随着国家大力发展石化化工产业，油品炼制生产的蒸馏加压过程中不可避免的会产生火炬气，火炬气是石油化工行业工艺过程中产生的废气，其成分比较复杂主要含有碳原子、氢气及碳氢化合物，另外还包含硫氧化物、氮氧化物等酸性气体，属于易燃易爆有毒有害气体。由于其回收再利用工艺复杂但又不能直接排放而且过去的环保要求也比较低所以传统化工行业都是将其直接燃烧排放，这样既造成大量能源浪费又排放大量的温室气体污染环境；直接排放火炬气带来了严重的污染问题，大量可燃气体排放也带来了能源的浪费。为了做好火炬气的回收与利用，解决降低生产成本和治理环境污染的重要问题。中国石化集团安庆分公司为配套800万吨/年炼化一体化扩能改造项目，我参与了火炬气回收系统的建设。 火炬气主要组分是氢气和烃类气体，此外还含有酸性H2S、NO2等物质，火炬气回收主要是利用压缩机的加压方式将火炬气中的可燃部分提取出来，压力的控制贯穿于整个火炬气回收过程中，传统的压力控制多采用PID经典控制来完成，在各个控制回路中以压缩机出口压力的控制最为复杂，采用了压缩机出口压力-入口流量串级控制，本文将重点分析压缩机出口压力的控制方式和实现过程。 为实现火炬气回收工艺，本论文设计出基于DCS系统的控制系统，该系统包含硬件子系统和软件子系统，硬件子系统包含控制层硬件、监控层硬件和管理层硬件；软件子系统包含控制层软件和监督层软件；本工程项目在设计完成后，经过近两年十个月的施工建设，安装调试，现系统已稳定运行超过270天，回收各类火炬气.3×108Nm3，累计节省燃煤7.64万吨，且各项参数指标均达到设计的要求，取得了经济效益和环保效益的双丰收。

As our countries take great account of petrochemical industry, a lot of the flare gas will be produced during the process of petroleum industry. The emissions of flare gas pollution is becoming more and more serious. How to recovery and utilize the flare gas became the key link of reduce the production cost and control environmental pollution problems.In 2010, Sinopec Anqing built a new set of flare gas recovery unit to complete the 8 million tons per year refining-chemical integration project. Hydrogen and hydrocarbon gas is the main component of the flare gas in petrochemical industry.The recovery of flare gas mainly use inflating to extract the combustible part of the flare gas.How to control the pressure is the main link in flare gas recovery.In this paper, I designed and implement the hardware and software of flare gas recovery system, and mainly analyse the pressure control mode of the compressor inlet. Thesis mainly launches the research from three aspects. First, determine the overall design of the technological process, and design the hardware of automatic control system. Second, take flare gas compressor inlet pressure as the research object, carries on the cascade PID control, and design the software of control system. Third, describe the realization of the control process and the full process of PID parameters setting. After completion of this project in the design, we took nearly ten months of construction, installation and debugging, the system runs stably. Various parameter indexes meet the design requirements. The project is run successfully in the very first try, and obtained economic benefit and environmental benefit of double harvest.