Sludge Dewatering via In-Situ CO2 Hydrate Crystallization
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Solution Overview
Problem
Existing sludge dewatering technologies face challenges with high chemical consumption, energy usage, and low efficiency in removing capillary and surface water, leading to environmental risks and inefficiencies in sludge treatment and disposal.
Innovation Solution
The method involves in-situ crystallization of water using a pressure vessel and carbon dioxide, where sludge is cooled and reacted with CO2 to form a hydrate, allowing for complete transformation of water into a hydrate, which is then decomposed to improve solid-liquid separation without conditioning agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coagulants and flocculants are used to improve dewatering performance, then solid-liquid separation is enhanced, but chemical consumption and environmental risks increase
Solution Approach 1:
The patent changes the physical parameters of water in sludge by converting liquid water into ice crystals through controlled freezing. This phase change alters the physical state of water, enabling separation from organic matter without chemical additives. The freezing process transforms capillary water and surface-attached water into removable ice crystals, improving dewatering performance while avoiding chemical consumption and associated environmental risks.
Solution Approach 2:
The core mechanism of this invention is the phase transition of water from liquid to solid state through freezing. By controlling temperature and pressure conditions, water in sludge undergoes phase change to form ice crystals that can be easily separated from organic matter. This physical phase transition replaces chemical coagulation and flocculation processes, eliminating the need for coagulants and flocculants while achieving effective solid-liquid separation.
2Quantity of substance
If traditional dewatering methods are used, then free water removal is achieved, but capillary and surface water remain
Solution Approach 1:
The patent applies parameter changes by controlling temperature to induce freezing. This temperature parameter change affects all water in sludge uniformly, including capillary water and surface-attached water that are difficult to remove by traditional mechanical dewatering. The freezing process transforms these retained waters into ice crystals that can be comprehensively removed, achieving deep dewatering beyond what traditional methods accomplish.
Solution Approach 2:
By utilizing phase transition from liquid to solid, the invention enables removal of capillary and surface-attached water that traditional dewatering methods cannot effectively address. The freezing process penetrates throughout the sludge matrix, transforming all water types into removable ice crystals, thereby achieving comprehensive water removal including the difficult-to-access capillary and surface water.
3Productivity
If high pressure and temperature treatment is applied, then dewatering efficiency improves, but energy consumption increases
Solution Approach 1:
The patent utilizes phase transition at relatively low temperatures (freezing point of water) to achieve dewatering. This approach contrasts with high-temperature thermal drying methods by using the natural phase change of water at lower energy input. The freezing process occurs at temperatures around 0°C, significantly reducing energy consumption compared to high-temperature treatments while maintaining effective dewatering efficiency through ice crystal formation and removal.
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 chemical consumption, enhances dewatering efficiency, and minimizes environmental risks, achieving significant improvements in sludge dewatering performance with reduced operational costs and secondary pollution.
Implementation Method 1
introducing carbon dioxide gas into the cooled sludge, and enabling a partial pressure of the carbon dioxide to be higher than an equilibrium partial pressure of a carbon dioxide hydrate (CO2·6H2O) at a corresponding temperature; continuing to stir to make the sludge react with the carbon dioxide at a constant temperature to generate a carbon dioxide hydrate
Implementation Method 2
enabling a partial pressure of the carbon dioxide to be higher than an equilibrium partial pressure of a carbon dioxide hydrate (CO2·6H2O) at a corresponding temperature; the water in the sludge is completely transformed into the carbon dioxide hydrate
Implementation Method 3
adding sludge into a pressure vessel and cooling the sludge
Implementation Method 4
releasing the gas pressure of the sealed reactor, starting to decompose the carbon dioxide hydrate, recovering released carbon dioxide gas for reuse
Implementation Method 5
decompose the carbon dioxide hydrate, recovering released carbon dioxide gas
Data Source
AI summary
The present disclosure relates to a method and system for improving solid-liquid separation performance of sludge by in-situ crystallization of water. The method comprises the following steps: adding sludge into a pressure vessel, intermittently introducing high-pressure carbon dioxide at a low-temperature condition to generate a carbon dioxide hydrate until a partial pressure of the carbon dioxide is stable, releasing the pressure, and stirring the sludge until no gas escapes, thus obtaining the treated sludge. Compared with the prior art, the method and system provided by the present disclosure are simple and easy to implement, has no consumption of sludge dewatering conditioning agents, and can achieve the recycling of carbon dioxide. The secondary environmental pollution risk caused by the sludge dewatering conditioning agent is reduced, the shortcomings of high dosage of chemicals, large sludge enlargement ratio, low sludge dewatering efficiency and the like in the traditional sludge dewatering process can be overcome.