CA2713077A1

CA2713077A1 - Line heater

Info

Publication number: CA2713077A1
Application number: CA2713077A
Authority: CA
Inventors: Ashim Joseph
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-08-17
Filing date: 2010-08-17
Publication date: 2012-02-17

Abstract

A line heater includes a container having an interior surface defining an interior cavity and an exterior surface. A flow conduit passes through the interior cavity of the container. A plurality of discrete solid bodies of heat transfer medium surrounds the flow conduit. A heat source is provided for heating the heat transfer medium, whereby heat is transferred from the heat source to the flow conduit.

Description

TITLE
[0001] Line Heater FIELD

[0002] There is described a line heater that is used to prevent fluids in a flow line from freezing.

BACKGROUND

[0003] Line heaters are used to prevent a wide variety of fluids, such as natural gas, oil, and water, from freezing. One fluid which routinely requires a line heater is natural gas.
According to the Joule-Thomson effect, as you reduce the pressure of a gas the temperature of the gas will also reduce. The rule states that for every 100 pounds per square inch (PSI) or.
(690 kPa) pressure drop there will be a drop of 7 degrees Fahrenheit (I 4"Q, in temperature.
When gas reaches its dew point, water molecules become free from the water, causing water molecules to freeze, thereby creating a hydrate plug known as (freeze plug, ice plug, etc.) This freezing will stop or limit the flow of gas. Removal or prevention of hydrates during well test operation improves the test results. Heated gases, fluids and solids are separated more efficiently inside test vessel, by using a line heater. During well test exact measurements of separated gas, oil water and solids are crucial for accurate well test data.

[0004] Line heaters are used to keep gasses, fluids, slurry's, bitumen, drilling /
production fluids etc. above its dew point within a flow line or system. In a conventional line heater, fuel gas is burned within a horizontal "U"-shaped firebox immersed in a lower portion of a fluid bath. Heat released by the burning fuel gas is quickly transmitted, through the firebox wall to the fluid bath. The gasses, fluids, slurry's, bitumen, drilling / production fluids etc. (effluent) to be heated flows through a -now coil, which is immersed in an upper portion of the fluid bath. Heat is transmitted from the hot water bath through a wall of the flow coil to the effluent flowing through the flow coil. A temperature controller maintains the fluid bath temperature at a desired level by controlling a supply of fuel gas to the firebox.
A temperature of 190 F (88 C) is considered the optimum temperature at which the bath of this type heater should operate, since above that temperature, water loss from the hot water bath will increase through steam vapors.

SUMMARY
[00051 There is provided a line heater which includes a container having an interior surface defining an interior cavity and an exterior surface- A flow conduit passes through the interior cavity of the container. A plurality of discrete solid bodies of heat transfer medium surrounds the flow conduit. A. heat source is provided for heating the heat transfer medium, whereby heat is transferred from the heat source to the flow conduit.

[0006) The line heater, as described above, provides a number of advantages, the particulars of which will hereinafter be described. Those advantages include an ability to operate at higher temperatures. Due to the heat medium being used operate at a higher temperature than conventional system and is well insulated to eliminate heat loss. Can be used in all five major sub-disciplines of the oil and gas industry: drilling, exploration, completion, production and refining.
[0007] It is preferred that the heat source utilized be an intrinsically safe electric heating element in order to eliminate greenhouse emissions and enable the line heater to function in hazardous environments, CLASS 1, ZONE I in accordance to OH&S, EUB, OSHA, API, CAPP, and ERCB_ This intrinsically safe electric heating element is positioned in the interior cavity against the interior surface.

[000$] The heat transfer medium may take a number of forms, such as granules, balls, pellets, shot, powder, shavings and. beads etc. Beneficial results will be obtained through the use of heat conducting material, with, a, high coefficient of heat transfer, to maximize energy transfer. Maximum heat transfer can be calculated used Fourier's Law: q - k A
dT / s, where q equals heat transferred per unit time (W, Btu/hr), A equals heat transfer area (m2, f), k equals the thermal conductivity of the material (W/m_K or W/m C, Btu/(hr '?F
f?*)), dT
equals the temperature difference across the material (K or C, F) and. S
equals the material thickness (m, ft)-x0009] In order to increase line heater efficiency even further the container will make use of newly recently developed insulating materials technology to mitigate heat loss.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:
[0011) FIG. I is a side elevation view, in section of a line heater constructed in accordance with the teachings of the present invention.
(0012] FIG. 2 is a top plan view, in section of the line heater illustrated in FIG. 1-[0013] FIG. 3 is at). end elevation view, in section of the line heater illustrated in FIG. 1.
[0014] FIG. 4 is a side elevation view of the line heater illustrated in FIG.
1, [0015] FIG. S is a side elevation view of the line heater illustrated in FIG.
I in use with a production tank.
[0016] FIG. 6 is a side elevation view of the line heater illustrated in FiG.1 in use with a drilling rig.
[0017) FIG. 7 is a side elevation view of the line heater illustrated in FIG.
I in use when testing a well.
[0018] FIG. 8 is a top plan view, in section of the line heater illustrated in FIG. I in use when vaporizing liquid propane.

