EP0240664A2 - Vessel for transporting fluid aromatic hydrocarbons melting at a high temperature - Google Patents

Abstract

In the case of double hull ships for the transport of pitch at 200 to 300 ° C, particular care must be taken to ensure that the tanks are well insulated and that the gas space in the tanks is inert (1). The thermal expansion is to be taken into account by expansion joints and slide bearings (3). Due to the high solidification point of the products, all pipe systems must be provided with trace heating and adequate insulation. A thermal oil system is suitable for this, which simultaneously supplies the emergency heating (4) of the tanks (1). Since the tanks must not be filled with water, separate ballast tanks (17) must be arranged between the hulls. The ship must be equipped in such a way that it complies with the safety regulations for K1 ships.

Description

The invention relates to a ship for the transport of liquid, high-melting aromatic hydrocarbons at a temperature of at least 100 K above the melting point, in particular for the transport of liquid coal tar pitch, but also for fractions with a high solidification point, such as fluoranthene fractions (above 90 ° C.),
Pyrene fractions (over 110 ° C) etc.

Special ships for the transport of flammable liquids are known per se. In addition to crude oil tankers with a single hull, there are liquid gas ships with insulated triple-shell spherical tanks and complex safety devices. However, these ships transport the flammable liquids at ambient temperature or at lower temperatures, such as in the case of liquid natural gas (LNG) in the Range of -165 ° C. The liquids are generally free of sediments and do not change their properties during transport. Heated tankers with double hulls for the transport of liquid bitumen are also known. For bitumen, the temperature range in which it is easy to pump is depending on the grade:
for waste bitumen between 67 and 90 ° C,
for distilled bitumen between 105 and 135 ° C and
for blown bitumen between 165 and 200 ° C.

Bitumen ships are built for this temperature range. However, the temperature of the bitumen transported is normally not higher than 180 ° C. As bitumens only contain up to 0.5% by weight of solids, the tank rooms are provided with floor heating. Due to the double hull design, direct cooling of the tank walls by the sea water is avoided. No further insulation is planned; the heat losses are compensated by the floor heating. As bitumen is only used in the construction industry, the minor changes in properties due to heating and contact with the air are insignificant for the given temperature ranges and the relatively short exposure time. The bitumen ships therefore have tank rooms that are open to the atmosphere. Of course, this makes loading and unloading the cargo easier. The level can be measured, for example, with a measuring plate from a manhole on the deck. The filling and emptying of the tank rooms takes place via pumps, which are located in an external pump room in the The ship's hull are housed. Since the refineries are mainly located in the coastal area, only seagoing vessels are built for bitumen transport. Seagoing vessels that have such a shallow draft that they can also sail the larger inland waterways are only known for general cargo.

Ships for the liquid transport of high-melting aromatic hydrocarbons, such as coal tar pitches, have to meet significantly different requirements than bitumen ships. In addition to the more frequent location of the tar refineries in the interior, the properties of the pitches and their use must be taken into account. Hartpeche has softening points of more than 150 ° C (Kraemer-Sarnow). At a softening point of approximately 100 ° C., electrode pitches contain up to 19% by weight of quinoline-insoluble constituents and a correspondingly high solids content. They are very reactive to oxygen and also sensitive to temperature. For example, the formation of higher molecular weight chemical compounds, characterized, for example, by an increasing content of insoluble in toluene, can begin at temperatures below 350 ° C. However, these newly formed compounds undesirably change the viscosity and wetting behavior of electrode pitches. Due to the health-threatening effects of aromatic vapors, special safety precautions are also required.

All known ships for the transport of liquid goods do not meet the sum of the necessary measures, as are necessary for the transport of liquid pitch, for example.
The task therefore is to develop a ship for the liquid transport of high-melting aromatic hydrocarbons that meets the special requirements of these substances.

