Techno-economic analysis (TEA) tool for NOx mitigation solutions
Zafar, Saqlain (2018)
Diplomityö
Zafar, Saqlain
2018
School of Engineering Science, Kemiantekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2018090434559
https://urn.fi/URN:NBN:fi-fe2018090434559
Tiivistelmä
Tight NOx limits set by the regulatory authorities have necessitated the suppliers of NOx removal technologies to consider the cost-effective alternatives for their industrial customers. The objective of the master thesis is to develop a techno-economic analysis (TEA) tool for industrial NOx mitigation technologies. The techno-economic comparison facilitates in the preliminary selection of the most feasible NOx abatement concept among various alternatives. Currently, the typical NOx control systems that prevail in the industrial market are selective non-catalytic reduction (SNCR), selective catalytic reduction (SCR) and NOx scrubbers. NOx scrubbers are categorized according to the oxidant type such as ozone (O3) scrubber and chlorine dioxide (ClO2) scrubber in this study. The number of choices for these concepts are further increased by combining these technologies to form a hybrid system such as SNCR + SCR and SNCR + NOx scrubber.
In the TEA tool, technology selection and economic evaluation tasks are executed for the above-mentioned concepts. Technology selection procedure depicts the functioning of NOx removal technologies according to the set criteria by an investor. The critical demands from an investor are typically the NOx out contents and ammonia slip in the exhaust flue gas after the treatment system. The economic evaluation of NOx control methods is assessed by taking into account the capital expenses (CAPEX) and operating expenses (OPEX) for lifetime.
Feasibility analysis is comprised of negative cash flows (costs) without any profit because there is no revenue generation in NOx abatement technologies.
The SCR and NOx scrubber technologies have a greater potential of NOx reduction efficiency up to 95% as compare to SNCR (25-50%). Similarly, more strict NOx out and ammonia slip limits in the exhaust flue gas are accomplishable through SCR and NOx scrubbers as compare to SNCR method. Economic outcomes clearly show that SNCR is the least expensive NOx reduction technique from both CAPEX and OPEX viewpoint, only in circumstances where its applicable in the combustion device and it meets the investor demands criteria. Tool findings of CAPEX in the SCR and NOx scrubbers are not explicit because it depends upon the scope of investment and varies from case to case. OPEX results are more clear because the ozone scrubber system proves to be the most expensive than all other alternatives mainly due to electricity and oxygen gas consumption in the ozone generator. Ozone consumption trend for the target NOx removal is analyzed through the simulation work in Aspen plus 9.0 software. Simulation results show that the optimal molar ratio of O3/NOx is between 1-2 for the oxidation and absorption of NOx in the scrubber. The ClO2 scrubber system can also turn out to be a costly option if the investment is requisite for the ClO2 plant. Auxiliary effects of the technology are considered too for economic comparison such as effluent wastewater treatment in NOx scrubbers. SCR method typically costs less than ClO2/O3 scrubber system in terms of OPEX according to the tool findings.
These economic findings differ in the scenarios where scrubber system removes the other pollutants simultaneously with NOx contents such as acid gases, dust and ammonia whilst this principle also applies to the SCR method for removing altogether the ammonia slip, dioxins and furans with NOx from the flue gas. In conclusion, there is no one rule of thumb for selecting the most feasible NOx mitigation concept in the flue gas cleaning because investment prospect, suitability and scope differ especially in the retrofit cases.
In the TEA tool, technology selection and economic evaluation tasks are executed for the above-mentioned concepts. Technology selection procedure depicts the functioning of NOx removal technologies according to the set criteria by an investor. The critical demands from an investor are typically the NOx out contents and ammonia slip in the exhaust flue gas after the treatment system. The economic evaluation of NOx control methods is assessed by taking into account the capital expenses (CAPEX) and operating expenses (OPEX) for lifetime.
Feasibility analysis is comprised of negative cash flows (costs) without any profit because there is no revenue generation in NOx abatement technologies.
The SCR and NOx scrubber technologies have a greater potential of NOx reduction efficiency up to 95% as compare to SNCR (25-50%). Similarly, more strict NOx out and ammonia slip limits in the exhaust flue gas are accomplishable through SCR and NOx scrubbers as compare to SNCR method. Economic outcomes clearly show that SNCR is the least expensive NOx reduction technique from both CAPEX and OPEX viewpoint, only in circumstances where its applicable in the combustion device and it meets the investor demands criteria. Tool findings of CAPEX in the SCR and NOx scrubbers are not explicit because it depends upon the scope of investment and varies from case to case. OPEX results are more clear because the ozone scrubber system proves to be the most expensive than all other alternatives mainly due to electricity and oxygen gas consumption in the ozone generator. Ozone consumption trend for the target NOx removal is analyzed through the simulation work in Aspen plus 9.0 software. Simulation results show that the optimal molar ratio of O3/NOx is between 1-2 for the oxidation and absorption of NOx in the scrubber. The ClO2 scrubber system can also turn out to be a costly option if the investment is requisite for the ClO2 plant. Auxiliary effects of the technology are considered too for economic comparison such as effluent wastewater treatment in NOx scrubbers. SCR method typically costs less than ClO2/O3 scrubber system in terms of OPEX according to the tool findings.
These economic findings differ in the scenarios where scrubber system removes the other pollutants simultaneously with NOx contents such as acid gases, dust and ammonia whilst this principle also applies to the SCR method for removing altogether the ammonia slip, dioxins and furans with NOx from the flue gas. In conclusion, there is no one rule of thumb for selecting the most feasible NOx mitigation concept in the flue gas cleaning because investment prospect, suitability and scope differ especially in the retrofit cases.