Problems with converter furnaces

This is a great question; why isn’t anyone answering it? Now, after 5 or 6 years of promotion for isothermal processing, all the necessary verifications have been carried out. Please, fellow sailors, come and discuss this :)

For pulverized coal gasification, it is recommended to use a first-stage isothermal process followed by a second-stage adiabatic process. The purpose of the isothermal stage is to increase the conversion rate in the first-stage reactor and reduce the temperature of the reactor bed, thereby protecting the equipment and catalysts. However, the isothermal process cannot generate superheated steam. For water-coal slurry gasification, it is recommended to use primary adiabatic and secondary isothermal processes. First-stage adiabatic operation can produce superheated steam, while second-stage isothermal operation can increase the conversion rate.

Agree with the opinion above. However, in my opinion, isothermal (controlled heat transfer) conversion is used in the coal gasification stage because the process gas contains a high level of CO and a low level of water vapor; without adding steam, heat transfer facilitates an increase in the degree of conversion, while also protecting the catalyst and the conversion furnace ； The choice of using insulation in this case is likely due to doubts regarding the reliability of isothermal conversion furnaces; therefore, it is appropriate to incorporate two sections of insulation in order to achieve the desired level of conversion.

Advantages of A isothermal conversion: 1. Axial or radial feeding (similar to methanol/ammonia synthesis towers, allowing for larger scale operations); low reaction temperature (290°C, with an outlet temperature of 219–222°C), and a small temperature difference across the bed, which prevents excessive temperature rise (the adiabatic conversion reaction temperature is 450°C)； The bed temperature is controlled through the steam pressure in the drum, allowing the auxiliary steam system of the drum to operate via natural circulation without the need for external power ； 2. Three lows and three highs: low pressure drop in the converter (≤5–20 kPa; it is possible to achieve a higher gasification capacity or to adjust the capacity by changing the space velocity), low temperature difference across the catalytic bed (≤5°C, resulting in reduced and more uniform thermal stress), and low heat losses in the system ； High conversion efficiency (≥98%), high energy recovery rate, and high catalyst utilization rate ； 3. Short process, simple operation, low heat loss, fewer devices, and lower investment (up to two stages, without inter-stage heat exchangers) ； There is no need to use a furnace for heating; the catalyst is heated by injecting steam through a water circulation system ； 304SS, 15CrMoR, or 2.25Cr1Mo (with the wall thickness dapat be reduced appropriately) ； 4. Long catalyst lifespan (≥5 years, adiabatic ≤3 years) ； 5. H2/H2S/dew point corrosion has been somewhat alleviated ； 6. Reduced operating costs and investment ； Disadvantages of B isothermal transformation: 1. When the internal heat exchange tubes suffer from stress corrosion, it is difficult to detect and repair them, which can easily lead to the waste of the catalyst ； 2. There are few cases of large-scale applications, and the reactors and catalysts lack reliable validation from long-term actual operation ； 3. The specifications of individual units and the large amount of catalyst required result in high risks associated with their manufacturing and maintenance ； 4. The quality of the by-product steam is moderate (3.5–4.0 MPaG in the first stage, 2.0 MPaG in the second stage) ； 5. Similar to adiabatic transformations, both the “bayonet” and the “tube box” have certain “dead zones”” ； In summary, isothermal conversion is suitable for applications such as powder coal gasification, conditions with a high hydrocarbon-to-carbon ratio and a high water vapor ratio (reducing steam consumption by 4.2 MPaG), and deep conversion ； This project has a high hydrocarbon-to-hydrogen ratio, but a relatively low water vapor content, which reduces the advantages associated with isothermal operation. However, if the patent holder can ensure that no steam needs to be added under conditions of a water vapor ratio of 0.75 (min) and 0.85% CO, then the savings in utility costs, compression work in the downstream system (at 0.2 MPaG), and heat losses resulting from isothermal operation remain advantageous.