IT8147799A1 - SOLID FUEL-OIL MIXTURES. - Google Patents

Description

Solid fuel-oil mixtures

Summary

A method of preparing a uniform dispersion of a friable solid fuel, oil and water, in which the solid fuel is ground into a medium consisting of substantially a greater proportion of oil and a smaller proportion of water, in the absence of an added dispersant or emulsifier , the air being excluded during the grinding operation, the solid fuel being present in the quantity? 15 to 55 weight percent of the dispersion and being ground to the average particle size of the solid fuel? reduced to a value in the range of 1 to 15 microns.

The present invention relates to the production of dispersions of a solid fuel, oil and water.

Coal-oil suspensions have already been illustrated, for example, see British Patent Description No. 975687. While these behaved as quasi-Newtonian fluids, non-sedimenting in pipelines, they separate in the quiescent state. Thus, these suspensions are suitable for use immediately after preparation or passage in oil pipelines, but are not suitable for transport or storage.

The description of the English proprietary patent? of the proprietor of the present invention No. 1523193 discloses and claims a method of preparing a uniform dispersion of coal in oil, which method comprises grinding the coal into a medium consisting substantially of oil and / or more petroleum fractions. heavy, up to what size of particle? reduced to a value below 10 microns and the dispersion contains from 15 to 55% carbon, expressed as a weight percentage of the total dispersion, and until there is a stable dispersion at the cessation of grinding.

The British Patent Description No. 1548402 illustrates the method of producing a fluid fuel which comprises the steps of mixing coal to a grain size of up to 6 millimeters with up to 30% by weight of water based on the mixture of coal and water. to pass the moistened coal to a mixer in which? mixed with liquid fuel hydrocartide, the cardboard forming no longer? of 50% by weight of the mixture and by passing the mixture so? formed through a grinding mill in which the cardboard grains are ground to particles of the maximum size of 500 microns to produce the fluid fuel.

The trevetto 1548402 states that? It is essential that the water and the carton are mixed before adding the liquid hydrocarbon fuel to obtain the desired product shape, in particular a flocculated structure in the coal particle oil in which the water preferentially moistens part of the surface of each cardboard particle and binds it to the other cardboard particles. It also establishes that if mixing? carried out in any other sequence, such as in USA No. 1431225, an omulsion of water is formed in the oil, the cardboard particles are not moistened by the water and the product? stabilized at a much more amplitude? small against sedimentation. According to Patent No. 1548402, adding water to the cardboard suspension in liquid hydrocarbon fuel simply forms an emulsion in the hydrocarbon which does not aid stability. for a long time.

The aforementioned U.S. Patent No. 1431225 discloses a method for preparing a fluid fuel in which a solid fuel? ground to a fineness of approximately 200 mesh (76 microns) or less. The pulverized solid is then mixed with a liquid fuel, water is added and the mixture? agitated to provide an emulsion. US Patent No. 1431225 recognizes that, under some conditions, there is the tendency, on the part of the emulsion, to become unstable and separate into its constituents, and to oppose this? , can? a stabilizing agent, such as a soap, be added.

Yup ? now surprisingly found that the stability? of solid fuel-oil dispersions of the type illustrated in the British patent 1523193 pu? be improved by adding water, before or during grinding. In particular, the stability? ? improved in the temperature range of 60 to 100 ° C. Alternatively, the grinding time required to produce a dispersion of the stability? desired is reduced.

So, according to the present invention,? provided a method for preparing a uniform dispersion of a friable solid fuel, oil and water, which method comprises grinding the solid fuel into a medium consisting of substantially a greater proportion of oil and a smaller proportion of water, in the absence of dispersant or emulsifier added, the air being excluded during the grinding operation, the solid fuel being present in a quantity? 15 to 55 weight percent of the dispersion and being ground to the average particle size of the solid fuel? reduced to a value in the range of 1 to 15 microns.

