CA2848572A1

CA2848572A1 - Waste water evaporators and methods

Info

Publication number: CA2848572A1
Application number: CA2848572A
Authority: CA
Inventors: Henry Giesbrecht
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-04-10
Filing date: 2014-04-10
Publication date: 2015-10-10

Abstract

A waste water evaporator is disclosed comprising: a tank with an evaporation chamber and a heat chamber in thermal communication with the evaporation chamber; the evaporation chamber having a waste water inlet and a gas outlet; and the heat chamber being associated with a temperature sensor and comprising a basin for holding a heat transfer fluid, and a heater disposed within the basin for immersion in the heat transfer fluid when in use.

Description

WASTE WATER EVAPORATORS AND METHODS
TECHNICAL FIELD
[0001] This document relates to waste water evaporators and methods.
BACKGROUND

[0002] Waste water, for example from a drilling rig at an oil or gas well site, may be contaminated with oil or other components. There are a variety of methods used to dispose of waste water. For example the waste water may be periodically trucked offsite for disposal in an injection well or for processing. Alternatively an evaporator may be used evaporate the water onsite. Such evaporators may use a high surface area steam or air heat exchanger inside an evaporation tank, or a burner, to supply the heat needed to evaporate the water.
Internal heat exchangers or electric coils may become caked with residue leading to reduced heat transfer and burnout. To reduce residue buildup an evaporator may incorporate a settling tank adjacent the evaporation tank.
SUMMARY

[0003] A waste water evaporator is disclosed comprising: a tank with an evaporation chamber and a heat chamber in thermal communication with the evaporation chamber; the evaporation chamber having a waste water inlet and a gas outlet; and the heat chamber being associated with a temperature sensor and comprising a basin for holding a heat transfer fluid, and a heater disposed within the basin for immersion in the heat transfer fluid when in use.

[0004] A waste water evaporator is disclosed comprising: a tank with an evaporation chamber, the evaporation chamber having a base, an enclosing side wall, a waste water inlet, and a gas outlet, the base and enclosing side wall defining an interior; and an electric heating element outside the interior.

[0005] A waste water evaporator is disclosed comprising: a tank divided by a partition into an evaporation chamber and a heating chamber, the evaporation chamber having a base, an enclosing side wall, a waste water inlet, and a gas outlet, the partition forming at least part of the base of the evaporation chamber; and a heater in the heating chamber.

[0006] A waste water evaporator is also disclosed for drilling fluids, the water evaporator having a first reservoir with an enclosing side wall or base adjacent or in contact with an enclosing side wall or ceiling of a second reservoir external to the first reservoir, the first reservoir receiving drilling fluids to be evaporated, the second reservoir containing a fluid medium, an electric heating coil, and a temperature sensor.

[0007] A combination is disclosed comprising the waste water evaporator and a boiler at a well site, in which the tank is connected to receive waste water from the boiler. 14

[0008] A combination is also disclosed of the waste water evaporator and a drilling rig at an oil or gas well site.

[0009] A method is disclosed comprising evaporating waste water using the waste water evaporators.

[0010] A method is also disclosed comprising: supplying waste water into an evaporation chamber, the evaporation chamber having a base and an enclosing side wall; and evaporating the waste water by operating a heat chamber to transfer sufficient heat, by conduction and radiation, across one or more of the base and enclosing side wall of the evaporation chamber; in which the heat chamber comprises a heater immersed in a heat transfer fluid.

