DE9318584U1 - Gas station - Google Patents

Description

Andrejewski, Honke & Partner Patent attorneys

European Patent Attorneys

Graduate Physicist

Dr. Walter Andrejewski, graduate engineer Drying. Manfred Honke, graduate physicist

Dr. Karl Gerhard Masch

Graduate engineer Drying. Rainer Albrecht

Attorney file:

78 892/Sc-

4300 Essen 1, Theaterplatz 3, PO Box 100254

10 February 1994

Utility model application G 93 18 584.7
U. Ammann Maschinenfabrik AG
Eisenbahnstrasse 25
CH-4900 Langenhai

Tank system

pursuant to GebrMG § 5 from P 43 28 984.3-42
of 28 August 1993

Technical area

The innovation relates to a tank system for storing a medium to be stored at an elevated temperature, in particular bitumen, with at least one tank and an electric heater for heating and/or keeping warm the medium or bitumen in the tank. The innovation also relates to such a tank system with a line

system for removing the medium or bitumen. Finally, the innovation also relates to a tank system of the type mentioned above with a filling station with which at least one tank can be filled from above with the liquid medium delivered on tank vehicles and to be stored.

State of the art

In the early days of bituminous mixture production, bitumen (and sometimes tar) was delivered in barrels and brought to processing temperature in melting vessels. With the introduction of transporting hot bitumen in tankers, heated storage tanks also had to be installed.

When heating storage tanks, a certain heating output must be provided on the one hand in order to heat up bitumen and store it at approx. 150-200 ⁰ C. On the other hand, it is important not to allow the heating surfaces to reach too high a temperature so that bitumen cannot crack.

Thermal oil heaters are therefore widely used to heat storage tanks. The thermally insensitive thermal oil is heated to the desired temperature and supplied to the consumers via pumps. Pipelines carrying bitumen can also be heated evenly using double-walled or accompanying pipes.

Thermal oil units for heating tanks have various disadvantages such as high investment costs, high maintenance

maintenance effort, poor efficiency in partial load operation, poor controllability of the heating circuits, etc.

In addition to systems heated by thermal oil, there are also electrically heated systems. The well-known electrical systems are relatively easy to maintain and their performance can be easily regulated, but they have not yet found much appeal in central European countries, where the price of electricity is considerably higher than the price of oil or natural gas.

Presentation of the innovation

The aim of the innovation is to provide a tank system of the type mentioned above that is characterized by a good energy balance, low maintenance requirements and high operational reliability.

According to the innovation, the solution consists in the fact that at least one tank is surrounded by a self-supporting outer shell and a space volume between the outer shell and the tank is completely filled with a granular insulation material.

Granular insulation materials ensure a much greater homogeneity of insulation and in practical applications their insulation values essentially do not deviate from the laboratory values. This is in contrast to fibrous insulation materials. Because the tank and the outer shell do not have to be connected to each other, thermal bridges can be systematically avoided. Preferably, two or more cylindrical tanks are provided, which are connected to each other.

are arranged quite close to each other in a common, essentially cuboid-shaped outer shell in a radiation-minimizing arrangement. In this way, heat loss can be kept fairly low.

The thickness of the insulation should be adapted to the thermal conductivity of the insulation material in such a way that the radiation is on average less than 20 W/m , in particular not more than 15 W/m .

According to a particularly preferred embodiment, the outer shell is formed by load-bearing insulation panels. The outer shell therefore not only has a statically supporting function, but also a thermally insulating function. Accordingly, the amount of granular insulation material can be reduced or, conversely, the overall insulation value can be increased.

Particularly preferred insulation materials are expanded or puffed perlite, which have a very low density. Vermiculite, for example, is also advantageous. These and other granular insulation materials can be made hydrophobic. The moisture, which usually significantly reduces the insulation value of conventional thermal insulation materials, cannot settle in the new insulation and is therefore largely kept away.

The tanks are immersed in the insulation material to their full height. The outer shell is so high that a weather-protected space is created above the insulation material to keep the tanks accessible. The roof space mentioned should allow any rising moisture to drain away.

Filling and emptying lines are, as far as possible, routed in the granular insulation material inside the outer shell (i.e. between the tank and the outer shell). A part located outside the outer shell, which serves, for example, to transport the bitumen to a mixing station, is provided with accompanying insulation in such a way that the lines mentioned are insulated with approximately the same effective value along their entire length.

To ensure that valves, pumps, etc. in the filling and emptying lines within the outer shell are accessible at all times, they are arranged in separate, granulate-free recesses that are accessible from the outside.

According to the innovation, a tank system with at least one tank and a pipe system for removing the medium is characterized by the fact that the pipe system includes metal pipes that can be directly heated electrically. This type of heating is extremely uniform and structurally simple. Furthermore, the risk of an undetectable power outage is eliminated.

Preferably, the metal pipes are made of stainless steel, which has a resistance value about five times higher than the typical pipeline materials (such as Fe). This creates a larger voltage drop across the pipe system, which simplifies the control of the current flow or the electrical structure of the power source.

Preferably, the line system is supplied with electricity by a transformer in such a way that the heating power is less than 1 kW/m, in particular approximately 0.5 kW/m. Such a power is sufficient to keep the line warm. A heating function of the line system is therefore not intended.

To connect the line system to a power source, two-sided electrically insulated flange connections are provided. Such a flange connection can also be used to bridge electrically controlled valves or other components. The two pipe sections connected to the valve are connected directly via a separate conductor (cable).

A transformer with several voltage taps is preferably provided as the power source. The voltages that can be tapped are all in a range that has been roughly calculated based on the length of the cable. By connecting the correct voltage tap, the effective heating output can be set to a desired value that is theoretically difficult to determine precisely.

The pipe system is preferably designed as a ring branch line with at least two pumps. The medium can therefore be extracted in two different ways (extraction via ring line, extraction via branch line), which is particularly advantageous if two different types of bitumen have to be used for one mixture. In addition, there is a certain degree of redundancy in the extraction system.

