Employing a Data Acquisition Handling System (DAHS) for New Source Performance Standards (NSPS) Ja Rule Reporting of Petroleum Refinery Emissions

Transcription

1 Technical Paper BR-1923 Employing a Data Acquisition Handling System (DAHS) for New Source Performance Standards (NSPS) Ja Rule Reporting of Petroleum Refinery Emissions Authors: D.C. Pretty Babcock & Wilcox Power Generation Group, Inc. Hatfield, Pennsylvania, U.S.A. Presented to: American Fuel & Petrochemical Manufacturers Date: October 19-21, 2014 Location: San Antonio, Texas, U.S.A.

2 Employing a Data Acquisition Handling System (DAHS) for New Source Performance Standards (NSPS) Ja Rule Reporting of Petroleum Refinery Emissions BR-1923 D.C. Pretty Babcock & Wilcox Power Generation Group, Inc., Hatfield, Pennsylvania, USA Presented to American Fuel & Petrochemical Manufacturers October 19-21, 2014 San Antonio, Texas, USA Abstract New environmental regulations have been promulgated in the Environmental Protection Agency (EPA) Federal Register that amend the existing new source performance standards (NSPS) of refinery sources including process heaters and flares. One of the many implications of the amended Ja rule include new Continuous Emissions Monitoring System (CEMS) installations for all affected sources, including (but not limited to) NO x CEMS, O 2 CEMS, H 2 S CEMS, and total reduced sulfur (TRS) CEMS. Owners will be subject to various performance specification (PS) standards in conjunction with operating the new CEMS. With each of the PS requirements, a data collection mechanism is specified to track the measurements, quality assurance (QA) activities, and overall CEMS operating time, to be reported on a quarterly basis at minimum (as needed). There are various data collection devices in the industry including, but not limited to, programmable logic controllers, data loggers, and various distributive control systems. Using a process control system for environmental reporting creates a challenge with the increase in QA and reporting activities needed to support monitoring for the new sources at the refinery. Data Acquisition and Handling System (DAHS) technology utilizes built-in logic engines to determine data validity, in both data collection and CEMS QA. With the amount of affected emissions sources growing and environmental staff not growing at the same rate, a DAHS streamlines the efforts of environmental staff by automating the human effort required for reporting. 1

3 The Rule NSPS Ja With the inception of the Clean Air Act in 1963, the federal government has taken an active and documented approach to monitoring and controlling air quality with regards to emissions from industrial sources. Refineries are among the industries with emissions sources affected by this legislation and continue to be affected with new regulations. The New Source Performance Standards (NSPS) Ja rule for petroleum refineries is documented in the Code of Federal Regulations, Title 40 (40CFR) Parts 9 and 60. The rule was initially proposed in May 2007 in the Environmental Protection Agency (EPA) Federal Register as an amendment to the existing NSPS of refinery sources including process heaters and flares, NSPS J rule. Through revisions during the following year, the rule became finalized in December 2008, but with an extension of the stay date for the rule. In September 2012, the final amendments were promulgated in the Federal Register. The final rule became effective in November 2012, effectually establishing a compliance deadline of November The Ja rule amendment applies to all process heaters newly constructed, reconstructed or modified after May 14, 2007, and flares newly constructed, reconstructed or modified after June 24, A flare is defined as a combustion device that uses an uncontrolled volume of air to burn gas. The rule further defines flares as a flare gas header system, hence creating it as a separate affected facility rather than a type of fuel gas combustion device, delineating it from other processes in a refinery (i.e., heater). In the case of multiple flares tying into the same header, each flare is considered an individual source to the header. Modifications to a flare as defined in Section a that trigger applicability to the rule are: Any new piping from a refinery process unit, including ancillary equipment A fuel gas system is physically connected to a flare Any alterations to the flare to increase flow capacity of the flare The Ja rule breaks down process heaters into different categories: natural draft process heaters, forced draft process heaters, co-fired natural draft process heaters, and co-fired forced draft process heaters. Natural draft process heaters are those that include induced draft systems and forced draft process heaters include balanced draft systems. The Ja rule is designed to achieve a reduction in emissions by stipulating new concentration-based limits for nitrogen oxides (NO x ), hydrogen sulfide (H 2 S) and total reduced sulfur (TRS) and volumetric flow - based limits for flow through a flare. The rule increases the amount of affected sources at a refinery for monitoring and applies additional limits to the monitoring sources to effectually reduce the NO x, sulfur dioxide (SO 2 ), and volatile organic compound (VOC) emissions emitted from these sources. The EPA estimates a reduction in SO 2 by 3,200 tons/year, NO x by 1,100 tons/year, and VOCs by 3,400 tons/year, with a co-benefit of CO 2 emission reductions by almost 2,000,000 metric tonnes a year. This emissions reduction will manifest with the EPA estimated 400 affected flares nationwide that will be subject to the final rule, an amount ten (10) times the estimates of 2008 with the original NSPS J rule. 2