[0011] In various embodiments, there may be included any one or more of the following features: A controller is connected to regulate the heat output of the heater in response to signals from the temperature sensor. The controller is connected to regulate the heat output of the heater to maintain a temperature of the heat transfer fluid in the basin within a predetermined range. The predetermined range is above the boiling point of water in the tank and below four hundred degrees Celsius. The heater comprises an electric heating element. The evaporation chamber has a base and an enclosing side wall; the tank is divided by a partition into the evaporation chamber and the heat chamber; and the partition forms at least part of the base. The base comprises a planar surface. The basin comprises oil as the heat transfer fluid. A storage tank with an inlet and an outlet, the outlet connected to the waste water inlet of the tank; and a mobile platform upon which the tank and storage tank are mounted. The inlet of the storage tank is connected to a boiler at an oil or gas well site. A
level sensor in the tank, the level sensor connected to operate a valve on the waste water inlet. The mobile platform further comprises a housing enclosing the tank and the storage tank. The tank is divided by a partition into the evaporation chamber and a heating chamber, and the electric heating element is within the heating chamber. The heat chamber further comprises a basin for holding a heat transfer fluid, a temperature sensor, and the electric heating element disposed within the basin for immersion in the heat transfer fluid when in use, and further comprising a controller connected to regulate the heat output of the electric heating element in response to signals from the temperature sensor. The heater comprises an electric heating element, and in which operating the heat chamber further comprises supplying electricity to the electric heating element. Regulating the heat output of the heater in response to the temperature of the heat transfer fluid. Maintaining a level of waste water in the evaporation chamber at or near a base of the evaporation chamber. The heater comprises an electric coil, and further comprising an electric generator connected to the heater.

[0012] These and other aspects of the device and method are set out in the claims, which are incorporated here by reference.
BRIEF DESCRIPTION OF THE FIGURES

[0013] Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which:

[0014] Fig. 1 is a side elevation view, partially in section, of a mobile waste water evaporator connected to a boiler.

[0015] Fig. 2 is a side elevation view of the waste water evaporator of Fig.1 adjacent a drilling rig at an oil or gas well site.
DETAILED DESCRIPTION

[0016] Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.

[0017] List of references numbers used in the drawings:

[0018] 10-evaporator

[0019] 12-tank

[0020] 14-heater

[0021] 15-electric heating element

[0022] 16-evaporation chamber

[0023] 18-base of the evaporation chamber

[0024] 20-enclosing side wall or side walls of the evaporation chamber

[0025] 22-waste water inlet to the evaporation chamber

[0026] 24-gas outlet from the evaporation chamber

[0027] 26-interior of the evaporation chamber

[0028] 28-skid

[0029] 30-waste water

[0030] 32-exhaust tube

[0031] 34-hinge point

[0032] 36-roof

[0033] 38-heat chamber

[0034] 39-manhole

[0035] 40-partition

[0036] 42-basin

[0037] 44-heat transfer fluid

[0038] 45-sight window or tube

[0039] 46-temperature sensor

[0040] 47-oil level

[0041] 50-controller

[0042] 52-electricity wires

[0043] 54-oil or gas well site

[0044] 55-well head

[0045] 56-on-site generator

[0046] 58-drilling equipment

[0047] 60-drilling rig

[0048] 62-fluid level

[0049] 64-float

[0050] 66-cable

[0051] 68-float operated valve

[0052] 70-outlet from the storage tank

[0053] 71-alert mechanism

[0054] 72-storage tank

[0055] 73-raised base

[0056] 74-corner posts

[0057] 75-on / off switch or lever

[0058] 76-inlet to the storage tank

[0059] 78-boiler

[0060] 80-housing

[0061] 81-roof

[0062] Referring to Fig. 1 a waste water evaporator 10 is illustrated having a tank 12 and a heater 14. Tank 12 has an evaporation chamber 16. The evaporation chamber 16 may have a base 18, an enclosing side wall or side walls 20, a waste water inlet 22, and a gas outlet 24. The base 18 and enclosing side wall 20 may define an interior 26.
The tank 12 may be of a suitable shape, for example a cylindrical or cuboid tank. The evaporation chamber 16 may contain waste water 30, which may have been added to the chamber 16 through inlet 22.
Gas outlet 24 may comprise an exhaust tube 32, which may be collapsible or adapted to hinge at a hinge point 34 for a reduced profile during transport. Exhaust tube 32 may extend out of and beyond a roof 36 of tank 12, in order to release heated vapors at an exit point spaced above the tank 12. A lid, such as a manhole 39 may be present in roof 36 or side walls 20 in order to permit access to the interior 26 of chamber 16. In some cases the roof 36 may be hinged, or provided as a lid with one or more locking devices, in order to allow the entire roof 36 to be opened, closed, or removed. A walkway, such as a grate (not shown) with a railing may be present on roof 36 for safety, and a ladder (not shown) may be provided on wall 20 for access to roof 36.

