Sulfur Daily Question: March 11, 2016. Participate to earn 5 wealth points; those who give good answers will receive 10 wealth points.

This post was last edited by Sulfur-Zinc-Aluminum on 2016-3-19 09:04. Both ammonia and hydrogen sulfide can dissolve in water and undergo ionization: NH3 + H2O = NH4+ + OH- (1) H2S = HS- + H+ (2) Ammonia has a higher solubility in water than hydrogen sulfide, and both solubilities decrease as the temperature rises. When hydrogen sulfide and ammonia coexist in water, they are in chemical ionization and phase equilibrium: HS- + NH4+ = NH4HS = (NH3 + H2S)liquid = (NH3 + H2S)gas (3). At room temperature, hydrogen sulfide and ammonia dissolve in water and ionize to exist as ions in the water. When the temperature increases, the three equilibria represented by equation (3) shift to the right. Wastewater stripping utilizes this principle by heating the wastewater to above 140°C, thereby disrupting the equilibrium of hydrogen sulfide and ammonia in water and prompting their transfer from the liquid phase to the vapor phase ； At the same time, water vapor is used to reduce the partial pressures of hydrogen sulfide and ammonia in the vapor phase, thereby lowering their concentrations in water and achieving the purpose of wastewater purification.

This post was last edited by Sulfur-Zinc-Aluminum on 2016-3-19 09:04. When processing sulfur-containing crude oil, units such as atmospheric and vacuum distillation as well as catalytic cracking generate large amounts of acidic water (sulfur-containing wastewater), which also contains high levels of ammonia and phenolic substances； Sulfur and ammonia in wastewater exist mainly in the forms of NH4HS and (NH4)2S. In acidic water, the sulfur- and ammonia-containing compounds are decomposed and separated through continuous heating in a stripping tower; acidic gas is produced at the top of the tower, crude ammonia gas is obtained from the outlet, and purified water is produced at the bottom of the tower.

Please briefly outline the operating principle of the acidic water stripping unit (or wastewater stripping unit)? Acidic water stripping refers to the use of an acidic aqueous solution as a desorbent to carry out desorption of the feedstock (in gas form). Desorption is the reverse process of absorption, and both belong to the unit operation of gas absorption. Absorption is an example of a mass transfer process aimed at separating various components in a mixed feed (gaseous).

Please briefly outline the operating principle of the acidic water stripping unit (or wastewater stripping unit)? Acidic water stripping refers to the use of an acidic aqueous solution as a desorbent to carry out desorption of the feedstock (in gas form). Desorption is the reverse process of absorption, and both belong to the unit operation of gas absorption. Absorption is an example of a mass transfer process aimed at separating various components in a mixed feed (gaseous).

Acidic water stripping refers to the use of an acidic aqueous solution as a desorbent to carry out desorption of the feedstock (in gas form). Desorption is the reverse process of absorption, and both belong to the unit operation of gas absorption. Absorption is an example of a mass transfer process aimed at separating various components in a mixed feed (gaseous).

