TREATMENT OF WASTE MATERIALS FIELD OF THE INVENTION THIS invention relates to a method of converting carbon-based waste products into stable, utile products. The terms"carbon-based products"or"carbon-based materials"are herein intended to embrace carbonatious materials, hydrocarbons and other compounds containing carbon atoms. More particularly, but not exclusively, this invention is concerned with the treatment of environmentally hazardous waste materials originating from the production of gaseous or liquid fuels from coal or gas. One embodiment of the invention is aimed at the production of solid fuel products. Such manufactured fuel may be adapted to be suitable for use, inter alia, in the generation of useful forms of energy, such as steam, electricity or heat, which may, for example, in turn be utilized in the plant in which the said carbon-based waste products were originally produced.

It may also be adapted to be used as a carbon source for the production of syngas and hydrocarbons. The product may further find various other applications such as a landfill site liner or road building component.

BACKGROUND TO THE INVENTION The production of liquid and/or gaseous fuel from coal gives rise to a large quantity of waste products of varied composition.

The first stage in such production is the mining, milling and transportation of the coal to a gasification plant. During this stage coal dust is produced in vast

quantities. It has been estimated that about 30% of mined coal converts to coal dust during this stage. While some of the coal dust may be used as fuel in certain furnaces, the difficulties associated with its transportation due to its powdery consistency, and the vast quantities thereof, inevitably leads to a substantial percentage of coal dust being treated as a waste material requiring disposal in an environmentally acceptable manner. Such coal dust is one of the carbon-based products with which this invention is concerned in seeking to find a solution for the environmental aspect thereof.

The second stage of the production process of gaseous and liquid fuels from coal involves the gasification of the mined coal to form synthesis gas, also <BR> known as"synga5', composed of hydrogen and carbon monoxide. In essence this stage involves the reaction between carbon, steam and oxygen in a gasifier. The gaseous and entrained reaction products produced in the gasifier are passed through a gas scrubber in which the desired syngas component thereof is separated from by-products which typically include hydrogen sulfide, ammonia, carbon dioxide, tars and phenols. Some of these by-products may be utilized in other chemical reactions. A large part thereof is however a waste product to which further reference is made below. Ash is a further waste product produced in large quantities during gasification stage, both in the gasifiers itself and in boilers used for the generation of the large quantities of steam consumed in the production of syngas.

Synthesis gas produced from coal in the manner referred to above may itself be used as a gaseous fuel, or may be utilised as a starting material for the catalytic conversion thereof into hydrocarbons useful as fuels. The Fischer-Tropsch process and the Synthol process as are, for example, utilized in South Africa by Sasol Limited [hereinafter'Sasol'] in the production of synthetic liquid fuels, such as gasoline and diesel, waxes and other chemical compounds, are examples of such synthesis processes. A more detailed outline of the Synthol process as operated by Sasol at its Sasolburg site in South Africa is contained in US patents and 4041094 all issued to Mobil Oil Corporation. The processes operated at Sasol's other site located at Secunda, also in South Africa, are similar in nature though not in detail.

The synthesis processes referred to above likewise give rise to large quantities of waste products of varied composition which need to be separated from the desired end product composition. Some of the separated by-products may be used in other processes. A large part thereof is however waste product for which no economically feasible use has thusfar been devised. One such waste product produced at the Sasolburg site of Sasol is known as"Funda"and is a spent filter medium. Its composition is presently unknown but is believed to be a spent activated carbon powder saturated with a variety of filtered solids and

adsorbed liquids of presently unknown composition. The waste streams from the synthesis process further comprise waxes, paraffin oils, tars, pitch, process water sludges (also sometimes called solids), process water commonly referred to in the case of the Sasol process as RASAMU, fatty acids (e. g. acetic acid), diesel, benzene, wash water containing a variety of salts and other solutes, <BR> spent catalysts and so-called"synthol gunk'. These streams are collected by a<BR> drainage system into so-caifed dam5"and are called"API sludge'.<BR> <BR> <P>The waste materials referred to above combined with"tank bottom5', a sludge removed during cleaning of fuel storage tanks are collectively referred to as <BR> "black products"by Sasol and that meaning is also intended to be applied to the expression where it is used in this specification.

