A company coke oven gas purification started using HPF positive pressure desulfurization process, but the desulfurization efficiency is low, and the pressure desulfurization gas to be cooled, sent to the desulfurization tower for desulfurization, cyanide removal, desulfurization, the gas into the ammonium sulfate unit, and The gas needs to be preheated. After the gas is cooled and preheated, there is a big waste of energy, which is not conducive to saving energy and reducing consumption. In this regard, the company changed the positive pressure desulfurization process to the negative pressure desulfurization process. After 3 years of operation, the desulfurization efficiency was increased , Significant energy-saving effect, with good economic and environmental benefits.
A positive and negative pressure desulfurization process contrast
Domestic and foreign coke oven gas desulfurization process is divided into two kinds of positive pressure desulfurization and negative pressure desulfurization.
A positive pressure desulfurization process
From the blower to about 55 ~ 60 ℃ gas, first into the pre-cooling tower, with circulating water cooled to about 30 ℃, and then into the desulfurization tower.
Precooling tower with cooling water from the self-circulatory system, the hot water discharged from the bottom of the tower by the pump to the cooler, with circulating cooling water heat transfer into the top of the precooling tower spray for cooling gas, pre-cooling circulating water on a regular basis Sewage, sent to mechanized clarification tank, while adding to the circulation system to add the remaining ammonia.
The gas from the precooling tower enters the bottom of the desulfurization tower and is in reverse contact with the desulfurization solution sprayed from the top of the tower. H2S and HCN are removed from the top to overflow into the ammonium sulfate unit.
The desulfurization liquid discharged from the desulfurization tower bottom enters into the reaction tank through the liquid sealing groove, and is circulated and pumped by the desulfurization liquid. After being partly cooled by the cooler and mixed with another part of non-cooled liquid, the desulfurization liquid is sent to the bottom of the regeneration tower via the pre-mixing nozzle Compressed air is blown in the bottom of the regeneration tower to regenerate the desulfurization solution in the tower, the desulfurization solution in the upper part of the tower is circulated through the liquid level regulator to the desulfurization tower for circulating spraying, and the floating sulfur foam is used in the expanded part of the top of the regeneration tower The liquid level difference flows into the sulfur foam tank. The sulfur foam produced is pumped to the centrifuge for centrifugal separation. The filtrate is returned to the reaction tank for export after the sulfur paste is packed.
Desulfurization finished ammonia used by the steam ammonia sent to desulfurization reaction tank desulfurization solution circulation system.
2 negative pressure desulfurization process
About 25 ℃ of electricity is captured into the bottom of the packed desulfurization tower. In reverse contact with the regenerated solution sprayed from the top of the tower, H2S and HCN in the gas are absorbed (at the same time, NH3 in the gas is absorbed to supplement the alkali source in the desulfurization solution). After desulfurization gas into the blower unit.
The desulfurization tower absorbs the circulating liquid of H2S and HCN and enters the pre-mixing nozzle at the bottom of the regeneration tower through the desulfurization liquid pump (when the temperature of the desulfurization liquid is high, some enter the plate and frame heat exchanger for cooling) and violently mix with the compressed air to form tiny Bubble into the regeneration tower bottom, along the regeneration tower rise process, the role of catalyst oxidation regeneration. After the regeneration of the desulfurization solution in the upper part of the regeneration tower through the liquid level regulator into the U-tube, into the top of desulfurization sparger, circulating spray gas.
Sulfur foam floating on the enlarged part of the top of the regenerating tower flows into the sulfur foam tank by liquid level difference, and the generated sulfur foam is pumped to the plate-frame filter press. After the filtrate enters the venting tank, it is sent from the venting tank to the desulfurization Continue to use the bottom of the tower, Sulfur paste bag export.
Desulfurization finished ammonia used by the steam ammonia sent to the desulfurization tower, adding desulfurization liquid circulation system.
3 positive and negative pressure desulfurization operation indicators comparison
In the case of the same amount of gas production, the desulfurization effect of the positive and negative pressure desulphurization process is monitored by the Infrared Gas Analyzer (explosion-proof type) Gasboard-3500, and then comprehensive desulfurization process operating parameters, can be obtained positive pressure desulfurization and negative Pressure desulfurization operation indicators are as follows.
As can be seen from the above table, the negative pressure desulfurization than the pressure desulfurization, desulfurization tower inlet gas temperature decreased by 6 ℃, desulfurization liquid temperature decreased by 5.5 ℃, desulfurization solution temperature is conducive to the increase of volatile ammonia (free ammonia) concentration, volatile The concentration of secondary salt increased from 300g / L to below 250g / L, decreased by 52.8g / L. The reduction of secondary salt concentration was beneficial to the improvement of desulfurization efficiency, and the desulfurization efficiency increased from 86.3% to 99.0%, an increase of 12.7%.
Two positive and negative desulfurization process characteristics contrast
1 temperature changes
Positive pressure desulfurization is located in the blower, into the desulfurization section of the gas temperature of about 55 ~ 60 ℃, and desulfurization reaction temperature is about 25 ~ 35 ℃, desulfurization section for the ammonium sulfate section, and ammonium sulfate section suitable for the absorption reaction temperature of 50 ~ 55 ℃, so the gas desulfurization by desulfurization into the ammonium sulfate section of the gas to be cooling and reheating, there is a big waste of energy.
Negative pressure desulfurization is located in the electric capture, the blower before entering the desulfurization section of the gas at about 25 ℃, to meet the desulfurization absorption, regeneration requirements, and after the fan directly into the ammonium sulfate section, to avoid the gas cooling and preheating, temperature changes Gradient more reasonable, saving cold energy and heat, reducing system energy consumption.
2 free ammonia concentration
HPF desulfurization is based on ammonia as the base of wet oxidation desulfurization, the absorption process for the chemical reaction, that is, by absorbing ammonia gas (or additional ammonia), increasing the concentration of ammonia to improve the absorption of hydrogen sulfide, hydrogen cyanide and other substances , The higher the concentration of free ammonia in the desulfurization solution is more conducive to the desulfurization reaction.
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