According to a particularly preferred embodiment, in order to heat up and/or keep warm the medium in the tank, a separately controllable second heater is provided in addition to a first heater as a booster for rapid heating. The two heaters differ significantly in terms of their power range, with the booster heater being dimensioned for rapid heating. The second heater should compensate for any heat losses with the lowest possible heating power. Typically, the power ranges differ by one-third.

a factor of 5-10. In order to ensure that heating is as even and as free from overheating as possible, both the temperatures of the heating surfaces and those of the medium are monitored and controlled.

The control circuit is designed in the sense of a cascade control so that the actual temperature of the medium is always kept as close as possible to the target temperature by finely adjusting the heating output and the actual temperature of the heating surface is never exceeded by a specified maximum temperature. According to the innovation, the system works not only according to the on/off principle, but also according to a temperature difference-dependent method (e.g. with a proportional-integral controller).

Preferably, the two heaters are designed as wall ring or floor heating. Both heaters act on the tank wall from the outside. Since no openings through the tank wall are required, this is a structurally simple and operationally reliable heater. Due to the large surface area, the wall ring heater can provide a much greater heating output than the floor heating, which is why the former serves as a booster.

The wall ring heater can be formed by a large number of flat, ring-segment-shaped heating rods attached to the outside. The heating rods are known designs with an electrically conductive core and an electrically insulating jacket. The heating rods are spaced apart from one another by typically 10-30 cm, in particular by approx.

2
20 cm in order to be able to deliver a maximum power of 2.4 kW/m.

8th -

Preferably, the heating elements are combined into separately operable heating areas. The heating areas can be switched on and off depending on the fill level. This means that even a half-full tank can be heated up in an energy-saving manner.

By clamping the heating rods with springs to pins that are provided as anchoring elements on the outer wall of the tank, good thermal contact can be ensured with relatively little manufacturing or assembly effort.

According to a particularly preferred embodiment, the booster heater comprises a register heater arranged inside the tank made of solid stainless steel strips that can be supplied with electricity by a low-voltage high-current source. The wide heating strips not only offer a large heating surface, but are also mechanically very stable.

Particularly when using a register heater arranged in the tank, it is important that a breakthrough heater is also provided, which creates a liquid passage upwards when the solidified bitumen is heated from below, through which the medium expanding during heating can escape. This is preferably a directly heated pipe arranged vertically in the tank, which runs through the tank essentially from top to bottom. This breakthrough heater is very effective. If a tank installation is undesirable, a heating rod mounted vertically on the outside wall of the tank can be provided instead. This also ensures that the solidified bitumen is initially melted along a vertical channel.

According to the innovation, the surface temperature of a register arranged inside the tank is measured not directly but indirectly. A pipe that extends into the interior of the tank and is closed at the inner end has the same surface and cross-section as the bands of the register heater. It is supplied with the same current as the register heater. In its bitumen-free interior, a temperature sensor measures the surface temperature, which essentially corresponds to the surface temperature of the heating register. In this way, the temperature sensor does not come into contact with the bitumen. The pipe is connected in series with the heater so that the same heating current flows through it.

The heaters' output is controlled by thyristors in a pulse group circuit. Pulse group circuit means that only whole half-waves are allowed through (no phase control) and that the output is set by the length of the pulse group. Since the power grid is only slightly disturbed in this way, a complex damping network can be largely dispensed with.

An automatic filling station for a tank system of the type mentioned, with which at least one tank can be filled from above with the liquid medium delivered on tank vehicles and to be stored, has, according to the innovation, a collecting tank, a riser pipe that can be emptied into the collecting tank and opens into the top of the tank, a filling pipe that can be connected to the tank vehicle and opens into the riser pipe, a pump for conveying the medium and a suction pipe for sucking in the medium in the collecting tank. A filling station control ensures that a column of liquid in the riser pipe after the tank has been filled is drawn into the collecting tank.

· 9 · a

is emptied and that the contents of the collection container are automatically conveyed into the tank at the start of the next filling of the tank. This prevents incorrect handling from causing the hot bitumen in the riser to flow backwards out of the filling line.

The filling and suction lines are connected upstream of the pump via a three-way valve and can be switched. The riser line can in turn be emptied into the collection container via a valve. The valves mentioned are automatically operated by the filling station control.

Preferably, the collecting tank also serves as a condensate collecting vessel. For this purpose, the tank's gas recovery line flows into the collecting tank. It is routed outside the outer shell for as long as possible and preferably has cooling fins so that the vapors condense in the gas recovery line.

In a tank system with several tanks, the tanks are connected to each other in the upper area with level compensation lines. The compensation lines mentioned are located slightly below the openings of the tank ventilation. If a tank is accidentally overfilled, its contents first flow into another tank before its contents (in the worst case) reach the collecting tank or outside via the tank ventilation.

The filling station mentioned can be operated as follows:

First, the contents of the collection container are pumped into the tank. After a predetermined time, the three-way valve is switched from the suction line to the filling line

and the contents of the vehicle are pumped into the tank. When the tank vehicle is empty, the valve is switched from the filling line to the suction line again and pumping continues for a certain period of time. The riser is then emptied into the collection tank by either running the pump backwards or opening the valve that closes the riser against the collection tank. This ensures that the contents of the riser can never flow backwards out of the filling line, but are always emptied into the collection tank. By always pumping out the liquid contents of the collection tank first, it is ensured that there is always enough space in it for the contents of the riser.

As a redundant additional safety measure, the fill level of the collection tank can be automatically monitored and, if a certain level is exceeded, a heater can be switched on, which ensures that the bitumen in the collection tank is always liquid the next time the tank is filled, so that the entire contents of the collection tank can be pumped into the tank system.

Further advantageous embodiments and combinations of features emerge from the following detailed description and the entirety of the patent claims.

Short description of the drawings

The innovation will be explained in more detail below using examples of implementation and in connection with the drawings.