Such black products have, in the case of the Sasol by-products, not found a process by which it may be converted into a useful product. The result is that it <BR> has over many years been accumulated in so-called"tar pit5'. These tar pits are in the form of large bunded wall reservoirs of which the walls are formed from coarse coal ash derived from the gasifiers or boilers in which steam is produced. The contents of these pits are, by their very nature, of heterogeneous composition. Over the years the large variety of by-products or waste streams referred to above have been disposed of in these pits. Water is present as a component of the composition of the pits as a result of rain falling on the

surfaces of the pits, and as a result of water being an ingredient of some of the waste streams and further as a result of ground water seeping into the pits. Emulsions are consequently also present in the pits. It has been observed by the present inventor that the water present in the tar pits of Sasol has an extremely high Chemical Oxygen Demand (COD) which measures as high as 75 000.

Over the years the various components in the pits have tended to separate into layers. Thus layers of waxes and paraffin oil typically form at the surface of the pits and layers of progressively denser material are stratified at deeper levels of the pits. None of these layers are of a homogenous chemical composition.

Over the years the ash layers of the bunded walls, which have periodically been increased in height and width, have become saturated with at least some of the components of the waste materials disposed of in the reservoirs. Such saturated layers of the ash walls and floor of the pits is commonly referred to as "underlag'. For the purpose of this specification the soil surrounding the tar pits, and which has become contaminated with at least some of the components present in the tar pit, shall be considered to constitute part of the underlay despite it not being composed primarily of the ash from which the walls and floor are constructed.

BRIEF DESCRIPTION OF THE PRIOR ART The manner in which the aforementioned waste products, including the coal dust, process waste products, ash and underlay have been disposed of in the past, is no longer considered to be environmentally acceptable.

Various attempts have been made by several people to convert the most unacceptable component of the aforementioned waste, namely the content of the tar pits, into a useful product, but with limited success.

The use of such tar as a fuel has been suggested in view of its high hydrocarbon content which gives it a relatively high calorific value. However, the conveyance of the tar pit contents to, and into, a furnace at a power station or steam generator present a major problem due to the sticky consistency thereof.

This property leads to blockages, and furthermore, some components in the tar pit content are aggressive to the rubber conveyor belts on which it would preferably be conveyed.

One of the attempts to convert such tar into a more manageable briquette-like form by mixing and compressing it with fine coal resulted in a product that, although reasonably acceptable at lower temperatures, is prone to disintegration and tended to melt while in stockpile, and was hence unacceptable as a solution.

Another approach was to render the tars environmentally inert and suitable as a landfill material by solidification or fixation of the tar with the aid of lime.

Although that process did render a solid product, it was not considered acceptable for two reasons. First the resultant product was in the form of a very fine powder which was poorly compactable and readily airborne and hence unsuitable from an ecological point of view. Secondly, the manner in which the process was performed gave rise to a reaction which was highly exothermic with the concomitant vaporization of components of the volatile components of the tar thus creating a danger of combustion of the evolved fumes.

The fixation of coal tars with the aid of lime has also been suggested in prior art publications. In the case of the Sasol coal-tar pits it would appear that its peculiar composition has so far defied the successful application of known lime fixation processes to render its content utile in a manner which is environmentally acceptable, economically feasible and meets required safety demands.

OBJECTS OF THE INVENTION <BR> <BR> <BR> <BR> <BR> <BR> It is an object of this invention to provide a novel approach to the long-standing challenge to deal in a satisfactory manner with the waste materials of the Sasol coal-to-fuel conversion process. It is however believed that the approach will

also find application in other industrial processes generating similar or comparable carbon-based waste products.

Whereas the aforementioned past approaches seem to have focussed primarily or even exclusively on the tar content of the tar pits in seeking solutions, the present invention is based on a more holistic approach. This approach involves essentially the entire gambit of such waste products and suggests the integration of the variety of such waste products into a utile product. The end product is preferably a fuel or gasifiable carbon source for the production of syngas. The product to be produced by the process of the present invention is thus intended to be composed largely of a carefully selected blend of a substantial part of the major components of the aforementioned waste materials.

The invention further has as an object that the product produced according to the invention shall be in the form of a solid, hard and stable substance from whence the ingredients will neither be leachable into the environment by the action of natural water, nor prone to significant evaporation or significant disintegration into airborne dust particles when the product is stockpiled in the open or subterraneously while awaiting utilization.

