Anna K. Nowak

Fertilisers production from ashes after sewage sludge combustion – A strategy towards sustainable development

&NA; Sustainable development and circular economy rules force the global fertilizer industry to develop new phosphorous recovery methods from alternative sources. In this paper a phosphorus recovery technology from Polish industrial Sewage Sludge Ashes was investigated (PolFerAsh – Polish Fertilizers form Ash). A wet method with the use of mineral acid and neutralization was proposed. Detailed characteristic of SSA from largest mono‐combustion plans were given and compared to raw materials used on the market. The technological factors associated with such materials were discussed. The composition of the extracts was compared to typical industrial phosphoric acid and standard values characterizing suspension fertilizers. The most favorable conditions for selective precipitation of phosphorus compounds were revealed. The fertilizers obtained also meet EU regulations in the case of the newly discussed Cd content. The process was scaled up and a flow mass diagram was defined. HighlightsComparison of Polish SSA to phosphate raw materials (MER, I&A).Non‐waste technology of SSA utilization according to circular economy.Obtained fertilisers fulfil requirements for all standardized metals.Technology tested in a semi‐technical scale.Sankey diagram of the P flow in the PolFerAsh recovery process.

Characteristic of wet method of phosphorus recovery from polish sewage sludge ash with

Abstract Sewage Sludge Ash (SSA) is a concentrated source of phosphorus and can be successfully recycled via a number of different routes. This paper presents research results on phosphorus recovery from differently combusted sewage sludge with the use of nitric acid extraction. Different SSA forms from Polish thermal utilization stations were compared. It was revealed that sewage treatment technology as well as combustion technology influence many physical and chemical parameters of ashes that are crucial for further phosphorus recovery from such waste according to the proposed method. Presented research defines extraction efficiency, characterized extracts composition and verifies the possibility of using SSA as cheaper and alternative sources of phosphorus compounds. Gdynia, Kielce and Kraków SSA have the best properties for the proposed technology of phosphorus recovery with high extraction efficiency greater than 86%. Unsuitable results were obtained for Bydgoszcz, Szczecin Slag and Warszawa SSA. Extraction process for Łódź and Szczecin Dust SSA need to be improved for a higher phosphorus extraction efficiency greater than 80%. Phosphorus content in extracts varies from 1.6 to 103.4 g PO43− per 1 dm3, nitrogen content was 167,4 g per 1 dm3 while the K content reached 0.2 to 2.37 g per 1 dm3. The lowest content of Fe, Ni, Cr, Cd is noted in extracts after phosphorus recovery from Gdynia SSA, where the phosphorus content is also at the highest level. The proposed solution can be considered as waste minimization technology by the rational recycling of phosphorus and could be used in industry to produce fertilizers.

Dry single-stage method of sodium tripolyphosphate production – technological and economic assessment

Abstract The study presents a technology of sodium tripolyphosphate (STPP) production with the use of a dry, single-stage method. The reacting substrates (concentrated wet-process phosphoric acid - WPPA and solid Na2CO3 ) are mixed with a recycled final product (STPP) in a mixer, then a „quasi-dry” mixture is calcined in a rotary kiln. Thanks to that, some stages of a classic method of STPP production are eliminated: one of the two-stage neutralization of the phosphoric acid with sodium carbonate at temperature ~80°C, filtration of the neutralised solution and its evaporation, as well as the stage of drying a solution of mono- and di-sodium orthophosphate in a spray dryer. According to the presented technical and economical analysis, the costs of STPP production using a single-stage dry method can be 10% lower compared to the classic method.

Analysis of sodium tripolyphosphate production processes with a cumulative calculation method

Analysis of sodium tripolyphosphate production processes with a cumulative calculation method Sodium tripolyphosphate - one of the condensed phosphates is an important ingredient in various types of cleaning substances and a food additive. The paper presents a comparison of different variants of STPP production with the application of the cumulative calculation method. The material balances of the processes were taken as the basis of the analysis. The method of the process analysis as shown in the cumulative calculation determines the influence of the emissions of dust and gas pollutions originating from a particular production process, as well as wastewater and solid wastes resulting from it, upon the natural environment. It was proved that the solution of the production STPP with the dry one-step method has the lowest impact on the environment among the three assessed solutions.