GB2448531A

GB2448531A - Fuel briquette

Info

Publication number: GB2448531A
Application number: GB0707579A
Authority: GB
Inventors: Neil Willis; Trevor Leslie Roberts; Andrew Bishop
Original assignee: COAL PRODUCTS Ltd
Current assignee: COAL PRODUCTS Ltd
Priority date: 2007-04-19
Filing date: 2007-04-19
Publication date: 2008-10-22
Anticipated expiration: 2027-04-19
Also published as: GB0707579D0; GB2448531B

Abstract

A process for the production of a fuel briquette comprising the steps of: ```providing wood and grinding/shredding to piece sizes screened to about 100 mm; ```torrefying the wood in an oven in an oxygen-controlled atmosphere at a temperature of about 300{C for sufficient time to reduce the volatile matter content of the wood to about 40% by weight; ```crushing the torrefled wood to a particle size screened to less than 10 mm; providing coal and optionally petroleum coke crushed to piece sizes screened to less than 5 mm and dried to moisture content less than 10% by weight ```mixing the components together in the following proportions to form a briquette feedstock: <EMI ID=1.1 HE=38 WI=115 LX=433 LY=1145 TI=UI> <PC>briquetting the feedstock and curing in a reduced oxygen environment at about 300 {C.

Description

Fuel briquette This invention relates to briquettes of fuel for use in

domestic and other open fires, and to a process for their manufacture. The invention also has potential application in boiler fuel.

BACKGROUND

Briquettes are manufactured lumps of fuel used in domestic and other fires and furnaces. Generally they contain coal or coke that has been granulated or powdered, mixed with a binder and then compressed and heated to consolidate the product. Many processes and variations exist and briquettes are characterised by a number of different parameters ranging from: * Heat output * Burn time * Appearance * Ease of ignition * Smoke The last of these is very important in the UK and other countries where regulations may control what product can be burned in fires in certain locations (smoke control areas, usually in urban areas) with regard to smoke generation, where generally only smokeless fuels can be burned. From a customer's point of view, however, while many of the other parameters are not irrelevant, perhaps the most important is the appearance of the fire, or the "flame picture", as it is also described. This simply refers to the flame generated and the aesthetic appearance of the fire as a result. Flame is caused by volatile hydrocarbons and other gases being driven from the solid fuel by the heat of the S...

fuel and burning in the air adjacent to the fuel. This gives the warm and aesthetically pleasing appearance of open fires, particularly when the fuel includes materials that have a high volatile content, such as wood.

* -It is known to include wood in briquettes, but the corollary problem with wood is that it S..

has a short bum time and low heat output. Also, wood does not comply with current UK smoke control legislation. However, it does have another benefit, which is that of environmental-friendliness Since wood comes from a renewable resource, it does not add to the net carbon content of the atmosphere compared with burning coal -it has a low "carbon foot-print". Other benefits include potentially low ash content.

RU-C-2098461 suggests the production of baquetted fuel, comprising mixing milled coal, milled waste from wood processing industry, hydrocarbon containing binder and water, forming briquettes from mixture under pressure up to 20 MPa, drying of the briquettes, and their subsequent thermal treatment. To improve results, thermal treatment is conducted at 350-500 C, until briquettes porosity reaches 30-60%. The fuel briquettes, especially of smokeless type, are for industrial and domestic use. The briquettes are easily ignited, generate no smoke on burning and have autonomic burning capability.

Milling wood is, however, problematic, because of its elastic and compressible nature.

Likewise WO-A-8501741 and WO-A-8606091 suggest a similar idea using sawdust.

Sawdust avoids the problem of crushing wood which, due to its open structure and usually high moisture content is not easily crushed to manageable particle sizes suitable for a bnquetting process. WO-A-9955806 makes a similar suggestion. However, sawdust in sufficient quantities is not always available. Accordingly it is an object of the present invention to provide a process for the production of fuel briquettes including wood, and to provide a briquette including wood.

