Externally Heated Carbonization Furnace with Moisture Control
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Solution Overview
Problem
Existing externally heated carbonization furnaces face challenges in maintaining stable carbide production due to fluctuations in moisture content of treated objects, leading to issues with gasification ratio, self-heat generation, pulverizability, and thermal efficiency, particularly in rotary kilns where evaporation and carbonization zones are affected by moisture variations.
Innovation Solution
The implementation of a series-connected externally heated carbonization furnace with independently rotating kilns, where the rotational frequency of each kiln inner cylinder is controlled based on the moisture content of the treated object, and the flow rate of heating gas is adjusted to maintain stable conditions, utilizing a control device that estimates moisture content through kiln shell temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the evaporation zone is extended to handle higher moisture content, then moisture evaporation capability is improved, but the carbonization zone is shortened resulting in decreased carbonization degree
Solution Approach 1:
The single rotary kiln is divided into multiple independent rotary kilns connected in series, with each kiln having its own heating zone and carbonization zone. This segmentation allows the evaporation function to be distributed across multiple kilns rather than requiring one kiln to perform both evaporation and carbonization, thus resolving the contradiction between extending the evaporation zone and maintaining the carbonization zone length.
Solution Approach 2:
The system transitions from a single-dimensional (one kiln performing multiple functions) to a multi-dimensional approach (multiple kilns working in series, each specialized for specific functions). By adding the dimension of multiple kilns connected in series, the system can simultaneously provide extensive evaporation capacity while maintaining adequate carbonization zones in each kiln.
2Productivity
If the rotational frequency is increased to improve moisture evaporation, then evaporation efficiency is improved, but the residence time for carbonization is reduced
Solution Approach 1:
The treatment process is segmented into multiple stages across different rotary kilns. Each kiln operates at optimized rotational frequencies suitable for its specific function (evaporation or carbonization), rather than requiring a single kiln to compromise its rotational speed for dual functions. This allows high rotational speeds for evaporation in dedicated evaporation kilns while maintaining appropriate residence times in carbonization kilns.
Solution Approach 2:
The system employs dynamic control of rotational frequencies for each kiln based on its specific function and the moisture content of the material. The rotational frequency can be independently adjusted for each kiln to optimize both evaporation efficiency and carbonization residence time, rather than using a fixed rotational speed for the entire process.
3Stability of the object's composition
If a dryer is installed before the carbonization furnace to control moisture content, then moisture content stability is improved, but equipment complexity and cost increase
Solution Approach 1:
The rotary kilns are designed to perform multiple functions - serving both as evaporation zones and carbonization zones depending on the operational stage. This multi-functionality eliminates the need for a separate dedicated dryer before the carbonization furnace, as the first rotary kiln(s) in the series perform the drying/evaporation function while subsequent kilns perform carbonization.
Solution Approach 2:
The carbonization furnace system itself provides the drying function through its first rotary kiln(s), eliminating the need for external drying equipment. The system serves its own preprocessing needs by incorporating evaporation capability within the carbonization furnace structure, thereby reducing overall equipment complexity.
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 configuration allows for stable carbide production even with significant moisture content fluctuations, improving thermal efficiency and responsiveness of temperature control by minimizing unheated sections and inhibiting air flow, while absorbing thermal expansion through expandable members.
Implementation Method 1
a heater that supplies heating gas to a section between the outer cylinder and the inner cylinder
Implementation Method 2
heating gas to a section between the outer cylinder and the inner cylinder
Implementation Method 3
a kiln inner cylinder that rotates relative to the outer cylinder; carries out a heat treatment while transferring the treated object
Implementation Method 4
the latent heat of vaporization of water requires an extremely large amount of heat
Implementation Method 5
the latent heat of vaporization of water requires an extremely large amount of heat compared with the latent heat of gasification
Implementation Method 6
produces a carbide with an improved calorific power, by indirectly heating mainly sewage sludge, woody biomass, low-grade coal, or the like at high temperatures ranging from 300° C. to 700° C. under the condition in which oxygen is cut off
Data Source
AI summary
Provided is an externally heated carbonization furnace that includes a plurality of rotary kilns connected in series, each of which includes an outer cylinder, a kiln inner cylinder that rotate relative to the outer cylinder, and a heater that supplies heating gas to a section between the outer cylinder and the kiln inner cylinder. The externally heated carbonization furnace further includes a drive device that rotates at least one of the kiln inner cylinders and the kiln inner cylinder different from the at least one of the kiln inner cylinders and a control device that controls the drive device according to moisture content of a treated object in the kiln inner cylinder.