Aniline Recovery Bottom Stream Pumpability via Methanol
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Solution Overview
Problem
The existing process for obtaining pure aniline from nitrobenzene through catalytic hydrogenation faces challenges in minimizing losses and ensuring pumpability of the discharge stream from the pure column, which can lead to pipeline blockage due to solidification of high-boiling components, resulting in increased costs for trace heating and potential blockages.
Innovation Solution
The process involves limiting the weight proportion of the discharge stream from the pure column to a maximum of 0.8% by adding technical methanol, ethanol, propanol, or acetone to the bottom stream in a proportion of 5-30% to maintain a temperature of 45 °C or higher, ensuring the stream remains pumpable and reducing aniline losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the weight proportion of the discharge stream from the pure column is reduced to minimize aniline losses, then aniline losses are reduced, but the discharge stream becomes more prone to pipeline blockage due to solidification of high-boiling components
Solution Approach 1:
The patent introduces methanol as an intermediary substance added to the discharge stream. The methanol acts as a mediator that prevents solidification of high-boiling components without interfering with the primary function of aniline recovery. It modifies the physical properties of the discharge stream to maintain pumpability while allowing reduced aniline losses.
Solution Approach 2:
The patent changes the compositional parameter of the discharge stream by adding methanol. This parameter change (introduction of a low-freezing-point substance) fundamentally alters the solidification behavior of the high-boiling components, enabling the stream to remain pumpable at lower temperatures and preventing pipeline blockages.
2Reliability
If trace heating is installed to prevent pipeline blockage, then pipeline blockage risk is reduced, but operational costs and device complexity increase
Solution Approach 1:
The patent replaces expensive, complex trace heating infrastructure with a simple, inexpensive chemical additive (methanol). Instead of installing and maintaining heating systems, the solution uses a disposable/consumable substance that is mixed into the discharge stream, achieving the same reliability goal at minimal cost and complexity.
Solution Approach 2:
The patent substitutes a mechanical/thermal system (trace heating) with a chemical solution (methanol addition). The heating system relies on thermal energy input and complex infrastructure, while the methanol solution relies on chemical properties (low freezing point) to achieve the same blockage prevention function.
3Reliability
If the discharge stream is kept at higher temperature to maintain pumpability, then pipeline blockage is prevented, but energy consumption increases
Solution Approach 1:
The patent changes a different parameter (composition) instead of maintaining the original parameter (temperature) at high levels. By adding methanol, the freezing point of the discharge stream is lowered, allowing pumpability to be maintained at lower temperatures, thus reducing energy consumption while achieving the same reliability goal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces aniline losses from 1% to 0.8% of the feed stream, saving approximately 2,000 tons of aniline per year and ensuring the bottom stream remains flowable without the need for extensive trace heating, thereby reducing operational costs and risks of pipeline blockages.
Implementation Method 1
adding technical methanol, ethanol, propanol, acetone or mixtures thereof to the bottom stream in a proportion by weight of 5-30%, based on the weight of the bottom stream
Implementation Method 2
a pure distillation in a pure column, from which pure aniline is withdrawn overhead, and a bottom stream which contains high boilers in addition to aniline
Implementation Method 3
aniline is mainly obtained from nitrobenzene through catalytic hydrogenation
Implementation Method 4
catalytic hydrogenation of nitrobenzene
Data Source
AI summary
The invention relates to a method for obtaining pure aniline by catalytically hydrogenating nitrobenzene and reprocessing the reaction mixture obtained therefrom, having the following method steps: - the catalytic hydrogenation of nitrobenzene; - optionally the partial condensation of the reaction mixture of the catalytic hydrogenation in one or more stages; - the separation of the reaction mixture obtained after the catalytic hydrogenation or the condensation, which is optionally carried out, into a gas phase, which contains hydrogen, and a liquid phase; - the liquid-liquid phase separation of the liquid phase obtained in the separation step, thereby obtaining an aqueous phase, which is further reprocessed or discharged, and raw analine as an organic phase, said raw analine containing 90-95 wt.% aniline, 4-9 wt.% water, and residual high boilers relative to the analine, in each case based on the total weight of the raw analine, and the sum of the components of the raw analine equaling 100 wt.%; and - the pre-cleaning of the raw analine by partly or completely separating the water via the head stream of a first distillation column, thereby obtaining a bottom stream that is fed as a feed stream to a purification column from which a pure aniline stream containing at least 99.9 wt.% aniline based on the total weight of the pure analine stream is drawn via the head and a bottom stream containing high boilers is drawn and fed to a combustion process. The invention is characterized in that the weight ratio of the bottom stream from the purification column is limited to maximally 0.8% relative to the weight of the feed stream, thereby ensuring that said bottom stream can be pumped under the effect of a corresponding trace heating of the lines provided for this purpose, said trace heating ensuring that the temperature of the stream conducted in the lines is 45 °C or higher, wherein the bottom stream is exposed to methanol, ethanol, propanol, acetone, or mixtures thereof in a weight ratio of 5-30% based on the weight of the bottom stream.