EP0177676A2 - Process carried out by heat recuperation for suspension hydrogenation with integrated gas phase hydrogenation - Google Patents

Abstract

According to the invention, process-relevant process parameters for the sump phase hydrogenation with integrated gas phase hydrogenation with economical heat recovery of the entire system are set in such a way that, despite increasing contamination of the mash heat exchanger and increasing deactivation of the gas phase catalyst, the process-relevant temperatures of the intermediate separator and the gas phase reactor and head cooler after the head cooler before the intermediate separator are set and the waste heat of the bottom phase products is partially recovered by heating the gas phase feedstocks and fed back to the mash heating.

Description

The invention relates to the process setting of the combined bottom phase / gas phase hydrogenation process and the heat recovery of the waste heat usable in the cooling and condensation of the product streams from the bottom phase and gas phase hydrogenation, which is expediently used for heating the two feedstocks of the bottom or gas phase reactor.

With such a heat recovery, the relevant process parameters of the bottom phase hydrogenation with an integrated gas phase reactor must be taken into account.

To increase the economy of a hydrogenation plant, the bottom phase hydrogenation and the gas phase hydrogenation are arranged in a common high-pressure circuit according to the older proposal.

In this case, the solvent is expediently largely drawn off in the bottom of an intermediate separator behind the bottom phase hydrogenation, so that mainly only the net products from the bottom phase hydrogenation (with a light and medium boiling point) are passed over the downstream gas phase reactor. This desired quantity split-up of the bottom phase products in the solvent fraction (liquid) on the one hand and the amount used for the gas phase hydrogenation (vapor) on the other hand takes place via a defined temperature setting in the intermediate separator behind the bottom phase hydrogenation.

This temperature setting is now made more difficult by the fact that the mash heat exchanger for heating the mash is incrusted by indirect heat exchange by means of cooling sump phase gases / vapors as the operating time progresses. As a result of the variable heat transfer performance of the mash heat exchanger, additional cooling is required in order to achieve the required temperature and thus the desired quantity distribution in the intermediate separator. It is also known that the incrustation of the mash preheater increases with increasing mash temperature. Therefore the mash outlet temperature of the mash heat exchanger must be limited.

For the bottom phase hydrogenation with an integrated gas phase reactor, it must also be taken into account that with increasing deactivation of the gas phase catalyst, the temperature of the gas phase feedstocks has to be raised (e.g. from 390 ° C. to 430 ° C.). After all, the system should be able to be started up quickly - if possible without additional heating capacity.

The invention is based, to ensure despite the variable heat output of the mash heat exchanger, an adjustment of the desired temperatures for the mash, the intermediate separator and the gas phase feedstocks and to achieve an economical heat recovery of the hydrogenation products. Furthermore, starting the plant should not require an additional heating furnace for the gas phase hydrogenation.

This object is inventively achieved in that, despite the variable _W of the mash heat exchanger ärmeübertragungsleistung (due to progressive incrustation) and variable gas phase reactor parameters (due to progressive catalyst deactivation) each required process temperatures for the intermediate separator and the gas phase reactor with the aid of a head cooler behind the Sumpfphasehydrierung and an overhead condenser be set before the intermediate separator. The head cooler behind the bottom phase hydrogenation also serves to start the gas phase hydrogenation and to limit the max. Mash outlet temperature of the mash heat exchanger (if necessary, with bypass).

As the running time increases, the temperature of the gas phase feedstocks must gradually be raised. This takes place - without an additional heating furnace - according to the invention in that the temperature level of the head cooler upstream of the intermediate separator is also increased as the mash heat exchanger progresses. At the same time, with increasing reduction in the heat transfer capacity of the mash heat exchanger, the waste heat generated from the bottom phase hydrogenation is transferred to the upstream mash preheating of the bottom phase hydrogenation via the path of gas phase hydrogenation and thus used economically.

The desired temperature in the intermediate separator is set by means of a final cooler, in which steam is expediently generated or hydrogenation gas is preheated.

With the head cooler behind the bottom phase hydrogenation, the temperature level of the bottom phase gases / vapors entering the mash heat exchanger can also be reduced. This reduces the usual fast incrustation of clean pipes of the mash heat exchanger, since the max. occurring mash temperature (at the same averaged mash outlet temperature) is reduced.

The desired temperature of the starting materials for the gas phase hydrogenation can be set by means of a head cooler (incl. Bypass) after the bottom phase hydrogenation.

