How to calculate the consumption of semi-water gas alkali desulfurization soda ash?

Basic reaction principle 3.1.1 Absorbing hydrogen sulfide is an acidic gas, while sodium carbonate solution is an alkaline solution. The principle of neutralization reaction can be used to remove hydrogen sulfide in the coal gas to generate sodium hydrosulfide and sodium bicarbonate. The reaction chemical equation is as follows: Na2CO3 + H2S NaHS+ NaHCO3 3.1.2. Principle of regeneration reaction (1) The sodium hydrosulfide generated through the reaction is oxidized under the action of the catalyst and precipitates into elemental sulfur. If the catalyst uses hydroquinone, vanadium pentoxide, and manganese sulfate. The mechanism is as follows: When vanadium pentoxide is added to the alkali solution, sodium metavanadate is quickly generated, which quickly reacts with sodium hydrosulfide in the desulfurization tower to generate reducing pyrovanadate and precipitate sulfur. 2NaHS+4NaVO3+H2O=Na2V4O9+4NaOH+2S↓ The generated sodium hydroxide reacts with sodium bicarbonate to form sodium carbonate. The reaction formula is as follows: NaOH+NaHCO3======Na2CO3+H2O The above reaction has basically ended before entering the regeneration tower, which greatly reduces the side reaction of generating sodium thiosulfate. (2) When hydroquinone is used as a catalyst, the hydrogen sulfide absorbed by the solution is oxidized by oxygen in the air into elemental sulfur and precipitated in the regeneration tower with the catalytic effect of hydroquinone in the solution. NaHS+1/2O2→NaOH+S↓ The catalytic mechanism of hydroquinone is generally believed to be first oxidized to quinone by oxygen in the air during the regeneration process.: HO--O-H+1/2O2 = O==O +H2O then reacts with S2- in the solution. The quinone form is reduced to hydroquinone, and S2- is oxidized to elemental sulfur and precipitates.: O=O: During the desulfurization process, when oxygen, carbon dioxide, and hydrogen cyanide are present in the gas, the following side reactions will occur: 2NaHS+2O2=Na2S2O3+H2O Na2CO3+CO2+H2O=2NaHCO3 Na2CO3+2HCN=2NaCH+H2O+CO2 NaCN+S=NaCNS 2NaCNS+5O2=Na2SO4+2CO2+2SO2+N2 The occurrence of side reactions is related to the total alkalinity and sulfur capacity of the desulfurization liquid, as well as the content of various impurity gases in the gas, so the desulfurization liquid must maintain a certain pH value. 3.1.3 Brief calculation 1. Calculation of liquid-gas ratio (1) Definition of liquid-gas ratio: The ratio of the desulfurization liquid flow rate and the gas flow rate passing through the desulfurization tower is the liquid-to-gas ratio of the desulfurization tower, generally expressed in L/G, with the unit of L/m2. Calculation of liquid-to-gas ratio: L/G=gas volume entering the tower under standard conditions (m3 standard/h)/desulfurization liquid circulation volume (m3/h) (2) The selection of liquid-gas ratio is generally calculated by the following formula: L/G=(C1-C2)/Sg C1, C2——H2S content in g/m3 at the inlet and outlet of the desulfurization tower respectively (standard) Sg——solution sulfur content (the amount of H2S absorbed by the liquid per unit volume) 2. Calculation of desulfurization efficiency The so-called desulfurization efficiency refers to the degree of H2S removal in coal gas, and is usually calculated by the following formula: =(C1-C2)／C1×100% 3.1.4 Principle of electrostatic decoking. To remove tar and other impurities in the raw gas, an electrostatic tar remover is used. The electrostatic tar remover is composed of three parts: a power control cabinet, a high-voltage silicon flow device, and a decoking tower body. It is used to output DC high-voltage electricity after the low-frequency current is rectified and boosted by a silicon controlled thyristor (SCR) power supply voltage regulator and a high-voltage silicon rectifier device. The DC high voltage is in the form of a negative output. The corona electrode and the coke collection electrode are added to the coke removal tower body, and a high-voltage electric field is established in the coke removal tower body. When the tar, sulfur, dust and other particulate impurities entrained in the semi-water gas entering the coke removal tower body pass through the electrostatic field, they are negatively charged, and under the action of the Coulomb force of the electric field, they are quickly adsorbed to the coke collection electrode to release the charge, thereby removing tar and other dust and purifying the gas. Currently, the synthetic ammonia plant has two electrostatic tar removers, which are used respectively for the purification of semi-water gas and pure oxygen crude gas. 3.2 Brief description of the production process 3.2.1 The semi-water gas produced by the semi-water gas process enters the 2000M3 semi-water gas holder. A 3# (or 4# or 5#) Roots blower is used to pressurize the gas in the gas holder. After cleaning the cooling tower, part of the dust is removed and the gas is reduced. After temperature, it enters the desulfurization tower from the bottom and comes into reverse contact with the alkali liquid entering the top of the tower. The gas is ejected from the desulfurization tower, and then passes through the electrostatic decoking tower to remove the tar in the gas and the cleaning tower to purify the gas