There are at least five advantages of the electron beam process:
- SO2 and NOx are removed together in the same piece of equipment by the addition of one chemical. The method can meet all New Source Performance Standards (NSPS) for SO2 removal because it has the potential to remove 98% of all SO2 and 70–90% NOx depending on the process condition (CFR‐40 1999). High SO2 removal can be achieved with very low power consumption (1% of the block). Most of the energy is consumed for NOx reduction. NSPS standards are complex, but in the case of 3–6% sulfur coal, a 90% reduction is required.
- Volatile organic compounds are removed in the process as well.
- Since no waste is produced, there is no need to devise a means of disposal.
- Since the process produces a dry product, high maintenance costs associated with abrasive and corrosive slurries are avoided.
- A salable product results.
Among the corresponding disadvantages and challenges associated with this process is the need to keep ammonia injection close to the stoichiometric point to alleviate any ammonia slip. In addition, large electron‐beam generators are needed for a large‐scale plant because the current electron beam has a limited range. Technical concerns about this process include questions about the ability to scale up the electron accelerators for a full‐scale application and the associated power requirements for the technology. To accelerate radiation, a combined microwave‐electron‐beam process has been developed and patented, and this hybrid radiation system will be suitable for a large‐scale plant (Das 2005; Ebara 2010).
Cost Analysis
Table 9.1 presents an annualized cost analysis, including a projected overall return on investment for the installation and operation of a system of E‐beam–ammonia conversion of SO2 and NOx. The cost analysis shows that the coal‐fired power‐generating industry can earn about $11 million/year from this process. The system itself is much cheaper than conventional flue‐gas treatments – with 25% less construction costs and 20% less running costs – and requires considerably less space.
Table 9.1 Return on investment calculations: electron beam–ammonia SO2 and NOx conversion.
Source: From Ebara Corporation (2010).
| Sample calculation | Total profit/cost ($ million) |
| Profit from product sales Fertilizer: 110 000 T/Y (400 T/day) × $100/T | 11/year profit |
| Operating cost Personnel expenses, etc. Ammonia: 29 000 T/Y (105 T/day) × $130/T | −0.9/year −3.8/year −4.7/year cost |
| Facility construction cost | −38.1 cost |
At an annual interest rate of 12%, facility construction cost would have been paid back within 15 years.
But there are caveats in all such calculations. For starters, the Ebara process would be sensitive to the cost of anhydrous ammonia. To control this variable, research is being conducted to discover a way to extract ammonia from municipal wastewater (Ebara 2010). If ammonia were available from a nearby municipal wastewater treatment plant, it would be even more economical to run this process. In any event, the fertilizer‐producing variant of the Ebara process would be economically beneficial only in locations well sited with respect to markets for the fertilizer materials produced as by‐products, and variability in capital and electricity costs.
Leave a Reply