\chapter{Oppsumering}
\textit{Should this be included at all?}

\section{Oppsumering 1. februar}
-Powerpoint presentation of the boiler. 
	Problems:
		-Uneven distribution of air in the bed. Results in NOx formation? Sintering? Yoo much air?
		-They have closed some of the secondary air inlets.
		-Flue duct was leaking. Results in unwanted air in the flue gas, which causes unwanted oxygen in the recycle.
		-Three boilers, what fuels are they using.
		-Have extra space for heat exchangers at the bottom
		-Burn everything. Problem with plastics/impurities depositing on the walls.

-Talk with operator
	-Highest steam production so far around 14 kg/s. Designed at 17.6. Steam pressure 54-55, should be 60. At this point the flue gas fan was operating at its limit (according to the operators).
	-The manual control consist of making sure NOx and CO are below limits. Controlling the O2 too? 
	-They have the ability to control air/fuel-ratio, but they usually don't change it. But they change the air inlet.
	-They control the pressure in the accumulater around 10-12 bar by changing the fuel.
	
\section{Oppsumering 16. februar}

\subsection{High pressure air/Sand system}
The high pressure system is used to prevent sand to block the recycle knee. High pressure fans operate at a constant speed. Downstream pressure is regulated by a damper that directs the surplus air to the primary air system.

15-16 metric tons of sand circulate through the boiler.

\subsection{Primary air}
-It is the only fan that is not speed variable (in addition to the high pressure fans). The air flow is regulated by using a damper/valve.

\subsection{Secondary air}
Norske Skog has done measurements to determine the \chemfig{O_2} distribution in the bed. The results prompted the engineers to close down all the secondary air inlets at the side walls, leaving only the front and back inlets open. This means that 10 out of 32 secondary air inlets are closed down. 

The secondary air comes in at 50 mbar (think the measurement is right before the air enters the furnace, but not sure. At the operation print screen it looks like the pressures in the furnace are 16 mbar and 7 mbar right next to the secondary air inlets.)

Operator: Uneven distribution of air and fuel is caused by both fuel and furnace design.

\subsection{Fuel}
-Types: Demolition wood, 3 types of sludge: "Tipslam"(Mostly clay and ink) 65\%-67\% Dry Matter, "Bioslam" 37\%-43\% DM, "Fiberslam"
-


\subsection{Recycle}
Recycle is used to control the temperature in the bed. Because of leaks in the air duct this stream is more oxygen rich than it should be. 

The recycle fan operates on a variable-speed. Very slow response. Takes around 15-20 minutes to change the speed from 60\% to 20\%. 

\subsection{Steam production}
-Pressure is controlled by a valve to the accumulator. The pressure are allowed to vary about 1.5 bars. The maximum and minimum constraints are 40-(60 or 65) bar.

-Temperature after the second overheater is controlled by injecting water between the first and the second overheater.

-Overall steam production is controlled manually by the operators by changing the fuel input. 

\subsection{Manual Control}
2 goals:\\
-Produce steam to keep accumulators filled. This is regulated by changing the fuel input to achieve a desired steam production [kg/s]. The time constant for this operation is around 5-10 minutes. 
\\
-Keep CO and NOx below limits. This is primarily done through the control of the O2-level by adjusting the air/fuel-ratio. This ratio usually/is allowed to vary between 0.80-0.94. 
\\
-Usually, high NOx-concentration means to much air, and high CO-concentration means to little air. If both are high, it usually means that they are burning to much sludge (why? Is this because of "tipslam" only?)

\subsection{Flue gas}
-Flue gas temperature usually too high due to saw dust burning in the flue duct. 

-Leakage causes false air to enter before (and inside?) the economizer. \chemfig{O_2}-levels in the chimney should be below 6\%, but are rarely under 8\%. Amount of false air is estimated (based on the \chemfig{O_2}-levels before the economizer and the levels inside the chimney) to be 40\% of the initial flue gas amount.

