我国首套净化厂污水处理蒸发结晶装置析盐试运行

四川盆地中部磨溪区块下寒武统龙王庙组气藏天然气净化厂年处理能力达100×10~8m~3,为了实现污水零排放,该厂引进了具备污水回收率高、工艺流程简单、运行连续化、自动化程度高等优点的多效真空蒸发结晶装置,其设计处理盐水能力为300m~3/d,年生产时间为8 000 h。为了确保装置一次性顺利投产,根据该蒸发结晶装置工艺流程的特点,制订了快捷、经济的析盐试运行方案,开展了热态投料联动带负荷析盐试运行。结果表明:①各效蒸发室料液的温度、蒸发室的压力是装置平稳运行的关键参数,需结合主蒸汽阀门开度、水环真空泵抽真空度及不凝气阀门开度来进行综合调试;②各效蒸发室液位必须控制在45%以上,以防止料液循环泵被烧坏;③采取根据排盐与否调整料液取样时机、根据取样结果调整取样频次的办法,可防止排盐不及时引起的料液循环泵过载,以及停止排盐不及时引起的排盐系统空载现象;④试运行初期以Ⅰ效加热室蒸汽进出口温差判定蒸汽流量大小更为准确,提出的现场操作注意事项可规避Ⅱ效蒸发室压力过载及料液循环管被抽空的风险。结论认为:该装置试运行获得成功,实现了快捷、经济析盐,仅10 h便成功实现析盐、排盐,耗盐量由23 t缩减为10t。

Commissioning of evaporation and crystallization device firstly applied to wastewater processing in a natural gas purification plant in China

The purification plant for the natural gas produced from Lower Cambrian Longwangmiao Fm gas reservoirs in the Sichuan Basin has a yearly processing capacity of 100×10⁸ m³. To achieve the zero discharge of wastewater, a multi-effect vacuum evaporation and crystallization device was introduced in this plant, with the designed saline processing capacity of 300 m³/d and yearly production time of 8 000 h. This device is characterized by high wastewater recovery, simple process, continuous operation and high automation. To ensure one-pass commissioning of the multi-effect evaporation and crystallization device, a reasonable salt precipitation scheme was prepared by taking the characteristics of its technological process into account. Then, such commissioning was carried out under actual operating conditions. The results show that pressure and temperature of each evaporation chamber are key parameters for the smooth operation of the device, and a comprehensive debugging should be carried out according to the opening of the main steam valve, the vacuum degree of the water ring vacuum pump and the opening of the non-condensable gas valve. The liquid level of each evaporation chamber should be kept above 45% so as to prevent circulation pumps from breaking down. It is necessary to adjust sampling timing according to the occurrence of salt discharge and to confirm sampling frequency according to sampling results so as to avoid circulation pump overloading which is caused by untimely salt discharge and to prevent zero load of the salt discharge system which is resulted in when salt discharge is not stopped in time. At the initial stage of commissioning, steam flow rate can be judged more accurately based on the temperature difference between the steam inlet and outlet of Heating Chamber #I. Pressure overload will not occur at Evaporation Chamber #II and circulation pipes will not be evacuated if the operation is complied with the proposed field operation considerations. It is concluded that its commissioning is successful with fast and economical salt precipitation. Salt precipitation and discharge occur only after 10 hours of running of the device and salt consumption drops to 10 t from 23 t.