Cellulose Ether Production By-Product Segmentation
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Solution Overview
Problem
Existing methods for producing cellulose ethers result in excessive indissoluble fibers and increased washing loads due to the circulation of by-products like methanol and alkylene glycols, leading to reduced productivity and higher costs, as well as air pollution from unprocessed exhaust gases.
Innovation Solution
A method involving a contact step with an alkali metal hydroxide solution and a heat removal solvent, followed by a reaction step with an etherifying agent, partial condensation of exhaust gases to separate reusable gas components, and incineration of non-reusable liquid components, which reduces indissoluble fibers and stabilizes burning temperatures, allowing for efficient disposal and reuse of by-products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If by-products like methanol and alkylene glycols are circulated into the reaction slurry for reuse, then resource utilization is improved, but washing load increases and productivity decreases
Solution Approach 1:
The patent segments the exhaust gas treatment into two distinct pathways: a partial condensation step that recovers and reuses condensable by-products (methanol, alkylene glycols), and an incineration step that destroys non-condensable by-products. This segmentation prevents the contamination of reaction slurry with excessive by-products while maintaining resource utilization benefits, thereby resolving the contradiction between by-product reuse and productivity.
Solution Approach 2:
The patent extracts harmful by-products from the system through partial condensation and incineration, separating them from the reaction process. By removing methanol, alkylene glycols, and other by-products through condensation and combustion rather than circulating them back, the washing load is reduced and productivity is maintained while still achieving resource utilization through controlled reuse of condensed components.
2Manufacturing precision
If multiple partial condensers are used with repeated reflux steps to improve component purity, then by-product purity is improved, but process complexity and cost increase
Solution Approach 1:
The patent applies partial condensation rather than multiple complete condensation-reflux cycles. By using a single partial condensation step that recovers a sufficient portion of condensable by-products without requiring exhaustive purification through multiple stages, the process achieves adequate component purity while significantly reducing device complexity and operational costs.
3Temperature
If dimethyl ether is added in the etherification step to remove heat, then heat management is improved, but the number of indissoluble fibers cannot be suppressed
Solution Approach 1:
The patent applies preliminary cooling to the exhaust gas before partial condensation, which improves the efficiency of heat removal and by-product recovery. By pre-cooling the gas stream, the system achieves better temperature control during etherification without relying solely on dimethyl ether, thereby suppressing indissoluble fiber formation while maintaining effective heat management.
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 reduces the number of indissoluble fibers in cellulose ethers, improves solution transparency, and efficiently disposes of and reuses by-products, thereby enhancing productivity and reducing air pollution.
Implementation Method 1
a partial condensation step, after completion of the reaction, of partially condensing a gas present in a reaction vessel used for the reaction to separate the gas into a gas component and a liquid component
Implementation Method 2
an incineration step of incinerating the liquid component and, when all of the gas component is not returned to the contact step, the remainder of the gas component
Implementation Method 3
Returning some or all of the gas component to the contact step of bringing pulp into contact with an alkali metal hydroxide solution as some or all of the heat removal solvent allows a temperature increase due to heat generated by mercerization during the formation of alkali cellulose to be suppressed
Data Source
AI summary
Provided is a method for efficiently and continuously producing a cellulose ether containing a reduced amount of indissoluble component. Specifically, the method includes a contact step of bringing pulp into contact with an alkali metal hydroxide solution in the presence of a heat removal solvent to obtain alkali cellulose; a reaction step of subjecting the alkali cellulose to a reaction with an etherifying agent; a partial condensation step, after completion of the reaction, of partially condensing a gas present in a reaction vessel used for the reaction to separate the gas into gas and liquid components for returning some or all of the gas component to the contact step for reuse as some or all of the heat removal solvent; and a step of incinerating the liquid component and, when all of the gas component is not returned to the contact step, the remainder of the gas component.