4 CEMS Implications NSPS Ja Of the many implications of the amended Ja rule, new Continuous Emissions Monitoring System (CEMS) installations are required for all affected sources, with certain exceptions. For flare gas header systems subject to the rule, each flare of the system must be equipped with a continuous sulfur CEMS. Certain exemptions are allowed for flares that have inherently low SO 2 concentration gas flowing through them, are used very infrequently, are equipped with recovery gas systems or are secondary flares. Emergency flares are those defined by use (i.e. no flow through them) less than 4 times a year. Those flares equipped with a flare recovery gas system must be designed and sized to capture all flows while secondary flares must have accurate measurement through its primary source. For process heaters subject to the rule, each must be equipped with a continuous NO x CEMS along with an O 2 CEMS to measure as the diluents. Certain exemptions apply for process heaters that are equipped with low or ultra-low NO x burners, that have a rated capacity <100 MBtu/hr and that choose to use a heat inputbased NO x emission reporting mechanism. In those instances, a CEMS is not required for compliance, but fuel consumption and compliance testing are required to demonstrate emissions limits. TRS emissions compliance requires owners to maintain and operate a TRS CEMS, with quality assurance (QA) activities as specified in 40CFR Part60, Appendix B, Performance Specification (PS) 5. Popular technologies for monitoring TRS are ultraviolet (UV) fluorescence measurements through various means of sample delivery. This technology provides a quick response (typically <5 sec) and reliable measurement of multiple sulfur species. For H 2 S emissions compliance, owners are required to maintain and operate an H 2 S CEMS, with QA activities specified in PS-7. Gas chromatography is the industry preferred technique, which employs separating sample gas in a column and using the retention of each gas in the column for detection. This method has a lengthy response time due to the measurement complexity, but it is the most accurate method for tracking H 2 S in the flare. For NO x emissions compliance, source owners are required to maintain and operate a NO x and O 2 CEMS, with QA activities specified in PS-2 and PS-3 respectively. A popular technology for NO x measurement is by chemiluminescence, as it provides a more accurate response when measured at lower levels (<50ppm) of NO x. The paramagnetic cell technology employed for O 2 measurement uses a strong magnetic field to separate oxygen molecules for analysis. Each type of CEMS has its own set of operation, maintenance and certification testing procedures, each of which represents material cost and personnel staffing requirement for the refineries. Material costs include the CEMS peripherals (enclosure, HVAC system, etc.), replacement/spare CEMS parts, and Relative Accuracy Test Audit (RATA) testers, while Instrument and Controls (I&C) technicians and environmental staff are part of the CEMS maintenance and reporting team. 3

