JPS5913241B2 - Reboiler for reconcentration of liquid desiccant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reboiler that reconcentrates liquid desiccant using exhaust gas from a prime mover.

Diethylene glycol or triethylene glycol (
Liquid desiccants such as glycols (hereinafter simply referred to as glycols) are currently widely used for dehydrating natural gas.

This dehydration is accomplished by intimately mixing the natural gas stream with a liquid desiccant to remove moisture from the gas stream, since glycols have a greater affinity for moisture than gases.

As a result, the moisture-entrained or moisture-rich glycol or liquid desiccant itself must be dehydrated for reuse.

Currently, dehydration of this liquid desiccant is accomplished by heating or reboiling the liquid above its boiling point, whereby the water is driven from the liquid and the water-poor liquid desiccant is returned to the area of contact with the collected superthermal gas. It is designed to be recycled.

A flame tube that emits a flame directly is usually used to heat the liquid desiccant.

The use of such flame tubes is often accompanied by an inherent fire hazard due to direct flame radiation.

For example, there is a risk of a fire occurring on offshore equipment several miles from a firefighting agency, and it is therefore necessary to take measures to minimize the risk of fire caused by flames.

Most natural gas gathering equipment includes an internal combustion type prime mover, such as a gas-fired turbine or piston-driven engine, that utilizes a hydrocarbon fluid as fuel.

These prime movers usually operate at a temperature of about 370 to 704°C (700° to 1
This produces fairly hot exhaust gases (300° F.) that are emitted directly to the atmosphere, resulting in significant thermal energy losses.

The losses incurred so far are considered to be unavoidable,
Furthermore, there have been only a few cases where efforts have been made to recover this energy.

Thus, the present invention aims to provide an apparatus for reconcentrating a liquid desiccant in a flameless state by utilizing the thermal energy of exhaust gas coming out of a prime mover.

In the present invention, liquid desiccant is continuously circulated between a closed upper reboiler drum and a lower reboiler chamber through riser and downcomer or return conduits.

The riser conduit is disposed within a closed heating zone through which exhaust gas from the prime mover flows to convectively heat the liquid desiccant in the riser conduit.

The water vapor released by this heating is removed through a first outlet in the upper reboiler drum, and the water-poor liquid desiccant is then removed from the reboiler drum through a second outlet.

Examples of the present invention will be described below.

Referring now to FIG. 1, the reboiler of the present invention consists of a closed vessel 10 divided into three main areas: a closed upper reboiler drum 12, a closed bottom drum or lower drum. It comprises a reboiler chamber 14 and a closed heating zone 16 located between both drums.

The upper reboiler drum 12 is connected to the central chamber 1 by means of a liquid suppression weir 24 and a liquid level control weir 26 suitably located within the drum.
8, a liquid holding chamber 20, and a moisture-poor/liquid desiccant chamber 22.

The upper edge of the liquid level control weir 26 is lower than the upper edge of the liquid suppression weir 24.

The upper reboiler drum 12 is also provided with an outlet 28 for the separated water vapor and an outlet 30 for the water-poor liquid desiccant.

The lower reboiler chamber 14 is a closed rectangular structure with an inlet for the moisture-rich liquid desiccant, which inlet communicates with the liquid holding chamber 20 via a conduit ``32''.

In FIG. 3, the lower reboiler chamber 14 communicates with the central chamber 18 of the upper reboiler drum 12 by a number of re-opening riser conduits 34, the riser conduits 34 being connected to the central chamber 18 of the upper reboiler drum 12.
6 and projects upward into the central chamber 18.

The riser conduit 34 is suitably sealed where it passes through the dividing plate 36, which connects the heating area 16 and the upper reboiler chamber 12.
and are separated.

To increase the rate of heat transfer, the outer surface of the riser conduit 34 is juxtaposed with a number of fins made of relatively thin plates.

A steam lid 38 is positioned over the upper end of each riser conduit 34.

Furthermore, the central chamber 18 and the lower reboiler chamber 14 communicate with each other by a return conduit or downcomer 40 which passes outside the heating zone 16 and whose upper end meets the upper end of the riser conduit 34. It is located in the upper reboiler drum 12 at a lower point than the reboiler drum 12.