They show:

Fig. 1a-d Schematic representations of innovative radiation-minimizing arrangements of storage tanks in a common outer shell;

Fig. 2 A schematic representation of an insulated tank in accordance with the new design in elevation;

Fig. 3 A schematic diagram of a preferred embodiment of a tank system with three tanks;

Fig. 4a-c Example of a tank system according to the innovation with two tanks shown in two side views and a top view;

Fig. 5a, b Side view and top view of an innovative register heater;

Fig. 6 Sectional view of a flange connection insulated according to the new design;

Fig. 7 Side view of an innovative automatic filling station.

In principle, identical parts in the different figures are provided with identical reference symbols.

Ways to implement the innovation

The new bitumen tank system is based in principle on a three-stage concept. In the highest stage (main goal), the aim is not to have to provide any heating power. The entire tank system should therefore be so well insulated that the heat loss during the season between refills can be neglected. If care is taken to ensure that the bitumen is always delivered at a sufficiently high temperature, the thermal losses between refills can be compensated for by the sufficiently hot, newly filled bitumen (passive heating).

Only in a second stage should active heating be used. The heating output should be as low and consistent as possible (floor heating in the lower output range).

Finally, in a third stage, a powerful (booster heater) is used. This heater can heat the medium up strongly within a short time. However, this should only happen in rare cases (e.g. at the start of the season, longer, extraordinary heating interruptions, etc.). At stage three, the system runs for a maximum of 5% of its operating time.

The 3-stage concept brings with it particular advantages in terms of operating costs. In electrical systems, it is not just the total energy consumption that counts, but also the power required in each case. By using the booster heating sparingly, the performance tariff naturally only has a limited impact.

The concrete technical implementation of this concept is shown in the following description.

Fig. 1 a-d show tank systems with 1 to 4 tanks 2, 2.1, 2.2, ..., 2.9, which are arranged in a radiation-minimizing arrangement. The illustrations show longitudinal axis cross-sections of the elongated, cylindrical tanks 2, 2.1, ..., 2.9. A tank 2, 2.1, ..., 2.9 of this type typically has a capacity of approx. 60 t of bitumen. The cylindrical tanks 2, 2.1, ..., 2.9 are arranged upright so that the surface of the bitumen level and thus the oxidation of the bitumen with the oxygen in the air is as small as possible. Depending on the required bitumen storage volume, 1, 2, 3 or 4 (Fig. 1a-d) tanks 2 or 2.1, 2.2 or 2.3, 2.4, 2.5 or 2.6, 2.7, 2.8, 2.9 are each arranged in a common outer shell 1 or 1.1 or 1.2 or 1.3. The tanks are as close to each other as possible. The space between the tanks 2 or 2.1, 2.2 or 2.3, 2.4, 2.5 or 2.6, 2.7, 2.8, 2.9 and the respective outer shell 1 or 1.1 or 1.2 or 1.3 is completely filled with a granular or powdered insulation material 3 or 3.1 or 3.2 or 3.3. The outer shell 1 or 1.1 or 1.2 or 1.3 has the primary task of holding the free-flowing insulation material 3 or 3.1 or 3.2 or 3.3.

If more than two tanks are planned, other low-radiation installation options can also be considered if desired. If the outer shell is essentially cuboid-shaped, it is particularly easy to construct (standard solution). In principle, however, triangular or other polygonal or prismatic floor plans or room shapes can also be selected.

Fig. 2 shows the system according to Fig. 1b in section I-I. The

* ■

· 4

- 15 -

The cylindrical tank 2.1 is elongated and has a domed or dome-shaped base 2.11, a domed ceiling 2.12 and a shell wall 2.13. A lockable hatch 30.1 is provided in the ceiling 2.12. The tank 2.1 is completely surrounded by the fine-grained insulation material 3.1. A roof space 5 is provided under a roof 4, which is accessible via a ladder 6. The tank 2.1 can therefore in principle be accessed at any time. The roof 4 is designed as a sloping roof. It keeps the weather at bay, but is otherwise not particularly thermally insulated.

Proper and good insulation of the storage tanks is an important aspect of the innovation. Unlike with thermal oil units, the heating energy can be introduced into the bitumen in a targeted manner. While with thermal oil heating, the heating system itself has a large heat radiation and heat capacity, which can only be reduced to a limited extent and at the same time at great expense with insulation, the electric heaters are installed in or at least directly on the tank.

With the new insulation concept, losses can be kept so small that heating is not required during the season between refills. This means that the cooling between periodic fillings does not normally exceed 2 ⁰ C, preferably 1 ⁰ C with a full tank and 24 hours. The bitumen can therefore be stored with little temperature fluctuations in a range of 160-180 ⁰ C. The insulation is therefore designed so that the total loss of a 60 t bitumen tank

2 2

with a surface area of approx. 100 m2 does not exceed 15 W/m2 (at a temperature difference of 150-200 ⁰ C). This is achieved with very good insulation and short cable routing, which is described in detail below.

As already mentioned, the uninsulated tanks are placed close to each other and completely immersed in the granular insulation material. The thickness of the insulation and thus the minimum distance between the tank wall and the outer shell is about 150-200 mm.

Puffed or expanded perlite, for example, is used as an insulating material. This is obtained in a known manner by heating a volcanic rock glass of rhyolite composition . When heated, the material expands into a light, pumice-like "rock foam". Another preferred material is vermiculite.

Compared to conventional insulation with rock wool, the powdered insulation material has the advantage that the density, which is very important for the insulation value, is largely independent of the type of manufacture and application of the insulation material. The free-form insulation material also has the advantage that no supporting connections are required between the tank and the outer shell (thermal bridges), that no air holes can occur (e.g. due to tank movements due to temperature fluctuations) and that the moisture that impairs the insulation capacity can be kept away by making the powder hydrophobic. Finally, if necessary, powdered insulation material can be removed for an inspection of the tank system or for repairs (it flows almost like a liquid) and refilled after the work has been completed.

