One 1. Desulfurization Methods for Coke Oven Gas

1. Overview

Coal gas and coke oven gas are important medium- to high-calorific-value gaseous fuels that can be used in steelmaking, supplied to urban residents, and employed as feedstock for the production of synthetic ammonia, methanol, and other products. Regardless of the specific application of coke oven gas, its sulfur content must be reduced to a specified level.

Coking coal feedstock contains 0.5% to 1.2%. of sulfur, with 20% to 45% of this sulfur entering the raw coke oven gas in the form of sulfides and forming hydrogen sulfide gas; in addition, a considerable amount of hydrogen cyanide is also present. The raw coke oven gas contains various impurities and therefore requires purification. Typically, coke oven gas contains 4 to 8 g/m³ of hydrogen sulfide. ³ , containing 4–9 g of ammonia per m ³ , containing 0.5–1.5 g/m of hydrogen cyanide ³ . Hydrogen sulfide (H ₂ S) and its combustion product sulfur dioxide (SO ₂ ) Both are toxic to humans, with hydrogen cyanide being more toxic. When hydrogen cyanide and ammonia burn, they produce nitrogen oxides (NO _X ), sulfur dioxide and nitrogen oxides are both major contributors to acid rain, and desulfurization, decyanation, and ammonia scrubbing of coal gas are primarily driven by environmental protection considerations. In addition, there are stringent requirements for the sulfur content of the fuel gas used in the rolling of high-quality steel; the sulfur content in coal gas is H ₂ The presence of sulfur compounds not only corrodes equipment in the crude benzol system but also causes the wash oil and water used for crude benzol absorption to form emulsions, thereby impairing oil–water separation. Consequently, the removal of hydrogen sulfide is of great significance for mitigating air and water pollution, strengthening environmental protection, and reducing equipment corrosion.

2. Desulfurization Methods for Coke Oven Gas

In recent years, the rapid development of the steel industry has spurred the growth of the coking sector. Concurrently, with the increasing global emphasis on environmental protection, desulfurization and decyanation technologies for coke-oven gas have been rapidly developed and refined both domestically and internationally, leading to the emergence of various desulfurization methods, including the dry ferric hydroxide process, the wet alkaline process, and the improved ADA process. In general, based on the form of the absorbent, gas desulfurization methods can be broadly classified into two main categories: dry processes and wet processes.

1) Dry Desulfurization Technology for Coke Oven Gas

The dry desulfurization process uses solid absorbents to remove hydrogen sulfide from coal gas, typically operating on the fixed-bed principle. It is simple and reliable, offers high desulfurization efficiency, and is well suited for treating low-sulfur gases; it is generally employed for secondary fine desulfurization. However, because the gas–solid adsorption reaction is relatively slow, the equipment used in this process tends to be large and bulky. In addition, due to the limited sulfur capacity of the adsorbent, the desulfurizing agent must be replaced frequently, resulting in substantial consumption and difficulty in regeneration, which in turn leads to high operating costs and heavy labor intensity. Furthermore, the process does not allow for recovery of elemental sulfur, and the spent desulfurizing agent, waste gas, and wastewater all require treatment. Consequently, in large-scale coking and steel industries, dry desulfurization is usually not considered unless the coke oven gas undergoes further deep processing (such as methanol production from coke oven gas); small and medium-sized coking plants, by contrast, predominantly adopt dry-process technologies.

Currently, dry-process desulfurization agents include iron oxide, zinc oxide, copper oxide, calcium oxide, manganese oxide, activated carbon, molecular sieves, and composite oxides; more recently, second-generation desulfurization agents such as cerium oxide have also emerged. Among these, iron-based and zinc-based desulfurization agents are the most widely used.

2) Wet Desulfurization Technology for Coke Oven Gas
The wet-process technology utilizes a liquid desulfurization agent to remove hydrogen sulfide and hydrogen cyanide from coal gas. Based on the absorption and regeneration characteristics of the solution, it is further classified into the wet oxidation method, chemical absorption method, physical adsorption method, and physicochemical absorption method.

The wet oxidation process is characterized by the use of a desulfurization catalyst (or oxygen carrier) to facilitate redox reactions in the liquid phase, whereby hydrogen sulfide absorbed by a weak alkaline solution is immediately oxidized to elemental sulfur, which precipitates out, while the absorbent solution is simultaneously regenerated. This method is widely used for desulfurization and decyanation of coke-oven gas; essentially, it involves converting HS ^- oxidized to elemental sulfur; chemical absorption, physical adsorption, and physical- The three chemical absorption methods are primarily used for desulfurization of natural gas and refinery off-gas, but they do not allow for direct sulfur recovery and are seldom employed in the desulfurization and decyanation of coke-oven gas.

3. Our company employs a wet oxidation desulfurization process using the DKT-6 active catalyst.

DKT-6 The wet oxidation method using an active catalyst is characterized primarily by the use of a specially formulated composite catalyst system based on titanium phthalocyanine cobalt sulfonate. It not only removes hydrogen sulfide but also effectively eliminates organic sulfur compounds and cyanides. A closed-loop process is employed, featuring ambient-temperature absorption for desulfurization followed by self-induced air oxidation for regeneration. Additionally, a continuous sulfur-melting sulfur recovery process is utilized to produce elemental sulfur.

DKT-6 The wet oxidation desulfurization process using an active catalyst absorbs H in fuel gas and coal gas at ambient temperature. ₂ S, which can produce by-product sulfur without requiring temperature-programmed desorption, features low operating costs and low overall energy consumption; this method is applicable to the feed gas containing H ₂ S The content has a wide adaptability range, and primary desulfurization can ensure that the purified gas contains H ₂ Sulfur content less than 100 mg/Nm ³ ; It can even be reduced to 50 mg/Nm³ as needed. ³ When combined with a specially formulated active desulfurization agent, this method can significantly reduce the formation of desulfurization by-products, thereby effectively lowering capital expenditures for treating these by-products and substantially reducing operating costs, ultimately decreasing overall production expenses. The DKT-6 active catalyst features a self-cleaning function that effectively prevents tower plugging.

  II. Coke oven gas desulfurization, denaphthalinization, and debenzolization

Technical Features:

1 , during naphthalene removal, virtually no elemental sulfur is precipitated, thereby avoiding blockage of the adsorbent’s micropores, and the regeneration temperature is relatively low. Approximately 150 degrees Celsius This ensures more complete regeneration of the adsorbent.

2 Using coal gas or nitrogen for adsorbent regeneration has minimal impact on adsorbent performance and allows for frequent regeneration.

3 , No treatment of regenerated wastewater is required.

4 1. The pressure swing adsorption desorption gas can be used as the regeneration gas, eliminating the need to consume nitrogen and purified synthesis gas and thereby reducing operating costs.