feature of the system is the ability to recover waste heat from an associated internal combustion engine. The process differs from conventional evaporation units in many ways, for example, by using a parallel feed rather than series forward flow or series counter flow. The series feed flow in either concurrent flow or counter flow toward the steam flow may also be used depending on the specific application and optimization.
For ease of understanding, an example process flow for a three-effect evaporator with parallel feed is shown and described, though those of ordinary skill in the art will readily appreciate that evaporators comprising series feed and more than three effects will also fall within the spirit and scope of the instant disclosure.
With reference now to attached
A. Brine Preparation
With reference now to
Heating the oily brine enhances the separation of oil from brine. The coalescer elements in Oil-Brine Two-Phase Separator Drum (2) coalesces minute particles of oil into larger particle and float, thereby separating it from the brine. The quantity of oil after the coalescing process is determined in large part by Liquid Level Controller (26a), which opens an Oil Return Control Valve (19) if a predetermined quantity of oil level is detected and deemed sufficient to be returned to Oil-Brine Separation/Storage Tank (1).
In a further embodiment, heat energy used to heat the brine in Oil-Brine Two-Phase Separator Drum (2) is derived from heat recovered from an Internal Combustion Engine (13) jacket cooling system. An engine pump circulates coolant to Oil-Brine Separator Heater Coil (18), thereby dissipating heat to the brine disposed in the Oil-Brine Two-Phase Separator Drum (2), which necessarily raises the temperature of the brine.
In one embodiment, an Engine Coolant Three-Way Valve (20) controls the temperature of the coolant entering the Internal Combustion Engine jacket cooling system by means of a Temperature Controller (29). The Engine Coolant Three Way Valve (20) port going to Oil-Brine Separator Heater Coil (18) is normally open, and the port towards Air Cooler (14) is normally closed.
When the temperature of the coolant coming back from Oil-Brine Separator Heater Coil (18) at the inlet of the Internal Combustion Engine is higher than the set point of the Temperature Controller (29), coolant is diverted to an Air Cooler (14) in order to vent heat to the atmosphere. In certain embodiments, the Air Cooler (14) fan only operates when heat from the Internal Combustion Engine jacket cooling system is more than the heating requirement of the oily brine in the Oil-Brine Two-Phase Separator Drum (2); otherwise, the fan is turned off.
B. Pre-Heating by Process Heat Recovery
In other embodiments, the feed brine is pre-heated with heat recovered from the process. The separated brine from the Oil-Brine Two-Phase Separator Drum (2) is fed to the system by Brine Feed Pump (17b). The brine passes to the Air Separator/Vent (28), where air is vented to the atmosphere. The brine is degassed from this air separator. The brine is pre-heated to a higher temperature after passing through the Condenser (10), and then further heated to a higher temperature with heat recovered from Product Heat Recovery Heat Exchanger (11).
C. Production of Heat Energy for Evaporation
In other embodiments, the heat energy required for evaporation of the single steam from the First Effect Evaporator/Heat Exchanger (4) is supplied by Exhaust Heat Recovery Heat Exchanger (3) and Electric Heater (16) via heat transfer fluid circulated by Heat Transfer Fluid Circulating Pump (22). The heat energy from heat Exhaust Heat Recovery Heat Exchanger (3) is the heat recovered from the exhaust gas of the Internal Combustion Engine (13). In other embodiments, the electric energy supplied to Heater Coil (16) is the electric energy produced by the Electric Generator (15). In this embodiment, the heat energy from both sources is needed to maximize the use of Engine-Generator set (13) and (15).
In further embodiments, the heat energy from Exhaust Heat Recovery Heat Exchanger (3) is controlled by Engine Exhaust Damper Control (21). This Engine Exhaust Damper Control (21) modulates to meet the energy requirement of Exhaust Heat Recovery Heat Exchanger (3). The Electric Heater (16) is controlled by its own temperature controller. Both energy sources (3) and (16) are monitored and controlled by the thermal controller of First Effect Evaporator/Heat Exchanger (4).
In still further embodiments, the heat transfer loop is a closed loop using high temperature oil heat transfer fluid. The heating loop is provided with Expansion Tank (27) to protect the system from high pressure due to expansion of the heat transfer fluid inside the piping and equipment in the loop when the system is subjected to different and varying temperatures.
D. Producing a First Steam in the First Effect Evaporator/Heat Exchanger
In other embodiments, a First Steam is produced in the First Effect Evaporator/Heat Exchanger (4). The heat energy as described above in Paragraph C (regarding Heat Energy for Evaporation), and is used to evaporate some of the water from the feed brine which was pre-heated as described in paragraph B (regarding Pre-Heating by Process Heat Recovery). In the depicted embodiments, the brine leaves First Effect Evaporator/Heat Exchanger (4) in two-phases (steam and brine). The mixture is then piped to the First Effect Brine Steam Separator (5) where the steam is separated from the brine. Subsequently, the steam is extracted from the top of the vessel of First Effect Brine Steam Separator (5) and brine exits at the bottom.
The pressure of the brine supplied to this stage is controlled by Pressure Regulating Valve (23a). The Pressure Regulating Valve (23a) pressure setting is set to the design pressure. This set pressure is higher than the pressure in the next stage. This set pressure also determines the steam saturation temperature of this stage. During operation, the steam pressure in this stage is controlled by the Back Pressure Control Valve (25a) located in the drip leg of Second Effect Evaporator/Heat Exchanger (6).
The liquid level of waste brine in First Effect Brine Steam Separator (5) is controlled by Liquid Level Controller (26b) that opens and closes the Liquid Level Control Valve (24a). The waste is collected in the waste header that mixes the waste from other waste legs.
