Superheated Steam Pasteurization of Divided Solids
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Solution Overview
Problem
Existing heat treatment methods for debacterization of divided solids face challenges in achieving precise temperature control, maintaining product quality, and reducing residence time while being cost-effective, as they often result in moisture loss, product degradation, or require high-pressure systems.
Innovation Solution
A continuous thermal debacterization device using a closed enclosure with controlled heated contact walls and a source of superheated wet steam at atmospheric pressure, where the steam temperature is matched to the contact wall temperature, allowing for efficient heat transfer and reduced moisture loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If steam is injected into the treatment enclosure to heat the product, then the heating efficiency is improved, but the product becomes moistened requiring post-treatment drying
Solution Approach 1:
The invention changes the temperature parameter of the steam from saturation temperature to superheated temperature (above saturation). By superheating the steam to temperatures matching or exceeding the contact wall temperatures (200-250°C), the steam remains in gaseous phase during heat transfer, providing efficient heating without condensation and thus without moistening the product
Solution Approach 2:
The invention replaces the mechanical drying system (post-treatment drying equipment) with a thermal field control system. By precisely controlling the steam temperature and contact wall temperature to be equal or slightly different, the system eliminates the need for mechanical drying while maintaining debacterization effectiveness
2Reliability
If the enclosure atmosphere temperature is increased above 100°C for better debacterization, then the debacterization effectiveness is improved, but the product may be degraded
Solution Approach 1:
The invention creates different thermal zones: the contact walls and superheated steam provide high temperature (200-250°C) for effective debacterization, while the product bulk temperature is controlled at lower levels (below degradation threshold). This local quality differentiation allows high reliability debacterization without product degradation
Solution Approach 2:
The invention uses periodic or controlled thermal exposure through the rotating screw conveyor system, where products are intermittently exposed to high-temperature contact walls and superheated steam atmosphere, allowing effective debacterization while limiting total exposure time to prevent degradation
3Temperature
If a double-envelope screw conveyor with steam injection is used, then the heating performance is improved, but the device complexity increases due to pressure containment requirements
Solution Approach 1:
The invention extracts the pressure containment requirement from the system by operating at atmospheric pressure. By using superheated steam injection and controlled contact wall heating, the system achieves high-temperature processing without requiring pressure vessels, valves, or special containment structures
Solution Approach 2:
The invention introduces superheated steam as an intermediary heating medium that can transfer thermal energy efficiently at atmospheric pressure. The steam acts as a mediator between the heat source and the product, enabling high-temperature processing without direct contact with heating elements and without requiring pressure containment
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 solution enables effective debacterization at controlled temperatures (100°C to 250°C) with adjustable residence times, preserving product quality and reducing processing time, while simplifying device construction and operation at atmospheric pressure.
Implementation Method 1
the heat treatment undergone by the products is in reality mainly due to the condensation of the steam
Implementation Method 2
steam is injected at a pressure of between 1.05 bar and 3 bar, or even more, so as to heat the product faster and stronger
Implementation Method 3
the product is conveyed and heated at the same time by its direct contact with a conveying screw which is itself heated by the Joule effect
Implementation Method 4
a conveying screw which is itself heated by the Joule effect
Implementation Method 5
Conveyors of the vibrated tube type with current passage have also been used, where the product circulates by vibration in a tube
Data Source
Figure 1
Figure 2~4
AI summary
The invention relates to a device for the continuous thermal pasteurisation of products in the form of divided solids, said device comprising a closed housing (13) into which the products are fed. Said housing contains controlled means consisting of heating contact walls (18) acting directly on the products as they are fed into the housing. According to the invention, the closed housing (13) is connected to a source (60, 62, 30) for supplying wet steam at atmospheric pressure, said steam being overheated, before entering the housing (13), by an element (62) for reheating gaseous fluids arranged outside the housing. The temperature control of said element is related to the temperature control of the contact walls (18) in such a way that the temperature (Tv) of the overheated wet steam at atmospheric pressure in the closed housing (13) is essentially equal to the temperature (Ts) of the contact walls.