Rapid Combustion And Energy Services (RCES)

Rotary Kiln Burner, accessories, and flame detection retrofit

This mining customer was struggling with burner reliability and process quality due to low kiln temperatures. A partner of RCES was tasked with providing a solution to the kiln problems, and RCES was tasked with the field retrofit and startup.

During a preliminary visit to site, RCES requested the end user allow us to remove the burners for inspection. The end user agreed, and RCES found all of the burners were in a state of severe degradation. Thankfully, this inspection was conducted early enough to allow for ordering and addition of new Fives burners for the upcoming fuel skid and flame detection retrofit.

RCES landed on site and removed the old 8 burners after clearing all air and electrical obstructions. While on site RCES welding crew began field fitting the new burner flanges and mounting the new burners. In tandem, RCES service engineers worked to replace all fuel solenoids, ratio regulators, switches, and main gas regulator.

Once the burners were completed, along with fuel skid and air system re-work, RCES moved onto mounting the new flame scanner junction boxes and installation of new flame scanners. RCES installed a new go between to interface the new scanners with existing Honeywell BMS systems. Once completed, RCES moved onto the first fire phase of the unit.

Firing was successful and RCES tuned all burners to optimal performance. Process temperature was back to target setpoint and provided a high quality material output as a result.

Unreliable Control Strategy for Ultra-Low NOx Natcom Burner on Auxiliary Boiler

This critical end user was unable to ramp their auxiliary boiler in automatic control since the boiler was installed and commissioned. Due to this, plant auxiliary boiler operations were touch and go, and bringing Waste heat systems online and offline was a challenge.

RCES service engineer dispatched to the customer site and found the burner to be unstable during load transitions. RCES attempted retune of the burner fuel and air curves, but was still unsuccessful. After connecting with the Allen Bradley PLC, we deduced the air control strategy was not correct. The current strategy tied FGR control and Fresh air damper control on the same PID controller as the other air elements, fan inlet and fan outlet damper. This control strategy was causing PID control “fighting” action. The control strategy was unable to properly change air flow for O2 trim without causing a major disruption in FGR flow, resulting in the PID control fighting action.

RCES offered a combustion control system program logic retrofit with new HMI graphics. The end user decided to move forward with this logic retrofit. After the logic retrofit was completed, RCES was able to tune the burner to sub 9 PPM cNOx and achieve a steady and reliable burner through all firing rate transitions. RCES was also able to reduce excess air and O2 to under 2% O2 at mid-range firing to high fire firing rates. Resulting in better unit efficiency overall. After the retrofit, the plant was able to remotely and reliably run the auxiliary boiler in automatic control, resulting in ease of operations and reliable plant startup and shutdowns.

Problematic Ultra-Low NOx RMB on Auxiliary Boiler

This end user was unable to reliably start and modulate this Ultra Low NOx RMB since time of installation. After years of problems, RCES was contracted to diagnose the cause of failure in the system and fix it.

RCES service engineer dispatched to the customer site and found the burner to be in a huffing, unstable condition. RCES service engineer place all control elements in manual control, and noted air flow process value swings, even when in manual. RCES investigated further and found the stack damper positioner was hunting in swings of +/- 3% position. This swing in position was causing changes in air flow and FGR, resulting in an unstable burner operation. The RMB operates within a tight fuel, air, and FGR ratio band, and cannot run reliably with swings of this magnitude. RCES worked with the end user and advised them to upgrade the stack damper positioner. The end user replaced the unreliable positioner with a DVC6200 smart positioner, and RCES was able to re-characterize the entire burner firing rate curve.

Retuning resulted in sub 9 PPM cNOx, steady fuel, air, and FGR flows, and a reliable and safe to operate burner. This burner now lights off at turndown reliably and safely modulates throughout the entire firing curve. The picture shown here shows all control loops in automatic with perfect alignment of SP, PV, and CV.

Major Malt Plant Control System Retrofit

This end user was experiencing significant product loss due to downtime and excessive fuel usage due to poor fuel and air ratio control. The antiquated control system utilized obsolete parts, relay logic, and single point position control. The system was also missing critical safety items. After significant fuel waste and damage, this end user was ready to upgrade their control system.

RCES supplied a full Allen Bradley programmed Burner Managment System, Combustion Control System, and HMI for this application. In addition, RCES added the following items to the motor system and fuel skid.

– Motor Control Cabinet with Allen Bradley Soft Starts
– Fuel, Air, FGR, and Mixing sleeve position control.
– New Safety shutoff valves, New low gas and high gas pressure switches, new main fuel supply regulator, and Fuel flow control valve.

– Minimum combustion air and purge air flow switches
– New Flame detection, upgraded from flame rod technology
– And an additional FGR PID control loop for better system temperature balance and less heat waste.

The retrofit resulted in an average lower firing rate to maintain process temperature, netting a 60% reduction in fuel utilization, when compared to other burners on site. Site was also provided new electricals and P&IDs for future troubleshooting. Since retrofitting, this burner has proven to be 100% reliable, and lost process is no longer a problem on site.

Major Milwaukee Power Plant Coal to Gas Retrofit

This end user was looking to reduce their carbon footprint, increase their efficiency, and supply Milwaukee with cleaner power and steam. The ultimate decision was made to convert the existing 4 units from pulverized coal firing to 100% natural gas firing units. I personally oversaw the mechanical installation of all 4 units natural gas burners, fuel skids, and supporting combustion air and flue gas ducting. Once mechanical inspection was completed, I oversaw the startup and commissioning of all 4 units and their associated natural gas burners. These units improved their operating efficiency by 4% and reduced their startup time from 8 hours to less than 1 hour. At peak firing rate these units were capable of running sub 60 PPM NOx at .5% O2.

