DE1442773A1 - Method and device for temperature control in reaction ovens by means of superheated steam - Google Patents

Description

PROCESS AND DEVICE FOR TEMPERATURE CONTROL IN REACTION FURNACES WITH SUPERHEATED STEAM.

When heat is to be removed from reaction furnaces in which exothermic chemical reactions take place, and when in particular the reaction between gases takes place with the help of fixed bed catalysts, the catalyst is generally divided into different layers. From the reaction medium between each layer the excess heat is dissipated so that the temperature assumes values that most suitable for a high reaction rate and a good synthesis yield are.

Various methods have been used for this purpose; either the heat was transferred to the inflowing medium through heat exchangers on the one side of the medium to be catalyzed and on the other side of that already converted medium were flowed through, or by cooling liquids dissipated by running heat exchangers.

For example, if sulfuric acid is made from sulfur, can be the one intended for dilution (for reasons of equilibrium) of the feed gas Dry air can serve as a coolant. There is an interest in this in the reaction To recover heat generated can be a boiling liquid, in general Water, serve as a means of removing heat, provided that the reaction temperature enough high is a steam of sufficiently high pressure for ordinary applications to obtain. However, this method causes some difficulties in temperature control of the reaction medium.

Because of the constant boiling temperature of the coolant that comes from for obvious reasons the pressure has to be kept constant, the temperature can through Changing the amount of liquid flowing into the cooler by means of a circulatory system can be set.

In this case, however, there is a mixer for the re-inflow of the medium in the reaction furnace necessary to maintain the uniform temperature of the im Recycle and the fraction flowing through the cooler. Other Systems, however, all of which are somewhat complex, can also are used, the present invention is a method for removal excess heat using superheated steam.

According to the present invention, the entire medium is fed to coolers, where on the other hand water vapor or another steam with a pressure circulates, which corresponds to a boiling temperature lower than that at any other of the reaction furnace is present. The steam flowing in is preferably saturated. This steam is superheated at the expense of the heat of reaction after flowing through it for a long time In the exchanger, the steam is fed to a superheated steam cooler, where it is mixed with water is mixed, its evaporation reduces the degree of overheating.

The steam can preferably be in countercurrent with the reaction medium by various exchangers arranged between the layers to be catalyzed stream.

There can even be several layers between two consecutive layers Exchangers are arranged in parallel, each of which is subdivided tube bundle or Has spirals, between which the superheaters are arranged.

The superheaters between the different exchangers are identical arranged. The number and location of the superheated steam cooler is such that the cheapest Reaction temperature is obtained in the reaction medium.

If several exchangers are arranged in parallel, it is advisable to use the to collect steam leaving the corresponding sections and a single one Feed steam boiler. After dissipating the superheat, the steam is in front of the Inflow divided into the following section of the parallel exchanger.

The flow rate of the water in the various hot coolers is controlled manually or automatically so that the steam is at the appropriate temperature which is favorable to the medium. The superheat of the steam at the outlet of the The last exchanger can be used for other purposes on a correspondingly cheap Value can be reduced.

The advantages of the present invention are numerous. The reaction would be is used to generate superheated steam, there the whole introduced water or the liquid evaporates and at the outlet as superheated Steam is obtained. The adjustment of the different layers of the furnace takes place in a substantially independent manner; this is different from the procedures in which exchangers are used between the inflowing and outflowing medium, whereby the heat carried off by the outflowing medium is returned to the interior of the Reaction furnace is transferred. On the other hand, temperature control is very simple, since it is enough to change the flow rate in the water superheaters and this can easily be done automatically.

The reacting medium maintains a uniform temperature in the all of the material flowing completely through the exchanger without any part of it must flow in countercurrent.

Regarding temperature control by means of evaporating liquids If the exchanger is destroyed, there is also the advantage that no catalyst will flood this flooding becomes more uncomfortable than the influx of overheated sound Is steam.

Thanks to their low weight and space requirements, the exchangers can which is sufficient for this process, directly at the reaction furnace and even be arranged tarin sumal no countercurrent system is available.

The method is particularly suitable for controlling reaction furnaces, If the medium to be catalysed is gaseous, the exetherme reaction at kohen is used Temperatures, such as in contact furnaces for production of sulfuric acid.

Saturated recuperator steam is generally present throughout the facility available. However, this external source can be dispensed with, if this is desired, if the return of some escaping steam is possible, for example by means of a steam jet pump, in which the superheated steam with the supplied water is mixed so that it is essentially saturated again in the first exchanger occurs, An embodiment of the apparatus as used in accordance with the invention Temperature control can be used is in the form of an example below explained. Of course, this arrangement does not limit the inventive concept, since other embodiments are also possible. The attached drawing relates only on one case as an example where sulfur trioxide is a mixture is produced by sulfur dioxide and air.

