行业：化工行业

Monitoring scheme for toxic and hazardous gases in chemical plants

行业痛点

化工厂是国家”重大危险源”管控核心场所 — 反应釜、储罐区、装卸栈台、罐区围堰、火炬系统、装置区、罐顶呼吸阀，每一个环节都同时面临可燃 + 有毒 + 缺氧 + 高温高压复合风险。常见气种横跨 50+ 个：氯气（光气合成 / 氯碱）、HCl / 氟化氢（氟化物生产）、氰化氢（VCM 工艺）、苯系（BTX 装置）、丙烯腈、环氧乙烷、光气、硫化氢、CO、氨气、甲醇、乙烯、丙烯、丁二烯…… 仅 2024 年危化品事故公开统计：80% 涉及气体泄漏先发，VOC 类挥发占 42%。监管层面要求严格 — GB 30871 受限空间作业、GB 50493 自动报警、GB 18218 重大危险源辨识、HSE 三同时审查、应急管理局”双控机制”、长输管道法 — 每一项都涉及监测点。一次大型化工事故（如 2015 年天津港爆炸）社会影响 + 罚款 + 赔偿往往数十亿级。

方案概述

优锐安针对化工厂提供全工艺链 + 全气种 + 多层级监测方案：① **装置区**：反应釜上方 / 管道法兰 / 阀门组 / 取样口部署固定式电化学 + PID + 红外多原理探头，对甲苯 / 苯 / VCM / 丙烯腈等高致癌物专项 PPM 级 PID；② **罐区**：每个储罐顶部 + 罐底 + 围堰 4-6 点，配压力 / 液位 / 温度联合，符合 GB 50493 一类危险区设计；③ **装卸栈台**：固定 LEL + H2S + VOC + 接地线状态四合一，杜绝静电起火风险；④ **火炬系统**：火炬燃尽率气体监测，环保合规 + 碳排放计量；⑤ **中央 SIS / DCS 联锁**：多级 SIL 等级气体探头按 GB 21109 接入安全仪表系统，超高报自动启动 ESD 紧急停车 + 罐区联锁切断阀 + 事故水池预备 + 周边人员定位疏散广播。设备防爆等级 Ex d IIC T6（最高级别）。

## Recommended Configuration Matrix (By Process Unit)

– **Chlor-Alkali / Chlorination Process**: Cl2 / HCl electrochemical sensor (range 0-10 ppm, PC-TWA 1 ppm) + phosgene-specific probe (range 0-1 ppm, IDLH at only 2 ppm, extremely hazardous)
– **Styrene/Acrylonitrile Plant**: Benzene + Acrylonitrile PID Composite Probe (PID Sensitivity at PPB Level) + Flash Point Interlock
– **Ethylene/Propylene Storage Tank**: LEL + Infrared CH4 Dual Probe (with explosion-proof design to prevent PID failure in high humidity environments)
– **VCM (Vinyl Chloride Monomer) unit**: dedicated PID for VCM (strong carcinogen, PC-TWA 7.5 mg/m³) + simultaneous measurement of hydrogen chloride and HCN
– **Ammonia synthesis unit**: NH3 + H2 + high-pressure leak detection (infrared imaging + laser remote sensing combination)
– **Methanol/Ethanol Distillation Area**: LEL + Benzene + Formaldehyde (intermediate product of methanol oxidation)
– **Tank farm cofferdam**: Each cofferdam is equipped with LEL + H2S + toxic gas sensors, depending on the product, and is 0.3m higher than the cofferdam itself
– **Loading dock**: oil and gas recovery monitoring + static electricity alarm + grounding wire monitoring + air detection before drivers exit the cabin
– **Flare system**: flare tail gas SO2 / NOx / VOC / flame photoelectric signal (flame extinction detection, prevention of direct emission)

## Key Technical Specifications

– Explosion-proof grade: Ex d IIC T6 (the highest level in the chemical industry, covering Class IIC gases such as hydrogen and acetylene)
– Protection: IP66 / IP67 (outdoor tank area + coastal humid and hot environment)
– SIL level: SIL 2 – SIL 3 (integrated into SIS safety instrumented system)
– Range: PPM-level sensitivity for toxic gases, 0.01 ppm; LEL 0-100% with three-level alarms at 10%, 25%, and 50%
– Response time: T90 < 15 seconds (toxic gas) - Operating temperature: -40℃ ~ +75℃ (outdoors in tank areas during winter in the north and summer in the south) - Communication: HART + Modbus + Profibus, compatible with DCS / SIS safety instruments ## Implementation Essentials (Determining Project Success) 1. **Mandatory for SIL Assessment**: Identify the SIL level (SIL2 = failure rate ≤ 10⁻³) of each monitoring circuit according to GB 21109-2007 / IEC 61508, and the probe selection must meet the standards 2. **Interlock Logic Levels**: Low Alarm → On-site Announcement; High Alarm → DCS Shuts Off Feed + Closes Tank Farm Valves; Ultra-High Alarm → ESD Emergency Shutdown + Activates Accident Water Pool + Notifies Emergency Rescue 3. **VOC LDAR Legal Requirements**: The plant area must conduct flange/valve leak detection (infrared imaging or PID inspection) at least four times a year, and the data must be reported to the local environmental protection bureau 4. **Calibration + Standard Gas Management**: Highly toxic gases (phosgene / chlorine / hydrogen fluoride) are scarce and highly hazardous, requiring high-purity standard gas cylinders + automatic dilution and dispensing stations 5. **Emergency Linkage**: Integrating with the plant's GIS map and wind direction and speed data, it automatically calculates the diffusion range after a leak, determines the affected personnel locations, and recommends evacuation routes ## Regulatory Basis (The Strictest for Chemical Industry) - GB 50493-2019 "Design Standard for Combustible Gas and Toxic Gas Detection and Alarm in Petrochemical Industry" - GB 18218-2018 "Identification of Major Hazard Installations for Dangerous Chemicals" - GB 30871-2022 "Safety Code for Special Operations in Hazardous Chemical Enterprises" - GB 21109 series "Functional Safety of Safety Instrumented Systems in the Process Industry Sector" - HJ 1093-2020 "Continuous Monitoring System for Pollution Source Flue Gas" - AQ 3013 General Specification for Safety Standardization of Hazardous Chemicals Employers - GBZ 2.1-2019 Limit Standards ## Applicable Customers Large petrochemical groups (Sinopec / PetroChina / CNOOC); coal chemical industry (Shenhua Coal Chemical / Middling Coal Shaanxi Yulin / Yankuang Yulin); fine chemical industry (Wanhua / BASF / Cabot / Rhodia); fluorine chemical industry / chlor-alkali (Juyuxin Materials / Binhua / Xinjiang Zhongtai); pharmaceutical active pharmaceutical ingredients (Huahai / Prolo / Hisun); enterprises in chemical industrial parks + central supervision platform of the park.