Suitable friable solid fuels include coals of varying grades, solvent-refined coal, coking coal, and petroleum coal. Favorite solid fuel? a bituminous coal.

Preferably, the solid fuel supplied to the grinding process? pre-ground to a particle size not greater than 250 microns.

A suitable oil? a petroleum based on the fraction of fuel oil having a viscosity? of no more? of 6000 seconds, preferably no more? of 3500 seconds, Redwood No. 1 at 100? F (37.8? C). The viscosity? request can? be obtained "by cutting", if necessary, with, for example, diesel.

In the case of some fractions of fuel oil pi? heavy, can? it may be necessary to heat them to make them sufficiently mobile to allow them to be used as a grinding liquid.

The quantity of solid fuel added? preferably in the range of 30 to 45% by weight of the total weight of the dispersion d? solid fuel, oil and water.

The quantity of added water? conveniently in the range from 1 to 15%, preferably from 5 to 10% of the total weight of the solid fuel, oil and water dispersion.

Water can be added to the oil before mixing with solid fuel or solid fuel can? be added to the oil before mixing with water, or all three can be added simultaneously before grinding.

The initial mixing can? take place in a high speed vortex mixer.

The grinding can? be carried out in commercially available ball mills, such as agitation, vibration or ball tumbling mills.

When is an agitation or vibration ball mill employed, coal? preferably pre-mixed with the oil prior to grinding, for example in a high speed vortex mixer. The grinding? preferably carried out until the average particle size of the solid fuel? reduced to a value in the range of 2 to 8 microns.

The grinding time will depend? by the nature of the mill. However, this time will generally be? about half? of the time required to produce a dispersion of similar stability? when grinding in the absence of water. For example, when using a stirring ball mill, the grinding time can be reduced. be shortened from about 6 minutes to 3 minutes.

It is necessary to exclude air during the grinding operation. This can? easily be obtained in the case of vibrating and stirring ball mills by completely filling the mill.

When using a ball mill it is, of course, desirable to use balls made of a material which does not react with the solid and which does not unduly wear both itself and the internal surface of the mill during grinding. Ball mills normally contain steel or glass balls, and these are suitable for the present purpose.

The dispersions will generally be prepared, used and stored at a high temperature and, under these conditions, they will be more? stability of the corresponding dispersions prepared in the absence of water.

They are suitable for use in blast furnaces, cement kilns and industrial, marine and heating boilers.

The stability of solid fuel-oil-water dispersion? a function of three important variables - the grinding method, the final particle size and the concentration of solid in oil - enhanced by a fourth - the presence of water during grinding. If all four are chosen correctly, then the scatter? of stability improved at elevated temperatures and at room temperature.

At room temperature, the dispersion? in the form of a thixotropic, weak gel, in which a physical lattice? formed by solid particles that interact with the oil reinforced by the bonds of water between solid particles. It? a uniform structure from which solid particles cannot separate as they form a part of it.

This ? unlike the foregoing solid fuel-oil-water dispersions which have been water-wetted coal particle dispersions suspended in oil or coal particle dispersions suspended in an oil and water emulsion.

At elevated temperature, although the gel-like structure is less evident, the same interactions occur to impart stability. exalted.

If the solid particles are not ground into the oil in the absence of air, the solid particles oxidize and interact unfavorably. If the size of the solid particle? too large, the forces will be insufficient to confer stability. The concentration of solid particles? also critical. If it? too low, the dispersion will be? unstable. If too high, the dispersion will become? too solid for pumping. Water improves stability by a complex mechanism, probably involving bridges between solid particles.

The invention? illustrated with reference to the following examples.

Example 1

Was the fuel oil a fuel oil from the source, is it with a visis? of 3500 Redwood No.

