Theoretical And Practical Research On The Recycling Of Low Concentration SO₂ Using Sodium Citrate Process

Flue Gas Desulfurization(FGD) are the main technologies in the controlling of acid rain and sulfur dioxide, but still have their own disadvantages respectively in their applicable scope, economic benefit, or even the technology itself. This paper compares some of the main wet FGD technologies synthetically, and finds that the Sodium Citrate Process has many advantages such as low investment, low operation cost, short technical flow, can separate SO₂ effectively, the absorbent can be recycled, no secondary pollution, and so on. Sodium Citrate Process has been applied in high concentration SO₂ Flue Gas Desulfurization for many years, but little research has been carried out in that of low concentration.This paper aims at low concentration SO₂ flue gas, investigates the Sodium Citrate Process and its application feasibility, and carries out theoretical and experimental research on kinds of influential factors, finds the basic rule of sodium citrate absorbing SO₂ from low concentration flue gas, confirms the main parameters of absorption and desorption process, ratiocinates its own calculational methods of liquid gas ratio. All of these provide authentic reference data for the industrialization design, and have a concernful significance for the treatment of low concentration SO₂ flue gas.The result of experimentation indicates: the Sodium Citrate Process has quite higher desulfurization efficiency;the treated flue gas can satisfy the requirement of air standards;the production (gaseous SO₂) is quite pure, more than 90% by volume. Therefore, the Sodium Citrate Process is a new FGD technology worthy to be generalized. In practical running, the concentration of absorbent, pH value, liquid gas ratio and temperature all have significant influence on desulfurization efficiency. Considering absorption/desorption efficiency and the running cost, we confirm the following parameters: the pH value of original absorbent should between 4 and 5;the optimal concentration of citric acid is 0.75-1.25mol/L;temperature should be controled in 20⁵0 °C;absorption efficiency is more than 98%;desorption efficiency and liquid gas ratio should be calculated according to the SO₂ concentration in the flue gas.