Sulfur Recovery Unit
SRU (Sulfur Recovery Unit) Introduction
Sulfur contained natural gas and coal chemical industry become more and bigger. Economy increase and environment protection make the desulfurization and sulfur recovery unit technology become more and more important. So. Sulfur recovery unit technology has been to an emerging industry in the new century.
Claus sulfur recovery unit techniques bring into industrialization in 100 years ago, which used to recycle sulfur contained in H2S gas. This technique is the standard technique processing in sulfur recovery unit system. With the advanced treatment developed, the increase of the Middle East crude oil and the high load continued production, reliable operation of the sulfur recovery unit system is required, which is important to ensure upstream equipment safely running. A lot of sulfur recovery unit equipment have been built all over the world. Plus the pollution material will be more and more critically restricted. Environment protection law will be stricter for the main pollution material processing equipment. All the factors above request to improve the skills in equipment designing and selection. The main equipment includes a combustion heater, burner, fans, reactor, waster heat boiler, heat exchanger and fluid transport pipe.
Sulfur Recovery Unit Process (Claus Process)
To be specific, there are 8 steps in a complete sulfur recovery unit.
- Generation and collection. Sulfur steam is produced in the heat reactor where the acid gas containing hydrogen sulfide is mixing proportionally with air, which is collected from the desulfurization equipment and the acid stripping system.
- Cooling down. Process gas from the heat reactor is cooled down to 315℃, where the medium pressure steam is produced.
- 1st level condensing. Process gas from the waste heat boiler is cooled down further to 130℃ in the primary stage condenser, where the sulfur stream is condensed and separated flowing to the sulfur pool.
- 2nd level condensing. The process gas from the primary condenser is heated up to 260-290℃ by the waste heat of the gas and come into the primary reactor where the sulfur stream is produced by the further reaction. Process gas in this step is cooled down to 130℃ in the second condenser, where the sulfur stream is cooled and separated flowing to the sulfur pool.
- Re-heat and 3rd level condensing. The process gas from the second condenser comes into the second reactor (where the sulfur stream produced by further reaction) after heated to 220-250℃ by the process gas from the primary reactor, and then the process gas comes into the third condenser cooled down to 130℃ and separated flowing to the sulfur pool. The recovery ratio can reach to 95%.
- TGTU to increase the recovery rate. In order to further increase the sulfur conversion ratio, hydrogenation deoxidizes treatment must be added to the tail gas that comes from the Claus SRU unit. This is also called the tail gas treatment unit. Tail gas from the sulfur recovery unit is mixed with hydrogen after heated and send to the hydrogenation reactor, where the H2S is formed under the catalyzing reaction. So the carbon disulfide can be hydrolyzed. The reaction equation is shown below:
SO2 + 3H2 → H2S + 2H2O
SY + yH2 → yH2S
COS + H2O → H2S + CO2
CS2 + 2H2O → 2H2S + CO2
- Process gas from the hydrogenation reactor is cooled down by heat exchange with water and then is sent to the absorber. H2S contained in the process gas is absorbed by amine and then is sent to the acid gas pipeline.
- The gas from the absorber contains minor H2S (usually lower than 200ppmv), which is transformed into SO2 before being emitted.
Ruichang SRU Advantages
Ruichang is highly competent to provide complete EPC (Engineering Procurement Construction) solutions of SRU for the petrochemical and coal chemical industry.
With more than 30 years’ experience and more than 200 sets of the applications installed, our system has been proven by numerous clients that the performance, as well as the technological standard is equal to the counterpart supplier abroad.
At present, the largest SRU project we participate in has a capacity of 150,000 tons/year.
The Key Equipment in SRU
Below listed are the main machinery that is used in a complete sulfur recovery unit. Click each title to learn more information.
As the main equipment in the sulfur recovery unit, the heat reaction furnace plays various roles in different areas including ignition, automatic operation, deep reaction, and high-temperature edulcoration. So the reliable running of the heat reaction furnace is important for all units.
“3T” of reaction furnace plays an important role in the design and reliable running of the equipment. “3T” includes Time residence, temperature, and turbulence mixing. 3T are interrelating and dispensable.
Burners are the core of sulfur recovery system, the fuel gas, acid gas, and oxidizing air pass through burners, they are mixed and reacted with each other in the heat reaction furnace. Functional burners have a great influence on many aspects, such as conversion ratio of elemental sulfur, eliminate bad effect of ammonium salt and other impurities, efficient and long-cycle operation of sulfur recovery unit.
For the sulfur recovery unit, applied types of burners include acid gas reaction furnace burner, acid gases directly incinerated burner, online heat furnace burner, and tail gas incinerator burner.
Catalyzing reactor refers to the equipment which realizes the catalytic combustion reaction process. It is a horizontal carbon steel container that generally need to be elevated. The bottom outlet is directly connected to the downstream condenser.
It is suitable to adopt sulfur recovery catalyst and catalyst blending technology. Both Activated alumina catalyst and deoxygenation protective catalyst are applied.
As a necessary part of sulfur recovery unit, the waste heat boiler is a typical fire tube boiler. The multi-pipe mouth of the waste heat boiler is connected with the outlet of the heat reaction furnace, which is both the rear wall of the reactor and the end of the transition zone. The function of the waste heat boiler can be divided into two aspects. Firstly, producing medium steam to recover high heat. Secondly, cool the gas from 1300 ℃ to 315 ℃ in the process.
Sulfur condenser is part of the heat exchanger, which is called the shell and tube boiler. The main function of this equipment is to cool condense the sulfur generated in the upstream reaction section. Generally, sulfur condenser is placed on the horizon.