DE3036259A1 - Disposal of phenol(s)-contg. waste water from coal hydrogenation - by feeding to gasification plants generating the hydrogen needed - Google Patents

Abstract

Waste water, contg. tar acids, from a coal hydrogenation process, is disposed of by using it in one or more gasification plants associated with the process. These plants gasify coal or distn. residues to make the H2 needed. The waste waters from gasification need merely to be neutralised before discharging to lakes or rivers. The capital and running costs of disposal are small, since the waste water merely replaces fresh water in gasification.

Description

Process for the elimination of tar acidic

Process wastewater The invention relates to a method for disposal Process wastewater containing tar acid from the hydrogenation of coal.

Under the coal hydrogenation is usually the addition of molecular Understood hydrogen on coal under pressure and under cleavage conditions, wherein generally catalysts are present.

When the coal is hydrogenated, some of that is contained in the coal Oxygen to tar acids, i.e. converted to phenols, cresols and xylenols. In the separators which are split after the hydrogenation reactors accumulate process wastewater. the very water-soluble phenols, crssols and xylenols go into these from Uuench- and reaction water over existing aqueous phase.

Another amount of tar-acid-containing wastewater falls under Addition of steam (stripping steam) carried out atmospheric distillation of the coal oil obtained in the hydrogenation.

The process wastewater can because of the tar acid and also as a result harmful hydrogen sulfide and ammonia content for environmental reasons are not simply released into public waters.

Therefore, it was previously necessary to separate the process wastewater of hydrogen sulfide and ammonia from a phenol recovery plant with a downstream To supply wastewater treatment. Only the wastewater treated in this way can with a small Residual content of phenols can be derived. This type of treatment of process wastewater requires a considerable expenditure on equipment and energy, which is all the greater the greater the amount of water to be cleaned.

The invention is therefore based on the task of processing the To improve process wastewater. According to the invention this is achieved in that the process wastewater is fed to a carbon gasification process. In carbon gasification is water or steam process agent. According to the invention, the wastewater added to the process agent water or steam and / or as a substitute for fresh water and live steam used. This is especially beneficial when the carbon in the form of a coal liquid suspension (coal / water slurry) or hydrogenation residues is pumped into the gasification reactor.

The carbon gasification plant that removes the process wastewater from the hydrogenation are supplied, is preferably in association with the hydrogenation plant in which the Process wastewater has accumulated. In this network, the gasification plant delivers the hydrogen required for hydrogenation. Below is an example of the The invention is explained with the aid of a process diagram according to FIG.

In the exemplary embodiment, gas flame coal from the Ruhr area is used for a coal liquefaction plant with a throughput of 5,000 t (waf) coal / day.

In a first process step, the coal is processed, i.e. it is dried and ground.

In a second process step 1 mashed. For mashing1 the coal, oil is returned from the hydrogenation process, i.e. it is mashed with circulating oil. The mashing process 1 added oil is called grind oil. The grind oil serves as a solvent, in which it is able to deliver singly bound hydrogen to the coal. That leads to incipient liquefaction, also known as anhydration or swelling can be. The solvent also facilitates the actual hydrogenation2 of the Coal, which is made with the addition of free hydrogen. This hydrogen comes from from a gasification plant, which will be explained below 2. The hydrogenation stage various separators are arranged downstream. In the separators the gaseous, liquid and solid-containing phases separated from each other.

A first deposition process 3 takes place by cooling and quenching with fresh water instead. The gaseous phase separates and it separates liquid products from the gas. Furthermore, they run out during hydrogenation2 The tar acids formed by the oxygen contained in the coal are partly transferred here to the aqueous phase consisting of quench and reaction water.

In addition to the aqueous phase, there are 3 liquid products Gas and solids-containing residue. The resulting gas is partly used as cycle gas returned to the hydrogenation 2. The remaining part of the resulting gas becomes one Gas scrubbing 4 supplied, from which it enters a low-temperature decomposition 5. In This process stage produces heating gas, SNG, LPG and H2. The hydrogen will also fed to the hydrogenation 2.

The liquid products resulting from the deposition 3 become atmospheric distilled with the addition of stripping steam. In the atmospheric distillation 6 During the cooling process, a water phase is created that contains tar acids. Main product the atmospheric distillation 6, however, are light oil and medium oil in one Process step 7 are subjected to a hydrogenating stabilization. Next to these products produce gas, which is passed into the low-temperature decomposition via the gas scrubber 4 5 arrives. The gas originating from the distillation 6 is dabsi in the same way how the gas originating from the deposition 3 is worked up.