Whilst "wood" is the term employed throughout this specification, it is to be understood, unless the context otherwise requires, that it includes within its meaning vegetable biomass generally, and is not to be deemed limited to the traditionally understood meaning of the term "wood" For example, within the ambit of the present invention, the following, non-exhaustive list of vegetable biomass, is also to be considered "wood" within the meaning of the present invention: Sugar cane waste * Tree bark * * Forestry strippings * Straw * Wheat grain * Bran * Nut kernels * Waste wood *S*.

* 25 The suitability of these and other biomass products in the present invention depends on factors that are clarified below and will be apparent to the person skilled in the art. They will understand whether particular biomass is suitable for the present invention.

Unsuitabie vegetable biomass is, of course, excluded from the ambit of the term "wood".

It is an object of the present invention to provide a process for the production of fuel briquettes incorporating wood, which process is convenient and effective. It is also an object of the present invention to provide a briquette comprising wood that has good heat output but also a desirable flame picture, as well as acceptable smoke emission.

BRIEF SUMMARY OF THE DISCLOSURE

In accordance with the present invention, there is provided a process for the production of a fuel briquette comprising the steps of: providing wood and grinding/shredding to a piece sizes screened to less than 200 mm; torrefying the wood; crushing the torrefied wood to a particle size screened to less than 10 mm; providing coal and optionally petroleum coke crushed to piece sizes screened to less than 5 mm and dried to moisture content less than 10% by weight; mixing the components together in the following proportions to form a briquette feedstock: Component % by weight, dry torrefied wood 5-40 coal 0-85 petroleum coke 0-60 binder 5-30 briquetting the feedstock and curing the binder.

Preferably, said feedstock comprises Component % by weight, dry torrefied wood 5-15 coal balance petroleum coke 15-25 binder 10-20

S 0*S.

Torrefactiori is conducted in an atmosphere of controlled oxygen content, to ensure that exothermic reactions do not develop into full-scale oxidation of the fuel. S..

* 20 The invention provides a bnquetted fuel made accordng to the preceding method. In addition, and in a second aspect of the present invention, there is provided a briquetted * fuel comprising the following components, optional amounts also being shown: Component % by weight, dry Optionally torrefied wood 5-40 5-15 coal -0-85 balance [etroleum coke 060 15-25 [der J 5-30 10-20 wherein the torrefied wood comprises between 30% and 75% volatile material.

For a smokeless fuel, preferably, said coal comprises from 20-80% anthracite.

1-fowever, if smoke generation is not important, or if certain appliances are being employed that reduce smoke generation (such appliances may be exempted from requirement to burn smokeless fuel by virtue of their performance), then said coal may comprise bituminous coal. Even a smokeless version may include up to 30% bituminous coal.

As mentioned above, the wood may comprise any form of biomass, but preferably is tree wood and ideally is waste wood from such sources as furniture manufacturers, old pallets, and building debris etc and the like. However, wood having the least moisture, minera' matter, tramp metal, plastics, and chemicals contamination is preferred.

Where the invention requires screened components, this is, in fact, merely a size limitation, the large majority of the components in question being capable of passing through a mesh of rectangular apertures of maximum size x by x mm, where x is the dimension given.

Preferably, said torrefaction is effected at a temperature between 250 C and 350 C.

Preferably, said torrefaction reduces the volatile matter content of the wood to between 30% and 75% by weight. Preferably, said torrefying step occurs at a temperature between 275 C and 325 C, and optionally between 290 C and 310 C. The volatile matter content of the torrefied wood may be between 40% and 50% by weight. *..

*... 25 "Volatile matter" is determined in accordance with British Standard BS 1016 Part 104.3 (ISO 562). The test involves heating fine coal/biomass (crushed to BSS-72 mesh) to :. 900 C for 7 minutes in an oxygen starved environment.