[0063] Heater 14 may be positioned in a heat chamber 38, which is in thermal communication with the evaporation chamber 16. Tank 12 may be divided into the heat chamber 38 and evaporation chamber 16 by a partition 40, which may form at least part of the base 18 in the example shown. The base 18 may comprise a planar surface, which includes surfaces that deviate nominally from a horizontal plane, for example if the base 18 has a concave or convex shape. Although one or both of a planar base surface and a heat chamber 38 outside the interior 26 of the evaporation chamber 16 will not maximize surface area between the heat chamber 38 and the evaporation chamber 16, such an arrangement makes it easier to remove residue that is caked on the base 18. To clean residue off of base 18 a worker may enter the chamber 16 and scrape the residue off the base 18 with a shovel or other scraping element. In other cases the heat chamber 38 may be adjacent, instead of contiguous with, the tank 12 or chamber 16.

[0064] Heat chamber 38 may comprise a basin 42 for holding a heat transfer fluid 44 and heater 14 disposed within the basin 42. A temperature sensor 46 is associated with the heat chamber 38, for example if the temperature sensor 46 is within the basin 42. In use the basin 42 contains heat transfer fluid 44 (such as oil) and the temperature sensor 46 and the heater 14 are immersed in the heat transfer fluid 44. A sight window or tube 45 may be provided off the basin 42 for visually assessing the level 47 and quality of the oil in the basin 42.

[0065] A controller 50 may be connected to regulate the heat output of the heater 14 in response to signals from the temperature sensor 46. The temperature sensor 46 may be outside the heat chamber 38 in some cases, or provided as part of the heater 14 in other cases. The use of a fluid or oil bath and a mechanism for monitoring the heat output in response to temperature reduces the chance of a burnout of the heater 14 caused by overheating. The controller 50 may regulate the heater 14 to maintain the heat transfer fluid 44 within a predetermined range, for example above the boiling point of water and below four hundred degrees Celsius, for example between two hundred and three hundred fifty degrees Celsius. A maximum temperature over four hundred degrees may be inadvisable at an oil or gas well site due to the risk of ignition of airborne hydrocarbons and oil in the basin 42.

[0066] The heater 14 may comprise an electric heating element 15. The element 15 may have contacts for connecting to electricity wires 52 for receiving electricity from a power source. Controller 50 may regulate the heat output of element 15 by reducing or increasing the current passing through the element 15 to lower or raise the basin 42 temperature. An electric heating element 15 may employ a resistor to convert electricity to heat. Referring to Fig. 2, an electrically powered evaporator 10 may be advantageous at an oil or gas well site 54 because such sites 54 contain an on-site generator 56 that is connected to power other components like drilling equipment 58 if a drilling rig 60 is on site 54. The generator 56 may be provided as part of the rig 60, and during operations usually uses less than half of the electrical production capacity at any given moment. Thus there is usually room left for extra power to be consumed by evaporator 10 operations to occur simultaneous with drilling operations. The evaporator 10 may be run by the main or backup generator, if a backup generator is provided. The main generator may run all the rig's electricity and drilling activities, including powering lights on the rig 60 tower. A well head 55 is illustrated as being present as part of a well site 54, which is understood to encompass the working area adjacent the well site 54.

[0067] The evaporator 10 may be run at an evaporation rate sufficiently low to avoid overdrawing current from generator 56 and to avoid interference with the operation of the other machinery connected to generator 56. Referring to Fig. 1, one way of achieving such a result is to maintain the level 62 of waste water in the evaporation chamber 16 at or near the base 18 of the evaporation chamber 16, much like a frying pan. The level 62 may be a foot or less in some cases, although the embodiments disclosed here are not limited to any particular level 62 and levels 62 above a foot may be used. When operated in such a manner the evaporator 10 may achieve more efficient evaporation and reduced heat loss than if the chamber 16 were filled to the roof 36 with waste water during evaporation. A
low fluid level in chamber 16 is expected to see an increase in evaporation efficiency due to the shortened residence time of waste water introduced into the evaporator, thus giving less time for retained fluids to lose heat to the surrounding environment.