5 With each of the PS requirements, a data collection mechanism is specified to track the operations of the CEMS system. PS-2, 3, 5 and 7 specify that a CEMS data recorder shall have an established high and low-level value which must be between 1.5 times the span and the span provided in the applicable regulation. Along with CEMS concentration data, the CEMS data recorder must also track QA activities and overall CEMS operating time to be reported on a quarterly basis at minimum, or as frequently as the particular state/air district requests. To track measurements, data collection devices must have the capability of collecting analog and digital signals over copper (hard-wired), through a communication protocol interface (i.e., Modbus), or a combination of both. The signal, either hard-wired or digital, will originate from the CEMS monitor (or analyzer). For reporting data to the agency, the CEMS data recorder must collect and retain certain peripheral information, outside of the CEMS measurements. When logging a calibration drift test or a certification drift test (7-day), the CEMS recorder must have the capability to track the CEMS readings along with the gas standard readings so that the percent (%) drift error can be calculated. With instrument diagnostics coming from the CEMS monitors/analyzers, the health of the CEMS can also be documented by a CEMS recorder. The maintenance, calibration, and malfunction inputs can be connected directly to the CEMS recorder, which is the preferred method, but it is not imperative that it be done in this manner. Whether manually entered by a responsible party for the CEMS (I&C technician or an environmental engineer) or logged directly from the CEMS system, the data recorder needs to recognize those periods of time to document overall CEMS downtime. With the rule asking for CEMS data to comply with emissions limits on a multi-hour or multi-day basis, an hour average recording is acceptable; however, during a RATA, the data collection system must be able to produce minute level readings for comparison with an external CEMS. CEMS Data Recorders NSPS Ja There is a myriad of devices which can collect data from a CEMS and peripheral process data. Programmable logic controllers (PLCs) are miniature digital computers that are used widely for process control throughout various industries. Like a computer, PLCs include a controller (central processing unit, CPU, with integrated memory) and input/output (I/O) receivers attached to the controller. The logic programming of a PLC allows the controller to collect inputs (analog or digital) and manipulate outputs (analog or digital) based on the particular logic written. Modern PLC s are designed for rugged installation, with a high tolerance for vibration, abrasion and temperature, withstanding temperatures generally over 100 F, 2g or better vibration rating, and 20g or better impact force. I/O blocks are a functionless version of the I/O used with a PLC, but carry all the same durable properties of a PLC. The I/O block needs a CPU (PLC controller, logger, or computer) to act as the storage device, since the I/O blocks do not come with memory. A data logger refers to any electronic device that collects and records data over time. Devices as primitive as a chart recorder or as sophisticated as a computer server are considered data loggers, as they all can record and maintain data over a continuous period of time. What separates a data logger from other devices with integrated memory (computer, PLC, etc.) is that loggers 4

6 traditionally do not handle logic, much like an I/O block; they simply record data. Distributed control systems (DCS) are a network of CPUs that handle functions across a plant or facility. The processes are physically spread out over a large physical area, usually covering several square miles (e.g., a refinery); hence it does not make sense for the CPU s to be centralized in one zone. These industrial systems are tied to a long-term recording device, typically a computer server. The storage mechanism is a database which houses the information and logs it in a logical format, recording the parameter (in this case emissions measurement), date and time, and measurement diagnostic. Information in the database, depending on its capabilities, can be aggregated, manipulated and reprocessed into a physical hard-copy report. For NSPS Ja compliance, the CEMS data must be collected to produce multi-hour and multi-day averages. Environmental staff and I&C technicians are both involved in managing emissions data at different stages of the process. When I&C technicians perform service on the CEMS for preventative or corrective maintenance, or calibrate the instrument, they log the periods of time in the data recorder and must keep a reason for the periods of CEMS downtime and a corrective action for getting the CEMS back online. Environmental staff then average the data, excluding the periods of CEMS downtime, per 40CFR60.13 and produce the appropriate calculations based on that particular emission limit. As dictates, each hour of emissions data becomes valid pending the CEMS downtime does not exceed 30 minutes, as logged in maximum 15 minute averages. If data is recorded on a minute-by-minute basis, the hour becomes valid if there are two quadrants of data with at least one minute of normal CEMS operation separated by 15 minutes. The valid hour data blocks are then averaged in 3-hour, 24-hour, and 30-day averages for H 2 S, SO 2 and NO x respectively. Those hours that are considered CEMS downtime must be collected and reported out each quarter to demonstrate CEMS operation at 90% or greater during source operation. Figure 1 shows an example report which denotes the information required for reporting for each emission parameter from each source at the refinery. It is the responsibility of the environmental staff to properly aggregate the CEMS operating data, categorize it into the proper performance summary category, and finally create a ratio (percentage) of CEMS downtime to total source operating time. At the end of each quarter 2,160 hours are reconciled, for each source in the plant, and with an estimated 400 newly affected flares across the country this means over 800,000 hours quarterly to properly track and manage for new sulfur CEMS nationwide. Technicians and environmental staff at refineries are burdened with this requirement, in addition to the CEMS currently being managed. 5

7 Figure 1 Summary Report Gaseous and Opacity Excess Emission and Monitoring System Performance Source: 40 CFR 60.7 Subpart A, General Provisions; Electronic Code of Federal Regulation, 2014; Web. CEMS Data Management NSPS Ja Virtually all operating refineries use a DCS system for process control, regardless of the particular process or product manufactured. A DCS infrastructure includes, but is not limited to, controllers, located at the plant level, a series of human-machine interface (HMI) terminals, including operator, engineering and management stations, and an overall plant data system, which collects data from all the controllers. Figure 2 is a sample DCS block diagram of the various functional levels. 6

