How can sulfur recovery be carried out, or what technical modifications can be made to reduce the pressure in the combustion furnace?
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This post was last edited by Shandong Huaxing on 2010-8-2 09:39. Our facility uses a split-flow method for Claus sulfur recovery, and the process flow is as follows: One-third of the acidic gas coming from the low-pressure section, together with the air supplied by the air fan, enters the acid gas combustion furnace where it reacts to produce SO2 (the temperature is generally maintained at 1100–1200°C). After that, the gas is cooled in a deionized water preheater; steam is generated as a by-product, and heat is recovered. The flue gas exiting this preheater (with a temperature of 300–350°C) mixes with the remaining two-thirds of the acidic gas (at a temperature of 200–230°C), and then enters the three-stage Claus reaction. The exhaust gas is sent to a boiler for combustion. The acidic gas with low methane content (at a pressure of 150 kPa) is sent partly to sulfur recovery and partly to the boiler. The pipeline leading to the boiler and the pipeline leading to the sulfur recovery system meet at a tee; the maximum pressure in the combustion furnace of the sulfur recovery system is 50 kPa. Therefore, if the valve that directs the low-methane gas to the boiler is opened too wide, it will cause an increase in the pressure within the sulfur recovery system. Normally, three boilers are in operation; the gases from sulfur recovery and low-carbon monoxide treatment are sent directly into the boilers’ furnaces. When there are five gas generation boilers, the amount of acidic gases is relatively large. The pressure in the sulfur recovery system generally fluctuates between 40-45 kPa. In our company, six boilers are in operation while one is on standby at full capacity. If more boilers are added, the pressure in the sulfur recovery system will exceed the allowable limit. What measures can be taken or what technical adjustments can be made to keep the pressure within the normal range? (The sulfur recovery system has a venting mechanism that can reduce pressure, but this approach is not environmentally friendly and causes severe pollution.)
Is the system pressure already at this level right from the start of operation?
This post was last edited by Shandong Huaxing on 2010-8-3 at 13:40; adding an acidic gas buffer tank will suffice to maintain a pressure of 0.5 bar. The pipeline leading to the boiler can be installed in front of the valve on the buffer tank, while the pipeline leading to sulfur recovery can be placed at the top of the tank.
This post was last edited by Shandong Huaxing on 2010-8-3 at 13:40. It’s possible that the backflow path is slightly blocked; it’s sufficient to take several points along the entire process flow and measure the pressure there to determine the situation. This problem has occurred in my company before, but we used the Klaus partial combustion method
Reply to 2# Shandong Huaxing: Since we started operating the plant, whenever all five gas generation furnaces are in use, the pressure almost always exceeds the limit; there is no blockage in the backflow path, and there is also no blockage within the industrial facility itself
Reply to 3# dragonzhang: Does that mean the H2S produced by low-pressure flashing goes directly into the buffer tank, where the pressure is stabilized at 0.05 MPa, and only then is it sent to the sulfur recovery unit and the boiler?
This post was last edited by Shandong Huaxing on 2010-8-4 13:04. I’m sorry; I didn’t express myself clearly. What I mean is: the pressure for sulfur removal and recovery needs to be maintained, so a buffer tank is required. The pressure going to the boiler does not need to be given excessive attention, but it is not desired that it affect sulfur recovery; therefore, its outlet should be located before the pressure stabilizing tank. This is just a suggestion for your reference; your system is different from the petrochemical industry that I am familiar with.
Where is your company located? How is it running now?
Generally speaking, if there is no blockage in the system, high pressure is usually caused by a high load. It is possible to consider making the control of the feed gas more stable, adjusting its concentration to a higher level if feasible, or considering implementing technical upgrades to increase the oxygen content and thereby reduce the load on the facility.
The high pressure is caused, first, by blockages in the tube bundle, and second, by sulfur deposition on the catalyst inside the reactor; it is recommended to increase the amount of air used for purging slightly