Multi-zone Hydrotreating Reactor for Renewable Paraffin Fuel
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Solution Overview
Problem
Current processes for hydrotreating renewable feedstocks, such as vegetable and animal oils, face challenges in promoting hydrodeoxygenation while effectively carrying out hydrodenitrogenation to preserve catalytic activity and reduce nitrogen content in fuel products, leading to issues like catalyst deactivation and reduced paraffin yield.
Innovation Solution
The process involves conducting hydrodenitrogenation and hydrodeoxygenation in the same catalytic zone by controlling temperature profiles, with increasing charge injection and significant recycling in the first zone to maintain low temperatures for hydrodeoxygenation and achieve high temperatures for hydrodenitrogenation, thereby favoring the hydrodeoxygenation route and reducing CO/CO2 formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature is increased to promote hydrodenitrogenation, then nitrogen removal efficiency is improved, but hydrodeoxygenation selectivity deteriorates and unwanted side reactions increase
Solution Approach 1:
The catalytic reactor is divided into multiple zones with different temperature profiles. The first zone operates at lower temperature (200-300°C) to favor hydrodeoxygenation, while subsequent zones operate at progressively higher temperatures (300-400°C) to promote hydrodenitrogenation. This spatial segmentation allows both reactions to occur optimally without competing for the same conditions.
Solution Approach 2:
Different regions of the catalytic bed are assigned different thermal characteristics. The inlet region maintains lower temperature to protect hydrodeoxygenation selectivity, while the outlet region allows higher temperature for effective nitrogen removal. This local quality variation resolves the contradiction by providing optimal conditions for each reaction type in its appropriate location.
2Productivity
If temperature is decreased to favor hydrodeoxygenation, then paraffin yield is improved, but hydrodenitrogenation efficiency deteriorates
Solution Approach 1:
The reactor is segmented into zones where the first zone operates at lower temperature to maximize paraffin yield through hydrodeoxygenation, while subsequent zones operate at higher temperatures to ensure adequate hydrodenitrogenation. This allows the system to achieve both high paraffin yield and sufficient nitrogen removal efficiency.
Solution Approach 2:
The multi-zone temperature profile ensures continuous progression of reactions from hydrodeoxygenation at the inlet to hydrodenitrogenation at the outlet. Each zone performs its designated function continuously, maintaining both high paraffin production and effective nitrogen removal throughout the process.
3Reliability
If decarboxylation reactions are promoted, then deoxygenation is achieved, but paraffin yield is reduced due to carbon loss
Solution Approach 1:
The temperature parameter is carefully controlled and varied across different reactor zones to favor hydrodeoxygenation over decarboxylation. By maintaining lower temperatures in the first zone and using specific catalyst formulations, the process selectively promotes HDO reactions that preserve carbon atoms in the paraffin chains, minimizing CO2 loss while achieving effective deoxygenation.
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 increases paraffinic hydrocarbon yield, reduces CO/CO2 formation, limits catalyst deactivation, and minimizes corrosion, allowing for the production of high-quality fuel meeting specifications like EN590 for diesel and ASTM D1655 for kerosene.
Implementation Method 1
hydrodeoxygenation (HDO) leading to the formation of water by consumption of hydrogen and to the formation of hydrocarbons with a carbon number (Cn) equal to that of the initial fatty acid chains
Implementation Method 2
hydrodenitrogenation reactions (HDN), by which we designate the reactions allowing the removal of nitrogen from the load with the production of NH3
Implementation Method 3
The hydrogenation of unsaturations of hydrocarbon chains (carbon-carbon double bonds) is strongly exothermic and the increase in temperature caused by the release of heat can lead to temperature levels where the share of decarboxylation reactions becomes significant
Implementation Method 4
decarboxylation/decarbonylation leading to the formation of carbon oxides (carbon monoxide and dioxide: CO and CO2) and the formation of hydrocarbons with one less carbon (Cn-1) compared to the initial fatty acid chains
Data Source
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Figure 2
AI summary
The process for hydrotreatment of feedstock from renewable sources for production of paraffinic hydrocarbons in the presence of 50% of excess hydrogen of theoretical hydrogen consumption and by hydrotreatment conditions in a fixed bed reactor having 3-6 catalytic zones arranged in series and comprising a hydrotreating catalyst, comprises dividing the flow (F) of the total feedstock into a number of different partial flows (F1 to Fn) equal to the number (n) of catalytic zones in the reactor to produce an effluent containing paraffinic hydrocarbons. The process for hydrotreatment of feedstock from renewable sources for production of paraffinic hydrocarbons in the presence of 50% of excess hydrogen of theoretical hydrogen consumption and by hydrotreatment conditions in a fixed bed reactor having 3-6 catalytic zones arranged in series and comprising a hydrotreating catalyst, comprises dividing the flow (F) of the total feedstock into a number of different partial flows (F1 to Fn) equal to the number (n) of catalytic zones in the reactor to produce an effluent containing paraffinic hydrocarbons, where a first partial flow (F1) is injected in a first catalytic zone (Z1), the second partial flow (F2) is injected in a second catalytic zone (Z2) and then if n is greater than 2, the different partial flows are injected in the successive catalytic zones in increasing proportions such that F1/F is less than or equal to F2/F or is less than or equal to F3/F until F(n-1)/F is less than or equal to Fn/F, subjecting the effluent to a separation step for separating a gas fraction containing hydrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, water and light gas and liquid fraction containing paraffinic hydrocarbon, recycling a part of the liquid fraction containing paraffinic hydrocarbon to the first catalytic zone so that a weight ratio between the recycle flow into the first catalytic zone and the partial flow (F1) introduced into the first catalytic zone is greater than 10. A weight ratio between the recycle flow into the first catalytic zone and total flow of feedstock is less than 0.5. The hydrotreatment step is operated at a temperature of 200-400[deg] C, a pressure of 2-15 MPa and a speed velocity of 0.1-5 h -> 1>and in a presence of total quantity of hydrogen mixed with feedstock such that a ratio of hydrogen or feedstock is 300-1500 Nm 3>hydrogen/m 3>of feedstock. The separation step is carried out by a high temperature high pressure separator operating without reduction of pressure at a temperature of 145-280[deg] C. The different partial flows are same or different. The feedstocks are co-treated with: a petroleum distillate type consisting of gas oils; kerosene atmospheric direct distillation of gas oil; and/or kerosene from conversion processes. The part of the liquid fraction containing paraffinic hydrocarbon undergoes hydroisomerization step in the presence of a hydroisomerization catalyst. The hydroisomerization step is operated at a temperature of 150-500[deg] C, a pressure of 1-10 MPa, a speed velocity of 0.1-10 h -> 1>and flow rate of hydrogen such that a ratio of hydrogen/hydrocarbon volume is 70-1000 Nm 3>/m 3>of feedstock. The hydroisomerization catalyst comprises a metal of group VIII and/or a metal of group VI B as a hydrogenating function and a molecular sieve or an amorphous mineral support as a hydroisomerization function. The effluent from the hydroisomerization step is subjected to a separation step to obtain a gaseous including a gasoline cut (150[deg] C-) and a distillate cut (150[deg] C+) containing kerosene and/or diesel.