[0068] The level 62 of waste water in chamber 16 may be monitored using a level sensor such as a float 64. The float 64 may be connected, for example by a cable 66 to a float operated valve 68 on the waste water inlet 22. Thus, as the level 62 rises past a predetermined level, the valve 68, such as a pivot valve, is shut off until the level 62 drops.

Other level sensors may be used, such an ultrasonic or conductive sensors. A
controller such as controller 50 may be connected to sensor 64 and valve 68.

[0069] The tank 12 may be mounted on a mobile platform such as a skid 28.
Corner posts 74 may be provided to protect tank 12 and other components from accidental contact with heavy equipment on site. The skid 28 may be adapted to be transported by truck, in order to provide a mobile evaporator 10 that can be transported to and from job sites.

[0070] A storage tank 72 may also be provided on the skid 28. Waste water inlet 22 may be connected to an outlet 70 of storage tank 72. Storage tank 72 may be raised or have a raised base 73 sufficiently high relative to tank 12 to permit gravity drainage of waste water in tank 12 into evaporation chamber 16 and thus avoid the need for a pump.

[0071] The storage tank 72 may also have an inlet 76 connected to a boiler 78. The boiler 78 may be responsible for heating the rig 60 and associated components, among other things. Boiler blow down is a common part of boiler maintenance and involves intentional removal of water from a boiler to avoid concentration of impurities during continuing evaporation of steam. Current practice is to blow down the boiler water into a tank on a truck for remote disposal if no evaporator is present on site. Well operations may be forced to pause until boiler blow down and refilling is complete. Pausing operations during sub zero temperatures may lead to equipment becoming frozen and temporarily inoperable.
However, with evaporator 10 a boiler 78 may be blown down into storage tank 72 in a short manner of time, reducing or eliminating the pause in operation.

[0072] The skid 28 may further comprise a housing 80 at least partially enclosing the tank 12 and the storage tank 72. A housing 80 provides a layer of thermal insulation and protection to the internal components of the housing 80. Thermal insulation may improve the efficiency of evaporator 10, particularly during operation in sub zero environments where ambient temperatures may drop below minus forty degrees Celsius. Housing 80 may also protect workers and equipment from accidental contact with the work surfaces of the tank 12. The skid 28 may be adapted to be carried by a winch tractor or picked up by a loader.
Loops (not shown) may be provided for a truck to hook onto the skid 28. The housing 80 may have a ladder, grating, and rails (not shown) to permit a user to access the roof 81 of the housing 80.

[0073] A heat chamber 38 external to the evaporation chamber 16 interior 26 may rely on conductive and radiative heat transfer across one or more of the base 18 and enclosing side wall 20 of the chamber 16. Such heat transfer is expected to transfer heat less efficiently than an in-tank heat exchanger, which circulates heated fluid through circuits within the chamber 16 itself and maximizes heat transfer surface area.
However, at least some of the disclosed embodiments are expected to reduce the negative effects of residue buildup within the chamber 16.

[0074] Although boiler fluid is taught above as one type of waste water processed in tank 12, other waste water fluids may be processed. In the well site 54 example above, drilling fluids may also be passed through evaporator 10. An oil removal device (not shown) such as a skim plate and outlet may be provided to remove oil that accumulates in the evaporator 10. Evaporator 10 may be used in other suitable applications. A
settling tank (not shown) or other processor may pre-process fluids prior to entry into chamber 16.

[0075] In some cases the electric heating element 15 may be enclosed by a body of solid conductive material like metal instead of a fluid bath provided by basin 42. In some cases the base 18 and at least a portion of the side wall 20 are nested within the heat chamber 38 like a double boiler. One or both base 18 and partition 40 may be provided by a plate as shown. A circulation mechanism such as a stirring apparatus (not shown) may be provided in basin 42 to ensure a consistent temperature throughout the basin 42 to avoid hot or cold spots.

