MXPA99003934A - Process for treating carbonaceous material - Google Patents

Abstract

The invention described herein relates to a process for treating carbonaceous material wherein the resulting product is resistant to undesired combustion. According to the process, carbonaceaous material is treated with a gaseous mixture comprising a major amount of inert gas and a minor amount of oxygen either during or subsequent to carrying out the upgrading step to at least partially oxidize the carbonaceous material.

Description

PROCESS FOR TREATING CARBONACEOUS MATERIAL BACKGROUND OF THE INVENTION The present invention relates to a process for the treatment of carbonaceous materials, more particularly, to improve carbonaceous materials of which the resulting product is resistant to unwanted combustion which tends to occur, for example , during periods of storage or loading. The process of the present invention can be carried out using various apparatuses to naturally improve carbonaceous materials. A number of inventions related to the carbonaceous fuel improvement have so far been used or proposed to produce more convenient carbonaceous fuels as solid fuel. While these systems are effective in increasing the caloric content or calorie values of the carbonaceous materials, effecting a reduction in the non-volatile content of the material or offering an economical means to obtain large quantities of high-quality carbonaceous materials, the carbonaceous materials Improved results are often susceptible to unwanted combustion after relatively short periods of time after improvement. Unwanted combustion can occur under a number of circumstances including, but not limited to, contact with a source of ignition, ie static electricity which may occur during storage or charging. Perhaps more commonly, undesirable combustion occurs as a result of the spontaneous combustion of the improved sarbonaceous material. While improved carbonaceous materials can be chemically treated with various flame retardants to reduce the possibility of unwanted burning, chemical treatment with flame retardant materials can inhibit the effectiveness of the fuel when the fuel is used for its intended purpose. In addition, improved carbonaceous materials treated with a flame retardant material, probably require additional chemical treatment to negate the effects of any flame retardant employed, before use, then, unnecessarily increasing the cost of using the improved carbonaceous materials as a fuel source . COMPENDIUM D? THE INVENTION The benefits and advantages of the present invention are achieved by a process, wherein the carbonaceous material is sufficiently oxidized either during the improved or subsequent process to reduce the possibility of unsuspected combustion occurring.

Ideally, the process will be carried out using an apparatus for improving carbonaceous material such as those described in U.S. Pat. Do not. ,290,523 which was granted on March 1, 1994, or the co-pending patent application of the U.S.A. serial number 08 / 513,199, which was filed on August 8, 1995; each of which is incorporated herein for reference. ~ The apparatus used to carry out the process of the present invention must have a relatively simple design, have a durable construction, be versatile in use and easily adapted to process different carbonaceous materials. In addition, the apparatus used must be simple to control and efficient in the use of heat energy, in order to provide economical operation and conservation of resources. A major advantage of the present invention over known carbonaceous material treatment systems is that the resulting product not only has a high energy value and is reduced by the content of the product, but is also resistant to unwanted combustion. BRIEF DESCRIPTION OF THE DRAWINGS Additional advantages and benefits of the present invention will be apparent from reading the description of the preferred embodiments taken in conjunction with the specific examples and drawings, wherein: Figure 1 is a side elevational view of a first heat exchanger embodiment useful for carrying a method according to the teachings of the present invention, - Figure 2 is a sectional view taken along line 2-2 of Figure 1; Figure 3 is a partially exploded side elevation view illustrating a second heat exchanger mode useful for carrying out a process according to the teachings of the present invention; Figure 4 is a sectional view taken along line 4-4 of Figure 3; Figure 5 is a graph illustrating the self-heating temperature of a sample treated by a method according to the teachings of the present invention; Figure 6 is a graph illustrating the auto-heating temperature of a sample treated by a method according to the teachings of the present invention; and Figure 7 is a graph illustrating the auto-heating temperature of a treated sample by a method according to the teachings of the present invention. DETAILED DESCRIPTION OF THE PREFERRED MQDAI.TnAn The method of the present invention relates to the treatment of carbonaceous materials including but not limited to ground mineral coal, lignite and sub-bituminous coals of the type widely in general in the range of wood, peat and coals bituminous minerals where the resulting products are resistant to unwanted combustion. In addition to obtaining carbonaceous materials that are resistant to unwanted combustion, the improved carbonaceous resulting materials typically have reduced amounts of by-products contained in the final product compared to the improved carbonaceous materials obtained by other known processes. With reference to Figure 1, there is illustrated a heat exchange apparatus 10, useful for carrying out the process of the present invention. The heat exchanger generally includes a cover 12 having a plurality of tubes 14 contained therein that typically extend along the length of the cover to retain the carbonaceous material. Each tube 14 is provided with an inlet 16 having a valve 18 and an outlet 20 including a valve 22.