DETAILED DESCRIPTION
[0019) A line heater generally identified by reference numeral 10, will now be described with reference to FIG. I through 8.
Structure and Relationship of Parts:
[0020) Referring to FIG. 1, a line heater 10 includes a housing or container 12 that has an interior surface 14 defining an interior cavity 16 and an exterior surface 18. Container 12 is, insulated to minimize heat loss. A flow conduit 20 passes through interior cavity 16 of container 1.2. Referring to FIG. 2, it is preferred. that flow conduit 20 follow a serpentine path to maximize retention time and heat exposure. Referring to FIG. 1, a plurality of discrete solid bodies of heat transfer medium 24 surround flow conduit 20.
Heat transfer medium 24 may be heat conducting beads 25 or other types of non flammable heat conducting media. An intrinsically safe heat source 26 is provided for heating heat transfer medium 24 that causes heat to be transferred from intrinsically safe heat source 26 to flow conduit 20. Intrinsically safe heat source 26 may be in the form of an intrinsically safe electric heating element 27. Intrinsically safe Electric heating element 27 that is positioned in interior cavity 16 against interior surface 14. Referring to FIG. 2, flow conduit 20 has an inlet end 28 terminating at exterior surface 18 in an inlet coupling 30 for coupling inlet end 28 to an incoming flow line 32. Flow conduit 20 has an outlet end 34 terminating in an outlet coupling 36 for coupling outlet and 34 to an outgoing flow line 38.

[0021] Referring to FIG. 1, line heater 10 has a temperature control and a shut down panel 40, pressure gauge 42 and temperature gauge 44 positioned for easy accessibility on exterior surface 18. Exterior surface 18 also has a low pressure rupture disk 46. Referring to FIG. 4, hinged coil inspection covers 48 open to reveal flow conduit 20 and allow for easy access for inspection during flow periods and repair during maintenance cycle.

Operation:
(00221 It will be appreciated that line heater 10 may be used with different types of fluids. Those fluids may be gases, liquids, slurry's, bitumen, drilling/produetion fluids, etc.
[00231 Intrinsically safe heat source 26 of line heater 10 heats heat transfer medium 24 and causes heat to be transferred to flow conduit 20, Fluid enters inlet end 28 of now conduit 20 and continues toward outlet end 34. While in flow conduit 20, heat is transferred to the fluids. Temperature and pressure within line heater 10 may be monitored via pressure gauge 42 and temperature gauge 44. Temperature control and shut down panel 40 may be utilized to control desired temperature and shut: down the system as required.

[00241 Referring to FIG. 5, line heater 10 may be used in conjunction with a production tank 50 to heat the contents of tank 50. Incoming flow line 32 and outgoing flow line 38 are fluidly connected to production tank 50 to allow circulation of the fluid.
Fluid enters incoming flow line 32 and proceeds through line heater 10 to outgoing flow line 38.
Referring to FIG. 1, intrinsically safe heat source 26 heats heat transfer medium 24 which, in turn, heats flow conduit 20 and the fluid within.

5 [0025] Referring to FIG. 6, line heater 10 may be used in conjunction with a drilling rig 60. Drilling fluid 62 is heated by line heater 10 prior to being utilized for drilling. Drilling fluid 62 from wellbore is pumped into holding area 64 before being pumped into line heater by mud pump 66. Incoming flow line 32 of line heater 10 is connected to mud pump 66.
10 Drilling fluid 62 continues through line heater 10 and, referring to FIG.
1, is heated by heat transfer from heat source 26 which heats heat transfer medium 24 to flow conduit 20.
Referring to FIG. 6, heated drilling fluid 62 exits into outgoing flow line 38 of line heater 10 and enters drilling rig 60.

[0026] Referring to FIG. 7, line heater 10 may be used when testing a well.
Fluid flows out of well head into flow line 70 and passes to incoming flow line 32 of line heater 10. Fluid is heated as it travels through line heater 10 and continues through outgoing flow line 38 to test vessel 72. Heated fluid in test vessel 72, separates and then liquids can be transferred to production tank 50, gases to flare stack 74 or gas and liquid can be transported by pipeline 76. Solids would stay in vessel 72.