The waste management approach of the present invention has as a further object that the fuel so produced may be used to generate at least part of the energy requirements of the fuel-from-coai process, such as, for example to generate electricity, heat or steam required in the gasification process, or could be applied to desaiinate waste water produced in the process and containing salts or other solutes thereby to be able to recycle such water as clean water to the plant.

In addition, the solid fuel product to be produced in accordance with the present invention may be designed to be suitable for gasification to produce syngas, and hence be available to be converted into hydrocarbons, thereby achieving a greater degree of optimization of the coal-to-fuel conversion process which is the primary object for which the coal was mined in the first place.

It is a further object of the invention to suggest alternative uses for the product produced in accordance with the invention.

DESCRIPTION OF THE INVENTION This invention stems from the finding that some of the individual waste products possess desirable properties which may beneficially be combined in the production of a fuel having the desired properties enunciated above by

subjecting a selected blend of such waste products to a fixation process with lime and water. This finding is surprising in the light of the fact that the individual waste components to be combined in the manner contemplated by the present invention have not been shown to be capable of yielding an acceptable or utile end product by individual treatment according to essentially the same fixation process.

This invention further relies on a finding that certain properties of water play a very important role in the reaction by which lime fixates such carbon-based materials. The chemistry involved in this process is not yet fully understood but what has become clear is that the stage at which water is made available to the reagents, i. e. the blend of the content of the tar pit and other waste products on the one hand, and calcium oxide in the form of quicklime on the other, has a major effect on the extent of heat generation during the reaction. It also affects the physical form in which the end product is obtained from the reaction.

It has further been realized that the presence of free water in the waste material renders the exact initiation time of the reaction with lime added to it unpredictable, and once initiated, gives rise to an uncontrollable exothermic reaction which resembles a runaway reaction, with attendant combustion dangers, and leads to an undesirable fine powdery end product. The quality of the water used in the reaction, as measured with reference to its Chemical Oxygen Demand or COD, also plays a role in the reaction and affects the

quantity of lime required to fixate a given quantity of carbonatious material. It is considered to be desirable to use as little lime as possible to fixate the carbonatious material so as to retain as high as possible calorific value in the end product, which value is measured in terms of energy per mass. The lime content in the end product makes no contribution to the energy potential of the end product but does of course contribute to its mass and is hence preferably minimized. It is believed that some of the embodiments of the invention will lead to the detoxification of the tar pits of Sasol and other sites, and that it will generally offer a feasible solution for the environmental management of a longstanding problem which needs to be addressed.

According to the present invention there is provided a reclaimed waste product which has a solid, particulate consistency at ambient temperature and which is the result of the reaction of lime with water carried out in the presence of a blend of made up to contain components selected from at least two of the following groups of waste products derived from the production of liquid or gaseous fuel from coal or similar processes, namely: (a) the group consisting of oils, tars, pitches and mixtures thereof; (b) the group consisting of coal dust, spent Funda filter medium and mixtures thereof; and (c) the group consisting of coal ash, underlay and mixtures thereof.

Further according to the invention the waste product blend, which includes at least two components selected from the groups (a), (b) and (c) referred to above, may be supplemented with other waste products derived from the aforementioned coal based industrial processes, such as Synthol gunk and waxes, with the proviso that such additional waste materials should not exceed 15% by mass of the total reaction composition.

It is preferred to incorporate in the waste product blend equal masses of components selected from at least two of the three groups of components referred to above. In the more preferred form of the invention at least one component of each of the three groups of components is incorporated into the blend. These three components are likewise preferably also present in equal mass quantities.

The preferred combination for such blends are tar, spent Funda filter medium and underlay present in equal amounts and is optionally supplemented with one or more of coal dust, ash, pitch, Synthol gunk and wax.

It has been observed in this regard, and this forms an aspect of the present invention, that increasing the amount of ash and/or underlay tends to increase the degree of brittleness of the end product, while increasing the pitch content tends to increase the hardness of the end product. The reduction of the ash

content in the blend in turn reduces the calorific value which value is increased by the addition of more coal dust or spent Funda filter medium. The supplementation of the latter two products also contribute to the suitability of the end product for use as a carbon source in a gasification process to generate syngas, for which application the product is preferably a hard product, capable of being broken up into lumps without undue dust generation and adapted substantially to maintain its lumpy integrity while being heated to the required temperature for the production of syngas in the presence of steam and oxygen.

According to a particular aspect of the invention the waste product blend is made up to result in a hard solid or particulate product having a calorific value of more than 10 Kl/kg.

