US2120296A - Heating up carbonaceous material - Google Patents

Description

June 14, 1938. M. PIER E1 AL 2,120,296

HEATING UPVICARBONACEOUS MATERIAL Filed Nov. 27, 1955 0: To 25R HOUR 1916' rnassoaa STEAM HEAT exam/men REA er/o/v V5335.

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our/lunar mvp 1-5 2 Patented June 14, 1938 UNITEDSTATES PATENT OFFICE.

Hanna Schappert,

Ludwigshateu on the- Rhine, Germany, assignors to I'. G. Farbeniudustrie Aktiengesellschatt, Frankiort-on-thev Main, Germany Application November 27, 1935, Serial No. 51,826 In Germany December 1, 1934 Claims.

The present invention relates to improvements in the heating up of carbonaceous materials.

The drawing is diagrammatic in form and illustrates a method by which the present invention may be carried into practice.

The destructive hydrogenation of carbonaceous.

materials of the nature of coals, tars, mineral oils and the like usually proceeds with considerable evolution of heat. From a certain size of plant upwards, the heat set free is greater than the heat losses, the latter being composed of two parts namely radiation losseswhich are dependent on the surface area of the apparatus and operating temperature. The time necessary for this purpose depends on the mass of iron-tobe brought to operating temperatures, the strength of the available source of energy and the radiation of the preheating system.

In the priorheating arrangements, the neces sary heat has usually been supplied to the initial materials in tubular preheating apparatus which is heated by gas or fed from a source of electric current.

The drawbacks of such a heating up are as follows:

(1) The naturally high speed of the initial material in the preheater which is necessary for the transference of heat causes a loss in pressure which must be continuously obviated by the gas circulation pump. If the heating up of the initial materials takes places in a preheater in front of the reaction chamber, it is impossible to avoid the pressure prevailing in the reaction chamber from being lower than the pressure set up by the pump to an extent corresponding to the resistance of this preheater.

(2) The preheater is very expensive in operation because in the case of gas-heated preheaters the degree of thermal efficiency is usually very bad by reason of the high temperatures (as for example more than 400 C.) and electrical energy on the other hand is not cheap.

Very frequently, especially when the reaction the temperature of the radiating surfaces, and losses in the heat-exchanger employed in the case, the whole plant must first be brought to the itself proceeds with great evolution of heat, the preheater has only to serve the single purpose of bringing the whole system at the beginning of the When operation to the necessary temperature. the reaction has been initiated, the preheater then usually is idle since the heat regeneration by means of the heat-exchanger brings the initial materials to a sufliciently high temperature but the preheater still consumes, heat and tails in pressure. If, by means of a by-pass, the preheater is short-circuited, there is then the danger that the residues of products remaining in the tubes will coke and render the preheater useless.

(3) Most preheaters, whether heated by gas, electricity or otherwise, transfer the heat to be supplied through a relatively small surface for the reasons already mentioned. The outer film oi the initial materials which transfers the heat to the inner parts of the materials is therefore usually-at a higher temperature than is desirable for the initial materials, and even if overheating can be reduced by employing special precautions,

such as regulating the supply of heat, ribbed tubes of different circuits, there still remain the said drawbacks of pressure difference and bad degree of efilciency. Even by heating one of the initial materials, as for example the gas, and then mix-. ing it with the colder initial material in order to produce the desired reaction temperature, a temporary marked exceeding of the initial reaction temperature desired to be set up cannot always be avoided in practice because the equalization of the mixture proceeds in wave-like fluctuations in temperature. This is also true in the casewhen the necessary heat is supplied by an additional exothermic reaction, as for example of the reaction CO+3H2=CH4+H2O.

We have now found that thesaid drawbacks are avoided by directly or indirectly supplying to the still hot products having left thereaction chamber further heat, by means of a medium heated outside the system, advantageously by means of a vaporized normally liquid medium having a high heat of vaporization, preferably a heat of vaporization of at least 500 kilocalories per kilogram the initial materials flowing towards the reaction chamber being heated by means of the products thus heated. The said heating medium cannot only be brought into indirect heat exchange relation with the reaction products as soon as the latter leave the reaction chamber but also some time after their issue from this chamber provided the said reaction products are still in heat-exchange relation with the initial materials to be heated. e

when the supply of heat is effected by means of a liquid, the latter'is preferably heated outside the system by any of theknown methods in a separate heating device, preferably a heating device simultaneously used for several systems. The burden ofthe resistance of this heating device does not fall on the system and moreover it is very. small. Furthermore, only a small expenditureof energy is necessary'i'or heating, es-

pecially as compared with a. preheater arranged in circulation.

