GB2534666A - Insulated tank with internal heating system - Google Patents

Abstract

A system for heating liquid in a tank optimises the heat to the discharge valve area and creates a vacuum filled cavity of cellular construction between a strong outer skin or the and thin inner skin or liner creating a robust outer tank for industry. This provides a pressure containment for hazardous liquids. The contents for the tank may be bitumen, tar or asphalt.

Description

Intellectual Property Office Application No. GII1520954.7 RTM Date:25 bMay2016 The following terms are registered trade marks and should be read as such wherever they occur in this document: Bitutainer (page 2) Rockwool (page 2) Intellectual Property Office is an operating name of the Patent Office www.gov.uk /ipo n Internal Heainq System The press nt invention relates to a tank used for the containment, storage, transporting, heating and discharge of contents such as petrochemical products but predominantly bitumen (known also as asphalt or tar, and similar materials that are either liquid, or become liquid when heated). The present invention also relates to improving heat retention of heated products, to increasing the efficiency to reducing the pre-discharge heat up time and to reduce the weight of the tank; all with a view to cost savings to the user.

To date transport tanks have been one of the more r al means of moving materials such as bitumen. A large proportion of these tanks have a tank body, or foam insulation around the tank body, a roof filling aperture, over-pressure protection, a low positioned discharge valve i.e. located towards the bottom of the tank, and internal pipes at floor level of the tank for heating, These tan designed for intermodal use by road, rail and sea. These tanks are designed to have heating pipes of calculated area so as not to burn (coke) the bitumen or product inside when heating. The ability to heat as quickly as possible, discharge early and maintain heat during delivery to the user provides the features that make such tanks sustainable and saleable in the market place.

The tanks are normally filled at a refinery's hot loading armacilities, Most of the in-tank heating takes place after the tank is delivered by which time the product (for example, bitumen) inside could be at ambient temperature.

As a resu contents cooling during transportation, for example, discharge pipes and valves can block (plug) causing delays in production and damage when attempting to reheat the areas locally. Also, this can damage other pumping equipment whilst being potentially dangerous.

re common knowledge to practitioners within the bitumen industry that ideally s should be delivered hot at a minimum of 120 to 180 degrees C, ready to discharge. The heating system should optimise heat up-times onsite, The heating can be from heavy fuel flame burners, oil, gas flame or steam, for example.

it is also well known to optirnise the heating of the discharge valve locally and heat in such a way that the heat-up can allow discharge from the upper part of the tank before the entire mass is completely heated.

It is also known to the industry that placing heater tubes low in the tank will melt the contents as the heat from these heating tubes rises. To have the heating pipes as low as possible and in the tanks inner space is to-date the fastest known means of heating such products using known heating pipe technology.

A transportable tank of ISO or a transportable dimension is known e.g. a tank known as the "Bitutainermi. This design uses a combination of heater pipe area, input heat and insulation to effect short heat-up times.

IA; It is known that high temperature resistant insulation materials such as fibrous wools, e.g. RockwooRD or even silicon materials are not as effective as a vacuum filled space. For example, hot drinks are kept hot in vacuum flasks. However these are normally single cell and vulnerable to damage.

Existing tanks traditionally have a single discharge valve at a low level, which is usually at the lowest point in the tank. This is, however, also the coldest area making early discharge of the content impossible until the entire mass is sufficiently hot to pump out of this low valve. Some designs have used a valve at high level to discharge from hot melted pools that form around the internal rising heating pipe exhausts.

Existing tanks for the carriage of bitumen are known in both cylindrical and rectangular form. The heat-up characteristics differ but the heater pipe methods are the same in most applications.

Existing tank systems are relatively expensive to heat up as fossil fuel prices increase. Also, conventional tanks are relatively heavy and have high heat losses by the nature of their construction and the material of insulation used. These losses impact the product's usefulness when compared with these existing tanks' competitors such as road ship bulk deliveries and -relatively new to the industry -bulk-bagged bitumen. For this reason better efficiency is sought.

The present invention aims to capitalise on operational experience and well known vacuum technology, by providing a vacuum filled space system which can hold temperature longer and a system that can re-use exhaust neat by heat recovery in a method that can reheat a tank to enable the discharge time to be reduced, The present invention also aims at reducing tear weight of the tank so the payload can be optimised, According to,a first aspect. the present invention provides a system as defined in claim 1, preferably with heating pipes that increase the heat around the discharge valve by joining the return flow of both:eft and right healer pipes; by using the full diameter and annulus diameter of heating pipes to exhaust the heating system; doubling the heat transfer to the bitumen in that specific area.

According to a second aspect, the invention provides a method of tank:eating that uses a low and centrally located single, double-wailed pipe to increase the heat in that area by forcing hot air through the centre and annulus of this central located pipe system to maximise heat transfer, while keeping both heat flow streams separate so that flow rates of one do not affect the other.

Additionaliy, in preferred embodiments, the tank is tided as a vacuum vessel but uses a series of pre-vacuum filled cells encased in a strong inner skin or rigid liner to insulate the hot bitumen away from the frame and the outer shell to provide redundancy to the insulation system.

