New Design And Optimization Of Flue-Gas Desulfurization By Seawater

The seawater FGD process uses alkanice to absorb SO₂ in flue gas, not only the technology is easy and economy, but also it has good prospect. The process can control the emission of pollution gases. It clearly changes the atmospheric quality. The technology is widely used by several power plants, the related theory has been reported. Laboratory have done experiments which study the fators of Flue-Gas Desulfurization by seawater: the salinity of seawater, alkalinity, temperature, pH Etc. The related pilot compared several types of structured packing. Using the research of laboratory and the related literature, this thesis studies the following respects in depth.1.The mechanism of SO₂'s absorption in SFGD is researched: absorbing SO₂ using seawater was simplified, basing on the principle of SFGD and the main fators, the true process is simplified to the process which using bicarbonate absorbing SO₂ in flue gas. With charge conservation and the materials conservation of full tower, the thesis studies the relationship between pH, y(Mole-Frac), S(IV)total and the bicarbonate's concentration, the result has certain error, but it still can be used for process design and analysis. The thesis also proposes and gives a solution of enhancement factor. At the same time, it revises the mass transfer rate equation's coefficient.2.Basing on the References, the thesis modifies the parameters of the absorber, it calculates the tower diameter, the filling height and the related design parameters of gas-liquid. The model for simulation of Flue-Gas Desulfurization by seawater is established, it based on flow-simulated software:Aspen. It displays out the influence of desulfurization by technical parameters such as gas-liquid ratio, the amount of flue-gas as well as composition of seawater, packing height, etc; besides, the thesis optimizes the feeding method. The results make known that liquid to gas ratio effects the desulfurization rate, liquid to gas ratio is higher, and the desulfurization rate is higher. The alkalinity of seawater is researched: If the [HCO3—] is more enough, the desulfurization rate is higher. Basing on the equilibrium and operation equation, the thesis discusses the relationship between the pH and the height of filler. It optimizatises the technology: one process is that making the total volume of liquid equal to the single volume, then calculate the desulfurization rate and make a comparison; the other process is that setting the desulfurization rate of two parts equal, then calculate the desulfurization rate of each part. The result shows that both processes are better than the original.3.Recovery system mainly takes place sulfites oxidation reaction, according to double film theory and data of the literature, the sulfites content of seawater from the tower is less than critical concentration, reaction is controlled by double membrane process, reaction series is not zero. The thesis discusses oxidation dynamic formula: when the air is enough, oxygen concentration doesn't influence reaction rate, the thesis fits the data of the literature, explores the relationship between the k and [H+], basing on equation, the thesis calculates retention time, optimal conversion rate is 80%, the thesis explores the relationship between the t and pH, oxidation time is shortest when pH=6, t=0.05h, basing on the retention time, the thesis calculates the parameters of aeration tank, the seawater from the tower is acidic, it needs adding seawater in order to recovering the pH at 6 around, basing on the experimental data, the dilution ratio is 3 and pH=6.04, basing on the above data, the thesis calculates the volume of aeration tank and drain tank, using economic perforated pipe as aeration device, the air drums into the bottom of the pool, the thesis calculates pressure drop of the longest pipe line, and the result is 2806.65kPa.