The bypass around the mash heat exchanger serves to limit the max. Mash outlet temperature of the mash heat exchanger (especially when the heat exchanger tubes are clean).

With the above Processes can thus be used to set all process-relevant temperatures - even if the mash heat exchanger progressively pollutes regardless of time and deactivates the gas phase catalyst.

The start-up process is carried out quickly by heating the gas phase feedstocks using a head cooler behind the bottom phase hydrogenation. The process is explained in more detail using two examples:

Two exemplary embodiments of the invention are shown in the drawing.

1, an operating case after a short running time - d. H. only slight incrustation of the mash heat exchangers 1 and 2 and fresh catalyst of the gas phase reactor 11 - described.

The gaseous and vaporous products from the bottom phase reactor 4 are partially cooled by means of mash heat exchanger 2 by indirect heat exchange, the mash-hydrogenation gas mixture being heated to the starting temperature of the bottom phase hydrogenation of approximately 440 ° C. on the heating side. In order to set the process temperature of approx. 300 ° C. in the intermediate separator 9, the bottom phase products are further cooled by indirect heat exchange in the head cooler 7 and in the final cooler 8. In the intermediate separator 9, the products from the bottom phase hydrogenation are divided into the solvent fraction (liquid) and the feed stream for the gas phase hydrogenation (gases / vapors). The latter is heated in the head cooler 7 and then in the indirect heat exchanger 10 to the gas phase reaction temperature of approximately 390 ° C.

The gas phase products are partially cooled by indirect heat exchange in the mash heat exchanger 1, whereby the mash-hydrogenation gas mixture is preheated. In the indirect heat exchanger 12, the hydrogenation gas is preheated by further cooling of the gas phase products. The entire process is self-sufficient in stationary operation. The mash heating furnace 3 serves only as a start-up furnace.

The waste heat from the heat exchanger 8 is preferably used to generate MD steam or to preheat the hydrogenation gas.

By means of head cooler 6, the gaseous and vaporous products from the hot separator 5 can be cooled somewhat before entering the mash preheater 2. In this way, the incrustation in the mash heat exchanger is reduced.

2, an operating case after a long running time - d. H. strong incrustation of the mash heat exchanger 1 and 2 and deactivated catalyst of the gas phase reactor 11 - described.

As a result of reduced heat transfer capacity of the mash heat exchanger 2, the feed temperature behind the head cooler 7 is increased by approximately 20 ° C. compared to example 1. The gas phase inlet temperature rises to approx. 425 ° C.

Claims (5)

1.) Process for bottom phase hydrogenation with integrated gas phase hydrogenation, with a defined temperature setting in the intermediate separator and in the gas phase reactor with economical heat recovery, characterized in that a head cooler behind the bottom phase hydrogenation and a head cooler in front of the intermediate separator is used for the purpose of defined temperature setting in the intermediate separator and in the gas phase reactor Waste heat from the bottom phase products is used to heat the gas phase feedstocks to almost light-off temperature, the waste heat from the gas phase products at a high temperature level is fed to the mash heating of the bottom phase hydrogenation and the desired mash outlet temperature of the mash heat exchanger through the head cooler behind the bottom phase hydrogenation and a bypass around the mash heat exchanger is set. 2.) Method according to claim 1, characterized in that for the purpose of defined temperature setting (intermediate separator) in a head cooler downstream of the mash heat exchanger, the waste heat of the bottom phase products is partially used for heating the feedstocks of the gas phase hydrogenation, so that the waste heat of the gas phase products with a high temperature level for the mash preheating of the bottom phase hydrogenation can be used economically. As a result, the temperature of the gas phase entry substances is raised at the same time as the mash heat exchangers become dirty and the gas phase catalyst is deactivated. 3.) Method according to claim 1, characterized in that waste heat of the bottom phase products is used for heating feed gas phase hydrogenation by means of a head cooler behind the bottom phase hydrogenation, on the one hand to start the gas phase hydrogenation and on the other hand to set the desired inlet temperature of the gas phase feed materials. 4.) Method according to claim 1, characterized in that a head cooler behind the bottom phase hydrogenation and a bypass around the mash preheater are used to adjust the mash outlet temperature of the mash heat exchanger. 5.) Method according to claim 1, characterized in that a final cooler is used in order to set the defined intermediate separator temperature, in which steam is generated or hydrogenating gas is preheated.

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