-

\subsection{Temperature in bed}
-Four new temperature sensors in the middle of the bed. The operator think the temperature is measured as an average of the two sensors in the middle (i.e. the sensors showing the highest and the lowest temperature are excluded)

\subsection{Pressure in bed}
Changes 3-5 mbar. Might be because of signal disturbance (to the flue gas fan).

\subsection{Feed water}
-Small recycle of feed water to control the inlet temperature of the feed water entering the economizer. The setpoint is \SI{160}{\celsius}, but the recycle pump is operating at its maximum and the inlet temperature is \SI{138}{\celsius}. This is done to make sure that the flue gas temperature stays at around \SI{145}{\celsius} (It was actually at \SI{152}{\celsius}).

-The effect of the small recycle is basically to lower the amount of heat exchanged.

\section{Møte 16. mai}

-Hvor mye luft lekker inn mellom de to O2-målerene.
	Ekstra 0.48, utgjør 0.33 av røykgass ved pipe. Gjennomsnitt over 15 dager (21.feb 11:00-8.mar 10:57)
	O2-måler ved pipe viser for lite O2, så egentlig er mengden falskluft enda større. \\

-Røykgassvifte på maks. Hvor mye ekstra strøm brukes pga dette?
	Må ha karakteristikk av røykgassvifte for å beregne dette. \\

-Tap pga lekkasje i Lufo \\
	Cp_{luft, 35C}=1.006 kJ/kg*K \\
	Cp_{luft,157.9C}=1.019 kJ/kg*K \\
	T_{røykgass}=157.9C \\ 
	Assume Cp_{luft}=1.013 kJ/kg*K \\
	(157.9-35)*1.013=124.5 kj/kg \\
	Mengde luft = 29.3 m3/s * 0.33 * 1.2 kg/m3 = 11.72 kg/s \\
	11.72 kg/s * 124.5 kJ/kg = 1459 kJ/s = 1.459\\
	Økonomisk tap bark: 166kr/MWh * 1.459 MW = 242.2 kr/h = 5812.7 kr/døgn = 2.123 mill/år \\
	
	Noe av dette blir sendt tilbake i recycle, så alt er ikke tap. Hvor mye blir sendt i recycle? \\
	
	

-Hvor mange rør er plugga i eko? Hvor mye reduserer dette varmeoverføringen.
	5\% av sek.luft. Ikke noe mer. Betyr at eko ikke er plugga \\

-O2 i recycle. Enda mer falsk luft lekker inn.
	Kan gå ut ifra at recycle ikke har lekkasjer. \\

-Dårlige flow-measurments på prim.luft. Andre målere som også er dårlige?
	Mest sannsynlig. Lav $\Delta$P i rør i forhold til det måleren er dimensjonert til. \\

-Ta i bruk ny beregning på primærluft. Er denne beregningen god nok?
	Må kanskje endre noe. Den opprinnelige beregninen er tilpasset et bedtrykk på 35, nåværende trykk er 65 \\

-Finnes det dokumentasjon på hvorfor luftberegningene er som de er?
	Norske Skog har tilgang til dette. Mest sannsynlig basert på modeller og erfaringer til FW.
	Dette betyr vel at man er avhengig av skikkelige flow-measuremnts for at beregningene skal være gode? \\

-Sek.luft
	Spjeld går noen ganger i max. Skyldes dette lekkasjer? Nei, skyldes mest sannsynlig plugging av rør \\

-Shunt pumpe
	Ingen effekt? Ser sånn ut. \\

-Dolezal-system
	Ikke høyt nok trykk til å oppnå tilstrekkelig turbulent strømning
	Høy temperatur gir mindre mulighet til regulering, og krever høyere flow
	Gir disturbances til level i drum
	Har også opplevd problem med at det ikke er nok kondensering i dolezalen
	Må kanskje ha dette systemet uansett pga at vann hele tiden etterfylles, og derfor ikke er rent nok.
	Husk å ta med attemperator i beskrivelsen