11 it is assumed that the temperature is sufficient to allow the mixture to ignite. The mixture is fed into the reaction furnace above and afterwards The gas flows through three catalyst layers C1, C2, C3 at the bottom however, after the layer C1 an exchanger S is fed, where SB before reaching the ßohioht C2 is subject to cooling. After layer 2, the gas flows into one Exchanger R, from which it is through di. last layer C3 flows and finally that Vessel leaves to be subjected to further process steps.

The exchangers R and 5 are tube systems in which the steam is below Pressure is directed. It is optionally possible to measure the heat content of the exiting The gas is used to generate saturated steam for use as a coolant in the exchangers to obtain.

The saturated vapor from E enters a first tube bundle R1 of the Exchanger R, where it is overheated by the heat from the gas. When leaving The steam flows from R into the ice steam cooler D1, into which water coming from M is injected whose flow rate is controlled by a valve V1 (automatically or manually regulated) is set.

The amount of superheat dissipation is based on the gas temperature changed how it is checked at the exchanger outlet. After the superheated steam cooler D1 occurs the steam re-enters the exchanger and flows through the tube bundle R2; then the superheat is reduced again.

In the accompanying drawing, two tube bundles R1, R2 are provided, whereas three (Sts 52 and S3) can be seen in FIG. Of course, the number of Tube bundle and exchanger changed according to the requirements of the process will.

The different. Tube bundles were lined up along the steam path tied together; she. can of course also be arranged in parallel or in a combined manner will. At the outlet of the tube bundle S3, the superheated steam flows through the superheated steam cooler D5 where the last overheating according to the subsequent requirements at the steam is stopped, and leaves the system at U. The amount of exiting at U. superheated steam is of course greater than that entering at E.

The catalyst layers and consequently also the superheaters and superheated steam coolers can of course be different from the number shown in the drawing, the represents only an example and does not limit the invention.

Example In a plant for the production of 100 t / day sulfuric acid the system described in the accompanying drawing is used. The flow rates and temperatures are listed in Table 1 and should be compared with the corresponding Values from Table 2 are compared, referring to a conventional method draws in, after which the heat of reaction has been dissipated by introducing it into an accumulator, in which on the other hand the cold dry air dilutes the out of the Oven kills reaction gases before they get into the reaction chamber As a comparison of the tables shows, the amount escaping from U is superheated Vapor according to the present invention is substantially greater than that entering at E. (Steam generation); in contrast, the conventional method uses heat carried the lift that enters the reaction space together with the gas; as soon as a stronger cooling of the incoming dases is necessary, got to the Kesselflaohe are enlarged. Even if you have the surface enlargement not taken into account, the exchanger surface is much larger than that according to of the present invention.

TABLE 1 Control by means of superheated steam Gas steam surface m2 Quantity temperature ° C Quantity temperature ° C Nm3 / h inlet outlet Nme / h inlet outlet R1 13.450 445 420 2.440 209 290 43 R2 13.450 470 445 2.570 230 308 S1 13.550 490 440 2.780 230 283 S2 13.550 540 490 3.180 230 370 110 S3 13.550 590 540 3.730 242 380 TABLE 2 Control by means of air Gas steam surface m2 Quantity temperature ° C Quantity temperature ° C Nm3 / h inlet outlet Nm3 / h inlet outlet 1st exchanger 13.450 512 420 7.000 65 254 120 2nd exchanger 13,550 590 480 7,000 254 470 300

Claims (4)

Claims t Vosfahren for temperature control in reaction furnaces for exothermic reactions by means of heat exchange between the reaction medium and the cooling liquid, characterized in that the exchange between the entire reaction medium and a steam (water vapor or other steam) takes place at a pressure, the one 8 corresponds to the boiling temperature, which is below that temperature, which in any Point of the reaction furnace. 2. The method according to claim 1, characterized in that the inflowing Steam is saturated. 3. Apparatus for performing the method according to claim 1 or 2, characterized in that exchangers (R, B) for the heat exchange between Reaction medium and the cooling steam in the form of tube systems (R1, R2; provided are, with superheated steam cooler (D1, D2 .......;) between the tubes for discharging the Superheat of the cooling steam are included, which is generally with water (M) an adjustable flow rate (V1 v20 ....) is fed, and where the exchangers and superheated steam coolers either inside with respect to the reaction furnace or provided outside. 4. Apparatus according to claim 3, characterized in that guide surfaces are arranged between the successive reaction units that the Pass the reaction medium through the exchangers (R, S).