Rita Aiello/5 December 2016/Johnson Matthey, Stationary Emissions Control

Transcription

1 Rita Aiello/5 December 2016/Johnson Matthey, Stationary Emissions Control

2 SCR systems have demonstrated very high reductions of NOx emissions from lean-burn engines used in oil and gas industry: Drill rigs - Wyoming Eight drill rigs powered by twenty-four diesel engines, each equipped with SCR+ASC systems Gas compression station - Pennsylvania Two natural gas engines equipped with Oxidation+SCR catalyst systems TWC technology used on thousands of rich-burn gas engines for gas compression o TWC catalyst validation program

3 SCR catalyst: for NOx reduction in lean engine exhaust uses ammonia or urea to reduce NOx to nitrogen 4 NH NO + O 2 4 N H 2 O 4 NH NO NO 4 N H 2 O NH 3 and NOx react in 1:1 ratio at typical engine conditions Ammonia slip catalyst (ASC): to minimize NH 3 slip contains both oxidation and SCR functions, selectively converts NH 3 to N 2 Oxidation catalyst: for CO and VOC reduction typically precious metal-based, very effective CO + ½ O 2 CO 2 HC + O 2 CO 2 + H 2 O

4 Relationship between NOx conversion, NH 3 slip and Ammonia NOx Ratio (ANR) At ANR < 1 Low NOx conversion, low NH 3 slip At ANR = 1.0 Better NOx conversion, higher NH 3 slip At ANR > 1 Max NOx conversion, highest NH 3 slip More catalyst, better mixing higher conversion, lower NH 3 slip

5 ASC allows operation at ANR > 1 when NOx is high, sufficient NH 3 for complete conversion when NOx is low ASC, converts excess NH 3 to N 2 ASC selectively converts NH 3 to N 2, not to NOx: Nearly complete conversion of NH 3 slip Formation of NOx, N 2 O very low HC is converted to CO 2, not CO

6 NOx control required for reduction in visible haze Environmentally sensitive area Aesthetics Each gas drill rig powered by multiple diesel engines Each diesel engine equipped with SCR+ASC system, above engine

7 Challenges Fluctuating engine loads fluctuating NOx levels load-based urea dosing strategy ASC used to minimize NH 3 slip Harsh environment (cold winter) urea tanks insulated to prevent freezing, crystallization electronics located inside engine enclosure Low-sulfur diesel (LSD) fuel SCR and ASC sulfur tolerant formulations

8 One drill rig with three engines was equipped with three SCR+ASC systems Engines: 1500 hp NOx = 7 g/bhp.h Single urea tank feeds three SCR systems Systems operated for 6 month demo period Three JM urea SCR systems installed above the engines powering the rig catalyst configuration

9 SCR operates only when the catalyst inlet temperature 500 F (260 ), corresponds to ~20% engine load Engine-out NOx concentration range 400 ppm (20% load) to 1000 ppm (90% load) Load bank was used to achieve engine loads of 20%-90% After 6 months, NOx conversion and NH 3 slip measured at 10 loads in this range, results averaged: Species Measured (at catalyst outlet) Engine 1 Engine 2 Engine 3 % NOx conversion ppm NH 3 slip NOx emissions measured with Testo 350 portable gas analyzer NH 3 measured by Drager tube

10 Project demonstrated that SCR+ASC could significantly reduce NOx at low NH 3 slip State of Wyoming and BLM implemented emissions limits NOx: 90% conversion NH 3 slip 10 ppm 21 more SCR+ASC systems were added Up to 24 SCR+ASC systems operate at one time Systems installed 2009, still operating and achieving emissions targets 2016 NOx and NH 3 emissions measured at loads in 25%-70% range, results averaged: Species Permit Measured Engine 1 Engine 2 Engine 3 NOx (as NO2) 90% conversion NH 3 10 ppm slip

11 Two 3500 kw natural gas engines installed on two pipeline compressors NOx g/bhp.hr CO 2.75 g/bhp.hr Permit limits NOx g/bhp.h CO 0.19 g/hp.h Emission control necessary to prevent aggregated emissions from exceeding the limit for that area Oxidation catalyst+scr was installed to achieve both CO and NOx reduction Commissioned early 2013

12 Skid-mounted systems, placed on ground Climate - winter temperatures below freezing heated and insulated urea tank, urea lines heated injection cabinets (electronics) SCR catalyst Flow NH 3 oxidation catalyst

13 Emissions measured upon commissioning of system: Species Permit (g/bhp.hr) Measured (g/bhp.hr) Engine 1 Engine 2 NOx (as NO 2 ) CO Emissions measured two years later: Species Permit (g/bhp.hr) Measured (g/bhp.hr) Engine 1 Engine 2 NOx (as NO 2 ) CO NOx and CO measured with Testo 350 XL portable gas analyzer

14 Since 1990s, JM has sold thousands of TWC systems for rich-burn engines used for gas compression State and local NOx limit as low as 0.07 g/bhp.hr Gas engine with three-way catalytic converter λ = actual oxygen stoichiometric oxygen

15 TWC (catalytic converter unit) field-aged on gas compression unit 118 hp, 8.3L engine Pipeline natural gas Field-aging for 8000 hrs continuous operation Samples removed periodically for laboratory performance evaluation Reactor test conditions GHSV 94k hr -1 Temperature (C) Test gas composition CH 4 C 2 H 6 (as C1) 1000 ppm 200 ppm CO 0.45% NOx 2700 ppm H % O 2 0.3% CO 2 10% H 2 O 10% N 2 balance Lambda 0.994

16 Baseline catalyst-out emissions measured on engine (full load) NOx 99% conversion 0.13 g/bph.hr (25 ppm) CO 98% conversion 1.23 g/bhp.h (93 ppm) Lab reactor performance at 500 C, approximates full load measured %NOx conversion measured %CO conversion 30 conversion req'd. to meet 2008 NSPS EPA NOx limit (2 g/bhp.h) 20 conversion req'd. to meet 2008 NSPS EPA CO limit (4 g/bhp.h) Hours System maintained performance for 8000 hrs

17 SCR systems and TWC technology can significantly reduce NOx from engines used in a wide variety of applications SCR is often coupled with ASC or oxidation catalyst to achieve specific emissions targets (NOx, CO, VOC) under different conditions Drilling conditions were especially challenging (fluctuating load/nox emissions, harsh weather, LSD fuel) but proper system design can overcome these challenges SCR systems presented here are still operating and meeting emissions limits Thousands of three-way catalytic converters are currently operating and achieving compliance for gas compression units

18 Please contact us for more information: Catalyst Development Scientist Sales Manager, Engine Systems Thank you for your interest!