[0027] Referring to FIG. 8, line heater 10 may be used for vaporizing liquid propane.
Liquid propane flows or is pumped from liquid propane vessel 80 into incoming flow line 32 of line heater 10. Liquid propane is heated as it travels through line heater J0 which causes the liquid propane to be vaporized and continues through outgoing flow line 38. Examples of practical use: projects where large quantities of propane, nitrogen, C02 etc.
is required to be vaporized in to gas to purge vessels, tanks, pipelines, facilities etc., of 02, sour gasses (H2S) or undesirable gasses. This process is called vaporization; equipmcnt used in prior art is a "vaporizer".
[0028] Referring to FIG. 1, the key to line heater 10 lies in its unique heat transfer

6 medium 24. Line heater 10 uses highly heat conducting non-flammable solid heat medium, instead of fluid medium which allows for higher temperature differential. This would enable faster heat transfer when fluid is pumped or flowing through flow conduit at high rates. This will decrease the retention time for the fluid inside the flow conduit The heat transfer medium may take a number of forms, such as granules, balls, pellets, shot, powder, shavings, beads, etc. The material used could be made of metal alloys such as aluminium, copper, steel, zinc, tin, nickel, etc., or combinations off metal alloys. Other material that could be used are ceramics, sand, powders etc., either man made or naturally occurring solids with high heat transfer coefficient will be used. According to Fourier's Law: q = k A dT / s, an increase in transfer coefficient k will increase heat transfer per unit of time.

Advantages: Environmental I Human interactions, Safety and Performance [00291 Line heater 10 provides a number of significant advantages over a conventional line heaters which utilize a hot water bath-1.5 [00301 Environmental / Human FACTOR
I I. The gas burners on a conventional line heater used to heat the hot water bath in the prior art are inefficient and create excessive green house gas emissions. According to the Petroleum Technology Alliance thermal energy heaters are only 30% to 60%
efficient.
With. thermal heaters having efficiency as low as only 30%, as much as 70% of their energy is wasted. Line heater 10 is fundamentally more efficient and has no green house gas emissions.
[00311 2. Line heater 10 has no build up of soot as does a conventional line heater. This soot is a heavy carbon deposit that builds up inside the u tube and chimney of a conventional line heater. This soot gets dislodged during operation and gets emitted into the atmosphere.
This heavy carbon deposit can be ignited by the burning of supply gas, which has the ability of having sparks leaving the chimney. In, a hazardous environment there is potential for flammable gasses, dust and liquids, these sparks could be very dangerous to safety of people, equipment and our environment The fact is that line heaters are left unattended in remote areas. This could have detrimental effect on dry forested area's grassy fields or nearby buildings.
(00321 3. Line heater 10 does not release airborne particulates which can be inhaled by

7 operators and be hazardous to the health of personnel in the area.
[0033] 4. Difficult or impossible to endanger human life by vandalism of the system.
Similar to big green "Utility" boxes in back alleys for power or cable, phone etc. Line beater can be built with hidden contro ls, to make it virtually tamper proof. This level of safety 5 and control in operation would be unobtainable with the prior art.
[00341 5. Line heater 10 has no noise emission, suitable for operation in noise sensitive locations. Comparatively, prior art produces nearly I00+dBA created by conventional line heaters.
[0035] 6. Line heater 10 poses no risk to the environment if heat medium 26 is 10 accidentally released in to the environment. Conventional line heaters which contain chemically treated water or mixture thereof can be harmful to the environment, due to boiling of liquids which normally over flow on to the ground, which could contaminate water supply. Prior art has to have a containment to catch overflow, spills or leaks and according to the Petroleum Technology Alliance it is estimated that there are between 20,000 to 40,000 fire tube heaters in Alberta with a significant number of heaters being rated between 1 and 2 MM RTU/hr. With the aging fleet of conventional line heaters, leaks and spills are inevitable.
[0036] 7. Line heater 10 has the capability to use renewable energy, such as solar or wind or tidal, to supplement power requirements, or as technology advances, could utilize 100% renewable energy as power source. The design of a conventional line heater dictates that it must combust fossil fuel to function., which causes harmful greenhouse gas pollution.
[00371 R. Line heater 10 due to advancements in insulation can be used in areas where radiant heat emissions are not allowed, such as the high arctic where losses of permafrost is an inherent problem with conventional line heaters.
[0038] 9. Can operate in extreme temperature, with no limitations as per prior on.
Limitations such as; fuel supply freezing or not flowing due to cold temperatures, draft in chimney being broken, fuel supply controller freezing, air intake freezing, water vapour accumulating in fire tube due to condensation from combustion and freezing, water vapour released from water bath freezing.
Safety [0039] 1. The gas burners used to heat the hot water bath in the prior art utilize an open

