Nitrogen Oxides Reduction Possibilities at Pulp Mill and Power Plant

Tutkimuksen tarkoituksena oli selvittää typenoksidien vähennysmahdollisuudet Stora Enson Varkauden tehtaiden sellutehtaalla ja voimalaitoksella. Tutkimuksessa käsiteltiin tehdasalueen suurimpia typenoksidien päästölähteitä: soodakattilaa, meesauunia, kuorikattilaa, öljykattilaa ja muovi-alumiinijakeen kaasutuslaitosta. Tutkimuksessa selvitettiin typenoksidipäästöjen syntymekanismit ja erilaisiin polttotekniikoihin soveltuvat typenoksidien vähennystekniikat. Varkauden tehtaiden typenoksidien vuosipäästö vuonna 2001 oli 836 tonnia. Kansallinen lainsäädäntö, kansainväliset sopimukset sekä paras käytettävissä oleva tekniikka (BAT) huomioiden selvitettiin kuhunkin kohteeseen parhaiten soveltuvat ratkaisut. Tutkimuksen perusteella laadittiin toimenpideohjelma, joka määrittelee suositeltavan toteutusjärjestyksen typenoksidien vähennystoimenpiteille. Toimenpideohjelman tärkeimpinä kriteereinä pidettiin vuonna 2004 tulevan uuden ympäristöluvan arvioituja luparajoja sekä toimenpiteiden kustannustehokkuutta. Toteutusjärjestyksessä ensimmäiseksi valittiin koeajojakson järjestäminen ajon optimoimiseksi kiertopetikattilalla ja toiseksi meesauunin ajon optimointi jatkuvatoimisen NOx-analysaattorin avulla. Seuraaviksi toimenpiteiksi ehdotettiin vertikaali-ilmajärjestelmän käyttöönottoa soodakattilalla sekä SNCR-järjestelmän asennusta kuorikattilalle. Saavutettava NOx-vähennys tulisi olemaan 10 – 45 % ja hinta 30 – 3573 EUR vähennettyä NOx-tonnia kohti. Tutkimuksen osana Ilmatieteen laitoksella teetetyn typenoksidien leviämisselvityksen mukaan Stora Enson tehtaiden NOx-päästöjen vaikutus Varkauden ilmanlaatuun on hyvin pieni. Suurin osa NOx-päästöistä aiheutuu liikenteestä.

Integration of a Bioethanol Process to a Pulp Mill

Tässä diplomityössä tutkittiin puuhakkeen esihydrolyysi- ja hakkuujätteen hydrolyysiprosessien integroimista sellutehtaaseen bioetanolin tuottamiseksi. Tällaisesta ns. biojalostamosta luotiin WinGEMS-simulointiohjelmalla simulointimalli, jonka avulla tutkittiin bioetanoliprosessin vaikutusta sellutehtaan massa- ja energiataseisiin sekä alustavaa biojalostamon kannattavuutta. Simuloinnissa tarkasteltiin kolmea eri tapausta, joissa mäntysellun tuotannon ajateltiin olevan 1000 tonnia päivässä ja hakkuujätettä käytettävän 10 % tarvittavan kuitupuun määrästä: 1) Puuhakkeen esihydrolyysi ja hakkuujätteen hydrolyysi etanolin tuottamiseksi 2) Puuhakkeen esihydrolyysi, hakkuujäte kuorikattilaan poltettavaksi 3) Ei esihydrolyysiä, hakkuujäte kuorikattilaan poltettavaksi Verrattuna tapaukseen 3, puun kulutus kasvaa 16 % esihydrolysoitaessa puuhake ennen keittoa tapauksissa 1 ja 2. Kasvaneella puun kulutuksella tuotetaan tapauksessa 1 149 tonnia etanolia ja 240 MWh enemmän ylimääräsähköä päivässä. Tapauksessa 2 tuotetaan 68 tonnia etanolia ja 460 MWh enemmän ylimääräsähköä päivässä. Tämä tuottaisi vuotuista lisäkassavirtaa 18,8 miljoonaa euroa tapauksessa 1 ja 9,4 miljoonaa euroa tapauksessa 2. Hydrolyysin tuoteliuoksen, hydrolysaatin, haihduttaminen sekä hydrolyysiprosessien orgaanisten jäännöstuotteiden haihduttaminen ja polttaminen kasvattavat haihduttamon ja soodakattilan kuormitusta. Verrattuna tapaukseen 3, tapauksissa 1 ja 2 haihduttamon vaiheiden määrä on kasvatettava viidestä seitsemään ja tarvittavat lämmönsiirtopinta-alat lähes kaksinkertaistettava. Soodakattilan kuormitus kasvaa 39 % tapauksessa 1 ja 26 % tapauksessa 2.