Additionally, in prijerred embodiments, the bitumen that tends pool a u exhaust stack can be drawn down sooner through the valve area that is from the pipe-works system's central double wall pipe.

The preferred embodiment is designed to:ensure h ne.o, with two barriers of spill oontainment.

The present invention is preferahiy configured to he constructed from materials that will withstand between 200 and 1300 degrees Celsius and can he installed in any tank or vessel, round or square or, indeed, any other shape. It can be used in shipping containers as known to the cargo wand and interne:jai operations.

The insulated bitumen tank with internal heating system is:preferably configured as described herein.

Various embodiments of the present invention will now be described, by way of example only, and with reference to the drawings, in which: Figure 1 shows an insulated tank with internal heating system in plan (birds-eye) view, and elevation and in side elevation views with a partial section through the discharge valve.

Figure 2 shows an insulated tank with internal heating system as a partial end elevation and partial side elevation.

Figure 3 shows an end elevation.

Figure 4 shows a simplistic comparison between the inventive system (Fig. 4A) and a conventional tank (Fig. 4B).

A preferred embodiment of the invention, in broad outline, will now be described with reference to Figure 1. This invention preferaoly uses tank like containers assembled from a structural material and heating pipes e.g. of steel and is self-supporting or in a fabricated frame or ISO frame, The frame may have shipping connections to its corners or lifting eyes (1). The frame often carries a vessel of either round or rectangular form (2). Into the tank run heating pipes (3) and (4) to which a heating source is connected. A discharge valve into the tank interior is normally of pipe diameter the same or iarger than the discharging valve diameter itse.if (5). The heater pipes are connected so that one side exhausts through the annulus of the centrally located exhaust pipe (6) and the other side of the heating pipe exhausts through the centre pipe (7). The central double skinned pipe (8) for the inner skin and (9) for the outer skin runs low towards the valve to increase the discharge valve heating. The pipes are flanged suitably (10) with pipes of different diameters mating Le. (11) and (12). Pipe radii are kept minimal (13). While the exhaust riser (14) helps to increase the heat again around the discharge valve, smaller pipe (15) brings a direct heat flow into connection with the discharge valve stub (16). This maximises heat to this area according to the design. Heat is measured by the operator via temperature gauge or sensing probe (17) lodged in the tank's conJent: revealing the temperature near the discharge velVe, so the operator can gauge when to start pumping the tank empty, La when the temperature of the content indicates it is sufficiently fluid to be discharged via the valve. Heat retention is improved in the design by installing a liquid containing, inner skin (18) inside the main, but substantiaily thicker, outer (19) tank. The inner skin is usually installed after the outer tank has been assembled. The object of the inner skin and the outer tank is to create a cavity that can be filled with an ambient insulation and/or vacuum.

In a preferred embodiment, insulating material is provided in he cavity. This may be in the form of pads or filling or panels in one preferred form, panels of perlite are provided to provide the insulative effect and these "puli' a vacuum into the cavity. This has been found to improve insulation by a factor of ten compared to conventional tanks and there is also no heat sink effect through the frame.

To assist the fit out of the inner skin or liner the pipes may be flanged. A third cowl may be used around the riser for safety purposes (21). The riser heats bitumen closest to it so bitumen can be drawn down this riser (22) with an external force such as a pump connected to the discharge valve. An internal auger shaped screw (23) is inserted in the heating pipes for improved heating performance via the heat transfer.

A preferred embodiment of the invention will now be described with reference to Figure 2. Figure 2 shows tanks (such as shown in Fig. 1) with partial views to show heating pipe plugs (29) that when swung into the respective heating pipe (24) and (26) will reduce heat loss from the pipes during transportation. On an arm (28) with hinges (27) these plugs can be locked at position (25) and (26) with e.g a padlock lug as shown (30). During heating the ends are cleared by retaining the plugs once swung upwards and retained by a holding mechanism or pin (31). For transport the plugs are then swung down (32) to stop neat loss from the larger area (33). The plug system on the exhaust outlet is similar (34) (35) and (36).

The novel heat recovery or hot top heat optimisation system as Fig. 3 allows the exhaust heat (41) frorn riser pipe (40) to pass under a shield (38) running close to the tank's outer wall (39) to reuse the exhaust heat (42). The arrangement ailows the exhaust to still be plugged (43) for shipping.

As can be seen from the comparison of Fig. 4A and 4E3, in conventional tanks, heat is lost through the frame of the tank, which is not insulated. The arrangement of the invention eliminates heat transfer to the frame of the tank.

With the insulated arrangement of the invention, the tank contents require less time and else' less fuellenergy to reach the required workingldispe,nsing temperature.

Tanks with external insulation have been found to 'sweat" causing corrosion of he tank. Also, the tank body needs to be fairly thin and is, therefore, not particularly robust. In contrast, the tank walls of the invention can be thick and hence more robust and durable, and the tank will not sweat and corrode.

The tank of the invention, with its Inner" insulation, is also easier and less expensive to construct and maintain than conventionai tanks.