The emission of smoke during the domestic combustion of carbonaceous materials is : broadly directly related to the material's volatile matter content. For this reason, in a standard smokeless fuel briquette the proportion of high volatile bituminous coal is usually controlled at a maximum of 20% addition, to allow the final product to comply with UK Smoke Control legislation. Surprisingly, it is possible to include at least 10% torrefied wood, in addition to the standard amount of high volatile bituminous coal in the feedstock mix, whilst still yielding a smokeless product, and this is despite the higher volatile matter content of torrefied wood. This demonstrates that the torrefaction process successfully removes many of the smoke producing volatile components, whilst leaving sufficient residual volatile matter content to give enhanced performance on a domestic fire. Also, it is considered that the bum characteristics of bnquettes according to the invention result in burning of more of the smoke that the wood content would otherwise produce. The rapidly established flame picture during combustion of the briquettes reduces smoke emission by efficiently combusting released volatile components.

The torrefacUon process may be conducted in a batch torrefaction unit.

Preferably, an inert atmosphere is maintained during torrefaction, for example, within the torrefaction unit when one is employed. This may be achieved by controlling the escape of water vapour, volatile matter and gases from the biomass bed as it is heated. These evolved gases progressively displace air (particularly oxygen) from the unit as the bed is heated, thereby maintaining an inert atmosphere and minimising combustion of the torrefied product. In addition, it is feasible for an inert atmosphere to be maintained by the injection of an inert gas (eg nitrogen) or steam into the torrefaction unit.

Equally, it would be possible to introduce controlled amounts of air (oxygen) into the unit, thereby generating some of the heating requirement by controlled partial combustion of the biomass bed. However, in this event, such introduction of air/oxygen is purely for the purpose of employing the wood as a fuel, and does not form part of the torrefying process, per Se, and thereby contradict the general requirement that torrefaction is effected without the presence of oxygen. In other words, the requirement of "an oxygen-*.* controlled atmosphere" does not mean that none is permitted, or even added; simply ***. . . . . . that there is insufficient to support exothermic reaction of the majority of the wood so *:. that the uncombusted wood is heated effectively in an inert atmosphere.

At the end of the thermal treatment process the torrefied product may be quenched in water, dry cooled using inert gas or fed directly to the briquetting plant.

One of the advantages of the present invention is the possibility of crushing torrefied wood to the sizes needed for bnquetting without having to source the wood from sawdust, or to use special equipment in order to comminute the wood to a sufficiently small size for briquetting. Instead, once torrefled, the wood can be crushed in the standard crushing machinery used for coat and coke, and with little wasted energy.

Also, by torrefying the wood, its compressibility and elasticity are reduced substantially.

This has the effect of assisting the binding of the components and preventing cracking and breaking of the briquettes once the pressure forming them has been released.

Preferably, said coat and/or petroleum coke is crushed to piece sizes screened to less than 3 mm. Preferably it is dried to a moisture content less than 3% by weight.

Preferably, there is between 40% and 70% anthracite in the briquette feedstock, in the case of smokeless fuel briquettes. In this event, there may be between 10 and 20% bituminous coal in the briquette feedstock.

Alternatively, for non smokeless fuel there is up to 80% bituminous coal, and possibly no anthracite at all.

Preferably, there is between 20 and 50% petroleum coke in the briquette feedstock.

Preferably, said binder is a molasses/phosphoric acid binder. Optionally, it is present in the briquette feedstock in the amount of between 10% and 25% by dry weight. Said curing step, depending on the binder, may be effected in a reduced oxygen environment at between 250 C and 350 C. Said binder may be starch-or resin-based, whereby the need for thermal curing can be avoided, or reduced, if desired.

A comparison of some of the main properties of torrefied wood and the typical properties S..

of the other solid feedstocks used in the manufacture of domestic smokeless fuel

S

briquettes is presented in Table 1.

Table I S..

* Comparison of feedstock properties (% dry basis) Property Torrefied Anthracite High Volatile Petroleum * ______________ Wood __________ Coal Coke Ash Content 0.2 to 10.0 3.0 to 10.0 2.0 to 8.0 0.4 to 1.0 : Volatile Matter 30.0 to 75.0 3.0 to 9.0 30.0 to 39.0 10.0 to 13.0 * Content Sulphur Content <0.3 0.3 to 1.5 0.5 to 2.0 1.5 to5i Chlorine Content <0.05 0.01 to 0.05 0.01 to 0.50 0.01 to 0.10 Carbon Content 50 to 60 83 to 90 78 to 84 >95? Calorjflc Value -20,000 to 33,000 to 31,000 to 34,000 to (J/kg) 23,000 35,000 33,000 -36,000 The main points to note from the above comparisons are:- * When manufactured in a strictly controlled inert environment, torrefied wood can have a very low ash content. The inclusion of this low ash additive in a domestic coal briquette therefore serves to reduce residual waste.