[0076] In some cases the controller 50 may shut off the heater 14 past a predetermined temperature. For example, the temperature may rise when all fluids in chamber 16 are evaporated, leading to heater 14 shut off. An alert mechanism 71, such as a light, may go off at such a point, signaling a user to perform an action such as manually filling the evaporation chamber 16 with more fluids or shutting off the entire system. In other cases, for example where no controller 50 is used, the alert mechanism 71 may go off when one or both the temperature rises or the level 62 decreases past a predetermined temperature or level, respectively. A winch (not shown) may be provided on skid 28. An on / off switch or lever 75 may be present on the exterior of housing 80 or tank 12 if no housing 80 is present for manually turning on and turning off the evaporator 10.

[0077] In the claims, the word "comprising" is used in its inclusive sense and does not exclude other elements being present. The indefinite articles "a" and "an"
before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A waste water evaporator comprising:
a tank with an evaporation chamber and a heat chamber in thermal communication with the evaporation chamber;
the evaporation chamber having a waste water inlet and a gas outlet; and the heat chamber being associated with a temperature sensor and comprising a basin for holding a heat transfer fluid, and a heater disposed within the basin for immersion in the heat transfer fluid when in use.

2. The waste water evaporator of claim 1 further comprising a controller connected to regulate the heat output of the heater in response to signals from the temperature sensor.

3. The waste water evaporator of claim 2 in which the controller is connected to regulate the heat output of the heater to maintain a temperature of the heat transfer fluid in the basin within a predetermined range.

4. The waste water evaporator of any one of claim 2 - 3 in which the predetermined range is above the boiling point of water in the tank and below four hundred degrees Celsius.

5. The waste water evaporator of any one of claim 1 - 4 in which the heater comprises an electric heating element.

6. The waste water evaporator of any one of claim 1 - 5 in which:
the evaporation chamber has a base and an enclosing side wall;
the tank is divided by a partition into the evaporation chamber and the heat chamber;
and the partition forms at least part of the base.

7. The waste water evaporator of claim 6 in which the base comprises a planar surface.

8. The waste water evaporator of any one of claim 1 - 7 in which the basin comprises oil as the heat transfer fluid.

9. The waste water evaporator of any one of claim 1 - 8 further comprising:

a storage tank with an inlet and an outlet, the outlet connected to the waste water inlet of the tank; and a mobile platform upon which the tank and storage tank are mounted.

10. The waste water evaporator of claim 9 in which the inlet of the storage tank is connected to a boiler at an oil or gas well site.

11. The waste water evaporator of any one of claim 9 - 10 further comprising a level sensor in the tank, the level sensor connected to operate a valve on the waste water inlet.

12. The waste water evaporator of any one of claim 9 - 11 in which the mobile platform further comprises a housing enclosing the tank and the storage tank.

13. A waste water evaporator comprising:
a tank with an evaporation chamber, the evaporation chamber having a base, an enclosing side wall, a waste water inlet, and a gas outlet, the base and enclosing side wall defining an interior; and an electric heating element outside the interior.

14. The waste water evaporator of claim 13 in which the tank is divided by a partition into the evaporation chamber and a heating chamber, and the electric heating element is within the heating chamber.

15. The waste water evaporator of claim 14 in which the heat chamber further comprises a basin for holding a heat transfer fluid, a temperature sensor, and the electric heating element disposed within the basin for immersion in the heat transfer fluid when in use, and further comprising a controller connected to regulate the heat output of the electric heating element in response to signals from the temperature sensor.

16. A method comprising evaporating waste water using the waste water evaporators of any one of claim 1 - 15.

17. A method comprising:
supplying waste water into an evaporation chamber, the evaporation chamber having a base and an enclosing side wall; and evaporating the waste water by operating a heat chamber to transfer sufficient heat, by conduction and radiation, across one or more of the base and enclosing side wall of the evaporation chamber;
in which the heat chamber comprises a heater immersed in a heat transfer fluid.

18. The method of claim 17 in which the heater comprises an electric heating element, and in which operating the heat chamber further comprises supplying electricity to the electric heating element.

19. The method of any one of claim 17 - 18 further comprising regulating the heat output of the heater in response to the temperature of the heat transfer fluid.

20. The method of any one of claim 17 - 19 further comprising maintaining a level of waste water in the evaporation chamber at or near a base of the evaporation chamber.