Biomass Riser Thermal Expansion Sealing
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Solution Overview
Problem
The existing devices for producing product gas from biomass face damage due to thermal expansion of the riser, which can lead to cracks and operational issues during start-up.
Innovation Solution
The riser is designed to be movably attached to the reactor walls, allowing for free expansion at its lower end through a through-opening in the base part, sealed by a gland packing or similar sealing means, which accommodates thermal expansion while maintaining the reactor's internal seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the riser is rigidly fixed to the reactor walls, then structural stability is improved, but thermal expansion damage occurs during start-up
Solution Approach 1:
The riser is designed with dynamic characteristics, allowing it to expand and contract freely in the longitudinal direction at its lower end through a through-opening in the base part. This dynamic design enables the riser to accommodate thermal expansion during start-up while maintaining structural stability through its suspended configuration from the circumferential or upper wall.
2Manufacturing precision
If the lower end of the riser is fixed to the base part, then positioning accuracy is improved, but thermal expansion accommodation is worsened
Solution Approach 1:
A sealing element is introduced as a flexible component between the riser and the base part. This sealing element maintains the positioning accuracy of the riser while allowing it to expand and contract freely. The sealing element deforms to accommodate the thermal expansion movements, thus providing both precise positioning and expansion accommodation.
3Adaptability or versatility
If the through-opening is left open to allow riser movement, then thermal expansion is accommodated, but reactor sealing is compromised
Solution Approach 1:
A sealing element is installed at the through-opening to maintain reactor sealing while allowing riser movement. This flexible sealing component deforms to accommodate the thermal expansion of the riser, thus preventing harmful factors from entering the reactor interior while maintaining the necessary mobility for expansion.
Solution Approach 2:
The sealing element acts as an intermediary between the riser and the base part. It mediates between the need for reactor sealing and the need for thermal expansion accommodation, allowing the riser to move freely while maintaining the seal of the reactor interior.
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 design reduces the risk of damage from thermal expansion, ensures the reactor's internal environment remains sealed, and allows for efficient operation by using a fluidised bed of sand to manage temperature gradients and simplify handling of sealing components.
Implementation Method 1
During start-up of the installation, the temperature rises within a relatively short time from chamber temperature to pyrolysis and gasification temperature. The riser is therefore subject to considerable thermal expansion.
Implementation Method 2
The through-opening between the riser and the base part is preferably sealed by a sealing component or means for the sealing of the interior of the reactor from the environment, the sealing means being configured in such a way that the riser is able to move, as a result of thermal expansion thereof, along the sealing means.
Implementation Method 3
at least one nozzle for the injection of a fluidisation gas is attached in the riser, the sealing means being attached substantially below said nozzle. During operation, the riser is partially filled with a granular material, such as grains of sand, which, under the influence of the fluidisation gas, fluidises above the nozzle.
Implementation Method 4
below the nozzle in the riser, the sand forms a 'dead zone' in which the sand is substantially quiescent. In contrast to a fluidised sand bed, quiescent sand is a heat insulator. A considerable temperature gradient is thus produced in the vertical direction of the riser
Data Source
AI summary
A device for producing a product gas from biomass includes a reactor which is delimited by a base part and reactor walls. The reactor walls include a circumferential wall and an upper wall. The reactor includes a supply opening for the supplying of biomass, and also at least one riser for the chemical conversion of supplied biomass to a product gas and a solid substance. The riser is attached within the circumferential wall and includes an upper end and a lower end. The reactor also has a discharge opening for the discharging of the product gas. The riser is fastened to at least one reactor wall. The base wall of the reactor has a through-opening through which the lower end of the riser movably extends.