Further according to the invention the total coal based waste product blend collectively make up at least 60% by mass of the reaction mixture used for the production of the particulate product of the invention, the balance being made up of lime and water. More preferably the waste product blend makes up between 70% and 90% of the reaction mixture. Most preferably the waste product blend constitutes between 75% and 85% of the reaction mixture.

In all the abovementioned reaction mixtures the mass ratio between the lime and the water in the reaction mixture may be between 2: 1 and 4: 1 but is preferably between 1: 1 and 3: 1.

The blend of carbon-based compounds may preferably be made up of two or more compounds selected from the groups referred to earlier and which are present in the blend in the percentage ranges as indicated: Coal dust 0 to 66% Tar 0 to 66% Underlay 0 to 66% Spent Funda filter medium 0 to 66% Wax 0 to 15% Synthol gunk 0 to 15% Pitch 0 to 66% Ash 0 to 66% provided that coal dust, tar, pitch, underlay, and Funda filter medium collectively make up at least 60% of the blend.

It has been found that higher percentages of some of the components listed above may be used in making up the waste product blend to produce a utile product according to the present invention. Such higher percentages fall within

the general scope of the invention defined above. The percentages as are listed above are aimed at achieving the further object of the invention of providing a waste product management approach in terms of which a variety of waste products are simultaneously consumed in the production of the end product. This aspect of the invention hence approaches the need to clean up the environment by consuming waste products which are not suited in themselves for economical environmentally acceptable disposal.

In carrying out the reaction to produce the product of the invention the ratio between the blend of coal based waste components and lime is preferably between 4: 1 and 30: 1. In the most preferred arrangement the ratio is between 20: 1 and 6: 1.

The lime may be substantially pure lime containing over 90% CaO as quicklime or it may be dolomitic lime in which the CaO quicklime content is about 50%.

References herein to lime percentages and ratios are intended to refer to available quicklime. The lime in the product is preferably in finely ground powder form having an average particle size of less than 500 micron.

It has also been found that a utile fuel product may be produced which comprises coal dust as the predominant component making up more than 50% of the fuel product of the fuel product, the balance being made up of the API oil

mix, ash, lime and water in combination with a binder which may be starch.

The API oil preferably accounts for more than 70% of such balance, and the ash and lime being present in a ratio of between 2: 1 and 1: 2 by mass, and the starch not exceeding 5%.

More preferably the coal dust comprises between 70% and 90% by mass of the end product, the API oil between 15% and 25% by mass and the ash and lime are present in substantially equal amounts collectively making up between 5% and 15% by mass of the end product which is bound by starch in an amount of up to 3% by mass into solid composition.

Further according to the present invention there is provided a method for <BR> producing a solid product from a blend of waste materials as defined above comprising the steps of: [i] dewatering, if necessary, the waste materials incorporated in the blend to remove substantially all free water therefrom; [ii] intimately mixing the waste material blend with calcium oxide; [iii] adding water with a low COD value to the mixture of dewatered waste material and calcium oxide with further mixing to obtain a firm slurry; [iv] allowing the mixture to react and to set; and [v] optionally, and if required, breaking the set mass into smaller particles.

In one form of the invention the waste material may be the oil and tar mixture obtained by taking a representative sample of the total depth of the tar pits, including underlay, of Sasol Limited located near Sasolburg. The Sasol oil/tar fraction is however preferably mixed with other substantially water free carbon- based materials such as uncontaminated waste streams of carbon-based materials. Such addition may be aimed at increasing the calorific value of the end product. The additional carbon-based material is preferably the spent filter medium derived from the Funda filters of the processes utilized by Sasol. As an alternative, fine coal dust may be added to the reaction mixture for this purpose. Such additions of carbon-based materials also has the benefit of introducing non-hydrocarbon carbon based materials into the reaction product thereby potentially rendering it suitable to be used as a carbon source in the production of syngas.

It is also in the contemplation of the present invention to add to the dewatered tar a quantity of solid material to affect the consistency of the slurry and thereby to affect the physical'properties of the set end product. Thus, ash may be added which ash may, for example, be directly removed from boilers used in the generation of steam or electricity. Carbonatious solid material, such as coal powder or coal dust may also be used which will of course also enhance the calorific value of the end product.

The waste material may be dewatered by any suitable process.

The dewatered waste material and lime may be mixed by means of any suitable mixing device but is preferably mixed by means of a pug-mixer.