In FIG. 1, the heating zone 16 surrounds the riser conduit 34 and includes an inlet 42 for receiving exhaust gases from a prime mover (not shown) and an outlet 44 for the exhaust gases opposite the inlet and connected to a chimney 46. ing.

A butterfly-shaped control valve 48 provided in the chimney 46 controls the heating zone 1.
It acts as a damper to control the flow rate of exhaust gas passing through the central chamber 18, and is also controlled by a temperature sensing element attached to the central chamber 18.

The wing-shaped control valve and its associated temperature sensing element require a bypass system for the exhaust gas around the heated area.

The construction of such bypass systems is well known and can be easily installed by those skilled in the art.

At least one baffle plate 43 is provided in the heating zone 16 near the inlet 42 to divert the hot exhaust gases to the riser conduit 3.
4 is distributed uniformly along its length.

An upright, elongated, cylindrical distillation column 50 is secured to the upper reboiler drum 12 over the detached steam outlet 28, which distillation column 50 is a reflux condenser having a steam vent 52, an inlet and an outlet. area 54, and tray area 5
It is equipped with 6.

Directly below the lower reboiler chamber 14 is installed a surge tank 58 which is disposed on legs 60 and has a heat exchange coil 62 disposed therein.

Surge tank 58 has an inlet 64 at one end of which conduit 6 is connected.
6 communicates with an outlet 30 for a moisture-poor liquid desiccant.

A water-poor liquid desiccant outlet connection 68 is provided at the other end of the surge tank 58 to return the water-poor liquid desiccant to the external gas dehydrator.

The inlet of the heat exchange coil 62 is connected by a conduit 70 to the outlet of the reflux condenser section 54, and the outlet of the heat exchange coil 62 is connected by a conduit 72 to the distillation column 50 above a portion of the tray section 56 to Desiccant flows through a portion of the tray area and is discharged into the distillation column.

A heat insulating coating 74 covers the top surface of the sealed container 10 to maintain internal heat and increase the efficiency of the fruiting device.

In operation of the reboiler, a cold water-rich liquid desiccant 76, such as glycol, returning from an external gas dehydrator is reboiled at the inlet of the reflux condenser 54 at the top of the distillation column 50. Enter the vessel.

Liquid desiccant exiting reflux condenser 54 enters heat exchange coil 62 via conduit 70 .

In this heat exchange coil, the water-rich liquid desiccant receives heat from the hot water-poor liquid desiccant flowing countercurrently within the surge tank 58.

The water-enriched liquid desiccant then enters the distillation column 50 from the heat exchange coil 62 through conduit 72 and flows down through a portion of the tray area 56 and into the upper reboiler drum 12. It enters the liquid holding chamber 20 and from there through the conduit 32 into the reboiler chamber 14 below.

The liquid desiccant then rises upwardly in the riser conduit 34 where it picks up heat from the hot exhaust gas 78 in the heating zone 16 until it flows into the central chamber 18 from the upper end of the riser conduit 34. communicated.

In the central chamber or main reboiler section 18, natural convection type reboiler action takes place.

That is, a portion of the liquid desiccant is returned to the lower reboiler chamber 14 through the return conduit 40 and from the tile back through the riser conduit 34 to the upper central chamber 18 of the reboiler drum where it is continuously carried. In the riser conduit, the liquid desiccant recirculates and enters the central chamber 18 as a part-vapour, part-liquid stream.

A steam flap 38 over each riser conduit 34 serves to return the exiting liquid desiccant into the central chamber 18.

The water vapor leaving the liquid desiccant at the top of the riser conduit 34 rises upwardly from the central chamber 18 into the distillation column 50 and passes through the tray section 56 and the reflux condenser section 54, where a portion of the water vapor is converted to a liquid. The remaining water vapor is condensed through the vent 5.
2 and is released into the atmosphere.

The reconcentrated hot water-poor liquid desiccant continuously moves from the central chamber 18 over the level control weir 26;
It flows from the upper reboiler drum chamber 22 through conduit 66 into surge tank 58 .

The high-temperature moisture-poor liquid desiccant is the heat exchange coil 6.
2 flows countercurrently with the cold, moisture-rich liquid desiccant flowing through 2.

This causes heat exchange between the low temperature moisture-rich liquid desiccant in heat exchange coil 62 and the high temperature moisture-poor liquid desiccant in surge tank 58 .

