Consultation on boiler generation too much electricity

a) Hello, I created the boiler with the code ```CHP_sys = create_coheat_and_power_system(combustible_slurries=slurries, combustible_gases=gases, mockup=True)```, ```slurries``` stream is the solid wastes stream in the process, and ```gases``` is the exhaust gas stream in the process. The default setting is ```satisfy_system_electricity_demand=True```. Therefore, the electricity generated by burning the inlet natural gas through the boiler should be equal to the power consumption in the process. However, the electricity generated by the boiler in the result (as shown in the following picture) is higher than the power consumption in the process, that is, the sum of the electricity in the figure below is not 0 (```27.347570976+ 301.2511441+ 1.745776495 -8671.624969+ 5706.175246+ 14.43222414+ 14.50076547+ 211.5285978+ 102.6740528+ 66.71913645+ 0.140129736=-2225.11```), but a negative value, may I ask you why?

b) The sum of the above electricity is not 0, but negative, does it indicate that the process is not converging? But in fact, the process has been running, and no errors have been reported.

c) If setting ```satisfy_system_electricity_demand=True```, is the power consumption of the boiler considered? The power consumption of the boiler does not seem to be seen in the following results.

d) If I set ```satisfy_system_electricity_demand=False```, I can see the boiler power consumption in the result.

e) When I added a heat exchanger to the process (just to heat the stream temperature to the required temperature of the reactor) and set ```satisfy_system_electricity_demand=False```, the boiler was still producing electricity, and the amount of electricity production seemed unreasonable (as shown in the figure below). The flow rate of the boiler feed natural_gas stream is also changed to 0. But if the heat exchanger is not added, also set ```satisfy_system_electricity_demand=False```, the boiler does not produce electricity, but consumes electricity, and the flow rate of the boiler feed natural_gas stream is not 0. In fact, the boiler should need natural_gas feed, the boiler should not produce electricity, but consume electricity.
May I ask you why this happens?

f) If ```setting satisfy_system_electricity_demand=True```, is it not necessary to set electricity price through ```bst.PowerUtility.price``` or ```bst.settings.electricity_price```? Because the power consumed by the process has already been supplied by the boiler.

g) If the price of electricity is set, is it through ```bst.PowerUtility.price``` or ```bst.settings.electricity_price```, could I consult you which one is right?

Thanks for your help. Wish you a good day.

Start from the create_coheat_and_power_system call and compare the results with satisfy_system_electricity_demand set to True and False. Then inspect the reported PowerUtility.price and settings.electricity_price behavior, including the heat-exchanger case. Done means documenting why the electricity balance, boiler consumption or generation, natural-gas flow, and electricity pricing differ across these configurations.

Written by the indexing model from the issue text.