8 flame, which creates a potential explosion hazard in the presence of a flammable gas vapour or dust. They must, by law (ERC13, EUB, CAPP, Oki&S, OSHA, API), be positioned at a distance of 25 meters from a wellhead or production tanks. Line heater 10 does not have an open flame and can, therefore, operate in Zone 1, Class ] areas.
(00401 2. The gas burners used to heat the hot water bath in the prior art requires air for combustion. The mass air flow in the combustion process cools the system which creates inherent inefficiency. Line heater 10 does not require combustion air in the heating process.
[0041.) 3. The line heater 10 does not require ignition of volatile fuel air mixtures (aka flaming rag on a stick), near well heads or separators or other hazardous areas to operate.
Line heater 10 does not require open flames it uses an "intrinsically safe"
heating element.
[0042] 4. Line heater 10 has, Referring to FIG. 4, hinged coil inspection covers 48 open to reveal flow conduit 20 and allow easy access for inspection during flow periods and repair during the maintenance cycle. This is very important with flowing gas and liquids with high abrasive and solids content, The abrasive solids cut out the internals of the 1$0 deg. bends in the flow conduit 20 (similar to sand blasting metals). Inspection can not be conducted until conventional line heater is shut down, complete dismantle; pull out flow conduit from the heater bath for inspection which equals down time, lost productivity and monetary losses.
Due to the financial burden, companies are likely to limit inspections to the bare minimum, resulting in increased potential safety hazards, beyond the scope of existing hazards disadvantages, Performance [0043] 1. The gas burners used. to heat the hot water bath in the prior art have temperature limitations, typically 2031T (95 C), water boiling point 212 F
(100 C).
Operating a conventional line heater above this temperature water losses are occurred by steam vapours. Due to its design line heater. 10 can be heated safely in excess of 572 F
(300 C), depending upon the heat transfer medium used and process temperature desired, [00441 2. Line heater 10 has a smaller foot print on location, relative to units of effluent heated vs. square area of base plate than prior art. Flow conduits in conventional line heater have to be longer in size, due to inherent inefficiency's, (reduced retention time and lower bath temperatures), chimneys occupy large spaces, liquids close to boiling temperatures cause a potential safety hazards at overhead areas. Due to its modular design, line heater 10

9 has the ability to be stacked one on top of the other when more that one line heater is required. This would reduce the foot print even more, [0045] 3. Referring to FIG. 8, line heater 10 can be used to vaporize pressurized liquids such as propane, nitrogen, C02, water, fuels, solvents etc. During propane fracturing flow back on oil wells there is a need to vaporize liquid propane that is entrained in the crude oil.
High heat is required and the prior art would use multiple line heaters to vaporize the liquid propane, due to the fact that conventional line heaters can not heat the crude oil and liquid propane mixture high enough with one line heater, because of the inefficiencies of the prior art, Line heater 10 can be used for vaporizing liquids at large volumes and transporting them to supply were gasses are required.
[0046] 4. Line heater 10 could be used to depressurize gas pipelines. Line heater 10 can be hooked up to pipeline to allow gas flow through line heater 10. Line heater

10 will achieve mass flow at desired temperature, with flameless heating technology.

[0047] In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

[0048] The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope of the claims. The illustrated embodiments have been set forth only as examples and should not be taken as limiting the invention. It is to be understood that, within the scope of the following claims, the invention may be practiced other than as specifically illustrated and described.

Claims

What is Claimed is:

1. A line heater, comprising:
a container having an interior surface defining an interior cavity and an exterior surface;
a flow conduit passing through the interior cavity of the container;
a plurality of discrete solid bodies of heat transfer medium surrounding the flow conduit; and a heat source for heating the heat transfer medium whereby heat is transferred from the heat source to the flow conduit.

2. The line heater of Claim 1, wherein the flow conduit has an inlet end terminating at the exterior surface in an inlet coupling for coupling the inlet end to an incoming flow line and an outlet end terminating in an outlet coupling for coupling the outlet end to an outgoing flow line.

3. The line heater of Claim 1, wherein the heat source is an intrinsically safe electric heating element.

4. The line heater of Claim 3, wherein the intrinsically safe electric heating element is positioned in the interior cavity against the interior surface.

5. The line heater of Claim 1, wherein the heat transfer medium is a non flammable heat conducting beads, balls, shot, pellets, powder, granules, shavings or the like.

6. The line heater of Claim 1, wherein the container is insulated to minimize heat loss.

7. The line heater in Claim 1, wherein the container has coil inspection covers which open to reveal the flow conduit and allow for easy access for inspection during flow periods and repair during maintenance cycle.