GEA supports South African customer Mpact with black liquor concentration

Published: 26-Jul-2023

Black liquor is an energy- and lignin-rich by-product of cellulose production using the sulfite process in the paper industry

Mpact, South Africa's leading company in the production and recycling of paper and plastic packaging, is taking delivery of a new black liquor concentration and drying plant from GEA, a machinery and equipment manufacturer and solution provider. 

Black liquor is an energy- and lignin-rich by-product of cellulose production using the sulfite process in the paper industry. It is produced when the lignin is separated from the pulp, which then forms the paper fibers. 

The technology solution for a modernisation project at the Mpact paper mill based in Mkhondo, Mpumalanga – a province of South Africa consists of a GEA decanter centrifuge, a GEA Mechanical Vapor Recompression (MVR) evaporator and a GEA spray dryer. 

Doubling pulp capacity with GEA technology

The modernization project with the new GEA plant will enable Mpact to increase its pulp capacity from approximately 55,000 tons to 110,000 tons per year. In addition, the GEA Spray Dryer in the pulping process will enable the recovery of up to 35,000 tons of the by-product sodium lignosulfonate (SLS) powder. The SLS powder is primarily destined for export and is used, among other things, as a concrete additive. 

Mpact selected GEA as technology supplier in a very competitive selection process due to the many successfully running reference plants, the good reputation in the industry and the high level of technical support. It was not only the GEA technology that convinced the customer. Other measures to reduce the CO2 footprint also led to the customer's positive decision. For example, GEA works with local producers and suppliers on site. By manufacturing locally, the CO2 footprint otherwise associated with transportation is reduced. 

Mechanical Vapor Recompression (MVR)

The operating costs for an evaporation plant are largely determined by energy consumption. Mechanical vapor recompression (MVR) and thermal vapor recompression (TVR) are technologies that GEA uses based on many years of experience. GEA provides customers with the optimal system tailored to their individual needs.

While steam jet compressors compress only a part of the vapor leaving the evaporator, mechanical vapor re-compressors (MVR) can re-circulate the entire vapor. The vapor is compressed – usually using electric motive power – to the pressure of the corresponding heating vapor temperature of the evaporator. The energy of the vapor condensate is often still used to preheat the incoming product. 

Depending on the operating conditions of the plant, a small amount of additional steam or condensation of a small amount of excess vapor may be required to maintain the overall heat balance of the evaporator and ensure stable operating conditions, especially during start-up.

Single-stage centrifugal fans (supplied as high-pressure fans) are used in evaporation plants because of their simplicity and low-maintenance design. These machines operate at high flow rates and therefore handle large throughput volumes at compression ratios of 1:1.2 to 1:2, with typical speeds ranging from about 3,000 to 12,000 rpm. Multiple blowers can be used for higher pressure rise.

Decanter centrifuges for black liquor clarification

GEA supports its customers in the realisation of pulp and paper plants with a comprehensive technology spectrum. Especially for the mechanical separation of sedimentation, centrifuges are an important component in the entire process flow. GEA's expertise includes the efficient separation of impurities or solids by centrifuges for solids and liquids. 

The use of a GEA decanter centrifuge can help maximise the yield of black liquor plant by efficiently separating the solids from the liquid, and the decanter centrifuge improves the subsequent process steps.

GEA decanter centrifuges are designed to operate with high efficiency and can contribute to energy savings in the production process. This aligns with sustainability goals and demonstrates environmental responsibility.

ZLD systems are designed to remove dissolved solids from wastewater and return distilled water to the process. GEA's ZLD technologies enable industrial processes to meet environmental regulations and are specifically designed to separate valuable salts from waste streams before disposal to generate added value.

To achieve complete ZLD, various technologies are typically combined. These include, for example, ultrafiltration, reverse osmosis, evaporation, crystallisation, desalination, separation and drying. GEA can offer a complete portfolio of technologies to recover valuable by-products that can be commercialised.

For example, GEA has custom designed and supplied numerous ZLD treatment systems for coal-fired power plants and waste incinerators. These systems effect precipitation of heavy metals, evaporation with seeding (as an anti-scaling measure) and crystallisation. In addition, GEA has many years of experience in dealing with corrosive materials, so each plant can be designed and built with corrosion-resistant materials as required.

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