We, Xiaoyu Wei (Cranfield University), Yuan Chen (University of Edinburgh), LABIB Mennatallah (University of Edinburgh) and David Cann (University of Chester), had the opportunity to attend the 5-day training course at the UKCCSRC Pilot-Scale Advanced CO2-Capture Technology (PACT) facility in Beighton, Sheffield from 9th to 14th September.
PACT facilities host a state of the art, pilot-scale CO2 amine-capture plant that can capture CO2 in flue gases from either a 250kW air/oxyfuel biomass combustor or two 330kW gas turbines, and the state-of-the-art analytical equipment available to researchers. The PACT facilities fuse a comprehensive range of integrated research equipment with significant analytical capability to close the gap between bench-scale industrial and academic research, demonstration & development and large scale industrial pilot trials.
The first day kicked off with site introduction and health & safety assessments. First, we are required to wear high visibility clothing and hard hats before we enter the plant. Also, our shoe sizes are required for suitable safety boots in case of dealing with large leaks (these safety boots became rewards for us at the end of training). After we equipped with that personal protective equipment, Dr. Kris introduced the general site safety introduction and lead tour of the PACT facilities. Following this comprehensive introduction to the site, all students were divided into four groups, which were led by Dr. Janos and Dr. Muhammad who would lead tours around the solid fuel grate combustion, gas turbine, carbon capture unit and gas mixing skid respectively. Risk Assessment and Control of Substances Hazardous to Health (CoSHH) assessment documentation were discussed to help us understand what can go wrong during our experiment, things in place to prevent it and safeguards & mitigations solutions. Finally, the sign-off of the assessments were duly followed.
Day 2: The 240kWth Biomass Grate Combustion Boiler (BGB)
Dr. János Szuhánszki instructed us to operate the grate boiler following the Standard Operating Procedure (SOP) with the strict execution during the pre-start up, the start up, the operation and the shut down. The wood chips be used in the operation of the grate boiler this time. It is visible that we can observe the ignition and the combustion condition from monitoring window (Figure 3). The system is fully automated, utilizing pressure, temperature and lambda sensors for optimal combustion control and high efficiency. The results, such as temperature, pressure, mass flow rate and flue gas composition, can be detected by the gas sampling probes in different ports, which enables detailed research of the combustion processes and emissions. The boiler could be connected with the Solvent-based Carbon Capture Plant (SCCP) in the PACT, which could support the studies on the Bio-Energy with Carbon Capture and Storage (BECCS).
Arguably the most exciting (obviously, this is an extremely biased opinion from a capture person) experiment was the amine capture plant. We were split into two groups, and each group got to spend a whole day working with the capture plant. The day started with a risk assessment of the work we were going to undertake and the safety measures associated with it (safety must always come first!). Finally, we were allowed to help start up the plant. We had been provided with the System Operation Procedure the previous day, and the plant was fairly easy to start up, as long as the procedure was followed closely. Dr. Muhammed Akram, Dr. Kris Milkowski and Abdul’Aziz A. Aliyu, a PhD student from Sheffield, were with us every step of the way. Hearing the pumps start whirring and the fan start blowing is very exciting.
The experiment that we ran was simple, but delicate. We were to try and maintain the capture plant at a 90% capture rate for a range of different flue gas concentrations, and collect data for these operating conditions. It must be admitted that is easier said than done. Any change to the operating conditions of the plant, no matter how small, had quite an impact on the plant’s capture rate. For each flue gas composition, we were to try and obtain the operating conditions that would produce a 90% capture rate. However, each change took a considerable amount of time to affect the capture rate, and so we had to observe the online data measurements to see whether we had reached steady state operation or not, and whether we had achieved our target or not.
For every change made, we had to collect both online and offline data on liquid and gas concentrations to determine whether we had achieved our target or whether further changes were needed. Sometimes we overshot our target, sometimes we didn’t meet it, and sometimes we were impatient and managed to miss it completely. Either way, we would readjust our conditions and start the wait for steady state all over again. The PACT capture plant taught us two main things in this regards:
- Patience really is a virtue.
- It pays a lot to understand your equipment, something that can only come with time and experience. Taking a leaf out of chefs’ books, it really does pay to know your oven.
We repeated this for several different flue gas concentrations (which were achieved by injecting carbon dioxide into the gas entering the plant to simulate various flue gas streams including those coming from selective exhaust gas recirculation). Each time we would swap tasks within our group so that everybody got a chance to work with all the aspects of the plant. The various tasks included:
- taking offline liquid samples from different stages in the plant and titrating them to find the solvent and carbon dioxide concentrations as well as the solvent loading.
- following online gas concentration measurements (this was done using an FTIR) to determine whether or not we had reached steady state operation, and whether or not we had achieved our capture rate target.
- following online measurements of flowrates, temperatures, pressures, etc. from all around the plant to make sure that the plant was operating within specified operating conditions to make sure that everything is running smoothly.
- changing the various operating conditions to achieve the target capture rate.
- changing the carbon dioxide inlet concentration to start a new experimental run.
After several flue gas concentrations were tested, and at the end of a tiring but rewarding day, we were shown how to safely shut down the plant and we had to bid the wonderfully exciting capture plant good night.
Day 4 Gas Turbine
The 12 attending PhD researchers were split into two teams, one team working on a micro gas turbine and another team working on an anime capture plant with both teams switching roles on different days.
The gas turbine featured two main running modes, a running mode with a CO2 injection and a running mode using just natural gas. The CO2 injection is done to increase the CO2 concentration in flue gas as the micro gas turbine produces a very lean gas compared to industrial turbines.
After a short briefing on safety and a run through of start-up checks and procedures, the gas turbine was started up and began producing 50kW of electricity. Once the gas turbine was running at steady state then measurements were taken including exhaust gas temperature, turbine outlet temperature, natural gas mass flow and exhaust gas composition. Then the turbine would be set to produce electricity between a range of 50-90 kW and comparative measurements taken at each condition.
With a range of base cases completed, CO2 injection started, to investigate the effect that CO2 concentration had on the turbine. One particular result of the introduction of CO2 resulted in the turbine rotational speed decreasing; this was due to the increased density of the gas so the same work done could be achieved through a lower rotational speed.
Day 5 CFD Introduction and Data Analysis
After 4 days onsite training, introduction to modelling and data analysis workshops were on Friday presided over by Oscar Farias, Dr Karen Finney, Dr Muhammad Akram and Dr Janos Szuhanszki. The methods of calculating CO2 capture rate and reboiler duty were introduced in the workshop. Data analysis compared data of CO2 capture rate, absorber profiles and reboiler duty for different CO2 concentrations. The detailed plant visiting and experimental data analysis enable us to understand the development, assessment and process optimization for post-combustion capture. The PACT experiment provides practical experience and economic sustainability, whilst research at academia can maximise the potential of technology and investigate routes that could be transformed into established processes. The opportunity offered in the PACT training course is therefore absolutely great to widen our thinking beyond academia and see how things work out in the industry, and how industry and academia can cooperate together to maximise results and achievements.
This blog was co-authored by Xiaoyu Wei, Cranfield University, Yuan Chen, University of Edinburgh, LABIB Mennatallah, University of Edinburgh, and David Cann, University of Chester.