21/05/2014 FTIR AS HCN MEASUREMENT METHOD IN A FLUID CATALYTIC CRACKING UNIT. G. Lenaers, E. Damen, R. Brabers, W. Aerts, B. Baeyens, W.

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1 21/05/2014 FTIR AS HCN MEASUREMENT METHOD IN A FLUID CATALYTIC CRACKING UNIT G. Lenaers, E. Damen, R. Brabers, W. Aerts, B. Baeyens, W. Wouters

2 Outline» Goal» Fluid Catalytic Cracking Unit FCCU and HCN» FTIR suitability testing» FCCU measurements» Experiments on the reconstructed gas matrix» Results HCN-measurements on the FCCU» FTIR as continuous HCN measurement method 21/05/2014 2

3 Goal» In the Flemish Region an official request was made to change the regulation for HCN emissions in the sector of oil refineries for installations for the catalytic cracking over the fluid bed method at regeneration of the catalyst.» Next to a proposed new monthly average limit value of 50 mg/nm 3 -up from 5 mg/nm 3 - the addition of FTIR as a continuous measurement method for HCN is requested.» At present the HCN emissions need to be determined over the draft EPA OTM- 29 wet chemistry method. This method specifically takes account for problems in the analytical determination of HCN emissions in catalytic cracking units mainly by using a 6N NaOH absorption solution to keep the ph above 12 and thus preventing the loss of gaseous HCN from this solution.» The goal of this study is to investigate if FTIR has the potential for an alternative HCN measurement method at a FCCU. The EPA OTM-29 wet chemistry method is used as a reference method.» The study is commissioned by the Flemish Government. 21/05/2014 3

4 Fluid Catalytic Cracking Unit FCCU and HCN P P T STOOKGAS HCN LCDO FRACTIONATOR TOREN ABSORBER HCDO ALKY BLENDING SCHOORSTEEN ESP REGENERATOR VAT REACTOR VAT GOFINATE FORNUIS LUCHT 21/05/2014 4

5 Fluid Catalytic Cracking Unit FCCU and HCN» In the refinery process of crude oil the residual fraction containing heavy components is fed to a FCCU for conversion to petrol, diesel, LPG etc. With the help of heat and a catalyst the long hydrocarbon chains are cracked.» Cokes are formed that deposit on the catalyst and deactivate it. To restore the activity of the catalyst the cokes are burned off in the regenerator under addition of air to the fluidised catalyst.» Nitrogen compounds on the cokes react in the regenerator with HCN formation 21/05/2014 5

6 FTIR Gasmet DX /05/2014 6

7 FTIR suitability testing» Recording of new water reference spectra with reproducibility check from 1 to 28 vol%, regression R 2 =1, repetition yields same regression line» Establishing a calibration line between 0.1 and 3 times the ELV for HCN in dry nitrogen gas including determination of linearity and reproducibility check from 0.5 to 150 mg/nm 3, regression R 2 =1, repetition = same regression line» Establishing a calibration line between 0.1 and 3 times the ELV for HCN in wet nitrogen gas including determination of linearity from 0.5 to 150 mg/nm 3, around 10% H 2 O, regression R 2 =1» Establishing a calibration line between 0.1 and 3 times the ELV for HCN in a fixed flue gas matrix including determination of linearity» Measurement of a flue gas matrix of varying composition together with HCN 21/05/2014 7

8 FTIR suitability testing Establishing a HCN calibration line in a fixed flue gas matrix The concentrations are at the expected level in the FCCU flue gas 21/05/2014 8

9 FTIR suitability testing Establishing a HCN calibration line in a fixed flue gas matrix the HCN regression has a R 2 of 1 and the calibration line shows a coefficient near 1 and an intercept of only -0.2 ppm 21/05/2014 9

10 FTIR suitability testing Measurement of a flue gas matrix of varying composition together with HCN» Can the individual matrix components be determined?» over a wide concentration range» in the presence of the other matrix components» in the presence of HCN» A partially optimised FTIR-libraryfile was used in analysing the spectrum. This file consists of:» the components present in the matrix,» a list of interfering components per component,» the selected areas in the infrared spectrum for analysis per component adapted to the interfering compounds,» and if necessary advanced corrections for remaining cross interferences. 21/05/

11 FTIR suitability testing Measurement of a flue gas matrix of varying composition together with HCN 21/05/

12 FTIR suitability testing Measurement of a flue gas matrix of varying composition together with HCN 21/05/

13 FTIR suitability testing Measurement of a flue gas matrix of varying composition together with HCN» HCN is measured rather well: about 1.5 ppm too low on a level of 30 ppm i.e. 5%.» The other components are measured within 10 % with a few exceptions.» Thus the composition of the FCCU gas matrix can be measured in a reliable way. This is required to be able to accurately generate this matrix when developing a dedicated libraryfile for the measurement of HCN at the FCCU. 21/05/

14 FCCU measurements 1. To enable the actual measurements on the flue gas of the FCCU-regenerator a measurement set-up was built that allowed next to the FTIR measurements simultaneous sampling according to EPA OTM-29 that serves as the reference method. 2. Then the measurements on the FCCU were executed. 3. Next the measured gas matrix was reconstructed over the gas generation facility of the reference lab and a dedicated FTIR-libraryfile realised. 4. Finally the measurements on the FCCU were analysed with this dedicated libraryfile and the results compared to those of the EPA OTM-29 reference measurements. 21/05/

