JP2907745B2 - Line heater for city gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line heater for city gas.

[0002]

2. Description of the Related Art A raw gas for city gas can be stably purchased over a long period of time from a synthesis gas mainly composed of methane and hydrogen obtained by steam reforming a petroleum hydrocarbon. It has been converted to liquefied natural gas (NG), which is also clean energy.
NG is a low-temperature liquid that is stored in a tank at the receiving terminal, pumped up, and then vaporized by an evaporator that uses a low heat source such as seawater, and further adjusted the calorie by LPG. It is supplied to the trunk line laid around the metropolitan area in a ring, decompressed by the governor station, which is a pressure control facility installed at a key point, and passed through the branch line radiating from the ring main line to the general demand. Supplied to the house.

As described above, since NG is stored in a liquid state in the tank at the receiving base, it can be efficiently pressurized by a pump, and the volume after vaporization decreases in inverse proportion to the pressure. The supply pressure of the main line is operated at a high pressure so that a large amount of gas can be supplied through a conduit having the same pipe diameter, and a pressure of 30 to 40 atm is employed.

However, when the pressure of the main line is increased, the following problems occur. That is, the temperature of the NG vaporized by the evaporator is never high and is usually in the order of 10 ° C. because the vapor is vaporized by a low heat source such as seawater.
Therefore, when the governor station reduces the pressure from 30 atm to 8 atm and feeds it to the radial branch line, the temperature of the NG vaporized by the adiabatic expansion drops considerably. Generally, the temperature after decompression falls to about 0 ° C. or less, particularly during winter, because the temperature drops by about 0.6 ° C. per atmospheric pressure, and butane and odorant in the vaporized NG are removed in the conduit. It may cause inconvenience such as condensation or freezing around the conduit.

[0005] Therefore, a governor station for branching and feeding from a ring main line to a radial branch line is provided with a vaporized NG heater, usually called a line heater, which uses hot water that uses combustion heat of city gas or the like as a heat source. Reduce vaporized NG
Once the temperature is increased by heating before pressing , zero degree C
The following is prevented.

Next, the structure of a conventionally used line heater will be described with reference to the drawings. FIG. 3 is a side view showing a partial longitudinal section of a conventional line heater, and FIG.
FIG. 4 is a transverse sectional view taken along line IV-IV of FIG. 3. In the figure, 21
Is a cylindrical shell, and a burner 23 using city gas as a fuel is attached to one end of the shell below the end plate 22. Numeral 24 denotes a furnace tube having a large-diameter tube horizontally fitted with both ends fitted between the end plates 22 and 25 of the shell 21. The combustion gas flows in the direction of the arrow inside the furnace tube to fill the inside of the shell 21 with water. Heat the water.

Reference numeral 26 denotes a smoke chamber provided on the side of the shell 22 opposite to the burner 23, and the combustion gas exiting the furnace tube 24 changes its direction once entering the smoke chamber, and changes its direction. The water flows in the direction of the arrow through the plurality of smoke tubes 27 whose both ends are fitted to 25, and efficiently heats the water in the shell 21. After that, the combustion gas exits the flue tube 27 and burner 2
3 enters the smoke chamber 28 formed around the combustion chamber, changes the direction again, flows in the upper smoke tube 27A in the direction of the arrow,
After the water in the shell 21 is heated, it enters the flue 29 and is released to the atmosphere via a chimney (not shown).

On the other hand, the vaporized NG to be heated is supplied from the inlet pipe 30 projecting from the end plate 25 of the shell 21 to the shell 2.
1, a heating tube 31 composed of a tube bundle of U-shaped tubes provided in the upper half portion, and heated by the warm water heated by the smoke tube 27 or the like to reach a predetermined temperature, and the outlet tube 32
Exits, enters a decompressor of a governor station (not shown), is depressurized to a predetermined pressure, and is fed to a branch line.

The above-described line heater of the hot water heating type has the features that it is safe because it uses hot water as a heat transfer medium, and that the device is compact because it has a good heat transfer coefficient. Although widely adopted, the following problems have recently arisen: In other words, due to the concentration of population in large cities and an increase in demand for NG, which is clean energy, the amount of transmission per branch line that branches off from the ring-shaped main line is following an increasing trend. That is, the line heater of the governor station also needs to have a large capacity.