* The sulphur, chlorine and carbon contents of torrefied wood are typically lower than those of the other briquette feedstocks. This results in reduced environmental emissions during combustion; specificaliy of sulphur dioxide, carbon dioxide, polycyclic aromatic hydrocarbons (PAH) and chlorinated micro pollutants (eg dioxins). Moreover, because the wood feedstock originates from carbon neutral, renewable sources, the bnquetting feedstock mix is viewed as more climate friendly, in terms of the carbon balance for the briquetting process.

* Although torrefied wood can have a wide range of volatile matter contents (ie 30% to 75%) depending on the degree of thermal treatment, the product manufactured in accordance with the present invention preferably is limited to a volatile matter content of the torrefied wood component to between 30% and 60%. This is significantly lower than wood that has not been thermally treated (which typically has a volatiles content of 80% to 85%) but is much higher than wood charcoal (which typically has a volatiles content of less than 30%). Charcoal is manufactured at higher temperatures (typically 600 C).

A consequence of this is that, whilst untreated wood bums with an attractive flame picture, the material per se does not comply with current smoke control legislation in the 10* . UK. These features are largely due to the high volatile matter content in untreated wood. In contrast, torrefaction removes sufficient of the smokey volatile components *.I.

from the wood to yield a part-devolatilised material which can be used as a component of smokeless fuel feedstocks, but which still retains sufficient volatile matter to support enhanced flame picture and a highly reactive product. Whilst charcoal can be, and has been, used as a component of smokeless fuel bnquettes, for example for use on barbeques, its lower volatile matter content results in an inferior flame picture and a relatively unreactive briquetted product. For example GB1438944 has an example in which charcoal dust is employed to make a briquette.

* The calorific value of torrefied wood is significantly lower than those of the other bnquetting feedstock components. Consequently, it could be expected that inclusion of torrefied wood in the feedstock mix may yield a product of inferior fire performance, particularly heat output. Surprisingly, this is not the case, since the products containing torrefied wood exhibit similar heat output to standard briquettes, but still have the enhanced flame picture and reactivity.

EXAMPLES -Fire Performance The invention is further illustrated with reference to the following examples. A series of trial feedstock formulations, incorporating between 5% and 25% torrefled wood in a standard open-fire, coal-based, feedstoclc mix, with 17% molasses/phosphoric acid binder system, were briquetted by roll press, followed by curing in a reduced oxygen atmosphere at approximately 300 C. Between 30kg and 100kg of intact, cured briquettes were produced. The composition of each example is given in Table 2 below.

Table 2

Exemplary and Comparative Formulations EXAMPLE 1 2 3 4 comparatIve Torrefled wood In solid 25 15 10 5 0 feedstock (%dry basis) Formulation (%wt) Torretied wood 20.8 12.5 8.3 4.2 0 S.., Anthracite 28.6 32.4 34.0 36.2 38.2 S... ____________________________ ____________ Bituminous coal 17.4 19.8 20.7 22.1 23.2 Petroleum coke 16.2 18.3 20.0 20.5 21.6 *5* _____________________________ Molasses/Phosphoric acid 17.0 17.0 17.0 17.0 17.0 e* In each case, the torrefied wood was made from waste wood heat treated to 300 C for minutes in a reduced oxygen environment, using a batch torrefaction unit. The torrefied wood had the following analysis:-Ash content 8.4% (dry basis), Volatile Matter content 44.7% (dry basis). Following quenching, the torrefied wood was dried and crushed to Ox5mm sizing in a swing hammer miii. The torrefied wood was then mixed in varying proportions with a base blend comprising 46% anthracite, 28% bituminous coal and 26% petroleum coke (dried and nominally Ox3mm in size).

Each formulation was bnquetted on a pilot scale rolls press, prior to curing at 250 degC for approximately 30 minutes in a nitrogen purged, reduced oxygen environment.

