JPS61108695A - Removal of sulfur deposit adherent to coke oven gas desulfurizer - Google Patents

Abstract

PURPOSE:To remove sulfur deposit in coke oven gas desulfurization equipment readily and completely, by performing washing with an aqueous soln. of sodium hydroxide and/or potassium hydroxide in a concn. of 10% or higher. CONSTITUTION:In a redox reaction type wet desulfurization process to remove hydrogen sulfide in coke oven gas, deposits consisting of sulfur-contg. gummy substances tend to adhere to a filler layer, a heat exchanger, etc. of a desulfurization tower as alkali-contg. absorbent liquid is brought into contact with the coke oven gas. When the equipment is blocked with the deposit, operation is stopped and an aqueous soln. of NaOH and/or KOH in a concn. of 10%, pref. 20% or higher is poured into the equipment for washing to dissolve out the deposits. The method is esp. effective when the deposits have a high sulfur content and it is recommended that the equipment is washed with a tar acid- contg. soln. before the above treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for cleaning sulfur-adhered blockages in coke oven gas desulfurization equipment.

Conventional technology Conventionally, the redox reaction type wet desulfurization method for removing hydrogen sulfide from coke oven gas involves the process of bringing gas into contact with an absorption liquid containing a catalyst to absorb hydrogen sulfide into the absorption liquid; A process in which oxygen-containing gas (e.g., air) is brought into contact with the absorption liquid that has absorbed hydrogen sulfide to oxidize hydrogen sulfide to elemental sulfur, and at the same time regenerates the alkali and catalyst in the absorption liquid, and the absorption waste liquid is wet-processed at high temperature and high pressure. It consists of an absorption waste liquid treatment process that involves oxidation or forced combustion at high temperatures.

Problems to be Solved by the Invention In this process in which the absorbing liquid and gas come into contact, trace amounts of oil and unsaturated hydrocarbons contained in the gas form a viscous mixture or gum with elemental sulfur, and the desulfurization tower In some cases, the desulfurization equipment adheres strongly to packed beds and heat exchangers, causing blockage, and eventually rendering the desulfurization equipment inoperable.

Conventionally, the countermeasure for this problem is to temporarily stop the operation of the equipment, take out the blocked packed bed if the blocked part is a packed bed, perform high-pressure jet cleaning, hot water, or hot ammonium water cleaning, and then restore the original condition again. The method involves putting the equipment into the equipment, assembling it, and restarting operation, which requires a great deal of labor and expense, including disassembly, removal, cleaning, and reassembly work.In addition to the installation of spare equipment and desulfurization work during this period, There were many problems, such as a decline in efficiency and environmental issues for cleaning.

In order to clean such blockages, the present inventors have disclosed Japanese Patent Publication No. 58-49593 and Japanese Patent Application No. 58-234007.
As disclosed in the above issue, cleaning with a mixture of ammonium water and phenol, a mixture of ammonium water and tar acid, or an aqueous tar acid solution is an extremely effective means.

However, this method also has the following problems depending on the nature of the obstruction.

■ If the composition of the blockage has a high elemental sulfur content (50% or more) and forms a dense and strong deposit, the cleaning effect will not be sufficient.

■ A cleaning solution containing tar acid easily dissolves tar and gum in the blockage, but elemental sulfur is difficult to dissolve.
The sulfur debris that fell off from the blockage is returned to the lower packed bed,
It may re-deposit on the heat exchanger.

Means for Solving the Problems The present invention is characterized by the fact that the concentration of elemental sulfur components in the blockage is high (50
% or more) to form a strong deposit,
This method has been developed to be suitable for cases where cleaning is difficult even with the methods disclosed in I3593 and Japanese Patent Application No. 58-234007.

In other words, blockages containing a large amount of elemental sulfur cannot be cleaned using conventional cleaning methods (
(Cleaning liquid containing tar acid), it becomes gummy.

Although the ability to dissolve tar is strong, the ability to dissolve elemental sulfur is weak, so the cleaning effect was low. However, the present invention utilizes the reaction between a small amount of gum and caustic alkali to create a caustic alkali aqueous solution of 10 % or more, preferably 20% or more, to strongly dissolve blockages mainly composed of solid elemental sulfur.

Function The principle of dissolving blockages mainly composed of solid elemental sulfur, including sulfur gum, is thought to be due to the following chemical reaction.

R@S * 511R' + 2NaOH+ ROH+
R'OH+Na2S+ S sulfur gum Caustic soda Na2S+ In this way, the sulfur bridge is broken to produce alcoholade and alkali sulfide, and further, this alkali sulfide undergoes an addition reaction with elemental sulfur to produce alkali polysulfide, which is dissolved.

The key point of the present invention is to use a relatively high concentration of caustic alkali to decompose sulfur gum and tar into alkali sulfide and alcolade, and use this to dissolve a large amount of elemental sulfur as alkali polysulfide. The present invention is based on the discovery that the combination of the dissolution of organic compounds, the desulfurization reaction, and the reaction of producing sodium sulfide by reducing elemental sulfur can be effectively used in the presence of sulfur. This requires a relatively high concentration of caustic alkali aqueous solution (a caustic alkali concentration of 10% or more, preferably 20% or more), and heating further promotes the decomposition reaction and the dissolving and cleaning effect.

The method of the present invention can be even more effective by carrying out the process after removing most of the gummy and tar components by washing according to Japanese Patent Publication No. 58-49593 or Japanese Patent Application No. 58-23400.

Example Embodiments of the present invention will be described below with reference to the drawings.

