Performance characteristics of combined wet desulfurization dust collector
Sustainable development and environmental pollution are the main issues of social development today. China is a large coal-producing and coal-consuming country. At present, coal accounts for about 75% of primary energy consumption, of which 84% is directly used for combustion. Due to the relatively backward combustion technology, the problem of low combustion efficiency has been brought. At the same time, the quality of a large number of desulfurization and dust removal equipment is not enough. The treated flue gas still contains a large amount of smoke, SO2, NOX and other pollutants. China emits 8 million tons of smoke, 6 million tons of SO2, more than 600 million tons of CO2 gas and a lot of harmful gases such as NOX to the atmosphere every year. The atmosphere has caused serious pollution.
Status of industrial boiler flue gas desulfurization technology
From the perspective of environmental protection, desulfurization technology can be divided into three major categories before combustion, during combustion, and after combustion, a total of more than a dozen technologies. The desulfurization of flue gas in industrial boilers in China generally uses post-combustion desulfurization. This is a desulfurization method that is widely used in various countries around the world. It is also a desulfurization method with mature technology and widely used in the world. The post-combustion desulfurization is divided into three methods: dry, wet and dry. Among these three desulfurization methods, wet desulfurization is commonly used, and the use of this method in Japan, Germany and the United States accounts for more than 90% of all desulfurization methods.
The basic process of wet desulfurization is to wash the flue gas with a desulfurizing agent solution in a desulfurization reaction tower to make the two undergo a strong chemical reaction and mass transfer process to remove sulfide in the flue gas and achieve the purpose of purifying the flue gas.
Existing industrial boiler wet desulfurization dust collectors can be divided into two categories, one is a separate dust collector that separates dust and desulfurization; the other is an integrated dust removal and desulfurizer that combines dust removal and desulfurization, and two types of desulfurization Dust removal methods have their own advantages and disadvantages.
Split wet desulfurization dust collector
There are two types of existing split wet desulfurization dust collectors: one is a multi-tube dust collector with a water bath sedimentation chamber desulfurization method; the other is a multi-tube dust collector with a spray type desulfurization method.
(1) Desulfurization method of multi-tube dust collector plus water bath settling chamber
This desulfurization and dust removal method is characterized in that the boiler flue gas first enters a multi-pipe dust collector for dry dust removal, and the flue gas after the primary dust removal is sent by a draft fan to a water bath sedimentation chamber for desulfurization. chimney. The water bath sedimentation chamber is a semi-underground flue. The lower part of the flue is a sedimentation tank. There are communication holes on the side wall of the sedimentation tank that communicate with the external pond to remove sediment sludge. There are 1 or 2 partitions above the sedimentation tank. To force the smoke to pass through the water bath from below the water surface. The advantages of this desulfurization method are: simple structure, low cost, and easy to use. Disadvantages are: a. Large floor area, enough site is needed to settle the settlement chamber; b. Water level control is difficult. When the water level is high, the resistance is too large, which causes the boiler to operate under positive pressure; When the water is low, the desulfurization is invalid; c. The desulfurization effect cannot be achieved.
(2) Multi-tube dust collector plus spray type desulfurizer
The characteristics of this type of dust removal and desulfurizer are that the flue gas of the boiler first passes through a multi-tube dust collector, and the flue gas after the dust removal enters the desulfurizer through the flue, and the flue gas is desulfurized in the desulfurizer and discharged into the chimney through an induced fan. The desulfurizer is composed of a 180 ° elbow, a spray device, a cylinder, a gas-water separation device, a water-sealed sewage pipe, a circulating water pump and a sedimentation tank. The water spray device is arranged on a 180 ° elbow. In Simplified Chinese, water and flue gas are fully mixed, and SO2 is absorbed by the water mist. The role of the separator is to separate the sulfur-containing water mist from the flue gas to achieve the desulfurization of the flue gas. The water-sealed sewage pipe continuously discharges the separated sewage into the sedimentation tank. The circulating water pump sends the sedimented water to the spray device. The sedimentation tank sediments the sludge in the desulfurized sewage, so that the desulfurized water can be recycled. The sedimentation tank Another function is that lime can be added to the water to adjust the PH value of the desulfurized water to keep it weakly alkaline, so as to achieve the desulfurization effect.
The advantages of this wet desulfurization dust collector are: a. Simple structure and easy installation; b. Better desulfurization effect; c. Because the desulfurized water contains only very fine dust, it can be recycled, save water, and can effectively avoid desulfurization Secondary pollution of the environment with water.
