【Haichuan’s Insights from Other Sources】Redirecting Hydrogenation Exhaust Gases to Boost Ethylene Production

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The 1.1 million tons per year ethylene plant is the main facility for producing ethylene at Dushanbe Petrochemical. Previously, the exhaust gas from the second-stage hydrogenation reactor of the hydrogenation unit was discharged into the suction tank of the second stage of the pyrolysis gas compressor. Due to the high volume of intake air, the pyrolysis gas compressor is often operating at full capacity and cannot handle any more pyrolysis gas, resulting in a situation where there is no way for the pyrolysis gas to flow onward, causing the compressor to \"swell up\". Dushanzi Petrochemical thoroughly implements the group company’s requirements regarding strict cost and expense management, issuing an initiative to maintain a tight budget over the long term. It calls on all employees and managers to take action from their own sides, to seek ways to reduce costs and increase efficiency, thereby fostering a stronger sense of responsibility, mission, and urgency in striving to create a version of operations that are of higher quality and more efficient. 　　To address the issue of hydrogenation off-gases limiting ethylene production, the technical staff from Ethylene Unit 1 visited the site on multiple occasions, reviewed relevant materials such as \"Principles of Chemical Engineering\" and \"Handbook of Chemical Process Design\", and after carefully studying the related processes of the plant, they proposed a solution to \"reroute\" the off-gases from the second-stage hydrogenation reactor of the hydrogenation unit, which previously flowed into the suction tank of the second stage of the pyrolysis gas compressor, to the separation tank in the fuel gas system. In this way, the inlet volume to the second-stage suction tank of the pyrolysis gas compressor can be reduced, allowing the capacity of the pyrolysis gas compressor to be fully utilized and further increasing the amount of pyrolysis gas. After clearing the path behind the cracking furnace, the amount of light hydrocarbons processed was further increased, resulting in a stable and increased production of ethylene. To ensure absolute certainty, technicians used process simulation software to verify the feasibility of the plan, and through analytical testing, they ruled out any impact that the \"redirection\" of hydrogenation exhaust gases could have on meeting the emission standards. 　　“The hydrogenation exhaust gas is ‘redirected’ to other systems, freeing up more space for the pyrolysis gas compressor to process the pyrolysis gas. More pyrolysis gas enters the compressor, clearing the path behind the pyrolyzer and increasing its capacity to process feedstock, thereby boosting ethylene production. ”Zhang Le said. The latest data show that after the \"re-routing\" of the exhaust gas from the two-stage hydrogenation reactor, the processing volume of high-quality light hydrocarbons as raw materials increased, resulting in a daily increase in ethylene production of 37.46 tons. It is estimated that the daily additional profit amounts to 80,000 yuan.