[0010] line heater, the a can body integrated consists welded structure as, and high-pressure vaporized NG
Since that is also a pressure vessel for pressurized heat, inevitably factory fabrication must be agreed. After the factory is manufactured, it is transported by land to the installation site. At this time, the size of the shell 21 is limited due to road transportation, and the diameter of the shell 21 is generally limited to 3 meters .

For the reasons described above, the heat transfer capacity is naturally limited unless the basic structure of the line heater is changed, and it differs depending on the temperature conditions on the hot water side or the vaporized NG side. About 1 × 10 ⁶
Kcal / Hr position. However, the capacity required for increasing the capacity is considered to be several times the amount of heat.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a capacity several times as large as that of a conventional hot water circulation type line heater, and is manufactured at a factory. It is an object of the present invention to provide a line heater for city gas having a novel structure that can solve the above-mentioned problems in land transportation.

[0013]

Means for Solving the Problems The gist of the present invention for solving the above problems is that a lower can body filled with warm water and having tube sheets at both ends, and both tube sheets of the lower can body are respectively provided. A furnace tube and a smoke tube whose both ends are fitted and through which a combustion gas flows, a smoke room provided adjacent to both tube sheets of the lower can body, a burner attached to the one smoke room, and a top of the lower can body An upper can body having a heating pipe composed of a plurality of connecting pipes and a U-tube that is filled with warm water and is mounted directly above the lower can body and is horizontally mounted, and an end plate of the upper can body. an inlet pipe and an outlet pipe for NG vaporized which is protruded communicates with the heating pipe, respectively, the upper can body plurality of connecting pipes and respectively projecting from the bottom is protruded from the top of the lower can body < A line gas for city gas, comprising a connecting pipe for connection. Located in.

[0014]

[Function] A high-temperature combustion gas obtained by burning city gas with a burner attached to the lower can body first flows through the furnace tube to heat hot water in the lower can body, and then changes direction in the smoke chamber. Similarly, the hot water flows through the flue pipe to heat the hot water, changes its direction again in the smoke chamber on the burner side, flows through the flue pipe, enters the flue, and is released to the atmosphere from the chimney.

[0015] The hot water in the lower can body heated as described above has a high and low temperature distribution due to the difference in the heat transfer rate along the axial direction of the furnace tube and the smoke tube can body. Generally, it will be higher on the opposite side of the tubesheet to which the burner is attached. Then, in this state, the hot water, whose specific gravity has become lighter due to the high temperature, rises in the connecting pipe having a higher temperature due to a difference in specific gravity and flows into the upper can body.

In the upper can body, the warm water that has risen via the connecting pipe on the high-temperature side as described above comes into contact with a heating tube bundle consisting of a U-shaped tube horizontally mounted in the upper can body, It is considered that the vaporized NG flowing in the heating pipe is heated to lower the temperature, and once flows horizontally along the heating pipe, the specific gravity increases due to the low temperature, and the NG flows down from the other connecting pipe into the lower can.

As described above, even if the combustion part and the heating part, which were conventionally formed integrally in one shell, are divided into two cans, they can be connected by two or more connecting pipes. It is considered that natural convection circulation is formed, whereby heat can be transferred as efficiently as the conventional integrated type. Then, the upper can body and the lower can body are separately manufactured in a factory, and can be integrated by being connected to the installation site and then flange-connected with a connecting pipe.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, and FIG.
FIG. 2 is a cross-sectional view taken along line II-II. Reference numeral 1 denotes a cylindrical lower can body, and tube sheets 2 and 3 are fixed to both ends. 4 is both tube sheets 2,
3 is a furnace tube having both ends fitted therein and provided horizontally, and a combustion gas of a burner 5 described later flows in the direction of an arrow to heat water filled in the lower can body.

Reference numeral 6 denotes a smoke chamber provided adjacent to the tube sheet 2 of the lower can 1, and a burner 5 for burning city gas is mounted at the center. Reference numeral 7 denotes a smoke chamber provided adjacent to the other tube sheet 3, and the combustion gas exiting from the furnace tube 4 changes its direction in the smoke chamber 7, and the smoke tubes whose both ends are fitted to the tube sheets 2, 3. 8 flows in the direction of the arrow to efficiently heat water in the lower can. After that, the combustion gas enters the above-mentioned smoke chamber 6 after leaving the smoke tube 8, changes the direction again, and heats the water in the lower can 1 while flowing in the upper smoke tube 8 in the direction of the arrow. The gas enters the flue 9 and is released to the atmosphere via a chimney (not shown).