In principle, it is sufficient if the outer shell provides static support for the powdered insulation material and prevents it from leaking out. However, it can be advantageous to 1.1

- 17 -

from self-supporting insulation panels or plates. This not only eliminates the need for a complex steel support structure, but also increases the insulation value and reduces the amount of expanded perlite required.

Fig. 3 shows a diagram of a tank system with three tanks 2.3, 2.4, 2.5. Each of the three tanks 2.3, 2.4, 2.5 has a floor or wall ring heater 7.1 or 7.2 or 7.3, a register heater 8.1 or 8.2 or 8.3 and a breakthrough heater 9.1 or 9.2 or 9.3. Floor or wall heaters 7.1, 7.2, 7.3 consist of conventional heating coils or heating rods (round or flat profiles with an electrically insulated core). The heating coils or heating rods are attached to the outside of the floor or wall. They therefore do not require any breakthroughs in the tank wall. The output of the underfloor heating is typically in the order of 6 kW, which leads to a target heating load of less than 0.1 W/m. Local overheating (which can lead to undesirable cracking of the bitumen) can thus be avoided.

The wall ring heater is formed by a large number of heating ring segments that are mounted on the outer wall essentially perpendicular to the tank's longitudinal axis. The individual ring segments are spaced apart by 20 cm, for example. They are preferably made of flat profiles (e.g. 15 mm wide) to ensure the greatest possible heat transfer to the tank wall. The spacing is chosen so that the tank wall is heated as evenly as possible. By spacing the ring segments relatively close together, a certain redundancy is achieved, which is an advantage in view of their difficult accessibility (they are completely surrounded by the powdered insulation material).

Preferably, the ring segments are clamped to pins provided on the outside wall of the tank using strong springs. In principle, pin anchoring can be dispensed with if two or more ring segments are clamped together using springs or the like. Of course, other fastening options are also conceivable.

According to a particularly preferred embodiment, the heating rings are divided into several (e.g. three to four) ring-shaped heating areas, which can be switched on or off depending on the fill level of the tank. If the tank is only half full, for example, only the lower half of the wall ring heater needs to be switched on. The power consumption can be adjusted accordingly to the fill level.

If the tank is full, a fairly large heating surface is available. Accordingly, the bitumen can be heated up relatively quickly with the help of the wall heating if necessary (e.g. at the start of the season). The wall ring heating can therefore be used as a booster heater. As a rule, however, the wall ring heating should work with the smallest possible temperature differences (e.g. approx. 5 ⁰ C).

The register heater 8.1 or 8.2 or 8.3 is a directly heated low-voltage, high-ampere register made of stainless steel. It is operated with three-phase current from a transformer 10.1 or 10.2 or 10.3.

As can be seen from Fig. 5a, b, the register heating comprises three stainless steel strips 33.1, 33.2, 33.3, which are suspended one above the other and not too far from the bottom 2.31 of the tank 2.3, in an electrically insulated manner. The cross-section of the stainless steel strips 33.1, 33.2, 33.3 is

19 -

ζ. β. 5 x 120 mm . Each of the three stainless steel bands 33.1, 33.2, 33.3 is bent into a "ring meander" with, for example, four 270° ring segments (see Fig. 5b). The ring segments are arranged concentrically and cover as large a cross-sectional area of the cylindrical tank 2.3 as possible.

Each of the three stainless steel bands 33.1, 33.2, 33.3 is connected to a phase of a 40 V three-phase current. The current values can reach 800 A (high current). The stainless steel bands 33.1, 33.2, 33.3 are attached with ceramic insulation opposite the suspension. The suspension comprises four structures 34.1, ..., 34.4 supported regularly along the circumference on the inner wall of the tank 2.3. The power supply is via a closable wall opening 35.

The effective surface of the described register heating is very large. 60 kW of heating power can be achieved without any problems. The solid stainless steel bands are also mechanically very robust, which is particularly advantageous when attacking an empty tank from above.

Instead of the special register mentioned above, a slide-in register based on the hot water boiler principle can of course also be used.

As is well known, the less hot bitumen is, the more viscous it becomes. Bitumen solidifies below 60-70 ⁰ C. If a solidified tank content is heated with the register heater, there is a risk that the tank will burst, as the lower part of the bitumen block liquefies before the upper part and cannot expand anywhere. Breakthrough heaters 9.1, 9.2, 9.3 are therefore provided, which melt a vertical breakthrough through the solidified block and prevent the liquefied

20 -

Bitumen enables.

According to a particularly preferred embodiment, the breakthrough heaters 9.1, 9.2, 9.3 are U-tubes that extend essentially from the bottom to the top of the tank. The U-tubes are directly heated stainless steel tubes. They are supplied with electricity by transformers. Instead of a tube, a steel strip can also be provided, for example. The breakthrough heater does not need to run along the longitudinal center axis. In particular, it can also be formed by a heating rod that runs along the outer wall parallel to the longitudinal axis of the tank.

A breakthrough heater is of course only necessary if there is a strong heating system close to the floor, which carries the danger described above. If a wall ring heater is used as a booster instead of a register heater, then a solidified bitumen block is melted from the outside to the inside, whereby the melted bitumen can always escape upwards.

As a rule, the bitumen is delivered at a sufficiently high temperature. If the tank system is sufficiently well insulated in accordance with the innovation and the system is filled regularly, then any heating is not necessary. The heat lost through radiation is then replaced by the newly delivered hot bitumen (see stage I of the system concept explained above).

Since it cannot be ruled out that at some point (e.g. at the start of the season or in the event of a breakdown) the tank contents will have to be heated up within a short period of time (a few hours), a booster heater is generally indispensable. However,

It is not the intention of the innovation to heat up on the one hand and keep warm on the other hand with the strong booster heater. Rather, the innovation focuses on ensuring that power consumption is as even as possible (preferably during off-peak times). This can be achieved with suitable regulation. According to the innovation, the temperature of the bitumen and the heating surfaces is therefore measured and the heating units are supplied with power in such a way that the desired bitumen temperature (if necessary using off-peak electricity at night) is maintained as constantly as possible or - when heating up - is achieved as without overshoot as possible. The power is therefore adjusted as finely as possible.