Fire performance testing of the cured briquettes was carried out on a Parkray Paragon open-fire to industry standard, HETAS-type, three peak, open-fire test procedures.

HETAS is the official body recognised by the United Kingdom government to approve solid fuel domestic heating appliances, fuels and services in the UK. In addition, briquettes containing 10% torrefied wood addition were subjected to smoke emission testing, to BS 3841. In each case, the fire test programme included a standard formulation containing no torrefied wood as a base for comparison. The key fire performance parameters are presented in Table 3.

Table 3

Summary of Fire Performance Test Results

Torrefied wood content (% 25 15 10 5 0 UK weight, dry basis) Standard Ignition time (mins) 26 25 30 34 38 <50 1st radiation peak (kW) 2.9 3.1 3.1 2.8 2.9 - 2nd radiation peak (kW) 3.6 3.9 3.9 3.2 3.2 - 3rd radiation peak (kW) 3.7 3.6 3.2 3.1 3.3 >3.4 Mean radiant output (kW) 2.5 2.6 2.7 2.3 2.5 >2.5 Fire recovery time after first 18 18 20 28 35 <30 refuel (mins) Fire recovery time after 22 19 20 30 36 <30 second refuel (mins) Fire life (time between 1st & 2.1 2.4 2.3 2.6 2.7 >1.5 :r 2nd refuels (hrs)) Fire life (time between 2nd 2.0 2.1 2.0 2.4 3.3 >1.5 -refuel & 2.5kW (hrs)) Smoke emission rate (g/hr) --3.5 --<5.0 -In reviewing the above fire performance data, it is important to consider the main requirements for a domestic smokeless fuel marketed for use on open-fires and multifuel stoves, especially in terms of consumer expectation, and industry and regulatory requirements. The main requirements can be summarised as follows:-a) the fuel must comply with UK Smoke Control legislation (unless burnt on an exempted appliance); b) the fuel should ignite quickly and the fire should recover quickly after refuel; c) the fire should give satisfactory radiant heat out into the room; d) the fire should have sufficiently long periods between refuels for consumer convenience; e) high and attractive flames should develop quickly and be maintained during ignition and after refuel; 1) the fuel should leave minimal waste at the end of combustion; g) the fuel must not be associated with excessive spitting during combustion; h) the briquettes should be of good appearance and mechanical strength; i) the fuel should be consistent with environmental expectations and objectives; j) ideally, the fuel should meet industry standard fire performance criteria; The main points to be noted from the results in Table 3 are as follows:- * The addition of torrefied wood to the feedstock blend significantly improved the reactivity of the resultant product, as evident from the substantially reduced ignition times and fire recovery times after refuel. These parameters were observed to progressively improve with the level of torrefied wood inclusion, to 15% addition. At the same time the life of the fire was reduced by torrefied wood addition, consistent with increased reactivity resulting in faster burning rates. However, in all cases the fire life :. comfortably achieved UK standards.

* *.. 25 *.* * The addition of torrefied wood had no detrimental effect on radiant heat output parameters. Indeed, bnquettes containing torrefied wood achieved UK industry standard fire performance criteria, for smokeless fuel coal briquettes.

* 30 * The inclusion of torrefied wood resulted in the earlier development of flames during the fire ignition and post refuel stages. In addition, throughout the combustion cycles a * substantially enhanced flame picture resulted from the torrefied wood inclusion.

* At torrefied wood addition rates of 15% and above the briquettes were, however, more prone to breakage and auto-ignition during the briquette curing stage. Furthermore, the additional fire performance benefits gained diminished at torrefieci wood addition rates above 10%. For this reason, it was concluded that the optimum level of torrefied wood addition is in the region of 10%.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. I. * S * ***

Throughout the description and claims of this specification, the words "comprise" and "contain" and vanations of the words, for example "comprising" and "comprises", means **S "including but not limited to", and is not intended to (and does not) exclude other * moieties, additives, components, integers or steps. S 30

Throughout the description and claims of this specification, the singular encompasses 5' * the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

S * * a **. S... * . S... *S.*

S S..' a.. * * * *.* a. * * . S * S.

