GB2542590A

GB2542590A - Railway platform de-icing material and method

Info

Publication number: GB2542590A
Application number: GB1516900.6A
Authority: GB
Inventors: Donmall Rodney
Original assignee: Bch Solutions Ltd; Santander Salt Ltd
Current assignee: Bch Solutions Ltd; Santander Salt Ltd
Priority date: 2015-09-24
Filing date: 2015-09-24
Publication date: 2017-03-29
Also published as: GB201516900D0

Abstract

A railway platform de-icing material comprises a blend of natural marine salt and sucrose, the sucrose making up at least 7.5% by weight of the material. Preferably the amount of sucrose ranges from 7.5 to 30% wt and the natural marine salt contains at least 98% wt sodium chloride. The de-icing material may be provided as a dry mixture of table sugar and sea salt, i.e. without any water added. The salt preferably makes up the balance of the railway platform de-icing material, which therefore consists solely of sucrose and salt. Alternatively, sodium chloride may form more than 50% wt of the de-icing composition, which may further contain magnesium chloride and/or calcium chloride. A method of removing ice from railway platforms by distributing said de-icing material on their surface is also claimed. The de-icing material of the invention is of low electrical conductivity and has a reduced corrosive effect on metals and on concrete. Furthermore, when it is carried inside trains by the passengers shoes, it does not discolour or react with the floors of train carriages, e.g. when these are carpeted. Transport, storage and distribution of the material in the form of a dry mixture is considerably simplified.

Description

Railway Platform De-Icing Material and Method Field of the Invention 5 The invention relates to the field of de-icing of railway platforms. In particular, the invention concerns materials for distribution on a railway platform, to prevent and/or treat the build-up of ice and/or snow. Corresponding methods are also provided.

Background of the Invention

D

De-icing compounds or various materials may be employed before snow or ice has formed, or may be distributed once snow or ice has already accumulated. Compounds or materials employed before snow or ice has formed are often referred to as 'anti-icers'. Compounds distributed once snow or ice has already accumulated are more 5 generally referred to as de-icers.

In chemistry, it is known that adding many materials to water will lower the freezing point of the water. Thus various materials have been used as de-icers, in various locations. Those materials have themselves often been suspended in water, to allow d them to be sprayed easily onto various surfaces.

Railway platforms provide a particularly challenging environment in cold weather. Firstly, people may run on railway platforms. People either running or walking on a railway platform may be equipped with a very wide range of footwear. Some of the 5 footwear only provides low levels of friction between the sole and railway platform, even on a dry platform. People's balance may be impaired. For these reasons, it may be important to de-ice a railway platform more completely than, for example, a road carriageway along which only vehicles may pass. d Railway platforms are, however, subject to many restrictions concerning the substances that can be applied to them. In England and Wales, there are particular concerns that materials applied to railway platforms should not corrode either aluminium or steel. These metals are used very close to railway platforms, and their integrity must be maintained. In addition, electrical components may be located in close proximity to railway platforms. Common examples of electrical components are switch gear and 'live' electric rails. Given the proximity of electrical components to platforms, a constraint on materials that can be applied to railway platforms is that they should be non-conductive, 5 or of very low conductivity.

Known chloride containing de-icers have corrosive effects, to different degrees on both steel and aluminium. Their solutions are highly conductive, which may therefore affect electrical components on the track. Magnesium and calcium chloride can also damage d concrete. Acetate and formate based de-icers have considerably fewer corrosive effects than those containing chlorides and are less conductive. However, they have a considerably higher purchase price. UREA based products are being phased out in the UK due to environmental concerns. 5 A further issue faced when de-icing railway platforms is that the materials may be carried on people's shoes into train vehicles, or road vehicles in which people travel away from stations. Thus, as far as possible, materials for use on railway platforms should not either discolour or react with the floors of carriages or cars, for example carpets. A further desirable characteristic is that compounds for use on railway d platforms should not discolour the platforms. This may be a more significant issue for railway platforms than, for example, for the carriageways of roads. Some de-icing compounds have used the relatively cheap residue from molasses processing in the food industry. However, this approach has significant drawbacks for railway platforms, because the molasses residue leaves visible markings on surfaces during and after use. 5

Table 1 below compares the performance of some known railway platform de-icing compounds and other materials against the various criteria described above. Each column is a generalisation, which is provided to aid understanding. Such generalisation is appropriate, because there are a variety of specific products available in each d category.

