旋转喷雾干燥法脱硫
  一、旋转喷雾干燥法脱硫
  旋转喷雾干燥法又称LSD法，该脱硫工艺是以石灰粉(CaO)为脱硫剂，经消化并加水制成消石灰乳[Ca(OH)2浆液]，消石灰乳由泵打入位于吸收塔内的雾化装置，在吸收塔内被雾化成细小液滴的吸收剂与烟气混合接触，与烟气中的SO2发生化学反应生成CaSO3和CaSO4,烟气中的SO2被脱除。与烟气反应的同时，吸收剂带入的水分迅速被蒸发而干燥，烟气温度随之降低。脱硫反应产物及未被利用的吸收剂(俗称脱硫灰)以干燥的颗粒物形式部分随烟气带出吸收塔，进入除尘器被收集下来:部分靠离心力作用从烟气中分离出来，从吸收塔底部排出。为了提高脱硫吸收前的利用率，一般将部分脱硫灰再循环送回制浆系统，和吸收剂浆液混合成固体浓度为30%~50%的浆液。脱硫后的烟气经除生器除尘后排放。

该工艺系统很关键的一个参数就是吸收塔出口温度，渣浆泵一方面要求有足够低的温度，以满足脱硫化学反应的需要；另一方面又要保证高于露点，以防止设备和烟道的腐蚀。因此，在烟气中S02浓度、钙硫比不变的情况下，就只能通过水的变化来控制吸收塔出口温度。

喷雾干燥法脱硫工艺的优点是脱硫渣为干燥固体、便于处理，工艺能耗低，无废水，无腐蚀，技术成熟，工艺流程较为简单，投资与运行费用均较低，系统可靠性高等。脱硫率可达到80%以上。该工艺在美国及西欧一些国家应用较为广泛，在125MW以下机组上有一定的应用业绩。

Desulfurization by rotary spray drying

Desulfurization by rotary spray drying

The rotary spray drying method is also called the LSD method. The desulphurization process is using lime powder (CaO) as desulfurizer, after digestion and adding water to make lime slurry [Ca (OH) 2 slurry. The slaked lime milk is pumped into the atomizing device located in the absorption tower by the pump. The absorber is atomized into tiny droplets and mixed with the flue gas to react with the flue gas to produce CaSO3 and CaSO4. SO2 in flue gas is removed. At the same time of reaction with the flue gas, the moisture brought in by the absorbent is evaporated and dried rapidly, and the flue gas temperature decreases accordingly. Desulfurization reaction products and unused absorbent (commonly known as desulfurization ash) in the form of dry particles, part of them are carried out of the absorption tower with the flue gas and are collected in the dust collector; part of them are separated from the flue gas by centrifugal force and discharged from the bottom of the absorption tower. In order to improve the utilization rate of desulfurization before absorption, part of desulfurization ash is recycled back to the pulping system and mixed with absorbent slurry to form slurry with solid concentration of 30% ~ 50%. The desulfurized flue gas is discharged after dedusting by the deaerator.

One of the key parameters of the process system is the outlet temperature of the absorption tower. On the one hand, the temperature should be low enough to meet the needs of desulfurization chemical reaction; on the other hand, it should be higher than the dew point to prevent the corrosion of equipment and flue. Therefore, the outlet temperature of absorption tower can only be controlled by the change of water when the concentration of S02 and the ratio of calcium to sulfur remain unchanged.

The advantages of spray drying desulfurization process are that the slag is dry solid, easy to handle, low energy consumption, no waste water, no corrosion, mature technology, simple process, low investment and operation cost, and high system reliability. The desulfurization rate can reach more than 80%. The process is widely used in the United States and some Western European countries, and has some application achievements in the units below 125MW.