Optimization Of Seawater Fgd Technology

The Rizhao power plant of Huan Neng is located at Rizhao City of Shandong Province, which is a seashore large-scale thermal power plant of coal-burning condensation type. The SO₂ emission concentration and yearly total quantity of two 2×350MW units respectively are 1757 mg/Nm³ and 23778 t. The plant is one of the largest SO₂ emission factories. The National Environmental Protection Bureau requested that the Rizhao power plant should start the desulphurization device to adapt to more and more serious air pollution by the end of 2005. Because the SO₂ concentration of burning coal is lower than 1%, the sea water alkalinity meets technologic requirement, and the sea area environmental effect appraisal passed the checking of the National Department, the sea water desulphurization is considered first.The sea water desulphurization technics used natural pure sea water as the absorbent to absorb SO₂ without any chemical additives and waste. The sea water desulphurization was one kind of new desulphurization technics, which had the advantagements of technologic maturation, the technologic simpleness, the running convenience and the high desulphurization efficiency, and got ahead of other desulphurization technics. The sea water desulphurization technics can effectively control the SO₂ emission of power plants, and meanwhile reduce the dust emission, which played an important role in improving the air quality.In this paper the sea water desulphurization of Rizhao power plant was researched. The desulphurization system was divided into four subsystems. The gas subsystem, absorbing tower subsystem, sea supply- emission subsystem, and sea renew subsystem are respectively studied. By the introductions of the desulphurization device, the analysis of the running process, and the running practice, the key problems of device running were proposed. The optimization measures were proposed from the point of running. Other power plants can learn these experiences.First the gas subsystem was studied. The time of the flue bypass baffle was adjusted to not more than five minutes. The baffle of the entrance desulphurization gas interlocked with the pressure fan. The pressure fan and the entrance and exit baffles were running first, and when the system ran normally, the flue bypass baffle was shut down. Two airproof machines of GGH were kept running and the drying temperature maintained at 90 centigrade degrees. The vanes were moved on schedule when the pressure fan shut down. GGH kept running when maintaining in order to advoid serious anomalous corrosion due to the difference of the flue relative humidity.In order to increase the desulphurization efficiency, the temperature of the entrance gas kept below 120 centigrade degrees. By blowing the accumulated ash of the GGH inner heat exchanging surface, good effect of heat exchange was achieved. When the temperature of the entrance gas was below 30 centigrade degrees, it passed through the bypass of absorbing tower for fear of the serious corrosion of the tower.The alarm of lower water level was added. When the alarm was given, the sea pressure pump and the desulphurization device were all shut down.Check the cooling water pressure, flux and the filter pressure difference of the pump. Adjust the pressure of the pump in time by load and the gas amount.When the pH of sea water was below 6.8, adjust the pH of air pool water exceeding 6.8 by the opening angle of the FGD bypass baffle. The sea water also can reach the standard by adjusting the fun pressure of the air pool, and making the acid and the alkali sea water neutralize and react mixed with the air.