Stirred Tank Reactors: Structure, Principles, Selection and Application Guidelines - A Comprehensive Guide to Core Knowledge

Working Principles of Stirred Tank Reactors A stirred tank reactor (STR), also referred to as a stirred vessel, operates on the core principle of mechanical agitation-driven mass transfer, heat transfer and reaction kinetics optimization. Its fundamental function is to use a rotating agitator to create controlled fluid flow patterns, ensuring uniform mixing of materials, enhanced contact between reactants, and efficient heat exchange between the reaction system and the external environment. The working process is divided into three key stages: 1. Material Charging and Preparation Raw materials—including liquids, solids (powders or granules) or gases—are fed into the tank through dedicated inlets. For gas-liquid or solid-liquid systems, the feeding sequence and speed are precisely controlled to prevent agglomeration or uneven dispersion. The tank is typically sealed to maintain specific operating conditions (e.g., pressure, inert gas atmosphere) required for the reaction or mixing process. 2. Agitation and Reaction/Mixing The motor drives the agitator to rotate at a preset speed, generating shear force and fluid circulation in the tank. The agitator disrupts the stagnant boundary layer of the fluid, creating three main flow patterns: radial flow (spreading outwa...

Alcohol Recovery Towers: Principles, Applications and High-efficiency Energy-saving Solutions for Industrial Upgrading

Working Principles of Alcohol Recovery Towers Alcohol recovery towers operate on the principle of differential distillation, leveraging the distinct boiling points and relative volatility of alcohol (ethanol, boiling point 78.5℃) and water (boiling point 100℃) to separate and purify alcohol from dilute aqueous solutions. The separation process is a continuous cyclic operation consisting of four core stages: 1. Feed Pretreatment The dilute alcohol-containing feed liquid (e.g., pharmaceutical fermentation broth, food processing wastewater, chemical solvent waste) is preheated to a temperature close to its boiling point via a heat exchanger. This step recovers waste heat from the tower’s top vapor or bottom residue, reducing the energy consumption required for subsequent vaporization. The preheated feed is then introduced into the middle section of the tower, matching the optimal concentration zone to enhance separation efficiency. 2. Vaporization and Fractionation Inside the tower, the feed liquid flows downward, while the bottom reboiler heats the liquid at the tower base to generate vapor. As the vapor rises countercurrently to the descending liquid, intensive mass and heat transfer occur at the interface between the two phases. Since alcohol has a lower boiling poin...

Scraped Surface Evaporators: Principles, Core Advantages and Multi-field Applications

Working Principles of Scraped Surface Evaporators A scraped surface evaporator (SSE) is a specialized thin-film evaporator designed for handling high-viscosity, heat-sensitive, and fouling-prone materials. Its operation relies on the synergistic effect of mechanical scraping and jacketed heating to form a uniform liquid film, enabling efficient heat transfer and rapid evaporation. The working process is divided into four key stages: 1. Feed Introduction The raw material—ranging from viscous pastes to suspensions containing solid particles—is pumped into the evaporator’s cylindrical shell from the top or bottom inlet. The feed rate is precisely controlled to match the scraping speed, ensuring optimal liquid film thickness (typically 0.1–1 mm). 2. Thin-film Formation and Heat Transfer The evaporator’s inner wall is equipped with a heating jacket, where a heat transfer medium (e.g., steam, thermal oil) circulates to provide uniform heating. A rotating shaft with fixed wiper blades (scrapers) rotates at a speed of 50–500 rpm along the inner wall. As the shaft turns, the scrapers continuously spread the incoming feed into a thin, turbulent liquid film across the heated surface. This mechanical action eliminates boundary layer resistance and p...

Extraction Columns: A Comprehensive Guide to Working Principles and Industrial Applications of High-efficiency Separation Equipment

Working Principles of Extraction Columns The core operating principle of extraction columns is liquid-liquid extraction, a separation technology that leverages the difference in solubility of target solutes in two immiscible or partially miscible solvents. One solvent (termed the extractant) has a high affinity for the target solute, while the other (termed the raffinate) is the original carrier phase of the solute. The separation process inside the extraction column involves three key stages: 1. Phase Contact and Mass Transfer The two immiscible liquid phases are introduced into the column from different positions, forming a countercurrent or co-current flow pattern. Countercurrent flow is the dominant mode in industrial applications due to its higher separation efficiency. In this mode, the extractant phase flows upward, and the raffinate phase flows downward (or vice versa). Intensive contact occurs at the interface between the two phases, driving the target solute to diffuse from the raffinate phase to the extractant phase. This mass transfer process continues until the solute reaches a dynamic equilibrium between the two phases. 2. Phase Dispersion and Enhancement To maximize the mass transfer rate, extraction columns are equipped with internal components that dispers...