Since the heating surface temperature must not exceed a certain value due to the risk of cracking, the heating output must be limited upwards. With a cascade circuit, the heating current is therefore controlled depending on the average heating surface temperature (ζ. β. determined by several temperature probes) and the bitumen temperature (determined at a representative location) in such a way that the heating surface temperature remains within the required range and the heating energy is reduced accordingly as soon as the actual temperature of the bitumen approaches the target temperature.

A thyristor pulse group circuit is preferably used to control the electrical power. This means that the thyristors only switch whole half-waves on or off. The amount of current is determined by the number of pulses per group or the ratio of the number of switched half-waves to the number of blocked half-waves. Instead of the thyristors, other switching elements can also be used if necessary.

Measuring the heating surface temperature of a high-current register located inside the tank is not without its problems. The arrangement described below represents an elegant solution to this problem.

A pipe made of the same material as the register heater and having the same cross-section and the same outer surface (= contact surface with the bitumen) is mounted in the lower part of the tank, protruding into it. It is electrically insulated from the tank wall and closed at the end so that its interior remains free of bitumen. The temperature of the inner surface of the pipe is measured using a temperature sensor. The temperature sensor therefore does not come into contact with the bitumen. The same current flows through the pipe as through a single stainless steel strip of the register heater. Since the same power loss is generated per length in the pipe as in the stainless steel strip and the same heat is released to the bitumen on the outer surface, the temperature on the inner wall of the pipe is essentially the same as that on the stainless steel strips.

Fig. 3 also shows the new pipe system for removing the bitumen from the tanks 2.3, 2.4, 2.5. This is a combined ring branch line 11. Each tank has two taps 11.11, 11.21 or 11.12, 11.22 or 11.13, 11.23, which can be opened or closed or switched on or off using valves 12.1, 12.2, ..., 12.5, 12.6. The ring branch line 11 leads to a bitumen scale 13 and back. There, the desired amount of bitumen can be removed using valves 12.8, 12.10 (particularly three-way valves). The bitumen is pumped using one of the two pumps 14.1, 14.2.

The ring stub line embodies two stub lines and one

ne ring line. The first branch line is formed by the line sections 11.1, the taps 11.11, 11.12, 11.13, the valves 12.1, 12.3, 12.5, 12.8 and the pump 14.1. The second branch line is formed by the taps 11.21, 11.22, 11.23, the line sections 11.2, the valves 12.2, 12.4, 12.6, 12.7, 12.10 and the pump 14.2.

The ring line finally includes the first branch line 11.1, the valve 12.9, and the second branch line without the pump 14.2 but instead with the bypass line 11.3.

The bitumen scale 13 is usually located in the upper part of an asphalt mixing plant, which is arranged in a separate structure next to the bitumen tank system. According to the innovation, essential parts of the ring branch line are embedded in the insulation powder within the outer shell of the tank system. At A or B (see Fig. 3 bottom right), the ring branch line leaves the bitumen tank insulation. It is then only insulated by an accompanying insulation. The effective insulation value of this should, however, be as close as possible to the insulation value of the remaining part of the ring branch line. This has advantages above all in connection with the control of the pipe heating described below.

The combined ring spur line 11 works as follows:

In normal operation, the line works as a ring line, i.e. the automatically adjustable taps or valves 12.1, 12.3, 12.5 lead the bitumen from the selected tank 2.3 or 2.4 or 2.5 via the pump 14.1 to the weighing vessel of the bitumen scale 13. There, the tap 12.8 carries out the dosing. The return flow leads via the valve 12.9 (connecting through tap) and the second dosing vessel closed for weighing.

cock (valve 12.10) via the bypass line 11.3 past the pump 14.2 into the same or another selected tank.

In branch line or emergency operation, valve 12.9 and bypass line 11.3 are closed. Both pumps 14.1, 14.2 now work as branch line pumps. The excess pressure during the dosing pauses is reduced via the bypass pressure relief valves built into pumps 14.1, 14.2.

This solution combines the advantages of the ring line with those of the spur line:

- Low wiring effort

- Pumping option

- Ring line operation over the majority of the operation

- Blending of bitumen possible

- Reserve pump installed.

According to a particularly preferred embodiment, the ring branch line 11 is directly heated electrically. For this purpose, the line pipes are made of stainless steel and connected to a transformer 10.4. Such a pipe heating system produces an optimally homogeneous heat distribution in the pipe wall. As the ring branch line 11 is now insulated approximately equally well along its entire length, not only can it be heated evenly, but also easily regulated.

Stainless steel has a resistance value that is typically several times that of iron. The aim is to have a voltage in the range of 10-40 V across the entire ring line. For typical pipe cross-sections and average line lengths, the voltage should be between 0.1-1 V/m

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In this way, a preferred heating output of 400-500 W/m can be achieved.

The ring branch line is also designed for heating. If a certain part of the line is not used for a longer period of time (e.g. because the bitumen in the corresponding tank is not needed and the bitumen in the corresponding part of the line is therefore not circulated), local undercooling can occur, which must be remedied when the corresponding bitumen is drawn off. The installed output of 400-500 W/m enables short heating (e.g. from 4 to 6 a.m.). Due to the new insulation, 20-30 W/m is sufficient to keep warm. This reduced output is of course only necessary during interruptions in operation, since during operation (i.e. when the bitumen pumps are running) the bitumen comes out of the tank and has the required temperature.

The ring line heating is also controlled by thyristor and cascade control. The bitumen temperature in the pipe and the pipe temperature at various points are measured and fed to the controller that controls the thyristor. The following control is provided to prevent local undercooling (e.g. in unused pipe sections) or overheating: Three temperature sensors are arranged at typical points along the pipe system, for example. Using an electrical circuit that is able to select the lowest or highest value.