The heating device for the heating mediumworks at a very high degree of eiflciency because its inlet temperature is low. Since the heat-supplied, for example when using water as the heating medium, is utilized for the greater part as heat of vaporization, the heat of condensation supplied in the regeneration increases the degree of eiliciency of the latter very considerably.

or Not only water, but also other media may be employed as heating media, as for example oils or gases. It is especially advantageous, however, to employ condensing steam because it has very good heat-transferring properties and the heat g5 transit value of the regeneration surfaces is increased to no small extent. Care should always be taken not to supply to the eiiluent substances so much heat that iniurious overheating takes place.

so The thermal reaction may be initialed by heating the first charge of initial material by preheaters preheated with gas. The further charges of initial material are then heated according to the present invention.

The process according to this invention allows of an easy adjustment of the supply of heat by regulation of the amount or temperature of the heating medium or both. It offers further greater advantages, for example, when working in the socalled sump phase, that is the phase in which the initial materials are present either as a liquid or as a pasty dispersion of solids in liquids. for example in the destructive hydrogenation of coals even when in the separator directly attached to the reaction chamber large amounts of liquid products are obtained the heat content of which is lost as far as the regeneration is concerned because these products are usually further worked up at the temperature which they so have in the separator, since in such case the reproducts passingthrough the second heat regenerator. In this case the heating medium need not be brought to a temperature as; high as is necessary when bringing -it into heat exchange with the products directly after their issue from the reaction space and nevertheless the necessary amount of heat is imparted to the products.

' The said kind of preheating may also be used with special advantagefor setting apparatus in operation. The initial material is thereby preheated in a cautious manner by heat exchange with the material leaving the reaction chamber and which latter material at first is still cold, the said chamber thus being slowly heated up by means of a medium outside the system. It hasthe advantage that especially with an exothermic course of the reaction the supply of heat can be readily interrupted when the operation requires 1 when working with the usual preheatcrs this is practically impossible in a satisfactory manner as already pointed out. p

Example 20 tons per hour of a tar are pumped together with 30,000 cubic meters per hour of hydrogen through two heat regenerators arranged in series and are then introduced while at the reaction temperature of 425 G. into the first of two reaction vessels; they leave the second vessel while at 450 C. From the adjacent separator two tons per hour of high boiling constituents are removed. To the mixture of vapors and gases leaving the separator 1 ton of steam superheated to 450 C. and maintained under superatmospheric pressure is then supplied before its entrance into the heat regenerators, the initial materials being in heatexchange with the said mixture of vapors and gases thus being heated to 425 C. before entering the first reaction vessel. Without the said operation a preheater would be necessary for the complete heating up to the reaction temperature which supplies the still lacking heat amounting to about 600,000 kilocalories per hour.

.The process according to the present invention is not only applicable to all varieties of destructive hydrogenation as for example aromatization, hydrofining or the usual splitting hydrogenation under pressure; but also with other heat treatments of carbonaceous materials in the presence or absence of hydrogen or steam or other gases, such as cracking or non-splitting hydrogenation, the necessary heat may be supplied with are shown in series. I'hese vessels are adapted to withstand the high pressure and temperature requiredfor the reaction and the reacted materials flow through a valved line ll into a separator II, from which any unvaporized material may be removedby a pipe II. The vaporized materials pass through a pipe it. If desired, a portion of the material from the second reaction vessel 8 may be passed directly into the pipe I! by a valved pipe ll. Steam at high temperature and pressure is also passed into the line II by means of a pipe I! and the mixture of the reaction product and steam then passes through the heat exchangers 5 and 4, in the order mentioned, by the pipes i6 and I1 and issues from the pipe i8 into a separator is. The liquefied products are taken from the separator by a pipe 20 and gas by a pipe 2|.

What we claim is:-

1. In the thermal conversion of distillable carbonaceous materials in one or more reactors the step of heating up the initial carbonaceous mate rials to the temperature requiredfor the sat? thermal conversion by indirect heat exchange relation with at least part of a prior charge of still hot reactants to which after issue from the last reactor a higher temperature has been imparted than they had in the said conversion, by a medium which has been heated by a foreign source of heat to a higher temperature than these reactants have at the place at which the said medium is supplied.

2. In the process as claimed in claim 1 supplying to the still hot distillable carbonaceous materials having undergone the thermal conversion a vaporized normally liquid medium having a high heat of vaporization.

3. In the process as claimed in claim 1 supplythermal conversion.

4. In the process asclaimed in claim I adjusting the temperature desired for the thermal conversion by supplying regulated amounts of heating medium and regulating the temperature of this heating medium.

In the process as claimed in claim 1 heating up the initial carbonaceous materials by indirect heat exchange relation with the constituents of the still hot reactants issuing as vapors from the last reactor and to which a higher temperature than they have in the conversion has been imparted by a foreign sourceof heat.

MATHIAS PIER. EUGEN ANTI-IE8. HANNS SCHAPPERT.

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