Water slurries of carbonaceous materials

Abstract

 A metal salt such as the sodium salt of a naphthalenesulfonic acid formaldehyde condensate is added to water slurry of carbonaceous materials such as a coal water slurry in an amount sufficient to reduce viscosity of the slurry to improve pumpability. From about 0.05 to about 0.1 parts by weight of the sodium salt of the condensate may be added to 250 parts by weight of a coal water slurry containing from about 40 to about 60% by weight of coal.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] This invention relates to water slurries of carbonaceous materials and more particularly to water slurries of coal stabilized with metal salts such as sodium salts of naphthalenesulfonic acid formaldehyde condensates.

2. Description of the Prior Art

[0002] Transport is one of the major problems involved in use of particulate carbonaceous materials such as coal. Aqueous slurries of finely ground coal containing over 55 weight percent solids are difficult to pump with slurry pumps because as the solids level is increased above 50 weight percent the water and solids tend to separate causing coal particles to build up in various areas in the pumping system. This dewatering of the slurry causes blockage and jamming in the pumping system.

[0003] Decreasing the weight percent of water in aqueous coal slurries is desirable because water is a major contributor to the cost of transport and processing operations. Further, water may be in short supply when coal is introduced into a pipeline so conservation of water may be desirable. The less water transported the greater is the volume of coal that can be moved, resulting in transport efficiencies. Also, during burning of coal, a significant amount of heat is required to vaporize the water vehicle. As the weight percent of the water vehicle decreases, the efficiency of the coal burning process increases. A method which allows the use of higher weight percent solids aqueous coal slurries than were heretofore feasible would be of great importance.

[0004] U.S. Patent No. 4,282,006 - Funk, issued August 4, 1981, describes a pipeline pumpable coal water, slurry having a high content of coal particles with a minimum of void spaces and a maximum of particle surface area to enhance dispersing effects generated by electrolytes and/or dispersing agents added to the slurry. One of the preferred dispersing agents is the sodium salt of a condensed naphthalenesulfonic acid.

SUMMARY OF THE INVENTION

[0005] A metal salt such as a sodium salt of a naphthalenesulfonic acid formaldehyde condensate is added to a water slurry of carbonaceous materials such as a water slurry of coal in an amount sufficient to reduce the viscosity of the slurry to improve pumpability. From about 0.05 to about 0.1 parts by weight of the sodium salt of the condensate may be added to 250 parts by weight of a coal water slurry containing from about 40 to about 60% by weight of coal.

DETAILED DESCRIPTION

[0006] Metal salts such as sodium salts of naphthalenesulfonic acid formaldehyde condensates are prepared by neutralizing naphthalenesulfonic acid formaldehyde condensates obtained by condensing formaldehyde and naphthalenesulfonic acid using a molar ratio of about 1 to about 3 moles of formaldehyde per mole of sulfonic acid. This condensation is carried out at temperatures from about 60°C to about 100°C, preferably from about 95°C to about 100°C. The condensation can be carried out until the condensate has specific properties such as the viscosities of aqueous salt solutions mentioned in U.S. Patent No. 3,277,162 - Johnson, issued October 4, 1966 or the elution volumes in U.S. Patent No. 4,164,426 - Sinka et al, issued August 14, 1979. Other useful metal salts include potassium, lithium, calcium, magnesium and the like salts. Naphthalenesulfonic acid and formaldehyde, as well as naphthalenesulfonic acid -condensates and their sodium salts, are well known articles of commerce.

[0007] The term "carbonaceous materials", as used herein, encompasses solid particulate carbonaceous fossil fuel materials which may have been powdered or pulverized to a size where 80% or more will pass through a 200 mesh screen. Useful carbonaceous materials include bituminous and anthracite coals, coke, petroleum coke, lignite, charcoal, peat, admixtures thereof and the like. These materials are crushed and milled to obtain finely divided particles suitable for use in formulation of pumpable water slurries of carbonaceous materials.

[0008] Water used in the slurry may be any available water, such as mine, well, river, or lake water or desalinated ocean water having a sufficiently low mineral salt content such that the electrochemistry of the bound water layer and carrier water interface can be controlled and corrosion of milling facilities, pipelines and furnaces will be minimized and controllable.

[0009] An effective amount of a sodium salt of a naphthalenesulfonic acid formaldehyde condensate sufficient to reduce viscosity of the slurry to improve pumpability is added as a dispersing agent to the carbonaceous materials water slurry. Concentration of the sodium salt of the condensate added, based on the total weight of the carbonaceous materials water slurry, can be added up to 10% by weight, preferably from about 0.01% by weight to about 5.0% by weight. These concentrations of dispersing agent reduce viscosities of slurries to improve their pumpability.

[0010] For a fuller understanding of the nature and advantages of this invention, reference may be made to the following examples. These examples are given merely to illustrate the invention and are not to be construed in a limiting sense. All quantities, proportions and percentages are by weight and all references to temperature are °C unless otherwise indicated.

EXAMPLE I

[0011] Samples of Black Mesa pipeline coal water slurries were treated with the quantities of sodium salts of naphthalenesulfonic acid formaldehyde condensate solutions shown in the table below. Black Mesa coal was a western United States sub-bituminous type coal from Arizona deposits having a dry specific gravity of 1.45 and a equilibrium moisture of about 11% by weight. Its ash content was about 10 percent. Solids concentration of the Black Mesa slurry ranged from about 44 to about 50% by weight of the above coal with balance of the slurry being water.

[0012] A 250 g sample of the coal slurry was treated by mixing from 0.05 to 0.10 g of the condensate solution with the slurry. After mixing, the Brookfield viscosity of each slurry sample was measured at 30 seconds using a No. I spindle at 60 rpm to obtain the following results:

[0013] While the invention has been described with reference to certain specific embodiments thereof, it is understood that it is not to be so limited since alterations and changes may be made therein which are within the full intended scope of the appended claims.

Claims

1. In a water slurry of carbonaceous materials composition comprising water and carbonaceous materials, the improvement of having present therein an effective amount of a metal salt of a naphthalenesulfonic acid formaldehyde condensate sufficient to improve pumpability.

2. The composition of claim 1 where the metal salt is the sodium salt.

3. The composition of claim 1 or 2 wherein there is present up to about 10% by weight of the condensate.

4. The composition of claim 3 wherein there is present from about 0.01 to about 5% by weight of the condensate.

5. The composition of one of the preceding claims wherein the carbonaceous materials are coal.

6. In a process of pumping a water slurry of carbonaceous materials composition in a pipeline, the improvement comprising having present the composition of one of the preceding claims.