In practice, it is often difficult to determine the transformer voltage required for a required heating output, taking into account the pipe diameter and length. It has therefore proven advantageous to use a transformer with a plurality of

26 -

(&zgr;. e.g. five) outputs with a voltage (&zgr;. e.g. by 1 V) step in order to then connect the appropriate voltage tap on site. The voltage taps are of course all in a roughly calculated range in advance. In this way, tolerances and smaller unforeseeable deviations can be compensated for in a targeted manner.

Stainless steel also has a very smooth surface, which makes it difficult for unwanted deposits and residues to form.

Instead of direct heating, trace heating from a heating tape or a coiled heating wire can be used. However, these alternatives are either less robust or more expensive than direct heating.

To store the current and to be able to bridge valves and pumps, the flange connection insulated on both sides, as shown schematically in Fig. 6, is preferably provided. Two adjacent pipes 36.1, 36.2 each have a flange 37.1, 37.2 with (several) holes 38.1, 38.2 at their ends. An insulating ring 39 is inserted between the pipe ends or the flanges 37.1, 37.2. The flanges 37.1, 37.2 are connected with several screws, e.g. 41 with nuts 42. The screw 41 and the nut 42 are electrically insulated from the flanges 37.1, 37.2 with the help of insulating sleeves 40.1, 40.2. The insulating sleeves extend essentially through the corresponding bore 38.1, 38.2 and have a collar with which they rest on the edge of the bore 38.1, 38.2 and insulate the head of the screw 41 or the nut 42 from the flanges 37.1, 37.2. On one flange 37.1 there is a tab 43 which projects radially outwards with respect to the axis of the tube 36.1 and to which a power cable 44 is soldered.

The current is supplied to the pipe via the power cable 44

36.1, whereby pipe 36.2 remains de-energized.

The taps or valves 12.1, ..., 12.10 and the pumps 14.1, 14.2 are also heated, which is shown schematically in Fig. 3 (resistance heating).

An automatic filling station is also shown in Fig. 3. It comprises a filling line 17 and a suction line 18, which can be optionally connected to a pump 23 via a three-way valve 21. The filling line 15 is connected to the outlet of the pump 23, which opens into one of the three tanks 2.3, 2.4, 2.5 depending on the position of two valves 16.1, 16.2 (three-way valves). The filling line 15 can be emptied into a collecting container 19 via a valve 22. The suction line 18 is used to pump the collecting container 19 empty. According to a preferred embodiment, the collecting container 19 can be heated with a heater 20. There are no great demands on this in terms of performance, since the collecting container is not very large (a few hundred liters).

The three tanks 2.3, 2.4, 2.5 are mutually connected with level compensation lines 24.1, 24.2. One above the level of the level compensation lines 24.1,

24.2 The ventilation line 25 leading into the tank 2.5 is designed as a condenser for the escaping vapors (finned tube, etc.) and leads to a condensate drain line 26 in the collecting tank 19 on the one hand and freely on the other hand.

A concrete structure of a filling station is shown in Fig. 7a, b. The collecting container 19 is preferably cuboid-shaped. The suction line 18 protrudes from above into the collecting container 19 and extends to just above the ground.

··

This allows the collecting tank 19 to be pumped out essentially completely. The three-way valve 21 is connected upstream of the pump 23, which is attached to the top of the collecting tank 19. The line section 15.4, which branches off from the main line section 15.1, also enters the collecting tank 19 from above and can be closed via the valve 22.

The collecting container 19 is on the floor. The filling line 15 rises up the outside of the tanks to fill them from above. This has the advantage that the filling does not have to be done under pressure, as is the case when filling the tank from below. However, after filling, a column of liquid remains in the rising filling line 15, which must be prevented from flowing out. This is now achieved with the new fully automatic filling station. Fully automatic means that the pump 23 and the valves 21 and 22 are operated by an electronic control and not manually.

Filling takes place as follows:

The tanker that delivers the hot bitumen is connected to the filling line 17. At this point, the three-way valve is positioned so that the suction line 18 is connected to the pump 23. The valve 22 is also open.

If a start button is now pressed, a check is made to see whether the tank to be filled is not already full. If not, the valve 22 is closed and the pump 23 is switched on. The collecting tank 19 is emptied (provided that the bitumen in it has not cooled down and thus solidified). After a predetermined time, the valve 21 is opened to

connecting the filling line 17 to the pump 23 is switched over automatically. The delivered bitumen is transported from the tank vehicle into the corresponding storage tank.

Once the tanker has been pumped dry, a stop button is pressed. The three-way valve is switched back to the suction line 18, with the pump 23 continuing to run. After a predetermined pumping time, the valve 22 is opened so that the contents of the line 15 leading up to the tank can be emptied into the collecting container 19. Then the pump 23 is switched off and the initial state is reached again.

In principle, the collection container is emptied in this way both before and after the tank is filled. To increase safety, a level sensor can be provided in the collection container, which adjusts the heater 20 (see Fig. 3) as soon as the level in the collection container 19 reaches a certain height. In this way, it can be ensured that the next time the tank system is filled, the bitumen in the collection container 19 is heated and thus liquid and can be completely pumped out.

In principle, valve 22 and line 15.4 can be dispensed with. To empty the riser line 15.1, pump 23 is then simply run backwards if valve 21 is switched to suction line 18.

In Fig. 4a-c a concrete structure of a bitumen tank system with two tanks 2.1, 2.2 is shown. As already mentioned several times, the tanks are completely surrounded by insulation material 3.1. They can be accessed via hatches 30.1, 30.2. Outside the insulation, but as close as possible to the outer shell 1.1, is the automatic filling station 29 (with

the collecting container 19). Within the outer shell

1.1 in the insulation material 3.1, two risers 27.1, 27.2 are provided, which lead into the tanks 2.1, 2.2 at the top. They can be optionally connected to the pump outlet of the filling station 29 using a changeover valve 28. The changeover valve 28 is preferably located at man height so that it can be easily operated (if manually operated) and maintained. This also keeps the part of the filling line outside the insulation as short as possible.