Claims

1. A process for the production of a fuel briquette comprising the steps of: providing wood and grinding/shredding to a piece sizes screened to less than 200 mm; torrefying the wood; crushing the torrefled wood to a particle size screened to less than 10 mm; providing coal and optionally petroleum coke crushed to piece sizes screened to tess than 5 mm and dried to moisture content less than 10% by weight; mixing the components together in the foliDwing proportions to form a briquette feedstock: Component % by weight, dry torrefied wood 5-40 coal 0-85 petroleum coke 0-60 binder 5-30 bnquetting the feedstock and curuijthe binder.

2. A process as claimed in claim 1, in which the wood comprises tree wood.

3. A process or fuel as claimed in claim 2, in which said wood is waste wood.

4. A process as claimed in claim 1, 2 or 3, in which said feedstock comprises Component -% by weight, dry torrefied wood 5-15 coal balance * petroleum coke 15-25 S..

binder 10-20

S * **.

5. A process as claimed in any preceding claim, in which said coal comprises from 20-80% anthracite, optionally between 40% and 70%.

6. A process as claimed in any preceding claim, in which said coal comprises bituminous coal.

7. A process as claimed in claim 6, in which there is up to 30% of said bituminous coal, optionally between 10 and 20% thereof.

8. A process as claimed in any preceding claim, in which said torrefying step occurs at a temperature between 250 C and 350 C, optionally 275 C and 325 C, and further optionally between 290 C and 3 10 C.

9. A process as claimed in any preceding claim, in which said volatile matter content of the torrefied wood is between 30% and 75% by weight, preferably between 40%and50%.

10. A process as claimed in any preceding claim, in which said components of the briquette feedstock indude 5-20% by dry weight of torrefied wood, optionally between 5-15%.

11. A process as claimed in any preceding claim, in which said wood is torrefied in a batch torrefaction unit.

12. A process as claimed in claim 11, in which an inert atmosphere is maintained within the torrefaction unit by controlling the escape of water vapour, volatile matter and gases from the wood as it is heated, said gases progressively displacing air (particularly oxygen) from the unit as the bed is heated.

13. A process as claimed in claim 12, in which said inert atmosphere is maintained by the injection of an inert gas (eg nitrogen or steam) into the torrefaction S... unit. *S.S

14. A process as claimed in claim 11, 12 or 13, in which controlled amounts of * air (oxygen) are injected into the unit, thereby generating some of the heating requirement by controlled partial combustion of the wood.

15. A process as claimed in any preceding claim, in which torrefaction of the wood is terminated by quenching the wood in water, dry cooling the wood using an inert gas or feeding the torrefied wood directly to a briquetting plant.

16. A process as claimed in any preceding claim, in which said torrefied wood, and/or said coal and/or petroleum coke, is crushed to piece sizes screened to less than 3mm.

17. A process as claimed in any preceding claim in which said crushing of the torrefied wood is effected in machine of the same type used to crush said coal and/or coke.

18. A process as claimed in any preceding claim, in which said coal and/or petroleum coke is dried to a moisture content less than 3% by weight.

19. A process as claimed in any preceding claim, in which there is between 20 and 50% petroleum coke in the briquette feedstock.

20. A process as claimed in any preceding claim, in which said binder is a molasses/phosphoric acid binder.

21. A process as claimed in any preceding claim, in which said binder is present in the briquette feedstock in the amount of between 10% and 20% by dry weight.

22. A briquetted fuel comprising the following the following components: Component % by weight, dry torrefied wood 5-40 coal 0-85 petroleum coke 0-60 binder 5-30 wherein the torrefied wood comprises between 30% and 75% volatile material. S...

23. A briquetted fuel as claimed in claim 22, comprising the following : * 25 components: * Component % by weight, dry * torrefied wood 5-15 coal balance petroleum coke 15-25 binder 10-20

24. A briquetted fuel and a process of forming same, substantially as hereinbefore described with reference to the Examples. * * * **. **S. * . be.. *... S. S.

S S S *5 S. *

S SS S 55