FAQ LysoTherm®

Data and dimensions

How is LysoTherm® sized?

LysoTherm® is a modular system. One module in loop configuration can treat approx. 15 dry tons of raw sludge fed to the digester.

What is the loop configuration?

In the loop configuration the raw sludge is fed directly to the digesters. The digested sludge then is treated with LysoTherm®. The hydrolysed sludge is fed back to the digester in a loop in general in a 1 to 1 ratio. In our experience this configuration has several advantages in comparison to the conventional “upstream THP”. It provides optimal results in terms of performance, operational stability, availability and heat recovery.

How many standard modules can be combined?

As many as you want adjacent to each other.
Alternatively: max 2 containers stacked, one upon the other.

What is the preferred DS content of sludge input?

Raw sludge:
Up to 12% dry solids

What kind of chemicals & volumes are used for cleaning?

Water, approx. 4 m3/rinse
NaOH, 50 %, approx. 60 L/chemical cleaning
HNO3, 65 %, approx. 60 L/chemical cleaning

What further media beside the chemicals and process water for rinsing and chemical cleaning are necessary to operate LysoTherm®?

LysoTherm® will be supplied with an automatic feeding system for the regenerative circuit. Potable water will be used to produce demineralised water, which will be provided automatically to the regenerative circuit in case of a pressure drop in the system.
The demand on potable water in our experience is limited to a few hundred liters per year.
Pressurised air (oil & water free, approx. 300 L/min, 6 bar) will be used for the pneumatic valves.

How much electricity is required per module?

Approx. 8 kWel

How much heat is required per module?

Approx. 120 kWth per module for one module in loop configuration in full capacity

What is the typical running time per day?

Sludge hydrolysis: 22 – 23 h/d
Water rinsing: 1 – 2 h/d

What is the footprint for a standard module?

For one fully containerised module four stacked containers are necessary.
Footprint: approx. 12.0 x 5.0 m

Is it possible to install a standard module also in an existing building?

Yes, in this case, two insulated containers with the heat exchanger modules will be supplied and the further plant components almost totally pre-mounted on racks.

How is the process control managed?

The process control is managed by a PLC with a touch screen as a HMI. Data from/to customer’s SCADA system will be provided via Industrial Ethernet and data blocks.

Maintenance

What is the daily time required for maintenance?

The required time for maintenance is limited to plausibility checks of measured values on the HMI resp. on the SCADA system. Also the noise of the system and leakages at the surroundings of the plant have to be checked daily.

Further time will be necessary for the analytical works like determination of the hydrolysis degree (COD measurements). Typically, only once or twice a week the hydrolysis degree will be determined. According to our experiences 1 – 1.5 h/d for all of these works are sufficient.

How frequent is the automatic cleaning?

With water: once per day, fully automatic.
With chemicals: once every three weeks, automatic with manual start.

Are there any special maintenance access provisions?

No, however, there should be enough space (approx. 10 m) next to one of the narrow sides of the containers to change single heat exchanger tubes, if ever necessary (not observed so far).

Is there any manual maintenance required and how often?

Visual inspection is recommended every 2 – 4 years.
In case of larger amounts of sticky deposits in the tubes (not expected) manual cleaning (high pressure washer) is recommended (duration: max. 2 – 3 days).

What kind of material is used for the heat exchangers?

Heat exchanger material:
Stainless steel, 1.4571 (= AISI 316)

What type of feed pump is used?

A standard progressive cavity pump is used. The maximum pressure provided by the pump is approx. 40 bar. Typical working pressures are below 20 bar.

What is the life time of the feed pump?

We recommend to service the pump every 1 – 1.5 years.
During that maintenance also stator and rotor of the pump should be renewed.

What is the life time of the thermal oil?

A yearly analytical check of the thermal oil is recommended.
Since the temperature in the thermal oil system is typically below 180 °C, the life time of the thermal oil can be predicted to more than three years.

Operation

How does LysoTherm® handle upstream fluctuations?

With LysoTherm® in loop configuration we make use of the biggest buffer tank that is available at a wwtp – the digester. The raw sludge is fed to the digester. The digested sludge is treated via LysoTherm® and fed back to the digester in a loop. Thus, there is no direct effect of upstream fluctuations (e.g. if there the raw sludge thickening equipment is out of operation). LysoTherm® can therefore operate very stable and continuously.

Are there any special screening requirements necessary to prevent clogging?

The wwtp has to be equipped with well-functioning and maintained screens (5 mm or below) at the waste water inlet. Macerators for the raw sludge provided to the digesters are recommended.

Are there special requirements for grit removal from sludge?

See above as for screening requirements.

Will grit cause abrasion?

Abrasion may occur, mainly in the sludge feed pump, therefore, a well-functioning and maintained grit removal at the waste water inlet is highly recommended.

What experience is there in regard to baking and clogging?

Prevention of baking and clogging starts with the optimal design of the heat exchangers. LysoTherm® is designed with a minimal temperature delta between sludge and heating medium which obviates baking. Additionally, LysoTherm® is equipped with cleaning in place equipment which is completely automated and removes any possible residues from the pipes in the first place.

How is possible baking and clogging detected?

Baking will be detected by the control system monitoring the temperatures in the several stages of the plant. Since the layers are relatively small, baking cannot be detected by pressure measurement.

Clogging will cause higher pressures in the system. If too high pressures are reached, the control system automatically shuts down the plant.

Is there a tendency for digester foaming?

No, in contrast, basically, thermal sludge treatment prevents digester foaming.
Cases where foaming is observed with thermally disintegrated sludge digestion can be assigned to inaccurate adherence to the digester feeding protocol during the restart of feeding with disintegrated sludge after a longer interruption period.

What experiences are there for the treatment of ferric polymer sludges?

All experiences gathered so far and reported above are based on partly ferric treated (i.e. Bio-P sludge with additional ferric treatment), polymer-flocculated prethickened sludge.

What is the effect of thermal disintegration with LysoTherm® on the gas production in the digester?

The gas production from disintegrated WAS typically increases from approx. 0.25 m³/kg VSfeed to approx. 0.5 m³/kg VSfeed, which corresponds to an increase of approx. 100 %.

Is there an effect on the downstream dewatering process?

DS content of the dewatered sludge will increase (approx. + 3 – 5 %, e.g. from 25 % to 28 – 30 % DS).
Polymer consumption may increase initially, it has to be adapted to the new sludge conditions and may then even be lower than before.

Is there after-sales service for remote monitoring and optimisation?

Yes, if required. Conditions to be discussed and agreed individually.

Safety

Are there any special safety requirements regarding the thermal oil system?

Thermal oil systems are pressureless systems, which means, that there is just a static overpressure at the suction side of the thermal oil pumps. In general, safety requirements for thermal oil systems are much lower than for steam systems. The national regulations for thermal oil systems have to be observed.

LysoTherm® is a pressurised system. What are the safety measures regarding overpressure in the system?

At several points in the system the pressures are monitored by the control system. In case of too high pressures, the control system automatically initiates measures to keep the system in a safe status. In case of a failure of the measuring devices, a rupture disc prevents damages on the system. The released hydrolysate will be automatically cooled and discharged into a drain pipe.