Destination of exhaust gas after desulfurization of refined liquefied gas

Off-gases from the liquefied gas desulfurization unit: The pressure is likely not sufficient for a low-pressure system, and the off-gases contain a large proportion of air components; therefore they probably cannot be used as fuel gas

For the exhaust gas testing after gasoline desulfurization, since it is within the explosive range, are there any special safety measures in place to prevent ignition and thus avoid explosions caused by the desulfurized exhaust gas?

This post was last edited by ylb913 on 2016-6-16 at 12:47. This gas is highly corrosive; currently we use low-wattage versions, as the pipelines cannot withstand more than 2 cycles of use. This gas cannot come into contact with an open flame directly, as it will explode; we once integrated it into the air flow of the exhaust gas incinerator. Over the years, an explosion occurred once when liquefied gas was present in the exhaust gases, and since then lower power levels have been used. There is one more thing regarding entering the incinerator, and it has a significant impact on sulfur dioxide in the flue gases. In other factories, gas is mixed in to exceed the explosion limit and then used as fuel for the heating furnace.

The desulfurization exhaust gas from liquefied gas contains unreacted oxygen, and it cannot be discharged directly into the low-pressure pipeline network. In design, it is usually discharged directly into a catalytic flue, but it can also be sent to high altitudes after passing through an alkali scrubber or an amine scrubber.

That section of the pipeline is severely corroded – is it the exhaust line or the low-voltage main pipe? Have you replaced it?

Entering the low-pressure gas system leads to the flare; high-pressure gas system is used as fuel gas

This post was last edited by ylb913 on 2016-6-16 at 21:56. 1. We replaced the exhaust lines with stainless steel ones many years ago; the initial reason for this was not corrosion-related leaks, but rather blockages in the pipes caused by rust. 2. It was only after the pipes were put into use at lower voltage levels that the severity of corrosion became apparent. The new pipelines were installed in 2007, and they were put into operation at lower voltage levels in October 2010; many leakage points appeared in the upper part of these pipelines by 2012. During a major maintenance campaign in April 2013, some of the pipelines were replaced. In 2015, multiple leakage points appeared successively in those pipelines that had not been replaced. ——As mentioned above, for pipelines with a diameter of DN200 or 150, the thickness should be at least 6 to 7 mm. However, to date, all corrosion-related leaks have occurred within the main pipes of the low-pressure lines in the liquefied gas desulfurization unit; there have been no problems with the low-pressure lines that combine the gases after desulfurization (the vapor from the amine-rich liquid flash tank in the gas desulfurization unit continuously enters these low-pressure lines). ——The liquid carryover in our LPG desulfurization tail gas is too severe; we carry out regular liquid removal, and basically no liquid gets carried out of the main pipes of the LPG desulfurization unit. 3. The disulfide separation tank – which is actually more appropriately referred to as a tank for separating alkaline solution from exhaust gases – was upgraded in 2004. In 2015, the upper part of the horizontal tank’s body suffered corrosion and perforation; a clamp with a diameter of 2600 mm was installed. Subsequently, the top cover of the separation column also developed corrosion and leakage, and another clamp was put in place. However, due to insufficient clamping force, there was still slight leakage. This situation persisted for over half a year. Just the day before yesterday, on June 14, 2016, the first day after the end of the middle school exams, we carried out the replacement of the top cover (using flange connections) without shutting down the plant.

So now, apart from regularly replacing the low-wattage pipelines, are there any other good solutions for you?

We once replaced some of them with stainless steel (pipes of DN40 and DN80), and that worked well; however, it wasn’t due to corrosion-related leaks, but rather due to blockages. But when operating at low power levels, the main pipe for low-power operation of the device is DN200 or larger; it would be necessary to replace it with stainless steel, yet no one has made a decision on this yet. It has to be replaced regularly. The Research Institute once tried to develop a method for low-temperature diesel absorption; they worked on it everywhere, but I don’t think it’s very reliable – mainly because there isn’t much that can be recovered, which results in such high energy consumption. But in the end, the main issue was a lack of space for installation, so it was simply given up.