Heat exchanger 10 also includes a network for circulating heat exchange medium through the cover including a plurality of channels 24 extending longitudinally within the cover. The network includes an inlet 30 for introducing a heat exchange medium in the cover 12 and an outlet 32 for removing the heat exchange medium from the cover after through circulation. Ideally, the heat exchange medium will be cycled through an oven (not shown) to reheat the heat exchanger medium before reintroduction into the heat exchanger. To carry out the process for treating carbonaceous material wherein the resulting product is resistant to unwanted combustion, using the heat exchanger of Figure 1, the carbonaceous material is loaded in the plurality of tubes 14 through inlets 16 after closing the valves 22 located along the outlets 20. By filling the tubes with the desired amount of the carbonaceous material, the valves 18 located along the inlets 16 close to keep the carbonaceous material in a closed system. As noted, a relatively wide range of carbonaceous materials can be processed in accordance with what is shown in the present invention. Regardless of the type of carbonaceous material that is processed, the carbonaceous material will generally include up to about 30.0 weight percent moisture as received. The present process advantageously converts the moisture contained in the carbonaceous material into steam over heated which in turn is used to displace by-products of the carbonaceous material. A heat exchange medium such as heated gas, molten salt, or preferably an oil, having a temperature of between about 121 to 649 ° C (250 ° to 1200 ° F), and preferably about 399 ° C (750 °) F), is preferably circulated continuously through the cover when introducing the heat exchange medium through the inlet 30. The heat exchange medium travels upwardly through the well 36 and then back through of the plurality of channels 24. The heat exchanger medium is discharged through the outlet 32 to reheat before being reintroduced through the inlet 30. Once the carbonaceous material is preheated, a gaseous mixture that includes a larger proportion of gas inert and a smaller amount of oxygen is injected into the plurality of tubes through inlets 28. The gas mixture, which is preferably injected as a single load with a pressure of approximately 10.55 kg / cm2 man. (150 PSIG) such that the tube or chamber containing the carbonaceous material is filled, serves a dual purpose in that the inert gas forms as a heat transfer carrier upon contact with the inner walls of the tubes 14, absorbing the heat and conducting the heat to the carbonaceous material. Additionally, oxygen assists at least to partially oxidize the carbonaceous material. While the pressure at which the gaseous mixture is introduced into the tubes 14 is generally about 10.55 kg / cm2 man. (150 PSIG), the initial pressure at which the gaseous mixture is introduced, can fluctuate between approximately 3.515 to 17.58 kg / cm2 man. (approximately 50 to 250 PSIG). By introducing the gaseous mixture at pressures on the aforementioned scale, the pressure of the system that occurs as a result of the improvement procedure can amount to approximately 210.9 kg / cm2 man. (3000 ~ PSIG), before completing the improvement procedure. After a predetermined amount of time, ie up to about 30 minutes, the improved carbonaceous material is removed from the heat exchanger. The gas mixture more broadly includes a greater or greater amount of inert gas and a lower amount of oxygen. Preferably, however, the mixture gaseous up to about 20.0% oxygen based on the total volume of the mixture and, more preferably between-about 5.0% to about 15.0% oxygen by volume with the remainder being known inert gas or mixture of inert gases. Preferably, the inert gas compound will include at least 60.0% nitrogen by volume and, more preferably at least 80.0% by volume based on the total inert gas. The improved carbonaceous material - as will be described in greater detail below in general is more resistant to undesirable combustion than improved carbonaceous materials formed by other known processes. In addition, the material includes relatively few by-products and typically has a heating value of approximately 6,687 Kcal / g (12,000 btu / lb). Referring now to Figure 3, an alternate embodiment of a heat exchanger apparatus 110 useful for carrying out the process of the present invention is disclosed as comprising an outer cover 112 having a relatively cylindrical chamber 114 contained as illustrated further. clearly in Figure 4. The chamber 114 generally extends over a significant length of the cover 112 and serves to retain the carbonaceous material during the treatment process. Internally, the camera 114 is provided with or a divider 140 which separates the chamber into a plurality of elongated sections to segregate the carbonaceous material before treatment, each section generally having approximately the same volumetric capacity as any other determined section. The heat exchanger 110 also includes one or more inlets 116 having valves 118 for introducing a charge of carbonaceous material into the sections of various sections of the chamber and one or more outlets 120 having valves 122 for removing the carbonaceous material from the heat exchanger after the treatment. Located proximal to the lower end of the cover 112 above the valve 122 is a valve 126 operable to close the chamber 114 while the carbonaceous material is being treated. Preferably, a cavity 128 is provided between the inner wall of the cover and the outer wall of the chamber within which insulating material 142, as shown in Figure 3, is arranged to retain heat within the heat exchanger. Still further, means for circulating a heat exchange medium (not shown) such as heat gas, molten salt or an oil can be supplied through the space to help reuse the temperature of the carbonaceous materials at approximately 399 ° C (750 ° F) before introducing the gas mixture.

