May 15, 2011 (Weekly Topic)
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This post was last edited by adsl121 on 2011-5-15 10:05. What type of steam is used in wastewater stripping? In the process of fully extracting steam from the top of a single tower, some designs use superheated steam at 1.0 MPa and around 250 degrees Celsius, while others use steam at 0.4 MPa. Which type of steam is everyone using? Is there any issue with the discharge of condensate water?
Reply to 1# adsl121: 1. The stripping steam is saturated steam at 1.0 MP； 2. There is no issue with sending the condensate away; a water distributor is installed at the outlet of the reboiler, and this distributor controls the pressure at 0.35 MP. Venting and pressure compensation systems are also provided at the top to regulate the pressure ； 3. In my opinion, the steam pressure level is not an issue; what’s important is that the steam temperature must be at least 20 degrees higher than the temperature at the bottom of the stripping tower. As for the condensate pressure, if it’s sufficient to transport the water, then that’s fine; otherwise, the water should be deaerated before being pumped
Basic principle of the stripping method: Similar to the blowing method, except that a different medium is used; stripping is achieved by utilizing water vapor as the medium. The process of separating pollutants using the stripping method varies depending on the nature of the pollutants, and can generally be divided into the following two types: 1. Simple distillation – For volatile substances that are miscible with water, this method takes advantage of the fact that, under gas-liquid equilibrium conditions, their concentration in the gas phase is higher than that in the liquid phase. It is directly heated by steam, causing it to become enriched in the gas phase at a certain proportion at its boiling point (a temperature between the boiling points of water and the volatiles). 2 Steam distillation – For volatile pollutants that are immiscible or practically immiscible with water. By taking advantage of the fact that the boiling point of the mixture is lower than that of its components, high-boiling volatile substances can be separated and removed at lower temperatures. For example, substances such as turpentine, aniline, phenols, and *** in wastewater can be separated using distillation at temperatures below 100°C. The main equipment for stripping is the stripping tower, which falls into two categories:
– Packed towers, in which various types of packing are placed in layers inside the tower.
– Plate towers, which are further divided according to their tower-plate structure into:
(1) Bubble cap towers
(2) Floating valve towers
(3) Screen plate towers.
Plate towers are more efficient than packed towers.
Applications of the stripping method
The stripping method was first used to recover volatile phenols from wastewater containing phenols. After the wastewater is preheated to 100°C, it is fed from the top of the stripping tower, where it meets the rising vapor stream. Mass transfer occurs within the packing layer or on the tower plates, and the purified wastewater is then discharged through a collection tank. The vapor-phenol mixture is discharged from the top of the tower and forced into the regeneration section by a blower to recover phenol. The phenol-containing steam is fed in from the bottom of the regeneration section, where it first meets the circulating alkali solution that flows downward in counterflow, and then encounters the additional fresh alkali solution (with a concentration of 10%). Phenol is removed through chemical absorption, and the purified steam is sent to the stripping section for reuse. Alkaline solution reacts with phenol to produce sodium phenolate
– Packed towers, in which various types of packing are placed in layers inside the tower.
– Plate towers, which are further divided according to their tower-plate structure into:
(1) Bubble cap towers
(2) Floating valve towers
(3) Screen plate towers.
Plate towers are more efficient than packed towers.
Applications of the stripping method
The stripping method was first used to recover volatile phenols from wastewater containing phenols. After the wastewater is preheated to 100°C, it is fed from the top of the stripping tower, where it meets the rising vapor stream. Mass transfer occurs within the packing layer or on the tower plates, and the purified wastewater is then discharged through a collection tank. The vapor-phenol mixture is discharged from the top of the tower and forced into the regeneration section by a blower to recover phenol. The phenol-containing steam is fed in from the bottom of the regeneration section, where it first meets the circulating alkali solution that flows downward in counterflow, and then encounters the additional fresh alkali solution (with a concentration of 10%). Phenol is removed through chemical absorption, and the purified steam is sent to the stripping section for reuse. Alkaline solution reacts with phenol to produce sodium phenolate
We have two sets of sewage systems side by side. The full-blown stripping tower uses 1.0 MP steam. The reboiler for the hydrogenation wastewater also uses 1.0 MP steam; these two streams of condensed water are combined in one pipe for heat exchange, and then pumped out of the system. Due to the difference in temperature between these two streams of condensate, water hammer is quite severe.
There is a problem of insufficient condensate water pressure, and I’m looking for experts to help solve it. Our reboilers for non-hydrogenated acidic water use superheated steam at 1.0 MPa, while the temperature of the condensate water is around 147 degrees; the pressure is insufficient by 0.4 MPa, making it difficult to feed this water into the condensate system. I’m not sure how to address this issue