Table 1: A comparison of general approaches to de-icing

In the United Kingdom, the high cost of acetate and formate based de-icers for use on railway platforms has in the past lead to some unauthorised use of rock-salt as a railway platform de-icer. However, rock-salt is both conductive and corrosive. The rules set out by 'Network Rail' forbid the use of rock-salt. The tension between Network Rail's rules and the high cost of many alternatives to rock salt has remained an unsolved problem, hitherto. EP-B1-0824575 (Kerti, et al.) was filed in 1996, and provides a solution to reduce the 'slipperiness' of surfaces for pedestrians and vehicles. The solution may be used in road, aviation or rail environments. The solution of EP-B1-0824575 has a water/urea/ ammonium nitrate mass ratio in the range of: water 4.5-5.5 : urea 3.6-4.4: ammonium nitrate 6.3-7.7

The urea component of the solution of EP-B1-0824575 would make it undesirable in a railway environment in the UK today. BE-B1-902 679 (Labofina S.A.) provides another liquid de-icing compound, and dates from 1985.

The solution of BE-B1-902 679 is designed to clear snow from surfaces that have been pre-treated, prior to a snow fall, but which have never-the-less experienced repeated snow falls. The solution comprises 80-90% by weight of: from 50-75% by weight of an aliphatic monohydroxyline alcohol, containing three to four atoms of carbon; and from 50%-25% by weight of alkyleneglycol having two or three atoms of carbon.

The requirements for thorough de-icing of railway platforms present a considerable challenge, when considering and respecting the restrictions on substances that can be applied. Thus there is a need for an improved railway platform de-icing compound or material and method.

In the remainder of this description, a 'de-icing1 material or method refers to a material or method used both before snow or ice has formed, and once snow or ice has already accumulated. Hence 'de-icing' material refers both to 'anti-icers1 and 'de-icers'.

Statement of Invention

In accordance with a first aspect of the present invention, there is provided a railway platform de-icing material. The railway platform de-icing material comprises a blend of sucrose, the sucrose making up at least 7.5% by weight of the railway platform de-icing material, and natural marine salt.

The railway platform de-icing material may comprise a dry mixture of sucrose and natural marine salt. The term 'materiaf is used to describe the railway platform de-icer, because it consists of a blend of dry sucrose and natural marine salt. Sucrose and marine salt do not react when blended together as solids, so the result of mixing them in dry form is better described as a 'material1 than a 'compound1.

The material is 'dry1 in the sense that it is dry to the touch. However, the specification for all salts for use on highways requires a moisture content of less than 4%. Thus, typically, all salts are available from suppliers with a moisture content of less than 4%. The natural marine salt used with the invention may typically have a water content of around 2.5% by weight. That 2.5% water content is bound up in the solid natural marine salt, which remains dry to touch even with the 2.5% water content.

The natural marine salt may comprise at least 98% by weight sodium chloride, excluding the 2.5% water content. The sucrose may make up between 7.5% and 30% by weight of the railway platform de-icing material. Natural marine salt may make up the balance.

When other ingredients than sucrose and natural marine salt are included, the natural marine salt may make up more than 50% by weight of the railway platform de-icing material. Additional ingredients may be one or both of magnesium chloride or calcium chloride, for example.

In accordance with a second aspect of the present invention, there is provided a method of railway platform de-icing. The method of railway platform de-icing comprises providing a railway platform de-icing material, the railway platform de-icing material comprising a blend of natural marine salt and at least 7.5% by weight of sucrose, and distributing the railway platform de-icing material over a least a portion of a railway platform.

The method of railway platform de-icing may further comprise preparing, storing and distributing the railway platform de-icing material in the form of a dry mixture. The natural marine salt may comprise at least 98% by weight sodium chloride. The sucrose may make up between 7.5% and 30% by weight of the material. Natural marine salt may make up the balance of the material.

An advantage provided by the present invention may be that it provides effective deicing, with low corrosive effects and low conductivity. In addition, discolouration of surfaces may be very low. It enables a chloride based material to be used as a de-icer on railway platforms.