The heat exchanger 110 also includes means for further including a steam injector 130, disposed along the top of the chamber 114 to optionally introduce steam into various sections of the chamber. As illustrated more clearly in Figure 4, the steam injector typically includes an inner ring 132 and an outer ring 134, each of which has a plurality of downwardly extending nozzles 136, for introducing the vapor into the various sections of the steam. the camera in a specific manner of area. The inner and outer rings are joined in at least one conduit 138 in which the vapor is originally introduced. The gas mixture includes a main amount of inert gas and a smaller amount of oxygen, can be introduced into the chamber containing carbonaceous material either through the injector 130 or through a separate inlet 14. To carry out the carbonaceous material treatment method used in the heat exchanger of Figure 4, carbonaceous material is charged into the chamber 114 through the inlets 116 that directly feed the chamber after it ensures that the valve 126 located in the lower end of the chamber is closed. By filling the various sections of the camera with material carbonaceous, the valves 118 located along the inlets 116 are closed to maintain the carbonaceous material in a closed system within the chamber. Subsequently, the steam optionally, but preferably is introduced through the injector 130 which, in turn substantially uniformly distributes the vapor through the various sections of the chamber. By distributing the vapor uniformly through each chamber section, the vapor is allowed to condense relatively uniformly in the carbonaceous material. Ideally, the pressure at which the vapor is maintained in chamber 114 will be in the order of between about 1406 and 210.9 kg / cm2 man. (approximately 2 to 3000 TSIG) depending mainly on heat requirements (Kcal) for any carbonaceous material load. As the vapor condenses and moves downward through the carbonaceous material, the divider 140 serves to ensure that the amount of vapor condensed in any section is approximately equivalent to that contained in another section. As a result of the uniform distribution of steam through the chamber, superior consistency with respect to the treated carbonaceous material can be achieved. Once the steam has been introduced continuously, the gaseous mixture is introduced continuously for a period of up to about thirty minutes at a pressure between about .1406 and 210.9 kg / cm2 man. (approximately 2 to 3000 PSIG) depending substantially on the amount and moisture content of the carbonaceous material as originally charged in the heat exchanger. The gaseous mixture as noted in Figures 5-7 preferably comprises about 90.0% inert gas and 10.0% oxygen wherein the inert gas is preferably nitrogen. After treating the carbonaceous material for a sufficient amount of time, the valves 122 and 126, respectively, are opened to vent any gases such as hydrogen sulfide gas generated as a result of the condensation vapor which reacts with the carbonaceous material. In addition, any by-products in the form of water transporting contaminants are also recovered through the valve 126. After the gases and any other by-products have been discharged, the carbonaceous material can then be recovered through a or more outlets 120 that are provided on the lower end of the heat exchange apparatus. With reference to Figures 5-7, several graphs are provided which illustrate the results of combustion tests conducted in a population of samples of carbonaceous materials with variable moisture contents. By "population", it is understood that the averages of three different compositions having the same moisture content were examined for self-heating temperatures with the average sum that is exhibited after introduction of 100.0% nitrogen and a gas mixture of 90.0 % nitrogen / 10.0% oxygen by volume, respectively. With particular reference to Figure 5, the graph presented illustrates the result of time against the heating temperature for a population of carbonaceous material with low moisture content. As with each of the test samples, the starting temperature of carbonaceous material was 75 ° C and the test apparatus is adjusted to a target temperature of 150 ° C. As illustrated in Figure 5, the samples treated in the presence of N2 (as indicated by the lighter colored line), reach a temperature of about 138 ° C in thirty minutes while the samples treated with a Gas mixture of 90.0% of N2 -10.0% of 02 reaches a temperature of only about 88 ° C (as indicated by the darker line of stroke) in thirty minutes. Moreover, the samples treated with ¿only reach the target temperature of 150 ° C in 47 minutes while the sample treated with 90.0% of N2 - . 0% of 02 took one hour and eight minutes. With reference to Figures 6 and 7, the graphs presented relate to contamination in test samples that have increasingly high moisture contents, whereas in general it can be said that an increased moisture content extends the period of time required to reach the target temperature of 150 ° C for each sample population, even with the increased moisture content, samples treated with the gas mixture of 90.0% N2 / 10.0% of 02 significantly require longer periods of heating than samples treated with 100.0% N2 of the same moisture content, based on the results of self-heating tests, it can be assumed that carbonaceous materials, that is to say improved carbonaceous materials treated with the gaseous mixture including a greater amount of Inert gas and a lower amount of oxygen are more resistant to unwanted combustion than the improved carbonaceous materials. all in the presence of inert gas only. The skilled practitioner will recognize other additional advantages of the invention after having the benefit of studying the specification, drawings and the following claims.