8 Figure 2 DCS Functional Level Block Diagram The DCS controllers have I/O blocks for collecting digital and analog signals, similar to a PLC, and instrumentation used in the plant is tied into the DCS system to monitor the specific process. The communication protocols between DCS controller, HMI terminals and plant data system can vary based on the manufacturer, and can be configured through a hard-wired interface, an open protocol like Modbus, or a proprietary protocol. A CEMS is logical to integrate into a DCS system as the CEMS components are instruments which can be tied into an individual controller. A DCS also has infrastructure to provide long-term storage required for CEMS data and can reprocess minute level information through residual calculations (e.g., NO x corrected to O 2 ) or by outputting data into a spreadsheet (Microsoft Excel) or as a hard-copy printout. Many refineries chose to go this route by implementing their DCS as their CEMS data recorder and continue to use a DCS as their data management tool. The main drawback of using a DCS as a CEMS recorder is that while it fits the purpose as specified by PS-2, it does not do much beyond that. DCS controllers can collect data from the instruments through various means (hard-wired interface, electronic protocol, etc.), and serve it up to a plant data historian where calculations can then be performed. Most DCS historians even have the means of producing up to 7

9 a 24-hour average, in any specified increment inclusive. They lack, however, the ability to handle the data validation algorithms as specified in 40CFR As specified to calculate an hourly average: At least four valid data points are required to calculate the hourly average, i.e., one data point in each of the 15-minute quadrants of the hour For a partial operating hour (any clock hour with less than 60 minutes of unit operation), at least one valid data point in each 15-minute quadrant of the hour in which the unit operates is required to calculate the hourly average For any operating hour in which required maintenance or quality assurance activities are performed o o If the unit operates in two or more quadrants of the hour, a minimum of two valid data points, separated by at least 15 minutes, is required to calculate the hourly average If the unit operates in only one quadrant of the hour, at least one valid data point is required to calculate the hourly average If a daily calibration error check is failed during any operating hour, all data for that hour shall be invalidated, unless a subsequent calibration error test is passed in the same hour Except as provided under paragraph (h)(2)(vii) of this section, data recorded during periods of continuous monitoring system breakdown, repair, calibration checks, and zero and span adjustments shall not be included in the data averages The above standards spell out five logic scenarios to be carried out for hourly average processing. This means that the CEMS data reporting tool must be able to collect source operation to handle partial operating hours, reconcile preventative maintenance, corrective maintenance, calibration checks, calibration failures and equipment failures, and finally validate them throughout the minutes of an hour to produce valid 15-minute averages (and hourly averages subsequently). To simply collect the CEMS operational data, a DCS would need to have input from CEMS equipment to indicate failure, user/operator inputs to determine preventative/corrective maintenance activities, and knowledge of a gas standard being introduced while performing a calibration and whether it has passed or failed based on the specific pollutant performance specification. Once this information is collected, it then takes a powerful algorithm to create the hourly averages as specified by 40CFR DCS systems are sophisticated machines, but this level of calculation is outside the purpose of a DCS, as it is by design a process control system. Logging process parameters is part of the DCS design since it needs to use them for process control (e.g., using process temperature as a feedback for controlling fuel firing rate), but collecting and averaging data as specified by NSPS Ja is not its intended purpose. This now becomes the duty of environmental staff to use external programs and their own time and energy to finish the task of producing the final emissions averages, along with the emission exceedence reporting, CEMS downtime reporting, and quarterly/annual QA activities reporting. Based on the practices of the refinery, the data required to include in quarterly reports may be stored in multiple systems, requiring human intervention to extrapolate the appropriate information for reporting. Environmental staff may have to pull records from 8

10 CEMS maintenance logs, instrument diagnostic logs, and a DCS to complete the compliance reports. The additional sources NSPS Ja estimates will add to the hundreds of sources already spread out across the country, thus increasing the already demanding workload of environmental staff. Employing a DAHS NSPS Ja A Data Acquisition and Handling System (DAHS) is a computer-based system which is a tool for CEMS data storage and processing. A DAHS is a combination of a data collection device, a historian, and a logic/reporting engine that performs data handling, validation and reporting. DAHS technology captures the data reporting requirements denoted in 40CFR60.13, in addition to tracking CEMS downtime and source operating time. Figure 3 Typical DAHS Architecture Diagram Figure 3 shows a typical DAHS architecture, where each component serves a purpose in the overall tracking of CEMS data and QA activities. The data collection device is the source level of the DAHS architecture, connecting to the instrumentation associated with the CEMS. The data collection device takes in information like raw emissions data, the analyzer performance and various process signals to send to the historian. Depending on the design, a user input can be entered into the data collection device to be collected and aggregated (i.e., a CEMS analyzer maintenance toggle switch) as an I/O point. A data collection device could be the aforementioned PLC, I/O block, data logger, or a DCS since they each collect I/O. Some DAHS manufacturers have historians and logic/reporting engines that are compatible with multiple data collection devices, and each DAHS manufacturer specifies the type, quantity and variety to be used with their particular application. The historian and logic/reporting engine are codependent and usually reside as one portion of the application, but each serve a different purpose in the data handling process. Information collected by the data collection device gets sent to the historian, which is in the form of a database or other proprietary storage format. Due to the compact and rugged nature of data collection devices, they are limited with storage memory for information, so historians become the long-term storage mechanism for the DAHS. User inputs such as calibration gas standard information, periods of corrective maintenance, or reasons for corrective action after an equipment failure 9