In particular, the conductivity may be lower than with known chloride containing deicers. There may be reduced corrosive effects on concrete, steel and aluminium when compared with known chloride containing de-icers. There may be a reduced impact on the environment when compared to UREA and other chloride based products. The present invention may be easier to store and/or cheaper than acetate and formate based de-icers.

Detailed description A railway platform de-icing material is provided. The railway platform de-icing material may comprise a blend of sucrose, with the sucrose making up at least 7.5% by weight of the railway platform de-icing material, and natural marine salt.

The natural marine salt used in the railway platform de-icing material of the invention may be produced in a variety of ways. Some natural marine salt is produced by drying seawater, for example, in the sun. However, some natural marine salt is produced by drawing salt water from underground brine aquifers, and then drying it, which again may be in the sun. Natural marine salt from both sources may be used in the railway platform de-icing material. Some natural marine salt is referred to as 'solar salt', because it is dried in the sun. Thus the term 'natural marine salt' covers each of these sources.

The performance of the railway platform de-icing material of the invention has been tested against various regulatory requirements. In addition, the railway platform de-icing material has been tested against various less tangible requirements, including the need to minimise discolouration to surfaces when the railway platform de-icing material is used. Table 2 below shows the performance of one specific railway platform de-icing material in accordance with the invention. The railway platform de-icing material whose performance is detailed in Table 2 comprised 10% by weight sucrose, with the remainder being 90% natural marine salt.

Table 2: Performance of the material of the invention in corrosion tests ‘Here a 'mil' is 1/1000th of an inch, i.e. 1 mm = 0.0254 mils, with 'mils' being a standard unit of measurement used in corrosion testing

As a comparison, the applicant has also tested a solution that does not fall within the terms of the invention, but which had 5% by weight sucrose, with the remainder being natural marine salt. The 'Total Immersion Corrosion' figure for Mild Steel with the 5% by weight sucrose solution was 0.67. This 0.67 figure is nearly twice the 'Total Immersion

Corrosion' figure of 0.36 for Mild Steel for the 10% by weight sucrose railway platform de-icing material of the invention, see again Table 2.

The conductivity performance of the railway platform de-icing material has also been tested. Table 3 below shows the performance of the invention, in comparison to known solutions. The railway platform de-icing material whose performance is detailed in Table 3 again comprised 10% by weight sucrose, with the remainder being natural marine salt.

Table 3: Performance of material of the invention in comparative conductivity test

So the conductivity of the railway platform de-icing material of the invention is less than half that of the rocksalt solution in Table 3.

The railway platform de-icing material of the invention may be provided as a dry mixture of the sucrose and natural marine salt. The natural marine salt used with the invention may typically have a water content of around 2.5%. That 2.5% water content is bound up in the solid natural marine salt, which remains dry to touch even with the 2.5% water content. Thus the railway platform de-icing material of the invention is typically a dry blend of crystals or solid pieces of sucrose and natural marine salt.

The dry mixture may offer several advantages. The mixture may be distributed by salt spreader, hand shovel or scoop. For ease of handling the product will generally be delivered in weatherproof 15kg bags on a pallet. When larger quantities are required, the mixture can also be delivered in bulk bags. In contrast, known liquid de-icing compounds must be transported and stored in liquid-tight containers. Where the mixture is to be used on a variety of small station platforms, the mixture can be: (i) Delivered by a vehicle that does not need to be liquid-tight; (ii) Stored in a variety of containers, such as the salt/grit bins that are sometimes provided near icy bends and hills on road networks; (iii) Distributed quickly onto a platform, without needing a functioning pump to be kept at each station. In fact, little training is needed to distribute the material; and (iv) There is a lower chance of the railway platform de-icing material itself making a surface slippery, as might for example occur with liquid de-icers that are sprayed onto areas of a platform that have no snow or ice on them.

Various forms of natural marine salt are available. However, the railway platform deicing material of the present invention may show particularly desirable effects when the natural marine salt comprises at least 98% by weight Sodium Chloride.

The railway platform de-icing material shows advantageous effects when sucrose makes up more than 7.5% by weight of the railway platform de-icing material. Those effects can be seen from Tables 2 and 3 above, with a material having 10% by weight of the railway platform de-icing material. However, the advantageous effects continue with higher percentages than 10%. The advantageous effects continue up to and beyond a mixture in which sucrose makes up 30% by weight of the railway platform de-icing material. However, the invention is preferably used in the form of railway platform de-icing materials in which the sucrose makes up between 7.5% and 30% by weight of the railway platform de-icing material.

