Chip Bin Cold-Top Control for Steam Pre-Treatment Gas Management
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Solution Overview
Problem
The steam pre-treatment of chips in cellulose pulp production generates large volumes of harmful and toxic gases, leading to energy losses and safety risks due to the expulsion of weak and strong gases, which are difficult to manage and can be explosive, and existing solutions either increase operational costs or result in energy inefficiencies.
Innovation Solution
Implementing a 'cold-top' control system with direct injection of cooling fluid during steam pre-treatment to maintain a temperature gradient within the chip bin, where the upper surface is kept at ambient temperature and the bottom is heated, and using a ventilation channel to manage weak gases, while injecting cooling fluid as finely divided drops to condense gases and prevent blow-through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If steam is used for heating in the chip bin to expel air, then air expulsion is achieved, but large volumes of harmful gases (TRS gases, NCGs) are released
Solution Approach 1:
The invention changes the temperature parameter by introducing cooling fluid to create a temperature gradient in the chip bed. The upper part is cooled to condense volatile gases, while the lower part remains hot for steam heating. This parameter change allows simultaneous air expulsion and gas condensation, reducing harmful gas release.
Solution Approach 2:
The chip bed is segmented into two temperature zones: a hot lower region for steam heating and air expulsion, and a cold upper region for gas condensation. This segmentation allows different functions to occur in different zones, solving the contradiction between air expulsion and harmful gas release.
2Ease of operation
If steam is blown through the complete bed of chips, then air is expelled, but large volumes of dilute weak gases are obtained that must be managed in weak gas systems
Solution Approach 1:
By changing the temperature parameter in the upper chip bed to cold conditions, the invention condenses volatile gases into liquid condensate. This reduces the volume of weak gases from large volumes of dilute gas to much smaller volumes of condensed liquid, easing the burden on weak gas systems.
Solution Approach 2:
The invention utilizes phase transition by cooling the upper chip bed to condense volatile gases from gas phase to liquid phase. This phase change reduces the volume and manages the quantity of weak gases more effectively.
3Ease of operation
If the temperature in the uppermost surface of the bed of chips is kept high, then air expulsion is facilitated, but steam energy is expelled with the gases leading to energy losses
Solution Approach 1:
The chip bed is segmented into hot and cold zones, allowing steam heating in the lower region for air expulsion while the upper region is cooled to condense gases. This segmentation prevents steam energy from being expelled with the gases by condensing them in the cold zone.
Solution Approach 2:
The invention converts the harmful effect of high temperature (which causes energy loss through gas expulsion) into a beneficial cold zone that condenses gases. The cold temperature, rather than preventing air expulsion, actually helps retain steam energy by condensing volatile components.
4Object-generated harmful factors
If pure steam is used for heating to minimise TRS gases release, then gas contamination is reduced, but the amount of steam available for electricity production is reduced increasing operational costs
Solution Approach 1:
The chip bed is segmented into hot and cold zones, allowing the use of black liquor steam (which contains TRS gases) in the hot lower region for heating, while the cold upper region condenses these gases. This segmentation enables the use of pure steam for heating without the harmful gas release problem, as the TRS gases are condensed in the cold zone.
Solution Approach 2:
The invention converts the harmful TRS gases in the steam into a beneficial process by condensing them in the cold upper zone. This allows the use of black liquor steam for heating while minimizing gas contamination, as the TRS gases are condensed rather than released.
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 significantly reduces the risk of gas blow-through, minimizes the release of foul-smelling gases, and maintains energy efficiency by ensuring that all heat is absorbed into the process, reducing the load on weak gas systems and minimizing condensate formation that can lead to gas expulsion.
Implementation Method 1
injecting cooling fluid as finely divided drops to condense gases
Implementation Method 2
maintain a temperature gradient within the chip bin, where the upper surface is kept at ambient temperature and the bottom is heated
Implementation Method 3
ensuring that all heat is absorbed into the process
Data Source
AI summary
The arrangement and method are for the steam pre-treatment of chips during the production of cellulose pulp to avoid the blow-through of gases in the steam pre-treatment vessel. This prevents foul-smelling gases from being released into the atmosphere. Spreader nozzles for the injection of cooling fluid are arranged in the gas phase of the steam pre-treatment vessel. In the event of the risk for blow-through of steam, cooling that is proportional to the risk is activated. It is possible to avoid the emission of gases from the chip bin when interruptions in the process occur, whereby the release of odors into the surroundings can be minimized.