New technology: introduction of reaction heat utilizing for process air dehumidification

May 08, 2023

The cooling, chilling and dehumidifying of process air in the traditional SO3 sulphonation process is to lower the process air to 40 C by recycling cooling water, then further reduce the temperature to 5 C by glycol chilling water solution; then the process air goes to sillica gel air dryers. In this case, the chilling water have to be generated by electrical chiller, for example, a 3.8t/h plant needs a 100KW chiller.


While, the new process Weixian newly developed is using the reaction heats of SO2 from outlet of sulfur furnace and SO3 from outlet of converter to generate steam directly. Minority of the steam goes to sulfur melting and the rest goes to lithium bromide absorption chiller for generating chilling water. The chilling water firstly lower the process air to 8 C and remove majority of the heat; then process air is lowered to 5 C by a 12-15KW electrical chiller. Or, directly lower the process air to 6 C by lithium bromide absorption chiller and directly go to sillica gel drying.


A 3.8t/h plant may save power 100KWH, one year saves about 800,000 kilowatt hour.


Detailed process as following:

The fin-type heat exchanger is made out of SS304 and upper part heat exchanging area is 80%. The lithium bromide absorption chiller generates 3 C - 5 C chilling water and lower the process air to 8 C. The lower part of heat exchanging area is 20%, which uses the 1 C glycol solution generated from a electrical chiller to further decrease the the process air to 3 C - 5 C. In the winter, electrical chiller may not need to run. The lithium bromide absorption chiller is driven by 0.4 Mpa steam from waste heat recovery system, equipped with a chilling water tank and pump. The electrical chiller also equips with a glycol solution tank and pump.


  • Start-up pre-heating

Start-up pre-heater is using 400KW electrical heater.


  • Sulfur combustion and conversion

The tubular heat exchanger which in the sulfur furnace SO2 outlet and converter forth pass SO3 outlet have been replaced by fire tube heat exchanger for steam production from waste heat. The steam is generated directly and the efficient therefore has been increased 100%. For example, a 3.8t/h plant when sulfur feeding is 400kg/h, steam production can be 1.4t/h, 0.5 Mpa; when sulfur feeding is 280kg/h, steam production can be 1.0t/h, 0.5 Mpa.


  •  Regeneration

The first pass cooler of converter generates 400 C + hot air mix with the 125 C hot air from second SO3 cooler gets 150 C - 180 C hot air, which is used for sillica gel regeneration. The rest hot air is for generating hot water for heat tracing.


  •  Recycling water station

Flowrate of recycling water stays unchanged 400m3/h.


  •  External steam supply

When plant shut-down, Liquid sulfur tank needs 300kg/h 0.4 Mpa steam and other tanks need hot water for heat tracing.


  •  Start-up pre-heating operation

Start-up needs dry air about 2500kg/h and heated by electrical preheater to 450C. In this case, small electrical chiller is able to chill and dehumidify this air, so the lithium bromide absorption chiller is unneeded to work. Sulfur is lighted by electrical lighter. Then SO2 goes into converter (electrical heater is still running) and SO3 temperature increases, and the fire tube heat exchanger start generate steam and drives the lithium bromide absorption chiller, which is also for process air chilling and dehumidifying, until the plant go normal. If there is external steam supply, which can drive the lithium bromide absorption chiller first.


  •  Minimum sulfur feeding flowrate

When a 3.8t/h sulphonation plant is running for SLES, minimum sulfur feeding flowrate is 280kg/h, the steam capacity is above 1t/h 0.5Mpa. 300kg/h will be used for liquid sulfur and the rest can guarantee the lithium bromide absorption chiller running normally. A 345KW chilling capacity lithium bromide absorption chiller can be selected, then steam consumption is less than 0.5t/h. Or, if select a 430KW chilling capacity lithium bromide absorption chiller, steam consumption will be less than 0.63t/h, electrical chiller will not be needed in this case.


  • Surpass steam capacity

In case steam production is more than the demand, SO3 first fire tube heat exchanger steam capacity can be reduced by open the bypass and let some heat cooled by the SO3 second cooler whose heat exchange area is increase by 50%.


China Unit 69 Reaction Heat Recovery, Unit 69 Reaction Heat Recovery Supplier -

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