Finally, there is still solvent for mashing 1 in the atmospheric distillation 6.

The solids-containing residue obtained in quenching 3 is topped 8 in a vacuum distillation.

On the one hand, this creates solvents for the mashing 1 and on the other hand a vacuum residue.

The vacuum residue from the distillation 8 is in a residue gasification 9 gasified according to the Texaco gasification process. The high-melting residue can Contains up to 50% solids. with the residue gasification 9 is according to the invention in contrast to wastewater treatment that would otherwise be considered by means of ammonia production 10 with downstream phenol production 11, biological processing and discharge In public waters at the same time a special waste application shown in dashed lines tied together. The use of wastewater in gasification serves to remove tar acid, without the considerable equipment and cnargetiscilem effort that would otherwise be required Reiniyunastufa.

According to the invention, those in the deposition and quenching 3 and process wastewater accumulating in the distillation 6, optionally from the residue gasification 9 and / or a coal gasification 12 with upstream suspension production 13 fed. The coal gasification 12 is used to generate the for the hydrogenation 2 and the stabilizing hydrogenation 7 required hydrogen, which in addition to the Hydrogen from the cycle gas of the low-temperature decomposition and residue gasification possibly required. is. The gasification 12 is like the residue gasification 9 one Gasification according to the Texaco process. It is an autothermal gasification negative pressure. In this gasification, pre-shredded material with a grain size mixed with water below 0.1 mm to form a stable, pumpable pulp, which is approx. 55 - Contains 60% solids.

This suspension is fed to a burner at the top of the reactor and vertically in downflow in the reactor under increased pressure in the presence of Gasified steam and supply of oxygen.

The reaction with oxygen results in temperatures of approx. 1400 OC. the Ash is a liquid. Synthesis gas is produced, which when carbon is converted of approx. 95% has approximately the following gas analysis: C ° 2 15 - 20% £ 0 45 - 55% H 2 30 - 40% CH4 approx. 1 The Texaco process is essentially due to the generation of the pumpable Slurry marked, which an entry of the coal or hydrogenation residues with the help one pump allowed.

Fresh water would be required for the production of the slurry, that according to the invention through the wastewater from the deposition and the squeezing 3 and the distillation 6 is replaced. The fresh water supply to be replaced by the waste water is shown in phantom and corresponds to the suspension production 13 the steam supply in the case of residue gasification, also shown in dash-dotted lines 9. The wastewater feed for residue gasification 9 and for the production of the suspension 13 is shown in dashed lines.

Specifically, with a throughput of 5,000 t of gas flame coal / day corresponding to an hourly output of approx. 208 t / h in the hydrogenation approx.

63 t / h of water with a tsersic acid content of approx.

7.4 g / dm3. About 4.4 t / h fall in the atmospheric distillation Water with a tar acid content 3 of approx. 1.58 g / dm3.

The amount of residue resulting from the vacuum distillation is approx. 74.2 t / h with a solids content of approx. 40. To gasify this amount of residue an addition of steam of approx. 28.9 t / h is necessary.

There is a hydrogen deficit, which is caused by the gasification of approx. 14.4 t / h coal is covered. For the mashing of this amount of coal is the use of 9.6 t / h water is necessary. By using the process wastewater listed above for gasification, the amount to be enforced in the wastewater treatment stages is reduced Water volume from 67.4 t / h to 28.9 t / h. At the same time, the decrease for them Wastewater disposal otherwise required considerable expenditure on equipment and energy corresponding.

The hydrogen is obtained from the synthesis gas in each case downstream Conversion and gas scrubbing 14 won and the hydrogenation 2 or stabilization 7 supplied.

The gasification only produces wastewater, which is less than Neutralization can be initiated in public waters.

Claims (3)

Claims Process for the removal of tar-acid-containing process wastewater from the hydrogenation of coal, characterized in that the waste water is a carbon gasification process are fed. 2. The method according to claim 1, characterized in that the waste water can be used to prepare a pumpable coal / liquid suspension. 3. The method according to claim 1 or 2, characterized in that hydrogen for hydrogenation is obtained from the resulting gas with conversion will.