The disadvantages of this wet desulfurization dust collector are: a. Due to the large area of the split type; b. There are also many elbows in the flue after the multi-tube dust collector plus the desulfurization device. In general, the wind resistance is large and needs to be increased. Induced draft fan power; c. Because the desulfurization water spray device is in line with the flue gas direction, the flue gas carries serious water and corrodes the induced draft fan and the flue; The impeller is out of balance. This shortcoming is fatal, resulting in that it can only cope with short-term environmental testing, and cannot be continuous and long-term normal operation. When users use this type of desulfurization dust collector, they do not know the disadvantages of this kind of desulfurization dust collector. It is too late to find the problem after the boiler is put into operation, and they have to stop the desulfurization operation after the environmental protection monitoring is qualified.
Integrated wet desulfurization dust collector
Existing integrated wet desulfurization and dust collectors have a variety of products, and their common features are: dust removal and desulfurization are performed in the same container, and desulfurization water and sewage are simultaneously discharged from the sewage outlet. Integrated wet desulfurization dust collectors can be divided into two categories: one is the common hemp water film dust collector. This type of dust collector has better desulfurization effect, but it has a large floor area, a long installation cycle, large resistance of the dust collector itself, overload of the induced draft fan with steam and water, large water consumption, and easy secondary pollution, and large sedimentation tank volume And need to be equipped with sludge fishing equipment. The other type is that the steel wet desulfurization dust collector has a small amount of water, and the desulfurization water is not reused. (Some can be reused). The water and sludge are discharged from the sewage outlet in a thin state. The principle of dust removal and desulfurization is: after the high-speed flowing flue gas hits the water surface, it returns to 180 ° and leaves the water surface. Dust particles are washed into the water under inertia to realize the process of secondary dust removal and desulfurization. The foam splashed by the air stream plays a secondary role in cleaning the flue gas, and the flue gas returns to 180 ° to separate the gas and water. Some designs discharge the sludge into the slag remover and send them to the ash yard along with the boiler slag removal. Some designs discharge the sludge into a small sludge tank, and the excess water is discharged into the sewer after being treated with water. , The sludge is manually removed (some designed sedimentation tanks).
The advantages of the integrated wet desulfurization dust collector are: a. The elimination of the multi-tube dust collector, the equipment has a small volume, a small footprint, and a small applicable boiler room; b. The flue gas flow resistance is small; c. The installation is simple; d. The desulfurization effect is better.
The disadvantages of the integrated wet desulfurization dust collector are: a. Desulfurized water is used once, which wastes water and is easy to cause secondary pollution; b. The pH value of the desulfurized water is difficult to adjust, and it depends on manual intermittent drainage. Desulfurization effect; c. Exhaust smoke and water, corrode induced draft fan and chimney.
Structure type of combined wet desulfurization dust collector equipment
The combined wet desulfurization dust collector is a patented product (patent number: ZL03111984.0). This equipment is a new type of desulfurization and dust removal integrated with dry and wet desulfurization and dust removal. Mainly consists of smoke inlet, lower cyclone sedimentation dust collector, ash discharge tube, ash discharge valve, spiral straight pipe, flue gas diffusion chamber, droplet separation chamber, water spray device, flue gas vortex chamber in the upper wet desulfurization dust collector. , Gas and water mist chamber, gas-water separation device, smoke sink, exhaust port, sewage valve, circulation pump, sedimentation tank and other parts.
Working principle of combined wet desulfurization dust collector
The dusty flue gas or sulfide discharged from the boiler enters the flue inlet of the combined wet desulfurization dust collector. After the lower dry dust collector removes more than 90% of the coarse dust in the flue gas, the flue gas is 8 ～ 22m / The s speed enters the flue gas diffusion chamber in the upper wet desulfurization dust collector by the spiral straight pipe. The dust-containing and sulfide-containing air stream directly impacts the liquid surface, a large number of vortices and water splashes collide, and large dust particles fall into the bottom of the pool. The flue gas and tiny dust particles enter the droplet separation chamber, are circulated and washed by the mixing spray device, and are fully contacted and mixed with the flue gas, diffuse and drift, return to the flue gas vortex chamber, and enter the gas and water mist chamber under a state of sharply turning to a high airflow. The smoke and sulfide were captured and separated again. Under the negative pressure of the induced draft fan, the flue gas carried part of the water vapor droplets and entered the flue gas chamber through the gas-water separation device. The purified flue gas was discharged from the smoke exhaust port. . At the same time, the sulfide in the flue gas is cyclically washed and reacted with a dosing balance tank containing lime milk or alkali to generate calcium sulfite crystals, which are sandwiched with stucco and sunk into the water, and are discharged into the sedimentation tank through a sewage valve.
Main technical performance indicators of combined wet desulfurization dust collector
(1) Dust removal efficiency: 96 ～ 99%
(2) Desulfurization efficiency ≥80%
(3) Resistance loss 900 ~ 1400Pa
(4) Lingerman smoke blackness below level 1
(5) Dust content of smoke and dust <80mg / m3
(6) Sulfur content of flue gas <900mg / m3
(7) Dust content of imported flue gas ≤15000mg