The water-poor liquid desiccant then exits the reboiler and returns to the external gas dehydrator.

Simultaneously with the flow of liquid desiccant described above, hot exhaust gases 78 coming from the prime mover enter heating zone 16 and deflection plate 4.
3 and natural agitation of the gas distributed around the outer surface of the riser conduit 34.

Due to the temperature difference between the hot exhaust gas and the water-rich liquid desiccant, heat is transferred to the liquid in the riser by heat transfer onto the metal surface of the finned riser and to the liquid desiccant in the riser. transmitted to the agent.

The liquid desiccant in riser conduit 34 is thus convectively heated.

The exhaust gas that has released heat is discharged to the atmosphere through the chimney 46.

The temperature of the liquid desiccant is controlled by regulating the flow rate of the exhaust gases by a temperature sensing element located in the central chamber 18 which actuates a butterfly control valve 48 in the chimney as described above.

In the detailed description of the present invention, specific terminology has been used for ease of understanding, but the present invention is not limited to these terms only, and similar embodiments may be used to achieve similar objectives. It will be understood that all operative terms are included.

[Brief explanation of the drawing]

FIG. 1 is an elevational view of the reboiler of the present invention, FIG. 2 is a side view of the reboiler of FIG. 1, and FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. It is. 12...Upper reboiler drum, 20...Receiving device, 28...First outlet for water vapor, 30...Second outlet for water-poor liquid desiccant, 14...Lower reboiler drum. boiler room,
34... Rise pipe, 40... Downpipe, 26...
Liquid level control weir, 16... Heating zone, 42.44... Inlet and outlet for exhaust gas, 50... Distillation column, 24...
・Suppression weir, 38...Steam puta.

Claims (1)

[Scope of Claims] 1. A reboiler that reconcentrates liquid desiccant using exhaust gas from a prime mover, comprising: a receiving device for receiving liquid desiccant rich in water; and a first outlet for separated water vapor. and a closed upper reboiler drum having a second outlet for the generally reconcentrated hot water-poor liquid desiccant, the receiving device being spaced from the second outlet; a boiler chamber, and a number of double-ended open riser conduits disposed essentially between the receiving device and the second outlet, each conduit having one end communicating with the interior of the reboiler chamber below and the other end communicating with the interior of the reboiler chamber below; a riser conduit projecting upwardly into the upper reboiler drum and allowing liquid desiccant to flow upwardly from the lower reboiler chamber into the upper reboiler drum; and the other end communicates with the interior of the lower reboiler chamber to direct the moisture-enriched liquid desiccant downwardly into the lower reboiler chamber as the liquid desiccant moves toward the second outlet. at least one downcomer pipe for circulating; and positioned in the upper reboiler drum near the second outlet;
A liquid level control weir that overflows the moisture-poor liquid desiccant toward the second outlet, and is located between the upper reboiler drum and the lower reboiler chamber and surrounds only the rising conduit. a closed heating zone having an inlet and an outlet for exhaust gases flowing from the prime mover across the riser conduit, the heating zone having an inlet and an outlet for exhaust gases flowing across the riser conduit from the lower reboiler chamber to the upper reboiler chamber by convection in the riser conduit; Reboiling for reconcentration of the liquid desiccant in which the liquid desiccant entering the boiler drum is indirectly heated by the exhaust gas to remove water vapor from the liquid desiccant, which eventually passes through the first outlet. vessel. 2. A distillation column having a dissipation and rectification section disposed over a first outlet for the separated water vapor and for flowing a water-enriched liquid desiccant mixture with the upwardly flowing separated water vapor and an outlet vent for the water vapor. and in the vicinity of the receiving device such that the receiving device constitutes a reservoir for receiving the water-enriched liquid desiccant flowing down from the distillation column and communicating with the reboiler chamber below via at least one downcomer pipe. a restraining weir positioned in the upper reboiler drum and having an upper edge higher than the upper edge of the level control weir. Reboiler. 3. Claim 1 in which a large number of fins are provided laterally along the length of the riser conduit to increase the heat transfer area.
Reboiler for reconcentrating the liquid desiccant described in Section 1. 4. The liquid desiccant of claim 1, wherein a vapor vent is arranged over the upper end of each riser conduit to direct the exiting liquid desiccant into the upper reboiler drum. reboiler for reconcentration.