I’m posting another desulfurization process for everyone’s feedback
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Brief description of the process: Gas desulfurization is a wet pre-desulfurization process that uses ammonia in the gas as the base source, along with PDS+tannin as a composite catalyst. The raw gas from the electrostatic tar catcher in the cold drum section enters the lower part of the pre-cooling tower, where it comes into countercurrent contact with the pre-cooling circulating liquid sprayed from the top of the tower. After being cooled to 28–32°C, it proceeds to the lower part of the gas desulfurization tower, where it again comes into countercurrent contact with the desulfurization lean solution sprayed from the top. The hydrogen sulfide in the gas is absorbed by this desulfurization solution, reducing its concentration from 5–8 g/Nm3 to below 300 mg/Nm3. After the mist droplets are removed in the mist capture section, the gas is sent entirely to the ammonium sulfate production section. The desulfurization liquid in the lean liquid tank is pumped by a lean liquid pump to the upper part of the desulfurization tower, where it is sprayed to absorb hydrogen sulfide from the gas. The desulfurization liquid that has absorbed hydrogen sulfide flows to the rich liquid circulation tank at the bottom of the tower, becoming rich liquid; this rich liquid is then pumped by a rich liquid pump to the injection and regeneration tank. There, the hydrogen sulfide absorbed by the desulfurization liquid reacts with oxygen in the air under the action of a desulfurization catalyst to form elemental sulfur. The elemental sulfur is carried upward by the excess air to the top of the regeneration tank, where it forms sulfur foam. This foam overflows from the top of the tank into the sulfur foam tank ； The regenerated desulfurization liquid enters the lean liquid tank via a level regulator for reuse. The sulfur foam is sold after dehydration. Selection of main equipment (1) Pre-cooling tower: The pre-cooling tower is an air-cooled tower, and its primary function is to cool the gas entering the desulfurization section to 28–32°C. The tower is a carbon steel tower. (2) Desulfurization tower: This tower is a packed tower, using 84 internal arc ring packing with a specification of Dg50, and its specific surface area is 121 m2/m3. The total amount of filler used is 96 m3. Each tower is equipped with three packing layers; a gas distributor is placed at the bottom of each packing layer, a liquid redistributor is located between two packing layers, a liquid distribution device is situated at the top of the uppermost packing layer, and a mist capture layer is installed at the top of the tower. The main material of the tower body is Q235-B, the material of the head is 20R, while the internal components of the tower are made of 304 and Q235-B. Corrosion protection inside the tower is achieved through an aluminum spraying process followed by epoxy resin sealing. (3) Regeneration tank: This device is a jet-type regeneration tank that uses a Venturi injector to draw in solution and thereby self-priming air for the regeneration of the desulfurization solution. The expanded section at the top of the tank is equipped with 16 injectors that draw air into the tank; the specifications of these injectors are 50 m3/h, with a liquid-to-gas ratio of 1:40. The equipment specifications are DN7600/DN8800×5300, with H=9050; the material is carbon steel, and the inside of the tank is treated for corrosion prevention using the same method as that applied in desulfurization towers.
This is the plan I intend to choose. Does anyone have any insights?
Is the Dg50 filler size a bit small? Hydrogen sulfide levels can reach 5–8 g/Nm3, which can easily cause tower blockages. Sulfur foam dehydration is sold for external use; it’s good for solutions. Could you explain the specific dehydration process?
Will the hydrogen sulfide content rise again after the desulfurized gas passes through the sulfuric acid processing unit, benzene washing towers, etc.? In our factory, there is such a strange phenomenon: after desulfurization, the hydrogen sulfide level is very low, usually around twenty to thirty milligrams. Yet after going through these two processing steps, its level increases again before reaching the gas storage tank. What could be the reason? Guys, please help! Thank you!
Is there a sulfide in the solution that comes into contact with the desulfurized gas? During their contact, does hydrogen sulfide move from the solution into the gas? Or could organic sulfur be present in the gas, which is hydrolyzed into hydrogen sulfide under the catalysis of the solution, resulting in an increase in the hydrogen sulfide concentration? Our company uses the catalytic thermal potassium-alkali method for two-stage decarburization, and as a result: 1. The total amount of hydrogen sulfide in the regenerated gas far exceeds that at the desulfurization outlet (due to the hydrolysis of organic sulfur) ； 2. The gas becomes contaminated during secondary decarburization; zinc oxide must be added for protection before methanation.
Going back to floor 4: it’s possible that there is a leak inside your valves, with a small amount of gas leaking through the bypass valve of the desulfurization tower. Our company faced the same issue in the past, and it took some time to identify the cause.
I fully agree with the views expressed on floors 4 and 5: one possibility is that organic sulfur is hydrolyzed into inorganic sulfur in the form of hydrogen sulfide, and the other possibility is that there is a leak in the bypass valve, allowing untreated gas to mix with the gas that has been desulfurized.
The selection of equipment should be based on your hourly gas consumption, with a margin left for extra needs. The PDS + tannin method is rarely used these days; many companies now use PDS alone, or PDS + hydroquinone. Of course, the prerequisite is that the quality of PDS must be good; currently, the PDS600 model is widely used.
What is the price of sulfur ointment after dehydration? Why can’t sulfur be used?