The cost of sucrose is greater than the cost of natural marine salt. Thus an additional consideration is that it may be more cost effective to use materials of the invention with closer to 7.5% by weight of sucrose than 30% sucrose.

Besides the sucrose, natural marine salt may make up the balance of the railway platform de-icing material. So the railway platform de-icing materials of the invention may comprise, for example, 10% sucrose and 90% natural marine salt.

However, the railway platform de-icing materials of the invention may have additional ingredients, beyond those listed above. In that case, the railway platform de-icing materials of the invention may advantageously comprise natural marine salt making up more than 50% by weight of the railway platform de-icing material. This formulation retains desirable properties, both in use and for storage. With natural marine salt making up more than 50% by weight of the railway platform de-icing material, the balance may then be sucrose of greater than 7.5% by weight and, for example, other salts such as Magnesium Chloride and/or Calcium Chloride.

Although the discussion above relates to the railway platform de-icing materials of the invention, a method of railway platform de-icing is also provided. The method of railway platform de-icing comprises providing a railway platform de-icing material, the railway platform de-icing material comprising natural marine salt and a blend of at least 7.5% by weight of sucrose, and distributing the railway platform de-icing material over at least a portion of a railway platform.

The method of railway platform de-icing may further comprise preparing, storing and distributing the railway platform de-icing material in the form of a dry mixture. The natural marine salt comprises at least 98% by weight sodium chloride. The sucrose may make up between 7.5% and 30% by weight of the railway platform de-icing material. Natural marine salt may make up the balance of the railway platform de-icing material.

However, the natural marine salt may make up more than 50% by weight of the railway platform de-icing material, with the balance being sucrose of greater than 7.5% by weight and, for example, other salts such as Magnesium Chloride and/or Calcium Chloride.

Thus, an improved railway platform de-icing material and method have been described, where the aforementioned disadvantages with prior art arrangements have been substantially alleviated. Whilst the specific and preferred implementations of the embodiments of the present invention are described above, it is clear that one skilled in the art could readily apply variations and modifications that would still employ the aforementioned inventive concepts.

Claims

1. A railway platform de-icing material, comprising a blend of: sucrose, the sucrose making up at least 7.5% by weight of the material; and natural marine salt.

2. The railway platform de-icing material of claim 1, wherein: the sucrose and natural marine salt are a dry mixture.

3. The railway platform de-icing material of claim 1 or claim 2, wherein: the natural marine salt comprises at least 98% by weight of sodium chloride.

4. The railway platform de-icing material of any of claims 1-3, wherein: the sucrose makes up between 7.5% and 30% by weight of the material.

5. The railway platform de-icing material of any previous claim, wherein: natural marine salt makes up the balance of the material.

6. The railway platform de-icing material of any of claims 1-4, wherein: the natural marine salt makes up more than 50% by weight of the material.

7. The railway platform de-icing material of claim 6, wherein: the material also comprises Magnesium Chloride.

8. The railway platform de-icing material of claim 6 or claim 7, wherein: the material also comprises Calcium Chloride.

9. A method of railway platform de-icing, comprising: providing a railway platform de-icing material, the railway platform de-icing material comprising a blend of natural marine salt and at least 7.5% by weight of sucrose; distributing the railway platform de-icing material over a least a portion of a railway platform.

10. The method of railway platform de-icing of claim 9, further comprising: preparing, storing and distributing the railway platform de-icing material in the form of a dry mixture.

11. The method of railway platform de-icing of claim 9 or claim 10, wherein: the natural marine salt comprises at least 98% by weight sodium chloride.

12. The method of railway platform de-icing of any of claims 9-11, wherein: the sucrose makes up between 7.5% and 30% by weight of the material.

13. The method of railway platform de-icing of any of claims 9-12, wherein: natural marine salt makes up the balance of the material.

14. The method of railway platform de-icing of any of claims 9-12, wherein: the natural marine salt makes up more than 50% by weight of the material.

15. The method of railway platform de-icing of claim 14, wherein: the material also comprises Magnesium Chloride.

16. The method of railway platform de-icing of claim 14 or claim 15, wherein: the material also comprises Calcium Chloride.