WO2016083824A1

WO2016083824A1 - Insulated tank with internal heating system

Info

Publication number: WO2016083824A1
Application number: PCT/GB2015/053620
Authority: WO
Inventors: Rex Edward MICHAU
Original assignee: Tetainer Uk Ltd
Priority date: 2014-11-27
Filing date: 2015-11-27
Publication date: 2016-06-02
Also published as: GB2534666A; WO2016083824A8; GB201520954D0; GB201421115D0

Abstract

A system for heating liquid is a tank while optimising the heat to the discharge valve (5) area and creating a vacuum filled cavity of cellular construction between a strong outer skin or shell (19) and thin inner skin or liner (18) creating a robust outer tank for industry, providing a pressure containment for hazardous liquids.

Description

Insulated Tank with internal Heatino System

The present 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 traditional means of moving materials such as bitumen. A large proportion of these tanks have a tank body, wool 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 healing. These tanks are 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 arm facilities. Most of the in- tank heating takes place after the lank is delivered by which time the product (for example, bitumen) inside could be at ambient temperature.

As a result of 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.

It is therefore common knowledge to practitioners within the bitumen industry that ideally tanks 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 optimise 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 tank's 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 "Bitutainer"^TM This design uses a combination of heater pipe area, input heat and insulation to effect short heat-up times. It is known that high temperature resistant insulation materials such as fibrous wools, e.g. Rockwool© 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 impossibie 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 tankers, ship bulk deliveries and - reiativeiy new to the industry - buik-bagged bitumen. For this reason better efficiency is sought.

The present invention aims to capitaiise 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 heat 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 left and right heater pipes; by using the fuli 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 heating that uses a low and centrally located single, double-walled 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.

Additionally, in preferred embodiments, the tank is constructed 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 tank main frame and the outer shell to provide redundancy to the insulation system.

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

The preferred embodiment is designed to ensure that all the contents are contained with two barriers of spill containment. The present invention is preferably configured to be constructed from materials that will withstand between 200 and 1300 degrees Celsius and can be 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 world and intermodal 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 interna! 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 preferably 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 larger than the discharging valve diameter itself (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 i.e. (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 content, revealing the temperature near the discharge valve so the operator can gauge when to start pumping the tank empty, i.e. 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 substantially 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 the 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 "pull" 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 heat 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 ) from 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 allows the exhaust to still be plugged (43) for shipping.

As can be seen from the comparison of Fig. 4A and 4B, 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 lime and also less fuel/energy to reach the required working/dispensing temperature.

Tanks with external insulation have been found to "sweat" causing corrosion of the 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 lank of the invention, with its "inner" insulation, is also easier and less expensive to construct and maintain than conventional tanks.

Claims

CLAIMS:

1. A system for heating a tank comprising:

an outer tank;

an inner skin mounted within the outer tank defining an insulation cavity between the inner skin and the outer tank, the inner skin configured to contain the contents of the tank;

a discharge valve extending through the inner skin and the outer tank to discharge content of the tank; and

a plurality of heating pipes configured to focus heat on and around the discharge valve as well as to heat the content of the tank.

2. The system of claim 1 , comprising a plurality of pro-vacuumed mats with a high insulator inside to line the cavity.

3. The system of claim 1 or 2, further comprising an auger shaped coil in the heating pipes.

4. The system of any of claims 1 to 3, wherein the heating pipes include a central double wall tube running horizontally or near horizontal through the tank to increase the heat transfer at or around the discharge valve.

5. The system of claim 2, wherein said mats comprise Perlite.