Claims (18)

1. CLAIMS 1. A process for treating wet carbonaceous material to render the material resistant to unwanted combustion, characterized in that it comprises the steps of: preheating the carbonaceous material to convert the moisture contained therein into "superheated steam, and then applying a gaseous mixture to the carbonaceous material preheated by up to about thirty minutes, the gas mixture comprises a major or greater amount of inert gas and a smaller amount of oxygen
2. 2. The method of claim 1, characterized in that the gas mixture includes up to about 20.0% oxygen based on the
3. 3. The method of claim 2, characterized in that the gaseous mixture includes between about 5.0% to about 15.0% oxygen based on the total volume of the gas mixture
4. 4. The method of claim 1, characterized in that the Inert gas includes at least approximately 60.0% nitro based on the volume of the inert gas. The method of claim 4, characterized in that the inert gas includes at least about 90.0% nitrogen based on the volume of the inert gas . The method of claim 1, characterized in that the gas mixture comprises approximately 90.0% nitrogen and approximately 10.0% oxygen 7. The process of claim 1, characterized in that the gas mixture is introduced at a pressure of between approximately 3.515 to 17.58 kg / cm2 man. (approximately 50 to 250 PSIG). 8. The product obtained by the process of claim 1. 9. The product of claim 8, characterized in that the product has an average fuel volume of about 6.687 Kcal / g (12,000 Btu / lb). 10. A process for producing improved carbonaceous materials, wherein the resulting product is resistant to unwanted combustion, characterized in that it comprises the steps of: (a) providing a heat exchanger that includes an outer shell and an inner chamber, an inlet for introducing carbonaceous material in either the outer shell or the inner chamber, an outlet for removing the carbonaceous material from the outer shell or the inner chamber and in at least one inlet for introducing a gaseous mixture comprising a greater amount of inert gas and a smaller amount of oxygen in said outer shell or inner chamber containing carbonaceous material; (b) circulating a heat exchange medium having a temperature of at least 121 ° C (250 ° F) through the outer shell or inner chamber that does not contain the carbonaceous material to effect an increase in the temperature of the carbonaceous material; (c) introducing the gaseous mixture into the heat exchanger portion including the carbonaceous material; and (d) recovering the carbonaceous material through said outlet. The method of claim 10 -, - characterized in that the gas mixture includes up to about 20.0% oxygen based on the total volume. The method of claim 11, characterized in that the gaseous mixture includes between about
5. 5.0% to about 15.0% oxygen based on the total volume of the gas mixture. The method of claim 10, characterized in that the inert gas includes at least about 60.0% nitrogen based on the volume of inert gas. 14. The method of claim 13, characterized in that the inert gas includes at least approximately 90.0% nitrogen and approximately 10.0% oxygen. 15. The process of claim 10, characterized in that the gas mixture comprises approximately 90.0% nitrogen and approximately 10.0% oxygen. 16. The method of claim 10, characterized in that the gas mixture is introduced at a pressure of between about 3.515 to 17.58 kg / cm2 man. (approximately 50 to 250 PSIG). 17. The product obtained by the process of claim 10. 18. The product of claim 17, characterized in that the product has an average fuel volume of about
6. 6.687 Kcal / g (12,000 Btu / lb).