11 are all examples of information that will be logged in the historian, along with the date and time of each occurrence. In addition to continuous CEMS data, the historian will also collect QA activities (Quarterly CGA, annual RATA) and initial certification data. DAHS applications vary, but some QA and certification activities can be automated while others require user data entry. Once data is collected in the historian, the logic engine takes over to perform data calculations and validations. The creation of hourly averages is only part of what the logic engine does; in total, a logic engine would: Perform arithmetic calculations to produce proper reporting units for an emission parameter and calculating hourly averages from the data based on CEMS performance for that particular emission as outlined in 40CFR60.13 Validate a calibration drift check (daily or CGA) passed or failed by applying user input on calibration gas standards and calculating the drift between the analyzer reading and the standard (following 40CFR60 Appendix F) Determine if an emission from a source (expressed as a 3-hr, 24-hr or 30-day rolling average) exceeds the limits of NSPS Ja, accumulate periods of excess, categorize them per Figure 1, and create a ratio of excess periods to total source operating time Sum up the periods of CEMS downtime, categorize them per Figure 1, and create a ratio of CEMS downtime to total source operating time Validate QA activity for completion, assess if it passed or failed, apply data validation (or invalidation) as necessary The reporting engine will pull from a combination of the historian and logic engine of a DAHS to handle compliance reports. Compliance reports output from a CEMS will include at minimum those specified in 40CFR60.7 Subpart A, which handle excess emissions and downtime reporting. Certification and QA activity reports are an output from the DAHS, as they are required for quarters where those activities were performed to demonstrate compliance. The format for reports can vary as necessary, but generally are a Microsoft Excel file format for easy viewing. A DAHS simplifies compliance for environmental staff with the logic/reporting engine inherent to the product. With a DAHS, the information which potentially was held in multiple systems is stored in one database, running one application for data access and report generation. In addition to streamlined compliance, other benefits of a DAHS include functional data and monitoring for process operations staff and I&C technicians who work on CEMS. For I&C technicians, a DAHS can monitor CEMS analyzer and sample system function through monitoring the instrumentation associated with the CEMS and create alerts for malfunction, hence decreasing CEMS downtime with proactive notifications. Also, I&C technicians can access the historian through a front-end application to manually categorize and provide corrective actions for a period of CEMS downtime immediately after it happens (e.g., after they 10

12 finish a maintenance activity). For operations staff, a DAHS can calculate predictive emissions exceedence alarms based on source performance to track emissions concentrations and rates and alert users prior to exceeding a compliance limit. Like I&C technicians, operations staff can access the historian to manually categorize and provide corrective actions for periods of CEMS emissions limit exceedence. While there have been no formal studies done on the effects of using a DAHS to decrease CEMS downtime or decrease CEMS emissions exceedence, the reduction of man hours and staffing requirements for CEMS compliance are real and tangible. The US Bureau of Labor Statistics reports the average annual salary for an environmental engineer is just above $80,000, while the average DAHS cost lies between $25,000 and $50, From a business management view, owners typically want to limit expenses that do not increase revenue or provide a return on their investments (i.e., environmental regulations compliance). However, a one-time equipment cost can be justified easier than a recurring personnel cost, whether for internal or external contract staffing. Owners will staff as they see fit for NSPS Ja compliance, but this sudden and large increase of emissions data collection and reporting requirements will not be met in proportion with the same staffing. While all DAHS products provide streamlined compliance, the product s flexibility to create an efficient and user-friendly experience is what differentiates one from another. 1 Data taken from top 5 DAHS vendors in the United States as of

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