continuous soniqueflo thermal processing of waste sludge...

LONDON\MGR\19810883.01

Continuous SoniqueFlo thermal processing of waste sludge and slurries for increased biogas in a community scale Anaerobic Digester (AD)

Report

STRICTLY PRIVATE AND CONFIDENTIAL

CELLULAC-WATER TREATMENT REPORT 2014

Objectives:

• Pre-treatment of waste water sludge's to maximise the biogas yields via anaerobic digestion. Particular focus on the biodegradability of secondary sludge (SAS)

• Assessment of the pasteurisation capability of the SoniqueFlo technology

Key Findings:

SoniqueFlo pre-treatment on primary sludge (PS) and secondary sludge (SAS) showed the following: High solubilisation of sludge, increase in sCOD (soluble Chemical Oxygen

Demand) o With 3-4 reactor passes on SAS an increase of sCOD/TS up to 800% observed o With 3-4 reactor passes on Primary Sludge a gradual increase of sCOD/TS up

to 300% observed

Decrease in E.coli counts after SoniqueFlo processing of waste water sludges o Significant decrease (99%) in E.coli count with 3 reactor passes on SAS o Significant decrease (99.999%) in E.coli count with 4 reactor passes on PS o Potential for SoniqueFlo technology to be applied in pasteurisation of food waste

and sludge

Biogas (methane) production increase o 1.4 - 12.9% increase - SoniqueFlo treatment at 75oC o 1.6 - 16.9% increase - SoniqueFlo treatment at 85oC o 5.6 – 23.0 % increase - SoniqueFlo treatment at 95oC

Aims and Objectives: This document summarises the feasibility study for an improved Anaerobic Digester by a novel pre-treatment process of waste water sludge undertaken during the period from 1 February through to 13 May 2013. The aim of this project, was to develop an advanced Reactor system for continuous thermal hydrolysis treatment, combined with material dispersal for achieving enhanced gas production in downstream anaerobic digestion (AD), accompanied by pathogen kill and improved dewaterability, expertise to support IP portfolio. The project objectives were:

1. To develop a steam injection system that allows fast and uniform heating of sludge to reach temperatures of up to 90 - 130°C within one minute

2. The system design has to be suitable for handling either Secondary Activated sludge (SAS, WAS), or to mixtures of SAS and primary sludge, as well as wide range of food and agricultural waste, as a small community-scale plant

3. To carry out an analytical tests to measure whether the developed system provided increase of biogas production, pasteurisation with compete pathogen kill, reduced particle size and improved dewaterability

4. To assess whether after reaching the set temperature, the overall performance of the system can also be enhanced by increased retention time



.

Design and building of the system: The SoniqueFlo HDC Reactor (formerly known as PDX Reactor) processing set rig was designed for this project comprising of a SoniqueFlo-13 Reactor mounted in a stand-alone frame (Figure 1) linked via quick-release pipe work. Control and instrumentation apparatus was also mounted to the test frame as well as additional hardware included pumps and flow peripherals as well as feed and evacuation vessels (Figure 2), layout of the test rig is shown in the P&ID in Figure 3. The steam equipment comprised of a trailer mounted boiler rated for this application. The work was carried out in order to fabricate, fit and test rigid steam piping. The principle component of the system is the SoniqueFlo annular nozzle, which allows injecting supersonic steam into process fluid with the most efficient energy transfer. The process material can be recirculated via the pipework described above (Figure 3), as required using the Seepex pump and return pipe-line back to the pump via a three-way valve since the prescription of the test will require recirculation processing. Once mixed, the sludge can be pumped through the system including the SoniqueFlo Reactor. The material can be heated to approximately 80°C before the system is sealed and internally pressurised. The SoniqueFlo Reactor is controlled by a single automated variable steam control valve fitted immediately above the unit. The steam control valves is of an automated variety for the initial commissioning and data-logging via feedback loop. The SoniqueFlo Reactor processes the test material and simultaneously provides the additional pumping force to propel the test material through the pipework. The exit flow from the SoniqueFlo Reactor can be either directed back to the pump (recirculation mode) or be fed directly into a separate collection hopper (sample point). Both were utilised in this process. In this instance, the outlet of the SoniqueFlo unit was connected to an expansion section in order to relieve any potential initial back pressure before being connected to the recirculation path or a sampling port, followed by a waste vessel via standard piping. The sampling port was an autonomously-actuated valve set into a t-section branch off the main process line. All connections were made in quick-release high-pressure couplings as described above. The test circuit was instrumented to measure the temperature and pressure of the test material entering and exiting the SoniqueFlo Reactor. Data acquisition techniques were used to collect the pressure and temperature of the steam supplied to the SoniqueFlo Reactor. Steam mass flow measurements were also taken using a modular flow meter. These measurements were displayed and recorded on a laptop computer, generally at a 1Hz frequency. The data logs were post-processed following the completion of the test program in order to provide a full time stamped plot of the operating conditions of the system. The balance between steam flow and process flow was adjusted to fast and uniform heating of sludge to reach temperatures of between 90 - 130°C within one minute ( Aims and Objectives - Item 1).