Reference numerals 10 and 11 denote connecting pipes projecting upward from the top of the lower can 1, and projecting downward from the bottom of a cylindrical upper can 12 mounted directly above the lower can 1. The connection pipes 17 and 18 are fluid-tightly connected via flanges.

Reference numeral 13 denotes a bundle of heating tubes, each of which is a U-shaped tube mounted horizontally in the axial direction in the upper can body 12, and is provided with an NG inlet tube 15 and an NG inlet tube 15 protruding from an end plate 14 of the upper can body 12. It communicates with the outlet pipe 16. Reference numeral 19 denotes an inspection manhole provided on the body of the upper can 12, and reference numeral 20 denotes a vent pipe for steam generated from warm water.

Next, the operation of the embodiment having the above configuration will be described. The high-temperature combustion gas generated by the combustion of the city gas in the burner 5 of the lower can 1
Then, the hot water in the lower can 1 is heated while sequentially passing through the upper smoke tube 8. Then, a temperature difference occurs in the temperature distribution of the hot water in the lower can 1. For example, when the temperature near the connecting pipe 10 increases, the specific gravity decreases, and the hot water in the lower can 1 rises in the connecting pipe 10. , Flows into the upper can 12, contacts the tube bundle of the heating tube 13, and efficiently heats the vaporized NG flowing in the tube.

After this, the hot water once flows in parallel with the heating pipe, the temperature decreases, the specific gravity increases, and the hot water descends from the other connecting pipe 18 into the lower can 1, and the furnace tube in the lower can 1 again. The temperature rises by being heated by the 4 and the smoke tube 8, the specific gravity becomes light, and the inside of the connecting tube 10 rises. As described above, the lower can 1
And the hot water in the upper can 12 is connected to two sets of connecting pipes 10-1.
It is considered that the connection of 7, 11-18 forms a natural convection heat transfer flow path and efficiently transfers heat.

In this embodiment, the number of connecting pipes is two, but three or more connecting pipes may be used depending on the capacity of the line heater. The cross sections of the upper can body and the lower can body are not limited to circular shapes as in the present embodiment, but may be square in some cases.

[0025]

According to the present invention having the above configuration and operation, the following effects can be obtained. (1) Both the upper heating section and the lower combustion section can be manufactured separately at the factory, and can be integrated at the installation site simply by connecting the connecting pipe. (2) Even if the heat transfer capacity is several times that of the conventional integrated type, land transportation is possible. (3) Even if it is divided into an upper heating section and a lower combustion section, the heat transfer performance is the same as the conventional integrated type.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

FIG. 3 is a side view showing a partial vertical cross section of a conventional line heater.

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3;

[Explanation of symbols]

1; lower can body; 2; tube sheet; 3; tube sheet; 4; furnace tube; 5; burner, 6; smoke room, 7; smoke room, 8; smoke tube, 9;
0, 11; connecting pipe, 12; upper can body, 13; heating pipe, 1
4; end plate, 15; inlet tube, 16; outlet tube, 17, 18;
Connecting pipe, 19; manhole, 20; vent pipe, 21; shell, 22; end plate, 23; burner, 24; furnace tube, 25;
End plate, 26; smoke room, 27; smoke tube, 28; smoke room, 29; flue, 30; inlet tube, 31; heating tube, 32;

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F24H 1/28 F24H 1/44

Claims (1)

(57) [Claims] 1. A lower can body filled with warm water and having tube plates at both ends, a furnace tube and a smoke tube which have both ends fitted to both tube plates of the lower can body and through which combustion gas flows, and A smoke chamber provided adjacent to both pipe sheets, a burner attached to the one smoke chamber, a plurality of connecting pipes protruding from the top of the lower can body, and hot water being filled with water and immediately above the lower can body An upper can body having a U-shaped heating tube mounted on and horizontally mounted thereon, and a vaporized NG inlet tube and an outlet tube projecting from the end plate of the upper can body and communicating with the heating tube. And a top portion of the lower can body protruding from a bottom portion of the upper can body.
A line heater for city gas, comprising: a plurality of connecting pipes protruding from each other; and connecting pipes respectively connected to the connecting pipes.