Major US Mine burner and control retrofit in UP Michigan

This project called for a complete retrofit of the original burner, boiler controls, and flame scanners of an existing packaged boiler. The packaged boiler was rated in excess of 150,000 PPH of steam capacity. During this startup I was able to find and fix unique grounding issues caused by poor grounding due to the site’s off-grid location. I fully checked out the burner and boiler’s fully metered control system and after overcoming many startup obstacles and working in almost total darkness, was able to get this boiler running in fully automatic mode. This boiler soon became a reliable and strong steam source for the plant.

Installation of NEW gas turbine with HRSG and Duct Burners in rural Mississippi

This customer was looking to increase plant steam and electrical efficiency. The decision was made to install a new gas turbine and waste heat recovery boiler with duct burners. This project presented unique challenges and had many neat features. Included with this HRSG was a diverter damper and fresh air firing option. I personally checked out the controls and instrumentation, which was 2 oo 3 based, and called for many field instruments. After fixing multiple connector wiring issues caused by a 3rd party, I was able to finally checkout the control panel and move forward with the startup. Once completed with mechanical and control checkout we moved into turbine status bit testing and forced turbine status bits between turbine controls and HRSG controls. Once completion of turbine testing was done, we moved into fresh air firing and eventually, turbine firing mode. All said and done I was able to commission the controls, fresh air firing mode, and turbine firing mode in 2 weeks. I stayed long days to complete this project in the timeline that fit the customer’s demanding production needs.

Tuning of OTSG burner in Fort McMurray

Upon arrival I found out this customer was experiencing major pulsation with the OTSG burner. After a visual inspection and combustion diagnosis I was able to determine this burner was running too much core gas and too much FGR. The burner was retuned with proper core fuel staging and the appropriate amount of FGR which resulted in a stable burner with NO panting or pulsation.

I have performed startups of many OTSGs in the Fort McMurray, Christina Lake, and Saskatoon areas.

Major Hospital SCR problems in Southern California

This customer was experiencing a variety of problems. Several technicians had attempted to fix this unit but were unable to resolve the issues. To start, I found a plugged impulse leg to the drum level transmitter which resulted in a swinging drum level and poor operation. After clearing the obstruction, retubing, and ranging the drum transmitter and PID controller, I was able to tackle the SCR problems. The customer was unable to meet the NOx and NH3 slip requirements of their tough district, some 2.5 PPM NOx and sub 5 NH3 slip. I shut the burner down and inspected the SCR catalyst and ducting and found a substantial buildup of UREA in the duct. I had the urea buildup removed, the catalyst pulled and cleaned, and all urea injection nozzles pulled and cleaned and reinserted. An SCR core sample was also taken to send off for catalyst poison verification.

Once the urea injection system was cleaned and cleared, I checked the burner combustion. I found the burner was improperly tuned and was running with 9+% O2 on an LNB register style burner which should have been tuned to 3% O2. After retuning the burner to 3% O2 I was able to stabilize the burner and cut CO emissions down from 150 PPM to 0 PPM. Once I had the new NOx numbers, I was able to determine the expected urea flow to adequately reduce the NOx. I tuned the urea injection system to reduce the NOx to 2.5 PPM and the NH3 to sub 5 PPM. A source test was subsequently passed and for the first time in over 3 years the boiler was 100% compliant and operational, saving the hospital thousands of dollars in air quality fines and NOV notices.

Major Combustion Problems with Aux Boiler

When I arrived at this site the boiler could not run. Site would light it off and as soon as they increased the burner firing rate it would flame out. I listened to the operations team about the problem details and then I went straight to the field to assess the unit. What I found was an improperly fuel staged and tuned burner. I lit the burner and ramped the unit up only to trip at about 20% MCR on flame failure. The CO was exceptionally high, and the fuel splits were incorrect. I re-characterized the burner fuel and air curves and tuned for best emissions performance. The unit ran very well afterwards and experienced no more flame failures. Years later the site has passed further source tests on the same fuel and air curves I set back then.

Burner Vibrations on Auxiliary Boiler

A major power generation facility was experiencing severe vibrations at the auxiliary boiler burner front during normal burner operations. The site had spent time adjusting the fuel and air curves but could not quite rid the system of the vibrations. RCES quickly dispatched and worked the weekend on the customer site. This was crucial as the auxiliary boilers were to soon be shut down and the opportunity to fix the burners would not be presented again for a long time. After spending the morning analyzing the post combustion flue gases RCES was able to determine that for this particular burner the site was running too much FGR and too low of NOx. RCES assisted the site in adjusting the FGR flow rates to the burner which resulted in a major alleviation of the burner vibrations and the site still able to run with the NOx in compliance.

Unison Fired Ultra Low NOx Burner Startup

This project consisted of two, one over the other, unison fired ultra-low NOx burners on a small, packaged water tube boiler. This boiler included with it an air preheater which relied on boiler steam for air preheating. This posed a unique challenge as the burner had to remain at low fire until adequate steam was available to be supplied to the air heater. The other unique challenge was meeting sub 5 PPM NOx on unison fired burners with air preheat. Upon completing the burner startup and tuning, the burners were able to run stably at 4.7 PPM NOx corrected to 3%O2 and less than 50 PPM CO.