• a) mittig eingesetzten, vollständig isolierten Tanks (1), die jeweils von einem Punkt (2), insbesondere in der Mitte der dem Bug oder dem Heck zugewandten Tankwand, fest mit dem Schiffsrumpf verbunden sind und von Gleitlagern (3) geführt bzw. getragen werden;
• b) mindestens einem von oben in jeden Tank eingeführten, mit einem mit Thermalöl beheizbaren Wärmetauscher (4) mit überwiegend senkrechten Wärmetauscherflächen, der über eine Temperaturmeßstelle geregelt wird;
• c) mindestens einer von oben in jeden Tank eingesetzte Tauchpumpe (5), an die sowohl die Spülleitung (6) wie auch die Produktleitung (7) zum Füllen und Entleeren des Tanks angeschlossen ist;
• d) einer mit den Tanks wahlweise verbundene Gaspendelleitung (8);
• e) einer mit jedem Tank wahlweise verbundene Inertgasleitung (9), die über einen Druckwächter geregelt Inertgas in den jeweiligen Tank einspeist;
• f) mindestens einem Sicherheitsventil (10, 11) für Über- und Unterdruck mit
  Flammrückschlagssicherung (12) am Überdruckaustritt und Inertgasanschluß an der Unterdrucköffnung;
• g) mindestens einer nicht mechanischen Füllstandsmeßvorrichtung (13) und einem bei einem Füllgrad von 96 bis 98 % einen Alarm auslösenden Sicherheitssystem in jedem der Tanks;
• h) einer Begleitbeheizung für alle Produkt- und Gasleitungen einschließlich der Flansche, Regel- ­und Absperrorgane
• i) und einem beheizten, isolierten Mannloch (14) auf jedem Tankraum.

The object is achieved by a double hull with

• a) Centrally inserted, fully insulated tanks (1), each of which is firmly connected to the hull by a point (2), in particular in the middle of the tank wall facing the bow or stern, and guided or carried by plain bearings (3) will;
• b) at least one introduced into each tank from above, with a heat exchanger (4) which can be heated with thermal oil and which has predominantly vertical heat exchanger surfaces and which is controlled via a temperature measuring point;
• c) at least one submersible pump (5) inserted from above into each tank, to which both the flushing line (6) and the product line (7) for filling and emptying the tank are connected;
• d) a gas suspension line (8) optionally connected to the tanks;
• e) an inert gas line (9) optionally connected to each tank, which feeds inert gas to the respective tank in a controlled manner via a pressure switch;
• f) with at least one safety valve (10, 11) for overpressure and underpressure
  Flame arrester (12) at the overpressure outlet and inert gas connection at the vacuum opening;
• g) at least one non-mechanical fill level measuring device (13) and a safety system in each of the tanks which triggers an alarm at a fill level of 96 to 98%;
• h) accompanying heating for all product and gas lines including the flanges, control and shut-off devices
• i) and a heated, insulated manhole (14) on each tank space.

Since the ship cannot hold ballast water in the tanks during empty voyage, because even small amounts of water when filling with the hot liquid hydrocarbons lead to enormous foam formation, additional ballast tanks (17) must be arranged between the inner and outer hull of the ship.
The hydrocarbons are filled into the tanks at a temperature between 180 and 300 ° C, preferably 220 to 260 ° C. The tank walls expand by about 3.8 mm per m. In order to avoid tension in the hull and the tank walls, which may increase Leaks could result, the tanks are on plain bearings, preferably made of pockwood or other water-resistant, heat-insulating bearing material with sufficient heat resistance, and are guided laterally with such bearings. In order to achieve good lateral guidance, it makes sense to equip these bearings with spring elements such as disc springs or pneumatic springs. A transverse bulkhead (22) is located between the tanks, so that the individual tank sections are hermetically sealed from one another. In order to be able to immediately detect any leaks or fires, a temperature measuring point can be provided in each tank section. There must also be the possibility of possible fires from the inside, for. B. to delete immediately with CO₂. The individual tank sections must also be accessible, either through manholes from the starboard or port side ballast tanks or through manholes with direct access from the open deck. Pneumatic or hydraulic damping elements (15) with a gas spring can be arranged between the transverse bulkhead (22) and the unfixed adjacent tank wall, so that the mass forces are transferred more evenly to the hull when there is strong movement and partially filled tanks. The tank bottom preferably has an inclination of 3 to 5 ° C. towards a corner, at which a tank sump is optionally arranged.

The tank insulation (16) consists of inorganic insulating material such as rock wool, foam glass and the like. For the pipelines are above all Insulating mats made of rock or slag wool are provided. The insulation must be covered from the outside to prevent it from getting wet. The thickness of the tank insulation should be such that the average temperature drop in the tank at an average temperature of 250 ° C. is not more than 10 K / d, in particular less than 5 K / d.
In order to take thermal expansion into account, all tank connections are connected to the deck when the deck is led through thin-walled corrugated pipes (metal bellows). All pipes are also equipped with expansion joints that can absorb thermal expansion.
Indirect heating of the tanks with thermal oil is controlled using standard temperature sensors, while the heating of the entire pipeline can be switched on manually if necessary.
A thermal oil which is compatible with aromatics is preferably used as the thermal oil, so that no flocculation can occur in the event of leaks. A methylnaphthalene oil is particularly suitable for this.