The ventilation line 25 is intended to act as a condenser and is therefore as short as possible within the insulation and as long as possible outside the insulation. It should be able to release as much heat as possible to the surrounding air and is therefore preferably designed as a finned tube.

In Fig. 4b and c, a level compensation line 31 is also shown. It is a relatively short connection between the two tanks 2.1, 2.2 in the uppermost area (but below the opening of the tank ventilation).

Furthermore, part of the ring branch line system is shown. It has four, in the lower part of the tanks 2.1,

2.2 opening lines 32.1, ..., 32.4, followed by four valves 45.1, ..., 45.4 and two lines 32.5, 32.6 rising to about half the height of tank 2.1. All of the line sections shown are located within the new insulation. Lines 32.5, 32.6 are routed to the height mentioned because the bitumen scale of the mixing station is at this height and because this means that the ring branch line is routed over the greatest possible length within the insulation.

A pump 46 of the ring main is also switched on in line 32.6. The pump 46 is also located at man height in an easily accessible location.

The valves 45.1, ..., 45.4 and the pump 46 are arranged in small boxes that are free of insulating material. The boxes are closed off from the outside with a removable cover, so that the valves and pumps housed therein are accessible for inspection purposes.

The innovation is not limited to the described embodiments. In particular, it should be noted that the innovative insulation principle, the electrically directly heated metal pipes, the combined ring branch line, the combination of permanent and booster heating and the automatic filling station can basically be used independently of one another (i.e. as independent features of a tank system). Finally, the innovation is not limited to tank systems for storing bitumen, but extends to the storage of liquid media at elevated temperatures in general.

Heating bitumen tank systems with electrical energy represents a huge technical advance, the benefits of which are immediately apparent to the user. In addition to significant energy savings, safe and clean operation can also be guaranteed. This innovation means that the potential of this technology is being fully utilized for the first time.

- 42 -

List of reference symbols

1,1- 1 , ... .3 1 .3 Outer shell 2, 2. 1 , ... .3 2.9 tank 2.11, 2.31 .3 Floor 2.12 1 Ceiling 2.13 Shell wall 3, 3. 1 , ... 3.3 Insulation material 4 Roof 5 1 Attic 6 1 Director 7.1, 7.2, 7 Wall ring heating 8.1, 8.2, 8 Register heating 9.1, 9.2, 9 Breakthrough heating 10.1 , 10.2, 0.3, 10.4 transformer 1 1 Ring spur line 11.1, 11.2 Line section 11.3 Bypass line 1 1 . ¹ 1 , . . . , 1 .23 Tapping 12.1, . . . . , 2.10 Valve 13 Bitumen scale 14.1, 14.2 pump 15, 1 5.1, . ., 15.4 Filling line 16.1 , 16.2 Valve 17 Filling line 18 Intake line 19 Collection container 20 Heating 21 Three-way valve 22 Valve 23 pump 24.1 , 24.2 Level compensation line 25 Ventilation line

- 43 -

4 » ■

•Φ;

26 , 27.2 27.1 28 29 , 30.2 30.1 31 32.1, , 32, , , 33.3 33.1 , , 34.4 34.1 35 , 36.2 36.1 , 37.2 37.1 , 38.2 38.1 39 , 40.2 40.1 41 42 43 44 , , 45.4 45.1 46

32.6

Condensate drain line Riser Changeover valve Filling station Hatch

Level compensation line Line

Stainless steel band support structure Wall breakthrough pipe

flange

drilling

Insulation ring Insulation sleeve Screw Nut

Tab

Power cable valve

pump

WR/hj/mn/jg-10093a-c/101B
24.08.1993

Claims (1)