E. Producing a Second Steam and First Distillate in Second Effect Heat Exchanger
In further embodiments still, the First Steam produced by the First Effect Evaporator/Heat Exchanger (4) via First Effect Brine Steam Separator (5) is piped to Second Effect Evaporator/Heat Exchanger (6). The steam in the hot side of the Second Effect Evaporator/Heat Exchanger (6) condenses, thereby transferring the heat energy to the brine on the cold side of the heat exchanger. This process evaporates some of the water from the feed brine which was pre-heated as described in paragraph B (regarding Pre-Heating by Process Heat Recovery).
The brine then leaves Second Effect Evaporator/Heat Exchanger (6) in two-phases (steam and brine). This mixture is piped to the Second Effect Brine Steam Separator (7), where the steam is separated from the brine. Again, the steam is extracted from the top of the vessel of Second Effect Brine Steam Separator (7), and brine exits at the bottom.
In alternative embodiments, the pressure of the brine supplied to this stage is controlled by Pressure Regulating Valve (23b). In the depicted embodiment, the valve pressure setting is set to the stage design pressure. This set pressure is lower than previous stage but higher than the pressure in the next stage. This set pressure also determines the steam saturation temperature of this stage. During operations the steam pressure in this stage is controlled by the Back Pressure Control Valve (25b) located in the drip leg of Third Effect Evaporator/Heat Exchanger (8).
The liquid level of waste brine in Second Effect Brine Steam Separator (7) is controlled by Liquid Level Controller (26c), which opens and closes the Liquid Level Control Valve (24b). The waste is collected in the waste header that mixes the waste from other waste legs.
The First Distillate produced in this stage is controlled by the Back Pressure Control Valve (25a) located in the drip leg of Second Effect Evaporator/Heat Exchanger (6), and the drip is collected in a header that mixes the distillate from other drip legs.
F. Producing a Third Steam and Second Distillate in a Third Effect Heat Exchanger
In further embodiments, the steam produced by the Second Effect Evaporator/Heat Exchanger (6) via Second Effect Brine Steam Separator (7) is piped to Third Effect Evaporator/Heat Exchanger (8). The steam in the hot side of the Third Effect Evaporator/Heat Exchanger (8) condenses, thereby transferring the heat energy to the brine on the cold side of the heat exchanger. The process evaporates some of the water from the feed brine which was pre-heated as described in paragraph B (regarding Pre-Heating by Process Heat Recovery). The brine leaves Third Effect Evaporator/Heat Exchanger (8) in two-phase (steam and brine). The mixture is piped to the Third Effect Brine Steam Separator (9) where the steam is separated from the brine. The steam is extracted from the top of the Third Effect Brine Steam Separator (9) and brine exits at the bottom.
The pressure of the brine supplied to this stage is controlled by Pressure Regulating Valve (23c). This valve pressure setting is set to the stage design pressure. This set pressure is lower than previous stage. This set pressure also determines the steam saturation temperature of this stage. During operations the steam pressure in this stage is controlled by the Back Pressure Control Valve (25c) located in the drip leg of Condenser (10).
In this embodiment, the waste liquid level of brine in Third Effect Brine Steam Separator (9) is controlled by Liquid Level Controller (26d), which opens and closes the Liquid Level Control Valve (24c). The waste is collected in the waste header that mixes the waste from other waste legs, and is then piped to a waste storage tank
The Second Distillate produced in this stage is controlled by the Back Pressure Control Valve (25b) located in the drip leg of Third Effect Evaporator/Heat Exchanger (8), and again the drip is collected in header that mixes the distillate from other drip legs.
G. Producing a Third Distillate and Process Heat Recovery in a Condenser
In other embodiments, the Steam produced by the Third Effect Evaporator/Heat Exchanger (8) via Third Effect Brine Steam Separator (9) is piped to Condenser (10). The steam in the hot side of the Condenser (10) condenses transferring the heat energy to the brine on the cold side of the heat exchanger and, in the process, heating feed brine coming from the Air Separator/Vent (28). The brine inlet temperature is lower that the steam saturation temperature. The brine leaves Condenser (10) at higher temperature.
The Third Distillate produced in this stage is controlled by the Back Pressure Control Valve (25c) located in the drip leg of Condenser (10), and the drip is collected in header that mixes with the distillate from other drip legs.
H. Process Heat Recovery in Product Heat Recovery Heat Exchanger
In still further embodiments, the drips collected from the drip legs and piped to Product Flash Tank (12). The Distillate being at high pressure and temperature will flash and produce steam as it enters Product Flash Tank (12) at lower pressure. The flashed steam is extracted and piped to Condenser (10) and condenses with the steam from Third Effect Brine Steam Separator (9).
The Distillate from Product Flash Tank (12) is piped to Product Heat Recovery Heat Exchanger (11). This serves as a hot fluid, and the brine from Condenser (10) serves as the cold fluid. The feed brine leaves the Product Heat Recovery Heat Exchanger (11) at a higher temperature passing through the final stage of pre-heating, thereby optimizing the heat recovery process of the system. The cooler Distillate leaving the Product Heat Recovery Heat Exchanger (11) will be piped to a product storage tank.
The foregoing description is intended primarily for illustrative purposes, and is not intended to include all possible aspects of the present invention. Moreover, while the invention has been shown and described with respect to a presently preferred embodiment, those of ordinary skill in the art will appreciate that the description, and various other modifications, omissions and additions, so long as in the general form and detail, may be made without departing from either the spirit or scope thereof.
The present application claims the benefit of prior U.S. provisional application No. 61/620,057 filed Apr. 4, 2012.
| Number | Date | Country | |
|---|---|---|---|
| 61620057 | Apr 2012 | US |