again. After purification, the moisture in the gas is separated by the buffer tank and sent to the first section of the ammonia compressor inlet. liquid process: The alkali pump drives the alkali solution from the alkali circulation tank into the alkali regeneration tower to regenerate the alkali solution. The regenerated alkali solution is adjusted by the liquid level regulator. The air release tank and U-shaped liquid seal at the upper part of the regeneration tower enter the top of the desulfurization tower and come into reverse contact with the semi-water gas (water gas) coming from the lower part. The desulfurized alkali solution comes out from the lower part of the desulfurization tower. After passing through the water seal, it returns to the alkali solution circulation tank. Alkali solution (soda ash and desulfurization catalyst) must be prepared with water or desulfurization lean liquid in the solution preparation tank each shift, and then driven into the alkali solution circulation tank with a solution preparation pump. The sulfur foam generated at the top of the regeneration tower overflows to the high tank. The sulfur kettle is pumped into the sulfur kettle to refine the finished sulfur product, and the sulfur kettle outlet is sent back to the alkali tank at night. 3.2.2 The water gas produced by the water-gas process gas production enters the 1000M3 water-gas gas holder. A 1# (or 2#) Roots blower is used to pressurize the gas in the gas holder. After cleaning the cooling tower to remove some dust and lower the gas temperature, it enters the desulfurization tower from the bottom and comes into reverse contact with the alkali liquid entering the top of the tower. The gas comes out from the top of the desulfurization tower and is sent to the amide section. 3.2.3 Analyzed Gas Process The analytical gas from the amide section is very dry and clean. It is sent to an approximately 73M3 analytical gas buffer tank (the buffer tank is connected to the inlet of the 2000 M3 semi-water gas cabinet, which can ensure that the analytical gas Roots blower inlet is in a stable positive pressure state for a long time). It is then inflated and pressurized by the 2# (or 3#) Roots blower and directly sent to the compressor section through the analytical gas cooler. 3.2.4 In order to ensure the stability of the inlet pressure of the M machine and H machine section, a DN500 connecting pipe is added at the main pipe between the outlet of the decoking tower and the inlet of the M machine section to balance the suction volume of the M machine and H machine.

Regarding the amount of soda ash used in semi-water gas desulfurization, 1. Let us take tannin extract desulfurization as an example to first look at the principle of desulfurization.: The desulfurization method is wet oxidation of tannins. The main component of the rubber tannins used in this method is hydrolyzed tannins. Their molecular structures are very complex, and most of them are polycarboxyl compounds with a phenolic structure. After tannin extract is prepared into an alkaline aqueous solution and heated and aired, most of the phenolic structure of tannin extract is oxidized by air into a quinone structure, which has a high potential and can oxidize low-valent vanadium into high-valent vanadium, thereby oxidizing the hydrogen sulfide radical in the solution and precipitating elemental sulfur. The desulfurization reaction principle is as follows: 2.1. The alkali solution absorbs hydrogen sulfide (H2S) to generate hydrogen sulfide (HS-): Na2CO3 + H2S == NaHS + NaHCO3 2.2, sodium hydrosulfide (NaHS) and sodium vanadate (NaVO3) react to generate Na2V4O9 and precipitate elemental sulfur: 2NaHS + 4NaVO3 + H2O == Na2V4O9 + 4NaOH+2S↓ T(OH)O2 + HS－ → T(OH)3 + S↓ 2.3. Oxidative regeneration of vanadium and tannins Na2V4O9 + 2T(OH)O2 + 2NaOH + H2O == 4NaVO3 + 2T(OH)3 2T(OH)3 + O2 == 2T(OH)O2 + 2H2O T(OH)3 + O2 → T(OH)O2 + H2O2 2.4. Reaction to generate sodium carbonate NaHCO3 + NaOH == Na2CO3 + H2O 2.5. Side reaction Na2CO3 + CO2 + H2O == 2 NaHCO3 2NaHS + 2O2 == Na2S2O3 + H2O Na2S2O3 + O2 → Na2SO3 + H2O Na2SO3 + O2 → Na2SO4 + H2O H2O2 + HS- → H2O + S+ OH- H2O2 + V4+ → H2O + V5+ When the gas contains cyanide, the cyanide will be removed to form cyanate or thiocyanate. 2.6. The tannin method only removes hydrogen sulfide and almost no organic sulfur. However, when some units have high alkalinity and high pH value, COS will pyrolyze into hydrogen sulfide in alkaline solution at 40-50°C and be removed. 3. It can be seen from the above principles: The amount of soda ash used for desulfurization of semi-water gas is proportional to the hydrogen sulfide content in semi-water gas. ； It is related to the regeneration situation, that is, the more complete the regeneration is, the less the relative alkali consumption will be. If the regeneration is incomplete, the more alkali consumption will be. ； The more side reactions there are in regeneration, the greater the alkali consumption. ； thus: Due to the uncertainty in the above reaction, during production operation, it is first necessary to ensure that the hydrogen sulfide after desulfurization of the system is qualified. Therefore, the amount of alkali is difficult to calculate using a formula, but the reaction equation can be roughly controlled to calculate material constants.