Water in the form of ordinary tap water with a low COD value is preferably introduced by means of water jets directed at the mixture of tar and lime at a point intermediate the feed and discharge ends of the pug-mixer.

The reaction typically takes between five and thirty days to reach completion and a slow increase in temperature from ambient to between about 40°C and 70°C occurs during the first 8 hours, without unacceptable levels of fume generation, after which it reduces again to ambient temperature while the mixture sets into a solid mass. Such solid mass may then be reduced to particles of a desired size by appropriate means such as milling and screening.

The use of lower percentages lime content lengthens the reaction time but also has the advantage of the reaction temperature remaining well below 50°C and thus reducing even further the risk of explosion or violent reaction.

In carrying out batchwise testing of the invention it has been found that the addition of water to the blended lime/waste mixture is advantageously done by

producing a stoichiometric slurry of part of the lime in a part of the water added to the mixture, and adding the slurry with mixing to the lime/waste mixture as soon as the lime/water reaction has commenced (as evidenced by the generation of heat) and while it is progressing. It is believed that the addition of such part of the lime as reacting lime to the bulk of the reaction mixture acts as a booster for the reaction and contributes, in a manner not yet fully understood, to the satisfactory product of the invention. This concept of adding a booster amount of reacting lime and water to the blend of waste material and lime, may appropriately be adapted for a continuous production process in which a mechanical pug mixer is used.

It has been found that the process is suitable to produce an acceptable solid fuel from the Sasol tar pits located at Sasolburg and other waste products. This fuel is not tacky, has little or at least acceptable odor emission, and is stable and leach resistant and has a calorific value comparable to that of the fuel coal used by Sasol.

The product produced in accordance with the present invention has further been found to have good compactibility features which is desirable for stockpiling the product should it not immediately be required for use as a fuel.

This compactibility feature, coupled with the fact that the product is not prone to leaching and may be made up to be crushable also renders it suitable for use in the construction of roads. It is further suitable for the construction of impermeable barrier layers for waste disposal sites to be used in stead of, or in conjunction with clays such as bentonite conventionally used in that application.

An approach to the execution of the present invention which has been found to be particularly useful in consuming, and hence to dispensing of large quantities of coal dust, involves a slightly modified process and utilisation of API sludges such as is collected in the API sludge drainage system at Sasol's Secunda site.

Such API sludge contains about 39% water by volume and small, sub-1% solids.

According to this aspect of the invention the API sludge is dewatered to a water content of less than 10%, the dewatered API sludge is used as a carbon-based component in making a solid product in the manner disclosed above by mixing it with between 10% and 20% by mass of a mixture of coal ash and lime in a ratio of between 2: 1 and 1: 2. A quantity of water in an amount up to 4% is added to the mixture, and resultant solid reaction product produced after a curing time of up to 30 days is then ground and mixed with coal dust in a mass to mass ratio of between 4: 6 and 1: 9 and an aqueous slurry of starch in a quantity to have about 2% starch by mass in the final mixture.

The present invention will now be illustrated by means of the following examples without thereby limiting the scope of the invention to those examples.

EXAMPLE 1 A representative sample of the oil/tar mixture contained in the No. tar pits of Sasol Limited near Sasolburg was removed. The oil/tar fraction removed from the pit was dewatered to remove substantially all free water by simply allowing all free water to run from a mound of the oil/tar under the force of gravity. Such dewatered oil/tar, which still contained about 30% entrained water, was used in all further experiments reported herein. It is henceforth simply referred to as "the oil/tM'.

Two forms of lime were used in the experiments, namely unslaked lime obtained from PPC Lime (Pty.) Limited of which the available lime content is about 90% (CaO as quicklime), and dolomitic lime, also obtained from PPC Lime (Pty.) Limited which contains about 50% available lime.

Various blends of waste material and lime/dolomite were made as set out in Table I below with the aid of a mixer. Ordinary tap water as supplied by Rand Water was added to the thoroughly mixed material in an amount of between 5 and 35% mass of the mixture as indicated in

Table 1. In most instances part of the water was added to the mixture in the form of 3: 1 slurry of CaO in water while the latter was reacting.

Such addition seemed to set off the reaction between the remainder of the lime and the waste materials and is considered to have a booster effect. Without the booster the oil/wax or other ingredients of the mixture seems to delay the reaction between the lime and the water. The reactions were allowed to progress to completion over a period of 24 hours. Observations were made with regard to the maximum temperature of the mixture during the reaction time, the emission of fumes, the texture of the mixture after 24 hours, the hardness of the end product, its compactibility and the calorific value of the product.