Experimental Rig Setup at Pilot Plant • Method Statement document for the tests including Equipment Installation & Risk

Assessment Summary was prepared by the qualified engineer

• The equipment (SoniqueFlo Reactor test rig, steam boiler, steam conditioning set, process pump) was delivered to site, installed in position (Figure 2) and the unit was commissioned

• Standard water and electricity extensions were used to route the required services

to the boiler • In order to route the steam line from the boiler unit to the SoniqueFlo Reactor rig, a

2” flexi steam pipe connection with end terminations suitable for additional flexi-pipes was used. This pipe was routed via a steam conditioning skid to reduce the feed supply from 24 bar down to 10 bar and remove any build-up of condensate. The required steam pipe certifications and welding conformities were present to confirm pressure tests and certification. The boiler plant was only operated and maintained by suitably qualified and trained personnel

• The equipment utilised for this project incorporated a single (1) SoniqueFlo-13

Reactor assembled in a recirculating configuration being fed by an upstream Seepex NS Model progressive cavity pump (Figures 2, 3)

• During operation the system pressurised to approximately 2-3 bar and self-regulated

via an integrated Programmable Logic Controller (PLC)

• The site survey has been created by the Company personnel in association with Cranfield University to determine the preferred arrangement of test equipment and carry out risk assessment. The test rig was configured for the specific requirements of this particular project and application was suitable for handling either Secondary Activated sludge (SAS, WAS), or to mixtures of SAS and primary sludge, as well as a wide range of food and agricultural waste, at a small community-scale plant ( Aims and Objective – Item 2)

Experiments, trials and sampling: • To examine the performance of the SoniqueFlo pre-treatment equipment on waste

activated sludge (WAS) and the subsequent impact on anaerobic digestion at the laboratory scale, the Company entered into a contract with a Subcontractor, the Centre for Energy and Resource at the Technology Department of Environment, Science & Technology, School of Applied Sciences, Cranfield University.

• An NDA and a Services Rendered Agreement was signed between the Company and Cranfield University for the purpose of the trials of the new technology. The pre-treatment equipment was delivered and installed by the Company and operated at the pilot hall facility of Cranfield University.



Work programme:

Municipal sewage sludge pre-treatment with SoniqueFlo equipment Analysis of the sludge before and after pre-treatment Operation of batch digesters to assess methane potential and digestate quality

The equipment was run with a sludge flow of 80 litre/min with SoniqueFlo pressure up to 8 bar and combined steam flow up to 924 lbs/hr. Sludge was run through the pre-treatment equipment at the following operational parameters: 1. 95°C without pipe retention 2. 95°C with 30 minutes retention; and 3. 130°C with 30 minutes retention

There were two replica runs of condition trials 1, 2, and 3, on two consecutive days. On each day, a control sample was also taken from the sludge prior to pre-treatment. The flow-through diagram of experimental design is shown on Figure 4. Waste activated sludge (200 L, 4% TS) was collected from Milton Keynes WWTP two days prior to the commencement of the trial and stored outside the pilot hall at ambient temperature (below 4°C).