Optimization of energy in a pulp mill

This study presents examination of ways to increase power generation in pulp mills. The main purpose was to identify and verify the best ways of power generation growth. The literature part of this study presented operation of energy pulp mill departments, energy consumption and generation by the recovery and power boilers. The second chapter of this part described the main directions for increase of electricity generation rise of black liquor dry solid content, increase of main steam parameters, flue gas heat recovery technologies, feed water and combustion air preheating. The third chapter of the literature part presented possible technical, environment and corrosion risks appeared from described alternatives. In the experimental part of this study, calculations and results of possible models with alternatives was presented. The possible combinations of alternatives were generated in 44 `models of energy pulp mill. The target of this part was define extra electricity generation after alternatives using and estimate profitability of generated models. The calculations were made by computer programme PROSIM. In the conclusions, the results were estimated on the basis of extra electricity generation and equipment design data of models. The profitability of cases was verified by their payback periods and additional incomes.

Stochastic variability of output levels in a pulp mill

Quite often, in the construction of a pulp mill involves establishing the size of tanks which will accommodate the material from the various processes in which case estimating the right tank size a priori would be vital. Hence, simulation of the whole production process would be worthwhile. Therefore, there is need to develop mathematical models that would mimic the behavior of the output from the various production units of the pulp mill to work as simulators. Markov chain models, Autoregressive moving average (ARMA) model, Mean reversion models with ensemble interaction together with Markov regime switching models are proposed for that purpose.

Ultrafiltration of pulp mill bleaching effluents

Main objective of this research was to find suitable polymeric ultrafiltration membranes with high retentions, good capacities and low fouling tendencies for the E2- and EP-effluent ultrafiltration. Purpose was to treat alkaline bleaching effluents with ultrafiltration in a way that permeates of the filtrations could be recycled back to process and the consumption of fresh water in the pulp mill could be reduced significantly. In the theoretical part of this work the challenges set by the pulp and paper indus-try processes for membranes were examined. An overview of the membrane tech-nology in the pulp industry was also provided. In addition process conditions in the chemical pulp bleaching and properties of bleaching effluents were discussed in literature study. In experimental part the E2- and EP-stage bleaching effluents from Stora Enso Imatra kraft pulp mill were ultrafiltered with CR250- and CR200-filters. Suitable membranes for ultrafiltration were chosen after screening experiments. Concentra-tion experiment was made for the E2-effluent in order to estimate water saving potential. The E2-effluent was finally ultrafiltered in the pulp mill in order to test the feasibility of ultrafiltration in a real industrial environment. Good membrane for the EP-effluent ultrafiltration based on the EP-screening ex-periments was polyethersulfone membrane UP020 with cut-off value of 20 000 Da. Polysulfone membrane UFX05 with cut-off value of 5 000 Da was promising membrane for the ultrafiltration of the E2-effluent. Based on the concentration filtration of the E2-effluent with UFX05 membrane the water saving potential could be 2.2 m3/Adt for the industrial scale ultrafiltration process. Retention re-sults, such as average COD retention of 60 %, from the trial filtration at the pulp mill with UFX05 membrane were modest compared to the screening experiments, where average COD retention was 75 %. Therefore tighter ultrafiltration mem-branes should be tested for the ultrafiltration of the E2-effluent. The UP020 mem-brane seemed to be suitable for the ultrafiltration of the EP-effluent however con-centration and pilot scale ultrafiltration experiments are needed to verify this.

Risk management measures for REACH registered intermediate substances in pulp mill

Tämän työn tavoitteena on antaa kuvaus riskinhallintamenetelmistä viidelle välituotekemikaalille, joita käytetään Stora Enson Imatran tehtailla. Välituotekemikaalit ovat mustalipeä, viherlipeä, valkolipeä, natriumbisulfiitti ja natriumsulfiitti. Nämä kemikaalit ovat jo rekisteröityjä ECHA:an ja rekisteröintiin liittyen ECHA:an on toimitettava myös kuvaus riskinhallintamenetelmistä. Työn alussa kuvaillaan työn kannalta olennaiset säädökset ja viranomaiset, jotka valvovat kemikaalien käyttöä ja valmistusta Euroopan Unionin alueella. Tämän jälkeen kerrotaan yleisesti välituotekemikaalien rekisteröintikriteereistä. Työn loppuosa käsittää kuvauksen riskinhallintamenetelmistä jokaiselle kemikaalille. Riskinhallintamenetelmät sisältävät eristyksen teknisin keinoin, menettelytapa- ja valvontatekniikat, johtamistavat ja henkilökunnan koulutuksen ja välituotekemikaalien kuljetuksen. Myös jokaisen kemikaalin ominaisuudet on kuvattu ja lyhyt prosessikuvaus kemikaalien valmistuksesta ja käytöstä on esitetty helpottamaan ymmärtämistä.