The submersible pump must be suitable for high-melting, high-solids liquids, ie it should not contain any valves and should start slowly so that the drive shaft is not sheared off at low temperatures. Thyristor-controlled positive displacement pumps with a bypass overflow valve are suitable, such as rotary lobe or capsule pumps, in particular Viking pumps or spindle pumps, or centrifugal pumps with back blading Avoidance of cavitation and smooth housing without guiding devices. A three-way valve (18) is connected to the pressure side of the submersible pump (5) and connects the pressure side either to the flushing line or to the line for emptying or filling the tank. The flushing line is provided in the corners distant from the suction side of the pump at the deepest point of the tank with outlet openings, preferably nozzles (19), which are directed so that no solid deposition can take place in the corners of the tank, and the tank contents into a rotating one Current is displaced. When filling the tank, the product is pressed directly into the flushing line via the three-way valve when the pump is switched off. It is of course also possible to run a separate filling line directly to the bottom of the tank.

Mechanical measuring devices, such as floats, are less suitable for level measurement, since the tank should be sealed against atmospheric oxygen and, because of the high melting point of the aromatics, incrustations on the float guide must be feared. For this reason, mechanical measuring devices are not used, such as temperature-resistant capacitive or inductive level meters. The level measurement by absorption of weakly radioactive radiation (γ-emitter) has also proven itself. Float-controlled electrical switches can also be used for the alarm system that prevents the tank from overfilling.

The inertization of the tanks is extremely important. The tendency of aromatic mixtures, especially pitches, to oxidize in the specified temperature range is known. In contrast to land tanks, in which a surface renewal is generally not to be feared - at most there can be a low thermosiphon flow in heated tanks due to thermal convection - the surface of the tanks according to the invention becomes constant due to constant pumping and the ship's own movement renewed. In the case of electrode and impregnating pitches in particular, the change in viscosity due to oxidation leads to difficulties in further processing and has a negative effect on the wetting and filtering behavior of the pitches. The tanks must therefore be carefully rendered inert with a non-oxidizing gas, preferably nitrogen, and air ingress avoided. This is achieved by means of a gas pendulum line that connects the tanks to the land tanks, which are also rendered inert, during filling and emptying. In addition, the tanks are connected via an inert gas line with an inert gas generator such as. B. connected to a nitrogen generator that constantly ensures a controlled low inert gas pressure in the tanks. In this way, air ingress is prevented even with certain leaks on the flanges or on the manhole cover.

The tanks can be divided into several, preferably two, chambers by longitudinal walls of the ship be subdivided, which are filled or emptied at the same time to prevent thermal stress. The invention is explained in more detail by way of example in FIGS. 1 and 2.

Fig. 1 shows a section of the ship without the outer hull, deck and upper tank insulation. Fig. 2 shows the section AB in Fig. 1.
The completely insulated tank (1) is divided into two tank rooms by the wall (20) amidships. A transverse bulkhead (22) is located between the tanks (1). The tank is firmly connected to the hull by the supports (2). Slide bearings (3) support the tank (1) and give it lateral guidance. They consist of steel brackets connected to the hull, on which the pockwood blocks connected to the tank (1), which protrude from the insulation (16), can move. Hydraulic damping elements (15) with gas springs are arranged between the transverse bulkhead (22) and the unfixed end wall of the tanks (1). On the tank roofs, heat exchangers (4) are flanged, which have vertically arranged heat exchanger surfaces and extend far into the tanks (1). They are connected in parallel to the thermal oil circuit (21) by means of valves that can be operated both manually and optionally controlled via a temperature sensor (not shown). In this way, individual heat exchangers can be pulled without having to interrupt the thermal oil circuit. It is also possible to have two manually operated heat exchangers Shut-off devices and a temperature-controlled one to use.

The tank bottom is inclined diagonally from an outer corner towards the center by about 3 to 5 °. The suction port of the submersible pump (5) is located at the lowest point, the preferably heated sump. The drive shaft and the pressure port are pulled out of the tank (1) and connected to the tank roof via a flange. The encapsulated thyristor controlled motor is located above the deck. The submersible pump (5) is inserted from above into a holder located in the tank (5) (not shown). The pressure port of the pump (5), the flushing line (6) and the product line (7) for filling and emptying are connected to each other via a three-way valve (18). During the journey, the product is pumped through the rinsing line (6), which is provided with nozzles (19) directed into the corners. When emptying, the tap (18) is changed over and the pressure nozzle is connected to the product line (7) and when filling the product line (7) to the flushing line (6). Pumps with reversible flow direction can also be filled via the pressure port. The flushing line (6) is fixed to the floor by means of fork-like holders. The filling and emptying process is controlled using a non-mechanical level indicator (13). The tanks (1) are also connected via a gas suspension line (8) to the respective inertized land tank, so that the inert gases - possibly loaded with aromatic vapors - are not blown off into the free atmosphere or by a flare must be burned off and the inert gas consumption can be kept as low as possible. In addition, the tank is connected to an inert gas line (9) if larger amounts of inert gas are required in the event of a sudden drop in pressure. The same or a different tank nozzle receives an overpressure (10) and a vacuum safety valve (11). The overpressure safety valve (10) is provided with a flame arrester (12). The vacuum safety valve (11) is connected to the inert gas line (9). For inspection and repair purposes, each tank room is provided with at least one insulated manhole (14) through the deck. In order to ensure the necessary stability when empty, the ship is equipped with ballast tanks (17) between the two hulls.