1 seconds to 37.8? C. It had the following properties:

The coal was a bituminous coal from the Rank 501 Durham coal field with the following final and initial particle size analyzes (air dried base):

The fuel oil (3.42 kg.) Was heated to 35 ° C and the pulverized coal (2.1 kg.) Was added with continuous stirring in a vortex mixer. Water (0.48 kg.) Was added to the resulting mixture and further mixing was continued until the mixture reached 54 ° C. The resulting slurry containing 35 wt% coal, 8 wt% water, and 57 wt% fuel oil, was pumped at speed. of 480 ml / min giving a nominal holding time of 1.5 minutes, to a stirred ball mill sold under the name Dyno Mill Type KD Pilot by Willy Bachofen Maschinenfabrik, Basel, Switzerland. The grinding chamber of the mill, a horizontally mounted cylinder with a volume of 1.4 liters, contained steel balls of 2 millimeters (nominally 5 kg.). The balls were stirred by agitator discs mounted on a horizontal shaft which ran parallel to the cylinder axis. The speed? of the shaft was established in 3350 revolutions per minute to give a speed? disk peripheral of 14 meters / second. The product was collected when it came out of the mill. The average particle size of the coal was 5.7 microns, as measured by the light microscope technique.

The coal-fuel oil-water dispersion did not show? signs of carbon deposits after 6 weeks of storage at room temperature. It did not present? signs d? instability after resting for 24 hours at 100 ° C.

For comparison, a cardboard-fuel oil dispersion containing 35 wt% coal in fuel oil under exactly the same grinding conditions as above was prepared. This sample did not show? again signs of deposit after 6 weeks of storage at room temperature, but showed? a considerable instability? after 24 hours at 100 ° C with the formation of a layer of sludge. It contained no added water. The average particle size of the coal was 5.1 microns.

To obtain a product of stability? comparable, a residence time of about 3.5 minutes in the mill was required. The average particle size of the coal was reduced to 4.1 microns.

This illustrates how the presence of water reduces the grinding time and so on. the energy requirements.

Example 2

The fuel oil was a combustible source oil with a viscous viscosity. of 3500 Redwood No. 1 second at 100? F (37.8? C). The coal was taken from a different batch of Durham coal used in Example 1. The analytical details of coal and fuel oil were similar to those used in Example 1.

Water (0.48 kg.) Was added to the fuel oil

Claims (13)

R I V E N D I C A Z I O N I 1. A method for preparing a uniform dispersion of a friable solid fuel, oil and water, which method comprises grinding the solid fuel into a medium consisting of substantially a greater proportion of oil and a smaller proportion of water, in the absence of added dispersant or emulsifier, the air being excluded during the grinding operation, the solid fuel being present in a quantity? 15 to 55% by weight of the dispersion and being ground to the average particle size of the solid fuel? reduced to a value in the range of 1 to 15 microns. A method according to claim 1, wherein the average particle size of the solid fuel? reduced to a nolia range from 2 to 8 microns. Method according to either of the preceding claims wherein the dispersion contains 30 to 45% by weight of solid fuel. A method according to any one of the preceding claims, wherein the dispersion contains from 1 to 15% by weight of water. A method according to claim 4, wherein the dispersion contains from 5 to 10% by weight of water. 6. A method according to any one of the preceding claims, wherein the friable solid fuel? coal, solvent-refined coal, coke carbon, or petroleum coal. 7. A method according to claim 6, wherein the friable solid fuel? bituminous coal. 8. A method according to any one of the preceding claims, wherein the solid fuel? pre-ground to a particle size not greater than 250 microns prior to grinding in the oil medium. 9. A method according to any one of the preceding claims, wherein the oil? a fraction of petroleum fuel oil, having a viscosity? of no more? of 6000 seconds Redwood No. 1 a 37.8? C. 10. A method according to claim 9, wherein the oil? a fraction of petroleum fuel oil having a viscosity? of no more? of 3000 seconds Redwood No. 1 at 37.8? C. 11. A method according to any one of the preceding claims, wherein the coal? added to the oil before mixing with water. A method according to any one of claims 1 to 10, wherein the water? added to oil before mixing with charcoal. A method according to any one of the preceding claims, wherein the grinding is carried out in a ball mill.