FR2461742A1 - PROCESS FOR THE PREPARATION OF COKEFIER CHARCOAL - Google Patents

Abstract

THIS PROCESS ALLOWS VERY SUBSTANTIALLY TO INCREASE THE COKE YIELD OF COALS RICH IN VOLATIVE COMPONENTS, BY DEHYDROGENING THEM WITHOUT COMPROMISING THEIR AGGLOMERABILITY AND BY VOLATIVATING VERY LITTLE ORGANIC MATTER. THE DEHYDROGENING AGENT USED IS SULFUR WHICH IS BROUGHT IN VERY DIVIDED FORM (FOR EXAMPLE IN THE FORM OF SULFUR VAPOR) TO CARBON ADVANTAGEOUSLY PREHEATED AT 150-250C. THE HYDROGEN SULPHIDE PRODUCED IS CAPTURED AND DISSOCIATED TO GIVE BACK SULFUR, WHICH IS RECYCLED. APPLICATION: COAL TREATMENT, COKEFACTION.

Description

246 1742

  The present invention relates to a process for the preparation of coal for coking, wherein the fractionated or fine-grained coal is preheated to a temperature above 1000C, preferably above 1400C, and treated in a reaction chamber. with a dehydrogenating agent. The word "coal" here must be understood in a very general sense and also refers to mixtures of coal or coal and all

  Coking bodies, alone or in mixture.

  The dehydrogenating agent used in the processes known in the art is oxygen, which is not particularly disadvantageous. Even with care, dehydrogenation with oxygen lowers the aggomeration characteristics of the treated coal. . In their technical, physical and chemical aspects, the technological background of the invention and the prior art lend themselves to the following comments: When producing coke at high temperature, the coke yield depends essentially on the components volatiles of coal used. The "volatile components" are those components of the dry coals that are released during a laboratory test with heating at the shelter

  air, at a temperature of the order of 900 to 950 C.

  Volatile components had a higher value than coke prior to the use of natural gas. The depreciation of the volatile components of coal, begun about twenty years ago, is today such that these components have only one value - reduced to the unit of heat - of about 60% of that of the coke. Such conditions have led to a steady increase

  coke yield to the detriment of volatile products.

  This has been done through the use of increasingly carbon-intensive mixtures of coal and carbon elements (such as coke breeze and petroleum coke). However, the possibilities of using such products are limited by the need to maintain the quality of the coke from the point of view of crush resistance and abrasion. Otherwise,

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  over the past two years, the supply of volatile charcoal with a high volatile content and low-volatile lean charcoal has declined while the supply of volatile coals is increasing, so that at the end of the The decrease in the proportion of volatile components has been limited not only by the amount of coke to be obtained but also by the nature of the raw materials used. This evolution has led to the permanent adoption of certain provisions in the processes implemented, which can be summarized by the keywords "preheating", "hot" and "molded coke". preheating the coal mixture to about 2000C and retaining the chamber oven as

  coking device, have retained some attention.

  None of these provisions lead to an increase in the coke yield. On the contrary, in some variants, this efficiency decreases significantly. The advantage of these provisions lies solely in the possibility of converting less-skilled coals into coke, which must, however, be subjected to very special preliminary treatment. If one examines the chemical constitution of the coking materials present in the coal, one finds at the beginning condensed systems with stones with side catches of different lengths. It can be observed that, as regards the thermal decomposition of this type of hydrocarbon during coking, it is firstly the lateral chains of the cyclic system, then the hydrogen,

  which, during the rise in temperature, are eliminated.

  If one wishes to avoid the fission of the lateral chalnes during

  heating, and therefore the formation of hydro-

  carbides that will then appear in the components

  volatile, there must be - before thermal stress

  a reaction eliminating hydrogen and thereby lowering the "volatility" of the compound. It is in this context that the arrangements are made, the coal being treated with oxygen at temperatures above 1500C. With

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  such treatment, one can observe the formation of water as well as monoxide and carbon dioxide. There is then a serious disadvantage, namely a sharp decrease, or even

  even a total disappearance, characteristics of

  meability of coals, attributable not only to the destruction of organic substances due to oxidation but also to the implantation of oxygen in the "coal molecule",

  hence non-fusible polar groups result.

  On the other hand, the purpose of the invention is to dehydrate

  generate the "coal molecule" before the actual coking, so that the coal's melting characteristics are compromised as little as possible, and so that the transformations occurring during the

  coking takes place with as little volatility as possible.

organic matter.

  To achieve this object, the invention recommends, starting from the known provisions, to use sulfur as a dehydrogenating agent and extract the hydrogen sulfide released from the reaction chamber. In principle, the sulfur can be supplied in any form, powder, vapor or gas, and be supplied before, during or after preheating. In a preferred embodiment of the invention, it is Finely divided state that sulfur is associated with coal. In the simplest case, this is done by bringing into contact with the sulfur sulfur coal, optionally accompanied by an inert gas. The coal may be at rest and constitute, so to speak, a filter bed traversed by the sulfur vapor and / or by a sulfur-carrying gas stream.

fine powder.

  In a preferred embodiment of the method

  according to the invention, the coal is put into a state of fluidisa-

  and the fluidized bed thus formed is traversed by sulfur in the vapor phase and / or by a gas bearing sulfur in fine powder. The grain size of the coal should preferably be less than 5 mm. In order to conduct the dehydrogenation with precision, the invention recommends that the coal be first preheated to a temperature of 2500C, and that this preheated coal be treated with sulfur, preferably with sulfur in the vapor phase at a temperature greater than 444,60C. The dosage is based on the degree of dehydrogenation desired. Satisfactory results have been obtained by bringing to coal a quantity of sulfur which, relative to coal, is 8 to 10% for 0.5% of hydrogen of the coal. The hydrogen sulphide extracted can then be decomposed to give sulfur in fine powder which is then reusable for

dehydrogenation.

