CONTINUOUS HYDROLYSIS SYSTEMData sheet

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Thermal disintegration by hydrolysis best achieves increased bio-availibility of organic carbon via cell disruption. This leads to a higher yield of biogas and reduces the amount of sludge; two economically positive effects that meet the requirements of a future-oriented sludge treatment perfectly.

Thermal disintegration of sewage sludge means that mechanically de-watered sludge with 14 -22% dry matter content is treated with saturated steam at about 6 bar with a temperature of about 165°C for about 30 min.

A sudden decompression results in the destruction of the cell walls and in the disruption of the cell material, which enhances the potential anaerobic decomposition in the digester. This results in an increased efficiency in the reduction of volatile solids. Class A 503 pathogen requirements for time and temperature are met. Complete pasteurization results in the destruction of pathogens, egg larvae and filamentous organisms.

CONTINUOUS HYDROLYSIS SYSTEM

Considering thermal disposal of sewage sludge becomes a mandatory

legal requirement, the costs of disposal will costs will increase.

That means the quantity of sludge to be thermally disposed of must

be reduced and the energy balance must be optimised.

continuous hydrolysis system

The costs of thermal biosolids disposal represents a significant amount of the operating costs of a municipal WWTP.

Thermal hydrolysis is a very efficient and economic process to reduce the volume of biosolids to be

disposed of by improving the dewatering characteristics as well as the usable energy potential. The elimination of pathogens is also ensured.

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With the HCHS process sewage sludge is first mechanically dewatered to a dry solids content in the range of 14‑22%. The higher the dry matter content, the lower the specific steam consumption in kg steam/tDS.

The characteristic of the HCHS process is the almost continuous process flow, in which the heating of the sludge and the entry into the reactor via a short timed Pressuriser is realised. The Pressuriser is supplied with sludge at low pressure using an eccentric screw pump. Subsequently the sludge is heated with saturated steam and pushed by vapour pressure into the Reactor. In the Reactor the sludge is heated further with live steam to about 165°C at 6 bar and kept at this temperature for 20-30 min. The almost continuous feeding of the Reactor is achieved by the heating of small incoming quantities of sludge (typically 50-70 kg) over a period of 1-3 min in the Pressuriser.

In the Economizer pressure is released via a valve, and the sludge is returned to near atmospheric pressure. The vapours released by depressurisation are fed back to the Preheater to preheat incoming dewatered sludge. The hydrolysed sludge can be introduced to the digester directly with, or without dilution-cooling using other centrates or untreated primary sludge. Alternatively, the hydrolysed sludge can undergo an additional process step of cooling in a Cooler prior to be introduced to the digester directly with, or without dilution..

The vapour produced in the Cooler is cooled by water in an indirect contact condenser and any non-condensable gases or liquid phase emitted from the scrubber are fed to the digester. Thereby a gas-tight design of the plant is ensured and odours are eliminated. In the HCHS process without Cooler the vapours are extracted from the Preheater and directly introduced into the digester.

HCHS PROCESS

continuous hydrolysis system

INTEGRATED ENERGY CONCEPT:• The exhaust heat from biogas power generation

in CHP can be used for steam generation.• The introduced heat in the form of hot saturated

steam is used for heating of the digester.• While not converting biogas into electricity a

heat-autonomous low temperature belt dryer may achieve full drying of sludge to a DS od 90%.

• By addition of co-ferment to the digester or low use of natural gas a complete self-supply with electricity and a heat-autonomous drying with a belt dryer can be achieved.

• With Low-Temperature Drying the drying area will be reduced by half due to the reduced volume implied by drying the sludge.

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In the Cooler an evaporative cooling to reduce the temperature of the hydrolysed sludge to approx. 60 °C takes place. The released vapours are condensed in the condenser and added to the hydrolysed sludge. To reduce the dry solids content for the anaerobic digestion the hydrolysed sludge can be diluted with the effluent of the WWTP.

The installation of the HCHS without Cooler is recommended when only the secondary sludge is hydrolysed and mixed with cold primary sludge prior its anaerobic digestion and thereby cooled to the mesophilic digestion temperature. Additionally, the sludge can be cooled and diluted with Co-ferment or effluent of the WWTP.

FUNCTIONAL PRINCIPLE: WITH COOLER

FUNCTIONAL PRINCIPLE: WITHOUT COOLER

EXAMPLE: SAVINGS ON SEWAGE SLUDGE TREATMENT BY OPERATION OF A THERMAL HYDROLYSIS PLANT IN COMBINATION WITH A LOW-TEMPERATURE BELT DRYER

The values are based on scientific studies measured and calculated on our reference plant (building with blue roof) on the WWTP Greves-mühlen (ZVG; Zweckverband Grevesmühlen).

continuous hydrolysis system

ADVANTAGES• Reduction of sludge amount to be disposed due to increased

degradation of organics during digestion• Significantly improved dewaterability of sludge after digestion• Reduced anaerobic digester volume or increased capacity of

existing anaerobic digesters• Increased biogas yield and quality in sludge digestion• Significant reduction of water to be evaporated during a joined

drying of biosolids.• Reduced viscosity of sludge for more efficient mixing and the

possibility to treat higher DS concentrations in the digester

• Pressure tanks• Pumps• Pipes

• Steam generator• Burner• Condenser

• Scrubber• Insulation• MCC / PLC / SCADA

OPTIONAL:

PERFORMANCE DATA:

HCHS 24

HCHS 16

HCHS 8

HCHS 4

30156

122

20105

82

1053

41

526

20

313

10HCHS 2

Retention time reactor: 30 min at 165°C (330°F), 6 bar

Throughout [t/d], wetThroughout [t DS/d], 22% DSThroughout [t DS/d], 17% DS

HCHS 24

HCHS 16

HCHS 8

HCHS 4

45236

184

30156

122

1578

61

840

31

419

15HCHS 2

Retention time reactor: 20 min at 165°C (330°F), 6 bar

Throughout [t/d], wetThroughout [t DS/d], 22% DSThroughout [t DS/d], 17% DS

HCHS 24

HCHS 16

HCHS 8

HCHS 4

30156

122

20105

82

1053

41

526

20

313

10HCHS 2

Retention time reactor: 30 min at 165°C (330°F), 6 bar

Throughout [t/d], wetThroughout [t DS/d], 22% DSThroughout [t DS/d], 17% DS

HCHS 24

HCHS 16

HCHS 8

HCHS 4

45236

184

30156

122

1578

61

840

31

419

15HCHS 2

Retention time reactor: 20 min at 165°C (330°F), 6 bar

Throughout [t/d], wetThroughout [t DS/d], 22% DSThroughout [t DS/d], 17% DS

HEAD OFFICEHaarslev A/S • Bogensevej 85DK-5471 Søndersø • Denmark

Telephone: +45 63 83 11 00Email: info@haarslev.com

www.haarslev.com

LOCAL EXPERIENCE - GLOBAL PRESENCEPlease contact us or visit our website

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