15 FCCU measurements Measurement system 21/05/

16 FCCU measurements Reference HCN determination: EPA OTM-29 method» Impinger method with 6N NaOH absorption liquid» equipped with a purpose built third impinger that allowed for the insertion of a ph electrode to make sure that the ph in this impinger did not fall below 12 21/05/

17 FCCU measurements 21/05/

18 Experiments on the reconstructed gas matrix» The FTIR measurements on the FCCU revealed the components and their concentration levels in the gas matrix. This allows reconstructing the gas matrix with known concentrations that are used as reference values to compare to FTIR measurements executed on this matrix. The FTIR library file is then fine tuned to a dedicated one that yields the best possible match with the reference values.» By varying -over different steps in the gas generation- the concentrations of some components versus each other while other remain constant, interferences become clearer and can be eliminated more efficiently.» Next to HCN the generated matrix consists of CO 2, H 2 O, SO 2, NO 2, NO en CO. 21/05/

19 Experiments on the reconstructed gas matrix Check on the EPA OTM-29 method» Two FCCU matrices are generated both with 15% CO 2 and 15% H 2 O and with resp. 20 and 42 ppm HCN. 20 ppm HCN is the level found in the FCCU whereas 42 ppm equals the requested ELV of 50 mg/nm 3. 15% of both CO 2 and H 2 O are the maximum levels in the flue gas. They represent the worst conditions as to lowering the ph level of the absorption liquid by acidifying (CO 2 ) and diluting (H 2 O) it. SO 2 and NO 2 will further acidify the liquid.» For each matrix three parallel wet chemical samplings are executed. The average result per matrix is compared to the reference value. As the differences are only 2% it is concluded that the EPA OTM-29 method was a good reference method for use during the measurements on the FCCU. wet chem. HCN measured HCN average HCN reference Differ. vs ref Differ. vs ref test mg/nm 3 mg/nm 3 mg/nm 3 mg/nm 3 % /05/

20 Experiments on the reconstructed gas matrix Main experiment» The generated water concentration varies between the steps from 10 to 15% and the CO 2 concentration from 12 to 15%.» HCN is generated between 5 and 150 mg/nm 3 i.e. from the current ELV -and also 0.1 times the requested ELV- till 3 times the requested ELV. The aim is to investigate if the FTIR analyser can be used to compare its measured values to an ELV.» The measured values are calculated starting from two libraryfiles: the dedicated FTIRVito4.lib and the FTIRbaselib. This last one is a base library that was included at delivery of the FTIR. It is not optimised for the gas matrix and serves here to show the difference to the dedicated library. 21/05/

21 Experiments on the reconstructed gas matrix 21/05/

22 Experiments on the reconstructed gas matrix 21/05/

23 Experiments on the reconstructed gas matrix 21/05/

24 » HCN: Experiments on the reconstructed gas matrix» The difference between the reference values and those from the FTIRVito4.lib are small: maximum 2.1 ppm at 125 ppm; 0.2 ppm at 42 ppm; 0.6 ppm at 20 ppm en 0.4 ppm at 4 ppm.» An increase in the differences below 4 ppm is not to be expected as the FTIR was shown to behave very linear for HCN in flue gas.» All interferences have been corrected for to a large extent.» The FTIRbaselib delivers values too low and suffers from interferences.» Other components:» The comparison yields differences of a few percent at maximum.» The FTIRbaselib is only at an acceptable level for H 2 O.» On the basis of these experiments it is concluded that FTIR has the potential to guard an ELV for HCN. 21/05/

25 Results HCN-measurements on the FCCU The measurements on the FCCU were analysed with the dedicated libraryfile and the results compared to those of the EPA OTM-29 reference measurements Date Time FTIR FTIR Wet chemical Difference FTIR VITO4 LIB 2012 base LIB VITO4 LIB VITO vs wet chemical mg/nm³ mg/nm³ mg/nm³ % 22/nov 11:10-12:10 13,8 17,5 20,0-12,4 12:19-13:19 15,1 18,8 18,8 0,0 26/nov 10:15-11:15 16,0 19,8 24,0-17,5 11:25-12:25 17,2 21,0 23,5-10,9 3/dec 12:35-13:35 19,4 23,3 23,1 0,8 13:45-14:45 21,9 25,6 24,0 7,0 average -5,5 STDEV 9,4 The dedicated libraryfile delivers comparable results to the reference method: the average difference is -5.5% +/- 9.4% 21/05/

26 FTIR as continuous HCN measurement method» FTIR has potential as a continuous measurement method for HCN at FCCU s. The term continuous measurement method covers two possible options as a FTIRanalyser intrinsically measures continuously:» A first option is the use in short term periodical measurements during which the FTIR analyser measures continuously. Within CEN TC 264 the new Working Group WG36 is working on an EN standard for periodical FTIR measurements. This standard will built on the UK Technical Guidance Note TGN M22 and the US EPA method 320 (or comparable ASTM D 6348 test method).» A second option is the use as AMS (Automated Measurement Systems) or CEMS (Continuous Emissions Monitoring Systems). In this case the FTIRanalyser measures continuously without interruption.» It should be stressed that quality assurance is necessary according to national, European or international standards.» The use of FTIR should be left to those with a sufficient knowledge of the base principles of FTIR as well as of the software for spectral analysis. 21/05/

27 Questions 21/05/