Example 1 Figure 1 shows equipment for treating desulfurization waste liquid using a wet oxidation method. Fluid 1, which is a mixture of desulfurization absorption waste liquid and high-pressure air, is preheated in a heat exchanger 3 and subjected to a wet oxidation reaction in a reaction tower 2. , the reaction product is discharged again through the heat exchanger 3. In this step, blockage occurs particularly in the heat exchanger 3, so if the progress of blockage is recognized from the ventilation resistance pressure difference during operation. , the operation is stopped, a 25% caustic soda solution is put into the dissolving and heating tank 8, and heating and circulation cleaning is performed using the heating steam 6, the circulation pump 5, and the circulation line 7.

The required amount of caustic soda at this time is to add more than the same amount (1.0 to 1.5 ratio) to the blockage, and heat at 60 ° C.
Circulation cleaning was carried out for 24 hours at 10 m3/hr.

The result is that the ventilation resistance is 5kg/crn' (pressure difference) before cleaning.
After cleaning, the weight returned to 0.5 kg/cm', which was the same as before the occlusion occurred.

Example 2 Figure 2 shows equipment for desulfurizing coke oven gas, with a desulfurization tower 11
The interior consists of four stages of packed layers 15.1B and 17.18. Pump 12 is an absorption liquid circulation pump, and 19 is absorption liquid regeneration equipment. Depending on the progress of operation, this packed bed 1
5.1B, 17.18, if an increase in ventilation resistance occurs and blockage is observed, the operation is stopped, and after extracting the absorption liquid, 25% NaOH is added to the bottom 14 of the desulfurization tower 11 to prevent the blockage. Add in absolute amount and 1.0 to 1.5 ratio, circulate and wash while heating to 50 to 60°C with an indirect steam heater lO,
After 8 hours, the ventilation resistance was measured and found that the filled layer 15, which was 150mmA before cleaning, was 20mmA after cleaning in the ventilation state.
It declined to .

The cleaning effect of the cleaning solution is determined by the fact that NaO is effective in decomposing blockages.
Since H is consumed, the cleaning solution is sampled and analyzed every few hours and judged by changes in free soda. If the free soda content falls below 5%, additional caustic soda must be added for cleaning.

Table 1 shows an example of compositional analysis of the occlusive material of the present invention.

Table 1: GPC analysis of occlusions Table 2: Dissolution of occlusions depending on NaOH concentration and temperature
2Amount of obstructed substance dissolved by NaOH concentration and temperature (The amount of dissolved object A in Table 1 was measured when it was immersed in NaOH solution of each concentration for 24 hours.) Table 3 shows that the amount of dissolved object is determined by cleaning with tar acid before cleaning with NaOH. This figure shows the difference in the state of dissolution of the occluded substance when this is done.

Table 3 Amount of occluded material dissolved by NaOH concentration (24% of occluded material
Comparison of amount of occluded material dissolved by time and 20°C immersion test. ) FIG. 3 shows the change in the amount of free alkali and the amount of dissolved elemental sulfur and organic matter over time of circulation of the cleaning solution in Example 2.

Curve ■ is a decrease curve of free @NaOH due to the elapsed time of circulating cleaning.Curve ■ is the concentration change of elemental sulfur dissolved in the cleaning NaOH solution.Curve @ is the decrease in free @NaOH due to the elapsed time of circulating cleaning.
The graph shows the change in concentration of decomposed and dissolved H solution.

In addition, in the method of the present invention, if the NaOH concentration is lower than 10%, the effect of dissolving and cleaning the obstructed material cannot be obtained, and if the NaOH concentration is higher than 50%, the viscosity is high and it solidifies at room temperature, making it difficult to handle for cleaning work. .

Further, in the examples, only NaOH (caustic soda) is described, but exactly the same effect can be obtained with a KO)+ (caustic potash) solution.

Effects of the Invention As described above, according to the present invention, sulfur-adhered blockages in coke oven gas desulfurization equipment can be completely cleaned without dismantling the equipment, reducing cleaning time and equipment dismantling costs. Excellent effects such as reduction of

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a simple flow of an example of coke oven gas desulfurization absorption waste liquid treatment equipment in Example 1 of the method of the present invention, and Fig. 2 is an explanatory diagram showing Example 2 of the method of the present invention in a coke oven gas desulfurization absorption waste liquid treatment facility. FIG. 3 is an explanatory diagram showing the cleaning flow of gas desulfurization tower equipment;
The figure shows the passage of time for circulation of the cleaning liquid and changes in the cleaning liquid. 1. Mixed fluid of desulfurization absorption waste liquid and high pressure air, 2...
Reaction tower, 3...Heat exchanger, 4...Discharged processing liquid, 5Φ...Circulation pump for cleaning, 6...Steam for heating, 7.Circulation line for cleaning, 8Φ... Melting heating tank, 1
0---Steam indirect heater, 11... desulfurization tower, 12
--Circulation pump, 1311 --Circulation line, 14j
・Cleaning liquid charging section at the bottom of the tower, 15 to 18 ΦΦΦ packed beds at each stage,
18...Absorption liquid regeneration equipment.

Claims (2)

[Claims] (1) Sulfur-adhered blockages in equipment that removes hydrogen sulfide from coke oven gas by bringing coke oven gas into contact with an alkali-containing absorption liquid are treated with one of sodium hydroxide and potassium hydroxide, or a mixture thereof. A method for cleaning sulfur-adhered blockages in coke oven gas desulfurization equipment, the method comprising cleaning with an aqueous solution having a concentration of 10% or more. (2) After cleaning sulfur-adhered blockages in equipment that removes hydrogen sulfide from coke oven gas by contacting coke oven gas with an absorption liquid containing alkali, using a cleaning liquid containing tar acid, remove sodium hydroxide and hydroxide. A method for cleaning sulfur-adhered blockages in coke oven gas desulfurization equipment, the method comprising cleaning with an aqueous solution of potassium or a mixture thereof having a concentration of 10% or more.