Fluidized-Bed Reactor Heating Process for Chlorine Production
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Solution Overview
Problem
The existing fluidized-bed reactor processes for chlorine production by oxidation of hydrogen chloride in the Deacon process face challenges in achieving rapid heating to operating temperature, leading to prolonged start-up times and potential catalyst sintering and heat exchanger damage.
Innovation Solution
A process that involves a two-phase heating approach, where the reactor is initially heated to a lower temperature using an inert gas or steam in a shell-and-tube heat exchanger, followed by further heating to the operating temperature using the exothermic oxidation heat of hydrogen chloride, with water circulation in the heat exchanger to manage steam pulses and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the fluidized-bed reactor is heated up using hot nitrogen to reach operating temperature quickly, then the heating time is reduced, but the maximum permissible temperature of 450°C may cause undesirable sintering of the catalyst
Solution Approach 1:
The patent applies preliminary action by first heating the reactor to a lower temperature (250-350°C) using hot nitrogen before introducing the HCl oxidation reaction. This preparatory heating step allows the reactor to reach a safe intermediate temperature without exposing the catalyst to damaging temperatures, and then the exothermic reaction is introduced to complete the heating to operating temperature (380-420°C).
Solution Approach 2:
The patent converts the potentially harmful exothermic heat of the HCl oxidation reaction into a beneficial heating source. Instead of using external high-temperature heating that could damage the catalyst, the reaction's own heat release is utilized to bring the reactor from the preliminary temperature to the final operating temperature, thus converting what could be a runaway hazard into a controlled heating mechanism.
2Reliability
If water is supplied to heat exchangers only after reaching operating temperature, then catalyst sintering is prevented, but steam pulses occur causing heat exchanger damage
Solution Approach 1:
The patent applies preliminary action by supplying water to the heat exchangers during the second heating-up phase, before the reactor reaches final operating temperature. This ensures that the heat exchangers are already filled with water and ready to absorb heat when the HCl oxidation reaction is introduced, preventing steam pulses and potential tube rupture while still protecting the catalyst from excessive temperatures.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the reactor temperature and adjusting the water supply to the heat exchangers accordingly. The temperature measurements trigger the water supply at the appropriate moment, creating a feedback loop that ensures heat exchangers are protected while maintaining catalyst stability throughout the heating process.
3Reliability
If the reactor is heated slowly to avoid catalyst damage, then catalyst sintering is prevented, but the start-up time becomes excessively long
Solution Approach 1:
The patent applies preliminary action by dividing the heating process into two distinct phases: a first phase using hot nitrogen to reach an intermediate temperature safely, and a second phase introducing the HCl oxidation reaction to complete heating to operating temperature. This staged approach accelerates the overall process while maintaining catalyst protection throughout.
Solution Approach 2:
The patent utilizes parameter changes by transitioning from a controlled low-temperature heating phase (250-350°C) to a high-temperature reaction phase (380-420°C) through the introduction of the exothermic HCl oxidation. This parameter transition allows rapid heating in the second phase while the first phase ensures catalyst protection, resolving the contradiction between speed and safety.
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 method significantly reduces the heating time to the operating temperature, preventing catalyst sintering and heat exchanger damage, while maintaining high chlorine conversion and extending catalyst life.
Implementation Method 1
the heat of reaction of the exothermic oxidation of hydrogen chloride is removed by means of water which circulates in the tubes of a shell-and-tube heat exchanger
Implementation Method 2
hydrogen chloride is reacted with oxygen in an operating phase at the operating temperature, wherein (i-2) hydrogen chloride and oxygen are fed into the fluidized-bed reactor and reacted in a second heating-up phase in which the fluidized-bed reactor is heated up to the operating temperature by the heat of reaction of the exothermic oxidation of hydrogen chloride
Implementation Method 3
A shell-and-tube heat exchanger is preferably used as heat exchanger
Data Source
AI summary
Process for preparing chlorine by oxidation of hydrogen chloride by means of oxygen in the presence of a particulate catalyst in a fluidized-bed reactor, where the heat of reaction of the exothermic oxidation of hydrogen chloride is removed by means of water which circulates in the tubes of a shell-and-tube heat exchanger, where (i) the fluidized-bed reactor is heated up to an operating temperature in the range from 350 to 420° C. in a heating-up phase and (ii) hydrogen chloride is reacted with oxygen in an operating phase at the operating temperature, wherein(i-1) the fluidized-bed reactor is heated up to a temperature below the operating temperature in a first heating-up phase and(i-2) hydrogen chloride and oxygen are fed into the fluidized-bed reactor and reacted in a second heating-up phase in which the fluidized-bed reactor is heated up to the operating temperature by the heat of reaction of the exothermic oxidation of hydrogen chloride.