  According to the invention, elemental sulfur is added

  with charcoal - or with mixtures of coals - with coking.

  Such a process has hitherto been unthinkable for the specialists because they considered that an increase of sulfur in coking coal should lead to a coke rich in sulfur. In fact, this could be the case under the old coking techniques, in

  which coal entering the kilns is wet.

  On the other hand, the current preheating techniques allow a solution according to the invention such that the coal or the mixture of coking coals is mixed, partially or completely, with elemental sulfur,

  before, during or after its preheating to 150 to 2500C.

  In the process according to the invention, the sulfur reacts with the hydrogen of the hydrocarbons of the coal, which gives the hydrogen sulphide and liberates valences of the carbon thus allowing the formation of other compounds which, surprisingly, have for the most part a

aromatic behavior.

  The consequences of dehydrogenation have very positive effects on the coke yield, which can be recognized by comparing the volatile components, the hydrogen content and the coke yield (see pages

  61 and 206 of the 1969 edition of the Handbook "Ruhrkohlen

  Handbuchn = Handbook of Ruhr coal). A decrease of about 0.5% in the hydrogen content lowers the volatile components of the coal by about%, for example from 37 to 27%. This results in an increase of about 10% in the coke yield, which is considerable economically. In addition to the increase in the coke yield inherent in the dehydrogenation of a part of the coal, a sufficient agglomerability is obtained which can moreover be influenced by the duration of the treatment since the sulfur - unlike the oxygen - can not penetrate, deeply, into the grain

  coal, and therefore can not change the characteristics of

  of this one. In addition, the invention takes advantage of the fact that the preheating of the char-bon is increasingly required in coking plants, so that it is available - apart from the place where the actual coking takes place - temperatures between 150 and 2500C. However, it is precisely the temperature range in which the elemental sulfur dehydrogenates the hydrocarbons of the coal, as described. The supply of sulfur to coal can be done in various ways, but must be done by ensuring the fineness of its distribution must be as good as possible. This means that the regularity of the dehydrogenation is optimal when the sulfur is used in vapor form or in a solvent. It is furthermore advantageous that the sulfur is brought to the already dry charcoal and

  hot, so that the reaction can occur without delay.

  The amount of sulfur to be supplied depends on the degree of dehydrogenation, which is related to the decomposition of

  volatile components sought. To remove 0.5% of hydro-

  gene of a very volatile coal, which is in most cases sufficient to arrive in the field of coals

  fat, it is necessary to dissociate 5 kg of H2 per 1000 kg of coal.

  5 kg of H correspond to 2.5 kmole of H2 removable by

  2.5 x 32 kg S, or 80 kg S, assuming a trans-

  complete formation according to the reaction of equation H2 + S - H2S. This amount of sulfur may seem specifically very high, but this is much less serious than it seems at first sight if, according to a preferred embodiment of the invention, the hydrogen sulphide formed is taken up to extract the sulfur, for example in a Claus oven, so that one then establishes a

  "Suffren cycle and only replace losses.

  These losses are in the coal and are released during coking. They can be removed by the usual washing of the coke oven gases. The speed of the dehydrogenation znection depends essentially on the temperature and degree of milling of the coal when sulfur and coal meet. This implies that the most advantageous would always be to dehydrogenate by operating in the high temperature range indicated. At a temperature above its boiling point (444.60C), the sulfur in vapor is so reactive that it forms hydrogen sulphide from its first contact with the coal. Local sulfur excesses can condense on coal, which although preheated, is relatively cold compared to sulfur vapor, but these excesses still react sufficiently quickly. It can be said that with the dehydrogenation according to the invention, the coal receives, so to speak, a specific slimming agent. Thus, in addition to a decrease in the volatile components and the resulting increase in coke yield, the most intimate combination of slimming agent and charcoal is obtained. As a result, it is also possible to produce, without additions, coke in large pieces resistant, from

  of coals with a high content of volatile components.

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Claims (8)

  1. A process for the preparation of coal for coking purposes, in which the fractionated or fine-grained coal is preheated to a temperature above 1000.degree. C., advantageously above 1400.degree. C., and treated in a reaction chamber with a dehydrogenating agent. this process being characterized by the fact that the sulfur is used as a dehydrogenating agent and that the hydrogen sulphide produced is discharged out of the chamber of reaction.   2. A process according to claim 1, characterized in that it is in the finely divided state that the sulfur is added to coal.   3. A process according to any of the claims   1 or 2, characterized in that the sulfur is added to the coal while being in the vapor state and   possibly being accompanied by an inert gas.   4. Process according to any one of the   cations 1 to 3, characterized in that the coal is placed in the fluidization state, and the fluidized bed constituted is traversed by sulfur in the vapor state   and / or by a carrier gas loaded with sulfur in fine powder.   5. Process according to any one of the   1 to 4, characterized in that the coal is first preheated to a temperature of 140 to 2500C, and   that preheated coal is treated with sulfur.   6. A process according to claim 5, characterized in that the preheated coal is treated with   sulfur in steam at a temperature above 444.60C.   7. A process according to any of the claims   1 to 6, characterized in that, relative to coal, the amount of sulfur fed to the coal is   8 to 10% for 0.5% hydrogen of the coal.   8. Process according to any one of the   cations 1 to 7, characterized by the fact that   sulfur from the hydrogen sulphide from the reaction chamber and that the sulfur thus recovered is   reused for dehydrogenation.