- 32 - Protection claims Tank system for storing a medium to be stored at an elevated temperature, in particular bitumen, with at least one tank and an electric heater for heating and/or keeping warm the medium or bitumen in the tank, characterized in that the at least one tank (2; 2.1, 2.2) is surrounded by a self-supporting outer shell (1; 1.1) and a space volume between the outer shell (1; 1.1) and the tank (2; 2.1, 2.2) is completely filled with a granular insulation material (3; 3.1). 2. Tank system according to claim 1, characterized in that several, preferably cylindrical tanks (2.1, 2.2; 2.4, 2.5, 2.6) are provided, which are accommodated in a common, essentially cuboid-shaped outer shell (1.1; 1.2) in a radiation-minimizing arrangement. Tank system according to claim 1 or 2, characterized in that a thickness of the insulation is matched to a thermal conductivity of the insulation material (3; 3.1; 3.2) such that the radiation is on average less than 20 W/m'
carries. in particular not more than 15 W/m Tank system according to one of claims 1 to 3, characterized in that the outer shell (1; 1.1; 1.2) is formed by load-bearing insulation plates. - 33 - 5. Tank system according to one of claims 1 to 4, characterized in that the insulating material (3; 3.1; 3.2) is a hydrophobic powder. 6. Tank system according to one of claims 1 to 5, characterized in that the insulation material (3; 3.1; 3.2) is expanded or puffed perlite or vermiculite. 7. Tank system according to one of claims 1 to 6, characterized in that the at least one tank (2.1) is immersed in the insulation material (3.1) over its entire height and that the outer shell (1.1) is designed in such a way that above the insulation material (3.1) a weather-protected free space (5) is formed in order to keep the at least one tank (2.1) accessible. Tank system according to one of claims 1 to 7, characterized in that filling and emptying lines (27.1, 27.2 or 32.1, ..., 32.6) are guided as far as possible in the granular insulation material (3.1) within the outer shell (1.1) and that a part of the said lines guided outside the outer shell (1.1) is provided with accompanying insulation, such that the said lines are insulated with approximately the same effective insulation value over their entire length. 9. Tank system according to claim 8, characterized in that valves present within the outer shell (1.1) in the filling or emptying lines (32.1, ..., 32.6) - 34 - le (45.1, . .., 45.4) pumps (46) and the like are each arranged in granulate-free recesses accessible from the outside. 10. Tank system for storing a medium to be stored at an elevated temperature, in particular bitumen, with at least one tank (2.3, 2.4, 2.5) and with a pipe system (11.1, 11.2, 11.3) for removing the medium, in particular bitumen, characterized in that the pipe system (11.1, 11.2, 11.3) comprises metal pipes that can be directly heated electrically. 11. Tank system according to claim 10, characterized in that the metal pipes are made of stainless steel. 12. Tank system according to claims 1 0 or 1 1, characterized in that the line system (11.1, 11.2, 11.3) is supplied with power from a power source (10.4) in such a way that the heating power is less than 1 kW/m, in particular approximately 0.5 kW/m. 13. Tank system according to claim 12, characterized in that for connecting the line system (11.1, 11.2, 11.3) to a power source (10.4) and/or for bridging electrically controllable valves (12.3, ..., 12.10) and the like, flange connections (36.1, 37.1, 36.2, 37.2) that are electrically insulated on two sides (40.1, 40.2) are provided. - 35 14. Tank system according to one of claims 10 to 13, characterized in that a transformer (10.4) with several voltage taps is provided as the power source. 15. Tank system according to one of claims 10 to 14, characterized in that the line system (11.1, 11.2, 11.3) is designed as a ring-branch line with at least two pumps (14.1, 14.2). 16. Tank system for storing a medium to be stored at an elevated temperature, in particular bitumen, with at least one tank and with an electric heater for heating and/or keeping warm the medium in the tank, characterized in that in addition to a first heater as a booster for heating, a separately controllable second heater is provided for keeping warm, the power range of the second heater being at least five times smaller than that of the first, and that a control is provided to monitor and control not only the actual temperature of the medium but also that of the heating surfaces. 17. Tank system according to claim 16, characterized in that the control circuit is designed so that, in the sense of a cascade control, the actual temperature of the medium always remains as close as possible to a predetermined target temperature through preferably finely stepped dosing of the heating power and the actual temperature of the heating surface in any case does not exceed a predetermined maximum temperature. - 36 - 18. Tank system according to claims 16 or 17, characterized in that the first of the heaters is a wall ring heater and the second is a floor heater. 19. Tank system according to claim 18, characterized in that the wall ring heater is formed by a plurality of externally applied flat, ring-segment-shaped heating rods. 20. Tank system according to claim 19, characterized in that the heating rods have a mutual distance of 10-30 cm, in particular of approximately 20 cm, in order to be able to deliver a power of at most 2.4 kW/m. 21. Tank system according to one of claims 19 or 20, characterized in that the heating rods are combined in a circuit-wise manner to form separately operable heating areas in order to enable heating depending on the fill level. 22. Tank system according to one of claims 19 to 21, characterized in that anchoring elements, in particular pins, are provided on the outer wall of the tank, and that the heating rods are clamped onto the outer wall with springs engaging the pins. 23. Tank system according to one of claims 16 or 17, characterized in that the first heater is a register heater (8.1) arranged inside the tank made of solid stainless steel strips (33.1, 33.2, 33.3) which is connected by a - 37 - Low-voltage high-current source (10.1) can be supplied with current. 24. Tank system according to one of claims 16, 17 or 23, characterized in that a breakthrough heater (9.1) is provided, which is designed as a directly heated pipe arranged vertically in the tank (2.3) or as a heating rod attached vertically to the outer wall of the tank. 25. Tank system according to one of claims 23 or 24, characterized in that for measuring a surface temperature of the heater arranged in the tank, a pipe is provided which projects into the interior of the tank and is closed at the inner end and has the same surface and the same cross-section as the heater mentioned, that a temperature sensor is provided inside the pipe for measuring the surface temperature of the inside of the pipe and that the pipe is connected in series with the heater in order to be traversed by the heating current. 26. Tank system according to one of claims 16 to 25, characterized in that the heater is power-controlled via a pulse group circuit. 27. Tank system for storing a liquid medium, in particular bitumen, with at least one tank (2.3, 2.4, 2.5) and with a filling station with which the at least one tank (2.3, 2.4, 2.5) is filled with the liquid medium delivered on tank vehicles and to be stored - 38 - can be filled from above, characterized in that a collecting container (19), a riser pipe (15) that can be emptied into the collecting container (19) and opens into the top of the tank (2.3, 2.4, 2.5), a filling pipe (17) that can be connected to the tank vehicle and opens into the riser pipe (15), a pump (23) for conveying the medium and a suction pipe (18) for sucking in the medium in the collecting container (19) are provided, whereby an automatic filling station control ensures that a column of liquid in the riser pipe (15) after the tank (2.3; 2.4; 2.5) has been filled is emptied into the collecting container (19) and at the start of the next filling of the tank (2.3; 2.4; 2.5) the contents of the collecting container (19) are filled into the tank (2.3; 2.4; 2.5). 28. Tank system according to claim 27, characterized in that the filling and suction lines (17 and 18, respectively) are connected upstream of the pump (23) in a switchable manner via a three-way valve (21) and that the riser line (15), which can be emptied into the collecting container (19) via a valve (22), is connected downstream of the pump (23). 29. Tank system according to one of claims 27 or 28, characterized in that a gas displacement line (25) of the tank (2.5) opens into the collecting container (19), wherein the gas displacement line (25) is preferably designed as a finned tube in order to simultaneously serve as a condenser for vapors which are collected as condensate in the collecting container (19). - 39 - 30. Tank system according to claim 29, characterized in that several tanks (2.3, 2.4, 2.5) are provided, which are mutually connected at the top by level compensation lines (24.1, 24.2), the level compensation lines (24.1, 24.2) being arranged slightly below the openings of the tank ventilations (25). WR/RK/mg-10198a-c/101B
07.02.1994