Table I Waste Products Components % Under-Coal% % Temp. Calorific Sample Oil/Tar Funda Lay dust Pitch Wax Ash Lime Water Rise Value Added Added °c MJ/Kg A50 50 15 5 60 17. 51 B 33 33 33 45 5 42 16.46 C 33 33 33 15 5 36 18. 56 D 33 33 33 15 10 65 17.53 E 33 33 33 20 10 69 18. 39 F 100 15 35 40 29.32 G 100 17 5 80 23. 54 H 33 33 33 15 5 Nd 16. 99 I50 50 15 10 Nd Nd J 1 50 50 15 5 49 12 K 12.5 12.5 12.5 50 12. 5 15 5 Nd 19. 13 L 30 30 30 10 15 5 58 Nd Nd-not determined

/cases except sample F and L the end product was a black or brown/black solid with hardness ranging from brittle to very hard. Sample F rendered a black soft sandy product and sample L a crumbly product. But for these products, the rest all had good compactibility and crushability properties. It was found that the end products were not tacky to the touch and that no leaching of the waste materials occurred from the product.

The calorific values of the products compare very favourably with the calorific value of the coal being used in the Sasol gasification plant that has a value of between 19 and 20 MJ/Kg.

The product of the present invention may thus be used to generate steam or electricity that may be supplie to the Sasol plant or delivered elsewhere.

Some examples of the end product were crushed to a fine powder and tested for suitability as a blast furnace fuel. They were found to compare very favorably with a commercially used coal in terms of igniting temperature, maximum temperature, burn-out time and ash content.

EXAMPLE 2 A quantity of the API sludge was collected from the API dam at Sasol's Secunda site in which it had been collected for about 2 years. It was volumetrically

analyse and found to contain 61% water, 38% oils and about 1% solids by volume. With the aid of a bowl-type centrifuge operated at 3000 rpm and Mach 5, the water content was reduced to between 5 and 15% as shown in Table II below for various samples reported on herein.

The resultant dewatered API sludge, also referred to as the oil in Table II in Table II was mixed with various quantities of lime and ash in the ratios as indicated in Table II. A quantity of the lime was premixed in ordinary tap water and as the exothermic reaction commenced the reacting mixture was introduced into and thoroughly mixed with the oil/lime/ash mixture. The reaction of the bulk mixture was also exothermic but the temperatures generally did not raise above 31°C.

The reaction mixture set into a hard solid mass over a period of about 30 days. The solid mass was ground into a powder and mixed with coal dust and starch and dried with hot air in a rotating drum for a period of 30 minutes to be formed into small hard spheres of dimensions between 1 and 5 cm cross section. The properties of these pellitised spheres in terms of hardness are reflected in Table II.

The calorific values of these spheres, recrushed into a powder as it would be introduced into a blast furnace, was found to be between 10 and 20 KJ/Kg : TABLE II<BR> PRODUCTION OF SOLID FUEL FROM COAL DUST AND API SLUDGE Dewatered API Fixation Mixture Results Fuel Product Mixture Results ludge .-o L z .-'S °o.. U v s a. °" CUZ'os a N o -"='5 CL'OC-n'O Q- : :-c XE a ; 0"' r"=' m--C-2 0 <x < 72 u U X iT-u_-u u V) 092 10 89 1 10 10 80 0 30 ç 20 77 3 V2 093 5 94 1 8 8 82 2 30 20 78 2 1/2 094 0 99 1 5 5 88 2 30 20 79 1'/2 098 5 94 1 5 5 88 2 30 VO r 20 79 1 r'lz 099 8 91 1 5 5 88 1 30 VO 20 79 1'/2 100 5 94 1 5 5 88 2 30 102 5 94 1 5 5 88 2 30 20 75 2 2 1 1/2 103 0 99 1 10 10 84 1 30 ç _ « 20 65 5 10'/2 104 5 94 1 4 4 84 7 30 20 79 1 105 5 94 1 5 5 84 7 30 VO 20 79 1 106 5 94 1 5 5 88 2 30 1 10 89 1 Y2 107 5 94 1 5 1 Many modifications of the invention may be devised without thereby departing from the spirit of the invention.