If the ships are also to operate on inland waters, they must have a relatively shallow draft and must comply with the rules of inland navigation, which roughly correspond to the ADNR rules for shipping on the Rhine.
In terms of equipment, the ships must comply with the safety regulations for K1 ships.

All pipe systems, including the gas pipes, are provided with trace heating, for example with thermal oil, and are well insulated.

In contrast to crude oil tankers, the tanks cannot be cleaned with water but only with solvents. In particular, good pitch solvents are like For example, anthracene oil suitable for this purpose, which are preferably heated to about 80 ° C. The tank to be cleaned is partially filled with the solvent, which is conveyed by means of the submersible pump (5) into one or more rotating washing guns that were suspended from the deck in the manholes. The solvent is circulated throughout the washing process. The contaminated solvent is then pumped into a separate tank, from where it can be pumped off for reprocessing. In order to save tank capacity, it makes sense to carry out the tank cleaning in the port, where the solvent in the tank truck can be started up and the one contaminated with pitch residues can be removed directly for processing.

Claims (10)

1. Double hull ship for the transport of liquid, high-melting aromatic hydrocarbons at temperatures of at least 100 K above the melting point of these substances, in particular for liquid coal tar pitches, characterized in that the ship is equipped with a) Fully insulated tanks (1) inserted in the center, each of which is firmly connected to the hull at a point (2), in particular in the middle of the tank wall facing the bow or stern, and guided or carried by plain bearings (3) ; b) at least one heat exchanger (4) which is introduced from above into each tank and can be heated with thermal oil and which has predominantly vertical heat exchanger surfaces and which is controlled via a temperature measuring point; c) at least one submersible pump (5) inserted from above into each tank, to which both the flushing line (6) and the product line (7) for filling and emptying the tank are connected; d) a gas suspension line (8) optionally connected to the tanks; e) an inert gas line (9) connected to each tank, which feeds inert gas to the respective tank in a controlled manner via a pressure switch; f) at least one safety valve (10, 11) for overpressure and underpressure with flame arrester (12) at the overpressure outlet and inert gas connection at the vacuum opening; g) at least one non-mechanical fill level measuring device (13) and a safety system in each of the tanks which triggers an alarm at a fill level of 96 to 98%; h) accompanying heating for all product and gas lines including the flanges, control and shut-off devices i) and a heated, insulated manhole (14) on each tank space. 2. Double hull ship according to claim 1, characterized in that the tanks are designed for temperatures between 180 and 300 ° C, in particular between 220 and 260 ° C. 3. Double hull ship according to claims 1 and 2, characterized in that ballast tanks (17) are arranged between the inner and outer hull and transverse bulkheads (22) are located between the tanks (1). 4. double hull ship according to claims 1 to 3, characterized in that the plain bearings on the tanks consist of pockholz, which are provided with spring elements for lateral guidance. 5. double hull ship according to claims 1 to 4, characterized in that pneumatic or hydraulic damping elements (15) with gas spring are installed between the transverse bulkhead (22) and the non-fixed adjacent tank wall. 6. double hull ship according to claims 1 to 5, characterized in that the tank bottom has an inclination of 3 to 5 ° and a heatable sump is installed at the lowest point. 7. double hull according to claims 1 to 6, characterized in that the tank insulation consists of inorganic material and is dimensioned such that the average temperature drop in the tank at an average temperature of 250 ° C not more than 10 K / d, in particular less than 5 K / d is. 8. Double-hull ship according to claims 1 to 7, characterized in that all tank connections are connected to the deck when carrying out the deck via thin-walled corrugated pipes and the pipes are provided with compensators. 9. double hull ship according to claims 1 to 8, characterized in that it is a seaworthy ship with which inland water can also be navigated. 10. Double hull ship according to claims 1 to 9, characterized in that the segments delimited by the transverse bulkhead and inner hull are accessible and are provided with a temperature measuring point and an extinguishing device.

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