This post was last edited by Sulfur-Zinc-Aluminum on 2016-3-19 09:05. Acidic water is an aqueous solution that contains volatile weak electrolytes such as H2S, NH3, and CO2. In water, the aforementioned components exist in the form of ammonium salts such as NH4HS, (NH4)2CO3, and NH4HCO3. These salts of weak acids and weak bases ionize in water, while also undergoing hydrolysis to produce H2S, NH3, and CO2 molecules. In addition to being in ionic equilibrium with other ions, these molecules are also in equilibrium with those in the gas phase. This system is a complex one in which chemical equilibrium, ionization equilibrium, and phase equilibrium coexist. Therefore, controlling the appropriate conditions for chemistry, ionization, and phase equilibrium is key to using acidic water and selecting suitable operating conditions. Since both ionization and hydrolysis are reversible processes, various substances exist in the liquid phase in both ionic and molecular forms. Ions cannot move from the liquid phase to the gas phase, hence they are referred to as being in a \"fixed state,\" while molecules can move from the liquid phase to the gas phase, and are thus in a \"free state.\" The amounts of various substances in ionic and molecular form in water are related to the operating temperature, operating pressure, and their concentrations in water. Based on the properties of the H2S, NH3, and CO2-H2O quadruple element system, the hydrolysis constant KH for compounds such as NH4HS (ammonium hydrosulfide) in water increases as temperature rises; in other words, the concentrations of free H2S, NH3, and CO2 molecules in water increase with rising temperature. Therefore, the temperature in the stripping tower should be above 110°C. Phase equilibrium is related to the concentration of each phase in the liquid phase, its solubility and volatility, as well as whether it can react with other molecules or ions in the solution. For example, CO2 has a very low solubility in water, as well as low relative volatility and reaction equilibrium constants with other molecules or ions in the solution; therefore, it can easily transition from the liquid phase to the gas phase. NH3, on the other hand, not only has a high solubility in water but also possesses high reaction equilibrium constants with H2S and CO2. Only when it reaches saturation under certain conditions can free ammonia molecules transition from the liquid phase to the gas phase. Clearly, the introduction of water vapor serves a dual purpose: it heats the mixture and reduces the partial pressures of H2S, NH3, and CO2 in the phase, thereby facilitating their transfer from the liquid phase to the gas phase and achieving the purification of acidic water.

This post was last edited by Sulfur-Zinc-Aluminum on 2016-3-19 09:05. An acidic aqueous solution is used as a desorbent to carry out the desorption process on the feed material (in gaseous form). Desorption is the reverse process of absorption, and both belong to the unit operation of gas absorption. Absorption is an example of a mass transfer process aimed at separating various components in a mixed feed (gaseous).

This post was last edited by Sulfur-Zinc-Aluminum on 2016-3-19 09:06. Principle of the acidic vapor stripping treatment process: Steam under certain pressure is used to vaporize volatile hydrogen sulfide and ammonia from the wastewater, thereby purifying the wastewater and extracting hydrogen sulfide and ammonia.

High-sulfur wastewater is a complex aqueous solution containing hydrogen sulfide, ammonia, carbon dioxide, and other substances. In water, hydrogen sulfide, ammonia, and carbon dioxide exist in the form of ammonium salts such as NH4SH, NH42S, NH42CO3, and NH4HCO3. These salts of weak acids and weak bases undergo hydrolysis in water, releasing free hydrogen sulfide, ammonia, and carbon dioxide molecules. These molecules are in equilibrium with their counterparts in the gas phase; thus, this system is a complex one characterized by chemical equilibrium, ionization equilibrium, and phase equilibrium all existing simultaneously. Therefore, controlling the appropriate conditions for chemistry, ionization, and phase equilibrium is key to properly treating sulfur-containing wastewater and selecting suitable operating conditions. The main factors affecting the above three balances are temperature and molecular ratio. Since hydrolysis is an endothermic reaction, heating can accelerate this process, increasing the amount of free hydrogen sulfide, ammonia, and carbon dioxide molecules. However, whether these free molecules can transfer from the liquid phase to the gas phase depends on their concentration in the liquid phase, their solubility and volatility, as well as whether they can react with other molecules or ions present in the solution. For example, carbon dioxide has very low solubility in water, a high relative volatility, and small equilibrium constants for reactions with other molecules or ions; therefore, it can easily transfer from the liquid phase to the gas phase. Ammonia, on the other hand, not only has high solubility in water but also has large equilibrium constants for reactions with hydrogen sulfide and carbon dioxide. Only when it reaches saturation under certain conditions can free ammonia molecules transfer from the liquid phase to the gas phase. The introduction of water vapor into the stripping tower serves a dual purpose: it heats the mixture and reduces the partial pressures of hydrogen sulfide, ammonia, and carbon dioxide in the gas phase, thereby facilitating their transfer from the liquid phase to the gas phase and achieving water purification