Tertiary Treatment and Re-use of Kraft Pulp Mill Effluent

The efficient use of materials and natural recourses, for ecological and economic reasons, has become more and more important in all industries. In the forest industries this means higher levels of closure in the material circulations of the mills. One possibility to reduce wastewater discharge is to re-use part of the 2nd clarifier effluent as process water. The main target of this thesis was to evaluate the technical suitability of several mechanical and chemical tertiary treatment methods for water re-use. Some of the tested methods seemed to have high potential for the removal of some specific constituents from the wastewater. Tertiary treatment is needed because higher levels of closure may cause problems with increasing amounts of non-process elements in different points of kraft pulp process. The aspect of sustainable development was taken into account by evaluating positive and negative environmental effects of the treatment processes. Environmental benefits can be gained by using some of the tertiary treatment methods tested. These methods should still be researched more for system optimization.

Production planning and optimization of a pulp mill: introduction of the optimisation based scheduling software for pulp industry

The objective of this project was to introduce a new software product to pulp industry, a new market for case company. An optimization based scheduling tool has been developed to allow pulp operations to better control their production processes and improve both production efficiency and stability. Both the work here and earlier research indicates that there is a potential for savings around 1-5%. All the supporting data is available today coming from distributed control systems, data historians and other existing sources. The pulp mill model together with the scheduler, allows what-if analyses of the impacts and timely feasibility of various external actions such as planned maintenance of any particular mill operation. The visibility gained from the model proves also to be a real benefit. The aim is to satisfy demand and gain extra profit, while achieving the required customer service level. Research effort has been put both in understanding the minimum features needed to satisfy the scheduling requirements in the industry and the overall existence of the market. A qualitative study was constructed to both identify competitive situation and the requirements vs. gaps on the market. It becomes clear that there is no such system on the marketplace today and also that there is room to improve target market overall process efficiency through such planning tool. This thesis also provides better overall understanding of the different processes in this particular industry for the case company.

Separation of lignin in Pulp Mill process and its effect on sodium sulphur balance

The aim of this thesis is to define effects of lignin separation process on Pulp mill chemical balance especially on sodium/sulphur-balance. The objective is to develop a simulation model with WinGEMS Process Simulator and use that model to simulate the chemical balances and process changes. The literature part explains what lignin is and how kraft pulp is produced. It also introduces to the methods that can be used to extract lignin from black liquor stream and how those methods affect the pulping process. In experimental part seven different cases are simulated with the created simulation model. The simulations are based on selected reference mill that produces 500 000 tons of bleached air-dried (90 %) pulp per year. The simulations include the chemical balance calculation and the estimated production increase. Based on the simulations the heat load of the recovery boiler can be reduced and the pulp production increased when lignin is extracted. The simulations showed that decreasing the waste acid stream intake from the chlorine dioxide plant is an effective method to control the sulphidity level when about 10 % of lignin is extracted. With higher lignin removal rates the in-mill sulphuric acid production has been discovered to be a better alternative to the sulphidity control.

Pyrolysis and combustion of pulp mill lime sludge

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Advanced oxidation process H2O2/UV combined with anaerobic digestion to remove chlorinated organics from bleached kraft pulp mill wastewater

This study investigated the application of an advanced oxidation process combining hydrogen peroxide with ultraviolet radiation (H2O2/UV) to remove recalcitrant compounds from Kraft bleaching effluent. Anaerobic pre-treatment was performed to remove easily degraded organics using a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. Bleaching plant effluent was treated in the HAIB reactor processed over 19 h of hydraulic retention time (HRT), reaching the expected removal efficiencies for COD (61 +/- 3%), TOC (69 +/- 9%), BOD5 (90 +/- 5%) and AOX (55 +/- 14%). However, the anaerobic treatment did not achieve acceptable removal of UV254 compounds. Furthermore, there was an increase of lignin, measured as total phenols. The H2O2/UV post-treatment provided a wide range of removal efficiencies depending on the dosage of hydrogen peroxide and UV irradiation: COD ranged from 0 to 11%, UV254 from 16 to 35%, lignin from 0 to 29% and AOX from 23 to 54%. All peroxide dosages applied in this work promoted an increase in the BOD5/COD ratio of the wastewater. The experiments demonstrate the technical feasibility of using H2O2/UV for post-treatment of bleaching effluents submitted to anaerobic pre-treatment.

Post biological solids characterization and removal from pulp mill effluents /

Mode of access: Internet.

Advanced filtration of pulp mill wastes /

Mode of access: Internet.