Analysis on the pre-treated sludge: Material was characterised using the analysis agreed at proposal stage. Biomethane potential (BMP) test was estimated in batch digestion mode. The TS and VS values of the feedstock used for the BMP test were calculated before each trial for every sample tested. The main aim of this project was to assess the optimal SoniqueFlo pre-treatment conditions to enhance biogas and biomethane production. The same thermal hydrolysis pre-treatment conditions were duplicated over 2 consecutive days produced very similar results and allowed an additional insight on the mechanism. The treatments resulted in remarkable changes in the biogas/methane production (Table1, Figures 5 and 6). The highest increases in the biogas production (25% and 23%) were provided by the pre-treatment at 95o C with no retention, and by the pre-treatment at 130oC with 30 min retention respectively. These uplifts in total biogas production comprised respectively 24% and 22% increase in methane output. As temperature seems to have a greater impact on biogas and methane yields, it was expected that the treatment at 130°C with no retention time would have produced a higher amount of biogas and methane.



Table 1: Biogas and methane production for control and pre-treated samples

All the pre-treatment conditions have produced a release of soluble COD (Figure 7). This increase ranges between 800% for 95°C with 30 minutes holding time and 1100% for the other two conditions compared to the control sludge. These also confirm the solubilisation effect (increase in soluble COD). The values of increased solubilisation match the value of biogas and methane production, and show lower values at 95°C with 30 minutes holding time compared to the other two conditions and the control.

The increase in contact time (no pipe retention and pipe retention for 30 minutes) at the same temperature (95°C) causes a 20% increase in soluble COD but losses in alkalinity and VFA (using the partial alkalinity as indicator for VFA content) which results in lower biogas and methane yields when longer contact time are applied. The increase in temperature from 95°C to 130°C with 30 minutes retention (the data at 130°C with no retention time is not available) causes a 17% increase in soluble COD and similar losses in alkalinity and VFA, which translate in higher biogas and methane yields at higher temperature.

The evaluation of the microbial analysis showed that all the pre-treatment conditions provided a significant reduction in E.coli count corresponding to a log reduction >3. This was the maximum that could be achieved in these conditions (since numbers of E.coli bacteria present in the original material were limited to 3 - 4 x 104) but it is possible that, where higher E.coli concentrations are observed prior to pre-treatment, log reduction of 6 or greater may be achieved with this technology.

Particle Size:

Particle size of the feedstock has a direct effect on the performance of the digester, smaller particles tend to produce an increase in the rate of substrate utilisation and hence an increase in biogas production. In this trial, the particle size changed, which, similarly to alkalinity and sCOD release, correlated to biogas and methane production with smaller particle size producing more biogas and methane. In accordance to the alkalinity and sCOD results, pre-treatment at 95°C with no pipe retention and at 130°C with 30 minutes retention time produced the smaller particle size and the higher biogas and methane production.

Before pre- treatments

Parameters units control 95 oC flush 95 oC hold 130 oC holdBiogas production day 1 ml/g VS 254 317 225 313Biogas production day 2 ml/g VS 248 310 275 303

ml/g VS 251 313.5 250 308% 100 125 100 123

Methane production day 1 ml/g VS 169 208 146 206Methane production day 2 ml/g VS 162 202 176 198

ml/g VS 165.5 205 161 202% 100 124 97 122

After pre- tratments

AVG Biogas production

AVG Methane production



Economic benefits of SoniqueFlo units for improved biogas production: The greatest uplift in total methane production achieved was 24% after treatment at 95oC with a flush. A similar increase of 25% was achieved by treatment at 130oC with holding time of 30 min, however the second process requires substantially more input of steam energy. This is not justified by an insignificant difference in output from the 95oC treatment. The 24% increase in methane production would result in production of an additional 0.9m3 of methane from each ton of sludge (containing 4% Total Solids) processed. If the Total Solids in the sludge are increased to 14 % (previously achieved by the Company), it would result in an increase of methane output to 3.3m3 per ton of sludge processed. The additional energy recovered from sludge in 3.3m3 methane is equal to 128 MJ per ton of sludge. While the energy spent on the pre-treatment (taking 1 ton of sludge from 20 to 95oC) by steam injection is equal to 365 MJ (143kg of steam at 170oC) it should be noted that overall positive energy balances are achieved and increased efficiencies are due to:

1. Increase of methane production per cubic meter of total solids 2. Heat recovery from the AD biogas to electricity production

Normally a by-product and excess released to atmosphere Reduction/Elimination of the cost of steam production

3. Improved dewaterability 4. Single step process allows rapid and continuous processing of waste sludge 5. Significant reduction in time for holding material in the AD 6. Higher volume throughput due to reduced particle size increasing specific surface

area of sludge solids accelerates decomposition within the AD 7. Complete pasteurisation of the processed material 8. Low Capital Expenditure 9. Small footprint

Heat recovery is a standard provision and is common place in commercial Anaerobic Digester installations. When choosing the optimal working conditions for the use of the technology as a pre-treatment, the overall energetic balance in addition to the above mentioned observations needs to be taken into account to achieve optimal biogas production in addition to the decreased amount of solids for disposal, improved separation of water from the solids, and if required, safe transportation of material after removal of potential biohazards by pasteurisation.



Exploiting Results: Demonstration-scale SoniqueFlo Continuous System for Combined Waste Pre-treatment utilising either four SoniqueFlo-13 or two SoniqueFlo-25 Reactors. The SoniqueFlo system is of modular design with volume throughput as required by additional reactors in parallel banks configured to act as an in-line continuous, or semi-continuous processing units for waste water sludge, and macerated food or agricultural waste slurries. The system is designed to meet the following requirements and assumptions. The demonstration system is capable of processing a maximum of 89.4 tonnes in a 24hr continuous operation. If higher throughput capacity is required parallel banks of two SoniqueFlo-25 units in series can be added to the process line as a modular upgrade. This would double throughput capacity for each bank added. Upgrades can be done on an individual installation basis. The number and size of tanks or piping depend on both individual specification and physical footprint restrictions. The SoniqueFlo Continuous System for Combined Waste Pre-treatment System has the following maximum dimensions: Steam Supply system and process line with two (2) SoniqueFlo-25 units, and mountings. 1. Length: 2.5m 2. Width: 1.2m 3. Height: 1.75m (excluding PLC control Box)

The height of the standard PLC box if located directly at the point of installation will increase the maximum height of this system to 2.2m

The SoniqueFlo Continuous System for Combined Waste Pre-treatment will be capable of: 1. Processing macerated mixed food/ agricultural waste slurries passed through a 1.2mm

screen with a solids maximum of 18% w/w, and waste water sludge with a solids maximum of 15% w/w

2. Processing sludge and slurries at a rate of 45-60L/min. (2.7-3.6 tonnes/hr), scalable to much larger throughput if required

3. Achieve output temperatures of 95° -130°C repeatedly and reliably 4. Filling output materials into insulated tanks or held in residence tubes (separate to this

quotation) for a 1 hour thermal hold 5. Full system automation with user manuals and maintenance guides 6. The PLC interface being installed in the same physical location as the system 7. The system being retro-fitted into existing transfer pipelines 8. The system being installed in a covered or sheltered installation site

Intellectual Property: IP derived from this study are already protected by patents granted and pending by Pursuit Marine Drive Limited, a wholly owned subsidiary of Cellulac PLC.



Additional Engineering Information:

Additional engineering and analytical information that supports the work can be found

below.

Figure 1. The support structure for the physical test rig. This was the main frame to which all testing peripherals were attached. The pump was housed in the recess seen on the left of the drawing and the support rail that runs in both the horizontal and vertical planes fixed the pipework in place before returning to the pump.



Figure 2. Photographs of the rig during trials at the subcontractor’s facilities.

Figure 3. The P&ID (piping and instrumentation diagram). The process line and all peripheral equipment have been noted in this diagram. Note that this is not to scale.

Note: The above images are trial rig, not continuous demonstration rig mentioned later in the report.



Figure 4. Diagram showing the design with process variables and sample points with indication of a number of replicas for each pre-treatment variant.

Figure 5. Biogas and methane yields of treated and untreated sludge.



Figure 6. Cumulative methane production (normalised) of control and pre-treated samples.

Figure 7. Indicator of availability of the organic matter for digestion - sCOD released by

the pre-treatment.

continuous soniqueflo thermal processing of waste sludge...

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